Do grade 3 flange forgings require tempering?
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The flange is a 16Mn grade 3 forged part, model DN50. Is the difference between grade 2 and grade 3 forgings merely whether ultrasonic testing is performed, and is tempering necessary?
Tempering is a heat treatment process in which quenched steel is heated to a temperature below Ac1, held at that temperature for a certain period of time, and then cooled to room temperature. Its main purposes are:  (1) to reasonably adjust the hardness and strength of steel, improve its toughness, so that the workpieces meet the required performance standards ； (2) Stabilize the structure, preventing structural changes in the workpiece over time and thus maintaining its shape and dimensions ； (3) ƒ reduces or eliminates the quenching internal stresses in the workpiece, thereby minimizing deformation and preventing cracking.
Doesn’t third-level forging mean that no further tempering is needed, and only ultrasonic testing is required?
Doesn’t third-level forging mean that no further tempering is needed, and only ultrasonic testing is required?
Yes, one tempering cycle is sufficient for ultrasonic testing.
The standards don’t mention tempering; only ultrasonic testing is specified. Does that mean only larger items are tempered?
There is no correlation between the forging grade and tempering
There are three heat treatment methods for 16Mn forgings: normalizing is applicable for thicknesses below 100 mm; normalizing plus tempering is suitable for thicknesses between 100 mm and 200 mm; while quenching plus tempering is used for thicknesses between 200 mm and 300 mm
Heat treatment is a forging manufacturing process, and it has nothing to do with the grade of forgings
The grade of a forging has nothing to do with heat treatment. Different heat treatment methods merely enhance certain properties of the forgings.