# The relationship between spring extension and tension

Talking about the relationship between spring elongation and pulling force

Studying the elongation of the spring: the elongation of the spring is related to the weight of the object hanging by the spring dynamometer, and the length of the spring is related to the hanging object. A spring dynamometer is used to hang a heavy object and a spring does not hang a heavy object. The length is different, and it is in a free state without hanging heavy objects.

The spring will stretch after hanging an object. The relationship between the length of a spring (cm) and the weight (kg) of the hanging object is known as the following table:

(1) The above table reflects the relationship between which variables, which is the independent variable and which is the dependent variable?

(2) When the weight of the object is 2kg, how does the length of the spring change?

(3) When the weight of an object gradually increases, how does the length of the spring change?

(4) If the weight of the object is xkg and the length of the spring is ycm, write the relationship between y and x according to the above table;

(5) When the weight of the object is 2.5kg, according to the relationship, there is no legend of heroes in the middle to find the length of the spring.

(1) Because the data in the table mainly relates to the length of the spring and the weight of the hanging object, it reflects the relationship between the mass of the hanging object and the length of the spring. The quality of the hanging object is the independent variable; the length of the spring Is the dependent variable;

(2) It can be seen from the table that when the mass of the object is 2kg, the length of the tension spring is 13cm;

(3) According to the data in the table, the length of the spring increases with the weight of the hanging object;

(4) According to the data in the table, when x=0, y=12, and every additional kilogram of weight increases the length by 0.5cm, so y=0.5x+12;

(5) Let x=2.5, substitute in the analytic formula of the function, and it can be solved. Spring manufacturer

Solution: (1) It reflects the relationship between the mass of Foshan ceramics and the length of the spring. The mass of the object is the independent variable; the length of the spring is the dependent variable;

(2) When the mass of the object is 2kg, the length of the spring is 13cm;

(3) When the mass of the object gradually increases, the length of the spring increases;

(4) According to the above table, the relationship between y and x is: y=12+0.5x;

(5) When x=2.5, y=12+0.5×2.5=13.75cm

# Spring wire

The strength of the spring steel wire varies according to the variety, standard and specification, and the tensile strength grade can be in the range of 1000-3000 MPa.

The diameter of the round spring steel wire is in the range of 0.08-20 mm.

The cross-sectional shape of 　　 spring steel wire is generally round, but also rectangular, square, oval and other shapes.The finished steel wire is generally delivered in rolls, or delivered in straight strips.

production method

Different types of spring steel wires have different production methods, and the common characteristics are that they require certain strength, high toughness and good coil spring performance.

The crafting methods of various spring steel wires are as follows:

Raw spring steel wire process: (steel) wire rod-surface treatment-wire drawing (mattress wire can be used in this way)

Lead-quenched spring steel wire: Lead bath quenching is performed on the wire rod size or the intermediate specification of cold drawn, and then surface treatment and wire drawing.

Galvanized spring steel wire: usually hot-dipped or electroplated in the finished size, but also cold drawn to the specified size after pickling and hot-dipping the wire rod.

Surface treatment: Generally, pickling and phosphating are used to remove the iron oxide scale to form a phosphating film; a few are treated by mechanical methods. The purpose is to meet the requirements of the cold drawing process and obtain a smooth surface. For spring steel wires that require high fatigue life , Such as the valve spring wire, the wire rod should be peeled to reduce surface defects. If the steel mill can grind the billet, it will also help reduce defects.

Oil-quenched spring steel wire: Carbon steel or alloy steel can be used according to the needs, surface treatment and cold drawn to the finished size, and then quenched and tempered. This process is used more on steel wires for automobile suspension springs and valve springs, ordinary springs Of course it can also be used.

Wire drawing: The drawing process of the finished product has a great influence on the product performance. Generally, a larger total area reduction rate of about 90% (see area reduction rate) and a smaller pass reduction rate (about 10%- 20%) to ensure the toughness of the product. For high-strength spring steel wire, the outlet temperature of each pass of the steel wire should be controlled to be lower than 150 ℃ during drawing to prevent the steel wire from torsion cracks due to strain aging, which causes the wire to be scrapped.

The main defect. For this reason, good lubrication and sufficient cooling must be provided during drawing. The use of a smaller pass reduction and drawing speed can help reduce the temperature rise of the steel wire. Heat treatment: lead bath is commonly used for carbon steel spring steel wire The quenching process can obtain a very fine pearlite structure (sortenite), which is beneficial for improving deep drawing performance and spring performance. The alternative process of lead bath fluidized bed has not been promoted, and there are currently some small diameters.

Application. Alloy steel wire generally adopts annealing heat treatment to make the microstructure suitable for drawing deformation. The heat treatment of stainless steel wire adopts solution treatment, and the purpose is to improve the structure to meet the needs of drawing. The oil quenching process is used on the finished steel wire, and induction Heating or gas or oil heating furnace, the steel wire is heated to the austenitizing temperature for a period of time, and then tempered at a medium temperature after quenching. Although it is called oil quenching in name, it basically uses water quenching or water with polymer materials. Quenching.

Classification

Hardware springs can be divided into static springs and dynamic springs according to their operating conditions. Static springs refer to springs that have a limited number of vibrations during the service period, such as safety valve springs, spring washers, weighing pan springs, constant load springs, mechanical springs, watch hair springs, etc.

Refers to springs that have a vibration frequency of 1×106 or more during the service period, such as engine valve springs, vehicle suspension springs, anti-vibration springs, coupling springs, elevator buffer springs, etc. The selection of static springs mainly considers tensile strength and stability, dynamic When selecting spring materials, fatigue, relaxation and resonance performance are mainly considered.

Springs can be divided into three states according to the load conditions: light load, general load and heavy load. Light load refers to springs that bear static stress, low stress, and small deformation, such as springs for safety devices and springs for vibration absorption. Design The service life is 103~104 times.

General load refers to a common spring with a design life of 105~106 times and a vibration frequency of 300 times/min. Within the allowable stress range, the life is guaranteed 1×106 times. The lower the load stress, the longer the life.

Heavy load refers to springs that work for a long time and frequently vibrate. For example, valve springs, air hammers, presses, and hydraulic controller springs have high loads, often used at about 10% below the allowable stress, and their service life is greater than 1×106 Times, usually 107 times.

# What are the functions of hardware springs

Squeeze function

Observing various electrical switches, you will find that one of the two contacts of the switch must be equipped with a spring to ensure that the two contacts are in close contact and are in good conduction. If the contact is poor, the resistance at the contact becomes larger and the current passes When the heat generated increases, and in severe cases, the metal at the contact will melt. The two metal posts of the bayonet base are equipped with springs for good contact; as for the central metal piece of the screw base and the plug-in metal of all sockets The blades are all reeds, and their function is to make the two sides in close contact to maintain the same good.

When the tape, there is a phosphor bronze reed, using the elastic force generated when it is bent and deformed to make the head and the tape close contact. There is a long coil spring in the stapler. On the one hand, it is used to tighten the staples. On the other hand, when the front staple is pushed out, the back staples can be sent to the front to prepare the staples to be pushed out comfortably. In this way, the nails can be pushed to the front automatically one by one until the nails are all pushed out. Many machines automatically feed materials. In addition, the clips on clothes, ballpoint pens, and pen holders all use the spring compression function Clipped to clothes.

Reset function

The hardware spring is deformed under the action of external force. After the external force is removed, the spring can be restored. Many tools and equipment use the nature of spring to reset. For example, many building door hinges are equipped with return springs. After entering and exiting, the door will automatically reset. People also use this function to make automatic umbrellas, mechanical pencils and other supplies, which is very convenient.

In addition, various buttons and buttons are also indispensable to reset springs. Mechanical clocks, clockwork toys are all on top The mainspring is driven. When the mainspring is tightened, the mainspring bends and deforms and stores a certain amount of elastic potential energy. After release, the elastic potential energy is transformed into kinetic energy, which is driven by the transmission device to rotate.

drive function

Mechanical clocks and clockwork toys are driven by winding up the mainspring. When the mainspring is wound up, the mainspring bends and deforms and stores a certain amount of elastic potential energy. After release, the elastic potential energy is converted into kinetic energy, which is driven to rotate by a transmission device.

Buffer function

A spring is installed between the frame of the locomotive and the wheel, and the elasticity of the spring is used to slow down the bumps of the vehicle.

Vibration and sound function

When air flows from the reed hole in the harmonica or accordion, it impacts the reed and the reed vibrates to make a sound.

measurement function

We know that within the elastic limit, the extension (or contraction) of the hardware spring is proportional to the external force. The spring scale is made by using the nature of the spring.

# What are the factors that affect the fatigue strength of springs

Factors affecting spring fatigue strength:

A. Yield strength There is a certain relationship between the yield strength of the material and the fatigue limit. Generally speaking, the higher the yield strength of the material, the higher the fatigue strength. Therefore, in order to improve the fatigue strength of the spring, we should try to increase the yield of the spring material. Strength, or use a material with a high ratio of yield strength to tensile strength. For the same material, the fine grain structure has a higher yield strength than the coarse grain structure.

B. The larger the size of the size effect material, the higher the possibility of defects caused by various cold and hot working processes, and the greater the possibility of surface defects. These reasons will lead to a decrease in fatigue performance. Therefore, when calculating the spring The influence of size effect should be considered when fatigue strength.

C. When the corrosive medium spring works in corrosive medium, it becomes a source of fatigue due to pitting corrosion on the surface or corrosion of the surface grain boundary, and it will gradually expand under the action of variable stress and cause fracture. For example, spring steel working in fresh water, The fatigue limit is only 10% to 25% in the air. The effect of corrosion on the fatigue strength of the spring is not only related to the number of times the spring is subjected to variable loads, but also to the working life. Therefore, when designing and calculating a spring affected by corrosion, you should The working life is taken into consideration.

For springs that work under corrosive conditions, in order to ensure their fatigue strength, materials with high corrosion resistance, such as stainless steel, non-ferrous metals, or surface protection layers, such as plating, oxidation, spraying, painting, etc. can be used. Cadmium plating can greatly increase the fatigue limit of the spring.

D. Metallurgical defects Metallurgical defects refer to non-metallic inclusions, bubbles, element segregation in the material, etc. Inclusions existing on the surface are the source of stress concentration, which will cause premature fatigue between the inclusion and the substrate interface Cracks. The use of vacuum smelting, vacuum casting and other measures can greatly improve the quality of steel.

E. The maximum stress of the surface state mostly occurs on the surface of the spring material. Therefore, the surface quality of the spring has a great influence on the fatigue strength. The defects such as cracks, defects and scars caused by the spring material in the rolling, drawing and coiling process It is often the cause of the fatigue fracture of the spring.

The smaller the surface roughness of the material, the smaller the stress concentration, and the higher the fatigue strength. It is the influence of the surface roughness of the material on the fatigue limit. As can be seen from the figure, as the surface roughness increases, the fatigue limit decreases. In the same In the case of roughness, different steel grades and different coiling methods have different fatigue limit reduction degrees. For example, the reduction degree of cold coil springs is smaller than that of hot coil springs. Because steel hot coil springs and their heat treatment are heated, due to Oxidation makes the surface of the spring material rough and produces decarburization, which reduces the fatigue strength of the spring. Figure 2 shows the effect of the depth of the decarburization layer on the fatigue strength. The surface of the material is ground, pressed, shot blasted and rolled. Both can improve the fatigue strength of the spring.

F. The fatigue strength of temperature carbon steel decreases from room temperature to 120°C, rises from 120°C to 350°C, and drops again after the temperature is higher than 350°C. There is no fatigue limit at high temperatures. Springs that work under high temperature conditions, Consider the use of heat-resistant steel. Under conditions below room temperature, the fatigue limit of steel increases.

# Commonly used spring metal material structure technical standards

The spring is to make full use of the physical characteristics of the material to realize its storage and release of energy through a certain conversion method. The characteristics of the material determine the physical and mechanical characteristics of the spring to a certain extent, and affect the design, development and particularity of the spring Increased requirements. The most commonly used materials are metal materials and non-metal materials.

The development of modern new material varieties is changing with each passing day, especially the continuous emergence and improvement of new high-strength metal alloys, which makes mechanical springs more efficient; at the same time, the subsequent processing methods of raw materials are continuously optimized, such as structural shape, heat treatment and surface quality. Etc., so that the application and development of springs can better meet its functional requirements, and further improve the safety, economy and environmental protection characteristics of spring products.

In recent years, with the rapid development of the chemical rubber industry, polyurethane materials are also widely used in spring products, widely used in the field of shock absorption and noise reduction mechanical structures; air springs with nitrogen or gas-liquid media are also widely used in stamping dies, Main engine dynamic shock absorption, constant force appliances, ultra-high temperature elastic structure and other fields

The application of spring materials initially used wood and bamboo materials, and after entering the industrial age, metal alloys began to be widely used. With the continuous improvement of mechanical spring characteristics, the characteristics of spring materials requiring high strength and high yield ratio have gradually formed special Special, special metal alloy spring steel. The general development trend of metal alloy spring steel is higher tensile strength and yield ratio, and more toughness. At the same time, special stainless steel spring steel can meet the application in severe corrosive environment; special resistance The high temperature constant elastic material can meet the application in higher temperature environment.

Spring steel is the main material specially used to manufacture various springs and elastic elements or structural parts with similar performance requirements.

A. Performance requirements ①High elastic limit σe and yield ratio σs/σb to ensure excellent elastic performance, that is, absorb a large amount of elastic energy without plastic deformation; ②High fatigue limit, fatigue is the main damage of the spring In one form, the fatigue performance is not only related to the composition structure of the steel, but also mainly affected by the metallurgical quality of the steel (such as non-metallic inclusions) and the surface quality of the spring (such as decarburization); ③Sufficient plasticity and toughness Prevent impact fracture; ④ other properties, such as good heat treatment and plastic processing properties, heat resistance or corrosion resistance requirements for working under special conditions, etc.

B. Composition characteristics The content and function of carbon and alloying elements in steel are:

(1) Medium and high carbon In general, carbon spring steel wc=0.6%~0.9%, alloy spring steel wc=0.45%~0.70%, after quenching and tempering at medium temperature, the tempered troostite structure is obtained, which can be compared Well ensure the performance requirements of the spring.

(2) Alloy spring steels for general use of alloying elements are generally low alloy steels. The main elements are Si, Mn, Cr, etc., and their main functions are to improve hardenability, solid solution strengthen the matrix and improve tempering stability; auxiliary addition The elements are strong carbide forming elements such as Mo, W, and V. The main functions are to prevent decarburization defects caused by Si, overheating defects caused by Mn, and improve tempering stability and heat resistance.

# Continuous quality and improvement technology of stainless steel spring wire

Fourth, the improvement plan

In line with the principle of 1S09001:2000 full participation, all relevant personnel are specially held to participate in the production site analysis meeting. The content of the meeting should be notified 3 days in advance, and more innovative measures are encouraged to promptly stop the negative evaluation of different views. Starting with the five factors of human, machine, material, law and environment, we have worked out improvement measures that are both in line with the actual production and practical.

1. The uniformity of the strength of the cleaning rod

YB(T)11-83 only stipulates the tensile strength range of steel wire, and does not specify the strength difference of a plate (batch) of steel wire. ASTM, BS, JIS, ISO and other standards all have different tensile strength of steel wire rods. In a nutshell, the dispersion of the tensile strength of a steel wire rod is ≤100MPa, and the dispersion of the strength of a batch of steel wire rod is ≤150MPa. The strength performance of the steel wire rod produced by Sanhe Company can also meet the above requirements. However, the strength difference of some foreign manufacturers’ cleaning rods is controlled within 50Mpa, and the current domestic spring steel wires cannot fully meet the requirements. It can be seen that domestic spring steel wires should not only meet relevant foreign standards, but also continue to improve their physical quality to reach the advanced level of foreign manufacturers’ physical quality. .While ensuring that the steel wire raw materials are imported high-quality wire rods, the following measures should be taken: (1) Improve the heat treatment temperature control and the precision of the winding equipment; (2) The wire drawing adopts a straight wire drawing machine; (3) The wire drawing machine coil The barrel and mold box should be cooled by circulating water; (4) The upper and lower ends of each finished steel wire are tested for tensile strength.

2. Flatness of steel wire

YB(T)11-83 stipulates: the wire reel should be regular, and when the wire reel is opened, it should not be scattered, twisted or shaped like “∞”. The steel wire with a diameter ≤ 4inm should be tested for flatness, that is, the length is about one and a half circle The sample is placed flat on the platform, and the maximum value of the tilt from the platform to the end of the steel wire is tested. The diameter is ≤0.50mm, the maximum value of the tilt is ≤40mm, the diameter>0.50mm, and the maximum value of the tilt is ≤30mm. The standard is as specified in ISO6931-1:1994: The steel wire should be wound in a regular manner after drawing, and the steel wire with a diameter of ≤5mm should meet the following requirements:

The distance between the shafts at both ends L=0.2D/d1/4 (1) In formula (1): D is the average free diameter of a single turn (turn) of the steel wire; d is the diameter of the steel wire.

Take a single turn (turn) of steel wire and hang it with a round rod. The axial distance L at both ends does not exceed the value calculated by formula (1), and 1 times the diameter of the reel D roll ≤ single turn (turn) of the steel wire average free diameter D ≤ Volume 1.5D is considered qualified.

Compared with well-known foreign manufacturers, the flatness of the steel wire is also behind them. A well-known foreign manufacturer of Φ1.0mm steel wire adopts the detection method shown in Figure 1, and the axial distance L value at both ends is almost zero. If the flatness of the steel wire is not good , It means that the residual stress on the surface of the wire drawing process is too large or uneven. During the coiling process, due to the residual force on the surface of the wire, the spring forming strain will be unstable, and the free height of the spring will rise and fall, and the size of the coil diameter will not change. 1. Defects such as loop cracks and axial twists. In order to further improve the flatness performance of the steel wire and narrow the gap, the following measures have been taken: (1) Improve the transmission accuracy of the wire drawing machine; (2) Modify the mold box to make It is more stable during drawing; (3) Find out a set of methods to adjust the mold box and straighteners by observing the upturn or downturn of the wire head on the wire drawing machine drum to make the wire regular and neat.

5. Evaluation effect

It is very important to evaluate the effect of the implementation of the above measures. If you exaggerate the improvement effect, you will mistakenly think that the problem has been solved, which will cause the problem to happen again; on the contrary, it will also lead to turning a blind eye to the improvement effect and damaging the enthusiasm for continuous improvement. Evaluate the effect using a bar chart. Compare the number and distribution of unqualified items detected by internal control before and after the implementation of the measures.

After the implementation of the measures, the quality of the cleaning rod strength and flatness of the steel wire has been improved significantly, but the effect of the surface quality of the steel wire is not ideal. In order to consolidate the results, the improvement measures have been standardized, and have been formulated or revised one after another. Use stainless steel wire production related work instructions, inspection procedures and other documents to provide the basis for the next continuous improvement.

# Continuous quality and improvement technology of stainless steel spring wire

1. Raising the problem

After more than two years of continuous improvement, in accordance with the principle of “customer-focused” in IS09001:2002, through visiting users, going to the user site to handle quality objections and collecting feedback information. Price and other non-technical issues are excluded, and user feedback is classified. After sorting out, the proportions of various opinions are as follows.

The back surface of the coil spring is scratched and punctured 14%

The dimensional accuracy of the spring after the coiled spring is not enough 29%

The tempered steel wire after the spring turns yellow and gray 21%

Uneven strength of steel wire cleaning rod 18%

The number of spring fatigue after coiling the spring is not enough 7%

Other 11%

It can be seen from the above that the reasons for customer complaints are mainly concentrated in the spring forming process, that is, the spring surface quality (such as color, scratches, etc.), dimensional accuracy and load fluctuations, etc., according to the severity of the problem, “improve the spring coil spring forming “Process stability” is a priority problem, and other issues such as spring fatigue performance are also given full attention and some inspection items are consciously added to collect more data and prepare for the next step of continuous improvement. Stainless steel spring.

2. Cause analysis

Since the products complained by customers are shipped after strict inspection, their mechanical properties, flatness and surface meet the domestic requirements of YB(T)11-83. Obviously YB(T)11-83 can no longer fully guide production. This decision started by studying advanced foreign standards and physical quality to find out the gaps. Compare YB(T)11-83 with related foreign standards such as ASTM A313/A313M-1993, BS2056-1991, JISG4314-1994, IS06931-1:1994 It shows that the foreign standards are more detailed and specific, and the maneuverability is strong. The performance of the collected foreign stainless steel wire samples for springs is higher than the corresponding foreign standards. For example, the springs of Japan Seiki and Sweden Sandvik use stainless steel.

The wire strength dispersion is controlled within 50MPa. The single-turn steel wire is freely placed on the ground, neither expanding nor shrinking, and the two ends are flat on the ground without any warping. The surface of the steel wire has two kinds of oil surface and powder surface. Through horizontal comparison, the three indicators of strength uniformity, flatness and surface quality of the products of Zhengzhou Sanhe Company lag behind foreign advanced products. The author once brought samples produced by several different processes to spring manufacturers for on-site coil spring tests. The results It is found that the coil spring performance of the steel wire with the above three good quality characteristics indicators is significantly improved. It can be seen that as long as the three quality characteristics of the steel wire rod’s strength uniformity, flatness and surface quality are improved, the stability of the spring forming process can be improved.

3. The surface condition of the steel wire

The surface condition of the steel wire can be divided into two categories: (1) The surface quality of conventional inspections such as dimensional tolerance, roundness and the existence of cracks, scratches and other defects. Domestic and foreign standards are basically consistent with this category, but YB(T)11 The tolerance specified in -83 is too large; (2) The quality of the lubricating layer on the surface of the steel wire, that is, the steel wire is drawn in powder or oil, and a coated and smooth surface can be obtained respectively. The two surfaces can also be coated with extremely thin nickel Or copper bottom layer.

The inner layer of the steel wire is nickel or copper plating, and the outer layer is powder or oil. The thickness of each layer is about 0.1~0.2μm. The nickel or copper bottom layer is helpful to improve a certain fatigue strength and lubricating ability. Coated surface (powder surface) ) The lubricating layer is composed of calcium salt and sodium salt. The lubricating layer is sensitive to moisture. Therefore, it must be protected from moisture during storage and transportation. The lubricating layer can be retained on the formed spring or can be cleaned off. Smooth surface (oil surface) The lubrication layer is a very thin oil film. In contrast, the surface of the oil-surface steel wire forming spring is bright after tempering, but the spring with a complicated winding must be additionally provided with lubricant, and the winding spring has the risk of scratching and fatigue failure. The safety is lower than that of flour noodles. This category stipulates that domestic and foreign standards do not have this requirement.

However, well-known foreign manufacturers can provide the above two surface conditions for delivery. In terms of surface quality of Gangsi, the following measures can be taken: (1 ) Change the tolerance requirements, and produce according to the tolerance requirements of JISG4314-1994; (2) Develop the production of oil surface steel wire, provide users with two surface states for delivery, for their choice; (3) Do a good job of technical service and introduce to users The comparison of the advantages and disadvantages of the springs formed by the powdered surface and the oil surfaced steel wire makes it understand that the spring formed by the powder surfaced steel wire is a little yellow and gray after tempering, and other properties are better than the oil surface steel wire, and the surface is yellow and gray. It can also be washed off.

# Static spring and dynamic spring

Springs can be divided into static springs and dynamic springs according to their operating conditions. Static springs refer to springs that have a limited number of vibrations during the service period, such as safety valve springs, spring washers, weighing pan springs, constant load springs, mechanical springs, watch hair springs, etc. Springs with more than 1×106 vibrations during the service period, such as engine valve springs, vehicle suspension springs, anti-vibration springs, coupling springs, elevator buffer springs, etc. The selection of static springs mainly considers tensile strength and stability, and dynamic springs When selecting materials, fatigue, relaxation and resonance performance are mainly considered.

Springs can be divided into three states according to the load conditions: light load, general load and heavy load. Light load refers to springs that bear static stress, low stress, and small deformation, such as springs for safety devices and springs for vibration absorption. Design The service life is 103~104 times.

General load refers to a common spring with a design life of 105~106 times and a vibration frequency of 300 times/min. Within the allowable stress range, the life is guaranteed 1×106 times. The lower the load stress, the longer the life.

Heavy load refers to springs that work for a long time and frequently vibrate. For example, valve springs, air hammers, presses, and hydraulic controller springs have high loads, often used at about 10% below the allowable stress, and their service life is greater than 1×106 Times, usually 107 times.

The principle of spring material selection is: firstly meet the functional requirements, secondly the strength requirements, and finally consider the economy.

Carbon spring steel is the most widely used steel in spring steel. The steel contains 0.60%~0.90% carbon and 0.3%~1.20% manganese, no other alloying elements are added, and the use cost is relatively low. After proper processing or heat treatment, plain spring steel wire can obtain high tensile strength, sufficient toughness and good fatigue life. However, the hardenability of carbon steel wire is low, the relaxation resistance and corrosion resistance are poor, and the elastic modulus The temperature coefficient is large (up to 300×10-6/℃), which is suitable for manufacturing springs with small cross-section and low working temperature (120℃>).

Alloy spring steel generally contains 0.45% to 0.70% carbon and a certain amount of Si, Mn, Cr, V, W, and B and other alloying elements. The addition of alloying elements improves the relaxation resistance of spring steel, increases the toughness of steel, and shows In order to improve the hardenability and service temperature of steel, it is suitable for the manufacture of springs with larger sections and higher temperatures.

# What are the requirements for springs in the hardware mold industry

What are the requirements for springs in the hardware mold industry?

1. Cold extrusion die

Cold extrusion is divided into forward extrusion, reverse extrusion and compound extrusion. The cold extrusion punch bears a large dynamic load. In order to prevent early fatigue failure of the die, excessive stress concentration should be avoided, and attention should be paid to the punch Stability, the length-to-diameter ratio (L:D) of the punch should not be too large, when extruding steel parts, L:D≤3:1, extruding copper and its alloy L:D≤5:1, extruding aluminum and The alloy L:D≤10:1. When the stress of the die exceeds σ0.2/2 of the material, the die needs to add a prestressed ring, and the taper (0.5°~1°) can be used between the die and the prestressed ring. ) Fit or hot press fit (red sleeve). Hardware spring

The cold extrusion die of low and medium carbon steel requires high hardness (59~66HRC), high compressive yield strength and appropriate toughness. Commonly used die materials include Cr12MoV, Cr12Mo1V1, W6Mo5Cr4V2 steel and base steel, etc., internal prestress The ring is usually made of 4Cr5MoVSi, 4Cr5MoV1Si steel (46~48HRC), and the outer prestressed ring is usually made of 4Cr5MoVSi, 5CrNiMo and other steels.

Cold heading is a cold forging process, which relies on the upsetting die to process part of the blank metal into a specific cross-sectional shape under one or more impacts. The blank is mainly wire or bar. Cold heading is widely used in the production of fastening Parts, such as screws and rivets. Materials suitable for cold heading include low-carbon steel wire or bar (75~78HRB), copper and copper alloys, aluminum and aluminum alloys, stainless steel and medium-carbon steel wires with a carbon content of less than 0.44% ( Spheroidizing annealing). The cold heading mold is divided into a punch (or hammer) and a concave mold. The concave mold is divided into an integral concave mold and an open concave mold. The overall concave mold can be made of one material or two Two kinds of materials, the center cavity part is made of different materials to make the concave mold insert. The open concave mold is composed of two modules with grooves on the surface, and the two modules are combined to form a cavity. Slots on different surfaces of the module, and then Multiple new slots can be formed by turning the module.

The surface of the cold heading mold requires high hardness (≥60HRC), and the cold heading mold of hard materials should be hardened as a whole to prevent collapse; under the premise of ensuring no collapse, in order to make the mold have sufficient toughness and prevent cracking, cold heading The hardness of the core of the mold is preferably 40~50HRC.

Commonly used cold heading die steels are T10A, 9SiCr, 9Cr2, Cr12MoV, etc., and the concave mold inserts can be made of Cr12MoV, W6Mo5Cr4V2, WC (containing 13%~25% Co), W18Cr4V steel, and punches with complex shapes and large impact can be used. Impact resistant steel 5CrW2Si, 60Si2Mn and base steel.

3. Aluminum alloy cold extrusion die can be made of T7A, T10A, Cr12, Cr12MoV, GCr15, 9SiCr and CrWMn steel.

Molds with excellent material, correct structural design, good cold and hot processing, and reasonable heat treatment may still fail early during service due to improper adjustment and use of the machine tool. Machine adjustment and operating factors include the accuracy, rigidity, clearance adjustment, and positioning of the machine tool Inaccurate and accidental overload, etc. Taking these factors seriously will help to find the real cause of mold failure. Large fluctuations in mold life in production are often related to machine tool adjustment and use operation factors, and sufficient attention must be paid.

# Hardware shrapnel is widely used in industrial production

Hardware shrapnel is a kind of mechanical parts that use elasticity to work. Generally, it is made of metal shrapnel steel. It is used to control the movement of mechanical parts, alleviate impact or vibration, store energy, and measure the size of force. It is widely used in machines and instruments. The types of hardware shrapnel are complex and diverse. According to the shape, they mainly include spiral hardware shrapnel, scroll hardware shrapnel, plate hardware shrapnel, etc.

Spiral hardware shrapnel is a twisted hardware shrapnel, which accepts torsion and deformation, and the working part is also tightly wound into a spiral shape. The end structure of the twisted hardware shrapnel is processed into various shapes of torsion arms instead of hooks. Torsion hardware shrapnels are commonly used It is widely used in the balance mechanism in machinery, and is widely used in industrial production such as automobiles, machine tools, and electrical appliances.

Hardware shrapnel introduction:

The metal shrapnel belongs to the category of metal stamping parts and electronic hardware materials. English name: Metal shrapnel. It is made of stainless steel or manganese after heat treatment. It is an important part of the switch. With the help of the conductivity of the metal shrapnel, It acts as a high-quality switch between the operator and the product. At the same time, it uses the stable resilience of the guozi (automatically return after pressing) and the long life to provide the operator with high-quality tactile feedback .

hardware shrapnel production process:

The production of metal shrapnel is a special process of processing materials (metal or non-metal) into parts (or semi-finished products) through cold stamping of stamping dies. Stamping is at room temperature, using a mold installed on a press to apply pressure to the material A pressure processing method to produce separation or plastic deformation to obtain the required parts.