One of the most widespread forms of welding, and at the same time one of the easiest to learn is Oxy-acetylene or gas welding. It’s used to create strong and lasting welds in a range of metals, and doesn’t require much in the way of equipment to get started. The high temperature (3500 degrees) at which oxygen and acetylene combust are enough to fuse thicker pieces of ferrous and non-ferrous metals. And lower temperatures run through the same (or similar) gear are ideal in other applications, such as soldering and brazing. This versatility can be put to good use in a range of different industries.
What is Gas Welding and How is it Done?
Two similar or different pieces of metal can be joined in different ways, but it’s only with gas welding where you don’t require electricity or the use of expensive welding machines to get the job done. Gas welding is one of the oldest forms of welding, existing for over a century, and still uses the same simple equipment and gas welding supplies. This includes mixing oxygen and acetylene from separate gas cylinders, each fitted with gauges to control pressure and flow, and connected to a welding torch by way of sturdy gas hoses.
It’s in the torch that the two gases are mixed. The torch is also where the proportion of gases can be tailored to get different types of flames, each suited for different purposes. Neutral flames (with the same ratios of oxygen and acetylene) are what fuse most metals, but a carburising flame (with more fuel) can be used for thicker workpieces and metals requiring more heat, and an oxidising flame (with more oxygen) in thinner pieces.
In all cases, a filler rod can be used to protect the weld pool (the area where the two metals melt and combine), but it’s the flame that keeps outside contaminants away so a filler rod isn’t a must. Any spatter produced is removed with a simple swipe or two of a wire brush or the use of a chipping hammer in more pronounced instances.
Gas welding is done by holding the torch above the weld pool at the required distance and angle and using small circular movements. Different techniques are preferred by different welders. Forward welding welds workpieces from right to left (with or without the addition of filler rod at the same time). Backwards welding is similar but done in the opposite direction, and vertical welding uses small movements from bottom to top and is required in overhead uses.
Besides acetylene, other fuel gases like LPG and hydrogen generate lower temperatures needed for soldering and brazing. Torches in these techniques differ slightly from what is used for welding purposes.
Oxygen and Acetylene Gas Cylinders
This house the pressurised gases inside. Cylinders are made of thick steel and have regulator valves at the top to adjust pressure. Acetylene cylinders are red or maroon in colour, often smaller than oxygen cylinders (in standardised D, E or G sizes), whereas oxygen cylinders are black, often taller and thinner and in E2 or G2 sizes. Both types will be marked with the contents, gas pressure ranges, and general safety info in terms of usage and handling. Additions like cylinder chains or restraints for transportation, and hooks for hanging are inexpensive but useful.
Regulator Valves and Gauges
Both cylinders have their own control regulator valves, to adjust the amount of gas coming out. These are also used to get different ratios of oxygen and acetylene in the different flame types. Pressure gauges inform the welder of the pressure of the gas in the cylinder, as well as the pressure in the hoses.
Separate hoses from the cylinders and connect them to threads or inlets in the lower part of the torch handle. Like the bottles, these too are in the appropriate colours for obvious safety reasons.
Flashback Arrestors and Flame Traps
These are essential safety devices fitted between the hoses and cylinder regulator valves to prevent the movement of gas back into the cylinder, and something that can cause an explosion or flashback if you’re not careful. The same can also be fitted just before the torch for additional safety.
Welding torches are where the magic happens. They’re the main part of any gas welding gear, and consist of several distinct components. The torch handle has inlets at the lower end to accommodate the hoses, in addition to the control valves to regulate gas flow and provisions for flashback arrestors. Here you’ll also find the mixing chamber, where the two gases are mixed before they combust.
The top part of the torch is where differently-sized nozzles and tips are attached. These also vary in shape and determine the intensity of the flame; something that you’ll change for different types and thicknesses of metals to get welds in the needed strength. For soldering and brazing, there are separate nozzle types, whereas if you also need to cut into metal, look for cutter torches with the right attachments.
What Else Do I Need?
To start a flame you’ll need a flint lighter. This is safely done by bringing the flint near the torch tip and with the gases at lower pressures. I previously mentioned filler rods, and here you need rods in the same materials as that of the workpiece. Rods are used to prevent possible spoiling of the weld pool and also help to get stronger welds. Other equipment and gas welding supplies increase convenience, and safety and speed up workflow. Look for various welding clamps and magnets when aligning and welding bigger and heavier workpieces, basic safety gear such as helmets, gloves, aprons and welding footwear, nozzle tip cleaners for smoother-looking welds and more.
Basic starter kits have all that you need and are (mostly) of good quality to ensure that welding is both safe and effective. Cylinders are bought separately. Compared to other equipment used in the different welding types, the gear is portable, lightweight (with everything fitting on a trolley), as well as inexpensive, meaning gas welding can be used in different settings (without a power supply) and won’t be hard on the back pocket.
The process gets good welds when doing general repair work, fabricating sheet metals or working with high-carbon steels, in addition to welds in automotive and aircraft components. Other accessories are also cheap to buy and extend use beyond welding. This is also the easiest form of welding to master, and tricks of the trade learnt here can benefit you if you choose to go on to TIG or MIG welding.