Bending in T4
Stretch and rotary-draw bending are easiest in T4 shortly after quenching. Plan the forming window, because natural ageing gradually raises strength and lowers ductility.
Automotive structural extrusions
4B01 T4 Automotive Aluminium Profile
4B01 is a heat-treatable aluminium grade listed in the Chinese automotive extrusion standard GB/T 33910 for body and chassis profiles. It is supplied in T4 for forming and bending, then aged to T6 for strength, much like the familiar 6xxx structural alloys. Metline supplies 4B01 profiles to drawing, and can also offer registered international alloys such as 6061, 6082 or 6005A where a project needs an ASTM or EN designation.
- Grade
- 4B01 (GB/T 33910)
- Tempers
- T4, T6
- Shapes
- Square, rectangular, hexagonal tube
- Alternatives
- 6061 · 6082 · 6005A
What is 4B01 aluminium?
In the GB numbering system the first digit shows the main alloying element, and "4" denotes silicon. 4B01 is therefore classed as an aluminium-silicon based wrought alloy, and the "B" marks it as a later national registration rather than an Aluminum Association grade. It appears in GB/T 33910-2017, the Chinese standard for aluminium extruded profiles for automobiles, alongside conventional 6xxx and 7xxx grades.
In practice, a silicon-led alloy with a magnesium addition behaves like a high-silicon 6xxx alloy: it can be solution heat-treated, quenched and aged, it extrudes into hollow sections, and it reaches medium strength in the T6 condition. Reference data for the grade list a minimum of about 270 MPa tensile strength, 220 MPa yield strength and 8 % elongation in the fully aged condition, which places it in the same class as 6061-T6 and 6005A-T6 profiles.
Because 4B01 is not registered with the Aluminum Association or in EN 573-3, it has no direct ASTM or EN equivalent. Buyers usually meet it on drawings from Chinese vehicle programmes or their suppliers. For projects outside that supply chain, it is often simpler to specify a registered alloy with the same strength class. We explain both routes below so you can decide with full information.
4B01 chemistry: what is published and what to check
The full composition limits of 4B01 are set out in GB/T 33910 and are not widely published. Database extracts confirm copper at no more than 0.25 % and chromium at no more than 0.20 %, with silicon as the principal alloying element and magnesium added for age hardening. Some supplier sheets in circulation show silicon below 0.7 % and magnesium of 0.8 – 1.2 %, which would describe a 6xxx alloy rather than a 4xxx one; treat those figures with caution.
| Element | 4B01 (GB/T 33910, published extracts) | 6061 (AA, for comparison) | 6005A (AA, for comparison) |
|---|---|---|---|
| Silicon (Si) | Principal alloying element (limits per GB/T 33910) | 0.40 – 0.8 | 0.50 – 0.9 |
| Magnesium (Mg) | Age-hardening addition (limits per standard) | 0.8 – 1.2 | 0.40 – 0.7 |
| Copper (Cu) | ≤ 0.25 | 0.15 – 0.40 | ≤ 0.30 |
| Chromium (Cr) | ≤ 0.20 | 0.04 – 0.35 | ≤ 0.30 |
| Iron, manganese, zinc, titanium | Limited per standard | Fe ≤ 0.7, Mn ≤ 0.15, Zn ≤ 0.25, Ti ≤ 0.15 | Fe ≤ 0.35, Mn ≤ 0.50, Zn ≤ 0.20, Ti ≤ 0.10 |
Every 4B01 lot we supply is certified with its measured analysis against the limits in the edition of GB/T 33910 named on your order. If you need the full limit table for a design review, ask us and we will provide it with the quotation.
Mechanical properties in T4 and T6
T4 means solution heat-treated and naturally aged: the profile is relatively soft and ductile, which is why automotive parts are often bent, hydroformed or crushed into shape in T4 and then artificially aged. T6 means solution heat-treated and artificially aged to near-peak strength.
| Temper | Tensile strength | Yield strength 0.2 % | Elongation | Basis |
|---|---|---|---|---|
| T4 | Lower; agreed per drawing | Lower; agreed per drawing | High, suitable for bending | Tested minimum on certificate |
| T6 | ≥ 270 MPa | ≥ 220 MPa | ≥ 8 % | Minimums listed for the grade |
| 6061-T6 extrusion (comparison) | ≥ 260 MPa | ≥ 240 MPa | ≥ 8 – 10 % | ASTM B221 |
| 6005A-T6 extrusion (comparison) | ≥ 260 – 270 MPa | ≥ 215 – 225 MPa | ≥ 8 % | EN 755-2, by wall thickness |
T4 values depend strongly on the time since quenching, because natural ageing continues for days. Agree the test timing and minimums on the order if the part will be formed in T4.
Physical properties (approximate, typical of Al-Si-Mg extrusion alloys)
- Density
- about 2.68 – 2.70 g/cm³
- Modulus of elasticity
- about 69 GPa
- Coefficient of thermal expansion
- about 23 µm/m·°C
- Thermal conductivity
- about 150 – 180 W/m·K depending on temper
4B01 profile shapes and sizes
4B01 is most often ordered as square, rectangular and hexagonal tube for frames, cross members and crash structures. Representative sizes:
| Shape | Typical sizes (mm) | Typical wall (mm) |
|---|---|---|
| Square tube | 20 × 20 to 150 × 150 | 1.5 – 5 |
| Rectangular tube | 50 × 30 to 120 × 60 | 2 – 4 |
| Hexagonal / multi-cell tube | about 100 × 50 to 150 × 75 envelope | 5 – 6 |
| Custom hollow and open profiles | to drawing | to drawing |
Typical supply range for 4B01 profiles
- Temper
- T4 (for forming), T6 (aged); T4 profiles can be aged after forming by the customer
- Section types
- Round, square and rectangular tube; angle, channel, T and I sections; flat bar; hollow and multi-cavity custom profiles to drawing
- Size envelope
- Small trim and tube sections up to large structural profiles; the feasible circumscribing circle and wall depend on the die and press, and are confirmed at quotation
- Wall thickness
- From about 1 mm on small sections; thicker walls on structural shapes
- Length
- Standard 6 m mill lengths; cut-to-length parts and longer lengths on request
- Finish
- Mill finish, anodised, anodised and electrophoretic lacquer, powder coated or wet painted
- Processing
- Precision sawing, punching, CNC machining, bending and deburring to drawing
Every custom profile is drawing-specific. Send the section drawing with critical dimensions and tolerances so feasibility can be confirmed.
Tolerances and inspection
Unless the drawing states tighter values, profile dimensions follow the general tolerance tables of the order standard. Automotive programmes often add their own limits on critical features such as mounting faces, wall thickness at crush zones and twist over the part length. For crash-relevant parts, buyers also commonly request microstructure checks (grain size and recrystallised surface layer depth) and axial crush tests on sample lengths.
Tolerance and inspection references
- Cross-section tolerances
- EN 755-9 (profiles), ASTM B221 with ANSI H35.2, or GB/T 14846 for orders to Chinese standards
- Straightness and twist
- Per the same tables, or as agreed for long automotive parts
- Surface quality
- Visible faces free of die lines, pick-up and blisters beyond the agreed limit sample
- Mechanical testing
- Tensile test per lot to ISO 6892-1 or ASTM B557; hardness checks on request
- Certification
- EN 10204 3.1 mill test certificate with chemistry and mechanical results
Forming, ageing, joining and finishing
Artificial ageing
After forming, parts are aged in a furnace to the T6 condition. The ageing cycle is set by the material specification; paint-bake cycles add only partial ageing.
Welding
MIG and TIG welding with ER4043 or ER5356 filler are normal for Al-Si-Mg alloys. The heat-affected zone loses part of its T6 strength, so design welded joints to reduced allowables.
Mechanical joining
Self-piercing rivets, flow-drill screws and adhesive bonding are widely used in mixed-material bodies.
Machining
Machines cleanly in T6 with carbide tools; high silicon gives good chip breaking but slightly faster tool wear.
Surface treatment
Suitable for conversion coating, e-coat and powder coat. Decorative anodising of high-silicon alloys tends to give a grey tone.
Where 4B01 profiles are used
- Body-in-white structures: sills, roof rails, pillars reinforcements and cross members
- Crash management: bumper beams and crash boxes, where T4 forming and T6 strength combine well
- Chassis and subframes: extruded rails and brackets for front and rear subframes
- EV battery enclosures: frame members and cross beams for battery trays
- Commercial vehicles: frames for bus bodies, truck boxes and trailers
Some older product descriptions list 4B01 for cylinder blocks, cylinder heads and brake discs. Those parts are cast (or, for discs, made from iron or composites), not extruded; an extrusion grade is not the right material for them.
4B01 compared with registered alternatives
| Point | 4B01 | 6061 | 6082 | 6005A |
|---|---|---|---|---|
| Standards system | GB/T 33910 | ASTM B221, EN 755, GB | EN 755, ASTM B221, GB | EN 755, GB |
| T6 strength class | about 270 / 220 MPa min | about 260 / 240 MPa min | about 290 – 310 / 250 – 260 MPa min | about 260 – 270 / 215 – 225 MPa min |
| Extrudability of thin hollows | Good | Fair | Fair | Good |
| Global availability | Mainly Chinese programmes | Worldwide | Worldwide, especially Europe | Worldwide |
If you are designing for a global supply base, 6005A or 6082 is usually the easiest substitute for a structural 4B01 profile, and 6061 where machined features dominate. For crash parts, any change of alloy must be validated by the vehicle maker.
How to order 4B01 profiles
- SpecifyGrade and temper (4B01-T4 or T6), section drawing, length, quantity and annual volume; say whether 6005A, 6082 or 6061 is acceptable.
- Confirm the standardGB/T 33910 (state the edition), or ASTM B221 / EN 755-2 if a registered alternative is chosen, plus any OEM material specification.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectProfiles are cut, inspected for dimensions and properties, and packed with separators to protect surfaces.
- Document and shipEach lot ships with an EN 10204 3.1 mill test certificate, lot traceability and a packing list, in seaworthy export packing. Third-party inspection can be arranged on request.
References and standards
- GB/T 33910-2017 – Aluminium and aluminium alloy extruded profiles for automobiles
- GB/T 3190-2020 – Chemical composition of wrought aluminium and aluminium alloys
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- IATF 16949 – Quality management system requirements for automotive production and relevant service parts organisations
4B01 automotive aluminium (aluminum) profile: frequently asked questions
What standard covers 4B01 aluminium?
GB/T 33910-2017, the Chinese standard for aluminium and aluminium alloy extruded profiles for automobiles. The grade is not registered with the Aluminum Association or in EN 573-3.
What is the equivalent of 4B01?
There is no exact equivalent. By strength class, 6005A-T6, 6061-T6 and 6082-T6 profiles are the usual alternatives, subject to the part designer's approval.
Why is 4B01 supplied in T4?
T4 is soft and ductile, so profiles can be bent or formed easily. After forming they are artificially aged to T6, which raises the strength to its design level.
What strength does 4B01-T6 reach?
Minimums of about 270 MPa tensile, 220 MPa yield and 8 % elongation are listed for the grade in the aged condition; the actual results are reported on the certificate for each lot.
Can 4B01 be welded?
Yes, by MIG or TIG with Al-Si or Al-Mg fillers, as for 6xxx alloys. The heat-affected zone loses some of its T6 strength.
Do you ship 4B01 profiles worldwide?
Yes. Metline supplies 4B01 and its registered alternatives worldwide from Mumbai with 3.1 certificates, on EXW, FOB, CIF or DAP terms.
Need 4B01 profiles or an equivalent?
Send the drawing, temper and volumes. We will reply with supply options, certification and a delivered price.
