What do the numbers in an electrode classification, like E7018, indicate?

The classification of a welding electrode, such as E7018, provides crucial information about the electrode's specifications and suitability for different welding applications. In this case, the 'E' stands for electrode, indicating that it is used for welding. The '70' indicates the minimum yield strength of the weld metal in thousands of pounds per square inch (psi), which in this case means a minimum yield strength of 70,000 psi.

The '1' refers to the welding position for which the electrode is suitable, meaning it can be used in all positions (flat, horizontal, vertical, and overhead). Lastly, the '8' denotes the type of coating on the electrode, which affects key aspects such as arc stability and deposition characteristics. The coating for E7018, for example, is primarily a potassium-based low hydrogen type, which provides good arc stability and helps prevent hydrogen-induced cracking in welded joints.

This classification system is designed to convey all of this pertinent information concisely, thus making it easier for welders to select the proper electrode based on their specific project requirements.