What polarity is typically used for SMAW with electrodes E 6010 and E 7018?

The use of DCRP (Direct Current Reverse Polarity) is the preferred polarity for Shielded Metal Arc Welding (SMAW) when working with electrodes E 6010 and E 7018. This polarity means that the electrode is connected to the positive terminal of the power source, while the workpiece is connected to the negative terminal.

For E 6010 electrodes, which are designed for penetrating welds on dirty or rusty surfaces, using DCRP allows for a more aggressive arc that provides better penetration. The positive polarity helps to promote the cleaning of the base metal and assists in the arc stability, which is critical when performing welds that may have contaminants.

For E 7018 electrodes, which are low-hydrogen and used for welding structural steels, DCRP also offers benefits such as a smooth arc and better control over the heat input into the base materials. This is important to avoid hydrogen-induced cracking, ensuring strong and ductile welds.

Given the welding characteristics and requirements associated with both types of electrodes, DCRP is consistently the correct choice to optimize performance in these applications. The other options related to AC or other D.C. polarities do not provide the same efficacy for these specific electrode types.