ASTM A193 Grade B7 specification covers requirements for high tensile alloy steel bolting material
for use in high temperature or high-pressure service and other special purpose applications.
It is a standard specification defining typical chemical composition, mechanical properties, hardness
requirement, preferential heat treatment, product marking, certification and other requirements,
suitable for bolting used in Pressure Vessel Service, Valves, Flanges and Fittings. ASTM A193
defines both SI (Metric) and inch-pound units.
Grade B7 is a heat-treated chromium-molybdenum low-alloy steel with minimum tensile strength
requirement of 125 ksi (860 Mpa), yield 105 ksi (720 Mpa), and maximum hardness of 35HRC.
Boltport uses Alloy Steel AISI 4140 bar stock or forging stock to produce B7 headed and non-headed
bolts. A193 Grade B7 is the most commonly used Bolt specification coupled with A194 Grade
2H Nuts for Bolting Carbon Steel pipeline. A193 B7 bolting is available in metric sizes from
M6 to M180 and imperial sizes from 1/4 to 7 inches, in diameter.
Find information on ASTM A193 Grade B7 chemical composition, mechanical properties such as
tensile strength; yield strength, hardness, marking requirements and reference product standards.
0.25 Inch To 4 Inch B8M ASTM A193 Grade B7 Threaded Rod
Originally approved in 1936, this specification is heavily utilized in petroleum and chemical construction applications. The ASTM
standard covers alloy steel and stainless steel bolting materials for high temperature or high pressure service. This specification
includes fasteners intended for use in pressure vessels, valves, flanges, and fittings. Although, this material is often available in
national coarse (UNC) thread pitches, if being used in traditional applications, threads are specified 8 threads per inch (tpi) for
diameters above one inch.
Below is a basic summary of a few of the common grades. ASTM A193 covers a number of other standard specifications not
covered in this description including B5, B6, and B16.
|Standard:||ASTM A193 B7/B7m Stud Bolt Full Thread Rods WZP Carbon Steel|
|Length:||Standard or Non-standard as Request & Design|
|Surface Treament:||Black, Zinc Plated, Zinc (Yellow) Plated, H.D.G. ,Dacromet,etc.|
|Material:||Carbon Steel, Alloy Steel, Stainless Steel,etc.|
|Packing:||25 kgs per box, 36 box per pallet, 900 kgs per pallet |
|Sample:||Sample are Free|
ASTM A193 Grade B7 Chemical Composition
|Elements||Range||Product Variation, Over or Under B|
|Carbon||0.37-0.49 % D||0.02 %|
|Manganese, max||0.65-1.10 %||0.04 %|
|Phosphorus, max||0.035 %||0.005 % over|
|Sulfur, max||0.040 %||0.005 % over|
|Silicon||0.15 - 0.35 %||0.02 %|
|Chromium||0.75-1.20 %||0.05 %|
|Molybdenum||0.15-0.25 %||0.02 %|
B Product analysis - Individual determinations sometimes vary from the specified limits on ranges as
shown in the tables. The several determinations of any individual element in a heat may not vary
both above and below the specified range.
D For bar sizes over 31/2 in. [90 mm], inclusive, the carbon content may be 0.50 %, max. For the
B7M grade, a minimum carbon content of 0.28 % is permitted, provided that the required tensile
properties are met in the section sizes involved; the use of AISI 4130 or 4130H is allowed.
B7 and B7M shall be heat treated by quenching in a liquid medium and tempering. For B7M fasteners,
the final heat treatment, which may be the tempering operation if conducted at 1150 °F [620 °C] minimum,
shall be done after all machining and forming operations, including thread rolling and any type of cutting.
Surface preparation for hardness testing, nondestructive evaluation, or ultrasonic bolt tensioning is permitted.
Unless otherwise specified, material for Grade B7 may be heat-treated by the Furnace, the Induction
or the Electrical Resistance method.
ASTM A193 Grade B7 Mechanical Properties - Metric Sizes
|Diameter mm||Min Tempering Temperature, °C||Tensile Strength min, MPa||Yield strength, min, 0.2% offset, MPa||Elongation in 4D min, %||Reduction of Area, min, %||Hardness, max|
|M64 and Under||593||860||720||16||50||321 HBW or 35 HRC|
|over M64 to M100||593||795||655||16||50||321 HBW or 35 HRC|
|over M100 to M180||593||690||515||18||50||321 HBW or 35 HRC|
ASTM A193 Grade B7 Mechanical Properties - Inch Sizes
|Diameter Inch||Min Tempering Temperature, °C||Tensile Strength min, ksi||Yield strength, min, 0.2% offset, ksi||Elongation in 4D min, %||Reduction of Area, min, %||Hardness, max|
|2.5 and under||1100||125||105||16||50||321 HBW or 35 HRC|
|over 2.5 to 4||1100||115||95||16||50||321 HBW or 35 HRC|
|over 4 to 7||1100||100||75||18||50||321 HBW or 35 HRC|
ASTM A193 Grade B7 Bolt Marking
|QBH B7||"QBH" Manufacturer's Logo & "B7" Grade Marking|
|B7||Alloy steel, AISI 4140/4142 quenched and tempered|
|B8||Class 1 Stainless steel, AISI 304, carbide solution treated.|
|B8M||Class 1 Stainless steel, AISI 316, carbide solution treated.|
|B8||Class 2 Stainless steel, AISI 304, carbide solution treated, strain hardened|
|B8M||Class 2 Stainless steel, AISI 316, carbide solution treated, strain hardened|
A193 Mechanical Properties
|Grade||Size||Tensile ksi, min||Yield, ksi, min||Elong, %, min||RA % min||HBW||HRC|
|B7||Up to 2-1/2||125||105||16||50||321 max||35 max|
|2-5/8 - 4||115||95||16||50|
|4-1/8 - 7||100||75||18||50|
|B8 Class 1||All||75||30||30||50||223 max||35 max|
|B8M Class 1||All||75||30||30||50||223 max||96 max|
|B8 Class 2||Up to 3/4||125||100||12||35||321 max||35 max|
|7/8 - 1||115||80||15||35|
|1-1/8 - 1-1/4||105||65||20||35|
|1-3/8 - 1-1/2||100||50||28||45|
|B8M Class 2||Up to 3/4||110||95||15||45||321 max||35 max|
|7/8 - 1||100||80||20||45|
|1-1/8 - 1-1/4||95||65||25||45|
|1-3/8 - 1-1/2||90||50||30||45|
A193 Chemical Properties
|Element||B7 (AISI 4140)||B8 (AISI 304)||B8M (AISI 316)|
|Carbon||0.38 - 0.48%||0.08% max||0.08% max|
|Manganese||0.75 - 1.00%||2.00% max||2.00% max|
|Silicon||0.15 - 0.35%||1.00% max||1.00% max|
|Chromium||0.80 - 1.10%||18.0 - 20.0%||16.0 - 18.0%|
|Nickel|| ||8.0 - 11.0%||10.0 - 14.0%|
|Molybdenum||0.15 - 0.25%|| ||2.00 - 3.00%|
A193 Recommended Hardware
|B7||A194 Grade 2H||F436|
|B8 Class 1||A194 Grade 8||SS304|
|B8M Class 1||A194 Grade 8M||SS316|
|B8 Class 2||A194 Grade 8||SS304|
|B8M Class 2||A194 Grade 8M||SS316|
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