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How to Do Thermite Welding

Thermite welding, sometimes written ‘thermit welding’, ‘the Goldschmidt process’ or ‘exothermic welding’, is the process of creating a welded joint by pouring molten metal between two or more workpieces. It was officially developed in 1895 and still has its uses on railroads today.

Thermit welding works on a railroad during night time

How to Do Thermite Welding

It is important that only qualified and supervised individuals attempt thermite welding as it can be very dangerous. Thermite welding is known for causing minor eruptions around the workpiece. Before you can even begin thermite welding, you’ll need to cast moulds to direct the metal mixture that you’ll be pouring into the gap. You’ll also need a special cauldron in which the metal will be melted, with side dishes for catching any excess flows. You will also need a blow torch for preparing the workpiece, as the workpiece needs to be hot before you start melting the mixture and applying it to the workpiece.

Thermite welding is a very specific manner of welding, but it is still used to fix railroad issues today. To fix an issue on a railroad, such as a dangerous imperfection caused by rust, you would first need to cut away the infected area.

The next step is to create the mould in which you will pour the heated metallic mixture. Next, you will secure the mould in place with high-heat-resistant clamps. Next, you will need to use a gas torch to heat the workpieces through the mould.

Now that the work area is prepared and ready, it is time to prepare the thermite itself. This may involve pouring a metallic mixture into a cauldron or it may involve using a pre-prepared bin of thermite that has the prescribed amounts of metals and metal oxides already balanced.

Thermite welding on a railway track in Dublin, Ireland

Once the thermite is in place with the workpiece and mould, it is lit. The metal-oxides catch light and the temperature rises until the metal inside the cauldron begins to melt and pour down into the mould. Excess metal escapes into two trays carefully positioned on the side.

It can take around five minutes for this process to finish, and during this time eruptions and sparks are not unusual. This is one of the most dangerous parts of the process, and if the mould is improperly clamped, or if the cauldron falls, you could find yourself with a very difficult metal mess to clear up.

Once the metal has settled in the mould, the cauldron is removed, and the excess dishes are also removed. Care must be taken as these items will still be extremely hot. Next, the mould is removed, sometimes by a hammer that simultaneously removes some of the excess metal around the edges. Some of this metal is still burning white-hot, so it is important not to swing your hammer wildly at the mould as you will need to control your swings and where you knock the metal to – you don’t want to hurt yourself or a co-worker.

Once the majority of the excess is broken off, you will need to use a metal grinder to ensure that the workpiece is smooth and ready for use. If you don’t use a metal grinder, you risk injury to people or things caused by a rough surface.

After the grinding, the workpiece should be finished. All that’s left now is to carefully clear away any remaining materials left over from the welding. Below is a video where you can watch examples of thermite welding on railroads in real life.


Why Would I Use Thermite Welding Techniques?

Thermite welding doesn’t demand the same level of skill as an electric arc, so while it has its own dangers that workers need to be aware of, it can be used by those with less skill. Thermite welding is also very effective for welding cross-sections. If you’re securing equipment for some thermite welding, we can help to supply you with equipment and fuel for your gas cutting and heating of the workpiece. Typically, oxy-fuel welding and cutting equipment is used in the preparation stages before the thermite mixture is released into the mould.

You can read more about the science and history of this process at ScienceDirect. Alternatively, if you’re realising that thermite welding isn’t the correct process for completing your current project, then we recommend that you take a look at our welding equipment for hobbyists and businesses. We have plenty of TIG welding gas and MIG welding gas for all of your projects, whichever gas solution they require.

Get in contact with us for more information on any of our products.