Flame cutting or plasma cutting?

Flame cutting or plasma cutting? Many companies ask themselves this question when they... Place orders with subcontractors. Both plasma cutting and oxyfuel cutting are thermal cutting processes and are used in... structural steel construction commonly used. In many cases both methods can be used, but this has an impact Steel construction costs. In this article will be exclusively stationary CNC cutting systems considered, no mobile handheld devices for flame cutting.

There are also combined systems which have both a plasma and an oxy-fuel cutting head.

Oxy-fuel cutting

How does oxyfuel cutting work

Oxy-fuel cutting uses the heat from the combustion of oxy-fuel and from the exothermic reaction of metal with oxygen to perform the cutting process.

Oxy-fuel cutting uses gases such as propane or acetylene as fuel. These burn and raise the temperature of the steel so that it starts to react with the oxygen. When metal reacts with oxygen, oxides and heat are formed. The oxides sink while the heat from the reaction encourages further cutting. Once metal oxide production begins, heat production is sufficient to sustain the cutting process.

However, the heat from the oxyfuel is still supplied to direct and support the cutting process. Oxyfuel cutting leaves behind melt residue that must be removed, requiring additional work and time.

For which steels is oxyfuel cutting suitable

Oxy-fuel cutting is suitable for Low and medium carbon structural steels. High carbon steels and stainless steels are more difficult to cut because they are more resistant to oxidation.

Material thicknesses in oxyfuel cutting

Oxy-fuel cutting mainly for medium and larger material thicknesses up to 1000mm. Current systems can process material thicknesses of approx. 5-300mm.

Oxy-fuel cutting advantages

• High material thickness
• Straight cutting edge

Oxy-Fuel Cutting Disadvantages

• High heat input
• scaling
• large heat-affected zone
• delay
• beard formation
• High gas consumption

plasma cutting

How does plasma cutting work

Plasma cutting uses plasma or superheated ionized gas to perform the cutting process. Plasma cutting is also known as plasma arc cutting. The temperatures reach up to 30.000 °C. When cutting metal, the plasma stream is directed at the workpiece at high speed and, due to its high temperature, melts any metal in its path. Plasma is generated by heating gases such as hydrogen, argon, nitrogen or their mixtures with the help of an electric current. The current is generated by an electrode in the torch and the workpiece as the anode.

It is a faster process than flame cutting and requires less gas, resulting in lower operating costs.

For which materials is plasma cutting suitable?

With the plasma cutting can any electrically conductive metal get cut. However, stainless steel, aluminum and carbon steel sheet and plate are common workpieces.

Material thicknesses in plasma cutting

Material thicknesses from 0,5 mm to approx. 150 mm can be processed. Sheet metal is mostly used about 10mm to 40mm cut with it. Laser cutting, which is even more precise, is often used for thinner sheets. Oxy-fuel cutting is often used for thicker sheet metal.

Plasma cutting advantages

• Higher cutting speed than oxy-fuel cutting (with a cutting thickness of approx. 20 mm, the cutting speed is approx. 4 times higher. The speeds only approach each other with greater material thicknesses.
• Plasma cutting is also suitable for stainless steel and aluminum
• The components can also be marked with the plasma cutter
• Less heat influence and therefore less distortion than with flame cutting

Plasma cutting cons

• High heat input (can be reduced by underwater plasma cutting)
• Heavy exhaust gas formation that requires extraction
• With plasma cutting, the cutting edge is not at right angles. The kerf is thicker at the top and narrows towards the bottom

Cost comparison of plasma cutting vs. oxy-fuel cutting

investment costs

The cost of a new CNC plasma cutting system is around €50.000 to €100.000, depending on equipment and performance. Combination flame cutting systems with plasma and oxy-fuel cutting heads are approx. 20% more expensive.

simple oxyfuelFlame cutting systems are slightly cheaper than plasma cutting machines. However, the costs depend on the table size, the number of burners and the load capacity of the table.

Running costs

The gas consumption in oxy-fuel cutting is significantly higher. In addition, autogenous flame cutting systems clear More maintenance and repair prone as plasma cutting systems.

For small and medium sheet metal thicknesses, plasma cutting is cheaper than oxy-fuel cutting. Flame cutting only becomes cheaper with greater sheet metal thicknesses of approx. 40mm. With very high sheet thicknesses, the costs for plasma cutting increase disproportionately.

Conclusion: flame cutting or plasma cutting?

Flame cutting and plasma cutting are both thermal cutting processes that are often used in structural steel construction. Both methods have their advantages and disadvantages and it is important to consider the individual requirements and needs of the use case in order to choose the most suitable method.

For most companies in structural steel construction Plasma cutter or combination systems recommended, Our Steel construction suppliers for halls, buildings or bridges They usually use both types of machines because the investment costs for the flame cutting system are relatively low. Autogenous flame cutting systems have their advantages for very thick, low-alloy sheets. Laser or laser technology is primarily used in sheet metal processing Water jet cutting systems for use