ASTM A320 Grade B8M Stud Bolts

ASTM A320 Grade B8M Stud Bolts

ASTM A320 Grade B8M Stud Bolts

Lightning Bolt is an ISO 9001 certified fastener manufacturer for ASTM A320 Grade B8M Class 2 Stud Bolts.  In addition to many different sizes and grades of ASTM A320 Grade B8 Stud Bolts, we also carry one of the largest inventories of ASTM A194 Grade 8 & 8M stainless heavy hex nuts in North America.   Very commonly used in the assembly of industrial pipe & valves, ASTM A320 Grade B8M Stud Bolts are considered nearly identical in chemical composition to grade 316 stainless steel.  Email us your inquiries at

Many of our customers may understand that ASTM A320/A193M is a specification that covers both inch and metric series carbon alloy steel and stainless steel bolting materials.  This includes externally threaded bolts, screws, and studs.  It is intended to cover alloy and stainless steel bolting material for pressure vessels, valves, flanges, and fittings for LOW temperature service.  Bars and wire shall be hot-wrought, and the material may be further processed by center less grinding or by cold drawing.  Austentic stainless steel, which is a 300 series stainless, has austenite, which is a a metallic, non-magnetic, allotrope of iron as its primary phase.  Such alloys contain chromium, nickel (and sometimes nitrogen and molybdenum) & although they can not be thru hardened, they can be carbide solution treated or carbide solution treated & strain-hardened (which is considered “class2”).

We stock a large amount of ASTM A320 ASTM A320 Grade B8M Stud Bolts. Call or email us Lightning Bolt and Supply today, where our fastener experts can meet all of your fastener needs… Any fasteners / any material.

ASTM A320 was specially engineered for LOW temperature performance. These fasteners are commonly used for valves, flanges, fittings, and pressure vessels . ASTM A320 specifications recommend a minimum Charpy impact value all grades except for a few exclusions (listed below). The Charpy impact test determines the total amount of energy that is absorbed by a material during fracture, thereby indicating the material’s notch “toughness”. This test, also known as a pendulum fracture test, dates back to the turn of the 20th century when it was first developed by S. B. Russell and Georges Charpy, and is still used to test high grade fasteners and other products to this day.

ALL materials under A320/A320M shall be charpy tested.  However, the only exceptions where impact tests are not required are:

  • carbide solution treated or strain hardened grades B8, B8F, B8P B8M, B8T, B8LNabove -325F;
  • for carbide solution treated grades B8, B8P, B9C, and B9LN above -425F
  • Fora all ferritic and austentic steel grades of bolting 1/2″ diameter and smaller.

Heat treated conditions for the austentic stainless steels include:

  • Carbide solution treated (Class 1)
  • Carbide solution treated after finishing (Class 1A)
  • Annealed and strain-hardened (Class2)

All austentic stainless steels shall receive a carbide solution treatment which applies to each class.  Class 2 materials shall be carbide solution treated by heating for the ambient temperature and holding at a sufficient time at a temperature at which the chromium carbide will go into solution and then cooling at a rate sufficient to prevent the precipitation of the carbide.

Why Lightning Bolt ASTM A320 Grade B8M Stud Bolts?

Lightning Bolt & Supply has been servicing North America’s industrial fastener needs for over 25 years.  Since then, our focus on the production of high quality parts at competitive pricing has allowed us to become an industry leader.  Our niche in exotic high nickel alloy fasteners include materials such as: hastelloy, Inconel, monel, A-286, 904L, Alloy-20, duplex stainless as well as many additional alloys.

Being centrally headquartered in Baton Rouge, Louisiana, we are capable of shipping to jobsites all over the world.  Many of our industrial projects that we supply material to include anchor bolts, and also stud bolts of many different ASTM grades.  These include B7, L7, B16, B8, B8M, stain hardened and many more.  In addition to being an ISO certified fastener manufacturer, we were awarded “Corporate Supplier of the Year” by WBENC.


ASTM A320 B8F, B8FA, B8M, B8MA

IdentificationB8F, B8FA   B8M, B8MA 
GradeWith Added Sulfur (Type 303)With Added Selenium (Type 303 Se)With Added Sulfur (Type 303)



Tolerance +/-


Tolerance +/-


Tolerance +/-

Carbon, max0.150.01 over0.150.01 over0.080.01 over
Manganese, max2.000.04 over2.000.04 over2.000.04 over
Phosphorus, max0.200.010 over0.200.010 over0.0450.010 over
Sulfur0.15, min.0200.06, max0.010 over0.030, max0.005 over
Silicon, max1.000.05 over1.000.05 over1.000.05 over


Grade and ClassDiameterHeat TreatmentTensile Strength Min KSIYield Strength 0.2% Offset KSIElongation in 2in. Min, %Reduction of Area Min, %Hardness max
L7, L7A, L7B, L7C, L70, L71, L72, L732-1/2" and underquench and tempered1251051650
L434" and underquench and tempered1251051650
L7M2-1/2" and underquench and tempered @ 1150F, min100801850235 HB / 99HRB
L11" and underquench and tempered1251051650
CLASS 1: B8, B8C, B8M, B8P, B8F, B8T, B8LN, B8MLNALLcarbide solution treated75303050223 HB or 96 HRB
CLASS 1A: B8A, B8CA, B8MA, B8PA, B8FA, B8TA, B8LNA, B8MLNAALLcarbide solution treated75303050192 HB or 90 HRB
CLASS 2: B8, B8C, B8P, B8F, B8T3/4" and undercarbide solution treated and strain hardened1251001235321 HB or 35 HRC
over 3/4 to 1" incl115801530321 HB or 35 HRC
over 1" to 1-1/4" incl105652035321 HB or 35 HRC
over 1-1/4" to 1-1/2" incl100502845321 HB or 35 HRC
CLASS 2: B8M3/4" and undercarbide solution treated and strain hardened110951545321 HB or 35 HRC
over 3/4 to 1" incl100802045321 HB or 35 HRC
over 1" to 1-1/4" incl95652545321 HB or 35 HRC
over 1-1/4" to 1-1/2" incl90503045321 HB or 35 HRC





L7A194 Grade 4 or 7F-436
L43A194 Grade 4 or 7F-436
B8 Class 1A194 Grade 8304-SS
B8M Class 1A194 Grade 8M316-SS
B8 Class 2A194 Grade 8304-SS
B8M Class 2A194 Grade 8M316-SS

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