1.What are the main types of substrates according to rolling process?
Cold-rolled Steel Strip/Steel Strip
Features: This is the most commonly used and primary substrate for galvanized coil. It offers a smooth surface, high dimensional accuracy, and uniform thickness.
Applications: Used in most applications requiring high surface quality and formability, such as automotive exterior panels, high-end appliance panels, and architectural roofing and wall panels.
Hot-rolled Steel Strip/Steel Strip
Features: Cost is generally lower than cold-rolled steel strip, but the surface may contain iron oxide scale, resulting in lower flatness and dimensional accuracy. When used as a substrate, it is typically pickled to remove the scale.
Applications: Primarily used in applications where surface requirements are less stringent but structural strength is required, such as certain building structures, truck beams, and container floors. The term "hot-dip galvanizing" refers to galvanized coil using hot-rolled, pickled steel strip as the substrate.
2.What types are there according to mechanical properties and uses?
Common Commercial Steel
Example Code: CQ
Features: Low strength and average formability. Primarily used for simple bending or forming.
Applications: General ventilation ducts, simple packaging, low-end building components, etc.
Stamping Steel
Example Code: DQ
Features: Good ductility, suitable for moderately difficult stamping and forming.
Applications: Appliance housings, automotive interior components, etc.
Deep Drawing Steel
Example Code: DDQ
Features: Excellent deep drawing performance, resists cracking during forming.
Applications: Automobile fuel tanks, washing machine drums, and complex parts requiring deep drawing.
3.What are the key performance indicators of the substrate?
Mechanical Properties:
Yield Strength: The stress at which a material begins to plastically deform.
Tensile Strength: The maximum stress a material can withstand before breaking.
Elongation: A measure of a material's plasticity; higher values indicate better formability.
Formability:
Plastic Strain Ratio: A measure of a material's resistance to thinning. Higher r values indicate better deep-drawability.
Work Hardening Index: A measure of a material's ability to increase strength during the forming process. Higher n values indicate greater uniform deformation and less prone to localized necking.
Surface Quality:
Surface defects in the substrate (such as scratches, pits, and inclusions) can be directly transferred to the galvanized surface, affecting the appearance and quality of the final product.
4.What is the logic behind material selection?
Ordinary commercial steel: low cost, average formability; ventilation ducts, simple structures.
Stamping/deep drawing steel: good formability, moderate strength, home appliance housings, automotive interior panels.
5.What are the key points in material selection?
The base material for galvanized coils isn't a single, but rather a complete family of steel materials.
The "galvanizing" is merely a protective coating on the surface, while the base material determines the product's "framework" and "physique" (strength, stamping capability, etc.).
When selecting galvanized coils, the desired base material must be determined based on the end product's application (whether it will need to bear weight), processing method (simple bending or deep drawing), and service environment.