Thanks for the clarification Johnathan, that makes sense. Do you have any access to any of these materials that you could do a mock-up with? Certainly, might pay-off in the long run, considering that these parts are so expensive. What you have included in your post essentially sounds correct, although my personal preference for process and filler metal would learn towards the E7018-1 SMAW. I would only say that you may wish to employ an induction heating system which allows for very exact preheat and temperature control and carefully monitor your interpass temperatures between weld passes. As to the slow cool down, there is a material that looks similar to regular insulation, it is white in color(at least the stuff I have worked with) and is called "k-o-wool"(I probably spelled that wrong). this is an amazing material and is really great at retaining heat, providing a barrier to heat while welding, and aiding with slow cool downs. Using it will provide for a nice long cool-down. I've used it on extrusion press blocks that were 2' thick x 6' tall x 5' wide with good results, we were running between 550 to 600 degrees of preheat. My $.02 to contribute to the conversation. Best of luck on your project and definitely do as much research as time allows to nail down the needed parameters to pull this off. Best regards, Allan

Hello again Johnathan, here are some photos from the work that I was describing in the previous post. This was from a couple years back. Best regards, Allan

Here is a preheat chart scanned out of Volume 4, 7th edition, AWS welding handbook...this suggests a min preheat and interpass temp. of 500F for 1.1" to 2" in thickness

Yes Allan, both were 4140.
The "Shop" had added it's own peening process to the procedure due to the cracking issues. Not sure if the restraint of the interference fitting of the two pieces was as much an issue as the difficulty of maintaining even heat with the unbalanced expansion and contraction.
Since it was not in the official procedure, welders were not penalised for not peening. However Gouging out, grinding and rewelding cracks made us BIG fans of the recommended peening.

I can't thank you guys enough for all the help on this particular problem. I appreciate the knowledge and willingness to help here on the AWS forum. This is the place to get these technical questions answered for sure. To try and answer some of the replies, (and as I can remember everyone's posts) is sounds like we are on the right track indeed with our pre and post heat as well as interpass temp. We will in fact begin our test pieces to be sent out for destructive testing at 400-450* F pre-heat and 700* F interpass using .045 ER70S-6 and see what happens in a bend and tensile test. Again, I will report back our findings there when we get results (few weeks). The Design Engineer did the thermal conductivity ratings of various materials and settled on KWool as the best solution, needing approx 2" thick of it to be sufficient. I have not used Kwool specifically but have used similar products in the past. As for heat induction, we are still looking into that but still feel that will be the best solution. It does, however, have some challenges when it comes to wrapping the product in the heating cables but we will get that resolved.

As for the filler material(s), all out WPS' are with solid wire (for GMAW) and this is what our company prefers over other fillers. We do have E7018 and the associated WPS' but will be choosing a solid wire for this application. I cannot argue some of the points presented as far as the low hydrogen content of flux and the efficiency of metal core but since our bosses don't care for the smoke and clean up, along with the fact that there is only one of these we will ever do, there would be no need to perform a WPS with another filler. I am working on WPS' with dual shield for A36 just to have when we need them though. I am trying to show them the advantages of other fillers as opposed to sticking with just ER70S-6 for most applications. Another reason the 70 series wire was selected is the A572 is a 50ksi material thus the 70 series wire exceeds the strength requirements. If you truly feel this is the incorrect filler I will be open to discussing that further.

And last, for the moment, Henry, on the Welding Tips and Tricks Forum you mentioned you can only see items 1 and 2. If you click on the picture it will expand it so you can see the whole image you can see here. I appreciate you sharing the link and pics here with everyone. I wanted to do the same but didn't get to it.

Now on to getting the testing of the 4140 to A572 Gr B done and see what happens there. Again, I say thank you to everyone who has contributes thus far and will be sharing this link with everyone involved, especially as it is updated.
-Jonathan

Our thoughts on welding sequence are two welders, one on each side with welding arcs back to back. Since these are not long runs and the gussets will be blocking the light, I believe this will be a good approach.

As for NDE, we will be doing a normal visual and die pen check for any cracking after 24 hours.

For the complete welding and heating of this part I have the cost study about done and will be presenting it tomorrow. Heat induction is the best solution, in my opinion, but it very cost prohibitive for the rental of the machine. I hope we use this as I don't want to stand there and use a flame to heat this chunck up!

The bad thing about this whole project is this is "just" a test bed for a machine we patented and built. We have to verify it will do what we say it will and this $300,000 225,000lb test bed will literally be set outside and who knows when, if ever, it will be used again. I technically can't share pics of the unit but I will try to get a few up for a general idea.
-Jonathan