I had this thought with me for quite some time, that you can't use the usual formula for estimating carbon content on a Nital etched hypoeutectoid sample (DarkArea*0.77) if the steel obviously has more than around 0.6% carbon.

I am pretty sure I read that somewhere, but I can't find that, and I might have been operating in a false premise for some time now.

  • How ist it obvious that the steel has more than 0.6% carbon? As a hypoeutectoid steel, it could lie between 0.6% and around 0.8%, right? – Andrew May 23 at 4:48
  • A steel with more than 0.6% carbon will have a very dark structure under nital etching after being annealed, because of the pearlite. If you're certainly dealing with a hypoeutectoid steel, and it looks very dark under the microscope, it is usually a very good bet you're dealing with more than 0.6%C. And yes, that is the issue you have to deal with, not knowing where in the 0.6%-0.8% scale it is, as I believe the usual formula won't give you the precise carbon content. But I'm not sure why I believe that, even though I think I read it somewhere. I wanted someone to maybe point me to a source. – Walther Wennholz Johnson May 23 at 5:55

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.