Ultrahigh-strength Al-Zn-Mg-Cu system aluminum alloy large-size flat cast ingot and making method thereof

Abstract

The invention discloses an ultrahigh-strength Al-Zn-Mg-Cu system aluminum alloy large-size flat cast ingot and a making method thereof, and belongs to the aluminum alloy making field. The flat cast ingot comprises, by mass, 2.0-2.4% of Cu, 1.95-2.5% of Mg, 5.5-9.0% of Zn, 0.08-0.15% of Zr, 0.0003-0.0015% of Be, below 0.06% of Ti, below 0.04% of Cr, below 0.10% of Mn, 0.085% or less of Si, 0.14% or less of Fe, and the balance Al and inevitable elements, wherein the content of each of the inevitable elements is lower than 0.05%, the total amount of the inevitable elements is lower than 0.15%, and a content ratio of Fe to Si is not less than 1.6. The making method disclosed in the invention improves traditional making methods, and does not need pure aluminum bottoming, and the flat cast ingot made in the invention has the advantages of large size, high strength, no cracks, and high casting success rate.

Description

technical field [0001] The invention relates to the field of aluminum alloy processing, in particular to an ultra-high-strength Al-Zn-Mg-Cu series aluminum alloy large-scale flat cast ingot and a manufacturing method thereof. Background technique [0002] Al-Zn-Mg-Cu series aluminum alloys belong to the 7XXX series ultra-high strength aluminum alloys. This series of alloys has high yield ratio and specific strength, high room temperature strength, good corrosion resistance and high toughness, and is widely used Used in aerospace, transportation and other fields. Due to the requirements of high strength and high toughness, Al-Zn-Mg-Cu aluminum alloy has high degree of alloying, wide crystallization temperature range and complex metallographic structure. When this series of alloys are smelted and cast, due to their wide crystallization temperature range and low plasticity of the as-cast structure, they have a high tendency to crack. The larger the size of the slab and its wid...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to solve the Al-Zn-Mg-Cu series aluminum alloy casting ingots produced by the existing method, which has a large tendency to crack, and it is difficult to form a large-scale slab. When casting, it is necessary to use pure aluminum as the bottom, the casting operation is complicated, and the aluminum melting is difficult. In view of the problems of large hydrogen content in the body, thick shell on the surface of the slab, poor surface quality, large amount of milling before hot rolling, and low yield, a large-scale ultra-high-strength Al-Zn-Mg-Cu aluminum alloy is provided. The flat cast ingot and its manufacturing method can produce large-scale flat cast ingots with ultra-high strength Al-Zn-Mg-Cu aluminum alloys with a maximum thickness of 620 mm and a maximum width of 1650 mm. The present invention does not need pure aluminum as a base , the resulting melt has high purity, hydrogen content < 0.08ml / 100gAl, the slab is not prone to cracks, the surface shell of the slab is thin, the amount of milling surface before hot rolling is small, and the yield is high

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