Designation: A 790/A 790M – 03

Standard Specification for

Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe1

This standard is issued under the fixed designation A 790/A 790M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.

1.     Scope*

1.1 This specification2 covers seamless and straight-seam welded ferritic/austenitic steel pipe intended for general corro-sive service, with particular emphasis on resistance to stress corrosion cracking. These steels are susceptible to embrittle-ment if used for prolonged periods at elevated temperatures.

1.2 Optional supplementary requirements are provided for pipe when a greater degree of testing is desired. These supplementary requirements call for additional tests to be made and, when desired, one or more of these may be specified in the order.

1.3 Appendix X1 of this specification lists the dimensions of welded and seamless stainless steel pipe as shown in ANSI B36.19. Pipe having other dimensions may be furnished provided such pipe complies with all other requirements of this specification.

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 the other. Combining values from the two systems may result in nonconformance with the specifi-cation. The inch-pound units shall apply unless the M desig-nation of this specification is specified in the order.

NOTE 1—The dimensionless designator NPS (nominal pipe size) has been substituted in this standard for such traditional terms as nominal diameter, size, and nominal size.

2.     Referenced Documents

2.1 ASTM Standards:

A 370 Test Methods and Definitions for Mechanical Testing of Steel Products3

A 941 Terminology Relating to Steel, Stainless Steel, Re?

1This specification is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.10 on Stainless and Alloy Steel Tubular Products.

Current edition approved Apr. 10, 2003. Published May 2003. Originally approved in 1981. Last previous edition approved in 2002 as A 790/A 790M – 02a.

2 For ASME Boiler and Pressure Vessel Code applications see related Specifi-cation SA–790 in Section II of that Code.

3 Annual Book of ASTM Standards, Vol 01.03.

lated Alloys and Feroalloys4

A 999/A 999M Specification for General Requirements for Alloy and Stainless Steel Pipe4

E 213 Practice for Ultrasonic Examination of Metal Pipe and Tubing5

E 309 Practice for Eddy-Current Examination of Steel Tu-bular Products Using Magnetic Saturation5

E 381 Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings6

E 426 Practice for Electromagnetic (Eddy-Current) Exami-nation of Seamless and Welded Tubular Products, Austen-itic Stainless Steel and Similar Alloys5

E 527 Practice for Numbering Metals and Alloys (UNS)4 2.2 ANSI Standards: 7

B1.20.1 Pipe Threads, General Purpose

B36.10 Welded and Seamless Wrought Steel Pipe B36.19 Stainless Steel Pipe

2.3 SAE Standard: 8

SAE J 1086

2.4 Other Standard:9

SNT-TC-1A Personal Qualification and Certification in Nondestructive Testing

3.     Terminology

3.1 Definitions—For definitions of terms used in this speci-fication refer to Terminology A 941.

4.     Ordering Information

4.1 Orders for material under this specification should include the following, as required, to describe the desired material adequately:

4.1.1 Quantity (feet, metres, or number of lengths), 

4.1.2 Name of material (ferritic/austenitic steel pipe),

 Annual Book of ASTM Standards, Vol 01.01.

 Annual Book of ASTM Standards, Vol 03.03.

Annual Book of ASTM Standards, Vol 03.01.

Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.

Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001.

 Available from The American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.

*A Summary of Changes section appears at the end of this standard.

Copyright ? ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

4.1.3 Process (seamless or welded),

4.1.4 Grade (see Table 1),

4.1.5 Size (NPS designator or outside diameter and sched-ule number of average wall thickness),

4.1.6 Length (specific or random) (see Section 11),

4.1.7 End finish (section on ends of Specification A 999/ A 999M),

4.1.8 Optional requirements (product analysis, Section 9; hydrostatic test or nondestructive electric test, Section 14),

4.1.9 Test report required (section on certification of Speci-fication A 999/A 999M),

4.1.10 Specification designation, and

4.1.11 Special requirements and any supplementary require-ments selected.

5.     General Requirements

5.1 Material furnished under this specification shall con-form to the applicable requirements of the current edition of Specification A 999/A 999M unless otherwise provided herein.

6.     Materials and Manufacture

6.1 Manufacture:

6.1.1 The pipe shall be made by the seamless or an automatic welding process, with no addition of filler metal in the welding operation.

6.1.2 At the manufacturer’s option, pipe may be either hot-finished or cold-finished.

6.1.3 The pipe shall be pickled free of scale. When bright annealing is used, pickling is not necessary.

6.2 Discard—A sufficient discard shall be made from each ingot to secure freedom from injurious piping and undue segregation.

6.3 All pipe shall be furnished in the heat-treated condition as shown in Table 1. For seamless pipe, 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.

7.     Chemical Composition

7.1 The steel shall conform to the chemical requirements as prescribed in Table 2.

8.     Heat Analysis

8.1 An analysis of each heat of steel shall be made by the steel manufacturer to determine the percentages of the ele-ments specified.

9.     Product Analysis

9.1 At the request of the purchaser’s inspector, an analysis of one billet or one length of flat-rolled stock from each heat, or two pipes from each lot, shall be made by the manufacturer. A lot of pipe shall consist of the following number of lengths of the same size and wall thickness from any one heat of steel:

NPS Designator                              Lengths of Pipe in Lot

Under 2                                      400 or fraction thereof

2 to 5, incl                                   200 or fraction thereof

6 and over                                   100 or fraction thereof

9.2 The results of these analyses shall be reported to the purchaser or the purchaser’s representative and shall conform to the requirements specified in Section 7.

9.3 If the analysis of one of the tests specified in 8.1 or 9.1 does not conform to the requirements specified in Section 7, 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.

10. Tensile and Hardness Properties

10.1 The material shall conform to the tensile and hardness properties prescribed in Table 3.

11. Lengths

11.1 Pipe lengths shall be in accordance with the following regular practice:

11.1.1 Unless otherwise agreed upon, all sizes from NPS 1¤8 to and including NPS 8 are available in a length up to 24 ft (see Note 2) with the permissible range of 15 to 24 ft (see Note 2). Short lengths are acceptable and the number and minimum length shall be agreed upon between the manufacturer and the purchaser.

NOTE 2—This value applies when the inch-pound designation of this specification is the basis of purchase. When the M designation of this specification is the basis of purchase, the corresponding metric value(s) shall be agreed upon between the manufacturer and purchaser.

11.1.2 If definite cut lengths are desired, the lengths re-quired shall be specified in the order. No pipe shall be less than the specified length and no more than 1¤4 in. [6 mm] over it.

TABLE 2 Chemical Requirements

A New designation established in accordance with Practice E 527 and SAE J1086.

B %Cr+3.3 3 %Mo+16 3 %N.

TABLE 3 Tensile and Hardness Requirements

                         Tensile                           Yield                Elongation                 

UNS                 Strength,                        Strength,          2 in. or

Designation     min, ksi                            min,                50 mm,

                        [MPa]                             ksi [MPa]            min, %            Hardness, max 

                                                                                                              Brinell         HRC

A Prior to A 790/A 790M – 87, the values for S31260 were: 92 ksi tensile strength, 54 ksi yield strength, and 30 % elongation.

B Prior to A 790/A 790M – 89, the tensile strength value was 90 ksi for UNS S32950.

11.1.3 No jointers are permitted unless otherwise specified. 12. Workmanship, Finish, and Appearance

12.1 The finished pipes shall be reasonably straight and shall have a workmanlike finish. Imperfections may be re-moved by grinding, provided the wall thicknesses are not decreased to less than that permitted, in the Permissible Variations in Wall Thickness Section of Specification A 999/ A 999M.

13.    Mechanical Tests Required

13.1 Transverse or Longitudinal Tension Test—One tension test shall be made on a specimen for lots of not more than 100 pipes. Tension tests shall be made on specimens from 2 pipes for lots of more than 100 pipes.

NOTE 3—The term lot for mechanical tests 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 (1) in a continuous heat treatment furnace, or (2) in a batch-type heat-treatment furnace equipped with recording pyrometers and automatically controlled within a 50°F [30°C] range, the larger of (a) each 200 ft [60 m] or fraction thereof or (b) that pipe heat treated in the same batch furnace charge.

13.2 Flattening Test—For material heat treated in a batch-type furnace, flattening tests shall be made on 5% of the pipe from each heat-treated lot. For material heat treated by the continuous process, this test shall be made on a sufficient number of pipes to constitute 5% of the lot, but in no case less than two lengths of pipe.

13.2.1 For welded pipe with a diameter equal to or exceed-ing NPS 10, a transverse guided face bend test of the weld may be conducted instead of a flattening test in accordance with the method outlined in the steel tubular product supplement of Test Methods and Definitions A 370. The ductility of the weld shall be considered acceptable when there is no evidence of cracks in the weld or between the weld and the base metal after bending. Test specimens from 5% of the lot shall be taken from the pipes or test plates of the same material as the pipe, the test plates being attached to the end of the cylinder and welded as a prolongation of the pipe longitudinal seam.

13.3 Hardness Test—Brinell or Rockwell hardness tests shall be made on specimens from two pipes from each lot (see Note 3).

14.    Hydrostatic or Nondestructive Electric Test

14.1 Each pipe shall be subjected to the nondestructive electric test or the hydrostatic test. The type of test to be used

shall be at the option of the manufacturer, unless otherwise specified in the purchase order.

14.2 The hydrostatic test shall be in accordance with Speci-fication A 999/A 999M, except that the value for S to be used in the calculation of the hydrostatic test pressure shall be equal to 50 % of the specified minimum yield strength of the pipe.

14.3 Nondestructive Electric Test:

Nondestructive electric tests shall be in accordance with Practice E 213 or E 309.

14.3.1 As an alternative to the hydrostatic test, and when specified by the purchaser, each pipe shall be examined with a nondestructive test in accordance with Practice E 213 or E 309. 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.

14.3.1.1 The following information is for the benefit of the user of this specification:

14.3.1.2 The reference standards defined in 14.3.1.3-14.3.1.5 are convenient standards for calibration of nondestruc-tive testing equipment. The dimensions of these standards should not be construed as the minimum size imperfection detectable by such equipment.

14.3.1.3 The ultrasonic testing (UT) can be performed to detect both longitudinally and circumferentially oriented de-fects. It should be recognized that different techniques should be employed to detect differently oriented imperfections. The examination may not detect short, deep, defects.

14.3.1.4 The eddy-current testing (ET) referenced in this specification (see Practice E 426) has the capability of detect-ing significant discontinuities, especially the short abrupt type.

14.3.1.5 A purchaser interested in ascertaining the nature (type, size, location, and orientation) of discontinuities that can be detected in the specific application of these examinations should discuss this with the manufacturer of the tubular product.

14.4 Time of Examination—Nondestructive testing for specification acceptance shall be performed after all mechani-cal processing, heat treatments, and straightening operations. This requirement does not preclude additional testing at earlier stages in the processing.

14.5 Surface Condition:

14.5.1 All surfaces shall be free of scale, dirt, grease, paint, or other foreign material that could interfere with interpretation of test results. The methods used for cleaning and preparing the surfaces for examination shall not be detrimental to the base metal or the surface finish.

14.5.2 Excessive surface roughness or deep scratches can produce signals that interfere with the test.

14.6 Extent of Examination:

14.6.1 The relative motion of the pipe and the transducer(s), coil(s), or sensor(s) shall be such that the entire pipe surface is scanned, except as in 14.6.2.

14.6.2 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. Othernondestructive tests may be applied to the end areas, subject to agreement between the purchaser and the manufacturer.

14.7 Operator Qualifications—The test unit operator shall be certified in accordance with SNT-TC-1A, or an equivalent recognized and documented standard.

14.8 Test Conditions:

14.8.1 For eddy-current testing, the excitation coil fre-quency shall be chosen to ensure adequate penetration yet provide good signal-to-noise ratio.

14.8.2 The maximum eddy-current coil frequency used shall be as follows:

On specified walls up to 0.050 in.—100 KHz max

On specified walls up to 0.150 in.—50 KHz max

On specified walls over 0.150 in.—10 KHz max

14.8.3 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. 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.

14.9 Reference Standards—Reference standards of conve-nient length shall be prepared from a length of pipe of the same grade, size (NPS, or outside diameter and schedule or wall thickness), surface finish and heat treatment condition as the pipe to be examined.

14.9.1 For Ultrasonic Testing, the reference ID and OD notches shall be any one of the three common notch shapes shown in Practice E 213, 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., 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.

14.9.2 For Eddy-Current Testing, the reference standard shall contain, at the option of the manufacturer, any one of the following discontinuities:

14.9.2.1 Drilled Hole— The reference standard shall con-tain 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 of welded 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 Designator                                  Hole Diameter 0.039 in. (1 mm)

above 1¤2 to 11¤4                                             0.055 in. (1.4 mm)

above 11¤4 to 2                                               0.071 in. (1.8 mm)

above 2 to 5                                                   0.087 in. (2.2 mm)

above 5                                                         0.106 in. (2.7 mm)

14.9.2.2 Transverse Tangential Notch—Using a round tool or file with a1¤4-in. (6.4-mm) diameter, a notch shall be filed or milled tangential to the surface and transverse to the longitu-dinal axis of the pipe. Said notch shall have a depth not exceeding 12 1¤2 % of the specified nominal wallthickness of the pipe or 0.004 in. (0.102 mm), whichever is greater.

14.9.2.3 Longitudinal Notch—A notch 0.031 in. 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 wallthickness of the pipe or 0.004 in., whichever is greater. The length of the notch shall be compatible with the testing method.

More or smaller reference discontinuities, or both, may be used by agreement between the purchaser and the manufac-turer.

14.10 Standardization Procedure:

14.10.1 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 manu-facturer’s option or may be required upon agreement between the purchaser and the manufacturer.

14.10.2 The test apparatus shall also be standardized after any change in test system settings, change of operator, equip-ment repair, or interruption due to power loss, process shut-down, or when a problem is suspected.

14.10.3 The reference standard shall be passed through the test apparatus at the same speed and test system settings as the pipe to be tested.

14.10.4 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.

14.10.5 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 restan-dardized. But all pipe tested since the last acceptable standard-ization must be retested for acceptance.

14.11 Evaluation of Imperfections:

14.11.1 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.

14.11.2 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 per Sections 12 and 13. To be accepted, a repaired pipe must pass the same non-destructive test by which it was rejected, and it must meet the minimum wall thickness requirements of this specification.

14.11.3 If the test signals were produced by visual imper-fections 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 imperfec-tion is less than 0.004 in. (0.1 mm) or 12 1¤2 % of the specified wall thickness (whichever is greater).

14.11.4 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 of grinding may be reduced by the amount so removed. To be accepted, retested pipe shall meet the test requirement.

14.11.5 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 en-croach on the minimum wall thickness.

15.    Product Marking

15.1 In addition to the marking prescribed in Specification A 999/A 999M, the marking shall include the manufacturer’s private identifying mark and whether the pipe is seamless or welded. If specified in the purchase order, the marking for pipe larger than NPS 4 shall include the weight.

16.    Keywords

16.1 duplex stainless steel; ferritic/austenitic stainless steel; seamless steel pipe; stainless steel pipe; steel pipe; welded steel pipe

SUPPLEMENTARY REQUIREMENTSFOR PIPE REQUIRING SPECIAL CONSIDERATION

One or more of the following supplementary requirements shall apply only when specified in the purchase order. The purchaser may specify a different frequency of test or analysis than is provided in the supplementary requirement. Subject to agreement between the purchaser and manufacturer, retest and retreatment provisions of these supplementary requirements may also be modified.

S1. Product Analysis

S1.1 For all pipe over NPS 5 there shall be one product analysis made of a representative sample from one piece for each ten lengths or fraction thereof from each heat of steel.

S 1.2 For pipe smaller than NPS 5 there shall be one product analysis made from ten lengths per heat of steel or from 10 % of the number of lengths per heat of steel, whichever number is smaller.

S 1.3 Individual lengths failing to conform to the chemical requirements specified in Section 7 shall be rejected.

S2. Transverse Tension Tests

S2.1 There shall be one transverse tension test made from one end of 10 % of the lengths furnished per heat of steel. This applies only to pipe over NPS 8.

S2.2 If a specimen from any length fails to conform to the tensile properties specified that length shall be rejected.

S3. Flattening Test

S3.1 The flattening test of Specification A 999/A 999M shall be made on a specimen from one end or both ends of each pipe. Crops ends may be used. If this supplementary require-ment is specified, the number of tests per pipe shall also be specified. If a specimen from any length fails because of lack of ductility prior to satisfactory completion of the first step of the flattening test requirement, that pipe shall be rejected subject to retreatment in accordance with Specification A 999/ A 999M and satisfactory retest. If a specimen from any length of pipe fails because of a lack of soundness that length shall be rejected, unless subsequent retesting indicates that the remain-ing length is sound.

S4. Etching Tests

S4.1 The steel shall be homogeneous as shown by etching tests conducted in accordance with the appropriate portions of Method E 381. Etching tests shall be made on a cross section from one end or both ends of each pipe and shall show sound and reasonably uniform material free of injurious laminations, cracks, and similar objectionable defects. If this supplementary requirement is specified, the number of tests per pipe required shall also be specified. If a specimen from any length shows objectionable defects, the length shall be rejected, subject to removal of the defective end and subsequent retests indicating the remainder of the length to be sound and reasonably uniform material.

APPENDIX

(Nonmandatory Information)

X1. Table X1.1 IS BASED ON TABLE 1 OF THE AMERICAN NATIONAL STANDARD FOR STAINLESS STEEL PIPE (ANSI
B36.19-1965)

TABLE X1.1 Dimensions of Welded and Seamless Stainless Steel Pipe

NOTE 1—The decimal thickness listed for the respective pipe sizes represents their nominal or average wall dimensions

A Schedules 5S and 10S wall thicknesses do not permit threading in accordance with the American National Standard for Pipe Threads (ANSI B1.20.1).

B These do not conform to the American National Standard for Welded and Seamless Wrought Steel Pipe (ANSI B36.10-1979).

A 790/A 790M – 03 SUMMARY OF CHANGES

Committee A01 has identified the location of selected changes to this standard that have been incorporated since the last issue (A 790/A 790M-02a) that may impact the use of this standard (approved April 2003).

(1) Added hardness test sampling requirements to new para-graph 13.3.

Committee A01 has identified the location of selected changes to this standard that have been incorporated since the last issue
(A 790/A 790M-02) that may impact the use of this standard (approved November 2002).

(1) Modified harness values referenced in Table 3: Tensile and Hardness Requirements.

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