What is Shielded Metal Arc Welding ?

Shielded Metal Arc Welding Process 

Stick welding or Shielded Metal Arc Welding (SMAW) is an electric arc welding process. In this process rod shaped metal electrodes that are covered with a flux material. The American Welding Society calls this process shielded metal arc welding or SMAW. Some people refer to this process simply as arc welding but stick welding is just one of many types of arc welding processes.

How Stick Welding Works

In stick welding electric current flows through a metal electrode or stick and arc which forms between the end of this electrode and the work piece. This arc melts both the metal in the rod and the metal and the pieces to be joined. The metal from the electrode is ejected into a molten weld pool and mixes or with the workpiece. The workpiece and the metal is called the base metal and the metal added to the joint from the electrode is called filler metal. This is welding process always adds filler metal to the joint because the electrode is constantly melting away and becoming part of the welded structure.

The electrode is heated by the arc in stick welding and hence it is known as a consumable electrode process. Some of the covering on the electrode releases protective gases that shield the weld and help to stabilize the arc. The remaining covering melts and then it covers the molten weld pool with a protective slag layer. This slag layer protects and helps to shape the weld as it solidifies. But it must be removed when the weld is cooled. Since the gases generated by the flux covering are able to completely protect the molten weld so there is no need for other shielding equipment such as high-pressure gas cylinders, hoses or regulator as compared to other welding processes.

How Stick Welding is Done

The quality of welds produced by stick welding process depends mainly on the operator skill. Insulated wires are connected to the welding machine. One lead goes to a clamp which is connected to the work is called the work lead. The other wire goes to an electrode holder. The end of the electrode is placed into a electrode holder. The polarity of the welding setup refers to how the electricity flows from the machine to the workpiece and back the current will either be AC or DC in AC or alternating current the direction of the flow of the electricity changes directions many times every second.

One lead is always set positive and the other is always negative. In stick welding we can set up DC in two ways. One way is called straight polarity in DC which is DC electrode negative or Dcen.  And the electrode is connected to the negative terminal and the work is connected to the positive the other way to connect DC is dcep which is DC electrode positive often called reverse polarity. Many stick welding electrodes operate on dcep but some are designed to work with DC and or AC.

Electrodes For SMAW

Stick welding electrodes are made with a variety of metal alloy compositions and flux chemistry's. We have to make sure the electrode that we plan to use will be strong enough and that it's compatible with the base metal and the position of the joint to weld. Often electrodes have the American Welding Society classification code printed on them. This code identifies tensile strength.

The Advantages Of SMAW

• This process requires lower equipment cost.
• This is most portable of all the other welding processes.
• It is well suited for large variety of commonly used alloys and metals.
• Separate gas shielding is not needed.
• The sensitivity to paint, dirt, corrosion is less at the welding point.

Disadvantages Of SMAW

• This process is slower than other methods of welding.
• Not suitable for welding thinner metals.
• Deposition rate is lower.
• It may spatter and cleanup is time consuming.
• It is complicated than other welding processes and requires highly skilled welder.

Conclusion

So in summary stick welding is an electric arc welding process. It uses a consumable electrode rod. This rod is covered with a flux material. While it gets heated the flux releases shielding gases that protect the weld by a layer of slag, which covers the weld while it solidifies and is removed when the metal cools. Electrodes used in stick welding are not all the same and it must be chosen for this specific job they need to perform.