Shielded metal arc welding (SMAW) is a manual arc welding process known as manual metal arc welding or stick welding. It uses a consumable and protected electrode. During the operation, the electrode melts and a cover from the electrode protects the weld area from oxygen and other atmospheric gases.
The primary purpose of shielded arc welding is to perform arc welding using a covered metal electrode to protect the weld. Requirements like a welding machine or power source provide electric current for the welding. Also, an electrode holder will be needed to hold the SMAW electrode and connect it to the welding machine.
SMAW techniques are often used on carbon steel, low and high allow steel, stainless steel, cast iron, and ductile iron. However, they are not suitable for non-ferrous metals. In this reading, we’ll explore SMAW, its applications, parts, equipment, diagram, advantages, disadvantages, and how it works.
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What is Shielded Metal Arc Welding (SMAW)?
Shielded metal arc welding is another type of arc welding process which is also known as stick welding or manual arc welding. it uses a metallic consumable electrode of a proper composition for generating an arc to the workpiece. This arc welding process is known as the simplest, less expensive, and most used type of arc welding process.
The SMAW process works with electrodes coated with a shielding flux, this flux melts together with the electrode metallic core, which forms gas and slag. This gas and slag shield the arc and the weld pool, and the flux cleans the metal surface. This flux supplies some alloying elements to the weld stabilizes the arc and protects the molten metal from oxidation.
In other words, the main function of the shielding is to protect the arc and the hot metal from a chemical reaction with constituents of the atmosphere. The SMAW process does not need filler metals as the electrode is already coated with fluxing agents, scavengers, and slag formers. The filler is obtained from the electrode.
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Applications of SMAW
The applications of shielded metal arc welding are so broad and one of the widely used arc welding. SMAW is often used on carbon steel, low and high alloy steel, stainless steel, cast iron, and ductile iron. Although it is less popular for nonferrous metals, it can be used on copper and nickel and their alloys, but not in most situations on aluminum.
SMAW is used for welding Pipelines, tanks, pressure vessels, structural, and fieldwork where deep penetration is necessary. It is ideal for pressure pipelines that cannot be welded from the inside. Storage tanks, gear blanks, machinery, steel furniture, truck bodies, foundry equipment, shaft build-up, etc.
Structures, building construction, tanks, pipelines, machinery parts, automobile bodies, steel window frames, farm machinery, etc. vessels, tanks and boilers, pipelines, bridges, railway wagons, ships, and trailers. Pressure pipelines that cannot be welded from the inside, oil storage tanks, and railway coach panels. Locomotive fireboxes, scooter frames. The above-listed applications can be welded using shielded metal arc welding.
SMAW Parts & Equipment
Shielded metal arc welding equipment typically consists of a constant current welding power supply and an electrode, with an electrode holder, a work clamp, and welding cables (also known as welding leads) connecting the two. The welding machine or power source provides an electric current for welding, electrode holder holds the SMAW electrode and connects it to the welding machine.
Cables help to power the welding machine and connect the electrode holder to the welding machine, ground clamp is used to hold the electric current between the welding machine and the workpiece. Protective items like helmet, overall, safety boot, google, are parts of shielded metal arc welding.
Welding Machine
A welding machine is essential for ensuring the safety of the workpiece and preventing electrical shock. It requires a ground clamp to prevent overheating and is connected to the workpiece or fixture. The welding cables used in SMAW are flexible and insulated, with two cables for the electrode holder and the ground clamp.
The arc length is a crucial factor in stick welding, as it determines the optimal arc length for the project. The amperage is influenced by the electrode selection, welding angle, and finish, with recommendations available in stick welder manuals and guides. Travel speed is also influenced by the electrode angle and type, with fast-filling electrodes allowing higher travel speeds.
Welding techniques are crucial in determining the quality of the weld. Whipping the electrode works best on low-flux electrodes like E6010, E6011, and E6013, while the circle technique is commonly used by beginners for consistent travel speed. Weaving is generally used when wider welds are required, performing side-to-side motions after striking the arc.
Diagram of SMAW
How Does of SMAW Works?
Shielded metal arc welding (SMAW) is a welding process that uses heat from an electric arc to create coalescence of metals between the tip of a consumable electrode and the surface of the base material in the joint being welded. This process involves an electric circuit including the power source, welding cables, electrode holder, and ground clamp.
The electrode and base metal are part of this circuit, and the welding begins when an arc forms between the base metal and electrode tip. Metal forms on the end of the electrode, transferring from the arc into a pool, and filler is deposited when the electrode is consumed.
Voltage is a key variable in stick welding, and it is regulated manually by moving the stick closer or farther from the work. Constant current power sources are used for most stick welding and other manual welding processes. Reverse polarity is almost always used in SMAW welding processes to provide the best bead profile and penetration, while reducing excessive spatter.
Some basic tools used in SMAW include an arc welding power source, electrode lead cable, electrode holder, leads, cables, cable connectors, ground clamp, and a cutting hammer. Safety equipment, such as helmets, gloves, and protective clothing, is also essential for the welder’s safety.
Stick Welding Electrode
Electrode type plays a crucial role in determining weld quality, as its chemical composition influences arc stability, deposition rate, and depth of penetration. Stick welding electrodes are classified into three main categories: cellulosic electrodes, rutile electrodes, and basic electrodes. Cellulosic electrodes have a high cellulosic proportion, suitable for deep arc penetration and high weld speeds.
Rutile electrodes contain high amounts of titanium oxide, promoting lower spatter, a good bead profile, and consistent arc operation. Basic electrodes have high quantities of calcium chloride and calcium carbonate, suitable for welds requiring good mechanical properties and resistance to cracking.
They are suitable for high weld speeds, but slag freezing is difficult to remove, leading to poor bead profiles. Metal powder electrodes have a flux coating with iron powder, promoting higher welding current and higher deposition rates and efficiency compared to electrodes without iron powder. These electrodes are suitable for various welding positions and power sources.
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Advantages and Disadvantages of SMAW
Shielded Metal Arc Welding (SMAW) offers numerous advantages, including easy and reliable operation results, the provision of shielding material on the electrode, and its affordability, simplicity, and portability. It can weld various metals, including carbon, low-alloy, steel, high alloy steel, coated steel, tool and die steel, stainless steel, cast irons, copper and copper alloys, nickel and cobalt alloys, and is flexible in application to various joint configurations and welding positions.
Stick welding is a versatile welding technique that can be performed at various angles, including flat, horizontal, vertical, and overhead positions. By understanding these factors, the welder can create a strong and efficient welding process.
However, SMAW has limitations, such as not being able to weld metals with low melting temperatures, affecting the deposition rate due to stub-loss, generating excessive heat within the electrode, and not being stable for welding reactive metals like titanium, zirconium, tantalum, and niobium due to insufficient shielding. Additionally, stick welding yields lower deposition rates than other welding processes like gas metal arc welding (GMAW) and flux core arc welding (FCAW) due to limited maximum useful current.