Time to read: 6 min
Gas welding is a process that joins metal pieces by melting and cooling parts of both. This is achieved by creating an extremely hot flame using oxygen and a fuel gas. The types of fuel gases that can be used include acetylene, gasoline, MAPP (methylacetylene-propadiene propane), butane, propane, or hydrogen. Although gas welding has been surpassed by electrical welding methods in many applications, its portability, effectiveness, and simplicity mean it is still widely used in the manufacturing industry.
The working principle of gas welding involves feeding both oxygen and fuel gas out of the end of a torch to produce a highly concentrated flame that can melt metal. Material is melted at the seam between two parts to create what is known as a weld pool. The pool then cools and bonds the pieces together to form a strong joint. The welder’s flame must be moved slowly to allow the joint to cool without oxidation, which can create brittle connections.
There are five main types of gas welding, differing by the fuel gas involved: butane or propane welding, hydrogen gas welding, MAPP gas welding, oxy-acetylene gas welding, and oxy-gasoline gas welding.
One of the primary uses of gas welding services is repair work. This technique is superior at bridging gaps between parts. Other applications of gas welding include the fabrication of sheet metal, joining of aircraft parts, automotive chassis and frame fabrication, and joining of high-carbon steel.
The process for using a gas welder is as follows:
- Check if the setup is safe and secure. Ensure that the torch, hoses, regulators, and cylinders are attached correctly, and check that the nozzle is clear.
- Adjust the fuel gas with the nozzle’s regulator closed. Open the cylinder shut-off valve, and then slowly open the regulator to the right pressure. Once the right pressure is achieved, close the fuel gas shut-off valve at the torch.
- Repeat step two with the oxygen supply.
- Turn on only the fuel gas at the torch and ignite the flame. The flame will let off black smoke from unburnt carbon, so be careful not to inhale it. Open the fuel valve at the torch until the smoke has stopped.
- Open the oxygen valve at the torch and adjust it until you have the neutral, oxidizing, or carburizing flame that you need.
- Ensure the metal to be welded is correctly positioned on a heat-resistant material such as fire bricks.
- Before fully welding, place a tack weld at each end of the joint to prevent the pieces from moving during the process. To do this, hold the torch at a 45-degree angle close to the metal and move in a zigzag pattern between the metals, heating them until a weld pool forms. Once a weld pool forms, remove the heat.
- To weld the joint, create a weld pool by zigzagging the flame at a 45-degree angle across the two pieces of metal until a melted pool starts to form. Push the pool along by slowly moving the torch from one end to the other.
- Once the weld is complete, allow the metal to air-cool. Do not use water as this will make the weld brittle.
- When turning off the welding equipment, always turn off the fuel gas first and then the oxygen. If there is no more welding to be done, ensure to close the shut-off valves at the cylinders.
Metals commonly used in gas welding can be of the same composition. For example, steel can be welded to steel. However, aluminum cannot be welded to steel. Here are some examples of metals that are commonly gas welded:
- Aluminum: Aluminum has a relatively low melting point of 1,220 degrees Fahrenheit and is welded using a carburizing flame. This type of flame is cooler than neutral and oxidizing flames. A unique step for aluminum is the removal of the oxide layer. The oxide layer has a much higher melting point than the aluminum itself; if you melt the oxide layer, you risk quickly melting all the way through the metal below as well. Instead, the oxide layer must be removed using a brush.
- Copper: Copper is extensively used to make pipes for water and gas supplies. Connections between copper pipes are usually either gas welded or formed using compression joints. Copper piping requires a different style of welding than other metals. To weld a copper pipe, a fitting is first placed over the pipe. Both the fitting and the pipe are then heated, but the heat is not applied directly to the joint area. Filler metal is then added to the joint, and capillary action sucks the melt into the joint.
- Stainless Steel: Stainless steel is an iron-based alloy containing at least 11% chromium. The chromium protects the steel from corrosion. Gas welding stainless steel is difficult because it has a higher melting point than regular steel, so it requires a lot of heat.
- Brass: Brass is an alloy of copper and zinc and has a melting point of 1,710 °F. It is welded using an oxidizing flame. Brass is also highly thermally conductive, so only a large nozzle will be able to apply enough heat to melt the metal.
Gas welding has many advantages, the best of which is its low cost. Other advantages include:
- It can join parts made of both ferrous and non-ferrous metals.
- It does not require electricity, which means it can be used in isolated areas.
- It does not require high-rated skills.
- Welding equipment is portable, requiring only a fuel and oxygen tank, control valves, and a torch.
The main disadvantage of gas welding versus other forms is that it is limited to relatively thin sections of metal. Other disadvantages of gas welding are:
- It usually requires post-processing if aesthetics are important.
- The heat affects the mechanical properties of high-strength steel.
- It is slower than other methods because it doesn’t get as hot.
- Its lack of flux shielding can cause weld defects.
Summary: This article introduced gas welding, explained it, and discussed its various types and applications. Unofactory provides a wide range of manufacturing capabilities, including gas welding and other services for all of your prototyping and production needs. Visit our quoting engine to request an instant quote.