measuring hardness for NACE services

[R.Eng]

Dear Experts,
Are we allowed to measure hardness of surface after finished machining of forged parts?
(The hardness is mentioned 23 HRC in Table A.18 in NACE Mr0175 Part3)
The part is Cross & Tee
Service has NACE Restrictions
Material is SS424
Manufacturing Code is API 6A

 

[SJones]

Yes - provided that the end user is satisfied with the number and location of the measurements.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[R.Eng]

Is there any codes or standards for your answer?

 

[SJones]

ISO 15156-3, subclause 6.2.1.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[R.Eng]

If hardness measurements on parent metal are specified, sufficient hardness tests shall be made to
establish the actual hardness of the CRA or other alloy being examined. Individual HRC readings exceeding
the value permitted by this part of ANSI/NACE MR0175/ISO 15156 may be considered acceptable if the
average of several readings taken within close proximity does not exceed the value permitted by this part
of ANSI/NACE MR0175/ISO 15156 and no individual reading is greater than 2 HRC above the specified
value. Equivalent requirements shall apply to other methods of hardness measurement when specified in
this part of ANSI/NACE MR0175/ISO 15156 or referenced in a manufacturing specification.
It doesn't refer to type of parent metal e.g. forged or finished part?!

 

[SJones]

Parent metal is parent metal, i.e anything other than weld metal. If the end user has any sense, they will demand acceptance measurements on the finished surface.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[jmec87]

Manufacturing Code is API 6A

The applicable requirements are in API 6A.

Per API 6A 21st Edition 10.4.2.4.1, one test per part is required if it is PSL1 or PSL2 and an additional hardness test is required on each end connector face if it is PSL3 or PSL4.

Furthermore:

Tests shall be performed at a location determined by the manufacturer's specifications and following the last heat-treatment cycle (including all stress-relieving heat-treatment cycles) and all exterior machining at the test location.

 

[R.Eng]

Thank you SJones & Jmec87
We measured hardness on finished surface after preparation and polishing the surface as per ASTM A956.
The minimum values are 290 HB. Whereas the value of witness forged sample (from impact test sample) was 226 HB. The HEAT TREATMENT of part was Quench + Double Temper.
What is the reason for this amount of value for the finished part? Is it common for SS424 ?