SGH340 galvanized sheet and SGH440 galvanized sheet primarily differ in the following aspects:

I. Mechanical Properties:

SGH340: Yield point not less than 245MPa, tensile strength not less than 340MPa, elongation not less than 20%.

SGH440: Yield strength ≥ 335 MPa, tensile strength ≥ 440 MPa. SGH440 exhibits significantly higher strength than SGH340, enabling it to withstand greater loads and stresses.

II. Chemical Composition:

SGH340: A low-carbon alloy steel primarily containing carbon (C ≤ 0.25%), manganese (Mn ≤ 1.70%), phosphorus (P ≤ 0.020%), and sulfur (S ≤ 0.005%).

SGH440: Typically produced by increasing manganese content based on SS400 to enhance strength. Specific chemical composition may vary by manufacturer and production process.

III. Thickness Range:

SGH340: Manufactured from hot-rolled base plates, with typical thickness ranging from 1.6 to 6.0 mm.

SGH440: While standards do not explicitly define thickness limits, common production specifications range from 2.0 to 3.0 mm.

IV. Application Fields:

SGH340: Due to its relatively lower strength, it is primarily used in applications with less stringent strength requirements. Examples include automotive body panels and chassis structural components, washing machine drums and refrigerator side panels in the appliance industry, as well as photovoltaic racks and color-coated steel tiles in construction.

SGH440: Its higher strength makes it suitable for applications demanding greater strength and stability, such as large steel structures in construction and automotive components subjected to significant stress.

Processing characteristics differ between SGH340 and SGH440 galvanized sheets as follows:

V. Stamping Formability: SGH340 features a yield strength of 180-300 MPa and an elongation of ≥18%-22%, characterized by high elongation and low yield strength. Consequently, it exhibits excellent stamping formability, making it suitable for complex processes like deep drawing and bending, such as manufacturing components requiring multiple stamping operations or deep drawing. In contrast, SGH440 exhibits higher yield strength and tensile strength with a relatively lower elongation rate, typically around 10%. This makes its stamping formability inferior to SGH340, rendering it more suitable for standard bending and medium-duty structural components.

VI. Weldability: When welding SGH340 galvanized sheet using pulse MAG welding, although the zinc coating on the weld surface may burn off, it transitions smoothly without defects such as arc interruption, undercut, porosity, or lack of fusion. The welded joint meets the requirements for weld integrity. However, due to the higher strength of SGH440 galvanized sheet, welding may require higher heat input. Additionally, changes in hardness and strength within the heat-affected zone may be more pronounced during welding, increasing susceptibility to issues like welding cracks and making the process relatively more challenging.

VII. Bending Performance: SGH340 galvanized sheet exhibits good bending performance, capable of withstanding significant bending without fracture. While SGH440 galvanized sheet can also undergo bending processing, relevant standards stipulate that when bent 180°, the portion within 7mm of the test specimen's edge must not peel off. Consequently, it imposes stricter requirements on bending precision and processing conditions.