SU1232688A1 - Inoculating mixture for cast iron - Google Patents

Description

The invention relates to the metallurgy of alloys, namely to modifiers of liquid iron, and can be used in the production of castings from ductile iron.

The purpose of the invention is to increase the mechanical properties of cast iron and reduce the duration of its annealing.

The proposed modifying mixture contains boric acid and copper oxide as a carbide-forming component, and silicobarium in the following ratio, wt.%, As a graphitizing component.

Copper oxide 20-30

Boric acid 50-60

Silobarium 10-30

The joint introduction of boric acid and copper oxide in the indicated ratios into the modifying mixture allows one to exclude from the mixture expensive, scarce and toxic bismuth, to improve the mechanical properties of the iron treated with the proposed mixture.

To obtain the modifying mixtures, 5 compositions of the components are prepared and in parallel with the known modifying mixture.

The composition of the modifying mixtures is presented in Table. I.

Each modifying mixture is prepared separately by mixing the components. In the course of liquid iron casting (composition, wt.%: C 2.4; Si Mn 0, D; Cr 0.06; S 0.06; P 0.07), duplex-melted melt furnace, modifying mixtures at sequentially introduced into the buckets, then the modified cast iron is poured into molds and at the same time cast prototypes for studying the mechanical characteristics of the cast iron. The optimum is the addition of a modifying mixture that provides an introduction to the cast iron, wt.% of the mass of liquid cast iron: boric acid 0.1-0. ,15; silicobarium 0.02-0.03; copper oxide 0.04-0.05.

The introduction of boric acid into the melt is accompanied by an acceleration of the graphitization process and a sharp increase in the number of graphite centers. Copper oxide when entering the melt decomposes, with the release of oxygen. Oxygen dissolved in liquid iron promotes bleaching due to an increase in the stable liquid phase. Into white copper cast iron, an increase in the number of graphite centers and their grinding. The presence in the silicobar modifier, increasing the number of graphite centers and increasing their growth rate while improving their form, accelerates the process of graphitization in the solid state.

The results of the modification of cast iron are given in table. 2

The mechanical properties of the cast irons (Table 2) are determined after carrying out heat treatment; heating to 960 ° C; blowing at this temperature for 5 hours; cooling in air to 730 ° C; drying at this temperature for 5 hours; and final cooling in air.

The presence in the modifying mixture of Brlee 30 wt.% Of Silikobari (Example 5) leads to the appearance of lamellar graphite in the structures, i.e. to the formation of gray iron, not white, and, accordingly, to a decrease in mechanical characteristics, and the presence of more than 60% by weight of boric acid and more than 30% by weight of copper oxide (example 4) in the modifying mixture leads to an excessive increase in the amount of cement in the structure and increase the duration of heat treatment. The presence in the modifying mixture of less than 10 wt.% Of silicobar (example 4) leads to a decrease in the rate of hardness of pig iron in the solid state and, accordingly, to an increase in the duration of annealing and a decrease in the mechanical properties of the iron. The presence in the modifying mixture of less than 50 wt.% Of boric acid and 2.0 wt.% Of copper oxide (example 5) leads to the appearance of gray iron in the structure, i.e. to the deterioration of the shape of graphite and the release of free lamellar graphite during the crystallization of liquid iron and, accordingly, to a decrease in the mechanical characteristics.

Samples of white cast iron of the following chemical composition, wt.%: C 2.4; Si i, l; Mp 0.4; Cg 0.06; S 0.06; P 0.07 modified

Descale technology compositions given in Table. I, is subjected to heat treatment in the furnace SNOL-1.6. Samples are heated in an oven to 960 ° C, kept at

described technology, the compositions given in table. 1, is subjected to heat treatment in the SNOL-1 furnace; 6. The samples are heated in the furnace to 960 ° C, kept at this temperature, then cooled in air to 730 ° C and, when reached, are kept in the furnace at this temperature and finally cooled in air and the duration of sample exposure at 960 C (the first stage of annealing) and at 730 C (the second stage of annealing) varies. The results are shown in Table. 3

The optimal duration of heat treatment of the specimens modified by the modifying mixture proposed is 17.5 hours, the duration of the first and second stages

38

50

49.5

48.5

reduced by 50%. A decrease in the annealing time below 17.5 h causes cementite and perlite to remain in the cast iron structure.

which reduces the mechanical properties of cast iron and is unacceptable according to GOST. The increase in the duration of heat treatment over 17.5 hours leads to a significant enlargement of the grain and

reduction of the mechanical properties of cast iron and, moreover, impractical from both an economic and a technological point of view.

The use of modifying mixture

The proposed composition allows to improve the physicomechanical characteristics of cast iron while reducing the duration of its heat treatment.

Table 1

10 52

table 2

144 137

141

1 2 3 4

5 6 5 9

5 6 5 11

5 Samples are discarded in the cast state due to the presence of

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Famous

11.5 12.5 32

Editor And Gunko

Compiled K, Sorokin

Tehred I.Popovich Proofreader And, tlycKa

Order 2738/27 Circulation 552

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5.

Production and printing company, Uzhgorod, st. Project, 4

Table 3

7.5 50 15.0 144 19.5 48 13.0 136 17.5 48.5 13.8 141

27.5

36

130

35

ten

120

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Claims (1)

MODIFICATING MIXTURE FOR CAST IRON, containing a carbide-forming component, a graphitizing component and boric acid, characterized in that, in order to increase the mechanical properties of cast iron and reduce the duration of its annealing, it as a carbide-forming component collectively contains boric acid and copper oxide, and as graphitizing silicobarium in the following relation Research Institute of Components, May L: Copper oxide 20-30 Boric acid 50-60 Q Silicobarium 10-30 £ u 00 b 05 05 5232688