ASTM A426 Centrifugally Cast Ferritic Alloy Steel Pipe
ASTM A426/A426M – 08
Standard Specification for
Centrifugally Cast Ferritic Alloy Steel Pipe for High-Temperature Service
1. Scope
1.1 This specification covers centrifugally cast alloy steel pipe intended for use in high-temperature, high-pressure service.
1.2 Several grades of ferritic steels are covered. Their compositions are given in Table 1.
1.3 Supplementary Requirements S1 through S12 are provided. The supplementary requirements provide for additional tests of an optional nature and when desired shall be so stated in the order (Section 4).
1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of each other. Combining values from the two systems may result in nonconformance with the specification.
2. Referenced Documents
2.1 ASTM Standards:
A 370 Test Methods and Definitions for Mechanical Testing of Steel Products
A 609/A 609M Practice for Castings, Carbon, Low-Alloy,and Martensitic Stainless Steel, Ultrasonic Examination Thereof
A 941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
A 999/A 999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E 94 Guide for Radiographic Examination
E 165 Test Method for Liquid Penetrant Examination
E 186 Reference Radiographs for Heavy-Walled (2 to 412-in. [51 to 114-mm]) Steel Castings
E 208 Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels
E 280 Reference Radiographs for Heavy-Walled (412 to12-in. [114 to 305-mm]) Steel Castings
E 446 Reference Radiographs for Steel Castings Up to 2 in.[51 mm] in Thickness
E 709 Guide for Magnetic Particle Examination
2.2 ANSI Standard:
B46.1 Surface Texture
2.3 ASME Boiler and Pressure Vessel Code:
Section IX Welding Qualification
3. Ordering Information
3.1 Orders for material under this specification shall include the following, as required, to describe the desired material adequately:
3.1.1 Quantity (feet, centimetres, or number of lengths),
3.1.2 Name of material (centrifugally cast pipe),
3.1.3 Specification number,
3.1.4 Grade (Table 1),
3.1.5 Size (outside or inside diameter and minimum wall thickness),
3.1.6 Length (specific or random) (Section on Permissible Variations in Length of Specification A 999/A 999M),
3.1.7 End finish (Section on Ends of Specification A 999/A 999M),
3.1.8 Optional Requirements S1 through S12 and Section 14.1,
3.1.9 Test report required (Section on Certified Test Report of Specification A 999/A 999M),
3.1.10 Service temperature if over 1000°F [540°C] (Note 1),and
3.1.11 Special requirements or additions to specification.
4. General Requirements for Delivery
4.1 Material furnished under this specification shall conform to the applicable requirements of the current edition of SpecificationA 999/A 999M unless otherwise provided herein.
5. Materials and Manufacture
5.1 Heat-Treatment—The pipe shall be furnished in the normalized and tempered or liquid-quenched and tempered condition (Note 1). The temperature for tempering shall not be less than 1250°F [675°C] except for Grades CP1, CP2, CP11,CP12, and CP15 for which the temperature for tempering shall not be less than 1100°F [595°C]. Grade CP91 shall be normalized at 1900 – 1975 °F (1040 – 1080 °C) and tempered at 1350 – 1470 °F (730 – 800 °C).
5.1.1 Heat treatment shall be performed after the pipe has been allowed to cool below the transformation range. Definition of heat-treatment terms shall be as given in Terminology A 941.
NOTE 1—Except for Grade CP91, it is recommended that the temperature for tempering should be at least 100°F [55°C] above the intended service temperature. The purchaser shall advise the manufacturer of the service temperature when it is over 1000°F [540°C].
5.2 Machining—The pipe shall be machined on the inner and outer surfaces to a roughness value no greater than 250 µ in. [6.35 µm] arithmetical average deviation (AA) from the mean line unless otherwise specified as in ANSI B46.1.
6. Chemical Analysis
6.1 Heat Analysis—An analysis of each heat shall be made by the manufacturer to determine the percentages of elements specified in Table 1. The analysis shall be made on a test sample taken preferable during the pouring of the heat. The chemical composition thus determined shall conform to the requirements specified in Table 1 (Note 2).
NOTE 2—The role of alloying elements in the development of Grade CP91 has been extensively investigated. V and Nb contribute to precipitation strengthening by forming fine and coherent precipitation of M(C,N)X carbo-nitrides in the ferrite matrix. V also precipitates as VN during tempering or during creep. Therefore, the addition of strong nitride forming elements, those with a stronger affinity for nitrogen than Nb and V, as deoxidation agents, interferes with these high-temperature strengthening mechanisms.
6.2 Product Analysis—Aproduct analysis may be made by the purchaser. The sample for analysis shall be selected so as to be representative of the pipe being analyzed. The chemical composition thus determined shall conform to the requirements of Table 1.
A Where ellipses appear in this table there is no requirement.
7. Tensile and Hardness Requirements
7.1 Steel used for the castings shall conform to the tensile and hardness requirements specified in Table 2.
A Elongation in 2 in. [50 mm] using a standard round specimen, in either the transverse or longitudinal direction.
8. Permissible Variations in Dimensions
8.1 Thickness—The wall thickness shall not vary over that specified by more than 1 ⁄ 8 in. [3 mm]. There shall be no variation under the specified wall thickness.
9. Number of Tests
9.1 One tension and one hardness test shall be made from each heat.
9.2 If a specimen is machined improperly or if flaws are revealed by machining or during testing, the specimen may be discarded and another substituted from the same heat.
10. Retests
10.1 If the results of the mechanical tests for any heat do not conform to the requirements specified, the castings may be reheat-treated and retested, but may not be re-austenitized more than twice.
11. Test Specimens
11.1 Test coupons from which tension test specimens are prepared shall be removed from heat-treated casting prolongations.
11.2 When agreed upon between the manufacturer and the purchaser, test coupons from which test specimens are prepared shall be cast attached to separate blocks from the same heat as the casting represented. The test blocks shall be heat treated in the same manner as the casting represented.
11.3 Tension test specimens shall be machined to the form and dimensions of the standard round 2-in. [50-mm] gage length specimens shown in Fig. 6 of Test Methods and Definitions A 370.
12. Hydrostatic Test
12.1 Each length of pipe shall be hydrostatically tested in accordance with Specification A 999/A 999M.
12.2 When agreed to between the manufacturer and the purchaser and so stated in the order, the hydrostatic test may be deferred and shall be performed later by the purchaser. Pipe furnished without the hydrostatic test shall include with the mandatory marking the letters “NH.” The manufacturer is responsible for the satisfactory performance of the casting when it is tested.
12.3 When certification is required by the purchaser and the hydrostatic test has been omitted, the certification shall clearly state “not hydrostatically tested.” The specification number and material grade shown on the certification shall be followed by the letters “NH.”
13. Visual Inspection
13.1 The surface of the casting shall be free from cracks and hot tears as determined by visual examination. Other surface imperfections shall be judged in accordance with visual acceptance criteria which may be specified in the order.
14. Rework and Retreatment
14.1 Defects as defined in Section 14 shall be removed and their removal verified by visual inspection of the resultant cavities. Defects that are located by inspecting with supplementary requirements S6, S7, S8, or S9 shall be removed or reduced to an acceptable size.
14.2 If removal of the defect does not infringe upon the minimum wall thickness, the depression may be blended uniformly into the surrounding surface.
14.3 If the cavity resulting from defect removal infringes upon the minimum wall thickness, weld repair is permitted subject to the purchaser’s approval. The composition of the weld rod used shall be suitable for the composition of the metal being welded.
14.3.1 Only welders and procedures qualified in accordance with ASME Boiler and Pressure Vessel Code, Section IX, shall be used. All repair welds will be inspected to the same quality standard used to inspect the casting.
14.4 Local or full heat treatment in accordance with tempering temperatures specified in 5.1 shall follow welding.
15. Rejection
15.1 Each length of pipe received from the manufacturer may be inspected by the purchaser and, if it does not meet the requirements of the specification based on the inspection and test method as outlined in the specification, the pipe may be rejected and the manufacturer shall be notified. Disposition of rejected pipe shall be a matter of agreement between the manufacturer and the purchaser.
16. Product Marking
16.1 Each length of pipe shall be legibly marked with the manufacturer’s name or brand, the specification number and grade. In addition, heat numbers or serial numbers that are traceable to heat numbers shall be marked on each length of pipe.
Standard Specification for
Centrifugally Cast Ferritic Alloy Steel Pipe for High-Temperature Service
1. Scope
1.1 This specification covers centrifugally cast alloy steel pipe intended for use in high-temperature, high-pressure service.
1.2 Several grades of ferritic steels are covered. Their compositions are given in Table 1.
1.3 Supplementary Requirements S1 through S12 are provided. The supplementary requirements provide for additional tests of an optional nature and when desired shall be so stated in the order (Section 4).
1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of each other. Combining values from the two systems may result in nonconformance with the specification.
2. Referenced Documents
2.1 ASTM Standards:
A 370 Test Methods and Definitions for Mechanical Testing of Steel Products
A 609/A 609M Practice for Castings, Carbon, Low-Alloy,and Martensitic Stainless Steel, Ultrasonic Examination Thereof
A 941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
A 999/A 999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E 94 Guide for Radiographic Examination
E 165 Test Method for Liquid Penetrant Examination
E 186 Reference Radiographs for Heavy-Walled (2 to 412-in. [51 to 114-mm]) Steel Castings
E 208 Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels
E 280 Reference Radiographs for Heavy-Walled (412 to12-in. [114 to 305-mm]) Steel Castings
E 446 Reference Radiographs for Steel Castings Up to 2 in.[51 mm] in Thickness
E 709 Guide for Magnetic Particle Examination
2.2 ANSI Standard:
B46.1 Surface Texture
2.3 ASME Boiler and Pressure Vessel Code:
Section IX Welding Qualification
3. Ordering Information
3.1 Orders for material under this specification shall include the following, as required, to describe the desired material adequately:
3.1.1 Quantity (feet, centimetres, or number of lengths),
3.1.2 Name of material (centrifugally cast pipe),
3.1.3 Specification number,
3.1.4 Grade (Table 1),
3.1.5 Size (outside or inside diameter and minimum wall thickness),
3.1.6 Length (specific or random) (Section on Permissible Variations in Length of Specification A 999/A 999M),
3.1.7 End finish (Section on Ends of Specification A 999/A 999M),
3.1.8 Optional Requirements S1 through S12 and Section 14.1,
3.1.9 Test report required (Section on Certified Test Report of Specification A 999/A 999M),
3.1.10 Service temperature if over 1000°F [540°C] (Note 1),and
3.1.11 Special requirements or additions to specification.
4. General Requirements for Delivery
4.1 Material furnished under this specification shall conform to the applicable requirements of the current edition of SpecificationA 999/A 999M unless otherwise provided herein.
5. Materials and Manufacture
5.1 Heat-Treatment—The pipe shall be furnished in the normalized and tempered or liquid-quenched and tempered condition (Note 1). The temperature for tempering shall not be less than 1250°F [675°C] except for Grades CP1, CP2, CP11,CP12, and CP15 for which the temperature for tempering shall not be less than 1100°F [595°C]. Grade CP91 shall be normalized at 1900 – 1975 °F (1040 – 1080 °C) and tempered at 1350 – 1470 °F (730 – 800 °C).
5.1.1 Heat treatment shall be performed after the pipe has been allowed to cool below the transformation range. Definition of heat-treatment terms shall be as given in Terminology A 941.
NOTE 1—Except for Grade CP91, it is recommended that the temperature for tempering should be at least 100°F [55°C] above the intended service temperature. The purchaser shall advise the manufacturer of the service temperature when it is over 1000°F [540°C].
5.2 Machining—The pipe shall be machined on the inner and outer surfaces to a roughness value no greater than 250 µ in. [6.35 µm] arithmetical average deviation (AA) from the mean line unless otherwise specified as in ANSI B46.1.
6. Chemical Analysis
6.1 Heat Analysis—An analysis of each heat shall be made by the manufacturer to determine the percentages of elements specified in Table 1. The analysis shall be made on a test sample taken preferable during the pouring of the heat. The chemical composition thus determined shall conform to the requirements specified in Table 1 (Note 2).
NOTE 2—The role of alloying elements in the development of Grade CP91 has been extensively investigated. V and Nb contribute to precipitation strengthening by forming fine and coherent precipitation of M(C,N)X carbo-nitrides in the ferrite matrix. V also precipitates as VN during tempering or during creep. Therefore, the addition of strong nitride forming elements, those with a stronger affinity for nitrogen than Nb and V, as deoxidation agents, interferes with these high-temperature strengthening mechanisms.
6.2 Product Analysis—Aproduct analysis may be made by the purchaser. The sample for analysis shall be selected so as to be representative of the pipe being analyzed. The chemical composition thus determined shall conform to the requirements of Table 1.
TABLE 1 Chemical Requirements A
| Composition, % | |||||||||
| Grade |
UNS Number |
Carbon | Manganese |
Phos- phorus, max |
Sulfur, max |
Silicon | Chromium | Molybdenum | Other |
| CP1 | J12521 |
0.25 max |
0.30- 0.80 |
0.040 | 0.045 |
0.10- 0.50 |
. . . | 0.44-0.65 | . . . |
| CP2 | J11547 | 0.10–0.20 |
0.30- 0.61 |
0.040 | 0.045 |
0.10- 0.50 |
0.50- 0.81 |
0.44-0.65 | . . . |
| CP5 | J42045 |
0.20 max |
0.30- 0.70 |
0.040 | 0.045 |
0.75 max |
4.00- 6.50 |
0.45-0.65 | . . . |
| CP5b | J51545 |
0.15 max |
0.30- 0.60 |
0.040 | 0.045 |
1.00- 2.00 |
4.00- 6.00 |
0.45-0.65 | . . . |
| CP9 | J82090 |
0.20 max |
0.30- 0.65 |
0.040 | 0.045 |
0.25- 1.00 |
8.00- 10.00 |
0.90-1.20 | . . . |
| CP91 | J84090 | 0.08–0.12 |
0.30- 0.60 |
0.030 | 0.010 | 0.20–0.50 | 8.0–9.5 | 0.85–1.05 |
nickel, 0.40 max.; columbium, 0.060–0.10; nitrogen, 0.030–0.070; vanadium, 0.18–0.25; aluminum, 0.02 max.; titanium, 0.01 max; zirconium, 0.01 max. |
| CP11 | J12072 | 0.05–0.20 |
0.30- 0.80 |
0.040 | 0.045 |
0.60 max |
1.00- 1.50 |
0.44-0.65 | . . . |
| CP12 | J11562 | 0.05–0.15 |
0.30- 0.61 |
0.040 | 0.045 |
0.50 max |
0.80- 1.25 |
0.44-0.65 | . . . |
| CP15 | J11522 |
0.15 max |
0.30- 0.61 |
0.040 | 0.045 |
0.15- 1.65 |
. . . | 0.44-0.65 | . . . |
| CP21 | J31545 | 0.05–0.15 |
0.30- 0.61 |
0.040 | 0.045 |
0.50 max |
2.65- 3.35 |
0.80-1.06 | . . . |
| CP22 | J21890 | 0.05–0.15 |
0.30- 0.70 |
0.040 | 0.045 |
0.60 max |
2.00- 2.75 |
0.90-1.20 | . . . |
| CPCA15 | J91150 |
0.15 max |
1.00 max |
0.040 | 0.045 |
1.50 max |
11.5- 14.0 |
0.50 max | . . . |
7. Tensile and Hardness Requirements
7.1 Steel used for the castings shall conform to the tensile and hardness requirements specified in Table 2.
TABLE 2 Tensile Properties and Hardness Requirements
| Tensile strength, min, psi [MPa]: | |
| Grade CP1 | 65 000 [450] |
| Grades CP11, CP22 | 70 000 [485] |
| Grades CP5, CP9, CPCA15 | 90 000 [620] |
| Grade CP91 | 85 000 [585] to 110 000 [760] |
| All other grades | 60 000 [415] |
| Yield strength, min, psi [MPa]: | |
| Grade CP1 | 35 000 [240] |
| Grades CP11, CP22 | 40 000 [275] |
| Grades CP5, CP9 | 60 000 [415] |
| Grade CPCA15 | 65 000 [450] |
| Grade CP91 | 60 000 [415] |
| All other grades | 30 000 [205] |
| Elongation, min, %: A | |
| Grade CP1 | 24 |
| Grades CP11, CP22 | 20 |
| Grades CP5, CP9, CP91, CPCA15 | 18 |
| All other grades | 22 |
| Reduction of area, min, % | |
| Grades CP1, CP2, CP11, CP12, CP15 | 35 |
| Grades CP21, CP22, CP5, CP5b, CP7, CP9 | 35 |
| Grade CPCA15 | 30 |
| Grade CP91 | 45 |
| Hardness, max, HB: | |
| Grades CP5, CP5b, CP9, CP91, CPCA15 | 225 |
| All other grades | 201 |
A Elongation in 2 in. [50 mm] using a standard round specimen, in either the transverse or longitudinal direction.
8. Permissible Variations in Dimensions
8.1 Thickness—The wall thickness shall not vary over that specified by more than 1 ⁄ 8 in. [3 mm]. There shall be no variation under the specified wall thickness.
9. Number of Tests
9.1 One tension and one hardness test shall be made from each heat.
9.2 If a specimen is machined improperly or if flaws are revealed by machining or during testing, the specimen may be discarded and another substituted from the same heat.
10. Retests
10.1 If the results of the mechanical tests for any heat do not conform to the requirements specified, the castings may be reheat-treated and retested, but may not be re-austenitized more than twice.
11. Test Specimens
11.1 Test coupons from which tension test specimens are prepared shall be removed from heat-treated casting prolongations.
11.2 When agreed upon between the manufacturer and the purchaser, test coupons from which test specimens are prepared shall be cast attached to separate blocks from the same heat as the casting represented. The test blocks shall be heat treated in the same manner as the casting represented.
11.3 Tension test specimens shall be machined to the form and dimensions of the standard round 2-in. [50-mm] gage length specimens shown in Fig. 6 of Test Methods and Definitions A 370.
12. Hydrostatic Test
12.1 Each length of pipe shall be hydrostatically tested in accordance with Specification A 999/A 999M.
12.2 When agreed to between the manufacturer and the purchaser and so stated in the order, the hydrostatic test may be deferred and shall be performed later by the purchaser. Pipe furnished without the hydrostatic test shall include with the mandatory marking the letters “NH.” The manufacturer is responsible for the satisfactory performance of the casting when it is tested.
12.3 When certification is required by the purchaser and the hydrostatic test has been omitted, the certification shall clearly state “not hydrostatically tested.” The specification number and material grade shown on the certification shall be followed by the letters “NH.”
13. Visual Inspection
13.1 The surface of the casting shall be free from cracks and hot tears as determined by visual examination. Other surface imperfections shall be judged in accordance with visual acceptance criteria which may be specified in the order.
14. Rework and Retreatment
14.1 Defects as defined in Section 14 shall be removed and their removal verified by visual inspection of the resultant cavities. Defects that are located by inspecting with supplementary requirements S6, S7, S8, or S9 shall be removed or reduced to an acceptable size.
14.2 If removal of the defect does not infringe upon the minimum wall thickness, the depression may be blended uniformly into the surrounding surface.
14.3 If the cavity resulting from defect removal infringes upon the minimum wall thickness, weld repair is permitted subject to the purchaser’s approval. The composition of the weld rod used shall be suitable for the composition of the metal being welded.
14.3.1 Only welders and procedures qualified in accordance with ASME Boiler and Pressure Vessel Code, Section IX, shall be used. All repair welds will be inspected to the same quality standard used to inspect the casting.
14.4 Local or full heat treatment in accordance with tempering temperatures specified in 5.1 shall follow welding.
15. Rejection
15.1 Each length of pipe received from the manufacturer may be inspected by the purchaser and, if it does not meet the requirements of the specification based on the inspection and test method as outlined in the specification, the pipe may be rejected and the manufacturer shall be notified. Disposition of rejected pipe shall be a matter of agreement between the manufacturer and the purchaser.
16. Product Marking
16.1 Each length of pipe shall be legibly marked with the manufacturer’s name or brand, the specification number and grade. In addition, heat numbers or serial numbers that are traceable to heat numbers shall be marked on each length of pipe.
17. Keywords
17.1 alloy steel; centrifugal; ferritic; high-temperature service; pipe; stainless steel; steel castings