Cast iron welding help

Found this excellent web page: http://www.surfbaud.co.uk/html/cast_iron_weld.html
which explains how to make a perfect repair to cast iron, using a low amp
MIG set. Be interested in what you all think.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The person that made the repair assures me it is perfect, had has been examined by coded welders, who support what he suggests. Is he wrong I wonder?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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 correctly.
Guy Fawkes wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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).
Any idea?
i

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 29 Jul 2006 21:12:39 GMT, Ignoramus3954

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...
Mark Rand RTFM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 29 Jul 2006 21:12:39 GMT, Ignoramus3954

Could be nickel or could be 7024.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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 customers. 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 suspect. Randy

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

<SNIP> 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. ERS
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Found?! You know damn well that's your own site.
Are you _such_ a stranger to the truth that you can't even be honest over something as trivial as that?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.