Method for enhancing the self-feeding ability of a heavy section casting blank

Abstract

The present invention relates to the field of casting blank manufacturing, in particular to a method for enhancing the self-feeding ability of a heavy section casting blank, which can solve the problems of poor centre quality, surface crack and high rejection rate of the heavy section casting blanks in the prior art. By controlling the outer cooling conditions of different solidification stages of the casting blank, the present invention quickly solidifies and crusts the outer surface of the casting blank to increase the strength and prevent surface crack at first, and then performs thermal insulation on the casting blank surface such that large area of the core forms the mushy region such that the solidified layer of the casting blank surface is maintained at a relatively high temperature to facilitate realization of the plastic deformation, thus realizing synchronous solidification and solid movement in the subsequent solidification and shrinkage processes of the casting blank, fulfilling the aim of radial self-feeding of the high-temperature deformable metal, eliminating the inner shrinkage voids and surface crack, and obviously eliminating the inner shrinkage of the casting blank. The present invention is applicable to the heavy section metal castings, in particular to the round and square heavy section casting blanks which have a large height-diameter ratio and cannot eliminate the axis shrinkage pipe through the feeder head.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field[0002]The present invention relates to the fields of manufacturing of casting blanks, such as wide and thick metal slabs, round / square / rectangular heavy section casting blanks, and in particular to a method for enhancing the self-feeding ability of a heavy section casting blank, and eliminating the shrinkage voids and the surface cracks of the casting blank.[0003]2. Description of Related Art[0004]Wide and thick slabs (special slabs) have been widely applied in economic construction. A great amount of wide and thick slabs are used in large-sized ships, ocean platforms, hydroelectric generating sets, thermal power generating units, pressure containers, dies, and long-distance pipelines. Therefore, there are huge demands on thick-large section wide and thick slabs for rolling the wide and thick plates. At present, the maximum thicknesses of the continuous casting slabs all are smaller than 400 mm. If the continuous casting slabs are a...

AI Technical Summary

Benefits of technology

The present invention provides a method to improve the self-feeding ability of heavy section casting blanks to eliminate centre shrinkage, porosity, and surface cracks in molded wide and thick slabs and round and rectangular continuous casting blanks. This technology is beneficial for manufacturing round casting blanks with a diameter of over 500 mm and square or rectangular casting blanks with a thickness of over 400 mm.

Problems solved by technology

Therefore, there are huge demands on thick-large section wide and thick slabs for rolling the wide and thick plates.

If the continuous casting slabs are adopted to roll the wide and thick plates with a thickness of 200 mm, it is difficult to ensure the performance of the core due to a small reduction ratio.

The mold casting method or electroslag remelting method for producing the wide and thick slabs has the disadvantages of low productivity, low success ratio, and high cost.

However, when the water-cooling molding method is used to produce the wide and thick slabs, the large water-cooling intensity easily causes large temperature difference between the centre and the surface of the wide and thick slab, large thermal stress during solidification, and cracks in the surface and core of the slab.

This technology also has defects: the height-diameter ratio of the casting blank produced by this technology is large, so realization of axis feeding of the casting blanks is difficult, and it is easy to cause shrinkage and porosity of the centre of the cast blanks;

moreover, the outer surface of the blank is usually processed with a forced-cooling process, which causes an extremely low temperature to the outer surface and results in cracks.

Those defects limit the development of the round continuous casting blanks to the bigger section size (≧Φ800 mm).

The square and rectangular heavy section continuous casting blanks with a thickness of over 400 mm also have the macro defects of inner shrinkage, porosity, and surface cracks.

However, the feeder head ratio of the heavy section continuous casting blank is very small, and the height-diameter ratio thereof is bigger than 4, so the axial gravity feeding of the casting blank cannot be realized.

In conclusion, the inner shrinkage, porosity, and surface cracks of the heavy section casting blanks are technical bottlenecks that limit the development of the casting blanks towards the bigger section sizes.

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