1、WORLDWIDEENGINEERINGSTANDARDSTest Procedure GMW14731Stress-Corrosion Cracking of Copper Based Alloys Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Originating Department: North American Engineering Standards Page 1 of 41 ScopeNote: Nothing in this standard supercedes applicab
2、le laws and regulations.Note: In the event of conflict between the English and domestic language, the English language shall takeprecedence.1.1 Purpose. Stress-corrosion cracking (or, as it is alternatively known, season cracking) is failure by crackingunder the combined action of corrosion and stre
3、ss - either external (applied stress) or internal (residual stress).1.2 Foreword. Not applicable.1.3 Applicability. This test method shall be used to determine the susceptibility of formed components andsemi-finished products made from copper based alloys, especially copper-zinc alloys, to stress-co
4、rrosioncracking.This test is carried out by exposing sample components to suitable corrosive media under controlled conditionsfor specified time periods and subsequently examining for induced cracking.Two alternative methods are described:x Method A using an atmosphere of ammonia as the corrosive me
5、dium.x Method B using acidic mercurous nitrate as the corrosive medium.2 ReferencesNote: Only the latest approved standards are applicable unless otherwise specified.2.1 External Standards/Specifications.None2.2 GM Standards/Specifications.None2.3 Additional References.Guidance Note EH17 from the He
6、alth and Safety Executive3 Resources3.1 Facilities. Not applicable.3.2 Equipment.3.2.1 Apparatus. Test vessel made of glass and of suitable size to contain test piece and requisite volume oftest medium.In the case of Method A, the test vessel (approximately 150 mm high) must be fitted with a gas tig
7、ht sealedglass lid and a suitable glass grid or frame to allow suspension of the test piece above the test medium.Laboratory hot plate or oven fitted with an efficient extraction system (for Method B).Suitable magnifying aid giving magnification of 10x.3.2.2 Test Solution. For preparing the test sol
8、ution reagent grade constituents are required and distilled ordeionized water shall be used.3.2.2.1 Method A Solution. Ammonia solution, 25% by weight, shall be diluted with water to volume relation1 + 1 (density at +20 C = 0.946 g/cm3 to 0.950 g/cm3).Copyright General Motors Company Provided by IHS
9、 under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14731 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 2 of 43.2.2.2 Method B Solution. Mercurous nitrate solut
10、ion containing 10 g HgNO3 and 10 mL HNO3 (specificgravity of 1.421) per liter is used.Prepared as follows: Dissolve either 11.4 g of HgNO3*2H2O or 10.7 g of HgNO3*H2O (equivalent to 10.7 g Hg2(NO3)2 x 2H2O) in approximately 40 mL of water acidified with 10 mL HNO3 (specific gravity of 1.421). Whencr
11、ystals have completely dissolved, dilute the solution with water to 1000 mL.Sulphuric acid, approximately 10% by weight.Nitric acid, approximately 30% by weight.3.3 Test Vehicle/Test Piece. The test piece wherever possible shall be the finished part. If thee size, shape,etc. of the finished part be
12、impracticable, then a suitable section should be taken from the part for testingpurposes. This section must be representative of maximum deformation encountered in forming of the part,and sectioning must be conducted in such a manner so as to minimize any relaxation of internal stresscontained withi
13、n the part.In the case of testing semi-finished products, suitable sections shall be used.For initial sample approval and arbitration purposes, at least three test pieces shall be tested. For routinequality control at least one test piece shall be tested.3.4 Test Time.3.4.1 Method A Test Time.Calend
14、ar time: 1 to 3 daysTest hours: 24 hours (maximum)Coordination hours: 2 hours3.4.2 Method B Test Time.Calendar time: 1 dayTest hours: 30 minutesCoordination hours: 2 hours3.5 Test Required Information. Not applicable.3.6 Personnel/Skills. Not applicable.4 Procedure4.1 Preparation.4.1.1 Test Piece Pr
15、eparation. The test piece shall be cleaned by degreasing in a suitable alkaline cleaner ororganic solvent and, if necessary, immersed for approximately 30 s in either sulphuric acid or nitric acid andsubsequently washed in clean running water to remove any adhered oxides and prior to test shall be d
16、ried.Surface coatings when present on test pieces shall be removed by suitable means before testing.For testing of semi-finished products or semi-finished product parts, the test piece, wherever possible, shall bepre-stressed such that the magnitude and direction of the applied stress shall equal th
17、at occurring within thefinished part. If this is impracticable, then the test piece shall be loaded such that the induced stress equalsapproximately 40% of the average ultimate tensile stress of the material under test.Note where used, any test piece clamping shall be effectively sealed against infl
18、uence of the test media.4.2 Conditions.4.2.1 Environmental Conditions. Unless otherwise specified the test shall be performed at a temperature of23 C 5 C.4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Suchrequirements shall be specified on compo
19、nent drawings, test certificates, reports, etc.4.3 Instructions.4.3.1 Method A Instructions. The test vessel shall be filled with test medium to a depth of approximately30 mm. The cleaned test piece shall be suspended at a height of 50 mm above the surface of the test mediumand the test vessel seale
20、d.Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14731 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 3 of 4
21、The test may be suspended (in instances when the exposure time exceeds the 8 h working day) by storing thetest piece overnight (16 h) in deionized water followed by re-exposure after drying.Upon completion of the required exposure time the test piece shall be pickled in either sulphuric acid or nitr
22、icacid at 23 C 5 C for 30 s to 60 s.4.3.2 Method B Instructions. The cleaned test piece shall be totally immersed in test medium contained inthe test vessel (using at least 1.5 mL of test medium per 100 mm2 of exposed test piece surface). After aperiod of 30 minutes 1 minute, the test piece shall be
23、 removed, washed in running water and any excessmercury wiped from the surface. To facilitate crack detection, the test piece may be heated on a hot plate or inan oven to volatilize the adherent film of mercury.Note: Due to the toxicity of mercury, heating shall be carried out in fume cupboard provi
24、ded with local exhaustventilation and having an air speed greater than 42.6 m/minutes across the opening. Spillages must becleaned up immediately. For further details regarding mercury-health and safety precautions, see GuidanceNote EH17 from the Health and Safety Executive or other legal precaution
25、s.5 Data5.1 Calculations. Not applicable.5.2 Interpretation of Results.5.2.1 Evaluation. Test pieces to both methods (A and B) shall be subsequently examined for cracks with theaid of the magnifying equipment.Test pieces shall be free from cracks.5.3 Test Documentation. The test documentation shall
26、contain at least 5.3.1 thru 5.3.9.5.3.1 All details necessary to identify the material/part.5.3.2 The type of coating, with an identification of its surface finish.5.3.3 Number of the test specimens of each coating or product subjected to the test.5.3.4 Dimensions and shape of the test specimens and
27、 the nature and area of the surface tested.5.3.5 Pretreatment of the test specimens, including any cleaning treatment applied and any protection given toedges or other special areas.5.3.6 Method, if any, used to clean the test specimens after test with, when appropriate, an indication of theloss of
28、mass resulting from the cleaning operation.5.3.7 If method A is used: Exposure period for each cycle and the number of cycle.5.3.8 A reference to this specification.5.3.9 Result of all inspections.6 SafetyThis standard may involve hazardous materials, operations, and equipment. This standard does no
29、t propose toaddress all the safety problems associated with its use. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and determine the applicability of regulatory limitations priorto use.7 Notes7.1 Glossary. Not applicable.7.2 Acronyms, Abbre
30、viations, and Symbols. Not applicable.8 Coding SystemThis standard shall be referenced in other documents, drawings, etc., as follows:Test to GMW14731Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted withou
31、t license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14731 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 4 of 49 Release and RevisionsThis standard was originated in October 2005. It was first approved by the Global Laboratory CorrosionTesting Harmonization Team
32、in December 2006. It was first published in August 2007.Issue Publication Date Description (Organization)1 AUG 2007 Initial publication.2 OCT 2012 Update template, references and technical content as needed for 5 year refresh.(Non-ferrous Metals and Castings GSSLT)Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
