Method of helical spring hot winding and mandrel to this end

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be used for producing springs by hot winding. Proposed method consists in using mandrel with outer surface layer made of metal that features lower heat conductance. This allows making the spring coil in tempering with metal martensite structure owing to eliminated heat removal from spring coil inner surface in contact with mandrel outer surface layer.

EFFECT: higher quality of springs.

2 cl, 2 dwg

 

The invention relates to mechanical engineering and can be used in the manufacture of coil springs, hot wound.

The known method of manufacturing large springs (ed. mon. SU # 1234018, publ. 30.05.86), including high-temperature thermomechanical processing of rod cross-screw before pulling wrapped and wrapped springs, followed by a final heat treatment, additional high-temperature thermomechanical processing spring during winding, which before wrapped perform high-speed heating of thermo-hardened rod to a temperature of 100-150°C. above the AC3 point of the phase transitions helical broaching is performed in the direction of deformation of a coil compression spring, and as the final heat treatment of springs used vacation.

The disadvantage of this method is the complexity of the process, as applied twice thermomechanical processing, and low reliability of the process of hardening, due to the fact that the second heating before the wound can lead to recrystallization in the volume of a bar of steel and negate the effect of hardening on thermomechanical processing of the rod.

Closest to the claimed solution is a method of manufacturing large springs of steel (patent RU No. 2377091, publ. 27.12.2009), kiuchumi heating the rod to a temperature ensure the homogenization of the high-temperature phase began winding the spring of the rod when the temperature of heating, pometkovo hardening spring, and quenching each coil is carried out after him winding and poslenovogodnee exposure over time, ensuring the processes of polygonization steel for trouble recrystalization rebuild its structure.

The disadvantage of this method is the possibility of reducing the quality of the springs due to the lower temperature of the inner surface of a coil spring in contact with the mandrel, the heat sink in the body of the mandrel and a partial hardening in this area.

Known also design devices for hot spring coiling of the rod (ed. mon. SU # 1542678, B21F 3/04, publ. 15.02.90, bull. No. 6). The device contains a download site bars, heater rod, a cooling bath located in her belt, the nodes of the winding spring, grip the end of the rod and moving the mandrel in a cooling bath, and the mechanism of removal of the finished spring. Node move the mandrel in a cooling bath is made in the form of a rigidly fixed on the rotary shaft of a drive of a Maltese cross with lock and drive. On the drive to turn freely set the axis on which is rigidly fixed to the frame.

A disadvantage of the known design is low to the quality of the products obtained, due to the hardening of the entire spring - i.e. fully wound. Simultaneous immersion of the entire spring having a different structure of the coils due to the time difference between the beginning of the forming coil and the beginning of cooling (quenching), leads to the production of springs having a non-uniform strength along the length of the spring and a zone of incomplete hardening of the contact surface of a wound spring and frame.

In the process of winding the coils of the spring on the mandrel and during the pause between wrapped and quenching in the quenching device of the internal surface of the coil spring is cooled by the heat sink to the metal mandrel. In the result, by the beginning of quenching cooling, the temperature of the inner surface of the coil spring in contact with the mandrel, is below the required for hardening. This leads to the fact that on the inner surface of the coil spring is formed in the area of incomplete quenching, which is presented in figure 1. The depth of this zone reaches several millimeters, the width corresponds to the width of contact of the coil and the mandrel. Due to incomplete quenching the inner surface of the coil springs are disqualified for operation and marriage.

Inadmissibility incomplete hardening of the metal of the inner surface of the coils of the springs due to the fact that in this area during operational loading of the springs arise maximum voltage. Cash is Chiyo zone incomplete hardening on the inner surface of the coils of the spring leads to early emergence of cracks and premature failure of the springs. The durability of the springs is reduced tenfold, and, in addition, the power spring characteristic is not relevant to the requirement of drawing.

The objective of the invention is to improve the quality of the springs, the exception obtain in the process of winding the springs zone of incomplete quenching in the inner surface of the coils of the spring. This increases the durability of the spring in operation.

The technical result consists in decrease of heat removal from the coil springs in the outer layer of the body of the mandrel through the creation on the outer surface of the mandrel a layer of material with low thermal conductivity.

This object is achieved in that the method of hot wound coil springs, comprising heating a metal rod winding the spring on the mandrel and training, using the mandrel, the outer surface layer which is made of metal with low thermal conductivity, which provides for reducing heat transfer from the inner surface of a coil spring in contact with the outer surface of the mandrel, receive at tempering coil springs with a uniform martensitic structure of the metal.

A mandrel for hot wound coil springs made with the possibility of the transfer of rotation and diameter of the outer surface corresponding to the internal demetrovics nalivaeva springs, thus the outer surface of the mandrel is formed of an outer surface layer made of a metal with low thermal conductivity, which provides for reducing heat transfer from the inner surface of a coil spring in contact with the outer surface of the mandrel, receive at tempering coil springs with a uniform martensitic structure of the metal.

Figure 1 shows a cross-section of a coil spring, which is formed by the usual method of hot winding, figure 2 shows a cross section of a coil spring, which is formed by the proposed method.

Coil springs (figure 1) has a line of contact 2 with the mandrel 3, which passes through the outflow of heat in the usual way hot winding, forming a zone 4 low temperature, which after hardening forms a zone of incomplete hardening.

When the winding of the spring by the proposed method is depicted in figure 2, coil spring 1 has a line of contact 2 with the outer layer 5 of the mandrel 3. Due to the low thermal conductivity of the material of the outer layer 5 of the mandrel 3, the heat sink from round 1 of the spring through the line of contact 2 is not happening. In the absence of lowering the temperature in the coil spring along the line of contact 2 zones incomplete quenching cross-section of a coil is not formed. The metal structure throughout the cross section VI the ka is the same and corresponds to a martensitic structure, that improves the quality of manufactured springs.

How hot winding the coil springs is as follows.

Heat the billet rod, wound from rod spring, the winding operation is produced on the mandrel, the outer surface layer which is made of a material with low coefficient of thermal conductivity, then tempering to produce continuously sequential move nauywaima coils of the spring into the quenching device, providing a constant time for each coil between the end winding and the start hardening.

Using the proposed method, hot wound coil springs hot rod coils on the mandrel, having on the surface of the metal layer with low conductivity.

In this case, the process poslerevolutsionnoi pause between the time of winding of each coil and its cooling in the quenching device there is no loss of temperature of the inner surface of a coil spring in contact with the mandrel, due to the heat sink at the outer surface layer of the mandrel, and at the onset of cooling is maintained uniformity (uniform) temperature cross section of a coil that provides for hardening uniform structure and hardness of the material of a coil spring.

A mandrel for hot winding the coil springs with the structural element and, for the transmission of rotation of the mandrel has an outer diameter corresponding to the inner diameter of coils nalivaeva spring. The outer surface layer of the mandrel is made from a material having a lower coefficient of thermal conductivity.

The outer surface layer of the mandrel may be formed by depositing a material with low thermal conductivity, or by press-fitting tube of material having low thermal conductivity, or screw the tube of material having low thermal conductivity.

The outer surface layer of the mandrel can be formed dowel insertion tube of a material having low thermal conductivity, or formed slotted pipe connection from a material having low thermal conductivity, or welding pipe connection from a material having low thermal conductivity.

Studies have shown that if the wrapped spring steel S, S on the mandrel, made of carbon structural steel on the inner surface of a coil spring formed area depth up to 30-40% of the radius of a coil and a width of up to 2-3 mm, when wrapped on the mandrel, the outer surface of which was formed by press-fitting the pipe of stainless is it steel, or surfacing of heat resistant material having a coefficient of thermal conductivity 3-4 times less than that of carbon structural steel, zone incomplete quenching is not formed.

1. How hot winding of coil springs, comprising heating a metal rod winding the springs on the frame and hardening, characterized in that the use of the mandrel, the outer surface layer which is made of metal with low thermal conductivity, provides for eliminating heat from the inner surface of a coil spring in contact with the outer surface of the mandrel, receive at tempering coil springs with a uniform martensitic structure of the metal.

2. A mandrel for hot wound coil springs made with the possibility of the transfer of rotation and diameter of the outer surface corresponding to the inner diameter of coils nalivaeva spring, characterized in that the outer surface of the mandrel is formed of an outer surface layer made of a metal with low thermal conductivity, provides for eliminating heat from the inner surface of a coil spring in contact with the outer surface of the mandrel, receive at tempering coil springs with a uniform martensitic structure of the metal.



 

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