|Title||GI steel coil after processing blackening reasons|
|Description||GI steel coil with spangles in stock is a kind of coating steel plate which is widely used. There are two kinds of products commonly, namely, hot plated pure zinc and electroplated pure zinc. In the process of stamping and bending, the surface blackening of pure zinc coated steel plate is easy to occur. Type of surface blackening of pure zinc coated steel parts There are two common types of surface blackening: smudges (foreign objects attached to the surface of the coating) and processing classes (changes in the surface characteristics of the coating caused by processing), of course, the two types may exist simultaneously in practical cases. Identification of smudgy black spots The most common source of dirt is oily zinc dust, such as shear linoleum accumulation of grease. Identification: this type of dark spot is usually alleviated or removed by wiping because it is a foreign body attached to the surface. Even when dry, you can see a distinct outline. Smudgy black spots can often be identified by observing part samples. Identification of processed black spots There are many reasons for the processing of black spots, the surface of galvanized layer because of friction caused by roughness is changed, or friction caused by zinc powder accumulation or hot dip galvanized coating oxidation (affected by coating composition), may form the appearance of black spots. Identification: processing black spots must be combined with the production process for analysis, when the parts appear black spots, first determine the rule on the parts, is the uniform appearance of the whole part or the law of a certain location. After determining the rule, conduct reverse inspection on the processing line to find out the procedure where there is no black spot at the entrance and exit. Processing blackspot is usually caused by friction between steel plate and equipment, adjustment is also focused on reducing clamping device pressure, reduce the roughness of concave and convex mold, improve lubrication, shorten the mold cleaning cycle, adjust belt speed and other aspects.|
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