A kind of production method of free-cutting plastic mold steel plate

Abstract

A method for producing free-cutting plastic mold steel plates, the process steps of which are molten iron pretreatment → 120-ton converter steelmaking → LF refining outside the furnace → vacuum treatment RH → continuous casting → heating → rolling → normalizing → tempering → finishing →Performance inspection→Ultrasonic flaw detection. It is characterized in that the chemical composition percentage of steel is: C=0.35~0.45, Si=0.25~0.35, Mn=1.50~1.60, P≤0.008, S=0.05~0.10, Als=0.010~0.045, Cr=1.80~ 2.00, Mo=0.15~0.20, the balance is Fe and unavoidable impurities. The production thickness is less than 120mm free-cutting plastic mold steel plate hardness is 30 ~ 36HRC and the difference is less than ± 0.5HRC, the first-class ultrasonic flaw detection is qualified, which meets the requirements of free-cutting plastic mold steel plate.

Description

technical field [0001] The invention belongs to iron and steel smelting technology, in particular to a production method of free-cutting plastic mold steel plate. Background technique [0002] Free-cutting plastic mold steel is widely used in home appliance manufacturing, computer casing molds and other large-scale long-life plastic injection molds, thermoplastic extrusion molds, blow molds, molding tools, structural parts and other fields, with uniform hardness and good polishing Performance, good machinability and good wear resistance. At present, the free-cutting plastic mold steel mostly adopts increasing the sulfur content in the steel to improve its cutting performance. 2 o 3 Such as super-hard point direct contact, thereby reducing the wear of the tool by the super-hard inclusion point, so that the machinability of steel can be improved. [0003] The current smelting method for producing high-sulfur plastic mold steel plates is mainly to reduce the loss of sulfur ...

AI Technical Summary

Problems solved by technology

However, the disadvantages of this smelting method are: low alkalinity, difficult deoxidation of molten steel, poor ability of slag to absorb inclusions, and difficulty in ensuring the high standard requirements of steel plates for flaw detection

The disadvantages of this smelting method are: a large amount of alumina inclusions are produced during the refining process, and calcium wires must be used to denature the inclusions, and feeding calcium wires will reduce the yield of sulfur wires, and at the same time produce new calcium aluminate inclusions and CaS inclusions thing

[0006] Chinese patent 200810141497.3 discloses a "smelting method of sulfur-added free-cutting plastic mold steel", in which the vacuum treatment method is VD, and the timing of feeding sulfur iron wire is VD After vacuum treatment, vacuum treatment is carried out again after feeding the sulfur iron wire. After the sulfur wire treated by this method is fed into the molten steel, the sulfur in the molten steel cannot be fully uniformed, which may easily cause sulfur segregation. Adsorption, difficult to control sulfur content, high energy consumption for secondary vacuum treatment, tense production rhythm

Chinese patent CN200910062748.3 discloses a "production process for low-carbon and high-sulfur free-cutting steel", which mainly produces billet products, wherein the vacuum treatment is RH, the steelmaking adopts electric furnace steelmaking, and there is no LF refining process, so the steel There are many inclusions in the medium, which cannot meet the production requirements of slabs with large width-to-thickness ratios

[0007] At present, there are many defects in the production of high-sulfur plastic mold steel plates: (1) there are many inclusions in the steel; (2) the yield of sulfur is low; (3) molten steel can Poor castability; (4) Continuous casting slabs are prone to serious segregation and cracks; (5) Hardness uniformity in the thickness direction of the steel plate is poor

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