Production method of -195℃ ultra-low temperature seamless steel pipe billet steel

Abstract

The invention belongs to the field of metallurgy and particularly relates to a production method for tube blank steel Gr.8 for a -195 DEG C ultra-low temperature seamless steel tube. The production method for the tube blank steel for the ultra-low temperature seamless steel tube includes the technological processes of smelting of a high-impedance ultra-high power electric arc furnace, LF refining and VD vacuum treatment. In the process of smelting of the electric arc furnace, the percent of C of smelting end-point molten steel is controlled to be smaller than or equal to 0.02%, and the percent of P of the smelting end-point molten steel is controlled to be smaller than or equal to 0.002%. During steel tapping of the electric furnace, pre-deoxygenation is conducted, and the content of Al of the molten steel is controlled to range from 0.09% to 1.4%. The steel tapping temperature of the electric arc furnace ranges from 1,650 DEG C to 1,670 DEG C. In the process of LF refining, lime and synthetic slag are adopted for slag making, and the total mass of the lime and the synthetic slag accounts for 1.4% to 2.0% of the mass of the molten steel. The mass percent of the lime ranges from 70% to 80%, the mass percent of the synthetic slag ranges from 20% to 30%, and the synthetic slag is prepared from 60%-68% of CaO, 15%-20% of Al2O3, 10%-15% of CaF2, 5% or less of SiO2, 3% or less of MgO and 0.1% or less of S. The tube blank steel, for the ultra-low temperature seamless steel tube, produced through the method is high in purity and can be directly used for rolling the seamless steel tube, and therefore volume production is achieved.

Description

technical field [0001] The invention belongs to the field of metallurgy, and is particularly suitable for the production method of tube blank steel Gr.8 for ultra-low temperature seamless steel tubes at -195°C. Background technique [0002] With the rapid development of my country's economy, domestic petroleum, chemical and other energy industries need a large amount of low-temperature steel to manufacture various production and storage equipment for liquefied petroleum gas, liquid ammonia, liquid oxygen, and liquid nitrogen. According to my country's "Twelfth Five-Year Plan", the development of petrochemical energy will be optimized in the next five years, and the development of oil and gas resources will be accelerated. This will provide a broad market and development opportunities for the energy production and storage equipment manufacturing industry under low temperature service conditions, and will also promote the development of low temperature resistant materials. Be...

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Problems solved by technology

[0004] It can be seen that the above methods are all used to produce ultra-low temperature plates, and all of them are produced by the long-process process line of the converter, and the molten iron is subjected to deep desulfurization pretreatment to ensure the purity of the steel. The production cycle is long, the cost is high, and the competitiveness is poor. The molten steel produced is all poured into slabs, which are forged or directly rolled into steel plates, which cannot solve the problem of directly rolling seamless steel tubes with continuous casting slabs

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