Quality control standards for galvanized steel sheet

The quality of galvanized steel sheet includes specification and size, surface, zinc coating, chemical component, model, machine function and packaging. The manufacturer should observe such requirements when producing and leaving factory. As follow details 

1. Packaging 

There are two types of packing: Galvanized steel sheet which cut into sizing length and coil Galvanized sheet. Generally by iron sheet, lined with Moist Proof Paper, tie the outside with iron strap so that the sheets will have no friction.

2. Specification and dimension

As for the product dimension (as hereunder mentioned), thickness, length, width should listed tolerance and available mistakes. In addition, width and length of the plate and width of coil can be confirmed by customers’ inquiry. 

3. Surface

General situation: The general situations of the galvanized steel sheet are different (including general situations of ordinary spangle, fine spangle, flat spangle, zero spangle and phosphating treatment) due to the difference of disposal methods in the plating process. Galvanized sheets and galvanized coils cut into specified lengths should be free from defects influencing the use (as hereunder mentioned), but the non-deformed parts of hot rolled coils (such as welding position) are allowed. 

4. Zinc coating 

Zinc coating: This is an useful method for suggesting the thickness of the galvanized steel sheet zinc layer which is widely used. There are similar Zinc coating on both sides (namely equal thickness galvanizing) and different Zinc coating on both sides (namely differential zinc coating). The unit of Zinc coating is g/m2. 

5. Machine function 

(1) Tensile test: Generally speaking, the tensile function requirement is only put forward against galvanized steel sheets for layout, stretching and deep drawing. 

(2) Bending test: It is a principal item for evaluating the sheet process and function. However, the dimension requirements against various galvanized steel sheets are different in various nations. Generally, it is required that after 180° bending of galvanized sheet, the outer surface of the sheet shall not be separated from the zinc layer, and the base of the sheet shall not be cracked or broken.