NB/T 20003.2-2021Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 2: Ultrasonic testing (English PDF)

Foreword

This document was issued on 7 January 2021 by the National Energy Administration of the PRC and takes effect on 1 July 2021.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 27.120.20, Chinese classification F69.

It replaces NB/T 20003.2-2010, which is superseded.

This document is drafted in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.

This document is Part 2 of NB/T 20003 Non-destructive testing for mechanical components in nuclear island of nuclear power plants. The following parts of NB/T 20003 have been published: Part 1: General requirements; Part 2: Ultrasonic testing; Part 3: Radiographic testing; Part 4: Penetrant testing; Part 5: Magnetic particle testing; Part 6: Eddy current testing; Part 7: Visual testing; Part 8: Leak testing.

This document replaces NB/T 20003.2-2010 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 2: Ultrasonic testing. Compared with NB/T 20003.2-2010, apart from structural adjustments and editorial changes, the main technical changes are listed below.

The scope of the document has been changed: the provisions on ultrasonic testing acceptance standards have been changed to ultrasonic testing quality grading (see Clause 1; Clause 1 of the 2010 edition).

Some normative references have been deleted (see Clause 2 of the 2010 edition), and some terms already defined in the referenced documents have been deleted (see Clause 3 of the 2010 edition).

Provisions on essential variables and non-essential variables in the testing procedure have been added (see Table 1), and the provisions on the content of the testing procedure have been changed (see 4.4.1; 4.2.2 of the 2010 edition).

The provisions on procedure qualification have been changed (see 4.4.1 and 4.4.3; 4.2.1 and 4.4.3 of the 2010 edition), as have the provisions on testing instruments and probes (see 4.5.1 and 4.5.2; 5.1 and 5.2 of the 2010 edition).

The provisions on similar acoustic properties of reference blocks have been changed (see 4.5.4.2.1; 5.4.2 of the 2010 edition), and requirements on surface curvature, surface condition and quality of reference blocks and on machining of reference reflectors have been added (see 4.5.4.2 and 4.5.4.3).

The requirements on performance tests and test periods have been changed (see 4.5.5 and Table 2; 5.5 and Table 1 of the 2010 edition), and the requirements on environmental conditions have been changed (see 4.6.6; 6.6 of the 2010 edition).

The provisions on identification of test objects and reference coordinates have been deleted (see 6.7 of the 2010 edition), as have the provisions on straight-beam testing, angle-beam testing and special or new techniques (see 8.2 and 8.4 of the 2010 edition).

The provisions on sensitivity setting by the distance-amplitude curve method have been changed (see 4.8.3.3; 9.3.3 of the 2010 edition), together with the provisions on attenuation compensation (see 4.8.4.2 and Annex A) and curvature compensation (see 4.8.4.3 and Annex B).

The provisions on verification have been changed (see 4.10; Clause 7 of the 2010 edition); provisions on probes for testing castings have been added (see 5.1.4) and the provisions on castability assessment of castings have been deleted (see 12.7 of the 2010 edition).

For plates, the scope has been changed (see 5.2.1, Annex D and Annex E), the provisions on probes and scanning modes have been changed (see 5.2.4 and 5.2.7), and the provisions on measuring back-wall echo loss of plates have been deleted (see 13.9 of the 2010 edition).

For forgings, provisions on testing timing have been added (see 5.3.3), the provisions on probes and reference blocks have been changed (see 5.3.5 and 5.3.6), and the provisions on grid scanning of forgings have been deleted (see 14.6.2.2 of the 2010 edition).

The provisions on testing timing, probes and scanning of bars have been changed (see 5.4.2, 5.4.4 and 5.4.7), and the provisions on testing timing, probes, reference blocks and scanning of bolting materials have been changed (see 5.5.2, 5.5.4, 5.5.5 and 5.5.7).

For tubes, the scope and the provisions on probes and reference blocks have been changed (see 5.6.1, 5.6.4 and 5.6.5), and the provisions on calibration and verification in tube testing have been deleted (see 17.11 of the 2010 edition).

For full penetration welded joints, the scope has been changed (see 6.1 and Annex G) and the provisions on testing timing, surface preparation, probes, reference blocks, scanning and recording have been changed (see 6.2, 6.4, 6.6, 6.7 and 6.10).

For weld overlay cladding and buttering, the scope has been changed (see 7.1, Annex E and Annex I) and the provisions on testing timing, surface preparation, probes, reference blocks, scanning and recording have been changed (see 7.2, 7.4, 7.6, 7.7 and 7.10).

The annexes on screen height linearity (Annex A of the 2010 edition) and on horizontal and vertical linearity tests (Annex B of the 2010 edition) have been deleted, and an annex on the recommended method for determining curvature compensation has been added (see Annex B).

The annex on the angle-beam ultrasonic testing method for castings has been changed (see Annex C), and an annex on the angle-beam ultrasonic testing method for plates has been added (see Annex D).

The annexes on scanning of critical forgings (Annex E of the 2010 edition), on ultrasonic testing of centrifugally cast austenitic stainless steel main pipes (Annex G of the 2010 edition) and on drawing the profile of welded joints (Annex I of the 2010 edition) have been deleted.

The annex on the ultrasonic testing method for austenitic stainless steel butt welded joints has been changed (see Annex G; Annex H of the 2010 edition), and an annex on thickness measurement by the contact ultrasonic pulse-echo method has been added (see Annex I).

Attention is drawn to the possibility that some elements of this document may be the subject of patents. The issuing body of this document shall not be held responsible for identifying any or all such patents.

This document was proposed by the National Energy Administration and is under the jurisdiction of He Gongye Biaozhunhua Yanjiusuo.

Drafting organizations: Guohe Dianzhan Yunxing Fuwu Jishu Youxian Gongsi, Zhongguanghe Jiance Jishu Youxian Gongsi, Zhongguo Diyi Zhongxing Jixie Jituan Gongsi, Dongfang Dianqi (Guangzhou) Zhongxing Jiqi Youxian Gongsi, Hadian Jituan (Qinhuangdao) Zhongxing Zhuangbei Youxian Gongsi, Shanghai Dianqi Hedian Shebei Youxian Gongsi, Huabei He yu Fushe Anquan Jianduzhan, Zhongguanghe Gongcheng Youxian Gongsi.

Main drafters: Shi Huan, Deng Li, Yuan Guanghua, Xiao Aiwu, Sun Jiawei, Sun Yuanxia, Luo Wei, Cheng Zhonghe, Zhou Yushan, Duan Minjie, Zhang Jin.

This document was first published in 2010; this is the first revision.

1 Scope

NB/T 20003.2-2021 is Part 2 of the Chinese standard for non-destructive examination of mechanical components in nuclear power plants, and it governs ultrasonic testing. It replaces the 2010 edition. Mechanical components of a nuclear plant - reactor pressure vessel, steam generators, pressurisers, main coolant piping, pumps and valves - are examined during manufacture, during construction and repeatedly in service, and the ultrasonic examination is the method that finds and sizes internal flaws in thick forgings, castings and welds. The standard sets the scope, the normative references and the defined terms, then the general requirements: the qualification of personnel, the written procedure, the equipment and its performance checks, the probes, the couplant, and the reference blocks with their reflectors. It covers the calibration of time base and sensitivity, the construction of distance-amplitude curves, and the examination technique for each product form - plates, forgings, bars, castings, pipes and tubes, bolting, cladding and its bond, and butt, nozzle and attachment welds - with the scanning directions, coverage and overlap. For each it gives the recording level, the characterisation and sizing of indications, and the acceptance criteria by quality class, tabulated by thickness and component type. Surface preparation, the treatment of geometric indications, re-examination after repair, and the examination report close the part. It applies to nuclear plants built in China.

This document specifies the ultrasonic testing methods and quality grading for raw materials or parts of mechanical components in nuclear island of nuclear power plants.

This document is applicable to ultrasonic testing, during manufacturing and installation, of raw materials or parts such as castings, plates, forgings, bars, bolting materials and tubes, as well as welded joints, weld overlay cladding and buttering, in mechanical components in nuclear island of nuclear power plants.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 12604.1 Non-destructive testing - Terminology - Ultrasonic testing

JB/T 8428 Non-destructive testing - General specification for ultrasonic test blocks

JB/T 9214 Non-destructive testing - Test methods for evaluating performance characteristics of A-scan pulse-echo ultrasonic testing systems

NB/T 20003.1 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 1: General requirements

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 12604.1 and NB/T 20003.1 and the following apply.

3.1 Reduction of back wall echo caused by the presence of discontinuities (BG/BF): in forging testing, the ratio of the first back-wall echo amplitude BG in a sound area adjacent to the discontinuity to the first back-wall echo amplitude BF in the discontinuity area, expressed in decibels (dB).

3.2 Reference sensitivity: the sensitivity obtained when the echo height of the reference reflector in the reference block, or of the back wall of the workpiece under test, is adjusted to a given reference level.

3.3 Scanning sensitivity: the sensitivity used for actual testing, obtained by raising the reference sensitivity (3.2) by an appropriate number of decibels (gain) according to the flaw detection requirements and the probe type.

3.4 Echodynamic patterns: the envelope of the variation of the echo amplitude from a flaw reflector with the probe movement distance.

4.1 Testing personnel

Unless otherwise specified, ultrasonic testing personnel shall comply with the relevant provisions of NB/T 20003.1.

4.10 Verification

4.10.1 The testing system shall be verified at the end of each examination, after at most 4 h of continuous testing, when the operator changes (except for automatic testing), and at any time the testing personnel doubt the validity of the testing system.

4.10.2 If the sound path deviation at any point exceeds 10% of its true sound path or 5% of the maximum range set on the instrument (whichever is greater), the range shall be readjusted, recorded indications re-examined and their position data recorded.

If the sensitivity has decreased by 2 dB or more, sensitivity shall be reset as specified and all workpieces tested since the last valid verification shall be re-examined.

If the sensitivity has increased by 2 dB or more, sensitivity shall be reset as specified, all recorded signals re-examined, and the records amended or remade according to the new results.

4.10.3 During verification, the ultrasonic testing system, including instrument, probes, cables, couplant and blocks, shall not be changed.

During verification, any control affecting instrument linearity, such as reject or filter switches, shall be set to 'off' or to the minimum level.

4.2 Testing documents

4.2.1 Basic requirements: testing documents, including the testing procedure or other testing documents, shall comply with NB/T 20003.1. Testing shall be performed in accordance with a valid testing procedure.

4.2.2 The testing procedure shall include at least the essential and non-essential variables in Table 1 and the following: scope of application (type, dimensions, testing extent and material of the workpiece); referenced regulations, codes, standards and design documents; qualification of testing personnel.

The procedure shall also cover testing equipment and materials (ultrasonic instrument, probes, couplant, automatic testing equipment where applicable, standard blocks and/or reference blocks) and testing conditions (testing timing, testing zone and surface condition).

The procedure shall further cover the testing method (testing technique, scanning including test surface, testing extent and scanning direction), verification method and requirements, recording and evaluation requirements, acceptance criteria, and content and format of the test report.

When the content of the procedure changes, the procedure shall be revised and reissued.

Table 1, essential variable: material type, geometry, thickness and product form of the workpiece under test.

Table 1, essential variable: the examination surface.

Table 1, essential variable: the testing technique (contact method, immersion method, etc.).

Table 1, essential variable: the angle and wave mode of sound propagation in the material.

Table 1, essential variable: the type, frequency and size of the probe.

Table 1, essential variable: special probes, wedges and probe shoes (when used).

Table 1, essential variable: the model of the ultrasonic instrument.

Table 1, essential variable: the standard blocks and reference blocks.

Table 1, essential variable: the scanning direction and extent.

Table 1, essential variable: the scanning mode (manual or automatic).

Table 1, essential variable: scan coverage (only when the coverage is reduced).

Table 1, essential variable: the data recording method.

Table 1, essential variable: the method for discriminating indication signals.

Table 1, essential variable: the method for determining the amplitude and size of indications.

Table 1, essential variable: the verification method.

Table 1, essential variable: data acquisition software (automatic testing).

Table 1, essential variable: data acquisition parameters (automatic testing).

Table 1, essential variable: personnel operating requirements (where required).

Table 1, non-essential variable: surface condition (test surface, reference block surface).

Table 1, non-essential variable: brand or type of couplant.

Table 1, non-essential variable: automatic alarm and/or recording devices (when used).

Table 1, non-essential variable: data to be recorded, including calibration data (such as instrument settings).

4.3 Testing extent

The testing extent and testing proportion of the object under test shall comply with the relevant technical specifications, product design documents or procurement technical documents.

4.4 Procedure qualification

4.4.1 Procedure qualification shall be performed when required by the relevant product design documents or procurement technical documents.

In addition, procedure qualification should be performed when ultrasonic testing is applied to a given type of test object for the first time, or when changes in the characteristics of the test object, testing conditions or testing parameters significantly affect the test results.

4.4.2 a) Testing during qualification shall be performed on qualification specimens containing representative flaws, which may be artificial reference reflectors or real manufacturing flaws whose nature, position, distribution, size and orientation are representative and meet the purpose of the qualification.

4.4.2 b) The organization undertaking non-destructive testing shall test in accordance with a valid procedure, demonstrating that the methods, techniques and testing systems described in the procedure meet the testing purpose and requirements for flaw detection and evaluation.

4.4.2 c) The organization undertaking non-destructive testing shall record the testing requirements, testing procedure, qualification specimens and test results of the qualification and compile them into written documents.

4.4.3 Requalification: when the value or range of an essential variable listed in Table 1 changes, the procedure shall be requalified; when the value or range of a non-essential variable listed in Table 1 changes, requalification is not required.

4.5 Equipment and materials

4.5.1 Testing shall use an A-scan pulse-echo ultrasonic instrument or another ultrasonic instrument with an A-scan pulse-echo operating mode. The operating frequency range shall include at least 0.5 MHz to 10 MHz, with linear display over at least 80% of full screen height; horizontal linearity error not greater than 1% and vertical linearity error not greater than 5%.

The ultrasonic instrument shall have a continuously adjustable attenuator of 80 dB or more with steps not greater than 2 dB, an accuracy within +/-1 dB for any adjacent 12 dB, and a maximum cumulative error not greater than 1 dB.

4.5.2 The nominal frequency of probes is generally within 1 MHz to 10 MHz. Crystals are circular (including elliptical) or square; circular crystal diameter is generally not greater than 40 mm, and any side of a square crystal is generally not greater than 40 mm.

To ensure stable and reliable acoustic coupling, the probe may be ground or fitted with a contoured wedge suited to the workpiece, or with a shoe that improves coupling; the same wedge or shoe shall be used for sensitivity setting and testing.

Probe types are generally single-element and dual-element probes; other types, such as creeping wave probes, may be used when necessary.

Each probe shall have a unique and permanent identification number and a quality certificate giving at least the nominal frequency, crystal size, bandwidth, nominal probe angle (where applicable) and front distance (where applicable).

4.5.3.1 A couplant with good wettability and sound transmission that does not damage the test surface shall be used, such as machine oil, paste, glycerine or water. The same couplant shall be used for sensitivity setting and testing.

After testing, couplant that would affect subsequent machining and testing shall be removed. Couplant shall be removed immediately after testing on austenitic stainless steel, titanium and nickel-base alloys.

4.5.3.2 Couplants used on nickel-base alloys, austenitic stainless steel and titanium shall have a certificate of contaminant content and meet the following: couplant used on nickel-base alloys shall have a sulphur content not greater than 200 mg/L.

Couplant used on austenitic stainless steel or titanium shall have a total halogen (chlorine and fluorine) content not greater than 200 mg/L.

4.5.4.1 Standard blocks are the No. 1 calibration block specified in GB/T 19799.1 and other standard blocks with essentially the same function or able to replace it, for example the No. 2 calibration block in GB/T 19799.2 or the CSK-IA block specified in JB/T 8428.

Standard blocks are mainly used for performance testing and verification of the testing system, and sometimes also for sensitivity setting.

4.5.4.2.1 The reference block material may be: a) an extension of the part under test; b) remnant material with the same material grade and heat treatment condition as the part under test.

c) Material with acoustic properties similar to the part under test: unless otherwise specified in other technical documents, acoustic properties are considered similar when the differences between the reference block and the part are within: sound velocity +/-5%, acoustic impedance +/-5%, attenuation coefficient +/-20%.

4.5.4.2.2 a) For workpieces with a diameter not greater than 500 mm, curved reference blocks shall be used. A curved block of any single curvature may be used for workpieces whose surface curvature is within 0.9 to 1.5 times the block diameter.

b) For workpieces with a diameter greater than 500 mm but less than 2000 mm, curved or flat reference blocks may be used; curved blocks follow a), and curvature compensation shall be applied when flat blocks are used.

c) For workpieces with a diameter not less than 2000 mm, curved or flat reference blocks may be used, and no surface curvature compensation is required when flat blocks are used.

4.5.4.2.3 The surface roughness of the reference block shall be comparable to that of the workpiece; otherwise coupling compensation shall be applied in accordance with 4.8.4.1.

Note: roughness is considered comparable when the difference in surface roughness Ra between the reference block and the workpiece does not exceed +/-2.5 µm.

4.5.4.2.4 Material used to make reference blocks shall be fully scanned with a straight-beam probe; along the beam paths of each probe used for sensitivity setting there shall be no indication greater than the equivalent of a 2 mm diameter flat-bottom hole.

4.5.4.3 a) The machining tolerance on the diameter of flat-bottom holes and side-drilled holes shall not exceed +/-10%, with a maximum of 0.4 mm.

4.5.4.3 b) The machining tolerance on the position of flat-bottom holes and side-drilled holes shall not exceed +/-3 mm.

4.5.4.3 c) The machining tolerance on the flatness of the flat-bottom hole bottom shall not exceed +/-0.05 mm.

4.5.4.3 d) The machining tolerance on the perpendicularity of flat-bottom holes and side-drilled holes shall not exceed +/-0.5 degrees.

4.5.4.3 e) The machining tolerance on notch depth shall not exceed +/-10%, with a maximum of 0.1 mm.

4.5.5.1 Before testing starts each day, the appearance and condition of the testing system shall be checked: a) the appearance of the instrument, probes, cables and blocks, confirming there is no physical damage or wear affecting operation and reliability; b) stable electrical connection between probe and instrument.

c) If the probe has a separable structure with a replaceable wedge, the assembly of probe and wedge shall be checked.

Performance testing of the testing system includes horizontal linearity, vertical linearity, signal-to-noise ratio, dead zone of straight-beam probes, and index point and refraction angle of angle-beam probes; the test periods shall be as given in Table 2.

Horizontal linearity, vertical linearity, straight-beam probe dead zone, angle-beam probe index point and refraction angle shall be measured by the methods described in JB/T 9214; the signal-to-noise ratio shall be measured as in 4.5.5.3; the dead zone may also be measured as in 4.5.5.4.

Performance test results shall be recorded in writing. Linearity shall meet 4.5.1; signal-to-noise ratio and dead zone shall meet the product design or procurement documents; the refraction angle deviation from the nominal angle is generally not greater than +/-2 degrees, and not greater than +/-3 degrees when the nominal frequency is less than 2 MHz.

Table 2 test periods: appearance and condition - daily; horizontal and vertical linearity - as specified in 4.5.5.2; front distance of angle-beam probes - daily; refraction angle of angle-beam probes - daily.

Note to Table 2: when specified, the signal-to-noise ratio of the testing system and the dead zone of straight-beam probes shall be measured.

4.5.5.2 Horizontal and vertical linearity of the testing system shall be tested on equipment acceptance, after equipment repair, before reuse after a period out of service, every 3 months for analogue instruments and every year for digital instruments.

4.5.5.3 During testing, the noise signal (excluding surface spurious indications) shall be at least 6 dB lower than the maximum echo of the reference reflector at the maximum sound path, or shall comply with the product design and procurement technical documents.

The signal-to-noise ratio may be measured as follows: place the probe on the reference block, find the maximum echo of the reference reflector at the maximum sound path, adjust gain or attenuator to bring it to 80% full screen height and record the system dB value delta 1.

Without moving the probe, adjust gain or attenuator so that the noise signal near the reference reflector signal used for delta 1 reaches 80% full screen height, record the system dB value delta 2; the difference between the two readings is recorded as the signal-to-noise ratio.

4.5.5.4 At a given sensitivity, the depth L from the test surface to the nearest detectable indication in the workpiece characterizes the size of the dead zone; the measurement is illustrated in Figure 1.

Unless otherwise specified, the dead zone shall be measured at the reference sensitivity. When required, the dead zone measurement result shall be recorded in the test report.

4.5.5.5 During performance testing of the testing system, any control affecting instrument linearity (such as reject or filter switches) shall be set to 'off' or to the minimum level.

4.6 Testing conditions

4.6.1 The testing timing shall comply with the relevant product design documents or procurement technical documents.

4.6.2 The testing zone shall comply with the relevant product design documents or procurement technical documents.

4.6.3 The examination surface shall be selected so that the testing zone of the workpiece can be adequately examined.

4.6.4 The test surface shall be free from foreign matter and surface irregularities that affect acoustic coupling, interfere with ultrasonic propagation or hinder probe movement; otherwise they shall be removed or suitably treated, with a treatment method chosen according to the workpiece.

The surface roughness of the test surface shall meet the testing requirements; unless otherwise specified, surface roughness Ra shall not exceed 12.5 µm. Machining that would hinder ultrasonic testing shall be carried out after testing.

4.6.5 Ultrasonic testing shall be performed under fully accessible conditions. Where access is restricted, for example partial inaccessibility or a restricted movement area of one of several probes, the factors affecting probe accessibility shall be recorded and illustrated in the test report.

4.6.6 For contact testing, the temperature difference between the block used for sensitivity setting and the test surface shall be within +/-14 degrees Celsius.

For immersion testing, the temperature difference between the couplant used for sensitivity setting and the couplant used during testing shall be within +/-14 degrees Celsius.

4.7 Testing technique

4.7.1 This clause applies to ultrasonic testing using a single probe or two probes.

4.7.2 Ultrasonic testing may use the contact method or the immersion method.

For contact testing, the probe may be ground or fitted with a contoured wedge or probe shoe suited to the workpiece.

4.8 Testing

4.8.1.1 The probe movement area shall be determined according to the testing zone, workpiece structure, test surface, probe and testing technique.

4.8.1.2 During testing the probe is moved over the test surface in a defined pattern. For 100% scanning, adjacent passes shall overlap; unless otherwise specified, the overlap shall be at least 10% of the crystal dimension perpendicular to the scanning direction (for dual-element probes, the total size of both crystals).

When selecting probes and determining the scanning process, the sound beam shall cover the entire testing zone of the workpiece. Areas that cannot be scanned because of workpiece geometry or inaccessibility shall be noted in the test report.

4.8.1.3 For manual scanning, the probe movement speed shall not exceed 150 mm/s.

When scanning with automatic alarm or automatic testing devices, the probe speed is not so limited, but at the maximum operating speed the maximum echo amplitude of a specified reference reflector shall be within +/-2 dB of the maximum echo amplitude obtained in manual testing.

The pulse repetition frequency shall be matched to the probe movement speed, avoiding insufficient coverage from too low a repetition frequency or 'ghost echoes' from too high a repetition frequency.

4.8.2 The sound path range may be set on a standard block, reference block or the workpiece; an appropriate range shall be chosen according to the shape, size and testing technique, meeting the requirements for flaw detection, observation of indication echoes and location of indications in the testing zone.

4.8.3.1 A suitable sensitivity setting method shall be selected according to the testing purpose and requirements; sensitivity shall generally be set by the method of 4.8.3.2 or 4.8.3.3, and the DGS method may also be used.

4.8.3.2 Single reflector method: the reference sensitivity is set using a single reference reflector such as the back wall of the workpiece or a single notch, i.e. the stable maximum echo from this reflector is obtained and the gain or attenuator is adjusted to bring it to 80% +/-5% of full screen height.

4.8.3.3 A distance-amplitude curve (DAC) is generally drawn on the reference block as follows: place the straight-beam or angle-beam probe over the reference reflector giving the highest amplitude, set its amplitude to 80% +/-5% of full screen height, then without changing gain measure the highest echoes of the other reference reflectors and connect the points to form the DAC (Figure 2).

A DAC generally consists of at least three points. It may be drawn electronically and shown on the screen, or drawn directly on the screen. The echo amplitude of each reference reflector within the testing range shall not be less than 20% of full screen height; if any is less, the DAC shall be drawn in segments.

If the instrument allows, the echo of each reference reflector may be adjusted to the same height, such as 80% of full screen height, and a distance gain compensation curve based on the required gain values used instead of the DAC.

Every DAC shall be extended horizontally before its first point and along the tangent at its last point after that point, so as to cover the entire testing range.

4.8.4.1 During testing and flaw sizing, coupling losses caused by differences in surface condition shall be compensated.

4.8.4.2 During testing and flaw sizing, sensitivity reduction and sizing errors caused by material attenuation shall be compensated.

When flaw equivalent size is determined by calculation, a correction shall be made if the material attenuation coefficient exceeds 4 dB/m; when it is determined with a distance-amplitude curve, a correction shall be made if the attenuation coefficients of reference block and workpiece differ by more than +/-4 dB/m. The calculation of the attenuation coefficient is given in Annex A.

4.8.4.3 During testing and flaw sizing, curvature compensation shall be applied for workpieces with a diameter greater than 500 mm but less than 2000 mm when a flat reference block is used for sensitivity setting. A recommended method for determining the curvature compensation value is given in Annex B.

4.8.5.1 During testing, the probe is moved to obtain the maximum echo of the indication, and under this condition the position coordinates of the indication are determined; they shall include at least the depth of the indication and its distance from the reference point or reference line.

4.8.5.2 When testing with the DAC method, the probe is moved to obtain the maximum echo of the indication, and the echo amplitude is expressed as the dB difference from the DAC at the same sound path; for example, an indication delta dB above the DAC is recorded as 'DAC + delta dB'. The amplitude may also be expressed as a percentage of the DAC.

When other sensitivity setting methods are used, the probe is moved to obtain the maximum echo, and the amplitude is expressed as the dB difference or percentage relative to the reference sensitivity.

4.8.5.3 The size of indications shall be measured by the methods specified in the relevant clauses.

4.9 Recording and evaluation

Recording and evaluation shall be carried out by the methods specified in the relevant clauses.

5.1 Ultrasonic testing method for castings

5.1.1 This clause applies to straight-beam ultrasonic testing and quality grading of carbon steel, low alloy steel and martensitic stainless steel castings; the angle-beam testing method and quality grading are given in Annex C.

5.1.2 Unless otherwise specified in other technical documents, ultrasonic testing of castings shall be carried out after heat treatment and before final machining of the external contour.

5.1.3 Ultrasonic testing of castings generally uses the contact method.

5.1.4 Single-element or dual-element straight-beam probes may be used. A probe shoe may be fitted to ensure satisfactory coupling with curved workpieces.

For casting thickness of 50 mm or more, a single-element straight-beam probe should be used; for thickness less than 50 mm, a dual-element straight-beam probe is generally used.

Probe frequency is generally 0.5 MHz to 5 MHz, chosen according to the signal-to-noise ratio; generally 2 MHz for single-element and 5 MHz for dual-element straight-beam probes, and the chosen frequency shall keep background noise below 25% of the DAC.

5.1.5 One reference block or a set of reference blocks shall be made; the form is shown in Figure 3, or it may be rectangular or of another form.

The reference reflector is a 6 mm diameter flat-bottom hole; the number and position of holes shall be representative of the casting and cover its whole thickness range. The distance L from the first hole to the test surface shall be at most 25 mm; the distance of the last hole shall equal the maximum thickness tested, within +/-20% of that thickness.

For castings thicker than 40 mm the reference block shall have at least 3 flat-bottom holes; for castings not thicker than 40 mm it shall have at least 2 flat-bottom holes.

5.1.6 For castings thicker than 40 mm, the DAC drawn from at least 3 flat-bottom holes at different distances from the test surface is the reference sensitivity; for castings not thicker than 40 mm, the DAC drawn from at least 2 flat-bottom holes is the reference sensitivity.

The scanning sensitivity shall be at least 6 dB higher than the reference sensitivity.

5.1.7 Probe movement shall ensure coverage of the specified testing zone.

5.1.8 Excluding the influence of geometry and coupling, the following shall be recorded: a) all indications with amplitude reaching or exceeding 100% DAC; b) all areas where an indication causes a back-wall echo reduction of 75% or more.

c) All areas with a back-wall echo reduction of 75% or more but no indication signal, which shall be further investigated as suspect areas. Records shall include the number, position, amplitude, length and area of indications.

5.1.9 Length and area shall be measured for all indications meeting the recording requirements.

When measuring length and area, the probe centre where the indication amplitude is 100% DAC or the back-wall echo is reduced by 75% is taken as the boundary, and the area is determined from the boundary points found by moving the probe in each direction.

For area calculation, lines may be drawn around the centres of the marks forming the indication area to define the flaw extent; to obtain an easily calculated polygon the whole indication may be drawn as a rectangle or other regular shape, and not all ultrasonic signals within the area need exceed the reference line.

Suspect areas of castings whose quality cannot be judged from ultrasonic results shall be supplemented by radiographic testing, and the casting quality judged on the radiographic results.

In some castings, a very long metal sound path or a curved test surface can make the indication length and area much larger or smaller than in the casting; in such cases indications shall be evaluated using a beam spread correction.

5.1.10 Table 3, grade I: maximum permissible indication area 500 square millimetres, maximum permissible indication length 40 mm.

Table 3, grade II: maximum permissible indication area 1000 square millimetres, maximum permissible indication length 50 mm.

Table 3, grade III: maximum permissible indication area 2000 square millimetres, maximum permissible indication length 60 mm.

Table 3, grade IV: maximum permissible indication area 3000 square millimetres, maximum permissible indication length 80 mm.

5.2 Ultrasonic testing method for plates

5.2.1 This clause applies to straight-beam ultrasonic testing and quality grading of carbon steel, alloy steel and austenitic stainless steel plates not less than 6 mm thick; nickel and nickel alloy plates and duplex stainless steel plates may also be tested and graded to this clause.

The angle-beam ultrasonic testing method and quality grading for plates are given in Annex D; the ultrasonic testing method and quality grading for the bond interface of clad steel plates with cladding not less than 2 mm thick are given in Annex E.

5.2.2 Unless otherwise specified in other technical documents, ultrasonic testing of plates shall be carried out after the heat treatment that improves mechanical properties (excluding stress-relief heat treatment).

5.2.3 Plates may be tested by the contact or immersion method. Straight-beam testing may be performed from one surface of the plate only, or from both the upper and lower surfaces.

5.2.4 Straight-beam probes may be selected according to Table 4. The focal zone of dual-element straight-beam probes shall suit the plate thickness.

If coarse grains or large thickness of austenitic steel plates prevent effective ultrasonic penetration, probes of other frequencies and sizes may be used by agreement of the parties.

Table 4: nominal thickness from 6 mm to less than 25 mm - dual-element straight-beam probe, frequency 4 MHz to 5 MHz, crystal diameter not greater than 14 mm.

Table 4: nominal thickness from 25 mm to less than 60 mm - dual-element straight-beam probe, frequency 2 MHz to 5 MHz, crystal diameter not greater than 30 mm.

Table 4: nominal thickness 60 mm or more - single-element straight-beam probe, frequency 2 MHz to 5 MHz, crystal diameter not greater than 30 mm.

5.2.5 The reference reflectors in the reference block are flat-bottom holes: a) for dual-element straight-beam testing a 5 mm diameter flat-bottom hole is used; b) for single-element straight-beam testing the hole diameter is chosen according to the quality grade, such as 5 mm, 8 mm or 11 mm.

c) Over the thickness tested there shall be at least three flat-bottom holes at different depths; the distance from the bottom of the first hole to the test surface is generally not greater than 10 mm, and that of the last hole shall be within the nominal wall thickness T +/-15 mm; d) the reference block form may follow Figure 4.

5.2.6 According to the quality grade, the DAC drawn from flat-bottom holes at different depths in the reference block is used as the reference sensitivity. The scanning sensitivity shall be at least 6 dB higher than the reference sensitivity.

5.2.7 A 100% scan shall be made over a given width of the plate edge zone; the width is given in Table 5 and Figure 5.

In the non-edge zone of the plate one of the following scanning modes may be chosen: a) 100% scanning; b) scanning along grid lines at 100 mm spacing, parallel and perpendicular to the rolling direction, with 100% scanning within 50 mm on each side of the bevel preparation lines (half the plate thickness when thickness exceeds 100 mm).

c) Scanning along grid lines at 200 mm spacing, parallel and perpendicular to the rolling direction, with 100% scanning within 50 mm on each side of the bevel preparation lines (half the plate thickness when thickness exceeds 100 mm).

When an indication is found, extended testing shall be performed over a 200 mm x 200 mm area centred on the indication.

When a dual-element straight-beam probe scans perpendicular to the rolling direction, its acoustic barrier shall be parallel to the rolling direction.

Table 5 plate edge zone width: nominal thickness from 6 mm to less than 50 mm - 50 mm; from 50 mm to less than 100 mm - 75 mm; 100 mm or more - 100 mm.

5.2.8.1 The following indications shall be recorded: a) indications that may cause complete loss of the back-wall echo; b) all indications with amplitude not less than 50% DAC. Records include number, position, amplitude, length and area of indications.

Note: at the reference sensitivity, the back-wall echo is considered completely lost when it is lower than 5% of full screen height.

5.2.8.2 When the back-wall echo is completely lost, the indication boundary is measured by the -6 dB method: move the probe away from the centre of the indication until the signal height equals half of its maximum, record the probe centre position, and repeat to determine the boundary.

When a single indication amplitude is not less than the recording threshold, move the probe along the main length direction of the indication; the positions where the echo falls to half of its maximum are the ends, and the distance between them is the indicated length.

5.2.9.1 The indicated length of a single flaw is its maximum indicated length, i.e. the maximum flaw dimension parallel to the plate edge as shown in Figure 5.

5.2.9.2 a) The indicated area S of a flaw is the single indicated area of that flaw, determined as the product of flaw length L and width W in Figure 5.

5.2.9.2 b) When two adjacent flaws are spaced less than 100 mm apart or less than the indicated length of the smaller flaw, the sum of their areas is taken as a single flaw indicated area, as shown in Figure 5.

5.2.9.3 In the non-edge zone, flaw density is evaluated by the total number of flaws within any 1 m x 1 m test area; whether a flaw counts is decided by its indicated area or equivalent size. For plates smaller than 1 m x 1 m, the maximum permissible number may be prorated.

For flaws at the plate edge and on both sides of the bevel preparation lines, density is evaluated by the maximum permissible total number within a 1 m length; if the tested length is less than 1 m, the maximum permissible number may be prorated.

5.2.10.1 Quality grading of the non-edge zone of plates is given in Tables 6 and 7.

Table 6 (dual-element probe), grade I: single flaw indicated area S not greater than 50 square millimetres; flaws counted with S greater than 20 and up to 50 square millimetres; maximum 10 flaws within 1 m x 1 m.

Table 6 (dual-element probe), grade II: single flaw S not greater than 100 square millimetres; flaws counted with S greater than 50 and up to 100 square millimetres; maximum 10 flaws within 1 m x 1 m.

Table 6 (dual-element probe), grade III: single flaw S not greater than 1000 square millimetres; flaws counted with S greater than 100 and up to 1000 square millimetres; maximum 15 flaws within 1 m x 1 m.

Table 6 (dual-element probe), grade IV: single flaw S not greater than 5000 square millimetres; flaws counted with S greater than 1000 and up to 5000 square millimetres; maximum 20 flaws within 1 m x 1 m.

Table 7 (single-element probe), grade I: single flaw S not greater than the equivalent area of an 8 mm flat-bottom hole; flaws counted between the 5 mm and 8 mm flat-bottom hole equivalent areas; maximum count 10.

Table 7 (single-element probe), grade II: single flaw S not greater than the equivalent area of an 11 mm flat-bottom hole; flaws counted between the 8 mm and 11 mm flat-bottom hole equivalent areas; maximum count 10.

Table 7 (single-element probe), grade III: single flaw S not greater than 1000 square millimetres; flaws counted with S greater than 100 and up to 1000 square millimetres; maximum count 15.

Table 7 (single-element probe), grade IV: single flaw S not greater than 5000 square millimetres; flaws counted with S greater than 1000 and up to 5000 square millimetres; maximum count 20.

5.2.10.2 Quality grading of the plate edge zone and of the areas on both sides of the bevel preparation lines is given in Table 8.

For plates not less than 60 mm thick, the following indications are also counted in the maximum permissible total: for quality grade I plates, indications with amplitude between the 5 mm and 8 mm DAC curves; for quality grade II plates, indications with amplitude between the 8 mm and 11 mm DAC curves.

Table 8, grade I: maximum permissible length Lmax 20 mm, maximum permissible area Smax 50 square millimetres, minimum counted indicated length Lmin 10 mm, maximum permissible total within 1 m length 2.

Table 8, grade II: Lmax 30 mm, Smax 100 square millimetres, Lmin 15 mm, maximum permissible total of flaws smaller than Smax but longer than Lmin within 1 m length 3.

Table 8, grade III: Lmax 40 mm, Smax 500 square millimetres, Lmin 20 mm, maximum permissible total of flaws smaller than Smax but longer than Lmin within 1 m length 4.

Table 8, grade IV: Lmax 50 mm, Smax 1000 square millimetres, Lmin 25 mm, maximum permissible total of flaws smaller than Smax but longer than Lmin within 1 m length 5.

5.3 Ultrasonic testing method for forgings

5.3.1 This clause applies to ultrasonic testing and quality grading of carbon steel, alloy steel, martensitic stainless steel and austenitic stainless steel forgings. Ultrasonic testing of cylindrical steel bars and bolting materials shall comply with 5.4 and 5.5 respectively.

5.3.2 According to shape and manufacturing process, forgings are divided into four classes (Table 9); classes I, II and III are forgings of simple shape and class IV are forgings of complex shape.

5.3.3 Unless otherwise specified in other technical documents, ultrasonic testing of forgings shall be carried out after the heat treatment that improves mechanical properties (excluding stress-relief heat treatment), but before drilling, keyway cutting, taper turning, grooving or machining of external contours.

If the shape of a forging required to be heat treated for mechanical properties would prevent complete testing after heat treatment, testing may be performed before that heat treatment, but the forging shall still be retested as completely as possible after heat treatment.

5.3.4 Forgings may be tested by the contact or immersion method, including straight-beam and angle-beam testing. Angle-beam testing generally uses shear waves; if coarse grains prevent shear wave testing or the workpiece structure is unsuitable for shear wave angle-beam probes, longitudinal wave angle-beam testing may be used.

All parts of a forging shall be 100% scanned with straight-beam probes from mutually perpendicular directions.

Ring or hollow forgings with an axial length of 50 mm or more and an outside to inside diameter ratio of 2 or less shall be tested with circumferential angle-beam probes. Where conditions allow, ring or tubular forgings made by boring cylindrical forgings shall also be tested in accordance with 5.6.

Table 9, class I: forgings resembling parallelepipeds or cylindrical, conical or truncated-cone forgings, possibly with a through bore much smaller than the outside diameter; bearing and bolting materials, e.g. sections, bars, rounds, shafts, journals and discs cut from bars; usual process: direct forging.

Table 9, class II: forgings with one dimension much smaller than the other two, e.g. tube sheets of steam generators or heat exchangers, core support pieces, heads and flanges, and pancake forgings (possibly bored at the end); usual process: upsetting.

Table 9, class III: ring or tubular hollow forgings, e.g. rims, shell rings, branch nozzles, reactor pressure vessel flanges and some reactor internals; usual process: mandrel drawing or expanding, or ring rolling.

Table 9, class IV: forgings of complex shape, e.g. valves forged directly or closed-die forged, and conical nozzles; usual process: closed-die forging or press forging.

5.3.5.1 Straight-beam probes may be single-element or dual-element; their frequency is generally 2 MHz to 5 MHz.

For austenitic stainless steel forgings or thick carbon steel forgings, considering sound transmission, a lower nominal frequency and larger crystal size may be chosen, but the frequency shall not be lower than 1 MHz; use of probes below 1 MHz shall be agreed by the contracting parties beforehand.

5.3.5.2 The frequency of angle-beam probes is generally 2 MHz to 5 MHz; if the beam cannot penetrate the whole thickness, lower-frequency probes are permitted by agreement of the contracting parties, but not lower than 1 MHz.

The angle of angle-beam probes is generally 45 degrees; considering the forging shape, probes of other angles may be used to ensure effective beam coverage of the whole forging volume.

5.3.5.3 To prevent probe rocking and ensure good, uniform coupling and a constant beam angle, a contoured probe shoe may be fitted.

5.3.6.1 For dual-element straight-beam testing, the flat-bottom hole diameter in the reference block is 2 mm. For single-element straight-beam testing, the hole diameter is chosen according to the quality grade specified in 5.3.11.

At least 3 flat-bottom holes of different depths shall be machined in the reference block; the distance from the bottom of the first hole to the test surface shall not be greater than 10 mm, and that of the last hole shall be within the nominal wall thickness T +/-15 mm.

For forgings thicker than 3 near-field lengths and with parallel surfaces, a large flat back surface of the forging may also serve as the reference for straight-beam testing.

5.3.6.2 The reflectors for angle-beam testing are notches or side-drilled holes parallel to the block test surface, machined across the width of the reference block; the block thickness shall not be less than the workpiece thickness.

For forgings with nominal thickness t not greater than 100 mm, at least two longitudinal notches shall be machined, one on the test surface and one on the bottom surface, with dimensions as in Table 10.

For forgings with nominal thickness t greater than 100 mm, at least 3 side-drilled holes of 2 mm diameter (generally through holes) shall be drilled at different depths through the block thickness, so that a DAC covering the forging thickness can be drawn.

Table 10 notch dimensions, nominal thickness t not greater than 20 mm: notch length at least 50 mm, width not greater than 1 mm, depth 0.1 +/-0.02 mm.

Table 10 notch dimensions, nominal thickness t greater than 20 mm and up to 50 mm: notch length at least 50 mm, width not greater than 1 mm, depth 1.0 +/-0.1 mm.

Table 10 notch dimensions, nominal thickness t greater than 50 mm and up to 100 mm: notch length at least 50 mm, width not greater than 1 mm, depth 1.5 +/-0.1 mm.

5.3.6.3 For stainless steel forgings, the grain size of the reference block shall be comparable to that of the forging. For forgings with marked variations in grain size and structure, a series of reference blocks of different grain sizes should be made, and the block whose grain size is closest to the region near the indication used for evaluation.

5.3.7.1 The reference sensitivity for straight-beam testing may be set by one of: a) the DAC method with flat-bottom holes as reference reflectors; b) the back-wall calculation method, when the thickness exceeds 3 near-field lengths and the test and back surfaces are parallel in the setting region; c) the DGS method.

The scanning sensitivity shall ensure detection of the smallest equivalent flaw size required by the recording level of the specified quality grade.

5.3.7.2 For angle-beam testing, the DAC drawn from the reference reflectors specified in 5.3.6.2 is used as the reference sensitivity; the scanning sensitivity shall be at least 6 dB higher than the reference sensitivity.

5.3.8 All forgings shall be tested over 100% of their volume; scanning modes for the different classes are given in Table 11.

For class Ia forgings, straight-beam probes shall be used radially from the circumferential surface and axially from the end faces. If axial straight-beam testing cannot penetrate the whole length, testing may be done from both end faces, each covering at least 60% of the forging length; where axial straight-beam testing is impossible, axial angle-beam testing may replace it.

For class III forgings, when circumferential shear wave angle-beam scanning is performed on the outer cylindrical surface, the effective depth is limited by the probe angle and forging diameter; see Annex F.

During scanning, adjacent passes shall overlap by at least 20% of the crystal dimension perpendicular to the scanning direction. For manual scanning, the probe speed shall not be greater than 100 mm/s.

Table 11, class Ia: straight-beam testing with 100% scanning around the circumferential surface and on both end faces; if end face testing is impossible, axial angle-beam testing may replace straight-beam testing from the end faces.

Table 11, class Ib: straight-beam testing with 100% scanning on at least two mutually perpendicular surfaces.

Table 11, class II: straight-beam testing with 100% scanning, generally on one end face and on the circumferential surface of the forging.

Table 11, class IIIa: straight-beam testing with 100% scanning around the outer cylindrical surface; angle-beam testing with 100% scanning on the outer cylindrical surface in both circumferential and axial directions, each in two opposite directions 180 degrees apart.

Table 11, class IIIb: straight-beam testing with 100% scanning around the outer cylindrical surface and on one end face; angle-beam testing with 100% scanning on the outer cylindrical surface in two opposite circumferential directions 180 degrees apart.

Table 11, class IV: the testing zone shall comply with the relevant product design documents or procurement technical documents.

5.3.9 The following indications shall be recorded: a) for single-element straight-beam testing, indications recorded according to the quality grade requirements of 5.3.11, with size characterized by the equivalent flat-bottom hole diameter; b) for dual-element straight-beam testing, indications with amplitude exceeding 100% DAC, recording position and amplitude.

c) For angle-beam testing, indications with amplitude exceeding 50% DAC, recording position, amplitude and indicated length, with length measured by the -6 dB method; d) for a recordable indication found from one test surface, supplementary testing shall be done where feasible from the opposite or other surfaces, and evaluation based on the most severe result.

If the ultrasonic testing result is doubtful, other testing methods may be applied and evaluation made on their results.

5.3.10.1.1 Class I echodynamic pattern: as the probe moves, a single clear sharp echo appears on the A-scan display; when scanning forward, backward, left and right its amplitude rises smoothly from zero to a maximum and then falls smoothly to zero, as in Figure 6 a).

Figure 6 b) is a beam profile echodynamic pattern drawn with a side-drilled hole, corresponding to a flaw smaller than the -6 dB beam profile of the probe at the flaw position.

5.3.10.1.2 Class II echodynamic pattern: at each probe position a sharp echo is displayed; when scanning forward, backward, left and right the amplitude first rises smoothly from zero to a peak, stays essentially constant or varies within +/-4 dB as the probe continues, and finally falls smoothly to zero, as in Figure 7.

Figure 7 represents a flaw larger than the -6 dB beam profile of the probe at the flaw position.

5.3.10.2 Where feasible, indications shall be classified from echodynamic patterns obtained by scanning in at least two mutually perpendicular directions.

Point indication: an indication with class I echodynamic characteristics and/or a diameter equal to or smaller than the -6 dB beam width [Figure 8 a)]. Elongated indication: an indication with class II echodynamic characteristics and/or a diameter larger than the -6 dB beam width [Figure 8 b)].

Isolated indication: adjacent point indications separated by a distance d greater than 40 mm [Figure 8 c)]. Clustered indication: adjacent point indications separated by a distance d not greater than 40 mm [Figure 8 d)].

Key to Figure 8: 1 is the -6 dB contour line; Dp is the beam width in the cross-section at the same depth as the flaw; D is the distance between two indications; L is the discontinuity length measured by the -6 dB method.

5.3.11 Tables 12 and 13 specify four quality grades for straight-beam testing of carbon steel and alloy steel forgings and of stainless steel forgings respectively.

Table 12 (carbon, alloy and martensitic stainless steel forgings), grade I: recording level equivalent flat-bottom hole diameter 2 mm or more, BG/BF 4 dB or more; acceptance limits single point discontinuity not greater than 3 mm, elongated or clustered point discontinuities not greater than 2 mm, BG/BF not greater than 26 dB.

Table 12, grade II: recording level equivalent flat-bottom hole diameter 3 mm or more, BG/BF 6 dB or more; acceptance limits single point discontinuity not greater than 5 mm, elongated or clustered not greater than 3 mm, BG/BF not greater than 26 dB.

Table 12, grade III: recording level equivalent flat-bottom hole diameter 5 mm or more, BG/BF 10 dB or more; acceptance limits single point discontinuity not greater than 8 mm, elongated or clustered not greater than 5 mm, BG/BF not greater than 26 dB.

Table 12, grade IV: recording level equivalent flat-bottom hole diameter 8 mm or more, BG/BF 20 dB or more; acceptance limits single point discontinuity not greater than 11 mm, elongated or clustered not greater than 8 mm, BG/BF not greater than 26 dB.

Table 13 (austenitic stainless steel forgings), nominal thickness t less than 75 mm: recording limits and acceptance criteria per quality grade II of Table 12.

Table 13, nominal thickness t from 75 mm to less than 250 mm: quality grade III of Table 12; recording level for BG/BF not less than 18 dB, with no acceptance limit.

Table 13, nominal thickness t of 250 mm or more: quality grade IV of Table 12; recording level for BG/BF not less than 18 dB, with no acceptance limit.

5.4 Ultrasonic testing method for bars

5.4.1 This clause applies to ultrasonic testing and quality grading of forged or rolled bars of carbon steel, low alloy steel, austenitic stainless steel, martensitic stainless steel, precipitation-hardening stainless steel, nickel-base alloys and cobalt-base alloys with diameters from 12 mm to 250 mm.