8.3 SMAW Electrodes
David Ridge
Electrode Classification
There are dozens of different SMAW electrodes on the market today to go along with the wide variety of metals that need to be welded. In all welding applications that require a filler metal, it is important to match that filler metal with the base metal since not all metals bond well to each other and welds made with metals that are too dissimilar to each other are likely to fail. For example, you would want to weld a steel alloy base metal with a steel alloy filler metal, a stainless steel with a similar stainless steel, and a titanium alloy with titanium. You would not try to weld steel with titanium filler metal, as the two would not mix well. Even within these broad categories of metals, it is necessary to accommodate the many variations in the type of base metal alloy. For instance, a high-strength steel would need to be welded with a similar high-strength steel filler metal. Additionally, some elements in the flux make different electrodes suitable for some applications but not others, such as electrodes that keep a weld low in hydrogen, a major cause of weld failure, versus an electrode that can weld underwater, a major source of hydrogen.
With all that being said, it is very important to be able to identify the filler metal you are working with. Since most metals cannot be easily identified just by looking at them, the AWS has devised the filler metal classification system, which is composed of letter and number codes that are printed on the electrodes themselves or on their packaging (American Welding Society, 2012).
With a quick glance, this system allows you to have the basic information needed in order to use the electrode properly. Each letter and number in the system has a meaning, appearing in the following order: prefix, tensile strength, welding position, flux type/polarity requirements, and suffix/additional requirements met (if any). The sections that follow discuss each component of this system in detail.
Before we begin, it is worth mentioning that it is in your best interest to memorize the order of the classification system so you can pick up how to read a SMAW electrode classification more quickly.
Finally, in the following sections the system covered is for identifying SMAW electrodes for welding carbon steel. There are separate filler metal classification systems for each different type of filler metal/electrode for each welding process. Those will be discussed in their respective chapters.
Prefix
The basic filler metal classification system for carbon steel electrodes takes this form: the capital letter E followed by four or five numbers.
The letter at the beginning of the classification is called the prefix and it tells you what form the filler metal takes. In the case of SMAW, the prefix will always be the letter E, which stands for “electrode.” For a filler metal to be classified as an electrode, the welding current must pass through it to complete the circuit.