Three kinds of flames for flame cutting

Three kinds of flames for flame cutting

The flame cutting machine is one of our commonly used cutting machines. The flame cutting machine is a kind of equipment that uses a high-temperature flame to cut materials. When we use the flame cutting machine, we can adjust the ratio of oxygen and acetylene to obtain three types of cutting flames. Let us understand the three flames of the flame cutting machine.

Neutral flame (normal flame)

Neutral flame

The neutral flame is the flame formed when O2/C2H2 = 1~1.2. The flame structure can be divided into three parts: flame core, inner flame, and outer flame. The flame core is composed of unburned oxygen and acetylene. A layer of carbon particles produced by the decomposition of acetylene is distributed on the outside of the flame core. The temperature is relatively high (about 900°C). The hot carbon particles emit bright white light, which is sharp cone-shaped and has a clear outline. The inner flame is mainly composed of acetylene and the products of incomplete combustion (H2 and CO). It is reductive, blue-white, with unclear contours, and has no obvious boundary with the outer flame. The temperature of the inner flame is very high, up to 3150℃. The outer flame is composed of CO2 and water vapor produced by the complete combustion of CO and H2 with O2 in the air, which is oxidizing. The temperature of the outer flame is in the range of 1200 to 2500°C, gradually changing from purple to orange-yellow from inside to outside.
The characteristic of a neutral flame is that there is no free oxygen and activated carbon in its reduction zone, there are three obvious areas, and the flame core has a clear outline (close to a cylindrical shape).

Oxidation flame

Oxidizing flame

Oxidation flame is the flame formed by burning when O2/C2H2> 1.2. The flame structure can be divided into two parts: flame core and outer flame. There is excessive oxygen in the flame, forming an oxidizing oxygen-rich zone outside the flame core. The flame heart is short, sharp, and blue-white. Outside the flame, the heart is a slightly purple outer flame, which is shorter than the Zhichang outer flame, and the flame is straight.
The oxidizing flame is produced under the condition of excess oxygen. Its flame core is conical, the length is shortened, the outline is not clear, and the brightness is dim. Similarly, the outer flame is shortened, the flame is purple-blue, and there is a sound when burning. The size of the sound is related to the pressure of oxygen, and the temperature of the oxidizing flame is higher than that of the normal flame. If the oxidizing flame is used for cutting, the cutting quality will significantly deteriorate.

Carbonized flame

Carbonized flame

The carbonized flame is the flame formed by burning when O2/C2H2 <1. Oxygen is not enough to completely burn acetylene, and excess acetylene is decomposed into carbon and hydrogen. Carbon will seep into the molten pool and cause the weld to increase carbon, so it is called carbonization flame. Carbonized flame has a strong reducing effect. The flame structure is also divided into three parts: flame core, inner flame, and outer flame. The flame heart is white with a slight bluish periphery. The inner flame is pale white. The outer flame is orange-yellow. When there is too much acetylene, black smoke begins to be emitted, which is caused by the lack of necessary oxygen in the combustion of acetylene in the flame.

As the thickness of the workpiece to be cut increases and the cutting speed increases, the energy of the flame should also increase. But not too strong, especially when cutting thick plates. The reaction heat generated by the burning of the metal increases, which strengthens the ability to preheat the front edge of the cutting point. At this time, the excessively strong preheating flame will seriously melt the upper edge of the incision. If the preheating flame is too weak, the steel plate will not get enough energy, which will reduce the cutting speed and even interrupt the cutting process. Therefore, the relationship between the strength of the preheating flame and the cutting speed is mutually restricted. Generally speaking, a neutral flame can be used to cut steel plates below 200mm to obtain better cutting quality. When cutting large-thickness steel plates, the reducing flame should be used to preheat the cutting, because the reduced flame has a longer flame.

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