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Up Topic Welding Industry / General Welding Discussion / A week of cracks...
- - By rebekah (**) Date 09-07-2007 14:39
Hey again,

Now they want me to weld some cast steel pipe fittings to 0.5" mild steel.  Never done it before.  First attempt, with no fancy prep, got a center split.  Second attempt, with a cleaner surface and a preheat to 900F, got a center split.  Thought I d dash off the question while I clean up and prepare for try number three.  Should I be brazing this?  My coworker, who has done this before said to TIG it with the E-Ni-Ci-A rod with the flux knocked off and cleaned with a wire brush.  That's what I used both times.  I also tried a section with just steel TIG rod and that cracked too.

Any suggestions would help.

Rebekah
Parent - By OBEWAN (***) Date 09-07-2007 15:02
Probably depends on the type of cast iron.  Not all cast is weldable.
Parent - - By reddoggoose (**) Date 09-07-2007 15:14
Make sure that what you are welding is acutally cast steel and not cast iron. Cast steel is readily weldable with mild steel electrodes. If it is cast steel I would give a slight preheat, and weld with a ER70S-6 rod.
Parent - - By rebekah (**) Date 09-07-2007 15:34
Maybe it isnt cast steel.  How do you check?

What is the difference between ER70S-6 and ER70S-2.  I used ER70S-2 after putting some heat in it and it cracked immediately.

If it is cast iron, how would I weld that?

Thanks
Parent - By pipewelder_1999 (****) Date 09-07-2007 16:05
The fittings should have some marks on them. Thos may refer to what they are. If they are gray cast iron the ground or filed surface will exhibit something similar to pencil lead type marks on the paper if paper is rubbed on it. Make sure the file or grinder is clean.

This is due t o the free graphite that exists in gray cast iron.
Parent - By OBEWAN (***) Date 09-07-2007 16:11
I used to have an old book of my Dads.  It had drawings of spark patterns used to identify materials.  Basically, a crude test involves grinding the material and looking at the spark pattern.  I don't know where you could get a book like that.  Otherwise, some cast irons are welded with great difficulty using nickel rod.  The welds need to be like overlapping tacks, with close control of heat input.  If the bead is too big at one time, it will crack.
Parent - By reddoggoose (**) Date 09-07-2007 17:25
It's been a long time since I had to do a spark test, if I am wrong I hope somebody will correct me. But I think that cast iron will throw kind of a dull yellow spark, and steel has a bright yellow spark.

The difference between ER70S-6 and ER70S-2 is deoxidation mainly in silicon content which will influence puddle fluidity. If the part is cracking as soon as heat is applied I would suspect it is cast iron as it has little ductility. If it is inf act cast iron, preheat heat the whole cast iron part and use a high nickel electrode, sometimes you can even substitute with a stainless ER309. These fillers will have more ductility and allow the part to shrink without cracking. The preheat will help the part cool more uniformly and reduce the thermal stresses. Also keep your welding heat input low, use a back step welding technique to help spread the heat, also don't restrain the part. When the shrinkage forces are applied the part needs to be able to move or you risk cracking.
Parent - - By RonG (****) Date 09-07-2007 17:31
Rebekah, the spark test is your best bet. Try this site.
http://shopswarf.orcon.net.nz/spark.html
Parent - - By reddoggoose (**) Date 09-07-2007 17:43
Excellent reference material
Parent - - By Kix (****) Date 09-07-2007 18:31
Whats the application for?  The farm, sewer, buddies fence or what?  Might want to be careful in what your getting into here.
Parent - - By rebekah (**) Date 09-07-2007 20:08
It is an antennae mount for a ship's deck.

So I guess it just isnt weldable.  I tried mild steel rod, nickle rod, brazing rod, and silicon bronze rod.  I thought the silicon bronze worked but then I saw that it centerline cracked just like the rest.  Then my super-type person came and went through the whole gamut and they all cracked for her too.  Nice to know it wasnt just me :-).  I went and found the guy and asked him what they were and he said they were cast steel--which should have made them easy to weld.  Must be a mistake in labeling, he's going to get me more for monday.  Apparently, there are 4 kinds of cast iron and not all of them are weldable.  Luck of the draw, I guess, to accidently get the one that isnt.

It was actually the perfect day for a puzzle!

Thanks for the posts, as always.  I try and find the answers online also but alot of times you have to wade through so much stuff that being able to directly ask a bunch of professional welders is way more efficient.
Parent - - By ZCat (***) Date 09-08-2007 01:09
chrome moly, maybe?
Parent - By Tommyjoking (****) Date 09-10-2007 05:04
zcat  if it was chrome moly I doubt it would have cracked that way......chrome moly will let you weld it wrong and exhibit undercracking and  tears at side tie in perhaps...but usually it will just fail in service and you will never see the defect unless it undergoes some rt ..
Parent - By Sean (**) Date 09-09-2007 23:44
Take the time and talk to a metallurgist to find out what it is.  They should be able to give you a basic idea of what the material is.  If its white cast iron it will be weldable.  If its some other type of cast iron then you will at least be able to determine what consumable to use as well as the pre and post heat (as applicable).

Although just trying things may work, it can save you a lot of time, cost and aggravation to just get the material analyzed.
Parent - - By MBSims (****) Date 09-10-2007 00:56
Probably malleable or gray iron threaded pipe fittings.  I'm puzzled by your description of "center cracking".  I would expect cast iron to crack along the heat affected zone next to the weld.  In any case, if you want a durable mount, you should thread a piece of carbon steel plate or bar with a pipe tap of the correct size.  Otherwise, you'll need to find fittings that meet ASME B16.11 spec.  The iron fittings typically meet B16.3 (malleable iron) or B16.4 (gray iron).
Parent - By DaveBoyer (*****) Date 09-10-2007 03:28
Pipe sleeves [uses to join 2 pipes end to end] are often made of steel pipe and weld easily. Cast ones are obviously castings due to thier shape. Pipe flanges are generally cast iron or maleable cast iron, and might or might not be weldable. My suggestion is find out if You can use a steel pipe sleeve to make the connection.
Parent - - By Tommyjoking (****) Date 09-10-2007 04:59
if it is iron it is much more likely to crack right at the sides of the weld.....but I never put a steel rod to cast iron either so........
Parent - - By darren (***) Date 09-10-2007 06:35 Edited 09-10-2007 06:43
did you try oxy fuel welding with cast iron rod and solar flux, preheat whole piece to 1100 degrees and keep there during the whole weld procedure, then post heat and completely bury in floor dry. leave it there for a day or two and let it cool to ambient in the floor dry, the welding is sort of a stirring motion between the flame, the consumable and parent metal. lotsa flux. neutral flame is important as well
ive welded some pretty ugly cast parts that were impossible to weld any other way.(e.g. 1953 corvette exhaust manifold for which i received no payment and water jacket heat exchanger that was around 150 years old, both were irreplaceable and would lead to very very expensive alternate solutions. a myriad of other one of parts as well)
lucky enough to have had a VERY GREAT teacher and awesome human being bob adams show me how. very old school technique.
they sell different types and grades of the consumable bars.
there has gotta be some of the more seasoned welders out there with a bunch of experience with this technique.
be prepared for an experience if you attempt it , takes team work and perseverance but it should get er done.

just as a side note i was told by a boss to weld a cast part with 7018 once. i said it wont work. he said just do what im told. 10 hours of welding and the next day there were dozens of cracks(which you could hear happening while welding) the next day the boss looked at it and said well i guess that we now know that it cant be done like that. i guess he was right cause i knew but "we" didn't
darren
Parent - - By Tommyjoking (****) Date 09-11-2007 09:39
Darren....I remember a fellow I use to work for was great at this...definitely a dying art.   He only pulled it out when the money was there and it was somthing that was "irreplaceable".......He showed me a little but I never got the technique down ...not enough chances...but in my opinion I never seen a better way to weld cast iron.   Here are some links for anyone interested:

http://www.cut-like-plasma.com/info_welding_cast_iron.htm
http://www.esabna.com/EUWeb/OXY_handbook/589oxy15_1.htm
http://www.ductile.org/magazine/2007_2/ductilewelding.htm
Parent - By ssbn727 (*****) Date 09-11-2007 17:54
Hi Tommy!
Excellent links - Thanks ;)
I've got a few also so, I'll post them when I find them... MUST GET A NEWER SERVER!!! :) :) :)

Respectfully,
Henry
Up Topic Welding Industry / General Welding Discussion / A week of cracks...

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