1、 FORD LABORATORY TEST METHOD EU-BA 050-01 Date Action Revisions 2000 08 30 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockman 1994 02 28 Printed copies are uncontrolled Page 1 of 4 Copyright 2000, Ford Global Technologies, Inc. DETERMINATION OF CASE
2、DEPTH - THROUGH HARDENED GEARED PARTS Application This test method defines two alternative procedures for visual case depth determination of carburized/carbonitrided gears made from through hardening steels. Apparatus Required Cut-off Machine Mounting Press and Mounting Media or Steel Clamps Metallu
3、rgical Grinders With coolant supply or equivalent. Polishing Papers Grades 240 - 600 Polishing Machine 2 % Nital Etch Solution Concentrated nitric acid in alcohol. Dry Air Blast Metallurgical Microscope 100X magnification with optical measuring device Procedure A Low Powered Optical Measuring Device
4、 8X or 10X Procedure B Conditioning and Test Conditions All test values indicated herein are based on material conditioned i n a controlled atmosphere of 23 +/ - 2 C and 50 +/ - 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specif
5、ied. FORD LABORATORY TEST METHOD EU-BA 050-01 Page 2 of 4 Copyright 2000, Ford Global Technologies, Inc. Procedure A The case depth should be measured only on stress relieved p arts. Items in the as quenched condition should be stress relieved to the specified hardness prior to testing. 1. Cut a sam
6、ple from one tooth of the gear as shown in the following sketch (unless otherwise specified on the blueprint). Note: If no c oolant is applied during the abrasive cutting operation, care must be taken to ensure that the temperature of the sample does not exceed 100 C. 2. Clamp or mount the sample. 3
7、. Prepare sample using the conventional metallographic grinding and polishing methods. 4. Immerse in the 2 % nital etching solution for 10 seconds. (23 +/ - 2 C) 5. Rinse immediately with water, and then alcohol and finally dry with hot air. 6. Examine microstructure of the case under the microscope
8、 at 100X magnification using t he eyepiece. Procedure B This can be used for non stress relieved items. Prepare sample as for Procedure A, up to and including Step 3. Then: 4. Temper the prepared sample at approx 260 C. A bunsen flame or hotplate can be used. When an overall bl ue temper colour is a
9、chieved, the sample is immediately quenched in water. FORD LABORATORY TEST METHOD EU-BA 050-01 Page 3 of 4 Copyright 2000, Ford Global Technologies, Inc. 5. Repolish sample and etch in 2 % nital solution for approx 10 seconds. 6. Rinse immediately with water and then alcohol and finally dry with hot
10、 air. 7. Examine under the micro scope using an optical measuring device (preferably a 8X graduated eyepiece). Evaluation Case depth is to be measured normal to the surface at the pitch diameter in a plane normal to, and mid way along the tooth flank face, if the pitch diameter is not clearly define
11、d, as for bevel gears, then for case depth measuring purposes, the pitch diameter shall be taken at that point mid way between the apex and the root, measured on the thrust face of the gear tooth. Procedure A It is reported as the perpendi cular distance from the surface to the transition zone (to 0
12、.01 mm). The transition zone is defined as the position at which the martensite needles become indistinct, i.e. where the difference between the case and core microstructure is marked. FORD LABORATORY TEST METHOD EU-BA 050-01 Page 4 of 4 Copyright 2000, Ford Global Technologies, Inc. Procedure B Cas
13、e depth is reported as the dark etching carbon penetration layer measured at the pitch diameter in a plane normal to, and mid way along the tooth flank face. If the pitch diameter is not clearly defined as for bevel gears, then for case In cas es of dispute or for referee purposes, the hardness grad
14、ient method (to EU - BA 50 - 2) will be used. Therefore, laboratories using either of the two procedures noted above must ensure good correlation with EU - BA 50 - 2. Accuracy of Measurement Since the tran sition zone cannot be clearly defined, a measuring error of +/ - 0.025 mm is possible and must
15、 be taken into account. If case depth is 0.025 mm from the upper or lower tolerance limit of the specification, then the part shall be accepted. Whenever results are noted, using this test method, the accuracy (+/ - 0.025 mm) has also to be reported. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and ha ndling in its facilities.
