Aluminum Alloy Stamping Plates: Process Requirements for Stamping and Welding

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  Key takeaways
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  Choose the alloy and temper before you cut the first blank
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  Blank preparation sets the tolerance for everything after it
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  Tooling clearance and springback control in the press
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  Weld preparation and heat input limits for aluminum plate
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  Step by step: from blank to welded assembly
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  Alloy and process comparison for stamped and welded plates
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  Stamping and welding parameters by thickness

Aluminum alloy stamping plates fail for one reason most of the time: the temper was picked for strength and not for forming. A 6061-T6 sheet at 2.0 mm cracks at an inside bend radius below about 2t. The same alloy in O temper takes a 0.5t radius without complaint. If the part needs post-weld strength, form it soft and let the weld or a later age cycle do the hardening.

For general enclosures and brackets, 5052-H32 is the safe default. It forms, it welds, and it resists corrosion without coating. For structural parts where weight matters more than weldability, 6061-T6 is common, but plan the bends around it. For high-strength brackets, 7075 offers the best strength-to-weight, though it welds poorly and is usually joined with fasteners or rivets.

Thickness drives the whole process window. Below 1.5 mm, handling damage and oil-canning become the main scrap sources. Above 4.0 mm, press tonnage climbs fast and springback compensation gets harder to hold. Most production aluminum alloy stamping plates sit between 1.0 mm and 3.0 mm.

One more check before release: confirm the sheet grain direction against the bend line. Bending across the rolling direction gives a cleaner result. Bending parallel to it raises the risk of edge cracking on tight radii, especially in 6061 and 7075.

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  5052-H32Best balance of formability, weldability, and corrosion resistance.
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  6061-T6Good strength, poor tight-radius formability. Use 2t minimum inside radius.
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  6061-O then ageForm soft, weld, then age to recover strength where the spec allows.
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  7075-T6Highest strength, not weldable by arc. Plan mechanical joints.

The blank is where most dimensional error is born. Laser-cut blanks carry a heat-affected zone of 0.1 to 0.3 mm with slightly different hardness along the cut edge. That hard edge forms differently from the parent metal. If the part has a bend within 3 mm of a laser-cut edge, expect a small radius variation run to run.

For tight parts, shear or fine-blank the perimeter and leave 0.2 to 0.5 mm of stock for a later trim. Deburr both faces before forming. A 0.05 mm burr on a 1.5 mm sheet becomes a crack starter at the bend line. A quick tumble or a hand pass with a 400 grit pad is enough.

Flatness of the incoming sheet matters more than most shops expect. Coil-set or a bowed sheet will not flatten in a single-hit die. Check flatness on a surface plate with a 0.1 mm feeler over a 300 mm span. If it fails, flatten or re-source before tooling is cut.

Cleanliness belongs here too. Stamping lubricant and shop dust sit in the grain of the sheet. If the plate goes straight from the press to the weld table, those residues burn into the weld pool. Degrease after forming, not only before welding.

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  Laser edgeKeep bends at least 3 mm away from a laser-cut edge.
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  Burr limitDeburr to under 0.05 mm on both faces before forming.
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  Flatness0.1 mm maximum gap over a 300 mm span on a surface plate.

Aluminum needs more die clearance than mild steel. A good starting point is 8 to 10 percent of sheet thickness per side for 5052 and 6061. Too little clearance gall the die and tears the edge. Too much clearance leaves a heavy burr and a rounded edge that will not sit flat on a weld fixture.

Springback is the number one reason a formed plate misses the drawing. Aluminum springs back about 2 to 3 times more than mild steel at the same R/t ratio. For a 90 degree bend in 2.0 mm 5052-H32 at a 3 mm inside radius, plan on 2 to 4 degrees of overbend and verify with a trial hit. Do not trust a table value alone.

For high-volume work, a bottoming or coining step controls the angle far better than air bending. Coining pressures are high, so check the press tonnage against the die area before you commit. For low-volume or prototype runs, air bending plus a shimmed overbend is faster and cheaper to adjust.

Radius and tonnage must be checked together. The minimum inside radius for 5052-H32 is about 0.5t across the grain and 1t along it. For 6061-T6, use 2t across and 3t along the grain. If the drawing calls for a tighter radius than the alloy allows, the fix is a different temper, not more tonnage.

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  Die clearance8 to 10 percent of thickness per side for 5052 and 6061.
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  Overbend2 to 4 degrees for a 90 degree bend in 2.0 mm 5052-H32.
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  Min radius0.5t across grain for 5052-H32. 2t for 6061-T6.

Aluminum oxide melts at roughly 2,050 °C, and the metal underneath melts near 660 °C. That gap is why aluminum welds go wrong. The oxide skin must be removed mechanically, not just chemically. Stainless steel brushing within 8 hours of welding is the standard practice. A wire brush used on steel will contaminate the aluminum surface with iron, so keep a separate brush for aluminum only.

AC TIG is the usual process for 1.5 to 4.0 mm plate. A starting point for 2.0 mm 5052 or 6061 is 60 to 90 A, 60 to 70 percent electrode positive balance, and 150 to 250 mm/min travel. Higher balance cleans the oxide better but puts more heat into the part. On thin plate, that heat shows up as distortion and burn-through at the edge.

Filler choice follows the base alloy. 4043 filler is the general-purpose choice for 6061 and 5052. It flows well and reduces hot cracking. 5356 filler gives higher strength and better ductility but is stiffer to run and less forgiving on fit-up. If the joint will be anodized, 5356 turns dark gray. 4043 anodizes closer to the base color.

Distortion control is a fixturing problem before it is a welding problem. Tack every 50 to 80 mm, alternate the weld sequence from the center outward, and let the part cool in the fixture. Never unclamp a hot weldment. Aluminum loses strength fast above 150 °C, and a hot part pulled from a fixture will spring into a new shape as it cools.

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  Brush within 8 hoursStainless brush, aluminum-only, then weld before oxide regrows.
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  4043 fillerGeneral purpose for 6061 and 5052. Anodizes near base color.
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  5356 fillerStronger and more ductile, but goes dark under anodize.
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  Cool in fixtureNever unclamp above 60 °C or the part will move.