El oxyfuel is a technique Very widespread for various industrial applications, especially in the preparation of edges of pieces to later weld them, and for cutting metal parts with great thickness (always steel or other ferrous materials). The thicknesses that are handled in the oxyfuel are not suitable to be cut using radial saws or normal torches.
Its name is due to the fact that the cutting is done by oxidation by a flame. A gas acts as a combustible gas for the flame (propane, acetylene, hydrogen, tretene, crylene, ...) and another gas will act as an oxidizer (always oxygen).
That is, the oxyfuel consists of two steps. In a first, these gases generate a flame that will heat the steel to temperatures of about 900ºC. In the second stage, a jet of oxygen will cut through the metal, as oxygen reacts with iron and generates iron oxide (ferric oxide or Fe2O3). And this is where the key is, since this ferric oxide, having a melting temperature higher than that of steel, melts in the form of sparks, also using it as a tractor flow due to the pressure exerted by the oxygen jet (about 6 Bar ) to cut metal.
For that to be possible, the torch used for flame cutting will have two conduits. One through which the gas circulates for the heating flame and another for oxygen cutting. But we will talk about the necessary equipment in the next section ...
El gas cutting equipment is quite simple, and consists of these elements:
- carboys: are the fuel and oxidizing gas bottles chosen. They are bottles specially designed for this task and pressurized to contain the gas safely. Keep in mind that gases are highly flammable and are contained at very high pressure, which requires specific measures for their use to be safe. There are even rules to regulate it, as well as its maintenance, transport and storage.
- Pressure gauges or pressure reducers: each cylinder will also have a pressure gauge to indicate the pressure and control the gas outlet pressure of each cylinder to adapt it to what is needed for oxyfuel cutting. The cylinders are usually around 200 atmospheres, but they will be reduced to between 0.1 and 10 Bar or atmospheres (they are almost equivalent). In addition, there must be a non-return valve so that the gases only circulate in one direction. Otherwise, when lighting the torch flame, the burning gas could return and ignite the gas in the hose and the cylinders, which would be a terrible disaster ...
- Hoses: these are the tubes that lead the gas from the pressure gauge outlet valves to the torch. They are sometimes rigid, although they are generally flexible. In any case, they must withstand high gas pressures and are also regulated by regulations to make their use safe. Normally, the blue ones are for oxygen and the red ones for fuel gas, so they are more easily identifiable.
- Torch or cutting tip: it is the head where the mixture of both gases is produced and with its shape directs the flame to focus it to the cut-off point. These torches have an interchangeable mouth, since the high temperatures to which it is subjected during the cutting process wear it down a lot and they need to be replaced periodically.
By the way, the flame is first lit with fuel gas. And with the flame the metal is heated where you want to cut. Later, when the trigger is pulled to open the jet of pressurized oxygen is when the cut actually occurs. Although it can be done manually, there are also robots that practice oxyfueling automatically.
The team should be the homologated and certified with security measures. Keep in mind that it is a dangerous process and you must work with all the guarantees.
Difference between oxyfuel and plasma cutting
There are differences between oxyfuel and plasma cutting. Although they may visually have similarities, you should not confuse it. With plasma, the temperature of the material is raised to more than 20.000ºC, but it is done in a very localized way. This is achieved by taking a gas to the fourth state of matter, that is, to the state of plasma.
This means that there is no flame as such and that it slowly heats a larger area of the piece to be cut, as in the case of oxyfuel. That way, they get better resolutions in the finishes and prevents deformations from occurring. In addition, since it does not depend on a chemical reaction as in the case of oxyfuel, it can be used on any metal.
Advantages and disadvantages
Oxyfuel, especially cutting with oxyacetylene has great advantages, despite the aforementioned. Some of the most notable are:
- Equipment portability: allowing you to easily carry the oxyfuel equipment wherever you need it. By not depending on an electrical source, you will not need to depend on a generator or an outlet. Only the amount of gas you have is the limitation.
- Applications- There are many industrial applications where this cutting procedure can be used economically, especially for large thicknesses. In addition, you can apply torches and bevel.
- Economic: it does not require a large investment and the maintenance (spare parts) and the fuel (gases) used are cheap.
But not all are advantages, it also has its disadvantages, for example, compared to the plasma cutting:
- MetalWhile oxyfuel is used for iron and steel, in plasma cutting any type of metal that conducts electric current can be cut, although the thickness or thickness must be adequate so that the jet and plasma can penetrate through it.
- Rapidity: the speed in plasma cutting is also higher. The reason is that it does not need the previous heating process. With the plasma directly begins to cut the piece.
- Precision- Plasma cutting can achieve fairly high precision, similar to that achieved with laser cutting. The flame cutting is not so precise in that sense, and it would need subsequent touch-ups to correct the flaws. In addition, some thin sheets may deform from the heat generated by the oxyfuel.
- Cost: it is cheaper than oxyfuel when working with ferrous parts not too thick.
- Human waste: All the material that melts and remains on the edges is cleaned more easily in plasma cutting than in oxyfuel, since in oxyfuel it remains adhered.
Therefore, for some applications Plasma cutting is probably best used, especially when more demands are placed on the finish of the part.
Look also water jet cutting, surely you also find it interesting.