RU2415729C1 - Method of spring recovery - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to plastic metal working and can be used for recovery of springs at diverse enterprises. Proposed method comprises expansion, heating and cooling of springs. Prior to expansion, spring is heated and tempered, and, then, it is expanded with the pitch exceeding that of finished spring. Then, it is thermally treated and shot-blast hardened, or thermally cambered. Now, spring coils are plastically hardened by compressing it at axial load of (10-300)F3, where F3 is spring force at maximum strain.

EFFECT: higher efficiency and quality.

4 cl

Description

FIELD OF THE INVENTION

The invention relates to the field of metal forming, in particular to methods for restoring the elastic properties of springs, and can be applied at enterprises for the repair of agricultural machinery, vehicles, weapons, lifting or other equipment.

State of the art

A known method of restoring the elasticity of the springs, which consists in the forced tension and heating of the springs to the required temperature. In repair practice, this method was not widely used due to the low productivity and the mismatch of the requirements of the technological process with the conditions of repair enterprises [1].

A known method of restoring springs, which consists in stretching the spring, heating and cooling using a special device [2]. However, it does not provide restoration of the elasticity of all springs falling onto the repair plant. For example, it is impossible to restore springs that have lost elasticity as a result of the non-perpendicularity of the ends or various changes in the pitch between the turns. Since here the spring is stretched beyond the extreme turns, then after the restoration of the spring, the ends have a non-perpendicularity or a different pitch between the turns. During operation, this leads to an uneven distribution of the load between the turns and causes stresses and deformations in the most loaded turns that exceed the permissible ones.

Closest to the invention in technical essence is a method of spring restoration, which consists in stretching a spring, heating and cooling, characterized in that the tension is carried out sequentially along its turns, while simultaneously with stretching, each coil is heated and crimped [3].

The disadvantage of this method is the duration of the process, depending on the need for sequential processing of each coil; it is impossible to correct the non-perpendicularity of the ends. The manufacture of a special complex device for each type of spring is beyond the power of most repair enterprises, which is also a disadvantage.

In the presented methods, there is no tempering after hardening necessary for ensuring the durability of the springs and shot blasting to eliminate stress concentrators arising after hardening, the surface of the springs is not provided for decarburization during hardening, which is a drawback.

Moreover, there are many springs subjected to hardening during manufacture, which cannot be stretched due to the large diameter of the coil and the high tensile strength associated with this circumstance. The moments of tensile resistance arising after stretching reduce the forces (F1, F2) of the spring restored in this way, which does not allow the restored spring to be considered equivalent to the original manufactured one.

Disclosure of invention

The technical result to which the invention is directed is to develop a technological process that allows to expand the technological capabilities of the method and improve the quality of the springs.

The technical result is achieved due to the presence of new operations of the technological process and their new sequence, namely: the essence of the invention lies in the fact that in the method of manufacturing springs, which includes stretching, heating and cooling the spring, characterized in that before stretching the spring is heated and normalized or annealed, then stretched with a step exceeding the step of the finished spring, heat treated and shot blasted, heat-shrink or gouge the springs, then or simultaneously with t The thermosetting produces plastic hardening of its coils by compressing the spring with an axial load of (10 ÷ 300) F3, where F3 is the spring force at maximum deformation. Plastic hardening of the coil of the spring is carried out by applying an initial load to it, providing the minimum allowable draft, and then applying a repeated load, increased in proportion to the ratio of the required draft to draft from applying the first load. In this case, the load can be vibrational. Upon reaching a predetermined spring height, re-pressing is not necessary. With increased requirements for power parameters, the spring is edited.

With this sequence of technological operations, technological spring settling is performed, which is larger in size than the spring draft in the product, from which favorable stress states are formed on the surface and inside the spring coils, which counteract the occurrence of precipitation during spring operation. Use the method of double application of the load [4], which reduces the dispersion of the power parameters of the springs relative to the specified standards. The load is applied vibrationally, which ensures its uniform distribution over the cross section of the spring coils [5]. This ensures an increase in the resistance of the springs when working in the product and the accuracy of its manufacture along the length and load, the rejection during the sorting of the springs is reduced, and the value of the relaxation of the load when tested by levitation for 48 hours at a temperature of 130 ° C is reduced to 2.5%. Since plastic hardening of coils by a load of (10–300) F3 occurs in fractions of a second, the duration of the plastic hardening operation is 1–5 s.

The determination of the allowance for the draft of the spring and the load are known and covered in the literature: the allowance should be greater than the sum of the allowance for draft in the above technologies and the draft during operation of the spring in the product - approximately 1.5 ... 2 allowances for normal regrowing, and specified by testing the springs [6 , 7].

It is assumed that the resource of springs restored in this way is increased by 1.5 ... 2 times relative to the resource of springs restored by known methods, which is consistent with the increase in the resource of springs shown in [6] when using contact backlash after the usual.

The method is as follows. The spring is heated and normalized or annealed, then it is stretched with a step exceeding the step of the finished spring. Produce heat treatment of the springs. After 100% lumontol and washing, a shot blasting is carried out. After heat shrinkage or gouging, plastic hardening of the coils is carried out until the desired height of the spring is achieved by compressing it with a load of (10 ÷ 300) F3, and heat shrinkage and plastic hardening of the coils can be carried out simultaneously. Then measure the parameters of the spring. Recent operations - the application of a protective coating, preservation and packaging or installation in the product. In the manufacture of springs accurate in terms of force, the springs are corrected after stretching.

Note. Under the heat treatment of the spring means its hardening with subsequent tempering in accordance with the modes adopted for a particular brand of spring steels [8]. Heat treatment is carried out in a protective environment. An easy-to-manufacture device is applicable for plastic hardening [6, p.29].

Information sources

1. Stand for the restoration of springs in an electrocontact way. Information Leaflet No. 47-75, 1975.

2. A.S. USSR No. 740842, Cl. C21D 9/02, 1977.

3. A.S. SU No. 1055574 A, B21F 35/00. Bull. 43, 1983.

4. A.S. USSR 554915, M. cl. B21F 35/00, 07/10/07.

5. A.S. USSR 580474, M. cl. G01M 13/00, B21F 35/00, 1976.

6. Tebenko Yu.M. Problems of production of high-speed springs and ways to solve them. Monograph. - Stavropol: LLC “Data World”, 2007, - 152 p.

7. Zemlyanushnova N.Yu. Calculation of helical cylindrical compression springs with contact overfilling. Monograph. - Stavropol: AGRUS, 2008 .-- 136 p.

8. Rakhstadt A.G. Spring steel and alloys. M.: Metallurgy, 1982, 400 p.

Claims (4)

1. A method of restoring compression springs, including stretching, heating and cooling the spring, characterized in that before stretching the spring is heated and released, then stretched in increments greater than the pitch of the finished spring, heat treatment and shot blasting are performed, annealing or heat shrinkage is carried out, and then at the same time produce plastic hardening of its coils by compressing the spring with an axial load of (10 ÷ 300) F3, where F3 is the spring force at maximum deformation. 2. The method according to claim 1, characterized in that the plastic hardening of the coil of the spring is carried out by applying to it an initial load that provides the minimum allowable draft, and then applying a reload increased in proportion to the ratio of the required draft to draft from the initial load. 3. The method according to claim 1 or 2, characterized in that the load for compressing the spring during its plastic hardening is applied vibrationally. 4. The method according to claims 1 or 2, characterized in that after stretching the spring is straightened.