The SMAW Process

SMAW process, called arc welding process that creates coalescence of metal through heating with arc between a covered metal electrode and the work. Decomposition of the flux coating used in the process to emitting a shielding gas and forms fluxing elements to protect the molten weld-metal droplets and the weld pool.

SMAW Process:  

  • The arc is initiated by momentarily touching or “scratching” the electrode on the base metal.
  • The resulting arc melts both the base metal and the tip of the welding electrode.
  • The molten electrode metal/flux is transferred across the arc (by arc forces) to the base-metal pool, where it becomes the weld deposit covered by the protective, less-dense slag from the electrode covering.

plasma-welding

SMAW welding 

Advantages and Limitations:

  • The SMAW process is the most widely used welding process. It is the simplest, in terms of equipment requirements, but it is, perhaps, the most difficult in terms of welder training and skill-level requirements.
  • Although welder skill level is a concern, most welders entering the field start as “stick welders” and develop the necessary skills through training and experience.
  • The equipment investment is relatively small, and welding electrodes (except the very reactive metals, such as titanium, magnesium, and others) are available for virtually all manufacturing, construction, or maintenance applications.
  • Shielded metal arc welding has the greatest flexibility of all the welding processes, because it can be used in all positions (flat, vertical, horizontal, and overhead), with virtually all base-metal thicknesses and in areas of limited accessibility, which is a very important capability.

Weld Quality:  

  • The quality of the weld depends on the design and accessibility of the joint, as well as on the electrode, the technique, and the skill of the welder.
  • If joint details vary greatly from established design details, then a lower-quality weld can result.
  • Other factors that also reduce quality are improper interbead cleaning, poor location of individual weld beads within the joint, and various problems with individual electrodes, including partially missing flux and core wires that are not centered within the flux covering.
  • Overall, welds of excellent quality can be obtained with the SMAW process, as demonstrated by its use in joining submarine pressure hull sections and high-pressure oil/gas pipe lines.

Welding Circuit:

  • The equipment consists of a power source, electrode holder, and welding cables that connect the power source to the electrode holder and the workpiece.
  • Alternating current (ac), or direct current, electrode negative (DCEN), or direct current, electrode positive (DCEP) can be used, depending on the electrode coating characteristics.
  • The DCEN source is also called dc straight polarity, whereas the DCEP source is also called dc reverse polarity

Arc welding machine from Hong Ky video:

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