Question about carbon steel(s) and rusting

[FlaMtnBkr]

From what I can tell chromium above 12% content is what makes a steel considered stainless. I have read a lot lately about O1 and its tendancy to rust. I know all high carbon steel will rust but was wondering if some are more prone than others?

From what I can tell both O1 and 5160 have a small amount of chromium while the 10XX steel does not. Will all these types of steel be about the same when it comes to oxidation or is there another factor that comes into play. I know a hardened steel, etched steel, and steel finished to a high grit is less prone but is there anything else to consider? Thanks as always!

Ryan

 

[rlinger]

I doubt O1 rusts more easily but it tarnishes real easy. The enzymes in meat will cause it to tarnish immediately.

RL

 

[Steve Hayden]

The 12% is an oversimplified definition. To be stainless, there must be enough Cr left after the carbides are formed, to form a CrO layer on the outside of the steel that protects it from oxidizing. Most of what I have read on this say there needs to be about 10 wt% left after carbide forming to do this.

This means that it depends on the wt% of Cr, O2 and all the other carbide forming metals in the alloy.

 

[mete]

The original definition for stainless steel was 12 %.But it can be higher if some of the chromium is tied up in carbides ....I always thought rusting of steel by meat was caused by hemoglobin which contains iron.I know some who have poked a deer with the muzzle of their gun to see if it was dead and the blood rusted the steel. Maybe it's more than one thing. But don't call that rust call it PATINA !!

 

[Stacy E. Apelt - Bladesmith]

One reason O-1 gets a bad reputation is that it is often a starter steel.When smiths are learning they often overheat the steel badly in HT.This creates large grains and poor solution.That gives you islands of carbides surrounded by pools of iron(oversimplified).After we get better at forging and HT we create a sandy beach of fine grains.The iron is what rusts.Shgeo is right that it is the amount of chromium carbides and free chromium that keeps the blade from tarnishing/rusting.Blood has several things going for it to create stains and rust.1) It is slightly acidic,and when it breaks down it becomes more acidic.2) It is sticky and binds to things tightly due to the agents in it that cause clotting.3) It is a busy place,full of chemical reactions (some of which release oxygen) and enzymes that can break down all sorts of things - like knife steel.
Stacy