Certainly, aluminum welding is an important sheet metal fabrication technique.
A reason today’s guide explores all the vital aspects of aluminum welding process.
Take a look:
1. Why Weld Aluminum?
It is very true that aluminum is very difficult to weld and for this, most welders make tremendous mistakes during the process.
However, there is no metal out there that can replace aluminum and its benefits.
The benefits are as listed below;
Welding aluminum
- Lightweight: Compared to steel, aluminum is much lighter in weight, which does not mean it is less strong.
It becomes easy to transport and to handle because of the light weight.
- Durability: Aluminum is resistant to corrosion and it does not rust and can also act as weather-proof for the applications it is used for.
It is also not reactive to UV- rays and this increases its durability.
- Flexibility: Aluminum can be formed into any kind of shape as required since it is flexible.
It can be forged, rolled, extruded or even casted.
- Environment friendly: It can be recycled over and over again, and there won’t be any need to dispose of it to the environment.
- The aluminum parts finishes and appearances are aesthetically pleasing to look at.
Other benefits are; good heat and electric conductivities and can resist fire, it is also very easy to maintain.
2. Challenges In Aluminum Welding
This material displays its own unique set of challenges when being welded.
Due to its unique set of challenges, welders are forced to use only welding techniques that can be able to overcome them.
Some of the challenges associated with welding aluminum include;
Unstable chemical composition: this unique characteristic makes aluminum prone to breakage under stress.
During welding, aluminum can also react to the metal used as filler material and this will definitely cause its breakage later on.
For this issue of breakage not to happen, the filler metal chosen, should be one whose chemical composition is less sensitive to cracking and heat.
Low melting point: the low melting point makes it vulnerable to cracking, warping and breakage during the process of welding.
This can be minimized through the use of GMAW process which is equipped with a pulsation capability.
The process uses a power source that can combine high break current and low background current which can be controlled.
If the two are combined together, it becomes easy to prevent application of excess heat that will cause burn throughs.
Discoloration: during welding, the magnesium oxides present in aluminum usually collect at the welded part of the material.
The collected oxides can cause discoloration of the part that has been welded.
It is therefore important to work with an appropriate filler metal.
Something else that can be done to avoid discoloration is to hold the welding gun in the right position and maintain the required contact-to-work distance.
Feedability: the aluminum wire tends to be softer compared to other types of wires.
This makes it very difficult to be fed through a gun compared to others.
There is therefore the need to use a spool gun, MIG gun or a push-pull gun to avoid bird nesting of the wire.
Hydrogen solubility: hydrogen can easily dissolve in liquid aluminum.
This causes the entrapment of the aluminum bubbles in the welded part after it is solidified and this makes the part porous.
3. Aluminum Welding Techniques
Aluminum and its alloys can be welded through selected welding processes as described below:
Welded aluminum surface
Arc Welding Aluminum
This is popular with industries that use welded aluminum alloys.
The arc-based processes include:
MIG welding aluminum vs TIG welding aluminum
MIG Welding Aluminum: this process is mostly recommended for thinner gauges of the aluminum material like aluminum sheet.
The amount of heat used here is less compared to the amount used for thicker materials.
The shielding gas used for this process is pure Argon, this will allow the process of spray transfer.
The chemical composition of the aluminum sheet should be almost same as the one for the filler wire.
TIG Welding Aluminum: TIG is also appropriate for welding aluminum alloys.
Since aluminum has high heat conductivity, the TIG welding technique is able to supply enough heat.
The kind that will ensure that the two aluminum metal sheets are joined together.
This technique is recommended for both thin and thick aluminum metal sheet sections.
The shielding gas recommended for this technique is pure Argon just like with the MIG technique.
The welding wire or filler material should be one that is closely similar to the metal sheets being welded in composition.
Laser Welding Aluminum
Laser welding
This technique can be used for welding various types of aluminum alloys just like with other welding processes like arc welding.
Laser welding is a very fast procedure and the speed cannot be compared to any of the welding techniques available.
This is due to the fact that it poses a high-power density at the surface of the material.
The keyhole laser welding can be able to produce aspect ratio welds that are very high creating narrow heat-affected sections.
The laser beam technique can be used with materials that are sensitive to cracks like the 600 series combined with the right filler materials.
It uses 4047 or 4032 as the filler wire.
The gas that is recommended for shielding during this process will be selected depending on the material grade to be welded.
Electron Beam Welding Aluminum
Electron beam welding
This technique is mostly applied with thicker aluminum metal plates.
It is a very fast process and creates small weld pools just as with other techniques like laser bean technique.
This technique doesn’t require the use of a shielding gas because it takes place in a vacuum and this leads to the creation of highly pure welds.
To avoid the risk of cracking when working with aluminum alloys when working with this technique, it is important to observe these;
The filler material should be selected carefully, the welding parameters should be selected with care and the design for the joint.
Friction Welding Aluminum
Friction welding
This process does not need the aluminum melted; it joins the two metals in their solid state.
This technique is best suited for creating welds between aluminum alloys and it can join all the series within the aluminum alloys.
There is no need for a shielding gas given the solid state of the two materials to be joined together.
The available friction processing procedures include;
Friction stir welding: This method uses a non-consumable tool, which is driven through rotation and is plunged through the interface of the two materials to be welded.
The non-consumable tool moves along the interface and the aluminum sheet gets heated and softened through the friction.
The softened sections of the two materials are then mixed together by the working to tool to create a weld.
This technique is most popular with aluminum plates or sheets.
Refill friction stir spot welding: This is an improved form of friction stir welding and is meant for spot welding technique.
Its main purpose is be the replacement for rivets used in applications that involve aluminum sheet metals.
Linear friction welding: This method oscillates one of the materials to be welded relative to the other while keeping it under a highly compressive force.
There is heat produced under these two oscillating materials in contact, this heat makes the material plasticize.
The material the forms the plastic is removed making the remaining material shorter in the direction facing the applied force.
At this stage, contaminants like oxides are expelled with the flash, this allows the contact between the two aluminum materials.
This kind of weld is mostly created between bulk aluminum parts and they create near-net shapes.
Rotary friction welding: There is almost no difference between this method and the linear friction welding.
However, this type of welding works with parts that are cylindrical in shape and the tools are rotated to create the heat needed to create the plastic surface.
4. Aluminum Alloy Grades For Welding
The available aluminum alloy grades that can be welded are discussed below:
- 1XXX alloys: This grade is near pure aluminum and are usually used for applications that conduct electricity and those that need to resist corrosion.
They can be welded very easily and are recommended to be used together with 1100 filler material.
- 2XXX alloys: They are very strong alloys and are the types used with aerospace industry.
They are usually available in the form of plates or sheets. 2XXX alloys are very strong.
They are not easy to weld and mostly not welded at all, but there are two alloys in this grade that can be welded; 2219 and 2519.
The filler materials available for both 2219 and 2519 materials are 2319 and 4043.
- 3XXX alloys: this grade of aluminum alloy is not that strong and it is very formable.
It is normally used in air conditioners and heat exchangers.
They are very weldable and are usually welded together using 4043 and 5356 as the filler materials.
- 4XXX alloys: This class is mostly used for the filler material.
If they are used as the base sheets or plates then the filler material becomes 4043.
- 5XXX alloys: This type of alloy is available as sheets or plates which are normally very strong.
They are easy to weld and they can be joined together by the use of 5183, 5356 or 5556 filler materials.
- 6XXX alloys: Alloys of this grade are mostly available in intrusion form but sometimes, also available in sheets and plates.
They can crack easily under high temperatures but if used with the right filler material they can last longer.
The appropriate filler materials can either be 4043 or 5356.
- 7XXX alloys: This grade is also applied in the aerospace industry.
Most of them are not welded at all except for a few like 7003, 7039 and 7005 using the filler material 5356.
5. Equipment For Aluminum Welding
TIG welder: This welding type uses a machine that that can control the current.
This is important because it prevents the material from overheating which can cause a burn through.
This equipment can be used with both thin and thicker aluminum materials.
Being able to identify the type of filler wire that works well with your type of aluminum alloy is a plus to the welder.
TIG welding machine
MIG welder: Generally, knowing the welding method to be used for any type of aluminum material is a necessity for the welder.
Pulse welding will need an inverter for power supply while spray arc welding will need constant current.
This welder type is used for welding thinner gauges of the aluminum material.
The gas used with this welder should be pure Argon.
The chemical properties of the aluminum material should be similar to that of the filler wire.
MIG Welding machine
Torch welder: compared to the rest, it is usually more difficult to use this type of welder in the welding processes.
It uses a gas fed torch during welding and controlling the amount of current being applied to the material is very difficult and quite a challenge.
This means there occur a lot of burn throughs during the welding process.
Using this welding equipment actually requires someone with a lot of experience.
Someone who is able to control the torch and the filler material adequately to avoid such burn throughs.
6. Application Of Aluminum Welding
Aluminum welding has applications in every industry in the world, some of these applications are described below:
Power lines: Due to the unique properties of aluminum material, it has become popular for making wires in the power lines.
This is because it balances well between weight and strength.
It is also cost effective compared to other metals with almost similar properties like copper.
High-rise buildings: Aluminum is malleable, strong versatile and light weight, making it usable in high-rise buildings and also skyscrapers
It is also preferred since it is very durable and very flexible in designing.
Window frames: frames made from aluminum are very durable due to the fact the material is resistant to corrosion.
They are also pocket friendly and also very strong.
Aluminum cannot offer insulator requirements of a house if needed during cold or winter seasons.
Consumer electronics: aluminum has become popular with the production of electronics of all kinds.
This could be phones, computers, tablets, tvs and many more.
Households and industries: the aluminum material is used to make precision tubing in air conditioners and refrigerators.
Aluminum material is also used in making frames for applications like dryers, dishwashers and many other appliances.
Aircraft components: due to the properties such as high strength to weight ratio, resistance to corrosion, and high ductility. It is an excellent material.
Ships: A ship requires a light weight and a strong material for its parts, and aluminum comes with both requirements.
It is also strong enough to withstand breaches and cracks at the hull.
Fabricated aluminum part
7. Aluminum Welding Defects
Porosity: The function of the shielding gas is to protect the liquid weld pool from being contaminated by other gases from the atmosphere.
The absence of the shielding gas could be as a result of poor setting of the equipment.
It could also be because there is a hole in the liner of the gun or maybe the shielding gas is being blown away by the wind.
This defect can be identified when there are pinholes on the surface or internal parts of the created weld.
Lack of fusion: This defect tends to happen a lot with aluminum welding because of the fact that aluminum conducts heat very fast.
So, at the start of each weld there is normally lack of fusion.
The fusion only happens when enough energy has been applied to the weld.
There are welds that are made with specific design to be able to produce a lot of heat at the start of the weld.
Craters: These defects normally occur at the end of the weld.
They need filling in because if not, they can cause cracking due to the presence of a stress point.
Some welding equipment are designed with crater timers meant to fill in any craters each time the gun trigger is let loose.
Burn through: This normally happens as a result of too much heat caused by high voltage or wire feed.
Another cause for burn throughs could be because the travel speed is too low which can also cause warping.
Aluminum needs a higher travel speed to avoid the burn throughs.
Welding defects
8. Benefits Of Welding Aluminum
Welding aluminum can never be avoided because of the various benefits it has.
Despite the fact that it is a unique material with a set of properties making it difficult to weld, the benefits are better.
It is non-corrosive and is not affected by oxidation which is normally a huge challenge during the welding processes.
This material is special when it comes to the transfer of heat and even electricity.
That is why there is a need to weld it despite the challenges it poses during the welding process.
The electrical conductivity is at the same level as copper.
It is lightweight and also balances well strength and weight making sure it is also strong enough and doesn’t break easily.
The kind of weight and strength in aluminum is needed for applications that need strength and lightweight.
Aluminum is also recyclable making it cost effective and also friendly to the environment because it has no waste.
Aluminum also has cosmetic and aesthetic qualities and can absorb sealant and paint effectively.
The aluminum parts finishes and appearances are aesthetically pleasing.
The aluminum material is very flexible since it can take any kind of shape as needed; be it rolling, forging, extrusion, or casting.
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