role of Mn in sour service 2

[lahane1443]

in one of the project requirement customer has given a specific chemical requirement for A333 Gr 6 pipe such as C< 0.21;Mn<1.1;S< 0.01;CE< 0.41.
Now we have submitted a TC in which only Mn is 1.29 other elements were well below requirement.specially S was 0.006 & i geuss S element is most imp in sour application.
Customer now not accepting the deviation in Mn & they say that it is not acceptable in sour service.
I want to know the impact of Mn in sour service?
as per my perception S is the only contributing factor in sour service.

 

[metengr]

What is the revised carbon equivalent (CE) for your material with the elevated Mn content? Mn plays a role in CE.

 

[lahane1443]

CE is 0.367 with Mn as 1.25 %.
I guess such low CE is acceptable to sour.

 

[lahane1443]

actually there 3 to 4 heats in all case CE is less than 0.37 with Mn% varing from 1.20 to 1.29.

 

[metengr]

lahane1443;
If this is the case, I don't see how the additional Mn is going to affect performance in service. You still have the customer’s specification requirements, and if I were you I would try to convince the customer that the slightly higher mass % content of Mn will not affect performance based on calculated CE values for comparison.
It will still be up to the customer to decide - that is business.

 

[blacksmith37]

S and Mn have only small indirect affect on steels in sour service. In mediocre steels with "high" S and Mn you can expect stringers / laminations which promote blistering and HIC /step cracking. Mn also increases hardenability (CE) , which will increase hardness of weld zones.

 

[stanweld]

Iahane1443,
Did you not provide the Customer's requirements with the P.O.? Why have you accepted pipe not meeting those requirements?
It is noted that higher %Mn is normally required to meet the -50 F impact toughness for A333 Gr6 depending on thickness.

The critical factor is whether this material will meet the hardness requirements in the HAZ and any cracking testing requirements, which it can.

 

[lahane1443]

thickness of pipe is 15 mm. Unfortunately we receive the order so late by the time said material was sold by the supplier to other purchaser.Now when we turn up to supplier he is offering us above material.
we will be carring PWHT for all the weld joint to control the hardness.
Will this help us stanweld?

 

[stanweld]

Yes, PWHT will assure meeting the Sour Service hardness requirements. We commonly used similar A333-Gr6 pipe in Sour Service with and without PWHT since the mid to late 1970's.