When it comes to cutting metal, several processes are available today. Two of the most widely used cutting technologies are oxy-fuel and plasma. Choosing whether to go plasma or oxy-fuel for your steel cutting job depends on a number of factors, including the type of alloy, its thickness and any specific requirements for tolerance and cut quality.
Both oxy-fuel cutting and plasma cutting have their own set of advantages and limitations. It’s important to understand each of these to properly choose the correct type of cutting for your application.
The oxy-fuel gas cutting process severs metal by utilizing the chemical reaction of oxygen with metal at elevated temperatures. The required temperature is provided by the combustion of a fuel gas and oxygen. The cutting action is supported by an additional stream of pure oxygen.
The torch used in the cutting process produces the preheating ﬂame by mixing fuel gas with oxygen in the correct proportions to support combustion. It also provides a concentrated stream of pure oxygen to the base metal. This oxygen oxidizes the hot metal and blows the molten metal out of the cut area, ideally leaving a narrow, square kerf (gap) with sharp edges. Generally, oxy-fuel cutting is used to cut thicker metal, approximately 1/2 inch thickness or greater. This is because other methods, namely plasma, are faster on thinner materials.
Depending on the fuel gas selected and the particular application, different cutting tips and torch mixing chambers are used. Among the fuel gases used are acetylene, propylene, propane, and natural gas.
Plasma cutting is made possible by introducing electricity into compressed air to create an ionized, imbalanced plasma gas. This plasma gas is pushed through a small opening in the nozzle by pressurized air, producing a controlled, electrically conductive stream of plasma gas. More energy can be added to increase the heat of the plasma arc, which improves the cutting capacity and efficiency of the system.
Plasma cutting offers quick starts and fast cutting speeds on thin and thick metals, including aluminum and stainless steel. It typically provides a clean cut, with minimal cleanup. Depending on input power and material thickness, plasma cutting speeds can range from 6 to 50+ inches per minute. However, as material thickness increases, the cutting speed advantage over oxy-fuel systems can be diminished.