machete from pressure vessel steel

[chuck 1]

 Making a machete with a unique design. The guy at the welding shop turned me on to some stuff he said they make pressure vessels out of. being as that i am kind of new at the knifemaking game and can't find a reasonably priced knifemaking steel plates

  It tempered out pretty well it is seriously springy and tough. I am a pretty big guy but cannot bend it more than a half an inch "handle, blade will not bend at all" without it snapping back into place. like i said tough  XXXXXX  but can't seem to get a really good edge on it. Then again i was never one to really pull a scary edge on a knife. i mean it can cut paper with no problem but i can't get it shaving sharp plus the edge can only achieve a grainy sharpness nothing more. Can anyone tell me where i am going wrong??  or where i can buy reasonably priced knifemaking steel plate without ordering something from china which i don't want do. preferably 12x24 inch to make these out of??

  If anyone here would like. i can repeat the process in a small blade and send to them to test. if interested. really would appreciate some input

[Steve Sells]

Pressure vessels are not known for using high carbon steels, sorry but nothing can get it a good edge.  Stating it tempered well is just about meaningless. To temper: a metal just sets in an oven a while.  Tempering does nothings unless you harden it first, and some steels do not harden.   What steel to use, and what to look for in steel, as well as why is explained in the knife making classes as well as supplier list for buying steel.

[Charlotte]

Obviously we have no accurate notion of what your alloy is.   Gas cylinders are made of an alloy which is referred to as chrome/molly steel.  Its whole purpose is not to work harden and to hold together under the worst sort of abuse. In general it is possible for one to explode by tearing apart like a steel balloon.  I have see examples of them being shot with armor piercing bullets without exploding.  Picture a 5 ft tall steel cylinder with entrance and exit holes and still in one piece.

All this is to tell you that pressure vessels are very different than knife steels.  When the start to stiffen up they are cut up and sold for scrap.    

[BIGGUNDOCTOR]

For a machete you may be OK since they are a rough chopping blade. For that application toughness may be a good thing if a rock, or other hard object is accidently hit.

For a knife, or other blade that needs to hold a keen edge you need to use steels that you know the specs, especially carbon content. Search for tool steel, once you know which alloy you want to use for a particular application.

There is a big difference between hard, and tough. Hard holds a good edge bit may be brittle. Tough won't hold a good edge, but won't snap when bent, or impacted.

Take some time, and start reading through the stickies in the knife forum.

[Crazy Ivan]

I used to work in a shop welding autoclaves which are pressure vessels. The steels we used were 316L 304L and 51670. I'm guessing you have 51670 boiler plate steel. 

[Crazy Ivan]

[chuck 1]

thanks for the comp page. i managed to drop by the welder's house earlier and the steel is 51670.  I suppose for a machete this stuff is really excellent. it can split a coconut with no effort, stabbed through a car door with little to no point deformation. and although nothing is indestructible it is extremely tough. Not too bad for a heavy thrower either.