Casting method and apparatus

Abstract

This invention is concerned with the productions of unidirectionally solidified castings and remelting-processed ingots such as ESR or VAR, which has paid special attention to the liquid flow phenomena within solid-liquid coexisting phase (mushy phase) during solidification, and made it clear for the first time that by applying high static magnetic field onto the whole mushy phase, the extremely slow interdendritic liquid flow responsible for the formation of macrosegregation can be suppressed, and thereby that the macrosegregation such as freckles can completely be eliminated. Thus, this invention provides with a novel casting technology for producing high quality castings and ingots without macrosegregation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This is a Continuation Application of PCT Application No. PCT / JP2007 / 059353, filed Apr. 24, 2007, which was published under PCT Article 21(2) in English.[0002]This application is based upon and claims the benefit of priority from prior International Application No. PCT / JP2006 / 309133, filed Apr. 25, 2006, the entire contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]This invention is concerned with the casting technologies for primarily improving macrosegregation defects in unidirectionally solidified castings which possess columnar dendrite structure consisting of polycrystalline grains (so called DS material) or dendrite structure consisting of a single crystalline grain (so called Monocrystal or SX material), and in the remelting-processed ingots such as Electroslag Remelting (ESR) and Vacuum Arc Remelting (VAR).[0005]2. Description of the Related Art[0006]A. Unidirecti...

AI Technical Summary

Benefits of technology

[0012]This invention is concerned with unidirectional solidification process and remelting processes such as ESR and VAR, and provides with casting technologies for producing high quality castings and ingots without such macrosegregation defects as freckles caused primarily by the liquid flow within the mushy zone during solidification. With special attention paid to the above-mentioned liquid flow phenomena within the mushy zone, this invention has clarified for the first time that the interdendritic fluid flow with extremely low velocity can be suppressed by exerting high magnetic field onto the whole mushy zone, and thereby the formation of the macrosegregation defects such as freckles can be eliminated.

Problems solved by technology

However, casting defects such as channel segregation (so called freckles), misoriented grains, microporosity tend to occur in these blades, thus lowering the yield of the products (for example, refer to p.

Also, dendritic growth tends to break down and misoriented grains are likely to form.

Despite that a vast amount of efforts have been paid to improve these casting defects by optimizing casting parameters such as sustaining temperature in the radiation heating zone, withdrawal rate, radiation cooling rate, etc. or by adjusting alloy compositions so as to add heavier elements than Ni (for example Ta), it still remains insufficient.

(2)), and that these macrosegregation defects can occur in the alloys of ‘downward type of buoyancy’ where interdendritic liquid density increases as solidification proceeds, as well as in the aforementioned alloys of ‘upward type’ of buoyancy.

However, as the cross-section of the ingots become larger, the formation of these macrosegregation defects is unavoidable.

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