Fish-scale welding places many special demands on welders, as detailed below:
1. Skill Requirements
- Hand Stability: Hands must remain extremely stable during welding to avoid shaking, which could damage the tungsten electrode and cause tungsten inclusions in the weld pool. Welders can use their index finger, holding the welding gun, to support the pipe or plate being welded, or place the ceramic nozzle against the workpiece to enhance stability.
- Precise Wire Feeding Technique: The wire feeding hand and the gun hand must be coordinated. The wire feeding speed should be adapted to the size of the weld pool to ensure adequate heat input. Different wire feeding methods should be used depending on the size of the groove. For smaller groove angles, the wire can be placed in the center of the weld pool and fed continuously. For larger grooves, point-feeding from both sides is recommended, but requires considerable skill to avoid contact with the tungsten electrode.
- Experienced Oscillation Pattern: The appropriate oscillation pattern can produce different weld textures, such as zigzag, crescent, or triangle. Welders should choose the appropriate oscillation method based on their needs. For example, when the molten pool cools to a dark red, quickly perform repair welding, ensuring that each layer overlaps by 2/3 to form a uniform fish-scale pattern.
- Good Observation and Adjustment Skills: TIG welding is an open arc operation, allowing the welder to directly observe the shape and flow of the molten pool and adjust welding parameters accordingly.
2. Theoretical Knowledge Requirements
- Familiarity with Welding Parameters: The welder must select appropriate welding parameters based on the characteristics, thickness, and shape of the weld material, including current, voltage, argon flow rate, tungsten electrode diameter, and angle. For example, higher current results in deeper weld penetration, while higher voltage results in wider weld width. An argon flow rate of 8-12 liters/minute is generally recommended.
- Understanding of Welding Material Characteristics: The filler wire should be the same or similar material as the base material to ensure the performance of the welded joint.
3. Experience and Qualification Requirements
- Extensive Practical Experience: Fish-scale welding is a complex technique requiring extensive practical experience. Mastery is generally limited to experienced welders. - **Relevant Qualification Certificates**: In industries with high welding quality requirements, such as aerospace and shipbuilding, welders may be required to possess relevant qualification certificates.
4. Mental Health and Concentration Requirements
- High Concentration: The welding process requires the welder to maintain full concentration and focus to ensure weld quality.
- Good Mental Health: When faced with complex welding tasks and high precision requirements, welders must remain calm and avoid being affected by nervousness.