1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards METHOD OF HARDENABILITY TEST FOR STEEL EDS-T-7102 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 EDS-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 1/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006
2、. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 1. SCOPE This standard specifies the method of hardenability test for steel based on JOMINYs end quenching method. 2. APPARATUS FOR QUENCHING 2.1. Support for test piece Test piece shall be supported vertically and its lower end to be quenched shall po
3、sition rightly 12.50.5mm above the orifice. Test piece EDS-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 2/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 2.2. Apparatus for cooling spray The apparatus shall make water to spout up from the mouth of
4、the pipe of 12.5 0.5mm inside diameter to the free height of 65 10mm. The stream of water shall be controlled to attain the specified free height immediately after the commencement of water cooling, and the free stream height shall be kept steady during the cooling process. For this purpose, the tan
5、k with the overflow apparatus shall be used, and plate may be preferably inserted between the test piece and the orifice as the stopping device for stream of water. 3. TEST PIECE 3.1. Dimensions Remark) The shape and dimensions of the portion marked with - - may be altered as required(Unit: mm). 3.2
6、. Preparation When the steel material is 50mm or less in diameter, the test specimen shall be used as it is. For steel more than 50mm in diameter, the test specimen shall be forged or rolled to 30mm in diameter. The test specimen thus obtained shall be normalized for 60minutes at a temperature as sh
7、own in the Table, removed the decarburized layer from the surface, and then finished to the specified dimensions. The end of the specimen to be water cooled shall be precision finished. The normalizing process, however, may be omitted when agreed. In addition, any heat treatment other than normalizi
8、ng applied to the specimen or any heat treatment applied to the test piece shall be reported as the heat treating record in the test report. For the steel material more than 50mm in diameter, when agreed, there are two alternative methods for making the test piece. A specimen of 50mm diameter is mac
9、hined directly from the steel material to make the test piece of specified dimensions after having been normalized as mentioned above, thus omitting the forging and rolling process, or the test piece of specified dimension is machined out directly from this steel material. However, in either case, t
10、he position of the test specimen or test piece taken from the steel material shall be clearly indicated. EDS-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 3/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology Table. Normalizing and Quenching Temperature
11、s for Test Specimen or Test Piece Specified value or the maximum value of chemical composition Ni% C% Normalizing temperature Quenching temperature 0.25 max. 925 925 0.26 0.36 900 870 3.00 max. 0.37 min. 870 845 0.25 max. 925 845 0.26 0.36 900 815 3.00 max. 0.37 min. 870 800 Spring Steel(SUP6, SUP7,
12、 SUP9, SUP10 EDS-M-1801, SPS7 : KSD 3701) 900 870 Aluminum Chrome molybdenum steel materials (KSD3756) 980 925 Remark) Tolerance on temperatures mentioned above shall be 5. 4. QUENCHING METHOD 4.1. Heating procedure The test piece shall be heated in a furnace being kept at a temperature given in the
13、 Table, and heated to be of uniform temperature from the surface to the centre, then kept at the temperature for 30 5 minutes. However, other quenching temperatures may be applied by agreement. The minimum necessary heating time shall be predetermined on the basis of the result of temperature measur
14、ement using a thermocouple buried in the centre part of the test piece. An adequate method1)shall be applied at the time of heating in order that the end of the test piece may be left free from scale, and that it may prevent oxidization and decarburization to such an extent that the decarburized lay
15、er beneath the surface to be measured may be completely removed by grinding. Note 1)Application of a protective gas, embedment of the end to be quenched in graphite or chips of cast iron, or application of a special heat resisting steel cap onto the end. 4.2. Quenching procedure The test piece heate
16、d to a quenching temperature shall be installed vertically on the support, stopping device for stream of water shall be opened immediately, and then the test piece shall be cooled for 10 minutes at least until it cools completely. Afterwards, the test piece may be cooled in water. The support for th
17、e test piece shall not be wet when the quenching starts. The time between taking out the test piece from the heating furnace and the starting the quenching shall be as short as possible so that the time will be within 5 seconds. 4.3. Quenching medium Water at a temperature of 5 30 shall be used. EDS
18、-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 4/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 5. MEASURING METHOD OF HARDNESS 5.1. After being cooled, the test piece shall be ground at 2 positions 180oapart to remove 0.4mm each in thickness along
19、 its overall length, and 2 planes this obtained shall be subjected to hardness measurement. For the test piece machined directly from the steel material with more than 50mm in diameter, the hardness measurement shall, in general, be made to planes equally distant from the axis of original steel mate
20、rial. 5.1.1. On grinding the test piece, care shall be taken to prevent any structural change being caused by the grinding heat. Figure 1. Grinding fixture 5.1.2. Structural change caused by grinding shall be detected as follows. (1) Etching reagent First reagent : Nitric acid(specific gravity 1.42)
21、5%+water 95% Second reagent : Hydrochloric acid(specific gravity 1.18)50% + water 50% (2) Procedure After being washed with hot water, the test piece shall be etched with the first reagent until the reagent changes black in color (for about 30-60 seconds). It is then rinsed with hot water, and dippe
22、d in a second reagent for 3 seconds. It is rinsed again with hot water and lightly blow-dried for detection. The presence of bright or dark spots on the etching surface indicates that the hardness and structure has been changed during grinding. The changed structure caused by grinding shall be remov
23、ed before testing the hardness. For this purpose, refinishing and reetching shall be applied, but, when the structural change is too conspicuous, fresh test planes shall be prepared for hardness measurement. 5.2. Hardness measuring points shall be 1.59mm(1.16“) apart from the quenched end in axial d
24、irection of the test piece. For drawing of the hardenability curve, measuring points shall be 1/16“-2/16“-3/16“-4/16“-5/16“-6/16“-7/16“-8/16“-9/16“-10/16“ from the quenched end and at 2/16“mm intervals thereafter. 5.3. Hardness measurement may be commenced from either side, from the quenched end or
25、the opposite side. EDS-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 5/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 5.4. Hardness measurement shall be Rockwell C hardness or Vickers hardness. For hardness measurement, test base shall be used to h
26、old correct measuring points and V block is not suitable for application. Figure 2. Test base for hardness test 6. RECORD Mean values of harnesses measured at each corresponding point on both test planes of the test piece shall be obtained and the hardness transfer along axial direction shall be plo
27、tted in hardenability2)chart shown in Appendix. Ordinate of the chart shows the mean value of measured hardness of corresponding points and abscissa the distance measured from the quenched end to the measuring points. In addition, steel charge number, austenite grain size(grain number and measuring
28、method), chemical composition, heat treatment temperature, sampling position of the test piece, water temperature and other special heat treatment shall be recorded. Note2)In Hardenability chart, either Rockwell hardness C scale or Vickers hardness scale may be omitted, and ordinate per abscissa rat
29、io shall be 2:3. For the presentation of hardenability, hardenability chart or hardenability index shall be used. Hardenability index shall be indicated by the hardness at a point of a predetermined distance(3 points) apart from the quenched end, or by the distance measured from the quenched end to
30、a point having a predetermined hardness. For hardenability presentation by hardenability index, the hardness notation may be omitted, when measured in Rockwell hardness. Examples) When the hardness of the point 12mm apart from the quenched end is HRC 36, or HV 354: J12mm = HRC 36, J12mm = 36 or J12 mm = HV 354 EDS-T-7102METHOD OF HARDENABILITY TEST FOR STEEL PAGE: 6/6 ISSUED DATE: 1988. 11. 18 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology Appendix
