multiple quench question

[neil g]

does anybody know if you can quench a blade more than once. I made a katana out of 1045 steel and quenched it in gunters super quench. I made a bowie the same way and the hamon turned out good. the quenchant was at the same temp as it was for the bowie and i heated them both up to past megnetic before quenching. I know people are saying why are you using 1045 when you could be using 1080 or 1095. I just wanted to see what it would turn out like. Any info would be greatly appreciated. I also scraped the clay off of the back of both blades , i cautious of cracking using super quench on 1045 and cracking.

 

[Stacy E. Apelt - Bladesmith]

Not exactly sure what the question is,but here goes.
1) You can quench a blade many times if you are referring to the full HT. Each time erases the hardness and hamon developed in the last quench. The grain gets finer each time,so there is some benefit to a triple quench. The pattern and hardness are the result of the final quench and the subsequent tempering.
2) You can quench a blade twice in an interrupted quench.This is often done on katanas. Plunge the blade in for 2-3 seconds,pull out for 2-3 seconds, plunge in again. This develops the sori to the maximum.Some say the hamon is more distinct this way,too.

There is nothing wrong with a katana made from 1045.It will be a bit softer than a 1080/84 blade,but it will be less likely to crack.The amount of martensite you get is a function of the amount of available carbon,so .45 is about the floor for a working blade.If the bowie is mostly for looks it will be a good knife.It won't be a great chopper,though.Super quench is the right media for a low to mid carbon steel.

Scraping the clay off the spine helps control the sori,which can cause cracking in some cases.I don't do it because I want the structure of the spine to be fine pearlite.
Stacy

 

[neil g]

thank you very much for the explanation, back to the shop now to fix it.

 

[deker]

1) You can quench a blade many times if you are referring to the full HT. Each time erases the hardness and hamon developed in the last quench. The grain gets finer each time,so there is some benefit to a triple quench. The pattern and hardness are the result of the final quench and the subsequent tempering.

Just a question about this Stacy. Wouldn't the grain size be more of a function of proper temperature and adequite soak time? My understanding was that once the steel is heated to critical the carbides begin to go into solution and if overheated grain growth occurs. Is the purpose of multiple quenches to ensure that all of the carbides are brought into solution? If so, wouldn't it be more effective to simply soak at a proper temp. for long enough for the carbides to be fully in solution?

Just trying to understand

-d

 

[Phillip Patton]

I don't think 1045 will have residual carbides. It doesn't even have enough carbon to make 100% martensite.
Someone please correct me if I'm wrong.

 

[Stacy E. Apelt - Bladesmith]

Phil and Deker,
Yes there is not enough carbon in 1045 to make it a worry about grain size or needing multiple quenches.
The answer was more on quenching in general. Multiple quenches done at the proper temperature allow for fine grain size.Any longer grains left by forging temps will be broken up and made smaller. If the time and temperature are not excessive the shorter grains won't get longer, so there can only be a benefit.
The thing to decide is if the multiple quench will actually gain anything in the first place (which it won't with 1045).
The best methodology is to apply all the best HT techniques to the steel. Properly anneal and spheroidize when forging. Normalize several times prior to HT quench.HT at the exact target temp. and for the proper time for the steel and thickness of the blade.Use the proper quenchant for the steel type.Temper twice at the proper temp,cooling fully to room temp between cycles.This will make the best blade possible.
mete will give a better answer.
Stacy

 

[deker]

Phil and Deker,
Yes there is not enough carbon in 1045 to make it a worry about grain size or needing multiple quenches.

*nod* I wasn't specifically referring to the 1045 in question, I'm more trying to figure out the general benefits of multiple quenching. I've had a few conversations about it lately, and some arguments I've heard just don't make sense to me.

The answer was more on quenching in general. Multiple quenches done at the proper temperature allow for fine grain size.Any longer grains left by forging temps will be broken up and made smaller. If the time and temperature are not excessive the shorter grains won't get longer, so there can only be a benefit.
The thing to decide is if the multiple quench will actually gain anything in the first place (which it won't with 1045).

So, is there some action that takes place with the repeated quench that serves to "break up" the larger grains developed in forging? This is the part that doesn't make sense to me I guess.

The best methodology is to apply all the best HT techniques to the steel. Properly anneal and spheroidize when forging. Normalize several times prior to HT quench.HT at the exact target temp. and for the proper time for the steel and thickness of the blade.Use the proper quenchant for the steel type.Temper twice at the proper temp,cooling fully to room temp between cycles.This will make the best blade possible.
mete will give a better answer.

That's generally the strategy I take, I'm just trying to make certain I understand WHY it works

-d

 

[Kevin R. Cashen]

1045 will not have excess carbides to worry about but it will have proeuctectoid ferrite (extra ferrite) to dissolve so while you won't have the same requirements in soak time for getting carbides, you will have some more austenitizing to get that ferrite into solution, this is why the iron-carbon equilibrium diagram (for steel) is shaped like a big "V" with the eutectoid (.8% carbon) being in the middle.

There should be no large or elongated grains from forging if one has done the process properly not to fall short of or exceeded the rate of recrystalization, and if they did - that is what normalizing is for.

Repeated cycling will refine grain, but once again that is what normalizing is all about. Refining grain is one thing, putting carbon into solution and refining carbides is another, and if one spends too much time heating and not enough time soaking, although there will be fine grains, there will also be large carbides and segregation, but then a lot of that is not as relevent with 1045. Cycling around and below Ac1 will tend to take carbon out of solution, heating closer to Acm (or in this case Ac3, due to that ferrite) will tend to put carbon, and ferrite, into solution. This is one of the biggest shortcomings of magic bullet recipes, steel is just too complex to obey our wishes for a magic cure all

So setting miraculous secret quenching techniques aside, 1045 is pretty simple stuff and I would say have a go at just doing it over to see if you can nail it better the next time with your only concern being a real buggaboo everytime you start unecesarrily heating the steel above critical- decarb There is scant carbon there to begin with in 1045 so I would be very careful not to lose any more than I had to.

 

[Stacy E. Apelt - Bladesmith]

Thanks,Kevin. I knew you or mete would have better technical info.
Main point - Done properly,even a minimum steel can produce a workable blade.Done wrong, even the best steel can produce a poor blade.Learning the metallurgy and HT requirements of the steel you are using is the key to getting the most out of the steel.
Stacy

 

[deker]

Thanks for the answer Kevin. I suppose I was not taking into account both carbide solution and grain growth as seperate events. (Or I'm just confused and trying to swim rather than sink in understanding the little teensy bits of metalurgy that I'm attempting to grasp )

-d

 

[Larrin]

Verhoeven talks about thermal cycling which is similar to a multiple quench: http://mse.iastate.edu/fileadmin/www.mse.iastate.edu/static/files/verhoeven/7-5.pdf He even lists grain size for 1045. The main difference is that with your continued quenching has shorter hold times (4 min.) at a lower temperature (1450F).

Kevin, or whoever knows, how do you calculate what time or temperature to use when thermal cycling? Does this lower temperature prevent duplex grain in air hardening steels? You get a duplex grain when you austenitize an air hardening steel twice.