welding/brazing ductile iron

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I have a question about the best process for attaching steel sheet to ductile iron.I wish to modify a differential housing for test purposes.  lightly loaded efficiency testing.i dont expect any long life out of this component.  it's a 350lb cast axle housing  I would like to remove a huge section and replace it with a 1/4" steel sheet rolled with  a 10" radiusmy first thoughts are to flush fit my plate into the cut out weld on steel lap joint tabs overhanging the edges of the hole in the housing and braze them to the housing.(by "I"  -I mean I intend to work with a large and capable fab & machine shop, this is not DIY)anyone recomend a braze or weld process?   pre-post heat treat availible.my iron spec: Ductile Iron Casting - Ferritic-Pearlitic4.0 COMPOSITION (%)Carbon 3.5-3.9Silicon 2.0-2.8Manganese 0.45 MAXSulfur 0.025 MAX*Phosphorus 0.05 MAXChromium 0.08 MAXTitanium 0.025 MAXMagnesium 0.020-0.060***Base Iron – Prior to Treatment**Mg may be below 0.020 if Nodularity and Mechanical Property Requirements are met.5.0 MECHANICAL PROPERTIES (MINIMUM REQUIREMENTS)Tensile Strength 415 MPaYield Strength (0.2% Offset) 275 MPaElongation 7 PercentSurface Hardness 4.1 – 4.8 mm (156-217 BHN)
Reply:Most ductile irons, with proper preheat, postheat, peening, etc. can be welded with either 7018, or a 45% to 55% Ni rod, and still have 70K tensile strength.   309 SS rod can also be used, especially if joining dissimilar metals.   Easy way out, especially if you don't need full strength, is a 99 Ni rod.
Reply:You should do what I do, rather than depend on possibly inaccurate info about rods, parameters, etc.,,,, over the interweb,  is contact the various rod manufacturers themselves, directly, get the straight scoop from the horse's mouth, almost all of them have very good tech people.    AND,,,,,   if a lady happens to answer the phone,,,,   don't automatically assume she's the secretary,  I've talked to a few ladies over the years, that could tell me exactly how to do it, how to lay it down, and they weren't reading from a book, either.  Check with Lincoln, Hobart, Esab, etc.I get my nickel rod from these people:  http://www.inweldcorporation.com/HI-ALLOY/products/
Reply:Depending on the actual composition of the ductile iron you are using, one or the other filler may or may not work satisfactorly.   I know you posted up numbers,,,,   but I work in the field, don't have time or the ability to analize the material, try one thing, see if it works without cracks, if it doesn't, go on to the next alternative.   You very well might have to experiment, unless you can list those ingredients, and percentages, to a weld engineer/tech whatever, that can tell you specifically what filler fits this application exactly.
Reply:I have tried about all forms of welding for cast, and have found Cronatron makes the best rod for any cast iron welding.  http://www.dawson-enterprises.com/prev_products.htmCheck it out!6"XX P5P8 6G
Reply:Cast, and ductile, are two different things.   I have personal knowledge and experience, of a foundry that fixes minor imperfections in the casting process, with ductile iron, using plain 6011 rod.   True cast iron, no.