SU1329909A1 - Method of producing steel ingots - Google Patents

Abstract

The invention relates to ferrous metallurgy, in particular, to the manufacture of short-cutting csfls, ingots of short circuits, which have a mass, for subsequent pressure treatment. The purpose of the invention is the expansion of technological possibilities (production of steel ingots with a mass of up to .4.5 tons, the cure of redistribution by reducing the carbide heterogeneity. Microcoolers are introduced into the metal stream from the moment of pouring 20-40% of the ingot mass to the time of filling profitable extension on 1 / 4-1 / 3 height. I 1 Cp f-crystals, 2 tab. (L

Description

one

The invention relates to ferrous metallurgy, in particular to the production of ingots from high-speed steels, which are subjected to further pressure treatment.

The purpose of the invention is to expand the technological capabilities of obtaining steel ingots with a mass of up to 4.5 tons, reducing the costs of redistribution by reducing the carbide heterogeneity.

A method for producing high speed plates is as follows.

After adjusting the melting in the furnace according to the chemical composition and temperature, the metal is released into the ladle at 1540-1580 ° C and after the end of the ladle in the ladle for 8-12 min. The metal is poured into molds with a capacity of 2.8-4.5 with simultaneous insertion through the center after filling metal with 20-40% of the ingot body to filling 1 / 4-1 / 3 the height of profitable extension of metal powder of steel similar or similar (chemical composition of the fraction 40-800 µm with the oxygen content in the powder 0.01-0.02% in the amount of 0.6-3.5% by weight of the metal in the mold with the subsequent transfer of The powder is added in such an amount as to prevent excessive cooling of the steel in the mold and the formation of crusting of the crust. The powder is obtained by spraying the fast-drying steels with argon in a special unit, which allows to obtain metal powder of a given chemical composition with oxygen content in the range of 0.01-0.02% of any fractional composition, but not more than 1 mm.

High-speed steels belong to the eutectic (carbide) class — the main redundant structural component in them is the eutectic. The crystallization of high-speed steels is accompanied by the segregation of alloying elements and increased carbide heterogeneity. The brittle mesh formed by the eutectic greatly reduces the plastic properties of cast steel, and only as this mesh is crushed does the plastic properties increase. The minimum plasticity gg weighing no more than 1250 kg. Further observed in the cast state, while the stretch (reduction rate) allows

to produce high-speed steel with carbide heterogeneity for 1-2 balancing the fragile eutectic mesh is most fully manifested. At temperatures of hot plastic matter below, what is achieved in the well-known

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Formations of maximum plasticity are achieved when the particles of the eutectic composition are sufficiently dispersed and evenly distributed in the bulk of the solid solution. For this reason, casting of these steels is carried out only in ingots weighing up to 1250 kg (preferably 0.5-0.7 g). Casting into larger ingots is not effective due to the formation of large carbide inclusions and the loss of ductility in the hot state.

Hot plastic deformation is the most radical way to reduce carbide inhomogeneity. Such a decrease occurs as a result of the fragmentation of fragile eutectic accumulations and the subsequent more uniform distribution of these particles in the mass of the solid solution. The greater the degree of stretching of the workpiece, the more fully the process of crushing the eutectic is completed and the smaller the carbide mesh. At the same time, in order to receive a large stretch of the same section, it is necessary to increase the cross section of the initial ingot and its mass. For this reason, according to the proposed method, the casting of high-speed steel was made into ingot molds for ingots with a mass of 2.8-4.5 tons. The limits of ingot mass oscillation were established practically and determined depending on the redistribution scheme used and the dimensionality of the workpiece pieces for subsequent redistribution.

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However, such an increase in the size of the casting leads to a significant increase in the degree of segregation. The addition of a metal powder of the 40–800 µm fraction to the crystallizing metal eliminates these drawbacks and contributes to grinding the carbide phase of the cast metal. The grain size of the powder is selected in such a way as to create centers of crystalline aliasadia with obtaining a carbide phase in the cast metal, the K9 score of the second varies from 6–8, i.e. carbide inclusions of such size that are present in the cast metal, obtained by known methods only on ingots

la below, what is achieved in the famous

way. This is achieved by the fact that the extraction of metal from an ingot is 2.8–4.5 tons by a factor of 2–3, more than on ingots with a mass of 0.5–1.25 tons, and the level of segregation due to the creation of additional crystallization centers and the increase in cooling rate will remain at the level of the known method.

Additive metal powder fraction less than 40 microns is impractical because it contributes to the sintering of the particles in the center to a significant amount. In addition, with a decrease in the metal powder fraction, the oxygen content in the powder increases and, accordingly, the oxygen concentration in the finished metal is up to 0.007-0.009% instead of 0.006-0.008%. The use of a powder with a fraction greater than 800 µm for a given ingot mass is not effective, since non-dissolved particles, observed by the naked eye, are found in the cast metal.

Entering the metal powder into the mold before filling with metal less than 20% of the height of the ingot body promotes the formation of torsional crust due to overcooling of a small volume of liquid metal in the mold (see Table 1).

Additive powder after filling 40% of the height of the ingot body limits the amount of powder injected.

In the production of blanks from high-speed steels of smaller cross-section (square mm), the nature of the change in the carbide heterogeneity score is preserved, but by absolute value, 1-2 points lower than in the case of production using standard technology. Thus, the casting of high-speed steels into ingots with a mass of 2800–4500 kg using inoculators makes it possible to produce billets of a large section (250–350 mm) with carbide heterogeneity at a level less than 0.6% of the metal mass and does not provide a reduction in the carbide score 35 Dart technology, but not only for the phase. The introduction of metal powder ingots weighing up to 1200 kg and a section after filling 1/3 of a profitable extension is impractical because the powder granules do not have time to dissolve.

Thus, the increase in mass

blanks up to 60 mm.

To test the production of high-speed steels, steel was melted 40 liters in an electric furnace with a capacity of 15 tons and cast into ingots for ingots.

the initial ingot, first of all its cross-section, and the creation of additional crystallization centers make it possible to significantly increase the degree of reduction of the cast metal and reduce carbide segregation.

The change in the carbide heterogeneity score during the redistribution of ingots of different mass is given in table. 2, With an increase in the mass of the initial ingot from 200 to I200 kg with the same cross-section of the workpiece, the carbide heterogeneity score decreases. Thus, the carbide heterogeneity of the workpiece 60 j mm, obtained from an ingot of 200 kg, is in the axial 5.0-6.5 points (62%) and decreases to 2.5-3.5 points during the redistribution of the ingot weighing 1200 k

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When receiving preparations large; The cross section (250-350 mm) of ingots of the same mass has a carbide heterogeneity of 7-8.5 points. A further increase in the reduction ratio due to an increase in the ingot mass to 2100– 2500 kg leads to a decrease in the carbide heterogeneity score to 5.0–6.5 points and stabilizes at the same level with an increase in the ingot mass to 2800 kg.

The addition of microcoolers allows the carbide heterogeneity score to be significantly reduced in the blanks. large section. Thus, the carbide heterogeneity in the blank circle of 350 mm for ingots weighing 2800-4500 kg averaged 4-5 points, which is 1-2 points lower than the indicators of the known method (Table 2, see blank 16-21).

In the production of blanks from high-speed steels of smaller cross-section (square mm), the nature of the change in the carbide heterogeneity score is preserved, but by absolute value, 1-2 points lower than in the case of production using standard technology. Thus, the casting of high-speed steels into ingots with a mass of 2,800–4,500 kg using inoculators makes it possible to produce billets of a large cross-section (250–350 mm) with carbide heterogeneity at the level of mill 20

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EC35 standard technology, but not only for ingots weighing up to 1200 kg and cross-section tdartnoy technology, but not only for ingots weighing up to 1200 kg and cross-section

blanks up to 60 mm.

To test the production of high-speed steels, steel was melted in an electric furnace with a capacity of 15 tons and cast into ingot molds for ingots.

3.6 t. The mass of the obtained ingot of steel Р6АМ5 was 3860 kg. Metal powder high-speed steel

200-250 microns fractions were introduced via: a central sprue with a special calibrated device. The powder was added after filling the ingot with 25% of the body height and finished with filling.

SRI 1/4 of the height of profitable extension. Metal powder injected in the amount of 1.46% by weight of metal in the mold. The oxygen content in the powder was 0.014%. Body

the ingot was filled in 210 s and the profitable extension - in 100 s.

Casting was performed with an exothermic mixture. After complete crystallization of the metal in the mold (after

130 minutes after casting and removal of the extensions, the ingots were sent to the heating furnaces-forging shop department by a hot horse. When the ingots were heated to a predetermined temperature, they were forged for three sizes from a square section of 520 mm to a circular 350 mm. Further redistribution of the metal part was carried out in the forging shop at the RCM to the size of the workpiece, square 100 mm, followed by rolling on small section mills into smaller profiles. Metal samples were taken at each reprocessing for quality control and carbide heterogeneity.

Carbide heterogeneity for round billets of 350 mm in size was 4-5 points, 250 mm in size was 3-4 points, 60 mm in size was 2 points, for a blank, 100 mm square was 2-3 points. These indicators are significantly better than the standard technology and are equated to the quality of the metal.

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Claims (1)

1. A method of producing steel ingots, mainly from fast-cutting steels, including smelting and pouring a melt with simultaneous introduction of micro-refrigerators into the stream,. characterized in that, in order to expand the technological capabilities of producing steel ingots with a mass of up to 4.5 tons, reduce the costs of redistribution by reducing carbide heterogeneity, microcoolers begin to enter 20-40% of the mass of ingot metal when casting and complete the input when filling 1 / 4-1 / 3 of the height of the upper extension. 2 The method according to claim 1, characterized in that the micro refrigerators are used with a fraction of 40-800 microns in an amount of 0.6-3.5% of the mass of the ingot. Poro ok don't yurete Udoaletvortip but . Dissolve on dissolve It is convenient Thats not Poro oh not rass Udoapaetitive-io Also Poroiok does not dissolve That “e Carbide heterogeneity in agotovhg with different slip weight Valid nsh technology T b “c 2