T4
Solution heat-treated on a continuous annealing line, quenched and naturally aged. Good formability, but bake response is weaker because room-temperature clusters must first dissolve in the oven.
Bake-hardenable closure panel sheet
6022 Aluminium Automotive Body Sheet (T4P / Bake-Hardened)
6022 is a 6xxx-series body sheet alloy designed for car closures: hoods, doors, deck lids, fenders and roofs. It is delivered in a soft, pre-aged T4P temper so it stamps and hems cleanly, then gains strength in the paint-bake oven to give the finished panel its dent resistance. Metline supplies 6022 sheet and coil in automotive thicknesses, with mill or EDT surfaces and the pretreatment and lubricant your press shop specifies, to vehicle and component makers worldwide.
- Alloy
- 6022 (Al-Si-Mg)
- Delivery temper
- T4 / T4P (pre-aged)
- Thickness
- 0.7 – 1.5 mm typical
- Use
- Outer and inner closure panels
What is 6022 auto body sheet?
6022 is a silicon-rich Al-Mg-Si alloy. Its silicon content (0.8 – 1.5 %) is well above the amount needed to combine with its magnesium (0.45 – 0.70 %), and that excess silicon speeds up the precipitation of strengthening Mg-Si clusters during the short bake that cures automotive paint. The result is a sheet that is soft enough to draw a deep door outer, yet ends up markedly stronger on the finished car.
The alloy was developed for North American vehicle programmes as an outer-panel material and is now used alongside 6016 (the usual European choice) and 6014 on closures around the world. Copper is held to a maximum of 0.11 %, which keeps resistance to filiform corrosion under paint high, an important difference from older copper-bearing body alloys such as 6111.
Body sheet is a far more demanding product than general-purpose 6061 or 6082 sheet. Beyond strength, the buyer specifies anisotropy (r-value), work hardening (n-value), hemming performance, surface texture, freedom from paint-brush lines and roping, and the pretreatment and lubricant on the coil. Every one of these affects whether a panel can be stamped at production rate without splits or visible defects.
6022 chemical composition (wt %)
The limits below are the registered Aluminum Association values for 6022. Vehicle makers often add tighter internal limits, for example on iron (which forms coarse particles that affect hemming) or on magnesium and silicon (which control bake response).
| Element | Minimum | Maximum | Effect in body sheet |
|---|---|---|---|
| Silicon (Si) | 0.8 | 1.5 | Excess Si accelerates bake hardening and raises strength |
| Iron (Fe) | 0.05 | 0.20 | Kept low to limit coarse intermetallics and improve hem quality |
| Copper (Cu) | 0.01 | 0.11 | Small amount boosts bake response; low level protects filiform resistance |
| Manganese (Mn) | 0.02 | 0.10 | Grain and texture control |
| Magnesium (Mg) | 0.45 | 0.70 | Forms Mg-Si strengthening phases with silicon |
| Chromium (Cr) | — | 0.10 | Grain structure control |
| Zinc (Zn) | — | 0.25 | Impurity |
| Titanium (Ti) | — | 0.15 | Grain refinement of the cast ingot |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Properties as delivered and after paint bake
Body sheet is specified in two states: the T4P condition in which it is formed, and the condition after a simulated paint bake, which represents the panel on the finished car. The standard laboratory simulation is a 2 % tensile pre-strain (representing stamping strain) followed by about 20 minutes at 170 – 185 °C. The values below are indicative ranges; your OEM specification and the mill test certificate for each coil govern.
| Property | T4P as delivered (typical) | After 2 % strain + bake (typical) |
|---|---|---|
| Yield strength Rp0.2 | about 110 – 150 MPa | commonly specified around 185 – 235 MPa |
| Tensile strength Rm | about 220 – 270 MPa | about 270 – 300 MPa |
| Elongation A50 | about 22 – 28 % | reduced; not normally specified |
| Strain-hardening exponent n (10 – 20 %) | about 0.23 – 0.27 | — |
| Plastic strain ratio r (10 %) | about 0.5 – 0.7 | — |
Tensile testing follows ASTM E8 or ISO 6892-1; n-value is measured to ASTM E646 or ISO 10275 and r-value to ASTM E517 or ISO 10113. Always check the test direction (0°, 45°, 90° to rolling) quoted in your specification.
Physical properties (typical)
- Density
- 2.69 – 2.70 g/cm³
- Modulus of elasticity
- about 69 – 70 GPa
- Coefficient of thermal expansion
- about 23 µm/m·°C (20 – 100 °C)
- Thermal conductivity
- about 170 – 200 W/m·K depending on temper
A practical point that buyers often overlook: T4-type 6xxx sheet continues to age slowly at room temperature. Yield strength creeps upward over the first months after solution treatment and formability declines with it. Pre-ageing (the "P" in T4P) stabilises the sheet and improves bake response, but coils should still be stamped within the shelf life stated by the specification, and stored away from heat.
T4, T4P and bake-hardened conditions explained
T4P (pre-aged)
A short low-temperature treatment straight after quenching creates stable clusters that grow quickly in the paint oven. This is the normal delivery condition for 6022 outer panels. Some suppliers and national standards add suffixes such as T4Pa to identify a specific pre-ageing practice.
Simulated bake (T8x / T6B-type)
Laboratory condition after 2 % stretch and an oven cycle. It is a test state used to prove the panel will reach its target strength, not a delivery temper.
T6 / T61
Full artificial ageing before forming. Rarely used for outer panels because formability drops sharply, but occasionally specified for flat reinforcements or brackets.
When you request a quote, state both the delivery temper and the bake-test condition required (pre-strain, temperature and time), because suppliers can tune pre-ageing to suit a particular paint shop.
Sizes, surfaces and pretreatment options
Typical supply range for 6022 body sheet
- Thickness
- 0.7 – 1.5 mm; outer panels most often 0.9 – 1.1 mm, inners 0.8 – 1.2 mm
- Width
- About 800 – 2400 mm, depending on blank layout
- Form
- Coil for blanking lines, or cut sheets and blanks about 800 – 5500 mm long
- Surface texture
- Mill finish (transverse Ra about 0.1 – 0.6 µm) or electro-discharge textured, EDT (Ra about 0.7 – 1.3 µm)
- Pretreatment
- Ti/Zr conversion coating or passivation to support adhesive bonding and paint adhesion
- Lubricant
- Electrostatically applied oil or dry-film (hot-melt) lubricant at an agreed coat weight
Surface class (outer "A-class" exposed surface or inner), texture and lubricant coat weight are agreed per part number.
| Surface treatment | Code often used | Purpose |
|---|---|---|
| Chemical cleaning | NP | Acid or alkaline cleaning to remove rolling residues and oxides |
| Passivation / conversion coating | P | Stable surface for adhesive bonding and phosphate-free paint lines |
| Dry-film lubricant | DO | Solid lubricant, uniform friction in deep draws, low mess in the press shop |
| Electrostatic oiling | EO | Thin, even oil film for corrosion protection and forming |
Dimensional tolerances and quality requirements
Automotive contracts usually tighten the general ASTM B209 or EN 485-4 tolerances. The values below are representative contract limits for 6022 sheet; the drawing or OEM specification takes precedence.
| Thickness (mm) | Width 800 – 1600 mm | Width > 1600 – 1800 mm | Width > 1800 – 2400 mm |
|---|---|---|---|
| 0.70 – 1.00 | ± 0.03 | ± 0.05 | ± 0.08 |
| > 1.00 – 1.20 | ± 0.04 | ± 0.06 | ± 0.09 |
| > 1.20 – 1.50 | ± 0.05 | ± 0.07 | ± 0.10 |
Other dimensional limits (representative)
- Width
- +3 / 0 mm up to 1600 mm wide; +5 / 0 mm to 1800 mm; +6 / 0 mm above
- Length
- +3 / 0 mm up to 2000 mm; +5 / 0 mm above
- Diagonal difference
- Proportional to width, roughly 0.8 – 1.2 × W/300
- Flatness
- End warp ≤ 10 mm; body unevenness ≤ 5 mm with no more than one wave per sheet
Hemming
Flat-hem and rope-hem tests grade the outer bend surface for cracking and orange peel. Outer-panel sheet normally has to reach the top one or two grades.
Paint-brush lines and roping
Lines parallel to rolling that appear after stretching and painting. Exposed panels are graded and must meet the agreed level.
Dent resistance and FLC
When requested, the supplier provides dent test data and a forming limit curve (ISO 12004-2) for simulation.
Microstructure
Solution-treated sheet must show no eutectic melting (overheating) and a fine, uniform grain.
Surface quality
Exposed outer surfaces must be free of scratches, dents and roll marks; inner panels accept minor cosmetic marks that do not affect forming.
Traceability
Each coil carries a unique number linked to cast, rolling and heat treatment records and the 3.1 certificate.
Stamping, hemming and joining 6022 panels
Aluminium body sheet behaves differently from deep-drawing steel. Its modulus is about one third of steel, so springback is larger, and its r-value is below 1, so it thins faster in deep draws. Die design, binder pressure and lubrication should be set up for aluminium rather than carried over from a steel tool.
- Stamping: generous die radii (typically 5 – 10 × thickness on draw radii), even lubricant film and compensation for springback in the die surface
- Hemming: 6022 outer panels are roller- or table-hemmed over the inner; a hem adhesive is normally used to seal and stiffen the joint
- Joining: self-pierce riveting, clinching, flow-drill screws and structural adhesive are the main methods; resistance spot welding is possible with tip dressing and high current
- Laser processes: laser welding and laser brazing are used on some roof and tailgate joints
- Paint shop: conversion coating and electrocoat adhere well to properly pretreated 6xxx sheet; the bake cycle completes the hardening
- Scrap handling: keep 6xxx closure scrap separate from 5xxx inner scrap to preserve its value in closed-loop recycling
Where 6022 sheet is used on a vehicle
| Part | Why 6022 suits it | Typical gauge |
|---|---|---|
| Hood (bonnet) outer | Large, shallow panel where dent resistance and A-class surface matter; also helps pedestrian-protection head-impact performance | 0.9 – 1.1 mm |
| Door and liftgate outers | Combines stretch-forming with hemming around the inner panel | 0.9 – 1.1 mm |
| Fenders and roof panels | Exposed surfaces where bake response gives stiffness at low weight | 0.9 – 1.2 mm |
| Deck lid outer | Complex styling lines that need good formability | 0.9 – 1.0 mm |
| Closure inners and reinforcements | Where an all-6xxx closure is wanted for recycling; 5182 or 5754 is the alternative | 0.8 – 1.5 mm |
6022 is not a chassis, radiator or fuel-tank material; those parts use extrusions, brazing sheet or 5xxx alloys. Keeping the choice focused on closures avoids paying body-sheet prices for parts that do not need its surface quality.
6022 compared with 6016, 6014, 6111 and 5182
| Property | 6022-T4P | 6016-T4P | 6014-T4P | 6111-T4 | 5182-O |
|---|---|---|---|---|---|
| Main use | Outer and inner panels | Outer panels (Europe) | Outers, good hemming | Older outer panels | Inner panels |
| Copper | ≤ 0.11 % | ≤ 0.20 % | ≤ 0.25 % | 0.50 – 0.90 % | ≤ 0.15 % |
| Bake hardening | Strong | Moderate–strong | Moderate | Strong | None (softens slightly) |
| Hemming | Good | Very good | Very good | Fair | Good |
| Filiform corrosion resistance | Good | Good | Good | Lower | Good |
| Stretcher-strain marks | No | No | No | No | Yes, so not used for A-class surfaces |
In practice the choice between 6022 and 6016 often comes down to the OEM's existing specification and regional supply. 6022 gives a slightly higher post-bake yield, while 6016 is frequently preferred where very tight flat hems are needed. 5182-O remains the low-cost choice for deep-drawn inner panels that are not visible.
How to order 6022 body sheet from Metline
- SpecifyAlloy and delivery temper (6022-T4P), thickness, width, coil ID/OD or blank size, surface texture, pretreatment, lubricant and coat weight, and annual volume by part number.
- Confirm the standardThe OEM material specification, including bake-test conditions, r and n targets, hemming grade and surface class; ASTM B209 or EN 485 apply where the OEM document is silent.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectCoils are checked for gauge, flatness, surface and lubricant weight, and interleaved or wrapped to protect exposed 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
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- SAE Technical Paper 1999-01-3195 – Development of 6xxx Alloy Aluminum Sheet for Autobody Outer Panels: Bake Hardening, Formability and Trimming Performance
- ASTM E517 – Standard Test Method for Plastic Strain Ratio r for Sheet Metal
- ASTM E646 – Standard Test Method for Tensile Strain-Hardening Exponents (n-Values) of Metallic Sheet Materials
- ISO 12004-2 – Metallic materials: determination of forming-limit curves in the laboratory
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate
6022 aluminium (aluminum) body sheet: frequently asked questions
What does T4P mean for 6022 sheet?
T4P is a pre-aged T4 temper. After solution treatment and quenching the sheet gets a short, low-temperature treatment that forms stable clusters. These make the sheet age less at room temperature and harden faster in the paint oven, so the panel reaches its target strength in a normal bake cycle.
How much does 6022 gain in the paint bake?
Typically the yield strength rises from roughly 110 – 150 MPa as delivered to around 185 – 235 MPa after a 2 % pre-strain and a bake of about 20 minutes at 170 – 185 °C. The exact gain depends on the pre-ageing practice, the strain in the part and the oven profile.
What is the difference between 6022 and 6016?
Both are low-copper Al-Mg-Si body sheet alloys. 6022 has higher silicon and a little copper, giving a stronger bake response; 6016 is the long-standing European outer-panel alloy and is often chosen for very tight flat hems. Many OEMs approve both for closures.
Does 6022 sheet have a shelf life?
Yes. T4-type sheet keeps ageing slowly at room temperature, which raises yield strength and reduces formability. Specifications usually define a period from solution treatment within which coils should be formed, and coils should be stored cool and dry.
Can 6022 be spot welded?
It can, but aluminium needs much higher current than steel and frequent electrode dressing. Most aluminium closures are joined by hemming with adhesive, self-pierce riveting or clinching instead.
Do you supply 6022 sheet outside India?
Yes. Metline supplies automotive sheet worldwide from Mumbai, with mill certificates, protective export packing and EXW, FOB, CIF or DAP terms.
Sourcing 6022 sheet for closures?
Send the OEM specification, gauge, width, surface and volume. Our team will confirm feasibility, test data and delivered terms.
