Differential hardening vs uniform hardening 5160

[RedWolf4]

Hi,

It seems to me there are advantages and disadvantages to both differentially heat treat and/or harden vs. uniform hardening steel. My question is, I may have access to some 5160 among other steels. This is a pre-emptive question as I do not possess these steels yet. There's a ton of info on heat treat for 5160, but I'm wondering if it can be done well and still get the full potential out of the steel with uniform hardening.

Because I saw a post somewhere a little while ago I think, (no idea which post) that mentioned how 5160 among other fairly simple carbon steels might benefit substantially (more than other steels from differential HT), and that if not it couldn't compete with uniform hardness high alloy steels like 3V or something like that. (Might not have been 3V but something like that.) Wondering if this is a valid statement.

Also, I'm aware that some makers who don't differentially harden/HT get great results out of fairly simple steels, such as 80CRV2 and stuff like that.

Wondering your opinions on this.

As always thanks for taking the time to answer, much appreciated!

 

[Stacy E. Apelt - Bladesmith]

With rare exception you are always best to fully harden the blade and if desired do a differential temper. That is done by doing the normal temper cycles and then drawing back the temper in the spine with a torch.

By fully hardening the blade first you will have a uniform grain structure and strength.

 

[Daniel Fairly Knives]

Fully harden ^^

Draw back the spine if you want that effect, it is better for the steels structure.

The one thing that is rarely mentioned is that if you only edge quench this usually sets your quench oil on fire. This is not good for safety reasons and for the life of the oil.

 

[RedWolf4]

Thanks for the replies guys, in that case would a steel like 5160 benefit from drawing back the spine with a torch more than a high alloy steel like 3V would benefit? Both would become tougher and more springy, but from what I read it seems like more of a necessity to do on simpler steels and more of an unnecessary luxury to do for complicated alloys, assuming the knife is intended for hard use. Is that true?

 

[Stacy E. Apelt - Bladesmith]

Unless the blade will be battoned there is no reason to draw back the spine. It will not affect springiness. Toughness is best set with the main temper.

 

[Larrin]

Thanks for the replies guys, in that case would a steel like 5160 benefit from drawing back the spine with a torch more than a high alloy steel like 3V would benefit? Both would become tougher and more springy, but from what I read it seems like more of a necessity to do on simpler steels and more of an unnecessary luxury to do for complicated alloys, assuming the knife is intended for hard use. Is that true?

High alloy steels like 3V have much higher tempering resistance so it is very difficult to temper the spine at a high enough temperature without also overtempering the edge.

 

[Willie71]

Thanks for the replies guys, in that case would a steel like 5160 benefit from drawing back the spine with a torch more than a high alloy steel like 3V would benefit? Both would become tougher and more springy, but from what I read it seems like more of a necessity to do on simpler steels and more of an unnecessary luxury to do for complicated alloys, assuming the knife is intended for hard use. Is that true?

If you need more toughness, 8670 is tougher, as is z-tuff. It would be pretty hard to break either of them. If you need even tougher, S7 comes to mind. We are getting out of knife steels at that point.