Tips about what metals to use in a iron melt.

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

  1. Billy Elmore

    Billy Elmore Silver

    First...the videos are awful compared to the program browser which is how you view them inside the program. On the browser you have full control to see everything and change how everything looks. I only use the videos to share with people and have to be really specific as to what I am trying to show them. I can choose the temp before running the sim and 2650 is about where we need to pour these thin wall castings and as you can see in the vid it was really cold at the top of the casting but still liquid so we would have tried it like that if we went that route. Not a typical gating system for us. the velocity at the ingate is much higher to prevent misrun with the CGI viscosity. It also loses head pressure as the casting fills, so you have to allow for that. The sims do not really have a set up for doing these types of processes with a delay between poured sections. I have to manipulate the program to pour a certain weight with a choke set in place that will not allow metal to pass through it until the weight is reached. I can also do a percentage of the mold filled but weight works best. So the time delay is not quite accurate but we do not need the basin to be full for a full three seconds...as long as the alloy has been saturated for at least three seconds you will be good. So if you take three seconds to fill the basin you can dump it instantly and be good. The design/shape of the pouring basin was new to the process and has not been tried in production but based on my sims is a huge improvement to the old style that we actually used. It is yet to be seen how well the reaction chamber speeds up the melting of the alloy...but it looks like it should mix it up well and gets the metal into the basin much faster and with much less inertia which would carry metal over the top of the basin if it was not controlled. The program does an excellent job of predicting shrinkage and other defects but was created mainly for shrinkage. We will see shrinkage at the 2650 temps around the handles and other thicker places which is why we have not went back to this process and have instead went went with higher strength grey iron and added guards around the castings to protect them against breakage through our process. I recently ran a sim of a large pipe adapter for Charlotte Pipe to compare to their program...Magmasoft. Our...NovaCast...found the shrink they were getting but they could not find it with Magmasoft. They are now looking at switching to NovaCast. I should get a seller's fee.LOL
     
    Melterskelter likes this.
  2. Billy Elmore

    Billy Elmore Silver

    Starting with ductile is a big plus as the sulfur will be low enough that it will not eat the NiMg3. You can add quite a bit of the stuff without hurting anything (only a little flare) so on the first attempt... alloy heavy and make adjustments based off of those results.
     
    Melterskelter likes this.
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    In this screenshot from 2:40 in the video you can see a powder being poured into the stream of iron coming out of the ladle. I guess they are making ductile castings here? Just before this scene you can see a guy beside the ladle release the can of powder so that it tilts with the ladle and allows the powder to sprinkle out this way. Thought it was interesting and (perhaps) DIY-adaptable.

    Jeff



    Capture+_2022-11-15-11-05-11_copy_813x432.png
     
    Petee716 and Melterskelter like this.
  4. Ironsides

    Ironsides Silver

    It would be adding ferrosilicon at the last moment so the fading effect will happen.
     
    Tobho Mott and Billy Elmore like this.
  5. Billy Elmore

    Billy Elmore Silver

    Just inoculant..if it were NiMg3 there would be lots of flaring and they usually try to get it under the melt...hence the reaction chamber in the in mold process.
     
    Tobho Mott likes this.
  6. Melterskelter

    Melterskelter Gold Banner Member

    And I think Billy is referring to FeSi as "inoculant."

    Denis
     
    Tobho Mott likes this.
  7. Billy Elmore

    Billy Elmore Silver

    Yes...sorry for any confusion. It was mpost likely FeSi with whatever trace amounts of only god knows what to make one suppliers better than the others.LOL If it had been a ductile treatment it would have been just a little brighter.
     
  8. metallab

    metallab Silver

    Well, NiMg3 is probably an alloy of Nickel and only 3% Magnesium, so that does not ignite when thrown into the iron bath.
    But for amateurs ? I tried adding Mg lathings into cast iron which indeed flared up, but to make ductile iron this is not enough. A heat treatment of several hours or even days with controlled temperature is required. This is only possible in commercial foundries, unless you are willing to pay several grand for such a heat treatment furnace.

    I have read that adding 20% Ni and a few % Cr makes it harder, but I don't know about ductility about such 'stainless cast iron'.
     
  9. Billy Elmore

    Billy Elmore Silver

    No sir...those things are not needed for ductile iron. You just need a low sulfur cast iron base metal (ductile scraps are best) and the right alloys to bring it into whatever specs you want. The higher the Sulfur the higher you must go on Mg addition to compensate. There are many studies that have been done on it that can be found on the web that discuss different levels of alloy and how it reacts to different levels of sulfur. I believe there is a level that can be reached on sulfur that you can not put enough Mg into solution to get full nodularity but if you are using ductile scrap as a base metal you should be good.
     
  10. Melterskelter

    Melterskelter Gold Banner Member

    But, Billy, some magnesium is needed, right? And the nodularizing effect of the mag is time limited and quite brief, right?

    I am using ductile scraps as feed stock. How much mag would I need to add add per pound and in what forms?

    Denis
     
  11. Billy Elmore

    Billy Elmore Silver

    Yeah buddy...The mag will fade out after a few minutes (they say ten in industry)...you probably pour as soon as possible to reduce cold metal defects so fading will not be an issue. You need about .04% Mg to be ductile so depends on which alloy you are using in order to obtain specific weight ratios. You basically can not use too much alloy. It will only absorb so much and after that it starts floating on top of the melt. We played around a lot with different ratios and finally learned that it is better to have too much than not enough. We had a really high sulfur base metal and had to use higher additions than normal. Im sure we used different types of alloys but usually averaged around 30 to 75 grams of alloy per mold and they varied between 15 lbs to 40 lbs. We did go crazy to see what would happen when an extremely excessive amount was added and there was no difference except the alloy stopped up the sprue initially and what did not go into solution floated on the top. We did not use pure Mg shavings or anything such as that so I can not say how those will react in a ladle, but the alloy additions we used were very low reacting....slight flare at initial contact but gone in a flash and no big deal. If you are using straight Mg you may see more of a volatile reaction. I do have some in here and suppose I could go throw a bit in a mold and see what kind of reaction we get. Ill let you know how it went later.
     
    Chazza and Melterskelter like this.
  12. Billy Elmore

    Billy Elmore Silver

    I added about 5 to 10 grams of pure Mg in a 25lb mold pour. Pretty big flare as opposed to our old additive. Seemed to take longer to go into solution as well. I would say pure Mg has a much more volatile reaction than the additive we used. If you are using pure Mg as an additive I would go with small melts at first to get used to the flaring effect and slowly step it up so you are comfortable with it and can establish a safe environment to reach your mold needs. If you are using a preblended additive such as we used I think you would be fine to go as big as we can at home with a suggested by manufacturer ratio. Denis with you already using ductile scrap you should be able to stay on the low end of the additive range and have ductility. The first thing you will notice is that you have more shrinkage than what you get on grey iron. Shrinkage is an easy gauge for ductility...the higher the ductility the more shrinkage you get.
     
  13. Melterskelter

    Melterskelter Gold Banner Member

    Billy, Thanks. Two greatly informative posts!

    Denis
     
  14. metallab

    metallab Silver

    Well, I did add a table spoonful of Mg lathings mixed with FeSi to about 700g of cast iron. A vigorous reaction occurred and then I stirred the metal and poured it. Before the pour, the metal looked like a lustrous mirror, so it was clean. The casting was OK, but just as brittle as ordinary gray cast iron. So I could saw off the sprues with an angle grinder, with I hacksaw In had no chance.
     
  15. Jammer

    Jammer Silver Banner Member

    I believe the most important part of using Mg for ductile iron is that it needs to boil up through the iron. If it's on top it just burns off.
    NiMg3 is heavier than iron so it sinks, some companies cover the Mg with steel punchouts and then fill the ladle with iron.
     
    Billy Elmore and Melterskelter like this.
  16. Billy Elmore

    Billy Elmore Silver

    If you had really high sulfur in your cast iron then it would just eat the Mg and you would not see any benefit. Also as Jammer mentioned above the iron needs to be above the additive or it will just float on top and not go into solution....so you need to add the shavings and then pour on top of them...it also needs to sit and homogenize for a couple of seconds...two or three at least before pouring. In mold is done with a metal disc at the bottom of a basin (in the top of the mold) which holds the mixture in the basin for a couple of seconds before melting away and releasing the iron above it. It sounds like you had some ductility in your sprue though...which gets more into letting it homogenize longer.
     
  17. metallab

    metallab Silver

    Billy Elmore: Adding Mg metal *under* the level of cast iron which is above the boiling point of Mg is like adding pieces of ice in an oil bath above 100 C resulting in explosions ?
    Maybe NiMg3 can be an option, but alloying Mg with Ni metal (I have some pieces, small balls of about 3/8" diameter) is not that simple. And putting a piece of Mg in the sand mold, would that not result in a similar vigorous and violent reaction destroying the mold before the metal is frozen ?
     
  18. Billy Elmore

    Billy Elmore Silver

    The size of the alloy addition will greatly influence your reaction. You have to use small granules or shavings that will dissolve quickly and go into solution faster and pour on top of it or have a chamber in the gating system that contains the addition. The melt goes through the chamber and into a basin where it sits and homogenizes for a few seconds. I would not recommend putting a 3/8" ball of Mg into a mold at home as the reaction would be considerably higher than you will get with granules. You may see an eruption with a mass that large. As an example of what you are asking if you put a penny in a mold and pour on top of it, it will erupt. They use to think it was funny to do that to a new iron pourer many many moons ago. We do not have iron pourers today and use an autopour system so I can safely add stupid amounts of alloy and stand a safe distance away to see the result. I highly recommend doing very small, minute amount of alloy additions on the first trial to see the reaction on a small scale if you are not using an industrial grade preblended alloy.
     
    Chazza likes this.

Share This Page