[MW:6088] NACE recommendation on Bolts & Nuts Material]

Hi Vineeth,

 

MR 175 accepts  ASTM A 193 grade B7M, for bolts and ASTM A 194 grades 2HM,7M for nuts. The hardness limit is  HRC 22 (235HB /247VHN). Also Carbon and low alloy steels must  contain less than 1 % nickel (which all these grades meet)

 

As per SA -193, B7/7M bolts can meet  the following mechanical requiremenst , when properly heat treated:

 

 

 

 

For SA -194 nuts, the required hardnesses are :-

 

 

 

If you look at the specs SA 193,194, ther are not much choices for  LAS materials  for bolts and nuts. Some grades such B-16 are very difficult to meet the specification requirements, UTS and hardness are very high not at all good for sour services

.

B7/7M,i.e Cr-Mo grades can generate very good mechnaical properties (see above) if properly heat- treated. That's the rationale for MR-175 to accept these materials for sour services.

 

 

Thanks.

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

 

---------------------------- Original Message ----------------------------

Subject: [MW:6081] NACE recommendation on Bolts & Nuts Material

From:    "Vineeth Thomas" <vtr.mech@gmail.com>

Date:    Thu, July 22, 2010 10:29 am

To:      "Materials & Welding" <materials-welding@googlegroups.com>

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Dear Sir,

 

Can anybody tell me why NACE recommends ASTM A193 Gr.B7M & ASTM A 194  2HM for Bolts & Nuts since it is not at all coming in contact with

well fluid. Then why this requirement?

 

Thanks & Regards

 

Vineeth Thomas

Piping Engineer

 

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