CAST IRON from HELL. Impossible to turn or mill

[@jimkibler786]

Hi, I'm a metallurgical engineer who worked in a ferrous foundry for a number of years. Your microstructure has a high percentage of carbides. This is the result of composition, and specifically a sufficient quantity of carbide producing elements. In addition, fast cooling or quick shake out contributes to their formation. Once carbides form, they are quite difficult to re-dissolve. With good work holding and the right tooling, you could probably cut them, but it wouldn't be easy.

[@JIMMY916]

Hi Jim! An explanation on my understanding and very relevant. Thank you very much !

[@Hydrazine1000]

Fellow metallurgist / materials scientist & engineer here! For the application of weight lifting weights you would ideally take the cast iron grade that is easiest to cast, the cheapest and something that is decently hard-wearing. It would not need any ductility or machinability. These discs don't need any machining, except grinding off its riser left after casting. This would suggest something like ASTM grade 20 (ASTM A48 class 20) or any equivalent. It is grey cast iron and one of the most widely used due to its low cost, ease of casting and a modest resistance to corrosion. If this educated guess is correct you're looking at 3,25-3,50 percent by weight carbon and around 2 wt% silicon. Uhhhmmm, yes, that would indeed be a challenge to work with. No matter how you heat treat, that very high carbon content will be problematic. Grinding will be your only viable option. *Edited to add:* The bright outline that you see on the fracture surface of the heat treated weight is from decarburisation during your annealing process. That is to be expected from high carbon steel in an open air furnace.

[@JIMMY916]

@@Hydrazine1000 Great comment ! Thank you sir !

[@davidt8438]

Watching him try to push the discs into the sand made me crazy. Why didn’t he just fill the bucket half way, push them into the sand and pour sand over them?

[@markrainford1219]

Theatre.

[@JIMMY916]

The sand was 150 degree Celsius. To do as you say I needed another metal bowl (I didn't have) to halve the amount of sand. If you had followed from the beginning you would have seen that moving the sand produced a lot of dust. (now hot dust) I didn't want this to happen a second time. I was amazed that I melted a disc and all I wanted was to not have my experiment compromised already, not to drive you crazy. I was in a hurry too. Thank you for ”watching” !

[@paulkurilecz4209]

Do you see the white areas in the fracture surface? That is white iron which is basically unmachinable. You do need to anneal this. The problem will be having a slow enough cooling. I would recommend a furnace cooling where the temperature is stepped down over several hours. My recommendation would be to heat at about 850 - 900C for one hour per inch of thickness with a one hour minimum. Then furnace cool to 650C and hold for 60 minutes per inch of thickness with a one hour minimum. Then shut off furnace and allow it to cool to ambient. This will not eliminate all of the iron carbide, but it should give you a more machinable cast iron. This should allow the cementite to convert to austenite and ledeburite, and then upon cooling convert to pearlite and the excess carbon to precipitate as spherical rather than flake carbon. This should produce a grey (or ductile) cast iron. I cannot be more specific as I do not know the percent Carbon content. A likely reason for the hardness of these weights is that they are a relatively thin section and were probably shaken out too quickly from the molds. The only machining done on them was probably to grind off the sprues, gates and risers. Hope that this helps. Please let me know how it turns out. PS: the liquidus and austenite temperature for greater than 2% C is only 1150C which is not hard to obtain in a propane fueled furnace. If you are going to sand cool items, put half of your sand in a separate container. Then you just pour this sand over the parts that have sand underneath them. When you were grinding on the heat-treated discs, I was looking at the sparks. It is definitely a cast iron with a high carbon content (which would have assisted the foundry in the casting process by having a lower melting point), but oddly enough, it looked like there may be some Chromium present which would also promote hardenability. These weights were probably made with whatever scrap that the foundry could get for as cheaply as possible.

[@JIMMY916]

Someone asked me why I make videos on KZbin ?? Well, here is the answer: that's the only way I can get advice from people of your caliper. Thank you very much for your free lesson !

[@paulkurilecz4209]

@@JIMMY916 My pleasure, glad that I could help. I was once a university professor and I like helping people to learn. I like how you approached your problem.

[@lucasandri5462]

If you cool down cast iron slowly after the casting proces you'll obtain mostly grey cast iron if you cool it fast you'll have white cast iron . I've never machined white cast iron but i know it's quite hard and could be what you're dealing with. It should also have a different chip formation from grey cast iron because there isn't graphite in the material structure. Also if you try to cool down slowly you'll still probably get the first layer that cools fast and you'll obtain white cast iron on the surface and grey one in the core which could be what you see in the video at 15:16

[@JIMMY916]

Very possible, but why I couldn't find a softer core in the file tests is still a mystery to me. All my file touched was an extremely hard surface and I also filed the surface from the core. The sound of the file remained unchanged. It is true that are two areas of different colors, but they have identical hardness. Thank you for your comment!

[@Tenneseejosh]

They make camshaft lifters from chilled iron which is like glass. The only way to work it is by grinding.

[@JIMMY916]

True.

[@johnrussell6620]

Final comment, try a different brand of weight to possibly get a different quality of base material, and try a heavier weight to increase the central area to shell area ratio. Maybe try recasting at an actual liquid phase of hot cast iron and scrape off as much dross as possible as that will just be even more hard material in your final casting. Good Luck and BE SAFE!!

[@JIMMY916]

@@johnrussell6620 Thank you very much for your suggestion !

[@GabrielFleseriu-bx2ee]

I think the problem is the manufacturing process of gym weights. As long as they turn out with an acceptable surface, not too rough and without visible inclusions, bubbles or the like, they are ok. Since there is no machining step to be done after casting, the manufacturers don't need to care about the composition of the material or the cooling process - that would only add unnecessary production costs. The learning I take from your video is that gym weights make for terrible raw material for machining and that there is not much you can do about it. Thank you for posting your findings! Cast iron break disks on the other hand are meant to be machined after casting. I expect them to be a better source of raw material for the home shop, if you can fit then in your lathe. I have to admit that I haven't tried to machine one though, it is just an educated guess.

[@JIMMY916]

Hi Gabriel ! It's a long story about these gym weights. I got the idea to use them from a KZbin video where someone said it was a simple and cheap idea to use these discs for flanges and it CAN be turned like other and common materials. I thought it was a brilliant idea but mine are impossible to process. Thank you very much for the appreciation and suggestion !

[@Lesfac]

Great , interesting video. I had thought such weghts might be a good material for making model steam engine flywheels. Ill forget that idea😁. I did think just turning the gas off and leaving them in the furnace to cool down would be a slower way for them to lose heat with less thermal shock. Probably would make no difference.

[@JIMMY916]

This is what I did in the video ”No mistake allowed”. I left the disc overnight in the furnace but without any positive result. Thank you for your comment !

[@johnrussell6620]

As you can see in the video at 13:45, there is a visible outer shell surrounding a different material quality inner core area. This is 1 of your problems as that shell is very tough, plus the ratio of outer shell to inner core is very disadvantageous to try to cut or mill or grind away. That shell is a remnant of the casting process. . . Second, the actual material is probably junk recycle that had a high quantity of "OUTER SHELL" material on it as well, before it was reprocessed into this weight disc, so it has a large quantity of "OLD OUTER SHELL MATERIAL, from the scrap that it was made from, spread throughout the current center section of your disc, causing you to have even more trouble with "HARD MATERIAL" to try to cut or grind away. Good Luck with your project.

[@JIMMY916]

@@johnrussell6620 Thank you John !

[@petersilva4242]

Ive turned weight plates. Its really hit and miss. most are junk but ive just turned and scraped one recently that is perfect grey cast iron. Your furnace definitely melted cast iron. It could be the one that melted was in the flame or a hot spot so it melted but the others did not. Cbn inserts are great for hardened materials and hard cast iron but don't like an interrupted cut.i would grind or use a normal cabide insert for interrupted cut then finish with cbn

[@JIMMY916]

Hi Peter! You are absolutely wright. I'm still learning. Thank you very much for your comment!

[@joejoejoejoejoejoe4391]

I wonder if it's a chilled casting, some guy at work used to leave chilled castings outside to rust, he said that this worked a treat, although he did sometimes use special armour plate drills.

[@JIMMY916]

Good to know. Thank you for your comment !

[@pvtimberfaller]

Hi Jimmy It has been too long since I read up on cast iron metallurgy so I can’t tell you for certain if you can make malleable iron out of any white cast iron or if it has to be a fairly specific alloy. I couldn’t tell from the video what the break looked like, but the normal test for cast iron is looking for gray white/white. It almost looked like there was a shallow white outer layer with gray inside, which is normal for a casting. Most likely you would have to remelt the material and raise the silicon content to get a machinable gray iron. Tramps like lead can cause good iron to go hard in very small percentages.

[@JIMMY916]

Thank you sir for your detailed comment. The information written by you is very important. Until now, I always believed that a metal object becomes softer by slow cooling. Just not now. It's a little more complicated for me :((

[@JIMMY916]

@Toastcado Thank you very much for your pertinent comment !

[@howardosborne8647]

This is low grade white iron very similar in composition to Pig Iron. The reason this stuff is extremely hard and brittle is it contains a high percentage of Cementites but a very low percentage of Graphite. Google for some reading on low grade Pig Iron and white cast iron.....Good quality cast iron has an evenly distributed high percentage of graphite and Ferro Silicon is added during the melting process to promote ductility and stop it from being as hard as hell.

[@JIMMY916]

Thank you very much for this informations!

[@RustyInventions-wz6ir]

Very interesting. Nice work sir.

[@JIMMY916]

Thank you sir!

[@D-B-Cooper]

I once had to cut up a 9000 lb cast iron keel from a sailboat. It was about 5” by 8” by 40’. It was not optimal and I had to figure out a way to do it. The only thing I could find that would touch it was a mill end in a magdrill. I drilled a series of holes in a line to where it would break. No saw or disk would touch it. I have some carbide files that could be used to work it if there was a need.

[@JIMMY916]

The material used for making it are really different from what is common found. It is impossible to process. Thank you for your comment !

[@stevethompson8504]

Try a large radiused carbide tip and don't tickle the surface ,set a goodcut on ..works on duplex.. worth a try .it likely comes down to whether you can get enough horsepower behind it .

[@JIMMY916]

Yes, it can be a solution but I give up :)) Thank you !

[@Cricket-lw6br]

Looks like cast steel.

[@JIMMY916]

Who knows ?? Yes, could be anything. Thank you for your comment !

[@vikingsofvintageaudio7470]

Hi! I love all your experimental stuff. And your style and videos. Keep it up! /A fellow machinist junkie

[@JIMMY916]

:)) Thnak you for your kind words, my friend! Your comment means a lot to me.

[@Rustinox]

I only know that a lot of people tried to machine these kind of weigts, with very little succes.

[@JIMMY916]

This material is a nightmare for me. I am overwhelmed by the situation. Thank you for your comment !

[@stevethompson8504]

Tried to machine a small cast iron weight once to make a steady for my mini lathe .used the same lathe to turn it .unsuccesfully .it was a nightmare .

[@JIMMY916]

Yes Steve, there is something specific about these weights. They are way too strong. Thank you for your comment !

[@gwheyduke]

If you heat hard cast iron to red hot in your furnace along with some charcoal. BBQ brickettes work. Then let it cool slowly. This will anneal the cast iron with carbon.

[@JIMMY916]

I didn't know that. Thank you sir !

[@michaelandersen7535]

Won't dissolving more carbon into it make the situation worse?

[@mike9500]

mummms the word! 🤣 designed my satin himself.. hahahaahahaaha Do we all need to pitch in to get you a QTP?

[@JIMMY916]

I suppose that in his spare time he tests some materials and designs new ones. Yes Mike, all of you :))

[@madsighntist14]

I have little "Ferous Metals" knowledge, my work(s) are in Brass, Bronze, Copper, Silver, etc. HOWEVER! I think that the METAL "SLAG" that is, what melted OUT of the "BASE METAL" (It can not really be named, as the ALLOYis unknown) The melted out, or SLAG, must be a LOWER TEMPETURE, (that is obvious) SO,is the SLAG magnetic ? if yes, then direct your studies towards Ferous Metak groups. IF it is NOT MAGNETIC, that puts the direction of study into another realm of Meturgy. In America, I worked with a LOT of Bronze. To save money, we bought BRONZE INGOTS, straight from smelting furnace! We found that the Bronze called #2 Bronze, was good for our needs. I do not know how many styles, or types, of "RAW BRONZE" there are, but there is a#1 Bronze, MORE EXPENSIVE, and the #2 met our NEEDS for our product. The making of WEIGHTS for exercise is probably NOT real precise, in my analogy, it might be #3, or #5 in other words not as precise in the SMELTING, anything could be in there! study the SLAG! I enjoy your channel, philip, from the Great Pacific NorthWET, Oregon, USA

[@JIMMY916]

Hi Philip! I left out this very important detail, unfortunately. These weights are attracted to the magnet. I had the belief until now that to produce and melt an object, the final hardness is a goal and difficult to achieve, not a simple result. It seems I was wrong. As for the slag... I'm sorry, I didn't pay any attention to it. Thank you my friend!

[@taranson3057]

Would it be possible to melt the cast iron and remove the carbides? Have you ever tried machining a brake disc from an automobile, it would be much easier to machine.

[@JIMMY916]

I understand from the comments that once those carbides are formed it is almost imposible to remove or dissolve. The disc brake ideea is great but the size I think is beyond the capabilities of my lathe. Thank you very much for your comment sir !

[@taranson3057]

@@JIMMY916 perhaps you could cut the disc brake to size that would work on your machine and clean up the outer edges to make it round again and voila back in business. That’s what I have done in the past. Buying a piece of cast iron, from a metals supplier, that would fit a small lathe would probably cost a couple hundred bucks.

[@JIMMY916]

Yes, what you say is indeed a solution to solve the problem of my lack of materials. I will definitely not try anything with these gym weights again. As you say, there are other solutions. Thank you very much for your suggestion ! And for your time.

[@taranson3057]

@@JIMMY916 you are welcome! I’m retired and have a good bit of time on my hands. I completely understand not having access to proper materials. There are metal suppliers about 100 miles from my house. I just don't always have the extra funds to purchase the materials that I need. My solution is to make and sell custom wood items. I basically find a need and fill the need. I usually make just enough money to buy one decent end mill, materials such as a piece of aluminum plate, or some exotic wood. I am sure that you will come up with something, I have faith in you!

[@hinz1]

Get some used CBN inserts, a diamond wheel and regrind them yourself. CBN will cut it easily, if you get rid of any interrupted cuts.

[@JIMMY916]

I give up !! No more cast iron :)) Thank you for your comment and for your suggestion !

[@jacksongault820]

I tried turning one of these and it was like trying to cut granite

[@JIMMY916]

:)) I know the feeling.. Thanks for the comment!

[@MrSeeuu]

Great video Jimmy. I’ll read the comments to find out what the weights are made of. 😃👍🏻

[@JIMMY916]

I'm waiting too. But usually the comments of connoisseurs appear later. We, the little fish, write first :)) The big fish are still waiting. Thank you for the appreciation MrSeeuu !

[@johnrussell6620]

At 15:00, polish that surface to a mirror finish and see what you can see around the edge and throughout the center area.

[@JIMMY916]

At 15:00 that surface is pre-polished. Acid application no longer revealed the inclusions. The material underwent structural changes but remaind as hard as the first disc.

[@johnrussell6620]

@@JIMMY916 The acid treatment only went a few atoms deep into the material surface and those atoms may have been converted into something else H2SO4 + Fe= ? HCl + Fe= ? I forgot my chemistry decomposition....

[@JIMMY916]

Yes, it's true, but the use of acid has the role of a contrast agent. It reacts differently with the different components in the structure. The same effect is achieved for checking the penetration of a weld, for example.

[@reamer1363]

There is a good chance that this cast iron is from recycled wear plates from inside a crusher or similar, I had something similar myself.

[@JIMMY916]

I'm sure thet poor quality materials are used, but how the composition is so hard I can't explain. My stereotype is thet cheap materials are soft and poor quality, while here they are extremely hard. And these discs are really cheap. Thank you for your comment !

[@bernardayala1128]

Easy way of knowing you have cast iron is the spark test. From what I saw in your video that is not cast iron. Cast-iron makes long flowing sparks. Your material barely sparked.

[@JIMMY916]

Yes, I noticed it in the video too. Following the suggestion of a comment, I checked a disk with a magnet and it is magnetized. What kind of metal this is, remains a mistery. Thank you Bernard for your comment !

[@rgmveraart]

I have had the same experience with some parts made from cast iron. Even attacking the parts with an angle grinding disc failed. I hope there wil be some "expert" who wil be able to enlighten us!

[@JIMMY916]

There will certainly be opinions of some experts. I'm really curious what this cheap and hard material is. Thank you for your comment!

[@deuce454]

It’s white cast iron.. you will need to add carbon to get it to a machinable grey iron grade .. not sure if you could make temper-gods

[@deuce454]

The spherical areas are grey cast iron that formed from slow cooling, the carbon content is too close to 2% so the edges are white cast iron.. forget about machining those discs

[@JIMMY916]

Thanks Jakob for the info. My technical capabilities are limited. I have already given up on these discs. I won't get closer to them unless I go to the gym (I don't think so). Thank you for your comment !

[@kentuckytrapper780]

I think that castiron is case harding, my fordge is similar to yours and it get 2000 degrees, aluminum makes a great back plate..good luck.

[@JIMMY916]

I never thought it could reach such a temperature. Thanks for the comment and good luck to you too, my friend.

[@mike9500]

it may be cast steel not normal iron.

[@JIMMY916]

:))

[@johnrussell6620]

If it was steel, it would have bent instead of break in 1/2 as shown at 13:45

[@roulbook1921]

Why use a righthand tool while turning to the left? Google annealing of cast iron.You cooled it off way too fast due to poor handling of the disks.Do it properly and you will succeed.

[@JIMMY916]

The best cooling is to leave the piece in the oven which I did with a disc. It is the slowest cooling but the result were the same. From your comments I learned that the impurities in this cheap cast iron are impossible to transform. Unfortunately, I think this is the explanation. Thank you very much for your comment!

[@notfeedynotlazy]

you didn't need to add "Celsius". It's hot, we already knew it wasn't 150 Kelvin.

[@JIMMY916]

Corect.Only with Fahrenheit could there be confusion. Sorry for that..

[@markrainford1219]

😂