SA 516 Gr 70, Tempering Temperature

[sanshu1111]

Recently I came across some SA 516 Gr 70 NACT(nornalized + Accelerated cooled + tempered) plates from some reputed mill where tempering temperature is indicated as 590 Deg in MTC.

As per SA 516 Gr 70, section 5.4
If approved by the purchaser, cooling rates faster than those obtained by cooling in air are permissible for improvement of the toughness, provided the plates are subsequently tempered in the temperature range 1100 to 1300°F [595 to 705°C].

Supplied plates have been certified as SA 516 Gr 70 by the mill and accepted by inspection agency including AI even though tempering was carried out at 590 Deg

Am I missing some thing here??

 

[unclesyd]

Unless something has changed in the plate world I see no difference in 590°C and 595°C as the 590°C should fall withing the tolerance of the specified temperature. If you have the specification there should be a tolerance on the temperatures specified. It would would take a special calibrated thermocouples to differentiate the two temperatures.

 

[metengr]

Actually, this is a nonconformance because the minimum tempering temperature as stated in the specification is 595 deg C or 1100 deg F. Thermocouple tolerance has nothing to do with this.

Now, disposition of the nonconformance is rather simple, if the MTR indicates compliance with the minimum stated mechanical properties and CVN requirements for SA 516 Grade 70 and client requirements, the plate can be accepted.