View Full Version : How hot pre heat for welding D2

03-16-2005, 10:33 PM
I got a chunk of D2 in a die that is in need of repair. I know that I have to preheat it before welding, but how hot? I dont want it to warp or crack & I dont want to draw it back. Currently it is in the Rc58-60 range.

Any thought or experience?

03-17-2005, 12:33 AM
All my MRO manuals recommend 750* - 900* F preheat for D2. Generally need a "slow" preheat of 100*/hour temp rise. Maintain preheat temp during weld. Cool down at 100* per hour.

03-17-2005, 02:31 AM
We weld heat treated D2 all the time. Use a 900 degree templestick. Works ok.

03-18-2005, 09:59 AM
The section has been hardened to Rc60 or so. Any temp above 400ºF or so will draw it back. When you preheat the material above this point, do you heat treat it again to get the hardness back up?

Honestly I got in a pinch and had to get it done. So I warmed it to 350ºF for 1 hour and had it welded. Seems to be going well right now. No cracks. When we are all done, I will need to check the hardnness and see what happened. Ahh, to repair crahsed dies, makes me wonder if I should have been a doctor. http://bbs.homeshopmachinist.net//biggrin.gif NEVER!

03-18-2005, 10:54 AM
It sounds like what you did will work O.K. Preheating D2 to 900* should cause no reduction in hardness. D2 is is hardened at 1825* - 1875*, then tempered at 900*. Hardness will stay at 58HRC as long as you don't exceed 900*. (If you go to 1000*, hardness drops to 55HRC).

Here's a section out of the Crucible Steel Manual:

Welding: Use air hardening tool steel filler material.

Annealed Material: Preheat 700-900°F, maintain the temperature of the workpiece at 700°F minimum during welding.

Hardened Material: Preheat 25-50°F below original tempering temperature or 350°F minimum. Maintain the temperature of the workpiece at 350°F minimum during welding.

[This message has been edited by precisionworks (edited 03-18-2005).]