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ASTM A420 Standard Specification

ASTM A420 WPL6 90 degree short radius Elbow
ASTM A420 Carbon & Alloy Steel Pipe Fittings for Low-Temperature Service

ASTM A420/A420M-07 Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service. ASTM A420 WPL6 Grade is associated with ASTM A420 for pipe fittings manufactured of Wrought Carbon Steel. WPL6 is a normalized grade of carbon steel that has been Charpy Impact tested at -50 degree F for use in low temperature service. See Also ASTM A333 Grades 1 and 6 (for pipe) and A350 LF2 for flanges.

ASTM A420 WPL6 Elbow after complete quality and performance measure inspection. These are widely appreciated for excellent quality, corrosion abrasion and high tensile strength with long life service.

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-welding, or machining. All welding 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 welding 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
Grade C Mn P S Si
WPL6(1)(2) 0.3 0.60-1.35 0.035 0.04 0.15-0.30
WPL9 0.2 0.40-1.06 0.03 0.03 -
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]

Impact Test Properties

Since these pipe fittings are primarily used for low-temperature service, the properties of charpy V-notch impact test must be considered.

Charpy Impact Requirements for WPL6, WPL9, and WPL3

Size of Specimen A* B*
mm ft·lbf J ft·lbf J
10 by 10.0 13 17.6 10 13.6
10 by 7.5 10 13.6 8 10.8
10 by 5.0 7 9.5 5 7.0
10 by 2.5 4 5.4 3 4.1

A*Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens)
B*Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set)Charpy Impact Requirements for WPL8

Size of Specimen A* B*
mm ft·lbf J ft·lbf J
10 by 10.0 25.0 33.9 20.0 27.1
10 by 7.5 21.0 28.5 17.0 23.1
10 by 5.0 17.0 23.1 14.0 19.0
10 by 2.5 8.0 10.8 6.0 8.1

A*Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens)
B*Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set)

Impact Test Temperature

Grade °F [°C]
WPL6 −50 [−45]
WPL9 −100 [−75]
WPL3 −150 [−100]
WPL8 −320 [−195]
Material and Manufacture

The raw material for these fittings shall be fully killed steel, consisting of forgings, bars, plates, sheet, and seamless or fusion welded tubular products(pipes, tubes, or cylinders).

ASTM A420 WPL6 concentric reducer
Conc. reducer 10″x6″(wt. 1.625″x1.062″),
The steels shall be made using recognized melting practices necessary to produce steels that shall meet the impact requirements of ASTM A420. The ASTM A420 fittings may be made by forging or forming operations including hammering, pressing, piercing, extruding, upsetting, working, bending, fusion-welding, or machining, or by a combination of two or more of these operations. The forming procedure shall be so applied that it will not produce injurious defects in the fittings. All the fittings shall be furnished free of welding repair. The welded joints of the fittings shall be finished in accordance with the requirements of Paragraph UW-35 (a) of Section VIII, Division 1 of ASME Boiler and Pressure Vessel Code.
Heat Treatment

All fittings shall be furnished in the normalized, normalized and tempered, annealed, or quenched and tempered condition. All welding shall be completed prior to the austenitizing heat treatment. After forming, the fittings shall be allowed to cool below the lower critical before applying one of the heat treatments. When specified, post-weld heat treatment may be required.

Product & Standards
Standards Product
ASME B16.9 Factory-Made Wrought Steel Butt Welding Threaded
ASME B16.11 Forged Steel Fittings, Socked Welding Threaded
ASME Section VIII Division 1 Pressure Vessels
MSS SP-25 Standard Marking System for Valves, Fittings, Flanges, and Unions
MSS SP-79 Socket Welding Reducer Inserts
MSS SP-83 Steel Pipe Unions, Socket-Welding and Threaded
MSS SP-95 Swage(d) Nipples and Bull Plugs
MSS SP-97 Integrally Reinforced Forged Branch Outlet Fittings-Socket Welding, Threaded and Buttwelding Ends
Tests and Inspections

Pipe fittings manufactured to ASTM A420 shall take the following tests or inspections: dimensional inspection, visual examination, hydrostatic test(when required), chemical analysis, tensile test, impact test, radiographic test(RT).

How a Butt Weld Fitting is Made?

There are numerous processes for manufacturing butt weld fittings, several examples listed as follows.

The hot-extrusion process consists of enclosing a piece of metal, heated to forging temperature, in a chamber called a "container" having a die at one end with an opening of the shape of the desired finished section, and applying pressure to the metal through the opposite end of the container.

One of the most common manufacturing methods for manufacturing Elbows from pipes. After heating the raw material, it is pushed over a die called "mandrel" which allows the pipe to expand and bend simultaneously.

One of the most common manufacturing methods for caps, where plate is cut out in a circle and formed by deep drawing.

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