Material Grade AISI 4130

[metboss]

Hi All

The required material grade for Wellhead equipment is AISI 4130 with NACE MR-0175 compliance or material class API 6A EE (carbon or low alloy steel with NACE MR-0175 compliance) whereas vendor supplied the item with material grade AFNOR 30CD4.

My questions are as follow:

• Is material grade 30CD4 equivalent to AISI 4130 ? I’ve reviewed specs for both grade and found to be closely matching.
• Upon review of NACE MR-0175, it’s been noted that 30CD4 is not listed in it. I sent the same query to vendor and they’ve submitted their material specs which reads as 30CD4 is compatible with H2S service. Can we accept this ?

Appreciate your feedback.

 

[yudhichen]

As far as I know,

API 6A doesn't mention that material for wellhead equipment need to be AISI 4130 for EE-NL class.
What API limit is steel composition (Table 9) which lead to mechanical properties (Table 6).
I've never come across with AFNOR material grade.
My opinion, given those AFNOR specs comply with all material constraint (i.e. Table 6 & 9) in API, then AFNOR 30CD4 might be acceptable.

for NACE constraint, NACE limit low alloy steel based on hardness (max 22HRC).
I think NACE gives us freedom to choose material (I believe its not necessary for NACE to mention all specs that comply with them as assurance).
Same comment, given the hardness comply, then it might be acceptable
unless there's another constraint that forbid us to challenge it, eg: client requirement that mention 4130 in exact or wellhead manufacturer material specs.

 

[metboss]

Thanks for your feedback Yudhichen.