Smelting method of low-sulfur and low-boron steel

Abstract

The invention provides a smelting method of low-sulfur and low-boron steel. The steel comprises, by weight, 0.05%-0.18% of C, 0.10%-0.35% of Si, 1.10%-1.60% of Mn, no more than 0.020% of P, no more than 0.003% of S, 0.010%-0.050% of Nb, 0.008%-0.025% of Ti, no more than 0.30% of Ni, no more than 0.20% of Mo, no more than 0.25% of Cr, no more than 0.0005% of B, and 0.010%-0.050% of Als. The smelting process includes a converter, an LF furnace, an RH furnace and CC. Pretreatment for desulfuration is not needed, the carbon content of steel discharged out of the converter is slightly decreased toreduce molten steel w[B], low-B alloys such as manganese metal and mid-carbon ferromanganese are added, liquid cast waste slag is used, and the quantity of recovered liquid cast slag is controlled, sothat rapid slagging and desulfuration are guaranteed, and the quantity of B dragged into slag is reduced; the LF furnace only adopts aluminum wire deoxidation, and a large quantity of argon is blownfrom the bottom to achieve stirring, so that the probability that boric oxide in the slag is reduced and molten steel enters the slag is lowered while the sulfur content in the molten steel is decreased; and when the sulfur content in the molten steel reaches a required sulfur content, the argon blown from the bottom is regulated to be weak, stirring is conducted to reduce the quantity of added B,and an obtained finished products meets w[S]<=0.003 and w[B]<=0.0005.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a method for smelting low-sulfur and low-boron steel. Background technique [0002] Boron is known as the "vitamin" of steel. As a trace alloying element, the main function of boron in steel is to increase the hardenability of steel, and a trace amount of boron can greatly improve the hardenability of steel. However, boron-containing steel is prone to cracks on the slab, because boron will segregate during the solidification process, reducing the zero plasticity temperature (ZDT) of the steel, widening the brittle range of the steel and increasing the crack sensitivity. In addition, the precipitation of BN in the prior austenite grain boundary, pinning the grain boundary leads to grain boundary embrittlement, which reduces the plasticity of the slab and increases the probability of crack formation. For Mn-containing steel, when the B content in the steel is high, a brittle eute...

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Problems solved by technology

[0004] Chinese patent application numbers CN201711131983.2 and CN201711176053.9 disclose two smelting methods for low-boron steel, both of which adopt molten iron pretreatment for desulfurization until the sulfur content of molten iron entering the furnace is controlled within 0.01%, which greatly reduces the pressure of desulfurization after tapping from the converter "Return" B with molten s

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