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1、BRITISH STANDARD BS 7475:1991 Incorporating Amendment No. 1 Specification for Fusion welding of austenitic stainless steels Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:1991 This British Standard, ha
2、ving been prepared under the direction of the Welding Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 29 November 1991 BSI 02-1999 The following BSI references relate to the work on this standard: Committee reference WEE/45 Draft for comm
3、ent 90/75780 DC ISBN 0 580 19972 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Welding Standards Policy Committee (WEE/-) to Technical Committee WEE/45, upon which the following bodies were represented: Associated Offices Technical C
4、ommittee British Nuclear Fuels Ltd. British Railways Board British Steel Industry Stainless Steel Fabricators Association of Great Britain United Kingdom Atomic Energy Authority Welding Institute Welding Manufacturers Association (BEAMA Ltd.) Amendments issued since publication Amd. No.Date Comments
5、 7642April 1993Indicated by a sideline in the margin Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:1991 BSI 02-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definiti
6、ons1 3Information and requirements to be agreed and to be documented1 4Storage, handling and workshop requirements1 5Parent metal2 6Welding process2 7Welding consumables2 8Equipment2 9Butt weld details3 10Fillet weld details4 11Preparation of fusion faces5 12Assembly for welding6 13Alignment of butt
7、 joints6 14Fit-up of parts joined by fillet welds6 15Tack welds6 16Temporary attachments7 17Stray arcing7 18Inter-run cleaning7 19Details of welding procedure7 20Approval and testing of welding procedures7 21Approval and testing of welders7 22Identification of welds7 23Inspection and testing7 24Qual
8、ity of welds7 25Correction of faulty welds8 26Heat treatment8 27Weld finishing8 Appendix A Metallurgical aspects9 Appendix B Recommended consumables for gas shielded arc welding and manual metal arc welding of austenitic stainless steels10 Figure 1 Fillet welds applied to the edge of a part5 Table 1
9、 Guidance for shielding gas selection3 Table 2 Recommended diameters and welding currents for TIG electrodes3 Table 3 Recommended weld preparation tolerances for butt joints5 Table 4 Alignment of butt joints for plates and sheets6 Table 5 Alignment of butt joints for pipes and tubes6 Table 6 Recomme
10、nded consumables for gas shielded arc welding and manual metal arc welding of austenitic stainless steels10 Publication(s) referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:19
11、91 ii BSI 02-1999 Foreword This British Standard has been prepared under the direction of the Welding Standards Policy Committee. It supersedes BS 3019-2:1960 which is withdrawn. This standard expands and updates the recommendations given in BS 3019-2:1960 and presents them in the form of a specific
12、ation. The standard is primarily intended for arc welding but it may be applied to other forms of welding, e.g. laser welding. The austenitic stainless steels covered by this specification generally contain in excess of 16 % chromium, together with more than 8 % nickel or nickel plus manganese. Stee
13、ls within this category may also contain additional alloying elements, such as molybdenum, titanium, niobium, carbon or nitrogen to provide particular properties. The combination of alloying additions in all of these steels is sufficient to give an almost entirely face centred cubic, “austenitic”, c
14、rystal structure. However, a small amount of the magnetic ferrite phase may be present in some steels and further small amounts of ferrite may form during autogenous welding. It is assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qua
15、lified and experienced personnel. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary
16、 of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside fron
17、t cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:1991 BSI 02-19991 1 Scope This British Standard specifies requirements for the manual, semi-automatic, automatic and mechanized arc welding of au
18、stenitic stainless steel in all product forms including hollow sections. In addition to the definitive requirements, this standard requires additional information and the requirements of the supplier and the purchaser to be documented. For compliance with this standard, both the definitive requireme
19、nts and the documented items detailed in clause 3 have to be satisfied. Some details of metallurgical aspects are given in Appendix A. Typical austenitic stainless steels covered by this specification are listed in Appendix B together with recommended filler wires and welding electrodes. NOTE 1This
20、standard is primarily intended for arc welding but may be applied to other methods of welding, e.g. laser welding. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purpose of this British Standard, the definitions given in B
21、S 499-1 apply. 3 Information and requirements to be agreed and to be documented 3.1 Information to be supplied by the purchaser The following information to be supplied by the purchaser shall be fully documented. The definitive requirements specified throughout the standard and these documented item
22、s shall be satisfied before a claim of compliance with the standard can be made and verified: a) the application standard to be used together with any supplementary requirements; b) specific requirements for materials; c) weld quality requirements including details of surface finish and cleanliness;
23、 d) the degree of oxidation tolerable on root beads or the maximum oxygen content in the purge gas; e) whether welds are to be identified to the individual welder performing the joint. 3.2 Requirements to be agreed The following items to be agreed between the contracting parties, which are specified
24、 in the clauses referred to, shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be satisfied before a claim of compliance with the standard can be made and verified: a) where no application standard exists, the weld
25、profile (see 9.3.1); b) whether the use of reactive backing strips is acceptable see 9.4 c); c) when it is not appropriate to use part of the structure as backing material, the material to be used (see 9.5.2); d) methods for edge preparation for welding (see 11.2); e) alternative technique for inter
26、-run cleaning (see clause 18); f) whether written welding procedures are not required (see clause 20); g) the need for welding procedure tests (see clause 20); h) if no application standard exists, the method and extent of inspection (see 23.2); i) if no application standard exists, acceptance requi
27、rements (see 24.2); j) if more than three attempts can be made to repair a weld (see clause 25); k) if no application standard exists, the heat treatment requirements (see clause 26). 4 Storage, handling and workshop requirements 4.1 General When storing, handling or fabricating austenitic stainless
28、 steel, the environment shall be controlled to avoid permanent breakdown of the surface oxide layer, known as the passive film, which gives austenitic stainless steel its good corrosion resistance. Stainless steel used for manufacture or fabrication shall be protected from contamination during all s
29、tages of storage and work. 4.2 Contact materials When using paints, dyes, tapes, glues, etc. care shall be taken that the residues do not contain substances causing permanent damage or marking. NOTE 1The advice of manufacturers of these substances should be sought to establish their suitability for
30、use on stainless steel. NOTE 2Austenitic stainless steel may corrode as a consequence of being in contact or having its surface contaminated with other materials. This may be as a result of the contact material itself being corrosive or because a contact material enables a corrosion phenomenon such
31、as crevice or galvanic corrosion to occur. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:1991 2 BSI 02-1999 4.3 Storage and handling A dry, covered building shall be used for the storage of all materi
32、als and shall be maintained in a clean condition at all times. Racking for materials shall be strongly built and shall be lined in a secure manner with materials that will not contaminate stainless steel, e.g. dry wood, nylon or stainless steel. Unlined or painted carbon steel racking shall not be u
33、sed. Lifting grabs shall be made from or lined with a non-contaminating material. 4.4 Manufacturing and fabrication facilities Manufacturing and fabrication facilities shall be protected from inclement weather and draughts and shall be dry. Facilities for fabrication of stainless steels shall be seg
34、regated from other works and kept free of all possible contaminating materials such as lead, zinc, copper/copper alloys or carbon steels, etc. (see 9.5.2 concerning the use of copper as a backing material). Forming tools shall be cleaned thoroughly before use to avoid cross contamination. All lubric
35、ants used in the forming operations shall be removed from the workpiece within 4 h of use. Welding fixtures, such as clamps or manipulators shall be either manufactured from or lined with non-contaminating material. 5 Parent metal In selecting the steel for the particular application, care shall be
36、taken to avoid grades that will suffer from corrosion in the area of the weld under the anticipated service conditions. NOTEAppendix A gives guidance on metallurgical factors affecting welds in austenitic stainless steels. 6 Welding process The austenitic stainless steels can be joined using the maj
37、ority of welding processes but care shall be taken with the high heat input processes to avoid metallurgical problems (see Appendix A) and distortion. The minimum necessary heat input shall be used for all processes and materials, consistent with obtaining satisfactory fusion. 7 Welding consumables
38、7.1 General Consumables shall be selected having regard to the application, i.e. joint design, welding position and the properties required to meet service conditions. Where there is an applicable British Standard, the consumables selected shall comply and be coded in accordance with that standard.
39、NOTEAppendix B gives a list of recommended consumables. Consumables shall only be used in accordance with manufacturers recommendations and shall only be used for their specified application. Coated electrodes shall not be stripped of their coating for use as filler wires. 7.2 Shielding gases For ga
40、s shielded arc welding processes, the torch shielding, reverse side protection and trailing shield shall be appropriate to the quality requirements and the consumable used. Shielding gases containing carbon dioxide shall only be used where specifically recommended by the consumable manufacturer. NOT
41、E 1Guidance on the selection of shielding gases is given in Table 1. NOTE 2For purging the reverse side of the weld during the welding cycle, argon, helium or argon containing up to 5 % hydrogen may be used subject to procedure approval. NOTE 3Carbon dioxide based shielding gases should not be used
42、with solid filler wires because there is a possibility of carbon pick-up. 7.3 Storage and handling All consumables shall be stored and handled with care and in accordance with the manufacturers recommendations; they shall be kept free from grease and other contaminents. Electrodes, filler wires and
43、rods and fluxes that show signs of damage or deterioration shall not be used. Consumables returned to stores shall be treated in accordance with the manufacturers recommendations before re-issue. NOTEConsumables that have been exposed to poor storage conditions or are suspected of being damp should,
44、 where appropriate, be baked in accordance with the manufacturers recommendations. 8 Equipment 8.1 Plant Welding plant, instruments, cables and accessories shall comply with the relevant Parts of BS 638. The fabricator shall be responsible for ensuring that the capacity of the welding plant and anci
45、llary equipment is adequate for the welding procedure to be used and for maintaining all welding plant and ancillary equipment in good working order. NOTEThe attention of the contractor is drawn to the advice on safety precautions contained in Guidance Note PM 64 “Electrical safety in arc welding” i
46、ssued by the Health and Safety Executive and published by HM Stationery Office. 8.2 Earthing All electrical plant in connection with the welding operation shall be earthed and shall use leads appropriate to the application and as specified in BS 638. Earth clamps and all welding connections to the w
47、orkpiece shall be manufactured from or lined with non-contaminating materials (see clause 4). Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:43:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7475:1991 BSI 02-19993 Table 1 Guidance for shielding gas selecti
48、on 8.3 Tungsten electrodes Tungsten electrodes shall comply with BS EN 26848. The size and type of tungsten electrode selected and the tip preparation shall be appropriate to the application. Contaminated electrodes shall be replaced or restored to their original condition. NOTEThe recommended elect
49、rode diameters and currents for direct current welding are given in Table 2. Table 2 Recommended diameters and welding currents for TIG electrodes 8.4 Instrumentation Means shall be provided for confirming compliance with the welding procedure. Electrode drying ovens shall be provided with means of measuring the oven temperature. All measuring instruments shall be calibrated and have a certificate traceable to national standards. 9 Butt weld details 9.1 General The details of all butt joints, e.g. form of joint, angle between fusion faces, and gap between
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