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In view of the common porosity problem of manual tungsten argon arc welding, according to the author's experience in manual tungsten argon arc welding for many years, the causes of porosity generated by argon arc welding are analyzed and some methods and attention matter. To help welders to deal with such problems encountered in the actual production, better grasp the manual TIG Welding technology
Argon arc welding is an inert gas "argon" as a protective gas arc welding method, argon from the nozzle in the welding area to form an inert gas protective layer, isolated from the invasion of the air, so the arc and melting Pool formation protection.
The welding method has many advantages: the protection effect is good, the welding quality is high, will not produce splash, weld appearance; welding deformation is small, can achieve single-sided welding double-sided shape, to ensure root penetration, can carry out various locations of welding ; Can be welded to a variety of metals and alloys; arc combustion stability, arc operation, no slag, easy to automate.
Therefore, in the actual production has been widely used. However, due to argon arc welding weak wind resistance, rust, water, oil is particularly sensitive to the purity of the gas, groove cleaning, welding process requirements are strict, easy to produce pores. In this paper, combined with the actual production of argon arc welding to produce stomata analysis, and put forward some treatment methods and precautions
Stomatal factors 1. Argon impure
When the carbon steel is welded, the purity of argon is not less than 99.7%, not less than 99.9% when welding aluminum, and 99.99% for titanium and titanium alloy.
Detection of argon gas purity method: (l) in the polished steel plate or pipe without welding wire welding, and then many times in the bead remelting, if there are pores, then argon is impure
(2) welding, the arc around a very small Mars also shows argon impure.
(3) Sometimes when the purity of argon is close to the purity requirement required for welding, it can not be tested by the above two kinds of detection methods. However, when the weld is welded, there will be intermittent pores in the root of the weld , Or in the face when welding surface pores, or weld surface with a layer of oxide.
(4) in the nickel plate spot number, the solder is silver-white, the surface, such as mirror, then the purity of argon qualified.
2. Argon flow rate
Argon flow is too small, the wind interference ability is weak; too large, the gas flow rate is too large, through the nozzle when the formation of the near-wall flow is very thin, gas jet, and soon disorder, and easy to air, The protective effect of the pool is deteriorated. Therefore, the flow of argon must be appropriate, the air can be stable.
3. Gas leaks
Gas interface or gas leakage will cause welding gas flow is too small, the air was sucked into the gas zone, resulting in poor protection.
4. the impact of the wind
The wind is slightly larger, will make argon protective layer to form turbulence, resulting in poor protection. Therefore, the wind speed> 2m / s to take measures to prevent wind; welding pipe, the nozzle should be blocked, to avoid the formation of the wind in the tube.
5. The effect of the Torch nozzle
Nozzle diameter is too small, when the arc around the effective range of argon is less than the pool area, it will cause poor protection and produce pores. Especially in the field, the use of larger diameter nozzles to weld large pipes to effectively protect the arc and bath.
6. The distance between the gun nozzle and the workpiece
The distance is small, the sensitivity of the impact of the crosswind is small; the distance is large, the ability of wind interference is weak.
7. The pressure inside the cylinder is too small
The cylinder pressure is less than 1MPa to be disabled.
8. The torch angle is too large
The angle of the torch is too large, on the one hand will bring the air into the pool, on the other hand cause the long arc side of the argon flow on the arc and bath protection effect worse.
9. Effect of hydrogen flow meter
Flow gauge instability, suddenly large and small will affect the protection effect.
10. Operation of the impact of the use of control with the button hydrogen arc welding gun, the first gas before the gas in order to avoid excessive pressure in the gas zone, caused by the arc when the air flow is too large, resulting in pores.
11. Torch accessories are not suitable
Tungsten folder is not matched, blocking the air is not smooth, the protection of gas from the side of the nozzle outflow, can not form a complete protection ring.
The impact of welding materials
1. The influence of wire type can not be replaced by submerged arc welding wire instead of manual tungsten arc welding wire, otherwise it will produce intermittent or continuous stomata.
2. Wire is not clean wire surface rust, oil, water will directly promote the weld to produce a lot of pores.
Effect of base material
1. The impact of sheet or pipe quality
If there is a sandwich in the plate or pipe, the impurities in the interlayer will cause the formation of the pores.
The influence of steel
Boiling steel (oxygen content, impurities and more) can not be welded with argon arc welding.
The influence of tungsten
1. the impact of the end of the tungsten extreme tungsten tip is not sharp, arc drift instability, destruction of argon protection zone, so that the molten pool metal oxidation pores.
2. arc arc when the arc caused by the protection of the poor use of high-frequency arc of the device, just when the tungsten pole at the end of the low temperature, do not have enough heat emission electrons, electronic easy to launch from the oxide film , Along the electrode crawling to find the place where the oxide launch, resulting in arc elongation, argon on the bath of the protective effect of deterioration, when the tungsten temperature rise, the electrons from the front of the tungsten fired, arc The length is shorter. At this time as long as the tungsten surface of the oxide on the surface can be ruled clean.
1. Slope cleaning the groove surface and the groove on both sides of the 10mm range must be polished to avoid welding when the arc generated by the magnetic melting of the molten pool near the molten pool pool.
2. Welding speed of the impact of welding speed too fast, due to the impact of air resistance on the protection of air flow, argon gas flow will bend, deviate from the center of the electrode and pool, the pool and arc protection is not good.
3. The effect of arc quenching method arc quenching when the use of attenuating current or welding wire, the arc to the groove side and lower arc arc quenching method, do not suddenly stop the arc caused by high temperature bath from the effective protection of argon flow, to avoid There is an air hole or a hole in the pit.
4. Effect of welding current The welding current is too small and the arc is unstable. The arc drifts irregularly at the end of the tungsten, destroying the protected area. Welding current is too large, the arc on the airflow disruptive effect, the protection effect is worse.
5. Tungsten pole extends long The effect of the tungsten pole extends too long and the hydrogen protection effect on the arc and the bath is worse.
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