CN-121992176-A - Production method of Q355B, C, D grade steel plate with thickness of 81-120mm

Abstract

The invention discloses a production method of a Q355B, C, D grade steel plate with the thickness of 81-120mm, which adopts a normalizing rolling and immersion type quick cooling process to roll a casting blank in a recrystallization zone, adopts a large-reduction process to crush, flatten and elongate original austenite, and aims to prevent uncrushed austenite grains from growing up, nb elements in the steel plate are separated out in grain boundary induction Nb (C, N), the Nb elements are bound and pinned to prevent woven grains from growing up, the steel plate is quickly cooled in water after being rolled, the temperature of the core part of the steel plate is reduced to below Ar3, and the steel plate is converted into 60% ferrite and 40% pearlite structure, so that the strength and low-temperature impact caused by the growth of the grains of the internal structure of the steel plate are avoided.

Inventors

• XU SHAOPU
• YUAN JIHENG
• LI LIANG
• LI ZHONGBO
• ZHANG TAO
• KANG WENJU
• ZHU XIANXING

Assignees

• 南阳汉冶特钢有限公司

Dates

Publication Date

20260508

Application Date

20260127

Claims (1)

1. 1. The production method of the Q355B, C, D grade steel plate with the thickness of 81-120mm is characterized by comprising the following steps: 1) Preparing raw materials and smelting, namely preparing a raw material ：C：0.10-0.14,Si：0.10-0.30,Mn：1.48-1.58,P≤0.015,S≤0.005,Cr：0.005-0.15,Ti：0.01-0.02,Al：0.02-0.05,Nb:0.015-0.025, of a steel plate according to the following chemical components in percentage by weight, namely adding the raw materials into an electric furnace or a converter for smelting, and controlling the tapping temperature to be 1600-1650 ℃; 2) Refining, namely transferring molten steel into an LF furnace for refining, adding slag-forming materials such as lime and fluorite, controlling the slag alkalinity to be 2.5-3.5, refining time to be more than or equal to 30min, feeding wires after refining, and feeding Si-Ca wires or Al wires for deoxidization and inclusion denaturation treatment; 3) Vacuum degassing, namely transferring refined molten steel into a VD furnace for vacuum degassing treatment, wherein the vacuum degree is less than or equal to 67Pa, the holding time is more than or equal to 15min, and H is less than or equal to 1.3PPm so as to remove gas and impurities in the molten steel; 4) Casting, namely casting the molten steel subjected to vacuum degassing by continuous casting, wherein the casting temperature is controlled to 1550-1560 ℃, and the continuous casting drawing speed is controlled to 0.8-1.0m/min; 5) Heating, namely feeding the casting blank into a heat accumulating type heating furnace for heating, wherein the heating temperature is controlled to be 1200-1240 ℃ and the heating coefficient is 1.2-1.4mm/min, so that the casting blank is uniformly heated; 6) Normalizing rolling is carried out on the heated casting blank, the final rolling temperature is 890-910 ℃, the rolling process gives consideration to the use of high-pressure water to reduce the surface temperature of the steel blank, the single-pass rolling reduction is more than or equal to 50mm, the rolling reduction is more than or equal to 12%, and the steel plate 20S is rapidly cooled by entering ACC; 7) Cooling, namely immersing a turning plate into the steel plate after rolling and stirring the steel plate with high-strength gas into water for cooling, wherein the water inlet temperature is 890-910 ℃, the water cooling time is 60-80S, the steel plate temperature is 820-850 ℃ when water is introduced, the water temperature is 20-40 ℃, and the reddening temperature is 560-600 ℃; 8) And (3) carrying out stack cooling, namely carrying out stack cooling on the rolled steel plate, wherein the stack cooling temperature is more than 420 ℃.

Description

Production method of Q355B, C, D grade steel plate with thickness of 81-120mm Technical Field The invention relates to the technical field of steel materials, in particular to a production method of a Q355B, C, D grade steel plate with the thickness of 81-120 mm. Background The chinese steel industry is moving from "scale expansion" to "quality improvement" and "structural adjustment". Development and application of advanced rolling and cooling control technology are the actual implementation of steel mill technology, and the Q355B steel plate with the thickness of 81-120mm adopts normalizing rolling technology. In order to solve the problems of uneven structure and insufficient toughness inherent in thick plates in a more economical and efficient manner, high-end structural steel with high performance, high reliability and cost competitiveness is stably produced. The normalizing rolling is used as an extension and supplement of an advanced TMCP technology, is one of key technical means for upgrading products and developing high-performance steel products in a steel mill, and helps the steel mill to occupy the market of high-end medium-thickness plates with better cost performance ratio in strong market competition. The related patents on the aspect of structure regulation under the normalizing rolling process of medium plates below 355MPa are as follows, namely a steel plate with uniform longitudinal performance obtained by normalizing rolling and a manufacturing method thereof (application number: 201910709706.8) applied to the steel jaw of the armed steel, mainly relate to low alloy steel, and the low alloy steel comprises the following components in percentage by mass ：C：0.12～0.20％,Mn：1.20～1.50％,Ti：0.008～0.022％,Si：0.2～0.4％,N：0.010～0.02％,Als：0.020～0.05％,S≤0.008％,P≤0.015％,, the balance of Fe and unavoidable impurities, and simultaneously satisfies 83 percent Si+354 percent N >23. The normalizing rolled steel plate adopts two-stage controlled rolling, relaxation and water cooling after rolling. The carbon equivalent of the steel is 0.35-0.52%, when the carbon equivalent exceeds 0.43%, the austenite stability is obviously improved, the transformation of upper bainite occurs during phase transformation, the structure is not a normal structure, and the plasticity and toughness of the steel plate with the upper bainite are relatively poor. The invention discloses a method for controlling the tissue uniformity of a 355 MPa-level normalized rolled thick plate with low carbon equivalent (application number: CN 202310621117.0) applied by Anshan, which comprises the following components in percentage by mass of ：C：0.12～0.20％,Mn：1.20～1.50％,Ti：0.008～0.022％,Si：0.2～0.4％,N：0.010～0.02％,Als：0.020～0.05％,S≤0.008％,P≤0.015％,, and the balance of Fe and unavoidable impurities. The thickness of the normalized rolled steel plate is only 16-80mm, and the temperature difference in the thickness direction of the steel plate is large due to laminar weak cooling to generate performance anisotropy, and if the whole plate is used, the processing stress deformation can occur. Disclosure of Invention In order to solve the technical defects, the invention aims to provide a production method of a Q355B, C, D grade steel plate with the thickness of 81-120mm, which adopts a normalizing rolling and immersion type quick cooling process to roll a casting blank in a recrystallization zone, adopts a large-reduction process to crush, flatten and elongate original austenite, and adopts a grain-boundary induced Nb (C, N) precipitation of Nb element in the steel plate to avoid the growth of uncrushed austenite grains, and adopts a binding nail to prevent the growth of weaving grains, the steel plate is quickly cooled by water after being rolled, so that the temperature of a core part of the steel plate is reduced to below Ar3 and is converted into a 60% ferrite+40% pearlite structure, the strength and low-temperature impact mismatch caused by the growth of the internal structure grains of the steel plate are avoided. In order to achieve the purpose, the invention adopts the following technical scheme that the production method of the Q355B, C, D grade steel plate with the thickness of 81-120mm comprises the following steps: 1) Preparing raw materials and smelting, namely preparing a raw material ：C：0.10-0.14,Si：0.10-0.30,Mn：1.48-1.58,P≤0.015,S≤0.005,Cr：0.005-0.15,Ti：0.01-0.02,Al：0.02-0.05,Nb:0.015-0.025, of a steel plate according to the following chemical components in percentage by weight, namely adding the raw materials into an electric furnace or a converter for smelting, and controlling the tapping temperature to be 1600-1650 ℃; 2) Refining, namely transferring molten steel into an LF furnace for refining, adding slag-forming materials such as lime and fluorite, controlling the slag alkalinity to be 2.5-3.5, refining time to be more than or equal to 30min, feeding wires after refining, and feeding Si-Ca wires or Al wires for deoxidization and inc