SU1480960A1 - Method of casting double-layer rolls - Google Patents

Abstract

The invention relates to the field of foundry, in particular to methods for casting iron casting rolls, and can be used to produce two-layer cast iron rolling rolls with a bleached working layer. The purpose of the invention is to increase the operational strength of the lower pouring (drive) necks of the roll and reduce the cost of washing. The method involves pouring the casting mold with alloyed iron to a level of 300-350 mm above the upper edge of the cavity of the roll barrel, aging for crystallization of the bleached working layer and subsequent washing of the mold with unalloyed barium-containing iron with a barium content of 0.02-0.04 wt.% To form cores and necks of the roll with the mass ratio of unalloyed barium-containing iron and the mass of doped iron equal to 1: (3.2-4.5), and as unalloyed barium-containing iron, cast iron of the following chemical composition, wt.% : carbon 3.2-3.6

silicon 1,3-1,9

manganese 0.4-0.6

phosphorus 0.10-0.25

sulfur 0.08-0.14

barium 0.02-0.04

iron - the rest. 1 tab.

Description

one

The invention relates to a foundry, in particular to methods for casting iron casting rolls, and can be used to produce two-layer cast iron rolling rolls with a bleached working layer.

The purpose of the invention is to increase the operational strength of the lower pouring (drive) necks of the roll and reduce the cost of washing.

The method involves pouring the casting mold with alloyed cast iron to a level of 300-350 mm above the upper edge of the cavity of the roll barrel;

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bleaching of the working layer and the subsequent washing of the mold with unalloyed barium-containing iron with a barium content of 0.02-0.04% to form a roll core and necks. The ratio of the mass of unalloyed barium-containing iron to the mass of doped iron is 1: (3.2-4.5), and cast iron of the following chemical composition is used as unalloyed barium-containing iron, wt.%:

Carbon3,2 -3,6

Silicon1.3 -1.9

Manganese0.4 -0.6

Phosphorus 0.10-0.25

Sulfur0.08-0.14

Barium0.02-0.04

IronErest

Barium within the specified limits (0.02–0.04%) has a strong inoculating and graphitizing effect on the structure of cast iron, core and necks, which enhances their criterion of operational strength. The effect of barium is extreme and, with a decrease in its concentration of less than 0.02%, its effect does not appear, and a concentration of more than 0.04% may cause a stabilizing effect on the graphitization of the iron.

The required amount of washing is determined as follows. When using unalloyed iron in an amount greater than the ratio to alloyed 1: 4.5, it introduces into the cavity of the mold, performing the lower neck (all the metal poured into the mold passes through it), a large amount of heat and heats it, which leads to an increase in the duration of solidification and, as a result, to a deterioration in the structure and a decrease in the strength of the metal (see table).

When using wash iron in an amount less than 1: 3.2, the upper neck metal is not completely renewed and due to the mixing of doped and unalloyed iron, the chromium content rises to concentrations that determine the release of cementite and the structure in the upper necks. cast iron, which leads to a sharp drop in their criterion of operational strength. Carbon within the specified limits (3.2–3.6%) in unalloyed iron for washing provides the necessary degree of eutecticity and complete graphitization of the iron in the core and roll necks. When the content is less than 3.2% of carbon, its casting properties are deteriorated and the graphitization of cast iron is not ensured. With a carbon content of more than 3.6%, the total amount of graphite, the size and branching of graphite inclusions increase, which leads to a decrease in the strength of the necks.

Silicon within the specified limits (1.3–1.9%) ensures the neutralization of the chromium's diabetic effect (shared by nickel of the main cast iron), which falls upon partial mixing of the cast irons during washing. When the silicon concentration is less than 1.3%, structurally free cementite crystallizes in the structure of the core and necks. An increase in silicon content of more than 1.9% is accompanied by partial ferritization of the metal base, an increase in the size and degree of branching of graphite inclusions, which also causes a decrease in the strength of the necks. There are difficulties with using

in the charge of return from the decommissioned rolls.

Manganese in the range of 0.4-0.6% contributes to the perlitization of the iron matrix. When its content is less than 0.4%, such an effect does not appear in the slowly cooling cast iron when the neck hardens. With an increase in manganese concentration of more than 0.6%, the strength of cast iron decreases due to the appearance of austenitic carbide eutectics in the structure due to the whitening effect of manganese.

Phosphorus within ODO-0.25 increases the degree of eutecticity and completeness of graphitization of cast iron, reduces the size of the eutectic grain and increases the flowability of cast iron. With a content of less than 0.1%, this effect is insignificant. An increase in the phosphorus content of more than 0.25% leads to the appearance in the structure of the necks of a closed mesh of phosphide eutectic, which encapsulates cast iron.

Sulfur in the range of 0.08–0.14% corresponds to its content in conventional cupola cast iron and is due to the presence of cupolas for producing undoped cast iron for washing the molds in the valleys.

Example. Cast rolls cast

performance LPHNdbZ with barrel sizes

01000X3100 mm 41.9 t. In the open-hearth furnace

Acid-lined furnaces melt doped cast iron of the following chemical composition, wt.%: C 2.9; Si 0.5; Mp 0.5; Cr 0.6; Ni 2.6; P 0.4; S 0.08. Cast iron is poured into a mold at 1310 ° C. The volume of cast iron is monitored according to the signal of the level of cast iron in the mold. After aging for 280 seconds, the mold is washed with cupola-shaped unalloyed iron with the following chemical composition, wt.% C 3.4; Si 1.6; Mp 0.5; P 0.15; S 0.11; Ba 0.03. The mass of the metal to be washed is 3 tons. And the pouring temperature is 1280 ° C. For mechanical processing of the rolls, ring-templates are taken from the ends of the necks, samples are cut from them to determine the mechanical properties and conduct metallographic analysis.

The results of the casting of the experimental rolls are shown in the table.

As can be seen from the table, the use of unalloyed barium-containing iron with a content of 0.02-0.04% Ba in relation to alloyed iron 1: (3.2-

Q 4.5) allows, in comparison with the prototype, to increase the criterion of the operational strength of the lower necks by 25-35% while reducing the cost of washing by 23-44%.

Claims (1)

Invention Formula The method of casting two-layer mill rolls, including the casting of the mold with alloyed iron to the level of 300-350 mm above the upper edge of the roll, the shutter speed for the crystallization of the bleached working layer and the subsequent washing of the mold with unalloyed iron to form the core and roll necks, characterized in that in order to increase the operational strength of the lower (drive) necks of the roll and reduce costs for washing, for washing the casting mold, unalloyed barium-containing iron with a barium content of 0.02-0.04% is used with a weight ratio unalloyed barium-containing iron to the mass of doped iron 1: (3.2-4.5), while iron, of the following composition, in wt.%, is used as unalloyed barium-containing iron: Carbon3.3 -3.6 Silicon1.3 -1.9 Manganese0.4 -.0.6 Phosphorus 0.10-0.25 Sulfur0.08-0.14 Barium0.02-0.04 Iron Else.