Ministry of Defence Defence Standard Requirements for Nickel Aluminium Bronze Castings and Ingots. Part 1

Transcription

1 Ministry of Defence Defence Standard Issue 3 Publication Date 21 August 2012 Requirements for Nickel Aluminium Bronze Castings and Ingots Part 1 Nickel Aluminium Bronze Naval Alloy Centrifugally Cast Category 2

2 Contents Foreword...iv 0 Introduction...vii 1 Scope Warning Normative References Definitions Abbreviations Chemical Specification Ingots Castings Heat Treatment Mechanical Property Requirements NonDestructive Examination Examination Procedure Dimensional Check Visual Optical Liquid Penetrant Radiographic/Ultrasonic Examination Radiography Radiographic Examination of Non Designated Regions on a Sample Basis Ultrasonic Examination Pressure Tests Rectification of Defects Defects Rectification of Dimensional Defects by Weld Deposition Rectification of Surface Defects by Blending Rectification of Surface and Sub Surface Defects by Welding Limits on Combined Weld Repairs Impregnation Special Repairs Quality Assurance Identification of Ingots Identification of Castings Quality Assurance Documentation Packaging...10 ii

3 Annex A Procurement Checklist...11 Tables Table 1 Chemical Composition of Ingots...4 Table 2 Chemical Composition of Castings...5 Table 3 Mechanical Properties...6 iii

4 Foreword AMENDMENT RECORD Amd No Date Text Affected Signature and Date REVISION NOTE This Defence Standard (Def Stan) is raised to Issue 3 to update its content. HISTORICAL RECORD This standard supersedes the following: Def Stan Part 1 Issue 2 19 January 2007 Def Stan Part 1 Issue 1 01 April NES 747 Part 1 Issue 3 August NES 747 Part 1 Issue 2 November NES 747 Part 1 Issue 1 January Sponsorship 1. This Defence Standard (Def Stan) is sponsored by the Defence Equipment and Support, Naval Authority Group, Material Technology (DES NAGMT), Ministry of Defence (MOD). 2. The complete Def Stan Issue comprises: Requirements for Nickel Aluminium Bronze Castings and Ingots Part 1 Part 2 Part 3 Part 4 Nickel Aluminium Bronze Naval Alloy Centrifugally Cast Nickel Aluminium Bronze Naval Alloy Ingots and Sand Castings with Welding Permitted to the Wetted Surface Nickel Aluminium Bronze Commercial Alloy Ingots and Sand Castings Nickel Aluminium Bronze Naval Alloy Sand Castings with Welding Permitted to the Nonwetted Surface (Class I and II Castings only) NOTE (Design and Manufacture of Nickel Aluminium Bronze Sand Castings (previously Part 5) now converted to a MAP, MAP 01102, available via DESNAG) 3. If it is found to be unsuitable for any particular requirement the MOD is to be informed in writing of the circumstances. iv

5 4. Any user of this Defence Standard either within MOD or in industry may propose an amendment to it. Proposals for amendments that are not directly applicable to a particular contract are to be made to the publishing authority identified on rear cover, and those directly applicable to a particular contract are to be dealt with using contract procedures. 5. No alteration is to be made to this Defence Standard except by the issue of an authorised amendment. 6. Unless otherwise stated, reference in this Defence Standard to approval, approved, authorised or similar terms, means the Ministry of Defence in writing. 7. Any significant amendments that may be made to this Defence Standard at a later date will be indicated by a vertical sideline. Deletions will be indicated by 000 appearing at the end of the line interval. 8. Extracts from British Standards within this Defence Standard have been included with the permission of the British Standards Institution. Conditions of Release General 9. This Defence Standard has been devised solely for the use of the MOD, and its contractors in the execution of contracts for the MOD. To the extent permitted by law, the Crown hereby excludes all liability whatsoever and howsoever arising (including but without limitation, liability resulting from negligence) for any loss or damage however caused when the Defence Standard is used for any other purpose. 10. This document is Crown Copyright and the information herein may be subject to Crown or third party rights. It is not to be released, reproduced or published without written permission of the MOD. 11. The Crown reserves the right to amend or modify the contents of this Defence Standard without consulting or informing any holder. MOD Tender or Contract Process 12. This Defence Standard is the property of the Crown. Unless otherwise authorised in writing by the MOD must be returned on completion of the contract or submission of the tender in connection with which it is issued. 13. When this Defence Standard is used in connection with a MOD tender or contract, the user is to ensure that he is in possession of the appropriate version of each document, including related documents, relevant to each particular tender or contract. Enquiries in this connection may be made of the Authority named in the tender or contract. 14. When Defence Standards are incorporated into contracts, users are responsible for their correct application and for complying with contractual and other statutory requirements. Compliance with a Defence Standard does not of itself confer immunity from legal obligations. v

6 Categories of Naval Defence Standard 15. The Category of this Naval Defence Standard has been determined using the following criteria: a) Category 1. If not applied may have a Critical affect on the following: Safety of the vessel, its complement or third parties. Operational performance of the vessel, its systems or equipment. b) Category 2. If not applied may have a Significant affect on the following: Safety of the vessel, its complement or third parties. Operational performance of the vessel, its systems or equipment. Through life costs and support. c) Category 3. If not applied may have a Minor affect on the following: MOD best practice and fleet commonality. Corporate experience and knowledge. Current support practice. Related Documents 16. In the tender and procurement processes the related documents in clause 3 can be obtained as follows: a) British Standards British Standards Institution, 389 Chiswick High Road, London, W4 4AL b) Defence Standards Defence Equipment and Support UK Defence Standardization, Kentigern House 65 Brown Street, Glasgow, G2 8EX c) Other documents Tender or Contract Sponsor to advise. 17. All applications to Ministry Establishments for related documents are to quote the relevant MOD Invitation to Tender or Contract Number and date, together with the sponsoring Directorate and the Tender or Contract Sponsor. 18. Prime Contractors are responsible for supplying their subcontractors with relevant documentation, including specifications, standards and drawings. Health and Safety Warning 19. This Defence Standard may call for the use of processes, substances and procedures that may be injurious to health if adequate precautions are not taken. It refers only too technical suitability and in no way absolves either the supplier or any user from statutory obligations relating to health and safety at any stage of manufacture or use. Where attention is drawn to hazards, those quoted may not necessarily be exhaustive. 20. This Defence Standard has been written and is to be used taking into account the policy stipulated in JSP430: MOD Ship Safety Management System Handbook. Additional Information (There is no relevant information) vi

7 0 Introduction 0.1 Historical Perspective a) In the 1960s shock tests on gunmetal hull valves showed failures. Nickel aluminium bronze (NAB) was selected as a replacement alloy for submarine hull valves and all first level systems. b) Conventional sand cast NAB was initially produced to early issues of DGS 8520 (Specification for copperbase alloy ingots and castings) until DGS 8520F (High tensile aluminium bronze ingots and castings) was introduced as a higher strength variant with tighter compositional limits (known as Naval alloy) in January DGS 348 (Nickel aluminium bronze ingots and castings) was introduced in 1975, this specification being for the Naval alloy variant incorporating a specific heat treatment to modify the microstructure to improve corrosion performance. c) It was in January 1983 that the first specification for NAB centrifugal castings and ingots was issued within the Naval Engineering Standards Series as NES 747 Part 1. The conventional sand cast NAB alloys were subsequently added as NES 747 Parts 2 and 3. Later NES 747 Part 4 was added for components with welding restrictions on wetted faces to prevent heat affected zone corrosion. NES 747 Part 5, a sand casting design and manufacturing guide, was also added. d) Thus NES 747 was comprised of: Part 1 Naval alloy (centrifugal cast) Part 2 Naval alloy (sand cast) from DGS 348 Part 3 Part 4 Part 5 Commercial alloy (sand cast) from BS 1400 AB2 Naval alloy (sand cast) welding restrictions Design and manufacturing guide for sand casting (now withdrawn, available as MAP 01102) e) NES 747 Part 1 was reserved for Naval alloy castings and ingots manufactured using a centrifugal casting technique. In this process the casting and mould are rapidly spun during pouring and solidification to ensure complete filling of the mould and the removal of porosity. Components are typically spun at high speeds to generate forces up to 60 times gravity. Any oxidised material is of lower density and accumulates in the central bore region which is removed in subsequent machining operations. This technique had been found to produce sound castings of high integrity that should not require weld repair of casting defects. The process is well suited to components having essentially a simple cylindrical geometry. f) The corrosion performance of components made in NES 747 Part 1 material has been reported to be better than material manufactured by conventional sand casting techniques. This better performance has been attributed to the formation of a preferential microstructure during the centrifugal casting process. However, there is no firm evidence to confirm this assumption. Other factors, such as flow and system application, may account for this view. Recent destructive examinations of exservice components have shown a wide range of corrosion depth measurements. These studies have actually indicated similar corrosion performance for centrifugally cast and sand cast NAB components. g) The perceived better corrosion performance, together with it being reported that centrifugally cast components are of high integrity and do not require weld repair, resulted in the absence of a mandatory heat treatment for centrifugally cast NAB castings manufactured to NES 747 Part 1. This has been maintained in this latest issue due the lack of evidence of any beneficial effect on corrosion performance and no welding being permitted on Class I and II castings. vii

8 h) There have been three issues of NES 747 Part 1. The changes in Issue 2 were only minor text amendments and an update of Sea Systems nomenclature. No significant technical modifications were made. The changes in Issue 3 included a title change and modification to the nondestructive test requirements, acceptance standards and rectification text. i) The NES 747 documents for all NAB alloys were transferred to the Defence Standard Series in 2000 as Def Stan Apart from minor reformatting, there were no technical amendments between the last issue of the NES 747 Parts and the first issue of the Def Stan Parts. j) Def Stan Part 1 Issue 2 clarified some of the areas of confusion, together with addressing technical issues raised by interested parties, users and commercial suppliers. The final composition and minimum mechanical properties were also amended for centrifugal cast material. It also emphasised that weld repair of Class I and II castings was not permitted. The centrifugal casting technique, if implemented correctly, should produce high integrity castings which do not require rectification of defects by welding. Whilst it is considered unlikely that Class III castings would specify the use of centrifugal cast material to this standard, weld repair requirements have been retained in the document for this class of casting. viii

9 0.2 TECHNICAL NOTE a) In conventionally cast NAB material it has been noted that the mechanical properties listed in the standards documents relate only to the requirements placed on material from test bars for the purposes of ensuring compliance with the standard. They do not relate directly to the expected mechanical properties of actual components. All design calculations should take into account that actual components, particularly those with a large section thickness, are likely to exhibit properties that are somewhat lower than those listed for test pieces in the specification. A test program examining the mechanical properties of actual NAB conventionally cast components has revealed that a proof stress of 220 MPa is a more realistic estimate for large castings manufactured to NES 747 Parts 2&4 (DERA Report DERA/MSS/MSMA1/CR003200). It should also be noted that BS1400 calls for a factor of 1.4 to be used when determining the minimum expected proof stress of copper alloy sand castings in relation to typical test bar results. In the case of conventionally cast NAB this would relate to a value of 180 MPa. b) In this standard for centrifugally cast castings, the mechanical test specimens used to confirm the acceptance of the centrifugally cast material are preferably machined from material integral to the actual casting, although it is sometimes necessary for these specimens to be taken from a separate casting made from the same melt. The actual size, location and directionality of the test pieces are to be agreed between the Design Authority and the founder. There may be a significant variation in mechanical properties across the cast blank. The material towards the outer surface of the casting is likely to have higher tensile properties than material towards the original inner surface of the cast blank. The property variation within a finished casting will depend on the amount of material removed, especially from the inner surface of the cast blank. When the mechanical properties are determined on test specimens from integral cast material these are more likely to represent those of the actual component, but their position within the casting needs to be considered. When the mechanical properties are determined on a separately cast test piece, even if they comply with the values given in Table 3, the mechanical properties of the actual casting may be below these values. This should be considered when structural design and performance is being addressed. c) It should be noted that copper nickel chromium alloy is generally more corrosion resistant than nickel aluminium bronze alloys due to it s single phase composition and due consideration should be given to this effect during the material selection. However, it is not possible to centrifugally cast copper nickel chromium alloy due to it s affinity to oxygen and the formation of oxides. ix

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11 Requirements for Nickel Aluminium Bronze Castings and Ingots Part 1 Nickel Aluminium Bronze Naval Alloy Centrifugally Cast 1 Scope 1.1 This standard provides requirements for the physical characteristics, test methods and acceptance standards of centrifugally cast nickel aluminium bronze naval alloy from ingots and approved scrap. 1.2 Castings are classified as either I, II, or III. These classifications are defined in Def Stan Warning The Ministry of Defence (MOD), like its contractors, is subject to both United Kingdom and European laws regarding Health and Safety at Work. Many Defence Standards set out processes and procedures that could be injurious to health if adequate precautions are not taken. Adherence to those processes and procedures in no way absolves users from complying with legal requirements relating to Health and Safety at Work. 3 Normative References 3.1 The publications shown below are referred to in the text of this standard. Publications are grouped and listed in alphanumeric order. BS 375:1993 BS EN 1976 BS EN 1978 BS EN 1982 BS EN ISO BS EN Def Stan 031 Def Stan Def Stan Def Stan Specification for Refined Nickel (Withdrawn) Copper and Copper Alloys, Cast Unwrought Copper Products Copper and Copper Alloys, Copper Cathodes Copper and Copper Alloys Ingots and Castings Metallic Materials Tensile Testing Part 1 Method of Test at Ambient Temperature Founding Ultrasonic Examination Part 1 Steel Castings for General Purposes Impregnation of Porous Castings Requirements for Non Destructive Examination Methods: Part 1 Radiographic. Part 4 Liquid Penetrant. Part 5 Ultrasonic. Requirements for the Classification, Dimensions, Tolerances, Weld Repair and General Standards of Acceptance for copper and Nickel Alloy Castings Requirements for the Classification, Dimensions, Tolerances and General Standards of Acceptance for Copper and Nickel Alloy Castings 1

12 Def Stan JSP 430 Procedures for First Level Nickel Aluminium Bronze Castings, Part 2 Validation MOD Ship Safety Management System Handbook 3.2 Reference in this Standard to any normative references means, in any Invitation to Tender or contract, the edition and all amendments current at the date of such tender or contract unless a specific edition is indicated. 3.3 In consideration of clause 3.2 above, users shall be fully aware of the issue and amendment status of all normative references, particularly when forming part of an Invitation to Tender or contract. Responsibility for the correct application of standards rests with users. 3.4 DStan can advise regarding where normative references documents are obtained from. Requests for such information can be made to the DStan Helpdesk. How to contact the helpdesk is shown on the outside rear cover of Def Stans. 4 Definitions 4.1 Acceptance Authority Either the MOD department/project Team or prime contractor specified in the contract as being responsible for design. 4.2 Approved Scrap Scrap that is derived from nickel aluminium bronze, the composition of which has been established with regard to the complete range of both the alloying elements and impurity elements and is segregated and identifiable to the satisfaction of the Acceptance Authority. 4.3 Cast The product of one furnace or crucible melt, or the product of a number of furnace or crucible melts where such are aggregated and mixed prior to sampling. 4.4 Centrifugal Castings A casting method involving the pouring of molten metal into a rotating cylindrical metal mould. The speed of rotation of the mould must be calculated to allow the effects of centrifugal acceleration to force nonmetallics, such as slag/oxides to the bore of the casting, where they can be removed by machining during the proof machining operations carried out to create the finished product. The mould must be of sufficient wall thickness to promote and cause directional solidification from the outside diameter to the inside diameter of the casting. 4.5 Contractor The Firm, Company, Organisation, or Establishment working within the scope of this standard. 4.6 Design Authority The MOD department, IPT or approved contractor specified in the contract as being responsible for design. 4.7 Ingots A mass of metal of proportions to suit the Founder s requirements. 2

13 4.8 Pinpoint Porosity Any circular bleed out of less than 0.5mm diameter revealed during liquid penetrant examination in accordance with Def Stan Part S 0 The cross section area of the gauge in a tensile piece, before testing as detailed in BS EN ISO Abbreviations BS Def Stan DStan HM JSP MOD NAB NES British Standard Defence Standard UK Defence Standardization Her Majesty s Joint Service Publication Ministry of Defence Nickel Aluminium Bronze Naval Engineering Standard 6 Chemical Specification 6.1 Ingots a) Centrifugal casting stock is to be cast from virgin metals of the following grades: Nickel Iron Aluminium Copper Manganese To the chemical composition requirements of BS 375:1993 Grade R99.9. Iron of high purity, 99.5% w/w, with a carbon content of less than 0.05% w/w. Commercially very pure Grade 99.90% w/w. Copper that complies with either BS EN 1976 (designation CuETP) or BS EN 1978 (designation CuCATH2). High purity electrolytic grade. b) A full chemical analysis is required from a sample piece taken from each cast. The analysis is to conform to the chemical composition specified in Table 1. 3

14 Table 1 Chemical Composition of Ingots Element Not Less Than Per Cent By Weight Not More Than Aluminium Iron* Nickel* Manganese Copper (by difference) Impurities Zinc Lead Tin Silicon Magnesium Chromium Remainder Total Impurities 0.20 * Nickel content is to be greater than iron content 6.2 Castings a) Only the manufacturer s own approved scrap as defined in Clause 4.2 may be included in the cast. No other scrap is permitted. Following acceptance of the analysis from the melt, no further additions are permitted prior to pouring into the mould. b) All ingots used are to be of known quality in accordance with Clause c) A full chemical analysis is required from a sample piece taken from each cast. The analysis is to conform to the chemical composition specified in Table 2. 4

15 Table 2 Chemical Composition of Castings Element Aluminium Iron* Nickel* Manganese Copper (by difference) Per Cent By Weight Not Less Than Not More Than Remainder Impurities Zinc Lead Tin Silicon Magnesium Chromium Total Impurities 0.25 * Nickel content is to be greater than iron content 7 Heat Treatment All castings are to be supplied in the ascast condition. No subsequent heat treatment is to be used. 8 Mechanical Property Requirements a) Tensile tests in accordance with BS EN ISO are to be carried out on suitable and representative cast material test pieces. The machined tensile test specimens should be proportional test pieces, as described in BS EN ISO with an effective diameter of 10mm or greater. It is advised that three tensile test specimens are made to enable retests in the event of failure of the initial test specimen. b) The size, location and directionality of the test pieces are to be agreed between the Design Authority and the founder (see Note below). These test pieces should be prepared from an integral part of the actual casting whenever possible. This might be, for example, from material adjacent to a flange or removed from the wall of the casting where a hole is to be subsequently machined. Where the casting is of such a configuration that test pieces cannot be accommodated as an integral part of the casting, a separately centrifugally cast test piece shall be cast in moulds comparable, particularly in type and orientation, to the moulds for the actual casting(s), and from the same melt as the casting(s) it represents. This test piece is then to be used for the production of the tensile test specimens. The tensile test result is to conform to the data given in Table 3 for the relevant test piece location. NOTE There may be a variation in mechanical properties within a casting. The material towards the outer surface of the casting is likely to have higher tensile properties than material towards the original inner surface of the casting blank. This should be considered when agreeing the location of integral test pieces. c) Retests. Should the original test specimen fail to meet acceptance standards, two further specimens from the same cast are to be broken in accordance with BS EN ISO Both tensile test results are to conform to the data given in Table 3 for the relevant test piece location. 5

16 Table 3 Mechanical Properties Test Piece Location Tensile Strength 0.2% Proof Stress Elongation (MPa) (MPa) (Per Cent) From integral part of casting From separately cast test piece NOTE If separately cast test pieces are used, it must be appreciated that the mechanical properties of the actual centrifugal casting may fall below the minima values quoted in the above table. All design calculations must take this into consideration. Please refer to Clause 0.2 for further information. 9 NonDestructive Examination 9.1 Examination Procedure a) Reference diagrams according to Def Stan are to be provided by the purchaser for all Class I and Class II castings to show Critical Test Regions and Test Regions which are to be subjected to non destructive testing. b) The manufacturer is to subject Critical Test Regions and Test Regions to either 100% radiographic or 100% ultrasonic examination. c) For Class III castings only, if subsequent weld repairs are required, the repaired areas are to be further examined, in accordance with Clauses 9.2 to 9.6. The area inspected shall extend 50mm from the weld boundary in all directions. Reexamination of other areas previously examined is not a requirement in this instance. The weld repaired casting must satisfy the requirements of Clause 9.6 if specified. 9.2 Dimensional Check a) All castings are to be fully dimensionally checked. b) Dimensions are to comply with the component drawing, and the requirements of Def Stan Visual Optical a) All castings are to be 100% visually inspected, assisted where necessary, by the use of x5 magnification optics. All imperfections are to be identified and recorded. b) The finished condition of all surfaces is to be clean and free from cracks or linear defects. Rounded forms of surface defects are unacceptable in Critical Test Regions and Test Regions but may be acceptable in Non Designated Regions at the discretion of the Acceptance Authority. NOTE Defects are deemed to be rounded when the aspect ratio of length to width is 3:1 or less. c) The surface finish is to meet the standard specified in the contract documents and drawings. 9.4 Liquid Penetrant a) All Class I and Class II castings are to be subject to 100% liquid penetrant examination in accordance with Def Stan Part 4. It is recommended that examination is carried out before any machining operations are commenced to prevent nugatory work. 6

17 b) A 100% liquid penetrant inspection is to be undertaken on all accessible surfaces of Class I and Class II castings with the surfaces examined in their finished condition. c) Indications of cracks, hot tears or chain like porosity and surface oxide inclusions in linear formations are not acceptable. d) Indications arising from porosity and surface oxide inclusions in non linear formations are to be assessed as follows: i) Isolated pinpoint porosity is acceptable except in areas where sealing of a housing against a running shaft is required, e.g. pump glands, propeller shaft seals etc, and in flexible couplings. ii) Clustered pinpoint porosity and other defects are acceptable provided that: The maximum size of any indication is not to exceed 3mm diameter bleed out, and the sum of the diameters of all indications in an area of 70 x 70mm is not to exceed 24mm. e) The indications identified in Clause 9.4d) are acceptable providing that the immediate area of the casting is acceptable when examined for sub surface defects. f) There may be instances where machined surfaces of castings manufactured to this standard require more stringent acceptance standards than those specified in Clause 9.4d). Where necessary this requirement is to be clearly stated in the contract documents and is to be the subject of discussion between the purchaser and the contractor prior to manufacture of the castings. 9.5 Radiographic/Ultrasonic Examination The manufacturer is to subject Critical Test Regions and Test Regions to either 100% radiographic or 100% ultrasonic examination Radiography Radiography is to be carried out in compliance with Def Stan Part 1. All sub surface imperfections are to be identified for subsequent assessment in accordance with the acceptance standards Radiographic Examination of Non Designated Regions on a Sample Basis a) In certain circumstances examination by radiography on a sample basis may be specified by contract or drawings to establish that a satisfactory general quality of product is being supplied. Typical examples are: 1) Lowly stressed Class II castings. 2) Sample positions on large Class II or Class III castings. 3) Batch supply of Class III castings. b) Acceptance Standards are defined in Def Stan Ultrasonic Examination a) Ultrasonic examination is to be carried out in compliance with Def Stan Part 5. All sub surface imperfections are to be identified for subsequent assessment in accordance with the acceptance standards. Where ultrasonic examination is used the assessment of the casting is to be confirmed by radiography of selected areas. A minimum of 10% of the total area examined by ultrasonics is to be radiographed. NOTE The grain structure of cast nickel aluminium bronze may preclude inspection by ultrasonics. The suitability for ultrasonic inspection is to be assessed in accordance with BS EN

18 b) Any defect that causes a signal greater than or equal to the signal produced by the approved calibration standard is to be deemed unacceptable and the casting repaired or rejected. Where the backwall echo is attenuated by 40% or greater, the examination by ultrasonics is unacceptable and radiography in accordance with Clause is to be employed. 9.6 Pressure Tests When stated in the contract the castings are to be subjected to the specified water pressure test for a minimum period of 15 minutes. Certain castings may require longer periods of pressure testing. When necessary this will be specified in the contract. Each casting is to show no evidence of leakage. 10 Rectification of Defects 10.1 Defects a) Any casting may be rejected for defects discovered during subsequent machining notwithstanding that the casting had been passed previously as conforming to this standard. b) The rectification of any defects (surface, subsurface or dimensional) by welding is not permitted on Class I and II centrifugal castings manufactured in accordance with this standard. Surface defects can be rectified by blending in accordance with Clause c) Weld repair of Class III castings is permitted, provided it is in accordance with Def Stan and is to be within the limits given in Clauses 10.2 and 10.4 below Rectification of Dimensional Defects by Weld Deposition a) For Class III castings only, correction of casting dimensions and machining errors may be made by weld deposition using an approved procedure in accordance with Def Stan for the material concerned, and shall be within the following limits: 1) Weld deposition thickness to be restricted to either: i) 20% of contract drawing section thickness when section thickness is between 12mm and 50mm. ii) A maximum of 10mm when section thickness is above 50mm. 2) Area of weld deposition in non designated regions is to be restricted to 20% of the inner or outer surface area of the region not including flange thickness and webs. b) Weld build up exceeding the tolerance on contract drawing section thickness is to be a reason for rejection Rectification of Surface Defects by Blending a) Unacceptable surface defects in Class I, II and III castings may be excavated by an approved process, providing the resulting depression does not reduce the contract drawing section thickness by more than 5mm for section thickness over 50mm, or 10% of section thicknesses up to and including 50mm. The excavation is to be smooth, and all sharp edges are to be removed. b) The depression sides and ends are to be smoothly blended out by a minimum radius of three times the maximum depth of blending and the edge formed with the surface is also to be faired smooth. The remaining section thickness in way of the depression is to be free from sub surface defects as revealed by radiography or ultrasonics, in Critical Test Regions and Test Regions. The total area subjected to blending, including the area affected by the fairing, is not to exceed 10% of any designated region or 20% of any non designated region. 8

19 c) In some instances extensive blending of surface defect excavations is unnecessary, and where approval is granted from the relevant acceptance authority, an excavation prepared in accordance with Clause 10.3a) may be acceptable without carrying out the operations described in Clause 10.3b). d) Rectification by blending is not permitted where this encroaches on any bearing or sealing surface. NOTE For Class III castings only, blending out of surface defects is preferable to weld repair whenever possible. (For Class I and II castings, blending is the only permitted rectification method permitted.) 10.4 Rectification of Surface and Sub Surface Defects by Welding For Class III castings only, unacceptable surface defects which cannot be blended out within the limitations of Clause 10.3 and unacceptable sub surface defects may be repaired by welding using an approved procedure for the material concerned in accordance with Def Stan In such cases, the area of excavation in non designated regions is to be restricted to 20% of the inner or outer surface area of the region, not including flange thicknesses and webs Limits on Combined Weld Repairs For Class III castings only, the total combined area of weld repairs from all causes, eg dimensional correction, surface and sub surface defects is not to exceed 20% of the surface area of the casting excluding flange thicknesses and webs Impregnation a) Impregnation will not be accepted as a recovery procedure for Class I or II centrifugal castings. b) Impregnation is recognised as a recovery procedure for Class III castings with the following limitations: 1) The procedure shall be in accordance with Def Stan ) The prior approval of the Acceptance Authority is required. c) The area of leakage necessitating remedial action does not exceed 10% of the total area pressure tested in non designated regions Special Repairs Where the repairs necessary to meet the acceptance standards are more extensive than are permitted by this specification and if it is considered that effective economical repair is possible the contractor s repair proposals, in accordance with Def Stan may be submitted to the Acceptance Authority for decision. 11 Quality Assurance 11.1 Identification of Ingots A unique cast number is to be assigned to each ingot to positively identify it with respect to its quality assurance documentation. 9

20 11.2 Identification of Castings a) Each casting is to be clearly identifiable during manufacture and be permanently marked for identification during service life with the following details: 1) Pattern or Ship s Identity Number plus Pt1. 2) Class of casting, i.e. CI, CII, CIII. 3) The legend NABCC. 4) The unique cast number which can be related to the quality control documentation. NOTE Castings subject to validation in accordance with Def Stan Part 2 are to be marked in accordance with that specification in addition to the requirements of this Clause. b) The markings detailed in Clause 11.2a) are to be stamped, engraved or vibro etched in the position indicated on the drawing. Markings are to be as conspicuous as the nature of the casting allows and provision is to be made for transferring identification markings during manufacture so that traceability is maintained throughout the service life of a casting. The markings are not to be made on the highly stressed region, e.g. Critical Test Regions of the casting. c) Where difficulty is being experienced in satisfactorily applying identification symbols, this is to be resolved by consulting the Design Authority Quality Assurance Documentation a) Each consignment of ingots is to be accompanied by Quality Assurance Documentation providing the results of the melt control analysis and the results of the chemical analysis specified in Clause 6.1b). b) Each consignment of castings is to be accompanied by Quality Assurance Documentation giving the actual results of the tests carried out and a certificate of compliance with this standard. c) There are specific requirements for Submarine First Level NAB castings that require validation in accordance with Def Stan Part 2. A check list for all Quality Assurance documentation required for a qualified casting is given in Def Stan Part Packaging Except where otherwise stated in the contract, packaging is to be in accordance with the contractor s normal practice subject to the affixing of a trade warning label and the addition of the following identification details on each package or case: 1) Description of castings. 2) Quantity. 3) Contract Number. 10

21 Annex A Procurement Checklist NOTES 1. This check list is to ensure that certain aspects of this Defence Standard are consulted when preparing a Statement of Technical Requirements for a particular application. 2. Clauses where a preference for an option is to be used or where specific data is to be added are included in the check list. 3. Each item is to be marked either: = included NA = not applicable Check No. Check Clause No. or NA 1 Position of test pieces to be agreed Surface finish to be specified. 9.3c) 3 4 Liquid penetrant acceptance standards for machined surfaces. Radiographic examination of nondesignated regions on a sample basis Pressure tests Blending of surface defects. 10.3c) 7 Impregnation of castings. 10.6b) 8 Special Repairs Packaging

22 Crown Copyright 2012 Copying Only as Agreed with DStan Defence Standards are published by and obtainable from: Defence Equipment and Support UK Defence Standardization Kentigern House 65 Brown Street GLASGOW G2 8EX DStan Helpdesk Tel: +44 (0) /2 Fax: +44 (0) Internet File Reference The DStan file reference relating to work on this standard is D/DStan/69/2/747/1. Contract Requirements When Defence Standards are incorporated into contracts users are responsible for their correct application and for complying with contractual and statutory requirements. Compliance with a Defence Standard does not in itself confer immunity from legal obligations. Revision of Defence Standards Defence Standards are revised as necessary by an up issue or amendment. It is important that users of Defence Standards should ascertain that they are in possession of the latest issue or amendment. Information on all Defence Standards can be found on the DStan Website updated weekly and supplemented regularly by Standards in Defence News (SID News). Any person who, when making use of a Defence Standard encounters an inaccuracy or ambiguity is requested to notify UK Defence Standardization (DStan) without delay in order that the matter may be investigated and appropriate action taken. Sponsors and authors shall refer to Def Stan 0000 part 2 before proceeding with any standards work.