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A Grain Refinement Method of High-strength and Long-life Gear Steel

A technology of grain refinement and gear steel, applied in the field of gear steel, can solve the problems of insufficient floating and nodule at the nozzle, and achieve the effect of avoiding early failure, reducing Al content, and improving purity.

Active Publication Date: 2021-01-29
JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, some domestic enterprises use AlN to refine the crystal grains, but the Al content is too high, and the nozzle nodules are serious during the pouring process. During the pouring process, the nozzle nodules will randomly rush into the crystallizer, Insufficient flotation to form large-sized inclusions in steel

Method used

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  • A Grain Refinement Method of High-strength and Long-life Gear Steel
  • A Grain Refinement Method of High-strength and Long-life Gear Steel
  • A Grain Refinement Method of High-strength and Long-life Gear Steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] Melt 40 tons of steel with the chemical composition shown below, carry out continuous casting, and make a continuous casting slab with a cross-sectional size of 200mm×200mm. The chemical composition of the obtained continuous casting slab includes: C: 0.25%, Si: 0.26% , Mn: 0.85%, P≤0.008%, S≤0.006%, Cr: 1.35%, Mo: 0.21%, Al: 0.022%, Nb: 0.035%, Ni: 0.75%, Ti: 0.0004%, Cu: 0.12% , N: 0.0074%, O: 0.0008%, B: 0.0006%, and the balance is Fe and unavoidable impurity elements.

[0032] The molten steel is continuously cast into continuous casting slabs, with 6 continuous casting furnaces, the continuous casting slabs are heated to above 1120°C, the holding time is ≥3 hours, and the billet is rolled at a temperature above 1050°C. The rolling method is continuous rolling, and the intermediate rolling process No water leakage is allowed. In the first five passes of rolling, a large compression ratio is adopted, and the compression ratio of a single pass is ≥1.33. Reasonable al...

Embodiment 2

[0034] Melt 100 tons of steel with the chemical composition shown below, carry out continuous casting, and make a continuous casting slab with a cross-sectional size of 200mm×200mm. The chemical composition of the obtained continuous casting slab includes: C: 0.26%, Si: 0.27% , Mn: 0.86%, P≤0.010%, S≤0.003%, Cr: 1.36%, Mo: 0.25%, Al：0.021％ , Nb: 0.033% , Ni: 0.80%, Ti: 0.0008%, Cu: 0.12%, N：0.0068％ , O: 0.0007%, B: 0.0005%, and the balance is Fe and unavoidable impurity elements.

[0035]The molten steel is continuously cast into continuous casting slabs, with 6 continuous casting furnaces, the continuous casting slabs are heated to above 1120°C, the holding time is ≥3 hours, and the rolling is started at a temperature above 1050°C of the billet. The rolling method is continuous rolling and intermediate rolling The process can't leak water. In the first five passes of rolling, a large compression ratio is adopted, and the compression ratio of a single pass is ≥1.33. In the...

Embodiment 3

[0037] Melt 100 tons of steel with the chemical composition shown below, carry out continuous casting, and make a continuous casting slab with a cross-sectional size of 300mm×340mm. The chemical composition of the obtained continuous casting slab includes: C: 0.26%, Si: 0.27% , Mn: 0.86%, P≤0.010%, S≤0.003%, Cr: 1.36%, Mo: 0.25%, Al：0.023％ , Nb: 0.045% , Ni: 0.80%, Ti: 0.0008%, Cu: 0.12%, N：0.0090％ , O: 0.0007%, B: 0.0005%, and the balance is Fe and unavoidable impurity elements.

[0038] The molten steel is continuously cast into continuous casting slabs, with 6 continuous casting furnaces, the continuous casting slabs are heated to above 1120°C, the holding time is ≥3 hours, and the rolling is started at a temperature above 1050°C of the billet. The rolling method is continuous rolling and intermediate rolling The process must not allow water to escape. In the first five passes of rolling, a large compression ratio is adopted, and the compression ratio of a single pass is...

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Abstract

The invention relates to a grain refining method of high-strength and long-life gear steel, which controls Al: 0.020-0.030%, Nb: 0.010-0.060%, N: 0.0060-0.0100%, Ti≤0.0035%, O≤0.0012 in the steel %. Reduce the content of Al and Ti, increase Nb, match a part of N, and use the joint action of Al+Nb+N to refine the grains. The rolling process has a key influence on the grain refinement. In terms of rolling, according to the research on the melting / precipitation temperature and precipitated phase of AlN, NbC, NbN, Nb(C,N), targeted improvements are made: when heating Melt Nb, C, Al, and N into γ-Fe, and use a large compression ratio in the first few passes of rolling to form a large deformation, refine the structure, and provide structure preparation for the precipitation of AlN and NbC in the subsequent pass; control the final rolling Temperature, so that a large number of NbC, AlN and other particles precipitate after rolling; slow cooling after rolling, cooling rate ≤ 8 ℃ / min, prolong the precipitation time of Al, Nb carbide, nitride or carbonitride. Through the above improvements, it is ensured that the grains of the gear steel are fully refined.

Description

technical field [0001] The invention relates to special steel smelting, in particular to a grain refinement method to obtain high-strength and long-life gear steel. Background technique [0002] For quenching + low-temperature tempering gear steel, the grain refinement can improve the resistance of the carburized layer to crack propagation, and increase the strength and toughness of the carburized layer. At present, the carburized gear steels at home and abroad use AlN or Ti to refine the grains. After carburizing and quenching at 930°C for 6 hours, the austenite grains are rated at 6-7.5 according to GB / T6394. [0003] However, purely using Ti to refine the grains inevitably exists in the steel such as figure 1 The large-sized sharp-edged TiN particles shown reduce the gear contact fatigue life. At present, some domestic enterprises use AlN to refine the crystal grains, but the Al content is too high, and the nozzle nodules are serious during the pouring process. During t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/42C22C38/44C22C38/54C22C38/58C21D8/02C21D1/84
CPCC21D1/84C21D8/0226C22C38/001C22C38/002C22C38/02C22C38/04C22C38/42C22C38/44C22C38/54C22C38/58
Inventor 杨高成曹红福黄镇孙鸿平
Owner JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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