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D igital patternless freeze-casting forming technology provides a green and rapid manufacturing method for single-piece and small-batch casting parts production in the fields of national defense industry, aerospace, power machinery, etc. [1]. The traditional sand mould casting process produces a large number of volatile organic compounds (VOC) and hazardous air pollutants (HAP) that are harmful to the human body and the environment. Of the 188 HAP listed by the U.S. environmental protection agency, more than 40 kinds have been detected in the sand mould casting process, including formaldehyde, benzene and phenol, etc. [2]. Therefore, it is urgent to develop new green casting processes and technologies.

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In this paper, the casting process optimization design of a certain type of headstock is carried out by numerical simulation technology of casting process. Designed the pouring plan based on theoretical calculation; based on the numerical simulation results, quantitatively designed the riser size, and rationally arranged the pouring riser system based on the equilibrium solidification theory, which can reduce the shrinkage porosity and shrinkage defects in the casting process and increase the process yield; Finally, a sand core production plan is provided based on the precision machining technology of the moldless casting mold, which provides a new idea for the process plan design of complex spindle box castings.

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The effect of chemical composition on the surface characteristics of the hot-dip galvannealed (GA) steel sheets with a carbon content as low as 15 ppm strengthened by Cu and/or Mn sulfides instead of Ti and/or Nb carbides has been studied. The most important goal for developing the new type of steel sheets is focused on the achievement of the extreme surface quality to fulfill the high aesthetical requirements for defect-free automotive outer panels. The shape and distribution of the surface enrichments of Cu, Mn, Al and O on the GA steel sheets were characterized by OM, SEM and TEM. Especially, formation mechanism of the narrow streaky mark with the width of 50–100 µ m occasionally observed on the surface of GA steel sheets will be presented.