W2 won't take an edge?

T

Tomaz L.

Joined
Jan 20, 2005
Messages
24
I ground several small blades from W2 and took them to heat treating this weekend. At first we tried quenching in water but it produced an edge that was too hard and very brittle, even after tempering. We switched to oil and were finally able to come up with a decently hard yet not overly brittle edge... But it turns out this edge is impossible to sharpen well by any method. I can put a sharp enough edge on it to carve soft wood fairly easily, but something is definitely wrong. It's hard to explain but the grain structure seems unusually coarse (the steel never got overheated though!). No matter how fine a grit I use I can't really get a fine edge. Is this common with W2?
 
What makes you think its W-2? If it didn't crack in water that would make me think it wasn't especially being a small blade.
 
I bought the W2 from a steel mill. It was also stamped with the correct designation. We didn't normalize the blades at first because they were ground rather than forged. We did normalize a couple to quench it again. The results were the same.
 
If you normalized and the grain structure didnt change ? Something is not right at all. The grain structure should change and I mean dramatic change from course to very fine. How are you judging when to quench ?
 
Tomaz, Im not the expert on W2 but if you will give us your exact method with the water quench I sure we can pinpoint the trouble. What do you use to heat the steel? At what temp and soak time before quench? How warm was the water before quench? Edge or full quench? Interupted quench? Tempering times and temp? Multiple tempering cycles? Ect. W2 is a water or brine quench so unless its cracks in water lets not talk about oil yet.

You came to the right forum, these boys know what theyre talking about. :)
 
No, I meant we normalized a couple of blades *after* water quench. We then quenched the same blades in oil, tempered. After heat treatment the blades still display a coarse grain structure (especially apparent on the edges) and cannot be sharpened properly.
 
Coarse structure ? you mean you broke the blade to check the texture of the fracture surface ? Give us a very detailed description of the entire process.
 
The samples were individually heated to bright red/orange, quenched in oil and tempered in an oven at 390°F for one hour. We tried several different procedures and quenchants but this turned out to work best (although the results were still poor). The quenched and tempered samples all displayed a coarse structure along the edge. So much in fact that it's pretty darn impossible to put a decent edge on it (although it's not excessively hard - you can definitely remove material with a file or stone, let alone a grinder). When some of the samples were deliberately broken the same coarse texture (light grey, beautiful uniform color) became apparent on the fractures. I will check them under a microscope later on to see what actually happened.

The guy who did the heat treatment has decades of experience (although he didn't recall ever heat treating W2 in particular). He thinks the steel is basically too hard and brittle for a knife blade. I'm curious though because I was under the impression that some knife makers were pretty fond of W2...... Am I missing something? Or did I get a really weird batch of W2 from the steel mill??
 
There's no such thing as to hard from quench, you just need to temper it at a higher temp if it's still too hard. Try doing three normalizations right before your water quench, then temper hotter then the 390F you tried.
 
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