JPH11302789A - Hyper-eutectoid steel for sliding member excellent in wear resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the abrasion loss of the mating material in hyper-eutectoid steel at the time of sliding, to increase its utilizability as a sliding member and to provide an inexpensive sliding member. SOLUTION: In hyper-eutectoid steel, quenching and tempering are executed to obtain the hardness of 40 to 65 HRC required as that of a sliding member, the average grain size of residual carbides after the quenching is regulated to <=0.20 μm, and the fine residual carbides are uniformly dispersed to suppress the abrasion of the mating material at the time of sliding and furthermore to improve the wear resistance of itself. For this purpose, after working into parts after spheroidizing, quenching treatment is executed after bainitic treatment shown in the fig. to disperse the residual carbides having <=0.20 μm average grain size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hypereutectoid steel excellent in wear resistance suitable for a sliding member.

[0002]

2. Description of the Related Art For sliding parts, alloy cast iron (for example, Mo-Ni-Cr alloy cast iron) is often used as a wear-resistant material. In addition, high carbon chromium bearing steel (JIS SU
Hypereutectoid steels such as J1-5) and carbon tool steels (JIS SK1-7) can easily obtain the required hardness by quenching and tempering, and hard carbide remains after quenching and tempering. Therefore, it has excellent wear resistance and can be used as a sliding part.

[0003] For example, high carbon chromium bearing steel can be manufactured by hot rolling a steel ingot from a steel ingot melted in a general electric furnace or a converter. With such a shape, it is possible to manufacture the ring by cutting the steel pipe at a relatively low cost, as compared with the case where the ring is manufactured by casting like an alloy cast iron. However, when high-carbon chromium bearing steel is used as the sliding member, the wear of the mating material during sliding may be reduced by the structure obtained by quenching and tempering from the spheroidized annealed structure as used in ordinary bearings. There was a problem of intense.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hypereutectoid steel in which the amount of wear of a mating material during sliding is suppressed, the utility as a sliding member is increased, and inexpensive sliding members are used. It is to provide a moving member.

[0005]

According to the present invention, there is provided a hypereutectoid steel which is quenched and tempered to obtain a hardness of 40 to 65 HRC required as a sliding member. By reducing the average particle size of the residual carbide after quenching to 0.20 μm or less and uniformly dispersing the fine residual carbide, the wear of the mating material during sliding is suppressed, and the self-wear resistance is improved. It is.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The residual carbide diameter after quenching is 0.20
When it is less than μm, the aggressiveness of the residual carbide to the counterpart material during sliding is small, and the amount of wear of the counterpart material can be reduced. Further, as the residual carbide diameter becomes smaller, the average interval between the residual carbides becomes smaller, and the hard residual carbides are uniformly dispersed, so that the wear resistance is improved.

When the average particle size exceeds 0.20 μm,
The aggressiveness of the residual carbide on the counterpart material increases, and the wear amount of the counterpart material increases. Further, the average interparticle distance of the residual carbides increases, and the wear resistance deteriorates.

[0008] In hypereutectoid steel, spheroidizing annealing is performed in order to improve workability at the time of forming parts, and quenching and tempering treatment is performed on the spheroidized carbide structure.

Usually, the quenching of the hypereutectoid steel is performed at a temperature in the two-phase region of austenite + cementite, so that carbide remains. At the time of quenching, since the spheroidized carbide after annealing becomes a supply source of carbon, the particle size and number of residual carbides are
Determined by previous organization. In order to improve the wear resistance and reduce the wear of the mating material during sliding, it is necessary to make the structure before quenching a fine carbide in order to obtain fine residual carbides. Therefore, hypereutectoid steel pays attention to the fact that fine carbides are uniformly precipitated by bainite transformation,
After the spheroidizing annealing, at the time when the processing for forming parts is completed, a bainite transformation process is performed, and then a quenching process is performed.

Thus, after quenching, the average particle size is 0.20 μm.
m or less can be easily obtained. Further, in the subsequent tempering treatment, the hardness can be easily adjusted, and a sliding part having excellent wear resistance can be obtained at low cost.

[0011]

EXAMPLE An example in which the test material is JIS SUJ2 will be described. After vacuum-melted SUJ2 was rolled by hot rolling and subjected to spheroidizing annealing, a test piece was prepared by cutting. Thereafter, the working steel was subjected to a solution temperature of 1 as shown in FIG. 1 in order to obtain fine carbides as a structure before quenching.
After holding at 050 ° C. for 20 minutes to dissolve carbides, bainite transformation was performed at a bainite transformation temperature of 450 ° C. for 60 minutes, followed by holding at a quenching temperature shown in FIG. 2 for 20 minutes, followed by oil quenching. Then, the steel sheet was kept at a tempering temperature for 90 minutes and air-cooled to perform a tempering treatment.

After cutting, the comparative steel was subjected to a quenching and tempering treatment shown in FIG. The residual carbide after quenching is
5 fields of view at 5,000 times by EM (total area 0.00139m)
m ² ) was photographed, and the average carbide particle size was measured with an image analyzer. 3 and 4 show microstructures of the steel of the present invention and the comparative material after quenching.

Abrasion test 1 In the Ogoshi type abrasion test, the rotating ring was used as the working steel and the comparative steel, and the plate as the mating material was used as the tool steel SKH51.
The wear amount of SKH51 was measured, and the aggressiveness to the partner material was evaluated. The hardness of the plate material SKH51 is 62.3.
HRC. The experimental conditions are described below.

Experimental conditions Wear distance: 600 m Wear speed: 0.054 m / sec, 0.099 m / sec, 0.173 m / sec, 0.058 m / sec, 0.63 m / sec, 1.14 m / sec Final load: 6.3kg

Quenching and tempering conditions for the working steel and the comparative steel;
Table 1 shows the hardness and average residual carbide diameter. Table 2 shows the experimental results. The aggressiveness to the mating material was evaluated with the amount of wear of the mating material as 100 when the comparative steel was a ring.

[0016]

[Table 1]

As shown in Table 2, when the working steel is a ring, the specific wear of the plate material is smaller than that of the comparative steel, and the working steel has less aggressiveness to the mating material during sliding. It can be seen that this is suitable for a sliding member.

[0018]

[Table 2]

Wear test 2 In the Ogoshi type wear test, the rotating ring was JIS SCM
420, using the plate as the mating material as the working steel and the comparative steel, the wear amount of the plate was measured, and the self-wear resistance was evaluated.

Quenching and tempering conditions for the working steel and the comparative steel;
Table 3 shows the hardness and average residual carbide diameter.

[0021]

[Table 3]

Table 4 shows the evaluation results when the specific wear amount of the comparative steel was set to 100. It should be noted that the rotating ring material SCM420
Had a hardness of 90.5 HRB. The experimental conditions are described below.

Wear distance: 200 m Wear speed: 0.054 m / sec, 0.099 m / sec, 0.173 m / sec, 0.308 m / sec, 0.63 m / sec, 1.14 m / sec, 1.97 m / sec sec, 3.62m / sec Final load: 6.3kg

As shown in Table 4, it can be seen that the working steel has a smaller specific wear amount than the comparative steel and has excellent wear resistance.

[0025]

[Table 4]

[0026]

The steel of the present invention is formed into a product after spheroidizing and annealing a hypereutectoid steel, and is subjected to a quenching treatment after a bainite treatment, so that residual carbide having an average particle size of 0.20 μm or less can be obtained. Evenly dispersed. Therefore, when the steel of the present invention is used as a sliding material, the wear of the mating material during sliding can be suppressed, and the wear amount of the mating material can be reduced. Further, the hard carbides are uniformly dispersed with a small average spacing of the remaining carbides, and the hardness is 40 to 65 HRC, so that the wear resistance is excellent. INDUSTRIAL APPLICABILITY The present invention has excellent effects such as high availability of a hypereutectoid steel as a sliding member and an inexpensive sliding member can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature pattern of a bainite transformation process in the present invention.

FIG. 2 shows the results after the bainite transformation treatment in the present invention.
(A) is a figure which shows a quenching temperature pattern, (b) is a figure which shows a tempering pattern.

FIG. 3 is a micrograph showing the microstructure of a steel according to the present invention.

FIG. 4 is a micrograph showing a microstructure of a comparative steel.

Claims (1)

[Claims] 1. The average residual carbide diameter after quenching is 0.20 μm.
A hypereutectoid steel for sliding members having a hardness of 40 to 65 HRC after quenching and tempering and having excellent wear resistance.