ASTM A420/A420M − 2022 is a standard specification that covers wrought carbon steel and alloy steel fittings for low-temperature service. These fittings are intended for pressure piping and pressure vessel applications, where materials must be able to perform well under low-temperature conditions.
Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service
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.
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.
ASTM A420/A420M Chemical Requirement
- NOTE 1—All requirements are maximum unless otherwise indicated.
- NOTE 2—Where an ellipsis (…) appears in this table, there is no requirement.
| Grade【A】 | Composition,% | ||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Nb【E】 | V | |
| WPL6 | 0.30 | 0.50-1.35 | 0.035 | 0.040 | 0.15-0.40 | 0.40 | 0.30 | 0.12 | 0.40 | 0.02【B】 | 0.08 |
| WPL9 | 0.20 | 0.40-1.06 | 0.030 | 0.030 | … | 1.60-2.24 | … | … | 0.75-1.25 | … | … |
| WPL3【C】 | 0.20 | 0.31-0.64 | 0.05 | 0.05 | 0.13-0.37 | 3.2-3.8 | … | … | … | … | … |
| WPL8【D】 | 0.13 | 0.90 | 0.030 | 0.030 | 0.13-0.37 | 8.4-9.6 | … | … | … | … | … |
【A】 When fittings are of welded construction, the symbols above shall be supplemented by the letter “W”.
【B】 By agreement, the limit for niobium may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
【C】 Fittings made from plate or forgings may have 0.90 % max manganese.
【D】 Fittings made from plate may have 0.98 % max manganese.
【E】 Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.
ASTM A420/A420M Tensile Requirements
NOTE1—There is no requirement where an ellipsis (…) appears in this table.
| Requirement | Grade | |||
| WPL6 | WPL9 | WPL3 | WPL8 | |
| Tensilestrength,minksi [MPa] | 60 [415] − 95 [655] | 63 [435] − 88 [610] | 65 [450] − 90 [620] | 100 [690] − 125 [865] |
| Yieldstrength,minksi [MPa] | 35 [240] | 46 [315] | 35 [240] | 75 [515 |
| Elongation Requirements | Grade | |||||||
| WPL6 | WPL9 | WPL3 | WPL8 | |||||
| Longitudinal | Transverse | Longitudinal | Transverse | Longitudinal | Transverse | Longitudinal | Transverse | |
| Standard round specimen, or small proportional specimen, min % in 4 D | 22 | 12 | 20 | … | 22 | 14 | 16 | … |
| Rectangular specimen for wall thickness 5/16 in. [7.94 mm] and over, and for all small sizes tested in full section; min % in 2 in. or 50 mm | 30 | 16.5 | 28 | 18 | 30 | 20 | 22 | … |
| Rectangular specimen for wall thickness less than 5/16 in. [7.94 mm]; min % in 2 in. or 50 mm (1⁄2-in.[12.7-mm] wide specimen) | A | A | A | A | A | A | A | … |
【A】 For each 1⁄32 in. [0.79 mm] decrease in wall thickness below 5⁄16 in. [7.94 mm], a deduction of 1.5 % (grades WPL6, WPL9, and WPL3) or 1.25 % (WPL8) for longitudinal and 1.0 % (grades WPL6, WPL9 and WPL3) for transverse from the values shown above is permitted. The following table gives the minimum value for various wall thicknesses:
| Wall Thickness | Grade | ||||||||
| WPL6 | WPL9 | WPL3 | WPL8 | ||||||
| in. | [mm] | Longitudinal | Transverse | Longitudinal | Transverse | Longitudinal | Transverse | Longitudinal | Transverse |
| 5/16(0.312) | [7.94] | 30 | 16.5 | 28 | 18 | 30 | 20 | 22 | ··· |
| 9/32(0.281) | [7.14] | 28.5 | 15.5 | 26.5 | 17 | 28.5 | 19 | 20.75 | ··· |
| 1/4(0.250) | [6.35] | 27 | 14.5 | 25 | 16 | 27 | 18 | 19.5 | ··· |
| 7/32(0.219) | [5.56] | 25.5 | ··· | 23.5 | ··· | 25.5 | ··· | 18.25 | ··· |
| 3/16(0.188) | [4.76] | 24 | ··· | 22 | ··· | 24 | ··· | 17 | ··· |
| 5/32(0.156) | [3.97] | 22.5 | ··· | 20.5 | ··· | 22.5 | ··· | 15.75 | ··· |
| 1/8(0.125) | [3.17] | 21 | ··· | 19 | ··· | 21 | ··· | 14.5 | ··· |
| 3/32 (0.094) | [2.38] | 19.5 | ··· | 17.5 | ··· | 19.5 | ··· | 13.25 | ··· |
| 1/16(0.062) | [1.59] | 18 | ··· | 16 | ··· | 18 | … | 12 | … |
Note—The preceding table gives the computed minimum elongation value for each 1⁄32 in. [0.79 mm] decrease in wall thickness. Where the wall thickness lies between two values above, the minimum elongation value is determined by the following equations:
| Direction of Test | Equations | |||
| WPL6 | WPL9 | WPL3 | WPL8 | |
| Longitudinal | E=48t+ 15.00 | 48t+ 13.00 | E = 48t + 15.00 | 40t+ 9.50 |
| Transverse | t=32t + 6.50 | 32t+8.00 | E =32t+ 10.00 | |
| where: E= elongation in 2 in.or 50 mm,%, and t= tactual thickness of specimen,in. | ||||
ASTM A420/A420M Charpy Impact Requirements
Charpy Impact Requirements for WPL6, WPL9, and WPL3【A】
| Size of Specimen, mm | Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens) | Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set) | ||
| ft·lbf | J | ft·lbf | J | |
| 10by10.0 | 13 | 18 | 10 | 14 |
| 10by7.5 | 10 | 14 | 8 | 11 |
| 10by5.0 | 7 | 9 | 5 | 7 |
| 10by2.5 | 4 | 5 | 3 | 4 |
| 【 A】Straight-line interpolation for intermediate values is permitted | ||||
Charpy Impact Requirements for WPL8
| Size of Specimen, mm | Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens) | Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set) | ||
| ft·lbf | J | ft·lbf | J | |
| 10by10.0 | 25 | 34 | 20 | 27 |
| 10by7.5 | 21 | 29 | 17 | 23 |
| 10by5.0 | 17 | 23 | 14 | 19 |
| 10by2.5 | 8 | 11 | 6 | 8 |
Impact Test Temperature
| Grade | Impact Test Temperature, F[°C] |
| WPL6 | -50 [45] |
| WPL9 | 100 [75] |
| WPL3 | 150 [100] |
| WPL8 | -320 [195] |
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