Sigma Fasteners

Manufacture and Distribute Fasteners for Energy

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Sigma Fasteners

B7M Bolts

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ASTM A193 Grade B7M Bolt

B7M Stud Bolts
B7M Studs

Bolt Description:

B7M bolts for High Temperature and/or High Pressure service are modified in our tempering furnace to meet the ASTM A193 /A193M  –  B7M standard for bolting covering both metric and inch bolting products. The A193 B7M standard covers threaded rod, bolts, studs, and stud bolts.  In accord with the A193 standard the final modification is the tempering at 1150° F minimum performed after all machining, roll threading and any type of cutting. The tempering furnace recording chart is kept on record with your order maintaining complete traceability of your final product. Tensile and 100% hardness records are also available and kept with your order.

Typical Usage:

Typical use for B7M bolting includes sour gas service where Hydrogen Sulfide gas exposure may lead to Hydrogen embrittlement problems in hard alloys.

Product marking:

All B7M bolting which has been 100% hardness tested must be marked B7M and will have the Sigma Trademarked S for manufacturer’s identification.

Testing:

B7M bolts are 100% indentation hardness tested to ensure conformance to the standard. Tensile Tests are performed after tempering.

Nuts:

ASTM A194 2HM heavy hex nuts are most commonly used with ASTM A193 B7M bolts.

Catalog: Stud Bolts Heavy Hex Bolts

Stainless Bolts

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304 Stainless Bolts – ASTM A193 Grade 8 Bolts

Grade 304 Bolting is the standard “18/8” stainless; it is the most versatile and most widely used stainless steel bolting, available in a wide range of bolting products.

Corrosion Resistance

Stainless Bolts are excellent in a wide range of atmospheric environments and many corrosive media. Stainless bolts are subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Commercial Stainless bolts are considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures.

Heat Resistance

304 Stainless bolts have good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. 304 stainless bolting in continuous at the 425-860°C range is not recommended if subsequent corrosion resistance is important.

316 Stainless Bolts – ASTM A193 Grade 8M

The grade 316 stainless bolt is the standard molybdenum-bearing grade, above the corrosion resistance of 304 bolts within the austenitic stainless steels. The molybdenum gives 316 stainless bolts better overall corrosion resistant properties than Grade 304 bolting, particularly higher resistance to pitting and crevice corrosion in chloride environments.

Corrosion Resistance

316 Grade 8M bolts are excellent in a wide range of atmospheric environments and corrosive media and are generally more resistant than 304. 316 Grade 8M bolts are subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Grad 8M bolts are considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures.

316 is usually regarded as the standard “marine grade stainless steel bolting”, but it is not entirely resistant to sea water. In many marine environments at elevated temperatures 316 bolting does exhibit surface corrosion, usually visible as brown staining.

Heat Resistance

Grade 8M bolts exhibit good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 316 bolts in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important.

Moly Coatings

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Moly Coatings – Molybdenum Disulfide Coatings

Moly coatings are molybdenum disulfide lubricant combuined high performance resins. The coating is thermally cured to bond to the coated part. Molybdenum disulfide coatings are used to improve the lubricity of a mating parts in extreme load conditions to reduce the coefficient of friction. The coating provides lubrication in many cases exceeding 250,000 psi. Moly coatings lubricate by transferring lubricant between the two mating surfaces, this reduces both wear and achieves the lower coefficient of friction.

Typical Applications:

Moly coated slide gates, Threaded fasteners, Moly coated bolts and moly coated studs.

Sigma Applies Coating manufactured by Everlube® Products  Everlube, Lube-Lok, Ecoalube, Ever-Slik