- Joined
- Apr 12, 2013
- Messages
- 562
Sorry I'm late to this...it's a favorite topic of mine. Disclaimer: I'm a hobby knifemaker and study heat treating a lot (about 20 years worth), but have only done a few torch to oil hardening blades and tools (non critical applications only) as the control and repeatability I require for high end blades is beyond such methods. I send those to professional HT shops.
Generally there is no need to both normalize and then anneal. Normalizing is a quicker way to get hard spots out (edges from plasma cutting, for example, and stresses from cold rolling) to a uniform medium soft. A full anneal will be longer and go to dead soft, possibly too soft for some working. Sagging of large sections is common in furnaces. Get some soft firebrick, cut into small strips about 1" WxH, and support the metal every few inches. Larger firebrick with slots cut in them can be used to stand the blades on end as well, which improves heating uniformity and speed.
Decarb will be an issue as every minute spent at high temp burns out some of your steel's carbon. Look into stainless tool wrap if the scaling and decarb is problematic for your purposes. Yes you can harden 10xx steels with tool wrap, but it's tricky. Leave extra on the end that you can cut off with snips right out of the furnace, and drop from the foil into your quench. Coatings are available to prevent decarb, but seem to be overkill for your current application (1045 steel). Leaving a sacrificial outer layer to be finish ground is another strategy.
Any part of your 10xx steel that takes longer than about 1 second to go from 1550F (or so, varies a bit by exact metal composition) to below about 500F will not be full hard, hence the soft core in larger sections. Study TTT curves till you understand this...
Test sections are a great learning tool. Every time you HT, add a small strip of the same steel and test it after...bend in a vise, grind, sharpen and use, etc.
Generally there is no need to both normalize and then anneal. Normalizing is a quicker way to get hard spots out (edges from plasma cutting, for example, and stresses from cold rolling) to a uniform medium soft. A full anneal will be longer and go to dead soft, possibly too soft for some working. Sagging of large sections is common in furnaces. Get some soft firebrick, cut into small strips about 1" WxH, and support the metal every few inches. Larger firebrick with slots cut in them can be used to stand the blades on end as well, which improves heating uniformity and speed.
Decarb will be an issue as every minute spent at high temp burns out some of your steel's carbon. Look into stainless tool wrap if the scaling and decarb is problematic for your purposes. Yes you can harden 10xx steels with tool wrap, but it's tricky. Leave extra on the end that you can cut off with snips right out of the furnace, and drop from the foil into your quench. Coatings are available to prevent decarb, but seem to be overkill for your current application (1045 steel). Leaving a sacrificial outer layer to be finish ground is another strategy.
Any part of your 10xx steel that takes longer than about 1 second to go from 1550F (or so, varies a bit by exact metal composition) to below about 500F will not be full hard, hence the soft core in larger sections. Study TTT curves till you understand this...
Test sections are a great learning tool. Every time you HT, add a small strip of the same steel and test it after...bend in a vise, grind, sharpen and use, etc.