Thick plate welded with the SMAW process should be welded using which type of electrical current?

The correct choice for welding thick plates using the Shielded Metal Arc Welding (SMAW) process is to use DC Positive current. When using DC Positive, the flow of electricity goes from the electrode to the workpiece, which generates a larger amount of heat at the electrode end. This is crucial when welding thick materials as it allows for better penetration into the base metal, creating a strong weld joint.

Using DC Positive also helps in stabilizing the arc and providing a cleaner weld, which is important for thicker plate applications. It improves the effectiveness of the electrode by enhancing metal transfer and arc stability, therefore reducing the risk of defects such as incomplete fusion or undercut. The heat generated at the workpiece side, as a result of the current flow, ensures that the base material is adequately melted, allowing for a proper bond.

In contrast, while AC current can be used for welding, it is less effective on thicker materials because it alternates the polarity and does not provide the same level of heat consistency as DC Positive. This can lead to issues with penetration and weld integrity, making it less suitable for thick plate welding.