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

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 Supplementary Requirements