Method for smelting steel plate with excellent performance in high-heat-input-welding heat affected zone

Abstract

The invention discloses a method for smelting a steel plate with the excellent performance in a high-heat-input-welding heat affected zone. The method sequentially includes the steps of molten steel pretreatment, combined-blowing converter steelmaking, LF refining, RH vacuum refining, alloy cored wire feeding and continuous casting. According to the method, the content of oxygen in molten steel and the adding conditions of key alloy materials at key stations are controlled, the content of Ti, the content of O, the content of Mg and the content of Zr in the steel meet the design requirements accordingly and can meet the conditions that Ti / O is larger than 5 and smaller than 12, (Mg+Zr) / (Ti+Al) is larger than 0.02, and one or two kinds of a large quantity of Ti-Mg composite-oxide inclusions, a large quantity of Ti-Zr composite-oxide inclusions and a large quantity of Ti-Mg-Zr composite-oxide inclusions with the size smaller than 1 micron are contained in the steel accordingly; in addition, the mass percents of chemical compositions of the inclusions meet the conditions that the mass percent of Ti is larger than 2% and smaller than 40%, the mass percent of Mg is larger than 2% and smaller than 30%, the mass percent of Zr is larger than 2% and smaller than 30%, and the mass percent of O is larger than 5% and smaller than 50%; and the areal density is larger than 300 per mm<2>. Due to the inclusions, growth of austenite crystal grains of the welding heat affected zone can be effectively pinned; and meanwhile nucleus forming of needle-shaped ferrite in the grains is promoted, and therefore the excellent performance in the high-heat-input-welding heat affected zone is guaranteed.

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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