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

Comparison between stainless steel spring and common spring

Compared with spring, stainless steel spring is actually the same. Both of them are widely used in mechanical and electronic industries. The spring can produce large elastic deformation when loaded, and convert mechanical work or kinetic energy into deformation energy. After unloading, the deformation of spring disappears and returns to its original state, and the deformation energy is converted into mechanical work or kinetic energy. It can be used in the range of anti-corrosion, temperature resistance and non-magnetic.

The material of stainless steel spring must meet the standard of Yb (T) 11-83 Ministry of metallurgy. The commonly used materials are domestic stainless steel 304302301, 316316L, 321.202.201.430.420, Korean elephant brand, Kos Koryo, etc. T316 is recommended for high corrosion resistance and non-magnetic applications, but its mechanical properties are lower than those of t302 / T304. As one of the most widely used steel, t302 / T304 is the most commonly used stainless steel spring material because of its superior mechanical properties, corrosion resistance, heat resistance and low temperature strength. However, t631j1 / t631 is used for heat-resistant spring and spring with high tensile strength after heat treatment, but its corrosion resistance is worse than that of t302 / T304.

There are many kinds of material surface state, such as bare wire, resin plated spring and nickel plated spring wire. Stainless steel spring is divided into bright surface, semi bright surface and fog surface. Customers can choose according to the requirements of product precision and beauty.

Stainless steel spring has uniform and beautiful surface state, good formability, uniform elasticity, high plasticity, good fatigue strength, heat resistance and corrosion resistance. According to the shape, stainless steel spring can be divided into plate spring, spiral spring, ring spring, truncated cone scroll spring, disc spring and torsion bar spring. According to the mechanical properties, stainless steel spring can be divided into tension spring, torsion spring, bending spring and compression spring. The common cylindrical spring is widely used because of its simple manufacture and simple structure.

Generally speaking, the spring should have high elastic limit, fatigue limit, impact toughness and good heat and corrosion resistance, etc. the commonly used materials are referred to above. Generally, the diameter of spring wire is less than 20 mm by cold rolling method. Some springs need to be pressed or polished after being made, which can improve the bearing capacity of spring.

Whether it is non-magnetic or weak magnetic stainless steel spring, can be widely used in household appliances, electronics, civil, industrial and other products. It is an indispensable and widely used component in economic society and industrial society, which promotes the steady development of social economy.

Heat treatment of lock spring

(1) Material and technical requirements of lock spring
The material of lock spring is 65Mn steel, and the hardness is hrc40 ~ 48, and the unevenness is less than 0.3mm. Finally, the process of plate forming, quenching and tempering is as follows. The lock spring is shown in Fig. 6-10. The heat treatment process of lock spring is shown in Fig. 6-11.

(2) Key points of heat treatment process for lock spring
In order to reduce the deformation and improve the strength of the lock spring, bainite austempering should be adopted
1) The lock spring is heated to 840 ℃± 10 ℃ in salt bath furnace after being installed with spreader and kept for 10 ~ 15min, then it is moved into the nitrate furnace at 340 ~ 380 ℃ for 15 ~ 30min, and then it is cooled by air.
2) The lock spring was Austempered in a salt bath at 380 ℃ for another time. The tempering holding time is 30min.
3) After tempering, the lock spring is cleaned in hot water at 60 ~ 80 ℃ and then dried in oven at 100 ~ 150 ℃.

Spring subjected to torsional deformation

Compression spring is a kind of spiral spring that bears the pressure. Its material section is mostly circular, and it is also made of rectangular and multi strand steel. The precision spring is generally of equal pitch. The shape of compression spring is cylindrical, conical, convex and concave, and a small amount of non-circular. There is a certain gap between the coils of the compression spring. When the spring is subjected to external load, the spring retracts Shrinkage deformation, storage deformation energy.

A spiral spring made of spring wire. There are many types of spiral spring, which can be divided into ordinary cylindrical spiral spring and variable diameter spiral spring according to the shape, and can be divided into left-hand spring and right-hand spring according to the helix direction. The cylindrical spiral spring has the advantages of simple structure, convenient manufacture and wide application. Its characteristic line is straight line and can be used as compression spring, tension spring and torsion spring. When the load is large and the radial size is limited, two compression springs with different diameters can be used together to form a combined spring.

 

There are taper coil spring, volute coil spring and concave spiral spring. The conical spiral spring has good cushioning performance and can bear large load. Volute spiral spring can store more energy and bear larger load, but the manufacturing process is more complex. The performance of concave spiral spring is similar to that of conical spiral spring, which is mostly used for cushion and mattress. The load surface of spring steel wire includes circle and rectangle, and circular section is the most commonly used.

Spiral spring, namely torsion spring, is a spring that bears torsion deformation, and its working part is also tightly wound into a spiral shape. The end structure of torsion spring is processed into various shapes of torsion arm, not hook ring. Torsion spring is often used in balancing mechanism of machinery, and is widely used in automobile, machine tool, electrical appliance and other industrial production.

A spring subjected to twisting and folding

Compression spring is a kind of spiral spring which withstands the pressure. Its material cross section is mostly circular, and it is also made of rectangular and multi strand steel. The circumferential spring is usually of equal pitch. The format of compression spring is cylindrical, conical, convex and concave, and a small amount of noncircular, etc. There is a certain gap between the coils of the compression spring. When it is subjected to external load, the spring will shrink and deform, and the deformation energy will be stored.

A spiral spring made of spring wire. There are many types of spiral spring, which can be divided into ordinary cylindrical spiral spring and variable diameter spiral spring according to its appearance; it can be divided into left-hand metal spring and right-hand rotation spring according to the helix direction. Cylindrical coil spring layout is simple, Easy to manufacture, all information network new 2. It can be used as compression spring, tension spring and torsion spring. When the load is large and the radial dimension is unlimited, two compression springs with different diameters can be used together to form a combined spring. There are taper coil spring, volute coil spring and concave spiral spring.

 

The conical spiral spring has good cushioning performance and can withstand large load. Volute spiral spring can store more energy and bear larger load. But the manufacturing process is relatively large. The performance of concave spiral spring is similar to that of conical spiral spring, which is mostly used for cushion and mattress.  The load surface of spring steel wire includes circle and rectangle, and circular section is the most commonly used.

The coil spring, that is, the torsion spring, is a kind of spring subjected to twisting and folding, and its task limitation is also tightly wound into a spiral shape. The end layout of torsion spring is made into torsion arm in various formats, not hook ring. Torsion spring is commonly used in mechanical equalizing mechanism. It is widely used in automobile, machine tools, electrical appliances and other industrial production.

Instrument for testing springs

As we all know, spring testing machine is a kind of professional spring testing instrument, which can test various data of spring, so as to evaluate the performance of spring. We must be very clear about this, but for the importance of the spring testing machine, we must have some confusion and confusion, the following will explain the performance of the spring testing machine.

The computer system of the spring testing machine is controlled by the controller and the servo motor is controlled by the speed control system. After the deceleration system is decelerated, the moving beam is driven to rise and fall through the precision lead screw pair. It can complete the tensile, compression, bending, shear and other mechanical property tests of the sample. It has the advantages of no pollution, low noise, high efficiency, wide speed range and beam moving distance It has a very broad application prospect.

 

The full digital servo speed control system and servo motor with high precision and stable performance are used as the driving system. The star controller is the core of the control system. The screen display of test force, peak value of test force, beam displacement, test deformation and test curve can be realized. All test operations can be completed automatically by mouse on computer. Good humanized design makes the test operation more convenient.

Combined with the above technologies, the machine can realize the closed-loop control of the test force, deformation and displacement, and realize the control modes of constant stress, constant strain and constant displacement, and the various control modes can be switched smoothly. So we can see how important spring testing is.
In the future development of science and technology and social progress, the testing machine and various functions of the testing machine will play a role in it incisively and vividly!

Standard for carbon spring steel wire

There are two types of current national and industrial recommended standards for carbon spring steel wire
1. Cold drawn spring steel wire
One is cold deformation strengthening steel wire, also known as cold drawn spring steel wire.
The cold drawn carbon spring steel wire is first quenched with lead to obtain sorbite structure, and then the surface is phosphated. The steel wire is drawn to the finished product size with a large reduction rate. The steel wire structure is fibrous, with high tensile strength and elastic limit, and good bending and torsion properties. Cold drawn spring steel wire has high dimensional accuracy, smooth surface, no oxidation and decarburization defects, stable fatigue life, and is the most widely used spring steel wire.

2. Oil quenched tempered steel wire
Another type of carbon spring steel wire is martensitic strengthening steel wire, also known as oil quenching and tempering steel wire.
Carbon steel wire can obtain good comprehensive mechanical properties by quenching and tempering. When the steel wire specification is small (φ ≤ 2.0 mm), the strength indexes of oil quenched and tempered steel wire are lower than those of cold drawn steel wire after sorbite treatment. When the size of steel wire is large (φ ≥ 6.0 mm), sorbitic steel wire can not obtain the required strength index by using large reduction ratio. However, oil quenched and tempered steel wire can obtain higher performance than cold drawn steel wire as long as it is fully quenched.

Under the same tensile strength, martensite reinforced steel wire has higher elastic limit than cold deformation strengthened steel wire. The microstructure of cold drawn steel wire is fibrous with obvious anisotropy. The microstructure of oil quenched and tempered steel wire is homogeneous tempered martensite, which is almost isotropic.
At the same time, the relaxation resistance of oil quenched and tempered steel wire is better than that of cold drawn steel wire, and the service temperature (150-190 ℃) is also higher than that of cold drawn steel wire (≤ 120 ℃). In recent years, medium and large size oil quenched and tempered steel wire will replace cold drawn steel wire.

Standard for alloy spring steel wire

There are three types of alloy spring steel wire in China: alloy spring steel wire, oil quenched and tempered silicon manganese spring steel wire, and oil quenched and tempered chromium silicon alloy spring steel wire for valve. According to the current use situation of alloy spring in developed countries, the proportion of oil quenched and tempered steel wire is increasing. According to Japanese industrial standard (JIS), all alloy spring steel wires are supplied in oil quenching and tempering state.

(1) GB / t5218-1999 alloy spring steel wire
The standard combines the original gb5218-85 “silicon manganese spring steel wire”, gb5219-85 “chromium vanadium spring steel wire” and gb5221-85 “chromium silicon spring steel wire” into one standard. The standard is applicable to the production of alloy spring steel wire for high and medium stress spring. The steel wire wound spring can only be used after quenching and tempering after forming.

The standard lists three grades of 60Si2MnA, 50CrVA and 55CrSiA, and stipulates that other grades of steel wire can be supplied according to the requirements of the demander.
The steel wire is generally delivered in cold drawn condition. The tensile strength σ B ≤ 1035mpa and Hb ≤ 302 are inspected for the finished steel wire with diameter ≤ 5.0mm, which is equivalent to the light drawing state. In the production of medium and large specifications (Ф > 8.0), the cold drawing reduction rate of finished products shall not exceed 25%, and the surface reduction rate of small steel wire (Ф ≤ 5.0) shall not exceed 30%.

 

The steel wire delivered in annealed state is too soft, so it is easy to produce dead bending. When winding the spring, the spring shape is not good and the pitch is uneven. When the reduction ratio of cold drawing is too large, the steel wire is too hard, and the rebound is large when the spring is wrapped, so the forming of the thick spring is difficult. Therefore, it is most suitable to supply the steel wire directly wrapped with spring in light drawing state. For the customers who need cold working (such as flattening, rolling into special cross-section, etc.) when the steel wire is purchased, the annealed steel wire shall be recommended for delivery.

In order to ensure the performance of the winding spring, the finished steel wire shall be wound for 6 turns on the mandrel with the diameter less than or equal to 5.0 mm, and shall not be broken or broken.
Decarburization and surface defects seriously reduce the fatigue life of spring, which must be strictly controlled. In particular, 60Si2MnA and 55CrSi have high silicon content and are easy to decarburize during annealing. Low temperature and long time annealing process is recommended for spheroidizing annealing and recrystallization annealing of semi-finished products. As mentioned above, for springs with high fatigue life requirements, polished steel wire must be selected, but it is necessary to distinguish between annealing polishing and cold drawing polishing. When 50CrV soft steel wire is polished, the grinding debris is easy to adhere to the steel wire surface and form irregular small white spots. Therefore, cold drawing polishing process should be adopted as far as possible to reduce the “white spots” on the surface.

Under the condition of surface quality assurance, the inclusion content becomes the most important factor affecting the fatigue life. Therefore, the standard stipulates that non-metallic inclusions and graphite carbon inspection can be added when the demander has requirements.

(2) Yb / t5104-93 oil quenched tempered silicon manganese alloy spring steel wire
After using oil quenched and tempered alloy spring steel wire, there is no need to carry out quenching and tempering treatment. As long as stress relief treatment is carried out like cold drawn carbon spring steel wire, it can be used. These two standards are more and more used for alloy spring with diameter less than 14.0 mm.
Yb / t5104-93 is supplied in three categories, class A is suitable for static spring with medium load, class B is suitable for dynamic spring with medium load and medium fatigue life, and class C is suitable for dynamic spring with high stress state, such as automobile suspension spring.

(3) Yb / t5105-93 oil quenched tempered chrome silicon alloy spring steel wire for valves.
Yb / t5105-93 is suitable for the valve spring of engine under severe dynamic load.

Why does the spring have a deformation range

Any material has a property.When the force gradually increases from zero, the deformation is proportional to the force for a period of time.At this time, the force is slowly returned to zero, and the shape of the object will recover.

But when the force reaches a certain level, plastic deformation will occur, and the shape of the object will permanently change, and the relationship between force and deformation is no longer proportional.

In our daily life, springs and other items use the proportional part of the object. We don’t want them to undergo permanent deformation, so there is a term of deformation range. The deformation range is related to the material of the object, the geometric shape of the object, the temperature and so on.

Steps of spring production technology

At present, the processing equipment and production lines of mechanical springs are developing towards the depth and breadth of numerical control (NC) and computer control (CNC). However, with changes in spring materials and geometric new shapes, processing techniques have also developed.

1) Suspension springs with variable spring outer diameter, variable pitch and variable wire diameter (three-variable) realize moldless plastic processing. Since the development of three-variable springs, tapered steel bars have been used for winding processing on CNC lathes, but the yield and price are not ideal. Now it is changed to use the spring coiling machine in the heating state to control the roll speed and drawing force to obtain the required cone shape, and use the processing waste heat for quenching.

2) The hollow stabilized spring rod is rolled and welded with low carbon boron steel plate.

3) The torsion bar is made of high-purity 45 steel. After high-frequency quenching, the surface has high hardness and large residual compressive stress, thereby improving fatigue life and anti-relaxation ability.

4) The leaf springs widely used in electronic products are basically formed by stamping and automatic bending. At present, it is mainly to develop the joining technology of composite materials.

(1) Cold forming process of spring

1) One-time automation capability of cold forming process. The cold forming machine has now developed to 12 jaws. The steel wire in the range of (0.3-14)mm can basically be formed at one time by the 8-jaw forming machine. The current development direction of forming process equipment: ①Improve the forming speed, the main development trend is to increase the forming speed of the equipment, that is, the production efficiency; ②Improve the durability of the equipment by improving the precision of equipment parts and strengthening the heat treatment effect; ③Increase the length sensor and Laser rangefinder, automatic closed-loop control manufacturing process for CNC forming machine.

2) Cold forming process range capability. At present, the maximum specification of large wire diameter spring coiling machine can reach 20mm, =2000MPa, and the winding ratio is 5. The cold forming process of reduced or equal diameter Minic-Block springs and eccentric springs still has limitations.

(2) Hot forming process of spring

1) Hot forming process speed capability. At present, my country only has CNC 2-axis hot coil spring machine for forming on (9~25) mm specifications, with a maximum speed of 17 pieces per minute. Compared with developed countries, the gap is large.

2) Large spring hot forming process control ability. Because there is only a CNC2-axis hot-coiling spring machine, the shape control is less effective in three directions, and the accuracy is poor; and there is no automatic bar rotation control and adjustment mechanism, so the hot-coiled spring forming process level and ability are low. Therefore, the precision level of the spring and the level of surface oxidation and decarburization are also low.