Peterbilt Front Leaf Springs

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DanManArk

Joined
Nov 8, 2022
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I may be in the wrong place(I've never posted before) but since this steel lends itself to high impact applications and gets acceptably hard I figured this would be the best application.

My brother recently had a leaf spring break on the front end of a Peterbilt and wondered if I could use the steel for knives. I cut a piece, heated, soaked and quenched in Parks 50. It's 3/8" thick so thinned out I'm expecting it to a touch harder but it Rockwelled at 58.

Anyhow - I'll attach the elemental composition of the steel and you can decide what you might finally do with those heavy leaf springs sitting in the corner of your shop.



https://imgur.com/a/fLyc2g3
 
I'm not a knife maker, but I'm pretty sure car & truck springs are commonly used for blades around the world.
 
SharpBits said:
I'm not a knife maker, but I'm pretty sure car & truck springs are commonly used for blades around the world.
Click to expand...
For sure - but different springs are from different steel compositions. This steel would be great for hatchets and such that don't require a super hardness for edge retention but have great impact resistance. ...I wouldn't make kitchen knives out of it. ;)
 
That carbon content would be considered a low carbon steel, and if I had to try this, I would use a faster quench, water or brine with that low of carbon to try to get some hardness.

One thing to think about is that the spring broke due to failure in the steel. That failure probably started as a micro-crack that eventually worked its way through the spring over years of use.
One reason most makers on this site tell folks not to use scrap steel is that there may be many more cracks in this used spring that might not show up until grinding or quenching (best case scenario) or when someone uses your knife or hatchet to try to pry something open (worst case scenario, especially if in an emergency).
 
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Backyard said:
That carbon content looks low. Even for a truck spring
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Looks low - IS low. ...but would still work okay for hatchets and such. Just thought the information might be helpful for some folks here that happen to have large truck leaf springs laying around and were wondering about them. Older jeeps, passenger vehicles and such often have a higher carbon content than these.
 
weo said:
That carbon content would be considered a low carbon steel, and if I had to try this, I would use a faster quench, water or brine with that low of carbon to try to get some hardness.

One thing to think about is that the spring broke due to failure in the steel. That failure probably started as a micro-crack that eventually worked its way through the spring over years of use.
One reason most makers on this site tell folks not to use scrap steel is that there may be many more cracks in this used spring that might not show up until grinding or quenching (best case scenario) or when someone uses your knife or hatchet to try to pry something open (worst case scenario, especially if in an emergency).
Click to expand...
That's why God(or someone) made magnaflux. Hahahaha I'll only be using more of the mid part of the springs where metal fatigue is less likely and I will check for cracks before I start forging/grinding.

Our metallurgist first said no brine, but water might give a better quench. Then he studied the rest of the alloy a bit more and said to use the high speed oil(Parks 50).
  • Low-carbon steel: Has a carbon content of 0.05–0.26%
  • Medium-carbon steel: Has a carbon content of 0.29–0.55%
  • High-carbon steel: Has a carbon content of 0.55–1%
  • Very high carbon steel: Has a carbon content of 1–2.10%
 
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