Continuous casting method of large-length hollow ductile cast iron sections and method for arcing hollow ductile cast iron sections after local continuous heating

Abstract

The invention relates to a continuous casting method of large-length hollow ductile cast iron sections and a method for arcing the hollow ductile cast iron sections after local continuous heating. Thesection comprises the following components by weight percent: 3.4-3.6% of C, 2.8-3.2% of Si, 0.40-0.60% of Mn, S less than or equal to 0.1%, P less than or equal to 0.1% and the balance Fe. Molten iron is subjected to shaping and continuous casting under multiple physical fields to become the hollow sections. The molten iron in heat preserving furnaces is separated from dross, sand and gas in twoways, thus completely solving the defects of dross inclusion, sand inclusion and pores; liquid column cores in a crystallizer carry out continual feeding on condensing tube shells, thus eliminating the possibility of shrinkage porosity inside the tube walls, obtaining highly dense cast structure of (ferritic matrix+spherical graphite) and eliminating crack initiation origins in thermoplastic deformation to be carried out later. The intense cooling speed in the crystallizer enables the volumes of eutectic cells to be only 1/15-1/25 of the volumes of traditional sand mould casts. The density ofthe graphite balls reaches around 500/mm<2>. In plastic deformation, the micro slip orientation is increased and the ductility is enhanced, therefore, the hollow cast iron sections can be arced by medium frequency induction heating and bending.

Description

technical field [0001] The invention relates to a continuous casting method of a large-length ductile iron hollow profile and a method for bending it into an arc by local heating 2. Background technology [0002] The sand casting production of ductile iron elbows has a history of more than 50 years. Its limitations are: 1. There are many defects such as slag inclusions, sand inclusions, pores, and shrinkage porosity in the as-cast structure, so the mechanical properties are low and can only be used as ordinary Water and gas pipeline connectors are used instead of other parts; 2. Limited by the size of the sandbox, the arc length of the elbow is limited, generally less than 1.5 meters, and rarely larger than 2 meters. [0003] However, in some occasions in industrial production, high-density, high-performance, and long-length ductile iron arc elbows are required. For example, in the electrolytic aluminum industry, in order to save energy and reduce consumption, the capacity ...

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Problems solved by technology

[0005] The purpose of the present invention is to provide the continuous casting method of large-length nodular cast iron hollow profiles and the production method of bending them into arcs after partia

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