SU1164273A1 - External layer of briquette for inoculating cast iron - Google Patents

Abstract

OUTDOOR LAYER OF BRIQUETTES FOR MODIFICATION OF CAST IRON, containing potassium chloride, calcium hydroxide and water glass, is distinguished by the fact that, in order to increase the effectiveness of the modifying effect of the briquette, to eliminate the formation of structurally free cementite in the iron and to reduce the enrichment cost of dissolution briquette, the layer additionally contains fluorspar and ferrosilicon with a silicon content of more than 70% with the following ratio of ingredients, may.%: Chloride 3-5 potassium Calcium hydroxide 5-9 calcium Liquid 15-20 glass Hydrofluoric acid 0.5-3.0 spar W Ferrosild tions with silicon content of more than 70% remaining

Description

The invention relates to metallurgy and foundry, and can be used to introduce low-boiling components into the cast iron. The outer layer of the briquette for the modification of cast iron is known, which contains chamotte, cast iron chips, potassium chloride and liquid glass pj. A disadvantage of the known outer layer of the briquette is that the protective coating does not contain modifying components and performs only the function of a heat-resistant coating that reduces the heating of the modifier at the initial moment of its contact with the iron. The closest to the proposed technical essence and the achieved effect is the outer layer of the briquette for the modification of cast iron containing pig iron chips, potassium chloride, calcium hydroxide, water glass and chamotte with the following ratio of ingredients, wt.%: Cast iron chips 10-20 Potassium chloride 3- 5 Calcium hydroxide 5-9 Liquid glass13-17 Chamotte Others The use of chamotte and cast iron shavings, which are ballast when modifying, in a known outer layer of briquette, causes additional Tel'nykh heat loss and cooling of the liquid cast iron, which requires additional energy consumption for the overheating of the metal. The absence of graphitizing additives in the known outer layer of the briquette leads to the formation of structurally free cementite in castings. The presence of an insoluble component in the composition of the protective layer (chamotte) leads to an additional increase in nonmetallic inclusions, which reduces the quality of the castings. In addition, due to the low thermal conductivity of the mixture containing chamotte, heating of the deposits to the temperature-evaporation is slowed down, which leads to an increase in the modification time. This causes additional cooling of the metal and a decrease in the productivity of the casting process. The purpose of the invention is to increase the efficiency of a modifying deistication of a briquette, to eliminate the formation of structurally free cementite in cast iron and to reduce the energy cost of dissolving the briquette. The goal is achieved by the fact that the outer layer of the briquette for modifying pig iron, containing potassium chloride, calcium hydroxide and water glass, additionally contains fluorspar and ferrosilicon with a silicon content of more than 70% in the following ratio of ingredients, wt.%: Potassium chloride Calcium hydroxide 5-9 Liquid glass 15-20 Fluorspar, 0.5-3.0 Ferrosilicon with a silicon content of more than 70% Remaining The invention is based on the use of additives that reduce the warm-up time of the protective layer of the modifier, reducing s melting temperature of the formed non-metallic inclusions, the thermal conductivity of the protective layer. This is achieved by dissolving ferrosilicon in molten iron while simultaneously modifying it, forming low-melting compounds based on fluorspar, increasing the porosity of the outer layer of the briquette due to the gas phase formed by the interaction of ferrosilicon with liquid glass. Spontaneous hardening of the mixture of the outer layer of the briquette eliminates the additional operations of blowing the mixture with carbon dioxide or its heat treatment, which reduces the process of preparing the modifier for input. The optimum parameters for the content of potassium chloride and calcium hydroxide are selected to obtain the outer layer of the briquette with maximum strength. When the content of KALI chloride is less than 3% and calcium hydroxide is below 5%, strength is insufficient, which leads to cracking of the outer layer of the briquette, premature evaporation of the additive reduces the degree of assimilation of the modifier and leads to the release of metal from the ladle and pyroelectric effect. An increase in the content of potassium chloride and calcium hydroxide in the outer layer of the briquette, respectively, above 5 and 9% is not economically feasible, since a further increase in their number slightly increases the mechanical strength of the outer briquette for modifying the cast iron. The choice of the amount of liquid glass in the outer layer of the briquette is determined from the condition of obtaining the necessary strength and the formation of a gas phase to increase the porosity of the outer briquette. A decrease in liquid glass of less than 15% leads to a decrease in the porosity of the outer layer of the briquette and a decrease in its mechanical properties, which ultimately affects the degree of absorption of magnesium, leading to a pyro effect and release of metal from the ladle. An increase in the content of liquid glass over 20% significantly increases the porosity of the outer layer of the briquette, which causes an increase in the volume of the outer layer of the briquette, complicating the introduction of the modifier into the liquid metal. In addition, the loss of ferrosilicon of the outer layer of the briquette on interaction with excess liquid glass increases, which reduces the graphitizing effect and increases the consumption of ferrosilicon. Fluorspar is introduced into the outer layer of the briquette to facilitate the removal of the reaction products from the pig iron. The positive effect of fluorspar, i.e. the formation of low-melting compounds begins to appear when it is contained in the outer layer of the briquette more than 0.5%. If its content exceeds 3.0%, an increase in the rate of dissolution of the outer layer of the briquette and an increase in the rate of heating of the entire briquette and boiling magnesium is observed. Ferrosilicon with a silicon content of more than 70% is introduced to produce a porous outer layer of the briquette, which reduces the start time of the 3.4 modifying process, reduces the thermal conductivity of the mixture, and also eliminates the appearance of structurally free cementite and sufficient heat generation necessary for self-cross outer layer of the briquette. Testing of the known and proposed outer layers of briquettes for the modification of cast iron was carried out under the conditions of the Kupn foundry. The compositions of the outer layers of briquettes used in modifying the cast iron with magnesium, as well as the degree of assimilation of magnesium, the mechanical properties of the cast iron are given in the table, where 1 and 2 are the known compositions of the outer layer of the briquette for modifying the cast iron. The mixture for the outer layer of the briquette was prepared by mixing the components in the laboratory mode runners. 016. The following components were used: ferrosilicon FS75 (GOST 1445-76), liquid glass with a modulus of 2.5, density 1.2510. kg / m (GOST 13078-67), calcium hydroxide (GOST 9262-77), potassium chloride (GOST 4234-77) and fluorspar (GOST 7618-70). Magnesium granulated MGP-1 (TU-6-01-904-74) was used as a modifier. Modifying briquettes were obtained by filling magnesium granules into glasses made of the outer layer of a briquette. with subsequent sealing of the hole in the glass with a stopper from a mixture of the same composition as the outer layer of the bri; chum salmon Glasses, which were shaped like a molded outer layer of briquettes, were strengthened by self-sintering, and, using the known composition of the outer layer of briquettes, by blowing carbon dioxide. Modifying cast iron containing, May. %: carbon 3.35-3.40J silicon 1.7-1.8, manganese 0.25-0.30 {phosphorus 0.07-0.08; sulfur 0.03-0.04 was produced by introducing special device briquettes for modification into the ladle. The temperature of the cast iron after melting in the electric arc furnace DSP-3 was 17401760 K, the temperature of the cast iron in a 2-ton ladle at the beginning of the modification was T690-1710 K. The consumption of modifying briquettes with the outer layer was 0.8-1.0%, with known outer layer of 1, 0-1.3%.

It follows from the table that the outer layer of the briquette for modifying the cast iron of composition 8 has an increased content of liquid glass, and the composition, 9 - an underestimate of the content of liquid flowed compared with that proposed.

The analysis of the data shows that the proposed outer layer of the briquette for modifying the pig iron in comparison with the known one allows to increase the degree of magnesium absorption

5-8%, exclude the formation of free-structural cementite, pyroeffect and simultaneously increase

5 cast iron strength by 9-13%. In addition, the use of the proposed outer layer of the briquette for the modification of cast iron allows reducing the energy losses during modification by 7-10 and shortening the modification time by 1.5-2 per.

The expected economic effect from the implementation of the proposed outer layer of briquette for the modification of cast iron will be 5-5.7 rubles. per 1 ton of suitable cast iron castings.

Content of components, wt.%: Potassium chloride Calcium hydroxide Liquid glass. Fluorspar 62 59 10-20 - Iron pigs Ferrosilicon chips (Si 70%) Residual 0, 035 0.05 0.04 mg,% Magnesium uptake rate,% -13 50 51 Structurally free cement,% Modified time, 5 7, 5 4.0 vani, min. Reduction of the temperature of the metal in the ladle. Energy loss 1§ ± 0 lliZ with modification of 32.5 iron castings, kJ / kW "h 0.5 76.5 0.5 3.0 3.0 3.0 3.0 3.0 - -. - - - - 2, 5 68,0 69,0 O 58,0 73 0,043 0,04 0,051 0,055 0,033 0,030 3 51 54 58 39 38 4,0 4 5,3 5,3 5,5 5,0 liZ 16.0 2.5 32.5 35 35 44 32.5 Mechanical properties of cast iron: Strength, MPa445 Elongation,% 5.6 Hardness, HB220 Durability of protective layer: MPa0.9 Presence of pyroelectric effectIs 485 505 511 517 521 532 428 420 . 1.3 6.3 6.0 6.0 5.7 5.5 2.7 5.6 310 205 207 210 215 220 260 205 1.6 1.8 1.9 2.1 2.3 2.5 2.8 0.6 No No No No No No No Yes.

Claims (1)

EXTERNAL LAYER OF BRIQUETTE FOR MODIFICATION OF PIG IRON, containing potassium chloride, calcium hydroxide and water glass, is distinguished by the fact that, in order to increase the efficiency of the modifying effect of the briquette, to eliminate the formation of structurally-free cementite in cast iron and to reduce the energy consumption for dissolution briquette, the layer additionally contains fluorspar and ferrosilicon with a silicon content of more than 70% in the following ratio of ingredients, May.%: Chloride potassium 3-5 Hydroxide calcium 59 _h Liquid glass 15-20 Fluffy so spar 0.5-3.0 L Ferrosilicon with content from: silicon bo less than 70% The rest is >