The steel plate has excessive scale
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During the inspection upon arrival at the factory, it was found that the sheets had excessive coating. The treatment methods are as follows: for mild cases of excessive coating, grinding is performed followed by magnetic particle testing; for more severe cases, grinding is carried out followed by ultrasonic testing. Is this approach acceptable? What do fellow sea freight professionals do when they find heavy packaging upon receiving the goods? Are there any with relatively severe skin thickening? Thank you,
It is a quality issue with the sheet material; the specific cause is unknown. It mainly appears in carbon steel plates, angle steel, I-beams, and channel steel.
We have found that flat plates (not sheets that are rolled out) develop thick layers of material and cracks. It cannot be used because the initial rolling temperature is insufficient. For mild excess skin, if it’s used in unimportant areas, your method will work. But if it exceeds the allowed negative deviation, it can no longer be used
Under normal circumstances, the acceptance criteria for steel plate manufacturing specify that defects such as scars, double layers, delamination, wrinkles, and pits are not allowed. Defects like scars and double layers must be removed before the products leave the factory; the depth of removal shall not exceed the specified negative deviation or absolute limit, and welding repairs are not permitted, unless approved by the ordering party； Generally, MT is sufficient (for ferritic materials); ultrasonic thickness testing is not necessary as long as the thickness is within the allowable range. If the skin thickening is severe, it means delamination has occurred, and the product is deemed unusable.
In our company, if there is heavy scaling on the pressure vessel plates, they are returned for replacement immediately. :handshake