Steel for wheel

Abstract

There is provided steel for wheel having a chemical composition consisting of, by mass percent, C: 0.65 to 0.84%, Si: 0.02 to 1.00%, Mn: 0.50 to 1.90%, Cr: 0.02 to 0.50%, V: 0.02 to 0.20%, and S: 0.04% or less, in which 34≦2.7+29.5×C+2.9×Si+6.9×Mn+10.8×Cr+30.3×Mo+44.3×V≦43, and 0.76×exp(0.05×C)×exp(1.35×Si)×exp(0.38×Mn)×exp(0.77×Cr)×exp(3.0×Mo)×exp(4.6×V)25, the balance being Fe and impurities, and the impurities containing P: 0.05% or less, Cu: 0.20% or less, and Ni: 0.20% or less. This steel for wheel is excellent in balance between the wear resistance, rolling contact fatigue resistance and the spalling resistance, and can give a long life to the wheel.

Description

TECHNICAL FIELD[0001]The present invention relates to steel for wheel. More particularly, the present invention relates to steel for wheel that is suitable as a material for a high-hardness wheel for railroad, the material being excellent in wear resistance, rolling contact fatigue resistance, and spalling resistance.[0002]Spalling is a phenomenon that a portion of wheel, when heated and rapidly cooled by emergency braking or the like, is transformed into brittle martensite called a white layer, from which a crack propagates, and the white layer is subjected to brittle fracture and peels off. This phenomenon is also called a “thermal crack” in some cases.BACKGROUND ART[0003]In recent years, with a worldwide increase in running distance and loading capacity, a wheel for railroad (hereinafter, also referred to as a “wheel”) having a service life longer than before has been demanded.[0004]There are three phenomena that mainly cause damages to a wheel: (i) wear, (ii) rolling contact fat...

AI Technical Summary

Benefits of technology

[0075]The steel for wheel in accordance with the present invention is excellent in balance between the wear resistance, rolling contact fatigue resistance and the spalling resistance, and can give a long life to the wheel. Specifically, for the wheel that uses the steel for wheel in accordance with the present invention as a material, the amount of wear decreases by 10 to 35% and the rolling contact fatigue life increases to 1.4 to 3.2 times as compared with the wheel that uses the railroad wheel steel of “Class C” of AAR, and spalling is less liable to occur. Therefore, the steel for wheel in accordance with the present invention is extremely suitable as a material for a railroad wheel used in a very harsh environment of increased running distance and increased loading capacity.

Problems solved by technology

There are three phenomena that mainly cause damages to a wheel: (i) wear, (ii) rolling contact fatigue, and (iii) spalling.

Especially in recent years, an increasing number of wheels have been damaged by wear resulting from the increase in running distance and by rolling contact fatigue resulting from the increase in loading capacity.

Empirically, it is known that the wear resistance and the rolling contact fatigue resistance are properties that are incompatible with the spalling resistance.

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