Oxy-fuel cutting has remained the go-to method for cutting thick carbon steel for decades. While newer technologies such as laser and plasma dominate thin and medium thicknesses, once thickness passes a certain point, oxy-fuel cutting continues to be the most sensible choice both technically and economically. This guide covers how oxy-fuel cutting works, where it is strong and where it falls short, and all its related aspects.
What Is Oxy-Fuel Cutting?
Oxy-fuel cutting (flame cutting) is a process that separates metal using a combustible gas together with pure oxygen. What sets it apart from other thermal methods is this: here, the material is separated not by melting but by burning.
The process happens in two stages. First, the preheat flame brings the steel's surface up to ignition temperature. Then a high-pressure jet of pure oxygen is directed at it, and the steel burns through oxidation. Because combustion is an exothermic reaction, the process generates its own heat and the cut progresses on its own.
Why Only Carbon Steel?
The most defining limitation of oxy-fuel cutting is the material, and the reason is purely chemical. For the method to work, the metal must react readily with oxygen.
- Carbon steels: Ideal thanks to a low ignition temperature and high heat of combustion
- Stainless steel: Not suitable — the chromium oxide layer prevents burning
- Aluminum: Not suitable — the oxide layer melts at a higher temperature than the base metal
- Copper and brass: Not suitable due to high thermal conductivity
Where Oxy-Fuel Cutting Excels: Thickness
What makes oxy-fuel cutting indispensable is its relationship with thickness. With laser and plasma, both cost and cutting time rise sharply as thickness increases; with oxy-fuel cutting, because the burning reaction generates its own heat, increasing thickness is far more manageable. This is why oxy-fuel cutting has no real rival on very thick carbon plate.
Gas Choice Affects the Result
The combustible gas used in the preheat flame — acetylene, propane, or natural gas — directly affects piercing time, cutting speed, and operating cost. Acetylene delivers the highest flame temperature and speeds up piercing; propane and natural gas are more economical but require longer preheating.
Cut Quality and Tolerance
In oxy-fuel cutting, quality is the combined result of nozzle size, preheat flame, cutting oxygen pressure, and travel speed. Cutting too fast leaves the cut incomplete; cutting too slowly causes melting and deformation at the edge.
What Happens After Cutting: The HAZ
The edge of a part separated by oxy-fuel cutting is different material than it appears. In a narrow band next to the cut line, the steel heats up and then cools rapidly, hardening in the process. Known as the heat-affected zone (HAZ), this band creates a risk of cracking and tool wear if the part will later be welded, bent, or machined.
Advantages and Limitations Summary
Advantages:
- Economical and efficient on very thick carbon plate
- Low consumable cost
- A mature and reliable technology
- Cost advantage grows as thickness increases
Limitations:
- Suitable only for carbon and low-alloy steels
- Produces a heat-affected zone and edge hardening
- Wider kerf compared to laser and plasma
- May require slag cleaning at the edge
- Falls behind in speed and precision on thin sheet
CNC Oxy-Fuel Cutting with DMK Makina
DMK Makina offers CNC-controlled oxy-fuel cutting service at its production facility in Lüleburgaz. Material grade and post-cut operations are evaluated together; preheating is applied when needed, appropriate machining allowance is planned for edges that will be welded, and parts are cooled in a controlled manner. For your thick-plate cutting work in the Thrace and Marmara region, you can contact us with your technical drawings.