SU1477515A1 - Method of manufacturing cast-iron metal-rolling rolls - Google Patents

Abstract

The invention relates to the field of foundry, in particular to methods of casting rolls, and can be used in the manufacture of iron rolling rolls. The purpose of the invention is to grind the primary structure of the iron and reduce the level of residual stresses in the working layer of the roll. The method includes smelting molten iron in a furnace, releasing it into a casting ladle at a temperature of 1450-1550 ° C, into which pig iron chips are preloaded in an amount of 2-10% by weight of iron in a ladle, followed by pouring into a mold at a temperature of 1280-1360 ° c, crystallization and cooling of the casting in the mold. 1 tab.

Description

one

The invention relates to the field of foundry, in particular to methods of casting rolls, and can be used in the manufacture of iron rolling rolls.

The purpose of the invention is the grinding of the primary structure of the cast iron and the reduction of the level of residual stresses in the working layer of the roll.

The method includes smelting molten iron in a furnace, releasing it into a casting ladle at a temperature of 1450-1550PC, in which iron pigment from rolls is preloaded in an amount of 2-10% by weight of iron in a ladle, aging the iron in a ladle and subsequent pouring into a mold at temperature 1280-1360 ° С

crystallization and cooling of the casting in the form.

Grinding of the primary structure of the working layers using the proposed method is achieved by enriching liquid iron with additional centers of crystallization when iron pigs dissolve and a significant decrease in the temperature gradient in the melt to the wall of the mold over the depth of the forming working layer. This reduces the preferred growth of primary austenite dendrites in the direction of the heat sink and they crystallize more branched and with a small distance between the branches of the highest order. This nature of crystallization determines

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and a lower level of residual stresses in the working layer of the roll, and also reduces the tendency to form cracks on the barrel.

An increase in the temperature of the metal before the introduction of chips above 1550 ° C leads to a weakening of the effect of processing chips due to deactivation of the crystallization centers formed in the iron, resulting in an enlarged structure and an increase in the level of residual stresses in the castings. At a cast iron discharge temperature below 1450 ° C, especially large particles of chips are slowly dissolved, and therefore it is not possible to obtain a sufficiently large number of crystallization centers in the melt, which does not allow a significant reduction in the level of residual stresses in the castings. In addition, the fluidity of cast iron is reduced, and blockages are present in the surface layers of the castings. The fluidity of cast iron also significantly decreases when the pouring temperature drops below 1280 ° C, which leads to defects in castings in the form of under-pouring and twisting and an increase in the level of residual stresses in the castings, and an increase in the pouring temperature above 1360 ° С to surface of chill molds. Using less than 2% of chips does not provide the necessary number of crystallization centers in the melt, which does not allow to significantly change the structure and reduce the level of residual stresses in the rollers, and an increase in chip additive over 10% leads to a significant decrease in the temperature and fluidity of cast iron and accordingly contributes on making marriages of castings for blockages and underfilling.

The cast iron rolls of the SPXN-45 version with a barrel size of 705 tons h1700 mm and a rough weight of 7.1 tons were cast. The initial cast iron in the amount of 8 tons was smelted in an industrial-frequency induction crucible furnace. The composition of cast iron,%, C 2.91i Si 0.72 Mn 0.47, S 0.06; P 0.22; Cr and Ni 1, 12. the furnace was heated to 1 420-

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and poured into the casting ladle, at the bottom of which, before release, 160-800 kg of cast iron chips (2-10% by weight of cast iron) from rolls of this design were laid, respectively. After cleaning the slag and measuring the temperature in the ladle, the cast iron was poured into casting molds at a temperature of 1280–1360 ° C.

During the machining of the resulting rolls, rings (templates) were cut from them for metallographic studies and measuring the level of residual stresses.

In addition, for comparison, such rolls were cast by known technology. The results of research and measurements are summarized in the table.

Comparison of the obtained results (table) shows that the proposed rolls, in comparison with the known ones, have a smaller primary structure (1–5–3 times) (the distance between the branches of the highest order dendrites), and the level of residual stresses in the working layer of these rolls in 2.2-3.5 times lower.

In addition, the cost of these rolls is also less by 12-20 rubles. on 1 t due to economy of the alloying elements at smelting of cast iron. Roll breakage over cracks is also reduced.

Claims (1)

Invention Formula A method of manufacturing iron casting rolls, which includes smelting liquid iron in a furnace, releasing it into a pouring ladle, holding it in a ladle, pouring it into a mold at 1280-1360 ° C, crystallizing and cooling the casting in a mold, characterized in that the primary structure of cast iron and reducing the level of residual stresses in the working layer of the roll, the liquid iron is released from the furnace into the casting ladle at 1450-1550 ° C, and before being released to the bottom of the casting ladle, cast iron chips from cast rolls after their mechanical rabotki in an amount of 2-10% by weight of iron in the ladle. 40