welding of 6061 aluminum


What is 6061-T6 Aluminum

Grade 6061 (Unified Numbering System (UNS) designation A96061) is a precipitation-hardened aluminum alloy, containing magnesium and silicon as its major alloying elements.

It is commonly available in:

1. 6061-O (annealed, pre-tempered grades),

2. 6061-T6 (solutionized and artificially aged tempered grades) and

3. 6061-T651 (solutionized, stress-relieved stretched, and artificially aged)

Below diagram gives overview of general aluminum alloys.

Click here to Get Guide on How to Weld various materials

Classification of aluminum grades

Chemical properties of 6061-T6 aluminum

AlMgSiFeCuCrZnTiMnRemainder
95.85 – 98.560.8 – 1.20.40 – 0.80.0 – 0.70.15 – 0.400.04 – 0.350.0 – 0.250.0 – 0.250.0 – 0.150.05 each, 0.15 total

Physical properties of 6061-T6 aluminum

Physical PropertyValue
Density2.70 g/cm³
Melting Point650 °C
Thermal Expansion23.4 x10^-6 /K
Modulus of Elasticity70 GPa
Thermal Conductivity166 W/m.K
Electrical Resistivity0.040 x10^-6 Ω .m

Spec: BS EN 755-2:2008

Mechanical PropertyValue
Proof Stress240 Min MPa
Tensile Strength260 Min MPa
Hardness Brinell95 HB

TIG/ MIG Filler wire for 6061-T6 Welding

Aluminum grade 6061-T6 is welded using ER5356 & ER4043. Both types are good for welding 6061 aluminum materials.

1. Filler ER4043 (TIG/MIG) –  4043 filler alloy, a 5% Silicon alloy, is often used to weld 6061 base materials, it is not commonly used when shear strength of the component is a predominant consideration. The 4043 filler alloy is a silicon based filler alloy that is often used to take advantage of the elements capability of promoting fluidity in aluminum. While groove welds can be made using this filler alloy that can characteristically pass minimum transverse tensile test requirements, this filler alloy has considerably lower shear strength when compared to the 5xxx series filler alloys. 

Filler ER5356 (TIG/MIG) – ER5356 Aluminum welding wire is mainly used where higher weld strength and greater ductility is required and is compatible with 5050, 5052, 5083, 5154, 5356, 6061 and 6363 alloys. 5356 has greater resistance to corrosion (salt water) and better color match after anodizing.

Use with DC Reversed Polarity. Argon shielding gas is required.

Selection of welding consumables for Aluminum Welding

Use this chart to find the best suitable GTAW/ GMAW filler wire to weld the various grades of the Aluminum.

Hot cracking can be prevented with using 4043 type filler wire, but it will give lower ductility and toughness compare to 5356 type wire. 4043 types due to high silicon content gives poor color match to 5XXX and 6XXX aluminum base metals after anodic oxidation treatment.

When welding 5XXX (high Mg, more than 3% usually), 4043 is a poor choice as it will make intermetallic compound of mg2Si in the weld metal. This will lower the weld metal ductility and increase its crack sensitivity.

Click here to see large size image.

Welding process:

Aluminum can be welded with TIG and MIG welding easily. TIG welding with AC current is used for thinner section welding. Using AC current gives half a cycle of cathodic cleaning in both manual and automatic processes. MIG is used for heavier sections.

Advance welding processes such as laser welding & Friction stir welding are now a days used heavily in Aluminum fabrication.

Aluminum TIG welding

TIG Aluminum Welding Parameters

MIG Aluminum Welding Parameters

Shielding gases:

Pure Argon is widely used. Argon-Helium mixture in MIG welding. Helium addition help for a better weld formation and increase the welding speed. Helium also minimize the risk of pores and lack of fusion. Pure helium is not used due to high Ionisation potential of the gas as well as high cost of the gas.

Preheating:

Preheat is recommended for thicker sections or whenever sufficient penetration can not be achieved due to high thermal conductivity of the aluminum.

So, if any of above issues being faced, a preheat temperature of 150 to 200°C can be applied. Also, when repairing 5XXX (Al-Mg) grades, it can crack in weld or HAZ area. Following a preheat in these conditions is very beneficial to mitigate the cracking inter-alia to using right filler wire.

Watch our YouTube video to Learn what is Preheat, Inter-pass & post heating.

Interpass Temperature:

Usually the interpass temperature is kept above the minimum preheat temperature.

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