Short Answer
Complete Explanation
The designation “7018” on a welding rod is part of the American Welding Society (AWS) A5.1 specification for carbon steel electrodes used in shielded metal arc welding (SMAW), commonly known as stick welding. The full classification is typically written as E7018, where the letter ‘E’ stands for electrode. Each digit and the letter convey specific mechanical properties and usage characteristics.
- E:
The prefix “E” indicates that the product is an electrode used for electric arc welding. - 70:
The first two digits (70) represent the minimum tensile strength of the weld metal in thousands of pounds per square inch (psi). An E7018 electrode produces weld metal with a minimum tensile strength of 70,000 psi (approximately 483 MPa). - 1:
The third digit (1) indicates the welding position in which the electrode can be used. A “1” means the rod is suitable for all positions: flat, horizontal, vertical (both uphill and downhill), and overhead. Other digits (e.g., 2 for flat and horizontal only) denote more limited position capability. - 8:
The fourth digit (8) specifies the type of coating and the current requirements. For E7018, the “8” signifies a low-hydrogen potassium or sodium coating with a high iron powder content (typically 25–40%). This coating produces a basic slag that helps reduce hydrogen in the weld, minimizing the risk of hydrogen-induced cracking. The electrode is designed to operate on direct current electrode positive (DCEP, i.e., reverse polarity) or alternating current (AC), though DCEP is most common for optimal performance.
FAQ
Can I use E7018 electrodes on AC current?
Yes, E7018 electrodes are designed to operate on both DC electrode positive (reverse polarity) and AC current. However, for best arc stability and low-hydrogen properties, DC reverse polarity is recommended. When using AC, some welders may experience a less stable arc, especially on thinner materials.
Why must E7018 electrodes be stored in an oven?
E7018 electrodes have a low-hydrogen coating that absorbs moisture from the air. Moisture in the coating can release hydrogen into the weld pool, leading to hydrogen-induced cracking (cold cracking). To prevent this, electrodes must be stored in a heated rod oven at 250–300°F (120–150°C) and used within a short time once removed.
What is the difference between E7018 and E7014?
E7018 is a low-hydrogen electrode with higher iron powder content, offering better crack resistance and mechanical properties, suitable for critical structural welds. E7014 has a rutile-based coating with some iron powder, produces a smoother arc, and is easier to use for less critical applications but has higher hydrogen potential.
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