Aluminium is the easiest of the common housing materials to draw and the easiest to ruin. The alloy choice looks like a strength question and is really a formability question, and the temper on the coil usually matters more than the alloy designation printed beside it. Getting the pair right is the difference between a part that draws clean and a part that tears at the bottom radius on the third delivery.
Which aluminium alloy is best for deep drawing?
For deep drawing, the workhorse is 3003 in the annealed O temper, a manganese bearing alloy with good ductility and enough strength to be useful. Where the part is not structural and the draw is severe, the pure grades 1050 and 1100 are even more formable and correspondingly softer. The magnesium alloys 5052 and 5754 are stronger and more corrosion resistant but less formable, so they suit moderate draws and need more stages or a softer temper for deep ones. 6061 is a heat treatable alloy and is the wrong answer for deep drawing: it is specified for machined and extruded parts and tends to crack under a deep draw. Whatever the alloy, the temper matters: O temper is the deep drawing condition, while H14 and H32 are half hard and quarter hard tempers intended for shallower work.
The four alloys that actually get drawn
| Alloy | What is in it | Where it is used | Where it stops |
|---|---|---|---|
| 1050 | 99.5 per cent aluminium | Deep housings, cosmetic shells, parts that will be anodised | Very soft; dents and marks in handling, and low finished strength |
| 1100 | 99.0 per cent aluminium | Similar to 1050, drawn covers and shells | Same softness, slightly higher strength than 1050 |
| 3003 | Aluminium with manganese | The default for drawn aluminium parts: housings, cans, covers | Reaches its forming limit on very deep or multi stage parts, where 1050 is easier |
| 5052 | Aluminium with magnesium | Moderate draws needing strength and corrosion resistance, marine and fluid parts | Work hardens quickly; needs more stages and a softer temper for deep work |
| 5754 | Aluminium with magnesium | Formable magnesium alloy for structural drawn parts | Same family behaviour as 5052 |
| 6061 | Aluminium with magnesium and silicon, heat treatable | Machined and extruded components | Not a deep drawing alloy; prone to cracking under a deep draw |
Temper decides more than alloy
Two coils of 3003 with different tempers behave like two different materials. O temper is fully annealed and is the condition deep drawing is designed around: lowest yield strength, highest elongation, and the least springback to compensate in the tool. H14 and H32 are work hardened tempers that hold their shape better and resist denting, which is exactly what you want on a shallow cover and exactly what you do not want on a deep cup. A drawing that names 3003 without naming the temper has left the most important variable open, and the same is true of steel: our temper selection guide sets out the four numbers that predict how a coil will run.
Why 6061 keeps arriving on the drawing
6061 is the aluminium most engineers meet first, because it is the standard for machined and extruded parts and it is easy to buy. It is a heat treatable alloy: its properties come from a precipitation treatment rather than from cold work, and it has far less capacity to stretch before it necks. On a shallow form it can survive. On a deep drawn housing it usually cracks, and the crack appears at the bottom radius rather than at the rim, which makes it look like a tool problem. When a design genuinely needs 6061 strength and a drawn geometry, the usual answer is to draw a formable alloy such as 3003 and machine the critical features afterwards.
Drawing aluminium: ratios, stages and annealing
Aluminium is normally worked between the mild steel and the stainless limits. For the first draw, 5052 and C1100 copper sit around 1.7 to 1.9, and the pure grades 1050, 1100 and 3003 in O temper will go further than that on the same geometry. What limits the schedule is the same work hardening that limits stainless: each stage raises the yield strength, so the second stage meets a harder material than the blank. The stage count follows the method set out in how many draws a part needs, and an interstage anneal is the release valve when the count grows. Springback also has to be planned into the tool rather than corrected afterwards, because aluminium recovers more elastically than steel at the same strength.
Surface, anodising and handling
Aluminium shows every handling mark. The same softness that lets it draw deep means the drawn surface can be scratched by a fixture, marked by a gripper, or bruised in a parts bin, and none of that is visible on a steel part of the same shape. Where the part will be anodised the surface condition is part of the specification rather than a finish applied later, because anodising is transparent to the substrate and will show draw marks and die polishing lines. The comparison between an aluminium housing and a stainless one, including where the corrosion and weight arguments actually land, is set out in deep drawing aluminium versus stainless steel.
What to put on the drawing
- Alloy and temper together, for example 3003 in O temper. Naming the alloy alone leaves the decisive variable open.
- The standard, since 1050 and 1100 in particular appear under several national designations with slightly different chemistry limits.
- Thickness and thickness tolerance. Aluminium is supplied to a wider thickness band than cold rolled steel, and that band becomes the wall tolerance on a drawn part.
- The surface requirement, including whether the part will be anodised, so the die polish and the handling route are chosen for it.
- The general tolerance class for anything not individually toleranced. Where a drawing is silent our default is ISO 2768-m, explained in ISO 2768 general tolerances.
Key point
For deep drawing, specify 3003 in O temper as the default, 1050 or 1100 where the draw is severe and strength is secondary, and 5052 or 5754 only for moderate draws where strength and corrosion resistance are needed. Never specify 6061 for a deep drawn housing. Always name the temper as well as the alloy.
Frequently asked questions
Is 5052 good for deep drawing?
It is workable for moderate draws, especially in a soft temper, but it is less formable than 3003 and work hardens faster, so a deep or multi stage part needs more stages or an interstage anneal. Choose 5052 when the finished part genuinely needs the extra strength and corrosion resistance, and 3003 when it does not.
Can you deep draw 6061 aluminium?
Not in the sense a deep drawn housing needs. 6061 is a heat treatable alloy with limited capacity to stretch before necking, so it tends to crack at the bottom radius under a deep draw. It is the right material for machined and extruded parts. Where 6061 strength is required with a drawn geometry, the usual route is to draw a formable alloy and machine the critical features afterwards.
What temper should an aluminium drawn part be specified in?
O temper, the fully annealed condition, is the one deep drawing is designed around. H14 and H32 are work hardened tempers, useful for shallow covers where dent resistance matters, and unsuitable for a deep cup. Naming the alloy without the temper is the most common omission we see on aluminium drawings.
Does anodising change which alloy I should choose?
It can. Anodising is transparent to the substrate, so it shows the drawn surface rather than hiding it, and different alloys take different anodised colours and finishes. Where the part will be visible and anodised, the alloy and the surface requirement should be decided together rather than the finish being added at the end.