RU2454294C1 - Complex exothermic mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: complex exothermic mixture is meant for treating bearing cast iron outside the furnace. The mixture contains the following, wt %: aluminium metal 25-38; ferrotitanium 12-25; calcium fluoride 11-17; copper oxides 14-27; nitrated ferromanganese 7-18; coal dust 1-5.

EFFECT: high crack resistance, output, impact strength, wear resistance and antifriction properties of alloys.

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Description

The invention relates to the field of foundry, in particular to exothermic mixtures used for out-of-furnace treatment of antifriction cast irons.

Known exothermic mixture (AS USSR No. 608608, IPC B22D 7/06, 1978), containing, wt.%: Material based on iron oxides 25-50; chrome ore 5-25; aluminum powder 10.5-18; carbon based material 5-12; refractory clay 5-10; refractory filler 3-25 and a binder 5-10. The known mixture has insufficient stability of the process of thermochemical reactions and does not provide a significant increase in temperature, wear resistance and yield during out-of-furnace processing of cast Fe-C alloys. The high content in the known mixture of chrome ore, refractory filler, iron oxides and refractory clay reduces the refining and modifying effects, mechanical, technological and antifriction properties of the alloys.

Also known complex exothermic mixture (French patent No. 2338097, IPC B22D 7/00, 1977), containing, wt.%:

Metal aluminum 10-40 Oxides of aluminum, calcium or magnesium 10-80 Perlite and / or vermiculite 0-30 Wood flour 5-30 Coal dust 0-5

This complex exothermic mixture causes an intense exothermic reaction and an increase in the temperature of the melt, but reduces the technological and antifriction properties of Fe-C alloys.

The closest in technical essence and the achieved effect to the proposed is a complex exothermic mixture (RF patent No. 2376101, IPC B22D 1/00, 2009, prototype), containing, wt.%:

Metal aluminum 25-38 Calcium fluoride 18-35 Alumina 14-27 Silicocalcium or Ferrotitanium 12-25 Coal dust 1-5

During out-of-furnace treatment of antifriction Fe-C alloys with various molded modifying tablets, exothermic liners and pressed briquettes made from this complex exothermic mixture, exothermic reactions occur intensively, the fluidity and temperature of the melts increase, the crack resistance of the castings and the yield increase (for cast iron to 63- 67%, for foundry steels - up to 44-50%). However, there is an insufficient microalloying effect of the mixture, a decrease in the wear resistance and antifriction properties of the alloys, which is especially observed at elevated concentrations of silicocalcium, calcium fluoride and aluminum oxides.

The objective of the invention is to increase the wear resistance and antifriction properties of the processed alloys.

The problem is solved in that the complex exothermic mixture containing aluminum metal, calcium fluoride, ferrotitanium and coal dust, additionally contains copper oxides and nitrided ferromanganese in the following ratio of components, wt.%:

Metal aluminum 25-38 Ferrotitanium 12-25 Calcium fluoride 11-17 Copper oxides 14-27 Nitrogenated Ferromanganese 7-18 Coal dust 1-5

The additional introduction of copper oxides is due to the fact that they are effective chemically active exothermic and modifying additives that have a positive effect on the temperature, thermodynamic and technological parameters of iron-carbon melts, their uniformity and dispersion of the structure, wear resistance, friction coefficient and other antifriction properties of alloys. With an increase in their content of more than 27%, the rate of exothermic reactions increases and the kinetic parameters of the melts increase, which increases the waste of metal and decreases the uniformity and wear resistance of the alloy in castings. When the concentration of copper oxides is less than 14%, their modifying effect, technological and antifriction properties of alloys in castings are insufficient.

The additional introduction of nitrided ferromanganese in an amount of 7-18% is due to the fact that it is an effective microalloying and modifying additive that has a positive effect on the dispersion of the structure and technological parameters of iron-carbon alloys, wear resistance, friction coefficient, and other antifriction properties. With an increase in its content of more than 18%, the kinetic parameters of the melts decrease, which causes a decrease in the fluidity of the metal, the uniformity and wear resistance of the alloy in castings. At a concentration of less than 7%, the microalloying and modifying effects are insufficient, and the dispersion of the structure, yield, technological and antifriction properties of the alloys in the castings are low.

For comparative tests of the effectiveness of the known and proposed complex exothermic mixtures, they were tested under industrial conditions during smelting in crucible induction furnaces and subsequent out-of-furnace treatment of modified antifriction cast irons. Table 1 shows the compositions of complex exothermic mixtures used for out-of-furnace treatment.

The crack resistance of the alloys (by the average number of cracks in the sample) was determined on star-shaped 250 mm technological samples 140 mm high, fluidity - on spiral technological samples, and strength properties - according to GOST 1497-84 on samples with a diameter of 14 mm with an estimated length of 70 mm. To determine the impact strength, 10 × 10 × 55 mm samples were used. Metallographic studies and analysis of the dispersion of the structure of cast iron was carried out in accordance with GOST 3443-87.

Experimental melts of ASF-3 antifriction cast iron were carried out in induction crucible furnaces using cast iron L3 and L5, cast iron scrap grade 17A, steel scrap 1A, carbon ferrochrome, nickel refineries, ferromanganese FMN 75 as charge materials. amounted to 1380 ... 1410 ° C. The content of components in cast iron before processing the mixture, wt.%: Carbon 3,5-3,6; silicon 2.3-2.5; manganese 0.5; nickel 0.2; copper 0.5; chromium 0.03; phosphorus 0.05; sulfur 0.02 and iron - the rest.

Complex exothermic mixtures in paper bags or in pressed cylindrical tablets with a diameter of 50 mm and a height of 50 mm were introduced to the bottom of the teapot ladle before casting. Cast iron with a temperature of 1370-1400 ° C was poured into sand and clay molds to obtain technological samples, castings such as bushings and samples for mechanical tests.

Table 2 shows the technological properties of antifriction cast irons obtained after out-of-furnace treatment of the known and proposed compositions of exothermic mixtures.

Field testing showed that the proposed complex exothermic mixture is an effective chemically active and microalloying additive during out-of-furnace treatment and has a positive effect on wear resistance, antifriction properties, temperature and technological parameters of antifriction alloys, contributes to a higher degree of hardness, crack resistance and yield, than famous.

Table 1 Mixtures The content of components in exothermic mixtures, wt.% Metal aluminum Calcium fluoride Copper oxides Nitrogenated Ferromanganese Ferrotitanium Coal dust Alumina 1 / Famous / 29.3 28 - - 17 four 21.7 2 22.3 eighteen 28 5 19.7 7 - 3 38 eleven 27 7 12 5 - four 32 fourteen twenty 13 17 four - 5 25 17 fourteen eighteen 25 one - 6 43 7 10 9.5 thirty 0.5 -

table 2 Mixture Hardness, HB Casting yield Crack resistance, the number of cracks in the technological sample Coefficient of friction Average wear, mg / gf Impact strength, J / cm ² 1 / Famous / 165 66 3.4 0.38 28 12 2 167 68 3.0 0.37 25 fourteen 3 180 71 2,3 0.35 22 17 four 188 74 2.5 0.32 eighteen 21 5 175 72 2.9 0.33 21 19 6 172 69 3.2 0.36 23 fifteen

Claims (1)

Complex exothermic mixture containing metallic aluminum, ferrotitanium, calcium fluoride and coal dust, characterized in that it additionally contains copper oxides and nitrated ferromanganese in the following ratio, wt.%:
Metal aluminum 25-38 Ferrotitanium 12-25 Calcium fluoride 11-17 Copper oxides 14-27 Nitrogenated Ferromanganese 7-18 Coal dust 1-5