Introduction to spring steel

Spring steel is the main material specially used to manufacture all kinds of spring and elastic components or structural parts with similar performance requirements. 1. Performance requirements: ① high elastic limit σ E and yield strength ratio σ s / σ B, to ensure excellent elastic properties, that is to absorb a lot of elastic energy without plastic deformation; ② For high fatigue limit, fatigue is one of the most important failure forms of spring. Besides the composition and structure of steel, the fatigue performance is mainly affected by the metallurgical quality of steel (such as non-metallic inclusions) and the surface quality of spring (such as decarburization); ③ sufficient plasticity and toughness to prevent impact fracture; ④ Other properties, such as good heat treatment and plastic processing performance, heat resistance or corrosion resistance requirements under special conditions.

The content and function of carbon and alloy elements in steel are as follows: (1) in general, medium and high carbon, carbon spring steel WC = 0.6% ~ 0.9%, alloy spring steel WC = 0.45% ~ 0.70%. Tempered troostite structure is obtained after quenching and tempering at medium temperature, which can meet the performance requirements of spring. (2) The alloy spring steel for general use is generally low alloy steel. The main additive elements are Si, Mn, Cr, etc. their main functions are to improve the hardenability, solid solution strengthening matrix and improving tempering stability; the auxiliary elements are mo, W, V and other strong carbide forming elements, which mainly prevent the decarburization defects caused by Si and overheat defects caused by Mn, and improve the tempering stability and heat resistance.

3. Common spring steels are listed in table 12-10 for the grades, performance characteristics and main uses of spring steels commonly used in China. Their composition, heat treatment process and mechanical properties can refer to relevant national standards (such as GB 1222-1984). Table 12-10 performance characteristics and application types of main spring steel grades and performance characteristics of main spring steels for main uses carbon spring steels with common Mn content of 65 have high hardness, strength and yield strength ratio, but poor hardenability, poor heat resistance, low ability to bear dynamic load and fatigue load, and low price. It is mainly used for small springs with working temperature less than 12mm The alloy spring steel Si Mn 55si2mn with small cross section less than 15mm has high strength, good elasticity and good tempering stability, but it is easy to decarburize and graphitize. The hardenability of steel containing B is improved obviously. The main spring steel is widely used. It can be used to manufacture all kinds of important spring with medium section less than 25 mm, such as automobile, tractor leaf spring, coil spring, etc. 60si2mn55si2mnb55simnvbcr series 50CrVA has excellent hardenability, high tempering stability, low decarburization and graphitization tendency; It has good comprehensive mechanical properties and certain corrosion resistance. The springs containing V, Mo, W and other elements have certain high-temperature resistance. Because they are all high-quality steel, their fatigue properties are further improved. They are used to manufacture heavy-duty and large-scale springs (50-60mm) with large load, such as engine valve spring, conventional weapon spring, crusher spring; Heat resistant spring, such as boiler safety valve spring, spray nozzle spring, cylinder expansion ring, etc.,

60crmna60crmnba60crmnmoa60si2cra60si2crva1) carbon spring steel (i.e. non alloy spring steel) has low price but poor hardenability, which is suitable for non important spring with small section size, among which 65 and 65Mn are most commonly used. 2) The alloy spring steel can be divided into two categories according to the main alloying elements: Si Mn spring steel and Cr spring steel. The former has higher hardenability than carbon steel, and its price is not very expensive, so it is widely used in all kinds of springs with cross-section size less than 25 mm, and 60Si2Mn is the typical representative; the latter has good hardenability, high comprehensive mechanical properties, and is not easy to decarbonize on the surface of spring, but its price is relatively high. It is generally used for important springs with large section size, and 50CrVA is its typical representative.

4. Heat treatment characteristics the heat treatment of spring steel depends on the processing and forming method of spring, which can be generally divided into hot forming spring and cold forming spring: 1) hot forming spring adopts hot forming (such as hot rolling and hot coil) for all kinds of large and complex springs with section size > 10 mm, such as leaf spring and coil spring of automobile, tractor and train. The simple processing route is as follows: cutting flat steel or round steel → heating bending or winding → quenching and tempering at medium temperature → surface shot peening treatment. The structure of the used state is tempered troostite. The surface fatigue property of the spring can be improved significantly. 2) Cold forming (such as cold rolling and cold rolling) can be used for various small springs with cross-section size less than 10 mm, such as coil spring, spring and spring sheet in instrument. This kind of spring should be cold drawn (cold rolled), Quenched and tempered at medium temperature or lead bath austempering before forming, and then cold drawn (rolled) strengthened. In this process, the metal will be further strengthened, but large internal stress and brittleness will be produced. Therefore, low temperature stress relief annealing (generally 200-400 ℃) should be carried out afterwards.

Basic knowledge of spring

1、 Functions, types, common symbols and units of spring:
Functions of spring: positioning, restoring, buffering or damping, impact, power, application of force, adjustment of pressure and measurement of force
Type of spring:
According to the material is divided into: metal spring (steel spring, non-ferrous metal spring), non-metallic spring
According to the spring shape, it can be divided into coil spring, leaf spring, volute spring, plate spring, ring spring and torsion bar spring
According to the service conditions of spring, it can be divided into:
Class I: the number of times subjected to alternating load is more than 106, which belongs to the category of infinite life calculation, and fatigue strength calculation should be carried out;
Class II: the number of times of alternating load is between 103 and 105, and the impact load is within the scope of finite life calculation;
Class III: under the action times of alternating load less than 103 times, it belongs to the category of static load strength calculation.
Common symbols and units of spring:
C — spiral spring winding ratio; disc spring diameter ratio; coefficient
D — spring pitch diameter
D1 — spring inner diameter (ID)
D2 — outer diameter of spring (OD)
D — diameter of spring material (wire diameter)
G — shear modulus of material (MPA)
F “- spring stiffness (n / mm)
H — working height of spring
H0 — free height of spring
T — spring torque
T — spring pitch

2、 Basic performance of spring
Spring is a kind of mechanical parts. It uses the elastic and structural characteristics of materials to produce deformation when working, and transforms mechanical work or kinetic energy into deformation energy (potential energy), or deformation energy (potential energy) into mechanical work or kinetic energy.
Spring applications:
Buffering or damping, such as support spring of crusher and suspension spring of vehicle, etc;
Mechanical energy storage, such as clocks, meters and automatic control mechanism on the original spring;
Control movement, such as valves, clutches, brakes and springs on various regulators;
A force measuring device, such as a spring scale and a spring on a dynamometer.
Characteristic line of spring: the relation curve between load and deformation is called spring characteristic line.
There are three kinds of characteristic lines of spring: 1) linear type 2) increasing type 3) decreasing type
Spring stiffness: the ratio of load increment to deformation increment, that is, the load required to produce unit deformation, is called spring stiffness.

The stiffness of compression and tension spring is k = (p2-p1) / (h1-h2)
The stiffness of torsion spring is k = (t2-t1) / (torsion angle 2-torsion angle 1)
The stiffness of the spring increases with the increase of load;
For the decreasing spring, the stiffness decreases with the increase of load;
The stiffness of linear spring does not change with the load, which is also called spring constant.
Deformation energy of spring
The deformation energy of the spring is inversely proportional to the shear modulus G and elastic modulus E of the spring material. Therefore, the low modulus is beneficial to the large deformation energy required. The size of the deformation energy is directly proportional to the square of the maximum working stress. Increasing the stress means that the material is required to have a high elastic limit, and a high elastic limit also corresponds to a high modulus (stress plays a decisive role).
In order to obtain large deformation energy, the volume or stress of spring material can be increased, or both can be increased.
Fatigue strength of spring

In mechanical equipment, there are two kinds of stresses in the working process of parts of machinery: static stress and variable stress.
The failure of parts or materials subjected to static stress is plastic deformation or brittle fracture, so their strength is measured by the elastic limit or yield strength and displacement limit of the material. The failure of parts or materials subjected to variable stress is fatigue fracture, so their strength is measured by fatigue strength.
The fatigue strength is lower than the static stress strength such as elastic limit or yield strength.
The types of variable stress are: stable cyclic variable stress, unstable cyclic variable stress, random variable stress.
The factors influencing fatigue strength are yield strength, surface state, size effect, metallurgical defects, corrosive medium and temperature
The factors affecting the spring fatigue test are internal factors, such as chemical composition, metallographic structure, etc;
External factors, such as surface state, shape and size, temperature and surrounding media.

Basic knowledge of spring

3、 Cylindrical helical compression spring
When the winding ratio is between 3 and 10, the spring end face is best ground flat; when the winding ratio is between 10 and 15, the end face can be ground or not; when the winding ratio is greater than 15, it can not be ground.
In order to avoid excessive additional force caused by eccentric load, the minimum number of working cycles is 2, but generally not less than 3.

Winding ratio C = spring pitch diameter / wire diameter
If the winding ratio C is too small, the bending deformation of the material is serious, and the required winding power is high. Sometimes the end of the cut mandrel is too thin and easy to break; if the winding ratio C is too large, the spring coil is easy to loosen and the diameter of the spring is difficult to control; in addition, due to the weight of the spring itself, the spring coil constantly vibrates. The ideal winding ratio is 4 ~ 9.
Spring stiffness F “= gd4 / 8d3n (n / mm)
In general, the number of effective coils of spring is more than 2.5, but for the spring with strict load requirement, the effective coil number is more than 4; the effective coil number is small and the load requirement is high, it is difficult to manufacture.
For the spring with small material diameter and strict load requirements, it is recommended to use support ring ≥ 2.
When there are two or more loads under the specified height, the free height shall not have tolerance requirements. The inner diameter and outer diameter of spring can not be marked with tolerance at the same time.

4、 Cylindrical spiral tension spring
Initial tension: when the tension spring is rolled and formed, the spring coils produce compression force with each other. When the external tensile load is applied to the spring, if the tensile force generated by the load does not reach this force, the spring will not deform, but will start to deform after reaching or exceeding the compressive force. The tensile load corresponding to this compressive force is the initial tensile force F0.
The bearing capacity of spring with initial tension is much higher than that without initial tension.
For the spring without initial tension, there will be more or less gap between the rings. When the number of coils of the spring is large, these gaps will affect the theoretical value of the free length of the spring, which needs to be negotiated with the customer.
The calculation formula of winding ratio and stiffness is the same as that of compression spring.
The total deformation of the tension spring is the sum of the deformation caused by the effective number of coils and the deformation caused by the hooks at both ends. It is equivalent to 0.1 turn for semicircular shackle and 0.25-0.5 turn for full circle shackle.
Springs with initial tension must be made of hardened steel wire.
It is difficult to ensure the quality of the spring with small diameter, large number of effective coils and large winding ratio.

5、 Cylindrical helical torsion spring
Spring type: ordinary torsion spring, parallel double torsion spring, in-line double torsion spring; two kinds of no gap and with space.
Generally, the number of effective working coils of spring shall not be less than 3;
The rotation direction of the torsion spring must be clear, and the rotation direction must be consistent with the direction of torque, so that the spring can be tightened when working.
The mandrel of the torsion spring must be 10% smaller than the inner diameter of the spring under the maximum working torque.
In order to avoid excessive stress concentration, the radius of each transition arc should not be less than 2 times of material diameter.
In order to prevent the torsion spring from instability, the maximum torsion angle should not be greater than the allowable value
The fourth power of the effective number of turns in the free state.
The tempering temperature of torsion spring with high precision should not be too high;
For the torsion spring to be electroplated, the radius of curvature of the bending arm should be as large as possible to prevent crisp.

6、 Spring manufacturing process
Coil spring – (correction) – stress relief tempering – rough grinding of end face – deburring inside and outside – (shot peening) – standing treatment (or strong pressure treatment) – fine grinding of end face – Inspection – antirust treatment – packaging
Shot Peening: increase fatigue life of spring
Standing or strong pressure treatment: the spring height is pressed to the working limit height or each coil is tightened several times or stayed for a period of time, so as to stabilize the size and improve the bearing capacity.

Definition of spring steel

1. Definition
Spring steel is a kind of steel which is specially used to make springs and elastic elements because of its elasticity in the state of quenching and tempering. The elasticity of steel depends on its elastic deformation ability, that is, within the specified range, the elastic deformation ability makes it bear certain load, and there is no permanent deformation after the load is removed.
Spring steel should have excellent comprehensive properties, such as mechanical properties (especially elastic limit, strength limit, yield ratio), elastic reduction performance (i.e. anti elastic degradation performance, also known as anti relaxation performance), fatigue performance, hardenability, physical and chemical properties (heat resistance, low temperature resistance, oxidation resistance, corrosion resistance, etc.). In order to meet the above performance requirements, spring steel has excellent metallurgical quality (high purity and uniformity), good surface quality (strict control of surface defects and decarburization), accurate shape and size.

According to GB / T 13304 “classification of steel”, according to the basic performance and service characteristic I, spring steel belongs to mechanical structure steel; according to the quality grade, it belongs to special quality steel, that is, the steel requiring special strict control of quality and performance in the production process. According to the custom of our country, spring steel belongs to special steel.

Heat treatment characteristics of typical spring

4. Heat treatment characteristics of typical spring
According to the size of the spring, the forming and heat treatment methods are different.
4.1 cold formed spring
The spring with smaller diameter or thinner thickness should be made of cold drawn spring steel wire or cold-rolled spring steel strip. Steel wire can be made of 60, 70, 65Mn, t7a, T8A and T9A. According to GB / t4357-1989, carbon spring steel wire is divided into three groups: B, C and D. The tensile strength of group B is 1080 ~ 2800mpa, which is used for general low stress spring and other purposes; group C is 1270 ~ 3140 MPa for medium stress spring; group D is 1520 ~ 3240 MPa for high stress spring. In the same group, the smaller the diameter, the higher the strength.

Cold formed spring steel wire can be divided into three types according to different manufacturing processes.
① Isothermal treatment of cold drawn steel wire in lead bath
The main feature of this production process is that the steel wire passes through a certain rapid isothermal cooling process in the cold drawing process, and then it is cold drawn to the required size.
Taking T8A steel as an example, the normalized steel wire is pickled and cold drawn for three times to make the total drawing amount reach 50%. Then the steel wire passes through the heating furnace at the speed of 3.5m/min, heated to the austenitizing temperature of 890-920 ℃, and then isothermal decomposed into sorbite structure in the lead bath of 500-550 ℃, and then the steel wire is repeatedly drawn to the required diameter.

This kind of steel wire is mainly made of 60, 70 and 65Mn, with the highest strength of over 3000 MPa and high plasticity. In order to eliminate the stress and fix the shape of the spring, only stress relief tempering is needed at 200-300 ℃.
The shock absorber spring of motorcycle is made of 55sicra steel wire which is quenched and tempered in lead bath. After forming, it is annealed at 250 ℃ for 2h. The service strength is about 1680mpa and the hardness is about 46-48hrc.
② Oil quenched tempered steel wire

This kind of steel wire refers to oil quenching and tempering after cold drawing to the specified size. The tensile strength of the steel wire is not as good as that of the cold drawn steel wire treated with lead bath isothermal treatment, but its performance is relatively uniform and the fluctuation range of its strength is small, so it is widely used in the manufacture of various power mechanical valve springs. After the steel wire is cold rolled into spring, only stress relief tempering is needed, and no quenching and tempering treatment is needed.

For example, the plunger spring and oil inlet needle valve spring on the vehicle are made of 65Mn steel. The diameter of oil quenched and tempered steel wire is 0.8 ~ 1.5mm, which will be hardened by cold work during cold lap, and has high strength. Therefore, stress relief tempering must be carried out at 200 ~ 250 ℃ for 1H. For 70 steel torsion spring and tension spring, the end of the coil processing, so the second tempering. The first tempering temperature is 200-250 ℃× 1H, and the second tempering temperature is 180-200 ℃× 1H.

The temperature of stress relief tempering should be appropriate. If the temperature is too low, the stress can not be fully eliminated; if the temperature is too high, the tensile strength and elastic limit will be reduced due to tempering softening. Table 1 shows the temperature range of stress relief tempering after several kinds of steel wire cold coil spring, the time is generally 30 ~ 60min, and the performance can not be improved if the time is too long.
Table 1 tempering temperature for stress relief of cold coil spring
Type of spring steel wire stress relief tempering temperature / ℃
Drawing carbon steel wire 230 ~ 260
Oil quenched tempered steel wire 230 ~ 290
Valve spring steel wire 230 ~ 400
CR-V alloy spring steel wire 315 ~ 370
CR Si alloy spring steel wire 425 ~ 455
③ Alloy spring steel wire supplied in annealed condition
The spring made of this kind of steel wire needs quenching and tempering treatment to achieve the required mechanical properties. This kind of steel wire includes 50CrVA steel wire, 60Si2Mn steel wire and 55simnb steel wire.

4.2 hot formed spring
Coil spring or leaf spring whose diameter of steel wire or thickness of spring leaf is more than 10-15mm are usually formed during heating and quenching. The manufacturing process of spring is roughly as follows (taking leaf spring as an example): flat steel cutting → heating to quenching temperature after bending with special fixture clamping direct quenching + medium temperature tempering → shot peening → assembly. At this time, the quenching temperature is 50-80 ℃ higher than usual. After forming, it can be quenched immediately by waste heat. It can also be heated in a salt bath furnace. When the oil is cooled to 100-150 ℃, it can be taken out for intermediate temperature tempering. The tempering temperature is selected according to the performance requirements of the spring, which is generally in the range of 450-500 ℃, and the hardness after tempering is about 38-52hrc. The hardness of leaf spring after tempering is 39-47hrc, that of spiral spring is 44-50hrc, and that of spring subjected to greater shear stress is 47-52hrc.

The maximum operating temperature of sliding nozzle spring of continuous casting machine in a steel company is 500 ℃. The diameter of cylindrical spiral spring is 12.6 mm, the inner diameter is 116 mm, the high temperature hardness is 45-55 HRC, the material is 30W4Cr2VA, the cylinder hollow mandrel (material: Q235) is used to heat and fix the spring, and the b84t true air quenching furnace is used, and the convection preheating at 850 ℃ for 120min is used to improve the uniformity of low-temperature heating, shorten the heating time, reduce the temperature difference of workpiece, so as to reduce the quenching deformation; Then it is heated in vacuum at 1050-1070 ℃× 70min. The heating rate is 10 ℃ / min, and the gas quenching pressure is 5 × 105Pa. The spring is cooled to about 80 ℃ and discharged from the furnace. If the furnace loading is large, the quenching pressure can be increased appropriately. Tempering must be carried out in time in this vacuum furnace with 600 ℃± 10 ℃× 90min. If the vacuum furnace is not used for tempering, the protective atmosphere furnace can be used. Pay attention to the oxidation or decarburization phenomenon, and detect the hardness of 48-51hrc.

The surface quality of spring has a great influence on its service life, because tiny surface defects (such as decarburization, cracks, inclusions, burr and scar) can cause stress concentration and reduce the fatigue strength of spring. In order to improve the fatigue strength of spring, shot peening can be carried out on the spring after quenching and tempering to eliminate the surface defects and stress caused by surface hardening. The test shows that the

Development of spring processing technology

At present, the processing equipment and production line of mechanical spring are developing to the depth and breadth of numerical control (NC) and computer control (CNC). However, with the change of spring material and geometry, the processing technology has also developed.

1) The suspension spring with variable outer diameter, variable pitch and variable steel wire diameter (three variable) can be machined without molding. Since the development of three variable spring, tapered steel bar has been used for winding on CNC lathe, but the yield and price are not ideal. Now it is changed to control the roller speed and drawing force by spring coiling machine under heating state to obtain the required cone shape and quench it with processing waste heat.
2) The hollow stable spring rod is rolled and welded with low carbon boron steel plate.
3) The torsion bar is made of 45 steel with high purity and high frequency quenching to obtain high hardness and large residual compressive stress on the surface, so as to improve the fatigue life and anti relaxation ability.
4) The leaf spring widely used in electronic products is basically formed by stamping and automatic bending. At present, the joint technology of composite materials is mainly developed.

(1) Cold forming technology of spring1) One time automation capability of cold forming process. The cold forming machine has developed to 12 claws. The steel wire in the range of (0.3-14) mm is basically formed in one step by 8-claw forming machine. At present, the development direction of forming technology and equipment is as follows: ① increasing the forming speed, the main development trend is to improve the forming speed of the equipment, that is to say, the production efficiency; ② to improve the equipment durability by improving the precision of the equipment parts and strengthening the heat treatment effect; ③ adding the length sensor and the laser range finder to control the manufacturing process of CNC forming machine automatically.

2) Cold forming process range capability. At present, the maximum size of spring coiler with large wire diameter can reach 20 mm, = 2000 MPa, and the winding ratio is 5. The cold forming process of minic block spring and eccentric spring with variable diameter or equal diameter is still limited.
(2) Hot forming technology of spring

1) Speed capability of hot forming process. At present, only CNC2 shaft hot coiling machine is used for forming (9 ~ 25) mm in China, with the maximum speed of 17 pieces per minute. Compared with developed countries, there is a big gap.
2) Large spring hot forming process control ability. Because there is only CNC2 axis hot coiling spring machine, the shape control has less effect in three directions, and the precision is poor; moreover, there is no automatic bar rotation control and adjustment mechanism, so the forming process level and ability of hot coil spring are low. Therefore, the accuracy level and surface oxidation decarburization level of the spring are also low.

Surface protection technology of spring

The surface protection technology of spring mainly includes: surface antirust in working procedure, blackening (bluing) of finished product, phosphating, antirust oil on paint, electrophoretic paint, electroplating, electrostatic powder spraying, etc. in particular, the last four surface treatment processes have been widely used and developed.
The corrosion resistance of some stainless steel wires and important carbon spring steel wires is equivalent to that of zinc plating. If another layer of znai (5%) alloy is plated, the corrosion resistance can be increased by 3 times.

For stainless steel wire or important carbon spring steel wire with resistance performance requirements, copper can be plated when the diameter of steel wire is less than 0.4mm, copper can be used for steel wire larger than 0.4mm, copper can be used inside and stainless steel is used outside. The conductivity of steel wire can be improved by Ni plating 5 N thick.

Generally speaking, the process of surface hardening to form residual stress (such as shot peening and surface nitriding) can improve the fatigue life strength. At present, non electrolytic Ni plating is being studied. By heating (300 ~ 500) ℃, 7% P can be precipitated as PNI, and the Vickers hardness can be increased by 500hv. After shot peening, if Ni is heated below 300 ℃, the hardness can be increased by 10%.

The new coating technology of dqcromet has many advantages, such as no hydrogen embrittlement, high corrosion resistance, high temperature resistance, high carbon permeability, strong adhesion and good environmental protection performance. At present, it has been used, but the quality should be paid attention to.
With the development of the information age, the spring industry has established some related websites, among which 888 spring net has played a certain role in the dissemination of information and communication technology.
Standardization of spring in China

Under the leadership and organization of national spring Standardization Technical Committee, China has completed 52 standards for springs and spring products (table 1-6), and initially formed a system. In addition, there are: rubber metal spiral composite spring, fatigue test program of spring, etc.
Table 1-6 standard name and standard number of spring and spring products in China
Serial number standard code standard name remarks
1 GB / t1239.1-2008 specification for cold rolled cylindrical spiral tension spring
2 GB / t1239.2-2008 specification for cold rolled cylindrical helical compression spring
3 GB / t1239.3-2008 specification for cold rolled cylindrical helical torsion spring
4 GB / t1239.4-2008 specification for hot coil cylindrical coil spring
Technical calculation of cylindrical helical spring
Specification for small cylindrical helical spring
Dimensions and parameters of small cylindrical spiral tension spring
Dimensions and parameters of small cylindrical helical compression spring
9 GB / T 2087-2001 dimensions and parameters of cylindrical spiral tension spring (semicircular hook ring type) are revised and submitted for approval
Cylindrical spiral tensile spring (circular hook and ring compression center type)
Revision of dimensions and parameters, submitted for approval
The dimensions and parameters of cylindrical helical compression spring (both ends tightly ground or forged flat type) have been revised and submitted for approval
12 GB / t4142-2001 dimensions and parameters of cylindrical spiral tensile spring (round hook and ring type) have been revised and submitted for approval
13 JB / t10591-2007 specification for valve springs of internal combustion engines
Specification for mercury injection, governor and injector spring for diesel engines
15 GB / t4036-1983 watch winding
16 GB / t4037-1983 watch hairspring
17 GB / t1972-2005 butterfly spring
Spring shock absorber
19 GB / t13828-1992 multi strand cylindrical coil spring
20 GB / t9296-1988 floor spring
Spring terms (GB / t1805-2001)
22 GB / t1358-1993 cylindrical coil spring dimension series revision, submitted for approval
23 JB / t6655-1993 specification for high temperature resistant spring
24 JB / t10416-2004 technical specification of coil spring for automobile suspension
25 JB / t10417-2004 technical specification for shock absorber spring of motorcycle
Technical calculation of 26 JB / t10418-2004 gas spring
27 JB / t6653-1993 cylindrical helical compression spring with flat steel wire
28 JB / t6654-1993 technical specification for flat scroll spring
29 JB / t7366-1994 technical calculation of planar scroll spring
30 JB / t8584-1997 rubber metal spiral composite spring
Metallographic examination of 31 JB / t9129-2000 60Si2Mn steel coil spring
32 JB / t10802-2008 technical specification for shot peening of spring
33 JB / t3338.1-1993 specification for cylindrical helical compression spring of hydraulic components
34 JB / t3338.2-1993 technical calculation of cylindrical spiral compression spring for hydraulic parts
35 JB / t8046.1-1996 compressed gas spring
36 JB / t8046.2-1996 lockable gas spring
37 JB / t7367.1-2000 ultrasonic testing method for cylindrical spiral compression spring
38 JB / t7757.1-1995 cylindrical spiral spring for mechanical seal
39 JB / t7283-1994 technical conditions for leaf spring of agricultural machinery
40 JB / t5002-1994 agricultural machinery leaf spring product quality classification
41 JB / t3383-1983 bench test method of automobile leaf spring
42 JB / t3782-1984 metallographic inspection standard for automobile leaf spring
43 JB / t539-1984 specification for leaf spring pin and lifting lug of automobile
44 ZB t06001-1988 specification for shot peening of automotive leaf springs
45 QC / n29035-1991 automobile leaf spring technical specification
46 QC / t29103-1992 automobile leaf spring quality grading regulations
47 JB / t53394-2000 butterfly spring product quality classification
Product quality classification of 48 JB / t3396-2000 hydraulic cylinder helical compression spring
49 JB / t58700-2000 general rules for quality grading of spring products
Quality grading of 50 JB / t58701-2000 small cylindrical spiral spring
Product quality classification of 51 JB / t58702-2000 cylindrical coil spring
52 JB / t7944-2000 sampling inspection of cylindrical coil spring

Material and characteristics of butterfly spring

Silicon manganese, chrome alum and chromium manganese alloy steel are widely used in the manufacture of disc spring. Special materials used in high temperature, low temperature and corrosive environment, such as diamagnetic, corrosion-resistant and heat-resistant materials.

Compared with other spring shapes, the disc spring has:
1. It has high stiffness, strong shock absorption capacity, and can bear large load with small deformation, which is suitable for the occasions with small axial space requirements.2. It has variable stiffness, and the spring has a wide range of nonlinear characteristics.
3. With the same disc spring and different combination methods, the spring characteristics can be changed in a wide range. It can be combined by means of lamination and lamination, and can also be combined with different thickness and different number of pieces. The more the number of springs, the greater the load. Compared with cylindrical coil spring, disc spring has the following characteristics:

1、 The load deformation characteristic curve is nonlinear.
2、 The disc spring is in sheet shape and easy to form a combination. It can be assembled and replaced by building blocks, so it is convenient for maintenance.
3、 The disc spring with radial groove has zero stiffness characteristic. This characteristic can be used in some deformation range where the spring force is basically stable.
4、 The vibration absorption performance of the disc spring is not lower than that of the cylindrical spiral spring. When the laminated combination is adopted, the disc spring has greater damping and dissipates the impact energy due to the friction between the disc springs. In the mechanical industry, the cylindrical spiral spring is replaced in a large range, which reflects the characteristics of miniaturization and multi-function of the new product (host). Such as: mold, support hanger, clutch, brake, bridge buffer (damping) device, bearing preloading, safety overload device, heavy machinery, mechanical starter, control device, valve, industrial furnace, indexing device, clamping device, etc.

Introduction of disc spring

Butterfly spring is a special spring of metal mechanical accessories. Because it looks like a dish, it is called butterfly spring.
Disc spring is widely used in mechanical equipment industry, petroleum industry, automobile industry, aerospace industry and other fields because of its strong impact resistance, small deformation, large bearing capacity and small space size in the loading direction. The cylindrical coil spring is widely replaced.

The disc spring was first invented by J. Belleville in France more than 100 years ago. In the early 1930s, engineers (G.M.) Almen and laszio developed theory, developed production and quality standards DIN 2092 and din 2093. As the first industrial standard of disc spring, these standards have been accepted all over the world and spread all over Europe. At present, they have been widely adopted by many multinational companies. Japan has developed its own standards, but the United States has not yet developed its own industrial standards for Belleville springs. Many American manufacturers use DIN standard as the quality standard of Belleville spring. In 1980, China formulated the corresponding standard according to DIN, and revised it in 1992. The standard number is GB / t1972-1992, which specifies the size series, technical requirements, test methods, inspection rules and design calculation of disc spring.

In our country, the disc spring is made of high quality spring steel 60Si2MnA, 50CrVA or special materials, such as stainless steel, chromium nickel iron alloy, etc. The special materials such as stainless steel and chromium nickel iron alloy are suitable for high temperature and corrosive environment. Shanghai Nuclear Industry disc spring manufacturing Co., Ltd. mainly added Al, Ti, Nb elements to Cr Ni Fe alloy, which further improved the strength, elasticity and plasticity of the disc spring.

Winding method of spring

The factory winding method of spring is divided into cold coil method and hot coil method.
(1) Cold winding method: the spring wire diameter D ≤ 8mm shall be wound by cold winding method. The high-quality carbon spring steel wire which is cold drawn and pre heat treated is usually used for the spring wound in cold state. Generally, quenching treatment is not required after winding, and only low-temperature tempering is required to eliminate the internal stress during winding.

(2) Hot coiling method: the spring with larger wire diameter (d > 8mm) is wound by hot coiling method. The spring rolled in hot state must be quenched and tempered at medium temperature.
The manufacturing process of different types of spring is different, and the basic operation is machine winding. After forming most elastic parts, heat treatment is required to form elasticity and keep it. Therefore, heat treatment is required in the production process of spring

It is difficult to “rework” a spring, whether it is a coil tension spring or a coil compression spring
Stress relief after quenching
1、 Operation: the workpiece is slowly heated to 500-600 ℃ and slowly cooled to below 300-200 ℃ with proper heat preservation (also known as softening annealing)
2、 Features: due to annealing temperature