Why do WCC and LCC castings have different maximum allowable temperatures in ASME B16.34?
This is a very good question and a commonly discussed topic among materials engineers. Unfortunately, the answer isn’t black and white-in fact, the “whys” are not very clear at all. What is clear is that the maximum allowable temperature values in B16.34 can be traced back to Section II Part D of the ASME Boiler and Pressure Vessel (B&PV) Code. However, that code contains no background information or notes to explain why those particular temperature limits were assigned. Because of this, much speculation among materials engineers exists- following along these lines: The standard carbon steel materials (i.e., those not impact-tested for low-temperature applications, such as A216/SA216 WCC) are most commonly heat treated by normalizing, sometimes followed by tempering. Normalized steels are relatively resistant to microstructural changes at elevated temperatures. Short excursions to temperatures below the lower critical temperature (727° C /1340° F) have little or no detrimental effect o
