Cast Iron

[HerbD]

My stepson brought over a cracked cast iron cooking range fiddle rail to be welded. A fiddle rail is used to keep pots on the stove from sliding off the burners. More typically you might see them on a stove used on a sailing boat, although this one is used on a high end chef's gas range. The cracked part is about a 1/8" thick casting with a small cross section shape of about 3/4" by 1/2" (similar to a cross section of small angle iron.) The grate is about 11" x 22" overall. The fiddle rail doesn't support the pots weight, and is mostly decorative on a stainless kitchen stove.

I've read about 15 articles on the web with regard to welding up cast iron and each one claims to have the solution. One says use TIG with stainless filler, another says ARC with 7013 rod, the next says MIG weld with wire and gas. Some say preheat the cast iron to 400 degrees, another says keep it as cool as possible. Peening the weld also was mentioned a number of times. About the only thing they all seem to agree upon is to let the piece cool slowly, even burying it in dry sand after welding. The variable and unknown makeup of cast iron seems to make for so many different approaches.

Because of the straight and flat nature of the piece, clamping shouldn't be an issue, although I was also wondering about grinding a grove along the break and filling it with weld.

A couple of pictures are attached. After welding I was planning on blackening the welded area by grinding and/or using a flap disk and then using gun bluing to bring back the dull black finish.

I'm open to ideas on how to approach what would seem (ha,ha) like a simple weld job.

HerbD

[KHK]

This is not so easy. The size and complexity of the casting is a real problem. You may weld it at the crack just to have it crack in anouther place. The expansion from the welding heat will stress the entire casting. Then when it cools the contraction will probably cause new cracks. If I were to attempt this I would heat the entire casting as hot as possible. Then TIG it with SS rod. Try to allow it to cool as slow as possible.

[HerbD]

Good day today. Not as hot as it has been (only 106 in the shade where I weld!)

Decided to try TIG on the cracked cast iron for the gas range (pix in earlier posts.) First I cleaned the metal with brake cleaner (NOTE edited by Gadget, using brake cleaner is a very bad idea from a safety standpoint, it can be DEADLY see link here Brake Cleaner = Phosgene Article) , then wire brushed it. I used a 1/2" x 1" steel bar and 4 clamps across 12" of the side that was cracked. Glad that I did because once I started welding the CI sounded like it wanted to jump out of the clamps.

Sharpened a 1/16" ceriated tungsten to a long point, about 1/4". With the crack closed up tight I began with a low amp and was surprised that the CI began to flow/puddle rather quickly. I did about a 1/4" stitch then let it cool. Turned the piece over and did the same thing at the other end. Repeated this several times until the whole length of the crack was joined or filled. Then I went in and had a cool drink!

After letting it cool for a while I touched it up with a flap disk on a 4 1/2" RI grinder. Went back over the welds with 1/16" filler rod to bring up the slight depression. Hit it with the flap disk once more.

Finished the job with some gun bluing that brought the shiny filler rod to a flat black oxide finish that blended well with the original CI.

[Gadget]

Nice looking work, I can hardly tell it was ever broken.

[torqueman]

Dang Herb you did it. It looks great to boot. Thanks for sharing the technique.

[KHK]

WoW I wish that I had your luck!! If I were to do it, it would have cracked in numrous places. Maybe it was not luck at all, maybe is is SKILL!!!
Thanks for sharing. Great lookong finised product. Great job.

[HerbD]

You guys are too kind. Can't say it was skill, still very early on the learning curve. Need a lot more practice!

Since I had dragged the welder out to the back yard I went on to weld up some ingot molds for my aluminum melting furnace. I'll upload some pictures as soon as I get a little time.

I think some of my previous frustrations have been because I've been spending almost all my weld time on thin stainless sheet. The 1/8" CI seems more forgiving than 20 g sheet. The mild angle iron was even easier to weld. I was going to ARC weld the ingot molds but decided that I could use the TIG time and experience.

TIG seems like overkill for something as utilitarian as a pig mold, but it gave me many inches of welding exercise. The mold has eight troughs each 8" long.

HerbD