As a welding expert with years of experience in the field, I can provide you with a comprehensive understanding of the polarity used in stick welding, also known as Shielded Metal Arc Welding (SMAW).

Polarity in Stick Welding

In stick welding, polarity refers to the direction of electrical current flow between the electrode and the workpiece. This is a crucial factor that influences the welding process and the quality of the weld. There are two primary types of polarity used in stick welding: Direct Current Straight Polarity (DC+) and Direct Current Reverse Polarity (DC-).

DC+ Polarity

DC+ polarity, also known as straight polarity, is the most commonly used polarity in stick welding. In this configuration, the electrode is connected to the positive terminal of the welding power source, and the workpiece is connected to the negative terminal. This polarity provides a number of advantages:


1. Higher Penetration: The DC+ polarity facilitates deeper penetration into the base metal. This is due to the magnetic effect of the welding arc, which pulls the electrode towards the workpiece, resulting in better fusion.


2. Beading Profile: The arc force in DC+ polarity helps to shape the weld bead in a more controlled manner. This results in a more aesthetically pleasing and structurally sound weld.


3. Electrode Melting: With DC+ polarity, the electrode melts at a slower rate compared to DC- polarity. This allows for a steadier arc and better control over the welding process.


4. Slag Removal: The slag, which is a protective layer that forms on top of the weld, is easier to remove when using DC+ polarity. This is because the arc force helps to push the slag away from the weld zone.

DC- Polarity

DC- polarity, or reverse polarity, is less commonly used in stick welding. In this setup, the electrode is connected to the negative terminal, and the workpiece is connected to the positive terminal. Here are some characteristics of DC- polarity:


1. Less Penetration: The penetration achieved with DC- polarity is typically less than that of DC+ polarity. This is because the arc force pushes the electrode away from the workpiece, which can lead to a shallower weld.


2. Higher Electrode Melt-Off Rate: The electrode melts at a faster rate with DC- polarity. This can be beneficial in certain applications where a faster welding speed is desired.


3. Preventing Burn-Through: DC- polarity is sometimes used on thin sheet metal to prevent burn-through. The reduced penetration helps to avoid damaging the material by overheating.


4. Slag Adherence: The slag tends to adhere more to the weld with DC- polarity, which can make it more challenging to remove.

Choosing the Right Polarity

The choice between DC+ and DC- polarity depends on several factors, including the thickness of the material being welded, the type of joint being made, and the desired weld quality. For most applications, DC+ polarity is preferred due to its benefits in penetration and control. However, DC- polarity may be chosen for specific situations, such as welding thin materials or when a faster welding speed is required.

In conclusion, understanding the role of polarity in stick welding is essential for achieving high-quality welds. By considering the properties of each polarity and the specific requirements of your welding project, you can make an informed decision on which polarity to use.

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Note that for stick welding in general, DC+ polarity is most commonly used. It produces a good bead profile with a higher level of penetration. DC- polarity results in less penetration and a higher electrode melt-off rate. It is sometimes used, for example, on thin sheet metal in an attempt to prevent burn-through.read more >>