ASTM A420/A420M-07 standard specification for piping fittings of wrought carbon steel and alloy steel for low-temperature service.
ASTM A420 is the standard specification for pipe fittings of wrought carbon steel and alloy steel for low temperature service. These fitting, either of seamless or welded construction, are primarily used in pressure piping and pressure vessel service at low temperatures. Metals-Piping can provide all the four steel grades covered by ASTM A420: WPL6, WPL9, WPL3, and WPL8.
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.
ASTM A420 Chemical Composition Requirements
| Elements | WPL6, % | WPL9, % | WPL3, % | WPL8, % |
|---|---|---|---|---|
| Carbon [C] | ≤0.30 | ≤0.20 | ≤0.20 | ≤0.13 |
| Manganese [Mn] | 0.50-1.35 | 0.40-1.06 | 0.31-0.64 | ≤0.90 |
| Phosphorus [P] | ≤0.035 | ≤0.030 | ≤0.05 | ≤0.030 |
| Sulfur [S] | ≤0.040 | ≤0.030 | ≤0.05 | ≤0.030 |
| Silicon [Si] | 0.15-0.40 | … | 0.13-0.37 | 0.13-0.37 |
| Nickel [Ni] | ≤0.40 | 1.60-2.24 | 3.2-3.8 | 8.4-9.6 |
| Chromium [Cr] | ≤0.30 | ... | ... | ... |
| Molybdenum [Mo] | ≤0.12 | ... | ... | ... |
| Copper [Cu] | ≤0.40 | 0.75-1.25 | … | … |
| Columbium [Cb] | ≤0.02 | ... | ... | ... |
| Vanadium[V] | ≤0.08 | ... | ... | ... |
*Fittings of WPL3 made from plate or forgings may have 0.90 % max manganese.
*Fittings of WPL8 made from plate may have 0.98 % max manganese.
ASTM A420 Mechanical Properties
| ASTM A420/ A420M | Tensile Strength, min. | Yield Strength, min. | Elongation %, min | |||
|---|---|---|---|---|---|---|
| Grade | ksi | MPa | ksi | MPa | Longitudinal | Transverse |
| WPL6 | 65-95 | 415-655 | 35 | 240 | 22 | 12 |
| WPL9 | 63-88 | 435-610 | 46 | 315 | 20 | … |
| WPL3 | 65-90 | 450-620 | 35 | 240 | 22 | 14 |
| WPL8 | 100-125 | 690-865 | 75 | 515 | 16 | … |
ASTM A420 Impact Test Properties
| 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 |
| 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)
ASTM A420 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). 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.