Precision and performance control method for superplastic forming sudden-change wall thickness thin-wall hemisphere

Abstract

The invention relates to a precision and performance control method for superplastic forming sudden-change wall thickness thin-wall hemisphere, and belongs to the technical field of titanium alloy superplastic forming. The method comprises the steps that 1, the size of a thin-wall hemisphere after a thin-wall blank is formed into the thin-wall hemisphere is determined; 2, a lower mold for forming the thin-wall hemisphere is designed; 3, an upper mold for forming the thin-wall hemisphere is designed; 4, polishing treatment is carried out on the inner molded surface of the lower mold and the inner molded surface of the upper mold; 5, the inner molded surface of the lower mold and the inner molded surface of the upper mold are evenly coated with welding stopping agents, and heating treatment is carried out; 6, the thin plate blank is placed on the top of the lower mold, and the upper mold covers the thin plate blank, and heating treatment is carried out; 7, reverse expansion treatment and forward expansion treatment are sequentially carried out on the thin plate blank, and the thin-wall hemisphere is formed; and 8, cooling is carried out, and the formed thin-wall hemisphere is taken out. The method can be used for forming titanium alloy hemispherical shell bodies with various sizes and large wall thickness distribution difference, and has good thickness distribution control and performance maintaining effects.

Description

technical field [0001] The invention belongs to the technical field of superplastic forming of titanium alloys, and relates to a method for controlling the precision and performance of superplastic forming with sudden wall thickness and thin-walled hemispheres. Background technique [0002] Superplastic forming is a method of forming that takes advantage of the extremely high elongation of materials in the temperature range close to the phase transition point and at low strain rates. Usually superplastic forming uses air pressure as the driving force for forming, and relies on the fit with the mold to ensure the final forming accuracy. Superplastic forming has the advantages of high precision, low pressure required for forming, and no residual stress, etc., and has been more and more widely used in various fields. At present, superplastic forming of titanium alloy pressure vessels is widely used at home and abroad. As early as the 1980s, the United States carried out exper...

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Problems solved by technology

The most conventional method of wall thickness control in forward and reverse forming, but the anti-expansion profile of this method is usually a ring design, which can only ensure the wall thickness conditions in local areas. For multiple sudden thickening structures, this method is difficult to achieve multiple wall thicknesses precise control of

At the same time, due to the addition of the reverse preforming process, the conventional forward and reverse forming greatly increases the forming time, which leads to an increase in the heat exposure time of the hemispherical shell at a high temperature close to the phase transition point, and the grain grows, resulting in a decrease in the final strength performance.

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