Today I will be discussing the definition, applications, diagram, equipment, working, advantages, and disadvantages of shielded metal arc welding (SMAW). Previously, metal inert gas welding was discussed. check out!
Read more: Understanding metal inert gas welding (MIG)
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 arc to the workpiece. This arc welding process is known as the simplest, less expensive, and most used type of arc welding process.
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.
Read more: Understanding tungsten inert gas welding (TIG)
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. 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.
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 which cannot be welded from 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, trailers.
Pressure pipelines that cannot be welded from the inside, oil storage tanks, railway coach panels. Locomotive fire-boxes, scooter frames. The above-listed applications can be welded using a shielded metal arc welding.
Read more: Understanding Arc stud welding and its techniques
Diagram of SMAW:
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.
Read more: Understanding gas welding process
Working principles of SMAW
SMAW is carried out closely just as other arc welding processes. It also uses an AC or DC power supply that transfers current to the electrode holder in order to produce an arc leading to intense heat to melt the tip of the electrode and the joining portion of the workpiece with the arc. This arc length is maintained by the welder by holding a consistent space between the electrode and the weld pool that is a form on the workpiece. This workpiece bonds as soon as the arc is taken off it. then the joint is obtained.
Watch the video below to learn the working of SMAW:
Read more: Understanding plasma arc welding
Advantages and disadvantages of Shielded metal arc welding
The followings are the advantages of SMAW:
- Operation results can be readily and reliably obtained.
- Filler and shielding material is provided on the electrode
- SMAW equipment is inexpensive, relatively simple, and portable
- Auxiliary gas shielding or granular flux is not required
- Ability to weld a variety of metals such as; carbon and low-alloy, steel, high alloy steel, coated steel, tool and die steel, stainless and heat-resisting steels, cast irons, copper and copper alloys, nickel and cobalt alloys
- The process is flexible and can be applied to a variety of joint configuration and welding positions
Despite the benefits SMAW offers, it also has some disadvantages. The following are the limitations of SMAW:
- Unable to weld metals with low melting temperature such as lead, tin, and zinc, and their alloys cannot be welded. This is because they have a low boiling point and for this welding process that produces intense heat. It will cause immediate vaporization from the solid-state.
- The grip end of the electrode (stub-loss) that will be thrown away with a small portion of flux can affect the deposition rate. The longer stub-loss change directly into lower deposition efficiency
- Too much high current and too long electrode generate excessive heat within the electrode. This will cause a premature breakdown of the flux when the welding starts. This breakdown triggers a deterioration of the arc characteristics and reduces the level of the shielding
- It is not stable for welding reactive metals such as titanium, zirconium, tantalum, and niobium, due to the shielding provided is not sufficiently inert to prevent contamination of the weld.
- It yields lower deposition rates than other welding processes like gas metal arc welding (GMAW) and flux core arc welding (FCAW) process. This is because the maximum useful current is limited.
Read more: Understanding submerged arc welding
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That is all for this article, where the definition, applications, diagram, equipment, working principle, advantages and disadvantages of shielded metal arc welding (SMAW). I hope you enjoyed the reading, if so, kindly share with other students. Thanks for reading, see you next time!