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1、BRITISH STANDARD BS 6208:1990 Method for Ultrasonic testing of ferritic steel castings including quality levels UDC 669.1514194.57:620.179.16 BS 6208:1990 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authori
2、ty of the Board of BSI and comes into effect on 30 April 1990 BSI 01-1999 First published February 1982 Second edition April 1990 The following BSI references relate to the work on this standard: Committee reference ISM/6 Draft for comment 88/42795 DC ISBN 0 580 17994 X Committees responsible for th
3、is British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/6, upon which the following bodies were represented: Associated Offices Technical Committee BEAMA Ltd. British Gas plc British Railways Board
4、 British Steel Industry British Valve and Actuator Manufacturers Association Electricity Supply Industry in England and Wales Engineering Equipment and Materials Users Association Institute of British Foundrymen Institution of Mechanical Engineers Lloyds Register of Shipping Ministry of Defence Proc
5、ess Plant Association Steel Casting Research and Trade Association Coopted member Amendments issued since publication Amd. No.Date of issueComments BS 6208:1990 BSI 01-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Information to be supplied by the pur
6、chaser1 4Zones of casting1 5Quality levels2 6Operator qualification3 7Equipment3 8Inspection procedure4 9Records of inspection5 Appendix A Options6 Figure 1 Division of casting wall into zones2 Table 1 Planar discontinuities: quality levels2 Table 2 Non-planar discontinuities: quality levels2 Table
7、3 Requirements for probe and flaw detector resolution3 Table 4 Minimum number of echoes to be obtained when checking sensitivity of equipment3 Table 5 Probe size and frequency for longitudinal wave probes3 Table 6 Probe size and frequency for transverse wave probes3 Publications referred toInside ba
8、ck cover BS 6208:1990 ii BSI 01-1999 Foreword This British Standard has been prepared under the direction of the Iron and Steel Standards Policy Committee and is a revision of BS 6208:1982, which is withdrawn. The scope has been widened to include castings of 15 mm to 30 mm thickness. A range of qua
9、lity levels has been provided, from which a choice may be made by the purchaser when referred to in product standards for steel castings. This range is not necessarily exhaustive but is believed to cover most normal requirements for steel castings intended for general engineering and pressure purpos
10、es. Attention is drawn to the indicated dimensions of defects for different quality levels. These can not be regarded as absolute sizes in any assessment of the serviceability of a casting. For small planar discontinuities in particular, the techniques may underestimate the absolute dimensions. No f
11、ormal qualifications have been specified for operators but those provided by a number of appropriate technical teaching and other establishments are recognized by industry and may be specified by the purchaser. This standard does not contain detailed descriptions of techniques. It has been assumed i
12、n the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct applica
13、tion. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date)
14、and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. BS 6208:1990 BSI 01-19991 1 Scope This British Standard describes a method for the ultrasonic testing of ferritic steel castings of as-cast section thicknesses of 15 mm and greater. Thi
15、s standard also gives the quality levels for internal discontinuities in the castings, as detected by the ultrasonic test method described. The method is not applicable to austenitic steel castings. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover.
16、2 Definitions For the purposes of this British Standard, the definitions given in BS 3683-4 apply together with the following. 2.1 discontinuity an imperfection as indicated by ultrasonic parameters 2.2 flat-bottomed hole a hole drilled from the underside of a calibration block to provide a referenc
17、e plane artificial reflector of known diameter at a known depth from the surface to which the probe is applied 2.3 planar discontinuity a discontinuity having two dimensions as determined by the techniques described in this standard 2.4 non-planar discontinuity a discontinuity having three dimension
18、s as determined by the techniques described in this standard 2.5 reference discontinuity echo size the smallest ultrasonic indication, usually expressed as an equivalent flat-bottomed hole diameter, specified as recordable during the assessment phase of an ultrasonic examination 2.6 sensitivity of t
19、he equipment a measure of the capability of the ultrasonic system to detect the sound energy from a specified reflector 3 Information to be supplied by the purchaser 3.1 General The following information shall be supplied at the time of the enquiry and order: a) the number and date of this British S
20、tandard, i.e. BS 6208:1990; b) the areas of the castings and number or percentage to which the ultrasonic testing requirements apply; c) the acceptance categories to be applied to the various zones or areas of the casting; d) the qualification or method of approval required for the ultrasonic testin
21、g personnel; e) any critical areas defined as a distance from a casting surface marked on the casting drawing; f) whether a written ultrasonic procedure is required from the founder. 3.2 Options If the purchaser does not specify his requirement to implement any of the options specified in Appendix A
22、 at the time of the enquiry and order, the manufacturer shall test in accordance with the basic specification. 4 Zones of casting 4.1 Wall thicknesses of 15 mm up to and including 30 mm The full thickness of the casting wall shall be one zone and shall be designated “the outer zone”. 4.2 Wall thickn
23、ess greater than 30 mm The wall thickness shall be divided into zones as shown in Figure 1. The outer zones shall be the positions of the casting that extend to the lesser of the following: a) a depth of 30 mm; b) one-third of the casting section thickness, at the time of dispatch. The mid zone of t
24、he casting shall be the central section located between the two outer zones. (For finished machined dimensions see option A.1. See also option A.2.) NOTEThe demarcation between mid and outer zones cannot always be interpreted exactly if castings are of complex configuration. BS 6208:1990 2 BSI 01-19
25、99 5 Quality levels The limits for quality levels for planar discontinuities shall be as given in Table 1 and the limits for quality levels for non-planar discontinuities shall be as given in Table 2. Weld repairs shall be inspected and assessed for acceptability in accordance with the quality level
26、s applying to the area and zone of the casting in which the weld repair is located (see options A.3 and A.4). Table 1 Planar discontinuities: quality levels Table 2 Non-planar discontinuities: quality levels Figure 1 Division of casting wall into zones Limits of indicated dimensions of discontinuity
27、 in a frame 317 mm 317 mm (100 000 mm2) Quality level 1 (see note 1)234 Maximum indicated through-wall length of a single defect (mm) 05811 Maximum indicated area of single discontinuity (mm2) (see note 2) 075200360 Maximum total indicated area of discontinuities (mm2) 0150400700 NOTE 1Quality level
28、 1 specifies complete freedom from any ultrasonic indication displaying planar characteristics. NOTE 2The area of a single discontinuity is defined as the product of the maximum through-wall length and the maximum indicated dimension. ZoneLimits of indicated dimensions of discontinuity in a frame 31
29、7 mm 317 mm (100 000 mm2) (see note 1) Quality level 1 234 Outer Maximum indicated discontinuity size (% of zone thickness)20.020.020.020.0 Maximum individual indicated discontinuity area (mm2) 2501 0002 0004 000 Maximum indicated total area of discontinuities (mm2) 5 00010 000 20 000 40 000 MidMaxi
30、mum indicated discontinuity size (% of section thickness)10.010.015.015.0 Maximum indicated total area of discontinuities (mm2) (see note 2) 12 500 20 000 31 000 50 000 NOTE 1The limits apply when the frame is placed in the most unfavourable position. NOTE 2The maximum indicated dimension of a singl
31、e discontinuity is 320 mm. The area of a single discontinuity is defined as the product of the maximum through-wall length and the maximum indicated dimension. NOTE 3Indications less than 25 mm apart are considered as one discontinuity. BS 6208:1990 BSI 01-19993 6 Operator qualification The operator
32、 shall be technically qualified to carry out the ultrasonic operations described in clauses 7 and 8 see 3.1 d). 7 Equipment 7.1 Flaw detector The equipment shall have an A-scope presentation and be capable of operating over a frequency range of at least 1 MHz to 5 MHz and shall be fitted with a gain
33、 control calibrated in steps of 2 dB or less. The equipment shall be calibrated using the procedure described in BS 4331-1 and using reference blocks complying with BS 2704. 7.2 Linearity of equipment gain The linearity of the equipment gain shall be checked by the method described in BS 4331-1. The
34、 amplification shall be linear within 2 dB within the usable sensitivity range. 7.3 Linearity of time base The time base shall be calibrated by the method described in BS 4331-1 and shall be linear; any deviation shall not exceed 2 % of the full scale graticule reading. 7.4 Pulse duration A check sh
35、all be made of the ability of the equipment to resolve small signals by measuring pulse duration by the method described in BS 4331-1. The resolution of probe/flaw detector shall be acceptable if the values given in Table 3 are not exceeded. Table 3 Requirements for probe and flaw detector resolutio
36、n 7.5 Sensitivity The sensitivity of the equipment shall be checked by the method described in BS 4331-1 and using the A2 block described in BS 2704. The sensitivity shall be such that the number of echoes visible on the screen when the first echo is at full screen height is not less than the number
37、 given in Table 4 for the appropriate frequency range. Table 4 Minimum number of echoes to be obtained when checking sensitivity of equipment 7.6 Probes One or more of the following probes shall be used as appropriate to the thickness of the cast section under examination: a) longitudinal wave probe
38、s (single and combined) for volumetric flaws; b) transverse wave probes (single and combined double) for planar flaws. NOTERecommended angles of refraction are 45, 60 and 70, but other angles may be applied depending on particular circumstances. Table 5 Probe size and frequency for longitudinal wave
39、 probes Table 6 Probe size and frequency transverse wave probes 7.7 Couplants A couplant shall be selected and used to ensure efficient transmission of ultrasonic energy between the probe and the material under inspection. NOTESuitable couplants include cellulose paste, light or medium oils and grea
40、ses and, in some circumstances, water. For the calibration of the equipment and for all subsequent examinations, attention shall be paid to the preservation of the casting surfaces to which the couplant is applied. Probe frequency Longitudinal wave probes Transverse wave probes 10 mm diameter 24 mm
41、diameter MHzmmmmmm 2 3 15 30 100252 NOTEFor subsurface investigations combined double probes or short pulse length single probes may be advantageous. Examined thickness Probe size (major dimension) Frequency mmmmMHz 0 30 10015 to 252 BS 6208:1990 4 BSI 01-1999 8 Inspection procedure 8.1 Point of ins
42、pection All areas of the castings and the proportion of the castings in the batch indicated on the enquiry and restated in the order shall be tested. Inspection shall be carried out after the final heat treatment as specified in BS 3100 or BS 1504. Where weld repairs have been carried out, these are
43、as shall be reinspected before delivery. (See options A.5 and A.6.) NOTEIt is recommended that, unless stress-relieving is carried out, the reinspection should be at least 48 h after completion of welding. 8.2 Assessment of suitability for ultrasonic examination 8.2.1 Surface condition. The casting
44、shall be examined visually to ensure that the surfaces from which ultrasonic examinations are to be carried out are uniformly suitable for such examination. The surface condition of the castings shall be such that the specified techniques can be applied to all specified areas of the casting and at a
45、n adequate sensitivity for application of the specified limits of acceptance. Any inadequate surface condition shall be rectified by additional fettling and/or grinding, or by machining. Cast surfaces shall not be fettled by hammering or peening. 8.2.2 Attenuation. An assessment of attenuation as fo
46、llows shall be carried out on selected areas of the casting representative of the surface finish throughout the total thickness range and having parallel surfaces. a) Set first back-wall echo to half screen height. b) Record attenuator reading in decibels. c) Set second back-wall echo to half screen
47、 height. d) Record attenuator reading in decibels. e) Calculate the attenuation as the difference between readings for b) and d). The casting is suitable for testing when the attenuation to ultrasound of the steel is equal to or less than 15 dB. It shall also be established that the signal height fr
48、om a 3 mm flat-bottomed hole at the back-wall distance is at least 6 dB higher than grass level. When attenuation is greater than 15 dB or the flat-bottomed hole signal height can not be achieved, the casting shall be reheat treated in accordance with the material specification. NOTEA test block of
49、similar material, heat treatment condition and section thickness containing a 3 mm flat-bottomed hole may be used providing the sensitivity is adjusted to compensate for any difference in attenuation between the test block material and the casting. 8.3 Preliminary scanning A preliminary scanning procedure shall be used to identify and locate both planar and non-planar discontinuities for subsequent diagnosis and assessment. A probe shall be selected as appropriate for the defect size and the section of the casting (see option A.7). The s
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