SU1217918A1 - Cast tool steel - Google Patents

Description

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The invention relates to metallurgy, in particular to tool steels for the preparation of a cast tool operating under cyclic loading conditions.

The purpose of the invention is to increase the fluidity of the proposed steel while maintaining heat resistance and heat resistance.

The deterioration of the casting properties is achieved by the introduction of copper and calcium into the composition of the steel. Copper reduces the melt viscosity of the steel, and calcium helps to clean the steel from chemical impurities and their globalization, as well as prevents oxide films from forming on the surface of the melt during casting, which leads to an increase in heat resistance.

With a high chromium content (11, 13.0%), in the cast structure of low-carbon steel (0.15-0.22% s), an excess high-temperature 8-ferrite in an amount of more than 10% is formed, which leads to a significant decrease in the alloy's high resistance. In order to eliminate the possibility of the formation of S-ferrite in the structure and to reduce heat resistance, nickel is introduced into the alloy in an amount of 0.5-1.5 May. % When the nickel content is less than 0.5 May. % in the cast steel structure, O-ferrite is detected, with a content of more than 1.5 wt.% O-ferrite is not formed, but residual austenite begins to appear, which negatively affects heat resistance, and the heat resistance of the alloy decreases . The decrease in the level of heat resistance of steel with the introduction of nickel into it, due to a decrease in the temperature of the core Y - transformation, compensated by complex microalloying with nitrogen and vanadium

Nitrogen is introduced into the steel to increase its heat resistance due to the formation of highly dispersed evenly distributed vanadium nitrides in the alloy structure. The nitrogen content is less than 0.04 wt.% With a high chromium content in the steel (up to 13.0 May,%) is not enough to form nitrides. When nitrogen is introduced, 0.12 wt.% In the process of solidification of the alloy, it is released from the solution, which leads to the formation of gas porosity in cast billets.

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The increase in the content of vanadium in steel (0.30-0.58 wt.%) Is due to the fact that part of the vanadium is spent on the formation of nitrides and its content is less than 0.3 May. % Nitrides in the alloy structure are not formed. When the vanadium content exceeds 0.58 wt.%, A decrease in hardness occurs and the formation of ferrite in its structure, which leads to a decrease in the alloy's extreme resistance.

The increase in the content of silicon (up to 0.1 May.%) And manganese (up to 0.8 May.%) Is due to the fact that when smelting metal in low-portion smelting furnaces of foundry shops, it becomes more intensely saturated with oxygen, which negatively affects the complex of operational heating. become. When co-deoxidized with silicon and manganese, low-melting manganese silicate is formed, which easily passes into the slag, the output from the melt

25 unrelated kielorod. When the content of silicon and manganese is less than 0.4% by mass, etal is not sufficiently acidified, which negatively affects the casting properties of steel. With

30 manganese content of more than 0.8 wt.% In the structure of the steel appears residual auretite, which leads to a decrease in heat resistance. The silicon content in the metal is more than 1.0% by mass. leads to a lower shock in the zo- nets and, as a matter of fact, to a decrease in unreliable resistance.

Steel is used in the heat-treated condition in the following mode: annealing at 920-950 ° C for 4-6 hours; oven cooling to 50020

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550 C, further air cooling; quenching from 1050-1070 ° С to oil; tumbling off at 610-620 ° С, holding 1.5-2 hours, further cooling in the air. Solidify after the heat treatment of the treatment 44-48HRC. The structure of the steel after a full heat treatment cycle is a trooetoorbit metal base with scarbides such as vanadium nitrides.

The chemical composition of the proposed and known steels, its heat resistance, high heat resistance and foundry properties are listed in the table (melting 1 — known steel, melting 2 and 6 have the contents of components outside the specified limits, 3-5 — steel offered).

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The proposed steel has 50 to the heat resistance at the former

60l higher fluidity level.

in comparison with known steel; The economic effect is achieved

while maintaining a high resistance to increased tool life.

Claims (1)

-CAST INSTRUMENTAL STEEL, containing carbon, chromium, molybdenum, manganese, silicon, tungsten, vanadium, niobium, iron, characterized in that, in order to increase the fluidity of the steel while maintaining The rest is wounded by heat resistance and heat resistance, it additionally contains nickel, nitrogen, copper and calcium in the following ratio of components, May. %: Carbon Chrome Molybdenum Manganese Silicon Tungsten Vanadium Niobium Nickel Nitrogen Copper Calcium Iron | C □ о