How to Weld Aluminum and Aluminum Alloy?

1. Welding materials:

1. The purity of argon gas for welding shall be ≥ 99.99%, dew point shall be ≤ – 55 ℃, and shall comply with the provisions of GB / T4842 or GB10624.

When the pressure of bottled argon is ≤ 0.5MPa, it should not be used.

(the nitrogen content of argon is ≥ 0.04%, otherwise the light yellow or grass green magnesium nitride and pores will be generated on the weld surface;

The oxygen content is ≥ 0.03%, otherwise dense black spots, unstable arc and large spatter can be found on the surface of the weld pool;

The water content is ≥ 0.07%, the weld pool will boil and gas pores will be generated in the weld).

How to Weld Aluminum and Aluminum Alloy? 1

2. Cerium tungsten electrode is used for manual tungsten argon arc welding.

The diameter of the electrode shall be selected according to the size of the welding current (generally, tungsten electrode with a size larger than that required by the welding current is used), and the end of the electrode shall be hemispherical (hemispherical fabrication method:

Use a tungsten electrode one size larger than the specification required by the welding current, grind the end into a cone, vertically clamp the electrode, start an arc on the test plate with a current 20 ~ 30A larger than the current required by the tungsten electrode and maintain it for a few seconds, and the tungsten terminal head will be hemispherical.

If the tungsten electrode is contaminated by aluminum, it must be reground or replaced;

In case of slight pollution, the current can be increased to make the arc burn on the test plate for a while (that is, the pollutants can be burned away):

Diameter of cerium tungsten electrode (mm)2.53.24.05.0
(positive connection) Welding current A100~200170~250200~300350~480500~675
(in reverse connection) Welding current A15~2517~3020~3535~5050~70
(at AC)Welding current A85~160120~210150~250240~350330~460

3. When use MIG welding aluminum alloy, because the aluminum welding wire is relatively soft, in order to avoid biting the welding wire, the wire feeding wheel with gear is not allowed to be used, and the wire pushing type is not suitable;

Related reading: MIG vs TIG Welding

It is not allowed to use spring tube for wire feeding hose, but polytetrafluoroethylene or nylon products, otherwise the hose will be polluted or blocked due to grinding.

MIG usually uses DC reverse polarity.

4. The main function of the flux is to remove the oxide film and other impurities.

When used, it can be mixed into paste with absolute alcohol or directly put the flux powder on the groove and both sides.

When welding fillet welds, those fluxes that can easily remove the slag after welding shall be selected;

The flux for aluminum magnesium alloy should not contain sodium.

5. When aluminum materials of different grades are welded, when there are no regulations in the drawings and processes, the welding wire materials shall be selected according to the base metal with better corrosion resistance and lower strength level.

Related reading: Guide for Selection of Solid and Flux Cored Wires

When welding corrosion-resistant aluminum alloys such as aluminum magnesium alloy or aluminum manganese alloy, welding wires with magnesium content or manganese content similar to or slightly higher than the base metal should be used.

Welding wire can be selected from GB / T10585 aluminum and aluminum alloy welding wire, GB / T3190 chemical composition of deformed aluminum and aluminum alloy and GB / T3197 aluminum and aluminum alloy wire for welding rod.

Related reading: Can Aluminum and Aluminum Alloy Be Welded?

The following tables can be referred to when selecting welding wires (Table 3 and table 4 are extracted from welding manual):

Table 1 welding wire for aluminum welding of the same brand

Base metal grade of the same grade

Welding stick

Base metal grade of the same grade

Welding stick

1060

SAL-3

5052

SAIMg-1

1050A

SAL-3

5A02

SAIMg-1

5A03

SAIMg-2

1200

SAL-1

5083

SAIMg-3

3003

SAlMn

5A05

SAIMg-5

3004

SAIMn

6061

SAIMg-1

SAlMg-5

SAISi-1

Table 2 welding wire for dissimilar aluminum welding wire

Heterogeneous base metalWelding stick
Pure aluminum + aluminum manganese alloySAIMn
Pure aluminum, aluminum manganese alloy + 5052, 5A02SAIMg-1, SAIMg-5
Pure aluminum, aluminum manganese alloy + 5A03SAlMg-2
Pure aluminum, aluminum manganese alloy + 5083, 5086SAIMg-3
Pure aluminum, aluminum manganese alloy + 5A06, 5A05SAIMg-5

Table 3 selection of welding wires for different materials and performance requirements

Material

Welding wires recommended according to different performance requirements

High strength is required

High ductility is required

Color matching is required after welding and anodizing

High strength is required

It is required that the crack tendency is low during welding

1100

SAISi-1

SAl-1

SAl-1

SAl-1

SAlSi-1

2A16

SAICu

SAlCu

SAlCu

SAlCu

SAlCu

3A21

SAIMn

SAI-1

SAl-1

SAl-1

 SAlSi-1

5A02

SAlMg-5

SAIMg-5

SAlMg-5

SAIMg-5

SAlMg-5

5A05

LF14

LF14

SAlMg-5

SAlMg-5

LF14ER

5083

ER5356

ER5356

ER5356

ER5356

5183ER

5086

ER5356

ER5356

ER5356

ER5356

5356S

6A02

SAlMg-5

SAIMg-5

SAIMg-5

SAlSi-1

AlSi-1

6063

ER5356

ER5356

ER5356

SAlSi-1

SAlSi-1

7005

ER5356

ER5356

ER5356

ER5356

X5180

7039

ER5356

ER5356

ER5356

ER5356

X5180

Note: ER aluminum welding wire is American Standard ANSI / AWSA5.10.

2. Preparation before welding:

1. The aluminum groove shall be processed by mechanical methods (including shearing).

If the plasma&flame cutting method is used, the discolored part shall be machined to remove not less than 3mm.

The processed groove surface shall be flat and smooth, free of cracks, layering, inclusions, burrs, flash and oxidation.

The groove surface shall have silver white metallic luster;

If necessary, 100% PT shall be carried out on the groove and at least 50 mm on both sides.

2. Surface cleaning (including removing surface oxide film, scale, pollution and unqualified oxide color) must be carried out on the welding wire, groove surface and at least 50 mm on both sides.

0.15 ~ 0.2 stainless steel wire disc brush, metal grinding head (i.e. electric milling cutter), manual disc milling machine, file (it should be an aluminum arc file), scraper and acetone (the white cloth stained with acetone should be clean, and cotton cloth or cotton yarn should not be used to avoid plush when wiping), but it should be noted that these tools should be cleaned before use, and the oxide film should not be pressed into the base metal during cleaning.

Therefore, do not use too much force during cleaning;

However, it is not allowed to grind with grinding wheel or ordinary sandpaper, because the aluminum material is very soft, resulting in sand particles remaining in the aluminum material, which is easy to produce defects such as porosity and slag inclusion after welding.

3. In principle, 100% PT shall be carried out on the surface of aluminum materials for outsourced hot processing parts, such as heads, etc. after entering the factory, and RT shall be carried out on uncertain parts if necessary.

4. The surface of welding wire can be scrubbed with stainless steel wire brush or clean oil sand paper;

For welding wires with thick oxide skin on the surface, chemical cleaning is also required after grinding before welding.

Chemical cleaning: soak in 5% ~ 10% NaOH solution at 70 ℃ for about 0.5 ~ 3min, then rinse with clean water, then soak in HNO3 solution at about 15% at room temperature for about 1 ~ 2min, then rinse with warm water, then dry with a hand-held blower (air compressor is not allowed, because there is water and oil in the air), and then put it into an oven for drying at 100 ℃.

This method can also be referred to for aluminum materials.

5. The cleaned welding wires and weldments shall be kept clean and dry, and the welding parts shall not be touched by hands or blown by mouth.

Welders generally wear white welding gloves, and do not wear dirty gloves for fear of trouble;

It is forbidden to pollute before welding, otherwise it should be cleaned up again, and local pollution can be cleaned up locally;

It is better to cover both sides of the groove with white paper.

Generally, welding shall be carried out immediately after mechanical cleaning.

If no welding is carried out within 4h after cleaning, it shall be cleaned again before welding.

6. The assembly of weldments shall be accurate. If the assembly is poor, the parts shall be replaced instead of forced assembly to avoid excessive stress.

Before formal welding, the groove size shall be checked, and welding can be carried out only after it is qualified.

7. The welding wire and process measures selected for tack welding are the same as the welding process.

8. During the assembly of weldments, tack welding shall be avoided at the stress concentration (such as the intersection of welds and the corner on the workpiece).

The length and spacing of tack welds can be as follows: (mm).

Base metal thicknessTack welding spacingLength of tack weld of each section
<3
3~6
>6
Nozzle or flange
40~50
50~60
50~80
2~4 point
4~6
5~10
10~12
every point 3~8

9. The tack weld shall be free of cracks, pores, slag inclusions and other defects, otherwise it must be removed and re welded.

Re welding shall be carried out in the nearby area instead of spot welding in the original place;

When the process does not specify the butt weld gap, it can be 2 ~ 4mm.

10. For the tack weld that will melt into the permanent weld, it is necessary to ensure full penetration and remove the oxide layer on its surface (only silver white is allowed), and make smooth transition at both ends of the weld to facilitate arc connection, otherwise it should be repaired.

When welding on cold parts, the arc should stay for a while at the beginning of welding.

When the base metal edge starts to melt, wire welding should be added in time to ensure the penetration of the beginning welding point.

11. When welding longitudinal joints, run on and run off plates must be placed at both ends of the weldment.

The run on and run off plates shall be made of aluminum materials with the same brand and thickness as the weldment.

Arc crater shall be avoided as far as possible when welding circumferential weld.

12. If the tack welds are cracked during welding, resulting in plate edge dislocation or gap change, the welding shall be stopped immediately, and the welding can be continued after repair.

13. During the welding process, the black ash and oxide on the upper weld surface shall be cleaned by wire brush first.

During welding, pay attention to handling the flame, that is, the arc stop.

The arc striking can be carried out at a distance of 10 ~ 20mm from the starting end of welding, and then quickly returned to the starting end.

The first layer is welded in a straight line.

In order to obtain a good shape, the other layers can swing laterally and stop at both sides for fusion.

14. Aluminum is prone to deformation and collapse during welding.

Therefore, clamps and backing plates shall be made before welding.

When using clamps, both the front and back sides of the parts need to be clamped, and the rigidity and clamping force of the clamps should be moderate, because too small can not control the deformation, and too large can easily lead to weld cracking due to too strong weld restraint.

The clamping force should be 350kg / 100mm.

Soft aluminum clamps can be carbon steel or stainless steel, which can slow down heat dissipation;

Strengthened aluminum: aluminum can be used to make clamps, which can enhance heat dissipation.

The jig for longitudinal seam can be of piano key type, and the jig for circumferential seam can be of hydraulic bulging type.

During longitudinal joint assembly, the gap can be properly increased so that there is room for contraction after welding;

The circumferential seam (including circular flange, flange, etc.) shall be reserved with some reverse staggered edges or flanges, because the flange will collapse and deform after welding.

The backing plate is generally made of stainless steel or carbon steel.

Graphite can be used to make the backing plate for welding aluminum materials with low requirements.

The influence of backing plate material on weld cooling rate shall also be considered.

When the aluminum plate is thick or the assembly gap of the backing plate is large, the gap can be sealed with clay mud and removed after welding.

The size of the base plate can be as follows:

How to Weld Aluminum and Aluminum Alloy? 2

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