[DL Brennan]

If you were preheating a piece of alloy steel that has been quenched and tempered, at about what temperature range would you start to risk ruining the temper? I'm guessing the exact temperature would depend on the particular alloy, but are there general guidelines?

[weldin mike 27]

We weld q and t steels of 2 different grades. The preheat is 80 degrees Celsius. If you know the manufacturer of the steel, check their website. There should be welding procedures available for you to download.
Regards, Mick