Aluminium welding

In spot or resistance welding, high mechanical pressure is exerted on a relatively small area through electrodes supplying a large amount of energy in the form of an electric current. Local melting of the aluminium sheets between the electrodes leads to a strong joint between the components.

The KUKA.Robospin application software optimises the spot welding of aluminium joints. The special feature here is that the robot performs a rotational motion about the weld spot during welding, thus decreasing the contact resistance and significantly reducing aluminium alloying of the electrode tips.

Advantages

• Improved weld quality

• Longer electrode tips

• Time savings due to less frequent tip dressing or changing of electrode tips

Gas metal-arc welding is an arc welding process in which an electric arc is ignited between an electrode and the component, fusing the workpiece and, if applicable, a filler metal. In aluminium arc welding, an inert gas flows around the electrode and the weld pool to creating a shielding effect to prevent an undesirable chemical reaction of the oxide and molten material. Influencing the arc through appropriate selection of the electrical parameters and shielding gas can have a targeted effect on the seam formation, weld pool temperature and welding speed.

MIG welding (metal inert gas welding): In MIG welding, a melting aluminium welding wire is used as an electrode. This filler metal serves to bridge gaps, if necessary, or increase the strength of the joint. The choice of aluminium alloy for the filler wire can also influence the properties of the joint in the MIG welding process. Argon is the most commonly used shielding gas in welding aluminium. MIG welders are good for thicker pieces of aluminium steel because MIG welding thin pieces of aluminium steel could result in burn-through. The minimum aluminium thickness for MIG welding should be 14 ga to 18 ga. If the alloy is thinner TIG welding is the more appropriate process.

TIG welding (tungsten inert gas welding): In TIG welding, a burning arc is placed between the aluminium component and a non-melting tungsten electrode. TIG robotic welding requires an alternating current with a high-frequency electrode that doesn't need to come into contact with the alloy therefore reducing contamination.

Plasma welding: Plasma welding is a variant of TIG welding in which the arc is constricted by a water-cooled nozzle and an additional plasma gas is supplied. This creates a focused arc with higher energy density. It also impedes oxide formation creating a strong aluminium alloy weld seam.

Advantages of the process

• High welding speed

• First-class aluminium weld seam

• High deposition efficiency and welding depth

• Simple handling 

Application 

• Wide range of materials and material thicknesses

In laser welding, a laser heats the material to melting temperature. The radiation is focused with the aid of optics. The low melt amount and high thermal conductivity of aluminium result in a high cooling rate, which often leads to hot cracks. This is why appropriately alloyed filler wire is often used in the case of sensitive aluminium alloys.

Advantages of the process

• High welding speed

• Large welding depth

• Low energy per unit length and thus low thermal distortion

• Material combinations with copper, for example, also possible

Application

• Thin sheets

• Demanding components that require a low heat input

In laser hybrid welding, the laser welding process is combined with a gas metal-arc welding process, usually MIG welding. Since a filler wire is normally used in laser welding due to the risk of hot cracking described above, it makes sense to feed filler wire which is already in liquid form through a welding arc.

Advantages

• High welding speed

• Large welding depth

• Low energy per unit length and thus low thermal distortion

• Material combinations with for example copper are also possible

   

Application

• Alloys sensitive to hot cracking

• Components subject to tolerances

• Thick aluminum alloy sheets

Friction welding is a joining process that produces full-surface contact joints. Friction is created by rotating one workpiece under pressure against another workpiece. This creates heat between the two surfaces and plasticizes the material. No filler materials, additional flux or shielding gases are required for processing the alloys.

Advantages of the process

• Very good joint quality

• Fully homogeneous joint over the entire joint area

• Joining of different metals

• Materials do not melt

• Increased speed and joint integrity

Application

• Material with low melting temperature 

• Rotationally symmetric components

Friction stir welding is a process in which a rotating pin is traversed along the contact surfaces between the workpieces. The frictional heat plasticizes the material, which is welded together.

Advantages of the process

• First-class weld quality

• No welding defects such as pores or cracks

• Joining of different metals and alloys possible

• Comparatively low heat input

• High seam strength with minimal welding distortion

Application 

• Welding of non-ferrous metals with low melting temperature

• Welding of mixed-material combinations