Polarity in Stick Welding: The Basics for Beginners

Stick welding, also known as Manual Metal Arc (MMA) or Shielded Metal Arc (SMAW) welding, is one of the oldest and simplest welding techniques in use today. It is favoured by many for its ease of setup and relatively straightforward learning curve, making it an excellent choice for beginners. In this article, we explore the basics of stick welding and specifically focus on the importance of polarity in this welding process.

What is Stick (MMA) Welding?

Manual Metal Arc (MMA) welding, or stick welding, is an arc welding process that involves creating an arc between a flux-covered electrode and the base metal. This arc melts the electrode and the base metal, creating a pool of molten metal that is a mixture of the consumable electrode and the base metal and this forms a weld. The coating of flux on the electrode is vaporised and creates a gas shroud around the molten weld pool that keeps out air and prevents oxidation.

How Does Stick Welding Work?

Stick welding is straightforward and requires minimal equipment. To initiate an arc, you need a complete electrical circuit. Here is a breakdown of how stick welding works:

• Electrode Holder: Connect the electrode holder to the welding machine and insert the electrode into the holder. The electrode holder's role is to secure the electrode and allow the welding current to pass through it.
• Arc Ignition: Strike or tap the electrode against the base metal. This action initiates an arc between the electrode and the workpiece. Stick welding electrodes are consumable, meaning they melt and blend with the base metal during the welding process.
• Flux Coating: Unlike MIG or TIG welding, stick welding doesn't require an external shielding gas. Instead, each electrode comes with an outer flux coating that vaporises and acts as a gas shield during welding, this prevents external contaminants from entering the weld. After welding, the flux coating solidifies, forming a layer of slag over the weld, this protects the weld pool whist cooling but needs to be removed afterwards.
• Earth Clamp: The electrical circuit is completed with an earth cable from the power source. The clamp must be connected to clean, bare metal for a strong and stable circuit as close as possible to the work piece.

Stick Electrode Selection

Various types of electrodes are available for stick welding, each with its own classification code indicating its properties. For mild steel electrodes, the code starts with 'E,' followed by a 4-digit number (e.g., E6013).

Here's what each part of the electrode code represents:

• 'E' stands for electrode, a common starting point for all mild steel electrodes.
• The first two numbers (e.g., 60) denote the electrode's tensile strength (in MPa), after welding.
• The third number (e.g., 1) indicates the positions in which the electrode can be used. It can be 1 (all positions), 2 (flat and horizontal), or 3 (flat only).
• The fourth number (e.g., 3) identifies the type of flux coating, with nine different variations available, each with distinct characteristics.

For beginners learning stick welding, E6013 electrodes are a popular choice. They are considered general-purpose, work well in various applications, can be used in all positions, and are easy to strike.

The size of the electrode you select depends on the thickness of the metal that is being welded. As a general guideline, a 2.5mm diameter electrode suits metal with a thickness of 3mm to 6mm, a 3.2mm electrode is suitable for 6mm to 12mm, and a 4mm electrode works for metal between 12mm and 25mm. Lots of data is available from the manufacturers of the consumables on grade selection, electrode diameter and suggested parameters.

Polarity in Stick Welding

Stick welding can be performed in both AC (Alternating Current) and DC (Direct Current). For most stick electrodes, the default polarity is Direct Current Electrode Positive (DCEP), meaning the current flows positively from the negative to the positive. In this setup, the current flows from the base plate into the electrode. Despite the counterintuitive direction, the heated electrode melts back into the base material, providing strong penetration, (the depth that the heat from the arc melts the base material). Consequently, DCEP is suitable for thicker section joints.

Some electrodes can also be used with Direct Current Electrode Negative (DCEN), where the current flows from the electrode into the plate. This method gives less penetration and gives the welder more control over it.

Some electrodes are developed for AC polarity welding, the penetration falls between DCEN and DCEP, as the current alternates between positive and negative polarities during welding. AC polarity can be used where there is a strong potential for ‘arc blow’, this is arc deflection caused by distortion of the magnetic field due to the welding current. AC polarity is also more forgiving with contaminated surfaces as it has an inherent cleaning action. 

It should be noted that each pack of electrodes will state which polarity is to be used with them, the electrodes will only weld successfully when these recommendations are followed.

Metals Suitable for Stick Welding

Stick welding is a versatile welding method and can be used on a huge range of materials, typically:

• Mild steel, low alloy steel
• High strength steel
• Stainless steels
• Duplex stainless steels
• Nickel alloys
• Cast irons
• Aluminium alloys
• Hardfacing
• Copper alloys

Advantages of Stick Welding

Stick welding offers several advantages that make it a preferred choice for many:

• Versatility: Stick welding can be used in a wide range of settings. It doesn't rely on a gas supply, making it highly portable and suitable for outdoor and on-site work. It can be used on a huge range of materials. Welding in every position is possible with the correct selection of electrodes.
• Portable: Cables up to 100m long are available making access into difficult areas possible. ESAB’s latest machine is powered by batteries so no external power supply, (power cables or generator,) is required.
• Ease of Learning: MMA welding is usually the first welding process that is taught, consequently there is a large knowledge base.
• Cost: MMA machines do not require a big investment to start up. Selection of the correct model is dependent on the size and thickness of the material to be welded. Thicker material means more amperage and a bigger power source. But also on the duty cycle, basically how many hours a day will the equipment have to deliver full power.
• Welding different thicknesses of material: MMA can be used to weld both very thick and thinner materials. This process is not recommended for very thin materials, where TIG welding is the more common, manual method.

Disadvantages of Stick Welding

While stick welding has many advantages, it also has some limitations:

• Slower Process: By definition, the welding stops when the electrode has been used, the process generates certain amounts of both fume and spatter although the level of these produced are related to the type of electrode.
• Post weld cleaning: After welding, the layer of slag needs to be removed. The ease of slag removal also depends on the electrode used.

Conclusion

In conclusion, stick welding is an accessible and cost-effective way to start welding, it can be applied to a huge variety of materials in almost all material thicknesses and in every welding position. Polarity is one of several factors that need to be understood when selecting the correct electrodes for any specific application to achieve welds with the required strength and appearance. The variety of flux coatings, their influence on the metallurgy of the weld and their effect on weldability is another subject worth investigating.

For further insights into welding, make sure to explore the following articles on ESAB University.