Metallic Material Limits for Wellhead Equipment Used in High Temperature for API 6A and API 17D Applications

API TECHNICAL REPORT 6MET SECOND EDITION, AUGUST 2018

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1. Scope 1

2. Procedure 3

   1. Phase I, Phase II, and Phase III Procedure 3

   2. Phase IV Procedure 3

3. Results 4

   1. Phase I Results 4

   2. Phase II Results 5

   3. Phase III Results 5

   4. Phase IV Results 5

4. Conclusions 6

5. Recommendations 6

Annex A (informative) AISI 4130 Test Results 11

Annex B (informative) AISI 8630M Test Results 14

Annex C (informative) 21/4 Cr 1 Mo Test Results 17

Annex D (informative) AISI 4140 Test Results 20

Annex E (informative) 410 Stainless Steel Test Results 23

Annex F (informative) F6NM Test Results 26

Annex G (informative) 25 Chrome Super Duplex Test Results 29

Annex H (informative) ASTM A453 Gr. 660 Test Results from Phase II 32

ASTM A453 Gr. 660 Test Results from Phase IV 34

Annex I (informative) 718 (per Spec 6A718) Test Results 40

Annex J (informative) 725/625 Plus Test Results 43

Annex K (informative) 925 Test Results 45

Bibliography 47

Figures

1 AISI 8630M Strength Reduction with Temperature 4

A.1 Plot of 4130 Test Results 13

B.1 Plot of 8630M Test Results 16

C.1 Plot of 21/4 Cr 1 Mo Test Results 19

D.1 Plot of AISI 4140 Test Results 22

E.1 Plot of AISI 410 Stainless Steel Test Results 25

F.1 Plot of F6NM Test Results 28

G.1 Plot of 25 Chrome Super Duplex Test Results 31

H.1 Plot of ASTM A453 Gr. 660 Test Results 34

I.1 Plot of 718 (per Spec 6A718) Test Results 42

J.1 Plot of 725/625 Plus Test Results 44

K.1 Plot of 925 Test Results 46

Tables

1. List of Alloys Included in Phase I Testing 1

2. List of Alloys Included in Phase II Testing 1

3. List of Alloys Included in Phase III Testing 1

4. List of Alloys Included in Phase IV Testing 2

5. Recommended Yield Strength Reduction Ratios in Percent by Temperature 2

6. Yield Strength Reduction Factors in Percent by Temperature (from Literature) 2

7. Alloy Composition for AISI 4130 Test Material 6

8. Alloy Composition for 8630M Test Material 6

9. Alloy Composition for 21/4Cr-1Mo (F22) Test Material 7

10. Alloy Composition for AISI 4140 Test Material 7

11. Alloy Composition for 410 Stainless Steel Test Material 7

12. Alloy Composition for F6NM Stainless Steel Test Material 8

13. Alloy Composition for 25Cr Super Duplex Test Material 8

14. Alloy Composition for ASTM A453 Gr 660 Precipitation-Hardened Austenitic Stainless

    Steel (Phase II) Test Material 8

15. Alloy Composition for ASTM A453 Gr 660 Precipitation-Hardened Austenitic Stainless Steel

    (Phase IV) Test Material 9

16. Alloy Composition for Nickel Alloy 718 (per Spec 6A718) Test Material 9

17. Alloy Composition for Nickel Alloys 725 and 625 Test Material 10

18. Alloy Composition for Nickel Alloy 925 Test Material 10

A.1 AISI 4130 Test Results 11

B.1 AISI 8630M Test Results 14

C.1 21/4 Cr 1 Mo Test Results 17

D.1 AISI 4140 Test Results 20

E.1 AISI 410 Test Results 23

F.1 F6NM Test Results 26

G.1 25 Chrome Super Duplex Test Results 29

1. ASTM A453 Gr. 660 Test Results 32

2. ASTM A453 Gr. 660 Class D Initial Aging Study Results—Using 1800 °F Solution Anneal 34

3. ASTM A453 Gr. 660 Class D Initial Aging Study Results—Using 1650 °F Solution Anneal 34

4. ASTM A453 Gr. 660 Class D Test Results 35

5. ASTM A453 Gr. 660 Class D Second Aging Study Results 39

6. ASTM A453 Gr. 660 Class D Derating Factors Developed From Linear Regression Analyses 39

7. ASTM A453 Gr. 660 Class D Recommended Derating Factors 39

I.1 718 (per Spec 6A718) Test Results 40

J.1 725/625 Plus Test Results 43

K.1 925 Test Results 45

Introduction

The initial basis for this document was an API-funded project that was conducted by a task group charged by the Association of Well Head Equipment Manufacturers (AWHEM). The task group examined mechanical properties of metallic materials used for API 6A and API 17D wellhead equipment for service above 250 °F. A total of eleven different alloys meeting API 6A, PSL 3 conditions were supplied “in condition” by a variety of suppliers. Materials in this test program included alloys common to the oil and gas industry. The alloys tested included low-alloy steels, martensitic, precipitation-hardened and duplex stainless steels, and nickel alloys. Yield strength reduction ratios at temperatures of 300 °F, 350 °F, 400 °F, and 450 °F are reported. As a result of testing, yield strength reduction ratios at 300 °F to 450 °F ranged from 92 % to 87 % for the low-alloy steels, 92 % to 88 % for the martensitic stainless steels, 81 % to 73 % for super duplex, 99 % to 89 % for the precipitation-hardened stainless steel, and 94 % to 89 % for the nickel alloys. The reported results represent an average over the different heats for each type of material. These results are intended to expand the data shown in API 6A for design and rating of equipment for use at elevated temperatures.

After the accuracy of the derating factors for the precipitation-hardened stainless steel as published in the First Edition and in API 6A, 19th Edition, Annex G was questioned, another API-funded project was conducted by a task group operating under the direction of API Subcommittee 21. The results of this project have been added in the Second Edition.

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Metallic Material Limits for Wellhead Equipment Used in High Temperature for API 6A and 17D Applications

1 Scope

Testing was performed in four phases, presented herein in chronological order as Phase I, Phase II, Phase III, and Phase IV. Initially, all testing was to be completed in two phases, but testing anomalies in Phase II prompted re-testing of some alloys in Phase III and later in Phase IV.

Alloy candidates were recommended by AWHEM membership for analysis and confirmed by API’s approval of New Work Item No. 2003-100786 in June 2002. Several material suppliers and several AWHEM member companies donated material for testing. Metallurgists on the task group screened material certificates to ensure a “normal” chemistry without enhancements for the material candidates listed in Table 1, Table 2, and Table 3.

Table 1—List of Alloys Included in Phase I Testing

Table 2—List of Alloys Included in Phase II Testing

Table 3—List of Alloys Included in Phase III Testing

Another API New Work Item approved in 2014 covered a new round of testing of austenitic precipitation-hardened stainless steel ASTM A453 Grade 660 Class D (see Table 4). Three mills donated the material for testing.

A summary of the yield strength derating factors from testing of the 11 alloys is provided in Table 5 and compares favorably with the available data from literature, as provided in Table 6.

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