Aluminum Filler Rod Chart: 4043 vs 5356 by Alloy

Aluminum filler rod chart by alloy

Each row is one joint. “Lincoln’s chart” is the filler in Lincoln Electric’s chart for structural welding, and “Hobart’s rule” is what Hobart’s selection rules say for the same two alloys. The other columns are this page’s pick for each job: always a filler one of the two makers names for that joint. “No good match” means neither maker lists a filler that suits.

• A dash under “Heat treated after” means neither alloy hardens by heat treatment, so there is nothing to pick for. A dash under “Hobart’s rule” means the text of Hobart’s guide gives no rule for that alloy.
• Lincoln’s notes to its chart: where it shows 4043, 4047 also works; where it shows 5356, so do 5556 and 5183.
• 4943 is Hobart’s own alloy, so it never appears in Lincoln’s chart. Hobart lists it for the jobs 4043 does on 1xxx, 3xxx and 6xxx alloys, 5052 and 356 castings.
• The makers disagree on 5454. Hobart’s guide rules out 4043 and 4943 on any 5xxx alloy above 2.5% magnesium, and its tables put 5454 at 2.7–⁠2.8%; a Hobart article draws that line at 3% instead; Lincoln’s chart uses 4043 to join 5454 to 1100, 3003 or 356 castings. Both columns are shown as each maker gives them.
• 2024 and 7075 are left out: Hobart lists them as non-weldable by arc welding, and Lincoln says most 2xxx and 7xxx alloys should not be arc welded.

This chart is for general repair and fabrication. Structural, pressure and marine parts follow a welding code or the designer’s filler call-out, and Lincoln notes that some jobs need a filler other than the one its chart shows. Where this chart and your filler maker’s own chart differ, the maker’s chart wins.

4043 vs 5356 vs 4943: the fillers compared

These are Hobart’s typical figures for its own filler metals, from the property tables in its Guide for Aluminum Welding. The tensile strength is for weld metal alone; the shear figures are Hobart’s minimums for fillet welds, loaded along the weld and across it.

• Puddle and bead: Lincoln’s side-by-side gives 4043 a smooth bead, good wetting and less porosity, and 5356 black smut and distinct ripples. Miller calls 4043 the more forgiving of the two.
• Strength: Lincoln rates 5356 higher in tensile strength and ductility, and 4043 “much lower” in shear. Hobart’s rule of thumb is three fillet passes of 4043 to match one pass of 5356.
• Color: Hobart’s table lists 6061, 6063 and 3003 as clear after anodizing and 5052, 5083 and 5086 as white, the same as 5356. Its 4xxx fillers come out gray.
• MIG feeding: Hobart says 5356 is twice as stiff as 4043 and feeds better. Lincoln: 3/64 in (1.2 mm) 5356 can generally be pushed through the gun, 3/64 in 4043 usually gives feeding problems when pushed, and at 1/16 in (1.6 mm) either can be pushed.
• 4943 is 4043 with a little magnesium added (0.4% on Hobart’s table). Hobart says it runs on the same welding procedures as 4043, gives about 25% more tensile and shear strength and 50% more yield strength, and does not rely on base metal mixing into the weld for that strength.

What welding does to the metal’s strength

The filler is only half of a weld’s strength. Heat softens the metal beside the weld: Hobart puts the loss at 30–⁠50% for 6xxx alloys, and Lincoln says welding codes ask 40 ksi (276 MPa) of 6061-T6 but only 24 ksi (165 MPa) of a weld in it. In a butt weld that soft zone usually breaks first, whatever the filler. In a fillet weld the filler’s shear strength carries the load, which is where 5356 or 4943 earns its place.

• Hobart’s 6061 figures assume 4043 filler with at least 20% of the weld made up of melted base metal; its 5xxx figures are for 5xxx fillers and do not depend on that mixing.
• The 5xxx alloys lose less: welding only undoes their cold work, while 6061 loses the strength its heat treatment gave it (Hobart, Lincoln).
• The second 6061 row is a full solution heat treatment and aging after welding. Hobart calls the filler choice critical for that, and says to get the filler maker’s advice first.

Before you weld aluminum

• Always add filler on 6061, 6063 and 5052. Lincoln says 6xxx alloys welded without filler almost always crack; Hobart warns about fusing thin outside corners with TIG and no rod.
• Keep the heat down on 6061. Lincoln recommends no more than 200°F (93°C) of preheat and 250°F (121°C) between passes, and no wide weaving. Hobart’s limit is 250°F (121°C) for no more than 15 minutes, for heat-treatable alloys and for 5xxx alloys over 3% magnesium.
• Fill the crater. Hobart: speed up at the end of the weld, double back a short way, or use the machine’s crater-fill setting, so the end of the bead does not crack.
• Clean first. Hobart: wipe with a clean towel and a cleaner such as acetone, then take the oxide off with a stainless steel brush kept for aluminum.
• Keep rod and wire dry and covered, and bring them into the shop a day before welding so they do not sweat (Hobart).
• Shielding gas is 100% argon for both 4043 and 5356 (Hobart).

For aluminum amps, tungsten, cup size, argon flow and filler rod size by thickness, use the TIG welding settings chart. The MIG welding settings chart covers steel wire only: for aluminum MIG, start from the chart on your machine. The welding gas cylinder calculator shows how long an argon cylinder lasts.

Quick answers

• Filler by pair of alloys: Lincoln Electric, “Aluminum GMAW Welding Guide” (publication C8.100), its table of filler metals for structural welding and its section on filler metal selection. The fillers are classed under AWS A5.10.
• Selection rules, filler properties, welded strength, hot service, anodizing and alloys that cannot be arc welded: Hobart Brothers, “Guide for Aluminum Welding”, and the notes on Hobart’s Aluminum Filler Metal Selection Chart. That chart’s letter ratings are not used here.
• 4943, cracking, cleaning and storage: Hobart Brothers’ articles on 4943, on aluminum filler rod, on aluminum TIG filler metals, and its guide page on avoiding cracking.
• Ease of welding: Miller Electric, “Aluminum Welding Made Easier with the Right System, Filler Metal”.
• Where the two makers differ, both are shown and named. The picks in the “General work” to “Easiest puddle” columns are this page’s reading of those sources, not a maker’s chart.