Oxy-fuel welding and cutting

Flame cutting is a type of thermal splitting of steel, wherein the previously oxidized to ignition heated metal with an oxygen gas stream and blown out of the cut.

Principle of operation

Of manually or automatically guided cutting torch consists of an annular and a heating nozzle, located in the center of the ring Sauerstoffschneiddüse. After the heating nozzle is heated with a combustion gas - oxygen mixture, the workpiece to ignition temperature locally to the gas supply of the cutting nozzle is opened, the oxygen is dispersed under high pressure and oxidized steel. The oxide, commonly called cutting slag consists primarily of iron oxide, has a much lower melting point than steel and is also thinner. The slag is blown by the oxygen jet from the joint, at the same time the burner is further performed continuously along the cutting line, so that the burner can not introduce sufficient energy into the workpiece and it is not able to melt. The base material can, therefore, with proper adjustment of the cutting speed without oxidation not be heated to the melting point. The result is a clean, strongly demarcated from the base material kerf. At the appearance of the cut can be seen whether the introduced heat and feed rate are correct.

As fuel gases acetylene - oxygen or propane - oxygen mixtures are generally used. In the industrial cutting machines or robots are used for automated oxy-fuel cutting.

Limitations of the Procedure

The metal must burn in an oxygen stream. The ignition temperature must therefore be less than the melting temperature. When steel or cast steel, a high carbon content reduces the distance between ignition temperature and melting temperature. Whether a steel is editable by torch cutting, however, depends not only on the carbon content of about 0.3 % should not exceed, but from the interaction of all alloying elements, the so-called carbon equivalent. At a high carbon equivalent of more than 0.45 %, preheating the work piece is recommended. Thus, a hardening of the cut edges is avoided. The practical limit for the Brennschneidbarkeit of carbon steel is 1.6 % C.

Irregularities

When flame cutting, it can be used for attachment of the slag, come to Kantenaufschmelzung and excessive cut grooving. In addition, angular deviations can occur at the interface. The causes can be many. Especially with hand-held torches only the torch is often dirty or damaged. Especially when autogenous flame cutting, the feed rate, the oxygen pressure and the burner exactly to the material, the thickness of the workpiece and the fuel gas must be tuned to achieve good cutting qualities.

Underwater torch cutting

For the underwater flame cutting using a ring burner. The in a ring around the flame escaping oxygen or additional compressed air keep away the water from the flame. The workpiece is cooled by the water at the same time and does not warp.

Economy

Despite the increasing importance of other processes, such as plasma cutting, laser cutting and water jet cutting oxyacetylene flame cutting is an economical process when the cut quality possible workpiece delay are not significantly influenced by the higher heat input and Aufhärtungsneigung of the material. For larger material thicknesses up to 600 mm, there is still no alternative to flame cutting.