I got the Invar/NiLo CF42 TIG filler today (Thanks Dan !) in the mail , now I need to learn how to use it . I have an old standpipe faucet body that got frozen and cracked a couple of winters back , I plan to attempt to repair it before I work on a piece for a customer . I have a couple of questions - am I looking for a puddle of molten CI like when welding mild steel or aluminum , or do I use the rod more like a brazing rod ? I watched as many welding videos as I could find , none were clear as to what I'm looking for . This stuff is widely praised for it's very very low thermal expansion , with preheat should I still peen the cooling welds and stop every 1/2 inch or so to peen ? The preheat will be to
The low CTE of Invar only applies near room temperature. At 500F its CTE is in the range carbon steel's, and continues to increase with increasing temperature. At 1000F Invar's CTE is close to that of other nickel alloys like Inconel.
The invar with lot expansion at room temperature is 36% nickel.
Invar 42 with a slightly higher percentage of nickel has less CTE at higher temperatures. I kind of assume that the CTE at 1000F is not a problem as the yield strength ought to be low at that temperature.
Obviously Nickel 55% rod must be better or they would not make it for welding cast iron. But the Invar 42 was cheap at Boeing Surplus.
I'm curious about why one would want to weld with Invar. The iron you're welding with it has a very different thermal coefficient of expansion. It seems likely that a gray-iron/Invar joint is going to be under stress from differential expansion at ALL temperatures except for one.
her temperatures. I kind of assume that the CTE at 1000F is not a problem a s the yield strength ought to be low at that temperature.
lding cast iron. But the Invar 42 was cheap at Boeing Surplus.
Why would you want to weld with nickel 55? Invar 42 is kind of close to N ickel 55. It is 42 % nickel, while the nickel 55 is 55 %. The Invar is n ot as high in nickel as Nickel 55 but it is relatively close.
One definition of an engineer is somebody that can make what any fool can m ake, but the engineer can make it cheaper. In this case the Invar 42 came from Boeing Surplus and was as I remember a dollar a lb. I would have pick ed up a bunch of Nickel 55 and Nickel 99 , but I never saw any at Boeing Su rplus.
Looking on line , I found a place that sells Nickel 55 for $22 per half lb. So if the Invar 42 will work, it will save Terry relatively a bunch of mon ey.
You are better at finding information on the internet than I am. If you ca n find anything that explains why Nickel 55 is good for welding cast iron ( as opposed to 50 % nickel or 60 % nickel ) let me know about it. I ha ve looked but not found anything that explains why everyone sells nickel 5
5 for welding cast iron and not some other percentage. There must be a re ason, but I have not found it.
If I get the time, I'll call "Choosing Stick Electrodes for Welding Cast Iron"
"Choosing electrodes for welding cast iron typically comes down to three things: cost, machine-ability, and whether the weld is single or multiple pass.
"Softweld 99Ni (AWS class ENi-CI) is a nominally 99% Nickel electrode. Nickel is expensive, and so, therefore, is this premium electrode. The electrode will deposit welds that are machine-able, an important consideration when the casting is to be machined after welding. Repairs made with Softweld 99Ni are often single pass welds with high admixture. Even with high admixture, the weld deposit will remain machine-able. It works best on castings with low or medium phosphorous contents.
"Softweld 55Ni (AWS class ENiFe-CI)is a nominally 55% Nickel electrode. The lower Nickel content makes this electrode more economical than Softweld 99Ni. Weld deposits are usually machine-able, but under conditions of high admixture, the welds can become hard and difficult to machine. It is often used for repairing castings with heavy or thick sections. As compared to Softweld 99Ni, welds made with
55 Ni are stronger and more ductile, and more tolerant of phosphorous in the casting. It also has a lower coefficient of expansion than
99Ni, resulting in fewer fusion line cracks.
"Ferroweld (AWS class ESt) is a lower cost, steel electrode. The weld deposits are hard, and are not machine-able, but can be finished by grinding. This is the lowest cost electrode for welding cast iron, and the electrode has a very user-friendly arc. It can tolerate welding on castings that cannot be completely cleaned before welding. Ferroweld deposits will rust, just like cast iron. This may be important when repairing cast iron parts such as exhaust manifolds on antique cars."
I think that welding cast iron has had enough written about it to fill a book. But this is a subject on which I'd want to talk to an expert, to fill in some of the questions that the books don't answer.
I think one of the problems is that each welding job on cast iron needs to be thought about and evaluated. In some cases the contraction of the weld material will not cause a problem. And example is when you are welding two pieces together. In other cases the contraction will put stress on the ca st iron. Like welding a spoke that broke on a spoked gear.
I'm curious about whether there is a good non-destructive way to measure the post-weld stress. I recall something about an exotic lab technique, which I read about years ago, but maybe there is something newer.
Anyway, I have to talk to the people at Lincoln pretty soon, so I'll see if I can remember to ask about these things.
Geez , I never meant to cause all this stir ... OK , today I did some testing . My neighbor gave me a broken CI door from an old stove , so I cut it up ... I cut some strips about 1/8 square and used some of that to run some test beads on a piece of the door . I also ran some test beads on the same piece with the NILO CF42 for comparison . Photos of the test piece will be posted to photobucket when I get a few minutes to resize and select . After trying both out on the scrap of CI I welded up the broken faucet head , with mixed results . I decided to do it without preheat ... started with the CI strips , ran into problems on the inside corner (those still give me problems with TIG) and decided to finish with the NILO . I should have preheated I think , there is what appears to be a hairline crack thru part of the repair . Photos of that repair (before and after) will also be posted when I get time to process them . The results of my tests are that if I need to build up a CI edge or lip I'll use either one , but for crack repair the NILO seems to give a better looking repair and is easier to use . I will be using preheat and light peening as the welds cool when I repair the stove grate . Decision of which filler will be made when I see the part .
Hey, this is the kind of stir we're here for. d8-) Welding c.i. has always been a really tough issue, and one that raises all kinds of questions. I'm sure that many of us wish we knew more about it. Advice tends to lead in all directions.
FWIW, years ago (1980s) I read about a c.i. welding job that would make anyone sweat bullets. Harrah's automobile collection included one of the few Bugatti Royales ever built -- there are only a few of them in existence, and they are truly in the "priceless" category -- and it had a cracked c.i. block. So they imported a guy from Italy who was supposedly the best at crack repairs in classic car engines. Not only did it have to be sound, but it had to be nearly invisible.
He used O/A (with lots of pre-heat, no doubt) and a cast iron rod. After he welded it up, they put the engine together, started it, ran it for a few seconds, and then shut it down, never to be run again. Supposedly.