Fred_V wrote: ↑Tue Dec 04, 2018 11:07 am
would coal or charcoal be best for heating it up?
I believe either would do fine. Coal coke would be the best and maybe even too much heat if you blast air through it. Like a blast furnace or blacksmith's hearth. You could get it too hot. Iron will distort with too much heat - but that's pretty hot so you may not need to worry about that. The slow cool down is the key. The iron crystal structure should be as large as possible - soft.
We use niobium here at the lab and the way it is refined is the key to its use and purpose. Some of it is cooled so slowly that a single crystal is close to ten inches in diameter - that makes it very expensive. But under normal cooling conditions the crystals are about half the size of a dime. Niobium is a super conductor at the temperature of liquid helium (-456°F) and the fewer crystal 'boundaries' the better conductor it is. This doesn't have much to do with a steam locomotive but it's somewhat interesting - at least these physicists and scientists here must think so. Some of them even drool when they talk about this stuff...
BC
Fred,
I had a friend that had the same problem with a pile of castings and he fired up his wife's pottery kiln and left them in there for a period of time and then brought them down slowly with the timer and they were able to be machined. This was an electric system that could be controlled well.
I have a bunch of misc iron castings of unknown origin. How can you tell ductile from gray iron with these existing castings, - E.G. do the two materials look different after machining? Is there some kind of scratch test, or spark test, I could do??
OK, two questions
THanks
Glenn
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Glenn Brooks wrote: ↑Tue Dec 04, 2018 3:12 pm
So one follow up question.
I have a bunch of misc iron castings of unknown origin. How can you tell ductile from gray iron with these existing castings, - E.G. do the two materials look different after machining? Is there some kind of scratch test, or spark test, I could do??
OK, two questions
THanks
Glenn
Probably the best way to tell gray iron from ductile iron is a fracture test. Gray iron has very little shock resistance so will fracture - and not bend. Ductile iron will bend before is fractures. The 'swarf' from filing gray iron when rubbed between your fingers will resemble the graphite from a lead pencil - ductile iron contains a harder more nodular graphite so will not transfer to your fingers so readily.
BC
Jacob's dad wrote: ↑Tue Dec 04, 2018 2:55 pm
Fred,
I had a friend that had the same problem with a pile of castings and he fired up his wife's pottery kiln and left them in there for a period of time and then brought them down slowly with the timer and they were able to be machined. This was an electric system that could be controlled well.
That would be ideal - and is the way it is done. A pottery kiln is very close to a heat treating oven... You could do a 'heat soak' and not be concerned with uneven heating of the casting by the other methods.
BC
Fred_V wrote: ↑Tue Dec 04, 2018 1:50 pm
Thanks. I've been reading about super conducting; very interesting study. Are you any closer to having it work at room temp?
The portion of science that we are involved with at the accelerator uses niobium for its cryogenic superconductivity characteristic because it is basically a perfect material to fabricate the accelerator cavities where the electrons are boosted in speed. We accelerate electrons (or protons) to the speed of light to bombard other electrons to break them into pieces and we are now at the point of bombarding the 'pieces of the pieces' of an atom. We continue to find more and more space and we're attempting to find out what is holding all of this together. The study of room temperature superconductivity is another area of this same science but sort-of outside of this phase and use of this 'conventional' 12 GEV accelerator. I wish I could drool better but I'm satisfied with what little I know about this stuff. I support these gifted folks who are often at a loss with the elementary things that I understand. But I'm old and ready... I've become much too frank with some of these wonderful people but I love and respect them...they are gray haired gifted children. Sorry for a much too long response....
BC
Jacob's dad wrote: ↑Tue Dec 04, 2018 2:55 pm
Fred,
I had a friend that had the same problem with a pile of castings and he fired up his wife's pottery kiln and left them in there for a period of time and then brought them down slowly with the timer and they were able to be machined. This was an electric system that could be controlled well.
That would be ideal - and is the way it is done. A pottery kiln is very close to a heat treating oven... You could do a 'heat soak' and not be concerned with uneven heating of the casting by the other methods.
BC
I have a pottery kiln that I used for burn out with lost wax casting. What temp. should I go to?
You will never melt iron in a pottery kiln - so you could go for maximum temperature that the kiln is able to produce for a time period, then do a slow graduated cool down. The maximum temperature and 'soak' time will be variable accordingly with mass of the crystallized casting and max temperature of the kiln - that data for the material temperature and time is probably available in a Machinerys Handbook
BC.
Fred,
Sometimes an iron casting is cooled too quickly and the result is a 'chilled' casting. That is about as hard as Gray Iron will ever be but that doesn't make it ductile iron - it will become 'chilled' iron. As H_V explains; the conversion from Gray Iron to Ductile Iron is a high temperature process while the gray iron is in its molten state. Magnesium ( or other modern concoctions) is inserted into a crucible of (contained) iron that will superheat it to a point that a carbon conversion takes place that converts Gray Iron to its more steel like state by converting its contained graphite - ductile iron. It becomes a very close cousin to steel. Our modern abilities have obviated 'ductile iron' to 'steel' castings. The similarities and differences become harder and harder to define as time and technology go on. Gray iron is very hard graphite....There is nothing like approaching a crucible of molten iron to inspire getting your life in order - if you melt outside.....
BC
