Hot Metal Processing Log

Thu Jul 2, 2020

MJ

Dan,

Maybe you can help us get to the casting part of steel using re-usable molds.

Pouring 200 lb/hour of stainless steel shaft makes for a robust business case on a small scale. I'd like to look at practical experiments for getting there.

Can you fill me in on the best technique that you can suggest - either to cast steel, or soft work steel - to rod form? We're interested in rod from 8 mm to 3" diameter.

I'm thinking, an easy but powerful experiment for small scale rod production. Casting or other hot metal work sounds good to me. You mentioned hot working material into shape. But I'd like to be starting from scrap steel, adding ferrochrome to it as needed to make stainless steel. The OSE strategy is to shift from rusting steels to non-rusting steels as general purpose steels, for the sake of lifetime design. When we make stainless, the value of the product goes from $5k/day value to triple of that.

Thus - what would you suggest for the simplest reusable cast experiment for making billet or bloom that can be processed to precision shaft from there?

The workflow I see is:

1. hot metal bloom or cast 2. rolling for good dimensional properties - for structural steel 3. CNC machining for finished precision products

MJ

Dan

Marcin,

In industry, as you probably already know, large forge presses are used to hot or cold work stainless steel to pound it into rough shape and obtain increased integrity and required grain structure. These finished billets are then used in secondary processes such as machining. If high tight tolerance diameters are needed, as the case of the 8mm 3D printer rids, centerless grinding machines are used to grind the rods to final diameter.

All of these processes are run by people who rarely question if there is a better less energy intensive way to process these metals.

Here is the thixotropic state process for casting that I think is under utilized: https://en.wikipedia.org/wiki/Semi-solid_metal_casting

However if you are going to make your own stainless steel, you will have to melt scrap steel to a liquid state. In doing so you will want to take that liquid stainless steel and processes it right away into the cooled shapes you want. Letting it cool and the re-heating it will cost a lot of energy. So having your process steps from liquid stainless steel to the final part right next to each other would be ideal. This is what lean manufacturing principles would dictate. Lean manufacturing is another under-utilized set of techniques. Of course lean manufacturing can use some hacking to improve it as well.

-- Daniel N. Meyer Fab Lab Senior Manager