Bismuth-containing free-cutting pre-hardened plastic die steel and preparation method thereof

Abstract

The invention discloses bismuth-containing free-cutting pre-hardened plastic die steel and a preparation method thereof. The die steel comprises the following chemical components of, in percentage bymass, 0.32%-0.40% of C, 0.15%-0.30% of Si, 1.50%-1.70% of Mn, 1.70%-2.00% of Cr, 0.85%-1.15% of Ni, 0.25%-0.40% of Mo, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.05%-0.10%of V, 0.05%-0.15% of Bi, and the balance Fe. The preparation method comprises the following steps that smelting and casting are performed into a cast ingot according to set chemical components, the cast ingot is subjected to high-temperature homogenization treatment into a forging stock, normalizing treatment is performed offline after forging to refine grains, and finally, quenched-tempered heattreatment is performed to obtain a uniform structure with the hardness of 32-48HRC. According to the bismuth-containing free-cutting pre-hardened plastic die steel, through reasonable chemical component design, the bismuth element is added to replace traditional free-cutting elements including sulfur and lead, and due to the fact that a sulfur content is controlled, reasonable forging and heat treatment processes are matched, the hot brittleness phenomenon and anisotropy caused by the sulfur element are avoided, meanwhile, the problems that the lead is harmful to human bodies and pollutes anenvironment are solved.

Description

technical field [0001] The invention belongs to the technical field of alloy steel, in particular to a bismuth-containing free-cutting pre-hardened plastic mold steel and a preparation method thereof. Background technique [0002] Plastic mold is an important process equipment in the plastic molding industry. The wide application of plastic products has driven the rapid development of the plastic mold steel industry. In the total output of mold steel in industrially developed countries, plastic mold steel accounts for the largest proportion, and the industry's demand for plastic mold steel is also increasing. In recent years, the large-scale home appliance manufacturing industry and the automobile manufacturing industry have continuously increased the strength demand for high-end plastic products, which has led to the development of plastic mold steel in the direction of high hardness, so as to ensure its higher strength and better wear resistance And polishing performance,...

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Problems solved by technology

[0004] In view of the above technical problems, the present invention provides a bismuth-containing free-cutting pre-hardened plastic mold steel, which replaces traditional sulfur and lead with bismuth, and solves the anisotropy of mechanical properties caused by sulfur-containing inclusions and the problem of lead pollution. At the same time, the Bi content is controlled, which solves the problem of affecting the mechanical properties of the steel when the Bi content is too high, and the prepared plastic mold steel has good mechanical properties and cutting performance.

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