SU1482973A1 - Graphitizing composition - Google Patents

Abstract

FIELD OF THE INVENTION The invention relates to foundry production, in particular, to the composition of graphitizing mixture modifiers for high-strength cast iron. The purpose of the invention is to reduce the tendency to shrinkage and reduce chipping of high-strength iron. The graphitizing mixture contains bismuth, carborundum production wastes, silumin and ferrosilicon chips in the following ratio, wt.%: Carborundum production wastes 15-30, silumin 10-20 chips, bismuth 5-10, ferrosilicon the rest. Entering the composition of the mixture as a silicon-containing material waste production of carborundum, silumin chips and ferrosilicon allowed to significantly reduce the tendency of high-strength pig iron to shrink and eliminate chill in the castings, as well as dispose of waste materials. The proposed graphitizing composition of the mixture for the inoculation treatment of cast iron can be recommended for the secondary modification of high-strength cast iron in the production of castings that are prone to the formation of shrinkable defects and chill. 1 tab.

Description

The invention relates to foundry, in particular, to graphitizing compositions of mixtures for processing high-strength cast iron, and can be used to improve the quality of iron casting.

The purpose of the invention is to reduce the tendency of the pig iron to shrink and reduce the chipping of high-strength pig iron.

The goal is achieved by the fact that the graphitizing mixture containing silicon-containing material and bismuth contains, as silicon-containing components, carborundum production waste and, additionally, chips of silumin and ferrosilicon in the following ratio, wt.%:

Carborundum15-30 production waste

Chips of silumin 10-20 Bismuth 5-10

Ferrosilicon Else To suppress the formation of structurally free carbides and reduce the tendency of pig iron to shrink, the waste products of carborundum and silumin chips are introduced as a silicon-containing material. Carborundum production waste

J1482973

in the form of sludge and contain the following ratio,

The following components are used in AE with%:

Silicon Carbide 80 - 85 Aluminum Oxide 8-15 Iron Oxide 1 - 3 Carbon2-3

Silicon Dioxide 1 - 2 Silicon up to 1

The use of wastes from the production of carborundum in the mixture allows the disposal of wastes from the production of abrasives. The presence of silicon carbide in the carborundum composition increases the carbon absorption coefficient due to the high deoxidizing ability of Sil. The carbon sequestration factor of silicon carbide is 0.65-0.70. The absorption coefficient of silicon is 0.35-0.3, which is slightly lower than that of ferrosilicon. However, this circumstance in the secondary inoculation modification eliminates the possibility of an increase in hardness in the absence of chill and a decrease in the strength properties of the castings, since the reduced silicon performs the functions of a graphitizer and not an alloying element.

The lower limit of the content of carborundum waste in the mixture (15 wt.%) Is due to the complete removal of chill in the castings, the upper content (30 wt.%) Is associated with a small increase in the reduction of iron shrinkage and the complete absence of structurally free carbides.

Entering silumin into the chip mixture effectively inoculates the melt due to the presence of aluminum, which, when modified, deoxidizes cast iron. Strengthening the graphitization process contributes to silicon from silumin chips, the content of which is in SIL2 (GOST 1521-76). is 10-13 wt.%, as well as silicon waste carborundum and ferrosilicon.

The lower limit of the silumin chip content (10 wt.%) Is associated with a significant intensification of the graphing process, sufficient for complete

eliminating chill and reducing shrinkage of cast iron, the upper limit (20 wt.%) is associated with the risk of introducing increased amounts of aluminum into the cast iron to form subcortical gas porosity in castings.

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35

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55

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The presence of J3 composition of a mixture of bismuth also increases the number of crystallization centers of graphite and enhances graphitization. The optimal content of bismuth in a mixture of 5-10 wt.%. When the content of bismuth in the mixture is less than 0.5 wt.%, The graphitizing ability of cast iron decreases, which leads to an increase in chill and shrinkage.

An increase in the bismuth content in the mixture of more than 10.0 wt.% Does not lead to a significant decrease in chilling and shrinkage of the pig iron due to the attenuation of the bitumen graphitization ability during the secondary modification of the pig iron.

Ferrosilicon is a constant modifying agent to increase graphite formation in cast iron.

EXAMPLE When conducting comparative tests of a known mixture and the proposed graphitizing composition, the depth of chipping of the samples and the amount of shrinkage are determined.

Cast iron containing,%: C 3.45, Si 1.9, Ml 0.5, S 0.02, melted in an LPZ-67 induction crucible furnace by acid lining with

In the manufacture of the known and proposed mixtures, the following components are used: FSB-15 ferrosilicobarium, TU 14-5-132-81, bismuth Bi2, GOST 10928-75, sludge produced by carborundum, silumin silage from Silumin SIL2, GOST 1521-76, ferrosilicon FS75, GOST 1415-75.

The technology of making mixtures consists in weighing and mixing the components. Before mixing, the carborundum sludge and silumin chips are dried in a dryer at 250 ° C to a residual moisture content of 0.12%.

The graphitizing mixture is fed to the bottom of the casting ladle (preheated but heated) and filled with liquid metal from the dispensing bucket, in which the cast iron is treated with spheroidizing magnesium-containing ligature FSMg7 (TU 14-5-134-86).

The depth of the chill is evaluated by fracture wedge-shaped samples. The tendency of the modified cast iron to shrinkage is determined by a technological sample having a cone shape of 76 cm (560 g). The volume of shrinkage defects is defined as the sum of the volumes of the concentrated shell and the shrinkage volume.

porosity. Last determined by i

hydrostatic weighing

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conditionally dense part of the sample (top of the cone) and portions of the sample affected by porosity.

The mixture compositions for conducting the experimental heats are made on the lower, middle, upper, as well as below the lower and above the upper limits of the content of the components of the proposed mixture. The known composition of the mixture is applied at an average level. The compositions of the mixtures and the results of the tests are shown in the table.

As can be seen from the data, the proposed graphitizing mixture contributes to a significant decrease in the volume of shrinkage defects and to a reduction in chill off compared with the known

Claims (1)

Invention Formula Graphitizing mixture, including silicon-containing material and bismuth, characterized in that, in order to reduce the tendency to shrinkage and reduce chipping off of high-strength cast iron, it additionally contains silumin and ferrosilicium chips, as silicon-containing material - waste products of carborundum in the following ratio of components, wt. %: Waste production carborundum15-30 Siluminum 10-20 Bismuth 5-10 chips Ferromilicium Else Editor M.Petrova Compiled by A. Barmykov Tehred L. Serdyukova Order 2787/22 Circulation 576 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Proofreader M.Vasilyeva Subscription