JPS6237691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment method for hardening crawler linking pins by high-pressure spray hardening.

The track connecting pins used in conventional tracked vehicles are
The aim was to improve the wear resistance, bending fatigue strength, and toughness of medium carbon, low alloy steels such as medium carbon steel, SCB, and SCM steel by subjecting them to material thermal refining and induction hardening.

However, the conventional method described above requires many heat treatment steps, which requires a lot of time and expense, and
Current induction hardening equipment does not have sufficient hardening capacity, resulting in problems such as the inability to use inexpensive materials and the inability to improve quality.

This invention was made with the aim of improving this problem, and is a track connection in which a track connection pin made of medium carbon steel is heated to a hardening temperature and then subjected to high-pressure spray hardening while being rotated by rolling spray or the like. The present invention provides a method for heat treating pins so that high-quality crawler linking pins can be obtained at low cost with a small number of heat treatment steps.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Medium carbon steels used as materials for the track connecting pins include S30C (0.33% C) and S35C (0.38% C).
C), S40C (0.39%C), S45C (0.43%C) S50C
(0.49% C), S55C (0.54% C), etc., using one or more of the above medium carbon steels, a track connecting pin with a diameter of 48.5 mm and a length of 294 mm is manufactured, and this is quenched at a temperature of 820 mm. After heating to ~850°C, high-pressure spray hardening is performed by pressurizing the peripheral surface while rotating with a rotating pressurizing means. The rotary pressure means is, for example, a rolling spray as shown in FIGS. 1 and 2, and a pair of receiving rollers 3, which are rotated in the same direction by a drive source 2, are supported on the bed 1. A workpiece to be rotated and pressed, that is, a crawler belt connecting pin 4 is placed on the receiving roller 3. Further, a pressure roller 6 is provided above the receiving roller 3 and is movable up and down by a pressure sill 5, and this pressure roller 6 applies pressure to the outer peripheral surface of the track connecting pin 4 on the receiving roller 3. I'm starting to be able to do it.

On the other hand, spray nozzles 7 are provided on both sides of the crawler linking pin 4, which are located diagonally above and with the spout 7a facing the track linking pin 4 side. ~
High-pressure water of 10 kg/cm ² is jetted toward the track connecting pin 4 at a rate of 0.5 to 3 tons per minute.

That is, the crawler linking pin 4 heated to the heat treatment temperature is placed on the receiving roller 3 of the rotary pressure means and rotated at a speed of 60 to 250 γpm per minute, while at the same time the pressure roller 6 is applied with a pressure of 0.1 to 2.5 γpm. Pressure was applied to the circumferential surface of the track connecting pin 4 with a pressurizing force of 1,000 tons, and in this state, high pressure water of 2 to 10 kg/cm ² was sprayed from the spray nozzle 7 toward the track connecting pin 4 to perform quenching.

When the surface hardness of the track connecting pin 4 obtained by the above heat treatment was measured, results as shown by curve A shown in FIG. 3 were obtained. For comparison, curve B in the figure shows the hardness of a similar crawler linking pin subjected to induction hardening.

As is clear from the above results, the track connecting pins heat treated by the method of the present invention have higher surface hardness than those subjected to induction hardening, and this tendency is more pronounced on the low carbon side.

Further, FIG. 4 shows the hardening depth of the track connecting pin obtained by the method of the present invention, and it is clearly seen that a sufficient hardening depth was obtained by high-pressure water spray hardening.

Furthermore, Fig. 5 shows the surface residual stress of the track connecting pin obtained by the same method as above, and it shows that a significantly higher compressive residual stress is acting on the surface compared to the one that has been induction hardened (curve B). , this can be expected to significantly improve fatigue strength.

On the other hand, Fig. 6 compares the bending fatigue strength of track connecting pins made of S45C and S55C after high-pressure water spray hardening and induction hardening. , the lifespan is more than three times longer than that of induction hardened ones, and based on the above results, the materials currently used for track connecting pins (S50C ~
This makes it possible to reduce the carbon content of S55C), thereby reducing susceptibility to quench cracking and improving toughness.

[Brief explanation of the drawing]

Fig. 1 is a front view of the rotating pressurizing means used in the method of the present invention, Fig. 2 is a side view of the same, Fig. 3 is a diagram showing the surface hardness of the track connecting pin obtained by heat treatment, and Fig. 4 5 is a diagram showing the quenching depth, FIG. 5 is a diagram showing the surface residual stress, and FIG. 6 is a diagram showing the bending fatigue strength.

Claims (1)

[Claims] 1. A crawler linking pin is manufactured using medium carbon steel with a carbon content of 0.35 to 0.55%, and after this track linking pin is heated to a hardening temperature, the outer circumferential surface is pressurized while rotating with a rotary pressurizing means. A method for heat treating a track connecting pin, characterized in that the track connecting pin is quenched by spraying high-pressure water onto the surface thereof.