SU859014A1 - Exothermic mixture for warming ingot top portion - Google Patents

Description

(54) EXOTHERMAL MIXTURE FOR HEATING HEAD PART INGOT

one

The invention relates to the metallurgy of ferrous metals, in particular to: the composition of exothermic mixtures for heating the head of steel ingots.

Exothermic mixtures are widely used KGs for heating the head of the ingots of calm steel. The additional amount of heat used during combustion of the mixtures contributes to the reduction of shrinkage defects in the ingots and to a decrease in the head trimming,

The composition of such mixtures includes combustible components, a solid oxidizing agent, a filler.

A known exothermic mixture containing a combustible component in the form of silicocalcium, an oxidizing agent in the form of nitrate and mill scale and cryolite.

However, the effectiveness of this mixture when casting sheet ingots, especially of large weight, is low. Due to the large specific surface of the metal mirror and the longer crystallization of sheet ingots, compared with the varietal, the intensity of heat removal through the metal mirror increases. Under these conditions, cryolite, by lowering the ignition temperature of the mixture, contributes to its rapid combustion and exposure of the metal mirror.

Also known is an exothermic mixture introduced onto a metal mirror, which contains, wt%: silicocalcium 35-50, oxidizer (iron oxide) 40-65, and ground chamotte the rest (up to 100 wt.%) 21.

ten

However, this mixture does not provide for effective heating of the head part of ingots with a large surface of the metal mirror, for example, sheet ingots.

15

Closest to the proposed technical essence and the achieved result is an exothermic mixture for heating and the head part of the ingot, containing, by weight%: ferro calcium and calcium 55-70; oxidizer (iron oxide) 25-38 and ground chamotte the rest 33.

However, this mixture does not provide a significant increase in the yield of 25% nano-metal due to insufficient thermal performance. In addition, blends with scale can form white spots in the macrostructure of heated ingots. These defects 30 are decarburized.

metal, impure impurities, crystallizing earlier than liquid metal of ordinary composition. Due to the high density, the crystals are deposited in the don (the second part of the ingot. On the templates, this metal has a low etching.

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

This goal is achieved by the fact that the exothermic mixture for warming the head of the slice, including ferrosil calcium, oxidant and chamotte, contains the indicated ingredients in the following ratio, wt.%:

Ferrosclycocalcium 17-25

Oxidizer28-40

Fireclay Else

The proposed exothermic mixture contains 25-35 wt.%, Manganese ore and Bes.% Sodium nitrate as the oxidant.

The content in the mixture as a combustible substance of ferrosilicon to manganese ore and sodium nitrate as an oxidizing agent makes it possible to obtain a slag of the SiO – H O – CaO – Na O system with a melting temperature of 10 СГО 1300 0,

The content of the combustible ingredient (ferrosilicogen alcium) is selected from the calculation of the heat required to expand the mixture and heat the formed cork to the temperature of the steel ISSO-ieOO-C.

Reducing the content of ferrosiliconum below 17% causes the amount of heat that was lost at the exotherm of the reaction, is not enough to heat the profitable part of the ingot, and its content over 25% is not economically feasible, since it does not achieve new technological advantages.

The content of march-antrum ore is in a stoichiometric ratio with the reducing agent, taking into account the purity of the component. Since the marx antz oxides decompose at a sufficiently high temperature, 3-5% sodium nitrate is introduced to reduce the ignition temperature, and its consumption less than 3% does not allow the temperature to decrease. light up to the required values, and the introduction of more than 5% leads to an undesirable increase in gas emission during combustion of the mixture.

As an inert filler, the mixture contains taamot powder.

The content of ingredients in the mixture is also determined by its purpose. When casting small weights (up to 10 tons) that crystallize within a relatively short period of time, mixtures with high eco-thermal properties are used:

content of ferrosiliconcium close to the upper limit (24-25%) and fireclay close to the lower limit (34-35%).

The duration of crystallization of large ingots (15 tons) is greater and the heat flux from the metal mirror is higher than that of an ingot of a smaller weight, in these conditions it is necessary to ensure higher heat insulating properties of the calcine mixture formed, and the exothermicity of the mixture is less important. Therefore, in the composition of the mixture for insulating large sheet ingots, it is necessary to have a content of ferro silicocalcium, close to the lower limit (17-18%) and, accordingly, a lower content of manganese ore and sodium nitrate, and the proportion of inert component (chamotte) should be close to the maximum ( about 50%).

The proposed exothermic mixture is an effective insulation for steel ingots. The consumption of the mixture, depending on its composition and the weight of the ingot, is 1.5-2.0 kg / ton of steel.

The exotherm 4ic mixture can be prepared by mechanical mixing of its initial components, the degree of grinding of which should

be basically 1-1,5 MM.J

When siphoning steel, the mixture sits on a metal mirror before the end of filling the head (profitable) part of the ingot.

In tab. 1 shows the compositions proposed and known exothermic mixtures.

In addition, the field of application of these mixtures and their consumption of 1 kg per 1 ton of liquid steel are as follows: Sheet ingots of carbon and low alloyed steel with a mass of 15 t2,0

Sheet ingots of carbon and low-alloyed steel weighing 13 tons 1.5-1.7 Grade ingots of steel weighing up to 10 tons, molds expanding downwards1.5

Below are the thermophysical characteristics for the proposed mixtures.

Heat conductivity coefficient of calcine, kcal / m.h ° C, at temperature, s

200,095

5000,220

8000,295

1000, 0.440

Heat value, kcal / kg 500-630 Burning rate, kg / min 0.6-0.7

The mixture ignition temperature, ° С1000-1050 Volumetric

weight, kg / m 1600-1700 The chemical composition of the calcine is as follows, wt.%;

Aluminum oxide 21.2 Silicon dioxide 48.7 Calcium oxide 23.2 Manganese oxide 2, 4 Alkali oxides

M Tc1LLOV1, 5

Iron oxides Else Exothermic mixtures of these compositions were tested when casting hoist brand ST.30 with casting Ferro silicocalcium ingots 17

Manganese ore

Sodium Nitrate

Iron oxide Chamotte

Length of shrinkage defects,% of roll length

The presence of white spots in the macrostructure of the metal ingot

Claims (2)

Claims. . 1. An exothermic mixture for insulating the head part of an ingot, including Ferro Silicocalcium, an oxidizer and chamotte, characterized in that, in order to improve the quality of the metal of the ingot and increase the yield of a suitable metal, it contains the indicated ingredients in the following ratio, in wt.%: 50 kg. The temperature of the metal before pouring into the mold. The consumption of the mixture for the insulation of the head of one ingot at each heat of 100 g Thus, the proposed exothermic mixture for warming the head part of the ingot allows to increase the yield of metal by reducing the length of shrinkage defects and improve the quality of the metal of the ingot by eliminating white spots in the macrostructure of the metal of the ingot. In addition, the cost of the metal is reduced by reducing the consumption of expensive ferrosilocalcium. five The results of the quality control of the experimental ingots are given in table. 2 .. Table 1 55 25 20 35 28 25 47 .3520 table 2 12.5 8.3 9.2 there is Not Not Ferrosilicone alcynia Chamotte Oxidizer 2. A mixture according to claim 1, characterized in that it contains 25-35% by weight of manganese ore and 3-5% by weight of sodium nitrate as oxidant.  8590148 Sources of information, 2. USSR authorship taken into account in examination No. 148206, cl. B22 D 7/10, 1960. 1. USSR author's certificate3. USSR authorship  336085, cl. On 22 D 27/06, 1970. I 495146, cl. B22 O 7/10, 1972.