Ferritic or Martensitic?
2

Question

Ferritic or Martensitic?

Jano6924 (Mechanical)

(OP)

16 Jul 17 17:25

For stainless steel plate specification SA-240 ASME-II part A (2015 edition) shows Table 1 with chemical composition of all grades. In this table the austenitic and duplex grades are perfectly identified. However ferritic and martensitic grades are both on same list at the end of Table 1.

I’m not a metallurgist, and I dig in the internet for hours not finding something conclusive, so my questions are:

How can we know which one is ferritic and which one is martensitic?

I think one of the clues is Chromium and Nickel content but, what are the limits on Chromium and/or Nickel content to determine which one is ferritic or martensitic?

Is it possible and acceptable to do that considering nominal composition only?

Are there any reference (document, article or book) to understand how to do that?

I hope someone can assist me with this. Thanks in advance.

metengr (Materials) · Answer 1 · 2017-07-16 18:15:19

Look closer at the chemical composition requirements in Table 1 of SA 240. The fine line between the ferritic and martensitic stainless steel containing the same chromium content is the carbon content. For example 410 is martensitic, however, 410S is ferritic. The 410 contains .08 to 0.15% carbon content, whereas, the 410S is ferritic because the carbon is 0.08% and below. Carbon increases the size of the austenite field favoring martensite formation upon quenching during heat treatment.

Quote:
Are there any reference (document, article or book) to understand how to do that?

http://www.asminternational.org/search/-/journal_c...

Jano6924 (Mechanical) · Answer 2 · 2017-07-17 16:47:38

Metengr:

Many thanks for your response, I really appreciate your help, and the book reference.

Based on your comments I see that for SA-240 grades 410, 429, 430, 434 & 436 are martensitic due to high Carbon content, remaining materials are ferritic.

One last question:

Shall I follow same rule for other stainless steel product forms such as tubing SA-268, plus other pipes, fittings and castings having similar ferritic/martensitic situation?

Best Regards.

Jano6924 (Mechanical) · Answer 3 · 2017-07-18 15:51:12

RE: Ferritic or Martensitic?

Jano6924 (Mechanical)

(OP)

18 Jul 17 15:51

Thanks again Metengr.

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Ferritic or Martensitic?
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