1、 FORD LABORATORY TEST METHOD BA 013-04 Date Action Revisions 2000 08 30 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockman 1980 09 26 Printed copies are uncontrolled Page 1 of 21 Copyright 2000, Ford Global Technologies, Inc. RESISTANCE SPOT WELDABIL
2、ITY TESTS FOR HIGH STRENGTH STEELS Application This test method describes the standard procedures for testing the weldability of all specified types of high strength steels for resistance spot welding applications. All materials ordered and supplied must be qualified and accepted on the basis of the
3、se test procedures. Reference to this specification is made in the current Ford HSS materials specification. A major (M) and minor (m) test series are described herein. The major te st series is intended for use in obtaining supplier approvals. The minor test series is intended for use by Ford Manuf
4、acturing Divisions for evaluation of incoming steel shipments or for product quality control by steel suppliers. It is applicable only t o steels having previously obtained approval. Apparatus Required Spot Welder This test shall be conducted on an air - operated, single - point type spot welder, fe
5、aturing a low inertia welding system, and in general complying with the specifications of the Resistance Welders Manufacturing Association for the size of the required machine. It shall be equipped with a Ford approved resistance welding control featuring 90 firing and phase shift adjustments for he
6、at control. It shall have sufficient electrod e force to meet the requirements of the materials to be tested, at air line pressure of 550 kPa (80 psig) or less. A transformer tap switch setting shall be selected to meet all secondary current requirements at phase angle settings (heat control) betwee
7、n 85 % and 100 %. The welder must be equipped with electrode holders conforming to Ford Drawing 2ZU - 265 or equivalent and shall have furnished to it sufficient water flow capacity so that 0.13 L/sec (2 gal/min) at 24 +/ - 5 C (75 +/ - 10 F) will flow th rough each electrode holder. Cooling water f
8、or transformer, secondary conductors, control panels, etc. is to be supplied by a separate water circuit. Welding Electrodes 19.0 mm (0.75 in) Ford standard design electrode caps shall be used for most tests. The applicable design shall be selected from Ford standard electrode cap specification shee
9、t WC 1 - 1, page 1. The single exception is the 4.6 mm (0.18 in) face diameter electrode. A standard 16.0 mm (0.63 in)electrode specified on sheet WC 1, Page 1, may be used. They will be manufactured from a RWMA Class II material, complying with Ford Standard M2A107 - E. The electrode caps, adapters
10、, and holders to be used will be found under the following identifications: FORD LABORATORY TEST METHOD BA 013-04 Page 2 of 21 Copyright 2000, Ford Global Technologies, Inc. M) Reference identifies items applicable to Major test series. m) Reference identifies items applicable to Minor test series.
11、Electrode Caps: WC1A25A, WC1 - 1A26B, WC1 - 1A26C, WC1 - 1A27D (Selected for steel thickness to be welded) Cap Adapter: WB1S or WB1T - (Selected to fit welding ma chine) Electrode Holder Assembly: Drawing 2ZU - 265 or equivalent Measuring Tools (a) Knife - edge dial caliper of high quality and accur
12、acy to measure button size. (M, m) (b) Low resistance ohm - meter to measure surface resistivity (see Appendix II, Page 20). (Needed only for major test series.) (M) (c) Calibrated force gauge to measure electrode force directly. (M, m) Procedure 1. Definition (M, m) The button is the part of the we
13、ld metal which remains in the peel test (see Appendix Ia Page 13). It differs from the nugget. The nugget represents the total amount of metal melted and resolidified, as seen in a metallographic cross section. 2. Sample Selection and Preparation (M, m) (Major and minor test series) Steels for this
14、test shall be suppli ed in full coil width from any part of the coil but with identification whether front end, tail end, or middle section was used. A materials identification sheet must accompany the sample (in addition to any information transmitted separately). The infor mation identified as “ma
15、ndatory“ shown on the Materials Data Sheet, Appendix III, Page 21, must be supplied for all samples which are tested (major as well as minor test series). The “optional“ data is desirable for all new or experimental steels, in addi tion to the mandatory items. The material shall be sheared in 100 x
16、150 mm (4.0 x 6.0 in) pieces (M), both in longitudinal (rolling) and transverse direction. If the 150 mm length is with the rolling direction, this coupon will be called longitudinal cou pon, and if it is perpendicular to the rolling direction, it will be called transverse coupon. FORD LABORATORY TE
17、ST METHOD BA 013-04 Page 3 of 21 Copyright 2000, Ford Global Technologies, Inc. From selected, representative pieces, prepare a number of smaller longitudinal coupons of the sizes listed in Table 1, Page 10 (the 100 mm direction is to be t he rolling direction). Small transverse coupons are not need
18、ed. All coupons must be free from burrs. Care shall be exercised so as not to remove or add to any oils used for corrosion or shipping protection. (Surfaces must remain “as received“). (M, m) 3. Surface Resistivity Check (Major test series only) All material selected for spot weldability qualificati
19、on tests must be representative of normal production material in the thickness ordered. (Grinding - down heavier stock is not permissible). The sur face condition of the sheet shall be such that the total electrical resistance of both surfaces and the metal thickness itself shall be not more than 10
20、00 micro - ohms, as measured with standardized probes (see Appendix II, Page 20) placed on opposite sides of a single sheet and using 2.2 kN (500 lbs.) of force. Surfaces must be “as received“; degreasing solvents shall not be used. If, due to surface conditions (residual oil layers, dust, etc.) res
21、istance values are not stable (they usually decrease with ti me after clamping) the reading shall be taken not more than 30 seconds after the current and clamping force have been applied. 4. Electrode Conditioning (M, m) Install the electrode caps in the machine so that they are in alignment in the
22、vertical planes and their welding faces are parallel under the electrode force required for the test of the particular material and thickness. If necessary, electrode faces may be dressed by using a piece of emery cloth on a flat piece of metal and grinding one electrod e until faces are parallel. C
23、heck this alignment and electrode face condition by making a series of 25 welds at welding currents at least 25 % below values shown in the Weld Schedule for the particular steel under test (Table 2, pages 10 and 11). Specime ns for this test are 25 x 100 mm (1.0 x 4.0 in) coupons of the actual test
24、 material. Alignment is satisfactory if for the last few specimens the heat distribution and the indentation appears uniform and even over the full area of the weld. 5. Welding Tests, Major Test Series (M) This procedure shall be followed for type approval for weldability for any new type of steel,
25、in particular steels of new chemical composition. The test is comprised of three basic parts or steps, so as to assure weld quality un der variable plant welding conditions as well as any interchange of different batches of materials with the same nominal properties. FORD LABORATORY TEST METHOD BA 0
26、13-04 Page 4 of 21 Copyright 2000, Ford Global Technologies, Inc. The evaluation of the welds is based on a button - peel test, as it is the only available quality control test that can be routinely applied. 5.1 Full Button Test (Sensitivity to Hold-Time*) a. Make two (2) welds on a pair of the larg
27、e 100 x 150 mm (4.0 x 6.0 in) coupons (Figure 1) using the appropriate welding schedule from Table 2 for the type of steel under test; use 5 cycle s of hold time; perform peel test. (See Appendix 1a, Page 13). Adjust welding current (using additional samples) to obtain a button diameter of the secon
28、d weld equal to or not more than 0.25 mm (0.010 in) greater than the specified electrode cap face dia meter. If this button size cannot be achieved without metal expulsion, then the largest button may be used for this test that results from a current magnitude that is just below the expulsion value
29、on the second weld. b. Increase the hold time to 30 cycl es. Without changing any other welding parameter, perform weld and peel tests on 3 longitudinal and 3 transverse 100 x 150 mm (4.0 x 6.0 in) pairs of coupons. Always peel in the 150 mm direction; this will show up differences, if any, connecte
30、d with the rolling structure. c. Assess weld quality. “Passing“ requires the absence of any sign of fracture at the weld zone proper; for good and bad examples of welds see the pictures in Appendix 1a. All 6 welds, and any additional welds which may be made, must p ass this “full button test“ at 30
31、- cycle hold time. d. If material fails this test the testing procedure is terminated. * See Appendix Ib, Page 18 for explanation. FORD LABORATORY TEST METHOD BA 013-04 Page 5 of 21 Copyright 2000, Ford Global Technologies, Inc. Figure 1 - Hold time Ductility Test Coupon Figure 2 - Measuring Button
32、Size After Peel Test FORD LABORATORY TEST METHOD BA 013-04 Page 6 of 21 Copyright 2000, Ford Global Technologies, Inc. 5.2 Welding Current Range Test a. Maintain the 30 cycle hold time. Using small coupons (Table 1) and the appropriate welding schedule from Table 2 make 2 welds per coupon 50 mm (2.0
33、 in) apart, adjusting the welding current as required to produce the maximum possible button size without producing expulsion on the second weld. Weld 10 consecutive samples without adjustment. There shall be no evidence of expulsion on each second weld on each of 10 coupons. If expulsion occurs, lo
34、wer curre nt and repeat the test. Record the associated weld current as the maximum value of the current range, I max . Measure the buttons obtained by the peel test; measure only the minimum dimension, as shown in Figure 1. Record the mean (average) value max and the stand deviation max (sigma)*. A
35、ssess the results. “Passing“ requires that the following conditions are met: BUTTON PEEL RESULTS FOR Imax SAMPLES: 1. No sign of fracture into the weld zone on any of the 10 test coupons. See pictures in Appendix 1a . 2. The smallest button size as defined by: D = ( max - max ) must exceed the minim
36、um acceptable size in Table 3. *Footnote: To determine and use pocket calculator having statistical functions built in, such as Texas Instruments Model TI - 57 or Hewlett - Packard Model HP - 22. The standard deviation is defined by: For 10 welds N = 10. For further details see ASTM Special Tech. Pu
37、bl. 15D, “Manual on Presentation of Data and Control Chart Analysis“, ASTM 1976. FORD LABORATORY TEST METHOD BA 013-04 Page 7 of 21 Copyright 2000, Ford Global Technologies, Inc. b. Reduce the welding cur rent by the amount of the minimum specified current range I min selected from Table 3 for the a
38、ppropriate type of steel and sample thickness. Call this value I low . Weld 10 samples at this lower current setting I low , then measure the size of the buttons a fter peeling. Measure only the minimum dimension, as shown in Figure 2. Record the mean value min and the standard deviation min as befo
39、re. Assess the results. “Passing“ the test requires that the following conditions are met: BUTTON PEEL RESULTS FOR ILOW SAMPLES: 1. No sign of fracture into the weld zone on 7 of the 10 test coupons. See pictures in Appendix IA. 2. The smallest button size defined by: D = ( min - min ) must exceed t
40、he minimum acceptable size in Table 3. c. If the above conditio ns for passing have been met, continue to reduce the welding current until the mean button size value, minus the value of 10 samples, reaches the minimum permissible value as listed in Table 3. Call this current I min . Record the actua
41、l current range ) I, defined by: I = I max - I min Note: If insufficient current range is encountered, then I min will be larger than I low (of paragraph b, above). I may still be recorded as shown, but the steel sample has then failed the current range test, which requ ired I to exceed the values o
42、f I min in Table 3. Even if min has been met, it is still necessary to determine I, because the following current level test may require a value of I larger than I min . (This explains why the values in Table 3 must not ne cessarily provide “overlap“.) FORD LABORATORY TEST METHOD BA 013-04 Page 8 of
43、 21 Copyright 2000, Ford Global Technologies, Inc. 5.3 Welding Current Level Test Determine from the previous measurements the following current values: I 1 = I max - 500 A I 2 = I min + 500 A “Passing“ requires that the nominal welding current I N of Table 3 lies between I 1 and I 2 , in other word
44、s, it is required that: I 1 greater than I N , and I 2 less than I N Note: For some thicknesses this condition can only be fulfilled if the actual current range I is greater than the minimum required value of min from Table 3. If the above condition for I 2 cannot be met, determine by means of anoth
45、er set of 10 test samples I min as described in para 5.2c above and see whether the current level can be met. Recording of Test Results Present the test results in tabulated form such as in dicated in applicable parts of Appendix III. (“Optional Supplier Data“ section.) 6. Welding Tests, Minor Test
46、Series This short form of the weldability test shall be followed to qualify all steels shipped and received, so as to assure compliance with th e previously established type approval for the steel. 6.1 Sample Preparation and Electrode Conditioning Follow the procedures of para 3.2 and 3.4 to prepare
47、 samples 25 x 100 mm (1.0 x 4.0 in) and condition the electrodes of the welder. 6.2 Welding Current Range Test a. Set welder for 30 cycle hold - time. Using small coupons (Table 1) page 10 and the appropriate welding schedule from Table 2, make 2 welds per coupon, 50 mm (2 in) apart, adjusting the w
48、elding current as required to produce the maximum possib le button size without producing expulsion on the second weld. Weld 6 consecutive samples without adjustment. There shall be no evidence of expulsion on any of the 6 welds. If expulsion occurs, lower current and repeat the test. Record the ass
49、ociated w eld current as the maximum value of the current range, I max . FORD LABORATORY TEST METHOD BA 013-04 Page 9 of 21 Copyright 2000, Ford Global Technologies, Inc. b. Reduce the welding current by the amount of the minimum specified current range I min selected from Table 3 for the appropriate type of steel and sample thickness. Call this value I low . We ld 10 samples at this lower current setting I low , then measure the size of the buttons after peeling. Measure only the minimum dimension, as sh
