A kind of smelting method of steel plate with excellent performance of welding heat affected zone with large heat input

Abstract

The invention discloses a steel plate smelting method with excellent performance in the heat-affected zone of welding with large heat input. The technological process is sequentially molten iron pretreatment, re-blowing converter steelmaking, LF refining, RH vacuum refining, wire feeding of alloy cored wire, and continuous casting . The present invention controls the oxygen content in molten steel at key stations and the addition conditions of key alloy materials, so that the content of Ti, O, Mg, and Zr in the steel can meet the design requirements, and can satisfy 5<Ti / O<12, ( Mg+Zr) / (Ti+Al)>0.02, so that the steel contains a large number of Ti-Mg, Ti-Zr, Ti-Mg-Zr composite oxide inclusions with a size of less than 1 μm or both, and the inclusions The mass percentage of the chemical composition of the product satisfies 2%<Ti<40%, 2%<Mg<30%, 2%<Zr<30%, 5%<O<50%, and the surface density is greater than 300 pieces / mm2. These inclusions can effectively pin the austenite grain growth in the heat-affected zone of welding, and at the same time promote the nucleation of acicular ferrite in the grain, thereby ensuring the excellent performance of the heat-affected zone during welding with large heat input.

Description

technical field [0001] The invention belongs to the field of high-weldability steel plate production, in particular to a method for smelting a steel plate with excellent performance in a large heat input welding heat-affected zone. Background technique [0002] In recent years, the steel materials used in shipbuilding, construction, oil and gas pipelines, and offshore platforms have gradually developed towards higher strength and thicker walls. In order to improve welding efficiency and shorten the construction period, multi-wire submerged arc welding, gas Efficient large heat input welding such as electric vertical welding and electroslag welding. From the point of view of ensuring safety, it is required that the weak link in the welded structure - the welded heat-affected zone must also have sufficient strength and toughness. [0003] However, it is generally known that with the increase of welding heat input, the austenite grains in the welding heat-affected zone will gr...

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Problems solved by technology

[0008] 1. O, as a key element of composite inclusions, is greatly affected by the alloying of molten steel at different smelting stations. Too high or too low O content will affect the alloying of the latter station, and make it difficult to form in the steel plate Effective size and sufficient number of inclusion particles

However, the above-mentioned technologies have not disclosed the O content control method and quantitative indicators in the smelting process.

[0009] 2. Ti, B, Mg, Zr and other trace elements play an important role in steel, but the above technology does not disclose the process parameters in the steelmaking process, such as alloy addition method (including cored wire size, wire feeding speed, etc.), alloy addition The temperature of the molten steel, the dissolved oxygen content in the molten steel, etc.; the above process parameters directly determine the type, size, density, and distribution of inclusions in the steel, and then directly determine the welding performance of the steel plate.

When the content is less than 0.005%, it is difficult to form a sufficient number of oxysulfide inclusions, and it is difficult to achieve the purpose of refining the grain structure; when the content exceeds 0.008%, coarse sulfides will be formed, and these coarse sulfides will act as cracks The starting point of the formation reduces the toughness of the base metal and the heat-affected zone of the weld. At the same time, too high S content will also lead to central segregation of the slab

[0011] 4. The composite inclusion technology disclosed in the above-mentioned patent is mainly based on oxysulfide and oxynitride. These particles are mostly inclusion particles with a size > 1 μm, while the smelting technology and chemical Lack of quantitative description of components, sizes, areal density, proportions and other characteristics

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