Aluminum 4N30: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

4N30 is a member of the 4xxx-series aluminum alloys, a family characterized by silicon as the principal alloying element. It sits within the Al-Si grouping used primarily for welding wire, brazing alloys, and wrought products where improved fluidity, wear resistance, or controlled melting behavior are required.

The major alloying constituent is silicon in the mid single-digit percent range, with residual levels of iron, manganese and traces of titanium and chromium introduced for grain control and inclusion modification. Strengthening in 4N30 is predominantly achieved through solid-solution effects and strain hardening rather than classical precipitation hardening; the low Si content does not create the strong age-hardening response seen in Mg-Si (6xxx) alloys.

Key traits of 4N30 include moderate strength, good thermal conductivity relative to many other alloys, and reliable weldability with low susceptibility to hot cracking when properly processed. Corrosion resistance is typical for Al-Si alloys — generally good in atmospheric environments but requiring design care in chloride-rich marine service and in galvanic couples with cathodic metals.

Typical industries using 4N30 include automotive for filler and joining applications, general fabrication for welded and brazed assemblies, electrical components where thermal conductivity is desirable, and some consumer goods for extruded or formed parts. Engineers select 4N30 when a balance of weldability, moderate strength and formability is needed, or when the Si chemistry provides improved molten metal behavior for joining or casting-adjacent processes.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for maximum ductility
H12	Moderate	Moderate	Good	Excellent	Lightly cold-worked, increased yield
H14	Moderate-High	Low-Moderate	Fair	Excellent	Quarter-hard cold work, common for structural sheet
H18	High	Low	Limited	Excellent	Full hard cold work for highest practical strength
T451 / T4 (if applied)	Moderate	Moderate	Good	Excellent	Stress-relieved after solution / limited artificial aging (rare for 4xxx)

Temper selection strongly affects yield and elongation because 4N30 gains most of its strength via work hardening. Cold working (H‑tempers) raises yield and tensile values while reducing ductility and formability, making H14/H18 common for structural sheet where higher strength is required.

The annealed O temper maximizes formability for deep drawing and complex bending operations and is typically used where subsequent welding or forming operations demand high ductility and minimal springback.

Chemical Composition

Element	% Range	Notes
Si	2.5–4.0	Primary alloying element; controls fluidity and reduces melting range
Fe	0.2–0.8	Impurity element; forms intermetallics that affect ductility and machinability
Mn	0.1–0.5	Grain structure modifier; improves strength and resistance to localized corrosion
Mg	0.05–0.3	Minor; can promote some precipitation effects if present at upper levels
Cu	≤0.10	Kept low to preserve corrosion resistance; higher levels increase strength but reduce SCC resistance
Zn	≤0.15	Minor residual; higher Zn not typical in 4xxx family
Cr	≤0.05	Grain refiner and dispersoid former in trace amounts
Ti	≤0.15	Used for grain refinement in castings and extrusions
Others	Balance Al / Residuals	Includes trace elements such as Sr, Zr in controlled processing grades

Silicon is the dominant performance driver in 4N30: it lowers melting range slightly and improves fluidity and wear resistance in contact applications. Iron and manganese control intermetallic morphology; iron tends to form brittle phases while manganese can beneficially modify their shape. Trace elements like titanium and chromium are used to refine grain size and improve mechanical uniformity after thermal or mechanical processing.

Mechanical Properties

Tensile behavior of 4N30 is characterized by a moderate ultimate tensile strength with a relatively low elastic modulus similar to other aluminum alloys. In the annealed condition the alloy exhibits ductile failure modes with substantial uniform elongation, while cold-worked tempers show higher yield strength at the expense of uniform elongation and notch toughness. Fatigue performance reflects the alloy’s microstructural constituents and surface condition; surface finish and residual stresses from forming are primary controls on fatigue life.

Yield and tensile values scale strongly with temper. Annealed (O) material generally exhibits low yield but good elongation, while H‑tempers provide an increase in yield up to two to three times the annealed level. Hardness follows the same trend: annealed material is soft and easily machined or formed, whereas cold worked material achieves higher Brinell or Vickers values useful for wear-limited components.

Thickness effects are important: thick sections may retain cast or as-extruded microstructural heterogeneities and can show reduced ductility and slightly lower strength compared with thin sheet that has been uniformly cold worked. Welding and HAZ regions typically show local softening when substantial cold work is present, and designers must account for HAZ-related strength reductions in joints.

Property	O/Annealed	Key Temper (e.g., H14)	Notes
Tensile Strength	110–140 MPa	200–260 MPa	Values depend on exact Si content and cold-work level
Yield Strength	30–60 MPa	140–200 MPa	Yield rises strongly with cold work; annealed yield is low
Elongation	20–35%	4–12%	High ductility in O; reduced ductility in H‑tempers
Hardness	30–40 HB	60–90 HB	Brinell hardness typical ranges for sheet; varies with processing

Physical Properties

Property	Value	Notes
Density	~2.70 g/cm³	Typical for Al alloys; slight variation with Si content
Melting Range	~610–650 °C	Narrower than high-Si alloys; solidus approaches pure Al with low Si
Thermal Conductivity	140–180 W/m·K	Lower than pure Al; Si and other solutes reduce conductivity
Electrical Conductivity	38–52 %IACS	Alloying reduces conductivity versus pure Al
Specific Heat	~900 J/kg·K	Typical for aluminum alloys at room temperature
Thermal Expansion	22–24 µm/m·K	Linear coefficient near other Al alloys; design for thermal cycling required

The physical properties reflect a trade-off: adding silicon reduces melting point and improves castability but lowers electrical and thermal conductivity relative to pure aluminum. For thermal management applications the alloy still provides good conductivity combined with lower density compared with copper, making it attractive for lightweight heat-dissipating components. Density and expansion coefficients remain close to the 2xx/6xx series, allowing relatively straightforward substitution in many designs.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Uniform through-thickness if cold rolled	O, H12, H14	Widely used for formed parts and welded assemblies
Plate	6–25 mm	May have slight strength gradient	O, H18	Thicker sections require careful control of homogeneity
Extrusion	Wall thickness 1–20 mm; profiles custom	Strength varies with cooling and work	O, T45, H12	Extrusion benefits from Ti or Sr grain refiners
Tube	Diameters 6–300 mm	Good dimensional stability	O, H14	Seamless and welded tubes available
Bar/Rod	Diameters 3–100 mm	Good machinability in softer tempers	O, H12	Cold drawing increases strength for bars

Processing route drives final properties: cold rolling and drawing increase strength and reduce ductility, while annealing or stress-relief restore formability. Extrusions allow complex cross-sections but require grain control to avoid anisotropy; plates and heavy sections are more susceptible to inclusions and require stricter quality control. Product form selection should align with the end-use environment and required joining/fabrication steps.

Equivalent Grades

Standard	Grade	Region	Notes
AA	4N30	USA	Manufacturer and supplier-specific designation within 4xxx family
EN AW	4030 (closest)	Europe	EN AW-4030 is a comparable Al-Si wrought alloy with similar Si levels
JIS	A4043 (comparable filler)	Japan	JIS A4043 is commonly used as an Al-Si filler; base alloy equivalence approximate
GB/T	4N30 (or AlSi3)	China	GB/T nomenclature may list comparable Al-Si wrought grades with close chemistry

Direct one-to-one equivalents are not always available because product specifications, impurity limits, and processing routes vary by region and manufacturer. The EN and JIS grades listed are approximate comparables within the Al-Si family; when substituting, engineers should compare detailed compositional limits, mechanical properties, and certification practices rather than relying solely on grade labels.

Corrosion Resistance

In atmospheric environments 4N30 typically shows good natural oxide protection similar to other aluminum alloys, and low percentages of copper help maintain resistance to general corrosion. Protective behavior is adequate for indoor and rural outdoor exposures, though surface condition, coatings and design details (drainage, crevice avoidance) strongly influence long-term performance.

In marine and chloride-rich environments, 4N30 has moderate resistance but is more vulnerable to localized pitting than highly alloyed 5xxx (Mg) or specially treated 6xxx alloys. Design approaches such as anodizing, cladding, or sacrificial coatings are common where long service life in saltwater is required. Stress corrosion cracking is less common in Al-Si alloys than in high-Cu or high-Mg alloys, but tensile stresses combined with corrosive media can still produce SCC-like failures; residual and applied stresses should be minimized.

Galvanic interactions must be managed: 4N30 is anodic relative to stainless steel and copper but cathodic to some magnesium alloys, so material pairing should avoid creating aggressive galvanic couples in wet environments. Compared with 1xxx series (commercially pure) alloys, 4N30 trades slight reductions in absolute corrosion resistance for higher strength and better weldability; compared with 5xxx series, it typically offers improved weldability but somewhat lower performance in pure chloride exposure.

Fabrication Properties

Weldability
4N30 is generally straightforward to weld with conventional fusion processes such as TIG and MIG, benefitting from silicon’s tendency to reduce hot cracking susceptibility. Filler wires in the Al-Si family (e.g., AlSi5) are commonly used to match chemistry and promote fluid weld pools; for structural joints matching base and filler chemistry optimizes mechanical properties. The HAZ can show localized softening if the parent material was cold worked to increase strength, so post-weld mechanical properties must be examined for critical joints. Preheat is rarely necessary for thin sections, but controlling heat input and using appropriate joint design minimizes distortion and porosity.

Machinability
Machinability of 4N30 in annealed tempers is good compared to harder Al alloys; it machines readily with standard HSS or carbide tooling. Chip behavior is typically continuous and can be controlled via appropriate feed and speed settings; coolants improve tool life and surface finish. The presence of intermetallics and iron-rich particles can cause increased tool wear relative to ultra-pure aluminum, so tool geometry and coatings (TiAlN, TiN) are recommended for production machining.

Formability
Formability in the O temper is excellent for deep drawing and complex bends, with typical minimum bend radii near 1–1.5 times thickness depending on tooling and surface condition. Cold-working (H‑tempers) reduces formability and increases springback; therefore H12/H14 are used only for simpler forming operations or when higher strength immediately after forming is needed. Elevated-temperature forming is feasible for complex shapes, but attention to surface oxidation and tooling lubrication is required to avoid galling.

Heat Treatment Behavior

4N30 is classed as a non-heat-treatable alloy for practical engineering purposes; it does not develop significant age-hardening response through traditional solution and artificial aging cycles. Attempts at solution treatment produce limited strengthening because the alloy lacks the Mg-Si precipitation system that yields high age-hardening in 6xxx alloys.

Strength is primarily developed by cold work: control of rolling, drawing and cold-forming sequences determines final mechanical performance. Standard annealing (softening) cycles are effective to restore ductility: heating into the appropriate annealing range followed by controlled cooling recrystallizes the microstructure and dissolves deformation structures. Where minor heat treatments are applied (e.g., stress relief), care must be taken not to introduce detrimental overaging or coarsening of intermetallics that can reduce ductility.

High-Temperature Performance

4N30 begins to lose significant strength as operating temperature rises above roughly 150–200 °C, with progressive softening at higher temperatures due to recovery and coarsening of solute clusters. Long-term exposure at elevated temperatures can promote microstructural changes that reduce both yield strength and fatigue life, making it less suitable for structural high-temperature applications. Oxidation resistance is typical of aluminum alloys; protective oxide films form rapidly but do not prevent application-specific degradation at high temperatures or in oxidizing environments containing chlorides or sulfur compounds.

Welded joints may exhibit extended HAZ softening at elevated exposures, and designs requiring creep or long-term load-bearing at high temperature should consider heat-resistant aluminum alloys or alternate materials better suited for sustained high-temperature service.

Applications

Industry	Example Component	Why 4N30 Is Used
Automotive	Filler wire, small structural brackets	Good weldability and moderate strength for spot and seam welding
Marine	Non-critical structures, fittings	Adequate corrosion resistance plus formability and weldability
Aerospace	Secondary fittings, clamps	Good strength-to-weight for non-primary structures and ease of fabrication
Electronics	Heat spreaders, housings	Thermal conductivity and low density for thermal management
Consumer Goods	Cookware rims, frames	Formability and surface finish after anodizing

4N30 fills a design niche where a balance of weldability, formability and moderate mechanical performance is required, especially where Si chemistry improves joining or casting-associated operations. Its use is prevalent where cost, ease of fabrication and adequate corrosion resistance supersede the need for the highest possible strength.

Selection Insights

Select 4N30 when your design requires reliable weldability, good formability in the annealed state, and moderate strength with favorable thermal conductivity. It is particularly appropriate for welded assemblies, extrusions, and components where Si-related fluidity or melting behavior is helpful for joining or casting-adjacent workflows.

Compared with commercially pure aluminum (1100), 4N30 offers higher strength and improved wear and weld pool behavior while trading some electrical and thermal conductivity and very-high ductility. Compared with common work-hardened alloys such as 3003 or 5052, 4N30 typically provides comparable or slightly higher weldability and similar formability, with strength levels sitting between 1xxx and 5xxx families depending on temper. Compared with heat-treatable alloys like 6061/6063, 4N30 is chosen when superior weldability and formability are prioritized over peak age-hardened strength, or where lower alloying levels and different melting characteristics are advantageous.

Closing Summary

4N30 remains a practical engineering alloy where a combination of good weldability, moderate strength, and formability is required alongside acceptable corrosion resistance and thermal performance. Its placement in the Al-Si family makes it a versatile choice for fabricated and joined components across automotive, marine, and general manufacturing applications where balanced properties and reliable processing are key.