Production method of steel ingot for large roll billet with low macro-segregation

Abstract

The invention discloses a production method of a low macrosegregation steel ingot for a large roller blank, relates to a production method of a steel ingot for a roller blank, and solves the problem of severe segregation of the steel ingot for a traditional roller blank. The method comprises the following steps: an inner-cooled steel rod blank is prefabricated, and is thermally treated and forged; the inner-cooled steel rod blank is machined to a cylindrical inner-cooled steel rod with a needed size, and dirt on the surface thereof is removed; the inner-cooled steel rod is preheated to a temperature of 50-700 DEG C; protective slag is added in a steel ingot mold of the steel ingot for casting the roller blank, and a steel ingot riser is added at a moth part; the preheated inner-cooled steel rod is fixedly hung in the center position of an inner cavity of the steel ingot mold, and a distance is generated from the bottom end thereof to the bottom surface of the inner cavity of the steel ingot mold; molten steel of the steel ingot for the roller blank is cast in the steel ingot mold; after the molten steel is condensed, the steel ingot mold is stripped to produce the steel ingot for the roller blank; and the inner-cooled steel rod and the molten steel are fused as a whole to become one part of the steel ingot. The method is feasible in operation, is easier in parameter control, and inhibits positive segregation of large center of the steel ingot for the roller blank.

Description

technical field [0001] The invention relates to a production method of a steel ingot for a roll billet, in particular to a production method of a steel ingot for a large roll billet with low macro-segregation. Background technique [0002] Macro segregation is a kind of defect in casting, and it is serious in large billets. [0003] The roll has a long service life and bears alternating bending stress for a long time, requiring the roll blank to have good yield strength, toughness and fracture resistance. However, the size of the backup roll billet is generally relatively large. Due to the large size, there are multi-phase flow and complex mass and energy transfer in the casting, the solidification time is long, and the difference in regional cooling rate is large, resulting in uneven grain size and serious segregation. Therefore, it is necessary to rely on repeated heating and deformation during later forging to obtain homogeneous steel, which greatly increases the cost. ...

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Problems solved by technology

For example, some scholars (Pei Zhao, Hui Zhang, New ideas to improvehompgeneity of as-cast structure of steel, International Conference of Ultra-fine Structures of Steel Materials, Australia, 2003, 11) proposed to add steel balls to steel ingots to form heterogeneous structures. Nucleation to speed up the cooling of the ingot, but this method cannot control the position of the steel ball in the ingot

There are also some scholars (Sang Baoguang et al., patent application number 200810011408.3) who have proposed a method of manufacturing large steel ingots with low segregation by speeding up the cooling of the bottom and side walls, adding air ducts to the bottom of the ingot mold and the middle and lower parts of the ingot mold, and strengthening the external surface by compressing gas. Heat dissipation, this method has no obvious effect on large ingots, because when the external heat dissipation conditions are good, the heat dissipation bottleneck of large ingots lies in the ingot itself

There are also some scholars (Li Dianzhong et al., patent application number 20091001086.2, a method for suppressing segregation of large steel ingots through multi-package co-casting) proposed multi-package co-casting, mainly by adjusting the composition of each bag: the bottom is higher than the normal level, and the top is lower The method is higher than the normal level, and the interval between each ladle is changed to suppress the macro segregation. This method can suppress the macro segregation to a certain extent, but the large ingot has a large amount of molten metal, and the metal flow between the ladles is fused with the macro segregation. Overall it will still be big

Some scholars (LAURENTIU NASTAC, Computational Fluid Dynamics Modeling of Macrosegregation and Shrinkage in Large-Diameter Steel Roll Castings, METALLURGICAL AND MATERIALS TRANSACTIONS B VOLUME 42B, DECEMBER 2011—1231) proposed that in order to overcome the positive segregation of the center, the center position should be used when casting The material is pre-emptied, and finally a relatively low-component and low-temperature molten metal is poured into the center. This research has some effects, but the operation is complicated, and the low-temperature low-component molten metal poured in at the end will also be affected by natural convection during the solidification process. Fusion with the surrounding molten metal, the effect is not great

Others (Kang Xiuhong, etc., Patent Application No. 200810228883.6, a kind of internal cooling method for suppressing macro-segregation of large steel ingots) propose a method of arranging at least one circle of chilled iron rods at a quarter or half radius of the ingot , this method is theoretically feasible, but it is more complicated to transfer mass and energy after adding steel rods, and its parameter size is difficult to determine, and the actual operability needs to be studied

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