JPS58189327A - Production of track bushing - Google Patents

Abstract

PURPOSE::To provide a track bushing having an outside circumferential surface which is excellent in wear resistance and an inside circumferential surface which is excellent in fatigue strength, by forming carbon steel contg. an element for improving hardenability to the track bushingand hardening the entire part then hardening only the inside circumferential surface further by induction heating. CONSTITUTION:Steel which contains 0.55-1.1% C, and if necessary, contains an element for improving hardenability such as Mn, Ni, Cr, Mo or the like is used as a raw material and is worked to a prescribed shape of a track bushing. The bushing is heated to 850 deg.C and is held for 0.5hr, whereafter the bushing is subjected to oil guencling then to tempering for 3hr at 180 deg.C. A hardened layer 7 of >=60 Rockwell hardness is formed over the entire part of the bushing by said hardening. An inside circumferential surface 8 is hardened by high frequency induction heating of 30KHz frequency, and during said time, a softened layer 9 which is tempered by the heat in the stage of induction heating is formed. The track bushing having the outside circumferential surface which is high in hardness and is excellent in wear resistance and the inside circumferential surface 8 which is excellent in fatigue strength is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a track bushing used for an oil-filled crawler track of a tracked construction machine.

The outer circumferential surface of this plum track bushing engages with the starting wheel (sprocket) and transmits traction force, so the outer circumferential surface must be wear resistant.

Fatigue strength is required on the inner eight surfaces. Also, recently a gap has been added between the pin and the track bushing.

Oil-filled crawlers are often used in which oil is filled in this gap. In this case, the dust seal comes into contact with the end face of the bushing to withstand the oil and prevent earth and sand from entering the gap. , small roughness in the buttish direction and wear resistance are required.

In order to satisfy the above-mentioned properties of truck bushings, the bushings are manufactured as follows.

In other words, the inner and outer surfaces are processed using hardened steel.

Then, carburizing and quenching is performed, and then the end faces are polished and lapped. As shown in Figure 1, the track bushing manufactured in this way has a hardened layer 1 of 2 to 3 m thick around the outer circumference of its cross-sectional shape. This hardened layer 1 has an outer periphery of the cross-sectional shape, that is, an outer periphery,
The inner circumference and both ends have approximately the same thickness, and the hardness distribution is K as shown in the second figure. On the other hand, for the wear resistance of the outer circumferential surface of the track bushing, it is desirable to have a thick hardened layer on the outer circumferential surface.

This requires increasing the carburizing time to 1! The cost of R construction will be high.Also, if the inner peripheral surface is oil-filled, it will hardly receive any single track, so it would be sufficient to have hardening 1 to maintain the fatigue strength.

In the conventional manufacturing method described above, a hardened layer is formed on this inner circumferential surface as well as on the outer circumferential surface.

The present applicant had previously proposed a method for manufacturing track bushings for crawlers as shown in Japanese Patent Application No. 47-106613 (Japanese Patent Publication No. 55-31171). First, a cylindrical track bushing is roughly machined using high carbon high chromium steel, and the rough machined track bushing is heat treated to a value lower than the specified Rockwell hardness, and then finished and machined into the specified size and shape. Then, the inner and outer peripheries are induction-heated and quenched using different electric powers to give the inner periphery a Rockwell hardness of 50 to 60.

Harden the outer surface to a Rockwell hardness of 60 or higher.
Although the inner and outer eight surfaces of the bushing can be made to a predetermined hardness, it is not possible to increase the hardness of both end surfaces. For this reason, in order to make the track bushing manufactured by the above manufacturing method suitable for oil-filled belts, it is necessary to add induction heating hardening of the bushing end face, m-curve grinding, and lapping finishing to the above manufacturing process. 0. Fig. 3 shows the hardening pattern of the track bushing manufactured by the above manufacturing method, with hardened layers 2 * 3 a 4 t on the inner and outer peripheral surfaces and both end surfaces.
5 has been generated. 6 is a pusher: a dust seal that is in contact with the L end face at an angle of m.

The present invention was developed in view of the above, and has a thick hardened layer with excellent corrosion resistance on the outer peripheral surface, and a relatively thin hardened layer on the inner peripheral surface to improve fatigue strength. Furthermore, after processing the track bushing into a predetermined shape, which can maintain the hardness of the end surface of the bushing that comes into contact with the dust seal with a Rockwell hardness of 60 or higher, the entire bushing is hardened and internally N!
A track bushing that can be obtained by performing two heat treatments of IJ surface quenching, and can significantly reduce the manufacturing cost of track bushings suitable for oil-filled crawler tracks filled with lubricating oil. The purpose of this paper is to provide a method for manufacturing.

The present invention will be explained in detail below.

As for the material, a copper material containing Mn, Ni, Cr, and Me is used as necessary to improve the hardenability of the carbon lid α55 to I1gk. Then, this material is processed into a predetermined shape of a track bushing, and then the entire material is hardened to a Rockwell hardness of 60 or more.

Next, only the inner peripheral surface is induction hardened.

Afterwards, the end faces are ground and lapped. The hardened pattern of the track bushing made in this way is as shown in Figure 4, with a hardened layer 7 formed by hardening the entire surface on the outer circumference and both end faces, and a hardened layer 7 on the inner circumference. Hardened layer 8 by induction heating quenching on the surface
During this time, Ni9 is softened by the heat during induction heating and then tempered. Of both the hardened layers 7 and 8, the hardened layer 7 on the outer peripheral side is thick, and the hardened layer 8 on the inner peripheral side is thin. The hardness distribution in the cross-sectional direction is as shown in Figure @5.

The example materials are Cα78%, Siα49fa, Mts
1.27%.

This material was processed into a predetermined shape using α8-〇 steel with 50% Crα, heated at 8°C, held for 05 hours, oil quenched, and tempered at 180°C for 3 hours. By this whole hardening, the entire bush had a hardness of 60 J:l or higher. Next, the inner circumferential surface was hardened using an induction heating hardening device with a frequency of 3 Q KHz. The hardness distribution thus obtained was as shown in FIG. In the figure, A is a hardness distribution curve obtained by the method of the present invention, and B is a hardness distribution curve obtained by conventional carburizing and quenching. Figure 7 shows the results of a bench fatigue test for truck bushings.C in Figure 1 shows the number of repetitions until cracking occurs with respect to the applied load.
The truck bushings manufactured by the method of the present invention are
cD indicates the case of track bushings manufactured by conventional carburizing and quenching.2 It can be seen that the track bushings manufactured by the method of the present invention are even more resistant to applied loads. With carbon 11, it is impossible to obtain a Rockwell hardness of 60 or more at α55 or less,
If it exceeds 1.1%, quench cracking will occur, so 1# is α
55 to II% is suitable ◎As described above, the present invention
Contains carbon content of α55 to 1.1%, and M%, Ni, Cr, as necessary to improve hardenability.
After processing a cylindrical track bushing into a predetermined shape using a steel material containing Mo, the whole is quenched, and then only the inner circumferential surface is quenched by rice conduction heating, so the outer circumferential part has abrasion-resistant properties. An excellent, relatively thick hardened layer can be created, and a relatively thin hardened layer can be applied to the inner fiber part to improve fatigue strength.Furthermore, both ends can be quenched as a whole to provide the specified hardness at the same time as the outer 8 parts. By performing the heat treatment twice, that is, whole hardening and inner periphery hardening, it is possible to significantly reduce the manufacturing cost of a track bushing suitable for an oil-filled crawler track.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the hardening pattern of a track bushing manufactured by a conventional method, Fig. 2 is a hardness distribution diagram thereof, and Fig. 3 is a cross-sectional view showing a hardening pattern of a track bushing manufactured by a conventional method. Figure 4 is a sectional view showing the hardening pattern of the track bushing manufactured by the method of the present invention, Figure 1m5 is its hardness distribution diagram, 516
The figure is a hardness distribution diagram in an example of the present invention, and Figure 7 is a diagram showing bench fatigue test results.
Komatsu Manufacturing Representative Patent Attorney Masaaki Yonehara Patent Attorney Tadashi Hamamoto

Claims (1)

[Claims] The carbon content is 055 to 1.1-, and Kn, A', Cr is added as necessary to improve hardenability.
. After processing a cylindrical track bushing into a predetermined shape using a steel material containing ITS, the whole is quenched. After that, only the inner peripheral surface is induction-hardened.