Here is my first attempt to MIG weld a cast iron exhaust manifold. Here is a small crack. I marked it with chalk I drilled a hole at each end of the crack I used an angle grinder to cut a notch to accept the filler wire. The filler wire was a stainless steel alloy wire ER308L. I used the gas that I had: Argon 75% and carbon dioxide 25%. Here you can see the tough part; the exhaust manifold was cracked in half. I ground the edges of the break at a 45 degree angle for the filler wire and checked for alignment. See the next picture. I had a heavy piece of commercial grade 2x6 framing steel that I used to align the two pieces. I drilled the holes according to the exhaust gasket. I should have drilled the holes as large as the holes in the manifold for proper alignment. But, I used smaller stove bolts to attach the manifold to the steel stud. I bolted the manifold to the steel stud. Then I used a 2x2 piece of heavy wall square tubing and used C-clamps to stiffen the clamped assembly, since I guessed that welding the manifold might cause the assembly to warp. Another view of clamping the assembly. I heated the assembly in an electric oven to 475 degrees for about half an hour. Then I held it in a vise and started welding. I welded about an inch at a time and then tapped each weld 40 to 50 times with a somewhat rounded tip body hammer. Someone told me this is called "pricking" the weld. Maybe some call it peening. I forgot to take a picture of peening the weld so I borrowed this picture from the Web. There was no rust on the piece I was welding. A view of my amateur welding. Another view. About a third of the way through the welding, I reheated the manifold assembly to 475 degrees. After another third of welding, I reheated the assembly again. After welding all that I could reach, I removed the manifold from the 2x6 and welded the backside of the manifold. When the welding was complete I reheated the manifold to 475 degrees and left it in the oven for several hours for it to cool to room temp. Ouch. More amateur welding. More ouch. Here I started to grind away my embarrassment. I finished by surfacing the manifold on a belt sander. While installing the manifold I discovered that one of the end holes did not align properly, so I used a die grinder to elongate the hole by about 1/16 of an inch. The manifold has been on the engine for more than a month, having run the engine to operating temperature several times, and NO leaks. This job made me sweat, but thank the Lord He guided me. Oh, by the way, I was looking for the stainless steel wire on eBay when I had the thought to check what I had. Low and behold, there on my welder was exactly the wire I needed. I must have picked it up at a garage sale years back. What a blessing.
You do know that they make a special nickel stick rod for welding cast iron, right? That MIG weld will likely just break again after some heat cycles...
Heated before welding And after welding And the truck is to have it cool slowly My guy wraps cast with a white heat insulation blanket looks like a cross between pink fibreglass Matt and cotton battling It has to cool down slowly Did it crack in half while you were trying to fix the small crack or this was all the original repair? Lotsa weld but looks good if it’s gonna last
That's a late '80s Ford truck manifold, shouldn't any problem finding a replacement... I just threw away two sets of these...
Welding cast iron should always be the last resort. Replace if possible. I have welded heavy cast iron things( think big winch housings) with success, using a DC welder and nickel rod. But they are not 5 cents apiece, they are over a dollar a rod. Preheat , clean iron , veeing, and position,are a must. Exhaust manifolds , for me,have always been difficult to weld or braze. Seems like they are dirty iron. Just my experiences. Bones
Several years ago i tried building up a new ear on a scrap cast iron cylinder, using my Dillon (a.k.a. Henrob) oxygen/acetylene welder, and cast iron piston rings out of a scrapped Briggs & Stratton lawnmower engine. The camera I used back then wasn't the best so most photos of the experiment were very blurry, but the result looks good and held up excellent to "test-tapping" with a hammer (the same hammer that broke off the original ear). Made similar tests on another cylinder, same result there. I'd prefer an O/A weld with cast iron filler over a MIG weld. But if your repair holds, good for you.
Is that manifold still available? Looks like a casting number out of the 90’s. I’d try to find a new or junk yard replacement. And continue to practice on what you have. Preheat to 450-500 stick weld while still at high temp with nickel rod. Very slow cool down about an hour. The trouble with exhaust manifolds is the thickness varies a lot. I usually place the manifold on my concrete floor and place a propane torch close to the manifold, surround it with clay brick with small gaps and a stone top. Light torch and start preheat. The propane torch I use is available at Home Depot, they sell them as a weed burning torch, but it has a large hot flame to heat the whole manifold. They also make melt sticks that melt at a specific temperature at you welding supply. Don’t MiG Sent from my iPhone using The H.A.M.B. mobile app
That works! I mention stick because I thought it may be a one timer Sent from my iPhone using The H.A.M.B. mobile app
I preheat mine and TIG weld it with 309L stainless and cover it with a welding blanket to cool slowly, also you can put it in a sand pile and cover it up. If you have to drill a hole in the weld you need a carbide bit and if you have to tap it you can only go about a 1/4 of a turn at a time. It really well nice and I have done it numerous times
A Henrob will give the best results with the least effort. I have been using mine for about 15 years with no problems. I have done several exhaust manifolds and none have broken. The Henrob weld can be machined, drilled and tapped. There is no pre-heat or controlled cool down needed and the welds look better than those in the first post
I have used Eutectic 2-25 rod and Heli-arc...Either keep the temperature of the part over 400° or under 150° while welding, after welding open air cooling...I chose to weld at the under 150° temp as I felt would be easier on me..Pre heat to about 125° and weld short welds, about the diameter of a cigarette, moving around till temp gets to 150° [doesn't take much!] , peen the welds to release stress and let air cool back down to 125°..Repeat.. When done the weld isn't pretty because of the peening but can can be ground or machined easily for looks..I have had 100% success with welding tapered axle brake drums which seem to be a clean cast iron compared to manifolds..I used to weld machine parts at work for Machine Repair and as far as dirty or clean cast iron it could be heaven or hell..Now the only cravat is that I have a stash of rods but don't know what is currently available..
Stainless steel alloy ER308L. Take another look at my post. I added a lot of details. Thanks for looking.
Looks like you did your research before you started. Good job with the pre-heat and maintaining the work piece temperature. Stress relieving the weld by peening was right on. Attaboy!!
You can peen the finished surface of the weld with a pointed chipping hammer to make it resemble a cast iron texture.finish.
With oxy/acet torch in one hand heating the weld zone and stick welder with nirod in the other hand, made a good long lasting weld. Have also welded exhaust manifolds that are cracked while still on the engine. Run the engine to heat up the manifold. After the prepped crack gets sealed from the initial weld, the remainder of the weld can be made with the engine running for the pre heat.
The main thing I found was to make sure the cast is clean, like no carbon buildup, rust etc. The last few cast iron welds I have done were with TIG, 100% Argon and Silicon Bronze rods. I will not go back to Nirod etc. The next best in the past was cast iron rod and oxy-acet.
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