0.25 Inch To 4 Inch B8M ASTM A193 Grade B7 Threaded Rod

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Model Number:A193-B7
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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.


ASTM A193 Grade B7 Specification

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.


ASTM A193 Grade B7 Chemical Composition

ElementsRangeProduct Variation, Over or Under B
Carbon0.37-0.49 % D0.02 %
Manganese, max0.65-1.10 %0.04 %
Phosphorus, max0.035 %0.005 % over
Sulfur, max0.040 %0.005 % over
Silicon0.15 - 0.35 %0.02 %
Chromium0.75-1.20 %0.05 %
Molybdenum0.15-0.25 %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.

Heat Treatment

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 mmMin Tempering Temperature, °CTensile Strength min, MPaYield strength, min, 0.2% offset, MPaElongation in 4D min, %Reduction of Area, min, %Hardness, max
M64 and Under5938607201650321 HBW or 35 HRC
over M64 to M1005937956551650321 HBW or 35 HRC
over M100 to M1805936905151850321 HBW or 35 HRC

ASTM A193 Grade B7 Mechanical Properties - Inch Sizes

Diameter InchMin Tempering Temperature, °CTensile Strength min, ksiYield strength, min, 0.2% offset, ksiElongation in 4D min, %Reduction of Area, min, %Hardness, max
2.5 and under11001251051650321 HBW or 35 HRC
over 2.5 to 41100115951650321 HBW or 35 HRC
over 4 to 71100100751850321 HBW or 35 HRC

ASTM A193 Grade B7 Bolt Marking

QBH B7"QBH" Manufacturer's Logo & "B7" Grade Marking

A193 Grades

B7Alloy steel, AISI 4140/4142 quenched and tempered
B8Class 1 Stainless steel, AISI 304, carbide solution treated.
B8MClass 1 Stainless steel, AISI 316, carbide solution treated.
B8Class 2 Stainless steel, AISI 304, carbide solution treated, strain hardened
B8MClass 2 Stainless steel, AISI 316, carbide solution treated, strain hardened

A193 Mechanical Properties

GradeSizeTensile ksi, minYield, ksi, minElong, %, minRA % minHBWHRC
B7Up to 2-1/21251051650321 max35 max
2-5/8 - 4115951650
4-1/8 - 7100751850
B8 Class 1All75303050223 max35 max
B8M Class 1All75303050223 max96 max
B8 Class 2Up to 3/41251001235321 max35 max
7/8 - 1115801535
1-1/8 - 1-1/4105652035
1-3/8 - 1-1/2100502845
B8M Class 2Up to 3/4110951545321 max35 max
7/8 - 1100802045
1-1/8 - 1-1/495652545
1-3/8 - 1-1/290503045

A193 Chemical Properties

ElementB7 (AISI 4140)B8 (AISI 304)B8M (AISI 316)
Carbon0.38 - 0.48%0.08% max0.08% max
Manganese0.75 - 1.00%2.00% max2.00% max
Phosphorus, max0.035%0.045%0.045%
Sulfur, max0.040%0.030%0.030%
Silicon0.15 - 0.35%1.00% max1.00% max
Chromium0.80 - 1.10%18.0 - 20.0%16.0 - 18.0%
Nickel8.0 - 11.0%10.0 - 14.0%
Molybdenum0.15 - 0.25%2.00 - 3.00%

A193 Recommended Hardware

Bolt GradeNutsWashers
B7A194 Grade 2HF436
B8 Class 1A194 Grade 8SS304
B8M Class 1A194 Grade 8MSS316
B8 Class 2A194 Grade 8SS304
B8M Class 2A194 Grade 8MSS316
China 0.25 Inch To 4 Inch B8M ASTM  A193 Grade B7 Threaded Rod supplier

0.25 Inch To 4 Inch B8M ASTM A193 Grade B7 Threaded Rod

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