GTAW - Gas Tungsten Arc Weld, also called Tungsten Inert Gas, TIG for short.

The following part will describe something about results on GTAW Arc Stability Test Results in High Pressure.

(1) To carry out the experiment, GTAW test apparatus for the high pressure environment appliance is designed, the apparatus consists of seven parts, they are: a high pressure gas pipeline system, high pressure gas deployment tank, high pressure welding test chamber, the welding process high-speed picture pick-up system, high pressure gas control system, cabin inner scene and welding process monitoring system and all-position automatic welder.

 (2) The test is arc stability test carried out under high pressure, the results shows that, at the condition of 0.2 / 0.4 / 0.7MPa, GTAW arc can burn steadily.

(3) The test also showed that several factors what influence the arc stability, including the state of the workpiece surface, tungsten electrode, and a shielding gas effect. Tungsten electrode damage will seriously affect the stability of the arc.

Arc stability refers to the degree that arc remains stable combustion without causing broken arc, drift and arc blow.



 

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GTAW（Gas Tungsten Arc Welding） arc stability test under high pressure showed that there are many factors can affect the arc stability, such as, the surface state of workpiece, tungsten electrodes, a shielding gas effect and other factors. This article describes that workpiece surface state impact on the arc stability.

Workpiece surface state would influence the stability of the arc. GTAW welding method is particularly sensitive to the oil and oxide films on workpiece / wire surface, if there is the presence of the oil or oxide films, the arc is not capable of ignition or stable combustion. So, before welding, the wire surface and the part near the joint weldment must be cleaned to remove the grease, moisture, dirt and other debris oxide film on metal surfaces and to ensure that arc strike stably and bur steadily. Cleanup methods can be divided into the following kinds; you can select one according to the materials.

(1) Chemical cleaning. This method is commonly used to cleanup weld wire, whose effect is good and production efficiency is high. For different metal materials, chemical cleaning agents and process procedures they been used are different, so it should be cleaned according to instructions.

(2) Mechanical cleaning. This method is simple and the results are good.

(3) Chemical - Mechanical cleaning, if it is a large workpiece, it needs twice cleaning. 



 

Tungsten Metals Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten.com.cn
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By GTAW arc stability test under high pressure environment, you can know that many factors can affect the arc stability of tungsten electrodes, including the effect of shielding gas, the tungsten electrode and the workpiece surface condition and other factors. This article is mainly about the effect of shielding gas effect on arc stability.

Shielding gas effect will affect the stability of the arc. Under certain conditions, the gas flow rate and nozzle diameter has an optimum range, shielding gas effect is best at this time, and the effective protection area is also the largest on the weldment. If the gas flow is too low, the air flow exclude the ambient air is weak, so that shielding gas effect will be relatively poor; if the gas flow is too fast, it is easy to form turbulence and involve air when gas exhaust, thereby reducing protection effect. When the gas flow rate is constant, if the nozzle diameter is too small, the protected area is relatively small, and it will lead to the formation of turbulence because of the high air velocity;

 if the nozzle diameter is too large, it will not only hinder observation, and will lead to a too low flow rate, that is to say, the protective effect is not very good. In addition, this test is carried out under high pressure environment, it also needs to consider the environmental pressure (air) impact on the protective gas - argon, and measure can be taken: ensure that the ambient air pressure is less than the argon gas pressure.



 

Tungsten Metals Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten.com.cn
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Test results of hyperbaric welding experiments (under three different pressure condition)

The above table shows that, it can get a stable combustion arc under three different pressure conditions. By high-pressure environment, GTAW arc stability test can found that, there are many factors will affect the stability of the arc, such as, tungsten electrodes, workpiece surface state, protective gas and other factors. This article is primarily concerned with the impact of tungsten electrodes on arc stability.

Because tungsten electrodes will directly affect the stability of the arc, we select lanthanum tungsten electrodes as the electrodes material, which owns large emission current, good ablation resistance and non-radioactive. The shape of the tungsten tip is important process parameters, under normal circumstances, a different shape should be chosen according to the ends of the welding current species (high current / low current). In the small current conditions, welding select tungsten electrodes with small diameter and the cone angle, which can make arc easier and stable; at high currents, when welding, the melt of the tip end due to overheating can be avoided when the cone angle increased, thereby reducing losses and preventing the expansion of the arc to affect the cathode spots stability. During use, tungsten electrodes require frequently trimming with wheel / special tungsten grinder.

Tungsten electrode damage will affect the stability of the arc, solution: choose better electrode materials; select appropriate welding parameters; with reasonable mechanical structure.



 

Tungsten Metals Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten.com.cn
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