Weld preheat for 4130 QT Steel?

[KMP04]

What is a recommended preheat and post heat temperature for welding (7018 electrode) around a 10" dia. 4130 steel shaft (Quenched and tempered)?

I have read that a suggested preheat is in the order of 300 deg.C but have not found any post treat recommendations? Any other precautions I should consider?

 

[metengr]

KMP04;
What is the specified hardness or strength of the AISI Type 4130 shaft? (I am guessing the hardness would be ~30-35 HRc for a shaft application)

What is the size of the weld and is this a solid or bored shaft?

The preheat should be 225 deg C with a maximum interpass of 350 deg C. The reason for my asking about the specified hardness is that the post weld heat treatment temperature should be kept 50 deg F below the tempering temperature of the 4130 to avoid affecting bulk properties of the shaft.

 

[KMP04]

Hi metengr;
This is a solid shaft, 4ft. long, Hardness = 22HRC, two welds around shaft circumference - spaced 10" apart , Weld size is 3/8".
Shaft was water quenched from 1600F; tempered at 1225F.

Thanks for your input.

 

[metengr]

OK. Several other suggestions;
1. Use E 7018 H4 weld electrodes, these are low hydrogen to avoid delayed cracking in the weld HAZ prior to PWHT.

2. PWHT between 1175 deg F and 1200 deg F for 30 minutes at temperature.

3. Perform a wet fluorescent MT or Liquid Penetrant (PT) inspection of the welds and surrounding shaft base metal when you are finished.