Aluminum Alloy for Deep Drawing

Cracking in deep-drawn aluminum parts often begins with material selection. Aluminum has a narrower forming range than steel and is more sensitive to alloy, temper, and incoming material consistency. To reduce cracking, do not rely only on die adjustments. Match the alloy, temper, mechanical properties, and process together. Selecting the right aluminum alloy for deep drawing is the first step.

Understand the Three Common Cracking Modes

– Punch radius fracture: Tensile stress exceeds the forming limit. It is often linked to low elongation or a radius that is too small.

– Wall thinning crack: The material becomes too thin in the thickness direction. It is often linked to a low r-value.

– Earing and wrinkle-related cracking: Differences in properties in different directions can create an uneven cup edge and local stress concentration.

These modes point to different properties: elongation, r-value, and how consistently the material behaves in different directions. Check them together during selection.

A Three-Step Method for Crack-Free Selection

Step 1: Choose the alloy series by drawing depth and strength requirements

– 1xxx pure aluminum (1050, 1060, 1100): Best formability and lower strength. Suitable for shallow to medium drawing depths, decorative parts, and lighting components.

– 3xxx aluminum-manganese (3003, 3004, 3104): A balance of strength and formability. A common choice for general deep drawing, cookware, electronic housings, and pressure vessels.

– 5xxx aluminum-magnesium (5052, 5182, 5754): Higher strength but lower formability than the first two. Suitable for high-strength deep-drawn parts, usually in O temper.

Shallow drawing does not require 5xxx. Deep drawing should not use harder H tempers.

Step 2: Start with O temper

For deep cups, deep cavities, and complex shapes, choose O temper first. O temper has good ductility. It also work-hardens naturally during stamping, so stressed areas become stronger after forming. H temper suits shallow drawing or simple forming, not large-deformation deep drawing.

Step 3: Cross-check with three properties

– Elongation: Overall stretchability.

– n-value: Ability to deform uniformly. A higher n-value means less local necking.

– r-value: Resistance to thinning. A higher r-value means more even wall thickness.

You can ask the supplier for Erichsen cupping test values. A higher cupping value usually means better cracking resistance.

Quick Selection by Deep Drawing Application

– Shallow drawing, decorative parts, lighting components: 1050/1060-O

– General deep drawing, cookware, electronic housings: 3003-O

– Deep cups, pressure vessels, fuel tank ends: 3004/3104-O

– High-strength structural parts, automotive parts: 5052/5754-O

– Extreme deep drawing, cans, can tabs: 5182-O

– Shallow drawing, simple forming: 3003/5052-H14/H24

Selection is not about the hardest or purest grade. It is about matching the forming demands and final strength requirements.

After the Material Is Right, the Process Must Match

– Die radius and clearance: Avoid radii that are too small. Keep clearance reasonable to prevent local stress concentration.

– Blank holder force and lubrication: Use moderate blank holder force and an aluminum-specific deep drawing lubricant to reduce friction and tearing.

– Drawing speed: The more complex the shape, the slower the drawing speed should be, giving the material time to flow.

After aluminum sheet leaves the mill, surface treatment or further processing is usually completed by the stamping plant. Therefore, consistency of incoming temper directly affects production yield.

What Actually Prevents Cracking

Crack-free deep drawing depends on matching the whole system: the right alloy, O temper, verified mechanical properties, and a coordinated die, blank holder force, lubrication, and speed. More verification during material selection means fewer trial runs in production.

For a stable supply of aluminum alloy for deep drawing, Mingtai Aluminum offers multiple grades in O temper and can help you select the right grade for your application. Contact us for samples.

FAQ

Q: Both 1050-O and 3003-O can be deep drawn. Which one should I choose?  

A: Choose 1050-O for shallow drawing and lower cost, or 3003-O for higher strength or deep cups.

Q: O temper feels soft. Will the formed part be strong enough?  

A: O temper work-hardens during stamping, so stressed areas usually become strong enough for many deep-drawn parts.

Q: How can I quickly judge whether an aluminum sheet is suitable for deep drawing?  

A: First confirm it is O temper, then check elongation, n-value, r-value, and cupping test values.