What is Gas Welding?
Gas welding is a type of liquid state welding process in which fuel gases burn to generate heat. This heat is further used to melt interface surfaces of welding plates which are held together to form a joint. In this process, mostly oxy-acetylene gas is used as fuel gas.
This process can be done with or without the help of filler material. If the filler material is used, it is fed directly into the weld area manually. Gas welding is one of the most important types of welding because of its scope of application.
It is one of the oldest forms of heat-based welding and remains the go-to option for many industries.
The reason why this welding technique is still very popular is because of its ease of use and low-cost nature. Carrying out a welding process with gas welding is relatively easy and does not necessarily require expert welders.
When a fuel such as acetylene is used, the flame can reach temperatures of just over 5,700°F (3200°C). This temperature is lower than what we get from an arc welding machine, but the advantages previously mentioned outweigh this drawback for various types of repairs and construction work.
How is gas welding done?
When metals are welded using gas welding equipment, fuel gases are mixed with oxygen to produce a concentrated flame at a high temperature. This flame directly strikes a weld area and melts the materials in question (often, but not always, with the addition of filler material).
The melted section of each piece of metal forms something called a melt or weld pool where the liquid metals diffuse into one another and, once cooled, form a strong joint. This form of welding can be used for many common types of metals.
Completion of weld requires the welder to slowly remove the flame from the joint, giving it time to harden without oxidation.
Most commonly, oxygen is mixed with gases like acetylene, hydrogen, propylene, butane, and others. The choice of gas used for welding depends on the type of project, cost, and flame control.
The most commonly used gas welding fuel gas is acetylene. This is so popular, in fact, that it is not uncommon to replace the term gas welding with either oxy-acetylene welding, depending on the fuel that is used.
Main Parts of Gas Welding
You can probably already guess some of the main components of a gas welding system, but what other parts are needed?
Let’s take a look:
- A fuel cylinder: One of the most important parts of a gas welding system is, obviously, the fuel gas. This is usually stored in a cylinder of some kind. The cylinder is sealed and is made from heavy-gauge steel to prevent the compressed fuel from weakening the cylinder. These cylinders are usually painted a maroon color.
- An oxygen cylinder: Another critical component of a gas welding system is a constant supply of pure oxygen. The oxygen cylinder holds the compressed oxygen required for the weld. Both the oxygen and fuel cylinders are made to withstand the pressure from the respective gases. These are usually, but not always, painted black.
- Pressure regulator: As both the fuel and oxygen gases are stored at high pressure, some method is required to reduce the pressure for safe use during the welding process. This is where a pressure regulator comes in very handy. Typically, this device helps supply oxygen at a steady pressure of between 70 and 130 KN/M2, and the gas supply at between 7 and 103 KN/M2.
- Control valves: Both gases have their separate control valves. A control valve is used to control the amount of gas being released from the cylinder. Control valves are also crucial for controlling the fuel to oxygen ratio.
- Mixer chamber: This device is used, as the name suggests, to safely mix the fuel and oxidant. The control valves are used to regulate the flow of gases from the cylinder to the mixer chamber.
- Welding torch: This is the “business end” of the gas welding gear. This usually contains the mixer chamber and the control values too. At the other end of the torch is a nozzle where the fuel-oxygen mixture is burnt together for ease of application by the welder.
Applications of gas welding
The applications of gas welding include welding and cutting metals. Below is the used gas welding:
- Joining of ferrous and nonferrous metals
- oxyacetylene welding can be used for joining carbon steels, alloy steels, cast iron, aluminum, and its alloys, copper and its alloys, nickel, magnesium, etc.
- Widely used in automotive and aircraft industries.
- oxyacetylene welding applications are used in sheet metal fabricating plants. finally,
- Can join materials that require a relatively slow rate of heating and cooling.
Advantages of Gas Welding
The following are the advantages of gas welding:
- Portable and Most Versatile Process: Gas welding is probably portable and most versatile process. The ranges of gas welding products are very wide. It can be applied to variety of manufacturing, maintenance and repair work.
- Better Control over the Temperature: Gas welding provides better control over the temperature of the metal in the weld zone by controlling the gas flame.
- Better Control over Filler-Metal Deposition Rate: In gas welding, the source of heat and filler metal are separate unlike arc welding. This provides better control over filler-metal deposition rate.
- Suitable to Weld Dissimilar Metals: The gas welding can be suitable to weld the dissimilar metals with suitable filler and flux material.
- Low Cost and Maintenance: The cost and maintenance of the gas welding equipment’s is low as compared to some other welding processes. The equipment is versatile, self-sufficient and portable.
Disadvantages of Gas Welding
- Not Suitable for Heavy Sections: Since the heat produced is not sufficient and hence heavy sections cannot be joined economically.
- Less Working Temperature of Gas Flame: The flame temperature is less than the temperature of the arc.
- Slow Rate of Heating: The rate of heating and cooling is relatively slow. In some cases, this is advantageous.
- Not Suitable for Refractory and Reactive Metals: Refractory metals like tungsten, molybdenum and reactive metals like titanium and zirconium cannot be welded by gas welding process.
- Larger Heat affected Area: Gas welding results in a larger heat affected area due to prolonged heating of joint.
- Flux Shielding is not so Effective: Flux-shielding in gas welding is not as effective as in case of TIG or MIG welding. The oxidation cannot be avoided completely.
- A problem in Storage and Handling of Gases: More safety problems are associated with the storage and handling of explosive gases e.g., acetylene and oxygen.