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Posts posted by kb0fhp

  1. I would also use a fast oil - one that is meant for quenching - there are a lot of them. ATF fluid is mineral oil (usually) and it would be too slow. Motor oil is an unknown, and likely to stain the parts. It also has an unknown flash temperature. There is a reason quench oils have been developed, to get properties and properly control distortion. There a variety of sources, even some on this board that sell them in the necessary quantities.

  2. I know it is commonly done with industrial castings - I am not sure or unfamilar with scuplture type castings. Perhaps the chalk was a bit damp....It really doesn't take much for the moisture to cause a problem. The benefits are reduced gas porosity, and reduced inclusions. Also most use a bottom pour for industrial sized castings to reduce gas porosity.

  3. I might try grinding the rocks down, acid leaching out the copper, then plating it out. Then I would have relatively pure copper to start with.....Or you could precipitate the copper out of solution using sufuric acid to dissolve the copper, then add something to cause the copper to precipitate out as copper sulfate. Then it is heated to drive off the sulfur, and an ingot of copper is left with stinky sulfur on top.

  4. Do you have the pin-out to the temperature controller and the relay - that would help a lot. If not - do you have the temperature controller description? I can search for the controller and help with the wiring. Also, what configuration are the elements (WYE or DELTA)? You will also need a thermocouple.


    I would also suggest a cheap excess temperature controller to shut down the elements in case of a thermocouple break.



  5. I dont know whats going on, I quenched it one more time, After I grinded it and the file still bit, I got so of frustration, I put it in the vice and hit it with a hammer and snap, relatively fine grain on the inside, but the damn file still bite.


    The destructive test tells me that it is hard enough to use as a knife, but Im going to do some testing.


    Thanks for the input.


    Tell me what you think.


    Looking at the pictures of the fracture, you have a very small region surrounding the blade that is uniform. This is very suggestive of decarburization. Not knowing the dimensions of the cross section, it is not possible to determine the depth of the region. But I strongly suspect that decarb is the source for the part being soft.


    On the broken piece, use a grinder and gently grind away about 1/16" and try the file again. It should be hard. You could also cut the piece in half with a saw and try the file on the inside of the piece - it should also be hard. If it is 5160 then just about anything will harden it - it is a very deep hardening grade. You could almost forced air cool it and it will get hard.





  6. I would strongly suggest heating the oil. Because of the thin viscosity, it will require just a bit of heat - it will make it a bit faster - to a point. If you heat it too much the vapor phase will dominate and it will become slower.


    Perhaps the clay is also too thick - also consider just a bit of agitation directed up - it will help break up the vapor phase and make it faster. Oil will not be faster or as fast as water - but that is the point. Agitation will make it faster but only to a point.



  7. A few more properties of new, little friend, iridium......


    " Rhenium's melting point of 3180º C is second only to tungsten. Only osmium, iridium, and platinum exceed its density of 21.04 g/cc. Because of its high melting point, rhenium is a refractory metal. In that classification, rhenium is unique. It is the only refractory metal that does not form carbides. Its crystal structure is hexagonal close-packed (hcp), while other refractory metals have a body centered cubic (bcc) structure. Rhenium also does not have a ductile-to-brittle transition temperature it maintains its ductility from absolute zero all the way to its melting point and also has a high modulus of elasticity. This means that structures made of rhenium will have very good stability and rigidity.


    A high re-crystallization temperature is a pre-requisite for good creep resistance and among refractory metals, rhenium is the highest. At temperatures up to 2800º C and high stresses, the rupture life of rhenium is longer than tungsten. The metal also accommodates wide swings in temperature - large thermal expansions and contractions - without incurring mechanical damage."


    Sound good?


    This is pretty interesting stuff. Initially, looking at the periodic table, I would expect it to act like Mn, but because the crystal structure is different - and the size of the lattice is different, it would probably be a dispersoid former, and act to raise the recrystallization temperature. It might also report to the grain boundaries, and act to pin the grain boundaries, preventing or minimizing grain growth. It could also act to slow creep. But regardless, it would not be soluble in Fe to any great amount because of the large mis-match in the crystal lattice. But then, it could also be fairly soluble like cobalt which is also hexagonal - it depends on the matching between the a and c values of the unit cell - I am not sure how much bigger the unit cell of Re is compared to cobalt. I have tried to look for a Re-Fe phase diagram with no luck. I would suspect that it would be similar to a Co-Fe phase diagram, but with a smaller solid solubility. I imagine that it would make some interesting intermetallics that may form at the grain boundarys - and become brittle because of the intermetallics, and result in intergranular fracture (the rock candy fracture)....I really don't know.


    OK - I found a really small portion of a phase diagram - valid from 0-45at% of Re....looks like it is soluble in austenite up to about 5% at about 500C, then forms an intermetallic. I would then suspect that it would report to the grain boundaries, and become a brittling agent....




  8. I don't have a problem with that at all - my problem is marketing it like snake oil, and providing anecdotal stories instead of real research by independent people - instead of just hawking their wares.....


    There must be something to it - otherwise so many people wouldn't claim otherwise. Unless a whole lot of people are fooled by a bunch of placebos...




  9. I got the paper - thank you. Essentially it described two mechanisms - first at -120F, the mechanism is conversion of retained austenite. At -320F, two mechanisms: the transformation of retained austenite to martensite, and the second is the precipitation of fine eta carbides between the larger carbides. He also indicated in passing that there may be a stress relief occurring.


    I am not happy with the explanation given - doesn't sound correct about carbon finding more preferred sites....the low energy sites are the intersitial ones - where the carbon is already residing.


    I need to do some research on the formation of eta carbides and the likely hood of it happening at -320F.


    I have never disagreed with the premise that -120 F would work. Nor particularly at -320 F (mostly due to conversion of retained austenite) - but I am not sure of the precipitation of eta carbides. Perhaps because of the lower temperatures, the precipitation of the carbides occurs from the conversion of retained austenite.....and the associated carbide precipitation.

  10. Whale oil was used a lot immediately before 1920. The problem was a shortage of whales, and the expense of the oil. THis was until alternative oils came out in the late 20s

  11. I would be interested in reading Dr Batson's article. Since the carbon in any steel is located in the intersitial spaces, I am a bit confused about it finding a preferred space.


    Cryo does work in converting retained austenite - all that is required is to use a temperature a bit below the Mf temperature. For alloys like 4340, 300M and HP9-430 (9% Ni, 4% Co, 0.30%C) - used in landing gear, as well as the newer AerMet 100 and AF1410, the temperatures are -100F for 24 hours.


    I depends on the steel - if it has a lot of nickel - then it would be a likely choice for a retained austenite treatment. Otherwise I would save my money. Unfortunately, there are a lot of people who REALLY believe - even to the point of fanaticism....and can't listen to reason, or independent study. My mind is not made up - but I need to be shown valid, peer reviewed literature to show that it works.




    BTW, for an interesting discussion of cryo treatment (that got a little heated) look at :




    BTW - serveral questions I posed were never answered....



  12. There are multiple quenchants that can be used - one effective one is the use of salts (about 10%)....it has the effect of breaking up the vapor barrior and nucleating the boiling phase.


    Use of any carbonated drink, or water for that matter, would have the effect of creating a very long and stable vapor phase. There are some applications that this may work for reducing residual stresses, but steel isn't one of them.


    There are still places in the US that quench in lead - for wire drawing and other applications that are similar.



  13. A quick search using Google and "snake oil" will uncover multiple references to cyro treatment.... (That ought to start some flames!)....just kidding.


    The use of a sub-zero treatment - typically 24 hours at -100F is very effective in reducing retained austenite. It is a standard practice for aerospace steels, or those that are prone to retained austenite. THe times and temperatures vary a bit, but this is the essential process. It does work.


    There have been claims that cryo sweetens the tone of brass instruments, reduces stresses, or cures global warming. Most claims are anecdotal, and do not have independent research or study behind them to validate the claims. At the present time, any claim other than reducing retained austenite is bogus.





  14. Mike - it is straight forward. Look at the Fe-C phase diagram. There is a range of chemistries that have Fe+C and then there is pure graphite. The graphite will diffuse into the melt up to the equilibrium limit.


    If you want a chemical equation, it is 3Fe +C(graphite) = Fe3C.


    You can simply prove this yourself. Take a graphite crucible, and fill it with pure iron, or low carbon steel. Cover the crucible to prevent oxygen making CO and CO2. Heat slowly to different temperatures. After a period of time - you will carburize your steel. Heat up til melt and hold for a period of time, then cool. Measure the carbon content - it will have increased......

  15. OK - Check out the book "Foundry Engineering", by Flemings, Taylor and Wolf....


    At a given chemistry, you can have either white iron or gray iron - the difference is the cooling rate. Cooled rapidly, you get white iron. Cooled more slowly you get gray iron. Refer to the diagram on page 98. I wish I had a scanner available now - I would include it.


    If you take white iron and heat it up and hold it isothermally for a long time, then the graphite will precipitate out and form malleable iron...


    Consider the same melt - if you add graphite, there is a solubility of graphite in liquid iron. Some of the graphite would dissolve in the melt, while some would remain as graphite - according to the equilibrium diagram. So it is possible for additions of graphite to increase the carbon content of a melt.


    Hope this helps eliminate any confusion.



  16. I would be interested in seeing the macro of that ingot that has been sectioned....easily done with nital or ferric chloride - but lightly....that way you could get an idea of the segregation present...and all sorts of other stuff....



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