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Medium-carbon boron-containing steel and controlled rolling and controlled cooling method for online normalizing treatment

A technology of normalizing treatment, controlled rolling and controlled cooling, which is applied in the direction of heat treatment process control, heat treatment furnace, heat treatment equipment, etc., can solve the problems of restricting mass production and application of products, increasing production costs, and low production efficiency, so as to improve product competition The effect of speeding up the production cycle and reducing the production cost

Active Publication Date: 2021-08-17
DAYE SPECIAL STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] In the manufacturing process, the existing technology generally requires off-line normalizing treatment of the steel to meet the steel structure hardness requirements, but because the finished material used in the production application is small in size (20-50mm), it is necessary to use professional normalizing The furnace is normalized off-line, not only the production efficiency is low, but also the problem of mixed crystals is prone to occur
At the same time, the off-line normalizing treatment of steel increases the production cycle by about one week, and the corresponding production cost increases by about 400 yuan / ton, which seriously restricts the mass production and application of this product

Method used

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  • Medium-carbon boron-containing steel and controlled rolling and controlled cooling method for online normalizing treatment
  • Medium-carbon boron-containing steel and controlled rolling and controlled cooling method for online normalizing treatment
  • Medium-carbon boron-containing steel and controlled rolling and controlled cooling method for online normalizing treatment

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] The cross-sectional size of the selected billet is 240mm×240mm; according to the mass percentage, the chemical composition of the billet of the medium-carbon boron-containing steel includes: C 0.38%; Si 0.25%; Mn 0.86%; Al 0.032%; B 0.0017%; Ti 0.047% ; P0.013%; S 0.005%; Cr 0.14%; Ni 0.03%; Mo 0.02%; Cu 0.02%;

[0044] Heating step: the heating temperature of the billet entering the heating furnace is 1140-1160°C, and the total heating time is 142min;

[0045] Rough rolling step: the inlet temperature of the rough rolling unit is 1038°C;

[0046] Finishing step: use the reducing and sizing finishing mill, and the inlet temperature of the finishing mill is 795°C;

[0047] Water-piercing cooling step: The finished steel rolled by the reducing and sizing finishing mill is cut by flying shear and then sprayed with water to cool the finished steel.

[0048] Cooling bed slow cooling step: carried out in a step-by-step cooling bed, the cooling rate of the finished steel is ...

Embodiment 2

[0052] According to mass percentage, the chemical composition of the medium-carbon boron-containing steel billet includes: C 0.38%; Si 0.25%; Mn0.84%; Al 0.028%; B 0.0020%; Ti 0.045%; P 0.012%; S 0.008%; Cr 0.12%; Ni0.02%; Mo 0.03%; Cu 0.03%; the rest is Fe and unavoidable impurities; the cross-sectional size of the selected billet is 240mm×240mm.

[0053] The steps of the controlled rolling and controlled cooling method suitable for on-line normalizing treatment of medium-carbon boron-containing steel are as in Example 1, wherein the parameters of each step of the controlled-rolling and controlled-cooling method suitable for on-line normalizing treatment of medium-carbon boron-containing steel are shown in Table 1. The finished product steel section 1 / 2 place hardness after the step of embodiment 2 is processed is 212 / 215HBW; Actual grain size is 9 grades; figure 2 As shown, the banded structure is grade 1.5.

[0054] Table 1 is each step parameter of embodiment 1 and embod...

Embodiment 3-5

[0057] The chemical composition of the medium-carbon boron-containing steel slabs of Examples 3-5 is the same as that of Example 1.

[0058] Heating in embodiment 3-5, rough rolling, finishing rolling, piercing water cooling, the parameters of cooling bed slow cooling each step are as shown in table 2, the performance of finished steel comprises hardness at 1 / 2R place, grain size and strip shape The organizational level is also shown in Table 2.

[0059] Table 2 is each step parameter of embodiment 3-5 and the performance of gained steel

[0060]

[0061]

[0062] It can be known from Table 2 that the hardness at 1 / 2R of the steel obtained in Examples 3-5 is 202-214HBW, the grain size is 8-8.5, and the band structure is 1.5-2.0.

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Abstract

The invention provides a medium-carbon boron-containing steel which includes the chemical components in percentage by mass: 0.37% to 0.45% of C, 0.17% to 0.37% of Si, 0.60% to 0.90% of Mn, 0.020% to 0.060% of Al, 0.0008% to 0.0035% of B, 0.030% to 0.060% of Ti, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.25% of Cr, less than or equal to 0.20% of Ni, less than or equal to 0.10% of Mo, less than or equal to 0.20% of Cu; and the balance of Fe and inevitable impurities. A controlled rolling and controlled cooling method suitable for online normalizing treatment for the medium-carbon boron-containing steel sequentially includes the following steps of heating, rough rolling, finish rolling, water cooling and cold bed slow cooling. The medium-carbon boron-containing steel can meet the requirements that the hardness is 190-220 HBW, the actual grain size is larger than or equal to grade 7, and the banded structure is smaller than or equal to grade 2.

Description

technical field [0001] The invention relates to the field of steel rolling, in particular to a medium-carbon boron-containing steel and a controlled rolling and cooling method for on-line normalizing treatment. Background technique [0002] Medium-carbon boron-containing steel is a kind of alloy structural steel with good hardenability. It is mostly used to manufacture important parts such as automobile constant velocity transmission shafts. Due to the requirements of processing and service conditions, there are strict requirements on the structure and hardness of the material. [0003] In the manufacturing process, the existing technology generally requires off-line normalizing treatment of the steel to meet the steel structure hardness requirements, but because the finished material used in the production application is small in size (20-50mm), it is necessary to use professional normalizing The furnace is normalized off-line, which is not only low in production efficiency...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/50C22C38/54C21D1/28C21D6/00C21D8/00C21D9/00C21D11/00
CPCC22C38/02C22C38/04C22C38/06C22C38/54C22C38/50C22C38/44C22C38/42C21D1/28C21D6/004C21D6/005C21D6/008C21D8/005C21D9/0081C21D11/005C21D1/84C21D1/60C21D1/02C21D8/065C21D9/5732C21D7/13C22C38/14C22C38/32C22C38/28
Inventor 张念郑文超凌鑫陈平黄国飘何英武
Owner DAYE SPECIAL STEEL CO LTD
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