Method for producing ultra-fine grains on surface layer of thick/ultra-thick low-alloy steel plate

A low-alloy steel and manufacturing method technology, which is applied in the field of ultra-fine-grained surface layer of low-alloy steel thick plate/extra-thick plate, can solve the problems of hindering crack propagation, high heat in the core, and not obvious refining effect, etc. Achieve good surface toughness at low temperature, good application prospects, and achieve the effect of surface structure

Active Publication Date: 2014-02-12
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0002]Steel structure refinement is an important method to ensure high strength and high toughness of steel plate; The ferrite nucleation provides more places, so that the ferrite grains are refined. On the other hand, rolling is carried out in a temperature region close to the two-phase region, so that the structure is deformed and the ferrite phase transformation is induced, so that the ferrite Microstructure refinement; In the production of steel plates, controlled rolling and controlled cooling methods are generally used to refine the microstructure of steel products. However, for thick plates/extra thick plates, due to their own thickness effects and production process characteristics, it is difficult to meet large deformation and Due to the high cooling rate and other conditions, it is difficult to achieve full-thickness microstructure refinement; therefore, it is feasible to only superfine microstructure on the surface of the steel plate and rationally refine microstructure in the center of the steel plate; The super-thick plate with crystal can hinder the crack propagation, h

Method used

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  • Method for producing ultra-fine grains on surface layer of thick/ultra-thick low-alloy steel plate
  • Method for producing ultra-fine grains on surface layer of thick/ultra-thick low-alloy steel plate

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Embodiment 1

[0017] The Q345 continuous casting slab with a thickness of 150mm is used, and the chemical composition is shown in Table 1, and a thick plate with a thickness of 40mm is produced. The continuous casting slab is heated to 1180°C, soaked for 30 minutes, and then released from the furnace. After descaling by high-pressure water, the first-stage rolling is carried out. The pass reduction is 18-22mm. The final rolling temperature of the first stage is 1060°C. The thickness of the intermediate slab is is 90mm. The intermediate slab is rapidly cooled at 10°C / s by the immediate rapid cooling device next to the machine, and the surface temperature of the slab drops to 550°C when it exits the cooling zone, and the second-stage rolling is carried out when the slab temperature reaches 900°C after fully reddening. The rolling reduction in the second stage is 8-15mm, and after rolling for 2 passes, the slab temperature is 880°C. At this time, the slab is cooled rapidly again. When leaving...

Embodiment 2

[0019] The Q345 continuous casting slab with a thickness of 150mm is used, and the chemical composition is shown in Table 1, and a thick plate with a thickness of 40mm is produced. The continuous casting slab is heated to 1100°C, soaked for 30 minutes, and then released from the furnace. After descaling by high-pressure water, the first-stage rolling is carried out. The reduction in each pass is 18-22mm. The final rolling temperature of the first stage is 1060°C. The thickness of the intermediate slab is is 90mm. The intermediate slab is rapidly cooled at 10°C / s by the immediate rapid cooling device next to the machine, and the surface temperature of the slab drops to 350°C when it exits the cooling zone, and the second-stage rolling is carried out when the slab temperature reaches 850°C after fully reddening. The rolling reduction in the second stage is 8-15mm, and after rolling for 2 passes, the slab temperature is 880°C. At this time, the slab is cooled rapidly again. When...

Embodiment 3

[0021] The Q420 continuous casting slab with a thickness of 320mm is used, and the chemical composition is shown in Table 1, and the extra-thick plate with a thickness of 80mm is produced. The continuous casting slab is heated to 1200°C, soaked for 60 minutes, and then released from the furnace. After descaling by high-pressure water, the first-stage rolling is carried out. The reduction in each pass is 25-35mm. After 5 passes, the first-stage rolling ends. The final rolling temperature of the first stage is 1080°C, and the thickness of the intermediate billet is 160mm. The intermediate slab is rapidly cooled at 15°C / s by the immediate rapid cooling device next to the machine, and the surface temperature of the slab drops to 350°C when it exits the cooling zone, and the second-stage rolling is carried out when the slab temperature reaches 910°C after fully reddening. The total number of rolling passes in the second stage is 5 times, and the reduction in each pass is 12-20mm. ...

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Abstract

The invention relates to a method for manufacturing a low-alloy steel plate, and particularly discloses a method for producing ultra-fine grains on the surface layer of a thick/ultra-thick low-alloy steel plate. The method specifically comprises the following steps of 1, uniformly heating a plate blank for 30 to 60 minutes, and taking the plate blank out of a furnace; 2, reducing the temperature of the surface layer of an intermediate blank to 350 to 550 DEG C at speed of more than or equal to 10 DEG C per second, and waiting for temperature rise; 3, when the temperature of the surface layer of the intermediate blank returns to 850 to 960 DEG C, and performing multi-pass rolling, wherein the temperature of the surface layer of the plate blank is reduced to be lower than Ar1 at speed of 10 to 80 DEG C per second between every two rolling passes, the rolling of the next pass is started after the temperature rise, and the final rolling temperature is 780 to 850 DEG C; 4, cooling the plate blank after the plate blank is rolled, namely quickly cooling the blank plate at speed of 1 to 20 DEG C per second, air-cooling the blank plate to 250 to 400 DEG C after the temperature rise, and performing stack cooling. According to the method, energy accumulatively stored on the middle part of the thick steel plate is fully used for performing controlled rolling and controlled cooling for multiple times to refine austenite grains on the surface layer on the premise of no remarkable increase of load of a conventional rolling mill.

Description

technical field [0001] The invention relates to a method for manufacturing a low-alloy steel plate, in particular to a method for manufacturing ultra-fine crystals on the surface of a low-alloy steel thick plate / extra-thick plate. Background technique [0002] Steel structure refinement is an important method to ensure high strength and high toughness of steel plate; structure refinement: on the one hand, the austenite grains are refined, which provides more places for subsequent ferrite nucleation, so that ferrite On the other hand, rolling is carried out in a temperature region close to the two-phase region, so that the structure undergoes deformation and induces ferrite phase transformation, thereby refining the ferrite structure; in the production of steel plates, controlled rolling and controlled rolling are generally used. The cold method refines the microstructure of steel. However, for thick plates / extra-thick plates, due to their own thickness effects and production...

Claims

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Application Information

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IPC IPC(8): C21D8/02C22C38/14
Inventor 曾周燏王从道党军
Owner NANJING IRON & STEEL CO LTD
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