1075 won't harden

Milt,

As I understand it, McMaster Carr has two speeds of oil, one an 11-12 sec, and one a 22 sec, (Nickel ball speeds.) The true 10 series steels, and the W-1 and W-2 steels actually require either the speed of water/brine or an oil such as Parks 50, which is a 7-9 sec NB. If you have the slower McM-Carr, that could explain the very low Rc.

The quickest test of the steel itself would be to cut a small section, heat to 1500f , and quench in water.

BTW, I just bought another 5 gal Parks 50 from Maxim Oil, very reasonable, and quick delivery.

John
 
If you just took off the scale you are still in decarb, especially with all of the reheating you did. Decarb will not harden because all of the carbon has migrated out of it so of course you are going to get soft readings. You need to always allow for decarb. You shouldn't have to remove metal covered by your guard slot, as that is not something that needs to be hard at the surface, but whatever area you are testing and the blade at the cutting edge need to be ground down substantially to get to hard metal, and yes that is going to pull your edge back a bit because in addition to the edge of the edge, you have intercepting decarb zones from both sides. Can't beat the laws of physics and metallurgical chemistry, but they'll give you a beating if you let them.

-Page
 
Update-
I tried quenching a piece of this 1075 in fresh oil- same result.

Apparently, this batch of 1075 has a high Manganese content- higher than I expected. Thus the need for a very fast oil. I guess I need water or Parks 50. Water scares me! I don't swim well.

Milt
 
Milt,

Higher manganese makes it a deep hardening steel. This requires a SLOWER speed. Now there is something that has been bothering me. You said you have a desk top RC tester. Is this a rebound type tester?? If it is from my experience they are not very accurate. Especially on thinner materials. Have you tried a file test? I know it is not the end all but it will give you a good backup to your desktop tester. If you have a rc45 the file should cut really easy. I would take the recommendation of forge a sacrificial piece of the same material and quench it in water. This will tell you right away if it is actually 1075 or a mix-up. Mix-ups happen, even at the best dealers. Heck they happen at the factory, one bad bar gets put in with 10 tons of good material.

Good luck, were pulling for you.
 
Just re-read your post about the desktop tester. I see it is a penetrator type. I think you may have gotten a bad piece. I would recommend ordering a new piece and see what happens then. You might have gotten a piece of 1045 or the like. Water will make it harder but still not quite as hard as 1075. Unfortunately you might have to either make a new guard or new blade. Chalk it up to experience.
 
Milt,

Where does a person find a penetrator desk top rockwell hardness tester? How much is something like that? That sure would be handy to have.
 
Milt said:
Update-
I tried quenching a piece of this 1075 in fresh oil- same result.

Apparently, this batch of 1075 has a high Manganese content- higher than I expected. Thus the need for a very fast oil. I guess I need water or Parks 50. Water scares me! I don't swim well.

Milt
Click to expand...

Hey Milt

If you want to send me a little coupon, I'll be glad to quench it in Houghton Quench K and hardness test it.

Rob!
 
I still want to know what happens when the blade ( or a piece of the steel) is quenched in water. If it gets Rc62+ it is OK, if not...it isn't any type of 1075.
 
Thanks for all the help fellas! This is a great forum.

My oil is the 11 second quench. I have been very happy with it. It works well with 1080 and 1095. A piece of 1095 once hit RC 66 with it. Usually ends up around 62.
McMaster is great to deal with. The 5 ga. bucket came the next day! But, I am going to try the Parks 50 next time.

My tester is the import model from Enco. It was on sale for $595 and they offered free freight, so I bought it about a year or so ago.

Late last night I went after the blade. I ground a lot of metal off which I did not want to do, but I am going to consider this a good learning experience as someone mentioned. Then, I tested as close to the edge as I could get. RC61!!!!!!!!!!!!

I will try to quench a piece of the 1075 in water tonight, but I have never done anything in water except bathe and swim. Suggestions welcomed. Do I heat up the water a bit?

Thanks again to all who have helped,


Milt
 
I quenched a small piece of the 1075 in question in water this evening. Hardness was 61-62. I noticed some very minute surface cracking, but they cleaned up when grinding.


Milt
 
Milt said:
Late last night I went after the blade. I ground a lot of metal off which I did not want to do, but I am going to consider this a good learning experience as someone mentioned. Then, I tested as close to the edge as I could get. RC61!!!!!!!!!!!!

I will try to quench a piece of the 1075 in water tonight, but I have never done anything in water except bathe and swim. Suggestions welcomed. Do I heat up the water a bit?

Thanks again to all who have helped,


Milt
Click to expand...

So I'm glad it was actually 1075, aint decarb a nuisance? sorry this had to be your learning experience, but at least these days with all the info out there and forums like this, learning curves can be pretty quick. Now that you know what the deal is you can adjust for it, and your work will in the log term be better. Looking forward to seeing some great knives from you in the future.

Best of luck!

-Page
 
I have had folks ask this question with the same results as yours.

Leave enough edge and blade thickness to have some to grind off after HT and the decarb will be gone. Decarb is about Rc40-45. Martensite is about Rc-55-65 (depending on the temper).
 
Milt said:
Update-
I tried quenching a piece of this 1075 in fresh oil- same result.

Apparently, this batch of 1075 has a high Manganese content- higher than I expected. Thus the need for a very fast oil. I guess I need water or Parks 50. Water scares me! I don't swim well.

Milt
Click to expand...


If it has high manganese then hell try water. It's not as violent as some say. I use both AAA fast quench and water. Depends on what I am quenching.

The surface cracking you saw was prob just in the scale. Had a recent w2 blade scare the crap out of me when I frist looked at it but all the cracks were in the scale. Sheeewwww!
 
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