RU2428272C1 - Method of spring recovery - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to metal forming and may be used in repair of whatever machinery. Proposed method comprises expanding, heating and holding stretched spring till cooling. Spring heated to tempering temperature is expanded to coil pitch exceeding that of finished spring and tempered as-expanded till cooling. Then, spring is peen hardened and pressed by axial load making 10Ç300 F3, where F3 is spring force at maximum strain. ^ EFFECT: expanded performances, higher 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 from cold-deformed pre-heat-treated, usually patented wire, and can be used in enterprises for the repair of agricultural machinery, transport, weapons, lifting or other equipment.

State of the art

, где P - упругость пружины; n - количество витков пружины. Обжатие витков по сечению осуществляют с помощью двух роликов, один из которых установлен внутри пружины, а другой - снаружи. Внешний ролик прижат к пружине с силой Р=60 кг и установлен точно напротив внутреннего ролика. Нагрев витков пружины обеспечивают электрическим током, который через трансформатор подается на обжимающие ролики. Параметры тока I=600…1000 A, U=2…4 В. Восстановление упругости происходит в следующей последовательности. Пружина надевается крайним витком на внутренний обжимающий ролик. Подводятся разжимающие ролики и разжимают крайний виток пружины. Подводится внешний обжимающий ролик и прижимается к пружине с силой Р=60 кг точно напротив внутреннего обжимающего ролика. Придается вращение внутреннему ролику и одновременно на внешний ролик подается электрический ток, нагревающий сечение витка, зажатое между обжимающими роликами. Под действием силы трения пружина постепенно втягивается между обжимающими роликами, подвергаясь одновременно растяжению (между растягивающими роликами), обжатию и нагреву (между обжимающими роликами). При первоначальной упругости новой пружины в 23 кг приращение упругости составляет от 0,7 до 1,1 кг, что соответствует от 3 до 4,78% [1].A known method of restoring springs, which consists in stretching the spring, heating and cooling, characterized in that the tension is carried out sequentially along its turns, while at the same time stretching each coil is heated and crimped [1]. The method is as follows. The tension of the spring coils of the engine timing mechanism of the YaMZ-238NB engine is carried out using taper rollers, providing the tension of each coil by force

where P is the spring elasticity; n is the number of turns of the spring. The compression of the turns over the cross section is carried out using two rollers, one of which is installed inside the spring, and the other outside. The outer roller is pressed against the spring with a force of P = 60 kg and is installed exactly opposite the inner roller. The spring coils are heated by electric current, which is supplied through the transformer to the compression rollers. The current parameters I = 600 ... 1000 A, U = 2 ... 4 V. The restoration of elasticity occurs in the following sequence. The spring is put on with an extreme turn on the inner compression roller. The expansion rollers are brought in and the extreme coil of the spring is opened. An external compression roller is brought in and pressed against the spring with a force of P = 60 kg exactly opposite the internal compression roller. Rotation is given to the inner roller and at the same time an electric current is supplied to the outer roller, heating the coil section, sandwiched between the compression rollers. Under the action of friction, the spring is gradually pulled between the squeezing rollers, being subjected simultaneously to stretching (between the stretching rollers), compression and heating (between the squeezing rollers). With an initial spring elasticity of 23 kg, a spring increment is from 0.7 to 1.1 kg, which corresponds to 3 to 4.78% [1].

The disadvantage of this method is the duration of the process, depending on the need for sequential processing of each coil, the inability to correct the non-perpendicularity of the ends. The disadvantage is that in the specified method the following circumstances are not taken into account. Alloy spring steels have low thermal conductivity [2]. In this regard, local uneven heating of the spring during hardening can lead to the formation of internal stresses and quenching cracks. In this case, it is necessary to pre-heat the spring to a temperature of 400 ... 500 ° C, which has not been done. And for uniform hardening of the springs, it is recommended [3] to use installations for electric contact heating or induction heating installations with high-frequency currents with a tube or with a machine (1500 ... 15000 per / sec) generator used to produce a hardened layer with a depth of more than 2 mm, which has not been done. The issue of the necessary protection of the spring surface from decarburization during quenching has not been resolved; there are no operations required to ensure the durability of the spring spring release operations after quenching and shot peening to eliminate stress concentrators that arise after quenching. There is no obligatory springing for the springs, which is also a disadvantage.

A known electrocontact method for restoring springs [4], adopted as a prototype: “A very effective method for restoring springs is an electrocontact method based on a combination of plastic deformation and heating of a spring part with electric energy, structurally in an austenitic state, followed by its quenching. The spring recovery technology is based on low-temperature mechanical treatment, where the spring is deformed in the temperature zone of the existence of supercooled austenite in the region of its relative stability of 400 ... 600 ° C. The deformation temperature is higher than the temperature of the onset of martensitic formation, but lower than the temperature of recrystallization. The degree of deformation is 70 ... 90%. Quenching is carried out immediately after deformation. The formation of the structure of hardened steel during processing occurs under conditions of increased dislocation density due to hardening. Such complex processing allows to obtain high strength. The high mechanical properties after heat treatment are explained by the high dislocation density in martensite, the crushing of its crystals into individual fragments with a micron fraction. After deformation of austenite, quenching leads to the formation of dense dislocations combining martensite fragments.

The restored spring is fixed in the device and stretched to its original length in accordance with the technical conditions. The coil of the spring is wetted with spent engine oil and an electric current of 18-36 volts is passed through the spring, current strength is 180-200 amperes (from the VDU-500 welding transformer). As a result, the spring is heated until the oil burns, which corresponds to a temperature of 350-400 ° C, after which the electric current is disconnected and the spring cools in the extended state. The spring elasticity is checked on a MIP-100-2 device ”[4].

The disadvantages are: the lack of the necessary protection of the spring surface from decarburization during heating and hardening; the absence of spring release operations required for ensuring the durability of the spring after tempering and shot peening to eliminate stress concentrators arising after quenching; lack of obligatory springing for springs.

These methods mainly relate to the restoration of hardened wire springs and are not intended for springs from cold-formed pre-heat-treated, usually patented wire, which is a disadvantage.

Disclosure of invention

The technical result to which the invention is directed is to develop a technological process for the restoration of springs, which allows to expand the technological capabilities of the method and improve the quality of springs from cold-formed, previously heat-treated, usually patented wire.

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 the method of manufacturing springs, including stretching, heating and cooling, is characterized in that the spring is heated to the tempering temperature and in heated state, they are stretched with a step of turns exceeding the step of turns of the finished spring, tempering in the extended state of a non-cooled spring is carried out and kept in the extended state until it cools. Then, a shot blast hardening and pressing of the spring with an axial load of 10 ... 300 F _{3 are} performed, where F ₃ is the spring force at maximum deformation, including with preliminary conventional covering, and pressing is repeated by a load increased in proportion to the ratio of the required draft to draft from the first application load. In this case, the load can be vibrational. Upon reaching the set spring height, re-pressing is not necessary. If necessary, the springs are corrected before heat treatment.

The operations used to stretch the heated spring, tempering and its cooling in the extended state are thermomechanical methods that lead to the formation of a special structure and substructure of martensite and bainite, as a result of which the steel acquires high mechanical properties [9, p.200]. And thanks to the pressing operation, plastic spring hardening takes place: a favorable stress state is created on the surface and inside the coils, which counteracts the occurrence of precipitation during the spring operation. Using the method of proportional application of the load [5] ensures the accuracy of the manufacture of springs in height and load. The load application time is seconds. For a more uniform distribution of the load over the cross section of the coil of the spring, it is applied vibrationally [6]. The determination of the load and allowance for the draft of the spring are known (approximately 1.5 ... 2 allowances for normal regrowing) and are specified by testing the springs [7, 8].

It is assumed that the resource of springs restored in this way is increased by 1.4 ... 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 [7, 8] when using contact backing, including preliminary normal backing.

The method is as follows. Heated spring to tempering temperature (~ 200 ... 600 C °) by means of electrocontact or t.v.ch. - installations, or heated in a furnace in a shielding gas medium, are stretched in increments greater than the step of the finished spring, and tempering is carried out in the extended state of the non-cooled spring, kept in the extended state until it cools. Then, a shot-blasting hardening is performed, the spring is pressed by an axial load in the range of 10 ... 300 F ₃ , including with preliminary conventional regrowing, and re-loading increased in proportion to the ratio of the required draft to draft from applying the first load. Next, the protective coating is applied and the spring parameters are measured, preservation and packaging or installation in the product. When restoring springs that are especially accurate in terms of power parameters, after tension, they are corrected.

Note. The spring recovery method is based on low-temperature thermomechanical processing [9]. Vacation is carried out in accordance with the modes adopted for a particular brand of spring steels [9, 10].

Information sources

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

2. Luzgin N.P. The manufacture of springs. - M .: Higher. School, 1980 .-- 144 p.

3. Ostroumov V.P. Production of coil springs. - M .; "Engineering", 1970. - 136 p.

4. The information is given on the Industrial Siberia website under the name: “Electrocontact method of spring restoration”, GRNTI code 688583 dated 11/27/2003, with the address of the information provider: Omsk, 644046, ul. Training, 199-B, building 410; tel. (3812) 31-17-14, contact person of Ivanov Anastasia; E-mail: adm@sibindustry.ru

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

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

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

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

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

10. Zhuravleva V.M., Nikolaeva O.I. Engineering steel. Directory. Ed. 3rd, rev. and add. - Engineering, 1981. - 391 p., Ill.

Claims (4)

1. A method of restoring compression springs, including stretching, heating and holding the spring in the stretched state before cooling, characterized in that the spring heated to the tempering temperature is stretched with a pitch of turns greater than the pitch of the turns of the finished spring, and tempering in the extended state of the non-cooled spring, withstanding to cool, then a shot blast hardening and pressing of the spring with an axial load of 10 ... 300 F _{3 are} carried out, where F ₃ is the spring force at maximum deformation. 2. The method according to claim 1, characterized in that before pressing the spring is worn out. 3. The method according to claim 1 or 2, characterized in that a repeated load is applied to the spring, increased in proportion to the ratio of the required draft to draft from the application of the initial load. 4. The method according to claim 1 or 2, characterized in that the load is applied vibrationally.