1、 Avoidance of Hydrogen Embrittlement of Steel SAE/USCAR-5 Revision 4 July 2012ISBN: 978-0-7680-2080-9 _ The research data, analysis, conclusion, opinions and other contents of this document are solely the product of the authors. Neither the Society of Automotive Engineers, Inc. (SAE) nor the United
2、States Council for Automotive Research (USCAR) certifies the compliance of any products with the requirements of nor makes any representations as to the accuracy of the contents of this document nor to its applicability for purpose. It is the sole responsibility of the user of this document to deter
3、mine whether or not it is applicable for their purposes. Copyright 2012 USCAR Printed in U.S.A. All rights reserved. QUESTIONS REGARDING THIS DOCUMENT: (248) 273-2470 FAX (248) 273-2494 TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX (724) 776-0790 SAE/USCAR-5 REVISION 4 Issued Reaffirmed 2012-07 AVOI
4、DANCE OF HYDROGEN EMBRITTLEMENT OF STEEL 1. SCOPE: This standard outlines the conditions that enhance the risk of hydrogen embrittlement of steel and define the relief procedures required to minimize the risk of hydrogen embrittlement. It is intended to control the process. 1.1 Hydrogen embrittlemen
5、t of steel, which can cause brittle fractures under stress, occurs as a result of the absorption of hydrogen during cleaning, phosphate coating and plating processes. The susceptibility to hydrogen embrittlement increases with increasing stress (internal or externally applied stress) and increasing
6、material strength. 1.2 Hardness readings in this specification are in Vickers scale. SAE J417 should be referred to for conversion to other scales. NOTE 1: All references to temperatures relate to part core temperature and not the indicated oven air temperature. Statistical data of verifications in
7、temperature at the center of the oven load and oven temperature shall be established to develop the oven profile. The temperature of parts in a batch type of baking furnace shall be monitored with a thermocouple placed in the middle of the load. For continuous bake ovens a temperature trace through
8、the oven must be run with a calibrated thermocouple in the lowest temperature position, at least once a year. 2. REFERENCES: 2.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J417 - Hardness Tests and Hardness Number Conversions. 3. REQUIREMENTS: The pa
9、rts shall be processed in accordance with this specification as applicable to minimize the risk of hydrogen embrittlement. Specific applications or customer requirements may require processing that goes beyond the requirements of this specification. 3.1 Cleaning Prior to Heat Treatment: All parts to
10、 be heat treated to a specified hardness (core or surface) greater than 353 HV must be cleaned prior to heat treatment to remove phosphate associated lubricant residues and detrimental contaminants from the surface. NOTE 2: The formation of a delta ferrite layer caused by the penetration of phosphor
11、us during the hardening process enhances the possibility of embrittlement. 1997-11SAE/USCAR-5 REVISION 4 Reaffirmed 2012-07 AVOIDANCE OF HYDROGEN EMBRITTLEMENT OF STEEL - 2 - 3.1.1 Acid Cleaning After Heat Treatment or Cold Working: Acid cleaning of parts to be heat treated to a specified hardness (
12、core or surface) greater than 353 HV or highly stressed cold worked parts enhances susceptibility to hydrogen embrittlement, and shall be minimized. If high hardness parts are to be acid cleaned, it is required that a procedure be established for processing the parts that limits the time in the acid
13、 bath to a maximum of 10 minutes. Parts which are acid cleaned and subsequently oiled, phosphated, mechanically (non-electrolytically) plated, or electroplated shall follow the requirements of 3.2, 3.3, 3.4, or 3.5, as applicable. All other partswhich are acid cleaned shall not be used for 48 hours
14、or alternately these parts shall be baked for 1 hour minimum at 110 5 C minimum following cleaning. 3.2 Oiled: All parts to be heat treated to a specified hardness (core or surface) greater than 353 HV, which are acid cleaned before application of oil shall not be used for 48 hours, or alternatively
15、 these parts shall be baked for 1 hour minimum at 110 C minimum after acid cleaning prior to oil application. 3.3 Phosphated: All parts to be heat treated to a specified hardness (core or surface) greater than 353 HV, which are acid cleaned and/or phosphate coated shall not be used for 48 hours, or
16、alternatively these parts shall be baked for 1 hour minimum at 110 C minimum following phosphate coating. 3.4 Mechanical Plated: All parts to be heat treated to a specified hardness (core or surface) greater than 353 HV which are acid cleaned before mechanical plating shall not be used for 48 hours,
17、 or alternatively these parts shall be baked for 1 hour minimum at 110 C minimum following mechanical plating. 3.5 Electroplated: The electroplated parts (see following table) shall be baked at a part core temperature of 200 C minimum. The 200 C core temperature shall be reached within 2 hours after
18、 completion of the electroplating process. No part shall take longer than 2 hours between receiving its plating layer and it attaining a core temperature of 200 C.3.5.1 Parts tempered or stress relieved above 200 CBaking times shall comply with table 1. Longer times at heat than those given may be n
19、ecessary if verification testing detailed in the Control Plan (see para 3.6) indicates a failure risk. Specified core or surface hardness Part core temperature Minimum bake time Less than 353HV Not applicable Bake not required 353HV to 390HV 200 C minimum 4 hours Greater than 390HV 200 C minimum 8 h
20、ours 3.5.2 Parts tempered or stress relieved below 200 CHardened parts which have been tempered or stress relieved at less than 200 C when electroplated shall be baked for 8 hours minimum at 110 C minimum. Longer times at heat than those given may be necessary if verification testing detailed in the
21、 Control Plan (see para 3.6) indicates a failure risk. 3.5.3.Tin or Tin Alloy Electroplated Coatings. Where tin or Tin alloy electroplated coatings are specified, relatively low, (near 200 C) de-embrittlement temperatures and longer times may be necessary to prevent Liquid Metal Embrittlement issues. In these cases the temperature and time shall be agreed between the coater and the end user, (Original Equipment Manufacturer). 3.6 Verification Test: The control plan shall include a verification test to demonstrate the effectiveness of de-embrittlement, such as SAE/USCAR-7.
