does forging too cold create "stresses?"

#21
I'm not sure what is being referred to the images, but the tangs were forged too cold due to the "I" beam type cross section. This happens with every single new forging student I have seen. I have a soapstone test that I use in my classes where I swipe the flat of the stone down the side of students blades and if the blade has a white outline they need to get the steel hotter and flatten the work out better. But this is not necessarily bad for the steel, it just makes for a bad forging. If over-done it can lead to black stress lines running down the center of the forging.
 

soundmind

Well-Known Member
#22
Excellent. I posted late last night and didn't play with photoshop to highlight the areas on the blades I was referring to. But I understand and this is a simple issue to correct.

As a beginner, I'm having better success forging 3/4 round stock - this 1.5" flat bar is a different story. Might be just an issue of quardination and getting a heavier hammer. ....and heat
Thanks Kevin
 

soundmind

Well-Known Member
#23
These lines in the tang are going away as I grind. But not the ones around the tip. I might remove material from around the tip and change the profile. Looks better that way anyway. I wanted to show a picture, but my internet won't upload. You might be able to tell what I mean from the picture above.

Had a couple questions come to mind as to why this would happen and if this steel is still any good for a knife.

Did normalizing reset the internal structure of the steel so that the damage (or hopefully only potential damage) was stopped? Or could the outside of the steel have cooled faster than the inside: so the steel overlapped only on the edges and not in the center and isn't damaged?

I might not be making any sense - just trying to think it through.
 

scott.livesey

Dealer - Purveyor
#24
i worked in a forging plant(front axle parts for ford honda and toyota) for several years. fine cracks were a symptom that steel was too cool or coolling was too high. maybe you can grind out cracks, maybe not. do you use a thermometer to tell you steel temp? just going by color is hit and miss.
 

soundmind

Well-Known Member
#25
maybe you can grind out cracks, maybe not. do you use a thermometer to tell you steel temp? just going by color is hit and miss.
I was measuring temp, but just installed my thermocouple the same day I was using this steel. It was also my first time using bar stock and a steel I bought and thought it was going to forge as easy as the spring steel I experimented with previously. I didn't even think to check out the correct forging temps for this new steel. I know them now though. Now that I think about it, I remember trying again after I did know the correct forging temp and still had a hard time. Anyway, thanks Scott, I'll be experimenting with your HT recipe.

Some of the cracks are going away at 80 grit and files but not all of them. In light of what Ed was saying about cracks showing up during the hand sanding stage, I'm going to be watching to see if they come back as I go up in grit. I 'll check again after HT and try to bend the knives in those areas. That's about the best I cn think for testing them to know if they're still any good.
 
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