JPS5973150A - Production of composite steel ingot - Google Patents

Abstract

PURPOSE:To produce easily and economically a composite steel ingot by forming a slag layer and a metallic bath, by electroslag melting, into the space between an upright core material and an annular water-cooled mold and moving an electrode thereby performing build-up welding on the circumference of the core material. CONSTITUTION:A circular cylindrical core material 1 made of a defect-free material is set upright, and an annular water-cooled mold 6 is installed around the same so as to enclose the core material. A slag layer 4 and a metallic bath are formed in the space between the material 1 and the mold 6 by using electroslag melting. While an electroslag melting electrode 5 is moved around the material 1, the welding position is moved successively upward to perform build up welding around the material 1, whereby a composite steel ingot is produced. The molten metal in the initial period of melting is supported by a stub 8 and the solidification in the upper part of the slag is prevented by a nonmetallic refractory material 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a composite steel ingot used as a hot-rolled or cold-rolled roll material as L, and more specifically to a method for building up around a core material by electroslag melting.

Regardless of whether a rolling roll is used for hot rolling or cold rolling, the surface material is the most important factor in determining the quality of the roll. In recent F rolling conditions, a roll material with high wear resistance is desired.

In order to improve the quality of roll materials, component-based improvement measures are very effective, and in particular, high alloying is the most effective measure [7]. That is, an increase in the Cr content, which is an essential alloying component of ordinary rolls, and/or M o
An increase in the content of monocarbide-forming elements such as , V, etc. is expected to improve wear resistance. However, when manufacturing rolls, these high alloying chemical components induce other problems.

Highly alloyed steel ingots generally have a sound internal steel ingot I)
It becomes difficult. That is, the so-called U゛zak J defect tends to develop in the center of the steel ingot, and even with forging work it is not possible to compress it, resulting in J[.

It may become impossible to produce a product that can be used as a rolled roll.

The development of this "grainy" defect is due to inevitable natural phenomena such as the expansion of the solidification temperature range and the decrease in viscosity of the molten metal promoted by high alloying.

Therefore, the increase in naturally occurring defects due to high alloying cannot be sufficiently avoided unless the agglomeration method itself is improved.

For this reason, conventional approaches have been taken to solve this problem by making the roll surface layer portion and the center portion of the roll have different compositions. Specifically, there are a hollowing method, a casting method, an ESR method (electroslag remelting method), and the like.

The hollowing method is a method in which a molten metal of a different composition is injected so that υ1 of the molten metal in the center comes out when the center of the steel ingot is still unsolidified after casting. In the hollowing method, it is necessary to prepare the external hot water and the internal hot water with different compositions, which makes the melting work complicated.
If the injection 111 period of the indoor bath is not properly matched, it will not be possible to mix with the outside temperature and achieve the desired purpose. Therefore, it is difficult to optimize the on-site timing, and since a portion of the inner hot water is discharged to the outside of the steel ingot, there are disadvantages in that it tends to deteriorate the working environment and lack economic efficiency.

The casting method is a method in which a core material of a different structure is inserted into the mold in advance, and molten metal is poured around it. In the casting method, the adhesion between the core material and the molten metal is incomplete, and it is difficult to achieve sufficient adhesion even by forging work.

In addition, in the conventional general ESR method, the entire steel ingot is remelted, so if it is highly alloyed, it is difficult to obtain an internally homogeneous steel ingot, and since the entire steel ingot is made of a high alloy, it is costly. It becomes an amplifier.

With the progress of rolling technology, rolling conditions have become increasingly severe, and it is essential that roll materials move toward l-1, that is, toward higher alloys. In this case, two problems must be solved at the same time: ensuring the internal integrity of the steel ingot and preventing cost increases.

The present invention was completed as a result of extensive research in order to solve the following difficulties in manufacturing steel ingots due to high alloying. That is, it is a method of building up around the core material by electroslag melting, and the outer peripheral layer is made of any alloy composition of any thickness, adheres to the core material and Shiden, and has high cleanliness. It is something that can be done.

The main purpose of the present invention is to solve the problem of internal defects by using a core material that has been manufactured soundly in advance, and to dissolve the core material and the outer layer by applying electroslag melting around the core material. By aiming for good adhesion of the material, obtaining a clean outer peripheral layer of arbitrary thickness by electroslag refining action, and highly alloying only the outer peripheral layer,
The objective is to produce economical composite steel ingots.

In order to achieve the above object, the present invention has the following features. In other words, a core material is made to stand 1α, a ring-shaped water-cooled mold is placed around it, a slag layer and a metal bath are formed using electroslag melting in the gap between the core material and the mold, and an electroslag electrode is formed. -1- Sequential welding while moving around the core material ``Move to one side and perform overlay welding around the core moon'' is the #+j feature.

This will be explained below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part explaining the present invention in detail.

In the figure, l is the core material of the build-up river, 2 is the supporting part of the core material for build-up, 3 is the build-up layer, 4 is the melted slag layer, 5 is the melted electrode,
6 is a water-cooled molding I, 7 is a nonmetallic refractory material, 8 is a melting stub, and 9 is an arrow indicating the moving direction of the core material.

The core material 1 is, for example, a cylindrical core material made of a defect-free material, and the axis A'r L is perpendicular to the axis, and 2 is a support portion of the core material I. The support part 2 has a small diameter because the stub 8
This is for reasons of operational convenience, to support the core material and to support the core material with two layers.

The water-cooled mold 6 has the function of forming a metal bath with the molten slag 4 by melting the core material 1 between the core material 1 and the core material 1. The build-up layer 3 is sequentially generated by lowering or by vertical relative movement of the water-cooled mold 6 and the core material l by the 1.4 of the mold 6.

The reason why the nonmetallic refractory material 7 is provided in a portion of the water-cooled mold 6 is to prevent the slag from solidifying in the upper part.

The electroslag melting electrode 5 rotates or rotates around the core material 1 around the axis of the core material 1 to generate a uniform overlay layer with a uniform shape. This is because depending on the chemical composition of the build-up layer, it may not be possible to obtain a build-up layer with a uniform shape just by moving the core material 1 and the mold 6 one-way.

The stub 8 is for supporting the melted metal 101. Further, an arrow 9 indicates the direction of movement of the core material 1, that is, the direction of relative movement between the -11 metal refractory material 7 and the core material 1, which is a cold water mortro, which is a coagulation accelerating device for the metal bath.

There is a risk that the outer periphery of the core material 1 will be rapidly heated and horizontal cracks will occur due to thermal expansion, and there is also a risk that the outer layer 3 may crack or the welded portion may peel due to the thermal balance between the heat content of the core material 1 and the heat of the outer periphery. Therefore, in order to prevent this, it is preferable to preheat to an appropriate temperature. Preheating conditions can be determined depending on the shape, dimensions, material, application conditions, etc.

The present invention has the following excellent effects.

l) It is possible to easily produce a composite steel ingot in which metals of different compositions are uniformly laminated around a core material without central defects.

2) Add a high alloy layer to the core material that has the required roll rigidity, breakage resistance, etc. and has the properties required for the rolled surface, such as abrasion resistance, crank resistance, heat check resistance, and surface treatment performance. Can be built up to any thickness without defects such as seams.

3) The manufacturing cost of the steel ingot material is economical.

4) Application is not limited to rolling rolls, but can also be applied to the production of other steel ingot materials with surface coatings.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view illustrating the present invention in detail. ■... Core material for overlaying, 2... Supporting part of core material for overlaying, ? ... Overlay layer, 4... Dissolved slag layer, 5...
Melting 'upper electrode, 6...Water-cooled mold, 7...Non-metallic refractory material, 8... Melting stub, 9...Arrow indicating the direction of the moving force of the core material! tl+-61 Applicant Kawasaki Steel Corporation] Agent
Patent Attorney Yoo Kosugi

Claims (1)

[Claims] ■ A ring-shaped water-cooled mold is placed around the upright core material, a slag layer and a metal bath are formed in the gap between the core material and the mold using electroslag melting, and an electroslag electrode is placed on the core material. A method for manufacturing a composite steel ingot, characterized in that overlay welding is performed around the core material while moving the composite steel ingot around the core material.