May I ask whether the tees specified in GB12459 are hot-pressed or forged?

I wonder what the original poster thinks about forging? As I understand it, it should be either hot pressing or forging. Section 5 of ASME B16.9 states that forged and rolled fittings are those made from tubes, pipes, steel plates, or forgings; thus, the forging and rolling processes can include hammer forging, die forging, punching, extrusion, rolling, bending, welding, or machining, or a combination of two or more of these methods. Similarly, in the new version of GB/T13401-2017 (used in conjunction with GB12459), pipe fittings can be manufactured using one or a combination of methods such as extrusion, pushing, molding, drawing, forging, welding, or machining. The above are purely my personal interpretations. :):):)

It was pressed out by heat; I went to the factory to see it

Thank you. It’s just that for the tees specified in ASME 31.1 and 31.3, there are 3-B16.9 tees and 6-extruded tees; the stress reinforcement factor for these two types differs by a factor of two, and I’m not sure which one to choose when doing the calculations.

I’m not sure if you’ve read Tang Yongjin’s book \"Stress Analysis of Pressure Piping\", which provides a detailed explanation of the stress increase coefficient.

The forging you’re thinking of is forging

What you say makes some sense. The question now is: how do we understand the differences between the 6-Extruded welding tee specified in ASME standards 31.1 and 31.3, and the 3-welding tee specified in B16.9?

Extruded welding tee, welded by extrusion welding

Chapter 5 of ASME 16.9 provides an explanation of the term “wrought,” which is the same explanation given on the second floor; therefore, it is translated as factory-manufactured forged and rolled welded pipe fittings. In reality, however, this concept of “forged and rolled” does not correspond to the meaning of forging and rolling in the Chinese linguistic context. GB/T 12459-2017/GB/T 13401-2017 specify the production methods for pipe fittings, but do not detail which production method should be used for each size. Generally, pipes below DN100 are indeed forged, but for the DN100 size category, hot-pressed versions exist; pipes above DN600 are usually welded. Therefore, my suggestion is to use forged fittings for diameters below DN100; for diameters of DN100 and above, fittings should be chosen based on the type of pipe. Heat-pressed fittings are used for seamless pipes, while welded fittings are used for welded pipes. For some welded pipes, heat-pressed fittings are also used to enhance safety, such as in turbine extraction pipes, but this is only applicable up to DN600. I haven’t yet checked whether factories produce heat-pressed fittings of DN600 or larger, but it’s certain that even if such fittings do exist, their price would be so high that the client or boss would want to kill you.