I made two birds models from cast iron and made a mold from sand made from play sand + bentonite + water. It is a small furnace, I melted about half a kilo cast iron until 1500ºC and af ter 20 minutes I could pour. All four risers filled. With brass it is not that easy. The casting still needs postprocessing with gringing (filing is not possible with cast iron). Here a video I made (if you don't like dance music, please mute). https://www.metallab.net/jwplayer/video.php?v=L2NsaXBzL0lyb24gY2FzdCAyMDIwMDYyNi5tcDQ6Ojo2MDA=
No, it is too hard and brittle, I was also unable to cut off the sprues and risers with an ordinary hacksaw. An angle grinder was the only option.
I would suspect it's very difficult to avoid rapid heat loss with such a small iron casting in greensand.......a more massive preheated mold in block or shell would likely be helpful to as cast condition of the iron. Maybe some post treatment? But if it's just an ornamental casting with no machining required, probably not worth the bother. It looked like a good pour temperature was achieved on propane so good furnace tune. Best, Kelly
I would suspect it's very difficult to avoid rapid heat loss with such a small iron casting in greensand.......a more massive preheated mold in block or shell would likely be helpful to as cast condition of the iron. Maybe some post treatment? But if it's just an ornamental casting with no machining required, probably not worth the bother. It looked like a good pour temperature was achieved on propane so good furnace tune. Best, Kelly
Rapid heat loss is likely a factor here. That is aided by the fact that the casting is low mass. But there may be two other factors to consider. How wet was the sand? This is the first effort, I think, for the OP, so overly moist sand is quite possible. And then there was no mention of ferrosilicon (1 ounce per 50 pounds of iron) having been added and stirred into the skimmed skimmed crucible moments prior to pouring. Of the two factors, lack of ferrosilicon is the most likely cause of difficulty with formation of white iron. It would be interesting for metallab to break a piece of his sprue or runner to see if the grain pattern shows grey iron or, much more likely, white iron. With appropriate technique, grey iron should be possible. Denis
I agree with Denis. Cast iron is usually very machinable and easy to work with a file. If we have any issues with our inoculate feeder which is a mix of different alloys but mainly ferrosilicon we will see white iron and shrinkage. We tend to see breakage increase on our thin wall castings as the first sign because they lose any flexibility and our cleaning process will break them.
