SMAW and GMAW
Introduction:
Welding is one of the most reliable and fastest joining techniques to join and assemble metals, plastics, and ceramics permanently without the application of heat, filler, and pressure. Although there is large number of welding processes available, you can classify it into two major parts; one is fusion welding, and the other is solid-state welding. In the case of fusion welding, you can apply heat from external sources like electric arc, gas flame, resistance heating, and high-energy beam, etc. to melt down the surface of your metal to form the joining. In arc welding, arc constituted between the electrode and the base metal is the source of heat that melts down the surface metal and the filler material. Among many arc welding methods, Shielded Metal Arc Welding (SMAW) and Gas Metal Arc Welding (GMAW) are the most prominent. Although SMAW and GMAW run on the same basic principle, they have substantial differences in terms of procedure, benefits, limitations, and areas of application.
Differences Between SMAW and GMAW:
i) Continuous Nature of Electrode/Filler:
An electrode or other filler materials meltdown continuously and accumulates on the weld bead. Longer the length of the filler, shorter the weld time, and vice versa. For a shorter length, you need to replace the electrode frequently that would reduce the rate of production and disturbs the process. Longer filler is congenial for a longer duration, and thus it is productive. SMAW method requires frequent changing of the filler since it uses small rod and thus interrupts the process. On the other hand, GMAW method allows welding for a continuously longer time without any stoppage for changing of electrode.
ii) Preferable Welding Mode:
You can perform arc welding in three different ways. When you perform welding with the application of filler, it is homogenous mode. If the applied filler and the metallic composition are same, it is homogenous mode. When the filler material and the metal components are different, it is heterogeneous mode. SMAW is suitable for homogeneous welding since it inherently supplies filler. On the other hand, GMAW is suitable for both homogeneous and heterogeneous welding.
iii) Electrode Material:
Filler material like electrode should have some basic features such as electrical conductivity, desire melting point, electron emissivity, etc. Keep in mind that if there is a difference in the compatibility between the filler and the parent metal, you will face the problem of right mixing that will lead to defective output. SMAW is suitable for compatibility with ferrous components for homogeneous joining. In GMAW, most electrodes are ferrous. But you can harness the varied metallurgical composition from it for the desired outcome.
iv) Coated or Bare Electrode:
You will find a coated electrode for protection of the weld mode against the oxidation and other environmental contamination. Apart from protecting against the oxidation, coating has some other functions like supplying shielding gas, inducing chemical elements into weld bead, stabilizing arc, reducing spatter, etc. However, coated electrodes will cost you quietly, and they get damaged over time. SMAW uses flux-coated electrode that supplies shielding gas to protect the consumable filler. GMAW uses a thin coating of stable material on the electrode to protect the filler material from oxidation.
v) Shielding Gas Supply:
At the time of arc welding, dispensing oxygen from the welding zone is very crucial, and shielding gas helps you out of this criticality. Shielding gas creates an envelope around the bead to protect it from getting oxidized. Shielding gas can come out directly from the gas cylinder or indirectly from the disintegration of chemical components at the time of welding. In SMAW method, flux coating disintegrates chemical elements to supply shielding gas. GMAW supplies shielding gas from the gas cylinder.
vi) Spatter Problem:
During welding, you have experienced spatter that is nothing but small droplets of melted filler material. Spatter happens for the scattering of the arc. Higher spatter can lead to loss filler metal that can cause a defective & negative reinforcement with inaccurate dimensions. It is bad for appearance and may require you to grind for removing them. SMAW method produces extreme level of spatter even if you set the process parameters at the optimum level. On the other hand, GMAW method, although produces spatter, can reduce it by optimally setting the parameters.
vii) Manual and Automation:
You can operate SMAW welding manually only. On the other hand, GMAW allows you to operate the welding in automated mode. While an automated process is fast and productive, the manual process is flexible, and you can apply it at any location.
viii) Productivity and Quality Issues:
SMAW is a better choice for household and general industrial purpose. You may not get a quality joint from SMAW method. In this method, you need to change the electrode very frequently that interrupts the process and thus doesn’t serve your longer welding requirement. GMAW method is highly productive since you carry out the welding for longer duration. It provides a higher volume of deposition rate and is suitable for wide root gaps.
Tips on Vertical GMAW:
Vertical Down GMAW Technique:
It is quite easy to start on the top and then work your way down. You need to tilt up the gun between the range of 35 and 45 degrees. Stay ahead of the puddle and place the filler material from the side. In contrast, the weld will not enter adequately. Till you are ahead of the puddle, patterns don’t count.
Vertical Up GMAW Technique:
GMAW welding for the vertical up position is the most challenging and difficult job. Like the vertical down technique, this position also requires you to tilt the gun from 35 to 45 degrees. For working upward on, you need to create a welded shelf. It is typically convex shaped. For the desired result, you can grind a small grove on the spot you are welding. If the metal you weld on is wide, you can expect decent looking outcome.
Conclusion:
Both SMAW and GMAW are the arc-welding techniques that provide you handy and convenient solutions for the day-to-day requirements.
