Why is steel pipe No. 10 specified in GB6479 not used?
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In GB150-2011, grade 20 steel has allowable stresses specified in three standards: GB8163, GB9948, and GB6479. However, for grade 10 steel, allowable stresses are only specified in GB8163 and GB9948. Why is it not permissible to use grade 10 steel according to GB6479 (i.e., no allowable stress is specified there)?
In fact, GB9948 and GB6479 involve the use of the same type of material, and the manufacturing process is similar; once the relevant standards are met during inspection, a quality certificate corresponding to that standard will be issued. 10 GB6479 is used little, so GB 150 is also not necessary. One specification is missing.
Low strength; generally used for heat exchange tubes