Nuts Material Grades Compatible with ASTM A453 Gr. 660 Bolts 2

[balven]

Hi all,

For duplex stainlees steel flanged joints, we had specified ASTM A453 Gr. 660 bolts and ASTM A194 Gr. 2HM nuts (as per API 6A). However, we propose to change the nuts to a corrosion-resistant alloy (CRA) material. Can someone let me know any CRA material grades for nuts that are compatible with Gr. 660 bolts ? The main concern here is galling. Can we use nuts to A453 Gr. 660 (same grade as bolts)?

Would appreciate if you could share your experiences/observations on CRA nuts on Gr. 660 bolts.

Thanks,

Balvendra Pal

 

[boo1]

Consider indicating your service, min Tensile Strength req and temp ranges

ASTM A453 specification covers standards for Grade 660 (Class A, B, C, and D) , Grade 651 (Class A and B), Grade 662 (Class A and B), and Grade 665 (Class A and B) of bolting materials,with ten classes of yield strength ranging from 50 to 120 ksi [345 to 827 MPa], for use in high-temperature service such as fasteners, for pressure vessels and valve flanges. Bolting materials in ASTM A453 are covered rolled, forged, or hot-extruded bars, and also bolts, nuts, screws, washers, studs, and stud bolts. Grade 660 (A286, UNS S66286) has a PREN of 16.8. Grade 660 nuts used with 660 bolts will gall at a low threshold galling stress (see link).

http://www.nickelinstitute.org/~/Me...lingCharacteristicsofStainlessSteel_9006_.pdf

 

[TVP]

Excellent link provided by boo1. TABLE XII on page 25 shows two data points for A286: self-mated and A286 vs. Nitronic 60.

 

[balven]

Thanks boo1 and TVP. So as per Table XII, A286 self-mated has low threshold galling stress, which is markedly improved by using Nitronic 60 with A286. These are the only combinations mentioned in this link and all other sources I have since found. If anyone has information or experience regarding use of nuts of any other stainless steel / Nickel alloy material with Gr. 660 bolts, please share.

For example, can we use ASTM A194 Gr. 8MA (SS316) nuts with Gr. 660 bolts ? Is there data available for threshold galling stress for this material combination ? Service is non-sour, low temperature (up to 40 deg. C) and 300 lb. pressure rating.

 

[TVP]

Conventional austenitic stainless steels like 302, 304, 316, etc. will have low threshold for galling too. Your best option will be special grades like Nitronic 60. If the joint doesn't require high preload/torque, you might be able to use a more common grade together with a thread lubricant optimized for stainless steels. LOCTITE 771 Nickel Anti-Seize, Fastorq FastLUBE, and Bostik Never-Seez® are examples of suitable products.