JP3158384B2 - Moving quenching method for axial workpiece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving quenching method used for surface quenching of an axial work such as a ball screw.
More particularly, the present invention relates to a moving quenching method suitable for surface quenching of a large-diameter axial work having an outer diameter exceeding 100 mm.

[0002]

2. Description of the Related Art Moving quenching is frequently used for the surface quenching of an axial work such as a ball screw from the viewpoint of efficiency and the like. A conventional moving hardening method for a ball screw will be described with reference to FIG. The ball screw 10 has a non-threaded portion 11 at one end and a threaded portion 12 at the other end. The surface quenching is performed in a range from A to B excluding a small portion at both ends of the screw portion 12. That is, A is a quenching start position, and B is a quenching end position.

In the hardening operation, first, the ball screw 10 is horizontally supported by grasping the end of the ball screw 10 on the non-threaded portion 11 side with the chuck 20 and supporting the other end with the roller unit 30 or the like. Next, the high-frequency heating coil 40 called a semi-open saddle coil is positioned at the quenching start position A as shown in the figure, and the output of the heating coil 40 is turned on while rotating the ball screw 10 in this state.

[0004] The heating at the quenching start position A is a kind of preheating for preventing cracking caused by suddenly performing heating for moving quenching, and is called stop heating. And the coil output at the time of stop heating is set lower by the coil output at the time of quenching movement for the purpose.

[0005] When the stop heating is completed, the coil output is increased and the quenching movement of the heating coil 40 is started. As a result, the surface of the threaded portion 12 of the ball screw 10 is sequentially heated from the quenching start position A to the quenching end position B to a temperature equal to or higher than the transformation point. When the main jacket 50 and the after-jacket 60 arranged behind the heating coil 40 reach the quenching start position A, the quenching liquid starts to be ejected from the main jacket 50 and the after-jacket 60. By continuing this, the surface of the screw portion 12 is induction hardened in the range from the quenching start position A to the quenching end position B.

[0006]

According to the moving quenching method, when the outer diameter of the ball screw 10 is about 100 mm, quenching is performed without any trouble. However, its outer diameter is 1
When the temperature exceeds 00 mm and reaches 200 mm, cracks occur in the quenching start portion of the ball screw 10 due to self-cooling after rapid heating when starting quenching movement despite stop heating. I will be. The reason is as follows.

As shown in FIG. 3, in the case of a ball screw 10 having a threaded portion 12 except for the end portion, the end portion on the non-threaded portion 11 side is gripped by a chuck 20, and
For 2, the quenching is usually started from the end on the non-threaded portion 11 side, that is, the end on the chucking side. As the outer diameter of the ball screw 10 increases, the heat capacity of the ball screw 10 increases, and not only the heat given by the stop heating is easily absorbed by the ball screw 10 but also the heat is close to the chuck 20 having a large heat capacity via the non-screw part 11. Easier to escape
As a result, the quenching start portion of the ball screw 10 is not sufficiently heated even by the stop heating. When the quenching movement is started in such a state, the quenching start portion is rapidly heated by the output increase accompanying the start, and induces cracking.

In order to prevent the quenching start portion from cracking due to an increase in output at the start of quenching movement, it is conceivable to increase the heating time and heating output in the stop heating. In such a case, cracking is surely prevented, but the surface temperature of the quenching start portion already exceeds the transformation point at the stage of stop heating, resulting in a so-called overheating state, and the quenching quality of that portion is significantly reduced. For this reason, measures to prevent cracking due to power-up during stop heating cannot be adopted. For this reason, in the case where the outer diameter of the ball screw 10 is large, high-efficiency moving quenching cannot be applied.

The present invention has been made in view of such circumstances, and even when the outer diameter of a shaft-shaped workpiece is large, it is possible to prevent a quenching start portion from being cracked due to an increase in output at the start of quenching movement. Moving and quenching of axial workpieces can avoid deterioration of quenching quality due to overheating of the quenching start part.
The purpose is to provide an entry method .

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for moving and quenching a shaft-like work. The heating coil is located closer to the end, and the axial work is preheated at a low output lower than the coil output during the quenching movement.After this preheating, the heating coil is moved to the quenching start position and subsequently quenched. After performing stop heating at a low output lower than the coil output at the time of movement, the coil output is increased and quenching movement is started.

In the method for moving and quenching an axial workpiece according to the present invention, preheating is performed before stop heating before quenching movement. In particular, the preheating is performed on the end side from the quenching start position. is important. By performing preheating on the end side from the quenching start position before the stop heating, the work surface temperature can be kept low at the quenching start position, so that sufficient preheating can be performed while avoiding overheating. With sufficient preheating, the overall temperature near the quenching start position rises, and as a result, it is possible to prevent cracking due to an increase in output at the start of quenching movement. In addition, since the preheating position is located on the end side from the quenching start position and is located at a portion not subjected to quenching, even if the surface temperature exceeds the transformation point, the quenching quality does not deteriorate.

The preheating position is preferably closer to the quenching start position from the viewpoint of increasing the overall temperature near the quenching start position, but if too close, the work surface temperature at the quenching start position is increased. Therefore, the distance from the quenching start position to the preheating position is 0.2D to 0.2D, where D is the outer diameter of the axial work.
0.5D is preferred.

As a method of increasing the overall temperature near the quenching start position while suppressing the increase in the workpiece surface temperature at the quenching start position, it is effective to perform the preheating twice or more with a pause period. is there. This is because the workpiece surface temperature decreases preferentially during the idle period.

[0014]

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a quenching apparatus showing a step-by-step operation procedure of a moving quenching method according to an embodiment of the present invention, and FIGS. 2A, 2B, and 2C are cross-sectional views of the quenching apparatus. FIG. 3 corresponds to the XX line arrow diagram, the YY line arrow diagram, and the ZZ line arrow diagram.

The shaft-shaped workpiece to be quenched is the above-described ball screw 10 in which one end is a non-threaded portion 11 and the other is a threaded portion 12. The heating coil 40 is a high-frequency heating coil called a semi-open saddle coil (see FIG. 2 (a)). The main jacket 50 is disposed at the rear of the heating coil, and the after jacket 60 is disposed at the rear. I have. As shown in FIG. 2 (b), the main jacket 50 is disposed on the upper side and on both the left and right sides and sprays a large amount of quenching liquid on the surface of the ball screw 10, whereas the after jacket 60 as shown in FIG. 2 (c). A small amount of quenching liquid is sprayed from directly above the ball screw 10. In the following description, the heating coil 40, the main jacket 50 and the after jacket 6 will be described.
0 is synchronously moved in the axial direction of the ball screw 10, but it is also possible to move the ball screw 10 in the axial direction.

In the quenching operation, first, as shown in FIG. 1A, the end of the ball screw 10 on the non-threaded portion 11 side is gripped by the chuck 20, and the other end is supported by a roller unit or the like. The ball screw 10 is supported horizontally. Then
The axial center of the heating coil 40 is located at a preheating position C which is separated from the quenching start position A by a distance L to the non-threaded portion 11 side, that is, the chucking side. Then, in this state, the ball screw 1
The preheating is performed by turning on the output of the heating coil 40 while rotating 0. The coil output at this time is set lower than the coil output during the quenching movement.

By this preheating, the ball screw 10 is heated from the front side around the preheating position C. The heat applied to the ball screw 10 is transmitted to the inside thereof and further transmitted in the axial direction, and the temperature of the directly heated portion does not rise rapidly. However, by continuing this, the temperature of the directly heated portion rises and the quenching start position The area around the direct heating portion including A is entirely heated. Even in such a state, since the quenching start position A is not directly heated, its surface temperature is kept lower than the transformation point, and overheating does not occur. At the preheating position C where the surface is directly heated, the surface temperature rises, but the portion is not quenched, so that there is no problem even if the temperature exceeds the transformation point.

If there is a risk that the surface temperature at the quenching start position A exceeds the transformation point, preheating is stopped halfway,
Preheating is started again after a pause period. Since the surface temperature decreases preferentially during the suspension period, the entire vicinity thereof can be sufficiently heated while suppressing the surface temperature at the quenching start position A.

When the preheating is completed, the heating coil 40 is advanced, as shown in FIG. During the movement of the heating coil 40, heating is stopped. When the heating coil 40 reaches the heating start position A, stop heating is performed at the heating start position A with the heating coil 40 stopped at this position. The coil output at this time is set lower than the coil output during the quenching movement.

In this stop heating, since the entire vicinity of the quenching start position A is sufficiently heated by the preliminary heating, the heat removal of the directly heated portion is small. Therefore, even if the surface temperature does not exceed the transformation point, the quenching start position A can be heated to such an extent that cracks can be prevented. Thus, even when the outer diameter of the ball screw 10 is large, it is possible to prevent cracking due to an increase in output at the start of quenching without deteriorating quenching quality.

When the stop heating is completed, the coil output is increased and the quenching movement of the heating coil 40 is started. Heating coil 40
Moves, the jacket 50 reaches the heating start position A with the movement as shown in FIG. Then, rapid cooling by the jacket 50 is started. When the heating coil 40 further moves, the after jacket 60 reaches the heating start position A as shown in FIG. Then, slow cooling by the after jacket 60 is started. By continuing this, the surface of the screw portion 12 is induction hardened in the range from the quenching start position A to the quenching end position B (see FIG. 3).

Slow cooling by the after jacket 60
This is effective for preventing tempering due to reheating when quenching a work having a large heat capacity such as a large diameter ball screw 10.

As described above, the distance L from the quenching start position A to the preheating position C is preferably 0.2 D to 0.5 D, where D is the outer diameter of the ball screw 10. If the coil output during preheating and stop heating is too high, the surface temperature at the quenching start position A will rise excessively, and if it is too low, the preheating effect will be insufficient. As 0.
3W to 0.5W is preferable. The preheating time, the pause time, and the stop heating time are appropriately selected based on the dimensions of the ball screw 10 and the coil output so that the surface temperature at the heating start position A and the preheating effect are satisfied.

When moving and hardening a ball screw having an outer diameter of 200 mm, preheating-pause-preheating-heating stop and heating coil 40 movement-stop heating-hardening movement were performed. The quenching start position A is 1 mm from the boundary between the non-threaded portion 11 and the threaded portion 12.
The distance L from the quenching start position A to the preheating position C was 50 mm. The first preliminary heating is 150 kW × 15 seconds, the rest period is 30 seconds, the second preliminary heating is 150 kW × 15 seconds, and the stop heating is 150 kW.
× 8 seconds. By the way, the coil output during the quenching movement is 2
80 kW.

The amount of the quenching liquid jetted was 25 L / min for the present jacket and 5 L / min for the after jacket.

Despite the ball screw having a large diameter of 200 mm, cracking due to an increase in output at the start of quenching movement was prevented. The quenching quality was good in the entire quenched part including the quenching start position A. As a result, stable moving quenching of the ball screw became possible.

[0028]

As described above, the method for moving and quenching an axial workpiece according to the present invention includes performing preheating on the end side from the quenching start position before stop heating prior to quenching movement. Accordingly, even when the outer diameter of the shaft-shaped workpiece is large, cracking of the quenching start portion due to the start of the quenching movement can be prevented, and furthermore, deterioration of quenching quality due to overheating of the quenching start portion can be avoided. . Therefore, even for a large-diameter work in which the application of the moving quenching has been hindered due to the cracks or the deterioration of the quality, the application of the moving quenching can be performed, and the quenching operation can be more efficiently performed by the application.

In particular, when the preheating is performed twice or more with the pause period interposed therebetween, if there is a risk that the surface temperature at the quenching start position exceeds the transformation point, the preheating is stopped halfway and the pause period is extended. Preheating is started again after the sandwiching. For this reason, the surface temperature decreases preferentially during the suspension period, so that the entire vicinity thereof can be sufficiently heated while suppressing the surface temperature at the quenching start position.

[0030]

[0031]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a quenching apparatus showing a step-by-step operation procedure of a moving quenching method according to an embodiment of the present invention.

2 (A), 2 (b), and 2 (c) are cross-sectional views of a quenching apparatus, which are shown in FIG. 3 as indicated by arrows XX, YY, and ZZ, respectively. Equivalent to.

FIG. 3 is a configuration diagram of a quenching apparatus for explaining a work procedure of a conventional moving quenching method.

[Explanation of symbols]

 Reference Signs List 10 Ball screw (axial work) 20 Chuck 30 Center pin 40 Heating coil 50 Main jacket 60 After jacket A Quenching start position B Quenching end position C Preheating position

Claims (2)

(57) [Claims] When an external surface of an axial workpiece is axially moved and quenched while leaving an end of the axial workpiece, a heating coil is positioned closer to an end than a quenching start position, and a coil output during the quenching movement is provided. After preheating the shaft-shaped work at a lower power, the heating coil is moved to the quenching start position after this preheating, and after the stop heating is performed at a lower power than the coil output during the quenching movement, the coil is heated. A method for moving and quenching an axial workpiece, wherein the quenching movement is started by increasing the output. 2. The method according to claim 1, wherein the preliminary heating is performed twice or more with a pause period interposed therebetween.