Jerrod Miller

Ideally the vents should go out of the mold well above the parts (typically out the top) and not be connected to the sprue at all. It is even possible (but not at all best practice) for the vents to not go all the way out. What you end up doing there is pushing the air out of your sprue and part cavity, and forcing it into the vent, which will build up pressure (in steel this would be ferro-static pressure, in water hydrostatic, in copper cuprostatic, but I am not sure if there is a proper term for bronze but I would guess cuprostatic). This requires a certain amount of head pressure (densi

Or heat up a block or two of steel in the forge prior to heating the blade for quenching. You can lay your freshly quenched blade on (or sandwiched between) the chunks of steel like Joshua does on his oven door. Or if your set-up allows for it, pre-heat a bunch of sand (like in a bread pan or roast pot) first. You can then bury your blade in the sand and the thermal mass will keep it hot enough long enough to do a bit of a snap temper. Just make sure whatever you use is the right temperature for your temper. It can be less than your final temper, but still needs to be at least 250F, 300F

You can certainly re-normalize to refine the grain. You do have to worry about decarb with too many cycles (especially when near the final shape), and it does get hard to balance "how much did the grains grow" with "how much did I shrink them", but you are usually pretty safe to err on the side of doing cycles to shrink them too much (better to over normalize).

Also, the actual specific chemistry of the metal will play into its solidification properties and viscosity. Pour temp can be played with a lot, too. Casting has a lot of variables. This is exactly the opposite of what is done in many industrial applications. The reason for wanting to flow up is to keep a uniform metal front (no splashing or spreading).

General rule for determining vents: Vent, vent, and vent some more. When you think you have enough, double it. Then maybe you really do have enough. Granted, my expertise is generally with sand casting, but I have poured a fair few investment castings, too. Always vent as much as is practically possible. Also, your pour cup looks extremely rough. You want that to be smooth to reduce turbulence. It also looks like you have cold lap in your pour cup.

I would guess it has to do with lack of venting. As the metal enters into the mold, the air that is in there needs a path out to make room for the metal. ETA: It could also be that your mold pre-heat is not adequate or that your pour temp is too low to begin with. Or a few other things.

Which is why using temper colors is a bad idea. Thermometers and ovens are cheap. You all knew I would have to chime in and say it.

I don't know of any that I am familiar with off the top of my head. A quick search and I found this link from the very trustworthy ASM International (the fine folks that put the Heat Treater's Guide together). I also found it funny that this video from Texas A&M started with the Cu-Al diagram (I just watched the first minute and last 2 minutes, where he came back to that diagram). I think it may be a great starting place.

I would highly recommend learning all about phase diagrams in general (because they're fun; maybe that's just me), but especially if you are going to try creating your own alloys. I wouldn't even think about building an alloy before consulting phase diagrams.

Things get crazy in these alloys. Little bit of copper in Al? No problem. Little bit of Al in Cu? *CRAZINESS!*

I feel I should note that I understand steel metallurgy fairly well (better than most, but there are still many better than I), but I do not have a strong interest in wootz, and thus don't know all there is to know about it. I have looked into it on a pretty technical level before, but after discovering that it isn't a great material (by modern standards), I deemed it as too much effort to be worth pursuing. Likewise I do not absolutely adore tamahagane/blister steel either. I have a lot of experience melting steel with modern means (induction and arc furnaces), but none with cupula or hear

Have you read this thread? If not, definitely do.

It isn't. Modern steel is definitely superior. Wootz is difficult to make and work, but looks nice. It was better than other "steels" centuries ago. What we refer to as damascus now is much easier, and often has a look that pops a bit more, as well as being able to control the patterns very well.

When going with any of the cold treatments, it seems to me that control isn't nearly as important as getting cold enough. Your freezer isn't likely to do too much. Those are typically around 0F to -15F. Ideally you want to be more like -100F or colder. Dry ice is generally the starting point for these things. "Cold" treatments are often considered at least -150F (colder than dry ice), and "cryo" at least -310F. That being said, I know there are alloys out there that do tend to respond to dry ice levels. Often people will say either "cold" or "cryo" when referring to either process, more

Not me. This is @Andrew W's thread.