4140 weld repair

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Hey Everyone,I've just been asked to make a 6" single bead 1/4" fillet weld repair on a 4140 rubber extruder die head. This thing is about 12" in diameter and appx 4" thick with a 2.5"x 5" oblong hole in the center. It has a hollow chamber inside for coolant to flow through. The weld in question has some pin holes that are leaking coolant. I've never had the pleasure of welding on this mat'l before so, I'm asking some advise on what is the best rod to use and what preheat/ post heat requirements I will have to keep to make a sound repair. I will be using the tig process to make this repair unless there is a problem with that. Can anyone drop some knoledge on me?
Reply:Try here for starters:http://cr4.globalspec.com/thread/491...and-Mild-SteelChromemoly steel apparently isn't the easiest steel to weld. First off, is the die head hardened?
Reply:Yep, I belive it is
Reply:I'm having a hard time visualizing this part. Rubber extrusion dies are usually O-1, S-7 or graph-mo tool steel. Is this the outside retainer and the die combined at the end of the extruder?4140 can be oil hardened and get near O-1 properties. If the material is file hard you would need a tool steel filler and use tool steel tig, or stick parameters. If it is a normalized weldment (cuts easily with a file), then you are working with a higher pre-heat with a slight undermatch filler. I have used both ER90S-D2 and ER100/110S for the fillers with normalized 4140. More info or pics could help.MattLast edited by Matt_Maguire; 10-23-2010 at 10:43 AM.