As a high-performance low-hydrogen type welding rod widely used in mild steel welding, the E7018 welding rod has strict requirements on temperature in the whole process from storage, pre-welding treatment to welding operation. Mastering its temperature range is not only related to the stability of the welding rod's performance, but also directly affects the quality of the weld, such as reducing the risk of hydrogen-induced cracks and ensuring the mechanical properties of the deposited metal. This article will systematically sort out the key temperature parameters of the E7018 welding rod and explain the practical operation specifications.
The most critical temperature parameter of the E7018 welding rod is the drying temperature before use. Due to its low-hydrogen coating, the E7018 welding rod is extremely sensitive to moisture. Once it absorbs moisture, the hydrogen content in the coating will increase significantly, which may lead to pores, cracks and other defects in the weld during welding. According to industry standards and manufacturer recommendations, the standard drying temperature for E7018 welding rods is 300–400°C (572–752°F). The drying time needs to be adjusted according to the moisture degree of the welding rod: for new and unopened welding rods that are stored in a dry environment, 1 hour of drying is usually sufficient; for welding rods that have been stored for a long time, exposed to humid air, or even have obvious moisture condensation on the surface, the drying time should be extended to 2 hours to ensure that the moisture in the coating is fully evaporated. It should be noted that the drying process must be carried out in a professional welding rod drying oven, and rapid heating or exceeding the maximum temperature limit is strictly prohibited, otherwise the coating may be decomposed or cracked, losing its protective effect.
After drying, the storage and insulation temperature of the E7018 welding rod is also a key link to maintain its low-hydrogen performance. If the dried welding rod is directly placed in the air, it will absorb moisture again quickly, especially in an environment with high humidity (relative humidity > 60%). Therefore, after taking out the welding rod from the drying oven, it should be immediately placed in a heat preservation cylinder. The ideal temperature in the heat preservation cylinder is 100–150°C (212–302°F). This temperature range can not only prevent the welding rod from absorbing moisture again, but also avoid the coating from being overheated for a long time and losing activity. The heat preservation cylinder should be kept closed when not in use, and the storage time of the welding rod in the heat preservation cylinder should not exceed 8 hours. If it exceeds this time, it needs to be dried again before use.
In addition to the temperature related to the welding rod itself, the preheating temperature of the base metal during welding is also an important auxiliary parameter, which is closely related to the thickness of the mild steel and the welding environment. For mild steel with a thickness of less than 12mm and welding in a room temperature environment (above 15°C), preheating may not be required; but when the following situations occur, preheating is necessary: when the thickness of the base metal exceeds 12mm, the welding environment temperature is lower than 0°C, or the structure has high rigidity (such as corner joints with large constraints), the preheating temperature should be controlled at 120–200°C (248–392°F). Proper preheating can slow down the cooling speed of the weld after welding, reduce the residual stress, and further reduce the risk of cold cracks. However, the preheating temperature should not be too high, otherwise it may cause oxidation of the base metal surface or change the metallographic structure, affecting the overall performance.
Another temperature that needs attention is the interpass temperature during multi-layer welding. When performing multi-layer and multi-pass welding (such as welding thick plates), the temperature of the previous weld bead must be maintained above a certain level before welding the next layer. For E7018 welding rods, the recommended interpass temperature is 150–300°C (302–572°F). This temperature range can prevent the weld from cooling too quickly, avoid the formation of hard and brittle structures, and help the gas in the molten pool to escape, reducing the occurrence of pores. During the operation, a contact thermometer or infrared thermometer can be used to monitor the temperature of the weld zone in real time to ensure that it is within the specified range.
In summary, the temperature management of E7018 welding rods runs through the whole process of storage, pre-treatment and welding. The drying temperature of 300–400°C ensures the low-hydrogen performance of the coating, the insulation temperature of 100–150°C prevents moisture absorption again, the preheating temperature of 120–200°C (when needed) and the interpass temperature of 150–300°C guarantee the welding quality. Only by strictly implementing these temperature standards and matching them with standardized operation methods can the E7018 welding rod give full play to its advantages in strength and toughness, and ensure the safety and reliability of mild steel welded structures.
