Tips about what metals to use in a iron melt.

Discussion in 'Sand Casting' started by Ironsides, Oct 10, 2022.

  1. Ironsides

    Ironsides Silver

    In my latest iron pour I go into detail about what to look for when using scrap for a iron melt.

     
  2. Melterskelter

    Melterskelter Gold Banner Member

    Interesting defect on the part. Could you please make a clear close-up photo of the defect? The reason I ask is that I thought your pour time of 52 seconds seemed very very long to me. You must have used a very small gate as the sprue looks adequate but clearly the pouring basin remained full throughout, so, there must have been a small downstream opening—-my guess is the gate or maybe runner. Anyway, the mold also appears to be level. So, the slow filling and level mold could allow a very broad disc of slowly filling and rapidly cooling metal.

    Bottom line is, is that defect actually a cold shut? It’s shape would be consistent. But the resolution of YouTube's video is low enough so as to prevent interpretation. I do not see how a hot tear could occur there. And a vacuum defect is very unlikely in that position and of that size.

    It might be interesting to re-pour it with a gate etc that would allow filling in maybe 10 to 15 secs and to incline the mold maybe 5 degrees.

    Thanks for putting up an informative, interesting, and thought-provoking video.

    Denis
     
    Last edited: Oct 11, 2022
  3. Ironsides

    Ironsides Silver

    I would like to post photos on the forum but every time I tried it would not work so I have give up on trying to post photos.

    Yes you were right, the gate from the sprue to the riser was way too small hence the long pouring time. It is not a hot tear because it has smooth sides and hot tears have really rough sides. I would like to re-pour it but as I said in the video I am using one side only so that defect does not matter. It is a sacrificial face plate for my four jaw chuck on my lathe.

    Thank you for watching my video. When I started to cut the large pieces I soon realized it was not cast iron and thought it would interesting for beginners to know the difference between cast iron, ductile iron and steel. I would not recommend for a beginner to melt ductile iron because the alloys used to make ductile iron are powerful carbide stabilizers and there could be chilling on the edges of castings.
     
  4. Melterskelter

    Melterskelter Gold Banner Member

    Cold shuts have smoothly curving shiny edges as the iron is freezing not in contact with the sand. Your technique may be good enough that you virtually never see cold shuts. But, I have experienced a few---always related to some screw up! It sounds like that cold shut does not matter for this particular casting.

    Interesting concern about ductile iron. My experience has been just the opposite. I am buying ductile returns from a foundry making ductile iron castings. I used to buy grey iron returns and had to be careful to not allow iron to be in thin sections (rapidly cooling) or I could get somewhat harder iron as measured with a Wilson Jr hardness tester and with a Leeb hardness tester. I was not getting white iron, mind you. The broken pieces in harder places had a fine (the faster the cooling the finer the grain) grey appearance and machined well. But, since switching to ductile returns my castings have been much more uniformly soft. I love the ductile as a melting stock. I think it has to be more tightly controlled as far as its chemistry is concerned and therefore behaves more predictably.

    Have you had hard iron result from ductile stock pours?

    One other interesting observation I have made is that my castings made from ductile iron are not truly ductile and I make no effort to make them ductile. But, they do exhibit slight ductile qualities. That is, I routinely score my ruined castings (sad but, of course, part of the game) runners and pouring sprue and basins and then strike them with a 10 pound maul. The castings made from grey iron break easily and without any bending at the score. My castings poured from ductile-stock are a pain to break as they tend resist breaking some and bend a bit prior to breaking. Of course, trying to break the ductile returns is utterly futile unless I score them 80% through and then support the piece on the ends and strike it.

    Denis
     
  5. Ironsides

    Ironsides Silver

    In the beginning I used 40% ductile iron and the rest was a very soft cast iron so there were no problems with chilling but I noticed a slight increase in tensile strength. Those castings did not have any ductility whatsoever. When I was getting close to running out of ductile scrap a 100% ductile melt was tried but with double the amount of ferrosilicon because they were thin castings and needed to be machined. I still had chilling on edges of those castings and they were like normal cast iron but they had higher tensile strength than my run of the mill cast iron castings. They also were not ductile in any amount.

    I agree with you that cutting large chunks of ductile iron to fit into my crucible was a real chore having to cut them all the way through. So I used a lot more cutting discs than I would have with cast iron and getting the same type of ductile scrap consistently was a real problem so I stopped using ductile iron.
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    Ironsides,

    Have you tried adding bone meal and charcoal to your iron melt? This was recommended to me in a post a year or so ago by Esc. I have been doing so and I think it helps maximize carbon in the iron (softer iron with minimal tendency to harden) and cleans the iron of sulfur. It also seems to make my crucibles last longer as the iron does not suck graphite from the crucible. At least that is my supposition as to why it is good for the crucible. They really do seem to hold up quite a bit better and would do it for that reason alone. But I am convinced they reduce any tendency to form white or even hard iron. My "formula" is rather crude---a small handful of bone meal and a fist-sized chunk of charcoal in 60 pounds of iron. Interestingly, at the end of the melt there is charcoal floating on top of the melt in the slag! If my melting atmosphere were not reducing, that charcoal surely would not survive.

    Denis
     
  7. Ironsides

    Ironsides Silver

    Haven't tried bone meal but I did put coke in before lighting up the furnace. All it did was float to the top to the slag and was removed when ready to pour. To see if there was any difference a wedge test was poured to see if there was chill. At that time I used a cast iron that would chill in small castings and the coke made no improvement to the softness of the iron I poured, also I kept adding more ferrosilicon each time until 1% level was reached and made no difference the chill was still there. One year later I was still using large amounts of ferrosilicon and adding coke to my iron melts so nothing had changed I then stopped adding coke and reduced the amount of ferrosilicon so the chill was still there. I realized then that iron had worked well for thick chunky castings but was not suited for thin castings that had to be machined.

    Adding coke did not improve the life of my crucibles, they lasted the same amount of melts when no coke was added. About the same time a friend of mine had a large vintage car collection and he said there was three engine blocks from 1920s dodge cars he did not need so I could have them to melt down. What a difference those engine blocks made, soft iron every time with the minimum amount of ferrosilicon.

    In a lucky break I met someone that was building a small induction furnace for home use. So he let me do experiments melting cast iron and at the same it tested the reliability of the furnace plus the all important electronics to make the furnace work. During that time I was able to test every type of method to melt cast iron and to make cast iron from steel.

    It was then I tried to dissolve graphite gouging rods in cast iron to find out why adding coke made no difference in my furnace. At first the rod was broken in small pieces and they floated on the surface of the molten iron. After an hour they were fished out and the sharp edges were sightly rounded so they did add carbon but the amount was so small and it made no difference to wedge test. The next time a gouging rod was held with pliers and plunged to the bottom of the crucible and stirred around. About 15 minutes later a lot more of the rod had dissolved and a soft iron resulted. The reason why it worked is because plunging the rod to the bottom of the melt exposes more surface area to dissolve plus the movement of the rod dissolves the carbon a lot quicker. So can you imagine doing this in a oil fired furnace while it is running and even if the furnace was shut down so there are no flames, the metal will cool off too much and more time is wasted reheating the iron to pouring temperature. Another way to get carbon to dissolve is to make the iron hotter than normal but all these methods tend to waste time in a oil fired furnace so are not practical for the backyard melter. Induction furnaces used in foundries operate on a low frequency compared to the experimental furnace I used so they have great stirring action which helps dissolve the carbon quicker.

    Using an induction furnace is the ultimate way of melting cast iron compared to a oil fired furnace but having said that induction furnaces will not become common place with backyard melters for two reasons,
    1. complex and expensive to build
    2. power supply to a home is not suited for a reasonable size furnace so that is why the furnace I used was only 2kgs max and took 2 hours to melt.
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    I am surprised the coke was no help. In my case, I put the charcoal and meal in the crucible before loading iron. So it is held down by unmelted iron for most of the melt. It’s chunkiness may help keep it down as well as a powder would wriggle up through all the little crevices more easily. I am convinced of its beneficial effects in my foundry.

    The amount of FeSi I use is 1:800 or 1 ounce per 50 pounds. I used to use much more but that seemed to be no better than my current practice. I have not seen any chilled iron even in runner edges, fins, or seam ridges for a long long time.

    I have dreamed of the incredibly low energy cost and simplicity of use for a 80 pound induction furnace. Sadly, it will never happen due to power supply unavailability. The only way the power supply could be solved would be with a diesel generator—-not likely for me.

    Denis
     
  9. metallab

    metallab Silver

    Click on Post Reply, then 'Advanced' => 'Upload a file' in which you can upload a photo.

    Ontopic: Is this ductile iron ?
    I wanted to try that by adding Mg chips to the melt, but it almost exploded because the Mg metal gets suddenly heated above its boiling point. How do commercial foundries do this ?
     
    Last edited: Oct 15, 2022
  10. Chazza

    Chazza Silver

    'Ontopic: Is this ductile iron ?...
    How do commercial foundries do this "

    I know little about the subject, but I did see a documentary somewhere on the net – which sadly I have not found again – where an Australian foundry was adding graphite to make ductile iron. The film looked to be from the '80's.

    From what I remember they said you can add it to the melt, or add it to the runner-system.

    Worth experimenting.
     
  11. Melterskelter

    Melterskelter Gold Banner Member

    The only method I have heard about involves addition of Magnesium to molten iron. Graphite is involved as the structure of the graphite inclusions change as part of the conversion to ductile iron. I've seen this done at a foundry located an hour from my house. It is quite a show as an intensely bright light and very large eruption of sparks occurs for maybe 5 or 10 seconds. I have tried to get my hands on some magnesium to do this at my own foundry.

    Here is a brief video showing the process:


    Denis
     
  12. Billy Elmore

    Billy Elmore Silver

    It is not too very complicated. Basically you can put alloy in the top of the mold..pour iron on top of it...let it sit for three seconds and then drain it into the mold...they use thin metal disc to control length of time for it to homogenize...when it melts out it drains the metal into the gating system. How much alloy and base metal controls level of nodularity. High sulfur will eat the mag out so starting with ductile scrap will help keep sulfur to low enough levels to be consistent. Ill see if I can add video to youtube later to show you a sim on it. I may not have one that I can share though...Ill look and see.
     
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  13. Melterskelter

    Melterskelter Gold Banner Member

    Let's see if I understand.

    By alloy you a referring to magnesium alloyed with?

    Pouring on top of the mold must mean pouring into a rather largish (must equal the volume of the mold cavity if I understand you correctly) pouring basin that has the sprue blocked by the metal disc.
    You pour in molten iron on top of the magnesium that was previously added to the basin. The mag vigorously mixes with the iron and puts on a light show. The disc melts a few seconds later and the now-ductile iron flows into the sprue and mold cavity. Right?

    And what is the composition of the disc? It has to be made of something that will not contaminate the iron. Such a disc sounds interesting. A year or two ago I experimatned with a "mousetrap" that held a silcate-bound plug in the sprue for a second or two until a trip wire melted and then the sprue filled. It worked. (http://forums.thehomefoundry.org/in...cate-and-plug-lift-mechanism-fabrication.657/) But the disc sounds a lot simpler. The disc would need to dissolve quite well as remnants of it could cause voids in a pour. Bismuth? Nickel?

    Denis
     
  14. ESC

    ESC Silver Banner Member

    Just for clarification, I started using oyster shell and charcoal when I was pouring steam radiator scrap as my feed. I switched to a graphite additive later when I needed very thin fins on the Indian heads.
     
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  15. Melterskelter

    Melterskelter Gold Banner Member

    Because graphite allowed pouring of finer detail than did the charcoal? What proportions do you use? How did you decide on the proportions? My “formula” is very in exact—-a small handful of oyster shell and half a fist volume of charcoal in 50 to 60 pounds of iron. I think that followed, roughly, your suggestion and I think it has been helpful to me.
     
    Last edited: Oct 27, 2022
  16. Billy Elmore

    Billy Elmore Silver

    You are correct on all fronts sir. The disc is steel. Usually .025" to .040" thick. The disc controls how long you want the metal to dwell in the basin on the top of the mold. A .040" disc will hold for about 3 to 3.5 seconds if poured around 2550 to 2650 if memory serves me right. We often changed temps during our trialing days so its kind of hard to be sure. I know we went higher on temps on a several occasions pouring as hot as 2670. We were not really wanting full ductile but CGI. We just lowered the amount of alloy until we reached the amount of ductility we wanted. The basin has to be large enough to carry the gating and the casting and we sometimes used a small chamber between the pouring cup and the basin that we called a reaction chamber. The alloy would be poured into the reaction chamber and the iron ran across it on its way to the basin. The reaction was not contained to the chamber and often just served as a connector for the cup and the basin. Everyone expects a major reaction and people probably have seen huge amounts of iron being converted and think it is going to be like that....but it isnt much..there is a little flare up but nothing major. We have used five times the required amount of alloy on some test and wasnt anything scary.LOL I liked getting close enough to the pour that I could see inside the reaction chamber when the metal front hit so I could see how much alloy stayed and how much was carried out and it was never that big of a deal. As far as alloy...we used many many kinds...most of them were magnesium based with some traces of other elements and some were titanium based. I believe we ran very consistently with the magnesium based alloy for the best part of the year. You can get the alloy as a premix blend from Globe Metals...at least we could...not sure if they deal with individual accounts or if they only deal with large companies. I can check on it the next time I see one of their reps around here. I do not think I will be able to upload the video due to company restrictions on certain sites but will try a little later.
     
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  17. Billy Elmore

    Billy Elmore Silver

    try this link
     
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  18. Melterskelter

    Melterskelter Gold Banner Member

    That is a very interesting video, Billy. And that is a rather exotic (I almost mispelled as "erotic":)) pouring basin/ "mixing bowl"/holding basin/time delaying button system.

    I looked at the side bar on the video and it I was having trouble putting together the pouring temp of around 2650 and the colorized graphic of the molten iron which seemed to only go as high as 2133F. But the initial pour, time delay, rapid filling and subsequent cooling was pretty cool. The mold fill time looks like it was only 4 to 5 secs according to the time stamps on the video. And the mold composition was said to be green sand. That surprised me as I would have thought you guys would be doing Airset or equivalent exclusively. I am sure that shrinkage on a thin casting like that would not be an issue. But, can the software also predict shrinkage issues? I would think so. That could be so handy...

    Denis
     
  19. Jammer

    Jammer Silver Banner Member

    Denis, have you tried the NiMg3 I sent you a while back. That is the alloy they used to use for ductile Iron, there are some new alloys that have Cerium, I think.
     
  20. Melterskelter

    Melterskelter Gold Banner Member

    I have not---yet. I got discouraged back then as the stock I was melting was ordinary grey iron and was informed by a metallurgist that there were too many impurities in the feedstock to allow conversion to ductile.

    However, I have since switched to melting pure ductile returns. So the chemistry of the returns should certainly favor ductile transformation if I add Mg. You may have read in other posts of mine that the iron I am pouring from these returns already is slightly ductile even without magnesium transformation. So, I suspect there is a decent chance that adding some Magnesium will cause full ductility. I will give that a try in the not distant future and report here. It would be nice to be able to make ductile iron for some of the things I cast.

    I have not forgotten your generosity.

    Denis
     

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