DC vs. DC Positive: Choosing the Right Polarity in Stick Welding

Introduction

When it comes to stick welding (SMAW), the choice between Direct Current (DC) and DC Positive (DC ) can significantly impact the weld quality and penetration of your work. Understanding the characteristics of each polarity is crucial for achieving the best results in various applications.

DC Direct Current: Negative Polarity

Electrode Polarity: In DC negative polarity, the electrode is negative and the workpiece is positive.

Heat Concentration: A higher amount of heat is concentrated in the workpiece, leading to deeper penetration. Weld Quality: Typically provides a stronger weld in terms of penetration and is preferred for welding thicker materials. Arc Stability: The arc is more stable, making it easier to control.

DC Direct Current Positive: Positive Polarity

Electrode Polarity: In DC Positive polarity, the electrode is positive and the workpiece is negative.

Heat Distribution: More heat is generated at the electrode, resulting in a softer weld bead. Weld Quality: Better for welding thin materials and can produce a smoother finish but may not penetrate as deeply as DC negative. Filler Material: Often used when a specific type of filler material is required or for certain types of alloys.

Conclusion

Generally, DC negative polarity is often considered stronger due to its deeper penetration and better suitability for thicker materials. However, the choice between the two depends on the specific application, material thickness, and desired weld characteristics. For optimal results, it is essential to consider these factors and select the polarity that best meets the needs of the welding task.

Understanding the Physics

Direct Current (DC) is used on most stick welding applications. Alternating Current (AC) is typically only used as a second option. DC positive polarity provides a high level of penetration into the steel. DC negative polarity results in less penetration but a higher deposition rate.

Electron Flow and Penetration

In DC Reverse Polarity (DCRP/DCEP), two-thirds of the electrons are on the positive side, and one-third of the cooling ions are on the negative side. The current travels from the negative to the positive pole. When the electrons bombard the electrode in DCRP/DCEP, the flow is concentrated on the narrow end of the electrode, melting it into fine droplets and shooting them hard at the plate. When the electrons bombard the plate in DCSP/DCEN, the flow is dispersed across the plate, minimizing the penetration.

Because AC alternates between DCRP/DCEP and DCSP/DCEN, it has both types of penetration. AC changes direction 120 times per second in a standard 60 cycle circuit, causing the arc to go out each time it travels across the neutral line. This results in the erratic or cracking sounds one hears while welding on AC. Because AC has the DCSP/DCEN side of the wave 60 times per second, you will need to increase your amperage by 10 to offset this cooler side.

Polarity is more about penetration than strength. Strength is more about weld quality, weld size, and the electrode’s tensile strength.