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Low alloy steel for forging steel products and crankshaft

A technology for low-alloy steel and steel products, applied in the field of low-alloy steel for forging steel products and crankshafts, can solve the problems of difficulty and inability to manufacture steel for forging steel products, and achieve the effect of excellent machinability

Inactive Publication Date: 2015-09-30
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, in steel for forging steel products using carbon steel, only a yield strength of 350 MPa or more and 380 MPa or less can be obtained.
In addition, in the case of using steel for forging steel products with low-alloy steel having a conventional composition, if it is large, quenching cracks will occur, so it cannot be manufactured that can be used for large combined crankshafts with shaft diameters larger than 650 mm. Steel for wrought steel products
In this way, it is difficult to manufacture steel for forging steel products that has a yield strength of 450 MPa or more and can be used for large combined crankshafts.

Method used

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  • Low alloy steel for forging steel products and crankshaft
  • Low alloy steel for forging steel products and crankshaft
  • Low alloy steel for forging steel products and crankshaft

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0062] In Example 1, steel having the composition shown in Table 1 was hot-forged at a temperature between 900° C. and 1230° C., and then formed into a crank throw with a shaft diameter of 950 mm by gas cutting. Next, the molded bellcrank was heated to 870° C., cooled by air cooling, and normalized. Then heat the cooled bellcrank to 620°C for tempering.

Embodiment 2～5

[0080] (Examples 2-5, Comparative Examples 5-15)

[0081]In Examples 2 to 5 and Comparative Examples 5 to 15, steels having the compositions shown in Table 2 were melted to manufacture test forged steels. First, steel having the composition shown in Table 1 was melted using a high-frequency furnace, and a 40 kg steel ingot having a width of 170 mm x a thickness of 120 mm x a height of 230 mm was cast. Next, the riser part of the steel ingot obtained was cut off, and it heated at 1230 degreeC for 5 hours or more and 10 hours or less. Next, using a free forging press, compress the heated ingot to a height ratio of 1 / 2, rotate the center line of the ingot by 90° for forging, stretch it to a width of 90 mm x thickness 90 mm x length 450 mm, and then let it cool in the atmosphere. Raw material. Thereafter, the raw material cooled to 250° C. to 300° C. was kept in a heating furnace for 10 hours or more, then heated at 50° C. / hr, and kept at 870° C. for 5 hours. After that, the ra...

Embodiment 6～9

[0088] In Examples 6 to 9, the steel with the same composition as in Examples 2 to 5 was used, and the average cooling rate of the cooling after normalizing was 5.0°C / min, and the others were the same as the manufacturing method of the above-mentioned Example 2, Thus, a test raw material was produced.

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Abstract

The invention provides low alloy steel for forging steel products, the low alloy steel is excellent in cutability, and the yield strength and the toughness of the low alloy steel can meet requirements of large-scale forging steel products. The low alloy steel for forging steel products comprises, by mass, 0.30 % to 0.40 % of C, 0 % to 0.45 % of Si, 0.50 % to 1.90 % of Mn, 0.70 % to 2.00 % of Ni, 1.00 % to 2.30 % of Cr, 0 % to 0.35 % of Mo, 0 % to 0.20 % of V, and the reminder comprising Fe and inevitable impurities, more than 17 % of bainite structure, martensitic structure or composite structure of bainite structure and martensitic structure, and the balance being pearlitic structure, ferritic structure or composite structure of pearlitic structure and ferritic structure, wherein the components meet that (1.5*Mn+2*Ni) / Cr < than 2.35 (1).

Description

technical field [0001] This invention relates to low alloy steels and crankshafts for forging steel products. Background technique [0002] Steel materials used for large crankshafts, which are transmission components of diesel engines used in ships and power generators, require high strength in order to increase the output and size of diesel engines. [0003] In response to this, a forging steel that can be used for crank throws of combined crankshafts has been developed (for example, refer to Japanese Patent No. 4150054). [0004] However, the combination type crankshaft is manufactured by caulking and joining crank throws and crank journals obtained by forming forged steel products. Therefore, in order to avoid slippage of the sintered portion during operation of the diesel engine, a high yield strength (YS) is required for the steel for forged steel products used in the crank throw. Recently, a high yield strength of 450 MPa or more is required as the output of diesel ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/58C22C38/46F16C3/06F16C3/22
CPCC22C38/44C22C38/46C22C38/58F16C3/06
Inventor 矢仓亮太
Owner KOBE STEEL LTD