ASTM A420/A420M

ASTM A420/A420M-07 Standard Specification for Fittings of Wrought Carbon Steel and for Low-Temperature Service. ASTM A420 WPL6 Grade is associated with ASTM A420 for fittings manufactured of Wrought Carbon Steel.

Materials shall consist of forgings, bars, plates, seamless or fusion welded tubular products with filler metal added, and shall be produced by open-hearth, basic-oxygen, or electric-furnace process. Forging or forming operations shall be performed by one or a combination of two or more of the following procedures: hammering, pressing, piercing, extruding, upsetting, working, bending, fusion-, or machining. All shall be completed prior to the austenitizing heat treatment, which shall be executed in the normalized, normalized and tempered, annealed, or quenched and tempered conditions. Steel specimens shall conform to required values of chemical composition, tensile strength, yield strength, elongation, wall thickness, and Charpy V-notch impact value. All fusion-welded butt joints shall undergo radiographic examination, while hydrostatic testing of fittings is not required in this specification. Repair shall be permissible for parts made to dimensional standards.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

Scope of ASTM A420

1.1 This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction, covered by the latest revision of ASME B16.9, ASME B16.11, MSS SP-79, MSS SP-83, MSS SP-95, and MSS SP-97. Fittings differing from these ASME and MSS standards shall be furnished in accordance with Supplementary Requirement S58 of Specification A960/A960M. These fittings are for use in pressure piping and pressure vessel service at low temperatures.

1.2 Optional supplementary requirements are provided for fittings where a greater degree of examination is desired. When desired, one or more of these supplementary requirements shall be specified in the order.

1.3 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.

1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

Chemical Composition (%) of ASTM A420
Steel No. Type Chemical composition
C Si S P Mn Cr Ni Mo Other ób ós δ5 HB
WPL6 0.3 0.15-0.3 0.04 0.035 0.6-1.35 0.3 0.4 0.12 Cb:0.02;V:0.08 415-585 240 22
WPL9 0.2 0.03 0.03 0.4-1.06 1.6-2.24 435-610 315 20
WPL3 0.2 0.13-0.37 0.05 0.05 0.31-0.64 3.2-3.8 450-620 240 22
WPL8 0.13 0.13-0.37 0.03 0.03 0.9 8.4-9.6 690-865 515 16
Grade Ni Cu Cr Mo V Nb
WPL6(1)(2) 0.4 0.4 0.3 0.12 0.08 0.02
WPL9 1.60-2.24 0.75-1.25

All values are maximum unless otherwise indicated.

(1) For each reduction of 0.01% C below 0.30%, an increase of 0.05% Mn above 1.06% will be permitted, up to a maximum of 1.35%.
(2) Fittings made from forgings may have 1.35% max Mn.

Mechanical properties of ASTM A420
Tensile Requirements WPL6 WPL9
Tensile Strength
min, ksi [MPa]
60-85[415-585] 63-88[435-610]
Yield Strength
min, ksi [MPa]
35[240] 46[315]

Where the wall thickness lies between two values above, the min elongation value is determined by the following equations:

Longitudinal E=48t+15.00,E=48t+13.00
Transverse E=32t+6.50,E=32t+8.00
E = elongation in 2in [50mm], %
t = actual thickness of specimen, in [mm]

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