Method for controlling microporosity of large-section ductile iron casting

Abstract

The invention relates to a microalloying element and an instantaneous metal-stream inoculant for controlling the microporosity of a large-section ductile iron casting. The microalloying element and the instantaneous metal-stream inoculant are characterized in that the microalloying element is a combination of Cu and Sn, and SiRE is adopted as the instantaneous metal-stream inoculant and comprises, by weight percentage, 65-80% of Si, 1.0-2.5% of RE, 0.65-1.35% of Ca, 4-6% of Al and the balance Fe. A method for controlling the microporosity of the large-section ductile iron casting has the beneficial effects that through the synergistic effect of the microalloying element and the instantaneous metal-stream inoculant, the spheroidization grade of molten iron is increased, the number of graphite in the later period of the solidification of the molten iron is increased, the graphite is refined, and the rejection rate generated due to the fact the quality and performance of the large-section ductile iron casting do not meet the requirements due to the microporosity is reduced.

Description

technical field [0001] The invention relates to a metallurgical technology, in particular to a method for controlling micro-shrinkage of large-section ductile iron pieces. Background technique [0002] The solidification time of large-section ductile iron parts is long and the cooling rate is slow. When the external chiller speeds up the cooling rate, the cooling capacity of the strengthened casting is limited, so the actual degree of undercooling during graphite nucleation of the casting is small. It is difficult to form round, fine and evenly dispersed graphite. In addition, the number of graphite decreases in the later stage of molten iron solidification, and micro-shrinkage defects are prone to occur in castings, resulting in the quality and performance of large-section ductile iron parts that cannot meet the requirements for use. The control of micro-shrinkage defects has become an urgent technical problem to be solved for large-section ductile iron parts. Contents of...

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Problems solved by technology

[0003] The purpose of the present invention is to solve the problem that the solidification time of large-section ductile iron parts is long, the cooling capacity of external chilled iron-strengthened castings is limited, and the castings are prone to micro-shrinkage defects, resulting in the quality and performance of large-section ductile iron parts. To meet the requirements of use, provide a method for controlling the micro-shrinkage of large-section ductile iron parts, aiming at improving the spheroidization level of molten iron, increasing the number of graphite in the late solidification period, and refining graphite, so that more can be obtained through the late solidification period Round, fine and evenly disperse the expansion of graphite to realize the self-feeding of castings, control the formation of micro-shrinkage defects in castings, and improve the quality and performance of large-section ductile iron parts

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