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kb0fhp

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Posts posted by kb0fhp

  1. The fact that is snapped in a vise indicates that you got a predominately martensitic structure. However, the ultimate hardness is governered by the carbon content. The range of carbon in a 1050 steel is approximately 0.48-0.55 - so can vary. Aslo, you may have some decarb.

  2. Right. The aluminum does help. There is a teeny bit of it in my steel, depending on the ratio I use. The great part about a 2 part crucible is that when the molten charge drops and hits something, it really separates impurities and slag, aluminum oxide included. The problem is the alloying chemicals start the process all over again. You cannot put the alloying chemicals in the reaction, as the reaction will grab them as fuel for the fire. Brent actually had ALL of his iron burn up. Didn't have a thing to show, except a chunk of slag.

    They tell me that a large charge, over 8 pounds, will exceed 7200F at the flame!!! :o

    Here is a chunk of steel I dug out of the large slage clinker from one of my early runs. It's brighter than the quarter. Funny, it will quickly darken after just a few hours in the air.

     

    That is really cool!

     

    I always wanted to make a small blast furnace using taconite, metallurgical coke, and lime. I used to have a design for a small cupola using two 55 gallon drums that I was going to modify for a blast furnace. Then I would have to make a small open hearth or BOF to get the steel just right....Never really had the time or property to do it. I think my suburban neighbors might complain - but then again, they may not....they put up with my antennas (I am also a Ham Radio Operator)......

  3. Please tell me why there is almost always a "belly button" in the middle of an ingot.

    I've seen huge ones in small crucible steel and small ones in large crucible steel. There is almost always one though, right in the middle of an ingot. Is there a way to prevent belly buttons?

    Not that I have a prejudice against belly buttons, just not in steel. :D

     

    I think what you are seeing is solidification shrinkage in the ingot....Is it an innie or outie?

  4. So what's the difference between the red hematite and the black shiney lustrous hematite? Just the way they form?

     

    I've got a hunk of the black that's been polished up.

     

    Hematite is Fe2O3, Magnatite is Fe3O4....the high temperature version of iron oxide is FeO....

     

    The black shiny hematite may be magnetite or have a large portion of it in it....try it with a magnet. If it sticks to the magnet - it is magnatite

  5. Canola oil is an excellent quenchant (make sure you dry it out - it is hydroscopic and loves to pick up water)....there are a variety of mineral oil quenchants available - talk to a local heat treater in your area (there are several) and ask them for some used quench oil that is going to be thrown away. Before you use it, heat it to above 212F and hold it there to make sure you have all the water out - water in oil is very bad.....

     

    A pyrometer is nice - but you can get by with a digital voltmeter, thermocouple, and a millivolt table (downloadable from the web).....might help associate temperatures with colors.....

     

    Hope that helps

     

    Scott

  6. 5160 will thru-harden in thicker sections. It also has better impact properties. The Cr will also slow down grain-growth. It will also have better secondary hardness and resist tempering - or rather it will be slower to temper. A much better steel than 1060.......

  7. If they are about the same carbon content, and it quenches out hard, then a temper of 400-450F several times for 1 hour should be about right. You can always try a lower temperature - say 350F - if it is too hard, then you can go up in temperature without any issues.....

     

    Scott

  8. Brian:

     

    You are right - Cr acts like a sort of multiplier to allow the steel to get harder deeper into the section. It does not cause the steel to get harder - that is governed strictly by the carbon content (the grain size plays a small part - with larger the grain the harder the steel - small grain adds toughness). The alloying elements allow a thicker section to be made with the same quench....all other things being equal.

     

    Scott

  9. Easiest way to determine whether the taconite is magetite or hematite is to check with a magnet. Magetite is magnetic - slightly so, but magnetic. Hematite is red - hence the root - "Hema" indicating blood. It looks like oxidized blood. Magatite is dark - almost black.

  10. I think the question you need to ask first is how hard do you want to make it?

     

    5160 and 6150 are two entirely different animals, with different alloy contents and carbon content.

     

    A good reference is "Heat Treaters Guide" by ASM...

     

    Scott

  11. There a couple of really good simple texts on heat treating - one book is ASM Practical Guide to Heat Treating...Another book on quenching that is simple and practical, and gives a bunch of Why and wherefors of quenching is Houghton on QUenching - it is a freebie. Do a search and it is posted somewhere on the site.

     

    Scott, aka KB0FHP

  12. DGentile:

     

    I am glad to see you like the Houghton Oils - I work for them in the corporate office (in Valley Forge, PA) as a marketing "guru" in heat treating. Houghto-Quench R is a good general purpose quench oil suitable for a large variety of work. Since most of the steels used are high hardenability - it should work very well.

     

    If you need some advice regarding polymer quenchants - please message me.

     

    Scott

  13. The surface roughness does impact the quench speed - as a general rule the rougher the surface, the faster the quench. HOWEVER, if you have too rough of a surface, the valleys actually hold on to the bubbles and the quench gets slower. THe direction of the grit lines also have an impact on holding on to the bubbles - vertical lines are much better. Now the question is - how much better? Standard metallurgist answer - it depends. It changes the shape of the cooling curve and helps defeat the vapor phase, resulting in a faster quench. THe size of this vapor phase depends on the size of the part. For water quenchants that have a very stable vapor phase, the effect is quite remarkable. For oils, the quench rates go up, but not as much. For both quenchants, nucleate boiling occurs at a much higher temperature, and the temperature of maximum cooling is also much higher.

     

    Hope that helps.

     

    Scott

  14. VERY Nice setup! Nice layout. I like your Quench-O-Tubes. What sort of agitation do you use? Light agitation upwards through the tubes would help - especially with water and polymer. Oil is more forgiving regarding agitation. I would not use air, but would use a small pump...

     

     

    A couple of other questions:

     

    What oil do you use?

    What polymer do you use?

     

    Thanks

     

    Scott

  15. Thank you WildRose - I appreciate it. I am trying to understand the physics/chemistry of what is happening. From what I understand from what you wrote, it is the color formation that occurs during quenching, from the formation of bubbles, selectively oxidizing the parts. The color is esentially the temper color of the temperature of the part localally when the bubble breaks?

     

    Surface roughness can effect how long the bubbles attach - the smoother the part, the more adherant the bubble - something to do with surface tension of the part vs. the surface tension of the bubble.

     

    That is pretty cool!

  16. Not sure about the wires...

    I got them from a kiln-maker & pottery supply store who repairs various ovens including the famous nabertherm things...

    he makes coils to custom-specifications...

    and uses the coil-wire from the swedish company "Kanthal"...

    that's all I know about.

     

    Kanthal is a trademark of HIGH QUALITY Moly Silicide heating elements. As the elements heat up, they make a thin amount of glass covering the elements. They are capable of very high temperatures, but are rather fragile. They also make good quality nicrome elements. I think the website is www.kanthal.se

     

    Scott

  17. Agitating the water is not to make a faster quench, it's just to break up the vapor phase. Color case hardening is a tricky thing and it's going to take some experimanting to get things right. Be patient !!

     

     

    Well, that is partially right. Agitation will make a faster quench - because it does break up the vapor phase and start nucleate boiling. Agitation also helps keep the heat transfer uniform on all sides.

     

    Maybe I don't understand the terminology - but coloring is one thing, and case hardening is another. Case hardening is achieved by adding additional carbon in the surface of the part, then quenching and tempering. Coloring by using temper colors actually is the creation of a patina on the part. For instance, you can create a nice blue color by tempering at about 500-600F (depends on the steel). You can make it even more blue by adding a bit of water or tempering when the air is humid. Other colors are possible. Black oxide is achieved using special salts that create a tightly adherent magnetite (Fe3O4?) on the part. It is a good protective surface.

     

    I don't know of other ways - can some one tell me?

     

    Scott

  18. Quenching is a function of the viscosity of the oil, the thermal conductivity, and the boiling point. It is also a function of the flashpoint. The more viscous the oil, the slower it is as a general rule. It also means that you can heat it up more too. The reason why, at the same temperatures, that a more viscous oil is slower (with out any added magic pixie dust to make it faster), is because of how well it wets the part. A heavier oil will wet the part less wel than a thinner oil. Also a thicker oil with generally have a higher boiling temperature, so it will have a higher nucleate boiling to convection transition, meaning lower distortion. THis is why the canola oils and similar vegetable based oils are such nice quenchants. Unfortunately, they are expensive, and tend to soluablize, creating an emulsion. This makes them more difficult to recycle. The vegetable oils also create a difficult to remove oxidation that has been cooked on to the parts - special cleaners are needed to remove it.

     

    I remember a large trail I had with our canola product. This was a large quench tank of approximately 4000 gallons. The product worked great, but the operators didn't like it because the heat treat shop smelled like french fries - and "it wasn't proper" that it smelled like a McDonalds - so they went back to conventional mineral oils.

  19. I recently read this too insome texts that I was reading for my paper I am writing on the history of quenching. I can't cite word and verse, but the Chinese used grease as a quenchant around the Han Dynasty as I recall - this was indicated several times.

     

    When I find the reference - I will cite it.

     

    Scott

  20. Where do you get the taconite? I've been having a tough time getting iron.

     

    Jeff

     

    Back in the dark ages, when I was still in school at Ohio State, when they still had a metallurgy program, we used to gather the taconite along the railroad tracks that traveled from the mines in the Iron Range in Minniesota, to the steel mills in Pittsburgh.....Unfortunately, there are no mills in Pittsburgh anymore, and very few blast furnaces left in the US.....I think the only ones I know of are in Weirton WVA, Inland Lake, IN, and maybe some in Detroit......Perhaps others have better sources....

  21. Thanks Don:

     

    Remember - I gave you the in-tank cost. Assuming a polymer cost of $20/gallon (and there will be some that go that high and higher - especially at very small quantites), a 10% solution would have an in-tank cost of $2/gallon.....

     

    If you have any questions regarding the proper quenchant to select - please contact me.....

     

    Scott

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