745 Welding, Cutting, and Brazing Safety

Oxygen-fuel Welding and Cutting

Oxygen-fuel welding and cutting use a flame produced by burning a fuel gas, such as acetylene or propane, with oxygen or air.

Oxyacetylene Welding (OAW)

Oxyacetylene welding is a gas welding process that produces a flame by mixing acetylene gas with pure oxygen. This creates one of the hottest combustion flames available, with temperatures reaching up to 5,580°F (3,082°C). The high heat makes it ideal for welding, cutting, and heating metals. OAW is particularly effective for joining carbon steel, low-alloy steel, cast iron, and non-ferrous metals such as copper and aluminum (when used with the proper fluxes). The flame is adjustable, allowing operators to create a neutral, carburizing, or oxidizing flame depending on the welding task.

In addition to welding, OAW is widely used for flame-cutting thick steel sections, heating seized components, and performing braze welding. Common applications include repairing heavy machinery, constructing metal frames, or fabricating structural steel components. For example, oxyacetylene welding is often used in automotive body shops to repair car frames and exhaust systems, or in shipyards for welding hull components. The process is highly adaptable, but it requires careful handling due to the flammability of acetylene and the high pressure of oxygen cylinders.

Pros:

• Produces a very hot flame, making it suitable for welding a wide range of metals, including steel, cast iron, and non-ferrous metals.
• Versatile: can be used for welding, cutting, brazing, and heating metals.
• Portable and does not require electricity, making it ideal for fieldwork and repairs in remote areas.
• Relatively low equipment cost compared to other welding processes, such as TIG or MIG welding.

Cons:

• Flame temperature can be difficult to control for very precise work.
• Requires frequent maintenance of equipment (hoses, regulators, tips).
• Less suitable for high-precision welding on thin materials, as the heat can cause warping.
• Oxygen and acetylene cylinders must be handled with care due to the high pressure and flammability of acetylene.

Oxypropane Welding (OPW)

Oxypropane welding, while similar in setup to oxyacetylene, uses propane as the fuel gas instead of acetylene. Propane, when mixed with oxygen, produces a flame with a temperature of approximately 4,600°F (2,538°C). While this temperature is sufficient for cutting and heating operations, it is generally not hot enough for welding ferrous metals effectively. However, it is widely used for tasks such as flame-cutting mild steel, preheating large steel components, and brazing non-ferrous metals like copper, brass, and aluminum (with flux).

One advantage of oxypropane welding is that propane is less expensive and more readily available than acetylene, making it a cost-effective choice for shops and contractors. For instance, maintenance crews often use oxypropane setups for dismantling old steel structures or removing corroded bolts and fasteners by heating them until they can be loosened. Scrap yards also rely on oxypropane for cutting scrap metal due to its affordability and efficiency in heating and cutting operations.

Pros:

• Lower cost of propane compared to acetylene, making it more affordable for some applications.
• Produces a cleaner flame compared to oxyacetylene, which is useful for cutting and brazing.
• More efficient for large-scale cutting and heating operations, especially on mild steel and other metals.
• Less toxic fumes and a less aggressive flame, which can make it safer in certain environments.

Cons:

• Lower flame temperature compared to oxyacetylene, which limits its use for welding ferrous metals effectively.
• Not suitable for high-precision or fine welding jobs.
• Requires special training to handle propane properly, especially in high-heat applications.
• Not as widely accepted in industries that require high-quality, precise welds.

Knowledge Check Choose the best answer for the question.