Aluminum 3A30: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

3A30 is a member of the 3xxx series of aluminum alloys, classically grouped as Al‑Mn alloys where manganese is the principal alloying addition. The 3xxx family is non-heat‑treatable and gains strength primarily through strain hardening (work hardening) and microalloying effects rather than precipitation hardening. Typical commercial designations for similar chemistries include AA‑3003 and related regional grades; 3A30 falls into this same engineering niche.

The dominant alloying element in 3A30 is manganese (Mn), supplemented by controlled amounts of silicon (Si), iron (Fe), copper (Cu), magnesium (Mg), and trace elements such as titanium (Ti) and chromium (Cr). These additions refine the grain structure, hinder dislocation movement, and contribute to modest solid solution strengthening while preserving excellent ductility and corrosion resistance. As a result, 3A30 offers a balance of formability and moderate strength with superior resistance to atmospheric and general corrosive environments compared with many higher‑strength alloys.

Typical applications for 3A30 include architectural panels, HVAC components, chemical handling equipment, and consumer goods where good formability, weldability, and corrosion resistance are prioritized over maximum strength. Engineers choose 3A30 where complex forming or deep drawing is required and where the cost benefits of an Al‑Mn alloy are attractive relative to higher‑cost heat‑treatable alloys. The alloy is frequently selected instead of purer commercial aluminum when designers need improved mechanical properties without losing the ease of fabrication associated with softer tempers.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, maximum ductility for forming
H14	Medium	Moderate	Very Good	Very Good	Strain‑hardened and partially annealed; common for sheet uses
H18	Medium‑High	Lower	Good	Good	Heavier strain hardening for higher strength in thin sections
H24	Medium	Moderate	Very Good	Very Good	Stabilized, with partial re‑anneal after strain hardening
T4 / T6 / T651	Not applicable/Low benefit	N/A	N/A	N/A	3xxx series are non‑heat‑treatable; T‑tempers not effective

Temper has a direct effect on manufacturing performance and in‑service behavior of 3A30. The annealed O‑condition is used for maximum drawability and deep forming, whereas the H‑series tempers are selected to balance higher yield and tensile strength with still‑acceptable formability for stamping and moderate presswork.

Work‑hardening (H‑tempers) raises yield and tensile values at the expense of elongation and some bendability; selecting the correct temper involves matching forming steps to the final mechanical property targets. Weldability generally remains good across tempers, but H‑tempers will show a slightly reduced ductility in the weld heat‑affected zone compared with O‑temper.

Chemical Composition

Element	% Range	Notes
Si	0.05–0.60	Controlled to limit casting defects and influence strength slightly
Fe	0.20–0.70	Typical impurity from melting; affects grain structure and strength
Mn	0.60–1.50	Principal alloying element providing solid solution and dispersion strengthening
Mg	0.01–0.20	Low levels for corrosion resistance; larger amounts move alloy toward 5xxx behavior
Cu	0.02–0.20	Small additions can increase strength but reduce corrosion resistance
Zn	0.02–0.15	Kept low to avoid susceptibility to stress corrosion
Cr	0.02–0.10	Trace amounts assist in grain structure control and recrystallization control
Ti	0.02–0.15	Added as grain refiner during casting and rolling processes
Others (each)	Balance / impurities	Remainder aluminium with strict limits on other impurities

The composition window of 3A30 is tuned to maximize the beneficial effects of manganese while keeping copper, zinc, and magnesium low enough to preserve corrosion performance and formability. Manganese forms fine dispersoids that inhibit recrystallization and provide strengthening without the need for precipitation heat treatments. Trace elements such as Ti and Cr act as grain refiners and inhibitors to control microstructure during thermomechanical processing, improving formability and surface quality.

Mechanical Properties

The tensile behavior of 3A30 is characteristic of strain‑hardenable aluminum alloys: annealed material exhibits low yield and moderate tensile strength with high elongation, whereas H‑tempers show increased yield and tensile strength with reduced ductility. Yield strength is sensitive to thickness and temper — thin sheet in H14 condition can achieve substantially higher yield values than thick plate in O‑condition due to more effective work hardening during cold rolling. The alloy displays a relatively flat strain‑hardening curve compared with purer aluminum, providing predictable springback behavior for forming operations.

Elongation in the O condition typically exceeds 20–30% in thin gauges, enabling deep drawing and complex stamping. Hardness tracks temper and processing history, with Brinell or Vickers hardness increasing as H‑tempers are applied; however, hardness levels remain moderate compared with heat‑treatable 6xxx or 7xxx series alloys. Fatigue performance is adequate for cyclic structural components at moderate stress amplitudes, but designers should account for notch sensitivity and surface finish effects on life.

Thickness has a marked effect on both strength and formability: as gauge decreases, achievable cold work strengthening increases and formability can be maintained in thinner H‑tempers. Welding and localized heating during fabrication will produce a softened HAZ that reduces yield locally; correct temper selection and post‑weld processing can mitigate this effect in critical components.

Property	O/Annealed	Key Temper (H14)	Notes
Tensile Strength (MPa)	100–150	180–230	Range depends on thickness and exact alloy batch
Yield Strength (MPa)	30–70	120–160	H‑tempers increase yield significantly via strain hardening
Elongation (%)	20–35	6–18	Thinner gauges show higher elongation in both tempers
Hardness (HB)	25–40	45–70	Hardness correlates with temper and cold work level

Physical Properties

Property	Value	Notes
Density	~2.70–2.73 g/cm³	Typical for commercial Al‑Mn alloys, slightly lower than steel
Melting Range	~645–665 °C	Solidus/liquidus depend slightly on alloying elements
Thermal Conductivity	~120–160 W/m·K	Lower than pure Al but high enough for many thermal management uses
Electrical Conductivity	~28–40 % IACS	Reduced relative to pure Al due to alloying; adequate for some conductors
Specific Heat	~880–910 J/kg·K	Typical of aluminum alloys at ambient temperature
Thermal Expansion	~23.0–24.5 µm/m·K	Moderate expansion coefficient for structural design

3A30 preserves many of aluminum’s favorable physical traits: low density yields good specific strength, and thermal/electrical conductivities remain usable for heat dissipation and lightweight conductor duties. The thermal conductivity reduction relative to 1000‑series Al is a trade‑off for increased mechanical robustness; designers needing maximum conductivity may choose purer alloys.

The melting range and solidification characteristics affect casting and joining practices; relatively narrow melting intervals simplify brazing and fusion welding control. The coefficient of thermal expansion is close to other Al‑Mn alloys, which must be considered when joining to dissimilar materials to avoid thermal stress.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Excellent formability in O; higher strength in H‑tempers	O, H14, H24	Widely produced for panels, cladding, and automotive inner parts
Plate	6–50 mm	Lower available cold work; typically supplied in O	O	Plate is used where thickness is needed but deep drawing is not required
Extrusion	up to large cross‑sections	Strength varies with section and work hardening	O, H18	Extrusions used for architectural profiles and heat‑dissipating shapes
Tube	OD small to 200 mm	Strength depends on wall thickness and temper	O, H14	Common for HVAC tubing and structural tubing
Bar/Rod	Diameters to 200 mm	Limited cold work hardening in thick sections	O, H14	Machined components and fasteners for light structural use

Forming routes differ markedly between products: sheet and thin strip are often cold‑worked to achieve H‑tempers after rolling, while thicker plate and bar may remain in the annealed condition due to limited cold working efficiency. Extrusions require careful control of billet temper and die design to balance surface finish, dimensional tolerance, and final mechanical behavior.

Welding and joining practices are influenced by form factor; for thin sheet, resistance spot welding and MIG/TIG are common, while larger extrusions and tubes may use orbitals or brazing depending on design requirements. Availability and cost are generally favorable for sheet and coil, with specialized sizes requiring lead times for custom production.

Equivalent Grades

Standard	Grade	Region	Notes
AA	3A30	USA	Commercial designation aligned with 3xxx family characteristics
EN AW	3003	Europe	Closest common European equivalent in chemistry and properties
JIS	A3003	Japan	Similar Mn‑bearing alloy used for general fabrication
GB/T	3A30	China	Local designation often chemically similar to AA‑3003 family

Equivalent grades listed above represent closest matches rather than exact one‑to‑one replacements; different standards specify slightly different impurity limits, maximum element contents, and mechanical property test methods. Procurement engineers should review specific standard certificates and mill test reports to verify trace element limits and guaranteed mechanical properties. In critical applications, trial coupons and weld tests are advised to confirm that the chosen regional equivalent exhibits the expected forming, joining, and corrosion behavior.

Corrosion Resistance

3A30 offers good atmospheric corrosion resistance due to its low levels of aggressive alloying elements like Cu and Zn and the passivating nature of aluminum oxide. In rural and urban atmospheres it performs comparably to other 3xxx series alloys, resisting pitting and general corrosion for long service life when properly detailed and coated. The alloy is often specified for building facades, roofing, and cladding where exposure to rain and humidity is routine.

In marine environments, 3A30 has reasonable resistance to salt spray compared with Al‑Mg alloys but is not as inherently resistant as specialized marine grades (5xxx series with higher Mg). Localized corrosion may occur in crevices and at dissimilar‑metal joints when galvanic couples are present; designers should avoid coupling 3A30 directly to noble metals or mitigate with insulating barriers. Stress corrosion cracking susceptibility is low relative to high‑strength heat‑treatable alloys, but anodic dissolution in aggressive chloride environments can still occur under tensile stress and must be considered for structural parts.

Galvanic interactions are moderate: 3A30 will generally be anodic relative to stainless steels and cathodic relative to more active metals; proper fastener selection and isolation materials reduce galvanic currents. Compared with 1xxx series (commercially pure aluminum), 3A30 trades slightly reduced electrical conductivity for improved mechanical strength without significant sacrifice of corrosion performance, making it a good multi‑purpose choice for exterior and mildly corrosive environments.

Fabrication Properties

Weldability

3A30 welds readily using common fusion processes such as MIG (GMAW) and TIG (GTAW), producing ductile welds with minimal hot‑cracking tendency. Filler alloys in the similarly alloyed 3xxx range or 4xxx Al‑Si series are commonly used to match mechanical properties and flow characteristics; using 4xxx fillers can improve bead wetting for lap joints. Heat‑affected zones in H‑tempers will experience softening due to local annealing; designers should account for reduced strength adjacent to weld seams in load‑bearing components.

Machinability

Machining 3A30 is moderate compared with wrought Al alloys; in the annealed condition it machines cleanly with good surface finish, while harder H‑tempers can increase tool wear slightly. Carbide tooling with positive rake geometry is preferred for higher cutting speeds and to manage chip evacuation, and cutting fluids enhance finish and reduce built‑up edge. Typical machinability indices place Al‑Mn alloys below free‑cutting 6xxx/7xxx alloys but above pure aluminum in terms of conventional machining productivity.

Formability

Formability is one of 3A30’s strengths: O‑temper exhibits excellent deep drawing and stretch‑forming capability, and H‑tempers retain good bendability for many stamping operations. Recommended minimum bend radii depend on temper and thickness but are typically in the range of 1–3× material thickness for H‑tempers and 0.5–1.5× thickness for O‑temper in typical sheet gauges. Springback should be considered in die design; strain‑hardened tempers produce more springback than annealed material and may require compensation in tooling.

Heat Treatment Behavior

As a non‑heat‑treatable alloy, 3A30 does not respond to solution treatment and artificial aging the way precipitation‑hardenable 6xxx or 7xxx alloys do. Attempts at traditional T‑type aging provide minimal additional strengthening; therefore, property tailoring is achieved primarily via mechanical deformation, controlled rolling, and stabilizing anneals. Thermal exposures above moderate temperatures will cause recovery and recrystallization, reducing cold‑work strengthening and softening the material.

Industrial heat‑treatment practices for 3A30 focus on annealing cycles to restore ductility or stabilize properties: a full anneal (O) at temperatures in the range of ~350–415 °C followed by controlled cooling produces the maximum soft condition. For work‑hardened H‑tempers, partial anneals (H2x/H3x variations) may be used to balance strength and formability or to relieve residual stresses after forming operations. Post‑weld heat treatments are generally not used to recover strength in the HAZ; instead, design allowances account for localized softening.

High-Temperature Performance

Service temperatures for 3A30 are typically limited to below ~150–200 °C for long‑term applications to avoid loss of strength and accelerated recovery. At elevated temperatures, the strain‑hardened microstructure will relax, reducing yield and tensile strength and potentially increasing creep deformation under sustained load. Oxidation is limited to the formation of a thin alumina film, but at high temperatures scaling and oxide growth can affect surface finish and subsequent finishing operations.

Welded joints exposed to elevated service temperatures may show greater softening in the HAZ, and post‑weld mechanical properties should be evaluated for critical applications involving heat or cyclic thermal loading. For short‑term or intermittent exposures to higher temperatures, 3A30 retains most of its integrity, but designers should consider alternative alloys if sustained high‑temperature strength is required.

Applications

Industry	Example Component	Why 3A30 Is Used
Automotive	Interior panels, heat shields	Good formability and corrosion resistance at lower cost
Marine	Non‑structural enclosures, ducting	Corrosion resistance in atmospheric and mild marine environments
Aerospace	Fairings, interior brackets	Favorable strength‑to‑weight and excellent formability for complex shapes
Electronics	Chassis, heat spreaders	Adequate thermal conductivity with good manufacturability

3A30 finds broad use wherever a combination of good formability, corrosion resistance, and moderate strength is required in a lightweight material. Its balance of properties makes it particularly attractive for formed panels, enclosures, and components that require complex shaping without the expense or fabrication limits of higher‑strength heat‑treatable alloys.

Selection Insights

When selecting 3A30, prioritize applications that require excellent formability, good weldability, and moderate strength with strong corrosion resistance. Choose O‑temper for deep drawing and complex shapes, and H‑tempers for stamped parts where higher yield is needed without sacrificing too much ductility. Cost and wide availability of sheet and coil are additional practical advantages for production.

Compared with commercially pure aluminum (e.g., 1100), 3A30 trades some electrical and thermal conductivity for significantly higher strength and better wear and dent resistance while maintaining comparable formability. Compared with work‑hardened alloys such as 3003 or 5052, 3A30 sits within the same practical envelope; it typically offers a good corrosion/strength balance, being stronger than 1100 and often comparable to 3003 while not quite matching the corrosion resistance of high‑Mg 5052. Compared with heat‑treatable alloys (e.g., 6061, 6063), 3A30 provides superior formability and often better corrosion resistance at similar or lower cost, making it preferable for complex formed parts even though peak achievable strength is lower.

Select 3A30 when manufacturing routes emphasize forming and welding over high‑temperature strength or maximum tensile targets, and verify temper, finish, and supplier certifications for critical structural or marine uses. Use short qualification tests (formability trials, weld coupons, corrosion soak tests) to confirm that the chosen temper and supplier produce the expected in‑service performance.

Closing Summary

3A30 remains a practical and versatile aluminum alloy for engineers seeking a balance between formability, corrosion resistance, and moderate mechanical strength in a cost‑effective package. Its predictable strain‑hardening behavior, good joining characteristics, and broad product availability make it a mainstay for architectural, automotive, marine, and general fabrication applications where complex forming and long service life are required.