JPS6270519A - Method and apparatus for working heat treatment - Google Patents

Abstract

PURPOSE:To obtain a large working degree with a simple constitution, by applying torsion working to plastic working to an austenitized bar steel stock in working heat treatment. CONSTITUTION:Upper and lower end parts of the bar shaped steel stock 10 are grasped by upper and lower clamping apparatuses 1, 2. The stock 10 is heated to temp. of >= its Ac3 transformation point by an induction heating apparatus 3 movable in up-and-down direction along the stock 10. Simultaneously, a motor 5 is driven to revolve an apparatus 4 connected to the apparatus 1 and torsion working is carried out so that angle of 20-70 degree is formed to axis line of the stock 10. Next, working part is immediately cooled rapidly by a cooling apparatus 6 movable with the apparatus 3 in one body to cause martensitic transformation. The process is continuously performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a processing heat treatment method and apparatus for subjecting a bar-shaped steel material to a combination of twisting and heat treatment to improve the mechanical properties of the steel material.

(Prior Art) Processing heat treatment is known as one of the methods for strengthening steel materials. Among these, the most effective method is ausform treatment, which involves plastic working in a metastable austenite phase and transforms it into martensite.

Ausform treatment involves rapidly cooling an austenitized steel material to a temperature below its transformation point, and then applying plastic working such as rolling or forging to the steel material before the austenite phase transforms into a different phase, that is, in the metastable austenite region.
It is immediately quenched to cause martensitic transformation.

When this ausformed steel material is tempered, it has higher strength and strength than normal hardened and tempered steel material.
It has been confirmed that mechanical properties such as toughness and fatigue strength are significantly improved.

(Problem to be solved) However, since the ausform treatment requires plastic working in the metastable austenite region, the steel used for this treatment must have a sufficiently wide metastable austenite region in its isothermal transformation curve. Therefore, it is necessary to use steel containing a large amount of alloying elements such as Cr, Ni, and Mo, which move the transformation point to the long-term side, and the target is inevitably expensive steel.

Furthermore, since accurate control of the temperature of the steel material and the timing of processing is required, ausform treatment has not been widely used due to constraints on the steel material and workability.

In addition, as a processing heat treatment method developed for the purpose of removing the material constraints and processing technology difficulties of the ausform treatment described above, plastic working such as rolling and forging is performed in the stable austenite region of Ac3 transformation point or higher. A processing quenching treatment is known in which the austenite phase is transformed to martensite by rapid cooling before recrystallization, and then tempering is performed to improve the mechanical properties compared to ordinary quenching and tempering materials.

Since this processing method processes the steel material in the stable austenite region, there is no time restriction in the plastic working region, so it is essentially a processing method that can be applied to any steel.

However, in conventional work hardening treatment methods, plastic working is limited to rolling or forging, which inevitably requires large-scale processing equipment, and the effect of improving mechanical properties is smaller than that of the orthoform treatment method. It was something.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned drawbacks of the prior art, and the present inventor has proposed a compact and simple structure for plastic working of austenitized workpieces in processing heat treatment. The degree of processing is the largest among the processing factors that affect mechanical properties in processing heat treatment.
As a result of various experiments on plastic working that can obtain a large degree of working, we succeeded in developing a process heat treatment method and its equipment that significantly improve mechanical properties using small-scale equipment.

The processing heat treatment method of the present invention uses a bar-shaped steel material as a material to be heat-treated, and uses high-frequency induction heating, which is capable of local heating, to heat the steel material to a temperature higher than the Ac3 transformation point and turn it into austenite. By grasping the two points and rotating one of them, plastic working by torsion is applied.

At this time, the heating section with low deformation resistance is twisted in a continuous manner. Then, the processed portion is immediately quenched to cause martensitic transformation, and then tempered. For long steel materials, it is possible to perform the above-mentioned treatment continuously along the longitudinal direction of the bar-shaped steel material.

Further, one processing heat treatment apparatus of the present invention includes a clamping device that grips a bar-shaped steel material while applying a tensile force to the vicinity of both ends in the longitudinal direction when applying plastic working by twisting to the bar-shaped steel material;
a drive device that rotates at least one of the clamp devices; an induction heating device that locally heats a bar-shaped steel material to an Ac3 transformation point or higher and is movable along the longitudinal direction of the bar-shaped steel material; A cooling device is provided that moves integrally with the heating device that immediately quenches the processed portion and causes martensitic transformation.

In addition, in another processing heat treatment apparatus of the present invention, it is possible to perform processing heat treatment by fixing the heating device and moving a bar-shaped steel material. In this case, it is possible to perform processing heat treatment by moving a bar-shaped steel material. At least any of the following: a clamp transfer device that grips the steel bar while applying a tensile force and transfers the bar-shaped steel material in its longitudinal direction; an induction heating device that locally heats the bar-shaped steel material to an Ac3 transformation point or higher; and at least any of the clamp transfer device. A device for twisting the steel material by rotating one of the devices, and a cooling device are provided near the heating device.

In the present invention, in order to apply plastic deformation to a bar-shaped steel material by torsion, the amount of torsion is 20 to 7
The reason for setting 0 degrees is that below 20 degrees, the effect of improving mechanical properties such as strength, toughness, fatigue resistance, and fatigue strength is small, and above 70 degrees, bending and distortion occur in the bar-shaped steel material due to torsion. This is because it becomes easier.

In addition, by induction heating a bar-shaped steel material, the A of the steel material can be locally heated.
When heating to a temperature above the c3 transformation point, the heating temperature is changed to Ac
The reason for setting the temperature range to be 100° C. higher than the third transformation point is that the twisting process can be completed in the austenite region before recrystallization and that crystal grains will become coarser if heated to a higher temperature.

Furthermore, the reason why a tensile force can be applied to the clamping device is to prevent bending distortion of the bar-shaped steel material due to twisting. Also, the lower limit of the tensile force is 0.1 kgf/m
The reason for setting the upper limit as m is that the tensile effect cannot be obtained below this value, and the reason that the upper limit was set to less than half of the high temperature yield point of the steel material is that if it is higher than that, the steel material may elongate in the longitudinal direction. It is from.

(Example) An example of the processing heat treatment apparatus of the present invention will be described below based on the drawings.

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. Reference numeral 1.2 denotes a clamping device having a recess into which the rectangular end of the workpiece 10, which is a rod-shaped steel material, is inserted; and 3, an induction heating device that moves vertically along the rod-like workpiece 10. 4 is a device driven by an electric motor 5 that rotates the clamp device 1 that grips the upper end of the rod-shaped material to be treated 10; 6 is a device that is installed near the induction heating device 3 and moves integrally with the device; This is a device that cools the heating section by applying a coolant such as water or oil to it.

7 is a device that applies tensile force to a bar-shaped steel material using a spring or the like.

Moreover, FIG. 2 shows a processing heat treatment apparatus in which an induction heating apparatus is fixed and a bar-shaped steel material is moved in its longitudinal direction. 11.
Reference numeral 12 denotes a pair of rollers that transport the rod-shaped material 10 to be processed while applying a tensile force in the longitudinal direction thereof and give twist to the material 10. Reference numeral 31 denotes an induction roller that locally heats the rod-shaped material 10 to be processed. A heating device 61 is provided near the induction heating device 31 and cools the heating section by applying a coolant such as water or oil to the heating section.

In the present invention, when carrying out processing heat treatment using a combination of plastic working and heat treatment, SUP 7 is used as a bar-shaped steel material with a diameter of 12 mm.
After locally heating the wire to 900°C using an induction heating device with a frequency of 20 KIIZ to austenitize it, grip the bar-shaped steel material at two longitudinal points while applying a tensile force of 0.5 kgf/mm. When rotated, plastic working by torsion is applied to the heated portion, which has low deformation resistance.

After applying a predetermined twist at an angle of 35 degrees to the axis of the bar-shaped steel material as shown in Figure 3 in the above temperature range, the processed portion is then rapidly cooled with water to undergo martensitic transformation. let

Then, in order to apply the processing heat treatment to the entire rod shape, the positions where the austenitization is to be made by induction heating are sequentially shifted,
When a bar-shaped steel material is twisted while being moved at a speed of 41111/sec, the heated part with low deformation resistance is twisted and subjected to plastic processing in the same way as above, and after processing, it is immediately quenched and transformed into martensitic processing. By performing these steps one after another, processing heat treatment can be applied to the entire length of the bar-shaped steel material. By the above method, a twisting process was applied to the bar-shaped steel material at an angle of 35 degrees with respect to its axis. Then, after processing and heat treating the entire bar, it was tempered using 4251'c.

Next, in order to examine the amount of set in the bar-shaped steel material 10 subjected to the processing heat treatment of the present invention with respect to the degree of twisting, the parallel part 9 was
A test piece of Hφ was prepared.

Note that a bar-shaped steel material formed by ordinary rolling was used as a comparison material.

Then, the test piece prepared from the comparative material was quenched and tempered so that it had the same hardness as the test piece made by the method of the present invention.

When measuring the fatigue resistance, a strain gauge was attached to the test piece, and the surface shear stress τ-110 kgf/mn? After applying torsional sefting so that The values were measured using a static strain meter.

The difference from immediately after the start of the test was defined as the amount of settling and is shown in FIG.

As is clear from Fig. 4, by applying the treatment method according to the present invention compared to the comparative material subjected to conventional rolling and heat treatment, the amount of set-off decreases as the degree of twisting increases, and the degree of twist decreases to 40 degrees. It can be seen that when the above value is reached, the amount of settling becomes constant, and the settling resistance of the steel material is greatly improved and the desired settling resistance can be obtained.

In addition, Table 1 shows the 5I treated with the heat treatment of the present invention.
This figure shows the mechanical properties of IP 7 steel and steel that has been quenched and tempered as rolled. Tensile strength, 0.2% proof stress, and reduction of area were measured using a JIS No. 4 test piece, and impact value was measured using a No. 3 test piece.

As is clear from Table 1, the steel materials subjected to the processing heat treatment according to the present invention have superior mechanical properties compared to the comparative materials.

Furthermore, Fig. 5.6 shows the tensile properties and torsional properties of test pieces treated by the method of the present invention. The tensile strength was measured using a test piece with a flat diameter portion of 7 lengths, and the torsional yield point was measured using a test piece with a parallel portion of 9flφ.

As shown in Figure 5.6, both the tensile properties and torsional properties were significantly superior to the test specimens that were heat-treated while being rolled by applying an appropriate degree of twisting. It has the following.

In this way, the mechanical properties and fatigue resistance of bar-shaped steel materials subjected to processing heat treatment using the method of the present invention were significantly improved due to the increased degree of processing compared to those subjected to conventional post-rolling heat treatment. .

(Effects of the present invention) As described above, the present invention uses twisting for the plastic working of the austenitized workpiece in the processing heat treatment, so that it can be carried out with a small and simple structure, and it can be carried out with a large-scale processing. degree is obtained, thus the mechanical properties,
This is a processing heat treatment method and apparatus that can significantly improve the resistance to fatigue, and will make an extremely large contribution to industry.

[Brief explanation of drawings]

Fig. 1.2 shows an embodiment of the present invention, and Fig. 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. Figure 3 shows a state in which a bar-shaped steel material is twisted, and Figure 4 is a diagram showing the relationship between the degree of twisting and the amount of set.
Figure 5.6 is a diagram showing the relationship between the degree of torsion, tensile strength, and torsional yield point. ■, 2.11.12: Clamp device 3.31: Induction heating device 6.61: Cooling device No. 1
Figure 2 Figure 3 Flash

Claims (5)

[Claims] (1) A bar-shaped steel material is locally heated by induction heating.
The heated part is heated to a temperature above the C3 transformation point, and the heated part is twisted at an angle of 20 to 70 degrees with respect to the axis of the bar-shaped steel material.Then, the processed part is immediately quenched to induce martensitic transformation. A processing heat treatment method characterized by continuously performing processing heat treatment along the longitudinal direction of a rod-shaped steel material, and then subjecting it to tempering treatment. (2) A bar-shaped steel material is locally heated by induction heating.
When heating the steel material to a temperature equal to or higher than the c3 transformation point and twisting the heated part so as to form an angle of 20 to 70 degrees with respect to the axis of the bar-shaped steel material, the heating temperature of the steel material is set to the A of the steel material.
The processing heat treatment method according to claim 1, characterized in that the temperature range is 100° C. higher than the c3 transformation point. (3) A bar-shaped steel material is locally heated by induction heating.
Heating to a temperature above the c3 transformation point, and placing 0.1 kg in the heated part.
While applying a tensile force of f/mm^2 or more and less than half of the yield point at the processing temperature of the steel material, twisting is performed so as to form an angle of 20 to 70 degrees with respect to the axis of the bar-shaped steel material, A process heat treatment method characterized in that a process heat treatment is then carried out in which the processed portion is immediately quenched to cause martensitic transformation continuously along the longitudinal direction of the bar-shaped steel material, and then a tempering process is performed. (4) A clamp device that grips the vicinity of both ends in the longitudinal direction of a steel bar, a device that applies a tensile force to the steel bar, and a device that locally heats the steel bar above its transformation point, and an induction heating device that is movable along the longitudinal direction; a device that applies torsional plastic deformation to the heated portion of the bar-shaped steel material by rotating at least one of the clamp devices; and a cooling device that moves integrally with the induction heating device. A processing heat treatment device characterized by being provided with a device. (5) A clamping device that grips a bar-shaped steel material while applying a tensile force to two points in the longitudinal direction, transfers the bar-shaped steel material in the longitudinal direction, and applies a twist, and locally moves the bar-shaped steel material above the transformation point. 1. A processing heat treatment apparatus comprising: an induction heating device that heats the steel material; and a device that cools the heated portion of the bar-shaped steel material in the vicinity of the heating device.