Hello, I have made two aluminum casting foundries and used the fireclay, portland cement, sand, and perlite blend for refractory. .... been doing a good bit of research for improved mixtures and found this post on Science Madness: - https://www.sciencemadness.org/whisper/viewthread.php?tid=2931 It looks like replacing sawdust or a similar material that can burn out is better than perlite. I also have been in contact with Trinity Ceramic in Dallas with questions about refractory mixtures. I am not finding any threads on this forum about custom refractory mixtures and would love to get feedback and conversation on this topic (or be directed to existing threads...) Thank you! Val
Hello Val, I think most here are skipping the advanced chemistry /experimenting and going right to commercially available mixes. Here are the offerings from my local (1 hour drive each way) firebrick supplier: https://ssfbs.com/product-category/refractory-products/castables-plastics-anchors/ My current project is using Kastolite 30.
Hi Val, Tried the Backyard Metal Casting DIY refractory of fireclay, cement, perlite, silica sand etc.. Once heated above a certain temperature the perlite fluxes the silica sand into a foamy green glass material so it's no good for temperatures much higher than say brass. Most commercial high temperature cement refractories are based on calcium aluminate cement which is an alternative cement to portland cement made from lime and aluminium oxide. This give a fast curing cement with 3-4 times the strength of Portland cement with high temperature capabilities. There are three types of "Ciment Fondu": grey, white and brown depending on the source of aluminium oxide used to make it. https://en.wikipedia.org/wiki/Calcium_aluminate_cements Here's an article with CAC based refractories up to 1900 degrees C/ 3452 deg F depending on the refractory aggregate used, some of which are quite expensive to buy: https://www.azom.com/article.aspx?ArticleID=1411
Figuring out the right ratio of magnesium chloride, magnesium oxide and vaporized silica to compress into bricks will give you a super refractory.
I certainly won't question your desire to DIY your refractory but you have a distinct advantage that many here don't have- a Harbison-Walker distribution center a half hour away in Dallas. They might not want to sell to you directly but the stuff is right there. HW makes the refractories we all know and love. Pete
Hi Pete - thank you for telling me about HW distribution! Now to see if they will sell me two bags of Kast o Lite 30 (I am going back and forth on whether or not to just focus on Aluminum casting for this build [and maybe an occasional copper or aluminum/copper alloy] to gain more experience before attempting larger copper or bronze pours).
I always look at their map and the new guy's location when this topic comes up. I also have the benefit of a distribution center nearby. My friend is a refractory brickie so I get it free from him, but even if they won't sell to you, they can refer you to someone who can.
Thank you Petee716! I was thinking that if they don't sell direct in small quantities they surely have a list of to-the-public suppliers. There are SOOOOO many formulations - almost overwhelming to select but I recognize the name Kast 0 lite 30. Any more recommendations for castables?
I'm in Australia and the only source I've found is the grey ciment fondu which is used for common construction purposes and is stocked by my local concretor's supply shop. The white and the brown appear to be specialist products with the white made by refractory companies. Common grey ciment fondu will still get you to a maximum of 1300 deg C/2372 deg F mixed with Chamotte/Fireclay. So while I haven't tested it, a mix of grey ciment fondu, aggregate made from fired pottery lumps and fireclay should give you a suitable high temperature concrete good for everything except cast iron temperatures. For the record I use a commercial refractory concrete made from white ciment fondu rated for 1600 deg C that costs about AUD $50 for a 25 Kilogram bag. The chunks of aggregate in the mix look like fired clay in colour. https://forums.thehomefoundry.org/index.php?attachments/maxicast-16lccf-pdf.21761/
Petee716 .... After emailing and getting a reply back from a sales rep at HW I could not wait to get off work to post this! The rep said "come on by and pick up small quantities of Kast o Lite 3000!"
