Causes of frequent stomata during welding

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Causes of frequent stomata during welding

Příspěvekod wangkiky v stř 14. srp 2019 4:03:01

1. Argon gas is not pure: the purity of argon gas is not less than 99.7 % when welding carbon steel, not less than 99.9% when welding aluminum, and the purity of argon gas for welding titanium and titanium alloy is as high as 99.99%.

Method for detecting argon purity: welding on a polished steel plate or pipe without welding wire, and then remelting on the weld bead several times. If there is pore, it means that argon is not pure; when welding, there is a very small Mars around the arc. It also shows that argon is not pure; sometimes when the purity of argon is close to the purity requirement of welding, it can't be tested by the above two methods, but when welding the gap with the weld, it will be produced at the root of the weld. Intermittent pores, or surface pores during the surface welding, or a layer of oxide on the surface of the weld; spot welding on the nickel plate, the solder joints are silver-white, the surface is mirror-like, indicating that the argon purity is acceptable.

2. Argon gas flow rate: the argon gas flow rate is too small, the wind resistance is weak; if the gas flow rate is too large, the near-wall laminar flow formed through the nozzle is very thin, and the gas is quickly dissipated after being ejected, and it is easy to put Air curling, the protection effect on the molten pool is worse. Therefore, the flow rate of argon should be appropriate and the gas flow can be stabilized.

3. Gas belt leakage: Air belt interface or air belt leakage will cause the gas flow during welding to be too small, and the air is sucked into the air belt, resulting in poor protection.

4. Wind effect: The wind is slightly larger, which will cause turbulent flow of the argon protective layer, resulting in poor protection. Therefore, wind speed measures should be taken when the wind speed is > 2m/s; when welding the pipe, the pipe mouth should be blocked to avoid the formation of wind in the pipe.

5. Influence of welding gun nozzle: The nozzle diameter is too small. When the effective protection range of argon around the arc is smaller than the area of ​​the molten pool, it will cause poor protection and generate pores. Especially in the field, when welding large pipes, larger diameter nozzles are used to effectively protect the arc and the molten pool.

6. The distance between the nozzle of the welding gun and the workpiece: the distance is small, and the sensitivity to the side wind is small; the distance is large, and the ability to resist wind disturbance is weak.

7. The pressure inside the cylinder is too small: it should be deactivated when the pressure inside the cylinder is less than 1 MPa.

8. The angle of the welding torch is too large: the angle of the welding torch is too large, on the one hand, the air will be brought to the people's molten pool, and on the other hand, the argon airflow on the long arc side will have a poor protection effect on the arc and the molten pool.

9. Influence of hydrogen flow meter: The flow meter is unstable, and the effect will be affected.

10. Impact of operation: When using a hydrogen arc welding torch with a control button, first deflate before welding to avoid excessive pressure in the gas belt, causing an excessively large outflow of gas during arc ignition, resulting in pores.

11. The welding torch fittings are not suitable: the tungsten pole clamp is not matched, the blocked gas path is not smooth, and the shielding gas flows out from the side inside the nozzle, and a complete protection ring cannot be formed.

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