JPS6184325A - Working heat treatment and its apparatus - Google Patents

Abstract

PURPOSE:To improve mechanical property of a steel material, by applying a treatment composed of heating to temp. of transformation point or above, austenitizing, then cooling to martensite transformation locally in order and continuously to the rod shaped steel material, and tempering it. CONSTITUTION:Both end parts of the rod shaped steel material 10 are grasped by clampers 1, 2, and the material 10 is revolved by a motor 5 through a driving gear 4. An induction heating apparatus 3 is moved from lower to upper end part of the material 10 to heat it locally in order, to temp. of transformation point or above, it is torsion worked and austenitized. The heated part is cooled immediately by a cooling device 6, and martensite transformation is caused. Working heat treatment is applied to whole of the material 10, then it is tempered. In this way, the material 10 having improved tensile strength, toughness and superior fatigue strength resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called processing heat treatment method and apparatus for subjecting a bar-shaped steel material to a combination of plastic working and heat treatment to improve the mechanical properties of the steel material.

Conventionally, as one type of processing heat treatment, ausform treatment is known in which plastic working is performed in a metastable austenite phase to transform it into martensitic phase.

In other words, ausform treatment involves rapidly cooling austenitized steel to a temperature below its transformation point, and then subjecting the steel to plastic working such as rolling or forging before the austenite phase transforms into a different phase, that is, in the metastable austenite region. After adding it, it is immediately quenched to cause martensitic transformation,
After that, the steel is subjected to a tempering treatment, which significantly strengthens the mechanical properties of the steel, such as its tensile strength, toughness, and fatigue strength.

However, in the ausform treatment, plastic working must be performed in the metastable austenite region, so the steel used for this treatment must have a sufficiently wide metastable austenite region in the constant temperature transformation curve. When the point is moved to the long-term side, it is necessary to use steel containing a large amount of alloying elements such as Cr, Ni, Mo, etc., and the target is inevitably expensive steel. Due to space limitations, it was not widely used.

In addition, it is a processing heat treatment developed to remove the material limitations of the ausform treatment described above, in which a stable austenite region phase of ζAc transformation point or higher is subjected to plastic working such as rolling and steel forming, and immediately quenched. However, a T-hardening process is known in which the material is transformed into martensitic material and then tempered to improve its mechanical properties compared to ordinary hardened and tempered materials.

This treatment method is essentially a treatment method that can be applied to any type of steel, since the plastic working region is a stable austenite I phase with no time constraints. However, plastic forming in conventional work hardening treatment methods is limited to rolling or forging, which inevitably requires large-scale processing equipment, and the effect of improving mechanical properties cannot be achieved by the above-mentioned orthoform treatment method. It was small in comparison.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and the present inventor has devised a method that allows plastic working of austenitized workpieces in processing heat treatment to be performed with a small and simple structure, and Since the degree of workability is the largest processing factor, even though it does not affect the mechanical properties in heat treatment, we have conducted various experiments on plastic working that can obtain a large We have succeeded in developing a processing heat treatment method and equipment that significantly improves properties.

That is, the present invention uses a rod-shaped steel material as the material to be treated, and when austenitizing the rod-shaped material, induction heating, which is capable of local heating, is used to locally heat the material to a temperature above the transformation point. Then, plastic working is applied by twisting to the austenitized part by the heating, and then the working 1° + 1 is immediately quenched to cause martensitic transformation, and then tempering treatment is performed. For a long steel material, the process heat treatment can be applied to the entire length of the bar-shaped steel material by sequentially carrying out the above-mentioned treatment sequentially along the longitudinal direction of the bar-shaped steel material.

Further, when plastic working is applied to a bar-shaped steel material, at least one of the clamping devices for gripping the vicinity of both ends in the longitudinal direction of the bar-shaped steel material and the clamping device for imparting twist to the bar-shaped steel material gripped at both ends is rotated. a drive device;
an induction heating device that locally heats a bar-shaped steel material above its transformation point and is movable along the longitudinal direction of the bar-shaped preparation; It is equipped with a heating device and a cooling device that moves integrally with it. It is also possible to fix the heating device and move the bar-shaped steel material to perform processing heat treatment. In this case, the processing heat treatment can be performed by moving the bar-shaped steel material At least one of the following: a clamp transfer device that grips two points, transfers them in a transverse direction, and applies twist; an induction heating device that locally heats a bar-shaped steel material to a temperature higher than its transformation point; and at least one of the clamp transfer device. A cooling device is provided near the heating device.

Fig. 1 shows a processing heat treatment apparatus of the present invention in which both ends of a bar-shaped steel material are gripped and an induction heating device is moved along the longitudinal direction of the bar-shaped steel material. 10 is a clamping device that has a recess into which the rectangular end is inserted; 3 is an induction heating device that moves vertically along the rod-shaped workpiece 10; and 4 is an induction heating device above the rod-like workpiece 10. an electric motor 5 that rotates the clamping device 1 that grips the end of the
6 is a device that is installed near the induction heating device 3 and moves integrally with the induction heating device 3 to spray a coolant such as water or oil on the heating section to cool it.

In addition, in Fig. 2, the induction heating device is fixed and a rod-shaped steel material is moved in its longitudinal direction, and 11.12 is a device in which a rod-shaped material to be treated 10 is transferred in its longitudinal direction, and the material to be treated is moved. 10 is a pair of rollers that apply torsion; 31 is an induction heating device that locally heats the rod-shaped material to be processed 10;
Reference numeral 61 denotes a device that is installed near the induction heating device 31 and supplies a coolant such as water or water to the heating section.

In the present invention, when carrying out processing heat treatment using a combination of plastic working and heat treatment, a bar-shaped steel material is locally heated by induction heating, and after being ausnitized, two points in the longitudinal direction of the bar-shaped steel material are heated. After being gripped and twisted by rotation, the processed portion is then rapidly cooled with water or the like to undergo martenzite transformation.

Then, in order to apply the processing heat treatment to the entire bar-shaped steel +1, the positions to be austenitized are sequentially removed by induction heating, and when twisting is applied to the bar-shaped steel H, the heated parts with low deformation resistance are similarly twisted and the plasticity It can undergo processing, and after processing, it can be rapidly cooled and heat treated.The entire bar was subjected to processing heat treatment, and then tempered.

The mechanical properties of the rod-shaped preparation subjected to processing heat treatment by the method of the present invention are that the tensile strength and toughness are significantly improved due to the large degree of processing compared to conventional processing methods such as rolling and forging. It also showed excellent values for fatigue strength.

As described above, the present invention can be performed in a compact and cylindrical configuration by performing the plastic working that is performed on the austenitized workpiece that undergoes heat treatment by twisting. By doing so, a large degree of processing can be obtained, which makes the process and heat treatment method and apparatus capable of greatly improving mechanical properties, making an extremely large contribution to industry.

[Brief explanation of the drawing]

Figure 1.2 shows one embodiment of the present invention (Figure 1 is a schematic diagram of a device that grips both ends of a bar-shaped steel material and moves an induction heating device along the longitudinal direction of the steel material. , FIG. 2 is a schematic diagram of a device for fixing an induction heating device and moving a rod-shaped steel material in its longitudinal direction.

Claims (1)

[Claims] 1. A bar-shaped steel material is locally heated to a temperature above the transformation point by induction heating, the heated part is twisted, and then the processed part is immediately rapidly cooled to cause martensitic transformation. A processing heat treatment method characterized by continuously performing processing heat treatment along the longitudinal direction of a bar-shaped steel material, and then subjecting it to tempering treatment. 2. A clamp device that grips the vicinity of both longitudinal ends of a bar-shaped steel material, and locally heats the bar-shaped steel material above its transformation point;
and an induction heating device that moves along the longitudinal direction of the bar-shaped steel material, a device that rotates at least one of the clamp devices, and a cooling device that moves integrally with the heating device. processing heat treatment equipment. 3. A clamp transfer device that grips a bar-shaped steel material at two points in the longitudinal direction, transfers it in the longitudinal direction, and applies twist; and an induction heating device that locally heats the bar-shaped steel material above its transformation point; A processing heat treatment apparatus characterized in that a device for cooling the heating section is provided near the heating device.