preheat temps

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Hi all, Can anyone point me in the right direction to find a chart showing the preheat temps for differant thickness and types of steel?I am welding some parts at work that has 5" solid round stock "lugs" welded to 2" plate not sure what the plate is I do know it's hot rolled though and the welding is done with 1/16th flux core.I am thinking the preheat should be about at least 125,but I was told just heat it enough to get all the moisture out of it.I did that and felt it and was I am guessing about maybe 80 degrees.We do alot of welding on heavy plates and would like a chart to referance off of.I do have some temp stix. Thanx,DDog
Reply:go look it up on lincolns website I am sure they have onehttps://ssl.lincolnelectric.com/The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:Thanks Jolly I found some answers to some of my other questions there also,but I didn't find a chart per say for preheats.I did read an artical that explained the why's,when's,where's so it was helpful.
Reply:I burn 70-100 pounds a week of Core Shield 8. Welding on material thickness between 1/2" and 3". My procedure cal for preheat temp of 70F, my experience call for enough preheat to prevent rood cracking.So I preheat anything 1" and over to about the 50% max inerpass temperature. or about 250F. That temp is at the root plus 1"-2" Hope that helpsJimmy
Reply:Thanks Jimmy it does help.on the lincoln website they had like a big a$$ formula to go by and that just confused me a little I am thinking that is a formula you plug into a computer program and it spits out the answer.
Reply:If you know the steel you are using you can look up the chemistry and plug the numbers in to the carbon equivulancy formula. Then plug that numer in to Min PreHeat =200*(CE)-20* that is an aws formula. --Gol'
Reply:Just wondering if you could get significant extra penetration by preheating metal to a very high temperature.  This would not be for a critical applications and I'm not concerned about changes in metal characteristics.
Reply:From what I have learned is that you preheat for several reasons such as:1)some material has alot of hydrogen in it and when you preheat it lets the hydrogen escape to prevent "hydrogen cracking".2)cast iron you preheat and post heat to control the cooling process if it cools too fast it will crack.3)thick material if you put hot weld on a cold plate it will cold roll lie crazy.never heard of extra penatration before thats usually done by joint fit up.Thats just what I know if I am wrong or missing something I would like to know also.
Reply:You have gotten about the best information you can expect to find from the replies thus far.  Legitimate across the board preheat charts really don't exist as far as I know.  This is because preheating is as often as not dependent upon the specific job or process as anything else.  Sometimes preheating is dictated by code, other times by past experience of welders, CWI's or engineers, and sometimes it's done just for the hell of it...My recommendation, if you are not up to running some numbers through a carbon equivalent calculation, would be to develop your own chart by preheating your parts to different temps, welding and then break them.  Note the differences in results and decide on the optimum preheat temps for your application.  That'll make YOU the expert!GL