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It depends on the purpose - if it needs to be machined o final shape then grey iron is better. If it needs to be hard - like for mining grinding balls - then white iron is better..

Standard metallurgist answer - "it depends...."

I go by Scott, Hey You or any of a variety of other names.....just ask my wife!

DO NOT PUT WATER IN THE SALT! It can blow up in your face! Fill the tube with a little bit of salt, then melt it slowly, then slowly add salt until it is at the desired level!

PLEASE BE CAREFUL! Wear all the appropriate personal protective equipment, and then some.

Do not hesitate to ask plenty of questions - they could save you from getting seriously burned.

Scott

Heating the oil makes it less viscous, so it better wets the part. However, increasing the temperature also increases the length and stability of the vapor phase. FOr most cold oils, the best temperature is around 140-160F. For the vegetable oil, it really doesn't have a stable vapor phase, so you can heat it up to 250F or so without any issues.

Probably the biggest advantage is more uniform quench, with better distortion control - less quench cracking on quenching. If the temperature of the quench oil is too high, then properties could suffer. It depends on the alloy and the quench oil.

Hope that helps.

Scott

Nice fracture - as Alan indicated, it looks like an impact fracture. You can see the initiation site (the V points to the origin) and the shear lip at the opposite side of the fracture. In the side view picture, there looks like a little thumbnail - it could also be a notch.

I love looking at fracture surfaces - I spent many years doing failure analysis for a major airframe manufacturer...landing gear failures, and that sort of thing.

Scott

The cause of distortion is differential thermal strains. This is surface to center, and center to center. Since they are thin, the thermal gradiants from the center to surface would be small, and generally unimportant. However, because the blade is long, the thermal gradiant from top to bottom can be large. This is because of the staqble vapor phase that forms at different times and dissapates at different times along the lenght of the blade. To minimize that you need agitation. Use of a baffle directed upwards (perhaps a pump connected to a piece of pipe at the bottom of the quench tank would work) - anything to direct the the flow upwards in a uniform manner and to knock off the vapor phase. Insert the blade straight down as was suggested earlier. This will help a lot. If it doesn't cure it, then you can clamp plates on either side to help reduce the distortion. I have had good luck with doing this industirailly. But I like to work on making the quench tank and flow more uniform first before I tried something part specific.

Hope that helps.

Scott

Just to stir things up:

Atoms of n-type MoS2, a common dry lubricant. The bright spots indicate S atoms, which account for its excellent lubrication properties.

If you do a search, it is also on this site someplace...I put it together so it is one pdf file.....

If you look for it, it is there....Often, if you ask for verification of a steel they give you C, Mn, S, P, Ni, Cr.....if you ask for a full analysis - they give you all the tramps.

One of the problems with the steel shortage (after the excess and all the mills closed down), is that people are now getting steel from a lot of places that no one knew made steel. Because of the high demand, mills in Sri Lanka and others are providing steel.

Cerium is often used for desulfurization - because many of the third-world mills do not have adequate controls, or are created by BOF or open-hearth, the S and P control is sometimes difficult. So they resort to in-ladle desulfurization before they pour the ingot. If they have a lot of S or P - in goes a lot of Ce. They more than likely do not have a continuous caster....

Equations, compensating for chemistry, can be found in Timken's "Practical Guide for Metallurgists". These equations allow you to calculate the important temperatures for your steel - Ms, A1, A2, A3, etc....

Hope that helps.

Scott

Here are the papers...

CFD_Pinions_MacKenzie_Revised_02_06_2007_Final.pdf

pinion_shaft_bw_final.pdf

That is pretty accurate - you need a fast oil. Peanut oil is not too bad, but it may be a bit on the slow side. Try using some agitation to reduce the vapor phase - it will also speed up the oil. Using a fast oil like the Park 50 or Houghto-Quench K will also help. The timing is a bit off, you have a bit more time than 1/2 second, but not a great deal. Remember the TTT curves or the CTT curves are for thin sections and small pieces. The thermal mass will push the curves to the right and down some.

I would recommend going to a higher austenitizing temperature too - around 1625F or so would work well - or a bright cherry red - almost orange would be a fair estimate by color...these temperatures are based on Timken's Practical Guide for Metallurgists - an excellent little book - I use it a lot.

MY BRAIN HURTS TOO!

Three papers AND chairing a section?

Going by the titles, I wonder do you also have to present the papers in German, or am I just looking at the German program guide?

Way to Abschreck them Ritzels, Dude!

 

The first sentence of the scope sounds great from a knifemaker's perspective until I remembered we have no control over the "function of the component" part, which is why we have to anticipate occasional use as a prybar or screwdriver or hammer in our knives...

 

"Heat treatment aims at establishing within a component a microstructure that is able to withstand any loading conditions that arise from the function of the component."

The conference is in English....You can get the paper titles in English...the papers I am presenting deal with the use of modeling to effect low residual stress and distortion. Using computational fluid dynamics to establish boundary conditions for finite element analysis to predict microstructure and distortion. This is the first time that some one has gone after an actual heat treating load, and modeled the complete load, predicted the distortion as a function of load position, and come up with proper answers, with the right direction and size of distortion. Hopefully it will be fairly ground breaking. The other paper determines the quench sensitivity of a specific aluminum alloy using the jominy end quench - very effective and simple way to predict properties. This ought to be a really fun and learning experience.

I can post the papers here, or at another location if any one is interested....It should be fun - how often do you get to do international travel on someone else's nickel and present papers to a very high-level audience? I am really looking forward to it - I missed the last one in Beigjing because it was over Thanksgiving, and I had already made plans with the family to go to Paris. I will let everyone know how it goes!

Scott

I will be attending the following conference and presenting a couple of papers....Some of the people there are EXTREMELY high caliber, and have written some of the most impressive works modeling quenching of Japanese Swords, and described the generation of sori.....It should be fun.

http://www.quenching-and-control-of-distortion.com/

Scott

I wouldn't worry about the PVC - unless you decide to cut it with the hot work!

LOL

Scott

Nice looking quench tank - nozzles properly oriented, and looks like adequate flow...How many GPM on the pump?

Ought to do well for you!

Scott

You have it right.....

Agitation will cause the nucleate boiling to occur faster, and be quicker - it is bringing cooler fluid to the surface of the part.

Agitation will also speed up the convection phase. This can cause problems with warping and distortion.

A lot of times, what I recommend in commercial applications, is high agitation at the beginning, ramping down slowly thru the nucleate boiling stage, then finally having the agitation at a light mull during the fianl convection phase. This helps a lot in reducing distortion and residual stresses....

Hope that helps.

Scott

When a steel or any material is quenched, the quenchant becomes superheated. A stable vapor film forms around the part. Heat transfer is very slow thru this phase. As the part cools, eventualy the Ledenfrost temperature is reached, and nucleate boiling occurs - heat transfer is very fast. Finally, convection occurs.

The transition from vapor/film boiling to nucleate boiling is governed by a variety of things - agitation, surface roughness - smooth and shiny prolongs it - too rough and it is also prolonged (traps bubbles)....oxides, phase of the moon, pressure, quenchant used, etc.

Look in the arcives for Houghton on QUenching - it gives a good, non-commercial description without a lot of PhD mumbo-jumbo.....

Scott

Nice pictures - nicely showing furnace temperature vs part!

The differences in grain size are subtle. Temperature would show much larger differences....

Scott

As a general rule, to prevent the oil quenchant temperature from being excessive (limit temperature rise to 100F increase), the rule of thumb is "one pound of parts, one gallon of oil". For water, it is one pound of parts, one-half gallon of water - but that will really slow things down. I would stick to the one pound of parts to one gallon of quenchant, and you will never be wrong.

Also make sure that you have adequate quenchant coverage over the top of the part, and good agitation.

From my practical heat treating experience, I prefer what Mr. Graham suggests, and doing a sperodatization heat treatment...Personally I would use a longer time that an hour - preferably a lot more - look at a TTT diagram and it will determine how long.

I personally prefer electric heat to gas - I can control it much easier. I like the idea of computer control - it appeals to the geek in me. It is also relatively easiy to do nowadays - it used to be a royal pain back in the 80's.

Cant get much better than Kanthal - I would be curious which types of Kanthal. Some of it you have to real careful, and make sure you wear gloves after you use it, if you ever have to replace it, because the Moly DIsilicide in the elements forms a glass surface, that will cut your hand. It is also this glass that protects the elements from oxidation.

I am looking forward to seeing this project!

Scott

That is an interesting article, but I think he made it a bit more complicated than he needed to make it.. For a FURNACE that size (it is not an oven), only one zone is required. This drastically reduces cost, by reducing the process controllers required. I would also strongly suggest an excess temperature controller to shut off the heating elements should it get too hot. Instead of using bricks, you can buy the elements already in place, and just stack them together. Or you can cast the refractory and elements in place. Just watch the outside shell temperature to make sure you don't create a burn hazard. I can help with the electrical design and heat transfer design if you are interested....For something that small you can probably get away with using 110V or 220V single phase. I would also consider finding an inexpensive SCR for precise temperature control.

Scott

That is an interesting article, but I think he made it a bit more complicated than he needed to make it.. For a FURNACE that size (it is not an oven), only one zone is required. This drastically reduces cost, by reducing the process controllers required. I would also strongly suggest an excess temperature controller to shut off the heating elements should it get too hot. Instead of using bricks, you can buy the elements already in place, and just stack them together. Or you can cast the refractory and elements in place. Just watch the outside shell temperature to make sure you don't create a burn hazard. I can help with the electrical design and heat transfer design if you are interested....For something that small you can probably get away with using 110V or 220V single phase. I would also consider finding an inexpensive SCR for precise temperature control.

Scott

That was weird.....

Using a microscope and the intercept method is probably the best and most accurate - other than using a Leco Carbon Analyser.

One book that would be invaluable to get is "alloying Elements in Steel" by Bain. Published by ASM back in the 60-70s - it is an excellent reference on alloying elements in steel, and what the results of response, etc.

One other book that is also very useful, is one of the very early Making Shaping and Banging - err I mean Shaping of Steel. I would suggest a volume printed just before WWI or WW II. In those volumes, it describes steel making using an open hearth, bessemer process, and lots of really cool information, along with heat balances, etc. You can usually find them on eBay fairly reasonably - that is where I found mine....

Making a small mill has always interested me, starting off with a blast furnace, to an open hearth or BOF, then to the forge shop.....all sorts of things you can do. Just make sure you use metallurgical coke instead of high sulfur coal - nearly got me thrown out of school a long time ago.....

Scott

Look for the distributors - they are local, and can help with small quantities.

It wasn't that kind of truss I was talking about.....

Regarding the Convention Center, there are so many things that could be wrong - deigned properly installed wrong - aka Hyatt Regency; Designed improperly, and installed per drawing; Properly designed, and pressure put on to change the drawings (The Big Dig) to save money....Improper design assumptions, procurement people changed the specifications because the engineer called for something more expensive (happens more times than you think)...Or properly designed, properly installed, but user abuse - that happens a lot!

But back to the discussion, the section modulus (only material property is E - the elastic modulus) governs stiffness. Microstructure only changes the modulus a couple of decimal points - probably not significant to measure with common shop tools....even a micrometer....