1、BRITISH STANDARD BS4204:1989 Specification for Flash welding of steel tubes for pressure applications UDC 621.643.23:669.14462:621.791.762.5:006.3/.8BS4204:1989 This British Standard, having been prepared under the directionof the Welding Standards Policy Committee, waspublished under the authorityo
2、f the Board of BSI andcomes into effect on 31 December1989 BSI 07-1999 First published September1967 First revision March1981 Second revision December1989 The following BSI references relate to the work on this standard: Committee reference WEE/33 Draft for comment87/75910 DC ISBN 0 580 17744 0 Comm
3、ittees responsible for this British Standard The preparation of this British Standard was entrusted by the Welding Standards Policy Committee (WEE/-) to Technical Committee WEE/33, upon which the following bodies were represented: Associated Offices Technical Committee British Chain Manufacturers As
4、sociation British Railways Board British Steel Corporation Electricity Supply Industry in England and Wales Water Tube Boiler Group, Power Plant Contractors Association Welding Institute Welding Manufacturers Association (BEAMA Ltd.) Amendments issued since publication Amd. No. Date of issue Comment
5、sBS4204:1989 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword iii 1 Scope 1 2 Definitions 1 3 Items for agreement between the manufacturer and the purchaser 1 4 Parent metal 2 5 Sizes of tube 2 6 Tube preparation 2 7 Cleanliness 2 8 Backing gas 3 9 Welding equipment 3 1
6、0 Welding sequence 3 10.1 Overhang 3 10.2 Clamping force 3 10.3 Alignment 3 10.4 Initial tube end squaring 3 10.5 Pre-heating 3 10.6 Flashing 3 10.7 Upsetting 3 11 Post-weld heat treatment 3 12 Procedure approval tests 4 12.1 General 4 12.2 Number of tests 4 12.3 Changes affecting approval 4 12.4 He
7、at treatment 4 12.5 Test specimens 4 12.6 Dimensions of bend test specimens 5 12.7 Examination of the bend test specimen 5 12.8 Macro-examination 6 12.9 Tensile testing 8 12.10 Hardness testing 8 12.11 Monitoring 8 13 Production control 8 13.1 Frequency of tests 8 13.2 Test procedure 8 13.3 Repeat t
8、ests 8 13.4 Parameter changes 12 13.5 Monitoring 12 14 Weld profile 12 15 Weld imperfections 12 16 Weld dressing 15 17 Non-destructive testing of production welds 15 18 Statement of results 16 Appendix A Welding equipment 18 Appendix B Typical information to appear on a welding procedure sheet for f
9、lash welding 18 Appendix C Generalized diagram illustrating monitoring variables 18 Appendix D Weld records 18BS4204:1989 ii BSI 07-1999 Page Figure 1 Tube preparation 2 Figure 2 Method of cutting bend test specimens from the test weld 6 Figure 3 Length of weld surface opened up during the bend test
10、 7 Figure 4 Dimensions of the tensile test specimens 9 Figure 5 Tube fault revealed as a result of a bend test 11 Figure 6 Large void revealed as a result of a bend test 13 Figure 7 Lack of adhesion revealed as a result of a bend test 13 Figure 8 Flat spot revealed as a result of a bend test 14 Figu
11、re 9 An example of break-up in the heat affected zone 15 Figure 10 Typical flash welding procedure test record 16 Figure 11 Typical flash welding procedure test report sheet 17 Figure 12 Generalized diagram illustrating monitoring variables 19 Publications referred to Inside back coverBS4204:1989 BS
12、I 07-1999 iii Foreword This revision of BS4204 has been carried out under the direction of the Welding Standards Policy Committee. It deals with the production of welds made by the flash welding process and is one of a series of British Standards concerned with the welding of pipework. It relates to
13、 the welding of steel pipes, tubes, and pipe fittings for pressure applications. For the automatic flash welding of ferrous metal sections other than these, reference should be made to BS6944. This British Standard follows the general pattern set by others in the series and is of the “process” type.
14、 It embodies the currently accepted practice of initial procedure approval tests followed by periodical production control tests. The standard also details the various parameters specific to the flash welding process which are required to be determined in establishing the procedure. In Appendix B, a
15、 list is given of the typical information to appear on a welding procedure sheet together with a typical test record sheet. As the acceptance level of certain aspects, e.g.the contour and form of the weld profile, is related to the service conditions of the joint, reference should be made, for these
16、 details, to the appropriate application standard, where such a standard exists. Where such guidance is not given, these aspects should be a matter of agreement between the manufacturer and the purchaser. For the purposes of this standard, no difference is intended in the meaning “pipe” and “tube”,
17、though idiomatic use prefers sometimes the one and sometimes the other. It has been assumed in 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 p
18、rovisions 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 of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1 to20, an
19、 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 front cover.iv blankBS4204:1989 BSI 07-1999 1 1 Scope This British Standard specifies requirements for the au
20、tomatic flash welding of steel tubes, pipes or pipe fittings for pressure applications. In addition to the definitive requirements, it also requires the items detailed in clause3 to be documented. For compliance with this standard, both the definitive requirements and the documented items have to be
21、 satisfied. NOTE 1The phrase “pressure applications” in this context applies to designs incorporating pressure and/or temperature requirements. NOTE 2For sections other than those covered by this standard, seeBS6944. NOTE 3The titles of the publications referred to in this standard are listed on ins
22、ide back cover. 2 Definitions For the purposes of this British Standard, the following definitions apply. For other relevant terms the definitions are as given in BS499-1. 2.1 formier gas a gas mixture nominally of composition90%nitrogen and10%hydrogen 2.2 manufacturer the user of the welding equipm
23、ent for the purposes of manufacturing welded tube products 2.3 automatic flash welding machine a flash welding machine that has an automatic sequence of events 2.4 inspecting authority the competent independent body or association that, where required, verifies compliance with this standard 2.5 upse
24、t current time the time after the commencement of upsetting during which the current flows 2.6 preheating (flash welding) the resistance heating of workpieces to facilitate the onset of flashing by a series of current pulses with a cool time in between each pulse. The pulsing is achieved by moving t
25、he work pieces together and apart (seeAppendix C) 3 Items for agreement between the manufacturer and the purchaser The following items to be agreed between the contracting parties, which are specified in the clauses referred to, shall be fully documented. Both the definitive requirements specified t
26、hroughout the standard and the following documented items shall be satisfied before a claim of compliance with this standard can be made and verified: a) the specification of the parent metal to be used (seeclause4); b) whether a backing gas is to be used and the type of gas (seeclause8); c) details
27、 of the post-weld heat treatment (seeclause11 and12.4); d) the type and extent of procedure approval tests and the necessary details, including acceptance criteria (see12.1); e) frequency of production control tests (see13.1); f) whether production test specimens are to be retained for examination b
28、y the purchaser or his representative (see13.2);BS4204:1989 2 BSI 07-1999 g) the procedure to be followed for batch inspection in the event of failure of repeat production test pieces (see13.3); h) the service conditions of the weld and the number and title of the particular application standard for
29、 determining the acceptability of the weld profile (seeclause14); i) the extent of dressing of the production welds (seeclause16); j) if non-destructive testing of production welds is required (seeclause17). 4 Parent metal The materials to be flash welded in accordance with the requirements of this
30、standard shall comply with the requirements of BS3059, BS3601, BS3602, BS3603, BS3604, BS3605 and BS3606. The use of equivalent alternative steels to those complying with the requirements of the above standards is permitted. It shall be determined by the procedure approval tests (seeclause12) that t
31、he steel, or combination of steels, dimensions and wall thickness can be satisfactorily flash welded. 5 Sizes of tube The diameter, thickness and length of tube which can be flash welded depends on the capacity of the machine to be used, and it shall be determined by the procedure approval tests tha
32、t the tubes come within this machine capacity (seeclause12). 6 Tube preparation The procedure for tube preparation shall be established during the procedure approval tests. The end of each tube to be welded shall be so cut that the end edge or surface lies in a plane at right angles to the axis of t
33、he tube. NOTEIt is desirable that the face areas to be in contact when welding should be approximately equal, the external diameters of the tubes being nominally equal. Where machining of each tube is necessary, boring shall be concentric with the outside circumference of the tube, and the machining
34、 shall run out smoothly into the bore (seeFigure 1). Machining shall not reduce the tube wall thickness below the specified design thickness. 7 Cleanliness Areas of electrical contact on tube and machine shall be cleaned prior to welding. NOTE 1The purpose of cleaning the contact area on the tube be
35、fore welding is to ensure a uniform current in the welding circuit. Loose matter and free moisture in the bore of the tube shall be removed. NOTE 2Cleaning by hand externally with emery cloth is generally sufficient, although mechanical cleaning (linishing, shot blasting) may be necessary for heavil
36、y scaled tubes. Internal cleaning may be necessary for scaled tubes as established at the procedure approval test stage (seeclause12). Figure 1 Tube preparationBS4204:1989 BSI 07-1999 3 8 Backing gas Where backing gases are used, the type of gas and the pressure at which it is to function depends on
37、 the type of material and dimensions of the tube to be welded. Nitrogen, Formier or an inert gas shall be used unless otherwise agreed between the purchaser and the manufacturer. The pressure shall be set at such a value that a positive pressure is maintained during the welding cycle. The pressure t
38、o be used shall be determined during the procedure approval tests. An effective purging period prior to the start of welding shall be used to ensure that the tubes are completely filled with the backing gas, and that the gas is present at the weld interface on commencement of welding. Where welds ar
39、e made to bifurcations, backing gas shall be applied to the ends of the bifurcation to eliminate air entrainment. 9 Welding equipment All welding shall be done on an automatic flash welding machine. NOTEGuidance on the choice of equipment is given in Appendix A. Where flash welding guards are used,
40、they shall be placed at such a distance from the clamped components as to minimize the possibility of particles, thrown off during the flashing period, ricocheting into the weld. 10 Welding sequence 10.1 Overhang The tubes shall be so clamped that the temperature gradients at the interface are balan
41、ced. 10.2 Clamping force The clamping force exerted on the tubes shall be sufficient to prevent the tubes sliding in the clamps during the welding cycle. This force shall not deform the tubes. 10.3 Alignment The outside diameter of the tubes to be welded shall be in alignment when clamped in the mac
42、hine. 10.4 Initial tube end squaring Where a flashing operation is used for initial tube end squaring, the heat generated shall not cause the tube to collapse during pre-heating. 10.5 Preheating Preheating is normally accomplished and resistance heating obtained by bringing the tubes into contact an
43、d separating them while the current is switched on. This operation shall continue until the temperature of the end of the tubes reaches a value where flashing can commence. 10.6 Flashing The speed of advance of the moving platen and the value of the welding current shall be regulated to ensure that
44、the flashing is continuous throughout the sequence. 10.7 Upsetting The upset or forging force required to weld different steels depends on the temperature gradient in the plastic zone and the compressive strength of the steel at high temperature. The upset shall be sufficient to ensure that all void
45、s are closed and oxide and molten metal are removed from the weld. It shall not be such as to cause distortion of the work or excessive protrusion. The current shall be maintained from flashing until after upset has commenced. 11 Post-weld heat treatment The post-weld heat treatment of flash welds s
46、hall be done in accordance with BS2633 or BS4677 for the steels specified in these standards unless an appropriate application standard specifies different requirements or an alternative treatment has been agreed between the manufacturer and the purchaser. For other steels post-weld heat treatment s
47、hall be by agreement between the manufacturer and the purchaser. The proposed heat treatment shall be stated in the welding procedure.BS4204:1989 4 BSI 07-1999 If post-weld heat treatment is carried out for a limited time in the flash welding machine by means of further resistance heating, the proce
48、dure shall be the subject of agreement between the purchaser and the manufacturer. 12 Procedure approval tests 12.1 General A procedure shall be established for each machine, size of tube and material or combination of steels to be used. The record of the procedure shall be based on the appropriate
49、items from the information given in Appendix B. NOTEIt is recommended that the procedure approval tests carried out in accordance with this British Standard and approved by a purchaser or his representative should be accepted by other purchasers, or their representatives, provided that all the requirements of this standard have been fulfilled. 12.2 Number of tests When the manufacturer is satisfied that appropriate machine settings have been obtained, a minimum of three test welds (see12.5) shall be produced using actual materials to be used in pro
