Grain refining method of high-strength long-service-life gear steel

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

Active Publication Date: 2019-10-18
JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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  • 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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  • Grain refining method of high-strength long-service-life gear steel
  • Grain refining method of high-strength long-service-life gear steel
  • Grain refining method of high-strength long-service-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]Continuous casting of molten steel into continuous casting slabs, with 6 continuous casting furnaces, heating the continuous casting slabs to above 1120°C, holding time ≥ 3 hours, starting rolling at temperatures above 1050°C of the billet, the rolling method is continuous rolling, 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 middle pass, the deformat...

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] Continuous casting of molten steel into continuous casting slabs, with 6 continuous casting furnaces, heating the continuous casting slabs to above 1120°C, holding time ≥ 3 hours, starting rolling at temperatures above 1050°C of the billet, the rolling method is continuous rolling, 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 ≥ 1.33, and the deformati...

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Abstract

The invention relates to a grain refining method of high-strength long-service-life gear steel. The grain refining method of the high-strength long-service-life gear steel comprises the following steps of controlling the steel 0. 020%-0.030% of Al, 0.010%-0.060% of Nb, 0.0060%-0.0100% of N, Ti is less than or equal to 0.035%, O is less than or equal to 0.012%, the content of Al and Ti is reduced,Nb is increased, a part of N is matched, and the crystal grains are refined by the co-action of Al+Nb+N. The rolling process has a key influence on grain refinement, in the aspect of rolling, according to the melting of AlN, NbC, NbN, Nb (C, N), the research on the precipitation temperature and the precipitation phase is improved in a targeted manner, during heating, Nb, C, Al and N are fused intogamma-Fe, a large compression ratio is adopted for the first several times of rolling, so that large deformation is formed; the tissue is refined, tissue preparation is provided for separation of theposterior particle AlN and NbC; the final rolling temperature is controlled, so that a large amount of particles such as NbC, AlN and the like after rolling are separated out; after rolling, slow cooling is carried out, the cooling speed is less than or equal to 8 DEG c./ min, the precipitation time of Al, Nb carbide, nitride or carbonitride is prolonged, through the above improvement, the grainsize of the gear steel is ensured to be 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 Applications(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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