Graphite Spray Technique to Improve Cast Iron Surface Finish? How to?

Discussion in 'Sand Casting' started by Melterskelter, Mar 21, 2020.

  1. Melterskelter

    Melterskelter Gold Banner Member

    A squirt of oil into the sprue! Had not heard of that one! Interesting. Not sure I have the nerve to try it for fear of losing the labor of ramming up a mold. But then hate not to, given it is potentially so simple and plausible. Please report if you give it a try.

    Denis
     
  2. Melterskelter

    Melterskelter Gold Banner Member

    I yesterday’s tried brushing graphite onto a sodium silicate found core. And then I opened the resulting Castings this morning. I can see that the core that was brushed with graphite did produce just a slightly better surface finish and was somewhat easier to clean the sand from there and the under brush core both scores had 5% see Cole included in the sand mix. My conclusion is that brushing on the graphite did help some. The amount that I brushed On is hard to quantitate but it was enough to make it to the surface decidedly gray. I will include a photo of the results It is the casting on the left which had brushed on graphite
    . 50D4FEE1-C5AB-4F1E-B3AC-D05260D55D59.jpeg

    Applying The graphite was so easy and it did save some work and clean up so that I think I will be including that in my process in the future.

    Denis
     
    Last edited: Mar 30, 2020
  3. Peedee

    Peedee Silver

    From someone with your experience with iron casting I'd take that as a credible endorsement. How did you find the effects on definition of letters and such?
     
  4. It looks noticeably cleaner, you can see the hard to reach with a brush areas have a bit of sand sticking to them. I was watching the Colchester Lathe Company film on YouTube and saw the foundry worker spray on a fairly solid coating of graphite: enough to make it dark grey in colour before burning off the alcohol. Some core pieces were almost black with the stuff but the entire underside of the casting not visible to the lathe user was left uncoated, possibly to aid gas venting.
     
  5. Melterskelter

    Melterskelter Gold Banner Member

    I don't think it made any difference in definition of the letters. But the graphite ones brushed off a little easier. IMG_6502[1].JPG

    I may also try putting a little more coal in the core sand as that too might improve the cleaning and surface finish. As it is the difference is noticeable but not large. Just looking for the easiest method to get good results.

    Denis
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    Interesting info about Colchester.

    Yes the graphite coated core (that has 5% sea coal as well) cleans up a bit easier than the uncoated 5% coal core. I will try 7% coal next time in the core to see how it works. And I will graphite one of them and leave uncoated one for comparison.

    Denis
     
    OMM likes this.
  7. Sawyer massey

    Sawyer massey Silver

    The graphite definitely helps
    You can see the wood grain from the patern
     

    Attached Files:

  8. HT1

    HT1 Gold Banner Member



    here is MLC Kitchens' mold wash info... anyone doing sand cast should watch and like all his videos,

    V/r HT1
     
    Chazza, _Jason and Tobho Mott like this.
  9. Chazza

    Chazza Silver

    A HUGE thank you HT1! Just what I have been looking for in vain for 35 years,

    Cheers Charlie
     
    HT1 likes this.
  10. Melterskelter

    Melterskelter Gold Banner Member

    Did you find a part of that video that deals with green sand molds? I remember looking at the video a year or two ago and I thought it dealt with bound core washes. I could rewatch the hour-long video, I suppose. But the delivery is so slow, I just am struggling to rewatch it.

    Denis
     
  11. Chazza

    Chazza Silver

    G'day Denis,
    Ha Ha! I didn't like to say so earlier, but if ever a man took over an hour to explain something, that at the most should have taken no more than 10 minutes, then this is he!

    No I couldn't watch it all; musing about whether Dextrin actually benefits the gut, or descriptions for those of us who are too dimwitted to imagine two grains of sand touching, did my patience neurons some harm. I was more interested in recipes for washes and cores, so I slid across the slides until I found his whiteboard work. I also tried to buy a copy of "Molder 3 & 2." but couldn't find one, so I jotted down notes from the University of California online partial copy.

    Anyway, the good news is that since your assistance with the problems I was having with my sodium silicate-cores, I have instead discovered the joys of making cores the old fashioned way.

    In answer to your question – would it be helpful if I posted the notes I have written from his video? They deal with recipes and application,

    Cheers Charlie
     
  12. Melterskelter

    Melterskelter Gold Banner Member

    No, I'n not so interested in core washes---just looking for clues on greensand graphite application.

    I keep thinking about those bulb sprayers that my mom used to aerosolize cosmetic powder. I need to look into how those work. At least I think I remember such a device. ;-)

    Denis
     
  13. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I think they are just ejectors Denis, like the old pump insecticide sprayers, flocking guns, etc. Infact I suspect a cheap dipstick siphon paint gun that uses plastic cups would siphon graphite/alcohol at the right pressure and viscosity combo.

    Best,
    Kelly
     
  14. Melterskelter

    Melterskelter Gold Banner Member

    Yes, Kelly, I strongly suspect it would suck a slurry properly adjusted. I, however, would like to spray dry powder and not a slurry so as to not disturb fine detail in the greensand---like lettering for instance. I think my mom had a bulb-type puffer that sprayed dry powder. (*Why aren't there any women on this forum when we need them, anyhow?)

    Denis
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    Talking about this again I started using my google-foo:I think I am going to investigate use of a puffer duster device like this for application of powdered graphite. There are several brands.


    Denis

    Denis
     
  16. Chazza

    Chazza Silver

    From memory he suggested a very soft brush for applying graphite; maybe the type coppers use when dusting for fingerprints would work.

    I think a puffer would be a better idea though,

    Cheers Charlie

    PS He did say that in all of his research about graphite application, there was not one mention of how much to use. His suggestion is to experiment.
     
  17. HT1

    HT1 Gold Banner Member

    That is actually what the Navy says , there are alot of variables, the additives already in the sand, the sand moisture level , is your graphite really dry ETC.
    I have only used a dry Graphite wash dusted on withn a parting bag, then brushed about with a soft artists brush, that one women use on there cheeks works good,

    you can suspent graphite in alcohol with some bentonite , then burn off the alcohol, works fine on green sand, or cores , if you contact IFSCO in california, they will sell it to you, that can be brushed on, but it can be put on so thick it will mess up diminsiones, and you must compensate venting , gas goes through a mold wash with clay slower then through sand, so corners at the bitter end of castings MUST be vented well

    V/r HT1
     
    Chazza likes this.
  18. CLR

    CLR Copper

    May I suggest that before mold closing you go through the cavity section with gas burner set for reducing (sooty) flame. That way you create a layer of soot over the mold. This practice can significantly increase fluidity and surface quality. Cheap and easy method (although not very clean, so be careful when you use it :D). Few decades ago it was a regular practice in many gray iron foundries, and still practiced today in some of them. Acetylene black formed from sooty burners enables casting thinner walls than commercial graphite paints, but OSHA is a problem for mass production. Should be fine for few pours in home setups if you have good ventilation and protection.
     
    Melterskelter likes this.
  19. Melterskelter

    Melterskelter Gold Banner Member

    That makes a ton of sense. There are some negatives about working solo, but a big plus is having no one looking over my shoulder. Right now my O/A rig is 15 miles from the foundry. But that could change. I think I’ll first try the bulb puffer with graphite. If that is not a clear winner, then I’ll surely give the acetylene a go. Acetylene makes soot so very efficiently!

    Denis
     
  20. Billy Elmore

    Billy Elmore Silver

    We used an alcohol based graphite solution on the Disa once as a test...we used a regular hand molding pattern sprayer to apply it to the molds. We did see a small improvement on some castings but also got lots of streaks. We decided it was not worth the extra cost and effort and we could change our sand properties cheaper and easier and without causing any changes to our process. I have found that by depressurizing the gating systems more and slowing down the velocity as much as possible you can reduce the roughness of your castings considerably....which also helps with sand inclusions as a bonus.
     
    Sawyer massey likes this.

Share This Page