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What will happen when you quench steel in liquid nitrogen is that the LN2 will immediately turn to vapor and you will get a very persistent vapor phase - it is a very slow quench. Only vigerous agitation will break up the vapor phase. Another thing to concern yourself with is that all the LN2 will also turn to gas and create a suffocation hazard. This was well documented about 30 years ago when several people died when a manufacturer tried it.

Canola will get faster if there is water present. It will not separate as canola or vegetable oil is hydrophillic (likes water). Oil that contains more than 1000 ppm of water can be a serious fire hazard as the water turns to steam and pushes the oil out. Often the oil ignites from the hot part. Then you have a real mess with flaming oil over everything

Why not nitride the blade edge of the stainless?

Wind turbines are really a favorite of mine. They have to be forged, machined, heat treated and then assembled. Good solid manufacturing work. It is really cool when they are quenched and knowing that you had a part in it when you see them erected.

Download Timken Practical Guide for Metallurgists - lots of good data there and free. There is a new edition out there - just go to the Timken site and download it. Timken Practical Data for Metallurgist.pdf

No - you are not missing anything. I misread it - I was thinking that you had a laminate of low carbon steel with a high carbon steel. I goofed. Thank you for calling it to my attention. The Ms temperature that you determined empirically is about right. Because the section size is small and the thermal mass of the salt is high, I would use a much shorter time at the martempering temperature.

That certainly makes sense. What you could have also done is created bainite in the 1070 - making it nicely tough, but still had martensite in the lower hardenability stuff. For grins - try a 1070 blade with only 1070 and austemper it, i.e., hold at Bs (°F) ~ 1526 - 486 x C - 162 x Mn - 126 x Cr - 67 x Ni - 149 x Mo for a period of time - then quench. You will end up with a baiitic structure - hard and tough. Maybe not real hard - maybe 53+ HRC but it will be real tough.

Ms temperature for 1065 is 525 and Ms for 1090 is 420F - so what you found empirically is about right. I have not found the Ms temperature for 15n20 but it is very high - much higher than 525F. I found the data on p 79 of "Practical Guide for Metallurgists" - very practical little booklet that is a freebie. As an approximation: Ms (°F) ~ 930 - 600 x C - 60 x Mn - 20 x Si - 50 x Cr - 30 x Ni - 20 x Mo - 20 x W from E. S. Rowland and S. R. Lyle, Trans. ASM, 37, 1946, p 27. I agree that you probably have a slight decarb.

There is always a "pucker" factor - Hopefully whenever I do a fill like that I have looked at all the mitigating factors like quench rate, part alloy, thickness, agitation, quenchant used - and how to control the concentration (if polymer). Luckily I have only had one failure and that was because of agitation issues. I thought it was stronger than it was - after we corrected it, it worked like a champ. Regardless of what you are doing - there is always a risk - that is why they pay me the big bucks - to minimize risk to the company; the customer, and to the part. One I get to the actual load - it is more of excitement and celebration than anything else. BTW, I am trying to put together some additional pictures. But to give you an idea of the size of the wind turbines - here are some small blades for 1.5MW turbines: Now each of these blades has a yaw and pitch bearing - that means numerous parts from rolled rings that bust be heat treated (typically either 52100 or carburized 9310). The rings, races and bearings (the balls) must be heat treated.

Thank you - I appreciate it. BTW, I am not a chemist but a simple metallurgist. I have chemist's for lunch.

Just call our customer service at 610-666-4000 (ask for customer service).

I would say that it would behave in a very similar manner

Depends on what you want (see - you can never get a straight answer from a metallurgist ) If you are looking to get the O1/O2 hard I would suggest using Houghto-Quench 100. The steel that you just cited has a very high hardenability because of the Cr and V. The V and W (Tungsten) will make nice carbides and help retain a nice edge. However, if you ever want to do lower hardenability alloys you will have a problem getting the lower hardenability parts hard. You may want to consider Houghto-Quench G - this is a medium speed oil that will get the high hardenability parts hard and should get your low hardenability parts hard too.

I wouldn't use diesel fuel - the flash point is way too low. I also wouldnt use motor oil either because of the additives and stuff that is in the oil for lubrication. A straight mineral with low viscosity will get you the speed you want a lot safer.

An 11-sec quench oil refers to the GM Quenchometer test. It is a pretty cool test - essentially it measures the time it takes to cool a nickel ball that is 0.5 inches in diameter, from 1600F to the curie point. There is a lot of variability in the test, but it has been used in the US for years it is hard moving people to a better test like a cooling curve. This would compare directly to Houghto-Quench G. And yes I do know

I am not familiar with DIN 1.5052 - is it similar to AISI 52100? Or could you give me a composition? O1 and O2 should be hardenable in thin sections with Houghto-Quench 100. It is the extra V (O1) and Mn (O1 and O2) that makes it better than 1090 steel and more hardenable. It should work.

It all depends on how hard you abuse them. As a general rule the oil would go rancid before it would not achieve metallurgical properties. A mineral oil, properly taken care of will last a very long time. Filter it occasionally using a good quality filter and mineral oil will last a long time. Even if it does get very oxidized, a mineral oil will tend to get faster because the shellac layer on the part. Vegetable oil would do the same thing. Take care of it and they will both last - but I can't quantify how long each will last as it is so dependent on a whole bunch of things. But in general I would suspect that the mineral oil would last longer.

I suspect that there is some residual moisture either in the atmosphere or on the steel.

I suspect that it more than likely Chinese steel. One of the real problems with Chinese steel is the tendency for low hardenability, uneven grain size and alloy banding.

I can't recall - did I send the information to you?

For a blade I would recommend plunging it downward and agitating it by moving it up and down. As an alternative, you could try ultrasonics for agitation. Back and forth will cause uneven cooling on one side or the other. I would not expect it to relax when tempering unless you put a LARGE weight on it and tempered at a fairly high temperature.

I have the pictures on my work PC - I will try loading some from work.

Next time I am there I will try and take some video. Lots of flames and stuff.

That is basically correct - they use special alloys - think 4320 for the core, and carburized. Distortion can be an issue but is generally controlled by racking and control of agitation (they also use our oil for precision quenching). It is very cool to see them quenching these gears, bearings and big shafts. It is the reason why I love heat treating.

Yes - they are the gears for the windmill transmission. These are 1.5MW wind turbines - the 5MW wind turbines are larger. The diameter of the blades is typically about 6+ feer in diameter - I can stand in the middle of the blades - they are also about 90 feet long. The pod at the top of the mast is about the size of a tractor trailer. Typical quench tank size is about 40,000 gallons, with many of the quench tanks being 60,000 gallons. These pictures were taken in the US, Brazil and China. One of the problems is that there is a shortage of qualified heat treaters with knowledge of quenching and control of distortion. One thing I saw was quenching a 800T part into 1,000,000 gallons of quench oil - very impressive. The forges are amazing from the basic shaping of the billet to the actual forging of the blank. Typical weight of the hear treated gears is 25,000 pounds each. Ring rolling is used extensively for the large bearings used for yaw and pitch of the turbine blades. I have more pictures if anyone is interested. But I thought you would be interested in seeing how forging a small blade is related to larger industrial applications.