With cold welding, you can join two pieces of metal or plastic at room temperature. This solid state welding is done without adding heat or melting at the junction point. It allows the rapid repair of certain broken objects, at least temporarily. We explain to you what cold welding consists of and how to use it…
The principle of cold welding
When we talk about welding, we rather think of the assembly of liquefied metal parts under the effect of heat. Contact welding works in the solid state. Performed at room temperature, this process makes it possible to securely assemble two pieces of metal or plastic, as simply as with glue.
There are two types of cold welding:
- chemical cold welding is the most common. It is a two-component polymer, to which is added a mineral or metallic component (powder or liquid). The polymerization of these three elements forms a hardening which allows the assembly of the two parts. This type of welding is in the form of glues or hard pastes to mix.
- Magnetic pulse cold welding is a newer process. No more soldering products. Through the use of a coil placed above the parts to be welded, the electromagnetic forces generate a field which fixes the metals to be welded.
This article deals mainly with chemical welding, which is more accessible to individuals.
What is the composition of a chemical solder?
Chemical cold welding, the most common, is made up of two main elements:
- An agent of hardeningforming the outer layer of the product;
- And a core of resin plastics (or epoxy) inside.
- To the resin is added a component made of dust metallic. Rolled powders of purified metals, intended to solidify the weld.
- others additives are present, giving particular characteristics and adapted to the target material. Each manufacturer having his little manufacturing secret, these components do not appear in the final recipe.
Cold welding comes in the form of specific products, most often designed for a single material. Their composition is completely chemically adapted to the target material. Without heat or fusion, the result is comparable to that of a classic weld, but less durable.
Cold welding: what for?
Cold welding products are mainly intended for metals : copper, silver, aluminium, nickel, lead… Materials plastics or polymers are also concerned, within the limit of their ability to deform without breaking.
The process reveals its usefulness in cases of repair metal objects or pipes. The industrial field itself uses this principle in the automotive or aerospace sectors, for example. It is a popular technique for joining cables or for controlling the fusion of dissimilar joints.
More concretely, you can use cold welding to to fix automotive parts, a manifold, a flange, or to restore rigidity to a part… Do not use it to join parts subjected to a significant load. Cold welding is a quick technique for repairing a broken part. This temporary – but nevertheless reliable – repair allows you to act immediately, while waiting to consider redesigning the element. Imagine that your gas tank is punctured; you can plug the hole quickly while waiting to entrust the repair to a mechanic… And this is just one example among many others. Broken objects, minor plumbing, punctured pipe, cracks to be filled, waterproofing, reinforcements of weakened objects… The list is long! You can even join parts underwater…
What materials can it be used on?
Cold welding involves most of the metals we use on a daily basis, as well as some plastics and PVC.
- L’aluminium is difficult to solder with the conventional hot method. Cold welding is perfect for this light, economical and resistant metal.
- The copper welds very well when cold. In case of breakage of copper elements (tanks, pipes, etc.), the repair will be done easily.
- L’inox is difficult to repair or assemble via hot welding, as it cannot withstand high temperatures. Cold welding is perfectly suited.
- The lead is a material on which cold welding is commonly practiced.
- Other metals can be added to this list such as moneythe source where the nickel.
Each metal is treated with a specific cold welding product. They cannot be interchanged. But some different materials can fit together.
For all plastic, polymer or PVC materials, cold welding depends on their ductibility. In short: their ability to deform plastically without breaking. After welding, the part must be able to regain its initial shape. Some plastics are susceptible to breakage and will not be suitable for cold welding. In general, it is practiced effectively on heating pipes or evacuation pipes, for example.
Cold welding for linoleum is suitable for gluing hard rubber products. On lino, this technique is more effective for making joints than traditional adhesives.
Universal cold welding
Perfect for the varied needs of everyday life, these universal products – with very stable results – are designed to work simultaneously on metal, wood and polymers. They are also found for ceramic or polypropylene elements.
The advantages of cold welding
In use, this assembly technique has a multitude of advantages.
- Simplicity. It is an easy technique to implement, as it does not require any specialized tools or special know-how. It replaces the classic methods for joining two elements (rivets, staples, etc.).
- Security. No smoke or toxic fumes.
- Speed. Assembly takes a short time, and full solidification takes no more than 24 hours.
- Economy. The products are financially accessible and their use can save you the intervention of a professional.
- Reliability. The welding is efficient, the result of quality and the finishes perfectly clean and smooth.
Let’s not forget other major advantages of cold welding:
- With this technique, one can intervene – in particular to count a leak – on an empty tank or pipe, but also completely filled or under pressure. No need to drain the liquid before intervention.
- You can repair hot water pipesince cold welding can transfer heat of up to 260° C.
- You can collect coins again wetalthough drying is always better.
- The repair is done on the site, without having to transport or move the equipment concerned. Save time and money!
There remain a few disadvantages to know. The gasket may have low mechanical strength; solder is less durable than its heat equivalent. It is for this reason that cold welding is reserved for small jobs or temporary repairs. This is effective but temporary troubleshooting. In addition, this process is not suitable for all materials.
How to make a cold weld?
If you want to get started, here is a reminder of the steps of a good cold weld. However, take care to follow the instructions given in the product manual. They may vary depending on the type of material and the manufacturer. Some tools can help you: spatula, putty knife, cloth and sandpaper.
- First of all, Protect yourself : appropriate clothing, rubber gloves and a properly ventilated work area.
- start with sand the surface of the area to be worked.
- Clean the area thoroughly.
- Sit on a flat surface to prepare the product. You have to to mix together with care the two components (the hardener and the resin), presented separately. Due to the rapid chemical reaction, prepare only the amount needed for your needs. What remains is not reusable (you must throw it in the trash).
- Apply the final product on the area. To fill the holes, cracks and interstices, do not hesitate to exert strong pressure. For some materials, it will be necessary to maintain pressure for 40 minutes.
- Mondel product until you get the desired result. For finishing, you can use a sander or sandpaper.
- Respect the time drying noted. After a fairly rapid hardening time, complete drying can take up to 24 hours. It mainly depends on the chemical composition of the product.
- Clean the surface after repair.
Of course, you must use the type of cold welding adapted to your needs. Note that there are several qualities of products. You might as well opt for those that offer the best resistance to heat and weather. And if you can choose a French-made brand, that’s just as well.