SU914634A1 - Process for producing high-quality cast iron - Google Patents

Description

The invention relates to the field of metallurgy, in particular to methods for producing high-quality cast iron.

A method of obtaining high-quality cast iron by smelting carbon-silicon intermediates - ⁵ in two metallurgical units, followed by mixing them, and the smelting is carried out in the cupola mines, and mixing is carried out in mountain cupolas or digger [1].

However, the known method does not allow to obtain various grades of cast iron, and due to the fact that the semi-products are mixed in the furnace or digger, it takes a long time before release into the ladle, which reduces the effect of modification and the quality of the casting.

The aim of the invention is the expansion of technological capabilities and increase the time of the effect of the modifying effect.

2

The goal is achieved due to the fact that according to the method of obtaining high-quality cast irons by melting carbon-silicon intermediates in two metallurgical aggregates with * * "following their mixing, the melting is carried out in two electric furnaces at 14101420 ° С and 1440-1450 ° С for each furnace , moreover, the carbon content in one furnace is maintained within 9.0-4.2%, and in the other 2.6-2.8% of the silicon content in both furnaces is maintained within 0.6-0.8%, and mixing is performed by feeding metal into the ladle from both furnaces in proportions from 2: 1 d about 1: 3 ·

The essence of the proposed method is that the smelting of iron is carried out continuously in two induction _m electric furnaces at 1410-1420 ° C and 14401450 ° C each, respectively. Carbon content ^: in the first furnace is adjusted to 4.0-4.2%, and in the second - to 2.5 “2.7%. The silicon content in both pe3 914634

Chach is maintained at the level of 0.6-0.8%. Production of traditional cast iron grades is achieved by mixing the liquid metal in a two-furnace ladle in appropriate proportions, with 5 ferrosilicon additives and, if necessary, alloying materials. The smelting of cast iron in induction furnaces ensures the production of cast iron of a strictly defined composition and the conduct of refining thermal processing.

The limits of carbon and silicon in the melts of furnaces 1 and 2 are chosen optimal, so that the mixing of cast irons of the indicated composition in proportions from 2: 1 to 1: 3 provides practically any type of cast iron. ' Carburization of the melt in an induction furnace 1 to a carbon content above 4.2% is difficult. The rate of naug-20 freezing at concentrations of carbon reaching 3.5 "4.0% is only 0.02-0.05% / min. The smelting of cast iron in a furnace 1 with a carbon content below 4.0% does not provide 25 low-grade cast-iron irradiation in thin-walled castings even with minimal mixing of cast iron from furnace 2. When using low-grade cast iron, only from furnace 1 does not receive a modifying / · effect when mixed. 7% does not provide a high marks Chu guna ₃₅ · ( h Bt ~ 5b and above.) When reducing the carbon content in furnace 2 to 2.5%, conducting refining thermal treatment at 1440-1450 ° C is not effective. Conducting smelting at higher temperatures increases the wear of the lining and carbon elements. carbon content in the suggested within reach substantial po- ₄₅ Vyshen quality casting.

The limits of the silicon content are chosen taking into account that. exceeding the silicon content above the upper limit of 0.8% ke provides ⁵⁰ specified strength characteristics for high grades of high-quality cast iron. Maintaining the silicon level on the lower limit of 0.6% is difficult due to the use metallootho- ⁵⁵ rows, which is present in the composition over a wide range of silicon? Some amount of silicon goes over4

the same on the lining of the furnace during thermal processing. Due to the maintenance of the silicon content in the iron in the range of 0.6-0.8%, the physical and mechanical properties of the castings are improved.

The temperature mode of the furnaces is chosen taking into account the fact that the refining of cast iron due to thermo-time treatment is determined by the flow of the silicon-reducing reaction, the equilibrium temperature of which for cast iron of furnace 1 is within 1360 1370 ° С, and the cast iron of furnace 2 1390 “1410 ° С.

The refining effect is fully manifested when the melt overheats above the equilibrium reaction temperature by 40-50 ° C, when nonmetallic inclusions are restored, and the resulting CO bubbles purify the melt. Keeping smelting at lower temperatures does not provide a positive refining effect and reduces the dissolution rate of charge materials, and the temperature rises from the upper limits for both furnaces leads to a noticeable frenzy of carbon and other elements.

Mixing cast irons from furnaces 1 and 2 and the addition of modifiers immediately before pouring into the mold (as compared with the known method) contributes to an increase in the time of preservation of the effect of modifying. The preservation effect of the modification while reaching 20-25 minutes

Example. Smelting of synthetic cast iron in two induction electric furnaces of industrial frequency with a capacity of 25 tons.

Steel scrap, electrode chips and ferrosilicon are used as charge materials. In a furnace, the iron of composition C = 4.1%, 5Ϊ 0.7% is smelted, and in the furnace 2 C = 2.7%, δΐ = 0.7%.

After the charge is dissolved and the cast iron of a given chemical composition is obtained, a refining thermo-time treatment is carried out in furnace 1 at 1410 ° C, and in furnace 2 at 1450 ° C. Then, castings of four grades of cast iron are poured with ladles with a capacity of 1 and 3 tons. The metal weight at release from the furnaces is controlled in appropriate proportions with the help of pressure conductors installed on induction furnaces. Additive ferrosilicon is produced in a ladle under the stream when the metal is drained from the furnaces.

5 914634 '6

The table presents the data for obtaining the required grades of cast iron after mixing the cast irons of furnaces 1 and 2.

Simultaneous production of various grades of cast iron due to spot blending

contributes to the reduction of the auxiliary time by approximately 20% for a change in the cast iron grade, which, in turn, increases productivity

5 'labor.

Cast iron brand Composition, % Ratio Oven 1 metal Oven 2 Additive FS-75,% . „L ...... ± ........ Oven 1 | Oven 2 MF 15-32 3.5-3.7 2.0-2.4 67.0 33.0 2.0 MF 21-40 3.3-3.5 1.4-1.7 53.0 47.0 1.2 MF 28-48 3.1.-3.4 1.2-1.5 43.0 57.0 0.93 MF 36-56 2.9-3.0 1.0-1.1 23.0 77.0 0.58

Improving the quality of casting and increasing the time of the effect of the modifying effect allows you to consistently receive suitable castings and reduce scrap by 10%.

Claims (1)

Claim The method of obtaining high-quality cast irons by smelting carbon-silicon intermediates in two metallurgical aggregates with their subsequent mixing, which differs from me in that in order to expand technological capabilities and increase the time of the effect of the modifying effect, smelting produced in two electric furnaces at 1410-1420 ° C and 1440-1450 ° C for each furnace, respectively, and the carbon content in one furnace is maintained in the range of 4.0-4.2%, and in the other - 2.6-2.8% silicon content in. both furnaces are maintained in the range of 0.6-0.8%, and mixing is carried out by feeding liquid metal from both furnaces into the ladle in proportions from 2: 1 to 1: 3 ·