NAVISTAR MPAPS AT-2-2016 Determination of Austenite Grain Size by Thermal Etching.pdf

1、 This document is restricted and may not be sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2016 by Navistar, Inc. APRIL 2016 Page 1 of x NAVISTAR, INC. Material, Parts, and Process Specifications

2、 (MPAPS) NUMBER: MPAPS AT-2 Former Designation: CEMS AT-2 TITLE: Determination of Austenite Grain Size by Thermal Etching CURRENT REV No.: 1604 DATE: April 2016 WRITTEN/EDITED BY: J. Goldschmidt APPROVED BY: R. Goluch SUPERSEDES: Rev. 0110 October 2001 PRINTED COPIES OF THIS DOCUMENT MUST BE VERIFIE

3、D FOR CURRENT REVISION This specification may involve hazardous materials, equipment, and procedures. This specification does not purport to address all of the safety issues associated with its use. The user is responsible to consult appropriate safety and health practices and to determine the appli

4、cability of regulatory limits prior to use. Change Notice: Updated from CEMS to MPAPS format. 1.0 SCOPE This specification covers a procedure for the determination of austenitic grain size by thermal etching in a vacuum or inert atmosphere. 2.0 APPARATUS 2.1 Vacuum or inert atmosphere (nitrogen, arg

5、on, etc.) furnace capable of maintaining a temperature within 10C (18F) of the specified austenitizing temperature. 2.2 Metallographic equipment suitable to prepare a sample for normal metallographic examination. 2.3 Metallurgical microscope suitable for 100X magnification. 3.0 PROCEDURE 3.1 Cut and

6、 polish the specimen to produce a surface finish suitable for metallographic examination. 3.2 Heat the specimen in a vacuum or inert atmosphere to the appropriate temperature indicated below for 1 to 2 hours at temperature (8 hours if the steel is intended for carburized application). Carbon Content

7、 of Steel Specimen, % TEMPERATURE* C F For Carburized Applications 955 10 1750 18 0.25 or Less 0.26 thru 0.50 0.51 thru 0.80 Over 0.80 925 10 900 10 870 + 10 845 + 10 1700 18 1650 18 1600 18 1550 18 * Longer times at temperature may be necessary to delineate the grain boundaries, especially for stee

8、ls with the lower austenitizing temperatures. However, a minimum time required for delineation should be used because excessive time may result in grain growth. NUMBER: MPAPS AT-2 TITLE: Determination of Austenite Grain Size by Thermal Etching REVISION: 1604 This document is restricted and may not b

9、e sent outside Navistar, Inc. or reproduced without permission from Corporate Technical Standards. Suppliers are required to assume all patent liability. 2016 by Navistar, Inc. APRIL 2016 Page 2 of 2 3.3 Cool the specimen to room temperature under vacuum or inert atmosphere to prevent oxidation. For

10、 high hardenability steels, a very slow cooling rate may have to be used to avoid martensitic transformation at the surface which makes grain boundary delineation difficult. Transparent temper coloring which may appear on the surface is not detrimental. 3.4 Examine the specimen under a microscope at

11、 100X and rate the grain size as prescribed in ASTM E112. Any oxide network outlining the grain boundaries will invalidate the test, requiring the test to be rerun. 3.5 The temperatures shown in the above table are a guide and should be followed unless other test temperatures have been noted elsewhere. 4.0 REPORT Report the ASTM Grain size, including duplex grain sizes if applicable.