JPS58171525A - Heat treating method of inside spiral groove - Google Patents

Abstract

PURPOSE:To perform a heat treatment of an inside spiral groove having high wear resistance, by removing a laser light absorbent painted to the spiral groove cut at inner surface of a pipe shape part only at the top part of the groove before the laser light irradiation. CONSTITUTION:A laser light 4 is irradiated to the spiral groove 2 cut at inner surface of a pipe 1. The light 4 is oscillated from a laser oscillator 3, advanced for the axis direction of the pipe 1 by a reflecting mirror 6 and condenced to the groove 2 by a condencing mirror 7. Thus the hardening treatment of the groove 2 is performed with rotating the mirror 7 by a rotating apparatus 9 attached to a guide 8 coincident to the groove 2. In this hardening treatment, the laser light absorbent painted to the groove is removed only at the top part of the groove 2 before the laser light irradiation. Thereby, this part is not overheated and melted during the quenching, the top part of the groove can be heated to the quenching temp. by the heat conduction from the heated bottom part, and whole of the groove 2 can be quenched uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for heat treating a spiral groove on the inner surface of a pipe using laser light.

(b) As is well known in the prior art, the female thread serves as a guide for converting the rotational motion of the male thread into linear motion, and it can be used for movement, traction, etc.
It performs tightening and other various control drives.

In this case, the allowable dimensional tolerance of the female thread and male thread is #1, which allows accurate control and drive.

However, if you use it for a long time, the contact surface of the screw will wear out. Due to wear, the contact area and dimensional tolerance between the female thread and the male thread change, rounding occurs, and errors occur in the initially precise control drive, making it impossible to obtain dimensional and precision. Therefore, stress concentration areas such as contact surfaces and threaded corners are required to have high strength and excellent wear resistance.

By the way, in the case of male threads, the surface can be easily hardened using conventional heat treatment methods. However, since the female thread has a complicated shape, it is extremely difficult to harden the surface of a desired portion.

Usually, a method has been considered in which a hard Or plating treatment is applied to the rounded grooves of the nine-screw grooves machined on the inner surface of the pipe-shaped member to improve the wear resistance, thereby increasing the strength. However, increasing strength through plating is often subject to certain limitations, ie.

In the case of plating, the thicker the plating is, the better, considering the wear of the material during use, but it is extremely difficult to control a part with a complex shape, such as a female thread, to a uniform thickness. In particular, when there are irregularities such as a screw, the plating thickness tends to be thinner in the recesses where stress is concentrated, and it is actually extremely difficult to obtain the appropriate thickness. Furthermore, in the case of plating, the working environment is deteriorated because harmful processing liquids are used.

i5 et al. 5 Surface hardening treatment methods include conventional quenching. This quenching method involves heating the whole or part of the product and quenching it in water or oil, which tends to cause quench cracking and deformation.Furthermore, the shape of the product is unique, so the work requires skill and is difficult to implement in practice. There are many problems.

It is also conceivable to use a material with high wear resistance and omit heat treatment of the threaded portion, although this is disadvantageous in terms of cost. but,
In the machining stage of such materials, the base material itself is hard and the rounding efficiency and machining accuracy are reduced, making the manufacturing method difficult and increasing the number of manufacturing steps.

(C) Purpose of Development v4 In view of the above points, the present invention provides a heat treatment method for an inner spiral groove that quickly hardens the inner spiral groove surface without melting the corners of the groove head and has high wear resistance. The purpose is to provide

(d) Summary of the Invention The present invention is characterized in that only the top part of the laser light absorbent applied to the spiral groove is removed before laser light irradiation.

(e) Examples of the invention An embodiment of the present invention will be described below with reference to the drawings.

A spiral groove (
A laser beam 4 oscillated from a laser oscillation device I13 is reflected by a nine-reflector member (6) which is supported by a suitable frame 5 so as to proceed in the axial direction of the pipe 1 (including the IT part and the bottom part). The laser beam reflected by the reflecting mirror 6 travels in the axial direction of the pipe 1 and is focused by the condensing mirror 7 onto the groove 2 spirally machined on the inner surface of the pipe 1, thereby hardening the surface of this part. Process. Here, the focusing mirror 7 is rotated by a rotating device 9 attached to a guide 8 that engages in the groove 2. Here, the rotating device 9 is configured to engage the groove 2 to be hardened and rotate the round guide 8 to move it in the rolling direction. Also, the reflecting mirror 6 is arranged so that the center of the condensing point 1 condensed by the condensing mirror 7 becomes the groove 2.
If the is installed, the converging point of the laser beam will be the
As it rotates, it rotates along the groove 2, and the surface hardening treatment of the groove 2 and the head can be performed continuously. The size of the laser focal point at this time differs from the size K of the screw to be heated, but generally it is slightly larger than the width of the groove, so that the outer periphery of the laser focal point partially touches the screw head. Adjust the size of the focal point so that it hits the As the rotating device 9, it is preferable to use a direct current motor that can accurately control the rotational speed.The portion to be hardened is coated with a laser light absorbing agent (for example, graphite type).

In the actual surface hardening process, the position of the p% rotation device 9, the ON/OFF state of the laser beam, the generation time, etc. are controlled by the control device 10.

As described above, the groove 2 on the inner surface of the pipe 1 is hardened, but in actual work, it is extremely difficult to harden the bottom and the head of the groove 2 at the same time. That is, if only the bottom part is hardened.

The head part is not sufficiently hardened, and if you try to harden the head part, the bottom part will likely not be hardened enough.

If you try to harden the head and bottom parts at the same time, there is a risk that a part of the corner of the head part will melt. Due to partial melting of the head, the quenching quality of this part becomes unstable,
In addition, the shape of a part of the corner changes due to melting, which increases the number of finishing steps. Therefore, it is desirable to remove the laser light absorbent applied to the hardened part only at the head of the groove 2 before hardening. The laser light absorption rate in this part has bottomed out,
It is not stupid and will not overheat and melt during quenching.
The head of the groove 2 is heated to the quenching temperature tC by heat transfer from the heated bottom, and the entire groove 2 is uniformly heated without any partial melting. As is well known, since laser light is a heat source with extremely high energy density, the groove 2 is heated in a short time.

The heat is absorbed by the base material, which remains at a low temperature, through thermal diffusion.
For example, the heated part is rapidly cooled and the surface hardening process is completed without using a coolant such as water.

(f) Other embodiments As shown in FIG. ing.

(g) Effects of the Invention As described above, according to the present invention, (1) The surface of the grooved surface of pipes, etc., which are machined into the inner surface and have round grooves, which was considered to be extremely sharp with conventional plating and heat treatment techniques. This hardening process is made possible by applying laser light, making it possible to manufacture pipes with high wear resistance.

(2) The width and depth of the surface hardening process can be adjusted by changing the rotational speed of the condenser rotating device, the beam output, and the spot diameter at the condensing point, making it easy to set the heat treatment conditions. The quality is also stable and the reproducibility is good, so it does not require any skill and can be automated.

(3) By irradiating the laser beam to harden the surface, the heat from the laser beam is absorbed by the base material at room temperature, so it can be rapidly cooled and hardened without using a coolant such as water. Since the work is completed, the change in the shape of the escaped part is small and there is no need for t.
It is not necessary to take the finishing allowance to the extent that it is possible, but even if it is necessary, only a very small amount of processing is required, which can significantly reduce the number of manufacturing steps.

(4) Laser light has high energy density, heating time is extremely short, and can be used continuously even on objects with complex shapes, so it can quickly harden surfaces and perform high-temperature work unlike conventional heat treatment. This improves the work environment.

(5) The work environment is improved because the hardening process shown in Table 1 can be performed without handling processing liquids that are harmful to the human body, unlike plating processes.

(6) By removing the laser light absorbent on the head of the threaded part before laser irradiation, it is possible to stabilize the quality without partial melting and to harden the spiral grooves on the inner surface of the pipe. can.

[Brief explanation of the drawing]

FIG. a11 is a block diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a device different from that in FIG. 1. 1... Pipe, 2... Spiral groove 3...
Laser oscillator, 7... Concentrating mirror ('131'l
) Agent: Patent attorney Kensuke Norichika C and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] In the case where the inner spiral groove is irradiated with laser light to form a hardened layer, the inner spiral groove Klk cloth is applied to the middle head of the laser light absorber and removed before the laser light irradiation. A method for heat treatment of an inner spiral groove characterized by: