P355NL1 - grouping

[Titirli123]

Hello.

I've made a WPQR acc. to EN ISO 15614-1 with the base material P355NL1. According to the certificate the chemical composition, mechanical properties and it's delivery status (normalization) I put the material in subgroup 1.3 according to ISO 15608.

The inspector follow CEN ISO/TR 20172 and he said that is subgroup 1.2.

Which is the primary standard that should be followed?

From my point of view the characteristics are the most important because they are influencing the weldability of the material.

Thank you!

 

[metengr]

The standard to be followed is either by client specification or the design/construction standard.

 

[DekDee]

The primary standard is ISO 15608.
See Clause 8.3.1 of EN ISO 15614-1
Cheers,
DD

 

[Titirli123]

Is the material specification relevant (if it's supplied in accordance with EN or ASME)? Does this affect the grouping of the material?

Thank you for your time and answers!

 

[metengr]

For ASME B&PV Code, the base metal grouping or classification of the material for welding is usually designated by the code committee based on chemical composition and weldability characteristics. In other words, one cannot indiscriminately assign a grouping or classification in a standard.

 

[kingnero]

Every metal can be assigned into a certain group or subgroup according to EN 15608, doesn't matter whether it is an american, japanese or european steel.

the ISO TR 20172, 20173 and 20174 are merely aids to determine the group or subgroup.

P355NL1 (werkstoffnr. 1.0566) is indeed 1.2 according to ISO TR 20172

P355NL1 (EN 10028-3) chemistry puts it in group 1.2, not 1.3. Why would you say 1.3 ? Yield is less than 360 MPa.
Only S and Mo may fall out of range, but you would have to check this on the mill test certificate.

 

[Titirli123]

The analyze of the mechanical properties showed a value of the yield strength = 372 MPa (this is for a pipe with dimensions 60.3x8.74)

It could be a mistake from the producer.

 

[kingnero]

15608 does say "specified" minimum yield strength of 360 MPa, but to be honest, I haven't encountered this situation before.
Specified could refer to either the product standard or the mill test certificate, so you could argue both ways.

 

[kingnero]

Discussion with collegues and a question on a LinkedIn forum all yielded the same result (values to be taken from the material standard), but nobody could say where this is written in ink.
I concur, but I would not back off to easily unless the inspector would show me on what grounds he imposes group 1.2
The ISO/TR 20172 is a guideline, but has its flaws as well.

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[DekDee]

Two points to consider:
1 There is no reference to ISO TR 20172 in ISO 15614.1 so the inspector cannot quote that standard.
2 A PQR qualified with sub-group 1.3 qualifies materials in sub-group 1.2 so again the inspector is showing his ignorance.

The sub-group is always taken from the material specification and P355NL1 is sub-group 1.2
Regards,
DD

 

[kingnero]

A PQR qualified with sub-group 1.3 qualifies materials in sub-group 1.2 so again the inspector is showing his ignorance.

If the OP were to perform a WPQR with a 1.3 base material, he would have a much larger approval field (all 1.3 materials), which is probably what the inspector does not want. I wouldn't link this to ignorance.

The sub-group is always taken from the material specification and P355NL1 is sub-group 1.2

ISO/TR 15608 explicitly states that the chemical analysis from the material standard is to be taken in consideration when determining the group and subgroup, but does not state where the yield strength needs to come from.

As I said above, this is with a very large probability the specified mech values from the material standard as well, but there is room for interpretation. Why does the 15608 state where the chemical analysis needs to come from, but gives no guidelines or directives which mechanical values you need to use?

http://www.fusionpoint.be

http://be.linkedin.com/in/fusionpoint

 

[DekDee]

kingnero,
In the first instance you are correct, I misunderstood the comments made. (refer reference to CEN ISO/TR 20172)
In the second instance - ISO 15608 states "specified minimum yield strengths" which can only come from the material specification.
This whole post has come because the OP mistakenly thought the Sub-group is based on the mill certificate (1.3) and not the material specification (1.2),
Cheers,
DD

 

[kingnero]

This whole post has come because the OP mistakenly thought the Sub-group is based on the mill certificate (1.3) and not the material specification (1.2)

Why would the 15608 explicitly state that the chemical analysis needs to be taken from the material standard, but does not demand the same about the mechanical values?

to specify has basically two meanings:
(1) to set forth as a specification
(2) to state as a condition

And here, the actual condition of the steel appears to be higher than the minimum requirements.

I do agree with you and the rest of the world though, that's why I said

this is with a very large probability the specified mech values from the material standard as well, but there is room for interpretation.

http://www.fusionpoint.be

http://be.linkedin.com/in/fusionpoint