In the welding industry, 7018 and 7018 - 1 electrodes are both widely used low - hydrogen electrodes, favored for their excellent welding performance and high - quality welds. However, there are subtle yet important differences between them. Understanding these differences is essential for welders to make the right choice in different welding scenarios.
Coating Composition
The coating of 7018 electrodes is a low - hydrogen iron powder type. Its main components include iron powder, calcium carbonate, calcium fluoride and other substances. The iron powder content in the coating is relatively moderate, which can provide a certain deposition rate. The low - hydrogen nature of the coating helps reduce the hydrogen content in the weld metal, thereby reducing the risk of hydrogen - induced cracking.
7018 - 1 electrodes, as an improved version of 7018, have a more optimized coating formula. On the basis of the 7018 coating, adjustments are made to the proportion of components such as iron powder and alloy elements. The iron powder content in 7018 - 1 electrodes is usually higher, which can further improve the deposition efficiency. At the same time, the addition of certain alloy elements in the coating enhances the mechanical properties and crack resistance of the weld.
Mechanical Properties of Weld Metal
Both 7018 and 7018 - 1 electrodes can produce welds with high strength. The minimum tensile strength of the weld metal welded by 7018 electrodes is 70,000 psi (pounds per square inch), and it has good ductility. The welds formed by 7018 electrodes have stable mechanical properties and can meet the requirements of most general - purpose structural welding.
7018 - 1 electrodes, due to the optimized coating formula, make the weld metal have better mechanical properties. Its tensile strength is also 70,000 psi or higher, but in terms of impact toughness, especially at low temperatures, 7018 - 1 electrodes show more excellent performance. This makes 7018 - 1 electrodes more suitable for welding projects that have higher requirements for impact resistance, such as some low - temperature environment equipment or structural parts that need to withstand impact loads.
Welding Performance
In terms of welding operability, 7018 electrodes have a stable arc and a smooth bead appearance during welding. They are relatively easy to control, making them suitable for welders with certain experience. However, 7018 electrodes have higher requirements for the welding environment. They are sensitive to moisture. If they absorb moisture, it will increase the hydrogen content in the weld, which may lead to cracks. Therefore, 7018 electrodes need to be stored in a dry environment and may need to be re - dried before use if they absorb moisture.
7018 - 1 electrodes inherit the stable arc characteristics of 7018 electrodes. At the same time, due to the improvement of the coating, their slag detachability is better. After welding, the slag can be removed more easily, reducing the workload of post - welding cleaning. In terms of moisture resistance, 7018 - 1 electrodes have certain improvements compared with 7018 electrodes. They can resist moisture absorption to a certain extent in a relatively humid environment, but they still need to be stored properly to ensure welding quality.
Application Scenarios
7018 electrodes are widely used in general structural welding, such as the welding of construction steel structures, bridges, and ordinary machinery parts. They are suitable for welding carbon steel and low - alloy steel, and can meet the basic strength and toughness requirements of these structures. For example, in the construction of steel frame buildings, 7018 electrodes are often used to connect steel beams and columns, ensuring the stability and bearing capacity of the structure.
7018 - 1 electrodes are more suitable for welding projects with higher requirements. They are often used in pressure vessel welding, such as the welding of oil storage tanks and chemical pressure vessels. These devices need to withstand certain pressure and may work in harsh environments, so the welds require higher toughness and crack resistance. In addition, 7018 - 1 electrodes are also used in the welding of some low - temperature equipment, as their welds have better low - temperature impact toughness, which can ensure the safe operation of the equipment in low - temperature environments.
Price
Due to the more optimized coating formula and better performance, the production cost of 7018 - 1 electrodes is slightly higher than that of 7018 electrodes. Therefore, in the market, the price of 7018 - 1 electrodes is usually higher than that of 7018 electrodes. When choosing, welders and enterprises need to balance performance requirements and cost factors. If the welding project has no special requirements, 7018 electrodes can meet the needs at a lower cost; if higher performance is required, 7018 - 1 electrodes are a more reliable choice despite the higher price.
In conclusion, 7018 and 7018 - 1 electrodes have their own characteristics. 7018 electrodes are cost - effective and suitable for general structural welding. 7018 - 1 electrodes have better performance in terms of mechanical properties, slag detachability, and moisture resistance, making them more suitable for high - demand welding projects. Welders should choose the appropriate electrode according to the specific welding requirements, material characteristics, and environmental conditions to ensure the quality and reliability of the welds.
