For fittings manufactured from steel bars, how is the allowable stress determined?
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GB/T150.2, §5.2.9 stipulates that it is permissible to use steel bars of grades S30408, S30403, S32168, S31608, S31603, S31703, and S31008 from GB/T 1220, with a diameter not exceeding 50 mm, for manufacturing fittings. Question: When manufacturing fittings using steel bars, is the allowable stress determined based on the corresponding grade of steel pipe? (The high-temperature mechanical properties of the material are not listed in GB/T 1220; therefore, it is not possible to perform calculations using Table 1 of GB/T 150.1) ； High-temperature mechanical properties were not evaluated when purchasing the steel bars either. ）
It is clearly stated in 150 that the high-temperature yield strength of high-alloy steel pipes is as per Table B4
In item b), “steel pipes of various grades” and in item c), “fittings of various grades” both refer to fittings made from steel rods, in which case there is no problem.