1、 FORD LABORATORY TEST METHOD EU-BA 053-01 Date Action Revisions 2000 08 22 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockma n 1993 01 04 Printed copies are uncontrolled Page 1 of 3 Copyright 2000, Ford Global Technologies, Inc. MICROSCOPICAL METHOD
2、OF MEASURING DECARBURIZATION ON SPRING STEELS Application This method is used to determine the depth of decarburization in hardened and tempered spring steels. Chemicals and Apparatus Required 1. Normal metallographic cutting, mo unting, grinding and polishing equipment necessary to take samples fro
3、m the springs and prepare the surface for microscopical examination. 2. 2 % solution of nitric acid in alcohol, or other suitable etching reagent. 3. A microscope capable of magnifying at X100 and being able to be used to make measurements at this magnification. Conditioning and Test Conditions All
4、test values indicated herein are based on material 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 conditions unless otherwise specified. Definitions Complete Decarburization A virtually complet
5、e loss of carbon from the surface layer. (See “Microscopical Method“ for the practical met hod of depth determination. Partial Decarburization Any measurable loss of carbon content less than complete, with respect to the carbon level of the base material. Total Decarburization The sum of both the co
6、mplete and partial decarburization. FORD LABORATORY TEST METHOD EU-BA 053-01 Page 2 of 3 Copyright 2000, Ford Global Technologies, Inc. Method Procedure The area to be examined shall be either a transverse or longitudinal section cut at right angle* to the surface. *Right angle is defined as being a
7、s close to 90 deg as is practical within the range 80 - 100 deg. Coil Springs A transverse secti on shall be taken from an active coil. Decarburization depth shall be the average of 4 measurements taken at 90 deg angles to each other. One of the measurement positions shall be at that position which
8、has the deepest decarburization anywhere around the perimeter of the transverse section. FORD LABORATORY TEST METHOD EU-BA 053-01 Page 3 of 3 Copyright 2000, Ford Global Technologies, Inc. The specimens must be prepared for examination using good metallographic techniques and the surface prevented f
9、rom rounding. Mounting in a suitable plastic material is recommended. After grinding and polishing t o give a virtually scratch free finish the specimens should be etched in 2 % nitric acid alcohol solution or other suitable etching solution for sufficient time to fully develop the microstructure. E
10、valuation of Decarburized Depth The surface being examin ed must be viewed at a minimum magnification of X100. Complete Decarburization Depth This is the depth, measured at right angles* to the surface, of the zone which contains at least 90 % of ferrite. Partial Decarburization Depth The depth of p
11、artial deca rburization is defined as that position at which a microstructural change is evident between the core and the partially decarburized surface. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities.
