Non-modified crankshaft

Abstract

The non-tempered crankshaft contains C: 0.30-0.35%, Si: 0.40-0.80%, Mn: 1.00-2.00%, S: 0.040-0.080%, Cr: 0.10-0.30%, V: 0.05% by mass % ~0.20%, the rest is Fe and impurities, and its microstructure is a ferrite-pearlite microstructure with a ferrite fraction α of 0.20~0.60 and an average pearlite particle size Dp of 0.08mm or less. And meet the value of Fn1 defined by the following formula (1) to be equal to or greater than 0.73, the value of Fn2 defined by the following formula (2) to be equal to or greater than 1.2 and the value of Fn3 defined by the following formula (3) to be equal to or greater than 0.64: ​​Fn1=C +0.10Si+0.20Mn-0.71S+0.23Cr+1.65V(1); Fn2=1.4-1.1(1-α)+0.16Dp -1 / 2 (2) and Fn3=(1-α)+α(0.3Si+0.8V) (3), wherein the element symbols in the formulas (1) and (3) represent the mass % content of the element in the steel. The non-tuned and tempered crankshaft of the present invention has good strength, low-temperature toughness and wear resistance, so it can be used in working machine engines or general-purpose engines.

Description

technical field [0001] The present invention relates to a non-tempered crankshaft that uses "non-tempered steel that has good strength, low-temperature toughness, and wear resistance even if heat-forging treatment after hot forging is omitted" and is suitable for mowing grass Used in general-purpose engines such as motors, generators, snowplows, pumps, outboard propellers, or outboard motors. Background technique [0002] In the past, when manufacturing mechanical structural parts for automobiles or construction machinery, etc., it was usually made by hot forging steel for mechanical structural use (such as carbon steel S48C for mechanical structural use specified in JIS G 4051, etc.) The shape of the part is then subjected to a quenching-tempering treatment (also known as quenching and tempering treatment) to give it the necessary strength and toughness. [0003] However, in recent years, the demand for cost reduction and shortened time interval has promoted the developmen...

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Problems solved by technology

[0013] This is because, if the above-mentioned mechanical structural parts adopt the conventional non-quenched and tempered steel that omits the quenching and tempering treatment and only undergoes hot forging, it cannot sufficiently satisfy low temperature toughness and wear resistance at the same time.

[0014] That is, because of the conflict between the low temperature toughness and wear resistance of steel, it is difficult to improve the above two properties at the same time in the non-quenched and tempered steel proposed in the past

For example, any of the non-quenched and tempered steels disclosed in the above-mentioned JP-8-120342, JP-10-277705, JP-2000-265242 or JP-2000-328193, etc., cannot guarantee to meet the requirements of the working requirements when quenching and tempering treatment is omitted. The low-temperature toughness and wear resistance required for crankshafts such as engines cannot fully meet the requirements of reducing costs and reducing manufacturing time by omitting quenching and tempering.

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