RU2429940C1 - Exothermic slag-forming mixture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: mixture contains the following, wt %: powder of oxidated component 9-36, oxidiser 9-36, catalyst 0.1-9, binding agent 0-9 and filler. In order to reduce heat losses with emission and heat conductivity, as filler there used is expanded vermiculite. In order to decrease the temperature of the beginning of reaction between mixture components, as catalyst there used are nitrates and/or fluorides of alkali, alkali-earth metals. Oxidated component contains the following, wt %: aluminium powder 0-30, nanopowder of pyrocarbon 1-10 and alloy combination powder. In order to increase dispersion ability, alloy combination powder contains the following, wt %: aluminium 18-30, silicon 16-25, manganese 15-45, carbon 0.1-3 and iron.

EFFECT: increasing operating efficiency of casting heads.

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Description

The invention relates to the field of metallurgy and can be used in foundry for heating foundry profits in order to improve the power supply of castings.

Famous / V.I. as an oxidizable component, iron oxide or ore as an oxidizing agent, fluorspar as a catalyst, ground fireclay as a filler and molding clay, water glass or sulphite-alcohol stillage as a binder in the following ratio of components in wt.%.

Aluminum powder or shavings eighteen Ferrosilicon 75% 5 Iron oxide or ore 52 Fluorspar 2 Ground fireclay eighteen Molding clay 5 Liquid glass or Sulphite-alcohol bard (over 100%) 8

The specified mixture is multicomponent and has a relatively low calorific value.

The closest in technical essence and the achieved effect is an exothermic mixture / “Exothermic mixture”. A.S. USSR No. 353787, V.V. Lempitsky et al. /, Containing aluminum powder and powder of a multicomponent calcium-manganese-silicon-aluminum alloy as an oxidizable component, iron oxide as an oxidizing agent, refractory clay, chamotte, wood sawdust, binder in the following ratio of components, wt.%:

Calcium-Manganese-Silicon-Aluminum Powder alloy 12-14 Aluminum powder 10-12 Oxidizer 34-36 Fire-clay 10-12 Fireclay 26-28 Sawdust 2-3 Binder (in excess of 100%) 20-20.5

A disadvantage of the known exothermic mixture is its low calorific value, large heat loss by radiation and thermal conductivity due to the formation of solid slag as a result of the use of components with high density, high thermal conductivity and melting point as a filler.

The aim of the invention is to increase the efficiency of foundry profits.

This goal is achieved in that according to a known exothermic mixture comprising an oxidizable component powder, an oxidizing agent and a binder, the mixture further comprises expanded vermiculite as a filler, nitrates and / or fluorides of alkali, alkaline earth metals as a catalyst in the following ratio of components in wt.%

Oxidizable component 9-36 Oxidizer 9-36 Catalyst 0.1-9 Binder 0-9 Filler rest,

however, as the oxidizable component, it contains aluminum powder, pyrocarbon nanopowder and ligature powder in the following ratio of components in wt.%

Aluminum powder 0-30 Pyrocarbon Nanopowder 1-10 Ligature powder rest,

and the ligature powder contains aluminum, silicon, manganese, iron, carbon in the following ratio of components in wt.%

Aluminum 18-30 Silicon 16-25 Manganese 15-45 Carbon 0.1-3 Iron rest,

The use of expanded vermiculite as a filler, having low thermal conductivity and relatively low density, allows to reduce heat loss by radiation and thermal conductivity, which ensures quick heating of the mixture to the temperature at which the reaction begins. Warming up vermiculite to 1300 ° C and above is accompanied by its melting with the formation of liquid slag, which has additional heat-insulating ability after the reaction between the oxidizing agent and the oxidizing product. The proposed ratio of the content of vermiculite and other components provides a stable, calm reaction between the components. The ligature of the proposed composition in the manufacture by casting after crystallization is destroyed (crumbles) into small particles no larger than 0.7 mm in size, which does not require additional grinding costs and eliminates the loss of ligature due to the lack of screening of the fine fraction. The use of this powder as an oxidizable product allows you to organize a homogeneous mixture with high calorific value. The use of pyrocarbon nanopowders helps to stabilize the combustion process.

The use as a catalyst of nitrates and (or) fluorides of alkali, alkaline earth metals, within the proposed range, allows to reduce the temperature of the onset of the reaction between the components of the mixture and expands the scope of the proposed invention for non-ferrous alloys.

The use of a binder within the specified limits allows you to use the proposed mixture both in the form of exothermic inserts and bulk mixture (in the absence of a binder or its minimum content).

The effectiveness of the known and proposed exothermic slag-forming mixture was evaluated by ball test.

Steel grade 25 L at a temperature of 1580-1600 ° C was poured into a spherical cavity with a diameter of 150 mm, lined with a 30 mm thick exothermal test mixture. As a control sample used the same form, lined with a liquid-glass mixture. Using a tungsten / tungsten-rhenium thermocouple, the junction of which coincides with the center of the ball, the solidification time of the metal in the ball sample was recorded. The efficiency coefficient of the Keff mixture was determined as the ratio of the solidification time of the sample lined with the test exothermic mixture to the solidification time of the sample, which was poured into the liquid-glass mixture. The data obtained are given in the table.

From the obtained data it is seen that the proposed exothermic slag-forming mixture has a higher efficiency coefficient.

The operating efficiency of the profit using the known and proposed mixture was evaluated by the effect of additives on the formation of a cylindrical casting with a diameter of 100 mm and a height of 300 mm, in the form of a dry core mixture.

The exothermic mixture in an aluminum foil bag was installed in a mold. As a result of the shielding action of aluminum foil, the interaction of the melt and the exothermic mixture began only after the mold was completely filled.

Profit efficiency with an exothermic mixture was evaluated by the height of the lower dense zone of the cylindrical casting. Moreover, the upper zone with a shrink shell and porosity, determined by the method of x-ray control, played the role of profit. The ratio of the lower dense zone to the profitable zone determined the coefficient of metal consumption for profit (Kpr). The value of the coefficient determined the efficiency of profit with an exothermic mixture.

The data obtained are given in the table.

From the obtained data it can be seen that the proposed mixture allows the formation of a dense casting with a minimum profit margin, which shows an increase in the efficiency of foundry profits when using the proposed exothermic slag-forming mixture.

The use of the proposed exothermic mixture for profits of steel castings, for example, valve bodies made of 25L steel, allows a 20% reduction in profit margins compared with known additives, which provides an increase in the utilization rate of liquid metal by 8-10%.

Given the approximately equal cost of known and proposed additives and the cost of smelting one ton of molten metal at OJSC Ikar in Kurgan, the economic efficiency of using the proposed exothermic slag-forming mixture is 3800 rubles per ton of suitable casting.

Claims (1)

An exothermic slag-forming mixture containing an oxidizable component powder, an oxidizing agent, characterized in that it additionally contains expanded vermiculite as a filler, nitrates and / or fluorides of alkali, alkaline earth metals as a catalyst and a binder in the following ratio of components, wt.%:
Oxidizable component 9-36 Oxidizer 9-36 Catalyst 0.1-9 Binder 0-9 Filler rest,
while as an oxidizable component it contains aluminum powder, pyrocarbon nanopowder and ligature powder in the following ratio of components, wt.%:
Aluminum powder 0-30 Pyrocarbon Nanopowder 1-10 Ligature powder rest,
and the ligature powder contains aluminum, silicon, manganese, iron, carbon in the following ratio of components, wt.%:
Aluminum 18-30 Silicon 16-25 Manganese 15-45 Carbon 0.1-3 Iron rest