1、 STD-AWS UEAW-ENGL 398b = 0784265 0536982 303 Handbook On the Ultrasonic Examination of Austenitic Welds Compiled by COMMISSION V - Testing, Measurement, and Control of Welds of THE INTERNATIONAL INSTITUTE OF WELDING Published on behalf of THE INTERNATIONAL INSTITUTE OF WELDING by THE AMERICAN WELDI
2、NG SOCIETY 550 NW LeJeune Road, P.O. Box 351040, Miami, FL 33135 1986 STD AWS UEAW-ENGL 39b = 0784265 0536983 2YT CONTENTS LIST OF WORKING GROUP MEMBERS 3 4 1. General 5 FOREWORD _. 2. 2.1 2.2 2.3 3. 3.1 3.2 3.2.1 3.2.2 3.3 3.4 3.5 3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.6 3.7 3.8 _. Introduction Scope and
3、Application Particular Problems Involved in the Examination of Austenitic Welds Principle of the Method Conditions to be Established prior to the Examination Personnel Required Information about the Welds Welding samples available Absence of weld samples Surface Preparation and Marking Condition of
4、the Parent Metal Agreements Before the Start of the Examination Extent of the examination Sensitivity required Special conditions Regular check of equipment Reporting Visual Inspection Surface Preparation Cou plants _ 4. Ultrasonic Propagation Behavior 4.1 Structure of Austenitic Welds 4.2 4.2.1 4.2
5、.1.1 Variation of velocity 4.2.1.2 Beam direction 4.2.1.3 Beam deformation 4.2.1.4 4.2.1.4.1 Reflection 4.2.1.4.2 Refraction 4.2.1.4.3 Mode conversion 4.2.1.4.4 Interaction with defects Effects of Austenitic Structures on Ultrasound Propagation Ultrasound propagation in an anisotropic structure Effe
6、ct of the weld fusion faces 4.2.2 4.2.3 4.2.3.1 4.2.3.2 4.2.3.3 4.2.4 4.2.4.1 4.2.4.2 5. 5.1 5.2 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 _ 5 5 5 6 6 6 7 7 7 7 7 8 8 8 8 9 9 9 9 9 9 9 11 11 12 12 13 14 14 14 14 14 - _ Attenuation in weld metal 14 Influence of weld metal on pulse characteristics 16 Pu
7、lse spectrum 16 Influence of attenuation of the ultrasonic pulse 16 Scattered u I trasou nd 17 Practical implications for ultrasonic testing on austenitic welds 18 Defect location 18 18 Amplitude assessment - _._ Description of Equipment Introduction Flaw Detector, Cables and Matching Angled Longitu
8、dinal Wave Probes Introduction General properties Single crystal probes Twin crystal probes 18 18 19 19 19 19 20 20 Surfacewave probes 22 Focussing probes - 23 1 6. 6.1 6.2 6.3 6.4 6.5 6.5.1 6.5.2 6.5.3 6.5.3.1 6.5.3.2 6.5.3.3 6.5.3.4 6.5.4 6.5.5 6.5.6 7. 7.1 7.2 7.3 7.3.1 7.3.2 7.4 7.4.1 7.4.2 7.4.
9、3 7.4.4 7.4.5 7.5 7.6 7.6.1 7.6.2 7.6.3 7.6.4 7.7 7.7.1 7.7.2 7.7.2.1 7.7.2.2 7.7.2.3 7.8 _- 8. 8.1 8.2 8.3 8.4 8.5 8.6 9. 9.1 9.2 9.3 1 o. STD*AWS UEAW-ENGL 1986 = 078Y2b5 051b984 LBb = Calibration and Characterization Introduction Calibration Blocks Steps in Time Base Setting Probe Characterizatio
10、n Block Steps in Characterizing the Probes Introduction Probe index for angled longitudinal wave probes Distance amplitude curve, beam angle and beam width Distance amplitude curve Beam angle Beam width Amplitude behavior for different reflectors Estimation of dominant frequency and bandwidth Dead z
11、one and near field Development of an Examination Procedure Outline of Activities Preparation of Preliminary Procedure Preparation of Reference Block General Artificial reflectors Selection of Probes Wave type Probe angle Frequency TY Pe Size and geometry of probe and component Use of Reference Block
12、s to Establish DAC-Curves Sensitivity Setting Introduction Setting test sensitivity Recording level Acceptance criteria Preparation of Detailed Procedure Written procedure requirements General exam i nation req u i remen ts Exam i nation cove rag e Rate of probe movement Scanning sensitivity Assessm
13、ent of Procedure and Documentation Inspectability of the Component Compared to Introduction Surface Conditions Geometrical Conditions Comparison of Attenuation Between Reference Block and Component Signal to Noise Ratio Weld Repairs Reporting and Evaluation Reporting Eva1 uat ion Add it iona I I nve
14、c t ig a t ions (for TRL or Focussing Probes) Nominal signal to noise ratio - _ the Reference Block _ - _ _ 24 24 24 24 25 26 26 28 29 29 29 29 30 30 30 31 31 31 31 33 33 33 34 34 35 36 36 37 37 38 38 38 39 39 39 39 39 39 40 40 40 _ _- General Recommendations and Comments _ _ _ 40 40 40 40 40 41 41
15、41 41 41 41 43 2 STD-AWS UEAW-ENGL 1986 0784265 0536985 012 Prepared by Working Group Ultrasonic Testing of Austenitic Welds of the Subcommission VC-Ultrasonically Based Weld Inspection Topics of Commis- sion V of the IIW LIST OF WORKING GROUP MEMBERS Edelmann, X. (Chairman) Ganglbauer, O. Gatti, G.
16、 M. Gray, B. S. Neumann, E. Hennaut, G. de Raad, J. A. Samman, J. Thomson, J. L. de Sterke, A. (Final editor) Sulzer Brothers Limited Voest-Alpine Breda Termomeccanica United Kingdom Atomic BAM Bundesanstalt fr Vinotte RTD Electricite de France EdF Babcock Power Limited RTD Energy Authority Material
17、prfung Winterthur Linz Milan Risley Berlin Brussels Rotterdam Paris Renfrew Rot te rd am The working group wishes to acknowledge valuable contributions by other members of the companies mentioned and the use of information obtained from studies carried out for the Community Bureau of Reference (BCR)
18、 of the Commission of the European Communities. The Handbook represents the agreed view of the working group experts but has not necessarily been endorsed by the individual organizations represented. For a definition of many of the terms used and further background informa- tion on the subject of th
19、is handbook, readers are referred to the existing IIW- publications listed below: (1) List of Terms Used in Ultrasonic Testing of the International Institute of Welding, 1967. (2) Handbook on the Ultrasonic Examination of Welds of the International Institute of Welding, 1977. (3) “Considerations on
20、Ultrasonic Testing of Austenitic Weld Joints” Weld- ing in the World, Vol 20 (1982), No 5/6, pp. 99-108. (4) “Geometrical defects in arc welded joints in steel materials - Classes of requirements” Welding in the World, Vol 22 (1984), No 1/2, pp. 34-52. 3 This Handbook has been produced by the Workin
21、g Group Ultrasonic Test- ing of Austenitic Welds of the IIW-Commission VC Ultrasonics. It is based on the Handbook on the Ultrasonic Examination of Welds (for carbon steel welds). Publications, practical experience, and available codes on ultrasonic examination of austenitic welds have been taken in
22、to account dur- ing preparation. The Handbook is intended to serve as a guideline for the preparation of procedures for specific applications but is not intended to pro- vide a detailed inspection procedure for any particular weld. Advice is given on how to devise procedures to take proper account o
23、f access available to the weld and of surface preparation. Methods are defined to ensure reproducible sensitivity setting for the ultrasonic examination and to provide a means of judging the test result. Specific problems such as the effects of grain structure and spurious indications, and the appli
24、cation of special probes are mentioned. In spite of the limitations still existing, the Working Group believes that publication of the Handbook should not be delayed until all the outstanding problems have been solved. This will help to spread present knowledge to the benefit of the many indus- trie
25、s and institutions involved in constructions using austenitic welds. The Handbook is intended to encourage a more uniform approach which should lead to better conditions for balanced evaluation and comparison of results. The latter is of prime importance in guiding further work aimed at improving ul
26、trasonic techniques as well as making progress in welding technology with regard to the metallurgical aspects involved. STD-AWS UEAW-ENGL 178b 1. GENERAL Until recent years, austenitic steel welds were widely regarded as uninspectable by ultrasonics. Research and development have made it possible fo
27、r a useful level of examination to be carried out in many situations. In general, though, the meth- ods are more complicated and the capabilities more limited than for the examination of welds in ferritic steel. The main practical implications of this are (1) Welding procedure and preparation geome-
28、 try have a strong influence upon the capabilities of ultrasonic examination, so that careful consid- eration of these factors at the design stage can be very beneficial to the examination. (2) Many technical aspects of the examinations are strongly influenced by the particular weld structure so tha
29、t only skilled, specially trained operators with a full appreciation of the physical basis of the examination should be employed. (3) The capabilities for defect detection, posi- tioning and size assessment are more limited than for ferritic weld examination. So, monitoring the occurence of small de
30、fects can rarely be used for the quality control of welds, as is usual with fer- ritic welds. Rather, it may be necessary to use fracture mechanics to set less rigorous defect acceptance standards for the particular compo- nent. These acceptance standards should be com- patible with the limitations
31、of the ultrasonic techniques. (4) The limited capabilities imply that it is pru- dent to supplement ultrasonic examination with radiography and surface examination techniques to a greater extent than is necessary with ferritic welds. 2. INTRODUCTION 2.1 Scope and Application This Handbook gives reco
32、mmendations for the ultrasonic examination of austenitic welds by man- ual scanning techniques which use the pulse- echo method and A-Scan presentation. The same recommendations can be extended to mechanical scanning techniques if special procedures are prepared for the data recording system. The Ha
33、ndbook advises on how to devise proce- dures for the detection, location, and evaluation of ultrasonic indications of weld defects. Tech- niques involving the use of advanced instrumen- tation for signal processing might give better detection and identification of flaws but are not covered in this d
34、ocument. The applications covered are limited to butt welds with weld metal of similar composition to the parent material. For dissimilar weld metals or for non butt weld geometries, procedures may be based on the general advice of this Handbook, provided attention is paid to the requirements of the
35、 specific geometry and material. The recommendations given are primarily aimed at post fabrication rather than in-service inspec- tion. Many sections of the Handbook will be rele- vant to both situations, but consideration of the specific problems of in-service inspection is out- side the scope of t
36、his document. This Handbook does not contain defect indica- tion acceptance criteria. 2.2 Particular Problems Involved in the Examination of Austenitic Welds The term austenitic covers a variety of materials and material combinations, including austenitic stainless steels and nickel chromium alloys
37、such as “lnconel”, “lncoloy”, etc. The capabilities of ultrasonics for the examination of welds in aus- tenitic materials are restricted compared to the ferritic case because of the presence of large elongated anisotropic grains (dendrites), often forming an ordered columnar structure, which are cha
38、racterisitic of the austenitic weld metal. This type of grain structure can lead to anisotropic ultrasonic behavior contrasting with the isotropic behavior of homogenous welds made in carbon or low alloy steels. The size, the arrangement, and the elastic anisotropy of the different grains result in
39、high scattering associated with mode conversion ef- fects, beam distortion, and a variation of ultra- sound velocity with direction and position in the weld. The scattering of energy is observed as a relatively high noise level (grass) and high atten- uation. The problems which occur in ultrasonic t
40、esting of austenitic welds differ according to the parent material production method (rolled, drawn, forged, or cast), the weld processes, and the heat treat- 5 STD-AWS UEAW-ENGL 1986 E 0784265 052b988 821 9 ment as well as the composition of the parent and weld metals. The guidelines given in this
41、Handbook take account of the above factors to indicate how optimum test procedures can be prepared. 2.3 Principle of the Method The ultrasonic methods applied to austenitic welds follow basically the same principles as those described in the Handbook on the Ultra- sonic Examination of Welds. Some im
42、portant differences do exist, however, which influence the ultrasonic method to be used and have implica- tions for the capability of ultrasonics to detect, locate, characterize, and to estimate the size of weld defects. The most important of these differ- ences are the following: (1) Scattered ener
43、gy from natural metallurgical discontinuities generates noise indications at higher amplitude than would be expected for the case of ferritic welds. The choice of wave mode (longitudinal, shear) and probe characterisitics (sound field, frequency, bandwidth, etc.) should be optimized to allow a relia
44、ble separation of weld defect indications from noise indications (see sec- tion 4.2). (2) The ultrasonic beam has to cross different regions in the parent metal and in the weld itself. The velocity of sound may vary along this path (see section 4.2) and this may change the direc- tion of the sound b
45、eam. Consequently, this may result in inaccuracy in determining reflector posi- tions. (3) Attenuation in the weld metal is generally more severe than for ferritic welds and can be more or less pronounced depending on the angle of the beam with respect to the preferred orienta- tion direction of the
46、 grain structure. Therefore, the ultrasonic technique should seek to minimize beam path length in the weld metal and, where possible, aim to take advantage of any directions of reduced attenuation in the weld. (4) Beam divergence can also be directionally dependent. The beam profile is usually diffe
47、rent from that measured in parent plate (whether fer- ritic or austenitic) so that size estimation methods which depend on a knowledge of the beam pro- file, such as the so-called dB drop methods, are not always suitable on austenitic welds. (5) Conventional instruments are used for exam- inations,
48、but in most cases, special probes need to be applied (see section 5.3). 3. CONDITIONS TO BE ESTABLISHED PRIOR TO THE EXAMINATION Since austenitic weldments present greater dif- ficulties for ultrasonic testing than ferritic ones, the preparation of ultrasonic procedures requires more attention. In g
49、eneral, it is considered of great importance that operators should be in- formed about relevant details of weld fabrication, as given in section 3.3.2. Particular written proce- dures which specify the examination conditions and detailed ultrasonic techniques must be pre- pared in conjunction with metallurgists and NDT operators and need to take account of information that can be considered as fabrication know-how. 3.1 Personnel The personnel applying this type of exami
