Why do square and rectangular pipes have residual stress?
Time： 2023-03-22 14:07:18
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Square rectangular pipe is a kind of closed section steel with a wide range of uses. Compared with the round pipe with the same cross-sectional area, it has the advantages of high strength, large modulus of bending section, easy assembly, stability and beauty, and is widely used in vehicles, subways, shipbuilding and other industries. Especially in the construction industry, large-size square and rectangular pipes have become the main load-bearing structural components in steel structure buildings. As a typical closed section steel, square rectangular pipe will leave residual stress in each process of manufacturing. The different processing technology of square pipe will inevitably produce different degree of residual stress.
There are two ways of forming cold formed square tube: direct square forming and circular square forming. In order to study the different effects of forming process on products, scholars from North China University of Technology took square tubes with specifications of 100mm×100mm×6mm and material of Q235 as the research object, measured the residual stress of each part of the tube by drilling method, and observed the microstructure of the weld. The results show that the distribution of longitudinal residual stress is greatly affected by different forming processes, and the residual stress at the weld is large. Applying large welding pressure in the process of "round square" makes the width of the welding heat affected zone smaller than that in the process of "direct square", and controls the growth of austenite grains, and obtains relatively small and uniform grains after cooling.
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