7003 is a weldable 7xxx extrusion alloy. It was developed so that a welded joint recovers most of its strength during service aging instead of being written off in the heat-affected zone — the problem that keeps 7075 out of welded structure.
It gets there by giving up copper. Copper is what lifts 7075 and 7001 to their peak strength, and it is also what makes them unweldable and prone to stress-corrosion cracking; 7003 caps it at 0.20% and leans on zinc, magnesium and zirconium instead. Its strength class sits below 7075’s and above 6061’s — the point of the trade is that the joint survives.
What Is 7003 Aluminum Alloy?
7003 is a heat-treatable alloy in the 7000 series. Zinc is the main alloying element and magnesium forms the MgZn₂ strengthening phase, with copper held low enough that the alloy can be welded by conventional processes.
Zirconium is the defining addition. At 0.05–0.25% it raises the recrystallisation temperature and keeps the grain structure fine through extrusion, which suppresses hot cracking in the weld pool and helps extruded sections hold strength after aging. No copper plus a controlled grain structure is what separates 7003 from the copper-bearing 7xxx grades.
| Element | Zakres (% mas.) | Rola |
| Cynk (Zn) | 5.0–6.5 | Główny pierwiastek wzmacniający |
| Magnez (Mg) | 0.5–1.0 | Tworzy fazę umacniającą MgZn₂ |
| Cyrkon (Zr) | 0.05–0.25 | Rozdrobnienie ziarna; odporność na pękanie na gorąco przy spawaniu |
| Chrom (Cr) | ≤0.20 | Kontrola struktury ziarna |
| Mangan (Mn) | ≤0,30 | Trace control |
| Miedź (Cu) | ≤0.20 | Utrzymywana na niskim poziomie dla spawalności i odporności korozyjnej |
| Żelazo (Fe) | ≤0,35 | Limit zanieczyszczeń |
| Krzem (Si) | ≤0,30 | Limit zanieczyszczeń |
| Tytan (Ti) | ≤0.20 | Rafinator ziarna |
| Inne (każdy / łącznie) | ≤0,05 / ≤0,15 | Limity śladowe |
| Aluminium (Al) | Równowaga | Metal nieszlachetny |
Ranges follow EN 573-3 and the AA registration — EN AW-7003, chemical designation AlZn6Mg0.8Zr, UNS A97003. Density is about 2.78 g/cm³.
One point about form matters before anything else: 7003 is an extrusion alloy first. Bar, tube, and profile are the standard product range under ASTM B221 and EN 755-2, and it is not a routine flat-rolled designation. Plate and sheet come under a different specification, so name the form and its governing standard on the enquiry — and where a section or size falls outside the standard range, it is produced to drawing.
Stany utwardzenia i typowe właściwości mechaniczne
Temper changes the delivered part more than the alloy choice does.
- T5 — cooled from the extrusion press and then artificially aged. This is the usual and most economical temper for 7003 profiles.
- T6 — solution heat treated, quenched, and artificially aged. One extra process step buys higher strength; press quenching can reach it on suitable sections.
- T651 — aged and then stress-relieved by stretching. It sits on the ASTM side for parts that will be machined to tight tolerances.
| Temperament | Wytrzymałość na rozciąganie, Rm (MPa) | Granica plastyczności, Rp0,2 (MPa) | Wydłużenie (%) | Podstawa |
| T5 | ~350 typical / 310 min | ~300 typical / 260 min | 10 (A50) | EN 755-2 minimums; producer typicals |
| T6 | ~370–390 | ~300–320 | 8–12 | Producer data; confirm against the governing standard |
| T651 | ~370–390 | ~300–320 | 8–12 | Producer data; ASTM-side temper |
Read the minimum column for design and the typical column for planning. EN 755-2 sets the T5 floor at 260 MPa proof and 310 MPa tensile, tabulated by wall-thickness class, and typical extruded material tests well above that floor. The figures a buyer can write into a drawing are the minimums for the applicable thickness class, confirmed on the MTC.
7003 vs 6061, 7005 i 7075
| Stop / stan utwardzenia | Wytrzymałość na rozciąganie, Rm (MPa) | Granica plastyczności, Rp0,2 (MPa) | Spawalność | Odporność korozyjna | Najlepsze dopasowanie |
| 6061-T6 | ~310 | ~276 | Doskonały | Dobry | General structural work; easy forming and anodising |
| 7003-T5 | ~350 | ~300 | Good; re-ages after welding | Moderate; stress-corrosion sensitive | Extruded welded frames and profiles |
| 7005-T5 | ~345 | ~290 | Doskonały | Umiarkowany | Spawane ramy o wysokiej wytrzymałości |
| 7075-T6 | ~572 | ~503 | Słaby | Ograniczona | Części lotnicze i inne o szczytowej wytrzymałości |
Ask one question first: will the part be welded? If it will, 7075 leaves the table because it is not fusion weldable in practice, and the choice narrows to 7003, 7005, or 6061.
Between the two 7000-series options, typical T5 yield values land within about 15 MPa of each other, so the tie-break is process rather than strength. 7003 extrudes thin, complex profiles more easily and holds grain structure better there; 7005 carries manganese and is the more common call where a welded frame needs the highest joint strength. If the part is machined and never welded, 6061-T6 stays cheaper, forms more easily, and stocks far wider.
Working With 7003
Spawanie
7003 welds with 5xxx filler wire. ER5356 (EN ISO 18273 AlMg5Cr(A)) is the default, ER5183 (AlMg4.5Mn0.7(A)) suits joints that need more as-welded strength, and ER5556 (AlMg4.5MnZr) appears on heavier structural work. Copper is held low precisely so these fillers behave.
Welding still softens the heat-affected zone, but 7003 recovers more of it than a copper-bearing 7xxx grade does. Published alloy data for 7003 reports joints returning to up to about 90% of parent properties once the weldment is aged — by natural aging over time or by a supplementary artificial age. Design the joint on those aged, as-welded values, not on the parent T6 column.
Obróbka skrawaniem
7003 cuts harder than 6061, so expect more tool wear and plan on sharp, high-rake tooling and a rigid setup. T5 and T6 take a cleaner finish than the softer conditions. Residual stress in extruded stock can show up as movement during machining or later during welding, so keep stock removal even across the section. These tempers are also notch-sensitive, which means form the part before it is aged and heat treat afterwards — not the other way round.
Corrosion and Stress-Corrosion Limits
General atmospheric corrosion resistance is good for a 7xxx grade: well ahead of the copper-bearing 7075, behind the 6xxx family. Marine service is the weak point, and 7003 alloy data rates marine resistance poorly, so bare saltwater or chloride immersion is not its job. Anodising, painting, or a protective film covers most outdoor and coastal exposure.
Stress-corrosion cracking needs separate attention. 7003 is susceptible to SCC under sustained tensile stress in a moist or chloride-bearing environment, so treat it as a design limit rather than an edge case: keep sustained stress inside the range your supplier’s data allows for the temper and section, and protect the surface wherever moisture is present.
Temperatura eksploatacji
Treat 7003 as a room-temperature structural alloy. Like every precipitation-hardened grade it over-ages and loses strength as service temperature rises, so check any hot application against temper-specific design data instead of assuming room-temperature values hold.
Zastosowania
- Scaffolding, staging, and access-platform components
- Mobile cranes, lifts, and other welded load-bearing structures
- Rail and metro car bodies and structural members
- Bicycle and motorcycle frames, and sports equipment
- Air cargo containers, truck and trailer frames
- EV battery-pack frames and light structural extrusions
Kryteria kwalifikacji (Go/No-Go)
Go — specify 7003 when:
- The part needs more strength than 6061-T6 delivers and it will be welded, because 7003 re-ages toward parent values where 7075 cannot be welded at all.
- The part is an extruded profile or tube and the section is thin or complex, where 7003’s extrusion behaviour pays off.
- Service is indoor, or the surface will be anodised, painted, or filmed.
- Sustained stress stays inside the SCC limits your supplier’s data allows for the temper and section.
No-Go — szukaj gdzie indziej, gdy:
- Peak aerospace strength above roughly 500 MPa yield is required. That is 7075 or 7055 territory.
- Bare saltwater or chloride immersion is expected with no coating. Use 5083 or a 6xxx grade.
- The part is machined and never welded. 6061-T6 is cheaper, forms more easily, and stocks more widely.
- Heavy cold forming after aging is planned. Form the part first, then heat treat.
- A drawing calls for 7003 as rolled plate under a flat-rolled standard. Confirm the form and its specification before quoting.
Uwagi dotyczące zaopatrzenia: Co potwierdzić przed złożeniem zamówienia
7003 is an extrusion alloy first. Bar, tube, and profile to ASTM B221 or EN 755-2 are the standard range, and flat-rolled 7003 sits under a different specification — so name the form and its governing standard on the enquiry. Shape is not the constraint: non-standard cross-sections, sizes, and product shapes are produced to your drawing.
Cztery pozycje w zapytaniu wykonują większość pracy:
- Obowiązująca norma — ASTM B221 or EN 755-2.
- Temperament — T5, T6, or T651, plus the aging route for any welded assembly.
- Governing wall thickness — minimum mechanical values in EN 755-2 are tabulated by thickness class.
- Poziom dokumentacji — MTC as standard; EN 10204 3.1 or SGS reports where the project requires independent verification.
On documents, the MTC that ships with every order carries the chemistry and mechanical results for that lot. Certificate levels are worth getting right: EN 10204 3.1 is signed by the manufacturer’s own authorised inspection representative, while 3.2 adds an independent third party such as a customer representative or a body like TÜV, BV, SGS, or DNV.
Wnioski
Aluminium 7003 gives you most of the 7xxx strength advantage in a form that extrudes cleanly and can actually be welded, but the trade-offs are real: corrosion resistance is moderate, stress-corrosion cracking is a genuine design limit, and flat-rolled forms sit under a different specification from the extrusion range.
We supply 7003 in extruded profile, bar, and tube, and produce custom shapes, sizes, and tempers to your drawing through low-MOQ production with lead times of 10–60 days. Every order ships with an MTC.
Send us the drawing with the temper and the weld route for a form, temper, and availability check.
Często zadawane pytania
What is the minimum order quantity and lead time for 7003?
Standard tempers and sizes ship from stock. Non-standard tempers and custom dimensions run as low-MOQ production, typically 10–60 days, driven by alloy, size and processing. Send the drawing and the quantity so both can be confirmed.
What documents come with a 7003 order?
A mill test certificate listing the chemistry and mechanical results for the lot, included with every order. SGS chemical, mechanical or ultrasonic reports are available on request at extra cost, and EN 10204 3.2 adds an independent countersignature.
Can you supply 7003 cut to length or machined to drawing?
Yes. Extruded bar, tube and profile are cut to finished lengths, and in-house CNC machining covers drilled, tapped and milled features. Send the drawing with the finishes and tolerances so the material and the processing can be quoted together.
Can 7003 replace 6061 in a welded frame?
It can, and it buys strength rather than saving cost. 7003 welds with a 5xxx filler and re-ages toward parent values afterwards, where 6061 gives up heat-affected-zone strength permanently. Where the frame does not need the extra strength, 6061 stays the cheaper route.
