As a general rule, plain carbon steel preheat values are, if you take the carbon content, in this case .45 and add a "0" to it you'll have the approx. preheat temperature, 450F as a maximum. but there are always considerations and other important issues, such as inter-pass temp. What is the part being welded to, thickness, rate of cooling, is post weld heat treat included in the operation, etc. I've welded plenty of 1040, 1045, 1050, and 1070 and the above "general rule" has been sufficient but PWHT has always been in the operation to some degree, ( tool an die repair ). My copy of "Weldability of Steels" ,1978, R.D. Stout and W.D. Doty, Welding Research Council, 3ed Edition, 345 East 47th St. NY, NY.10017, MACK PRINTING CO., Easton, PA 18042 This one of the most important books I have EVER bought, 1st printing was in 1971
Page 380, item 153, SAE 1045, up to 1/2 inch, low-hydrogen - 300 deg., over 1/2 in. up to 4 in. , low-hydrogen - 400 deg., PWHT 1100-1250 deg. Hope this helps...............
Gotta watch out for those "general rules".
"Page 380, item 153, SAE 1045, up to 1/2 inch, low-hydrogen - 300 deg., over 1/2 in. up to 4 in. , low-hydrogen - 400 deg., "
You've managed to dispute your own "Rule of thumb".
I once observed a welder preheating a 6 inch thick piece of Heel (Wear) bar on an Esco Shovel Bucket to 600F. Print/procedure called for 300F. Welder and shop foreman informed me that "XXX" QC guy told him preheat is "100 degrees per inch of thickness". This particular piece weighed in the neighborhood of one thousand pounds, plus the entire assembly was in excess of 30,000 lbs. Monumental task for one welder and a weed burner. The welder was preheating until 1st break and then after coffee had to reheat. Supervision was backing up the welder, justifiably so, and of course QC was being blamed for this lack of production.
I was just the FNG in the QC Dept. Since one of my team members was distributing this false info, it took some politicing to get everyone on the same page. It is hard sometimes to resolve these issues and still keep all parties on low decibel speaking terms.