MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > Heat Treating and Metallurgy

Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

Reply
 
Thread Tools Display Modes
  #1  
Old 04-26-2013, 03:20 PM
Any 22 Any 22 is offline
Member
 
Join Date: Dec 2011
Posts: 13
Differential tempering question?

I like differential tempering and usually temper a straight temper line in my knives after thinking about this it looks to me this would be a stress riser, now if that would be a stress riser how could a piece of steel take a Hammon line ( I think that refers to a wavy temper line). Would any of the professionals try to explain this to me or am I just all wet in my thinkin. I know that when two pieces of pipe are welded togeather in a plant they are stress relieved because of different hardness in the weld and both sides of the pipe. Some one straighten me out Im gettn stresssed just thinkin about it.
Reply With Quote
  #2  
Old 04-26-2013, 05:23 PM
Doug Lester Doug Lester is offline
Hall of Famer
 
Join Date: Sep 2006
Location: Decatur, IL
Posts: 2,612
First of all, I think that you are mixing up differential tempering with differential hardening. Differential tempering would be hardening the whole blade and then apply heat to reduce the temper, usually in the spine. All you are doing is applying heat to an area to allow more carbon to escape from the body centered matrix of the iron crystals to relieve stress on the atomic bonds on the atomic bonds holding the crystals together. This will make the spine tougher but less strong. As in it will flex more easily but be less likely to break but the whole blade, depending on the steel, will still be martensetic.

Differential hardening allows you to quench just the edge and point areas of the blade to form martensite and allow the unquenched spine to form pearletic steel. It's the difference in the crystalline structure of the steel that causes the two sections to polish or etch differently and show a hamon or quench line. Yes, the two different size crystals will cause stress in the blade. It's that stress that can change a straight blade into a curved blade, as in the Samurai sword. The spine will, however, be less strong and more tough than a blade that had been differentially tempered from the same steel.

It's not a problem in the knife because, like the pipe welder, you will be relieving that stress when you temper the blade. If you have a problem it would probably be from delaying the tempering of the blade as might happen if one tries to harden a batch of blades one at a time then hold them at room temperature to batch them together in the tempering oven.

The main question for you is why do either. Neither technique is going to be very useful in a small blade that would not be used in chopping where the softer spine will take up some of the shock to the blade and support the harder edge. Would there be an advantage of giving up some strength in the blade for some added toughness?

Doug


__________________
If you're not making mistakes then you're not trying hard enough
Reply With Quote
Reply

Tags
apply, bee, blade, blades, edge, etch, hamon, heat, iron, knife, knives, make, polish, quenched, steel, toughness


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Differential hardening or quenching vs. differential tempering Ed Tipton Heat Treating and Metallurgy 27 04-18-2017 05:34 AM
a2 tempering question crpkoki The Newbies Arena 4 05-23-2006 11:33 PM
Differential tempering Bearman High-Performance Blades 13 03-19-2003 03:58 PM
Tempering question Josh Blount Ed Caffrey's Workshop 1 03-27-2002 12:14 PM
Differential heat treat question JohnM Ed Caffrey's Workshop 1 02-02-2002 11:09 PM


All times are GMT -5. The time now is 04:19 AM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved