A193 B6-Ferritic or martensitic? 1

[a7992]

I have a question about the microstructure of A193 B6. It is listed as a ferritic steel under the spec. Isn't B6 410SS which has a martensitic structure? I'm confused as to why it says ferritic instead of martensitic. Does the heat treatment transform in into a ferritic structure?

 

[metengr]

This Grade is listed in ASTM A 193 as 12% Cr, AISI Type 410 stainless steel, and by carbon content is a martensitic stainless steel. The term ferritic used in the ASTM specification refers to a predominantly iron-base alloy, not ferritic as in ferritic grade of stainless steel.

 

[TVP]

Yes, B6 is the designation for a Type 410 stainless steel, which is typically referred to as a martensitic stainless steel. Notice that there is no designation in ASTM A 193 for martensitic steels, only ferritic and austenitic. This is because the final microstructure is really ferrite + fine carbides. In North America, steels that are quenched and tempered are conventionally called martensitic, because the form martensite upon quenching. However, upon tempering, this martensitic structure decomposes into ferrite + carbides, but is usually referred to as a "tempered martensite" structure. Other parts of the world still use the terms sorbite and troostite to describe the various ferrite + carbide or ferrite + cementite microstructures.

 

[stanweld]

The term ferritic is only used to differentiate from austenitic steels. Martensitic grades are not defined. B6 is only required to be tempered; not quenched and tempered. All that is required for heat treatment is a tempering treatment as defined on 7.2 of A-193 to meet the mechanical properties defined in Table 2. The microstructure may be tempered martensite.

 

[a7992]

Oh, good! I'm relieved to hear the answers. Thanks for all of the help!!