Aluminum 3303: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

3303 is a member of the 3xxx-series aluminum alloys, defined by manganese as the principal alloying addition to commercially pure aluminum. As a 3xxx-series alloy it is non-heat-treatable and its primary strengthening mechanism is work hardening achieved through cold deformation and controlled tempering operations rather than precipitation hardening. Major alloying elements include manganese (which controls strain-hardening response and grain structure) with smaller amounts of iron, silicon and trace copper and chromium that tune strength, formability and corrosion behavior.

Key traits of 3303 are moderate tensile strength combined with excellent ductility and good corrosion resistance for many atmospheric and mildly corrosive environments. The alloy offers good weldability with conventional fusion welding methods and excellent formability in annealed tempers, making it well-suited for sheet metal fabrication and roll-forming processes. Typical industries include building/architectural facades, HVAC components, beverage and packaging, light structural framing and general sheet metal applications where a balance of formability, corrosion resistance and cost is required.

Engineers select 3303 where improved strength over very-pure alloys (like 1100) is needed without the processing complexity of heat-treatable systems (6xxx/7xxx series). Its performance window is attractive when moderate strength, deep drawability and reliable weldability are primary drivers and when service environments are not highly aggressive (e.g., chloride-rich marine immersion). The alloy is chosen over stronger heat-treatable grades when forming, joining and post-fabrication flexibility are prioritized and when cost/availability constraints favor widely produced Mn-bearing alloys.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition; best for deep drawing and complex forming
H111	Low-Moderate	High-Moderate	Very Good	Very Good	Essentially strain-hardened slightly from O; used for light forming with slight strength increase
H14	Moderate	Moderate-Low	Good	Very Good	Quarter-hard temper from cold work; common for moderate-strength sheet applications
H16	Moderate-High	Low-Moderate	Fair	Very Good	Half-hard temper; used when stiffness and springback control are important
H18	High	Low	Poor-Moderate	Very Good	Full-hard cold-rolled temper; used for maximum as-rolled strength and stiffness
H24 / H26	Moderate-High	Low	Fair	Very Good	Strain-hardened and partially stabilized; used when some thermal stability is needed

Temper has a strong, predictable effect on mechanical and forming performance in 3303 because it is non-heat-treatable and relies on cold work. Moving from O to H18 increases yield and tensile strength substantially while reducing elongation and formability, therefore designers choose the temper to balance forming operations against final part stiffness and strength.

Chemical Composition

Element	% Range	Notes
Al	Balance	Principal element; remainder after alloying additions
Si	≤ 0.6	Impurity that can reduce ductility and slightly increase strength
Fe	≤ 0.7	Common impurity; forms intermetallics that affect toughness and surface finish
Mn	0.8–1.5	Primary strengthening element in 3xxx series; refines grain and improves strain-hardening
Mg	≤ 0.3	Small amounts may slightly increase strength without major loss of formability
Cu	≤ 0.2 (typical)	Trace levels may improve strength but reduce corrosion resistance if elevated
Zn	≤ 0.2	Usually low; higher values not typical for 3xxx family
Cr	≤ 0.1	Trace addition used to control grain growth and improve HAZ stability
Ti	≤ 0.15	Grain refiner in cast or wrought products
Others (each)	≤ 0.05	Includes V, Ni, Sn; kept low to avoid deleterious phases

The alloy’s performance is dominated by manganese which provides solid-solution strengthening and improved work-hardening capability. Iron and silicon are tolerated as common impurities and influence formability and finishing; controlling their levels improves surface quality and reduces the risk of brittle intermetallic particles. Trace additions such as chromium and titanium are used to refine microstructure and stabilize grain growth during thermal cycles and mechanical processing.

Mechanical Properties

3303 exhibits classic non-heat-treatable tensile behavior: relatively low yield in annealed condition with a wide elongation window, and progressively higher yield and tensile values as cold work increases. The alloy is capable of substantial uniform elongation in O temper, making it suitable for deep drawing and incremental forming; in H tempers ductility drops as dislocation density rises and the material work-hardens. Hardness correlates with cold work and is a practical on-line indicator of temper state; hardness increases with H-number and provides better fatigue endurance up to a point before ductility loss accelerates fatigue crack initiation.

Fatigue life is dependent on surface finish, thickness and applied mean stress; polished, annealed sheet will outperform cold-rolled sheet at a given nominal strength due to reduced crack nucleation sites. Thickness effects are significant: thinner gauges are generally stronger in rolled alloys due to greater cold work imparted during rolling and smaller defect populations. Design for fatigue-sensitive components should target temper states and surface treatments that minimize notches, avoid machining burrs, and control residual stresses.

Property	O/Annealed	Key Temper (H14)	Notes
Tensile Strength	100–140 MPa	150–200 MPa	Typical ranges; depends on gauge and cold-work level
Yield Strength	35–70 MPa	110–150 MPa	Yield increases markedly with strain hardening
Elongation	25–40%	6–12%	Elongation drops as temper hardens; O is preferred for forming
Hardness (HB)	30–45	55–80	Brinell ranges approximate; correlates to temper and cold work

Physical Properties

Property	Value	Notes
Density	2.70–2.72 g/cm³	Typical for Al-Mn wrought alloys
Melting Range	~640–650 °C	Solidus/liquidus close to pure Al; localized melting point varies with impurities
Thermal Conductivity	120–160 W/m·K	Lower than pure Al due to alloying; still high compared to steels
Electrical Conductivity	~20–35% IACS	Reduced conductivity compared with pure aluminum; varies with temper
Specific Heat	~900 J/kg·K (0.90 J/g·K)	Typical value used for thermal design and heat capacity calculations
Thermal Expansion	23–24 µm/m·K (20–100 °C)	Reasonably high linear expansion typical of aluminum alloys

3303 combines relatively low density with good thermal conductivity, giving it favorable specific stiffness and thermal management capabilities for non-critical heat-sink applications. Electrical conductivity is attenuated by alloying but remains adequate for some busbar or conductive-sheet roles where mechanical performance is more important than absolute conductivity. The melting and thermal expansion characteristics must be considered for brazing, welding and multi-material assemblies to control distortion and joint integrity.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Strength increases with cold-rolling	O, H111, H14, H16	Widely produced; used for panels, enclosures and formed parts
Plate	>6.0 mm (up to 25 mm)	Lower uniform cold work compared to thin gauges	O, H111	Thicker product may show slightly reduced work-hardening response
Extrusion	Complex profiles up to 200 mm	Strength depends on extrusion ratio and subsequent cold work	O, H14	Less common than 6xxx extrusions but used for lightweight sections
Tube	Ø small to large (seamless/welded)	As-welded or drawn work hardening	O, H14	Used for HVAC and furniture; seamless options have better fatigue properties
Bar/Rod	Ø 3–50 mm	Strength increases with cold drawing	H14, H18	Used for fasteners, formed components and rivets

Cold-rolled sheet versus extrusions and plate differ in both microstructure and achievable work-hardening; sheet production inherently imparts significant rolling strain that is useful for final tempering to H numbers. Extrusion is feasible but less common than for heat-treatable 6xxx alloys because Mn-containing alloys do not age-harden; designers choosing extruded 3303 trade off ultimate strength for ductility and surface finish. Tube and bar forms are typically processed with additional cold work (drawing, straightening) that increases strength while reducing ductility, so selection of temper must follow expected forming and joining steps.

Equivalent Grades

Standard	Grade	Region	Notes
AA	3303	USA	Industry designation for wrought alloy in 3xxx family
EN AW	3303	Europe	Common European designation (EN AW-3303) used in procurement; composition tolerances can vary
JIS	A3303 (approx.)	Japan	Japanese standards may use a different numbering convention but the alloy chemistry is comparable
GB/T	3303 (approx.)	China	Chinese national standards reference similar Al-Mn alloys; exact limits may differ

Equivalency across standards is approximate because regional specifications set different limits for impurities and sometimes different test requirements for mechanical properties and temper nomenclature. Buyers must verify the precise chemical and mechanical limits on supplier certificates and refer to the controlling procurement specification for critical components, especially where corrosion resistance or formability are mission-critical.

Corrosion Resistance

3303 provides good atmospheric corrosion resistance in most inland environments due to a protective aluminum oxide film and the absence of high copper content which can exacerbate pitting. In lightly aggressive marine atmospheres it performs acceptably for above-deck components and architectural elements, but prolonged immersion in chloride-rich seawater will accelerate localized corrosion relative to dedicated marine alloys such as 5xxx-series Al-Mg grades. Surface treatments and coatings (anodizing, paints) significantly extend life, and anodized 3303 offers improved aesthetics and additional barrier protection.

Stress corrosion cracking susceptibility is low compared with certain high-strength heat-treatable alloys because 3303 lacks age-hardenable precipitates that promote SCC; however, residual tensile stresses from forming or welding should still be minimized. Galvanic interactions are significant: 3303 is anodic relative to stainless steel and copper and will preferentially corrode when electrically connected in a conductive electrolyte; isolation strategies and compatible fasteners are recommended in mixed-metal assemblies. Compared to 5xxx and 6xxx families, 3303 trades slightly reduced pitting resistance for improved formability and simpler processing, making it a pragmatic choice where deep draws and weldability are prioritized over ultimate corrosion performance.

Fabrication Properties

Weldability

3303 welds readily with common fusion methods (MIG/GMAW, TIG/GTAW, and resistance welding) and shows low susceptibility to hot cracking when good practices are followed. Recommended filler metals are similar to those used for other Al-Mn alloys (e.g., Al-Mn filler compositions) and aluminum-silicon fillers may be used where fluidity is required; selection must consider corrosion compatibility. Heat-affected-zone softening is modest compared with heat-treatable alloys because the alloy does not rely on precipitation strengthening, but over-heating and excessive grain growth can reduce fatigue resistance and change forming behavior adjacent to welds.

Machinability

As a relatively ductile, soft alloy, 3303 has moderate machinability and tends to produce long, continuous chips under inappropriate cutting conditions. Carbide tooling with positive rake and chip breakers is recommended for turning and milling to control chip formation and reduce built-up edge; lower cutting speeds and adequate coolant prevent galling. Typical machinability index is lower than free-machining aluminum alloys but comparable to general-purpose wrought Al-Mn grades; allowances for tool wear and deflection must be made for thin-walled sections.

Formability

Formability is excellent in the annealed O condition, enabling deep drawing, stretch forming and complex bending with small radii. Minimum bend radii depend on temper and thickness; annealed sheet commonly conforms to R/t ratios well below those required for half- or full-hard tempers. Cold working increases strength but decreases ductility and increases springback; therefore planners should sequence forming before final bake-out or stress-relief and select H-temper only where further forming is limited or not required.

Heat Treatment Behavior

As a non-heat-treatable alloy, 3303 does not respond to solution-treatment and aging to develop additional strength through precipitation hardening. Thermal processing is focused on annealing and stabilization: full anneal cycles typically use temperatures in the vicinity of 370–415 °C followed by slow or fast cooling depending on desired grain size and residual stress profile. After anneal the O temper restores maximum ductility and formability; subsequent cold work moves the material into H tempers where strength is increased by dislocation accumulation.

Stabilization or low-temperature bake cycles can be used to partially relieve work-induced stresses without significant softening when small adjustments to dimensions or mechanical property relaxation are needed. Thermal excursions during fabrication such as welding locally alter temper in the HAZ; because 3303 gains strength primarily from cold work, welded areas in previously cold-worked material will generally be softer unless post-weld mechanical treatment or localized cold working is applied.

High-Temperature Performance

3303 shows progressive strength loss with increasing temperature; significant reduction of yield and tensile strength typically occurs above 150 °C and becomes pronounced past 200 °C. The alloy is not intended for elevated-temperature structural service and will experience softening and creep under sustained loads at high temperature. Oxidation resistance is similar to other aluminum alloys: a stable oxide layer forms quickly, but protective behavior does not prevent mechanical degradation at elevated temperatures.

For welded or heat-exposed components, grain coarsening in the HAZ and loss of work-hardened strength are primary concerns and can affect fatigue life and dimensional stability. Design for intermittent elevated-temperature exposure should apply safety factors and consider alternative alloys (e.g., certain Al-Si or high-temperature alloys) where sustained strength above 150 °C is required.

Applications

Industry	Example Component	Why 3303 Is Used
Automotive	Interior trim and non-structural panels	Good formability and surface finish for stamped parts
Marine	HVAC housings and architectural fittings	Reasonable corrosion resistance and excellent workability
Aerospace	Non-critical fittings, ductwork	Favorable strength-to-weight for secondary structures
Electronics	Heat spreader panels and housings	Good thermal conductivity and ease of fabrication
Packaging / Consumer	Cans, decorative trim	Formability and surface finishing advantages

3303 fills a pragmatic niche for parts that require complex forming, good weldability and respectable corrosion resistance without the expense or processing constraints of heat-treatable alloys. Its balance of properties makes it particularly efficient for high-volume formed components and architectural elements where economy and manufacturability are primary drivers.

Selection Insights

When choosing 3303, favor designs that require deep drawing or extensive forming and where final strength needs are moderate rather than maximized. The alloy is attractive when weldability and post-forming flexibility are important and when procurement simplicity and cost control are considerations.

Compared with commercially pure aluminum (1100), 3303 provides higher strength at modest loss of electrical conductivity and still retains good formability. Compared with common work-hardened alloys such as 3003 and 5052, 3303 typically sits near the middle ground: it offers somewhat higher strength than very-pure grades while maintaining better formability than many Mg-bearing 5xxx alloys; corrosion resistance is good but not as high as top marine-grade Al-Mg alloys. Compared with heat-treatable alloys like 6061 or 6063, 3303 will have lower peak strength but is preferred for complex forming, superior weldability without post-weld aging constraints, and lower processing cost.

Closing Summary

3303 remains a relevant and practical alloy for modern engineering where the combination of formability, weldability and moderate strength is required; its Mn-based chemistry and work-hardening response provide a reliable platform for sheet metal, tube and stamped parts across numerous industries. Its straightforward processing and balanced properties make it a sensible selection for designers prioritizing manufacturability and cost-effective performance.