Cold laser welding machine: everything you need to know

Welding, as implied by the name, usually involves the joining of two metal parts through fusion and heating; however, cold welding involves the joining of two metal parts at room temperature through the use of pressure. The processing of ductile metals such as aluminium, copper, lead, etc., by cold welding is becoming increasingly common

We will be discussing cold welding in aluminium and other metals, TIG and cold welding, as well as related topics.

What is cold welding, and how it happens

In any workshop, most of us have seen welding in action. In order to weld two metal parts, we heat them to their melting temperature in order to allow them to fuse together. Different types of welding, such as arc welding and TIG welding, require heat energy. A welding process uses heat to soften two metals to the point of diffusion or to blend them with a third metal (filler).

However, cold welding can join two metal parts without any heat being used; how does it work?

On a regular basis, we may have brought flat pieces of the same material (say aluminum) into contact or rubbed them together and nothing happened. It is possible that the metal aluminium parts will stick together if they are thoroughly cleaned and brought together under vacuum. This phenomenon is known as cold welding.

Oxygen triggers the formation of an oxide layer on metal surfaces when two flat pieces of the same metal (such as aluminium) are exposed to the air. Even if pressure is applied directly to the oxide layer, the pieces won’t weld, regardless of whether grease or oil are present on the surface.

In contrast, by cleaning the surfaces (to remove the oxide layer) and bringing the two pieces into contact under vacuum (without oxygen), the pieces are cold-welded since the atoms in both the aluminium parts cannot distinguish themselves and jump into each other, resulting in a physical bond.

If sufficient pressure is applied to both parts to make the surface contact 100 percent, the bond will be as strong as the parent metal. When applying pressure, a vacuum is not necessary to achieve a weld. In order to make sure that both metal parts are fully in contact, the appropriate pressure must be applied to each.

Cold welding requirements

Cold welding requires clean surfaces and ductile metals. The surface of the metal should be flat and clean. A wide range of nonferrous metals, such as aluminium, copper, lead, and gold, can be cold welded.

Joints formed in cold welding

In cold welding, butts and laps can both be created. Welding aluminium and copper wire from 0.5 mm to 10 mm diameter or more are commonly performed with butt joints. Some cold welding machines allow cutting the wire or flat ends before loading them into the machine.

Trimming ensures that the end is clean and flat. Pressure is normally applied on both ends. It is possible, but not mandatory, to clean body surfaces prior to fusion of butt joints due to the removal of the oxide layer.

Advantages of cold welding

• Since it is difficult to weld aluminium and copper with other methods, this process is a perfect method of combining aluminium and copper.
• The bond formed between aluminium and copper by cold welding is sufficiently strong, lasts a long time, and is not composed of brittle intermetallic compounds.
• Among the different metals that are commonly welded together with cold welding, there are a number of alloys, such as Copper, aluminium, silver, nickel, etc. Wires can be welded perfectly using cold welding, eliminating problems associated with hot welding.
• Metals like copper and aluminium, and wires of different diameters can be welded together with this process.
• In contrast to conventional welding, there is no heat-affected zone.

Limitations of cold welding

If you have read the above paragraphs, you may wonder why it is not extremely popular and utilised in everyday industries. Although cold welding appears to have many advantages, there are limitations to its use.

• The secret to perfect cold welding is having flat welding surfaces and following the fabrication process techniques correctly in order to establish a strong cold weld having the same mechanical strength as its parent metals. Cold welding is easier when the weld surfaces are flat and regular.
• There are various reasons for the lack of perfection, including: Irregularities and contamination of the surface, as well as oxide layers. Oxidation layers and contaminations may be difficult to remove, and irregularities on the surface of the metals may make it difficult for them to bond (even after thoroughly cleaning).
• Additionally, cold welding is only possible for non-ferrous materials like lead, copper, aluminium, etc. Work hardening and other hardening processes should not have taken place on the workpiece. Hence, only non-ferrous and non-carbon metals can be cold-welded.

Due to the above limitations, cold welding is limited in its applications and isn’t feasible to use where there is a requirement to weld different combinations of metals.

The applications of cold welding

In cold pressure welding, aluminium or copper wires/rods of up to 12 mm diameter are joined by a butt joint, typically 0.5-0.5 mm in diameter. Cold welding can also be performed on wire metals combined with copper, such as aluminium. Due to the possibility of explosive gasses present during the underwater laying of wire lines, this method is extremely useful.

Cold pressure welding is an useful method for sealing thermosensitive containers (containers containing explosives for detonation),.

Cold pressure welding is used in the electronic industry to manufacture semiconductor devices that are sensitive to heat.

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In addition to being classified according to the temperature of the workpiece, rolling can also be classified into hot and cold rolling. A metal that is above its recrystallization temperature is said to be hot rolled, while one that is below it is said to be cold rolled.

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