Shielded Metal Arc Welding (SMAW), or Stick Welding, is an arc welding process completed by hand using an electrode covered with a flux laying the weld. The method uses a welding power supply that arcs the melting electrode to the metal. As it does so, it forms a small weld pool. When the weld pool cools, it creates a weld bead. The flux coating role gives off a shielding gas when the electrode melts, helping protect the weld area.
Stick welders need to strike an arc between the electrode and the metal. Lightly touching the electrode to the metal creates the arc. The arc started, the electrode and the metal melt, creating the weld bead. WeldNotes.com provides an excellent overview of the process.
SMAW is the most widely used form of welding, mostly used for ferrous metals of all thicknesses, like carbon steels, stainless steels, alloy steels, and iron.
We find welding using the SMAW method in many industries, such as:
- Field Repair
- Structural Welding
Two people in history are responsible for SMAW or stick welding. In 1888, Russian inventor Nikolay Slavyanov introduced the concept of arc welding with consumable metal electrodes. Although Nikolay Bernardos invented arc welding, Slavyanov was the first person to make practical use of this welding method.
Slavyanov worked at the Perm cannon factories and used the electric arc to liquefy metal to improve the quality of metal for forging gun barrels. Using consumable metal electrodes, he developed a better method of degassing the metal fluid to avoid blowholes weakening the strength of the metal.
In 1890, Charles L. Coffin patented an arc welding process that used metal electrodes. While Slavyanov used the electric arc for casting metal in a mold, Coffin’s idea was using melted metal as a filler material in the joint, creating a weld.
Today stick welding is still a manual trade, but electrodes have become more advanced, and the equipment used is much more efficient.
Stick welding is a relatively simple process because the needed equipment is simple.
- Power supply
- Electrode holder
- Welding leads
- Correct PPE
AC or DC forms the arc between the working metal piece and the electrode. Arc length, determined by the electrode’s type and diameter, determines the amount of required voltage. Higher amps provide the power needed for welding thicker metals.
Knowing what electrodes to use and how they work is essential. There are three groups of electrodes:
- Fast-fill: electrodes that melt fast-for fast, flat, and horizontal welding
- Fast-freeze: electrodes that solidify quickly used for welding in all positions
- Fill-freeze: electrodes that are intermediate and are ideal for general use.
Electrodes have a flux coating, which converts to gas, giving weld protection by reducing contamination, increasing the joint’s purity and weld quality.
Although stick welding is relatively simple, the learning curve may be higher compared to other welding methods. Despite its simplicity, the process needs skilled and experienced welders for quality results.
Advantages and Disadvantages
As with every other welding method, stick welding has its own set of advantages and disadvantages.
Some advantages are comparatively significant:
- No separate shielding gas is required.
- Stick welding uses basic equipment.
- A wide range of types and sizes of electrodes are available.
- Operators can use it with a variety of metals.
- It works well outdoors and indoors, rain or shine.
- Operators can learn it fairly quickly.
- It’s suitable for a range of projects.
Disadvantages of stick welding include:
- Need to remove slag after welding. Entrapment of slag also is an issue in SMAW forming inclusions, which need to be removed.
- Unused electrode stubs—need to stop welding when reaching the last 2 inches of the electrode.
- The slow relative speed of SMAW.
- Spatter cleanup and slag removal labor-intensive
- Creates more sparks and heat than other welding methods
- Chipping and grinding on completed welds creates harmful dust.
- Need to stop during the welding process to replace used electrode and to chip away slag
Common Stick Welding Problems
Besides the list of disadvantages, there are several problems that, if occurred, compromises the quality of the weld.
- Shallow penetration
- Poor fusion
- Wandering arc
- Unstable arc
There are several kinds of cracks possible along the weld leading to the chance of fractures. The three principal reasons for cracking include high sulfur, alloy, or high carbon content in the base metals. Also, there is a greater chance of cracks if the parts are rigid.
Penetration is how deep inside the base metal the weld reaches. Because of the process used in stick welding, the ability to see if it has reached the correct penetration is difficult.
When a solid bead forms through the entire joint and the weld pool strongly bond both sides of a joint, proper fusion has occurred. When poor fusion occurs, it is easy to see.
Porosity is the measure of voids in material and is not ordinarily visible. This is one of the more common issues when stick welding. If the base metal’s surface is dirty or if the weld poor does not remain molten very long, then gas bubbles created during the welding process don’t have time to escape.
Stray magnetic fields may cause the arc to wander off its intended direction, typically an issue when using DC.
If the arc is unstable despite proper polarity and current, there may be a simple cause: wet electrodes.
Although it may seem to be an aesthetic issue, when a groove develops at the base of the metal, it leads to undercutting. Fixing undercutting problems cuts production speed and is expensive.
There is no effect of weld strength after a weld spatters, but the poor surface finish takes time resulting in increased cleanup costs.
What’s New in SMAW
The SMAW process has changed little since its invention. It still needs an arc to get the process underway, and the welder lays down a bead with the melting electrode.
The improvements in stick welding have been in advances in electrodes and welding power sources’ innovations.
In the old days, hydrogen cracking was a big issue. Cracking happens when the welding cracks at the joint, caused by electrodes releasing.
Introducing low hydrogen electrodes helped overcome the cracking problem. When using low hydrogen electrodes, there are some storage issues associated with them. Opening the packaging exposes the electrodes to moisture. Correctly storing the packages reduces moisture-related problems.
It’s advisable to use them within the 9-hour working day period; otherwise, they could revert to their hydrogen cracking behavior.
Advanced electrodes increase the strength of the welds required for military applications.
The same goes for the welding of high-pressure vessels such as boilers or equipment required to operate at low temperatures.
Sticking an electrode is a problem caused by a natural drop in voltage, stopping the arc. Today, there are SMAW power devices designed to expect the problem. When sticking is about to happen, the power source increases the current, preventing sticking from occurring.
Inverters eliminate the need for three-phase power sources. Inverters prevent interruptions from occurring during welding, stopping dips in the power supply.
These inverter units are much easier to transport, and they offer much more welding versatility.
The portability of stick welding means it is used in a variety of industries, indoors or out. The simplicity of the equipment means the process is less expensive to set up. However, that simplicity is misleading in the sense that it is a challenging welding process to master.
Production speed is slower, and the results may not be as pretty as TIG welding, but SMAW remains one of the most popular arc welding methods.