Semi-continuous casting process of VW64M high-strength heat-resistant magnesium alloy big ingot blank

Abstract

The invention discloses a semi-continuous casting process of a VW64M high-strength heat-resistant magnesium alloy big ingot blank. An alloy contains, by weight, 5.0-7.0% of Gd, 2.5-4.0% of Y, 0.1-0.3% of Ag, 0.15-1.0% of Zn, 0.25-0.65% of Zr, 0.002-0.050% of Ca and the balance Mg. The process mainly includes the following steps that a magnesium ingot is molten at the temperature ranging from 670 DEG C to 720 DEG C; a Mg-Ca intermediate alloy and a fluxing agent are added; alloy elements are added at the temperature of 750 DEG C to 800 DEG C; refining and slagging-off are performed; gas feeding and stirring are performed; the temperature is adjusted to reach 680 DEG C to 700 DEG C and maintained for still standing for 1.5-3.5 hours; and low-temperature low-speed electromagnetic casting is performed. By coordinating the process parameters of all the steps, the magnesium alloy ingot blank being free of cracks, smooth in surface, small in grain size, uniform in structure and free of solute segregation and having the diameter phi of 300-630 mm and the length of at least 1000 mm is obtained.

Description

Technical field [0001] The invention relates to the field of magnesium alloy casting, in particular to the field of semi-continuous casting of Mg-Gd-Y-Ag-Zn-Zr-Ca series magnesium alloys with a diameter of Ф300-630mm. Background technique [0002] In recent years, magnesium and magnesium alloys, as important structural materials, have the advantages of low density, high specific strength, high damping performance, and good cutting performance. In automobiles, information electronics and aerospace, materials that require light weight and high strength Large-size magnesium alloy structural parts have broad application prospects. Adding rare earths to magnesium greatly improves the strength and heat resistance of the alloy, but the plasticity is low. The study found that Mg-Gd-Y-Ag-Zn-Zr-Ca series magnesium alloy has high strength, good heat resistance, strong plastic deformation ability and high ductility. After plastic deformation, room temperature elongation δ≥10%, tensile stre...

AI Technical Summary

Problems solved by technology

[0003] In the process of preparing large magnesium alloy ingots by conventional semi-continuous casting, the melt is easily burned, resulting in a large number of defects such as inclusions, pores, porosity, and central cracks inside the ingot, which reduces the quality of the ingot and directly affects the subsequent deformation process and structure. normal use of the

In the casting process of the rare earth magnesium alloy billet, due to the large amount of rare earth added, the density of the melt is increased, the fluidity of the melt is reduced, and the surface of the ingot is severely cold-shocked; the addition of rare earth causes a large amount of metal shrinkage, and the casting thermal stress increases sharply , making various casting defects more likely to appear, especially the penetrating cracks running through the billet, which significantly increases the difficulty of forming

Especially the addition of Zn element increases the tendency of edge cracking and hot cracking, which increases the difficulty of casting