Low carbon high sulfur free-cutting steel production process

Abstract

The invention provides a low carbon high sulfur free-cutting steel production process, comprising the following steps: 1) an electric furnace is used to blow oxygen for melting without supplying electricity, the ratio of hot molten iron and waste steel reaches 7.0:1.0-3.0, a carbon-oxygen gun arranged on a furnace door and an oxygen-coal sublance gun arranged on a furnace wall are used for blowing oxygen for melting with rich carbon in the furnace; 2) the operation of eccentric bottom tapping and retained slag and steel are carried out, pre-deoxidation is processed on the furnace rear, then slag is produced; 3) low-basicity slag is produced in a refining furnace, the refined slag comprises the following components by weight percentage: 40-50% of CaO, 15-30% of SiO2, 20-35% of Al2O3 and 5-15% of MgO; when each element chemical composition in the steel reaches the requirements under the temperature of 1580-1600 DEG C, Ca lines or Ca-Si lines are put in the refining furnace, the time of soft blowing is 8-15min, crater formation modified atmosphere packaging is put on a continuous casting platform; 4) a four pass arc continuous casting machine is used for continuous casting, a long nozzle arch welding joint is used for sealing and protecting and argon is blown in an intermediate container to protect casting; low cooling process is adopted for secondary cooling, electromagnetic mixing is adopted by a crystallizer, wherein the electric current is 600-700A and the frequency is 4-5 Hz.

Description

technical field [0001] The invention relates to a production process method of low-carbon high-sulfur free-cutting steel, in particular to a production method of low-carbon high-sulfur free-cutting steel comprising Consteel electric furnace + refining furnace + continuous casting. It belongs to the metallurgical industry. Background technique [0002] Free-cutting steel is a steel grade characterized by excellent cutting performance. Because this steel grade has lower cutting force and cutting temperature in the cutting process, it has the advantages of good chip handling, good surface finish and improved tool life. , and are widely used in industries such as automobiles, tractors, machine tools, instrumentation and IT with a large amount of cutting and high degree of processing automation. As a result, the cutting cost has been doubled, the product quality has been greatly improved and the production efficiency has been doubled. Foreign free-cutting steel is mainly produc...

AI Technical Summary

Problems solved by technology

[0006] Free-cutting steel is one of the three major types of steel that are difficult to continuously cast in the world. The main difficulties in the development of its continuous casting process are: the high oxygen content and high sulfur content of free-cutting steel greatly reduce the surface tension of molten steel, making it difficult to separate steel slag. As a result, steel slag is mixed and rolled, forming a large number of surface and subcutaneous defects, and even causing steel breakout, making continuous casting difficult; free-cutting steel has high manganese and oxygen content, and will have physical and chemical reactions with certain components in refractory materials at high temperatures , so that the refractory material is corroded, resulting in steel overflow or tundish leakage in continuous casting production; free-cutting steel liquid has high viscosity and poor fluidity. In order to ensure its castability, the pouring temperature must be increased, but at the same time, free-cutting steel It is also crack-sensitive steel, and weak cooling system must be adopted. These contradictory requirements make it very difficult for free-cutting steel to change from die casting process to continuous casting process, and it once became a forbidden area for continuous casting workers.

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