What is Gas Welding?
Gas welding, also known as oxy-fuel welding, oxyacetylene welding, and oxy welding, is a metal joining process developed in 1903 by French engineers Edmond Fouche and Charles Picard.
This process involves using fuel gases and oxygen to weld and cut metals, producing a shared pool of molten metal at a temperature of 3,773 K (3,500 degrees Celsius).
You can add filler materials to the joint to improve its strength. In oxyacetylene cutting, a special cutting flame heats the metal to its kindling temperature, resulting in a molten oxide known as slag.
The torch valve contains a mixing chamber that helps mix oxygen and acetylene before it releases as flame.
Applications of gas welding
The applications of gas welding include welding and cutting metals. Below are the types of gas welding used:
- 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.
- Sheet metal fabricating plants use oxyacetylene welding applications. finally,
- Can join materials that require a relatively slow rate of heating and cooling.
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Components of Gas Welding
The major parts of gas welding are fuel cylinders, oxygen cylinders, pressure regulators, control valves, and welding torches. Other parts for safety include overalls, boots, hand gloves, goggles, and shield glass.
1. Acetylene Gas Cylinder
The fuel gas is one of the most important parts of the gas welding system. Typically, we store this in a cylinder. We seal and construct the pressurized fuel cylinder from strong-gauge steel to prevent it from weakening. Typically, these cylinders have a golden brown color.
2. Oxygen Cylinder
A constant flow of pure oxygen is another essential part of the gas welding system. Compressed oxygen is also stored in oxygen cylinders and is required for welding.
The design of fuel and oxygen cylinders resists the pressure of the gases they contain. Usually, but not always, they are painted black.
3. Pressure Regulator
Welding requires a method to reduce the high pressure of oxygen and fuel gases for safety. A pressure regulator is useful in this situation. The apparatus normally delivers gases at 7–103 KN/M² and oxygen at a steady pressure of 70–130 KN/M².
4. Regulating valves
There are separate control valves for each gas. Control valves regulate the release of gas from the cylinder. Control valves are essential for managing the fuel-to-oxygen ratio, as well.
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5. Mixing chamber
This apparatus, as its name implies, is used to safely combine fuel and oxidant. To control the flow of gas from the cylinder to the mixer chamber, a control valve is employed.
6. Welding Torch
The “end of the job” for gas welders is this. This typically includes control settings and mixer chambers. To make the job of the welder easier, a combination of fuel and oxygen is burnt together in a nozzle at the other end of the torch.
Gas Welding Tools and Equipment
The welding process involves the use of gas cylinders, regulators, hoses, welding torches, fittings, and protective clothing to achieve cutting and joining operations.
Gas welding is a process that burns gas fuel (acetylene) with oxygen to produce enough heat to melt metal items and join them together. The various types of gas welding tools and equipment include gas cylinders, regulators, hoses, welding torches, fittings, and protective clothing.
Heat-treated steel is used to make gas cylinders, which store gases at high pressure. They are designed to maintain a constant temperature and pressure by reducing or increasing pressure supplies from the cylinder.
Hoses and fittings transport gases from the cylinder regulator to the torch, with each cylinder having its own hose. Fittings are designed for proper tightening and should be free from grease or oil to avoid explosion.
The welding torch plays a crucial role in mixing oxygen and acetylene, producing a controlled flame, preventing flashback, and obtaining a specific flame. There are two types: the equal pressure (medium-pressure torch) and the injector (low-pressure torch).
Flame arrestors protect operators and equipment against flashback, while an economizer saves oxygen and fuel gas when the torch is not used. Other personal safety equipment includes eye goggles, apron, gloves, booth, fluxes, welding rod, hammer, etc.
Diagram of Gas Welding
Related: How Does Metal Inert Gas (MIG) Welding Work?
Types of Gas Welding
The various types of gas welding are oxyacetylene welding, oxy-gasoline welding, MAPP gas welding, propane/butane gas welding, and hydrogen welding.
1. Oxy-acetylene welding
These types of gas welding channel two gases into a welding chamber, which aids in mixing the gases and producing a flame. Oxy-acetylene welding has two cylinders containing acetylene and oxygen gas. These gases flow from different indicated hoses to the torch.
Gas welding techniques are commonly used. It produces the highest flame temperature of all fuel gases. However, the high cost of acetylene improves other techniques.
2. Oxy-gasoline welding
When acetylene canisters are unavailable and fuel is a concern, we resort to oxy-gasoline welding. Torch use in these types of welding is more effective than oxyacetylene when cutting thick steel plates.
Pressure can be pumped manually by hand from the cylinder, making the pressure level controllable.
3. MAPP Gas welding
MAPP is an abbreviation for methylacetylene-propadiene-petroleum. It is a mixture of gases with more inertness than other gas mixtures, making it safe for operators.
MAPP, just like oxy-gasoline, can operate at very high pressure, making it useful in cutting operations. However, due to the flowing of hydrogen in mixtures, the gaseous medium is unsuitable for joining steel.
4. Propane/butane gas welding
Propane and butane are similar gases that can be a mix or used alone to produce a flame. It is less expensive and easier to transport. Propane torches are suitable for soldering, bending, and heating.
However, propane offers a lower flame temperature compared to acetylene. In these types of gas welding, propane requires different torch tips for different operations.
Related: How Does Tungsten Inert Gas (TIG) Welding Work?
5. Hydrogen welding
Hydrogen welding uses higher pressure than any other fuel gas, which makes it useful for underwater welding. Most hydrogen welding equipment works on electrolysis. It is achieved by splitting water into hydrogen and oxygen.
How Does Gas Welding Work?
In the working of gas welding, oxygen and acetylene burn at about 3,773 K (3,500 degrees Celsius). The two basic operations of oxyacetylene welding include welding and cutting.
The welding operation is carried out when two parent metals are heated to a temperature that produces a shared pool of molten metal. It cools and produces a joint.
Sometimes, we add filler materials to the joint. It improves the strength of the joint and produces a stronger joint, even stronger than the parent metal.
When cutting with oxyacetylene, a torch valve releases oxygen gas and then acetylene to create a unique cutting flame. We use the torch to heat the metal to its kindling temperature.
It reaches stages where metal burns into a molten oxide as it flows out of the kerf as slag. It contains a mixing chamber, which helps in mixing oxygen and acetylene before it releases as flame.
Advantages and Disadvantages of Gas Welding
Gas welding offers several advantages over other welding methods, including the ability to bond different metals, no need for electricity, improved temperature control, and precise control over filler metal deposition.
It also requires low-cost equipment, requiring minimal initial capital, and does not require specialist labor.
Gas welding equipment is portable, making it easy to carry and handle. However, it is not suitable for thick sections, has a poor surface finish, and is not suitable for high-strength steel due to its heated zone affecting the mechanical properties of the base material.
It also has lower heat and metal joining speed compared to other welding methods, cannot reach the boiling temperature of arc welding, and lacks a dedicated flux protection system, which can lead to serious welding defects.
Despite these advantages, gas welding has limitations, such as not being suitable for thick sections, having a poor surface finish, and not reaching the boiling temperature of arc welding.
Read more: 15 Different Types of Welding and Their Uses
Safety Precautions in Gas Welding
Gas welding is a hazardous process that requires strict safety precautions due to the hazardous nature of the gas used. The process involves the mixing of flammable gases like acetylene and oxygen in a torch, which can ignite and condense.
The resulting flames can be explosive if exposed to fire.
To prevent this, it is crucial to follow safety regulations in industries and fabrication shops, including personal protection, storage and handling safety, environmental safety, operation, and equipment safety. Below are areas where safety precautions are required in gas welding:
Personal protective equipment
Use safety glasses or eye goggles to shield your eyes from infrared radiation. Protective clothing such as a flameproof apron, gloves, cap or helmet, and boots should be worn before welding.
The apron should be well-fitted to avoid fraying. The shirt should be long-sleeved, and the trousers should be long enough to cover the top of the boot.
Protective clothing should be free from oil or grease. All these clothes should be in excellent condition before operators or students use them.
Storage and Handling Safety
Cylinders should not be exposed to heat and should be securely chained to prevent them from falling. they should be kept away from flammable and combustible materials, the same as in an upright (vertical) position.
Store the acetylene and oxygen cylinders separately in a well-ventilated area. It should not be a drag, but rolling on a slow movement on the bottom edges.
Valves on cylinders should be closed before moving. Regulators and protective caps should be kept in place. Keep hands off grease or oil when opening or closing valves and regulators.
Environmental safety
Industries or shops where gas welding is used should have proper ventilation, lighting, walkways, storage, escape routes, safety posters, etc. The floor should be kept clean and free from water, grease, and oil.
Fire extinguishers should be easily accessible and welded jobs should be properly stored.
Sets of gas welding equipment should be at least 10,000 cubic feet away from each other. The ceiling height should be at least 16 feet from the ground. Finally, all equipment should be inspected before welding.
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Operation and Equipment Safety
You must install flame arrestors in the acetylene and oxygen cylinder lines. One of them should be fitted beside the low-pressure regulator and the other near the touch. Higher pressure should release more oxygen than acetylene to prevent the flame from going back.
However, acetylene should not be used when welding at a pressure exceeding 1 bar of atmospheric gauge to avoid explosion.
Whenever a backfire occurs, the oxygen valve should be closed first and acetylene should follow immediately. It should be rectified before operations continue.
In case of a flashback (explosion in gas hose), the first thing to do is to set both cylinder valves apart. Whenever a flashback occurs, all hoses should be replaced with new ones.
Fittings should be used to securely tighten all hose connections. Finally, there should be working time for the acetylene cylinder. The reason because using acetylene at a high temperature can cause exposure. The time of use will be determined by the size of the cylinder. Learn about types of gas welding here!