ASTM A437/A437M Grade B4B Bolting Specification

Stainless Steel & Alloy Steel Bolting Specially Heat Treated for Steam & Gas Turbine

ASTM A437/A437M Grade B4B Hex Bolts, Turbine Bolts, Studs, Socket Head Cap Screws, Threaded Rods, Nuts & Washers

ASTM A437/A437M Grade B4B alloy steel bolting material and bolting components are specially heat treated for high temperature service, such as steam turbine, gas turbine, and similar uses. The high-temperature properties of the bolting materials and components covered by this specification are dependent upon special heat treatment, which is required. Although the high-temperature properties are not specified, they are implied by control of the chemistry, heat treatment, and room-temperature properties of the bolting material. Three levels of bolting strength are covered, designated Grades B4B, B4C, and B4D. Hex Bolts, Turbine Bolts, Studs, Socket Head Cap Screws, Threaded Rods, Nuts & Washers can be manufactured from ¼” to 4” in imperial and M6 to M100 in metric variants both fine threads and coarse threads

ASTM A437/A437M Grade B4B Chemical requirements

Element Grades B4B
Range, % Product Variation, %
Over or Under
C 0.20-0.25 0.02
Mn 0.50-1.00 0.03
P, max 0.025 0.005 over
S, max 0.025 0.005 over
Si 0.20-0.50 0.05
Ni 0.50-1.00 0.03
Cr 11.0-12.5 0.15
Mo 0.90-1.25 0.05
V 0.20-0.30 0.03
W 0.90-1.25 0.05
Al, max  C 0.05 ...
Ti, max 0.05 ...
Sn, max 0.04 ...
  • (A) Steel to which lead has been added shall not be used.
  • (B) UNS S42200.
  • (C) Total, Soluble + Insoluble

ASTM A437/A437M Grade B4B Mechanical Properties

Hardness Requirements for Bolts and Studs

Grade Brinell Hardness Number, max
ASTM A437/A437M Grade B4B 331

Hardness Requirements for Nuts and Washers

Grade Brinell Hardness Number Rockwell Hardness Number
ASTM A437/A437M Grade B4B 293-341 C 31-37

Tensile Requirements

Grade Diameter, in. [mm] Tensile Strength, min, ksi [MPa] Yield Strength (0.2 % offset) min, ksi [MPa] Elongation in 2 in. or 50 mm, min, % Reduction of Area, min, %
ASTM A437/A437M Grade B4B ... 145 [1000] 105 [720] 13 30

ASTM A437/A437M Grade B4B Impact Test Requirements

Grade Marking Minimum Impact Value, ft·lbf [J]
ASTM A437/A437M Grade  B4B 10 [14]
  • (A) For bars over 5-in. [127-mm] diameter only. 

ASTM A437/A437M Grade B4B Heat Treatment

  • (A) Grades B4B and B4C shall be heated to a temperature range of 1875 to 1925 °F [1025 to 1050 °C] and liquid quenched to below 600 °F [316 °C]. The material Grades B4B and B4C shall then be uniformly reheated for tempering at a tempering temperature at least 100 °F [55 °C] higher than the proposed operating temperature but not less than 1150 °F [620 °C], then air or furnace cooled to room temperature. The material shall be at the tempering temperature for a minimum of 2 h. Double tempering may be used to enhance properties.
  • (B) Grade B4D shall be heated to a temperature range of 1700 to 1750 °F [925 to 954 °C] and oil quenched. The material shall then be uniformly reheated or tempered at a temperature of 1200 °F [650 °C] minimum, followed by air or furnace cooling to room temperature.
  • (C) Stress relieving treatment of the bar material is required after any stretcher, roller, or rotary-straightening or cold-finishing operations performed after heat treatment for mechanical properties. Local gagging or press straightening to correct camber limitations in excess of 1/4 in. in any 5 ft [6 mm in any 1.5 m] shall be followed by a stress relieving heat treatment. The minimum stress relieving temperature shall be 100 °F [55 °C] below the minimum tempering temperature 1875 to 1925 °F [1025 to 1050 °C] for Grades B4B and B4C or 1700 to 1750 °F [925 to 954 °C] for Grade B4D.

ASTM A437/A437M Grade B4B Bolting Surface Treatment Specifications

A153/A153M Specification for Hot Dip Galvanising (Zinc Coating) on Iron and Steel Hardware
B633 Specification for Electrodeposited Coatings of Zinc on Iron and Steel
B695 Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel
B696 Specification for Coatings of Cadmium Mechanically Deposited
B766 Specification for Electrodeposited Coatings of Cadmium
F1941/F1941M Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric
F2329/F2329M Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners

ASTM A437/A437M Grade B4B Bolting Components Marking

Product Shall be Marked with our manufacturing trade mark "TorqBolt" or "TB" along with the designated Grade.
Grade and manufacturer’s identification symbols shall be applied to one end of studs and to the heads of bolts and screws of all sizes. (If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.) For bolts and screws smaller than 1⁄4 in. [6 mm] in diameter and studs smaller than 3⁄8 in. [10 mm] in diameter and for 1⁄4 in. [6 mm] in diameter studs requiring more than a total of three symbols, the marking shall be a matter of agreement between the purchaser and the manufacturer.

Grade Grade Symbol
ASTM A437/A437M Grade B4B TB B4B

ASTM A437/A437M Grade B4B Bolting Certifications

  • EN 10204 3.1
  • EN 10204 3.2
  • PED 2014/68/EC
  • MERKBLATT AD 2000 W2/W7/W10
  • API 20 E BSL 1/ BSL 2
  • NACE MR 0175
  • NACE MR 0103

ASTM A437/A437M Grade B4B Testing Standards

E112 Test Methods for Determining Average Grain Size
A962/A962M Specification for Common Requirements for Bolting Intended for Use at Any Temperature from Cryogenic to the Creep Range

ASME Threading Specifications

ASME B1.1 Unified Inch Screw Threads (UN and UNR Thread Form)
ASME B1.3 Screw Thread Gaging System for Dimensional Acceptability - Inch Screw Threads (IN, UNR, and UNJ)
ASME B1.13M Metric Screw Threads- M Profile
ASME B1.21M Metric Screw Threads - MJ Profile
ASME B1.2 Gauges & gauging for Unified Screw Threads(Imperial)

ASTM A437/A437M Grade B4B Supplementary Requirements

S1 Non-Destructive Examination
S2 Stress Rupture Testing-Grade B4B
S3 Grain Size-Grades B4B and B4C