SU922154A1 - Method for modifying grey cast iron - Google Patents

Description

(5) METHOD FOR MODIFICATION OF GRAY CAST IRON

one

The invention relates to foundry, in particular to the modification of gray iron.

We know a method for modifying gray iron with ferrosilicon 1.

The closest in technical essence and the achieved effect to the proposed method is a method of processing iron, in which FS-75 G2 ferrosilicon is introduced together with tellurium to control the thickness of the transition zone.

A disadvantage of the known methods is the impossibility of their use in the production of thin-walled machine-building castings from gray cast iron, since their use causes chilling and, as a consequence, a decrease in mechanical performance characteristics.

In addition, the known methods cannot be used to increase the mechanical properties of gray iron of eutectic and hypereutectic composition, since the efficiency of modification with increasing amount of C + Si decreases and for C b, 3 is almost zero. Moreover, in a number of cases even a decrease in mechanical properties is noted.

The purpose of the invention is to improve the mechanical properties of cast iron.

This goal is achieved by the fact that according to the method of modifying pig iron, which includes treating the melt with ferrosilicon and tellurium, before entering the ferrosilicon, tellurium is introduced into the melt as a compound with bismuth (Bi.Tej) in an amount of 0.002 0, 01% by weight of liquid iron with a ratio ferrosilicon to compound-; the tellurium with bismuth 1: (0.010 0, 50).

The ratio of ferrosilicon is chosen equal to 1: 0.010-1: 0.050. The NIZh NII limit for ratios was chosen with. the volume of the required residual content of bismuth and tellurium in the iron for the effect of grinding of graphite inclusions and perlithization of the metal base, and the upper one is the boundary after which cementite appears in the structure.

The amount of modifier introduced depends on the composition of the cast iron and the required level of mechanical properties of the Metal.

Due to the fact that it has a large specific gravity (7.7 g / cm) and a low melting point (585 ° C), the modification process is stable and the modifier is well absorbed by the iron.

PRI me R. The cast iron melted in the ITCH-2.5 induction furnace is processed with the following chemical composition, weight: С Si 2.50; Mp 0,6; S 0.05; P 0.3; Cr 0.07.

Modification of cast iron is carried out

at 1-120-150 C with BiijtTe compound, which is placed on the bottom of a 500-kg bucket in the amount of 0.002; 0,005; 0.01 and 0.015% by weight of molten iron. Then, when casting iron at 1380-G 00C, FS-75 is introduced. in the amount of 0.2%.

Modifier consumption changes

by changing the ratio of ferrosilicon to compound B1, e in the range of 1: 0.015-1: 0.075. For comparison, cast iron is treated with FS-75 by a known method. Standard 30 mm samples are poured to control the mechanical properties and chisel wedge samples. The test results of the initial cast iron chemical composition (No. 1) modified by the proposed (No. 25) and known (W 6) methods are presented in the table.

Claims (1)

Claim A method of modifying gray cast iron, including treating the melt with ferrosilicon and tellurium, characterized in that, in order to improve the mechanical properties of cast iron, tellurium is introduced into the melt in the form of a compound with bismuth (BiqTe |) in an amount of 0.002-0, before entering the mechanical properties of cast iron. 01% by weight of molten iron at a ratio of ferrosilicon to the tellurium compound with bismuth ⁴⁵ 1: (0.010-0.050).