1、Designation: B 849 02 (Reapproved 2007)Standard Specification forPre-Treatments of Iron or Steel for Reducing Risk ofHydrogen Embrittlement1This standard is issued under the fixed designation B 849; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONWhen atomic hydrogen enters steels and certain other metals, for example, aluminum and ti
3、taniumalloys, it can cause a loss of ductility, load carrying ability, or cracking (usually as submicroscopiccracks) as well as catastrophic brittle failures at applied stresses well below the yield strength or eventhe normal design strength for the alloys. This phenomenon often occurs in alloys tha
4、t show nosignificant loss in ductility, when measured by conventional tensile tests, and is referred to frequentlyas hydrogen-induced delayed brittle failure, hydrogen stress cracking, or hydrogen embrittlement. Thehydrogen can be introduced during cleaning, pickling, phosphating, electroplating, au
5、tocatalyticprocesses, porcelain enameling, and in the service environment as a result of cathodic protectionreactions or corrosion reactions. Hydrogen can also be introduced during fabrication, for example,during roll forming, machining, and drilling, due to the breakdown of unsuitable lubricants as
6、 well asduring welding or brazing operations. Parts that have been machined, ground, cold-formed, orcold-straightened subsequent to hardening heat treatment are especially susceptible to hydrogenembrittlement damage.The results of research work indicate that the susceptibility of any material to hyd
7、rogenembrittlement in a given test is related directly to its trap population. The time-temperaturerelationship of the heat treatment is therefore dependent on the composition and structure of steels aswell as plating metals and plating procedures. Additionally, for most high-strength steels, theeff
8、ectiveness of the heat treatment falls off rapidly with a reduction of time and temperature.1. Scope1.1 This specification covers procedures for reducing thesusceptibility or degree of susceptibility to hydrogen embrittle-ment or degradation that may arise in electroplating, autocata-lytic plating,
9、porcelain enameling, chemical conversion coat-ing, and phosphating and the associated pretreatmentprocesses. This specification is applicable to those steels whoseproperties are not affected adversely by baking at 190 to 230Cor higher (see 6.1.1).1.2 The heat treatment procedures established herein
10、havebeen shown to be effective for reducing the susceptibility ofsteel parts of tensile strength 1000 MPa or greater that havebeen machined, ground, cold-formed, or cold-straightenedsubsequent to heat treatment. This heat-treatment procedure isused prior to any operation capable of hydrogen charging
11、 theparts, such as the cleaning procedures prior to electroplating,autocatalytic plating, porcelain enameling, and other chemicalcoating operations.NOTE 11 MPa = 145.1 psi.1.3 This specification has been coordinated with ISO/DIS9587 and is technically equivalent.1.4 The values stated in SI units are
12、 to be regarded as thestandard.2. Referenced Documents2.1 ASTM Standards:A 919 Terminology Relating to Heat Treatment of Metals2B 242 Guide for Preparation of High-Carbon Steel forElectroplatingB 322 Guide for Cleaning Metals Prior to ElectroplatingB 374 Terminology Relating to ElectroplatingB 851 S
13、pecification forAutomated Controlled Shot Peening1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.02 on Pre Treatment.Current edition approved June 1, 2007. Published June 2007. Originallyapprove
14、d in 1994. Last previous edition approved in 2002 as B 849 02.2Discontinued 1999; see 1999 Annual Book of ASTM Standards , Vol 01.02.Replaced by Terminology A 941.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of Metallic Articles P
15、rior to Nickel, Autocatalytic Nickel,or Chromium Plating, or as Final Finish2.2 ISO Standards:ISO 2080 Electroplating and Related ProcessesVocabulary3ISO/DIS 9587 Pre-Treatments of Iron or Steel for Reducingthe Risk of Hydrogen Embrittlement32.3 Federal Standard:QQ-C-320 Chromium Plating (Electrodep
16、osited)43. Terminology3.1 DefinitionsMany of the terms used in this specifica-tion can be found in Terminology B 374, A 919,orISO 2080.4. Requirements4.1 Heat treatment shall be performed on basis metals toreduce the risk of hydrogen embrittlement in accordance withTable 1. The duration of heat trea
17、tment shall commence in allcases from the time at which the whole of each part attains thespecified temperature.4.2 Parts made from steel with actual tensile strengths $1000 MPa (with corresponding hardness values of 300HV10kgf, 303 HB, or 31 HRc) and surface-hardened parts shallrequire heat treatme
18、nt unless Class SR-0 is specified. Prepara-tion involving cathodic treatments in alkaline or acid solutionsshall be avoided.4.3 Table 1 lists the stress-relief heat-treatment classes to bespecified by the purchaser to the electroplater, supplier, orprocessor on the part drawing or purchase order. Wh
19、en nostress relief treatment class is specified by the purchaser, ClassSR-1 shall be applied (see Note 4).NOTE 2The treatment class selected is based on experience with thepart, or similar parts, and the specific alloy used or with empirical testdata. Because of factors such as alloy composition and
20、 structure, size,mass, or design parameters, some parts may perform satisfactorily with nostress relief treatment. Class SR-0 treatment is therefore provided for partsthat the purchaser wishes to exempt from treatment.NOTE 3The use of inhibitors in acid pickling baths is not necessarilyguaranteed to
21、 minimize hydrogen embrittlement.NOTE 4Class SR-1, the longest treatment, is the default when thepurchaser does not specify a class. The electroplater, supplier, or processoris not normally in possession of the necessary information, such as designconsiderations, induced stresses from manufacturing
22、operations, etc., thatmust be considered when selecting the correct stress relief treatment. It isin the purchasers interest that their part designer, manufacturing engineer,or other technically qualified individual specify the treatment class on thepart drawing or purchaser order in order to avoid
23、the extra cost of thedefault treatment.5. Categorization of Steels5.1 With the exception of surface-hardened parts, heattreatment conditions shall be selected on the basis of actualtensile strength. When only the minimum tensile strength isspecified, or if the tensile strength is not known, the heat
24、treatment condition shall be selected by relating known ormeasured hardness values to equivalent actual tensilestrengths. The tensile strength shall be supplied by the pur-chaser.5.2 Steels that have been wholly or partly surface hardenedshall be considered as being in the category appropriate to th
25、ehardness of the surface-hardened layer.6. Stress Relief6.1 For high-strength steels, the following conditions apply.Stress relief treatment is not essential for steels of actual tensilestrength below 1000 MPa. The conditions given in Table 1 areapplied for steels of actual tensile strength above 10
26、00 MPa.The heat treatment shall be conducted before the commence-ment of any preparations or cleaning treatments using pro-cesses liable to cause embrittlement such as cathodic electro-cleaning or acid pickling. Other cleaning processes, such asthose described in Practices B 242 or B 322, may be use
27、d.6.1.1 Suitable combinations of a shorter time at appropriatehigher temperatures may be used if they have been shown notto be detrimental. For tempered steels, items shall not be heatedabove a temperature that shall be at least 50C below thetempering temperature.6.1.2 If stress relief is given afte
28、r shot peening in accor-dance with Specification B 851 or other cold working pro-cesses to introduce beneficial compressive stresses, the tem-perature shall not exceed 230C.6.1.3 Items having surface-hardened areas that would sufferan unacceptable reduction in hardness by treatment in accor-dance wi
29、th Table 1 shall be heat-treated at a lower temperature,but not below 130C, for a minimum period of 8 h. Thistreatment is applicable for items made of steel with actualtensile strengths below 1400 MPa.7. Keywords7.1 delayed brittle failure; heat treatment; hydrogen em-brittlement; hydrogen induced c
30、racking; hydrogen stress crack-ing; pre-treatments of iron or steel; stress relief3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbin
31、s Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.TABLE 1 Classes of Stress Relief Requirements for High-Strength Steels (See Sections 4 through 6 for Details on theUse of Table 1)ClassStress-Relief Heat-Treatment Classes for High-Strength SteelsSteels of Tensile Strength(Rm), MPaTemper
32、ature,CTime, hSR-0 not applicableSR-1 over 1800 200230 min 24SR-2Aover 1800 190220 min 24SR-3 1401 to 1800 200230 min 18SR-4A1450 to 1800 190220 min 18SR-5A1034 or greater 177205 min 3SR-6 1000 to 1400 200230 min 3SR-7A1050 to 1450 190220 min 1SR-8 surface-hardened parts # 1400 130160 min 8AClasses
33、SR-2, SR-4, SR-5, and SR-7 are traditional treatments used inFederal Standard QQ-C-320. They do not apply to any other standard.B 849 02 (2007)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of t
34、his standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five y
35、ears andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical comm
36、ittee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B 849 02 (2007)3
