Ferritic & martensitic steels: please help me to understand. . .
Ferritic & martensitic steels: please help me to understand. . .
(OP)
Hi there,
This is so stupid that is going to be embarassing.
I am trying to figure out when a steel is martensitic, or ferritic, or more precisely, when I want a particular final structure from a certain chemical composition.
I am aware of the two main families of elements that, added to the iron, change its behaviour:
- Ferritizing elements: Al, Fo, Si, V, Mo, W, Cr, C
- Austenitizing elements: Ma, Ni, Co.
Therefore, we can take two materials in our example: 1Cr 0.5Mo and 12Cr-1Mo-V.
The first one is ferritic, the second one is martensitic.
Now, my question would be: when the transition from Ferritic to Martensitic happens ? What is the percentage of elements that would let me guess that I want a martensitic structure at the end of the transformation (or, that in case of welding, would ring the bell "Hey, cool down to 100 Celsius before the PWHT to allow the martensitic transformation") ?
It's a stupid and awfully worded question, and I do apologize for that.
In other words: I have to study those 5, 10 , 20 materials I will be delaing with on regular basis (and that would cover 99% of my needs), knowing which-one-is-what (and that's fine); os is there a way to say that, once I have a certain percentage of X Y Z elements, I will be looking for a martensitic structure (plain words - I not taking into consideration at this stage the cooling rate).
Thank you in advance!
This is so stupid that is going to be embarassing.
I am trying to figure out when a steel is martensitic, or ferritic, or more precisely, when I want a particular final structure from a certain chemical composition.
I am aware of the two main families of elements that, added to the iron, change its behaviour:
- Ferritizing elements: Al, Fo, Si, V, Mo, W, Cr, C
- Austenitizing elements: Ma, Ni, Co.
Therefore, we can take two materials in our example: 1Cr 0.5Mo and 12Cr-1Mo-V.
The first one is ferritic, the second one is martensitic.
Now, my question would be: when the transition from Ferritic to Martensitic happens ? What is the percentage of elements that would let me guess that I want a martensitic structure at the end of the transformation (or, that in case of welding, would ring the bell "Hey, cool down to 100 Celsius before the PWHT to allow the martensitic transformation") ?
It's a stupid and awfully worded question, and I do apologize for that.
In other words: I have to study those 5, 10 , 20 materials I will be delaing with on regular basis (and that would cover 99% of my needs), knowing which-one-is-what (and that's fine); os is there a way to say that, once I have a certain percentage of X Y Z elements, I will be looking for a martensitic structure (plain words - I not taking into consideration at this stage the cooling rate).
Thank you in advance!





RE: Ferritic & martensitic steels: please help me to understand. . .
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RE: Ferritic & martensitic steels: please help me to understand. . .
RE: Ferritic & martensitic steels: please help me to understand. . .
http://www.asminternational.org/materials-resource...
RE: Ferritic & martensitic steels: please help me to understand. . .
C is an austenite stabilizer, as is N.
You can make 12Cr-1Mo with low enough C so that it won't form any martensite.
Look at 410S and 410 as an example.
Once you add carbon to an iron based alloy it is martensitic, but how much martensite forms and what the structure looks like depends on both composition and thermo-mechanical history.
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P.E. Metallurgy, Plymouth Tube
RE: Ferritic & martensitic steels: please help me to understand. . .
Thank you so much for all your inputs. Much appreciated, and I do apologize again for the overly ignorant question.
A few clarificaitons, though.
I am not talking about stainless steels. Mainly, my concerns are steels for power industry (e.g. P2; P 5; P9; P91; P11; P12; P21, P22; X12 CrMoV5).
On general basis, depending on the chemical composition and the cooling rate, you can obtain different structures, or you have to do mandatorily the PWHT. Again, just an example, you want to do the PWHT in P22, as well as in X12CrMoV5. But, in the second one, you have to make sure to cool down below 100 Celsius first, to allow a complete martensitic transformation, before the PWHT (this from the pressure equipment code I am using).
Therefore: is there a general rule of thumb to say "yes, if you have this chem composition you have to do this, this, and that to achieve the desired structure"; do I just have to memorize 10/20 grandes of the most common steels (which is fine) and their behaviour, desired final structure, limits, etc, or what ?
Thanks again.
RE: Ferritic & martensitic steels: please help me to understand. . .
RE: Ferritic & martensitic steels: please help me to understand. . .
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P.E. Metallurgy, Plymouth Tube