Oversized high-strength heatproof magnesium alloy ingot blank semicontinuous casting technique

Abstract

The invention relates to an oversized high-strength heatproof magnesium alloy ingot blank semicontinuous casting technique. The alloy comprises the following components by weight percent: 6-13% of Gd, 2-6% of Y, 0.3-0.8% of Zr and the balance of Mg and irremovable impurity elements. The technique comprises the steps of melting magnesium ingots, adding solvents, adding alloy elements, refining, degassing, removing impurities, preserving heat and standing, and semicontinuously casting under the low casting speed by using a counter-pressure gas fluid-guiding method at low temperature and under low cooling speed. In the invention, technique parameters such as the casting temperature, the cooling speed, the ingot pulling speed, the inner liquid level height of a crystallizer, and the like are controlled to obtain the oversized high-strength magnesium alloy ingot blank with flat and smooth surface, refining and uniform tissue and no solute segregation, and the diameter of the ingot blank is from 220 mm to 505 mm. The length of the ingot is 1000-5000 mm. The invention meets the requirements for the oversized ingot blank required by high-strength heatproof magnesium alloy materials in the fields of aerospace, information electronics, communications and transportation, and the like.

Description

technical field [0001] The invention relates to the casting field of magnesium alloys, in particular to a semi-continuous casting process of a super-large-sized novel high-strength heat-resistant magnesium alloy ingot billet. Background technique [0002] Magnesium alloy is currently the lightest metal structure material available, with high specific strength and specific stiffness, good diamagnetism, high electronegativity and thermal conductivity, as well as good shock absorption and machinability. With the increasing demand for high-strength and lightweight materials in industries such as aviation, aerospace, information electronics, and transportation, the application range of magnesium alloys is becoming wider and wider. [0003] Magnesium alloy smelting and casting processes directly have an important impact on magnesium alloy ingots, and the quality of the ingots has an important genetic influence on subsequent forming processes and properties. The traditional semi-c...

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Problems solved by technology

The traditional semi-continuous casting method can only cast ordinary magnesium alloy ingots, and the super-large diameter ingots (diameter 305-450mm) often have many inclusions inside, and are prone to coarse grains, loose structures, Defects such as surface or core cracks seriously reduce the performance of products after subsequent processing. After subsequent processing, the strength of the ingot at room temperature is lower than 400MPa, and at 300°C, its strength is lower than 200MPa; More rare earth elements can greatly improve its mechanical properties at room temperature (strength greater than 450MPa) and high temperature mechanical properties (strength greater than 200MPa at 300°C) and corrosion resistance (salt spray test is twice as long as AZ31 and MB8), but The addition of a large amount of rare earth elements increases the shrinkage of the solidified body of the alloy, and the casting thermal stress increases sharply, resulting in various casting defects that are more likely to occur in the semi-continuous casting process than ordinary magnesium alloy casting, especially the penetration through the ingot. permanent cracks, it is more difficult to cast ingots for super-large ingots

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