Welder working on brazing.

5 Interesting Welding Types and How They Work

As a welder you can learn a number of different welding processes. The processes you choose to learn depend on the type of welding job you want to do and whether you are welding for fun in your free time or as your career. Here are five interesting welding types that you may not know. From the more basic types to the more specialized, all of these processes are commonly used today and show how versatile the welding industry is. Which of these have you mastered?

1. Soldering

Soldering is a type of welding that has been around for at least 5000 years. It is one of the original metal joining processes that was used when metalworking first originated. Typically used to make jewelry, cooking items, tools, and stained glass, it is now most commonly used for combining metal components of electronics. The difference between this welding process and others is that the filler material has a lower melting point than the work material. This causes more of a tacking application and keeps the work material from melting. However, with the work material staying a solid, there is more of an opportunity for the surface to gain contaminants so a special flux is used.

2. Brazing

When most people think of welding, they imagine molten metal joined and then cooling as one piece. Brazing is the art of using a filler material only, to join two pieces of metal together. While very similar to soldering, brazing differs by operating at higher temperatures. Brazing is typically used on higher strength materials and can create a very strong bond. The filler materials used in this process still melt at a lower temperature of the work material, and there is a wider variety of filler material that can be used. The most common method of brazing is with a torch, taking multiple passes and using a puddle method to apply to filler. Another common method is furnace brazing, which is easier when mass-producing items. Brazing also tends to produce a cleaner joint with no secondary finishing necessary.

3. Atomic Hydrogen Welding (AHW)

AHW is an older process used to manufacture “lifting chains” that were used on shipyards or construction sites. The biggest difference with this welding process is that it uses hydrogen gas, with two tungsten electrodes. The high temperature of the arc between the electrodes causes the hydrogen molecules to disassociate into atoms. With most of the heat absorbed by the gas molecules, the atoms leave the arc, move to work site, and reform into hydrogen releasing the energy stored. This hydrogen then burns normally using oxygen from the atmosphere. With the intense heat (4000 degree C.) produced by this process, it is used when quick welding is needed. One of the most important parts of this process is that it prevents oxidation of the metal and the electrode as well as reducing the amount of nitrogen picked up.

4. Electroslag Welding (ESW)

This is a heavy duty, highly productive, single pass welding process that is for thicker materials between 1 inch and 12 inches in a vertical or close to vertical position. It is used mainly to join low carbon steel plates or sections that are very thick. Electroslag welding can also be used in types of welding with structural steel if certain precautions are observed. Beginner welders can get this certification during a basic welding course. The plates and section to be welded are sided with mold plates to keep the molten metal and slag in. The consumable electrode is places vertical in the workspace and is slowly drawn out as the edges of the work material are welded together. The advantage to this welding process is that it only requires one pass and as long as the weld is carefully planned it is less likely to have any imperfections. The slag collecting on the top of the molten pool helps to retain heat and ensures proper penetration of the work materials. The slag also helps to ensure even cooling, which is important when working on large materials and structural pieces.

5. Thermite Welding

Ensuring a consistent, high-quality weld requires full penetration of the filler material into the base material. This is especially important when dealing with thicker material that must withstand a high stress environment with a wide range of temperatures. Railroad tracks hold an immense amount of weight and regularly have to flex. Creating a high-quality weld between two sections of track is very important.

The most commonly used process for creating these welds is known as Thermite or Exothermic welding. This process uses a combination of thermite and strengthening alloys to create a weld with higher mechanical strength and resistance to corrosion. Leaving a 1-inch gap between the ends of the rails, a mold is placed around the joint. After pre-heating the work pieces and mold with a torch or other heat source, the thermite and alloying metal are ignited. These materials are allowed reach completion, which means completely melting and mixing the alloy or steel. The molten material then flows into the mold combining with the rail ends and forming the weld. The steel or alloy used is heavier then the slag, which helps to ensure a sound quality weld. The slag from the top of the molten metal siphons onto two trays on the side of the mold and is removed first. The entire setup is allowed to cool, and the mold is removed. Hot chiseling as well as grinding the joint with a special rail-grinder cleans the weld and removes any extra material. This process can also be controlled remotely and is used for joining electrical conductors from a distance.