Doing things very slowly, tiny stitches, back grind it, and long waits
will get you a weld that appears solid. But the boundary layer between
the mild steel filler and the base cast iron in the heat affected zone
will be high carbon, quite brittle, and subject to cracking at any time.
Using the same techniques with a high nickle rod/wireand light peening
to expand the resulting bead would be a much better idea.
I would NOT describe it as a "perfect" repair.
Guy Fawkes wrote:
IMHO the weld is suspect. It may look ok but I would expect it to fail
with any sort of use. YMMV
Unless a "typical weld" done with this method using mild steel wire has
been sectioned, etched, and photographed as well as tensile tested to
provide speicific data to the contrary, I would assume it is inferior.
The mild steel wire will provide a high carbon boundary layer that would
be clearly visible in a cross section and would be very brittle. You
should note that the web site you mentioned says that it should not be
used for any application that might be subject to either stress or
fatigue. A visual examination of a fully ground down weld joint by coded
welders merely assures that the weld was done in a workmanlike manner
with no porosity or inclusions. IMHO
I happen to be partial to brazing for repairs of this sort. Things like
a cast alternator bracket subject to both high stress and high
vibration. I would expect the repaired part to last longer than the
original.The brazing material has a higher psi rating than the base
material plus I can add appropriate fillets and other mechanical
support. Nickle rod is stronger than brazing, just a bit touchier to do
Guy Fawkes wrote:
Roy, you seem to know a thing or two about welding cast iron. I have
some welding electrodes that I suspect of being cast iron electrodes
(came from a die shop). They are pretty thick, like 5/32 at least, and
have a dark grey and very thick layer of flux. (much darker than what
one would see on regular 7018 or 6013 electrodes).
If the flux is dark grey and the rod itself has got the slightly yellowish
shiny look of nickel it may well be a nickel rod. The don't go rusty if you
get them wet... How you tell if it's a 98% or 45% I don't know.
I used mild steel MIG wire to fill in the craters in a cast iron drill press
table a number of years ago. No pre-heat because it was too large to do
easily. Small welds mostly. When I came to try to machine the welds flat I
found that it smeared HSS like butter and crumbled carbide tools on the
shaper. In the end I mounted an angle grinder on the clapper box and 'surface
ground' the table flat. The end result was very good but this was a cosmetic
repair, I wouldn't trust the technique for the slightest bit of tension or
vibration and not for any weld to hold two pieces together.
OTOH, over last weekend and this one, I've machined off the remaining teeth on
the traversing gears on the shaper, built them back up with 98% Nickel rods,
machined the faces and circumferences and cut new teeth. With a little more
work I'll be able to traverse horizontally or vertically without taking the
bloody shaper apart for the first time since I got it...
The "repair" was done to the outside of the casting. If the repair had been
done to the actual cylinder barrel it would not have survived and would have
been much too hard to machine.
Yes you can weld ferrous alloys with just about any other ferrous alloy
but the result will be questionable.
I don't think he is wrong. He is naive.
As Roy commented on braze repairs: I personally have seen many arc welded
repairs of cast iron fail because of poor welding procedures. If the piece
is small enough I do a proper braze weld and they don't come back again.
Cast iron also is a very general term that describes many alloys. You
never really know what you are welding on ... Unless you want to send a
piece away to be analysed and stress tested. At work we regularly do
repairs on pile driving equipment and often we have no idea what the exact
alloy is. We cross our fingers, use lots of preheat and have understanding
A coded welder just welds to a code. They are not metallurgists with a
weld engineering background. If someone guarantees that the a weld on cast
iron is going to hold and has no hesitation in his voice I would be highly
Over 15 years ago a bench vise at work broke when someone hammered
hard on the movable jaw. The break occurred on the telescoping part of
the vise. I wanted to braze it but the boss said that if brazed the
repair wouldn't last. I took it into welding class and built an open
topped oven type enclosure out of fire brick. The broken parts were
veed out and placed in the oven. After heating the vise parts a bit I
sprinkled powdered flux on the freshly ground out surfaces. When the
parts got hot enough I used brazing rod dipped in flux to wet all the
surfaces. Rubbing the rod on the surface and under the flux pushed any
oxides away so that the surfaces were all wetted with brazing rod.
Then it was easy to fill in the vee with brazing rod. I still use the
vise most every day.
If you want strength in cast iron there's no substitute for brass.
IMHO nickel rod is a very poor method. I've tried it on a number of
less critical jobs and never been satisfied. In fact many times I've
tried to nickel with no luck (trying to short cut some job) and
finally gave up and brazed it without a problem.
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