| 摘要 |
The invention involves using a short arc welding process employing a self-shielded cored electrode which is capable of satisfying the requirements for welding American Petroleum Institute (API) Grade X-80 pipe line, or higher. The invention uses a short arc welding system using a power source with a digital controller which is operated by an adjusting circuit to perform a waveform (210). AC current waveform (210) has a negative melting pulse (212) where the melting pulse produces molten metal on the end of electrode. The level of current in pulse (212) is below current needed for spray arc so there is a transfer by a short. The time t1 starts the Joule measurement. The pulse has a start position (212a) at time t1 and a stop position (212b) at time t2. Following the melting pulse, in accordance with standard practice, there is a positive low current quiescent transfer section (214) wherein an electrode is formed into a ball by surface tension action awaiting a short circuit which occurs at time t3. Consequently, the time between t2 and t3 is the time between the end of the melting pulse and the short circuit event. A current pinch action separates the molten metal from the puddle. This electrical pinching action is accelerated in accordance with standard practice by a negative short circuit pulse (216) having a first current section (216a) with a steep slope and followed by a second current section (216b) with a more gradual slope. Ultimately, the shorted metal separates and the SC logic shifts to start the next current pulse at time t1 indicated by a transition section (218). Waveform (210) is an AC waveform having a negative melting pulse (212), a low current quiescent section (214) and a clearance pulse (216) transitioning into the next negative pulse (212) at time t1. The corresponding voltage has a waveform (230) with negative section (232), a low level positive section (234) that plunges at short (236) and is followed by a negative voltage section (238) that transitions at section (240) into the next melting pulse voltage (232). The total cycle time is from t1 to the next t1 and the positive transfer (214) has a time less than 20% of the total cycle time. This prevents stubbing. The present invention involves a power source and method for controlling waveform (210) by a waveform generator of a controller so the time between the end of melting pulse (212) at t2 and the time of the actual short event t3 is constant based upon an adjustment of circuit. |
