Section 179.220-11 - Postweld heat treatment(a) Postweld heat treatment of the inner container is not a specification requirement.(b) Postweld heat treatment of the cylindrical portions of the outer shell to which the anchorage or draft sills are attached must comply with AAR Specifications for Tank Cars, appendix W (IBR, see § 171.7 of this subchapter).(c) When cold formed heads are used on the outer shell they must be heat treated before welding to shell if postweld heat treatment is not practicable due to assembly procedures.Amdt. 179-9, 36 FR 21341, Nov. 6, 1971, as amended at 68 FR 75762 , Dec. 31, 2003