1.What are the causes and consequences of zinc peeling and powdering?
Cause: Although the zinc layer forms a metallurgical bond with the steel substrate, its ductility is limited. Under intense tension and compression, the zinc layer may not deform synchronously with the steel substrate, resulting in microcracks, flaking, or powdering.
Consequences:
Damage to the die: Dislodged zinc powder acts as an abrasive, accelerating wear and scratching of the stamping die.
Impaired Surface Quality: Scratches, bright spots, or uneven zinc layer distribution may appear on the part surface.
Reduced Corrosion Resistance: Areas of damaged zinc layer become the starting point for future corrosion.
2.What are the impacts of surface lubrication problems?
Stamping, especially deep drawing, relies heavily on effective lubrication to reduce friction and prevent cracking and die sticking.
The surface properties of galvanized coils (such as the passivation film and oil film) may be incompatible with certain stamping lubricants, or the lubricity they provide may not be sufficient to withstand the extreme conditions of deep drawing.
3.What are the effects of welding and painting difficulties?
If this deep-stamped part is subsequently welded, the zinc layer will evaporate at high temperatures, creating pores and toxic fumes, requiring specialized welding processes.
If painting is required, an uneven or damaged zinc layer after stamping will impair paint adhesion.
4.What kind of galvanized coils can be "tried" for deep drawing?
Choosing the Right Substrate
Deep-drawing or ultra-deep-drawing grade steel strip must be used as the substrate. This type of steel typically has an extremely low carbon content and excellent ductility (e.g., IF steel - interstitial-free steel).
Never use standard structural or commercial-grade steel.
Choosing the Right Type of Galvanizing
Electrogalvanizing is generally more suitable for stamping than hot-dip galvanizing.
Reason: The electrogalvanized layer is thinner and more uniform, bonds differently to the substrate, and follows deformation better, making it less susceptible to the severe flaking that can occur with thicker zinc layers.
Alloyed galvanizing: After hot-dip galvanizing, the zinc-iron alloy layer undergoes heat treatment, resulting in a very hard and brittle coating. This makes it extremely unsuitable for deep drawing and prone to pulverization and flaking.
Pure zinc coating: Compared to alloyed coatings, pure zinc coatings have slightly better ductility.
5.What are some more reliable alternatives?
Cold-rolled steel sheet
The most commonly used material for deep drawing. It offers excellent surface quality, exceptional ductility, and no concern for zinc peeling.
Disadvantages: The part itself lacks rust resistance. Post-processing such as electroplating or painting is required for rust prevention after stamping.
Stainless steel sheet
Combines excellent formability with inherent corrosion resistance. Suitable for parts requiring both high aesthetics and corrosion resistance.
Disadvantages: High cost and a high work hardening rate.