What does the 'X' in E70C-X signify?

The 'X' in E70C-X signifies that the wire has a composite core. This designation implies that the filler metal includes additional alloying elements and characteristics that provide enhanced performance, particularly in terms of its weldability and strength.

In the context of the American Welding Society (AWS) classification system for welding electrodes and fillers, the letter 'E' indicates that the material is an electrode; '70' denotes the minimum tensile strength of the deposited weld metal (70,000 psi); and 'C' refers to the type of electrode or the welding process. The 'X' indicates a specific type or formulation of the core material that sets it apart from other types, which may not have that composite feature. Its inclusion points to enhanced properties that may not be present in standard filler materials.

Understanding these classifications is crucial for selecting appropriate materials for specific welding applications and achieving desired performance characteristics in welded joints.