Final answer:
In welding electrode classification, the '1' after the dash in 'E7018-1H4R' indicates that the electrode meets the impact strength requirements at -30 degrees Celsius, with 'H4' specifying low hydrogen content and 'R' indicating moisture resistance.
Step-by-step explanation:
The student's question is about understanding the meaning of the numeral '1' after the dash in the designation 'E7018-1H4R'. In welding electrode classification, the 'E7018' specifies the type of electrode and its characteristics. In this designator:
- The 'E' stands for electrode.
- '70' indicates a tensile strength of 70,000 pounds per square inch.
- '1' refers to the electrode being suitable for all welding positions.
- '8' signifies the coating, current, and polarity types.
The '1' after the dash in 'E7018-1H4R' specifies the impact properties of the electrode. It indicates that the electrode meets the impact strength requirements at -30 degrees Celsius. The 'H4' indicates the amount of diffusible hydrogen the deposit can contain, which is less than 4 milliliters per 100 grams of weld metal, and 'R' denotes that the electrode has moisture resistance. This alphanumeric code is essential for welders to select the appropriate electrode for their welding applications.