The flame cutting aggregate consists of a ring-shaped heating nozzle, a separate fuel gas-oxygen supply and an oxygen cutting nozzle placed in the middle.
With a heating flame, the material is heated locally to the individual ignition temperature and prepared for the cutting process. The heating flame is created by feeding a fuel-oxygen mixture into the heating nozzle. The oxygen escaping under high pressure (with a purity of at least 99.5 percent) oxidizes the carbon-containing metal and burns a kerf into the material.
The carbon content of the workpieces must be taken into account here: a high carbon content increases the ignition temperature and simultaneously reduces the melting temperature. Workpieces to be processed by flame cutting must always have a lower ignition temperature than their melting temperature. Metals with a carbon content below 0.3 % can be cut without any problems. For materials with a carbon content between 0.3 % and 1.6 %, the area to be cut should be preheated or even reheated in order to minimize or completely avoid cracks and stresses in the workpiece. However, the processability of a material using oxyfuel technology also depends on the composition of the alloys. Thus, other elements such as chromium and nickel influence the flame-cuttability.
Components processed with oxyfuel
Manual or automated flame cutting
In the field of oxyfuel flame cutting, manual cutting torches and machine cutting torches can be distinguished from each other. Depending on requirements, material and industry, there are numerous possibilities for oxyfuel technology.
Manual flame cutting
Manual oxyfuel cutting – also known as hand cutting torch, flame cutter or flame-cuting saw – is mainly used on construction sites, in workshops and in the basic equipment of rescue units, such as the Federal Agency for Technical Relief (THW) and the fire departments. In these applications it is not the precision and reproducibility of components that is important, but the flexible and fast processing of large material thicknesses of relatively small workpieces. However, fire hazard and workpiece distortion due to thermal influence greatly limit the application possibilities for manual flame cutting here.
Automated flame cutting
Automated CNC oxyfuel cutting systems have become indispensable, especially in precision-oriented metal construction. The CNC machines are sometimes equipped with more than just one oxyfuel torch for efficient parallel cutting operations and can usually be combined with various components such as plasma cutting units and pipe cutting devices. The precision and high automation degree of the cutting machines make working with metal easy and efficient. They therefore offer the optimum solution for almost all material thicknesses and score with functionality and flexibility.
In recent years, oxyfuel technology has undergone considerable improvements where fuel gases and burner heads are concerned, which have a positive effect on cost-effectiveness and cutting quality. The cutting range of oxyfuel technology covers material thicknesses starting from 5 mm, for material thicknesses above 160 mm flame cutting technology is the only possible cutting method within the thermal cutting comparison.
The limit of oxyfuel cutting is drawn by the chemical composition of the material: If the carbon content of the material is less than 0.3 %, flame cutting is possible without problems, between 0.3 % and 1.6 % C, preheating of the area to be cut is necessary. If the carbon content exceeds 1.6 %, the component is no longer suitable for oxyfuel flame cutting.
The quality of the flame cut is influenced by various parameters. The choice of fuel gas – usually a propane-oxygen or acetylene-oxygen mixture – and the resulting flame temperature are decisive for the cutting speed. Higher flame temperatures mean that the optimum ignition temperature is reached more quickly. The acetylene-oxygen mixture reaches flame maximum temperatures of 3160 °C and ensures maximum cutting speed and lower cutting costs. But also high oxygen pressure and an optimum distance between nozzle and workpiece contribute to good cutting results in oxyfuel technology.
Where is flame cutting used?
The application range of oxyfuel technology is diverse. It can be found in all industries that specialize in the processing of steel in the high material thickness range. It is therefore impossible to imagine shipyards, steel construction, plant engineering and mechanical engineering without it. But also in the basic equipment of the Federal Agency for Technical Relief (THW) and the fire department, on building sites, in junkyards and in workshops, hand cutting torches with oxyfuel technology are used; wherever an efficient and flexible cutting process of metals is required. Modern oxyfuel cutting solutions can be combined on a CNC machine with a variety of other equipment options for processing sheet metal, pipes and profiles: for example, for plasma cutting, drilling, tapping, countersinking or marking. Special solutions with flame cutting technology are also used successfully: for instance, a plasma cutting system for sheet metal processing with an additional robot arm including oxyfuel technology for 3D processing of large pipe formats with higher wall thicknesses.
The oxyfuel rotator creates completely new possibilities: Compared to the triple torch unit, completely new geometries can be cut, for example for the weld seam preparation. Simple V cuts as well as complex X, Y or K cuts are possible on a wide range of sheet thicknesses. Compared to robot solutions, the system also impresses with significantly lower investment costs. Production sites all over the world benefit from the endless rotating bevel unit with oxyfuel technology every day.