Welding a bolt to cast iron

admin

Here's my dilemma:I recently replaced the head gasket in my car.  When I was taking one of the nuts off the flange holding the catalytic converter to the cast iron manifold, the stud broke off flush with the manifold.I drilled out the stud, but the bit walked on me leaving the hole oblong and too big to drill and tap for a larger stud.  To keep from having to buy another manifold, I cut the head off of a bolt, and welded it into the hole.  I used what I had available to me at the time: 110v, 90amp harbor freight flux-cored mig welder.  It seemed to be okay, until I put a couple thousand miles on it and then the weld broke, the cat sagged down and now there's a nasty exhaust leak (so bad that it actually melted my spark plug boots a few inches above the leak.)Well, I've got to take off the manifold and weld a headless Grade 8 bolt in the hole, but now I now have a Lincoln AC-225.  I was told to use Nickel 55 for this little project of mine, so I picked up 5 sticks of that in 3/32".What would you recommend for amperage and technique (pre-heating or cold, etc.) to get a good weld on this thing??Thanks in advance for your advice -- this is a great forum!!!!   God bless,ChrisLast edited by charlesfarm; 08-22-2007 at 11:03 PM.
Reply:I'd just weld the hole closed and redrill correctly and tap it.
Reply:Wouldn't it be easier to get another manifold from the wrecking yard? I enjoy a good challenge but some things I throw in the towel on.                                        MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:our hardware store sells some crazy looking stepped studs that work WONDERS on these projects....I was working with something just like this that was a 5/16" stud and got ruined, helicoil wasnt gonna work good even... Got a stud thats 5/16" on one end and 3/8" on the other end... drilled it bigger, tapped it, and ran it home.  So as long as you drill it centered, you get a 5/16" stud again as expected.In a pinch, you could probably make something like that... I dunno?Just my .02, may help, may not...
Reply:Please don't try to weld in a high carbon or heat treated bolt. If push comes to shove and the manifold is off, consider brazing the hole shut and redrill and tap to suit, then use a stud for the attachment. Ni rod is also a good choice. Sometimes manifolds are not made of the choicest iron and are difficult to repair.
Reply:What about cast iron rod?.......maybe.
Reply:The problem you are having is that of too much carbon in the weld metal. Cast iron is very high carbon content, then when you weld with a mild steel rod you add even more carbon. You need to remove carbon from the weld metal and slow cool. First thing to do is not try welding with a carbon filler. A stainless ER309 rod will work for your application. Austenitic stainless such as 309 are ductile and also have limited amount of carbon. This will allow the weld to be ductile enough to move when shrinkage stresses are applied and limit the amount of carbon into the weld metal. You could also use a nickel based filler, which is much more common for welding cast. This will follow similar principles as the stainless. Nickel has low solubility for carbon. During cooling the weld metal will expel carbon from the solidifying weld metal leaving a low carbon weld. Nickel is also very ductile and will allow shrinkage to take place without cracking the HAZ. A preheat on the cast will also help stop cracking by allowing the carbon more time to diffuse from the austenitic phase of the heating cycle.It is important when welding cast that you keep the heat input low. Too much heat will put thermal stress into the part, not too mention increase the size of the Heat Affected Zone (HAZ). If possible make short beads in different areas of the joint. This will allow one area to cool down while welding is continued in a different spot. Sometimes peening will also help stress relieve the joint.Last edited by reddoggoose; 08-24-2007 at 09:16 AM.Arguing with a Welding Engineer is like wrestling with a pig... after a while you realize the pig likes it
Reply:Originally Posted by reddoggooseThe problem you are having is that of too much carbon in the weld metal. . . .