What is 4000 series aluminum?
4000 series aluminum (the 4xxx wrought series) are Al-Si alloys where silicon is the main addition. Silicon lowers the melting range, improves fluidity, and boosts wear and corrosion resistance. That’s why many 4xxx grades are favored as welding filler and brazing cladding/sheet. Some grades (with Mg) can be heat-treated for higher strength; most are non-heat-treatable but respond well to work-hardening.
Closely related are the 4xx.x cast Al-Si alloys (note the decimal). These are the aluminum–silicon casting families used for permanent-mold, sand, and high-pressure die casting (HPDC). Think of them as the casting “mirror” to the 4xxx wrought series: still Al-Si, but named with a decimal.
What makes 4000 series aluminum different?
- Lower melting range and excellent fluidity → ideal for brazing sheet, cladding, and welding fillers that wet and flow cleanly.
- Better wear and galling resistance than pure Al or low-Si alloys → suitable for moving/abrasive interfaces (e.g., pistons with 4032).
- Good corrosion resistance in many atmospheres.
- High thermal conductivity → useful for heat exchangers and thermal management.
- Color/match in welding → Si filler (4043, 4047) reduces hot cracking and produces smooth beads.
- Strength range → mostly moderate; select heat-treatable grades (e.g., 4032) when you need higher strength plus wear resistance.
Quick map: wrought 4xxx vs cast 4xx.x
- Wrought 4xxx (no decimal) → rod, wire, sheet, strip, extrusions; heavily used as welding filler and brazing clad.
- Cast 4xx.x (with decimal) → die castings and other castings where fluidity, thin-wall fill, and pressure-tightness matter.
Which 4000 series wrought alloys are most common?
4043 aluminum (filler wire, cladding)
- Typical chemistry: ~5% Si (low Mg)
- Why choose it: Industry-standard welding filler for 6xxx/3xx.x castings; low hot-crack tendency, smooth bead, good flow.
- Where used: Structural welding of 6xxx extrusions, repair of castings, brazing cladding on heat-exchanger sheet.
4047 aluminum (filler and brazing, very fluid)
- Typical chemistry: ~12% Si
- Why choose it: Lower melt, outstanding wetting/flow vs 4043, excellent for brazing and crack-sensitive joints.
- Where used: Heat-exchanger cores, tight-tolerance brazed structures, sealing rings.
4032 aluminum (heat-treatable, wear-resistant)
- Typical chemistry: ~12% Si with ~1% Mg (plus Ni/Cu traces in many specs)
- Why choose it: Can be T6/T7 strengthened; low expansion, good scuff resistance → pistons, sliding parts.
- Where used: Automotive pistons, compressor components, high-wear bushings and sleeves.
4045 and 4343 aluminum (brazing clad sheet)
- Why choose them: Controlled melting ranges tailored for controlled-atmosphere brazing (CAB) of heat-exchanger fin/tube/plate.
- Where used: HVAC/R coils, charge-air coolers, radiators, battery thermal plates.
(Other 4xxx wrought fillers exist—4145, 4643, etc.—optimized for specific base alloys or brazing cycles.)
4000 Series Aluminum and Die Casting
4xxx wrought = Al–Si sheet/extrusions for welding/brazing; what we actually die-cast are 4xx.x Al–Si casting alloys (e.g., A380/ADC12, AlSi10Mg, 413) with excellent fluidity for thin walls and complex ribs.
Notes
- A380/ADC12 (Al–Si–Cu): best all-round castability, thin-wall fill, good cosmetics after powder/paint; cost-effective for housings and brackets.
- AlSi10Mg (A360/356 family): supports T6 heat treatment; better toughness and machinability for structural castings.
- Wrought 4xxx (4043/4047/4032, etc.) ≠ cast 4xx.x families—different compositions and behavior.
Wrought → Cast Substitutes (practical)
| Wrought intent | Castable substitute | Why / when |
|---|---|---|
| 4xxx sheet “thermal cover / fins” | A380 / ADC12 | Superior fluidity for thin ribs and fins; economical |
| 4xxx parts needing strength & machining | AlSi10Mg (T6) | Higher as-cast strength + post-machining stability |
| Decorative, anodized-look face | A380 + powder/e-coat | Consistent color/texture with durable coating |
Need thin-wall, complex Al–Si die castings (A380/ADC12, AlSi10Mg)? We handle DFM, tooling, casting, CNC, and finishing in-house.
4000 series properties that drive selection
- Joining and brazing: Lower melting plus excellent wetting enable robust brazed cores and low-crack-risk welds.
- Wear and heat: Elevated Si improves abrasion resistance and maintains properties at temperature better than pure Al.
- Thermal management: High k supports heat spreaders, fins, plates.
- Corrosion: Generally good—especially when chloride exposure is controlled and proper finishing is used.
- Strength: Moderate in brazing/filler grades; 4032 and selected cast Al-Si can be heat-treated for higher strength.
Typical applications and components
Welding and repair
- 4043/4047 filler wire/rod for 6061/6063/6082 frames and structures
- Repair of casting porosity, cosmetic blend-outs on housings and covers
Brazed heat-exchangers and thermal plates
- 4045/4343 brazing clad sheet for HVAC coils, charge-air coolers, battery cold plates, inverter coolers
Wear-resistant moving parts
- 4032 pistons, compressor shoes, sliding pads, small bushings
Die-cast housings
- 413.0 (4xx.x) instrument housings, lighting bodies, pump covers where fluidity and surface are critical
At-a-glance selection table
| Use case | Best-fit 4xxx choice | Why it fits |
|---|---|---|
| General welding of 6xxx | 4043 | Low hot-cracking, smooth bead, easy to source |
| Crack-sensitive joints or tight gaps | 4047 | Higher Si → lower melt, superior wetting and flow |
| Brazed heat-exchanger sheet | 4045 / 4343 | Controlled melt range for CAB brazing, stable fillets |
| Wear + moderate strength | 4032-T6/T7 | Heat-treatable, low expansion, good scuff resistance |
| Thin-wall die casting requiring flow | 413.0 (4xx.x) | Very fluid Al-Si casting alloy for complex ribs/slots |
Finishes that pair well with 4xxx
- Anodizing: Produces gray to dark charcoal on high-Si surfaces; great for functional or stealth aesthetics.
- Conversion coatings + powder coat: Common for cast housings and welded assemblies.
- Impregnation (castings): Improves pressure-tightness for 413.0 parts used with fluids.
FAQs
Is 4000 series aluminum heat-treatable?
Most 4xxx wrought fillers/clads are non-heat-treatable; 4032 is the common exception and can be T6/T7. Cast 4xx.x Al-Si families are typically heat-treatable (T5/T6) depending on Mg/Cu content and casting process.
4043 or 4047—how do I choose?
Pick 4043 for standard 6xxx welding with low crack risk and good bead look. Use 4047 when you need more flow, tighter capillaries, or higher crack resistance (e.g., brazing-like joints).
Can I die-cast with 4xx.x and then weld with 4xxx filler?
Yes. That’s a common workflow: 4xx.x cast part + 4043/4047 weld repair for cosmetics or leak-fixes, followed by finishing.
Casting notes for engineers
- Fill and gating: Al-Si alloys like 413.0 offer excellent filling of thin ribs and fine textures—design gates accordingly to avoid erosion.
- Porosity control: Vacuum/venting and shot profiles remain critical; plan for impregnation if pressure-tightness is mandatory.
- Heat treatment: Check Mg content; some Al-Si cast alloys respond well to T6, improving strength without sacrificing too much ductility.
- Finishing color: Expect gray/dark anodize on high-Si surfaces—confirm appearance samples early.
Need custom aluminum die cast parts or welded/brazed assemblies?
We specialize in custom aluminum die-cast components (HPDC) backed by CNC machining, surface finishing, and assembly. If your design targets thin-wall flow, clean surfaces, or brazed thermal cores, our engineers can recommend the right 4xx.x casting and 4xxx filler/clad to hit cost, performance, and lead-time targets.
Tell us your drawing and annual volume—get DFM feedback and a fast quotation.
