Austenitic stainless steel sheet

A soft nitriding part, non-quenching and tempering technology, applied in the direction of centrifugal force-resistant rotating parts, furnace types, bearings, etc., can solve problems such as surface cracks, and achieve high bending fatigue strength and excellent bending correction effect.

CN107075628AActive Publication Date: 2017-08-18NIPPON STEEL CORP +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2017-08-18

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Abstract

A non-tempered soft-nitrided component that comprises a base steel material having a chemical composition which comprises, in terms of mass%, 0.35-0.50% C, 0.10-0.35% Si, 2.3-2.8% Mn, up to 0.10% S, 0.0030-0.0250% N, 0-1.0% Cu, 0-0.3% Mo, 0-0.5% Ni, 0-0.020% Ti, and Fe and impurities as the remainder and which satisfies 3.10 <= (0.316C+0.122)*(0.7Si+1)*(5.1Mn-1.12)*(0.364Ni+1)*(2.16Cr+1)*(3Mo+1) <= 6.00, the impurities including P, Al, and Cr in amounts of up to 0.08%, up to 0.05%, and less than 0.20%, respectively. In the non-tempered soft-nitrided component, a stress concentration part has a hardness HV, as measured at a depth of 0.05 mm from the surface, of 410-480 and a hardness HV, as measured at a depth of 1.0 mm from the surface, of 200 or greater and has a compound layer depth of 5 [mu]m or less. The metallographic structure of the base steel material is a bainite structure. The non-tempered soft-nitrided component has excellent straightenability and high fatigue strength.
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Description

technical field

[0001] The invention relates to non-tempered nitrocarburized parts. More specifically, it relates to a non-tempered nitrocarburized part having high bending fatigue strength and excellent bending straightening properties.

[0002] "Non-tempered nitrocarburized part" refers to a part that is subjected to nitrocarburized treatment without undergoing the so-called "tempering treatment", that is, "quenching-tempering treatment" after machining. Hereinafter, the above-mentioned "parts subjected to nitrocarburization treatment" will be simply referred to as "soft nitrocarburized parts". Background technique

[0003] Crankshafts, connecting rods, etc. used in automobiles, industrial machinery, and construction machinery are manufactured by forging and machining into desired shapes, and then performing nitrocarburizing instead of quenching and tempering. . In particular, in the manufacture of automobile parts requiring high fatigue strength, wear resistance, etc.,...

Examples

Embodiment

[0132] Steels A to N having the chemical compositions shown in Table 1 were smelted in a 70-ton converter, continuously cast, and then initially rolled into billets with cross-sectional dimensions of 180 mm×180 mm.

[0133] Next, each billet was hot-forged at a heating temperature of 1200° C. and a final temperature of 1000 to 1050° C., and processed into a steel bar with a diameter of 90 mm. The steel bar after hot forging is left to cool in the atmosphere and cooled to room temperature.

[0134] Steels A to H in Table 1 are steels whose chemical compositions are within the range specified in the present invention, and steels I to N are steels whose chemical compositions are outside the range specified in the present invention.

[0135] [Table 1]

[0136] Table 1

[0137]

[0138] The steel bar with a diameter of 90 mm thus obtained was heated to 1200° C., and hot forged at a final temperature of 1,000 to 1,050° C. to produce a steel bar with a diameter of 50 mm. The st...