RU2601015C2 - Method of helical springs hardening - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building and can be used during helical compression springs hardening. Method comprises spring winding with pitch exceeding pitch of finished spring, thermal treatment, wheel blasting, penetrant inspection and thermally treated spring ends polishing. At final stage, spring outer and inner surfaces cold-hardening is carried oud and spring surface cold-hardening along turns to each other contact line. Spring outer and inner surfaces cold-hardening is performed by stamping using hardening device when spring is in female die opening by means of spring turns expansion to female die opening surface by male die entering into it. Gap between female die and male die surface opening is selected less than spring turn diameter for 0.2…2 mm. Spring surface cold-hardening along spring turns contact line between each other is performed by spring compression with force of 5…300F₃, where F₃ is spring force at maximum strain_.

EFFECT: higher efficiency of hardening and spring elastic properties stability.

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Description

FIELD OF THE INVENTION

The invention relates to mechanical engineering, in particular to a method for hardening helical cylindrical compression springs.

State of the art

A known method of spring hardening is shot blasting, which is the most common in the production of springs. The essence of the process by processing shot is that the parts after the final mechanical or heat treatment are subjected to the impact of the flow of steel or cast iron shots. Shot blasting of springs is performed on mechanical or pneumatic shot blasting machines with steel or cast-iron beads with a diameter of 0.4 to 1.8 mm (Ostroumov, V.P. Production of coil cylindrical springs / V.P. Ostroumov. - M.: Mechanical Engineering, 1970. - 135 p., P. 74 ... 75).

When shot blasting, double-sided residual compressive stresses are created on the surface of the coils, which prevent the opening of fatigue cracks and increase the endurance limit by 40-80%. (Lavrinenko, Yu.A. Spring hardening / Yu.A. Lavrinenko, EG Belkov, VV Fadeev. - Ufa: Business Partner Publishing House, 2002. - 124 p. 16).

The disadvantage of this method is that shot blasting does not eliminate the uneven distribution of stresses over the cross section of the coil of the spring. Coils of a coil spring usually have significant curvature. This leads to a significant increase in stresses, reaching 40% on the inner fiber of the coils, compared with the stresses arising on the outer fiber of the coils. (Ponomarev, S.D. Calculation of the elastic elements of machines and devices / S.D. Ponomarev, L.E. Andreeva. - M.: Mashinostroenie, 1980. - 326 p., P. 88). During operation of the spring, fatigue cracks develop on the inner side of the coil section.

It is known that the greatest stability of elastic properties, depending on the type of spring treatment, is shown after processing in a stressed state (Ostroumov, V.P. Production of coil cylindrical springs / V.P. Ostroumov. - M.: Mashinostroenie, 1970. - 135 p., p. 93 ... 96). By analogy with this, the shot blasting of the springs should be carried out in a compressed state until the coils touch. During shot blasting of a compressed spring, the shot flow will reach only the outer side of the coils, and the inner side of the coils will remain unstressed, which is a drawback.

A known method of hardening cylindrical coil springs, including winding, hardening, tempering, bead-blasting and troweling, and at the final stage, the inner surface of the springs is hardened. Hardening is carried out by pulling the mandrel or by impact on the inner surface of the coil of the spring. The proposed device for implementing the method - the mandrel or reinforcing head with rollers - is installed on a lathe, in the clamping device of which a spring is fixed (Patent RU 2462519, IPC C21D 9/02, C21D 7/06, B21F 35/00. The method of hardening coil springs / Shavrin O.I., 2011115786/02; Stated April 20, 2011; published September 27, 2012. Bull. No. 27).

The disadvantage of this method, adopted as a prototype, is the difficulty of securing the spring in the clamping device of the lathe and the possibility of damage to its coils with an uneven distribution of clamping forces and forces from pulling the mandrel or from the impact of the rollers of the head of an unnamed model (brand).

The disadvantages are the duration of the processes: installing the spring in the device and removing from it, bringing the spring and the working tool (mandrel or head with rollers) into rotation, supply and removal of the working tool. The issue of removing the spring from the working tool is not resolved, which is also a drawback.

In this method, the term “regrowing” refers to a 3- or 5-fold compression of the spring until the coils touch, which is not in fact a regression, but is considered as preliminary draft, which is used to detect gross deviations from the process. The main draft of the springs, including cyclic ones, is carried out by the gouging operation, which occurs in the first 20-30 hours, and then increases slightly. (Ostroumov V.P. Production of coil cylindrical springs / V.P. Ostroumov. - M.: Mashinostroenie, 1970. - 135 p., P. 65 ... 68).

It is known that the greatest stability of elastic properties, depending on the type of spring processing, is shown after processing in a stressed state (Ostroumov, V.P. Production of coil cylindrical springs / V.P. Ostroumov. - M.: Mechanical Engineering, 1970. - 135 p., p. 93 ... 96). By analogy with this, the hardening of the inner surface of the spring in the present invention should be carried out in a compressed state, which is not done. This is also a disadvantage of the prototype method.

The disadvantage is that this method does not strengthen the coils of the springs working with the contact, since when this method is implemented, hardening does not occur along the contact line of the coils.

Disclosure of invention

The objective of the invention is to increase the stability of the elastic properties of the spring and reduce the installation time and removal of the spring from the device and the hardening time of the springs in a compressed state. The technical result to which the invention is directed is to create plastic deformations with riveting along the outer and inner surfaces of the coils of a compressed spring and surfaces along the contact line of the coils with each other.

The technical result is achieved by the fact that the method of hardening coil coil springs includes winding a spring from a pre-hardened or hardened wire with a step exceeding the step of the finished spring by the amount of allowance for tapping and stamping (6-14% of the height of the finished spring), heat treatment is tempering for springs from pre-hardened wire or hardening and tempering for springs from hardened wire, lumocontrol, grinding of the ends, shot blasting. The hardening of the outer and inner surfaces and the hardening of the surfaces of the spring along the contact line of the coils between themselves, located in the hole of the matrix of the device for strengthening the compressed spring, is made by stamping, and the hardening of the outer and inner surfaces is made by bursting its coils to the surface of the hole of the matrix with a punch, the diameter the hole of the matrix is equal to the diameter of the compressed spring, and the gap between the hole of the matrix and the surface of the punch is chosen less than the diameter of the coil of the spring by 0.2 ... 2 mm depending on t of coil diameter. Hardening of the surfaces along the contact line of the coils between each other is done by compressing the spring with a force of 5 ... 300F ₃ . In this case, the hardening of the inner and outer surfaces of the spring and the hardening of the surfaces of the spring along the contact line of the coils are carried out in a single operation or separately.

The implementation of the invention

The method of hardening coil springs is as follows. The spring is wound with a step exceeding the step of the finished spring by the amount of allowance for tapping and stamping (6 ... 14% of the height of the finished spring), heat treatment, lumocontrol, grinding the ends, shot blasting. The outer and inner surfaces of the spring are hardened and the spring surfaces are hardened along the contact line of the coils by stamping by means of a hardening device when the spring coils are compressed to the contact in the matrix hole, while the external and internal surfaces of the spring are hardened by bursting the spring coils to the surface of the matrix opening into it with a punch, and the diameter of the hole of the matrix is equal to the diameter of the compressed spring, and the gap between the hole of the matrix and the surface of the punch ayut smaller diameter coil spring. Hardening of the surfaces of the spring along the line of contact between the coils is produced by compressing the spring with an axial force of 5 ... 300F ₃ .

In this case, the hardening of the inner and outer surfaces of the compressed spring and the hardening of the surfaces along the contact line of the turns between themselves are carried out in one operation or separately.

For hardening by stamping the inner and outer surfaces of the spring and the surfaces in the contact line of the coils with each other in one operation, it is proposed to use the device depicted in FIG. 1 (RF Patent No. 2403465 C1, IPC F16F 1/06, B21F 35/00. Device for contact covering of springs. Tebenko Yu.M., Zemlyanushnova N.Yu., Zemlyanushnov N.A. - No. 2009139101/11; decl. 10/22/2010; publ. 10.11.2010. Bull. 31. - 7 p.). When lowering the top plate 1, the sleeve 7 compresses the hardened spring 8 located in the bore of the matrix 9 until the coils touch, and the mandrel 5 enters the compressed spring 8 and bursts it against the surface of the matrix bore. Since the gap between the surface of the bore of the matrix 9 and the surface of the mandrel 5 is less than the diameter of the coil of the spring 8, there is a radial compression of the coils of the spring, which causes hardening on the inner and outer surfaces of the compressed spring. After the punch 5 enters the spring 8, the sleeve 7 abuts against the end of the punch 5, transmitting from the press an axial force of 5 ... 300F3 to the coils of the spring 8, from which a riveting occurs in the contact line of its coils.

For hardening by stamping the inner and outer surfaces of the compressed spring, it is proposed to use the device shown in FIG. 2 (AS 825253 USSR, M. Cl. ³ B21F 35/00, F16F 01/00. Device for covering the springs / Tebenko Yu.M. - No. 2822172 / 25-12; decl. 06.08.79; publ. 04/30/81, Bull. No. 16 for 1981 - 3 pp.). Hardening is performed as follows. The upper plate 2 is lowered by the movement of the press. The entrance part of the mandrel, and then the spreading part, enter into the spring that is restrained 5, after which the movable sleeve 9 abuts the spring, compressing it until the coils touch. Next, the working part of the mandrel enters the inside of the spring 5, bursting its coils and pressing them to the surface of the bore of the cup 6. Due to the fact that the gap between the surfaces of the bore of the cup and the working part of the mandrel is less than the diameter of the coil of the spring, the inner and outer surfaces of the compressed spring are riveted. After exposure, the upper plate 2 with the punch 1 is raised. The movable sleeve 9, sliding along the mandrel under the action of the springs 10, pushes the spring 5 from the mandrel 4, leaving the spring 5 in the bore of the glass 6, from where it is removed mechanically or manually.

For hardening by stamping the surfaces of the spring along the contact line of the coils with each other, it is proposed to use the device shown in FIG. 3 (patent RU 2429932 C1, IPC B21F 35/00, F16F 1/02. Device for contact covering of springs. Tebenko Yu.M., Zemlyanushnova N.Yu., Zemlyanushnov N.A. - No.2013171731 / 02, claimed 28.07 .2010, publ. 09/27/2011. Bull. 27. - 4 p.). Hardening is performed as follows. The punch 1 is lowered by the movement of the press, causing the spring 4 to compress, increasing its outer diameter until all its coils come into continuous contact with the inner surface of the cup 2. After exposure to a load of 5 ... 300F ₃ , which provides riveting along the contact line of the coils, the punch is lifted, the spring is removed from the device.

Using the presented devices, it is possible to create plastic deformations (hardening), which accelerate the draft and increase the service life of the spring, working, including, with a single operation or separately on the inner and outer surfaces of the spring compressed to the contact of the coil turns and on the surfaces of the contact line of the coils. power or shock contact of the coils under conditions of prolonged cyclic loading.

The presented operations of spring hardening in a compressed state make it possible to create compressive residual stresses on the inner and outer surfaces of the coil turns and on the surfaces in the contact line of the coils that add up to tensile stresses arising during the spring operation and reduce them.

The heat-treated spring (hardening and tempering for hardened wire springs and tempering for springs from hardened wire), grinding of the ends, shot blasting, is subjected to additional processing of the inner and outer surfaces of the coils and surfaces in the contact line of the coils with each other.

The presented operations of hardening the inner and outer surfaces of the compressed spring and the surfaces in the line of contact between the coils by stamping are more productive than the known operation of hardening the inner surface by turning, since they occur on a high-speed stamping press, and can be mechanized using devices used in stamping for installation in device and removing parts from it. The installation time of the spring in the hardening and recessing device of the spring does not exceed 1 ... 2 s, while the duration of the installation of the spring in the clamping device of the lathe, the rotation and pushing of the mandrel or rolling rollers on the inner surface of the spring and the time of removal of the spring from the clamping device of the lathe is significantly exceeds the time of the hardening operation according to the proposed method.

It is supposed to increase the durability (resource) of springs hardened in this way by 1.4 ... 2 times relative to the durability of the springs hardened by known methods, which is consistent with that shown in the paper (Tebenko, Yu.M. Problems of production of high-speed springs and ways to solve them. Monograph / Yu .M. Tebenko. - Stavropol: PA "World of Data", 2007. - 152 p.) Increase in durability (resource) of springs when using plastic hardening of coils with loads of 10 ... 300F ₃ .

The invention in comparison with the prototype and other known technical solutions has the following advantages:

- hardening of the inner and outer surfaces of the spring and the surfaces in the contact line of the coils between themselves is carried out in a compressed state in one operation or separately;

- the greatest stability of the elastic properties of the springs;

- high performance spring hardening.

Claims (3)

1. A method of hardening coil cylindrical springs, including winding the spring with a step exceeding the step of the finished spring, heat treatment, shot blasting, light control and grinding of the ends of the heat-treated spring, characterized in that at the final stage the outer and inner surfaces of the spring are hardened and the spring surface is hardened according to contact lines of the coils with each other, while the hardening of the outer and inner surfaces of the spring is produced by stamping by means of a hardening device when the spring is in the hole Holes of the matrix by bursting the coil of the spring to the surface of the hole of the matrix by the punch included in it, and the gap between the hole of the matrix and the surface of the punch is selected 0.2 ... 2 mm less than the diameter of the coil of the spring, and the spring surface is riveted along the contact line of the coils with spring force 5 ... 300F ₃ . 2. The method according to p. 1, characterized in that the hardening of the inner and outer surfaces of the compressed spring and the hardening of the spring surface along the contact line of the coils between themselves is carried out in one operation. 3. The method according to p. 1, characterized in that the hardening of the inner and outer surfaces of the spring is carried out separately from the hardening of the spring surface along the contact line of the coils with each other.

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