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A 780 MPa class high heat input welding steel for improving the toughness of the heat-affected zone and its manufacturing method

A technology of large heat input welding and heat affected zone, applied in the field of high-strength steel welding, can solve the problems of deterioration of HAZ toughness of high-strength steel, increase of MA component distribution, increase of stress concentration points, etc., so as to promote the reduction of quantity and reduce the cost of raw material input. , the effect of reducing the number distribution

Active Publication Date: 2022-03-29
LONGYAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Although this method has played a certain role in improving the HAZ toughness, this method is only applicable to steel grades with a strength level of 500 MPa to 600 MPa, and is not suitable for steel grades with higher strength. When the strength of steel grades is increased to 780 MPa grades, The microstructure of the base metal will be upgraded to lath bainite structure. Under the condition of high heat input welding, the austenite grain coarsening is serious, and the lath bainite structure in the austenite grain is further coarsened, and the MA component The distribution began to increase, causing more stress concentration points. After the superposition of various factors, the HAZ toughness of 780 MPa high-strength steel was seriously deteriorated.

Method used

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  • A 780 MPa class high heat input welding steel for improving the toughness of the heat-affected zone and its manufacturing method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] A 780 MPa grade high heat input welding steel plate, its components and mass fractions are: C: 0.03%, Si: 0.45%, Mn: 1.46%, P: 0.05%, S: 0.017%, Mo: 0.73% , Ni: 2.80%, Ti: 0.11, the balance is Fe and unavoidable impurities.

[0019] The manufacturing method of the above-mentioned 780 Mpa high heat input welding steel for improving the toughness of the heat-affected zone is as follows:

[0020] (1) Smelting: According to the composition design of 780 MPa-level high-heat input welding steel, the required alloy raw materials are smelted at 1650°C, molten steel is smelted, and steel ingots are obtained by pouring at 1600°C;

[0021] (2) Rolling: Heat the steel ingot to 1200°C and keep it warm for 2 hours. After fully austenitizing, the steel ingot is subjected to rough rolling for 3 passes. The pass reduction rate is 10%, the cumulative reduction rate is 30%, and the rough-rolled plate is obtained; the rough-rolled plate is subjected to 3 passes of finish rolling, the fini...

Embodiment 2

[0025] A 780 MPa class high heat input welding steel plate, its components and mass fractions are: C: 0.03%, Si: 0.7%, Mn: 1.1%, P: 0.04%, S: 0.015%, Mo: 0.9% , Ni: 2.20%, Ti: 0.17, the balance is Fe and unavoidable impurities.

[0026] The manufacturing method of the above-mentioned 780 Mpa high heat input welding steel for improving the toughness of the heat-affected zone is as follows:

[0027] (1) Smelting: According to the composition design of 780 MPa-level high-heat input welding steel, the required alloy raw materials are smelted at 1600°C, molten steel is smelted, and steel ingots are obtained by pouring at 1600°C;

[0028] (2) Rolling: Heat the steel ingot to 1200°C and keep it warm for 4 hours. After fully austenitizing, the steel ingot is subjected to rough rolling for 3 passes. The pass reduction rate is 10%, the cumulative reduction rate is 30%, and the rough-rolled plate is obtained; the rough-rolled plate is subjected to 3 passes of finish rolling, the finish ...

Embodiment 3

[0031] A 780 MPa class high heat input welding steel plate, its components and mass fractions are: C: 0.05%, Si: 0.4%, Mn: 2.3%, P: 0.045%, S: 0.013%, Mo: 0.4% , Ni: 3.40%, Ti: 0.08, the balance is Fe and unavoidable impurities.

[0032] The manufacturing method of the above-mentioned 780 Mpa high heat input welding steel for improving the toughness of the heat-affected zone is as follows:

[0033] (1) Smelting: According to the composition design of 780 MPa-level high-heat input welding steel, the required alloy raw materials are smelted at 1650°C, molten steel is smelted, and steel ingots are obtained by pouring at 1600°C;

[0034](2) Rolling: Heat the steel ingot to 1300°C and keep it warm for 2 hours. After fully austenitizing, the steel ingot is subjected to rough rolling for 3 passes. The pass reduction rate is 10%, the cumulative reduction rate is 30%, and the rough-rolled plate is obtained; the rough-rolled plate is subjected to 3 passes of finish rolling, the finish ...

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Abstract

The invention discloses a 780 MPa grade high heat input welding steel for improving the toughness of a heat-affected zone and a manufacturing method thereof. The mass fraction of each component of the steel is: C: 0.03%-0.05%, Si: 0.40%-0.70%, Mn: 1.10%-2.30%, P: ≤0.05%, S: ≤0.02%, Mo: 0.40 % to 0.90%, Ni: 2.20% to 3.40%, Ti: 0.08% to 0.17%, and the balance is Fe and unavoidable impurities. In the present invention, through reasonable composition design and process control, O-type inclusions are formed in the base metal and become the starting point for the nucleation of lath bainite. The arrangement forms a multi-directional bainite structure, which can effectively hinder the expansion of cracks and make the base metal have higher mechanical properties. After high heat input welding, the austenite grain size in the HAZ increases slightly, and it is still a multi-directional bainite structure, which makes the HAZ have higher low-temperature impact toughness and improves welding efficiency.

Description

technical field [0001] The invention belongs to the technical field of high-strength steel welding, and in particular relates to a 780 MPa grade high heat input welding steel for improving the toughness of a heat-affected zone and a manufacturing method thereof. Background technique [0002] In recent years, in shipbuilding, oil storage tanks, offshore platforms and other fields, with the increase in size and high strength of processing components, in order to reduce the amount of steel used, 780 MPa high-strength steel is often used as processing materials. These high-strength steel plates are usually joined by welding. In order to improve the efficiency of welding construction and reduce manufacturing costs, large heat input welding methods such as gas-electric vertical welding, submerged arc welding, and electroslag welding have been adopted in the field of medium-thick plate manufacturing. Widely used, but when the welding heat input is higher than 50kJ / cm, the peak temp...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/08C22C38/12C22C38/14C21D8/02C22C33/04
CPCC22C38/02C22C38/04C22C38/12C22C38/08C22C38/14C22C33/04C21D8/0205C21D8/0226C21D8/0263C21D2211/001C21D2211/002
Inventor 宋峰雨
Owner LONGYAN UNIV
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