Hey guys. I’ve been heat treating 1095 for a few months and at first it seemed to harden consistently for me but the past few weeks have been different. The 1095 doesn’t seem to want to harden all the way. I’m heating them up in a forge. After three normalization cycles I quench the blade in vegetable oil. The blades seem to get hard but not to the level they need to be. I broke one in half to see the grain and the grain structure was pretty big. Is it an issue in the temperature not being accurate enough in the forge or is it the oil. I’m not sure why it’s doing this and would appreciate any help. Also a side question. How long does oil usually last before it needs to be changed?
Hello Colin,
The larger grain size would indicate overheating, but would also result in deeper hardening. Canola is a vegetable based oil and being organic will break down over time, and even more so from quenching. But I would suspect the overheating is resulting in heavier decarburization. If the blade broke easily but still bit too much with a file, I would lay odds on decarb.
"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.
@kevin-r-cashen so if I bring back the heat then they should harden fine? Here is a picture of the 1095 next to a 1084 knife.
Yes, the grain is too coarse. By the way that it broke, and the larger grain, I would suspect decarb, if you are checking with a file. Less time in the fire, and lower heats will help.
"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.
Also keep an eye on the viscosity of your vegetable oil. Ideally you want a fast oil for 1095, so your vegetable oil may need to be preheated to lower the viscosity. I used to go with 120 - 140 deg. F for my canola before I switched to Parks 50 (which is fine at room temperature). This will have little effect on your grain size, but may help with hardness provided you follow Kevin's suggestions.
