When the material is formed by stamping, it will harden, different steel, different degree of hardening. Generally high strength low alloy steel only slightly increased 20MPa, less than 10%. Note: the yield strength of 140MPa steel increases with the increase of more than 40%! In the process of forming, the metal will be completely different.
The yield strength of these steels increases with the stress. The higher yield stress of the material plus the work hardening is equal to the increase of the flow stress. Therefore, the cracking, rebound, wrinkling, workpiece size, die wear, micro welding wear and so on
After a quick rebound for a period of time before the last week, the domestic steel market price increase is slowing down, continue to rise in power weakened; poor turnover situation, the market weakness gradually, plus the steel market to weak weak shocks, further aggravating the business mentality, so last week, steel price shocks narrow down, both supply and demand a wait-and-see attitude, and influence by rain in the south of businesses in the end of the month due to financial pressure reproduction demand fundamentals, expected short-term domestic steel prices will continue to run the main weak shock. The focus of the problem.
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