Must the flange be made of forgings?

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Flange: Must a flange necessarily be made of forged material? The answer is definitely no; when the requirements are not high, it is possible to use sheet metal for fabrication, but under strict conditions forgings must be used. Pipe flanges: Standard HG/T 20592-2009. The materials for pipe flanges should generally be forgings or castings; the use of steel plates is not recommended. The fact that it is not recommended does not mean it cannot be used. The following 5 types of flanges can utilize sheet metal: (1) Flange cover, (2) Lined flange cover, (3) Plate-type butt-welded flange, (4) Ring-type loose-flange with butt welding, (5) Butt-welded ring-type loose-flange. Although it can be used, there are additional requirements, as follows: (1) Ultrasonic testing of the steel plate to ensure no delamination defects ； (2) It should be cut into strips along the rolling direction of the steel plate, bent and welded together to form a ring, with the surface of the steel forming the upper and lower surfaces of the ring ； (3) The butt weld shall be a fully penetrated weld ； (4) The buttwelds shall undergo post-weld heat treatment, and 100% radiographic or ultrasonic testing shall be carried out. The radiographic testing shall meet the Class II requirements of NB/T47013.2-2015, while the ultrasonic testing shall meet the Class I requirements of NB/T47013.3-2015. Equipment flanges: Standard NB/T 47020-2012 – Type A and Type B flat welding flanges may be manufactured from sheet metal ； Long-neck butt weld flanges must be made of forgings. Type B flat welding flanges should not be made of Cr-Mo steel. There are also additional requirements: 1. When manufacturing necked flanges from steel plates: (1) The steel plates shall be subjected to ultrasonic testing to ensure there are no delamination defects ； (2) Strips should be cut along the rolling direction of the steel plate; after bending and butt welding, they form a ring, with the surface of the steel plate serving as the side surfaces of the ring ； (3) The butt joints of the rings shall adopt a fully penetrated weld structure ； (4) Ring butt joints shall undergo post-weld heat treatment and 100% radiographic or ultrasonic testing, with the acceptance criteria specified in NB/T 47020-2012. 2. The butt welds of the flanges must be subject to 100% radiographic or ultrasonic testing.