Talk to our experts to explore ways of bringing the speed and quality of acetylene to your oxyfuel cutting operations
Oxyfuel Cutting with Acetylene
Customized Gas Supply Solutions for Greater Productivity in Oxyfuel Cutting
Leverage the speed gains of acetylene for oxyfuel cutting to accelerate preheating and cutting speeds while lowering production costs and improving the quality of your cuts
What is Oxyfuel Cutting?
Oxyfuel cutting is also referred to as flame cutting, fuel gas cutting and oxygen cutting. It involves heating a metal to its ignition temperature with a fuel gas and then adding a jet of pure oxygen. The oxygen reacts with the metal to create the cut. As the torch begins to move, more metal is preheated and the oxygen jet burns more of the steel, extending the cut.
The oxyfuel cutting process is very versatile, supporting both manual cutting operations or automated cutting using single or multiple torches for higher operating efficiencies. However, considerable operator skill is required to produce cut surfaces that are suitable for welding. Cutting techniques include piercing, round surface cutting, stack cutting and nesting.
What Materials Are Suited to Oxyfuel Cutting?
Oxygen cutting is suited to most steels and titanium but is unsuitable for stainless steel and aluminum. The composition of some steels may require some other flame treatment process, such as preheating, prior to cutting.
In the case of steel, a localized area is preheated until the metal reaches a bright cherry red at about 900°C (1652°F). At this point, a jet of cold oxygen is passed through the center of the cutting nozzle onto the red-hot steel. This causes a chemical reaction between the steel and the oxygen, generating more heat by burning the iron in the steel. This is referred to as an exothermic reaction. The steel immediately below the oxygen jet is converted to a metal oxide or slag, and is blown away by the jet.
Why are Gases So Important for Oxyfuel Cutting?
Success factors in oxyfuel cutting include the fuel gas chosen for preheating. Acetylene, propane, an intermediate fuel gas, or natural gas can be used as the fuel gas. The fuel gas combines with the preheat oxygen either in the cutting torch or nozzle to create the preheat flame. The ideal fuel gas will depend on the thickness of the material to be cut, the equipment being used and operator preferences.
Due to its higher flame temperature, acetylene typically offers faster, higher-quality, and more economical results than other fuel gases. The flame temperature of oxy-acetylene is 3160°C (5720°F), compared for instance with 2828°C (5122°F) for oxy-propane, which means cutting would commence sooner with oxy-acetylene.
The advantages of acetylene as the fuel gas grow with the thickness of the material to be cut. Acetylene is also beneficial when beveling plates as the cut length is greater than the thickness of the material. The higher, more concentrated flame temperature of acetylene additionally offers speed gains when piercing components. And acetylene tends to produce cuts with much smaller, less pronounced drag lines on the surface.
Work has also shown that the maximum depth of hardening with acetylene is less than for other fuel gases. Although the depth and level of hardening is not important for all applications, a hard edge can compromise welded joints if the component is welded after cutting. This can result in cracks forming.
Importance of Oxygen Purity for Cutting
The purity of the cutting oxygen stream is very important. The preheat flame acts as a barrier, preventing atmospheric nitrogen from reacting with the cutting oxygen (as this would otherwise produce nitrogen oxides, which would compromise cutting speeds and increase oxygen consumption). Hence the oxygen purity should be 99.5% or higher. If the oxygen stream isn't powerful enough, or the cutting speed is too quick, the slag will solidify in the cut, and a cut will not be achieved. The temperature of the molten slag must always be lower than the metal being cut.
Equipment Required for Oxyfuel Cutting
Much of the equipment required for oxyfuel cutting is the same as that used for other oxyfuel processes. However, the torch and nozzle are specific to cutting. The two main torch types are nozzle mix torches, where the preheat fuel gas and oxygen are mixed in the nozzle, and injector torches, where the preheat gases are mixed away from the nozzle; sometimes this is in the body of the torch or in the torch head.
Injector torches can use fuel gases supplied at lower pressures than nozzle mix torches, which is particularly useful where large pressure drops over long hoses mean that the fuel gas pressure at the torch is lower.
The cutting nozzles depend on the fuel gas used, material thickness to be cut, the type of torch being used, and whether the cutting process is manual or mechanized.
Cutting machines come in many forms, varying from very simple straight line cutting machines to complex computer-controlled multi-head profile cutting machines.
Comprehensive Support for Your Oxyfuel Cutting Needs
We offer the full range of oxyfuel cutting gases. In particular, we can help you leverage the productivity and quality gains of acetylene for your oxyfuel cutting process. Benefits include rapid preheating, fast cutting speeds and high-quality cuts. Our application experts can also help you fine-tune your operating parameters for optimum results, also supporting you with cost analyses, equipment and gas management services.
Linde for Oxyfuel Cutting: Benefits at a Glance
- Increased cutting speed: +20% with acetylene
- High cutting quality
- Lower production costs compared with other fuel gases due to speed gains of acetylene
- Customized gas supply solutions
StarFlame™ NG for Performance, Safety and Cost Gains
See how our cutting-edge StarFlame™ NG mix of hydrogen and natural gas accelerates preheating and piercing time for enhanced quality and faster oxyfuel cutting speeds, while also lowering cutting costs and contributing to safety through cleaner combustion and less likelihood of flashbacks.