Carbon Manganese Steel Definition 1

[Keith Morris]

Hi all

I'm writing a sub-sea fatigue standard based on DNVGL-RP-C203. The standard states that it is valid for carbon manganese steels (C-Mn) but nowhere in any DNV standard does it define a carbon manganese steel. Does anybody know of any other standard that gives a technical definition of carbon manganese steel?


Kind Regards

Keith Morris

 

[ulyssess]

DNV-GL RULES FOR CLASSIFICATION Ships
Edition July 2019
Part 2 Materials and welding
Chapter 2 Metallic materials
Section 6 Castings
1.5 Grading system
1.5.1 The castings concerned are classified by chemical composition into three steel types: — carbon and carbon-manganese (C and C-Mn) steel — alloy steel — stainless steel.
1.5.2 Where applicable, C and C-Mn steels and alloy steels are covered by several grades designated by their specified minimum tensile strength. Stainless steels are designated by chemical composition.
Guidance note: For the purpose of this grading system, C and C-Mn steels are classified as one type and considered to be those steels in which carbon and manganese are the principal alloying elements.

A similar definition is given in Section 5 for forgings.
For rolled steel another grading system is used.
For pipes for low temperature Service, the term C-Mn-steel is used in Section 4 table 3 without any further explanation.

Generally there are definitions for unalloyed (resp. carbon steel) and alloyed steels in ISO 4948-1 or ASTM A941. In both standards Mn is limited to maximum 1,65% for unalloyed (carbon) steel. The designation C-Mn is often used for an unalloyed (carbon) steel if a certain minimum Mn-content is required, e.g. 1.00%.

 

[Keith Morris]

ulyssess

Many thanks for this information. I've already spent a considerable amount of time trying to sort this out.

I assumed that there would be an allowable range of carbon and manganese but perhaps from the DNV guidance note this isn't the case and I need not worry about it. Most of the steels we use are to EN 10025. This standard seems to only specify maximum content and manganese can be up to 1.80% for S450. I'll have a look through ISO 4948-1 and ASTM A941 but maybe these standards need not be met.

 

C steel is generally also C-Mn steel, given that it is omnipresent in some fraction of 1%. 'Carbon steel' is in the majority and it brings no confusion. When you get closer to 2% Mn you are probably into another category such as HSLA.
Any metallurgist I know is not too bothered about the distinction, but standards writers might get a bit anal about it.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."