Oxy-Fuel Cutting Technique

If you’re curious about Oxy-Fuel Cutting Technique, you are not alone. This thermal cutting process, utilising a combination of pure oxygen and fuel gas, is a staple in various industrial applications, particularly in the realm of steel fabrication. Let’s delve deeper into what oxy-fuel cutting entails, its applications, and the critical factors influencing its efficacy.

What is Oxy-Fuel Cutting?

Oxy-fuel cutting, also known as “burning,” “torch cutting,” or “flame cutting,” is a process wherein heat from a specialised torch raises the surface or edge of a metal, typically steel, to an approximate temperature of 1800 degrees Fahrenheit. Subsequently, a high-pressure stream of pure oxygen is directed to the heated area. This intense oxygen stream initiates a chemical reaction with the metal, causing rapid oxidation and forming a cavity. The combination of heat and oxygen stream, moving at a consistent speed, facilitates precise cutting into the metal.

The Chemistry Behind Oxy-Fuel Cutting

The chemical reaction underlying oxy-fuel cutting is often referred to as “rapid rusting” or “rapid, controlled rusting.” This terminology encapsulates the rapid oxidation process that occurs when steel interacts with pure oxygen under intense heat.

Applications and Limitations

Oxy-fuel cutting finds extensive use across various industrial sectors, primarily in cutting steel. It is a versatile method capable of cutting steel of various shapes and sizes, with thicknesses ranging from 0.5 mm to 250 mm. However, its effectiveness is limited to metals with oxides having a lower melting point than the base metal itself. This restricts its application to materials such as low carbon, mild steel, and certain low alloy steels.

Critical Components: Oxygen and Fuel Gases

The purity of the oxygen source is paramount for achieving optimal cutting speed and quality. Oxygen with a purity of no less than 99.5% ensures efficient cutting performance. Additionally, nozzle design plays a crucial role in maintaining the purity of the oxygen stream by preventing air entrainment, which can compromise cut quality.

Fuel gases are equally important in oxy-fuel cutting systems, with different gases impacting factors such as flame temperature, heat distribution, and cutting speed. Common fuel gases include propane, acetylene, propylene, liquified petroleum gas (LPG), MAPP (methylacetylene-propadiene), and natural gas.

Factors Influencing Fuel Gas Selection

• Acetylene: Known for its high flame temperature, acetylene facilitates rapid piercing and produces an intense flame, reducing the Heat Affected Zone (HAZ) and distortion.
• Propane: With a lower flame temperature than acetylene, propane leads to slower piercing but similar cutting speeds.
• MAPP: MAPP gas is a popular alternative that offers a more evenly distributed heat source than acetylene. It ensures consistent heat flow for precise cuts.
• Propylene: Similar to MAPP, propylene provides a uniform heat source, concentrating heat on the outer edges of the heat cone for efficient cutting.
• Natural Gas: Having the lowest flame temperature among the fuel gases, natural gas exhibits slower piercing times but remains a viable option for certain applications.

In conclusion, oxy-fuel cutting stands as a versatile and effective method for cutting steel in various industrial settings. Understanding its principles and the role of oxygen and fuel gases is essential for optimising cutting performance and achieving desired outcomes.