Non quenched and tempered nitrocarburized parts

Abstract

A non-quenched and tempered nitrocarburized part, the chemical composition of the blank steel is calculated in mass%, C: 0.35-0.50%, Si: 0.10-0.35%, Mn: 2.3-2.8%, S≤0.10%, N : 0.0030~0.0250%, Cu: 0~1.0%, Mo: 0~0.3%, Ni: 0~0.5%, Ti: 0~0.020%, balance: Fe and impurities, 3.10≤(0.316C+0.122)× (0.7Si+1)×(5.1Mn‑1.12)×(0.364Ni+1)×(2.16Cr+1)×(3Mo+1)≤6.00, P, Al and Cr in impurities are P≤0.08% , Al≤0.05% and Cr<0.20%; in the stress concentration part, the HV hardness at the position 0.05mm away from the surface is 410-480, the HV hardness at the position 1.0mm away from the surface is above 200, and the depth of the compound layer is below 5μm; and the blank The metallographic structure is bainite. The non-tempered nitrocarburized part has excellent bend correction and high fatigue strength.

Description

technical field

[0001] The invention relates to non-tempered nitrocarburized components. 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, ...

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...

technical field

[0001] The invention relates to non-tempered nitrocarburized components. 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, ...

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...

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