A387 Grade 11 Class1 steel is a low-alloy pressure vessel steel known for its excellent corrosion resistance and high-temperature properties. Welding A387 Grade 11 Class1 steel plates requires proper techniques and considerations to achieve optimal results.
Preheating
Preheating the base metal is crucial when welding A387 Grade 11 Class1 steel plates. Preheating helps to reduce the cooling rate during welding, minimizing the risk of hydrogen-induced cracking and ensuring better weld quality. The recommended preheating temperature for A387 Grade 11 Class1 steel is typically between 150°C to 200°C (300°F to 400°F), depending on the plate thickness and ambient conditions. It is important to ensure uniform preheating throughout the welding area for consistent results.
Interpass Temperature Control
Maintaining appropriate interpass temperatures is essential to prevent excessive cooling and thermal stress build-up during multi-pass welding. Rapid cooling can lead to increased hardness in the heat-affected zone (HAZ) and potential cracking issues. Controlling the interpass temperature within the range of 150°C to 250°C (300°F to 480°F) helps maintain favorable mechanical properties and minimizes the risk of HAZ cracking. This can be achieved by using insulation methods or local heating techniques, if necessary.
Filler Material Selection
Selecting the correct filler material is critical for achieving sound and reliable welds in A387 Grade 11 Class1 steel plates. Matching or overmatching filler metals with similar alloy composition are typically used to maintain the desired mechanical properties. For welding A387 Grade 11 Class1 steel plates, low-alloy filler materials such as AWS E/ER 80S-B2 or AWS E/ER 90S-B3 are commonly recommended. Consultation with welding engineers or referring to the manufacturer's guidelines can help in choosing the appropriate filler material.
Post-Weld Heat Treatment
Performing post-weld heat treatment (PWHT) can further enhance the properties and integrity of welded A387 Grade 11 Class1 steel plates. PWHT involves heating the welded structure to a specific temperature range, followed by controlled cooling. This process relieves residual stresses, improves toughness, and promotes microstructural homogeneity. The recommended PWHT temperature for A387 Grade 11 Class1 steel typically ranges between 620°C to 680°C (1150°F to 1255°F), with a suitable holding time based on plate thickness.
Quality Control and Inspection
Conducting thorough quality control and inspection procedures throughout the welding process is essential. This includes visual inspection of weld joints, non-destructive testing methods like ultrasonic or radiographic examination, and mechanical testing of weld samples. Adhering to established welding procedures, employing qualified personnel, and following industry standards help ensure the quality and integrity of the welded A387 Grade 11 Class1 steel plates.
