SU1323227A1 - Method of producing castings - Google Patents

Abstract

The invention relates to foundry, in particular, to a technology for producing castings from alloyed wear-resistant cast irons. The purpose of the invention is to increase the abrasive and impact-abrasive resistance of castings. An increase in abrasive and shock-abrasive resistance is achieved by using an eutectic (carbon content 4.5-5.5%) high-chromium cast iron cooled at a speed of 1000-1400 ° C / s. Achieve at least a twofold increase in the service life of parts operating under conditions of abrasive wear. S

Description

The invention relates to foundry, in particular, to the technology of producing: wok from alloyed wear-resistant cast irons

The purpose of the invention is to increase the abrasive and impact-abrasion resistance of castings.

Cast iron is poured with a carbon content of 4.5-5.5%, for example, in a copper chill die, which is cooled at a speed of 1000-1300 ° C / s.

The use of high-chromium (Cr-18-22) prosthetic iron, combined with a high cooling rate of the melt in the crystallization range, results in the formation of a structure of fine-needled martensite with an optimal amount of evenly dispersed chromium type carbides after casting. This combination of structural components provides an increase in the abrasive and impact-abrasive resistance of parts.

At a carbon concentration in the range of 4.5–5.5%, in the crystallization process, an initial nucleation occurs, even in a liquid melt, to a large number of highly dispersed reinforcing carbides. higher hardness than and subsequent formation of a solid phase - austenite, which transforms from a decrease in temperature to a high-strength martensitic base, which leads to an increase in abrasive and shock-abrasive resistance of castings. At the same time, a high cooling rate prevents further growth of carbides and fixes their uniform distribution over the entire matrix volume. When the carbon content is less than 4.5% in combination with

in combination with a cooling rate of 1000-1400 C / s, the carbide phase is formed in an amount insufficient to increase the shock-abrasive wear resistance. In addition, a eutectic is formed, drastically reducing the viscosity and structural strength of the cast iron. With a carbon content of more than 5.5%, along with the formation of chromium carbides, cementite-type carbides will appear, also embrittling the metal and reduce the wear resistance of the casting.

The cooling rate of the molten iron in the crystallization range is integral and one of

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Factors of the method of manufacturing castings from high-chromium engineering iron, so it determines the amount, size and distribution of the carbide phase, as well as the degree of doping of the metal base and the formation of small-needle martensite, on which the wear resistance of castings depends. At a cooling rate of 1000-1400 C / s, the structure is crushed, a large amount of highly dispersed evenly distributed primary carbides of high hardness is formed, and fine-needle doped martensite is formed, which ensures high values of both abrasive and impact-abrasive resistance. The cooling rate of zigzid cast iron of less than 1000 C / s leads to the formation of very large primary hypereutectic carbides, which are very embrittling.

metal. When the cooling rate is over.

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Above 1400 C / s, a high-alloyed austenitic structure without carbide inclusions, possessing high strength, is formed in the alloy. Carbides in such a structure are released later — in the process of working parts and their separation in the form of large particles of the type (Cr, Fe) jCj along the boundaries of austenitic grain leads to embrittlement and reduction of its impact-abrasive resistance and strength of castings.

The method allows to obtain martensitic-carbide structure of cast iron with highly dispersed carbides,.

Example. Spent smelting of zavtektichesky high-chrome iron in an induction furnace with an acid lining of the following composition, wt.%: Carbon 5,2; chromium 22.3; manganese 1.84; silicon 0.65; iron. AT

shyu: you used carbon steel scrap, ferrochrome FH650 and FH800, carbonizing additives, as well as ferroalloys silicon and manganese. Cast iron was cast at t 1550 ° C to a water-cooled copper chill mold. The castings have the shape of rectangular plates 100x60x16 mm. The melt was cooled in the mold until solidified completely at a rate of 1200 C / s. In addition, cast samples were cast for bending tests. The proposed method provides improved abrasive wear resistance

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3 13232274

2.3-3.2 times, and impact-abrasive high-chromium cast iron and wear resistance 2.2-2.9 times. according to its cooling, distinguishing compared with the prototype. with the fact that, in order to improve

The formula of the invention i bone castings, pouring carried out

carbon with a 4.5 carbon content; a method for producing castings, including 5.5%; and cooling is carried out with a rapid filling of the mold with a doping of 1000-1400 s / s.

Claims (1)

Claim A method of producing castings, including baking into a mold of alloyed high-chromium cast iron and its cooling, characterized in that, in order to increase the abrasive and impact-abrasive resistance · 5 of the castings bone, casting is carried out with cast iron with a carbon content of 4.55.5%, and cooling is carried out at a speed of 1000-1400 ° C / s.