High carbon steel sheet superior in fatiugue lifeand manufacturing method thereof

Abstract

The present invention relates to a high carbon steel sheet that is superior in fatigue life and a method of manufacturing the high carbon steel sheet. The high carbon steel sheet includes about 0.75 wt % to about 0.95 wt % of carbon, smaller than about 1.8 wt % of silicon, about 0.1 wt % to about 1.5 wt % of manganese, about 0.1 wt %˜1.0 wt % of chromium, smaller than about 0.02 wt % of phosphorus, smaller than about 0.02 wt % of sulfur, a residual amount of iron, and inevitable impurities. A layer interval between laminar carbides included in the high carbon steel sheet is smaller than about 0.5 μm. The high carbon steel sheet may include a fine pearlite having a lamellar structure. The fine pearlite included in the high carbon steel sheet may have a volume percentage of larger than about 90%. A ratio of length to width of the lamellar structure may be larger than about 10:1.

Description

TECHNICAL FIELD [0001]Embodiments of the present invention relate to a high carbon steel sheet and a method of manufacturing the high carbon steel sheet. More particularly, embodiments of the present invention relate to a high carbon steel sheet that is superior in fatigue life and a method of manufacturing the high carbon steel sheet.BACKGROUND ART[0002]Recently, a high degree of safety of an automobile has been required. Thus, fatigue life of a spring is also required to manufacture a safe automobile. The fatigue life of the spring is relatively long when the spring operates in an elastic deformation region. As a result, to increase the fatigue life of the spring, yield strength of a material included in the spring is increased to increase the elastic deformation region of the spring. Thereafter, the spring preferably operates within the elastic deformation region.[0003]However, the operation region of the spring is sometimes included in a plastic deformation region according to t...

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Benefits of technology

[0006]Embodiments of the present invention provide a high carbon steel sheet that is superior in terms of fatigue life.

[0017]A high carbon steel sheet according to the embodiments of the present invention has a large amount of laminar carbide having a relatively large ratio of length to width of over about 10:1. Thus, growth of a crack may be efficiently prevented.

[0018]In addition, fatigue life of the high carbon steel sheet may be improved because the growth of the crack is prevented.

[0019]Further, in the case that a spring is formed using the high carbon steel sheet according to the embodiments of the present invention, a generated crack may not easily grow. Thus, the spring may operate for a relatively long time even though the spring operates in a plastic deformation region.

Problems solved by technology

In this case, a crack may be rapidly generated rather than a case where the spring operates in the elastic deformation region.

However, laminar carbide is relatively large and yield strength thereof is not large.

Thus, the fatigue life is not long.

However, in the case that the plastic deformation region is included in an operation region of the spring, the fatigue life decreases in spite of an increase in the yield strength due to the formed and mixed bainite.

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