SU863697A1 - Mixture for modifying cast iron - Google Patents

Description

(54) MIXTURE FOR MODIFICATION OF IRON

This invention relates to linear production, in particular, to modifier compositions, preferably for gray iron with lamellar graphite. To increase the strength properties and to obtain as a result of modifying higher grades of cast iron, doping with chromium is applied, followed by subsequent double modifying with ferrosilicon, the second modifying directly into form 1. Double machining makes the casting modification much more complicated and possible only for simple simple casting since in complex castings, uneven structure and properties over the section are obtained. Doping with chromium with rG subsequent modification of the effect only on receipt of cast iron grades no higher than SCH24-44, SCH28-48. The closest to the invention in its technical essence and the effect achieved is a mixture of modifying the cast iron 23 of the following composition, wt.%: Ferrochrome Silikocalcium 30-40 base The disadvantage of this mixture is the formation of carbides in thin-walled casting due to the introduction of a chromium-forming element, and simultaneous addition silicocalcium in this ratio is insufficient to suppress the carbide pattern of ferrochrome, which is particularly pronounced at elevated cooling rates, i.e. in thin sections. There is no uniformity of structure and properties in different sections of the casting. Poor absorption of the ligature takes place, resulting in increased consumption. It is practically impossible to produce unalloyed cast iron with high tensile strength. The aim of the invention is to increase the strength of cast iron and reduce chill. To achieve this goal, the modifying mixture, containing ferrochrome and silicon-containing graphitizer, additionally contains ferromanganese, and silicobarium as the graphitizer in the following ratio of components, wt.%: Ferrochrome 15-20 Ferromanganese 10-15

Silicobaric 65-75

The content of ferrochrome in the amount of 15-20% provides noBitjaieHHe of the mechanical properties of the modified cast iron, ensures the prevalence of the pearlitic fine-grained structure of the metal structure of the cast iron, i.e. chromium is a carbide-forming element.

A further increase in the FeCr content in the modifying mixture can lead to the formation of chromium carbides, which lead to a significant increase in the hardness of the iron and the through bleaching of the castings. The lower limit of the content of FeCr - 15% - is determined by the smallest amount of melt absorbed by the impact on the strength characteristics.

The content of RemPP within 10–15% in the composition of the modifying mixture performs a double role as one of the active stabilizers of perlite, which contributes to an increase in the mechanical properties of cast iron and for better assimilation and distribution of the modifier in the pig iron melt. The upper limit of Remn content is determined by the property of manganese to prevent graphite formation, which entails an increase in the tendency to chill iron in thin sections of castings. The lower limit is determined by the ability of manganese to affect the strength characteristics of the iron.

Silicobarium introduced into the composition of the modifying mixture in the range of 65-75%.

Offered

Known

The lower limit of the silicobar content is determined by the graphitizing ability of the modifying mixture. This amount is quite enough to limit the carbide-forming effect of the GeSg and RhoMn components. The upper limit of the silicobar content is determined by the mechanical properties of the modified, cast iron; further increase in the content of silikobari: may lead to a decrease in the mechanical properties of the iron, since the graphitizing effect of the modifying mixture will prevail over the carbide-forming.

The effectiveness of the modifying mixture is checked by increasing the mechanical properties ((g) of the modified cast iron. The advantage of the proposed modifying mixture is that, simultaneously with the increase in the mechanical properties, the tendency of the modified cast iron to chill is significantly reduced while the hardness of the differential casting is improved) A reduction in the chalking tendency is checked by wedge test (chill depth). A significant decrease in the tendency of the modified cast iron to tbelu and alignment structures and properties in different sections is achieved due to the content x in silikobari soe- tave modifier mixture.

The composition of the mixture is given in table 1, the properties of cast iron in table 2.

Table 1

15 12 10

20 18 15 70 65 60

65 70 75

30 35 40

table 2

Claims (1)

Claim A mixture for modifying cast iron containing ferrochrome and a silicon-containing graphitizer, aphids Ferrochrome 15-20 Ferromanganese 10-15 Silicobarium 65-75