MTS NEWSLETTER. Welcome to the first issue INSIDE THIS ISSUE

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1 May 2016 Issue 1 MTS NEWSLETTER Welcome to the first issue INSIDE THIS ISSUE Welcome to the first quarterly MTS newsletter. The purpose of this newsletter is to help keep you up to date with what is happening at MTS, our capabilities and personnel and what is happening throughout the industry. In this issue we look into the reasons why we use replication techniques when it comes to microstructure examinations, as well as possible issues with the 2015 amendment of the AS/NZS 3992 pressure vessel welding specification. As always, if you have any queries, technical questions or suggestions, please don t hesitate to contact any of our friendly staff. Examination of Microstructures via Replication Staff Focus: Johann Petrick Client Focus: Wittenbaker Engineering Services AS/NZS 3992: Changes and issues with procedure and welder qualifications

2 2 MTS METALLURGICAL TESTING SERVICES Replica microstructure of boiler tube. Examination of Microstructures via Replication. A brief explanation of what replication is and why we do it. In-situ metallurgical replication is a non-destructive method for assessing the microstructure of items and equipment at high magnifications, this technique is particularly useful in situations where a sample cannot be removed for analysis in a laboratory. Replication allows for the assessment of any microstructural degradation that may have been caused by the thermal and/or high pressure operating conditions and in many cases allows for the assessment of the remaining life of the component. Where cracks or crack like indications are detected using NDT methods, replication can be used to determine the cause of the cracking and whether the cracks are active and need to be addressed immediately. For the replication process a small area of the item is polished to a 1µm finish and etched with an appropriate etchant. The area is then replicated using either cellulose acetate film, which has been softened using acetone, or by applying a thixotropic fast curing compound. The replica essentially makes a mould of the etched surface which provides a negative image of the replicated microstructure. When the replica has solidified it is removed and returned to the laboratory for examination. In many cases replicas can also be prepared for SEM analysis.

3 MTS METALLURGICAL TESTING SERVICES 3 The area replicated may be approx. 20mm x 20mm for bulk material and approx. 20mm x 40mm for weld HAZ. The area for replication does not necessarily need to be plane or flat as irregular surfaces can often be replicated. Once all of the scale and/or decarburised layers have been removed, the replication process can remove as little as mm of material from the thickness of the item. What equipment do we use? MTS utilizes NSK Emax Evolution rotary tools for the majority of replication roughand-fine polishing work however depending on the site requirements battery or pneumatic tools may also be used. The replicas are mounted on standard glass slides and examined on-site using a portable microscope or brought back to the laboratory for examination using an Olympus metallurgical microscope with a camera attachment for taking images of the microstructure. Why our clients can have confidence in MTS to do their replication work. MTS has a team of metallurgists and metallurgical technicians with experience in power station, chemical plant and general industrial in-situ replication and remaining life assessments covering materials such as carbon steels, stainless steels, Inconel and Nickel alloys. These technicians have confined space and working at heights certification allowing for replication under the conditions Replica microstructure slide being examined on microscope often found during maintenance outage works. MTS has portable microscopes that allow for the assessment of replicas on-site during outages to improve the turnaround of results during the time critical operations of the outage.

4 4 MTS METALLURGICAL TESTING SERVICES Staff Focus: Johann Petrick Metallurgical Manager Where did you study? I obtained my honours degree in Metallurgical Engineering at the University of Pretoria in South Africa. I have also various management qualifications from other institutions. How long have you been in the metallurgical industry? I have been working in the metallurgical field for more than 14 years in various sectors. My experience includes primary steelmaking, steel manufacturing, automotive steels, product development, failure investigations and metallurgical assessments. What attracted to you to metallurgy? I was always fascinated by all types engineering from a very young age. Upon discovering the field of metallurgy I have become passionate about learning about metals and understanding the nature of materials around us. What are some of the interesting projects you have been involved with? One of the projects I worked on involved eliminating the formation of paint blisters on Electro galvanized steel sheet used for exposed body panels at BMW and Toyota. Even though the problems of paint blisters are purely cosmetic it is of big concern to automotive manufacturers. No one likes to have a new car with paint blisters. The metallurgy of blister formation is quite complex as it is influence by both the surface morphology of the steel substrate, the zinc coating, body panel pressing and the paint process at the automotive manufacturer. The problem was ultimately resolved by a cross functional team addressing different key parameters throughout the whole production process from steel manufacturing to paint application. How does MTS compare to other laboratories you have worked with? MTS has a large range of testing equipment as well as a team of metallurgists and metallurgical technicians with experience in diverse fields enabling them to conduct testing and investigations on a wide range of materials and applications. Specialist equipment such as water jet cutting and lapping of large samples enables unprecedented examination of large and difficult to cut metallurgical samples enabling faster and more accurate determination metallurgical failures.

5 MTS METALLURGICAL TESTING SERVICES 5 Client Focus: Wittenbaker Engineering Services Wittenbaker Engineering are a multi-disciplined engineering company employing 30 people and based in Henderson. They have a vast array of services including CNC machining, site machining, mechanical fitting, site fitting and maintenance engineering solutions. MTS were commissioned to conduct metallurgical analysis on bogie wheels machined and flame hardened by Wittenbaker. The test regime included case depth hardness traverses, core hardness testing, chemical analysis, microscopic examination and tensile testing in accordance with both Wittenbaker and their client s requirements, as well as providing technical advice on improving and refining the process. All of the testing was conducted in-house at the MTS Bibra Lake laboratory. One of the major challenges in completing this testing was machining the test specimen. The section that required testing was 150mm thick and in sections was up to 60HRc thick. To overcome this, MTS waterjet cut the section out using our Omax water jet cutting machine, surface ground the cut surfaces to ensure flatness and polished the full cross section using our Kemet automatic lapping machines. The result of this best practice preparation method is shown in the image above. The hardness testing was conducted on this polished section using our Zwick/Roell Automatic Vickers Hardness testing machine, which conducts the hardness test, reads the impressions and assesses the results with minimal operator intervention. The results, which complied with the clients requirements, are shown in the chart above. Overall, the results obtained and the speed in which they were delivered have assisted the client in securing further work of a similar nature. Wayne Wittenbaker, the Managing Director of Wittenbaker Engineering, had this to say about the service he received during this project MTS have provided excellent turnaround and technical expertise thoughout this process. I would strongly recommend them for future metallurgical work. Please note: All details and results of the testing conducted have been released with the client s permission.

6 6 MTS METALLURGICAL TESTING SERVICES AS/NZS 3992: Changes and issues with procedure and welder qualification Author: John Carroll, CMatP General Manager MTS Metallurgical Testing Services References AS/NZS 3992:1998 (with 2000 amendment) - Pressure equipment - Welding and brazing qualification AS/NZS 3992: Pressure equipment - Welding and brazing qualification ASME IX: Boiler & Pressure Vessel Code (BPVC) AS 4037: Pressure equipment - Examination and testing AS 1210:2010 (with 2013 & 2015 amendments) - Pressure vessels ASTM A333: Standard Specification for Seamless and Welded Steel Pipe for Low-Temperature Service and Other Applications with Required Notch Toughness ASTM A240: Standard Specification for Chromium and Chromium- Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications AS/NZS : Structural steel welding - Welding stainless steels for structural purposes AWS D1.6: Structural Welding Code - Stainless Steel AS : Metallic materials - Vickers hardness test - Test methods ASTM E384: Standard Test Method for Knoop and Vickers Hardness of Materials AS : Methods for destructive testing of welds in metal - Weld joint hardness test

7 MTS METALLURGICAL TESTING SERVICES 7 In August 2015, AS/NZS 3992 Pressure equipment - Welding and brazing qualification specification was revised for the first time since 1998 (an amendment to this standard was issued in 2000). The preface of the 2015 version states that The objective of this standard is to reduce misunderstanding, costs and delays in qualifying welding, avoid unnecessary duplication of testing, promote greater confidence in reciprocal acceptance of approved procedures, and improve safety. It also aims for great alignment with ASME and ISO standards, and to be consistent with the current work health and safety laws However, in altering this specification, there appears to be some inadvertent or intentional alterations which vastly change the qualification criteria for both procedure and welder qualification. Some of these alterations also seem to deviate from the intent of previous versions of this code as well as the ASME Boiler & Pressure Vessel Code (BPVC) IX and other relevant specifications. This article seeks to address some of these major destructive testing changes from the 1998 edition (including the 2000 amendment) to the 2015 edition, some pre-existing concerns with this standard, the effects this has on day to day qualifications and the interpretations used at MTS Metallurgical Testing Services in the following sections; Weld Test Pieces (Section 6) Mechanical Testing of Welds for Procedure Qualification Testing (Section 7) Procedure Qualification for Special Welds (Section 8) Welder Qualification (Section 9) Weld Test Pieces (Section 6) Overall, the changes in this section are minimal and are generally to bring the testing regime in line with ASME IX. However, there are some anomalies that may require further testing to bring previously qualified AS/NZS 3992 procedures into line with the new 2015 edition, in accordance with section 3.5, which states where additional tests have to be carried out to make the approval (of the welding procedure) technically equivalent, it is only necessary to do the additional tests on a test piece which should be made in accordance with this Standard.

8 8 MTS METALLURGICAL TESTING SERVICES Some common examples are shown below, with the destructive tests required and quantities taken from AS/NZS 3992:1998 Table 6.1, AS/NZS 3992:2015 Table 6.1 & ASME IX:2015 Table QW respectively; Example 1 WPS NB, 10.97mm wall thickness ASTM A333 Grade B Pipe GMAW-s Process Welded in the 6G position Impact testing -46ºC in accordance with AS 1210 and client requirements No hardness required. As you can see, an additional two side bend tests are required to bring the existing weld procedure qualification test in line with the requirements of the 2015 edition. This would also qualify the procedure to ASME IX:2015 as the test regime for this specification has now been satisfied (qualification ranges not withstanding). Another significant change is the requirement for root bend tests on single sided welds over 10mm thick has been removed from the 2015 edition, which is more in line with ASME IX. * Impact testing is not required in ASME IX but may be specified in accordance with ASME IX Clause QW (a). A weld test coupon with a transverse weld tensile test, side bend test and macro specimen removed by water jet cutting. As you can see, an additional transverse weld tensile test is required to bring the existing weld procedure qualification test in line with the requirements of the 2015 edition. However, a further face bend would also be required to qualify the procedure to ASME IX. For new welding procedures to be qualified, while AS/NZS 3992:2015 table 6.1 specifies two face bends, Note 14 associated with this test states Single-sided welds require one face bend test and double-sided welds require one bend test for each side. Example 2 WPS NB, 8.56mm wall thickness ASTM A240 Grade 316L GTAW Process Welded in the 6G position No hardness or impacts required

9 MTS METALLURGICAL TESTING SERVICES 9 As this is a single sided weld, only one face bend would be required. At MTS, we would always recommend extending the qualification testing to cover as many specifications as possible. In this instance, this would be to conduct the testing required for ASME IX & AS/NZS 3992, which would subsequently cover the tests required for other standards, including AS/NZS & AWS D1.6 (qualification ranges and operating conditions not withstanding). Mechanical Testing of Welds for Procedure Qualification Testing (Section 7) The only changes in this section relate to impact testing and have been made to bring this section into line with the requirements in AS AS/NZS 3992 Table 7.2 has been altered to include these requirements as well as the new material groups in the 2015 edition of this standard. Below is an example of the changes as they relate to WPS001 mentioned previously; In the example above, the impact testing requirements have relaxed slightly. Provided the original impact results complied with the 1998 requirements, there would be no requirement to conduct additional impact testing to update the WPS. Procedure Qualification for Special Welds (Section 8) This section was previously titled Weld Overlay Qualification Testing and, by and large, still covers this area, along with the addition of extensive instruction on temper bead welding. Overall, the requirements for clad plate welding, corrosion resistant weld overlays and hard facing weld overlays have not changed from the 1998 edition and mirror the requirements of ASME IX. The temper bead qualification process is also broadly in line with and based on the requirements of ASME IX. One potential area of conflict is the hardness testing requirements for temper bead welding in section (b). This section reads; (b) Hardness test using Vickers method with 10 kg load in accordance with AS 1817 (series) or equivalent. Measurements shall be taken across the weld metal, heat-affected zone and not greater than 0.25 mm apart. The issue with this is the specified distance between adjacent impressions may not comply with the requirements of AS This is demonstrated below with impressions which are 249HV10 in a carbon steel weld;

10 10 MTS METALLURGICAL TESTING SERVICES For comparison, ASME IX section QW290.5 (c) states that increments between measurements shall be as specified in ASTM E384, which would be that the distance between the centres of consecutive indentations shall be at least 2.5 times the diagonal length. AS goes down a slightly different path, specifying that consecutive impressions shall be 0.5mm ± 0.025mm apart. However, in specifying that the hardness scale is to be HV5 unless the hardness is above 350HV, it is unlikely that subsequent impressions will influence preceding impressions, particularly in steel welds. Weld Qualification (Section 9) There have been some major changes to the scope and intent of this section from the 1998 edition which has resulted in some departures from what would be considered typical for welder qualification testing for pressure vessels. Examples of the changes and potential issues are shown below; AS/NZS 3992:1998 section reads as follows Methods of examination and testing. All tests pieces shall be examined visually. If acceptable in accordance with the pressure equipment Standard they shall then at the fabricator s option be- (a) examined by radiographic examination, or by ultrasonic examination (supplemented by surface NDE methods when applicable), and assessed for acceptability in accordance with AS 4037; or (b) tested using the test specimens given in Table 9.3. Test pieces welded by the gas metal-arc welding process and examined by radiographic or ultrasonic examination as in Item (a) above shall additionally be subjected to the bend tests specified in Table 9.3. However, section the 2015 edition reads as follows (with the critical changes highlighted); Methods of examination and testing All test pieces shall be examined visually (see Clause 6.2). If they are acceptable and in accordance with the pressure equipment Standard, they shall then, at the manufacturer s option, be- (a) examined by radiographic examination, or by ultrasonic examination (supplemented by surface NDE methods when applicable), and assessed for acceptability in accordance with AS 4037; or (b) tested using the test specimens given in Table 9.3. Test pieces welded by the gas metal-arc welding process and examined by radiographic or ultrasonic examination as in Item (a) above shall additionally be subjected to the bend tests specified in Table 9.3 However, section the 2015 edition reads as follows (with the critical changes highlighted);

11 MTS METALLURGICAL TESTING SERVICES Methods of examination and testing All test pieces shall be examined visually (see Clause 6.2). If they are acceptable and in accordance with the pressure equipment Standard, they shall then, at the manufacturer s option, be- (a) examined by radiographic examination, or ultrasonic examination (supplemented be surface NDE methods when required); or (b) macro tests destructively tested in accordance with Clause 9.5.2, assessed for acceptability in accordance with AS/NZS 3992 or AS 4037, or both. The likelihood of having a successful outcome when conducting this testing is low due to the inherently low ductility of the weld overlay. Bend tests are not required when qualifying a hard facing overlay procedure and while there is provision in section 7.6 of this standard for dissimilar consumable / material combinations, the mandatory test coupon size would preclude the use of a sufficiently large former to have any chance of a positive test result. In this instance, MTS would recommend only conducting a macro examination in a similar fashion to what is allowed for corrosion resistant weld overlays. When short-circuiting mode GMAW is used, test pieces shall be subject to ultrasonic test or bend test or macro test. This means that, to qualify a welder to the previously described weld procedure WPS001, the 1998 edition would require you to either conduct volumetric NDE with supplementary bend tests (as GMAW is highly susceptible to low ductility and brittle failure) or conduct two macro examinations and four bend tests (3 x root, 1 x side), while in the 2015 version, you would be able to qualify a welder using a macro examination only. As a comparison, ASME IX would require this same test coupon to be subjected to four side bend tests. For WPS002, ASME IX & AS/NZS 3992:1998 would require volumetric NDE at a minimum to qualify the welder whereas AS/NZS 3992:2015 still only requires a macro examination.these changes are almost certainly erroneous and will in all likelihood be amended in the future. As such, MTS would recommend that all welder qualifications are conducted in accordance with the test regime in the 1998 edition to ensure the continuity of qualification. Should this test alone be sufficient to qualify a welder to a pressure vessel specification? Disclaimer: The information supplied above is general in nature and may or may not be applicable in each particular instance. Should you require advice or further clarification, please do not hesitate to contact MTS Metallurgical Testing Services.

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