A billet continuous casting method for free-cutting steel with high sulfur content

Abstract

The invention discloses a high-sulfur free-cutting steel square billet continuous casting method. Molten steel comprising, by mass, 0.1-0.3% of C, 0.1-0.3% of S, 0.02-0.1% of Si, 1.0-1.5% of Mn, and the balance Fe and impurities is subjected to continuous casting through a continuous casting machine, and the section of a casting billet manufactured by the continuous casting machine is 250-350 mm wide and 400-500 mm high. According to the characteristics of the high-sulfur free-cutting steel continuous casting billet and the continuous casting machine, the casting speed of the continuous casting billet is reasonably controlled, the water distribution amount of a secondary cooling zone is optimized, the secondary cooling area is divided into a plurality of loops, the water amount of each loop is adjusted independently, the size of a columnar zone and the size of a center equiaxed zone of the continuous casting billet are controlled by changing heat transfer of all cooling zones, thus, the structure solidification process during continuous casting can be controlled, the high-sulfur free-cutting steel continuous casting billet is prevented from generating intercrystalline cracks and center cracks, the center equiaxed crystal ratio of the casting billet is increased, and center segregation and center porosity of the continuous casting billet are perfected.

Description

technical field [0001] The invention relates to a continuous casting method of free-cutting steel, in particular to a billet continuous casting method of high-sulfur content free-cutting steel. Background technique [0002] Free-cutting steel refers to alloy steel in which a certain amount of free-cutting elements such as sulfur, phosphorus, lead, calcium, selenium, and tellurium are added to the steel to improve its machinability. For sulfur-containing free-cutting steel, a certain amount of sulfur is added to the steel to make sulfur, manganese and iron form manganese sulfide and iron sulfide inclusions. Such inclusions can interrupt the continuity of the base metal and promote chip breaking during cutting. Form a small and short crimp radius, which is easy to remove, reduces tool wear, reduces surface roughness, and improves tool life. Generally, the machinability of steel increases with the increase of sulfur content in steel, but at the same time, the longitudinal and ...

AI Technical Summary

Problems solved by technology

[0004] In order to prevent the occurrence of intergranular cracks and central cracks in continuous casting slabs of free-cutting steel with high sulfur content, and improve the central segregation and central porosity of continuous casting slabs, weak cooling systems are often used in continuous casting production, but even weak cooling cannot completely eliminate high sulfur content. The above-mentioned defects of free-cutting steel continuous casting slab