[MW:12370] Hardness in Tube to tube sheet welding

I seek some guidance in the above.
Our Hardness for tube to tube sheet welding is coming above 250HV and
the desired value is 210 Avg.
Can some body explain me the below:
1) Which code clealy specifies the maximum acceptable value of
hardness in TTS welding.?
2) How to control the hardness without PWHT in TTS welding?

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