Flame Cutting also named Oxy Fuel Gas Cutting is a high productivity cutting method developed more than 100 years ago. The process is a Thermo-Chemical Process requiring a source of intense heat and pure oxygen. The purer the oxygen, the better.
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Method
The metal is first heated by the flame until the ignition temperature is reached, which is lower than the melting point. The fuel gas can be e.g. methane, acetylene or propane. Then oxygen is supplied to the pre-heated area and reacts with metal by forming iron oxide and producing heat exothermically. It is the exothermic reaction that continues the cutting process. As the metal burns, it immediately turns to liquid iron oxide and flows away from the cutting zone. Some of the iron oxide remains on the work piece forming a hard slag, which can be removed by grinding.
The choice of fuel type and nozzle selection make the flame cutting process faster, which, in turn, reduces labor costs. While the oxygen jet determines the speed of a cut, the gas used in pre-heating also influences the initiation time of cutting.
The choice of gas used in the process depends on whether the operation is manual or mechanized, on the type of work carried out, and on the material type. For instance, acetylene has a flame temperature of 3160 degrees Celsius, making it ideal for thin sheet and bevel cutting. However, acetylene costs more than other gases and does not generate much heat. It is thus not suitable for cutting larger metal plates.
When small parts are cut, the heat supplied by the cutting torch and by preheating will be accumulated in the work piece. The smaller the size of the cut part the greater the risk of softening. When oxy-fuel is used for cutting 30 mm or thicker plate, the distance between two cuts should be enough to avoid loss of hardness of the entire component.
Oxy-fuel cutting supplies more heat and thus raises the temperature of work pieces than all other cutting methods. The quality of the final cut surface can be excellent with a sharp top edge, square/flat cut surface, and a sharp slag-free lower edge.
Flame cutting features
Benefits
- Low equipment and consumables costs
- Easy to use
- Broad range of material thickness, from 1 to above 400 mm (in general >25mm)
- Could be portable equipment (usable outside the workshop)
- Suitable for the preparation of welds and for bevel cuts
Drawbacks
- Wide HAZ through the entire thickness
- Poorer tolerances compared to plasma
- Risk of hydrogen embrittlement on high grades and thick plates
- Slow cutting process compared to plasma or laser for thinner plates
- Process difficult to automatize compared to laser or plasma cutting methods because of heat distortion
Recommendations
Flame cutting is the most economical cutting method for thick plates (>25mm) when narrow tolerances are not demanded.
Our offer
SSAB can offer flame cutting services from our own centers globally and in addition we have a service partner network that can be utilized. Our offer includes:
- Lengths up to 37,000mm
- Thickness up to 380mm
In many of our service centers we have the possibility to combine flame cutting of parts with other metal processing methods, for example press bending, to fulfil your complete requirements.
