Gas welding is one of the most common forms of welding. It’s relatively easy to learn, uses simple and inexpensive equipment and has a range of uses covering many industries. In addition, it is the go-to option for simple repairs. The heated gases can be used to create strong and lasting welds in both ferrous and non-ferrous metals, and welders won’t need a nearby mains connection to power expensive welding machines like in other welding types. By following simple safety precautions, you can both weld and cut through the most commonly used metals.
What is Gas Welding?
Gas welding, also commonly called Oxy-Acetylene welding uses oxygen and acetylene (most often), heated to around 3200°C to fuse two metal pieces together. The high temperatures first melt, then fuse the metals together. Though this doesn’t create the cleanest welds in commercial metals like steel, aluminium or copper, for most applications, like sheet fabrication, it does the job. A cleaner and stronger weld is achieved with the use of filler rods or electrodes melted into the weld pool.
The Equipment Used
The popularity of gas welding is down to the accessibility and affordability of the required equipment. You’ll find welding gas supplies and equipment at larger hardware chains and more reliable gear from independent welding retailers. Either way, welders don’t need much to get decent, strong, and long-lasting welds.
• Fuel cylinders – Acetylene is the only fuel gas that can reach the high temperatures needed for welding. And this is stored in tough steel cylinders and is pressurised. Acetylene cylinders are a maroon colour, smaller than oxygen cylinders, and are operated by turning a pressure valve to the closed or open position. A pressure gauge displays the pressure and another gauge the remaining gas in the cylinder. Similar are red LPG bottles used in soldering and brazing.
• Oxygen cylinders – Pure oxygen is used to modify the temperature (and properties) of the flame. Oxygen is stored in a pressurised black steel cylinder, to distinguish it from the acetylene cylinder. It shares the same valves to open and close gas flow, as well as a pressure and regulator gauge. Both cylinders should be affixed with bottle or cylinder restraints when not in use.
• Pressure regulators and Control valves– to reduce the high pressure in both cylinders, pressure regulators control the amount of oxygen entering the connected hoses and reaching the torch. Oxygen flows at a higher rate than acetylene, around 10 to 18 psi (0.7 to 1.25 Bar) compared to 0.15 to 15 psi (0.1 to 1.03 Bar). Do not operate cylinders with damaged or faulty pressure regulators.
• Flashback Arrestors/Flame Traps –These are installed at the outlet end in cylinders to prevent the flow of gas back to the cylinders. And if that happens you know you’re in trouble.
• Hoses – There are separate hoses from each cylinder and each terminates in threads/inlets at the lower end of the torch handle. Hoses and connecting ends are appropriately colour-coded.
• Torches – This is one of the more important pieces of welding gas supplies. There are torches used for welding, those used for cutting, or for both purposes. Torches consist of the torch body or handle separate control valves that control the flow of oxygen and acetylene, and a mixer chamber where the two gases combust. There can also be a connection for additional flashback arrestors. Torch barrels and tips are the parts that redirect the flame onto the weld. Tips can be fitted with differently-sized nozzles to control the intensity and type of flame. This determines the overall strength of the weld.
The initial spark is provided by a flint lighter. This is brought close to the mixed gases to ignite them. This should be done at lower pressures. With the gases ignited, you can adjust the separate torch valves to get the right mix and the right type of flame. Usually, a neutral flame is required, but higher temperatures are achieved by increasing the flow of oxygen, in an oxidising flame.
Another thing to consider is the use of a filler rod. This is optional but can lead to stronger and better-looking welds. Different filler rods are used for different workpieces. Stainless steel pieces for instance are joined with filler rods in varying stainless-steel grades.
And let’s not forget welding safety gear, like gloves, auto-dimming helmets, aprons, and the right footwear. Temperatures won’t get as hot as in other forms of welding, but 3000 degrees Celsius is more than enough to cause serious injury. Additionally, eyes need to be shielded, and workpieces handled with pliers. Similar tools, in the form of welding clamps and magnets, can be used in fixturing larger workpieces when there’s no extra pair of helping hands.
Why Choose Gas Welding?
Gas welding can be used to fuse ferrous and non-ferrous metals together, particularly thinner sheet metals. And it produces welds of adequate strength. The gear is simple, safe to use (when the necessary precautions are obeyed), affordable, portable and won’t take up a lot of space. The same layout, with minor changes, is used for cutting purposes. Most welders learn the tricks of the trade with gas welding techniques, before moving on to MIG and TIG welding.
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