What do the first two digits in a welding rod identified as E 7018 represent?

The first two digits in the designation of a welding rod, such as E 7018, indicate the minimum tensile strength of the weld metal in thousands of pounds per square inch (psi). In this case, '70' signifies that the electrode can produce a weld with a minimum tensile strength of 70,000 psi. This numbering system is part of the American Welding Society (AWS) classification, which helps welders select the appropriate welding rod based on the required strength and application.

Understanding the composition of the code is crucial for welders, as it ensures that they choose a rod suitable for the materials they're working with and the stresses the welded joint will experience. The tensile strength is vital, especially in structural applications where the integrity of the weld is critical. This specific information helps in making informed decisions regarding welding applications, ensuring safety and performance.