What Is 4047 Aluminum?
4047 is an aluminum-silicon brazing filler alloy with 11–13% silicon content — not a structural wrought grade. Its defining feature is high fluidity at brazing temperatures and a narrow freezing range that resists hot cracking. It is primarily used as filler wire, foil, or clad layer in brazing sheet for joining aluminum components, especially in automotive heat exchangers, HVAC systems, and refrigeration.
Химический состав
The high silicon content drives the physical behavior — low melting point, narrow solidification range, and excellent capillary flow into tight joints:
- Silicon: 11.0–13.0%
- Iron: ≤0.8%
- Copper: ≤0.3%
- Manganese: ≤0.15%
- Magnesium: ≤0.1%
- Zinc: ≤0.2%
- Balance: Aluminum
Основные свойства
Brazing Performance
The high silicon content lowers the melting point to approximately 577–582°C, making 4047 the standard filler for torch and furnace brazing of aluminum. The near-eutectic composition produces a narrow freezing range of only a few degrees — the liquid solidifies quickly and uniformly, reducing hot-cracking risk in the joint.
Fluidity and Joint Penetration
At brazing temperature, 4047 flows like thin oil — it wicks into capillary gaps well below 0.1 mm. This makes it suitable for tight-tolerance assemblies such as radiator cores, condenser tubes, and intercooler plates where filler penetration governs joint integrity and leak-tightness.
Strength of Brazed Joints
The as-brazed joint strength depends on the base metal, joint design, and brazing cycle. With proper surface preparation and controlled atmosphere (vacuum or inert gas), 4047 produces joints that are generally stronger than the filler metal itself because the thin capillary gap constrains the filler under the base metal’s mechanical load.
Устойчивость к коррозии
4047 provides moderate corrosion resistance — adequate for automotive coolant, HVAC refrigerant, and indoor environments. It is not rated for direct saltwater exposure or strong chemical contact. The high silicon content makes the filler more cathodic than pure aluminum, so galvanic pairing with some base metals should be checked in wet service.
4047 vs. Other Filler Alloys
4047 vs. 4043
4043 contains 4.5–6.0% silicon — the standard general-purpose aluminum brazing filler. 4047, with roughly double the silicon, offers better fluidity, lower melting point, and narrower freezing range — making it the preferred choice for thin-gap brazing and leak-tight assemblies. 4043 is the more common, lower-cost option for general brazing work where joint gaps are wider and leakage tolerance is higher.
4047 vs. 5356
5356 is an aluminum-magnesium filler (4.5–5.5% Mg) designed primarily for welding 5xxx-series base metals. It is not a brazing filler — 5356 melts at a higher temperature and does not have the fluidity or capillary action of a silicon-rich filler. 4047 is the dedicated brazing choice; 5356 is the dedicated 5xxx welding choice.
4047 vs. 6061 (Base Metal)
This is not a filler-to-filler comparison — 6061 is a structural wrought alloy, not a filler metal. 4047 is one of the common fillers used to braze 6061 components. The choice sequence is: select 6061 for the structural parts, then select 4047 for the brazing joint.
Go/No-Go Limits
Use this quick reference to decide whether 4047 is the right filler alloy.
Go — use 4047 when:
- Tight-gap brazing of aluminum components (joint gap below 0.1mm) is required with leak-tightness as a specification requirement — 4047’s high fluidity and narrow freezing range produce reliable capillary penetration. Typical applications: automotive radiators, condensers, evaporators, intercoolers.
- Furnace or torch brazing under controlled atmosphere (vacuum or inert gas) is the joining method — 4047 is compatible with controlled-atmosphere brazing (CAB) and vacuum brazing processes.
- The base metal is 3003, 6061, or similar wrought alloy and the brazing cycle can remain below the base metal’s solidus temperature — 4047 melts at 577–582°C, giving a safe process window below most алюминиевый сплав solidus points.
No-Go — do not use 4047 when:
- The joint requires fusion welding (TIG or MIG) — 4047 is a brazing filler, not a welding filler; select 4043 or 5356 for welding depending on the base metal.
- Joint gaps exceed 0.2 mm — the high fluidity of 4047 can cause filler to drain out of wide gaps before solidification; 4043 or a pre-placed filler ring is more suitable.
- Post-braze anodizing or cosmetic finishing is required on the joint area — the high silicon content creates a dark, non-uniform anodized finish.
- The base metal is a 7000-series alloy sensitive to liquation cracking at brazing temperature — verify base metal compatibility before selecting the filler.
Приложения
The Go/No-Go criteria above cover selection logic. The list below maps specific systems where 4047 is standard practice:
- Automotive — radiator cores, heater cores, charge-air coolers, air-conditioning condensers and evaporators
- HVAC — aluminum heat exchanger coils, refrigerant circuit joints
- Refrigeration — evaporator and condenser plate assemblies
- Aerospace — aluminum heat exchangers, fuel-cooled oil coolers, environmental control system heat exchangers
Заключение
4047 aluminum is not a structural alloy — it is a dedicated brazing filler whose 11–13% silicon content gives it the fluidity and narrow freezing range that make tight-gap, leak-tight aluminum joints possible. The main trade-off is that it works only in the brazing context; welding, anodizing, and wide-gap applications need a different filler.
Linsy Aluminum supplies 4047 in wire, rod, and foil forms, with custom diameter and coil specifications available at low minimum order quantities. Full MTC documentation and composition certification are standard for every order. If the project requires a specific filler form or diameter, send the specification for a technical review.
Часто задаваемые вопросы
What is the difference between 4047 and 4043 filler?
4047 has roughly double the silicon content (11–13% vs. 4.5–6.0%), which gives it better fluidity, a lower melting point, and a narrower freezing range. 4043 is the economical general-purpose choice for wider joint gaps; 4047 is selected when tight-gap capillary penetration and leak-tightness are the critical requirements.
Can 4047 be used for TIG or MIG welding?
No — 4047 is a brazing filler, not a welding filler. For aluminum TIG or MIG welding, select 4043 (for 6xxx base metals) or 5356 (for 5xxx base metals) based on the parent alloy and required weld properties.
What temperature is required to braze with 4047?
4047 melts at approximately 577–582°C depending on the exact composition. The brazing cycle should reach 590–610°C to ensure full filler flow, while keeping the peak temperature below the solidus of the base metal. Controlled-atmosphere or vacuum brazing is standard for production-quality joints.
Does 4047 leave a visible residue after brazing?
The high silicon content produces a slightly darker post-braze appearance than lower-silicon fillers like 4043. This is cosmetic and does not affect joint strength or leak-tightness. If the joint area will be anodized, the silicon-rich surface will produce a non-uniform finish.
What forms is 4047 available in?
Common forms include brazing wire (spooled or cut lengths), rod, foil strips, and as the clad layer in multilayer brazing sheet. Custom diameter and coil weight specifications are typically available — confirm the required form and quantity with the supplier before ordering.
