RU2483123C1 - Method of making composite tool material - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises loading charge composed of the mix of steel and iron chips into alundum crucible, smelting in furnace at 1250-1300°C, holding at said temperature for 3-4 min, unloading from the furnace and tempering in water to produce a ledeburite form inhomogeneity composed of white pig iron. Then, obtained ingot is heated to 680-800°C, forged and tempered to obtain composite structure martensite-white pig iron.

EFFECT: simplified process, homogeneous properties.

1 tbl, 8 dwg, 1 ex

Description

The invention relates to metallurgy, and in particular to a method for producing a wear-resistant composite tool material steel - white cast iron and can be used in mechanical engineering for the production of low-cost tools (smoothers for parts from non-ferrous metals).

Currently, composite materials are finding wider application - materials consisting of two or more components that differ in their chemical composition and are separated by a pronounced boundary. Such materials have properties that differ from those of their constituent components.

Laser hardening significantly increases the wear resistance of the surface of cast iron parts due to surface melting, rapid cooling and obtaining a layer of white cast iron. Laser hardening tracks have a rough rough surface and resemble welds in appearance (Samsonov V.I., Shnybkin B.C., Boytsov P.Yu. Laser hardening of cast-iron machine parts // MiTOM, 1989. No. 11. P.6-9).

The main disadvantages of this method include the complexity and high cost of laser systems, low resistance of the laser working bodies, low laser efficiency, the need for light-absorbing coatings, low productivity, insufficient depth of the wear-resistant layer, the unevenness of its properties, the impossibility of hardening low-carbon steels.

The known process for producing instrumental composite material steel - white cast iron, which is used for ironing parts from non-ferrous metals (Gurevich Yu.G., Marfitsyn V.V. Electrocontact chemical-thermal treatment of tool steel for ironers // Engineering Technology, 2009, No. 4. - p.23-25).

White cast iron has a low coefficient of friction and high hardness (wear resistance), so it, unlike the cermets used for smoothers, does not allow scoring during ironing.

The process of obtaining a layer of white cast iron on steel is based on eutectic (contact) melting of iron and graphite. In order for the process to be controlled, local heating was used due to electrical contact heat generation.

Installation for electromechanical processing (EMO) consists of a rotation drive part, a DC or AC power source and a device for supplying current to the roller electrode (Figure 1). A current is passed through the place of its contact with the surface of the part, which, due to the large contact resistance, causes a strong heating of the surface of the part to 1250-1350 ° C. Graphite was used as a roller electrode. As a result, the surface layer of the steel part, up to 1.00 mm thick, turned into a drop of molten iron, which bleached at high speed after cooling (Figure 2).

White cast iron was obtained in the form of tracks resembling welding seams. After grinding on the surface of the part, a wear-resistant composite material steel - white cast iron was obtained (Figure 3). Porous parts made of PK60 powder steel with a coating of ≥20% showed abrasion resistance comparable with chrome cast iron.

The described method of obtaining a wear-resistant composite material steel - white cast iron is laborious, as it requires the manufacture of a special installation and is suitable only for flat surfaces of the part.

The technical result is a significant simplification and cheapening of the production of technology for producing instrumental composite material steel - white cast iron.

The technical result is achieved by the fact that the method of manufacturing a composite tool material includes batching, smelting in an oven, cooling and forging an ingot, the mixture being made in the form of a mixture of steel and cast iron shavings, loaded into an alundum crucible, smelted at a temperature of 1250-1300 ° C, maintained at this temperature for 3-4 minutes, removed from the oven and quenched in water, the forging of the ingot is carried out at a temperature of 680-800 ° C, and then subjected to hardening to ensure the composition of martensite - white cast iron.

An alundum crucible is placed in a furnace providing a temperature of 1250–1300 ° C, into which steel shavings mixed with shavings of gray cast iron are loaded. The amount of cast iron shavings should provide a total carbon content of 1.6-1.7% in the alloy. The crucible with the charge is placed in an oven, heated to a temperature above the melting point of cast iron, maintained at this temperature for 3-4 minutes and quickly cooled in water. The resulting ingot is subjected to forging and subsequent hardening.

Quenching of the ingot in water provides the ledeburite heterogeneity in steel in the form of white cast iron. After heating the steel to a temperature of 680-800 ° C, forging and hardening obtained forgings with structural heterogeneity martensite - white cast iron.

Example. Cast iron and steel shavings were crushed to particle sizes of 3-5 mm, placed in a mixer of the "drunken barrel" type and mixed for 8 hours. The resulting mixture was loaded into an alundum crucible (diameter 25 mm, height 100 mm). The crucible was installed in an oven, heated to a temperature of 1250-1300 ° C, held for 3-4 minutes at this temperature, and then cooled in water.

The ingot was forged at a temperature of 800-680 ° C and a forging was obtained, which is a composite material of eutectoid steel - pre-eutectic white cast iron (Figure 4).

The experiments showed that the preparation of a composite material with the necessary microstructure depends on the heating temperature and the exposure time at this temperature (see table).

Table The temperature of the mixture, ° C Exposure min Microstructure of the ingot before forging The macrostructure of the ingot after forging Forgings microstructure 1250-1300 <3-4 Ledeburite mesh, FIG. 5 Not forged - > 3-4 Widmannstett structure, Fig.6 Not forged - = 3-4 Thin inclusions of ledeburite in martensite, Fig. 7 Well forged The inclusions of ledeburite crushed and extended into arrows, Fig. 8 <1250 3-4 Cast iron has not melted - - > 1300 3-4 Cast iron completely dissolved in steel - -

The proposed method for the manufacture of instrumental composite material by melting a mixture consisting of waste iron and steel production is simpler and cheaper than the known methods, since it does not require:

- special installations for producing composite material;

- reliably provides the necessary chemical composition of the composite;

- application of compact steels;

- high costs for its implementation in production.

Claims (1)

A method of manufacturing a composite tool material, including blending, smelting in an oven, cooling and forging an ingot, characterized in that the mixture is in the form of a mixture of steel and cast iron shavings, loaded into an alundum crucible, and the smelting is carried out at a temperature of 1250-1300 ° C, is held at this temperature for 3-4 minutes, they are removed from the furnace and quenched in water, the forging of the ingot is carried out at a temperature of 680-800 ° C, and then it is quenched to ensure the composition of martensite - white cast iron.

Images