JPS58100973A - Plasma cutting method - Google Patents

Abstract

PURPOSE:To prevent adhesion of slag to the cutting face and improve wear resisting property of electrodes by using shield gas for plasma jet made by mixing oxygen and nitrogen at a fixed proportion at the time of plasma cutting. CONSTITUTION:In a plasma cutting device consisting of a tungsten electrode 1, the first mantle 2, the second mantle 3 and a jetting nozzle 4, gaseous nitrogen is spouted from a gas passage 5 between the electrode 1 and the first mantle 2, and gaseous oxygen is spouted from a gap passage 6 between the first mantle 2 and second mantle 3. By performing plasma cutting making the composition of the gas 40-95mol% oxygen, 5-60% nitrogen, adhesion of slag to the cutting face, generation of nitride layer on the cutting face, and consumption of the electrode 1 due to oxidation are prevented and durability or the electrode 1 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shielding gas ejected during plasma arc cutting, and more specifically, when used as a shielding gas for a plasma jet as a mixed gas of 40 to 95 moles of oxygen and 5 to 60 moles of nitrogen. The present invention relates to a plasma cutting method with a percentage characteristic of .

(1) In the conventional plasma arc cutting of yuzu (for example, as shown in Japanese Patent Publication No. 66-7860), the operating gas used was argon, helium, hydrogen, nitrogen, or a mixture of these gases. However, when nitrogen is used, there is a drawback that slag adheres to the bottom of the cut part, especially when cutting mild steel.
As shown in Publication No. 669, a cutting method using air as the operating gas has been developed, and it has become possible to prevent slag adhesion to some extent. It is difficult to completely prevent slag build-up when cutting mild steel, and this technique generates a nitride layer on the cut surface, which re-precipitates during welding, resulting in blowholes on the weld surface. It had a defect that caused it.

(2) In order to further improve the drawbacks of the above-mentioned technology, for example,
As shown in Japanese Patent No. 8924, a method using oxygen as the operating gas has been developed, but when using oxygen as the operating gas, the electrode material oxidizes and wears out rapidly.
A's! In this case, there were disadvantages such as the electrodes lasting only about 6 hours.

The present invention is a completely new technology developed in view of the drawbacks of the conventional techniques.In particular, during plasma cutting, oxygen and nitrogen are mixed at a certain ratio, and the cut surface is improved by using a plasma jet as a shielding gas. The present invention relates to a technology that makes it possible to prevent the adhesion of slag and improve the wear resistance of the electrode.

One embodiment of the present invention will be specifically explained with reference to the drawings. (3
) The 17fc position in FIG. 1 is a plasma cutting device used when implementing the method of the present invention, in which 1 is a tungsten electrode, 2 is a first mantle, 6 is a second mantle, and 4 is a jet nozzle. and a gap passage 5 between the electrode 1 and the first mantle 2. The structure is such that nitrogen gas is ejected, and oxygen gas is ejected from the gap passage 6 between the first mantle 2 and the second mantle 6.

Next, when nitrogen and oxygen are ejected from these passages 5 and 6 and mixed at the ejection nozzle 4, various tests were conducted regarding the mixing ratio and the slag adhesion range, and the results are shown in Fig. 2. was gotten. That is, the concentration of oxygen is 4
It has been found that when the coefficient exceeds 0, the slag adhesion range shown by diagonal lines does not change even if the cutting speed changes. Further, as a result of analyzing the cut surfaces obtained by this method, it was found that surface nitridation of the cut surfaces did not occur when the acid (4) concentration was 60 or higher. Therefore, when these results are taken together, it is clear that if the ratio of mixing oxygen to nitrogen is 40 or more vc\ to oxygen/nitrogen, there will be no slag adhesion and no nitriding phenomenon will occur.

On the other hand, after researching the durability issue of electrode 1, as shown in Figure 6, when the oxygen concentration was increased to 95 or higher, it was maintained for only about 6 hours, which was not much different from when pure acid was used. I couldn't do it, but if I set the oxygen concentration to 0, it would take about 4 hours.
It was found that if the ratio was set to 50, the durability time would be approximately 7 hours, and if the ratio was set to 40 or less, the oxidation of the electrolyte 1 would hardly be observed, and the durability could last for about 8 hours. Shi1ko.

Furthermore, we investigated the relationship between the thickness of the cut steel plate and the oxygen concentration, and found that when the plate thickness was less than 6N, the oxygen concentration (5) was higher.
It is sufficient to set the oxygen degree to about 90%, and the plate) I is 12
It is clear that when the temperature is higher than that of dragon, if the oxygen concentration is set in the range of 60 to 40, there will be no slag adhesion and the durability of the electrode 1 will be improved.

As another embodiment, in the conventional torch structure shown in FIG. 1 with the two first mantles removed, the shielding gas supplied to the passage 6 is supplied to a mixer (not shown), and oxygen and nitrogen gases are pre-filled. After mixing and conducting 7 cutting tests, we were able to obtain good results similar to the above example.

As a result of the above σ) investigation results, it has become clear that it is extremely effective to use a shielding gas with a mixing ratio of oxygen and nitrogen of 40 to 95 molar ratios to 5 to 60 molar ratios.

(6) As mentioned above, the method according to the present invention is a method in which the mixing ratio of the shielding gas of the plasma jet is set to a specific mixing ratio. , or no nitride layer is generated on the cut surface,
Moreover, it has the characteristics that the durability of the arc electrode used can be extremely increased, and therefore an ideal cutting surface can be obtained for a person with good work efficiency.

[Brief explanation of the drawing]

Figure 1 (a cross-sectional view of the equipment for carrying out the construction method; Figure 2 is a diagram showing the layered state of slag; Figure 6 (a diagram showing the durability of the construction electrode); 1 is an electrode; 2; 3 is the cloak, and 5 and 6 are the passages. (7) 337 - Figure 1 Figure 2 Figure 2

Claims (1)

[Claims] Oxygen 40-95 as shielding gas for plasma jet
A plasma cutting method characterized in that it is used as a mixed gas with a molar width of 5 to 60 molar nitrogen.