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Controlled rolling and controlled cooling method for steel with low yield ratio and low welding crack sensitivity

A technology with low welding cracks and low yield ratio, applied in metal rolling, furnace, heat treatment equipment, etc., can solve the problems of complex manufacturing process, long production cycle, high alloy cost, etc., and achieve simple manufacturing process, high production efficiency, Effect of narrow rolling temperature range

Active Publication Date: 2019-11-22
HUNAN VALIN XIANGTAN IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Chinese patent CN105063472A announced "low-cost 345MPa grade low-alloy steel plate and its production method". The steel adopts C-B-N without adding any alloy elements. The strength is 370~430MPa, and the impact energy at -20℃ is 70~150J
Chinese patent CN101660099A announced "high-strength low-alloy hot-rolled ferritic bainite weathering steel and its production method", and US patent US6056833A announced "Thermo mechanically controlled processed high strength weathering steel with low yield / tensileratio", the Pcm of these steels ≤0.20, yield ratio ≤0.85, but lower carbon content is used, and more precious metals such as Ni, Cr, Mo, Cu are added, and the alloy cost is high
Chinese patent CN102080192A announced "a low yield ratio high plasticity ultra-fine grain high-strength steel and its manufacturing method", Chinese patent CN101906569B announced "a large deformation resistant pipeline steel prepared by heat treatment method and its preparation method", Japan Patent JP2009235548 announced "Low yield ratio high tensile strength thick steel plate having excellent toughness in super-large heat input weld affected zone, and method for producing the same", although these patents can meet the requirements of Pcm≤0.20 and yield strength ratio≤0.85 , but the heat treatment process of sub-temperature quenching in the critical zone, or sub-temperature quenching + tempering is adopted, the manufacturing process is complicated, and the production cycle is long

Method used

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  • Controlled rolling and controlled cooling method for steel with low yield ratio and low welding crack sensitivity
  • Controlled rolling and controlled cooling method for steel with low yield ratio and low welding crack sensitivity
  • Controlled rolling and controlled cooling method for steel with low yield ratio and low welding crack sensitivity

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Example 1: 10mm thickness Q370qD.

[0027] The chemical composition of the steel is shown in Table 1. The thickness of the continuous casting slab is 260 mm, and the thickness of the steel plate is 10 mm. The key process parameters of controlled rolling and controlled cooling are:

[0028] (1) Controlled rolling: when the rolling temperature is 1046°C, the pass reduction rate is 25.5%; when the rolling temperature is 1038°C, the pass reduction rate is 24.8%; when the rolling temperature is 975°C, the pass reduction rate is 25.0%; When the rolling temperature is 954°C, the pass reduction rate is 20.8%; when the rolling temperature is 925°C, the pass reduction rate is 17.4%; when the rolling temperature is ≤900°C, the cumulative reduction rate is 33.5%; the final rolling temperature is 858°C.

[0029] (2) Controlled cooling: accelerated cooling to 600~620°C after final rolling, with a cooling rate of 4~5°C / s.

[0030] Carry out microstructure observation to embodiment ...

Embodiment 2

[0031] Example 2: 50mm thickness Q420qD.

[0032]The chemical composition of the steel is shown in Table 1; the thickness of the slab is 300 mm; the thickness of the steel plate is 50 mm. The key process parameters of controlled rolling and controlled cooling are:

[0033] (1) Controlled rolling: when the rolling temperature is 1055°C, the pass reduction rate is 23.5%; when the rolling temperature is 1051°C, the pass reduction rate is 21.7%; when the rolling temperature is 958°C, the pass reduction rate is 22.5%; When the rolling temperature is 954°C, the pass reduction rate is 21.8%; when the rolling temperature is 949°C, the pass reduction rate is 10.5%; when the rolling temperature is ≤900°C, the cumulative reduction rate is 29.1%; the final rolling temperature is 870°C.

[0034] (2) Controlled cooling: accelerated cooling to 580~600°C after final rolling, with a cooling rate of 5~6°C / s.

Embodiment 3

[0035] Example 3: 32mm thickness Q460GJC.

[0036] The chemical composition of the steel is shown in Table 1. The thickness of the continuous casting slab is 260 mm, and the thickness of the steel plate is 32 mm. The key process parameters of controlled rolling and controlled cooling are:

[0037] (1) Controlled rolling: when the rolling temperature is 1054°C, the pass reduction rate is 22.0%; when the rolling temperature is 1052°C, the pass reduction rate is 27.7%; when the rolling temperature is 973°C, the pass reduction rate is 20.1%; When the rolling temperature is 970°C, the pass reduction rate is 18.0%; when the rolling temperature is 967°C, the pass reduction rate is 18.6%; when the rolling temperature is ≤900°C, the cumulative reduction rate is 39.6%; the final rolling temperature is 863°C.

[0038] (2) Controlled cooling: accelerated cooling to 580~600°C after final rolling, with a cooling rate of 5~6°C / s.

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Abstract

The invention relates to a controlled rolling and cooling method for low-yield ratio low welding crack-sensitivity steel. The steel comprises the compositions of, by weight, less than or equal to 0.10% of C, 0.30-0.50% of Si, 1.2-1.8% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.010-0.050% of Nb, 0.01-0.03% of Ti, less than or equal to 0.30% of Cr, 0.02-0.06% of Alt, less than or equal to 0.0005% of B, and the balance Fe and unavoidable impurity elements, wherein C*Nb is equal to 0.18-0.22ppm, and Pcm is less than or equal to 0.20%. A steel plate comprises 45-55% of ferrite, 40-50% of bainite, and a small amount of pearlite, and the yield ratio of the steel plate is less than or equal to 0.85%. The steel plate produced by the controlled rolling and coolingmethod has low cost and high production efficiency and the plate shape is easy to control.

Description

technical field [0001] The invention belongs to the field of low alloy steel, in particular to a controlled rolling and cooling method for steel with low yield ratio and low welding crack sensitivity. Background technique [0002] For low-alloy steel, the mixed structure of ferrite + pearlite or bainite is a common way to obtain low yield ratio. Usually, the yield strength mainly depends on the yield strength of ferrite, while the tensile strength follows the law of mixture. Therefore, obtaining a certain amount of pearlite with sufficient carbon content or obtaining bainite with sufficient strength is the key to ensure a low yield ratio. Relevant literature shows that in the strengthening mechanism of iron and steel materials, the role of displacement solid solution strengthening in improving tensile strength is slightly greater than that of improving yield strength, while dislocation strengthening and fine grain strengthening are mainly to significantly improve yield stren...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/26C22C38/28C22C38/32C22C38/38C21D8/02C21D9/00B21B1/22
CPCB21B1/22B21B2001/225C21D8/0226C21D9/0081C22C38/02C22C38/04C22C38/06C22C38/26C22C38/28C22C38/32C22C38/38
Inventor 彭宁琦汤伟罗登范明史术华李中平刘丹熊祥江陈奇明
Owner HUNAN VALIN XIANGTAN IRON & STEEL CO LTD
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