Cross-sectional shape of strip plate for machining sheet metal strip having U-shaped cross section

Abstract

The invention relates to a cross-sectional shape of a strip plate for machining a sheet metal strip having a U-shaped cross section. The shape is a holosymmetric pattern which is symmetric both longitudinally and bilaterally; and a transition zone realizing the gradual change of thickness is arranged between a thin material t2 and thick material T2, thereby effectively improving the cooling uniformity of the thick and thin materials, and reducing or eliminating the generation of a solidification shrinkage partial internal stress at the junction of the thick and thin materials during the solidification shrinkage of the materials. Compared with the prior art, the cross-sectional shape has the beneficial effects that cracks of the strip plate are reduced or eliminated, the yield is increased, the stress state of a die is improved, the abrasion to the die is reduced, and the service life of the die is prolonged.

Description

technical field [0001] The invention relates to a strip blank sectional shape for processing a U-shaped cross-section metal strip, in particular to a strip blank cross-sectional shape for processing a U-shaped cross-section copper alloy strip for power transistors. Background technique [0002] The section of U-shaped cross-section copper alloy strip used for power transistors is usually formed by two specifications: thin and thick. The thin material is used as a lead for circuit connection, and the thick material supports the chip and heat dissipation. The common section is shown in figure 1 , is a U-shaped section, the middle of the section is thin material, the edge of the thin material and the edge of two adjacent thick materials form a concave trapezoid, and the two sides of the section are thick materials of equal size. The requirements for frame punching have very strict technical requirements for the dimensional tolerance, surface roughness, side bending, and residua...

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Problems solved by technology

[0008] The rectangular cross-section strip used in method 1 is usually obtained through multiple processes such as ingot hot rolling, cold rolling, and slitting. In the forming of U-shaped section, the processing process becomes complicated due to the difference in processing rate between thick material and thin material

And method 2 is to use the cross-sectional shape similar to the finished product cross-section as the mold shape to continuously cast U-shaped billets or extrude U-shaped billets. The process is short and the project investment is low. In the subsequent forming of the U-shaped section, the subsequent processing becomes simple due to the basically the same processing rate of the thick material and the thin material. Inhomogeneous, internal stress will be generated locally at the junction of thick and thin materials during solidification and shrinkage. When the internal stress is greater than the tensile strength of the material, it will cause small internal cracks that cannot be recognized by the naked eye. In severe cases, obvious cracks will appear. The internal cracks that cannot be recognized by the naked eye will be elongated and appear intermittent long cracks during cold pressure processing, so that the product will be scrapped. At the same time, judging from the shape of the blank ( figure 2 ), due to the excessive size of the step at the junction of thick and thin materials and the asymmetry of the overall shape, the overall force of the mold is uneven and the local wear is too large, which leads to early failure and affects the service life of the mold

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