ASTM A376/A376M Seamless Austenitic Steel Pipe
ASTM A376/A376M
Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Service
1. Scope*
1.1 This specification covers seamless austenitic steel pipe intended for high-temperature service. Among the grades covered are H grades and nitrogen grades that are specifically intended for high-temperature service.
NOTE 1—This specification was originally developed for use for piping in the central stations of electric-power generating thermal plants. However, its use is not restricted to such applications and it may be used in other applications for which the attributes ofthe materials, as defined by this specification, are appropriate.
1.2 Optional supplementary requirements (S1 through S10) are provided. These supplementary requirements specify additional tests that will be made only when stated in the order,together with the number of such tests required.
1.3 Grades TP321 and TP321H have lower strength requirements for nominal wall thicknesses greater than 3 ⁄ 8 in. [9.5mm].
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 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. The inch-pound units shall apply unless the “M”designation of this specification is specified in the order.
NOTE 2—The dimensionless designators NPS (nominal pipe size) and DN (Diametre Nominel) have been substituted in this standard for such traditional terms as “nominal diameter,” “size,” and “nominal size.”
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E112 Test Methods for Determining Average Grain Size
E213 Practice for Ultrasonic Testing of Metal Pipe and Tubing
E381 Method of Macroetch Testing Steel Bars, Billets,Blooms, and Forgings
E426 Practice for Electromagnetic (Eddy Current) Examination of Seamless and Welded Tubular Products, Titanium,Austenitic Stainless Steel and Similar Alloys
2.2 Other Standards:
SNT-TC-1A Personnel Qualification and Certification in Nondestructive Testing
3. Ordering Information
3.1 Orders for material to this specification should 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 (seamless austenitic steel pipe),
3.1.3 Grade (Table 1),
3.1.4 Size (nominal size, or outside diameter and schedule number or average wall thickness),
3.1.5 Lengths (specific or random), (Permissible Variations in Length Section of Specification A999/A999M),
3.1.6 End finish (Ends Section of Specification A999/A999M),
3.1.7 Optional requirements (Section 8) (see Hydrostatic Test Requirements Section and the Permissible Variation in Weight for Seamless Pipe Section for weighing individual lengths, of Specification A999/A999M), (see 9.6, repairing by welding; 13.3, die stamping),
3.1.8 Test report required (Certification Section of Specification A999/A999M),
3.1.9 Specification designation, and
3.1.10 Special requirements or any supplementary requirements selected, or both.
4. General Requirements
4.1 Material furnished to this specification shall conform to the applicable requirements of the current edition of Specification A999/A999M unless otherwise provided herein.
5. Materials and Manufacture
5.1 Manufacture—At the manufacturer’s option, pipe may be either hot finished or cold finished, with a suitable finishing treatment, where necessary.
5.2 Heat Treatment:
5.2.1 All pipe shall be furnished in the heat-treated condition unless the order specifically states that no final heat treatment shall be applied. When the order is furnished without final heat treatment, each pipe shall be stenciled “HT-O.”
5.2.2 As an alternate to final heat treatment in a continuous furnace or batch-type furnace, immediately following hot forming while the temperature of the pipes is not less than the specified minimum solution treatment temperature, pipes may be individually quenched in water or rapidly cooled by other means.
5.2.3 Grades TP304, TP304N, TP304LN, TP316, TP316N,TP316LN, TP321, TP347, TP347LN, TP348, 16-8-2H,S 31725, and S 31726—Unless otherwise stated in the order,heat treatment shall consist of heating to a minimum temperature of 1900 °F [1040 °C] and quenching in water or rapidly cooling by other means.
5.2.3.1 The purchaser may specify controlled structural or special service characteristics which shall be used as a guide for the most suitable heat treatment. If the final heat treatment is at a temperature under 1900 °F [1040 °C], each pipe shall be stenciled with the final heat treatment temperature in degrees Fahrenheit or Celsius after the suffix “HT.”
5.2.4 Grades TP304H, TP316H, TP321H, TP347H,TP348H, and 16-8-2H—If cold working is involved in processing, the minimum solution-treating temperature for Grades TP321H, TP347H, and TP348H shall be 2000 °F [1100°C], for Grades TP304H and TP316H, 1900 °F [1040 °C], and for Grade 16-8-2H, 1800 °F [980 °C]. If the material is hot-rolled, the minimum solution-treating temperatures for Grades TP321H, TP347H, and TP348H shall be 1925 °F [1050°C], for Grades TP304H and TP316H, 1900 °F [1040 °C], and for Grade 16-8-2H, 1800 °F [980 °C].
5.2.5 Grade S34565—Heat treatment shall consist of heating to a temperature in the range of 2050 °F [1120 °C] minimum and 2140 °F [1170 °C] maximum, and quenching in water or rapidly cooling by other means.
5.2.6 Grade S31266—Heat treatment shall consist of heating to a temperature in the range of 2100 °F [1150 °C] minimum and quenching in water or rapidly cooling by other means.
5.3 A solution annealing temperature above 1950 °F [1065°C] may impair the resistance to intergranular corrosion after subsequent exposure to sensitizing conditions in TP321,TP321H, TP347, TP347H, TP348, and TP348H. When specified by the purchaser, a lower temperature stabilization or re-solution anneal shall be used subsequent to the initial high temperature solution anneal (see Supplementary Requirement S9).
5.4 The grain size of grades 304H, 316H, 321H, 347H, and 348H as determined in accordance with Test Methods E112,shall be No. 7 or coarser.
6. Chemical Composition
6.1 The steel shall conform to the requirements as to chemical composition prescribed in Table 1.
TABLE 1 Chemical Requirements
A Maximum, unless otherwise indicated. Where ellipses (. . .) appear in this table, there is no requirement and analysis for the element need not be determined or reported.
B The method of analysis for nitrogen shall be a matter of agreement between the purchaser and manufacturer.
C The titanium content shall be not less than five times the carbon content and not more than 0.70 %.
D The titanium content shall be not less than four times the carbon content and not more than 0.70 %.
E The columbium content shall be not less than ten times the carbon content and not more than 1.10 %.
F The columbium content shall be not less than eight times the carbon content and not more than 1.10 %.
G The columbium content shall not be less than 15 times the carbon content.
J This grade is intended for special purpose applications.
7. Product Analysis
7.1 At the request of the purchaser, an analysis of one billet from each heat or two pipes from each lot shall be made by the manufacturer. A lot of pipe shall consist of the number of lengths as a function of size, as shown below, of the same size and wall thickness from any one heat of steel:
7.2 The results of these analyses shall be reported to the purchaser or the purchaser’s representative, and shall conform to the requirements specified in Table 1.
7.3 If the analysis of one of the tests specified in Section 8 does not conform to the requirements specified in Section 6, an analysis of each billet or pipe from the same heat or lot may be made, and all billets or pipe conforming to the requirements shall be accepted.
8. Tensile Requirements
8.1 The material shall conform to the requirements as to tensile properties prescribed in Table 2.
A For grade TP304, NPS8 or larger, and in schedules 140 and heavier, the required minimum tensile strength shall be 70 ksi [480 MPa].
B Prior to the issuance of A376/A376M – 88, the tensile and yield strength values were 75 [520] and 30 [210] respectively, for nominal wall greater than 0.375 in.[9.5 mm].
9. Workmanship, Finish, and Appearance
9.1 The pipe manufacturer shall explore a sufficient number ofvisual surface imperfections to provide reasonable assurance that they have been properly evaluated with respect to depth.Exploration ofall surface imperfections is not required but may be necessary to assure compliance with 9.2.
9.2 Surface imperfections that penetrate more than 12 1 ⁄ 2 % of the nominal wall thickness or encroach on the minimum wall thickness shall be considered defects. Pipe with such defects shall be given one of the following dispositions:
9.2.1 The defect may be removed by grinding provided that the remaining wall thickness is within specified limits.
9.2.2 Repaired in accordance with the repair welding provisions of 9.6.
9.2.3 The section of pipe containing the defect may be cut off within the limits of requirements on length.
9.2.4 Rejected.
9.3 To provide a workmanlike finish and basis for evaluating conformance with 9.2, the pipe manufacturer shall remove by grinding the following:
9.3.1 Mechanical marks, abrasions (see Note 3), and pits,any of which imperfections are deeper than 1 ⁄ 16 in. [1.6 mm].
NOTE 3—Marks and abrasions are defined as cable marks, dinges, guide marks, roll marks, ball scratches, scores, die marks, and so forth.
9.3.2 Visual imperfections commonly referred to as scabs,seams, laps, tears, or slivers found by exploration in accordance with 9.1 to be deeper than 5 % of the nominal wall thickness.
9.4 At the purchaser’s discretion, pipe shall be subject to rejection if surface imperfections acceptable under 9.2 are not scattered, but appear over a large area in excess of what is considered a workmanlike finish. Disposition ofsuch pipe shall be a matter of agreement between the manufacturer and the purchaser.
9.5 When imperfections or defects are removed by grinding,a smooth curved surface shall be maintained, and the wall thickness shall not be decreased below that permitted by this specification. The outside diameter at the point ofgrinding may be reduced by the amount so removed.
9.5.1 Wall thickness measurements shall be made with a mechanical caliper or with a properly calibrated nondestructive testing device of appropriate accuracy. In case of dispute, the measurement determined by use ofthe mechanical caliper shall govern.
9.6 Weld repair shall be permitted only subject to the approval of the purchaser and in accordance with Specification A999/A999M.
9.7 The finished pipe shall be reasonably straight.
9.8 The pipe shall be free of scale and contaminating iron particles. Pickling, blasting, or surface finishing is not mandatory when pipe is bright annealed. The purchaser may request that a passivating treatment be applied.
10. Hydrostatic or Nondestructive Electric Test
10.1 Each pipe shall be subjected to the Nondestructive Electric Test or the Hydrostatic Test. Unless specified by the purchaser, either test may be used at the option ofthe producer.
10.2 Hydrostatic Test—Each length of finished pipe shall be subjected to the hydrostatic test in accordance with Specification A999/A999M, unless specifically exempted under the provisions of 10.3 and 10.4.
10.3 For pipe sizes NPS 24 [DN 600] and over, the purchaser, with the agreement of the manufacturer, may complete the hydrostatic test requirement with the system pressure test, which may be lower or higher than the specification test pressure, but in no case shall the test pressure be lower than the system design pressure. Each length of pipe furnished without the completed manufacturer’s hydrostatic test shall include with the mandatory marking the letters “NH.”
10.4 Nondestructive Examination—Each pipe shall be examined with a nondestructive test in accordance with Practice E213 or Practice E426. Unless specifically called out by the purchaser, the selection of the nondestructive electric test will be at the option of the manufacturer. The range of pipe sizes that may be examined by each method shall be subject to the limitations in the scope of the respective practices.
10.4.1 The following information is for the benefit of the user of this specification:
10.4.1.1 The reference standards defined in 10.10.1 through 11.10.4 are convenient standards for calibration of nondestructive testing equipment. The dimensions of these standards should not be construed as the minimum size imperfection detectable by such equipment.
10.4.1.2 The ultrasonic testing (UT) can be performed to detect both longitudinally and circumferentially oriented defects. It should be recognized that different techniques should be employed to detect differently oriented imperfections. The examination may not detect short, deep, defects.
10.4.1.3 The eddy-current testing (ET) referenced in Practice E426 has the capability of detecting significant discontinuities, especially the short abrupt type.
10.4.1.4 A purchaser interested in ascertaining the nature (type, size, location, and orientation) ofdiscontinuities that can be detected in the specific application of these examinations should discuss this with the manufacturer of the tubular product.
10.5 Time of Examination—Nondestructive testing for specification acceptance shall be performed after all mechanical processing, heat treatments, and straightening operations.This requirement does not preclude additional testing at earlier stages in the processing.
10.6 Surface Condition:
10.6.1 All surfaces shall be free of scale, dirt, grease, paint,or other foreign material that could interfere with interpretation oftest results. The methods used for cleaning and preparing the surfaces for examination shall not be detrimental to the base metal or the surface finish.
10.6.2 Excessive surface roughness or deep scratches can produce signals that interfere with the test.
10.7 Extent ofExamination:
10.7.1 The relative motion ofthe pipe and the transducer(s),coil(s), or sensor(s) shall be such that the entire pipe surface is scanned, except as in 5.2.
10.7.2 The existence of end effects is recognized, and the extent of such effects shall be determined by the manufacturer,and, if requested, shall be reported to the purchaser. Other nondestructive tests may be applied to the end areas, subject to agreement between the purchaser and the manufacturer.
10.8 Operator Qualifications—The test unit operator shall be certified in accordance with SNT-TC-1A, or an equivalent recognized and documented standard.
10.9 Test Conditions:
10.9.1 For eddy-current testing, the excitation coil frequency shall be chosen to ensure adequate penetration yet provide good signal-to-noise ratio.
10.9.2 The maximum eddy-current coil frequency used shall be as follows:
10.9.3 Ultrasonic—For examination by the ultrasonic method, the minimum nominal transducer frequency shall be 2.00 MHz and the maximum nominal transducer size shall be 1.5 in. [38 mm].
10.9.3.1 If the equipment contains a reject notice filter setting, this shall remain off during calibration and testing unless linearity can be demonstrated at that setting.
10.10 Reference Standards:
10.10.1 Reference standards of convenient length shall be prepared from a length ofpipe ofthe same grade, size (NPS, or outside diameter and schedule or wall thickness), surface finish, and heat treatment condition as the pipe to be examined.
10.10.2 For Ultrasonic Testing, the reference ID and OD notches shall be any one of the three common notch shapes shown in Practice E213, at the option of the manufacturer. The depth of each notch shall not exceed 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in. [0.1 mm],whichever is greater. The width of the notch shall not exceed twice the depth. Notches shall be placed on both the OD and ID surfaces.
10.10.3 For Eddy-Current Testing, the reference standard shall contain, at the option of the manufacturer, any one of the following discontinuities:
10.10.3.1 Drilled Hole—The reference standard shall contain three or more holes, equally spaced circumferentially around the pipe and longitudinally separated by a sufficient distance to allow distinct identification of the signal from each hole. The holes shall be drilled radially and completely through the pipe wall, with care being taken to avoid distortion of the pipe while drilling. One hole shall be drilled in the weld, if visible. Alternately, the producer ofwelded pipe may choose to drill one hole in the weld and run the calibration standard through the test coils three times with the weld turned at 120° on each pass. The hole diameter shall vary with NPS as follows:
10.10.3.2 Transverse Tangential Notch—Using a round tool or file with a 1 ⁄ 4 -in. [6.4-mm] diameter, a notch shall be filed or milled tangential to the surface and transverse to the longitudinal axis of the pipe. Said notch shall have a depth not exceeding 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in. [0.102 mm], whichever is greater.
10.10.3.3 Longitudinal Notch—A notch 0.031 in. [0.8 mm] or less in width shall be machined in a radial plane parallel to the tube axis on the outside surface of the pipe, to have a depth not exceeding 12 1 ⁄ 2 % of the specified wall thickness of the pipe or 0.004 in. [0.1 mm], whichever is greater. The length of the notch shall be compatible with the testing method.
10.10.3.4 More or smaller reference discontinuities, or both,may be used by agreement between the purchaser and the manufacturer.
10.11 Standardization Procedure:
10.11.1 The test apparatus shall be standardized at the beginning and end of each series of pipes of the same size (NPS or diameter and schedule or wall thickness), grade and heat treatment condition, and at intervals not exceeding 4 h.More frequent standardization may be performed at the manufacturer’s option or may be required upon agreement between the purchaser and the manufacturer.
10.11.2 The test apparatus shall also be standardized after any change in test system settings; change of operator; equipment repair; or interruption due to power loss, process shutdown, or when a problem is suspected.
10.11.3 The reference standard shall be passed through the test apparatus at the same speed and test system settings as the pipe to be tested.
10.11.4 The signal-to-noise ratio for the reference standard shall be 2 1 ⁄ 2 to 1 or greater. Extraneous signals caused by identifiable causes such as dings, scratches, dents, straightener marks, and so forth, shall not be considered noise. The rejection amplitude shall be adjusted to be at least 50 % of full scale of the readout display.
10.11.5 If upon any standardization, the rejection amplitude has decreased by 29 % (3 dB) of peak height from the last standardization, the pipe since the last calibration shall be rejected. The test system settings may be changed, or the transducer(s), coil(s) or sensor(s) adjusted, and the unit restandardized, but all pipe tested since the last acceptable standardization must be retested for acceptance.
10.12 Evaluation ofImperfections:
10.12.1 Pipes producing a signal equal to or greater than the lowest signal produced by the reference standard(s) shall be identified and separated from the acceptable pipes. The area producing the signal may be reexamined.
10.12.2 Such pipes shall be rejected if the test signal was produced by imperfections that cannot be identified or was produced by cracks or crack-like imperfections. These pipes may be repaired in accordance with Sections 12 and 13. To be accepted, a repaired pipe must pass the same nondestructive test by which it was rejected, and it must meet the minimum wall thickness requirements of this specification.
10.12.3 If the test signals were produced by visual imperfections such as:
(1) Scratches,
(2) Surface roughness,
(3) Dings,
(4) Straightener marks,
(5) Cutting chips,
(6) Steel die stamps,
(7) Stop marks, or
(8) Pipe reducer ripple.
The pipe may be accepted based on visual examination provided the imperfection is less than 0.004 in. [0.1 mm] or 12 1 ⁄ 2 % of the specified wall thickness (whichever is greater).
10.12.4 Rejected pipe may be reconditioned and retested providing the wall thickness is not decreased to less than that required by this or the product specification. The outside diameter at the point ofgrinding may be reduced by the amount so removed. To be accepted, retested pipe shall meet the test requirement.
10.12.5 If the imperfection is explored to the extent that it can be identified as non-rejectable, the pipe may be accepted without further test providing the imperfection does not encroach on the minimum wall thickness.
11. Mechanical Tests Required
11.1 Lot—For tension and flattening tests, the term “lot”applies to all pipe of the same nominal size and wall thickness (or schedule) that is produced from the same heat of steel and subjected to the same finishing treatment in a continuous furnace or by directly obtaining the heat treated condition by quenching after hot forming. When final heat treatment is in a batch-type furnace, the lot shall include only that pipe which is heat treated in the same furnace charge.
11.2 Transverse or Longitudinal Tension Test—The tension test shall be performed on 1 % of the pipe from each lot.
11.3 Flattening Test—For pipe heat treated in a batch-type furnace, the flattening test shall be made on 5 % of the pipe from each heat-treated lot. When heat treated by the continuous process or when treated condition is obtained directly by quenching after hot forming, this test shall be made on a sufficient number of pipe to constitute 5 % of the lot but in no case less than two pipes.
12. Certification
12.1 In addition to the certification required by Specification A999/A999M, the certification for pipe furnished to this specification shall identify each length of pipe which is furnished without the manufacturer’s completed hydrostatic test, in accordance with 10.3.
13. Product Marking
13.1 In addition to the marking prescribed in Specification A999/A999M, the marking shall include the ANSI schedule number, the heat number or manufacturer’s number by which the heat can be identified, the marking requirements of 5.2,and, if applicable, NH when hydrotesting is not performed and ET when eddy-current testing is performed, or UT when ultrasonic testing is performed.
13.2 If the pipe conforms to any of the supplementary requirements specified in S1 through S10, compliance shall be so indicated by adding the symbol “S” directly followed by the number of the applicable supplementary requirement to the marking prescribed in 13.1.
13.3 No steel indentation stamping shall be done without the purchaser’s consent.
14. Keywords
14.1 austenitic stainless steel; central station service; feedwater heater tubes; stainless steel tube; steel tube; welded steel tube
Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Service
1. Scope*
1.1 This specification covers seamless austenitic steel pipe intended for high-temperature service. Among the grades covered are H grades and nitrogen grades that are specifically intended for high-temperature service.
NOTE 1—This specification was originally developed for use for piping in the central stations of electric-power generating thermal plants. However, its use is not restricted to such applications and it may be used in other applications for which the attributes ofthe materials, as defined by this specification, are appropriate.
1.2 Optional supplementary requirements (S1 through S10) are provided. These supplementary requirements specify additional tests that will be made only when stated in the order,together with the number of such tests required.
1.3 Grades TP321 and TP321H have lower strength requirements for nominal wall thicknesses greater than 3 ⁄ 8 in. [9.5mm].
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 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. The inch-pound units shall apply unless the “M”designation of this specification is specified in the order.
NOTE 2—The dimensionless designators NPS (nominal pipe size) and DN (Diametre Nominel) have been substituted in this standard for such traditional terms as “nominal diameter,” “size,” and “nominal size.”
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E112 Test Methods for Determining Average Grain Size
E213 Practice for Ultrasonic Testing of Metal Pipe and Tubing
E381 Method of Macroetch Testing Steel Bars, Billets,Blooms, and Forgings
E426 Practice for Electromagnetic (Eddy Current) Examination of Seamless and Welded Tubular Products, Titanium,Austenitic Stainless Steel and Similar Alloys
2.2 Other Standards:
SNT-TC-1A Personnel Qualification and Certification in Nondestructive Testing
3. Ordering Information
3.1 Orders for material to this specification should 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 (seamless austenitic steel pipe),
3.1.3 Grade (Table 1),
3.1.4 Size (nominal size, or outside diameter and schedule number or average wall thickness),
3.1.5 Lengths (specific or random), (Permissible Variations in Length Section of Specification A999/A999M),
3.1.6 End finish (Ends Section of Specification A999/A999M),
3.1.7 Optional requirements (Section 8) (see Hydrostatic Test Requirements Section and the Permissible Variation in Weight for Seamless Pipe Section for weighing individual lengths, of Specification A999/A999M), (see 9.6, repairing by welding; 13.3, die stamping),
3.1.8 Test report required (Certification Section of Specification A999/A999M),
3.1.9 Specification designation, and
3.1.10 Special requirements or any supplementary requirements selected, or both.
4. General Requirements
4.1 Material furnished to this specification shall conform to the applicable requirements of the current edition of Specification A999/A999M unless otherwise provided herein.
5. Materials and Manufacture
5.1 Manufacture—At the manufacturer’s option, pipe may be either hot finished or cold finished, with a suitable finishing treatment, where necessary.
5.2 Heat Treatment:
5.2.1 All pipe shall be furnished in the heat-treated condition unless the order specifically states that no final heat treatment shall be applied. When the order is furnished without final heat treatment, each pipe shall be stenciled “HT-O.”
5.2.2 As an alternate to final heat treatment in a continuous furnace or batch-type furnace, immediately following hot forming while the temperature of the pipes is not less than the specified minimum solution treatment temperature, pipes may be individually quenched in water or rapidly cooled by other means.
5.2.3 Grades TP304, TP304N, TP304LN, TP316, TP316N,TP316LN, TP321, TP347, TP347LN, TP348, 16-8-2H,S 31725, and S 31726—Unless otherwise stated in the order,heat treatment shall consist of heating to a minimum temperature of 1900 °F [1040 °C] and quenching in water or rapidly cooling by other means.
5.2.3.1 The purchaser may specify controlled structural or special service characteristics which shall be used as a guide for the most suitable heat treatment. If the final heat treatment is at a temperature under 1900 °F [1040 °C], each pipe shall be stenciled with the final heat treatment temperature in degrees Fahrenheit or Celsius after the suffix “HT.”
5.2.4 Grades TP304H, TP316H, TP321H, TP347H,TP348H, and 16-8-2H—If cold working is involved in processing, the minimum solution-treating temperature for Grades TP321H, TP347H, and TP348H shall be 2000 °F [1100°C], for Grades TP304H and TP316H, 1900 °F [1040 °C], and for Grade 16-8-2H, 1800 °F [980 °C]. If the material is hot-rolled, the minimum solution-treating temperatures for Grades TP321H, TP347H, and TP348H shall be 1925 °F [1050°C], for Grades TP304H and TP316H, 1900 °F [1040 °C], and for Grade 16-8-2H, 1800 °F [980 °C].
5.2.5 Grade S34565—Heat treatment shall consist of heating to a temperature in the range of 2050 °F [1120 °C] minimum and 2140 °F [1170 °C] maximum, and quenching in water or rapidly cooling by other means.
5.2.6 Grade S31266—Heat treatment shall consist of heating to a temperature in the range of 2100 °F [1150 °C] minimum and quenching in water or rapidly cooling by other means.
5.3 A solution annealing temperature above 1950 °F [1065°C] may impair the resistance to intergranular corrosion after subsequent exposure to sensitizing conditions in TP321,TP321H, TP347, TP347H, TP348, and TP348H. When specified by the purchaser, a lower temperature stabilization or re-solution anneal shall be used subsequent to the initial high temperature solution anneal (see Supplementary Requirement S9).
5.4 The grain size of grades 304H, 316H, 321H, 347H, and 348H as determined in accordance with Test Methods E112,shall be No. 7 or coarser.
6. Chemical Composition
6.1 The steel shall conform to the requirements as to chemical composition prescribed in Table 1.
TABLE 1 Chemical Requirements
| Grade |
UNS Desig- nation |
Composition, % A
|
||||||||||||
| Carbon |
Man- ganese |
Phos- phorus |
Sul- fur |
Sili- con |
Nickel | Chromium |
Molyb- denum |
Tita- nium |
Colum- bium |
Tan- talum |
Nitro- gen B |
Others | ||
| TP304 | S30400 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 8.0–11.0 | 18.0–20.0 | . . . | . . . | . . . | . . . | . . . | . . . |
| TP304H | S30409 | 0.04–0.10 | 2.00 | 0.045 | 0.030 | 0.75 | 8.0–11.0 | 18.0–20.0 | . . . | . . . | . . . | . . . | . . . | . . . |
| TP304N | S30451 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 8.0–11.0 | 18.0–20.0 | . . . | . . . | . . . | . . . | 0.10–0.16 | . . . |
| TP304LN | S30453 | 0.035 | 2.00 | 0.045 | 0.030 | 0.75 | 8.0–11.0 | 18.0–20.0 | . . . | . . . | . . . | . . . | 0.10–0.16 | . . . |
| TP316 | S31600 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 11.0–14.0 | 16.0–18.0 | 2.00–3.00 | . . . | . . . | . . . | . . . | . . . |
| TP316H | S31609 | 0.04–0.10 | 2.00 | 0.045 | 0.030 | 0.75 | 11.0–14.0 | 16.0–18.0 | 2.00–3.00 | . . . | . . . | . . . | . . . | . . . |
| TP316N | S31651 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 11.0–14.0 | 16.0–18.0 | 2.00–3.00 | . . . | . . . | . . . | 0.10–0.16 | . . . |
| TP316LN | S31653 | 0.035 | 2.00 | 0.045 | 0.030 | 0.75 | 11.0–14.0 | 16.0–18.0 | 2.00–3.00 | . . . | . . . | . . . | 0.10–0.16 | . . . |
| TP321 | S32100 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 9.0–13.0 | 17.0–19.0 | . . . | C | . . . | . . . | . . . | . . . |
| TP321H | S32109 | 0.04–0.10 | 2.00 | 0.045 | 0.030 | 0.75 | 9.0–13.0 | 17.0–19.0 | . . . | D | . . . | . . . | . . . | . . . |
| TP347 | S34700 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 9.0–13.0 | 17.0–19.0 | . . . | . . . | E | . . . | . . . | . . . |
| TP347H | S34709 | 0.04–0.10 | 2.00 | 0.045 | 0.030 | 0.75 | 9.0–13.0 | 17.0–19.0 | . . . | . . . | F | . . . | . . . | . . . |
| TP347LN | S34751 |
0.005– 0.020 |
2.00 | 0.045 | 0.030 | 1.00 | 9.0–13.0 | 17.0–19.0 | . . . | . . . |
0.20– 0.50 G |
. . . | 0.06–0.10 | . . . |
| TP348 J | S34800 | 0.08 | 2.00 | 0.045 | 0.030 | 0.75 | 9.0–13.0 | 17.0–19.0 | . . . | . . . | E | 0.10 | . . . | Co 0.20 |
| TP348H | S34809 | 0.04–0.10 | 2.00 | 0.045 | 0.030 | 1.00 | 9.0–13.0 | 17.0–19.0 | . . . | . . . | F | 0.10 | . . . | . . . |
| 16-8-2H | S16800 | 0.05–0.10 | 2.00 | 0.045 | 0.030 | 0.75 | 7.5–9.5 | 14.5–16.5 | 1.50–2.00 | . . . | . . . | . . . | . . . | . . . |
| . . . | S31725 | 0.030 | 2.00 | 0.045 | 0.030 | 0.75 | 13.5–17.5 | 18.0–20.0 | 4.0–5.0 | . . . | . . . | . . . | 0.20 max | Cu 0.75 |
| . . . | S31726 | 0.030 | 2.00 | 0.045 | 0.030 | 0.75 | 14.5–17.5 | 17.0–20.0 | 4.0–5.0 | . . . | . . . | . . . | 0.10–0.20 | Cu 0.75 |
| . . . | S34565 | 0.030 | 5.0–7.0 | 0.030 | 0.010 | 1.00 | 16.0–18.0 | 23.0–25.0 | 4.0–5.0 | . . . | . . . | . . . | 0.040–0.060 | Cb 0.10 |
| . . . | S31266 | 0.030 | 2.00–4.00 | 0.035 | 0.020 | 1.00 | 21.0–24.0 | 23.0–25.0 | 5.2–6.2 | . . . | . . . | . . . | 0.035–0.060 |
Cu 1.00–2.50 W 1.50–2.50 |
A Maximum, unless otherwise indicated. Where ellipses (. . .) appear in this table, there is no requirement and analysis for the element need not be determined or reported.
B The method of analysis for nitrogen shall be a matter of agreement between the purchaser and manufacturer.
C The titanium content shall be not less than five times the carbon content and not more than 0.70 %.
D The titanium content shall be not less than four times the carbon content and not more than 0.70 %.
E The columbium content shall be not less than ten times the carbon content and not more than 1.10 %.
F The columbium content shall be not less than eight times the carbon content and not more than 1.10 %.
G The columbium content shall not be less than 15 times the carbon content.
J This grade is intended for special purpose applications.
7. Product Analysis
7.1 At the request of the purchaser, an analysis of one billet from each heat or two pipes from each lot shall be made by the manufacturer. A lot of pipe shall consist of the number of lengths as a function of size, as shown below, of the same size and wall thickness from any one heat of steel:
| NPS [DN] Designator | Lengths of Pipe in Lot |
| Under NPS 2 [DN 50] | 400 or fraction thereof |
| NPS 2 [DN 50] to NPS 5 [DN 125], incl | 200 or fraction thereof |
| Over NPS 5 [DN 125] | 100 or fraction thereof |
7.2 The results of these analyses shall be reported to the purchaser or the purchaser’s representative, and shall conform to the requirements specified in Table 1.
7.3 If the analysis of one of the tests specified in Section 8 does not conform to the requirements specified in Section 6, an analysis of each billet or pipe from the same heat or lot may be made, and all billets or pipe conforming to the requirements shall be accepted.
8. Tensile Requirements
8.1 The material shall conform to the requirements as to tensile properties prescribed in Table 2.
TABLE 2 Tensile Requirements
| Grade |
Tensile A strength, min, ksi [MPa] |
Yield strength min,ksi[MPa] |
Elongation in 2 in. or 50 mm (or 4D) min, % | |
| Longitudinal | Transverse | |||
|
TP304, TP304H, TP304LN, TP316, TP316H, TP316LN, TP347, TP347H, TP347LN, TP348, TP348H, 16-8-2H, S31725 |
75[515] | 30[205] | 35 | 25 |
|
TP304N, TP316N, S31726 |
80[550] | 35[240] | 35 | 25 |
| S34565 | 115[790] | 60[415] | 35 | 30 |
| TP321, 321H | ||||
|
#0.375 in. [9.50 mm] |
75[515] | 30[205] | 35 | 25 |
|
>0.375 in. [9.50 mm] B |
70[480] | 25[170] | 35 | 25 |
| S31266 | 109 [750] | 61[420] | 35 | 25 |
A For grade TP304, NPS8 or larger, and in schedules 140 and heavier, the required minimum tensile strength shall be 70 ksi [480 MPa].
B Prior to the issuance of A376/A376M – 88, the tensile and yield strength values were 75 [520] and 30 [210] respectively, for nominal wall greater than 0.375 in.[9.5 mm].
9. Workmanship, Finish, and Appearance
9.1 The pipe manufacturer shall explore a sufficient number ofvisual surface imperfections to provide reasonable assurance that they have been properly evaluated with respect to depth.Exploration ofall surface imperfections is not required but may be necessary to assure compliance with 9.2.
9.2 Surface imperfections that penetrate more than 12 1 ⁄ 2 % of the nominal wall thickness or encroach on the minimum wall thickness shall be considered defects. Pipe with such defects shall be given one of the following dispositions:
9.2.1 The defect may be removed by grinding provided that the remaining wall thickness is within specified limits.
9.2.2 Repaired in accordance with the repair welding provisions of 9.6.
9.2.3 The section of pipe containing the defect may be cut off within the limits of requirements on length.
9.2.4 Rejected.
9.3 To provide a workmanlike finish and basis for evaluating conformance with 9.2, the pipe manufacturer shall remove by grinding the following:
9.3.1 Mechanical marks, abrasions (see Note 3), and pits,any of which imperfections are deeper than 1 ⁄ 16 in. [1.6 mm].
NOTE 3—Marks and abrasions are defined as cable marks, dinges, guide marks, roll marks, ball scratches, scores, die marks, and so forth.
9.3.2 Visual imperfections commonly referred to as scabs,seams, laps, tears, or slivers found by exploration in accordance with 9.1 to be deeper than 5 % of the nominal wall thickness.
9.4 At the purchaser’s discretion, pipe shall be subject to rejection if surface imperfections acceptable under 9.2 are not scattered, but appear over a large area in excess of what is considered a workmanlike finish. Disposition ofsuch pipe shall be a matter of agreement between the manufacturer and the purchaser.
9.5 When imperfections or defects are removed by grinding,a smooth curved surface shall be maintained, and the wall thickness shall not be decreased below that permitted by this specification. The outside diameter at the point ofgrinding may be reduced by the amount so removed.
9.5.1 Wall thickness measurements shall be made with a mechanical caliper or with a properly calibrated nondestructive testing device of appropriate accuracy. In case of dispute, the measurement determined by use ofthe mechanical caliper shall govern.
9.6 Weld repair shall be permitted only subject to the approval of the purchaser and in accordance with Specification A999/A999M.
9.7 The finished pipe shall be reasonably straight.
9.8 The pipe shall be free of scale and contaminating iron particles. Pickling, blasting, or surface finishing is not mandatory when pipe is bright annealed. The purchaser may request that a passivating treatment be applied.
10. Hydrostatic or Nondestructive Electric Test
10.1 Each pipe shall be subjected to the Nondestructive Electric Test or the Hydrostatic Test. Unless specified by the purchaser, either test may be used at the option ofthe producer.
10.2 Hydrostatic Test—Each length of finished pipe shall be subjected to the hydrostatic test in accordance with Specification A999/A999M, unless specifically exempted under the provisions of 10.3 and 10.4.
10.3 For pipe sizes NPS 24 [DN 600] and over, the purchaser, with the agreement of the manufacturer, may complete the hydrostatic test requirement with the system pressure test, which may be lower or higher than the specification test pressure, but in no case shall the test pressure be lower than the system design pressure. Each length of pipe furnished without the completed manufacturer’s hydrostatic test shall include with the mandatory marking the letters “NH.”
10.4 Nondestructive Examination—Each pipe shall be examined with a nondestructive test in accordance with Practice E213 or Practice E426. Unless specifically called out by the purchaser, the selection of the nondestructive electric test will be at the option of the manufacturer. The range of pipe sizes that may be examined by each method shall be subject to the limitations in the scope of the respective practices.
10.4.1 The following information is for the benefit of the user of this specification:
10.4.1.1 The reference standards defined in 10.10.1 through 11.10.4 are convenient standards for calibration of nondestructive testing equipment. The dimensions of these standards should not be construed as the minimum size imperfection detectable by such equipment.
10.4.1.2 The ultrasonic testing (UT) can be performed to detect both longitudinally and circumferentially oriented defects. It should be recognized that different techniques should be employed to detect differently oriented imperfections. The examination may not detect short, deep, defects.
10.4.1.3 The eddy-current testing (ET) referenced in Practice E426 has the capability of detecting significant discontinuities, especially the short abrupt type.
10.4.1.4 A purchaser interested in ascertaining the nature (type, size, location, and orientation) ofdiscontinuities that can be detected in the specific application of these examinations should discuss this with the manufacturer of the tubular product.
10.5 Time of Examination—Nondestructive testing for specification acceptance shall be performed after all mechanical processing, heat treatments, and straightening operations.This requirement does not preclude additional testing at earlier stages in the processing.
10.6 Surface Condition:
10.6.1 All surfaces shall be free of scale, dirt, grease, paint,or other foreign material that could interfere with interpretation oftest results. The methods used for cleaning and preparing the surfaces for examination shall not be detrimental to the base metal or the surface finish.
10.6.2 Excessive surface roughness or deep scratches can produce signals that interfere with the test.
10.7 Extent ofExamination:
10.7.1 The relative motion ofthe pipe and the transducer(s),coil(s), or sensor(s) shall be such that the entire pipe surface is scanned, except as in 5.2.
10.7.2 The existence of end effects is recognized, and the extent of such effects shall be determined by the manufacturer,and, if requested, shall be reported to the purchaser. Other nondestructive tests may be applied to the end areas, subject to agreement between the purchaser and the manufacturer.
10.8 Operator Qualifications—The test unit operator shall be certified in accordance with SNT-TC-1A, or an equivalent recognized and documented standard.
10.9 Test Conditions:
10.9.1 For eddy-current testing, the excitation coil frequency shall be chosen to ensure adequate penetration yet provide good signal-to-noise ratio.
10.9.2 The maximum eddy-current coil frequency used shall be as follows:
| Specified Wall Thickness, in. [mm] | Maximum Frequency, KHz |
| <0.050 [1.25] | 100 |
| 0.050 to 1.50 [1.25 to 3.80] | 50 |
| >0.150 [3.80] | 10 |
10.9.3 Ultrasonic—For examination by the ultrasonic method, the minimum nominal transducer frequency shall be 2.00 MHz and the maximum nominal transducer size shall be 1.5 in. [38 mm].
10.9.3.1 If the equipment contains a reject notice filter setting, this shall remain off during calibration and testing unless linearity can be demonstrated at that setting.
10.10 Reference Standards:
10.10.1 Reference standards of convenient length shall be prepared from a length ofpipe ofthe same grade, size (NPS, or outside diameter and schedule or wall thickness), surface finish, and heat treatment condition as the pipe to be examined.
10.10.2 For Ultrasonic Testing, the reference ID and OD notches shall be any one of the three common notch shapes shown in Practice E213, at the option of the manufacturer. The depth of each notch shall not exceed 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in. [0.1 mm],whichever is greater. The width of the notch shall not exceed twice the depth. Notches shall be placed on both the OD and ID surfaces.
10.10.3 For Eddy-Current Testing, the reference standard shall contain, at the option of the manufacturer, any one of the following discontinuities:
10.10.3.1 Drilled Hole—The reference standard shall contain three or more holes, equally spaced circumferentially around the pipe and longitudinally separated by a sufficient distance to allow distinct identification of the signal from each hole. The holes shall be drilled radially and completely through the pipe wall, with care being taken to avoid distortion of the pipe while drilling. One hole shall be drilled in the weld, if visible. Alternately, the producer ofwelded pipe may choose to drill one hole in the weld and run the calibration standard through the test coils three times with the weld turned at 120° on each pass. The hole diameter shall vary with NPS as follows:
| NPS [DN] Designator | Hole Diameter |
| 0.039 in. [1 mm] | |
| above 1 ⁄ 2 to 1 1 ⁄ 4 [15 to 32] | 0.055 in. [1.4 mm] |
| above 1 1 ⁄ 4 to 2 [32 to 50] | 0.071 in. [1.8 mm] |
| above 2 to 5 [50 to 125] | 0.087 in. [2.2 mm] |
| above 5 [125] | 0.106 in. [2.7 mm] |
10.10.3.2 Transverse Tangential Notch—Using a round tool or file with a 1 ⁄ 4 -in. [6.4-mm] diameter, a notch shall be filed or milled tangential to the surface and transverse to the longitudinal axis of the pipe. Said notch shall have a depth not exceeding 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in. [0.102 mm], whichever is greater.
10.10.3.3 Longitudinal Notch—A notch 0.031 in. [0.8 mm] or less in width shall be machined in a radial plane parallel to the tube axis on the outside surface of the pipe, to have a depth not exceeding 12 1 ⁄ 2 % of the specified wall thickness of the pipe or 0.004 in. [0.1 mm], whichever is greater. The length of the notch shall be compatible with the testing method.
10.10.3.4 More or smaller reference discontinuities, or both,may be used by agreement between the purchaser and the manufacturer.
10.11 Standardization Procedure:
10.11.1 The test apparatus shall be standardized at the beginning and end of each series of pipes of the same size (NPS or diameter and schedule or wall thickness), grade and heat treatment condition, and at intervals not exceeding 4 h.More frequent standardization may be performed at the manufacturer’s option or may be required upon agreement between the purchaser and the manufacturer.
10.11.2 The test apparatus shall also be standardized after any change in test system settings; change of operator; equipment repair; or interruption due to power loss, process shutdown, or when a problem is suspected.
10.11.3 The reference standard shall be passed through the test apparatus at the same speed and test system settings as the pipe to be tested.
10.11.4 The signal-to-noise ratio for the reference standard shall be 2 1 ⁄ 2 to 1 or greater. Extraneous signals caused by identifiable causes such as dings, scratches, dents, straightener marks, and so forth, shall not be considered noise. The rejection amplitude shall be adjusted to be at least 50 % of full scale of the readout display.
10.11.5 If upon any standardization, the rejection amplitude has decreased by 29 % (3 dB) of peak height from the last standardization, the pipe since the last calibration shall be rejected. The test system settings may be changed, or the transducer(s), coil(s) or sensor(s) adjusted, and the unit restandardized, but all pipe tested since the last acceptable standardization must be retested for acceptance.
10.12 Evaluation ofImperfections:
10.12.1 Pipes producing a signal equal to or greater than the lowest signal produced by the reference standard(s) shall be identified and separated from the acceptable pipes. The area producing the signal may be reexamined.
10.12.2 Such pipes shall be rejected if the test signal was produced by imperfections that cannot be identified or was produced by cracks or crack-like imperfections. These pipes may be repaired in accordance with Sections 12 and 13. To be accepted, a repaired pipe must pass the same nondestructive test by which it was rejected, and it must meet the minimum wall thickness requirements of this specification.
10.12.3 If the test signals were produced by visual imperfections such as:
(1) Scratches,
(2) Surface roughness,
(3) Dings,
(4) Straightener marks,
(5) Cutting chips,
(6) Steel die stamps,
(7) Stop marks, or
(8) Pipe reducer ripple.
The pipe may be accepted based on visual examination provided the imperfection is less than 0.004 in. [0.1 mm] or 12 1 ⁄ 2 % of the specified wall thickness (whichever is greater).
10.12.4 Rejected pipe may be reconditioned and retested providing the wall thickness is not decreased to less than that required by this or the product specification. The outside diameter at the point ofgrinding may be reduced by the amount so removed. To be accepted, retested pipe shall meet the test requirement.
10.12.5 If the imperfection is explored to the extent that it can be identified as non-rejectable, the pipe may be accepted without further test providing the imperfection does not encroach on the minimum wall thickness.
11. Mechanical Tests Required
11.1 Lot—For tension and flattening tests, the term “lot”applies to all pipe of the same nominal size and wall thickness (or schedule) that is produced from the same heat of steel and subjected to the same finishing treatment in a continuous furnace or by directly obtaining the heat treated condition by quenching after hot forming. When final heat treatment is in a batch-type furnace, the lot shall include only that pipe which is heat treated in the same furnace charge.
11.2 Transverse or Longitudinal Tension Test—The tension test shall be performed on 1 % of the pipe from each lot.
11.3 Flattening Test—For pipe heat treated in a batch-type furnace, the flattening test shall be made on 5 % of the pipe from each heat-treated lot. When heat treated by the continuous process or when treated condition is obtained directly by quenching after hot forming, this test shall be made on a sufficient number of pipe to constitute 5 % of the lot but in no case less than two pipes.
12. Certification
12.1 In addition to the certification required by Specification A999/A999M, the certification for pipe furnished to this specification shall identify each length of pipe which is furnished without the manufacturer’s completed hydrostatic test, in accordance with 10.3.
13. Product Marking
13.1 In addition to the marking prescribed in Specification A999/A999M, the marking shall include the ANSI schedule number, the heat number or manufacturer’s number by which the heat can be identified, the marking requirements of 5.2,and, if applicable, NH when hydrotesting is not performed and ET when eddy-current testing is performed, or UT when ultrasonic testing is performed.
13.2 If the pipe conforms to any of the supplementary requirements specified in S1 through S10, compliance shall be so indicated by adding the symbol “S” directly followed by the number of the applicable supplementary requirement to the marking prescribed in 13.1.
13.3 No steel indentation stamping shall be done without the purchaser’s consent.
14. Keywords
14.1 austenitic stainless steel; central station service; feedwater heater tubes; stainless steel tube; steel tube; welded steel tube