Yearly Archives: 2025

　　On August 20th, an intercity bus from Lai ‘an County, Anhui Province to Nanjing Forest Farm Station caught fire while driving. Two passengers were killed in the fire, and five others were partially burned. After preliminary investigation, the cause of the fire was the spontaneous combustion of a lithium battery carried by a passenger.Actually, it’s not just this reason, cathode material in lithium ion battery:140 Its own advantages are also obvious, and it is normal for the market to perform well. https://www.canrud.com/products?categories=Energy+materials,Not+specified&function=Cathode

　　

　　In recent years, battery explosions have been frequently searched, which are not far away from us. The Paper (www.thepaper.cn) looked up 1092 complaints about “battery explosion” and “battery spontaneous combustion” on the black cat complaint platform, and found that battery explosion would appear on electric cars, mobile phones and even children’s toys. And 276 refereeing documents about “battery explosion” revealed that even if consumers sue businesses, the proportion of final compensation is limited and the litigation takes too long.

　　

　　The battery explosion is around.

　　

　　After reading 1092 complaints, we found that mobile phone batteries are the high-risk areas for battery explosion, followed by remote control and electric vehicle batteries. “There was a loud noise in my sleep, and I found that the battery of the air conditioner remote controller exploded, and I couldn’t hear the sound instantly, and the bedside table also blew a corner.” Some netizens wrote on the black cat complaint platform.

　　

　　These complaints about battery explosion, ranging from daily digital products and daily necessities to vehicles and accessories, are closely related to people’s daily life.

　　

　　On the platform of Little Red Book, many netizens shared similar experiences. Netizen @know4014 said: “The battery No.5 that has been placed on the table suddenly exploded, just like a firecracker was placed in front of it.” Netizen @ Bangbangbutang didn’t find the source of the explosion at first. “I thought it was mom’s sour bean jar that exploded.” After several searches, I found that it was two batteries No.5. Netizen @QIAO woke up in his sleep. “The battery directly pushed out of the back cover of the air conditioner remote control and flew over my head.” Although it did not cause serious damage, it also left him a psychological shadow.

　　

　　Relevant complaint data show that the consequences of battery explosion are different, ranging from minor property losses to serious personal injuries. Some consumers said that after the battery spontaneously ignited and exploded, a large number of items in the shoe cabinet were stained and smelled, the cabinet was blackened, and toxic smoke even caused the fire station to go out. He and the landlord fell into a dispute for this. What is more serious is that some consumers have been injured in the stomach and have severe abdominal pain and dizziness.

　　

　　According to reports, before the Nanjing intercity bus fire accident, passengers carrying lithium batteries put them in their backpacks and got on the bus, but the bus driver did not find them at that time. After the fire was found during driving, the driver pulled over the car and opened the door for passengers to evacuate. Due to the large fire, some passengers could not escape in time, eventually causing 2 deaths and 5 injuries.

　　

　　Consumer rights protection is difficult: it is difficult to prove.

　　

　　In the daily complaints about battery explosion, almost no consumers’ rights protection is very smooth.

　　

　　Consumers often don’t realize it until they defend their rights. The simple online shopping process makes it difficult for them to find out who will bear the responsibility for the battery explosion. On the black cat complaint, some consumers spoke out about the experience of communicating with the merchants. “I waited for nearly 2 months, but I didn’t give any reply. I just said that I should wait. I don’t know when it is, so I should wait.” There are also consumers who have to post on public platforms for help because they have been blacked out by merchant customer service: “The customer service attitude is extremely poor and (very) arrogant. After admitting that they are fakes and frauds, they directly blacked out consumers.”

　　

　　Among the above complaints, only about 6.4% of consumers can successfully defend their rights. They can only rely on online shopping platforms to contact merchants, and it is difficult to advance their rights protection to the next step. In the long wait, victims often give up their rights protection because of the cost of time and energy, while businesses continue to sell products with unknown quality.

　　

　　The road to litigation: limited compensation and long time-consuming

　　

　　In the end, some consumers who suffered heavy losses could not afford the follow-up expenses, and they had to go to court under the prevarication of the platform and merchants.

　　

　　Among the 276 refereeing documents about “battery explosion”, we selected 81 documents belonging to disputes between merchants and consumers. Through these instruments, we can find out the reasons for the success or failure of battery explosion prosecution.

　　

　　Among these documents, “the cause of explosion and fire is unknown” has become the most commonly used reason for refusing to pay compensation, while the lack of evidence and the use of consumers themselves may make consumers lose the case.

　　

　　This road to litigation takes a long time, requires a lot of energy, and may not be compensated. Among the 81 judgment documents, more than half of consumers have gone through two or more court trials, and about 77% of consumers have gone through more than one year from the explosion to the end of rights protection.

　　

　　Sometimes, even if the court finds that the main cause of battery explosion is battery quality, consumers still have to bear part of the responsibility.

　　

　　In the documents we have counted, the problem of “improper use” by consumers ranks first-some consumers charge indoors, use mismatched chargers, and consumers change the structure of their own houses, which may lead to battery fire and explosion. For example, a civil judgment of first instance shows: “The direct cause of the fire in this case is the failure of lithium battery, but the plaintiff changed the original house use, illegally occupied people, changed the stair form, removed the indoor fire hydrant, and installed an anti-theft grille outside the window, which made it difficult for people to escape and rescue.”

　　

　　In addition, “failure to fulfill the duty of care” has also become an important factor for the court to determine the responsibility of consumers. Simply put, in the battery explosion, if consumers do not notice the existing safety hazards, they may also bear legal responsibility.

　　

　　A civil judgment of the second instance shows that the prosecutor did not read the battery reading instructions carefully, which led to improper protection and he had to bear part of the responsibility. The judgment mentioned in detail that “experts suggested that the battery should be equipped with protective glasses and the battery should be affixed with safety warning signs. Upon inquiry, the consumer said that he saw the warning sign, but did not pay attention to it. It was seen that the consumer did not read the instruction manual carefully before using the battery involved, and he should bear 20% responsibility for his failure to fulfill his duty of safety care. “

　　

　　It can be seen that if you want to avoid battery explosion, in addition to the efforts of merchants in product quality, consumers’ own awareness of fire safety is also very important.

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　　Classification of fasteners and related accessories

　　

　　1. Fasteners:

　　

　　Bolts, studs, nuts, screws, washers, wood screws, tapping screws, pins, rivets, retaining rings, assemblies and connecting pairs, welding nails, innovative and non-standard products;

　　

　　2. Equipment:

　　

　　Molding equipment: cold heading machine, cold extrusion molding machine, heading machine, nailing machine, etc.

　　

　　Thread forming equipment: thread rolling machine, thread rolling machine, tapping machine, etc.

　　

　　Heat treatment equipment: industrial furnace, tempering line, high and medium frequency induction heating equipment, material annealing furnace, etc.

　　

　　Surface treatment equipment: phosphating line, oxidation line, zinc plating line, dacromet production line, etc.

　　

　　Auxiliary equipment: grinding machine, slotting machine, vibrating plate, marking machine, etc.

　　

　　Testing equipment and devices: hardness tester, material tension and compression tester, microscope, etc.

　　

　　3, tooling:

　　

　　Bolt forming die: including cutting die, upper die (pre-die, fine die, trimming die, etc.) and lower die (cold upsetting die, reducing die, ejector pin, etc.)

　　

　　Nut forming die: including cutting die, punch, punch, hole die, forming die, thimble, etc.

　　

　　Thread forming tools: thread rollers, thread washboards, taps, etc.

　　

　　4, surface treatment:

　　

　　Surface treatment process: electroplating, blackening, heat treatment, hot dip zinc, phosphating, mechanical plating and dacromet.

　　

　　Auxiliary materials: brightener, cleaning agent, antirust agent and degreasing agent.

　　

　　5. Raw materials:

　　

　　Medium carbon steel, low carbon steel, alloy steel, stainless steel (including wire, bar, plate, pipe, etc.)

　　

　　2

　　

　　The meaning of bolt performance grade

　　

　　The performance grades of bolts used for steel structure connection are divided into more than 10 grades, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched and tempered), which are generally called high-strength bolts, and the rest are generally called ordinary bolts.

　　

　　The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield ratio value of the bolt material. For example, a bolt with performance grade 4.6 means:

　　

　　1. The nominal tensile strength of bolt material reaches 400MPa;

　　

　　2. The yield ratio of bolt material is 0.6;

　　

　　3. The nominal yield strength of the bolt material reaches 400X0.6=240MPa, and the performance grade is 10.9. After heat treatment, the material can reach:

　　

　　1. The nominal tensile strength of bolt material reaches 1000MPa;

　　

　　2. The yield ratio of bolt material is 0.9;

　　

　　3. The nominal yield strength of bolt material reaches 1000X0.9=900MPa.

　　

　　The meaning of bolt performance grade is an international standard. Bolts with the same performance grade have the same performance regardless of the difference of material and origin, so only performance grade can be selected in design.

　　

　　The so-called 8.8 and 10.9 strength grades mean that the shear stress grades of bolts are 8.8GPa and 10.9Gpa.

　　

　　8.8 Nominal tensile strength 800N/MM2 Nominal yield strength 640N/MM2.

　　

　　Generally, the strength of bolts is expressed by “X.Y”.

　　

　　X*100= tensile strength of this bolt,

　　

　　X*100* (Y/10 )= yield strength of this bolt.

　　

　　(Because according to the marking: yield strength/tensile strength =Y/10)

　　

　　Such as 4.8.

　　

　　Then the bolt’s

　　

　　The tensile strength is 400MPa.

　　

　　The yield strength is: 400*8/10=320MPa. In addition, stainless steel bolts are usually marked as A4-70 and A2-70, and the meaning is otherwise explained.

　　

　　three

　　

　　magnanimity; tolerance

　　

　　There are mainly two types of length measurement units in the world today. One is metric, with the measurement units of meters (m), centimeters (cm) and millimeters (mm), which are widely used in Europe, China and Japan, and the other is English, with the measurement unit of inch, which is equivalent to the old city inch in China, and is widely used in the United States, Britain and other European and American countries.

　　

　　1. Metric measurement: (decimal system)

　　

　　1m =100 cm=1000 mm

　　

　　2. English measurement: (octal)

　　

　　1 inch =8 minutes 1 inch =25.4 mm3/8 00×25.4 =9.52

　　

　　3, 1/4 0 of the following products use serial numbers to indicate their address diameter, such as:

　　

　　4#5#6#7#8# 10# 12#

　　

　　four

　　

　　screw thread

　　

　　1. Thread is a shape with uniform spiral protrusions on the cross section of solid outer surface or inner surface. According to its structural characteristics and uses, it can be divided into three categories:

　　

　　(1) Ordinary thread: the tooth shape is triangular, which is used to connect or fasten parts. Ordinary threads are divided into coarse thread and fine thread according to pitch, and the connection strength of fine thread is higher.

　　

　　(2) Transmission thread: the tooth shapes include trapezoid, rectangle, saw and triangle.

　　

　　(3) Sealing thread: used for sealing connection, mainly including pipe thread, taper thread and taper pipe thread.

　　

　　Second, the thread matching grade:

　　

　　Thread fit is the size of looseness or tightness between screwed threads, and the level of fit is the prescribed combination of deviation and tolerance acting on internal and external threads.

　　

　　(1) For unified English thread, there are three thread grades for external thread: 1A, 2A and 3A, and three grades for internal thread:

　　

　　1B, 2B and 3B, all of which are clearance fit. The higher the grade number, the tighter the fit. In English thread, the deviation is only specified as Grade 1A and Grade 2A, the deviation of Grade 3A is zero, and the grade deviation of Grade 1A and Grade 2A is equal.

　　

　　The greater the number of grades, the smaller the tolerance.

　　

　　Classes 1, 1A and 1B, very loose tolerance classes, which are suitable for tolerance fit of internal and external threads.

　　

　　Grade 2, 2A and 2B are the most common thread tolerance grades specified by English series mechanical fasteners.

　　

　　Grade 3, 3A and 3B, which are screwed to form the tightest fit, are suitable for fasteners with tight tolerances and are used for the key design of safety.

　　

　　4. For external threads, there is a fit tolerance for Grade 1A and 2A, but not for Grade 3A. The tolerance of Class 1A is 50% greater than that of Class 2A and 75% greater than that of Class 3A. For internal threads, the tolerance of Class 2B is 30% greater than that of Class 2A. Class 1B is 50% larger than class 2B and 75% larger than class 3B.

　　

　　(2) Metric thread. There are three thread grades for external thread: 4h, 6 H and 6g, and three thread grades for internal thread: 5H, 6h and 7H. (The thread accuracy grade of Japanese standard is divided into I, II and III, which is usually Grade II) In metric thread, the basic deviation between H and H is zero. The basic deviation of G is positive, and the basic deviations of E, F and G are negative. As shown in the figure:

　　

　　1. H is the commonly used tolerance zone position of internal thread, which is generally not used as surface coating or extremely thin phosphating layer. The basic deviation of G position is used in special occasions, such as thick coating, which is rarely used in general.

　　

　　2. G is commonly used to plate a thin coating of 6-9um. For example, the bolt required by the product drawing is 6h, and the thread before plating is 6g tolerance zone.

　　

　　3. It is best to combine the thread fit into H/g, H/h or G/H. For refined fastener threads such as bolts and nuts, the standard recommends 6H/6g fit.

　　

　　(3), thread marking

　　

　　Three, the main geometric parameters of self-tapping and self-drilling thread:

　　

　　(1) The major diameter/tooth outer diameter (d1) is the imaginary cylinder diameter with overlapping thread crests. The major diameter of the thread basically represents the nominal diameter of the thread size.

　　

　　(2) Small diameter/root diameter (d2): it is the imaginary cylinder diameter with overlapping thread roots.

　　

　　(3) Pitch (P): refers to the axial distance between adjacent teeth corresponding to two points on the meridian. Pitch is expressed by the number of teeth per inch (25.4mm) in the British system.

　　

　　According to the latest data of China Automotive Power Battery Industry Innovation Alliance, from January to December, 2023, a total of 52 power battery enterprises in China’s new energy vehicle market achieved vehicle loading facilities, 5 fewer than the same period of last year, and the elimination rate was close to 10%.Mentioned in the article battery separator film:50 Born with strong vitality, you can turn a cocoon into a butterfly and become the best yourself after wind and rain. https://www.canrud.com/products?keyword=separator

　　

　　On the other hand, the top ten power battery enterprises have loaded 375.3GWh, accounting for 96.8% of the total vehicle. Compared with 95% in 2022, 93.5% in 2021 and 91.8% in 2020, power battery companies have staged the drama that the stronger the stronger.

　　

　　Power battery companies ranked lower are struggling.

　　

　　Gateway Power, a lithium battery factory owned by Galaxy, is obviously one of them. From January to October, 2023, the loading capacity of Gateway Power was only 0.88GWh, ranking 13th. Now, the company has stopped production for two months.

　　

　　Source/Weibo New Energy Prospective Screenshot

　　

　　Jiewei Power was established in 2009 with a registered capital of 1.218 billion yuan. It is a 15-year veteran lithium battery enterprise. Once, it was full of lofty sentiments. It became the top 3 in the power battery industry in five years, ranked among the top 3 in the world in 10 years, applied for IPO of A shares in 2022, and strived for listing in 2023. After all, it was “but before he could conquer, he was dead”.

　　

　　Obviously, in the power battery industry, there are still many battery manufacturers that are not as good as Jiewei Power. They are also facing many problems, even life and death tests. How do you spend this winter?

　　

　　01

　　

　　Small battery factories are getting worse every year.

　　

　　The person in charge of the lithium battery manufacturer who suffered in 2023 will definitely miss 2022, especially the “small factory” of lithium batteries.

　　

　　Wu Sujun, a grassroots employee who has worked in Jiewei Power for more than ten years, once told the media that the company still has some orders in 2022, but the quantity is not large. Mainly small modules, not finished products. In 2023, there was no order, and the factory could only do some battery repair work, and about 200 sets were repaired every month.

　　

　　Compared with more than 2,400 employees in the glorious period, gateway power had only about 400 employees left in its headquarters before the production stopped, and 200 people left after the production stopped. The 2022 annual report shows that in 2022, the number of social security participants of Jiewei Power was 882, which dropped by more than 70% in less than one year.

　　

　　The closed production lines record the cruelty of the lithium battery industry. According to the Shenzhen Communique of the 10th G20！-Lithium Battery Summit, since 2023, the average capacity utilization rate of domestic power batteries is less than 60%, and that of energy storage batteries is less than 55%.

　　

　　Figure/Jiewei Power Electric Center Workshop

　　

　　Source/Gateway Power Official Website New Energy Prospective Screenshot

　　

　　In fact, in addition to the power battery companies such as Jiewei Power, there are also four major materials (cathode materials, anode materials, separators and electrolytes) for lithium batteries.

　　

　　In terms of capacity utilization rate, many companies disclosed that the overall capacity utilization rate of the anode industry decreased significantly in 2023. Even the leading enterprise Shangtai Technology announced the suspension of production in the first quarter of 2023.

　　

　　On the evening of March 27, 2023, Shangtai Technology announced that Licheng Road Base had stopped production. It is reported that Licheng Road Base started construction in 2008. It is the earliest production base of Shangtai Technology, and also the starting place and birthplace of the company’s entrepreneurship, with an annual production capacity of over 10,000 tons.

　　

　　”The supply and demand of the entire anode material industry has reversed, facing a situation of overcapacity.” Shangtai Technology clearly stated in the announcement.

　　

　　The performance of Ferrous lithium phosphate cathode manufacturers in operating rate is also relatively sluggish. According to market data, in November 2023, the average operating rate of manufacturers was less than 50%, and it has accelerated to about 20% since December. The output of cathode materials in Ferrous lithium phosphate has reached a new low since June 2023.

　　

　　02

　　

　　Solve overcapacity

　　

　　”Surplus” became the label of lithium battery industry in 2023.

　　

　　Mr. Gang ‘an, the technology developer of Jiewei Power, said that the company kept investing in building factories, which eventually led to overcapacity.

　　

　　How many lithium batteries did Gateway Power produce? According to the information of official website, Jiewei Power has two production bases, Yancheng and Changxing, with an effective production capacity of 10GWh. Jiewei Power CEO Lu Chenli announced in 2022 that the company plans to reach the power battery production capacity of 100GWh in 2025.

　　

　　Source/Gateway Power Official Website New Energy Prospective Screenshot

　　

　　Zhu Huarong, Chairman of Changan Automobile, once predicted that by 2025, the demand for power batteries in China will be 1000GWh, while the production capacity of the industry has reached 4800GWh, and the degree of excess can be imagined.

　　

　　The four major materials of lithium battery also have different degrees of surplus. Some organizations predict that the global electrolyte capacity planning will exceed the demand by 3.4 million tons in 2025.

　　

　　It is also a means of self-help for the lithium battery factory and the four major material enterprises behind it to delay the production capacity and adopt the low inventory procurement policy.

　　

　　The semi-annual report of Contemporary Amperex Technology Co., Limited in 2023 shows that its inventory is only 48.91 billion yuan, which is 27.76 billion yuan less than that at the end of 2022. Zhongchuang Singapore Airlines, the third in the industry, cleared its inventory slightly, and its inventory decreased from 11.82 billion yuan at the end of 2022 to 10 billion yuan, a decrease of 18.2%.

　　

　　Enterprises in the upper and middle reaches of lithium batteries have been kidnapped by the “game theory” of production capacity, forcing low inventory.

　　

　　Jin Yiteng, an open source securities company, said that as the pace of production scheduling in downstream battery factories declined and the price of lithium battery materials in the middle reaches continued to fall due to overcapacity, battery factories also adopted a lower raw material inventory procurement strategy, forcing middle-stream lithium battery materials enterprises to reduce their start-up, maintain low inventory, and delay the launch of new capacity.

　　

　　Low inventory is obtained on the premise of price reduction. According to the data of Xinyi Lithium Battery, an industry research institution, on January 24th, 2024, the average price of square Ferrous lithium phosphate power battery and energy storage battery was 0.38 yuan /Wh and 0.43 yuan /Wh, respectively, which was more than 50% lower than the price of 0.9 yuan /Wh in early 2023, and the price has reached the lowest point in history.

　　

　　The seriousness of the price reduction can be seen. According to the statistics of Hi-Tech Lithium Battery, compared with 2022, the gross profit margin of diaphragm listed companies in the third quarter of 2023 decreased by about 40%, the electrolyte field decreased by about 25%, the cathode field decreased by about 20%, the ternary cathode decreased by about 9%, and the iron-lithium cathode decreased by about 5%.

　　

　　03

　　

　　Power Battery 2024: More Fierce Fight

　　

　　”After experiencing rapid growth in demand and production capacity, the lithium battery field is currently facing the challenge of overcapacity. It is expected that supply and demand will further deteriorate in 2024 and it is expected to ease in 2025. ” Huatai Securities pointed out.

　　

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　　Classification of fasteners and related accessories

　　

　　1. Fasteners:

　　

　　Bolts, studs, nuts, screws, washers, wood screws, tapping screws, pins, rivets, retaining rings, assemblies and connecting pairs, welding nails, innovative and non-standard products;

　　

　　2. Equipment:

　　

　　Molding equipment: cold heading machine, cold extrusion molding machine, heading machine, nailing machine, etc.

　　

　　Thread forming equipment: thread rolling machine, thread rolling machine, tapping machine, etc.

　　

　　Heat treatment equipment: industrial furnace, tempering line, high and medium frequency induction heating equipment, material annealing furnace, etc.

　　

　　Surface treatment equipment: phosphating line, oxidation line, zinc plating line, dacromet production line, etc.

　　

　　Auxiliary equipment: grinding machine, slotting machine, vibrating plate, marking machine, etc.

　　

　　Testing equipment and devices: hardness tester, material tension and compression tester, microscope, etc.

　　

　　3, tooling:

　　

　　Bolt forming die: including cutting die, upper die (pre-die, fine die, trimming die, etc.) and lower die (cold upsetting die, reducing die, ejector pin, etc.)

　　

　　Nut forming die: including cutting die, punch, punch, hole die, forming die, thimble, etc.

　　

　　Thread forming tools: thread rollers, thread washboards, taps, etc.

　　

　　4, surface treatment:

　　

　　Surface treatment process: electroplating, blackening, heat treatment, hot dip zinc, phosphating, mechanical plating and dacromet.

　　

　　Auxiliary materials: brightener, cleaning agent, antirust agent and degreasing agent.

　　

　　5. Raw materials:

　　

　　Medium carbon steel, low carbon steel, alloy steel, stainless steel (including wire, bar, plate, pipe, etc.)

　　

　　2

　　

　　The meaning of bolt performance grade

　　

　　The performance grades of bolts used for steel structure connection are divided into more than 10 grades, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched and tempered), which are generally called high-strength bolts, and the rest are generally called ordinary bolts.

　　

　　The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield ratio value of the bolt material. For example, a bolt with performance grade 4.6 means:

　　

　　1. The nominal tensile strength of bolt material reaches 400MPa;

　　

　　2. The yield ratio of bolt material is 0.6;

　　

　　3. The nominal yield strength of the bolt material reaches 400X0.6=240MPa, and the performance grade is 10.9. After heat treatment, the material can reach:

　　

　　1. The nominal tensile strength of bolt material reaches 1000MPa;

　　

　　2. The yield ratio of bolt material is 0.9;

　　

　　3. The nominal yield strength of bolt material reaches 1000X0.9=900MPa.

　　

　　The meaning of bolt performance grade is an international standard. Bolts with the same performance grade have the same performance regardless of the difference of material and origin, so only performance grade can be selected in design.

　　

　　The so-called 8.8 and 10.9 strength grades mean that the shear stress grades of bolts are 8.8GPa and 10.9Gpa.

　　

　　8.8 Nominal tensile strength 800N/MM2 Nominal yield strength 640N/MM2.

　　

　　Generally, the strength of bolts is expressed by “X.Y”.

　　

　　X*100= tensile strength of this bolt,

　　

　　X*100* (Y/10 )= yield strength of this bolt.

　　

　　(Because according to the marking: yield strength/tensile strength =Y/10)

　　

　　Such as 4.8.

　　

　　Then the bolt’s

　　

　　The tensile strength is 400MPa.

　　

　　The yield strength is: 400*8/10=320MPa. In addition, stainless steel bolts are usually marked as A4-70 and A2-70, and the meaning is otherwise explained.

　　

　　three

　　

　　magnanimity; tolerance

　　

　　There are mainly two types of length measurement units in the world today. One is metric, with the measurement units of meters (m), centimeters (cm) and millimeters (mm), which are widely used in Europe, China and Japan, and the other is English, with the measurement unit of inch, which is equivalent to the old city inch in China, and is widely used in the United States, Britain and other European and American countries.

　　

　　1. Metric measurement: (decimal system)

　　

　　1m =100 cm=1000 mm

　　

　　2. English measurement: (octal)

　　

　　1 inch =8 minutes 1 inch =25.4 mm3/8 00×25.4 =9.52

　　

　　3, 1/4 0 of the following products use serial numbers to indicate their address diameter, such as:

　　

　　4#5#6#7#8# 10# 12#

　　

　　four

　　

　　screw thread

　　

　　1. Thread is a shape with uniform spiral protrusions on the cross section of solid outer surface or inner surface. According to its structural characteristics and uses, it can be divided into three categories:

　　

　　(1) Ordinary thread: the tooth shape is triangular, which is used to connect or fasten parts. Ordinary threads are divided into coarse thread and fine thread according to pitch, and the connection strength of fine thread is higher.

　　

　　(2) Transmission thread: the tooth shapes include trapezoid, rectangle, saw and triangle.

　　

　　(3) Sealing thread: used for sealing connection, mainly including pipe thread, taper thread and taper pipe thread.

　　

　　Second, the thread matching grade:

　　

　　Thread fit is the size of looseness or tightness between screwed threads, and the level of fit is the prescribed combination of deviation and tolerance acting on internal and external threads.

　　

　　(1) For unified English thread, there are three thread grades for external thread: 1A, 2A and 3A, and three grades for internal thread:

　　

　　1B, 2B and 3B, all of which are clearance fit. The higher the grade number, the tighter the fit. In English thread, the deviation is only specified as Grade 1A and Grade 2A, the deviation of Grade 3A is zero, and the grade deviation of Grade 1A and Grade 2A is equal.

　　

　　The greater the number of grades, the smaller the tolerance.

　　

　　Classes 1, 1A and 1B, very loose tolerance classes, which are suitable for tolerance fit of internal and external threads.

　　

　　Grade 2, 2A and 2B are the most common thread tolerance grades specified by English series mechanical fasteners.

　　

　　Grade 3, 3A and 3B, which are screwed to form the tightest fit, are suitable for fasteners with tight tolerances and are used for the key design of safety.

　　

　　4. For external threads, there is a fit tolerance for Grade 1A and 2A, but not for Grade 3A. The tolerance of Class 1A is 50% greater than that of Class 2A and 75% greater than that of Class 3A. For internal threads, the tolerance of Class 2B is 30% greater than that of Class 2A. Class 1B is 50% larger than class 2B and 75% larger than class 3B.

　　

　　(2) Metric thread. There are three thread grades for external thread: 4h, 6 H and 6g, and three thread grades for internal thread: 5H, 6h and 7H. (The thread accuracy grade of Japanese standard is divided into I, II and III, which is usually Grade II) In metric thread, the basic deviation between H and H is zero. The basic deviation of G is positive, and the basic deviations of E, F and G are negative. As shown in the figure:

　　

　　1. H is the commonly used tolerance zone position of internal thread, which is generally not used as surface coating or extremely thin phosphating layer. The basic deviation of G position is used in special occasions, such as thick coating, which is rarely used in general.

　　

　　2. G is commonly used to plate a thin coating of 6-9um. For example, the bolt required by the product drawing is 6h, and the thread before plating is 6g tolerance zone.

　　

　　3. It is best to combine the thread fit into H/g, H/h or G/H. For refined fastener threads such as bolts and nuts, the standard recommends 6H/6g fit.

　　

　　(3), thread marking

　　

　　Three, the main geometric parameters of self-tapping and self-drilling thread:

　　

　　(1) The major diameter/tooth outer diameter (d1) is the imaginary cylinder diameter with overlapping thread crests. The major diameter of the thread basically represents the nominal diameter of the thread size.

　　

　　(2) Small diameter/root diameter (d2): it is the imaginary cylinder diameter with overlapping thread roots.

　　

　　(3) Pitch (P): refers to the axial distance between adjacent teeth corresponding to two points on the meridian. Pitch is expressed by the number of teeth per inch (25.4mm) in the British system.

　　

　　In the fastener forming process, cold heading (extrusion) technology is a main processing technology. Cold heading (extrusion) belongs to the field of metal pressure processing. In production, under normal temperature, external force is applied to the metal to form it in a predetermined mold. This method is usually called cold heading.So, I believe left thread rock bolt In the future, it will be promising to create a miracle belonging to the industry. https://www.chinatianlong.com/

　　

　　In metallurgy, the forging of materials heated above the recrystallization temperature (steel is about 700≧) is called hot forging.

　　

　　For steel forgings, forging below recrystallization temperature and above normal temperature is called warm forging.

　　

　　Figure 1 Forging temperature and common name

　　

　　01

　　

　　Advantages of cold heading (extrusion)

　　

　　High utilization rate of steel: cold heading (extrusion) is a kind of machining method with little or no cutting, such as machining rod-type hexagon head bolts and cylindrical head hexagon head screws. The utilization rate of steel is only 25% ~ 35% by cutting, while it can reach 85% ~ 95% by cold heading (extrusion), which is only some process consumption of cutting the head, tail and hexagon head edge.

　　

　　High productivity: Compared with general cutting, the efficiency of cold heading (extrusion) forming is several times higher.

　　

　　Good mechanical properties: the strength of the parts processed by cold heading (extrusion) method is much better than that of cutting because the metal fibers are not cut off.

　　

　　Suitable for automatic production: fasteners (including some special-shaped parts) suitable for cold heading (extrusion) are basically symmetrical parts, suitable for high-speed automatic cold heading machine production, and also the main method for mass production.

　　

　　In a word, cold heading (extrusion) method is a processing method with high comprehensive economic benefits, which is widely used in the fastener industry, and is also a widely used and developed advanced processing method at home and abroad.

　　

　　02

　　

　　Cold forging process

　　

　　Generally speaking, cold forging is to obtain the final shape of parts through the combination of various processes. Fig. 2 is an example of cold forging. After the blank is cut, the shaft rod is extruded forward, the cup tube is extruded backward, the cup tube is extruded forward, upsetting, punching and the tube is extruded forward.

　　

　　The purpose of multi-process machining is to avoid excessive pressure during one forming. Because the fewer processes, the lower the cost. Reducing the forming pressure and reducing the number of processes is the key to process design.

　　

　　Fig. 2 Example of cold forging process

　　

　　03

　　

　　Summary of main processing methods of cold forging

　　

　　upsetting

　　

　　Fig. 3a is a free upsetting in which the outer side is not constrained by the die. The machining pressure increases with the friction constraint. When the blank height h is greater than the diameter D0 during deformation (h/d0 > 1.0), C=1.2, but when the blank is thinned, C will rise to 2.5.

　　

　　When the reduction rate increases, as shown in fig. 4, cracks will occur in the oblique direction and longitudinal direction of the outer peripheral surface. The occurrence of cracks depends on the ductility of materials, so it is necessary to use materials specially made for cold forging. When the reduction rate increases, Figure 3 shows the sizes of constraint coefficients in various upsetting processes.

　　

　　Fig. 3 Constraint coefficient during upsetting

　　

　　Figure 4 Upsetting crack

　　

　　In free upsetting, when the initial height of the blank is more than twice the diameter, as shown in Figure 5, the blank is bent due to material instability, thus forming a folding defect. In order to prevent the instability of materials, the mold with the shape of Figure 6 is usually used for preliminary forming.

　　

　　Figure 5 Instability

　　

　　Fig. 6 Preliminary upsetting to prevent instability

　　

　　Semi-closed forging

　　

　　As shown in fig. 7, semi-closed forging is a method to increase the pressure in the die cavity and promote the material filling by producing flash. The technical big coffee is known in the Chinese screw net screw. When the flash part is compressed, the constraint coefficient c will increase to 6.0 ~ 9.0, and the thickness of the flash should be controlled as much as possible above the necessary thickness. Fig. 8 is an example of cold forging using semi-closed forging.

　　

　　Fig. 7 Final stage of flash die forging

　　

　　Fig. 8 Semi-closed forged products

　　

　　Extrusion of shaft rod

　　

　　Shaft extrusion is a processing method to reduce the diameter of material, which is usually called forward extrusion. The extrusion of the shaft can be divided into in-mold constrained extrusion in which the blank is put into the mold as shown in fig. 9 and free extrusion as shown in fig. 13b. Free extrusion is applied to forming with small machining degree.

　　

　　(a) In-mold extrusion (b) Free extrusion

　　

　　Fig. 9 The shaft rod is being squeezed.

　　

　　As shown in fig. 10, internal cracking is easy to occur. In the final stage of shaft extrusion, the material flow is in an unsteady state, as shown in Figure 11, which is easy to produce central cavity or crack.

　　

　　Fig. 10 Core extrusion crack Fig. 11 Unsteady extrusion defect

　　

　　Cup-tube extrusion

　　

　　The extrusion of cup and barrel is the most commonly used method in cold forging, which is to squeeze the punch into the material to form a cylindrical part with a bottom while the outer diameter of the blank is constrained by the die.

　　

　　Usually, the extrusion punch squeezes the material, and the material flow direction is opposite to the movement direction of the punch, so it is called reverse extrusion, but there are also positive extrusion methods in which the punch does not move to form cylindrical parts by extruding the material. As shown in fig. 12,

　　

　　Fig. 12 Back extrusion of cup shell

　　

　　04

　　

　　Cold forging method with compound drive

　　

　　As shown in fig. 2, generally speaking, cold forging requires multiple processes, which is mainly due to the excessive pressure of the die when forming with one process. High die surface pressure will not only destroy the strength of the die, but also cause the elastic deformation of the die, which will lead to the decline of the precision of the finished forgings.

　　

　　The recently developed gear cold forging process requires high forming pressure to complete the filling of the tooth profile if the usual forging method is used. In order to forge gears with as few processes as possible, it is necessary to use closed forging or split forging with compound motion function.

　　

　　Closed forging

　　

　　Fig. 15 shows the principle of closed forging and bevel gear forging. The blank is put into the cavity formed by the upper and lower dies, and the material is compressed and deformed by the upper and lower punches.

　　

　　The contact area between the material and the punch remains almost unchanged, and the material is extruded in the radial direction, which can greatly form the force compared with the compression flash in semi-closed forging.

　　

　　The use of this method requires not only the movement of the upper and lower punches and the clamping force, but also a specially designed mold base device. Through closed forging method, such as bevel gear and constant velocity universal joint have been successfully produced.

　　

　　Fig. 15 The principle of closed forging and bevel gear forging.

　　

　　Shunt forging

　　

　　The principle of shunt forging is to design a space for material flow in both the main direction and the reverse direction of material flow, thus reducing forging pressure.

　　

　　In the reverse extrusion as shown in fig. 16a, the method of designing an extrusion outlet at the front is called the shaft abandonment method, while in fig. 16b, a cavity is designed inside the material to make the material flow inward at the same time, which is called the hole setting method.

　　

　　(a) shaft method (b) hole setting method

　　

　　(a) convex shaft forming (b) split forging

　　

　　Fig. 16 helical gear formed by shunt forging

　　

　　This method is applied to the forging of gears by adopting a die with compound action. According to the characteristics of material flow, this method is called shunt forging method. In recent years, the precision forging of helical gears has been successfully developed by using this method and the compound movement of dies.

　　According to the latest data of China Automotive Power Battery Industry Innovation Alliance, from January to December, 2023, a total of 52 power battery enterprises in China’s new energy vehicle market achieved vehicle loading facilities, 5 fewer than the same period of last year, and the elimination rate was close to 10%.However, in other words, we should know more about it. sodium foil:20 The law of development has brought new vitality to the whole industry and revitalized the market. https://www.canrud.com/products/detail/6a65d3b2d5084d24b10540fe9edae280

　　

　　On the other hand, the top ten power battery enterprises have loaded 375.3GWh, accounting for 96.8% of the total vehicle. Compared with 95% in 2022, 93.5% in 2021 and 91.8% in 2020, power battery companies have staged the drama that the stronger the stronger.

　　

　　Power battery companies ranked lower are struggling.

　　

　　Gateway Power, a lithium battery factory owned by Galaxy, is obviously one of them. From January to October, 2023, the loading capacity of Gateway Power was only 0.88GWh, ranking 13th. Now, the company has stopped production for two months.

　　

　　Source/Weibo New Energy Prospective Screenshot

　　

　　Jiewei Power was established in 2009 with a registered capital of 1.218 billion yuan. It is a 15-year veteran lithium battery enterprise. Once, it was full of lofty sentiments. It became the top 3 in the power battery industry in five years, ranked among the top 3 in the world in 10 years, applied for IPO of A shares in 2022, and strived for listing in 2023. After all, it was “but before he could conquer, he was dead”.

　　

　　Obviously, in the power battery industry, there are still many battery manufacturers that are not as good as Jiewei Power. They are also facing many problems, even life and death tests. How do you spend this winter?

　　

　　01

　　

　　Small battery factories are getting worse every year.

　　

　　The person in charge of the lithium battery manufacturer who suffered in 2023 will definitely miss 2022, especially the “small factory” of lithium batteries.

　　

　　Wu Sujun, a grassroots employee who has worked in Jiewei Power for more than ten years, once told the media that the company still has some orders in 2022, but the quantity is not large. Mainly small modules, not finished products. In 2023, there was no order, and the factory could only do some battery repair work, and about 200 sets were repaired every month.

　　

　　Compared with more than 2,400 employees in the glorious period, gateway power had only about 400 employees left in its headquarters before the production stopped, and 200 people left after the production stopped. The 2022 annual report shows that in 2022, the number of social security participants of Jiewei Power was 882, which dropped by more than 70% in less than one year.

　　

　　The closed production lines record the cruelty of the lithium battery industry. According to the Shenzhen Communique of the 10th G20！-Lithium Battery Summit, since 2023, the average capacity utilization rate of domestic power batteries is less than 60%, and that of energy storage batteries is less than 55%.

　　

　　Figure/Jiewei Power Electric Center Workshop

　　

　　Source/Gateway Power Official Website New Energy Prospective Screenshot

　　

　　In fact, in addition to the power battery companies such as Jiewei Power, there are also four major materials (cathode materials, anode materials, separators and electrolytes) for lithium batteries.

　　

　　In terms of capacity utilization rate, many companies disclosed that the overall capacity utilization rate of the anode industry decreased significantly in 2023. Even the leading enterprise Shangtai Technology announced the suspension of production in the first quarter of 2023.

　　

　　On the evening of March 27, 2023, Shangtai Technology announced that Licheng Road Base had stopped production. It is reported that Licheng Road Base started construction in 2008. It is the earliest production base of Shangtai Technology, and also the starting place and birthplace of the company’s entrepreneurship, with an annual production capacity of over 10,000 tons.

　　

　　”The supply and demand of the entire anode material industry has reversed, facing a situation of overcapacity.” Shangtai Technology clearly stated in the announcement.

　　

　　The performance of Ferrous lithium phosphate cathode manufacturers in operating rate is also relatively sluggish. According to market data, in November 2023, the average operating rate of manufacturers was less than 50%, and it has accelerated to about 20% since December. The output of cathode materials in Ferrous lithium phosphate has reached a new low since June 2023.

　　

　　02

　　

　　Solve overcapacity

　　

　　”Surplus” became the label of lithium battery industry in 2023.

　　

　　Mr. Gang ‘an, the technology developer of Jiewei Power, said that the company kept investing in building factories, which eventually led to overcapacity.

　　

　　How many lithium batteries did Gateway Power produce? According to the information of official website, Jiewei Power has two production bases, Yancheng and Changxing, with an effective production capacity of 10GWh. Jiewei Power CEO Lu Chenli announced in 2022 that the company plans to reach the power battery production capacity of 100GWh in 2025.

　　

　　Source/Gateway Power Official Website New Energy Prospective Screenshot

　　

　　Zhu Huarong, Chairman of Changan Automobile, once predicted that by 2025, the demand for power batteries in China will be 1000GWh, while the production capacity of the industry has reached 4800GWh, and the degree of excess can be imagined.

　　

　　The four major materials of lithium battery also have different degrees of surplus. Some organizations predict that the global electrolyte capacity planning will exceed the demand by 3.4 million tons in 2025.

　　

　　It is also a means of self-help for the lithium battery factory and the four major material enterprises behind it to delay the production capacity and adopt the low inventory procurement policy.

　　

　　The semi-annual report of Contemporary Amperex Technology Co., Limited in 2023 shows that its inventory is only 48.91 billion yuan, which is 27.76 billion yuan less than that at the end of 2022. Zhongchuang Singapore Airlines, the third in the industry, cleared its inventory slightly, and its inventory decreased from 11.82 billion yuan at the end of 2022 to 10 billion yuan, a decrease of 18.2%.

　　

　　Enterprises in the upper and middle reaches of lithium batteries have been kidnapped by the “game theory” of production capacity, forcing low inventory.

　　

　　Jin Yiteng, an open source securities company, said that as the pace of production scheduling in downstream battery factories declined and the price of lithium battery materials in the middle reaches continued to fall due to overcapacity, battery factories also adopted a lower raw material inventory procurement strategy, forcing middle-stream lithium battery materials enterprises to reduce their start-up, maintain low inventory, and delay the launch of new capacity.

　　

　　Low inventory is obtained on the premise of price reduction. According to the data of Xinyi Lithium Battery, an industry research institution, on January 24th, 2024, the average price of square Ferrous lithium phosphate power battery and energy storage battery was 0.38 yuan /Wh and 0.43 yuan /Wh, respectively, which was more than 50% lower than the price of 0.9 yuan /Wh in early 2023, and the price has reached the lowest point in history.

　　

　　The seriousness of the price reduction can be seen. According to the statistics of Hi-Tech Lithium Battery, compared with 2022, the gross profit margin of diaphragm listed companies in the third quarter of 2023 decreased by about 40%, the electrolyte field decreased by about 25%, the cathode field decreased by about 20%, the ternary cathode decreased by about 9%, and the iron-lithium cathode decreased by about 5%.

　　

　　03

　　

　　Power Battery 2024: More Fierce Fight

　　

　　”After experiencing rapid growth in demand and production capacity, the lithium battery field is currently facing the challenge of overcapacity. It is expected that supply and demand will further deteriorate in 2024 and it is expected to ease in 2025. ” Huatai Securities pointed out.

　　

　　Bolt looseness is common, but if you don’t pay attention, it will often cause equipment vibration, component damage, and even casualties. How to tighten a small nut has always been a long-lasting topic in mechanical design. Today, let’s talk about the most basic method of fixing nuts in work.So, I believe left thread rock bolt In the future, it will be promising to create a miracle belonging to the industry. https://www.chinatianlong.com/

　　

　　In general, we analyze the bolt fracture from the following four aspects:

　　

　　First, the quality of bolts

　　

　　Second, the pre-tightening torque of bolts

　　

　　Third, the strength of bolts

　　

　　Fourthly, the fatigue strength of bolts.

　　

　　In fact, most cases of bolt fracture are caused by looseness, specifically, it is damaged due to looseness. Because the situation of bolt loosening and breaking is basically the same as that of fatigue fracture, finally, we can always find the reason from the fatigue strength. In fact, the fatigue strength is so great that we can’t imagine it, and the fatigue strength is not used at all in the use of bolts.

　　

　　01

　　

　　The bolt fracture is not due to the tensile strength of the bolt.

　　

　　Take a M20〜80 8.8-grade high-strength bolt as an example. Its weight is only 0.2kg, and its minimum tensile load is 20t, which is as high as 100,000 times its own weight. Under normal circumstances, we only use it to fasten 20kg parts, and only use one thousandth of its maximum capacity. Even under the action of other forces in the equipment, it is impossible to exceed 1,000 times the weight of the parts, so the tensile strength of threaded fasteners is sufficient and it is impossible to damage them because of insufficient strength of bolts.

　　

　　02

　　

　　The fracture of bolts is not due to the fatigue strength of bolts.

　　

　　Threaded fasteners can be loosened only 100 times in the transverse vibration loosening experiment, but they need to be vibrated repeatedly for one million times in the fatigue strength experiment. In other words, the threaded fastener is loose when using one ten thousandth of its fatigue strength, and we only use one ten thousandth of its great capacity, so the loosening of the threaded fastener is not due to the fatigue strength of the bolt.

　　

　　03

　　

　　The real reason for the damage of threaded fasteners is looseness.

　　

　　When the threaded fastener is loosened, it generates huge kinetic energy mv2, which directly acts on the fastener and equipment, causing the fastener to be damaged. After the fastener is damaged, the equipment cannot work in a normal state, further causing the equipment to be damaged.

　　

　　When the fastener is subjected to axial force, the thread is damaged and the bolt is pulled off.

　　

　　When the fastener is subjected to radial force, the bolt is cut and the bolt hole is oval.

　　

　　04

　　

　　Choosing thread locking mode with excellent locking effect is the fundamental solution to the problem.

　　

　　Take hydraulic hammer as an example. The weight of GT80 hydraulic hammer is 1.663 tons, and its side bolts are 7 sets of M42 bolts of grade 10.9. The tensile force of each bolt is 110 tons, and the pre-tightening force is half of the tensile force, and the pre-tightening force is as high as 300 to 400 tons. However, the bolt will break, and now it is ready to be changed to M48 bolt. The fundamental reason is that the bolt locking cannot be solved.

　　

　　When a bolt breaks, it is easy for people to conclude that the strength is not enough, so most of them adopt the method of increasing the strength grade of the bolt diameter. This method can increase the pre-tightening force of the bolt, and its friction force is also increased. Of course, the anti-loosening effect can also be improved, but this method is actually a non-professional method, and its investment is too large and its income is too small.

　　

　　In short, the bolt is: “If you don’t loosen it, it will break.”

　　

　　Cause analysis of bolt looseness

　　

　　The threaded connection is designed according to the self-locking condition: ψ ＋ρv, and the friction pair generated in the threaded pair makes the bolt self-lock to tighten the bolt, so the connection will not loosen automatically under static load. However, under impact, vibration, variable load and great temperature change, the friction force f of the screw pair will decrease or disappear instantly. If this phenomenon occurs repeatedly, the connecting bolt will gradually loosen. After the threaded fastener is loosened, the kinetic energy mv2 is generated, and the fastener subjected to axial force, the thread is destroyed and the bolt is pulled off. Fasteners subjected to radial force, bolts are cut and bolt holes are broken.

　　

　　Bolt locking principle: limit the relative motion between screw pairs or increase the difficulty of relative motion.

　　

　　Introduction of common anti-loosening methods

　　

　　There are three commonly used methods for locking bolts: friction locking, mechanical locking and permanent locking. Among them, mechanical locking and friction locking are called detachable locking, while permanent locking is called non-detachable locking.

　　

　　01

　　

　　Friction locking

　　

　　1. Spring gasket locking

　　

　　The anti-loosening principle of the spring washer is that after the spring washer is flattened, the spring washer will generate a continuous elastic force, so that the threaded connection pair between the nut and the bolt will maintain a friction force continuously and generate a resistance moment, thus preventing the nut from loosening. At the same time, the sharp corner at the opening of the spring washer is embedded into the surface of the bolt and the connected piece respectively, thus preventing the bolt from rotating relative to the connected piece.

　　

　　2. Lock the top nut (double nut)

　　

　　3. Self-locking nut locking

　　

　　One end of the nut is made into a non-circular convergent or radially convergent after being slit. When the nut is tightened, the closure expands, and the screwing threads are pressed by the elastic force of the closure.

　　

　　4. Locking of elastic ring nut

　　

　　Fiber or nylon is embedded in the thread to increase friction. The elastic ring also plays a role in preventing liquid leakage.

　　

　　02

　　

　　Mechanical locking

　　

　　Locking of groove nut and cotter pin

　　

　　2. Stop gasket

　　

　　After the nut is tightened, the single-ear or double-ear stop washer is bent and attached to the side of the nut and the connected part respectively to realize locking.

　　

　　3. Locking of series steel wire

　　

　　Use low-carbon steel wire to penetrate the holes in the head of each screw, and connect the screws in series to brake each other.

　　

　　03

　　

　　Permanent locking

　　

　　Commonly used permanent locking are: spot welding, riveting, bonding, etc. This method mostly destroys threaded fasteners during disassembly and cannot be reused.

　　

　　In addition, there are other ways to prevent loosening, such as: coating liquid adhesive between screwing threads, embedding nylon rings at the end of nuts, riveting and locking. Mechanical locking and friction locking are called detachable locking, while permanent locking is called non-detachable locking.

　　

　　1, punching method to prevent loose

　　

　　After the nut is tightened, the thread is damaged at the end of the thread.

　　

　　2. Adhesive Locking-Nut Locking Solution

　　

　　Apply the nut locking liquid to the bolt tightening position, and then screw on the nut. After self-curing, the locking effect is good.

　　Playing mahjong is an entertainment that many players like. Because it is interesting and can be used as a daily communication tool, more and more small partners are involved. For novice players, I don’t know where to start learning mahjong. What mahjong knowledge do I need to know to learn to play mahjong? Today, Xiaobian compiled an article about the basic knowledge of mahjong beginners, hoping that more people will help.Doing these simple things can also make Jilibet download Sowing high-quality genes will eventually grow into towering trees and become the leader in the industry. https://www.bl77777.com/

　　

　　Basic knowledge of mahjong

　　

　　1. What are the mahjong tiles?

　　

　　A mahjong set consists of 144 mahjong pieces, including 108 tubes, 10,000 stripes, 28 east, south, west, north, middle, hair and white, and 8 flower cards, namely, plum, orchid, bamboo and chrysanthemum in spring, summer, autumn and winter. These are all mahjong tiles. Of course, in many places, mahjong does not need to use flower tiles, and even some rules of playing do not even need to be white in the southeast, northwest and middle.

　　

　　2. The process of playing mahjong

　　

　　Step 1: Shuffle and code cards

　　

　　Step 2: Determine the dealer.

　　

　　Part III: Dice to determine the opening position and touch the cards in turn.

　　

　　Step 4: Touch cards and play cards, and make the cards in your hands into Hu cards as soon as possible.

　　

　　Step 5: Hu card ends the game of this bureau.

　　

　　3, mahjong basic card type

　　

　　Pair: A card type consisting of two identical mahjong tiles;

　　

　　Kanzi: a card type consisting of three identical mahjong tiles;

　　

　　Gangzi: a card type consisting of four identical mahjong cards;

　　

　　Straight: a card type consisting of three consecutive mahjong tiles;

　　

　　Partner card type:

　　

　　Embedding: two poor middle cards in a straight card type, for example, a partner like 350 thousand;

　　

　　Side-by-side: one of the two sides that make up a straight card, and there are only two situations of side three and side seven, for example, 120,000 and 89,000;

　　

　　Partner: form two consecutive straight cards and both ends can be combined, for example, 340 thousand;

　　

　　4, mahjong touch card playing order

　　

　　The order of playing mahjong, touching cards and playing cards is in counterclockwise order. Each round of the game starts with the dealer and then goes on in counterclockwise order.

　　

　　The above is the basic knowledge that beginners of mahjong need to master. In fact, these basic knowledge are introduced in detail in our mahjong rules. As long as you have really read the rules of playing mahjong, I believe you have got all these points, and the rest is to participate in actual combat practice. Of course, there are still many new knowledge and skills to learn in mahjong. Come on, I hope everyone can win more cards in mahjong.

　　In the chess game, listening to cards is a skill, and listening to cards is a craft. Listening to cards means that you are about to enter the stage of Hu cards, which means that the final victory will not be too far away. Generally, players on the field basically start to listen to cards at the later stage of the game. At this time, whoever listens well and can master the skills of listening to cards will win the game earlier. Today, the new recruitment game will come to say for everyone?Only by working together can we turn BL777 Casino The value of the play out, the development of the supply market needs. https://www.bl77777.com/

　　

　　1. Listen to multiple cards-in a card type, players usually choose to listen to several cards. For example, 2,345,000, and the cards drawn at this time are 20,000 and 50,000. If it’s 2,345,600, then the draw cards are 10,000, 40,000 and 70,000. However, players need to pay attention to the fact that if some of the cards in Hu are likely to destroy the overall card type, such as one-stop, flat Hu and so on.

　　

　　2. Listening is monotonous-it means that when players listen to cards, they just listen to a single card and want to make a pair.

　　

　　3. Listen to the hole-for a simple example, if the cards in the player’s hand are 20,000 or 40,000, then the card type that the player listens to at this time is 30,000 holes.

　　

　　4. Listen to the side card-listening to the side card is similar to listening to the hole. For example, at this time, the cards in the player’s hand are 70,000 and 80,000, so the card type that the player listens to at this time is 90,000.

　　

　　5. Listen right-if there are two pairs in the player’s hand, at this time, you only need to make another set of engravings, and the other set will be used as a card. In this case, the player needs to listen to two cards, and this card drawing type is called listening right.

　　

　　When listening to cards, players must pay attention to the card type of their family, and try not to listen to the same card type as their family, so as not to be called Hu by their family in advance. If your last family happens to be the dealer of the game in this bureau, it’s like avoiding listening to the same cards as your last family. If you can hide, you can hide!

　　Playing mahjong is an entertainment that many players like. Because it is interesting and can be used as a daily communication tool, more and more small partners are involved. For novice players, I don’t know where to start learning mahjong. What mahjong knowledge do I need to know to learn to play mahjong? Today, Xiaobian compiled an article about the basic knowledge of mahjong beginners, hoping that more people will help.It is strictly required by such a standard, BL777 Only with today’s development scale, can we have the proud momentum to crush our competitors. https://www.bl77777.com/

　　

　　Basic knowledge of mahjong

　　

　　1. What are the mahjong tiles?

　　

　　A mahjong set consists of 144 mahjong pieces, including 108 tubes, 10,000 stripes, 28 east, south, west, north, middle, hair and white, and 8 flower cards, namely, plum, orchid, bamboo and chrysanthemum in spring, summer, autumn and winter. These are all mahjong tiles. Of course, in many places, mahjong does not need to use flower tiles, and even some rules of playing do not even need to be white in the southeast, northwest and middle.

　　

　　2. The process of playing mahjong

　　

　　Step 1: Shuffle and code cards

　　

　　Step 2: Determine the dealer.

　　

　　Part III: Dice to determine the opening position and touch the cards in turn.

　　

　　Step 4: Touch cards and play cards, and make the cards in your hands into Hu cards as soon as possible.

　　

　　Step 5: Hu card ends the game of this bureau.

　　

　　3, mahjong basic card type

　　

　　Pair: A card type consisting of two identical mahjong tiles;

　　

　　Kanzi: a card type consisting of three identical mahjong tiles;

　　

　　Gangzi: a card type consisting of four identical mahjong cards;

　　

　　Straight: a card type consisting of three consecutive mahjong tiles;

　　

　　Partner card type:

　　

　　Embedding: two poor middle cards in a straight card type, for example, a partner like 350 thousand;

　　

　　Side-by-side: one of the two sides that make up a straight card, and there are only two situations of side three and side seven, for example, 120,000 and 89,000;

　　

　　Partner: form two consecutive straight cards and both ends can be combined, for example, 340 thousand;

　　

　　4, mahjong touch card playing order

　　

　　The order of playing mahjong, touching cards and playing cards is in counterclockwise order. Each round of the game starts with the dealer and then goes on in counterclockwise order.

　　

　　The above is the basic knowledge that beginners of mahjong need to master. In fact, these basic knowledge are introduced in detail in our mahjong rules. As long as you have really read the rules of playing mahjong, I believe you have got all these points, and the rest is to participate in actual combat practice. Of course, there are still many new knowledge and skills to learn in mahjong. Come on, I hope everyone can win more cards in mahjong.