SUB-COMMITTEE ON CARRIAGE OF CARGOES AND CONTAINERS … · 2017-08-02 · CCC 4/4/1 Annex, page 3...

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SUB-COMMITTEE ON CARRIAGE OF CARGOES AND CONTAINERS 4th session Agenda item 4

CCC 4/4/1

9 June 2017 Original: ENGLISH

SUITABILITY OF HIGH MANGANESE AUSTENITIC STEEL FOR CRYOGENIC SERVICE

AND DEVELOPMENT OF ANY NECESSARY AMENDMENTS TO THE IGC CODE AND IGF CODE

Observations on the comments from the participants of the Correspondence Group on

Suitability of High Manganese Austenitic Steel for Cryogenic Service

Submitted by the Republic of Korea

SUMMARY

Executive summary: This document provides the observations of the Republic of Korea on each comment from the first and second rounds of the Correspondence Group on Suitability of High Manganese Austenitic Steel for Cryogenic Service

Strategic direction: 5.2

High-level action: 5.2.1

Output: 5.2.1.26

Action to be taken: Paragraph 3

Related documents: MSC 96/23/5; CCC 2/INF.18; CCC 3/8, CCC 3/15; CCC 4/4, CCC 4/INF.2 and CCC 4/INF.3

Introduction 1 In order to assist the Sub-Committee in its consideration of test acceptance criteria and the suitability of high manganese austenitic steel for cryogenic service, the Republic of Korea has provided observations for each comment in the answer sheets from the first and second rounds of the Correspondence Group on Suitability of High Manganese Austenitic Steel for Cryogenic Service. The observations can be found in the annex. 2 Reflecting the observations, the Republic of Korea has also submitted updated technical information for high manganese austenitic steel in document CCC 4/INF.3.

CCC 4/4/1 Page 2


Action requested of the Sub-Committee 3 The Sub-Committee is invited to consider the comments and the corresponding observations in the annex, and take action as appropriate.

***

CCC 4/4/1 Annex, page 1


ANNEX*

OBSERVATIONS ON THE COMMENTS AND PROPOSALS FROM THE PARTICIPANTS OF THE CORRESPONDENCE GROUP

In this document, note that "the technical document by the Republic of Korea" refers to the information document CCC 4/INF.3 entitled "Updated technical information of high manganese austenitic steel for cryogenic service" submitted by the Republic of Korea.

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No. Comments Observations of the Republic of Korea

1 CHINA 1 It is recommended that the temperature of CTOD (Crack Tip Opening Displacement) test be changed to -165°C and the test specimen increase the welding fusion line (BL) See the table below:

Item Condition Requirement Reference

CTOD test

BM, BL, HAZ, WM,

-165℃

- BS 7448

<Justification> The welding fusion line is the weakest part of the entire welded joint, so it is recommended that the test be added to the CTOD test. The test temperature shall be -165 ° C in accordance with the IGC Code and the IGF Code.

Table 2 and table 3 in the technical document by the Republic of Korea specify the CTOD test at fusion line (FL) corresponding to CGHAZ (Coarse Grain Heat Affected Zone) under -165 °C. Those results are shown in table 19 in the technical document by the Republic of Korea. Table 23 in the same document can be also referred to for WM, FL (CGHAZ), FL+2 of SAW.

2 CHINA 2 (1) We suggest increasing the mechanical test and welding procedure test of pipes.

The product type of high manganese austenitic steel is a plate, which can be used as structural material of independent-type LNG tanks. Currently, the pipe of high manganese austenitic steel is yet to be available for cryogenic service so that the evaluation regarding pipe applications and amendment of table 6.4 in the IGC Code and table 7.4 in the IGF Code are not considered at the moment.

* This annex is presented in English only.



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3 CHINA 2 (2) We suggest increasing the welding conditions for GMAW (Gas Metal Arc Welding).

We are of the view that the welding conditions for SAW (Submerged Arc Welding) and FCAW (Flux- Core Arc Welding) (or GMAW (Gas Metal Arc Welding)) are sufficiently provided in table 12 of the technical document by the Republic of Korea.

4 CHINA 2 (3) We would like to know about the changes in microstructure and properties of the plate after cold processing, such as head forming.

The austenitic microstructure of high manganese austenitic steel is stable so that there is no phase transformation after cold forming or fracture event. The participants may refer to slide 7 of annex 1 and slide 10 of annex 2 to document CCC 3/J/7. Based on several practices to fabricate LNG tanks using high manganese austenitic steel, it is recommended that the maximum deformation ratio needs to be below 45% during the cold forming for C type LNG tanks.

5 FRANCE 1

Item Condition Requirement

Reference

Fatigue test on raw material and welded joint

S-N curve, 25°C and Design Temperature

-

ISO 12107 IIW XIII 2140-06 – Fatigue testing of welded joints

Cumulative fatigue damage ratio calculation

FEM (Finite Element Method) analysis

- 4.18.2 in IGC Code

[Justification] We think there is no reason to limit the high manganese steel for hot rolled product only. The addition of this kind of cryogenic metallic material has to be generic as per the austenitic

Cold-rolled products of high manganese austenitic steel are yet to be available for cryogenic service. Therefore, evaluation of cold-rolled products cannot be performed at the moment. If cold-rolled products become available later, such test items and requirements needs to be reconsidered accordingly.



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stainless steels specified in the current IGC Code table 6.3. Consequently, we shall also consider high-manganese cold rolled product (down to 0.5 mm thickness). So, fatigue tests and calculations for these thicknesses are to be included in the table 2.

6 JAPAN 1 General proposal 01: Japan proposes not to incorporate the new material, i.e. high manganese austenitic steel, into the IGC and IGF Codes until trial constructions and operations of several ships with tanks made of the new material are carried out, in order to check all the issues specified by the CG and in the relevant documents, taking into account that the new material will be used for LNG tanks of ships in the near future according to the information provided by the Republic of Korea.

We recognize the importance of track records for cryogenic applications. However, track record should not be a critical condition for the inclusion of new technology in IGC Code, because the number of track records will be significantly limited without being listed in the Code. It should be optional as reference. We are of the view that the suitability of high manganese austenitic steel for cryogenic service can be sufficiently examined by qualification tests of base metal and welding process.

7 JAPAN 1 General proposal 02: Japan is of the opinion that fracture scenarios should be determined, prior to further development of table 2 in the coordinator's remarks. In view of this, Japan proposes to check the following issues, as explained in the annex to this answer sheet, prior to the application of the new material to LNG tanks in order to maintain safety: (1) Scope of application; (2) Fracture scenario; (3) Required fracture toughness; (4) Comparison with low carbon existing austenitic material and evaluation; (5) Condition of fabrication and inspection; (6) Safety assessment; (7) Precautions for fabrication; and

We recognize the importance of scenario-based safety assessment, which is important for, not only limited to, ship applications with LNG tanks of high manganese steel, but every ship applications with LNG tanks. However, we are of the view that the scenario-based safety assessment is not suitable for general qualification of high manganese steel for cryogenic service. The scenario-based safety assessment requires that the project can describe specifically the application of high manganese steel such as "(1) Scope of application," "(2) Fracture scenario," and "(3) Required fracture toughness". Based on the configuration of that project, shipbuilders and tank fabricators will be able to perform the scenario-based safety assessment for the tank. Due to the same reasons, large scale tests such as wide plate test proposed in "(6) Safety assessment" are not suitable for general



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(8) Conditions of design of the tanks and operation of ships.

qualification of high manganese steel. The main purpose of wide-plate testing is to simulate as closely as conceivable the service performance of base metals and their welded configurations for a certain application so that the results of the wide-plate test would be meaningful to that application. We wonder if a wide-plate test has been required for general qualification of the other cryogenic materials in the IGC and IGF codes and if there are any internationally recognized standards for the procedure of wide-plate testing. However, we agree with Japan on the evaluation of ductile fracture toughness of high manganese steel at low temperature utilizing J-R curves and JIc proposed in "(6) Safety assessment,", because the testing and evaluation procedure of J-R curves and JIc is well specified in internationally recognized standards. Particularly, JIc is a size independent value of fracture toughness, referring to ASTM E1820, so that it can be utilized for general qualification tests of high manganese austenitic steel for cryogenic service. Japan proposed the evaluation of J-R curves and JIc of high manganese austenitic steel in document CCC 3/8/1, and the Republic of Korea provided the detailed J-R curves and JIc values of WM, HAZ, BM in compliance with ASTM E1820-15a in document CCC 3-J-7. We are of the view that the test acceptance criteria to consider high manganese austenitic steel for cryogenic service should be based on chapter 6 "materials of construction and quality control" in the IGC Code, because the goal of this chapter is described as "to identify the required properties, testing standards and stability of metallic and non-metallic materials and fabrication processes used in the construction of cargo containment and piping systems to ensure they serve the functions for which they have been selected, as required in chapters 4 and 5." In addition, IACS UR W1 "Material and welding for gas tankers" and W2 "Test specimens and mechanical testing procedures for materials" can be referred to for testing procedures in detail.



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8 JAPAN 1 General proposal 03: Furthermore, the conditions of use such as plate manufacturing, welding and fabrication should be restricted within the ranges that are evaluated at the trial constructions of ships. The conditions of use should also be evaluated and clarified.

Related to the observations for "General proposal 01", we are of the view that there is no reason to restrict the use of high manganese steel only within the ranges that are evaluated at the trial constructions of ships. The specific conditions of usage of high manganese steel should be determined by shipbuilders and tank fabricators for a certain project.

9 JAPAN 1 Notwithstanding the above-mentioned general comments, Japan would like to cooperate to determine the requirements for toughness in table 2, including Charpy V-notch tests, through the discussion of this CG. Detailed proposal 01: Japan proposes to add notes to table 2 in order to clarify that the evaluation of fracture toughness shall be carried out at the most conservative condition of the following parameters: - Minimum thickness, maximum thickness and the most conservative thickness; - carbon content; - welding condition; and - parts, i.e. Weld Metal (WM) or Heat Affected Zone (HAZ), etc.

We agree with Japan. Regarding "detailed proposal 01", the detailed test items for base metal and welded joints are proposed in the table 1, table 2 and table 3 of the technical document by the Republic of Korea.

10 JAPAN 1 Detailed proposal 02: Japan proposes to add "tests on strain aged specimens" in "Charpy impact tests" for confirmation of material properties, for the reason that such data is not included in the technical documents provided by the Republic of Korea.

Please refer to the table 1 in the technical document by the Republic of Korea. The corresponding data can be found out in 2.6 "Strain-aged Charpy Impact Test" in the same document.



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11 JAPAN 1 Other comments: (1) The common understanding of the CG should be established on basic parameters including mechanical properties of weld joint, tank types (e.g. type A, B, C, etc.) for which this material is intended to be applied, allowable stress proposed to use for design (or material factors A, B, etc. as in 4.22.3.1/4.23.3.1 of the IGC code) and dimension of the initial crack, prior to conducting fatigue crack propagation and ductile fracture instability analysis for crack in weld joint concerned.

Please refer to the slides 15 to 19 in annex 2 to document CCC 3/J/7. Both high manganese austenitic steel and austenitic stainless steel can be categorized as a group of austenitic steel for cryogenic service. Therefore, the design parameters for austenitic steel shown in 4.22.3.1.1 and 4.23.3.1 of the IGC code are applied to high manganese austenitic steel for cryogenic service. Furthermore, chapter 6 of the technical document by the Republic of Korea shows that the allowable design stress given by the design parameters for the category of austenitic steel are low enough that unstable fracture cannot occur.

12 JAPAN 1 (2) The test material information (including the chemical composition, mechanical properties, thickness, cooling condition after hot-rolling and reheating-heat-treatment condition after hot-rolling, etc.) to be used for the development of acceptance criteria should be clarified.

Please refer to the table 1, table 2 and table 3 of the technical document by the Republic of Korea. Manufacturing conditions after hot rolling can be found out in slide 21, slide 22, and Slide 23 of annex 2 to document CCC 3-J-7.

13 JAPAN 1 (3) It is preferable that international specifications are established for material, welding consumable and Non-Destructive Inspection (NDI), prior to commercial production.

High manganese austenitic steel is listed to ASTM as ASTM A1106/A1106M-17, "Standard Specification for Pressure Vessel Plate, Alloy Steel, Austenitic High Manganese for Cryogenic Application." Welding consumable has been type-approved by classification societies. The ultrasonic testing results of the plate product of high manganese austenitic steel can be found at 2.9 Ultrasonic test in the technical document by the Republic of Korea. Non-Destructive Inspection of the tanks made of high manganese austenitic steel should comply with 6.5.6 Non-destructive testing in the IGC Code.



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14 JAPAN 2 General Proposal 1: Japan has made three general proposals in the first round. These general proposals have not been taken on board in the second round, while some technical information, insufficient in our opinion, has been provided by the Republic of Korea. Similarly, proposals by the other participants have not been taken on board, while the Republic of Korea replied on some of these comments. Japan seeks clarification on the treatment of various proposals in the first round. Japan proposes to discuss various comments in the first round further, after summation of the comments by the coordinator. It is very much appreciated if "the coordinator" and "the Republic of Korea", i.e. one of participants to the CG, are clearly distinguished.

Please refer to the above-mentioned observations.

15 JAPAN 2 Detailed Proposal 1: Japan is of the opinion that more precise values of chemical compositions should be included in table 5, taking into account the accuracy of the tolerance of chemical compositions. Precise chemical compositions are indispensable to evaluate the data for safety assessment.

The numerical values of each chemical composition in table 5 are rounded down because of the steel maker's confidential information. We are of the opinion that these values are enough for the evaluation of the tested plate.

16 JAPAN 2 Detailed Proposal 2: Japan considers it appropriate to add microstructures of typical austenitic steel such as SUS304 in table 6, in order to clarify the difference between the new material and typical austenitic steel for cryogenic service in microstructure.

Direct comparison between the microstructure images of high manganese austenitic steel and type 304 austenitic stainless steel is not suitable. High manganese steel and type 304 stainless steel show different characteristics in their images of microstructure, because the different etching methods are used to capture microstructure images for each material. Electrolytic etching of type 304 stainless steel using solution containing HNO3is not effective for high manganese austenitic steel. Instead, the two-step



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etching method (1st etching: 1.4% picral+HCl, 2nd etching: 10% aqueous sodium metabisulphite solution) is used for high manganese austenitic steel. To confirm the austenitic phase of high manganese steel, the CG participants can refer to XRD (X-ray Powder Diffraction) and EBSD (Electron Backscatter Diffraction) results shown in slide 6 and 7 of annex 1 and slide 10 of annex 2 to document CCC 3/J/7.

17 JAPAN 2 Detailed Proposal 3: Japan proposes to add longitudinal tensile test results to table 7. Not only transverse direction but also longitudinal direction should be checked.

Tensile test in transverse direction shows more conservative results than those of the test in longitudinal direction. We are of the view that section 2.4 tensile test and section 3.5 cross-weld tensile test in the technical document by the Republic of Korea show sufficient results to evaluate high manganese austenitic steel in terms of strength.

18 JAPAN

2 Detailed Proposal 4: Japan is of the opinion that required tensile strength (TS) should be included in table 16, in order to evaluate suitability. The required tensile strength of base metal is equal to or more than 800 MPa. If the required tensile strength of welded joint is the same as base metal, table 16 shows that the material tested does not have sufficient strength. The required tensile strength should be determined based on fracture scenarios.

The strength requirements for welded joints were provided in slide 17 in document CCC 3/J/7. The requirement of tensile strength is added to table 17 in the technical document by the Republic of Korea.

19 JAPAN

2 Detailed Proposal 5: Japan is of the opinion that hardness distribution of weld should be clarified. Imprints of hardness test are shown on macro-structure in table 13. This technical information is very important for understanding the weakest point of mechanical properties of weld. JIc must be evaluated at the weakest point.

The hardness information is added to section 3.4.Hardness test in the technical document by the Republic of Korea.



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20 JAPAN

2 Detailed Proposal 6: Japan is of the opinion that technical information such as chemical compositions should be added to the annex entitled "Evaluation of fracture toughness". Origin of these J-R curves should be clarified for right safety assessment. Furthermore, requirement of JIc should be added in order to evaluate safety. JIc requirement must be decided based on fracture scenarios.

The welding direction is along a rolling direction of the plate. The loading is in transverse direction and the crack propagation in longitudinal direction with respect to a rolling direction. The chemical compositions of the plate for JIc test were the same with the table 5 in the technical document by the Republic of Korea.

21 JAPAN

2 Other Comments: ASTM standard A1106/A1106M-17 is referred to in table 4. Generally, ASTM specification does not concern any safety issue. There is following sentence in all the ASTM specification. "This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use."

We agree with Japan. The standards and technical codes cannot cover all the requirements concerning the safety of new technology. The necessary safety assessment should be performed by the users based on the configuration of their projects. This information about standard is provided, responding to the comment of Japan (Comment No.13) and other member states.

22 REPUBLICOF THE

MARSHALL ISLANDS

1 General Proposal 1: Create a new column on sampling condition. A sufficient number of samples covering range of production condition, chemical composition need to be established. Maximum thickness may also need to be considered. Attention should also be paid to maximum heat input during welding.

Testing and sampling conditions are more elaborated in table 1 – table 3 in the technical document by the Republic of Korea.

23 REPUBLIC OF THE

MARSHALL ISLANDS

1 General Proposal 2: Clarify test conditions and requirements as follows: 1. revise "CTOD (Crack tip opening displacement) test" as "Fracture toughness" (combine elements of two tests indicated) The fracture toughness

In the technical document by the Republic of Korea, 1. please refer to chapter 6. Ductile fracture instability of high manganese austenitic steel was performed based on CTOD R curve under -165°C. 2. "Cross-weld tensile test" is added in tables 2 and 3.



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acceptance criteria such as CTOD should be derived and verified based on the assessment using Structural Integrity or Fit for Service assessment method in which the load conditions e.g. the design safety factor, small scale fracture toughness test results, the maximum defect size developed in service and wide plate test data, are to be used as input. 2. add "Cross-weld tensile test" for the condition of "Tensile test". 3. revise temperature to -165°C. Also include another condition as "CTOD Value of JIc, -196°C"

3. The temperature for CTOD tests is revised to -165 °C and JIc test

is added to tables 2 & 3.

24 REPUBLIC OF THE

MARSHALL ISLANDS

1 General Proposal 3: Add following tests and requirements: 1. the material & weldment properties in the strained condition e.g. after forming/ bending should also be assessed. (Cold forming and strain ageing effect) 2. add tests for SSC, Hot Cracking and Carbide Precipitation with acceptance as no susceptibility 3. add microstructural examination with acceptance as no significant carbide precipitation

In the technical document by the Republic of Korea, 1. strain-aged Charpy Impact test is added. 2. annex 1 of CCC 3/J/7 provides the data for SCC in slide 21 and Hot Cracking in slide 22. Annex 2 of CCC 3/J7 provides the condition for carbide precipitation in slide 21 ~ slide 23. 3. microstructural examination is added.

25 REPUBLIC OF THE

MARSHALL ISLANDS

1 Specific Proposal 1: Remove reference to IACS UR W1 & W2

We agree with the Republic of the Marshall Islands.

26 REPUBLIC OF THE

MARSHALL ISLANDS

1 Specific Proposal 2: Address welding in table 2. Requirements

We agree with the Republic of the Marshall Islands.



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27 REPUBLIC OF THE

MARSHALL ISLANDS

2 General Proposal 1: The WG coordinator has not provided a consensus document reflecting the reviews of the WG members. Specifically, the coordinator's remarks for round 1, TOR #1 item 4, calls for additions/revisions to table 2. Provisional Test Items and Requirements for High Manganese Austenitic Steel. The coordinator's remarks for round 2 do not provide a consensus document for TOR #1.

The technical document by the Republic of Korea updated the test items and acceptance criteria in table 1 ~ table 3.

28 REPUBLIC OF THE

MARSHALL ISLANDS

2 Specific Proposal 1: The strain age charpy impact values at -196oC are comparable to that of the base material in an unstrained condition; however, the specimens should be tested at a range of temperatures to establish the impact behaviour of the material (transition curve) in a strained condition.

High manganese austenitic steel does not show the characteristics of brittle-ductile transition even though the temperature lowers

to -196 °C. Please also refer to slide 10 in annex 1 of CCC 3/J/7 for

the smooth transitioning trend of impact energy.

The values of strain-aged Charpy impact test at -196°C are

comparable to the values of unstrained condition. As temperature increases, the values of strain-aged Charpy impact test increase smoothly following the similar characteristics of the values of unstrained condition.

29 REPUBLIC OF THE

MARSHALL ISLANDS

2 Specific Proposal 2: The weldability COT values are only for fusion line specimens and the GCHAZ (grain coarsened heat affected zone) was not tested

Both base metal and weld metal are austenitic steels. CGHAZ (coarse grain heat affected zone) region of the welded joints in high manganese austenitic steel is rarely distinguishable. It is assumed that CGHAZ is almost equal to FL. That is why CTOD value of FL is considered to be that of CGHAZ in high manganese austenitic steel.

30 REPUBLIC OF THE

MARSHALL ISLANDS

2 Specific Proposal 3: The test results are for plates of almost identical composition. Testing of heats with different compositions and mechanical properties are needed to generalize the behaviour of the material

The numbers of each chemical element are rounded down due to the manufacturer's confidential information such that the chemical composition of the products look almost identical. In real manufacturing conditions, the plates of high manganese austenitic steel are produced with an aim to meet the specific narrow range of chemical composition.



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31 NORWAY 1 Based on the attached information from the Republic of Korea, the suitability of High Manganese steel seems to be a good candidate for cryogenic service in line with Ni alloys and traditional austenitic steels. Norway are aware of the ongoing work in the IACS expert group on Material & Welding (EG/MW) on HiMn steel for cryogenic service, and the expert groups work on developing a guideline on "Approval of High Manganese Austenitic Steel for Cryogenic Service". Therefore, we are of the opinion that CGHiMn work should be coordinated with the ongoing IACS work on the subject. In general, we find the documentation presented as a basis for amendment of the IGC and IGF Code acceptable; however, some clarification is needed: • The chemical composition of the high Mn steel specified in document CCC 3/J/7, annex 1, has a wide range on some of the elements, and does not give the aimed chemical composition or the composition of the materials tested. It can also be mentioned that in the draft IACS Guidelines (Rev. 5) being prepared, a chromium (Cr) content of 3-4% is specified, while in annex 1, as referred to above, no Cr is specified. There are also other minor deviations in C, Si, Mn, B, N and Cu.

In 2013, the chemical requirements of high manganese austenitic steel were established as follows: <Table 1.>

This table had been used for the manufacture's approvals by classification societies in 2013 and Korean Industrial Standard in 2014. Since 2015, the works for draft IACS recommendations and draft ASTM standards have launched. Particularly, ASTM required the narrower ranges for each chemical element and did not allow the Ni-equivalents and Cr-equivalents. Therefore, the chemical requirements with narrower chemical ranges for each element and specific ranges for Cu and Cr was submitted to ASTM and IACS as follows: <Table 2.>

C Si Mn P S B N Nb+Ti+V

0.2~0.6 0.1~1.0 22.0~26.0 < 0.03 < 0.01 0~0.01 0~0.15 0~0.3

The content of other elements used for alloying and fine grain treatment may be specified by steelmaker, as appropriate. However, the amount is to satisfy the following equations.Cr equivalent (Cr + 1.5Si + Mo + 5V + 3Al + 0.5Nb + 1.5Ti): 0~20.0Ni equivalent (Ni + 0.87Mn + 0.33Cu + 30C + 30(N-0.045)): 28.0~48.0



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Table 2 contains the final chemical requirements for high manganese austenitic steel listed in ASTM A1106/A1106M-17. In conclusion, table 1 and table 2 are not different. Table 2 is nothing but a representation of the chemical requirements in a more specific and detailed way than in table 1. The plates of high manganese austenitic steel have been produced, maintaining the target of the same chemical compositions, while only the chemical requirements in the standards have been revised by the requirement of standard organization.

32 NORWAY 1 • The same minimum yield strength is specified for both the base material and weldments (400 MPa); however, the specified tensile strength for the base material (800-970 MPa) is somewhat higher than for weldment (660 MPa). We have, however, not seen documentation on the actual yield and tensile strength of the base material and weldment. If the actual yield strength in the weldment is lower than the base material strain in the weld could be an applicable design scenario, then the lower toughness in the weld metal may need to be documented further.

Welded joints of high manganese austenitic steel show under-matched properties. Refer to table 7 and table 17 in the technical document by the Republic of Korea.

33 NORWAY 1 • In document CCC 3/J/7, annex 2, the Republic of Korea has presented information regarding the sensitivity of high Mn steel to carbide precipitation; however, no information is provided with respect to the actual chemical composition of the material tested. Has material with different Cr and C content been tested? It is also obvious that if thickness' above 30 mm are to be supplied, additional documentation on the cooling rate during manufacture of the steel and welding needs to be documented.

Actual chemical compositions of some sampled plates are shown in table 20, which demonstrates that chemical composition of high manganese austenitic steel has been controlled within narrow ranges with targeted points regardless of thickness. Currently, the maximum thickness of plates of high manganese austenitic steel is 30 mm.



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34 NORWAY 1 • CTOD tests of welded samples show very consistent values around 0.5 mm for TTN (Bx2B) in weld metal and 0.36 mm for FL as lowest reported value (out of 3 samples). • Ductility is also presented as J-R curves (elastic–plastic fracture test) tested according to ASTM E1820-15a comparing base metal High Mn steel to 304 stainless steel (ref. to document CCC 3/J/7). Both materials show an elastic–plastic behaviour with stable crack growth tearing up to just below 5 mm for High Mn steel and 4 mm for the 304 stainless steel. The material's ability to absorb and redistribute energy is higher for High Mn steel (800 J (kJ/m2) compared to 304 (approximately 560 J (kJ/m2). However, the results are YS dependent, with 304 stainless steel having less yield strength than high Mn steel than expected.

High manganese austenitic steel shows cryogenic characteristics comparable to the cryogenic materials listed in the IGC and IGF Codes.

35 NORWAY 1 • Fatigue crack growth tests have been carried out and the results are similar to 9% Ni performance; however, the threshold value is 14 MPa(m0.5) higher compared to approximately 10 MPa(m0.5) for 9% Ni steel. It is, however, not stated if the test data is from BM, WM or HAZ.

The test data is from BM.

36 NORWAY 1 • The fatigue performance of welded high Mn steel is expected to be similar as for 9% Ni with reference to the crack growth tests presented. However, no S-N fatigue data of welded high Mn steel has been reported in order to confirm the possibility of using the same fatigue design curve generally applied for 9% Ni steel. Hence, the fatigue performance of high Mn steel should be further documented.

The S-N fatigue data for welded joints of high manganese austenitic steel will be reported to CCC 4.



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37 NORWAY 1 • Regarding wide-plate testing as proposed by Japan, we are of the opinion that wide-plate testing to establish crack arrest properties is relevant for specific applications/design, and decided on a case-by-case basis depending on the design and material thickness. However, we are of the opinion that this should not be required as a qualification test of the high Mn material. It is also questioned whether relevant crack arrest data are available for any of the other materials used for cryogenic applications for comparison.

Please refer to Comment No. 7.

38 NORWAY 1 • The comments from Japan regarding the importance of conservatism in testing and evaluation especially related to the welded joints are also highly relevant. The welded joints are normally the weak spot in all structural integrity assessment, especially with respect to sudden brittle failure.

We agree with Norway, also recognizing the concern of Japan. Fracture toughness JIc was evaluated focusing on the welded joints. In addition, chapter 6 of the technical document by the Republic of Korea shows the results of ductile fracture instability analysis for crack in welded joints.

39 NORWAY 1 Comment relating specifically to Hydrogen: • In the proposed list of tests (table 2) there should in our opinion be a test for assessment of the potential detrimental influence of hydrogen on the structural integrity of the steel, especially on the welds. Hydrogen is well-known to contribute to sudden, brittle failure. • In transport of hydrogen (and related activities such as filling and emptying the containers), it can be assumed that the steel and welded joints will be exposed to atomic hydrogen that will enter the metal. Even if the temperature is low, which implies low hydrogen diffusivity in the metal and the fact that the fcc steel (if stable) in general have high

Currently, high manganese austenitic steel is not considered for the transportation of liquid hydrogen of -253°C. It is applicable only at the minimum design temperature of -165°C.



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resistance towards hydrogen embrittlement, to follow the principle of conservatism, this is an aspect that should be addressed. A suitable approach for such an evaluation would be slow strain rate fracture mechanics testing of hydrogen charged specimens (base metal, weld metal and heat affected zone) at cryogenic temperatures. If possible hydrogen pre-charging and then testing in liquid hydrogen would be the most realistic test environment. The results should be compared to not H-charged specimens tested in cryogenic conditions without hydrogen. Low frequency fatigue testing of hydrogen charged specimens (BM, WM, HAZ) at cryogenic temperatures would be another appropriate approach.

40 NORWAY 2 Some of our comments and questions raised are addressed by the "Technical information of high manganese austenitic steel for cryogenic service", prepared by Republic of Korea. However, we believe that the Republic of Korea will specifically address all comments given by the 8 CG participants in TOR#1. For this reason we will not give further comments at this stage, but wait for 3rd / 4th round.

Refer to this table.

41 UNITED KINGDOM

1 At this early stage of this CG, the United Kingdom has some initial questions regarding table 2. Although table 2 contains a preliminary list of testing requirements, there are a few key elements which have not been addressed:

In general, we follow the sampling and testing number specified by classification societies for manufacturer's certificate. Every plate for commercial production will be examined by classification societies.



No. CG

Participants

CG Round


- How many tests are to be conducted to obtain an appropriate statistical set of data? Do we have a calculation method agreed for collating the results (e.g. should we be averaging the results or conducting a statistical analysis?)

42 UNITED KINGDOM

1 - How many batches of material should be tested? And should this material be produced by more than one manufacturer?

The data for the technical document by the Republic of Korea was obtained from a batch of products. Currently, only a Korean steelmaker produces the plates of high manganese austenitic steel for cryogenic service.

43 UNITED KINGDOM

1 - On what forms of material should these tests be conducted? (e.g. plate/bar? Which thicknesses? Rolled/forged?, etc.)

Currently, the plates with maximum 30 mm thickness are being produced by rolling process.

44 UNITED KINGDOM

1 - To what standard should welds be manufactured against prior to testing?

Welding consumables are listed in Korean national standards, KS-D-7142 (SMAW), 7143 (FCAW), 7144 (SAW). Those are also type-approved by classification societies.

45 UNITED KINGDOM

1 In addition to the first set of questions above, the UK would also like further clarification of the material specification. Without an approved specification/standard for the material with details of the material composition, the tests will be meaningless. There are also many references within table 2 which are not complete at this time. It is hoped that the CG might obtain suitable references for these tests, e.g. IMO procedures or internationally agreed standards (e.g. ISO).

High manganese austenitic steel is listed to ASTM as ASTM A1106/A1106M-17, "Standard Specification for Pressure Vessel Plate, Alloy Steel, Austenitic High Manganese for Cryogenic Application". The detailed test items with the test standards are listed in table 1 ~ table 3 in the technical document by the Republic of Korea.

46 UNITED STATES

1 (1) An internationally recognized materials standard for high Mn steel is needed. Is there an equivalent steel standardized by ASTM or ISO or other international standards organization?

High manganese austenitic steel is listed to ASTM as ASTM A1106/A1106M-17, "Standard Specification for Pressure Vessel Plate, Alloy Steel, Austenitic High Manganese for Cryogenic Application."



No. CG

Participants

CG Round


47 UNITED STATES

1 (2) Mechanical properties from a single heat of steel are not sufficient to demonstrate the applicability of the steel for cryogenic tests. The basic mechanical properties from at least 3 heats of steel should be supplied for evaluation of the suitability of high-Mn steel.

Table 20 in the technical document by the Republic of Korea shows the routine records of sampled products. This table shows the consistency in terms of mechanical properties and chemical compositions.

48 UNITED STATES

1 (3) High carbon in austenitic alloys is a concern for welding. Can these steels be sensitized, i.e. are they subject to grain boundary carbides? (as are 304 and 316 for example)

Carbide precipitation is controlled by cooling speeds during the production. Please refer to slides 21 to 23 in document CCC 3/J/7. Sensitization causes the reduction of corrosion resistance of stainless steel, while it is not relevant to high manganese austenitic steel for cryogenic service.

49 UNITED STATES

1 (4) A significant limitation of high manganese steels is their susceptibility to delayed fracture (Materials Science and Engineering A 528 (2011) 2922-2928). Is delayed fracture an issue in this application due to hydrogen uptake during welding?

High manganese steel in Materials Science and Engineering is a TWIP (Twinning Induced Plasticity) steel for automotive frames. High manganese austenitic steel for cryogenic service (designated as ASTM A1106/A1106M-17) is different from TWIP steel in terms of chemical compositions and physical properties such that the delayed fracture is not an issue for high manganese austenitic steel for cryogenic service

50 UNITED STATES

1 (5) Are there other international standards that could be referenced for table 2, e.g. ISO, ASME, ASTM? What requirements for each test should be applied?

Please refer to tables 1 to 3 in the technical document by the Republic of Korea.

51 UNITED STATES

2 We propose adding another column to the tables which lists the requirements for acceptance for each test. This information is included for some tests in the "Test Method" column, but this information needs to have a separate column. All test methods need to have criteria for acceptance.

The column "Requirements" is added to tables 1 to 3 in the technical document by the Republic of Korea.

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