SU814554A1 - Exothermic mixture for pouring steel - Google Patents

Description

I

The invention relates to ferrous metallurgy, in particular, to mixtures for casting steel into molds.

Known exothermic mixture for steel casting, containing, wt.%: Silicocalcium 5-30 Sodium nitrate 5-25 Boron-containing materials 10-25 Soda Else- 1 The disadvantage of the mixture is that it contains boron-containing materials that interact with steel to reduce boron, which in a number of cases it has a negative effect on the properties of the steel.

The closest in terms of the components used and the achievable goal is a mixture for metal refining, used also for steel casting, containing, wt.%: Calcium alloy with silicon (silicocalcium) 0.1-25 Alkaline salts of nitric acid (potassium or sodium nitrate) 0.1-20 Blast furnace slag 40 -90 Thinner (alkali metal carbonate, soda ash} 10-30 / 2 /

The disadvantage of the mixture is that it contains an increased amount of blast-furnace slag with an insufficient amount of thinner of soda ash, as a result of which the slag builds up on the walls of the mold and the quality of the surface of the ingot deteriorates.

The purpose of the invention is to improve the quality of the ingot surface and increase the yield of the metal.

The goal is achieved by the fact that in a mixture containing silicocalcium, potassium

5 or sodium nitrate, blast furnace slag and soda ash, the components are introduced in the following ratio, wt.% Silicocalcium 15-25

Kaliyev or sodium nitrate15-25

0

Blast furnace slag5-15

Calcined soda Rest When in contact with the molten metal, exothermic reaction starts and, under the action of the heat generated, the slag-forming components melt to form a liquid-fluid slag, which lubricates the surface of the mold and protects the surface of the molten metal from oxidation.

0 Silicocalcium in a mixture is an exothermic component that provides a rapid formation of a liquid movable calc-silicate slag. The introduction of silicocalcium into the mixture in an amount of less than 15% results in slowing the formation of liquid slag and degrades the bottom part of the ingot. With the content of silicocalcium in a mixture of more than 25%, a heated exothermic reaction develops, resulting in emissions of the mixture and the liquid metal. Potassium or sodium nitrate is introduced into the mixture as an oxidizing agent and is the oxygen supplier for the combustion of silicocalcium. The alkali metal oxides resulting from the decomposition of nitrate accelerate the formation of slag and reduce its viscosity. When the nitrate content is less than 15%, an insufficient amount of oxygen is introduced into the mixture, the combustion reaction is slowed down and incomplete. When the nitrate content is more than 25% in the atmosphere at the workplace, the concentration of nitrogenous emissions harmful to the caster increases. Blast furnace slag is an inert slag-forming filler and inhibitor of exothermic reactions. When the content of blast-furnace slag is less than 5%, an increased amount of alkali metal oxides is contained in the slag being formed, the viscosity of the slag decreases sharply and the surface of the ingot deteriorates. An increase of more than 15% in the amount of blast furnace slag leads to an increase in the viscosity of the forming slag and a slower rate of its formation. Soda ash is a thinner slag due to the decomposition of sodium oxides during its decomposition, and the emitted carbon dioxide contributes to the mixing of the mixture and acceleration of the process of its melting. The mixture is prepared by mixing the minced components, for example, in a rotary drum-type mixer, and then packaged in paper bags. To prepare the mixture, it is recommended to use components dried up to a moisture content of not more than 0.5% with a particle size of 0.2-1 mm. It is recommended to use the mixture when siphon casting steel. Before starting the casting, the mixture in bags is loaded onto the bottom of the molds in an amount of about 1.5 kg per ton of steel. Examples Mixtures 1-3 were prepared by mixing for 20 minutes in a drum-type mixer crushed to a size of 0.2-1 mm SK-30 silicocalcium and blast furnace slag and commercially produced powdered soda ash and sodium nitrate. The compositions of the mixtures are given below. Ill III IV V VI Silicocalcium 12 25 15 SC 30 15 20 25 Sodium 15 20 25 12 25 15 Nitrate 5 18 40 5 10 15 Blast furnace slag Calcium soda 65 50 35 71 32 30 nirovanny Mixes, packaged in paper bags of 5 kg, were loaded into molds before casting steel Х18Н10Т. The weight of the ingot is 2.8 tons. The ingots were rolled on a blooming and then on a varietal mill for a round billet. Data on the quality of the metal surface are given in the table,

90.0 100.0 100.0 70.6 80.0 60.0

90.0 100.0 100.0 41.4 60.0 40.0

97.7 98.5 97.2 83.0 90.0 10.0

As can be seen from the table, the surface and the yield of suitable metal spilled with mixtures 1-3 are much higher than those spilled with mixtures 4-6.

Claims (2)

1. Author's certificate of the USSR 637195, cl. at 22 D 7/10, 1976. 2. Patent France No. 1584146, cl. From 21 C, 1969.