440c heatreat

[balibalistic]

I just recieved my oven last night.and am seeking some info from you pro's if you could?i've done plenty of research but cant get a solid opinionj on heatreating 440c.

admiral recommends a 5 min soak at 1850-1950,then single temper at 500 fo4r r/c of 57. others recommend a longer soak (25 min) then double temper at 350 for two hours.

Whats your opinions on this?the reason i ask is i'd like to get my oven programmed properly to start.i'm 100% new to heatreat. appreciate any input.

 

[knarfeng]

Here is the Carpenter Technologies web page for 440C, including their heat treat recommendation :

http://www.cartech.com/common/frame...ftn=our_products&lefto=nav_tlo&lefti=nav_tlo2

 

[J.D.]

I would'nt call myself a pro. But this is how I do 440C, heat to 1880 degrees f hold for 8 minutes, plate quench in the foil with a fan blowing across the plates, then temper for 2 hrs. at 350, let it cool down slowly and repeat for another 2 hrs.at 350. Some do a cryo. treatment, but I have not done that and have had good results.

 

[mete]

As the carbides are for the most part chromium carbides I think ~ 10 minute soak is enough. Plate quench is very convenient. The 300-350 F is for max hardness .Does anyone have experience with tempering temperature vs chipping ??

 

[balibalistic]

I would'nt call myself a pro. But this is how I do 440C, heat to 1880 degrees f hold for 8 minutes, plate quench in the foil with a fan blowing across the plates, then temper for 2 hrs. at 350, let it cool down slowly and repeat for another 2 hrs.at 350. Some do a cryo. treatment, but I have not done that and have had good results.

And what hardness are you getting with this method? i dont have a tester yet,so i'll be playing the guessing game for a while

 

[J.D.]

balibalistic, I don't have a tester either, so I am just guessing also. I know they are hard and hold an edge well as we used one this deer season on field dressing several deer with just a touch up on a diamond stone, did not cut the pelvis bone but did go up the chest bone with no chips or edge rolling over. I need a RC tester.

 

[balibalistic]

Thank you sir!! i will give your method a shot..,along with a couple others

 

[J.D.]

you welcome, you might check out Evenheat.com, they have heat treat temps and procedures on their site for 440C and other steels, also estimated RC.

 

[RJ Martin]

I'd recommend 1875 for 30-35 minutes, plate quench in foil w/o a fan.

Double temper @ 350 to 375F for Rc of about 57.

The longer soak is never a problem if your furnace is accurate and the blade is in foil, and there is a greater risk of problems from undersoaking than oversoaking.

BTW, the data ia gave you is from the Crucible steel handbook.

 

[Rob!]

BTW, the data ia gave you is from the Crucible steel handbook.

The what???

I have the 440C datasheet from Crucible. There's a handbook too????

Rob!

 

[balibalistic]

I'd recommend 1875 for 30-35 minutes, plate quench in foil w/o a fan.

Double temper @ 350 to 375F for Rc of about 57.

The longer soak is never a problem if your furnace is accurate and the blade is in foil, and there is a greater risk of problems from undersoaking than oversoaking.

BTW, the data ia gave you is from the Crucible steel handbook.

Thanks! will give it a try.undersoaking was also a concern..,i figured i'd try a couple methods then have a friend check hardness for me of each.

i've test fired my programs,and oven will hold with in a few degree's + or -.how much does temp fluctuate on average?my tempering program is set at 375 for 2 hours..,it sits between 371 and 379 for first few minuts,then balances out and fluctuates only a couple degrees.same with heatreat process!

thanks again for input guys!

 

[mete]

Soaking - Time to explain this again ! Starting out with annealed steel the matrix is primarily iron and the carbon is in the spherical carbides [normal structure]. We want to dissolve the carbides and diffuse the carbon throughout the matrix and saturate the matrix with the carbon.With the high carbon grades you'll always have some carbides that are un- dissolved. Unless this is done you won't get the maximum properties. Each carbide forming element bonds with carbon differently. The weaker the bond the easier to dissolve. Weakest bond is Fe, followed by Cr and the tightest bonds are V, Mo, W. D-2 ,mostly Cr carbides, requires less soak time than an alloy high in V,Mo,or W, such as S30V. Grain growth is far more effected by excessive temperature than by time. I know RJ will hold his temperature precisely I hope the rest of you do the same !!! There is a balance for properties for the temperatures listed [1850-1950 F] , temperature vs time vs grain size and other properties.Something you should experimant with. Also some of the data from the steel makers is for a 1" or larger section .