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Control method for preventing machining cracking of 20Ni2MoA gear steel

A control method and technology of gear steel, which is applied in the control field of preventing cracking of 20Ni2MoA gear steel processing, can solve problems such as poor dimensional accuracy of carburized gears, cracking, and influence on carburizing uniformity, and achieve good toughness

Active Publication Date: 2021-11-30
XINJIANG BAYI IRON & STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For gear steel, severe band structure will affect the uniformity of carburizing, increase the degree of quenching deformation, make the dimensional accuracy of carburized gear poor, and prone to cracking during forging

Method used

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Examples

Experimental program
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Effect test

Embodiment Construction

[0027] A control method for preventing cracking of 20Ni2MoA gear steel,

[0028] (1) The composition and mass percentage of the gear steel is as follows: C content is 0.18-0.21%, Si content is 0.20-0.30%, Mn content is 0.70-0.80%, P content is <0.018%, S content is < 0.005%, Ni content is 1.65-1.75%, Mo content is 0.20-0.26%, residual elements Cr≤0.15%, Cu≤0.15%, the rest are iron and unavoidable impurities;

[0029] (2) Electric furnace smelting:

[0030] [1] The electric furnace must be equipped with molten iron of 38-45t / furnace, and it is required to use fine materials: the cut head, tail cut and purchased heavy materials returned from steel rolling, and the total loading is controlled at about 85 tons / furnace;

[0031] [2] The electric furnace slag is mixed with 3000kg of lime in advance through the silo;

[0032] [3] Use carbon retention operation to strictly control the carbon content at the end point of the electric furnace, and the control range is 0.10 to 0.15%. Ov...

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Abstract

The invention discloses a control method for preventing machining cracking of 20Ni2MoA gear steel. The 20Ni2MoA gear steel is prepared from 0.18%-0.21% of C, 0.20%-0.30% of Si, 0.70%-0.80% of Mn, smaller than 0.018% of P, smaller than 0.005% of S, 1.65%-1.75% of Ni, 0.20%-0.26% of Mo, smaller than or equal to 0.15% of Cr, smaller than or equal to 0.15% of Cu and the balance of iron and inevitable impurities. Electric furnace smelting and refining furnace smelting are adopted, wherein the superheat degree of a continuous casting furnace is controlled within 30 DEG C; deoxidation, desulfurization control and calcium treatment are performed; during continuous casting, low-superheat-degree constant-pulling-speed casting is adopted, the superheat degree of a tundish is controlled to be 10-25 DEG C, center segregation of a casting blank is controlled, and casting blank rolling is conducted, specifically, the heating rate of a cold-state 20Ni2MoA gear steel casting blank in the steel rolling procedure is controlled to be 3-5 DEG C / min; the preheating temperature is not higher than 840 DEG C, the soaking temperature is 1160-1200 DEG C, the finish rolling temperature is set to be 880 DEG C, the cooling rate is 8-10 DEG C / s, and the steel structure is granular bainite and a small amount of ferrite.

Description

technical field [0001] The invention relates to a control method for preventing 20Ni2MoA gear steel from cracking during processing. Background technique [0002] 20Ni2MoA steel has good hardenability, and the finished product is bainite in the state of non-temperature-controlled hot rolling. As a steel for making large modulus gears, it not only has extremely high tensile strength values, but also has very good impact toughness values. Due to the high Ni content in the steel, the presence of retained austenite in the steel is increased, which provides an effective resistance to contact fatigue under high frequency and strong load. The structural characteristics of the steel grade determine that it is extremely sensitive to the rate of temperature rise and fall during processing. This is not only the point that gear manufacturers pay close attention to, but also the top priority in the production process of steel mills. The quality accidents that often occur in production...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C33/06C22C38/02C22C38/04C22C38/08C22C38/12C22C38/16C22C38/42C22C38/44B21C37/04C21C7/00C21C7/06C21C7/064
CPCC22C33/06C22C38/02C22C38/04C22C38/08C22C38/12C22C38/16C22C38/42C22C38/44C21C7/0006C21C7/06C21C7/064B21C37/04
Inventor 汤新彦吾塔陈刚
Owner XINJIANG BAYI IRON & STEEL
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