1、 FORD LABORATORY TEST METHOD EU-BA 050-02 Date Action Revisions 2000 08 30 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockman 1992 12 11 Printed copies are uncontrolled Page 1 of 5 Copyright 2000, Ford Global Technologies, Inc. DETERMINATION OF EFFEC
2、TIVE CASE DEPTH OF CASE HARDENED COMPONENTS Application This method is used for the determination of the effective case depth of carburized and carbo - nitrided parts, in the specified finished condition, by hardness gradient. Appli cation is limited to low alloy carburizing steel parts, with an eff
3、ective case depth above 0.25 mm where there is a difference in hardness of 100 HV between case and core. Apparatus Required Cut-Off Machine Mounting Press and Mounting Media Metallurgical Grinders or equivalent Polishing Papers - Grades 280 - 600 Polishing Machine Vickers Hardness Testing Machine Me
4、tallurgical Microscope with Calibrated Graticule Conditioning and Test Conditions All test values indicated herein are based on mater ial conditioned in 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 conditio
5、ns unless otherwise specified. FORD LABORATORY TEST METHOD EU-BA 050-02 Page 2 of 5 Copyright 2000, Ford Global Techn ologies, Inc. Procedure A. Sample Selection and Preparation 1. Unless otherwise specified, components shall be sectioned in such a manner as to permit measurement in the following po
6、sition: (a) Helical and Spur Gear Teeth Case depth is to be measured normal to 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 defined as for bevel gears, then for case depth measuring purposes, it shall be taken as tha
7、t point mid way between apex and root, measured on the thrust face of the gear tooth. (b) Ge ar End (Thrust) Faces Normal to the surface at the mid - width position in a radial plane parallel to the axis of the gear (see Sketch 2). (c) Shafts, Bearing Journals and Pins Normal to the surface at a pos
8、ition one third along the length of the shaft or j ournal and in a plane normal to the axis of the shaft or journal (see Sketch 3). (d) Other Components Normal to the surface, position is dependent on the function of the component. 2. Cut a specimen approximately 10 mm thick from the component under
9、 test in the specified area, avoiding any overheating/burning or rounding of edges. 3. Mount the specimen in the media and then polish the relevant surface, using the polishing papers and machine, ensuring that the finish surface is suitable for microscopic ex amination. B. Hardness Determination (S
10、ee Page 5, Figure 1) 1. Preferably with the specimen in the unetched condition, determine the hardness of the case using the Vickers machine with a 5 kgf load at regular intervals from the surface of the specimen, e nsuring that: (a) All impressions are within a band normal to the surface and of 2 m
11、m maximum width. (b) The first impression is a minimum of 0.2 mm from the surface. (c) The distance from the center of any impression to the next impression is not less than 2 1/2 times the diagonal of the impression. FORD LABORATORY TEST METHOD EU-BA 050-02 Page 3 of 5 Copyright 2000, Ford Global T
12、echn ologies, Inc. (d) The difference between the distances of consecutive impressions must not exceed 0.1 mm. (e) A minimum of five impressions are taken and that these span the depth of the effective case. (f) The avera ge value of the two diagonals of each impression is taken to calculate HV. (g)
13、 The distance of individual impressions from the surface of the component must be measured with an accuracy of 0.025 mm. (h) Hardness difference between case and core is in exc ess of 100 HV. Note: A 5 kgf load is preferred to minimize errors in reading the diagonals of the HV impressions but a mini
14、mum band width of 1.3 mm is necessary. Impressions with a 1 kgf load may be positioned in two parallel lines of 0.2 mm minimum dis tance apart. Evaluation (See Page 5, Figure 2) Plot a curve representing change in hardness in relation to the distance from the surface of the specimen. The effective c
15、ase depth is then determined by interpolating the depth at which a specific hardness value occurs (see Fig. 2). The hardness values for the various grades of steel are as follows: Nominal Carbon Content Of Base Material Effective Case Depth Hardness Maximum Permissible Core Hardness Less than 0.25 %
16、 550 HV 450 HV 0.26 0.32 % 600 HV 500 HV Over 0.33 % 650 HV 550 HV Note: Report effective case depth, and unless specified, state where and in which way the determination has been made. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each par
17、ty is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD EU-BA 050-02 Page 4 of 5 Copyright 2000, Ford Global Techn ologies, Inc. DETERMINATION OF EFFECTIVE CASE DEPTH OF CASE HARDENER COMPONENTS FORD LABORATORY TEST METHOD EU-BA 050-02 Page 5 of 5 Copyright 2000, Ford Global Techn ologies, Inc. DETERMINATION OF EFFECTIVE CASE DEPTH OF CASE HARDENER COMPONENTS Figure 1 Position of Hardness Test Impressions (Minimum 5 impressions must be taken) Figure 1 Interpolation of Effective Case Depth
