Questions for castweld

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Although I use the search on this site extesivley> I still have some questions. I recently aquired a job welding a 1931 US mailbox. I will try to post pics. There are many problems with cracks in it that I am going to attempt to repair.  The main problem is a break on the front door about 3 inches long. The cast iron is about 1/8 inch thick. I was all set to preheat to 500 degrees and stick it with 3/32'' 99Ni rod when my friend advised I would blow it to bits. He suggested preheating until cherry red then TIG welding it with stainless filler rod (I think I have 1/16'' 308L). Then peening it with an air chisel. If anyone has other suggestions please let me know. ThanksIMG_0272.jpg[IMG] Attached ImagesLast edited by ironsharpensiron; 01-12-2012 at 08:50 AM.Reason: want to ad pics
Reply:Hey i-s-i,Although your question is directed to member castweld, looking at that repair & the age/condition, you would probably have much more success using silver-solder to get it back together. Sil-sol has a much lower heat application, the capillary action would give a much better bond & it has a 32ksi rating, & very easy to use. Clean, bare metal, slight V groove, & a good flux such as Handi-Harmon would make this m/b usable again. Fighting cast can end up a nightmare to a total disaster. Just some fodder to contemplate.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Looks like its a corner? An end or corner can be welded with out extensive pre/postheat. I would probably bevel and braze it, or cold tig it with ni99. When I tig non critical iron parts I use 309 although 308 will work. ni99 is more forgiving (for cracking).Silver braze would likely work, I don't use it for stuff like this, bronze is much cheaper.PeterEquipment:2  old paws2  eyes (that don't look so good)1  bad back
Reply:Peter, Thank you for getting back to  me. I definetly appreciate it.  Yes it is a corner piece.Can I knock the flux off the Ni99 and use that as filler? How hot would you recommend preheating it? 100 degrees then weld an inch at a time?  Should I peen in between? Sorry about all the questions.  Thanks  again, MikeLast edited by ironsharpensiron; 01-12-2012 at 10:06 PM.
Reply:Originally Posted by ironsharpensironPeter, Thank you for getting back to  me. I definetly appreciate it.  Yes it is a corner piece.Can I knock the flux off the Ni99 and use that as filler? How hot would you recommend preheating it? 100 degrees then weld an inch at a time?  Should I peen in between? Sorry about all the questions.  Thanks  again, Mike
Reply:Braze it!Cherry red is too hot.  You'll crack it if you do that.
Reply:Okay. Now that I have taken it apart and bead blasted it I noticed it was welded before in the same place. Now hopefully my last and final questions. How will this previous heating affect the metal? Is it more likely to crack now? If so is cold Tig still the best route to take or should I attempt brazing which I have never tried? Or am I just asking for trouble?
Reply:Originally Posted by 76GMC1500Braze it!Cherry red is too hot.  You'll crack it if you do that.
Reply:Once you get brass in the pores its a mess to do anything else with it. I would stick to your original plan and tig it. Go slow and I bet it will be fine, if the original weld repair can be ground out this will also allow a good groove to use for your good weld. JMO.A young green pipe welder asked an old salt one day...How can I make the weld on the bottom of the pipe look like the top.......The old salt replied....Screw up the top......
Reply:If you're going to use TIG with stainless, do not use 308L filler.  It does not have enough nickel in it.  Use 309L, 310, 312 only.You don't use brass for brazing.  If you know what you're doing, brazing is an ideal repair for this case.  It is true that welding after an attempted braze repair is difficult.  But grinding out failed nickel welds and chasing spiderweb cracks due to welding is also difficult.  On lighter castings like this, slower warming and cooling effect from the torch is about all of the preheat and post heat you need.Anybody who knocks brazing for cast iron repairs has probably had bad experiences with it because of inexperience.  The temperature window you have to work in when using silicon bronze filler is very narrow and difficult to recognize.  If you're seeing red, you're too hot.  Also, the side you're facing may be too hot and the backside may be too cold.  This is why preheat is so important with brazing, you need to part to be heated evenly through to get complete penetration.  Don't be afraid to really gouge out the crack to remove damaged sections.  It's no problem brazing 1/4"+ gaps with silicon bronze.  I generously gouge cracks to give some extra surface area for the bronze to adhere to.   I like to leave a few sections of the fracture surface as it aids in alignment and fixturing.Last edited by 76GMC1500; 01-15-2012 at 02:00 PM.