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Method for reducing strip grade of CrMo series semi-axle steel in completely annealed state

A fully annealed, shaft steel technology, applied in the field of iron and steel, can solve unspecified problems, reduce the formation of banded structure, etc., and achieve the effect of reducing heat treatment costs, realizing banding structure, and reducing the level and quantity of product inclusions

Active Publication Date: 2020-09-08
CHENGDE JIANLONG SPECIAL STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] Although some studies in the prior art have found that the segregation of alloying elements and impurities other than C in steel is the reason for the formation of banded structures, it has not explained how to control the components and whether the change of components depends on the configuration of process conditions. Reduces band formation

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0060] This embodiment provides a method for reducing the fully annealed band grade of CrMo-based semi-shaft steel, the method includes: sequentially performing molten iron pretreatment-converter steelmaking-refining-continuous casting-slab heating-rolling ;

[0061]Wherein, the rotating speed of the stirring head in the molten iron pretreatment is 80r / min; the temperature of the molten iron in the molten iron pretreatment is 1300°C; the desulfurizer in the molten iron pretreatment is a mixture of lime powder and fluorite; The amount of lime powder added in the mixture is 700kg / furnace; the amount of fluorite added in the mixture is 70kg / furnace; the mass percentage of calcium oxide in the desulfurizer is 82%; the mass percentage of sulfur in the desulfurizer The percentage content is 0.03%; the part of the desulfurizer with a particle size ≤ 3mm is 95% of the total mass of the desulfurizer; the stirring time in the pretreatment is 22 minutes; the mass of sulfur in the molten ...

Embodiment 2

[0064] This embodiment provides a method for reducing the fully annealed band grade of CrMo-based semi-shaft steel, the method includes: sequentially performing molten iron pretreatment-converter steelmaking-refining-continuous casting-slab heating-rolling ;

[0065] Wherein, the rotating speed of the stirring head in the molten iron pretreatment is 100r / min; the temperature of the molten iron in the molten iron pretreatment is 1500°C; the desulfurizer in the molten iron pretreatment is a mixture of lime powder and fluorite; The amount of lime powder added in the mixture is 650kg / furnace; the amount of fluorite added in the mixture is 90kg / furnace; the mass percentage of calcium oxide in the desulfurizer is 90%; the mass percentage of sulfur in the desulfurizer is The percentage content is 0.01%; the part of the desulfurizer whose particle size is ≤3mm is 98% of the total mass of the desulfurizer; the stirring time in the pretreatment is 30min; the mass of sulfur in the molten...

Embodiment 3

[0068] This embodiment provides a method for reducing the fully annealed band grade of CrMo-based semi-shaft steel, the method includes: sequentially performing molten iron pretreatment-converter steelmaking-refining-continuous casting-slab heating-rolling ;

[0069] Wherein, the rotating speed of the stirring head in the molten iron pretreatment is 180r / min; the temperature of the molten iron in the molten iron pretreatment is 1800°C; the desulfurizer in the molten iron pretreatment is a mixture of lime powder and fluorite; The amount of lime powder added in the mixture is 900kg / furnace; the amount of fluorite added in the mixture is 65kg / furnace; the mass percentage of calcium oxide in the desulfurizer is 98.2%; the mass percentage of sulfur in the desulfurizer The percentage content is 0.012%; the part of the desulfurizer with a particle size ≤ 3 mm is ≥ 99% of the total mass of the desulfurizer; the stirring time in the pretreatment is 15 minutes; the mass of sulfur in the...

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Abstract

The invention relates to a method for reducing strip grade of CrMo series semi-axle steel in a completely annealed state. The method comprises the following steps of sequentially carrying out molten iron pretreatment, converter steelmaking, refining, continuous casting, casting blank heating and rolling to obtain steel with the strip grade of less than or equal to 2.5 level, wherein the mass percentage content of sulfur in the molten iron obtained after molten iron pretreatment is less than or equal to 0.01%, the end point of operation in converter steelmaking is that the mass percentage of carbon in molten steel is greater than or equal to 0.08%, the mass percentage of phosphorus is less than or equal to 0.01%, and the slag amount is 5-7 t; the mass percentage of sulfur in the molten steel in the refining process is less than or equal to 0.005%; the content of O in the refined molten steel is less than or equal to 12 ppm, and the mass percentage content of Al is 0.025%-0.035%; the final temperature of rolling ranges from 830 DEG C to 980 DEG C. According to the method provided by the invention, through component design and finish rolling temperature selection in the molten iron pretreatment, converter steelmaking and refining processes, the strip grade in the prepared steel is less than or equal to 2.5 grades, and the heat treatment cost after hot rolling is also remarkably reduced.

Description

technical field [0001] The invention relates to the field of iron and steel, in particular to a method for reducing the band level of CrMo-based semi-shaft steel in a fully annealed state. Background technique [0002] The banded structure is one of the internal defects of the steel. It is arranged in parallel along the rolling direction, distributed in layers, and shaped like strips of ferrite grains and pearlite grains. This is because ferrite is preferentially formed in the strips formed by dendrite segregation and non-metallic inclusions when the steel undergoes phase transformation during the cooling process after hot rolling, resulting in the formation of ferrite strips, ferrite strips There is pearlite between them, and the two are distributed in layers. [0003] CrMo series bar products for automobile axle shafts are mainly medium carbon steel CrMo series, and there are two reasons for the banded structure: ①The segregation of alloy elements and impurities other tha...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C33/04C21C5/28C21C7/064C21C7/076C21C7/10C21D8/06
CPCC21C5/28C21C7/064C21C7/0645C21C7/076C21C7/10C21C2007/0093C21D8/065C22C33/04Y02P10/20
Inventor 施进卿巩飞董诗朋冯晓明张川崔红军王志利
Owner CHENGDE JIANLONG SPECIAL STEEL
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