SU1650707A1 - Method of producing cast iron with vermicular graphite - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of iron with vermicular graphite. The purpose of the invention is to reduce the cost of iron while maintaining the level of tensile strength. The method includes overheating of the melt in an electric furnace up to 1500-1550 ° C, holding the melt in the furnace for 10-20 minutes, releasing the melt into the bucket with a ligature additive containing rare-earth elements, ferrotitanium and steel trimming in a quantity that provides Ti in the melt 0.07-0.10 May %, the secondary modification of the molten iron with ferrosilicon. The additional melt of iron, steel trimmings and ferrothitan, in comparison with the overheating of the melt and its aging in the furnace, reduces the cost of iron by reducing the consumption of ligature from rare-earth metals by 3-4 kg / t. 1 tab.

Description

The invention relates to metallurgy, in particular, to the development of methods for producing iron with vermicular graphite (CVG).

The purpose of the invention is to reduce the cost of pig iron while maintaining the level of the tensile strength of the iron during stretching.

The choice of parameters in the proposed method of obtaining cfg is determined as follows. When the iron overheats less than 1500 ° C, it is not possible to ensure effective purification of the melt from gases, in particular oxygen, which does not allow to increase the tensile strength of the iron upon stretching. In addition, insufficient deoxidation of liquid iron leads to an increased consumption of ligatures with rare-earth metals.

If the iron overheats to more than 1550 ° C, the tendency of the iron to chill increases, which reduces its tensile strength.

When the duration of exposure of superheated pig iron to less than 10 minutes, complete homogenization of the pig iron does not occur, as a result of which a high degree of degassing cannot be achieved, which does not allow reducing the consumption of ligature from rare-earth metals.

When the melt is exposed for more than 20 minutes, the oxygen content in the iron does not decrease further. Therefore, the exposure of the melt in the furnace over this time is ineffective. In addition, cementite appears in the cast iron structure, which reduces its strength.

ON SL O

3

Vj

When the content of titanium is less than 0.07% in the cast iron, it is not stable, to obtain vermicular graphite, which leads to a decrease in the tensile strength of the cast iron upon stretching.

When the content of titanium is more than 0.10%, structure-free cementite appears in the structure of cast iron, which reduces the strength properties of cast iron.

When the ligature consumption of the REM is less than 2 kg / t of pig iron, lamellar graphite appears in its structure, which reduces the tensile strength of the cast iron under stretching.

The consumption of ligatures with rare-earth metals more than 3 kg / t in the proposed method leads to the appearance of structurally free cementite in cast iron. Therefore, it is not possible to increase its tensile strength. In addition, it is not possible to reduce the consumption of ligatures with REM. Melting of cast iron is carried out in a high-frequency induction crucible furnace EAST-OOb with acid lining, as the charge materials use the following components, wt.%: Limit blast furnace iron 100

FS 453.5 ferrosilicon (100)

Ferromanganese FMN 751 (100)

In the crucible of the furnace load pig iron of chemical composition, wt.%: C 4,2; Si 0.7; Mp 0,2; S 0.02; P 0.06, after melting, ferroalloys are introduced. The resulting melt is overheated in a furnace up to 1500 ° C, and then kept at this temperature for 10 minutes. After that, cast iron is produced in a bucket with a capacity of 20 kg, at the bottom of which a Scemis 1 ligature is laid (ZP3M 36.7%; Si 44.3%, AI 5%, Fe else) and ferrotitanium PTyZO (L 30%). The flow of ligature 2.0 kg / t of pig iron (0.04 kg per bucket with a capacity of 20 kg), and ferrotitanium - 5 kg / t of cast iron (0.10 kg). The titanium content in the pig iron is 0.07%. To reduce the temperature of the melt before pouring, simultaneously with the release of the cast iron from the furnace into the ladle, the metal stream is given a coolant - a steel cut in the amount of 100 kg / t of pig iron (2 kg in the ladle).

After downloading the slag at 1320 ° C, a wedge sample is cast, from which samples are cut to determine the mechanical properties of the cast iron. Strength of cast iron at tensile strength of 395 MPa. The structure of cast iron is as follows: Fe55, P45, Tsnet, Gfb-70; GF1-30.

By changing the melting modes and the consumption of additives, the iron is smelted by the proposed method. For comparison, the pig iron is smelted by a known method.

The results of a comparative analysis of the known and proposed methods for the production of CVG are presented in the table.

As follows from the table, additional processing of molten iron

trimming and ferrotitanium, as a result of which 0.07-0.10 wt.% of titanium is introduced into the melt, allows to reduce the consumption of ligature containing REM by 3-4 kg / t.

25

Claims (1)

Invention Formula The method of producing pig iron with vermicular graphite, including heating the melt in an electric furnace, releasing the melt into a ladle, primary modification by introducing additives containing rare earth metals to its bottom; secondary modification of the melt by ferrosilicon, characterized in that reducing the cost of iron by reducing the consumption of ligature with rare earth elements while maintaining the level of strength of the iron during stretching, the melt is heated in the furnace to 15001550 ° C, held for 10-20 minutes, and steel trimming and ferrotitanium are additionally placed on the bottom of the ladle before release in an amount to ensure the residual content in the iron titanium 0.07-0.10 wt.%.