SU1585067A1 - Method of casting two-layer pig iron rolling mill rolls - Google Patents

Abstract

The invention relates to a foundry, namely the production of iron rolling rolls. The purpose of the invention is to improve the quality of the rolls. According to the method of the invention, the outer layer is cast with alloyed cast iron, the shutter speed is made to form the working layer, and the inner layer is cast with cast iron with reduced to 2.4-2.9% C with a content of 0.7-1.2% SI

0.3-0.6% MN

up to 0.25% P, up to 0.1% S, moreover, the pouring is carried out in 2 stages: first 60-70% of the iron is poured, kept for 40-50 s, then the remaining cast iron is filled up with modifying it with a graphitizing modifier on the jet.

Description

The invention relates to foundry, specifically to the production of iron casting rolls.

The purpose of the invention is to improve the quality of rolls.

According to the method of the invention, alloyed cast iron is poured into the mold, it is held to form the working roll layer, then the inner layer is cast with cast iron containing 0.7-1.2% Si, 0.3-0.6% Ml to 0.25% P up to 0.1% S and reduced carbon content up to 2.4-2.9%.

In this case, the casting is carried out in 2 stages: first, 60-70% of the cast iron volume of the specified composition is poured, the shutter speed is made for 40-50 seconds, and the remaining cast iron volume is modified with a graphitizing modifier on the jet.

As a modifier, a mixture of aluminum powder and 65% powdered ferrosilicon in a mass ratio of 1: 4 or silicobarium is used.

The essence of the method consists in forming between the outer and inner layers of the casting an intermediate layer of low-carbon iron, which hardens with little precipitation. graphite and pre-expansion (0.03-0.06%), which significantly reduces the foundry stress and the impact of cold

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fissures). Graphitizing modification is carried out with the aim of increasing the strength of the core of the roll axles and does not have a significant effect on the occurrence of dropped defects.

As a result of the search, no technical solutions with similar features and decisive set goals were found, therefore, the proposed solution has significant differences.

If the carbon content in the cast iron of the inner layer is higher than 2.9% C, the degree of graphitization increases, pre-shrinkage expansion and the likelihood of cracking in the castings. If the carbon content in the cast iron of the inner layer is lower than 2.4%, the casting properties of the cast iron deteriorate. This necessitates an increase in its overheating, which, in turn, causes the hardening of the hardened outer layer to melt and the depth of the clean chill on the rolls to be reduced.

If the fill volume of the inner layer before aging is accepted, more than 70%, the necessary effect of graphitization of the core is not achieved, the strength of the pins and the overall strength of the plug are reduced.

If the fill volume of the internal surface before exposure is less than 60%, then the necessary thickness of the intermediate layer is not reached, sufficiently high casting stresses remain, rolls are subject to rejects on cold nym (hair-like) cracks.

If the holding time of the unmodified cast iron before the casting continues to take more than 50 seconds, the runner system hardens. If this time is taken less than 40 s, the thickness of the intermediate layer decreases, it increases

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marriage on cold (hair-like) cracks.

Example. The total casting weight of the roll with a barrel size of 700x1700 mm is 9.2 tons.

Claims (1)

The casting of the alloyed cast iron to a level higher than 0.3 of the height of the upper roll neck is carried out, maintained for 60-70 seconds, 50-70 kg of cast iron is introduced into the sprue system to defrost it, re-produce the shutter speed 50-60 seconds, and then proceed to pouring unalloyed low carbon iron, the estimated total volume of which is 4 tons. 2.5 tons of iron are poured, 40-50 seconds are made, they start to refill 1.5 tons of pig iron, while entering by pneumatic transport using a special device, the powder graphitizing modifier for the jet. The siphon metal supply system provides for the modification of cast iron over the entire height of the roll core. Invention Formula The method of casting double-layer cast iron rolling rolls, which includes pouring the outer layer with alloyed cast iron, holding it to form the working layer, pouring the inner layer with undoped cast iron containing carbon, 0.7-1.2% Si, 0.3-0.6% Ifn, up to 0.25% P, up to 0.1% S, about t-l and due to the fact that, in order to improve the quality of the rolls, the inner layer is filled with cast iron with a carbon content of 2.4-2.9% in two stages , while at the first stage 60-70% of the iron of the inner layer is poured, it is kept for 40-50 s, and at the second stage the remaining iron is added n with the introduction of a graphitizing modifier into the cast iron stream.