What causes friction black spots on DX51D+Z steel coils?
A: There are two categories: narrow and broad. Narrowly defined, they are mostly caused by friction during storage and transportation due to hoisting and stacking. Broadly defined, they can form during production due to interlayer friction, or during use when parts are roughened.
What causes orange peel defects during stamping of DX51D+Z steel coils?
A: This is related to the dissolved carbon atoms in the substrate, and is also affected by the hot rolling coiling temperature, galvanizing soaking temperature, and finishing elongation. Improper control of these factors can lead to orange peel-like textures on the surface after stamping.
How to improve the orange peel defect in DX51D+Z steel coils?
A: Reduce the dissolved C and N content in the substrate, precisely control the hot rolling coiling temperature and galvanizing soaking temperature, stabilize the finishing elongation, and optimize the entire process parameters.
What causes transverse bright stripes on DX51D+Z steel coils?
A: The most likely cause is the passivation solution coating roller. If the upper and lower surfaces are treated separately during coating, it easily leads to single-sided horizontal stripes. If the stripes are raised, they can disappear after polishing, confirming this as the cause.
Can a DX51D+Z with horizontal bright stripes still be used?
A: If it's only due to uneven passivation solution coating and doesn't affect corrosion resistance, the striped side can be used as the inner surface. If there is exposed steel, further evaluation is needed.