Medium and thick steel plates refer to steel plates with a thickness between 4-60mm, and their production processes mainly include hot rolling cold rolling, and medium and thick plate rolling. Hot rolling is to produce steel plates by continuous rolling after heating the steel billet to a certain temperature; cold rolling is to produce steel plates by continuous rolling after cooling the steel billet to a certain temperature; medium and thick plate rolling is to roll the steel plates produced by hot rolling or cold rolling again to achieve the required thickness.

Hot rolled steel plates refer to flat steel plates produced by hot rolling, and their thickness is generally between 3-20mm. The production process of hot-rolled flat plates mainly includes hot rolling, pickling, and leveling. Hot rolling is to produce steel plates by continuous rolling after heating the steel billet to a certain temperature; pickling is to remove the iron oxide and impurities on the surface of the steel plate; leveling is to level the steel plate through a leveling machine to achieve the required flatness.

PE lining is made of thermoplastic plastic pipes such as polyethylene (PE), heat-resistant polyethylene (PE-RT), cross-linked polyethylene (PE-X), and so on, which are lined on the inner wall of steel pipe according to the requirements of the conveying medium, so it has the advantages of both steel pipe and plastic pipe.
Plastic-coated composite steel pipe is a steel-plastic composite product with steel pipe as the base material and plastic powder as the coating material, with a plastic layer melt-coated on the inner surface and a plastic layer or other material anti-corrosion layer melt-coated on the outer surface.
According to the different inner coating materials, there are two types, one is polyethylene-coated steel pipe. The other is epoxy resin-coated steel pipe.

Hot-dip galvanized square tubes are generally judged to be qualified based on the appearance of the product. If the outer wall of the square tube has plating defects, pitting, white spots, heavy skin, bubbles, greening, etc., and the frequency of occurrence is too high, it is judged as an unqualified product. However, the product standard has a specified range for the allowable deviation of the product, which should meet the design requirements and relevant standards.