The processing technology of galvanized channel steel is relatively complex. During processing, the main technology is heat treatment. Heat treatment is not only heating, but also has many limitations. In order to complete the structural transformation, dissolution of carbides, and homogenization of austenite composition of the internal and external parts of the workpiece, it is necessary to heat it for a certain period of time during the treatment process.
1. The effect of pre plating treatment on the surface roughness of the galvanized layer of channel steel, resulting in "acid washing".
After pickling, "the surface of the steel is roughened or bean marks appear, which is one of the reasons for the roughness of the workpiece surface after Hot-dip galvanization.
2. Excessive zinc bath temperature or soaking time can affect the surface roughness of the galvanized layer on channel steel.
When the temperature of the zinc bath is too high, the zinc immersion time is too long, or due to the influence of channel steel composition and Saint Delin effect, there are too many or uneven Zn-Fe alloy phases, and the surface roughness is also caused. The thicker the zinc coating, the rougher the surface.
After being taken out of the zinc liquid, the Hot-dip galvanization channel steel cools slowly, or the steel part is too thick, or the channel steel does not accumulate immediately after Hot-dip galvanization, and the surface may be rough.
3. The manufacturing of channel steel adopts the composition or surface condition of the steel, and the influence of the surface roughness of the galvanized layer of the channel steel.
Relatively speaking, the smoothness and roughness of the surface of the galvanized layer. Different from steel plate, steel pipe or steel wire, "continuous hot-dip galvanizing", Hot-dip galvanization of steel channel belongs to batch Hot-dip galvanization process, and the galvanized layer is not blown by air knife. If the steel surface used for Hot-dip galvanization channel steel is rough, there are rust pits or obvious rolling strips. After Hot-dip galvanization, the surface is usually not smoother than the original surface. Galvanized channel steel is usually used for quenching oil during the heat treatment process, and mineral oil is often used. For different mold parts, different heat treatment companies use different quenching oils. The higher the oil number, the higher the viscosity, and the higher the flash point, usually between 150 and 300 ℃. Its temperature has a certain impact on the safety of galvanized channel steel parts.
Usually, a rough galvanized layer is also acceptable because it not only does not affect usage, but also has higher corrosion resistance and longer service life, as rough galvanized layers tend to be thicker than smooth galvanized layers, but the appearance of channel steel is not very attractive.