I am wondering what the process is for mig welding cast iron. I know it can be done via arc welding with certain nickel alloy rods and by brazing as well. I have some cast iron hubs off of a large forklift that have wear grooves in them. the grooves are approx. 1/8" deep by 2" long and the hubs are 11" in diameter. so, needless to say, it is a lot of welding and would probably be most efficient if done with mig. I have already attempted to do one hub using .035 ER-70S-6 wire. The welds came out decent, but when we went to machine the welds down to original 11" dia., the welds were super hard and extremely difficult to machine. I guess what i am asking is, is there a softer wire i can use or am i not doing somthing right (pre heat, post heat, slow cool???) Any knowledge on this subject would be greatly appreciated!!
Those hubs are probably a ductile iron -
Use a Ni Rod 55 electrode or the equivalent wire for FCAW if you can justify a 30 # spool -
Hello RyanWIW, sometimes it is easier to machine the hub down in an instance like this and machine a sleeve that can be heated and shrunk onto the OD to make the repair. I would also ask if you are sure that this material is indeed cast iron and not cast steel? Just some food for thought. Best regards, aevald
Never thought of doing a sleeve. That is a good idea, but i have to check the thickess of the hub wall. i am fairly certain that it is not more than 1/4"-3/8" in which case, that would be difficult. As far as the material, the machined chips indicate that the material is cast iron (dirty, fragmenting chips) and not cast steel (semi-uniform curls). Is there a better way of testing? Thanks.
Hello again RyanWIW, as ravi theCobra suggested and from the chips that you describe, it is likely that it is a form of iron. You can also do a spark test, but I don't do these very often and don't have any reference materials handy to give you the specifics. I know that there are many who frequent this forum that will have the necessary information to provide you with ways to determine the material you are working with more specifically, hopefully they will see these postings and chime in. Is this a fairly common forklift?, if so you may want to look into finding a set of used hubs. I say that because the description of what you are facing could be very challenging and possibly very expensive. Good luck on whatever method you pursue. Best regards, aevald
I suggests to apply MAGNA 770 electrode, welds all types of cast iron and steel to cast iron, extraordinary machinability without hard spots, crack free, no porosity, no preheat,welds cast iron without dismanteling.
Good guestion aevald I was thinking the same thing I don't think a hubwould be made of cast iron.
As has been mentioned before, not all cast iron is the same. Ductile iron as mentioned by ravi is tough & strong. An interesting point, back when Pontiac made their own engines, they all had crankshafts made from some type of cast iron, even in the high performance engines. Pontiac NEVER had one break in their testing.
Hi Dave they have already welded this with ER70-6 filler wire and said the welds look decent would you weld this ductile iron with this filler wire. What would you weld this type of cast iron with?
Milton, I am not a metalurgist, but it is My guess that the high carbon from the cast iron [even if it is ductile cast iron] is what caused the welds to be too hard to machine. Some sort of "machinable-cast iron" filler would be in order. I have only stick welded cast iron, but some of the others have mentioned specific products.
We frequently repair cast Iron at our shop. Primarily we use a NI99 wire for GMAW Pre heat is a min. of 450 deg. higher if time allows. We weld, using short stringer beads no longer than 2" and peen each pass. Always slow cool with a heat blanket or by covering with clay. All of our cast iron repairs are undercut prior to welding to prevent hardness at the HAZ. On occasion we will use a SMAW process and again we use 99NI, sometimes with a difficult repair we will use a 55NI. Recently we had a repair on a brake hub that was around 70" in dia. the night shift welders elected to use a 70 series rod because they could not stop the welds from cracking. Origially there was to be no machining on the repair area. However a change was made and the face had to be machined. Our machinist accused us of welding with Kryptonite. Go figure.
Alumtig
All of our cast iron repairs are undercut prior to welding to prevent hardness at the HAZ.
alumtig, I'm not familiar with this technique. Can you elaborate on it?
Most of the cast iron products we weld are remachined to size. We have found that if there is not a great amount of wear it is better to reduce the size of the part or premachine about .030 under the finished size. If we weld a part that is .010 to .015 undersize the HAZ becomes harder and is more difficult to finish. The more weld passes the less dilution and therefore we have a more ductile area to machine. We have also had issues with the weld peeling off or chipping out on the final machine cut if we don't premachine(undercut).
alumtig
You've been given a lot of good advice and I will say that you sure as heck don't want to weld cast iron with ER70S-6 wire. Good luck with your project and remember that sometimes going slower is actually going faster for some cases.;-)
By Rick Hoople 
Date 05-06-2008 03:19
Edited 05-06-2008 03:51
RyanWIW
We are in the process of welding cast iron myself, and we went with a product from ESAB called NICOR 55, it worked perfectly using the FCAW process with a 75% Arg. & 25% Co2. we had to build up some surface material for remachining. Oh, and pre-heat to about 500°F, and a slow cool will help.
