SU1668450A1 - Alloying composition for hot metal - Google Patents

Abstract

This invention relates to cast iron ligatures. The goal is to increase the elastic properties, technological plasticity, impact resistance and duration of the modifying effect of the cast iron. The ligature contains, in wt.%: Nickel 3 - 7

silicon 3.0 - 7.5

copper 11 - 27

chrome 1 - 3

carbon 1,2 - 5,0

cobalt 0.2 - 0.5

yttrium borides 1,5 - 15,0 magnesium nitrides 1,3 - 7,5

iron else. When doping hypoeutectic cast iron with the proposed ligature, we obtained BE60 and BE65 brand cast iron with impact strength of 0.978 - 1.02 MJ / m ² , relative elongation of 18.9 - 19.5%, fracture toughness of 575 - 612 kgf ^. m ^-3/2 , shock resistance of ^1720–1880 cycles at an impact energy of 10 MPa and hot plasticity of ^17–21 twists. At the same time, the duration of the modifying effect increased from 23 to 46.5 - 49.1 minutes. 2 tab.

Description

The invention relates to metallurgy, in particular to master alloys for the production of cast iron parts with enhanced plastic properties.

The purpose of the invention is to increase the elastic properties, technological plasticity, impact resistance and duration of the modifying effect.

The ligature is melted in 150 kg open induction electric furnaces using a mixture of ferrosilicon, ferronickel, electrical copper, ferrochrome, cobalt carbon, bo electrodes, steel scrap, and yttrium borides. When the temperature reaches 1370 ° C, magnesium nitrides are introduced into the melt;

min and casting into flat molds.

Experienced smelting of cast iron with a hypoeutectic composition containing, in wt.%: Carbon 2.8; silicon 1.35; manganese 0.72; chromium 0.1; nickel 0,2; phosphorus 0,1; sulfur 0.12; iron - the rest, was produced in an induction retractable electric furnace with overheating of the melt 300-380 ° C above the liquidus temperature. Modification of cast iron was carried out with the release of the melt in the buckets at 1400-1430 ° C with crushed ligature in an amount of 0.08-0.1% by weight of the cast iron. In the process of casting modified cast iron ligatures proposed and known compositions (Table 1) according to standard methods cast samples for mechanical testing and

(O CO

with about

microscopic studies of structure and technological samples.

Table 2 shows the results of a study of the stability of the modifying effect and the mechanical properties of cast iron in castings using known and proposed ligatures.

Metallographic studies have shown that ligatures with yttrium borides and magnesium nitrides produce a finer-grained metal base structure and compact graphite in castings.

The impact viscosity was determined on samples of type 12 according to GOST 9454-78 on a MK-ZOM tilting machine, and thin sections were studied on an X-ray microanalyzer.

Yttrium borides are introduced into the proposed ligature in the amount of 1.5-15 wt.% As an effective modifier for cast iron, which increases the uniformity and stability of the structure and prevents the formation of black spots and interdendritic graphite in it, contributing to an increase in the isolation and compactness of graphite and other components. structure and increase the mechanical characteristics of iron in castings, especially plastic properties. When the concentration of yttrium borides is up to 1.5 May, the modifying effect is weak and the plastic properties of cast iron in the castings are low, while increasing the concentration of yttrium borides more than 15 wt.%, The stability of the modifying effect decreases, the number of non-metallic inclusions and reduced mechanical properties of cast iron, durability of cast parts.

Magnesium nitrides in the amount of 1.3-7.5 wt.% Significantly crush the structural components, reduce the gas porosity and increase the uniformity of the modification, the absorption of the alloy by the molten metal and the duration of preservation of the modifying effect of the alloy, which provides an increase in the relative elongation and impact cast iron viscosity in castings. When the concentration of magnesium nitrides is up to 1.3 wt.%, The refinement of the structure and the improvement of plastic properties is insufficient, and with an increase in the concentration of magnesium nitrides more than 7.5 wt.%, The waste of metal increases and the structure homogeneity, mechanical and operational properties of cast iron in the castings decrease.

The contents of the other components are selected in accordance with their accepted content in the master alloys used to modify cast iron with enhanced plastic properties. Effective. The silicon content in the ligature is 3-7.5 wt.%, carbon 1.2-5 wt.% and copper 11-27 wt.%. Such a concentration of graphitizing components with a chromium content of 1-3 wt.% Increases the uniformity and stability of the cast iron modification, contributes to the improvement of mechanical properties.

The presence of cobalt in the master alloy of 0.2–0.5 wt.% Contributes to the improvement of the modifying stability and mechanical properties. With an increase in the cobalt concentration of more than 0.5 wt.%, The melting point of the alloy increases, and at a concentration of up to 0.2 wt. the stability of the modification is low.

Thus, as can be seen from Table 2, the pig iron treated with the proposed ligature in an amount of 0.1% by weight of the melt has higher elastic properties, more technological ductility and impact resistance than when using a ligature of known composition. In this case, the modifying effect is maintained for a longer time.

The proposed ligature is technological during smelting, well absorbed by iron at temperatures of 1330-1400 C.

Claims (1)

Ligature for cast iron containing nickel, silicon, copper, chromium, carbon, cobalt and iron, characterized in that, in order to increase the elastic properties, technological plasticity, impact resistance and duration modifying effect of iron, it additionally contains yttrium borides and magnesium nitrides in the following ratio, wt.%: Nickel3-7 Silicon3.0-7.5 Med11-27 Chrome1-3 Carbon 1.2-5.0 Cobalt 0.2-0.5 Bortids yttri 1,5-15,0 Magnesium nitride 1,3-7,5 IronErest oh t with CO SO table 2