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MitchYurko (Mechanical) (OP)
20 Aug 10 9:08
I have an 8" Dia x 24" long rod of 4140 annealed steel which I am welding to a 1" thick plate of A36.  The plate will be midway up the rod, so 12" from the end.  I'm only welding on one side of the plate as the other side is inaccessible (inside a pipe).  My question is two fold:
1) When I preheat the 4140 before welding, do I need to worry about heating the inaccessible end of the rod too, or can I just concentrate on the area around the weld?
2) I am heating the rod to 1075F after welding, then control cooling it to stress relieve the weld.  Same question as 1)... do I need to worry about heating the inaccessible end of the rod equally?

My concern lies in that I want the stresses in the rod to be as homogenous as possible, but I worry about uneven stress if the rod is not evenly heated each time.  Any advise and knowledge would be greatly appreciated.  Thanks all!

Sincerely,

Mitch Yurkovich

metengr (Materials)
20 Aug 10 10:10

Quote:

1) When I preheat the 4140 before welding, do I need to worry about heating the inaccessible end of the rod too, or can I just concentrate on the area around the weld?

Concentrate the preheat around the weld region.



Quote:

2) I am heating the rod to 1075F after welding, then control cooling it to stress relieve the weld.  Same question as 1)... do I need to worry about heating the inaccessible end of the rod equally?

Same answer
 
MitchYurko (Mechanical) (OP)
24 Aug 10 9:43
Another question regarding the setup explained above:

The first weld we do is of the 4140 rod to the A36 plate, and we can stress relieve this weld joint after the weld is done.  The last weld we do is another piece of A36 to these 4140 rods.  I've found that when this weldment is done, the whole part will be too big to fit in our stress relieving oven.  We can't do this weld any other time but last.

We'd like to do this final weld with the preheat needed then slow cool the weld before sending it out to a subcontract stress relieve company who can fit the whole weldment in their oven.  Do we risk embrittlement from martensite if we preheat, do the weld, and slow cool without properly stress relieving?

Thanks in advance for any help anyone can provide.

Sincerely,

Mitch Yurkovich

metengr (Materials)
24 Aug 10 12:58

Quote:

We'd like to do this final weld with the preheat needed then slow cool the weld before sending it out to a subcontract stress relieve company who can fit the whole weldment in their oven.  Do we risk embrittlement from martensite if we preheat, do the weld, and slow cool without properly stress relieving?

No, provided you use low hydrogen electrodes for welding and use a generous preheat (350 deg F).
brimstoner (Materials)
29 Aug 10 18:45
Resist the use of any type of low alloy filler metal.  
Although your shop foreman will know better and insist upon it.   
emonje (Mechanical)
2 Sep 10 3:01
"Resist the use of any type of low alloy filler metal."

Could you please elaborate a little bit?

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