What this page settles. 1) Which of the three aluminum grades suits a part that has to bend, and which one suits a part that has to carry load. 2) Why the temper written after the alloy number moves the answer further than the alloy itself. 3) What to do when 6063 turns up on a stamped print. 4) How the choice shows up later in tooling, finishing and unit price.
Three aluminum grades come up again and again when a stamped part is quoted from China: 5052, 6061 and 6063. They are not interchangeable, and the differences that decide a project are not the ones a materials table happens to list first.
Strength ratings, corrosion tables and cost per kilogram sit within a narrow band across these three alloys. Formability spreads across a much wider range, and that single property decides whether a tool settles into a steady rhythm or spends its first month in the tryout press.
This page is written for the engineer who has to put one grade on a drawing, and for the buyer who has to defend that choice afterwards. It compares the three grades the way a press sees them, then turns the comparison into callouts and questions. A service page answers whether your part can be made; grade selection is a different job, and the custom aluminum stamping capability page covers that first question.
A purchase order that reads 5052 tells the mill and the press very little on its own. Two or three characters that follow the alloy number carry the mechanical state of the sheet, and by the time it reaches the stamping line that state has already been set at the mill through cold work or heat treatment.
Chemistry sets the ceiling on what a grade can do. Temper decides how much of that ceiling has already been spent. Aluminum 5052 in the annealed O condition folds back on itself at a radius near zero; the same chemistry in H32 has taken a measured amount of cold work, and its elongation has dropped with the strength it gained. H34 pushes harder in both directions and is where tight radii begin to crack.
1) O means annealed. Softest and most formable condition, used where a part will be formed hard and heat treated afterwards.
2) H32 means strain hardened to a quarter hard and stabilised. This is the workhorse temper for sheet that has to bend, and it holds a useful balance of strength and ductility.
3) H34 moves one step harder. Panels gain stiffness and lose the ability to take a small radius without complaint.
4) T4 means solution treated and naturally aged. The grade forms while it is still soft and reaches full strength later in a furnace.
5) T6 means peak artificial aging. Highest strength, shortest strain range, and the temper that causes most aluminum cracking arguments.
| Alloy and temper | Forming behaviour | Where it fits |
| 5052-O | Folds at a very small radius | Severe forming before aging |
| 5052-H32 | Bends tight without cracking | Brackets, enclosures, cabinets |
| 5052-H34 | Tight radii carry more risk | Stiffer panels, light forming |
| 6061-T4 | Forms, then reaches full strength | Structural parts with bends |
| 6061-T6 | Needs a generous radius | Flat or lightly formed parts |
| 6063-T5 | Extrusion temper, limited sheet use | Decorative and architectural profiles |
Elongation figures for the two common tempers sit closer together than the consequences do. Published values land around 10% to 14% for 5052-H32 and 8% to 12% for 6061-T6, and a buyer comparing those two numbers side by side could reasonably conclude that the grades are near neighbours. What separates them is how the sheet behaves in the instant after the punch lifts: how much of the bend strain stays elastic, and how much of it the outer fibre can absorb before it tears.
Sending an alloy without a temper is the most common reason a first article cracks. Mills supply a default condition when nothing is specified, and that default is often the harder one, because harder sheet survives storage and shipping with fewer scratches. Omitting the temper hands a decision to whoever fills the order.
A stamping engineer asked to name one general-purpose aluminum grade usually answers without pausing. 5052 carries enclosures, chassis panels, cabinets and communication equipment housings, and that list matches the application notes our own material documentation keeps for the grade.
Magnesium is the alloying addition behind 5052, and it explains why the sheet holds up outdoors, near salt water and inside humid cabinets where condensation collects on cold metal. Corrosion resistance is the property our material reference lists ahead of everything else for this grade, and marine and coastal work is where that ordering earns its place.
Lower forming force is the second dividend. Aluminum needs roughly 60% to 70% of the tonnage that mild steel of the same thickness demands, and within the aluminum family 5052 sits at the easy end of that range. Tool life on a progressive die follows the same line, because softer sheet is kinder to punch edges and the forming stations work at lower pressure. Soft aluminum also galls, picking up on hard tool steel until a die that ran clean on cold-rolled sheet starts dragging smears of metal across the face within a few thousand hits. Lubricant choice, polished or coated die surfaces, and a clearance that is generous enough for the alloy all belong in the tooling conversation rather than in the tryout report.
Strength draws the boundary. A 5052 panel will flex under a load that a 6061 part would carry without moving, and a bracket that has to stay rigid under a compressor or a drive motor belongs to a different grade. Machined content points the same way, because 5052 is gummy at the cutting edge and holds a tapped thread less cleanly than 6061 does.
Stamping this grade covers brackets, panels, housings and mounting plates made from aluminum sheet, and the aluminum metal stamping parts page shows the shapes that come off that line.
Second on the shop list is 6061. It earns its place with higher mechanical strength and clean machinability, and our material notes point it at industrial equipment, mounting frames and mechanical components. Magnesium and silicon together make the alloy heat treatable, so its strength arrives through aging instead of through cold work.
Strength comes packaged with a shorter strain range. That trade sits behind most of the friction between designers and fabricators on this grade.
Fabricators who bend both grades in the same shop put the practical minimum inside radius for 6061-T6 at two to three times material thickness, rising to three or four times when the bend line runs along the rolling direction. Equivalent figures for 5052-H32 in thin gauges sit near one to one and a half times thickness. Everything above turns on that gap.
Push a tight bend into T6 and the failure sequence is predictable. A rough orange-peel texture appears on the outer surface first, at the point where the strain concentrates. A crack follows from the sheared edge and walks across the bend, and by the time it is visible the part is scrap rather than rework.
Step 1, form in T4 and age afterwards. 6061-T4 keeps elongation in the 18% to 22% band, forms like a far friendlier alloy, and reaches full strength in a furnace once the geometry is set. Post-form aging adds a heat-treat step and several days of lead time, and it is ordinary practice on brackets where strength and shape both matter.
Step 2, split the part. Where post-form aging has no place in the schedule, geometry can be divided instead. A formed 5052 shell takes the envelope and a straight or machined 6061 plate carries the load path. Two components sound expensive until the scrap rate on a single over-formed part is counted against them.
A shop that accepts a 6061-T6 drawing with tight bends without asking about radius has not done the buyer a favour. Cutting the die comes first, the first article cracks second, and the argument about who pays for the rebuild begins after hardened steel is already sitting in the tool.
One caveat on the softer-temper route deserves a line of its own. Forming in T4 and aging later works only when the part can survive the furnace. Formed panels with a cosmetic surface may pick up distortion during the heat cycle, and that risk belongs in the decision before the temper is written rather than after.
Third on our aluminum list is 6063. Our material documentation describes it through surface finish, anodizing behaviour and extrusion properties, and it routes the grade to decorative components and architectural products. Read that description closely and notice what it leaves out: bending, drawing and shearing never appear.
That omission reflects the design intent of the alloy rather than a gap in the paperwork. 6063 was developed to be pushed through a die as a continuous profile, and its low quench sensitivity and clean surface make it the standard choice for window frames, heat-sink profiles, furniture trim and architectural sections. Sheet formability was never the priority it serves.
Grade drift arrives through assemblies rather than through analysis. A product family uses an extruded 6063 frame or a 6063 heat sink, a single material callout fills the bill of materials for the family, and the stamped bracket that shares that bill inherits the same three letters. Nobody chose to stamp 6063. The drawing carried the material down from the profile above it, and the error survives review because the alloy name is perfectly valid.
Spotting it takes one glance once the pattern is known. If the same three digits appear on an extrusion and on a flat stamped part in one assembly, the stamped part is worth a second look before the tool is ordered.
1) Move the stamped part to 5052 or 6061 sheet. Nothing changes except one line on one drawing, and the part keeps the geometry it was designed around.
2) Keep 6063 and verify the sheet. Our supported-material list does carry the grade, so it can be processed. Sheet stock, temper and thickness tolerance have to be confirmed against the mill, and the geometry has to suit an alloy with a narrower forming window than the other two.
3) Delete the stamped version. Where the function is a constant section carrying load or moving heat, an extrusion does the job more cheaply, and the sensible answer is to remove the stamped part rather than press an alloy into a process it was never designed for.
If a stamped 6063 part is already running and passing inspection, leave it where it is. Banning the grade would miss the point of this section. Somebody has to choose it on purpose, because an unjustified material callout is a risk that stays quiet for years and then surfaces when the supplier changes, the mill temper drifts, and a flange that used to form cleanly starts cracking.
Aluminum that has to be drawn into a cup or a deep shell brings its own set of rules, and the aluminum deep drawing parts page covers that route separately.
Aluminum springs back more than steel, and the cause is arithmetic rather than exotic. Elastic modulus for aluminum sits near 69 GPa while steel runs at roughly 200 GPa, so a comparable bend stores around three times as much recoverable strain. Recovery of four degrees in steel becomes eight to twelve degrees in aluminum.
Typical recovery figures for a 90 degree bend put 5052-H32 at four to six degrees and 6061-T6 at eight to twelve. Both numbers scale with the ratio of bend radius to thickness, so a generous radius on thin sheet recovers furthest. Thick stock and tight radii push more of the section into plastic strain and leave less stored energy behind.
Step 1, overbend in the form station. The tool is cut with more angle than the finished part needs, and the sheet relaxes into the target as the punch releases. This is the first choice on aluminum, and it costs nothing beyond the die cut itself.
Step 2, bottom or coin the bend. Forcing material against the die face removes most of the recovery, at three to five times the tonnage of an air bend and with extra work hardening left in the part. That trade suits a tight angle tolerance on a grade that can absorb the strain.
Step 3, confirm the angle on the first article. Springback is designed into the form stations and verified on the tryout part. Bend angle is also the dimension that moves first when a new coil arrives with a slightly different temper, so it belongs on the first article report and on the in-process check sheet.
Bend angle tolerance tells you how mature a tool is. Hardened progressive dies that have been tuned hold around plus or minus one degree on a formed feature, while a first article off a fresh tool is looser and gets corrected. A quotation that promises a tight angle on the first piece is describing a restrike station or a hand adjustment, and the price will say which. Worked examples of those mechanics sit on the springback in stamping page.
On parts where the bend angle is functional rather than cosmetic, a restrike or calibration station can hold the angle after the main form. Paying for that station makes sense when the alternative is hand adjustment on every piece. It is also one of the few changes that becomes genuinely expensive after the strip layout is frozen, so it belongs in the discussion before layout approval.
Most cracked flanges and wandering hole positions trace back to four decisions on the drawing, and all four are free to change while the part is still a model. They stop being free once the strip layout is approved.
☐ Bend across the coil direction. Rolled aluminum carries an elongated grain along the rolling direction, and forming across that grain is the more forgiving orientation. Bending along it raises the minimum radius by roughly 25% to 30%, which is often the difference between a part that forms and a flange that tears.
☐ Keep holes and notches off the bend line. A pierced hole or notch sitting on the bend line acts as a stress raiser and starts the crack. Keeping features about two times material thickness plus the inside radius away from the bend covers most geometry.
☐ Set clearance for aluminum, not for steel. Aluminum shears at roughly 6% to 10% of thickness per side, wider than the setting used on mild steel. Too tight and the punch picks up metal and builds an edge; too loose and the cut face rolls over and throws a heavy burr.
☐ Name the burr side and the burr limit. Burr forms on the face the material leaves, so the punch side of the part carries it. A limit under 10% of stock thickness is a common target, and a part that will be anodized or handled by hand usually needs a deburr or tumble operation written into the routing.
☐ Dimension holes at the sheared diameter. Clearance makes a pierced hole taper, wider at the entry than at the exit. Hole size measures smallest at the sheared diameter and outside features measure largest at the sheared face, so a drawing that ignores the taper invites a gauge argument at incoming inspection.
Tight parts put these rules against each other. A design that needs a narrow flange close to a hole cannot satisfy feature spacing and flange height at the same time, and the drawing then has to say which one carries the function. Sending the mating component along with the drawing settles that faster than an email thread, because the supplier can see which dimension the assembly actually reads instead of guessing.
Tolerances behave the same way. Ronghai publishes 0.05 mm on precision features, and a stamped aluminum part can be held that close on a mature die, but the cost curve steepens as the band narrows. The public guide on realistic stamping tolerances puts grades and cost side by side so the band can be chosen on purpose, and the DFM rules for stamped parts cover the checklist from the tooling side. Bend geometry itself is worked through on the bend radius and bend allowance page.
The one a fastener, shaft, seal or mating panel reads. Everything else can take general tolerance, and the saving appears in tool cost and in scrap rate rather than in the function of the part. A drawing that puts a precision band on a cosmetic edge has paid for accuracy nobody will measure.
Anodizing grows an oxide layer on aluminum through an electrochemical bath, and it is the finish our own documentation routes aluminum parts to. Corrosion resistance, wear resistance, a decorative surface and electrical insulation all come from that layer, and it accepts a broad colour range.
The grade changes how that finish turns out, and published guidance does not agree on the direction. One fabricator writes that 5052 produces the cleaner, more uniform anodized appearance and steers cosmetic panels that way. Another states the opposite, describing 6061 as the clearer finish after clear or colour anodizing and noting that the magnesium in 5052 can shift the shade. Both accounts come from shops that anodize aluminum every week.
Anodized appearance depends on oxide thickness, dye chemistry, alloy grain and the amount of deformation the surface has already taken, and those variables differ between finishing lines. Forming work-hardens the skin of the part and leaves die lines that can telegraph through a clear anodize, which is why cosmetic parts often receive a light grain or bead blast before the tank.
Running a first-article panel through the finishing line that will handle production is the reliable tie-breaker. Two sample blanks, one per grade, sent through the same anodizing batch answer the appearance question in days. Picking a grade on the strength of a supplier blog post answers it six weeks later, in a rework claim.
Where a purchase order needs a standard behind the finish, ISO 7599 is the anodizing reference our documentation carries, and finished parts arrive with a coating thickness report. Powder coating and passivation sit in the same finishing list for parts whose environment or appearance rules anodizing out, and the finish often settles the grade question before formability does.
Grade decisions look free at the drawing stage and expensive at the press. Tooling quotes published by North American fabricators run from roughly USD 2,000 to 8,000 for a simple blanking die, through USD 8,000 to 25,000 for a compound tool, up to USD 25,000 to 150,000 for a complex progressive die. Chinese pricing differs, and the direction of the movement is what carries across: more stations, more forming and a harder grade all push the number the same way.
Volume decides whether tooling makes sense at all. Crossover between laser blanking with press-brake forming and hard tooling sits somewhere around 2,500 to 10,000 parts, depending on complexity. Below that band, an aluminum part is often cheaper to cut and form; above it, a progressive die earns its cost back.
1) Heat treatment, when the grade forces it. Forming in 6061-T4 and aging to T6 adds a furnace step, a handling risk and several days of lead time to every batch.
2) Finishing as an outside process. Anodizing and conversion coating usually travel to a specialist line, and published lead times add three to ten business days on top of the stamping schedule.
3) Over-specification. Specialty alloys that a mill does not stock have to be melted in large volumes, and that premium reaches the part price long before the first coil is cut.
4) Scrap between the blanks. Skeleton web left in the strip is paid for and thrown away, so a nested layout that wastes less sheet improves the unit price on every part that follows.
A stronger alloy can still be the expensive choice. 6061 and 5052 trade within a narrow band per kilogram, and a specifier who picks the stronger grade for a panel that only has to close a gap buys a larger bend radius, a longer tryout and a scrap rate that shows up on the third delivery rather than the first. Ronghai stamps aluminum from 0.3 mm to 20 mm on presses up to 315 tons, so thickness is rarely the constraint that decides the grade. Geometry and finish decide it, and those two are already on the drawing.
Quotations are only as good as the drawing behind them. Six lines of specification remove most of the assumptions a supplier would otherwise make on your behalf.
☐ Alloy and temper together. Write 5052-H32 rather than 5052. Grades without a temper leave the mill and the tool shop to fill in a decision that changes the bend radius.
☐ Thickness with its tolerance. Sheet thickness varies within a mill band, and on a formed feature that variation reaches the finished dimension. State the band that the assembled part can live with.
☐ Inside bend radii and bend direction. Radius on the drawing lets the tool shop confirm the grade can take it, and a note on orientation lets the blank be nested so bends run across the grain.
☐ Finish and the surface that matters. Naming the cosmetic face tells the tool shop where to protect the sheet and whether a deburr or grain operation belongs in the routing.
☐ Documents wanted with the shipment. Material certificate, certificate of compliance, chemical composition, mechanical property report, heat number traceability and a first article inspection report cover most incoming inspection systems, and a CMM report covers the features a drawing marks as critical.
☐ Annual quantity and delivery pattern. Volume decides whether the part belongs on hard tooling or on a short-run route, and the split point moves with part complexity.
They can, and on assemblies with both a formed shell and a structural plate they usually should. The formed part takes 5052-H32 for the tight bends, and the structural part takes 6061 in whichever temper the load path demands. What does not work is averaging the two and stamping both parts from one grade chosen for convenience.
An anodic layer grows out of the aluminum surface rather than sitting on top of it, so the movement is smaller than a coating thickness figure would suggest, and it still matters on a threaded or press-fit feature. Raising the question once on the RFQ is cheaper than finding out at assembly.
Mills stock the grade mainly as extrusion billet and as extruded profile, so sheet supply and temper have to be confirmed rather than assumed. That check costs a day and settles whether the third option in the section above is even open.
Whichever face the customer sees. Sheet is nested and stacked so the cosmetic surface stays away from the die face, and the routing adds a protective film or a light grain where a clear anodize would show every contact mark.
Designers own the functional minimum and suppliers own the practical one. Putting both numbers on the RFQ, with a note on which features are cosmetic, lets the tool shop reply with a radius that forms reliably instead of quoting the drawing and absorbing the scrap.
Ronghai runs aluminum stamping on progressive, compound and transfer tooling, with engineering review and DFM completed before tool design starts. ISO 9001 and IATF 16949 are held, and automotive programs bring their own document requirements, including PPAP where the customer's quality system asks for it. Sending a drawing with the alloy, the temper, the annual volume and the finish to the custom aluminum stamping team gives the reply enough to quote the process instead of the guess.
Grade selection on aluminum comes down to a short list of questions, and they are answered on the drawing rather than in the press. Leaving the temper off the drawing leaves the specification unfinished. Tight radii on 6061-T6 are cracks waiting for a coil change. A 6063 callout on a flat stamped part usually arrived from an extrusion one line above it.
| Put the temper on the drawing. 5052-H32 covers most formed aluminum parts. Where a load path needs more strength than that, design for 6061-T4 and age afterwards, or split the part. Two characters after the alloy number decide more of the outcome than the alloy itself. | Settle the finish before releasing the tool. Anodized appearance varies enough between alloys and between finishing lines that a first-article panel through the production line is the only honest test. Running that panel before the die is cut keeps the appearance question on the drawing instead of in a rework claim. |
Most of the decisions on this page belong to the engineer and the buyer rather than to the press. Whoever writes the material callout, the radius and the tolerance band decides which argument will be settled cheaply and which one will be settled after the tool is hardened.
About the Manufacturer Behind These Aluminum Stamped Parts
Ronghai is a Chinese OEM metal stamping manufacturer producing progressive die, transfer die, compound die and deep drawn components for buyers worldwide, with aluminum processed from 0.3 mm to 20 mm on 315-ton presses. ISO 9001 and IATF 16949 are held, and standard documentation includes material certificates, first article inspection reports, CMM reports and salt spray reports, so grade and temper claims can be checked against the heat number.
Related Aluminum Stamped Parts and the Processes Behind Them
Typical aluminum output includes brackets, enclosures, chassis panels, cabinet parts, mounting frames, heat-sink supports, terminals and housings, produced in 5052, 6061 and 6063 alongside carbon steel, stainless steel, copper alloys, galvanized steel and spring steel. Send the 2D drawing, 3D model, alloy and temper, annual quantity and the tolerances that will be inspected, and the reply covers process route, tooling approach and an inspection plan sized to your volume.
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About the Manufacturer Behind These Aluminum Stamped Parts
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