1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 7670 : Part 2 : 1997 I
2、CS 21.060.10; 21.060.20; 25.160.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Steel nuts and bolts for resistance projection welding Part 2. Specification for welding of weld nuts and weld boltsBS 7670 : Part 2 : 1997 This British Standard, having been prepared under the
3、direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 March 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference WEE/29 Draft for comment 95/703043 DC ISBN 0 580 25550 6 Amendment
4、s issued since publication Amd. No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee WEE/29, Resistance welding, upon which the following bodies were represented: British Iron and Steel Producers Associa
5、tion Railway Industry Association Society of Motor Manufacturers and Traders Limited Welding Institute IIW-UK Briefing Group III Co-optedBS 7670 : Part 2 : 1997 BSI 1997 i Contents Page Committees responsible Inside front cover Foreword ii Specification 1 Scope 1 2 References 1 3 Definitions 1 4 Ste
6、el 1 5 Information and requirements to be agreed and to be documented 1 6 Surface conditions 2 7 Edge conditions and form of component 2 8 Shape and dimensions 2 9 Materials for electrode assembly 2 10 Design of electrode assembly 2 11 Weld assessment 4 12 Routine inspection of welded components 4 1
7、3 Reclamation 4 Annexes A (informative) Recommendations for appropriate welding equipment 5 B (informative) Typical welding conditions 5 C (informative) Welding procedure information 6 Tables 1 Weld nut size relative to sheet thickness 4 2 Typical torque values for weld nuts 4 B.1 Typical welding co
8、ndition for square weld nuts 6 B.2 Typical weld conditions for weld bolts 6 Figures 1 Positioning of square and hexagonal nuts prior to welding 3 2 Location of weld bolt 3 List of references Inside back coverii BSI 1997 BS 7670 : Part 2 : 1997 Foreword This Part of BS 7670 has been prepared by Techn
9、ical Committee WEE/29. It specifies weld nuts and weld bolts for resistance welding processes. It supersedes BS 2996 : 1958 which is withdrawn. This Part should be used in conjunction with Part 1: Dimensions and properties which specifies weld bolts and weld nuts. In a standard of this type, which c
10、overs a wide range of engineering applications, it is not practicable to set out specific requirements for equipment or welding conditions to be used. However, guidance on these subjects is given in annexes A to C. Similarly, it is not possible to specify acceptance requirements. Compliance with a B
11、ritish 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. BSI 1997 1 BS 7670 : Part 2 : 1997 Specification 1 Scope This British Standar
12、d specifies projection welding of weld nuts and weld bolts singly to uncoated and coated steel sheet from 0.5 mm to 5.0 mm thick. Annex A gives recommendations for appropriate welding equipment and annex B outlines typical welding conditions. NOTE 1. It is emphasized that this type of weld is loaded
13、 in compression only. The purpose of the weld is to prevent the fastener from rotating during assembly or disassembly of a fabrication. It is not intended as a structural weld. This standard specifies weld nuts and weld bolts, the design, dimensions and materials of which are detailed in Part 1 of t
14、his standard. Annular projections are not included. In addition to the definitive requirements specified throughout the standard, the documented items detailed in clause 5 shall be satisfied before a claim of compliance with the standard can be made and verified. 2 References 2.1 Normative reference
15、s This Part of BS 7670 incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any
16、subsequent amendments to or revisions of the cited publication apply to this Part of BS 7670 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Pa
17、rt of BS 7670 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions For the purposes of this British Stand
18、ard the definitions in BS 499 : Part 1 : 1991 apply. 4 Steel The steel sheet or plate to which the nuts or bolts are to be welded shall be flat rolled in coil or cut length. The thickness shall be from 0.5 mm to 5.0 mm. Uncoated sheet and strip material shall conform to BS 1449 : Part 1 : Section 1.
19、1. Uncoated plate material shall conform to BS 1449 : Part 1 : Section 1.1, BS EN 10025, or BS EN 10113-3, as relevant. Coated material shall conform to the relevant requirements and chemical composition specified in BS EN 10142, BS 6536, BS 6582, BS EN 10152, BS EN 10215, and BS EN 10147. NOTE 1. T
20、he recommended application of hole diameter and sheet thickness is given in table 1. NOTE 2. For a fixed fastener diameter, welding becomes more difficult the larger the sheet thickness. Greater care should be taken when welding coated steels. 5 Information and requirements to be agreed and to be do
21、cumented 5.1 Information to be supplied by the purchaser The following information to be supplied by the purchaser 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
22、 standard can be made and verified. a) Whether a special surface treatment is to be applied (clause 6). b) Whether a gap between the components to be welded can be tolerated (clause 12). c) Which methods of reclamation, if any, are permitted (clause 13). d) Whether it is the intention of the purchas
23、er to inspect the production and testing of the parts ordered. 5.2 Requirements to be agreed 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 throughout the standard
24、 and the following documented items shall be satisfied before a claim of compliance with the standard can be made and verified. a) The hole diameter for square nuts (10.2 and table 1). b) The procedure for welding assessment tests (11.1). c) Whether a peel test is to be carried out (11.2.3). d) The
25、number, form and frequency of testing of test pieces. e) Whether a torque value is to be the acceptance criterion for the torque test and, if so, the level of this torque value (11.2.2). f) Whether a peel test or a torque test is to be used to confirm a satisfactory weld in the routine inspection of
26、 welded components (clause 12). g) Any reclamation of faulty work, other than by further projection welding, to be made and the method to be used (clause 13).2 BSI 1997 BS 7670 : Part 2 : 1997 6 Surface conditions Prior to welding, all surfaces to be projection welded shall be free from grease, scal
27、e, rust, paint, dirt or excessive pitting. NOTE. Certain surface treatments such as the application of rust prevention treatment, oiling or plating may be applied before welding, provided that the coating is uniform in thickness and that it has been proved that consistent welds which conform to this
28、 standard can be obtained. It should be recognized that different welding conditions may be necessary, depending on the type of pre-treatment used, e.g. phosphate- or chromate-treated coated steels. 7 Edge conditions and form of component The surfaces of the component to which the fastener is to be
29、welded shall be free from burrs or other defects that would in any way interfere with the proper collapse of the projections during welding, or cause current to flow other than through the projections. NOTE. No identification or makers mark should be on the face in contact with the electrode. The fo
30、rm of the sheet metal component shall be such that the collapse of the projections on the fastener can take place unrestrained by any other surface contacts. The form of the sheet metal component shall be such that the welding force is equally distributed over all the projections, prior to and durin
31、g welding. 8 Shape and dimensions The shapes of projections and dimensions for the fasteners shall conform to figures 1, 2, and 3 and tables 1, 3 and 4 respectively of BS 7670 : Part 1. 9 Materials for electrode assembly The electrode holder shall be of copper alloy of sufficient section and strengt
32、h to carry the welding current and electrode force (see table B.1) without overheating or deforming. NOTE. The electrode assembly can consist of an electrode holder and electrode(s) with or without insert(s). The part in contact with the workpiece shall be either the electrode(s) or the insert(s) in
33、 accordance with annex A of BS 4577. 10 Design of electrode assembly 10.1 Contact faces The electrode in contact with the fastener shall support the complete area of the weld nut or bolt head. The electrode in contact with the sheet metal component shall have a minimum section of 1.5 times the cross
34、-sectional area of the weld nut or bolt head. If copper alloy inserts are used, the electrode shall be capable of supporting the electrode force used without distortion. The insert shall be attached to the electrode in such a manner as to give good electrical and thermal contact. NOTE 1. Contact fac
35、es should ensure intimate contact with workpieces for minimum contact resistance. NOTE 2. Cooling arrangements should bring the cooling water as close as possible to the contact faces, in order to minimize electrode wear and maintain weld quality. 10.2 Location of components 10.2.1 Weld nut The weld
36、 nut shall be located as shown in figure 1 either by means of a central pin or by the outer form of the weld nut itself. In all cases where a pin is used as a locator, the welding current shall pass only through the projection and not through the means of location, particularly between the pin and t
37、he thread inside the nut. NOTE 1. In some cases the location pin can be provided with a shoulder to locate the sheet metal component relative to the nut. The pin may also be spring loaded to retract into the electrode by the descent of the upper electrode, or may be retracted by means of a pneumatic
38、 cylinder. Dimensions for the hole in the sheet shall conform to table 1. For hexagonal nuts, the values quoted for d 5 are a requirement. NOTE 2. For square nuts d 4 , the values are recommended values only, as d 4 can vary according to the method used for location of the nut. In this latter case,
39、the hole diameter should be agreed between the manufacturer and the purchaser (see 5.2). If ceramic pins are used, the diameter of the clearance hole for square nuts d 4 shall be 1 mm greater than the thread clearance. This is not applicable to collared nuts. 10.2.2 Weld bolt The weld bolt shall be
40、located as shown in figure 2. BSI 1997 3 BS 7670 : Part 2 : 1997 a) Square nut b) Hexagonal nut Figure 1. Positioning of square and hexagonal nuts prior to welding Figure 2. Location of weld bolt4 BSI 1997 BS 7670 : Part 2 : 1997 11 Weld assessment 11.1 General Welding procedure information shall be
41、 recorded for each machine, for each combination of weld nut size and sheet metal thickness. The record of procedures shall be based on the appropriate items listed in annex C. The following tests shall be carried out: a) thread test (see 11.2.1); b) torque test (see 11.2.2); c) peel test (see 11.2.
42、3) (applies to weld nuts only); (optional, by agreement between the contracting parties). 11.2 Test methods and conditions 11.2.1 Thread test A bolt of the specified thread size shall be engaged in the nut and shall travel freely through the whole length of the thread of the nut and the sheet to whi
43、ch the nut is attached. 11.2.2 Torque test Hold or clamp the welded assembly so that minimal panel distortion occurs during the test. Using a torque spanner fitted with a socket or adaptor to fit the weld nut or bolt, apply torque in a steadily increasing manner up to the agreed value. On the torque
44、 test, the bolt shall fail or the thread shall strip before the joint fractures unless a torque value, previously agreed between the contracting parties, is achieved. NOTE. Typical guideline values are given in table 2. 11.2.3 Peel test If required (see 5.2 item c), the peel test shall be as follows
45、. Hold the welded assembly, by means of the fastener, firmly in a vice. Using a hammer and chisel or pliers, peel the sheet away from the fastener. A portion of the material from either component at each projection shall be pulled away. 12 Routine inspection of welded components At the beginning of
46、each welding period, a peel or torque test, as agreed between the purchaser and supplier (see 5.2) shall be performed in accordance with clause 11. In the event of this pre-production test failing, any subsequent welding shall be deemed not to conform to this British Standard. In the event of the te
47、st piece tested at the end of the shift or work period failing, 2 % or 10 pieces, whichever is the greater, shall be selected from the production during the period following the previous test on that machine and shall be tested in accordance with clause 11. In the event of any of the selected compon
48、ents failing, the whole of the production during that period shall be deemed not to conform to this British Standard. For visual inspection, no dressing, painting or other operation interfering with the examination of the weld zone shall be carried out on the assemblies until after the welding has b
49、een inspected. The welded components shall conform to the design drawings and unless otherwise specified, a gap shall be allowed between components provided they conform to clause 11. 13 Reclamation Faulty work shall not be reclaimed by further projection welding of the same components. NOTE. Other methods of reclamation may be used, by agreement between purchaser and manufacturer (see 5.1). Table 1. Weld nut size relative to sheet thickness Thread size as specified in BS 7670 : Part 1 Sheet or strip thickness, a Hole diameter d 4 and d 5 min. max. M3 0.50 2.5 4.5 M4 0.75 3 6 M5
