ASTM A437 Specification

This specification covers stainless and alloy-steel bolting specially heat treated for high-temperature service, such as steam turbine, gas turbine, and similar uses. See Specification A962/A962M for the definition of bolting. This material requires special processing and should not be used in generalpurpose applications. Bolting furnished as bars shall be hot wrought and may be further processed by centerless grinding or by cold drawing. The high-temperature properties of the bolting 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 material. Three levels of bolting strength are covered, designated Grades B4B, B4C, and B4D.

Chemical Composition

Element Grades B4B, B4CB Grade B4D
Range, % Product Variation, %, Over or Under Range, % Product Variation, %, Over or Under
Carbon 0.20–0.25 0.02 0.36–0.44 0.02
Manganese 0.50–1.00 0.03 0.45–0.70 0.03
Phosphorus, max 0.025 0.005 over 0.04 0.005 over
Sulfur, max 0.025 0.005 over 0.04 0.005 over
Silicon 0.20–0.50 0.05 0.20–0.35 0.02
Nickel 0.50–1.00 0.03 ... ...
Chromium 11.0–12.5 0.15 0.80–1.15 0.05
Molybdenum 0.90–1.25 0.05 0.50–0.65 0.03
Vanadium 0.20–0.30 0.03 0.25–0.35 0.03
Tungsten 0.90–1.25 0.05 ... ...
Aluminum, maxC 0.05 ... 0.015 ...
Titanium, max 0.05 ... ... ...
Tin, max 0.04 ... ... ...
Note:

A. Steel to which lead has been added shall not be used.
B. UNS S42200.
C. Total, Soluble + Insoluble.

Mechanical Properties

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, %
B4B ... 145 [1000] 105 [720] 13 30
B4C ... 115 [790] 85 [585] 18 50
B4D 21⁄2 [65] and under 125 [860] 105 [720] 18 50
  over 21⁄2 to 4 [65 to 100] 110 [760] 95 [655] 17 45
  over 4 to 7 [100 to 180] 100 [690] 85 [585] 16 45