We have a number of (AC/DC) welding machines for submerged arc welding. In high ampere currents we have a extreme current fluctuation that result in some welding defects.
Factors responsible for fluctuations:
1) deposition rate
2) depth of penetration
3) Workpiece dimensions/size
In subarc, arc length is continously regulated by the constant voltage characteristics of the power source (see : https://www.twi-global.com/technical-knowledge/job-knowledge/power-source-characteristics-121 ), at the extremity of the wire the metal melts in fine droplets that are projected at high frequency inside the arc plasma down in the weld pool. The transit of molten droplets inside the arc perturbates the electrical resistance of the electric arc that can be assimilated to an electrical resistance. So if such electrical resistance is constantly changing by the droplets transition, the flow of current and the voltage value at its extremities constantly moves in direct relation with the electric resistance value. Additionally, the fact that in welding the arc is moved the generate the weldment, introduce also some disturbances that influence also Arc current and voltage values.
Generally there is for every welding conditions, a parameter window into which an stable optimum of arc voltage and amperage is possible. But if you change suddenly the current or the voltage value, you might get out of this stable optimum box to enter to another box where it would be necessary to adapt either the voltage or current value in order to find another stable optimum. In others terms, if you chage the current value, it will be necessary to adapt the arc voltage and the other way round. it is possible that if the change is too wide an unstable equilibrium could be installed, and could create defects in the weld metal.
https://books.google.ru/books?id=ZdLMa3w_ZXEC&printsec=copyright&redir_esc=y#v=onepage&q&f=false
http://eng.esab.co.kr/Web-App/Upload/2012/04/05/SUBMERGED%20ARC%20WELDING.pdf
I understand that you are experiencing current fluctuation in your SAW welding machines and that this is causing welding defects. Here are some possible reasons why this might be happening, and some steps you can take to troubleshoot the problem:
- The welding machines may not be properly calibrated. This can cause the machines to output too much or too little current, which can lead to currency fluctuation. To check the calibration, you can use a calibrated ammeter to measure the output current of the machines.
- The welding machines may be dirty or damaged. Dirt and debris can build up on the contact tips of the machines, which can cause them to arc erratically. Damage to the machines can also cause them to output inconsistent currents. To check for dirt and damage, you can visually inspect the machines and clean them as needed.
- The welding parameters may not be correct. The welding parameters, such as the welding voltage and wire feed speed, can affect the current fluctuation. If the parameters are not set correctly, the arc can become unstable and the current will fluctuate. To check the welding parameters, you can consult the machine's operating manual.
- The welding wire may be contaminated. Contaminated welding wire can cause the arc to become unstable and the current to fluctuate. To check the welding wire, you can visually inspect it for dirt or debris. You can also try using a different brand of welding wire.
If you have checked all of these possible causes and the problem persists, you may need to contact the manufacturer of the welding machines for further assistance.
Here are some additional tips for troubleshooting current fluctuation in SAW welding:
- Use a constant current welding power source. This will help to stabilize the arc and reduce current fluctuation.
- Use a welding wire that is the correct size and type for the application. The wrong size or type of welding wire can cause the arc to become unstable and the current to fluctuate.
- Keep the contact tips clean and free of impurities. Dirty contact tips can cause the arc to become unstable and the current to fluctuate.
- Use a shielding gas that is the correct type for the application. The wrong type of shielding gas can cause the arc to become unstable and the current to fluctuate.
- Maintain the welding equipment in good condition. Worn or damaged welding equipment can cause current fluctuation.
- Badges
- Science topic
- Similar topics
- Automotive Engineering
- Machines