I have been using a piece of 3/8 1018 (often somewhat incorrectly called "mild steel") to stir ferrosilicon into my crucible of cast iron moments prior to pouring. Even though it takes only maybe 10 seconds to do the stirring, the end of the rod invariably melts back 5 inches or so. I have been aware of needing a graphite rod to do the stirring but really have not seen one used to stir a crucible. So, I was left to dream up a workable solution to the problem. What I did was to use a 4 foot piece of electrical conduit for the main length of rod shaft and make a steel plug to fit into the stirring end into which I swedged a 1/2" diameter graphite shaft. I used a modified tubing cutter to roll depressions into the socket of the plug pressing those depressions into the groove machined into the graphite rod. There are a number of ways a person could fix the graphite into the shaft, but this method seemed pretty easy and should be pretty secure. Even if the shaft heats up a thousand degrees, a most unlikely occurrence, the swedging should not let go of the graphite rod given the expected expansion for that amount of heat and the interference produced by grooving the rod and swedging the plug. Attached are a few pics that demonstrate the method used. It remains to be seen if this whole thing falls apart on the first use or not. FWIW and looking forward to comments on how this might better be done. Denis
I use a clamped affair to hold the graphite rod. This is my first attempt at making a holder. It is two pieces of angle iron welded onto a thin-walled steel tube. A but crude, and the rod did fall out once due to differences in expansion rates between steel and graphite, but it does work and the graphite rod can be replaced if it breaks or wears out. It helps to keep the shaft as light as possible in order to give some feel to the stirring process. I think this design could be improved if the angle iron was bent inwards along its length at slightly less than 90 degrees, and some ridges ground into the mating surfaces of the angle iron, to allow the angle iron to grip the graphite rod better. A small hole could be drilled through the angle iron and the graphite rod, and a pin pressed in, and that would prevent the rod from sliding out even if it was slightly lose in the holder. A small screw could also be used as a pin, and a threaded hole tapped in the angle iron. .
Is this a gouging rod? I ask because although graphite is a form of carbon, the carbon gouging rods are not graphite which is more resistant to reduction. I'll be interested to see how many dips you get. Isn't carbon soluble in iron? The gouging rods are inexpensive but will burn in air. It happens fairly slowly at aluminum temps but not sure when heated to iron. The portion in metal contact seems to do fine but when removed it will be reduced. They also don't seem to have much strength when hot. Were you also using gouging rods or some other source. How many dips were you getting from a rod? Best, Kelly
I bought 1/2 graphite "mixing rods" sold for the purpose of mixing cast iron and other high temperature metals. Morgan sells them, for instance, though I bought mine from JETS on eBay. In looking further for rods I came across graphite skimmers made by Morgan which are blocks of clay graphite intended to skim iron and other metal. They are advertised as non-wetting. I wonder if anyone has used them on iron and what their experience is. I also have subsequently seen rod holders that Morgan and others sell that consist of a 20 inch handle with an angle socket that uses a set screw. Denis
I'll have to have a look. I have bought crucibles from them and from "Favorites USA" also an eBay seller. They are both authorized Morgan dealers with good prices. -Lots of counterfeits on eBay. I looked pretty hard but couldn't find any reasonably priced graphite stock. I get a lot of dips (somewhere between 50-100) out of the gouging rods as sheaths for aluminum contact, as long as I limit their exposure to hot air to just the measurement time. It's a bit of a pain to drill them but at $1.25 each, they're very practical. I've accidently broken almost as many when not in use than I have worn out. That's how I retain them. I drill them to receive the TC in the lathe and also turn the end to a nice fit to the stainless tube holder. Then I just drill a shallow drill point in the rod through the set screw holes and install the set screws. The inside of the stainless tube is stuffed with wool and the stainless is such a poor conductor the exposed portion remains cold enough to touch with bare hand.......in aluminum service. Best, Kelly
I have no idea. They were purchased online from a generic source. I think I have used one of them twice to stir iron, and have not noticed the iron having any effect on the rod. .
It seems like iron tends to try and overheat everything, and push materials to their limits (often melting the ends off of the skimmers, etc), and iron pushes me to my limits too, but it can be done. There are several here who make iron melting look downright trivial, but I am here to say it is not. It is rather a matter of people being good at making a difficult endeavor look simple in a video. .
I am reporting on the performance of the graphite stirring rod I made from a 1 foot length of 1/2" diameter graphite rod. https://www.ebay.com/itm/Graphite-R...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649 Please see the first post in this thread for details of construction. The rod worked great. It seemed strong enough to vigorously stir in manganese and ferrosilicate added to my 45 pound melt today. The molten iron is, obviously, pretty dense and giving it a good stir requires some force be applied which the rod tolerated well. There was no sign of damage to the rod by immersion with no erosion seen. So, I think this rod is well suited to the task. I am happy with the swedging method I used, but I think the rod could also be threaded, held in place with a set screw or pinned into place. I chose the swedging as it was easy and did not put any concentrated pressure on the rod. Denis
Glad that worked out. The graphite rods seem to be pretty strong. I did break one off while storing and handling the holder, and I may make a sheath to protect it during storage. Its impressive how well graphite holds up to iron temperatures, but I guess that is why crucibles are "clay-graphite".
Yes, being the clumsy sort, I figured I'd break mine in storing it more likely than in using it. So, I made a sheath for it to slide over the rod and up onto the mounting tube. The sheath would be way to loose a fit had I not "elegantly" used a center punch to make a few strategic dents so that now the tube slides on with enough resistance to retain the sheath in position. In addition, I put an 80 degree bend in the tube similar to the bend I put into my lightweight skimmer so that I could stir while my hand were down out of direct radiant line of the open white-hot furnace. It takes a few (6-10?) vigorous swirls of the mixer a couple times to get what seems to be a good mix of the iron and inoculants. Denis
I don't wrap my ferrosilicon in foil or anyting; I just dump it in, and it seems like it goes straight to the bottom as I recall, but easily mixes in with a few stirs of the rod (as you say). The ferro seems to give the iron an interesting hue; sort of a red and silver shimmering swirling look, which is very cool to watch, not that you can sit around and observe it for very long. I have an optical pyrometer, and one day would love to use it at the end of a melt. To date I have had not luck with it, but I have never focused the view on finished skimmed hot iron either, so I need to try it again. Maybe I will try it with the crucible in the furnace so it does not cool off too much.
My FeSi definitely floats. There could be a very good reason for yours sinking and mine floating: mine is 75% silicon which is about 1/3 the density of iron. I think you once said you did not know the percentage of yours. If it is 45%, it's density is 2/3 that of iron and the momentum of dumping it in could carry under the surface. And I know of no reason to wrap it in anything. I just put it on a steel coal shovel (plastic would quickly melt) and dump it in at the end of the melt with all slag skimmed. And the melt looks very brilliantly swirly (Van Gogh would have loved it) as the silicon mixes in. Denis
My memory may be off on how the ferro acts in iron. I have tried several fluxes and such with various metals, and it has been a while. so I am probably confusing things. I am pretty sure what I used was 75%. The swirling colors are impressive. I need to somehow get that on video. Perhaps a telephoto lens.
I would not expect a reply to your question, Dennis. PatJ has not posted here for quite a while. I use 90% at a rate of 1 ounce per 50 pounds as recommended to me by a commercial foundry owner who has mentored me. Seems to work out quite well with good fluidity and nice soft iron. Denis
Thanks for the reply. Not much progress these days on the Iron front; seems I'm the one doing most of the pushing of late. Need to get the burner pipe next, 304 stainless... I wonder about a trace of Nickel. I bought some a while back.
