In reply to message posted by Jim Hogan:
Sylvan. How do you weld/repair a cast iron crack
With GREAT CARE
OK now lets talk a little technical,
You failed to mention what kind of “cast Iron” or the application your going to do.
For example welding cast Iron boilers or ASNY pressure vessel should only be performed by someone with a “R” stamp rating as per ASME/NBBI codes NOT a regular plumber/welder as they maybe semi skilled even a certified welder but a lot cannot pass the R stamp requirements.
Even thought I had my certification I legally was not allowed to weld a ASME rated boilers Or pressure vessels without letting the owners know once I did weld it that this boiler was no longer considered ASME rated.
The R stamp is for your protection ENOUGH SAID
Now for the practicable aspect of welding Cast Iron
Cast Iron is not that hard to weld compared to aluminum or lead welding (Lap joints etc)
I taught several helpers how to weld no big deal.
What you must do to properly weld CI is to wire brush the area very well to remove loose particles.
Then find exactly where the crack starts and ends.
Drill a hole by both ends of the crack as this will prevent more cracking during the heating and welding process
After these holes are drilled get a grinder or file and open these cracks wider into a “V” shape
Now you have a choice of filler metals.
My personal choice of welding methods/brazing is using an Oxyacetylene torch if available.
The reason I like using a torch it is much easier to use for following reasons
Someone non skilled in welding may have a hard time comprehending the fact Cast Iron is very brittle and needs to be preheated before using an electrode (electric welding)
So I figure if your going to have to preheat why bother with an electric machine at all?
OK now for the actual filler metals.
You can use a cast Iron rod with lots of flux t BUT the filler is not going to be any stronger then the base metal and considering they both melt at the same temperature a little more skill is required, but it not impossibly to learn with a little practice.
I find using a bronze rod flux coated like the Union Carbide 25 M makes even the non skilled Billy Butt Cracks look like a hero as these rods make up for a majority of sins the stumble bums dabbling in these fields make.
The key to this higher temperature brazing is watching the flux for the proper temperature ranges. Also knowing how to read the cone shape (feather) of the torch gives a great indication of the flame temperature Max around 5,800
Adding extra flux is always advisable with pig iron welding/brazing as cast Iron has so many unknown metals in the making and it is almost impossible for the welder to know the exact composition of metals used in the manufacturer especially with the pure garbage being imported with no ASME specifications.
The flux is a great tool to the folks who bother to read AWS books and manufacturer literature.
For example, when I braze I mix my own powdered flux with water.
At 212 the water boils out and the flux turns to a white powder
Around 900 degrees it turns into a clear liquid (forget the other changes going on as this will only confuse the Stumblebums who don’t believe in “books”)
Now as these changes are happening the semi skilled will now know this is the time to test the area with the rod as it is almost at the rods melting point around 1,100-1,900 degree this flux will protect against oxidation occurring and if you have some silver present in some of the brazing rod this will add in the wetting action. BETTER FLOW
Now considering there as so called “welders out here with NO “R” stamp I think you should E Mail me before they give you erroneous advice.
The key to “welding ” is having a 6th grade reading level and knowing about preheating and AFTER welding heating as a slow cool down period to prevent stress cracks or thermo shock.
Welding is not as complicated as it may seem, trade schools have classes worth taking, UNLESS you go to college but why bother when you can hire these guys for a heck of a lot less then a “plumber”
Almost every union apprentice is taught to weld and to be a welder requires a certain mind set to want to inhale fumes all day long.
If this is for a boiler DO NOT ALLOW the stumblebums without the R stamp near your boiler.
Please E mail me so I know exactly what the application is.
Again it doesn’t take a rocket scientist to be a “welder” Certification is just practice and a good eye sight and PRACTICE.
Want a really great “Welder” find an active Navy Ship fitter or Navy repair boilerman.
By the way next time Jim please try to make the letters Bigger when you ask for me as a lot of these folks are illiterate or have what we call FLASH BURNS as they cant read your asking ME the question and they sort of forget who they are.
Notice they don’t even have a license number or a list of qualifications.
Therefore to avoid any more confusion for these poor folks who do not know who YOU are addressing contact me directly.
Told you some welders cant read “S Y L V A N” Now you see why as I became more skilled I backed away from the title “welder” or medical as brazer or lead wiper as welding is just another tool plumbers,steam fitters have been doing for years.
Shame some folks only know ONE aspect of a field
Hey Nick you read my mind Guy