US 2014/0212660 A1 · MEDIUM CARBON STEEL SHEET FOR COLD WORKING AND METHOD FOR MANUFACTURING THE SAME

Abstract

Disclosed is a medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV when subjected to high-frequency quenching in which a temperature is raised at an average heating rate of 100° C./second, the temperature is held at 1,000° C. for 10 seconds, and a quick cooling to a room temperature is carried out at an average cooling rate of 200° C./second. The medium carbon steel sheet includes, by mass %, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, the balance composed of Fe and inevitable impurities. An average diameter d of a carbide is 0.6 μm or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d (μm) of the carbide and the spheroidizing ratio p % of the carbide satisfy d≦0.04×p−2.6.

Claims11

Dependent claims

A medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV in a case of being subjected to high-frequency quenching in which a temperature is raised at an average heating rate of 100° C./second, the temperature is held at 1,000° C. for 10 seconds, and a quick cooling to a room temperature is carried out at an average cooling rate of 200° C./second, the medium carbon steel sheet comprises, by mass %,

C:
0.30 to 0.60%,
Si:
0.06 to 0.30%,
Mn:
0.3 to 2.0%
P:
0.030% or less
S:
0.0075% or less,
Al:
0.005 to 0.10%,
N:
0.001 to 0.01%, and
Cr:
0.001 to 0.10%,
and a balance composed of Fe and inevitable impurities, wherein
an average diameter d of a carbide is 0.6 μm or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d (m) of the carbide and the spheroidizing ratio p % of the carbide satisfy d≦0.04×p−2.6.

15 more elements

The medium carbon steel sheet for cold working according to 1 or 2,

wherein the medium carbon steel sheet further includes a surface treatment film that contains a chemical composition derived from a silanol bond that contains a metal component X and is expressed by Si—O—X, a heat-resistant resin, an inorganic acid salt and a lubricant on at least one surface,
the surface treatment film has a concentration gradient for each of the chemical composition in a film thickness direction, and has three layers including an adhesion layer, a base layer, and a lubricant layer, wherein the three layers are positioned in order from an interface between the surface treatment film and the medium carbon steel sheet for cold working of the adhesion layer, the base layer and the lubricant layer,
the adhesion layer contains largest amount of the chemical composition derived from the silanol bond among the three layers, and has a thickness of 0.1 nm to 100 nm,
the base layer contains largest amount of the heat-resistant resin and the inorganic acid salt among the three layers, contains 0.01 to 0.10 parts by mass of the inorganic acid salt to 100 parts by mass of the heat-resistant resin, and has a thickness of 0.1 μm to 15 μm,
the lubricant layer contains largest amount of the lubricant among the three layers, and has a thickness of 0.1 μm to 10 μm, and
a ratio of the thickness of the base layer to the thickness of the lubricant layer is 0.2 to 10.

3 more elements

Dependencies are inferred from the claim text.

Medium carbon steel sheet for cold working and method for manufacturing the same

Life of this patent

Medium carbon steel sheet for cold working and method for manufacturing the same

Life of this patent

Abstract

Claims11