Tensile test
Confirms the wire is within the maximum strength for H14. Too high and heads crack; too low and the coil may be over-annealed.
Al-Mn rivet wire
3A21 Aluminium Wire for Rivets
3A21 is the Chinese designation for an aluminium-manganese alloy that is practically equivalent to 3003, and in H14 temper it is one of the most common wires for solid, non-structural rivets. It heads easily, resists corrosion and needs no heat treatment. This page sets out what a 3A21 rivet wire specification contains and how to check incoming coils.
- Grade
- 3A21 (≈ 3003, EN AW-3003)
- Temper
- H14
- Diameter
- 1.6 – 10 mm
- Standard
- GB/T 3195
What is 3A21 rivet wire?
3A21 (formerly LF21 in older Chinese designations) is a non-heat-treatable Al-Mn alloy. Its strength comes from manganese in solution and fine dispersoids, plus cold work from drawing.
As rivet wire it is drawn to final diameter and given an H14 (half-hard) temper. This leaves enough strength for useful shear capacity and enough ductility to upset a head without splitting. Because it never needs solution treatment, 3A21 rivets can be stored indefinitely and driven at any time, unlike 2017 or 2024 "ice-box" rivets.
Buyers in India, the Middle East and Europe often meet 3A21 on drawings from Chinese-designed equipment. In most cases 3003-H14 wire to ASTM B316 or EN 1301 can be supplied against such drawings once the designer agrees; the composition table below shows why.
3A21 composition and its 3003 equivalent (wt %)
| Element | 3A21 (GB/T 3190) | 3003 (AA / EN AW-3003) |
|---|---|---|
| Silicon (Si) | ≤ 0.60 | ≤ 0.60 |
| Iron (Fe) | ≤ 0.70 | ≤ 0.70 |
| Copper (Cu) | ≤ 0.20 | 0.05 – 0.20 |
| Manganese (Mn) | 1.0 – 1.6 | 1.0 – 1.5 |
| Magnesium (Mg) | ≤ 0.05 | — |
| Zinc (Zn) | ≤ 0.10 | ≤ 0.10 |
| Titanium (Ti) | ≤ 0.15 | — |
| Aluminium | Remainder | Remainder |
The overlap is almost complete. The practical differences are that 3A21 may contain no copper at all, while 3003 must contain at least 0.05 %, and 3A21 allows manganese up to 1.6 %. Neither difference changes heading behaviour or corrosion resistance in a way that matters for rivets. ISO and EN name the alloy AlMn1Cu (EN AW-3003); Japan uses A3003.
Strength requirements for 3A21-H14 wire
Rivet wire specifications control strength from both sides. A maximum tensile strength stops the wire being too hard to head; a minimum shear strength, tested on the wire or on driven rivets, ensures the joint carries its design load.
| Property | Typical 3A21 / 3003-H14 | How it is specified for rivet wire |
|---|---|---|
| Tensile strength | 145 – 165 MPa | Maximum, about 180 MPa in H14 |
| Yield strength (0.2 %) | about 140 MPa | Usually not specified |
| Shear strength | about 95 – 100 MPa | Minimum per standard and diameter band |
| Elongation | about 8 – 12 % | Usually not specified for wire |
| Hardness | about 40 HB | For information |
Typical values from published 3003-H14 data. Contract limits are those of the standard and edition named in your order; ask for them to be printed on the certificate.
Physical properties
- Density
- 2.73 g/cm³
- Melting range
- about 643 – 654 °C
- Electrical conductivity (H14)
- about 40 – 42 % IACS
- Thermal expansion
- about 23 µm/m·°C
Tests that prove rivet wire will head and hold
Shear test
Double-shear test on wire (ASTM B565 or the national equivalent). The result is sensitive to fixture geometry, so state the method.
Upsetting (heading) test
A sample, typically 1.5 × diameter long, is compressed to a set fraction of its height. No cracks may appear on the barrel.
Riveting test
Some standards drive a rivet in a test joint and check that the head forms fully with no cracking at a set protrusion ratio.
Dimensional check
Diameter and ovality measured along the coil with a micrometer; coil ends sampled.
Surface inspection
Visual check for cracks, laps, scratches, inclusions, corrosion and blisters, which are not allowed on rivet wire.
Diameter tolerance and surface quality
Rivet wire standards offer several tolerance grades, from tight one-sided (minus only) bands for high-speed heading to wider symmetrical bands for general work. For 3A21 in 1.6 – 10 mm, buyers commonly specify around ±0.02 mm on small diameters and up to about ±0.04 – 0.06 mm on larger ones. State the grade or the actual limits on the order.
| Defect | Typical requirement for rivet wire |
|---|---|
| Cracks, laps, peeling, blisters | Not permitted |
| Metallic or non-metallic inclusions pressed in | Not permitted |
| Surface corrosion | Not permitted |
| Light scratches, scuffs, small dents | Permitted if depth is no more than half the minus tolerance |
| Light oil marks | Usually permitted |
What to put in a 3A21 rivet wire enquiry
- Grade and standard3A21-H14 to GB/T 3195, or 3003-H14 to ASTM B316 / EN 1301 if the equivalent is accepted.
- Diameter and toleranceNominal diameter and tolerance grade or limits, plus allowed ovality.
- TestsTensile, shear and upsetting tests per lot; riveting test if your customer requires it.
- Coil formatCoil weight, inner and outer diameter, winding direction and whether coils are on spools or loose.
- Surface and packingLubricant type, protective wrapping, and export packing (wooden cases or eye-to-sky pallets).
- DocumentsEN 10204 3.1 certificate; third-party inspection if needed.
Where 3A21 rivets are used
- Light transport: trim, interior panels and non-structural body attachments on buses, rail cars and trailers
- Aircraft interiors: secondary fittings and cabin parts that carry low loads
- Building products: window and door frames, curtain-wall accessories and cladding attachments
- Appliances and electronics: housings, brackets and earthing points
- Furniture and consumer goods: chairs, cases, ladders and cookware handles
- Agricultural and general machinery: guards, covers and nameplates
Where a joint needs more than about 100 MPa shear, consider 5A02, 5052 or 5056 wire, or a heat-treatable 2xxx grade for structure.
References and standards
- GB/T 3195 – Aluminium and aluminium alloy wire for rivets
- GB/T 3190 – Chemical composition of wrought aluminium and aluminium alloys
- ASTM B316/B316M – Aluminum and Aluminum-Alloy Rivet and Cold-Heading Wire and Rods
- ASTM B565 – Shear Testing of Aluminum and Aluminum-Alloy Rivets and Cold-Heading Wire and Rods
- EN 1301-2 / -3 – Aluminium and aluminium alloys: drawn wire, mechanical properties and tolerances
3A21 aluminium rivet wire: frequently asked questions
What is the international equivalent of 3A21?
3003 (EN AW-3003, AlMn1Cu, UNS A93003, JIS A3003). The chemistries overlap almost completely and H14 properties match.
Why is 3A21 rivet wire supplied in H14?
H14 balances heading ductility and shear strength. Softer O temper is used for large upsets or tubular rivets; harder tempers tend to crack at the head.
What shear strength does a 3A21 rivet have?
Typically around 95 – 100 MPa in H14. The minimum you can rely on is the value in the governing standard for your diameter band.
Does 3A21 need heat treatment after riveting?
No. It is non-heat-treatable; the strength comes from cold work, and the head work-hardens slightly during forming.
Can you supply 3003 wire against a 3A21 drawing?
Yes, where the designer accepts the equivalent. We can also supply wire certified as 3A21 to GB/T 3195.
Need 3A21 rivet wire?
Send the diameter, tolerance, coil weight and tests you require. We will confirm grade, certification and shipping to your plant.
