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ER4043 and ER4047 are both very common aluminum-silicon (4xxx series) welding wires, and their differences, while subtle, are crucial for specific applications.
Here’s a detailed breakdown.
This is the most fundamental difference that drives all other properties.
ER4043: Contains ~5% Silicon (Si). This is a "hypo-eutectic" alloy, meaning it solidifies over a temperature range.
ER4047: Contains ~12% Silicon (Si). This composition is very close to the eutectic point of the aluminum-silicon system (~12.6% Si). A eutectic alloy solidifies at a single, distinct temperature (like water turning to ice), not over a range.
This difference in solidification behavior is the key to understanding when to use each wire.
| Feature | ER4043 | ER4047 |
|---|---|---|
| Silicon (Si) Content | 4.5 – 6.0% | 11.0 – 13.0% |
| Solidification | Over a temperature range (Mushy) | At a near-eutectic, sharp temperature |
| Weld Pool Fluidity | Good | Excellent (More fluid, "wetter") |
| Melting Point | Higher | Lower (Due to high Si) |
| Crack Resistance | Very Good | Superior (Less susceptible to hot cracking) |
| Shrinkage & Distortion | Moderate (More shrinkage during solidification range) | Lower (Solidifies quickly at one temp) |
| Weld Strength | Moderate (~30 ksi UTS) | Slightly Lower (~29 ksi UTS) |
| Ductility | Moderate | Lower (More brittle due to hard silicon particles) |
| Feedability | Excellent (Standard choice) | Can be stiffer, may be more prone to bird-nesting |
| Color Match after Anodizing | Excellent (Matches 6061, 6063) | Poor (Weld turns dark gray/black) |
| Post-Weld Machinability | Fair to Good | Poor (Abrasive due to high Si) |
Welding 6xxx Series Alloys (6061, 6063, 6060): This is its primary use. Its lower silicon content provides a better color match after anodizing, which is critical for architectural applications (e.g., window frames, railings).
General-Purpose Fabrication: Where appearance, machinability, and good overall performance are needed.
Applications Requiring Some Ductility: The weld metal has slightly better ductility than ER4047.
Easier Feeding: It's the standard, most readily available wire and feeds very reliably.
High Heat Applications & Poor Fit-Up: Its superior fluidity helps bridge gaps and handle imperfect joint preparation.
Thin Materials & Complex Joints: The excellent crack resistance and lower shrinkage make it ideal for sheet metal, intricate welds, and situations prone to hot tearing.
Brazing and Welding-Brazing Operations: The lower melting point and high fluidity are perfect for these processes.
Applications Where Anodizing is NOT Required: If the part will be painted or used as-is, the anodizing mismatch doesn't matter.
Casting Repair (Sometimes): Its fluidity can be beneficial for filling voids in castings.
ER4043 is like a chocolate bar melting over a range—it gets soft and mushy before becoming fully liquid.
ER4047 is more like chocolate syrup—it's already very fluid and transitions quickly from liquid to solid.
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