机械镀锌资料-英文版

This standard is under the fixed designation B-695; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. Anumber in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1、 Scope 1.1 This specification covers the requirements for a coating of zinc mechanically deposited on iron and steel basis mctals. The coating is provided in several thicknesses up to and including 107 μm. The seven thickest classes are ususlly referred to as “mechanically galvanized.’’ 1.2 This standard does not purport to address all of the safety concerns, if any associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Note 1—The performance of this coating complies with the requiremcnts of Specification A 153 and MIL-c-81562. 1.3 The values stated in SI units are to be regarded as the standard. The inch-pound equivalents of SI units may be approximate. 2. Referenced Documents 2.1 ASTM Standards: A 153 Spedification for Zinc coating (Hot-Dip) on lron and Steel Hardware2 A 194/A 194M Specification for Carbon and Alloy Steel Nuts of Bolts for High-Pressure and High-Temperature Service3 A 325 Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensilc Strength4 A 490 Specification for Heat-Treated, Steel Structural Bolts,150 ksi Mimimum Tensile Strength4 A 563 Specification for Carbon and Alloy Steel Nuts4 B 117 Practice for Operating Salt Spray (Fog) Apparatus5 B 183 Practice for Preparation of Low-carbon steel for electroplating6 B 242 Practice for Preparation of High-carbon steel for electroplating6 B 322 Practice for Cleaning Metals Prior to Electroplating6 B487 Test Method for Measurement of Metal and Oxide Coating Thicknesses by Microscopical examination of a Cross Section6 B 499 Test Method for measurement of Coating Thicknesses by the Magnetic Method: Nonmagetic Coatigs on Magnetic Basis Metals6 B 571 Test Methods for adhesion of Metallic Coatings6 B 602 Test Method for attribute Sampling of Metallic and inorganic Coatings6 F 1470 Guide for Fastener sampling for Specified Mechanical Properties and Performance lnspeetion7 2.2 Military standard: MIL-c-81562 Coating, Cadmium,tin cadmium and Zine (mechanically deposited)8 2.3 AISC Standard: Specifications for Structural Joints Using ASTM A 325 or A 490 Bolts9 3. Classification 3.1 Classes—Zinc coatings are classified on the basis of thickness, as follows: Class minimum Thickness, μm 110 107 80 81 70 69 65 66 55 53 50 50 40 40 25 25 12 12 8 8 5 5 3.2 Types—Zinc coating are identified by types on the basis of supptementary treatment required, as follws: Type 1—As coated, without supplementary treatment (Ap-pendix X2.1) Type 11—With colored chromate conversion treatment (Appendix X2.2). 4. Ordering information 4.1 To make the application of this standard complete, the purchaser should supply the following information to the seller in the purchase order or other governing document: 4.1.1 Class, including a maximum thickness, if appropriate, type, and for type II, color and need for supplemental lubricant (3.1,3.2and6.2.5). 4.1.2 Nature of substrate (for example, High-strength steel), need for stress relief (6.2.1), and cleaning precautions to be followed (6.2.2 and 6.2.3) 4.1.3 significant surfaces (6.3). 4.1.4 requiremcnts for and methods of testing for one or more of the following, if required:need for and type of test specimens (8.1), thickness (6.3 and 8.3),adhesion (6.4 and 8.4),corrosion resistance (6.5 and 8.5), adsence of hydrogen embrittlement,and the waiting period before testing and testing loads(6.6 and 8.6). 4.1.5 Inspestion responsibility (Section II) and sampling plan for each inspection criterion (section 7),and 4.1.6 Requirements for certified report of test results (Section 10). 5. Workmanship 5.1 The coating shall be uniform in appearance and substantially free of blisters. Pist, noduses, flaking, and other defects that can adversely affect the function of the coating. The coating shall cover all surfaces as stated in 6.3 including rools of threads, thread peaks, corners, recesses, and edges. The coating shall not be stained or discolored throughout to an extent that would adversely affect appearance as a functional requirement. However superficial staining, that results from rinsing or drying, and variations in color or luster shall not be cause for rejection. Note 2—The nature of the mechanical plating process is such that coatings characteristically will not be as smooth or as bright as some electroplated coatings. 6. Requirements 6.1 Appearance—The coating as deposited shall have a uniform silvery appearance, and a matte to medium-bright luster. 6.2 6.2 Process: 6.2.1 Stress-Relief Treatment—All steel parts that have an ultimate tensile strength of 1000 Mpa and above and that contain tensile stresses caused by machining, grinding, straightening, or cold-forming operation shall be given a stress-relief heat treatment prior to cleaning and metal deposition. The temperature and time at temperature shall be 190±15℃ for a minimum of 3 h so that maximum stress relief is obtained without reducing the hardness below the specified minimum. 6.2.2 High-strength steels (which become embrittled when charged with hydrogen) and that have heavy oxide or scale shall be cleaned before application of the coating in accordance with Practice B 242. In general, nonelectrolytic alkalinc, anodic-alkaline, and some inhibited acid cleaners are preferred to avoid the risk of producing hydrogen embrittlement form the cleaning prccedure. 6.2.3 For low-carbon steels, see Practice B 183. useful guidelines are also given in Practice B 322. 6.2.4 Mechanical deposition of zinc coatings shall consist, in general, of all of the steps listed below, and in the sequence as shown: 6.2.4.1 Preparation of the surface of the parts to be coated, by chemical (generally acidic) procedure to an extent that permits uniformly satisfactory results from subsequent steps. 6.2.4.2 Deposition of a thin metal coating, generally of copper, by immersion in appropriate chemical solutions, without the use of clectric current. There are no thickness requirements for this coating. 6.2.4.3 Tumbling of the parts that have been treated according to 6.2.4.1 and 6.2.4.2 in a container with the following: (i) the zinc metal to be deposited, in powder form; (ii) impact media, which may be glass or other substances that are essentially inert to the chemicals of the deposition process. The function of this media is to aid in providing mechanical forces to drive the metal powder onto the substrate parts; (iii) a “promoter” or “accelerator” which aids in the uniform deposition of the metal powder; (iv) a liquid medium, generally water. 6.2.4.4 sepatation of the parts from the solid and liquid media. 6.2.4.5 Rinsing. 6.2.4.6 Drying. 6.2.5 Supplementary Treatments: 6.2.5.1 Colored chromate conversion Treatments (Type II)—Colored chromate conversion treatment for Type II shall be done in a solution containing hexavalent chromium ions. This solution shall produce a bright or semi-bright continuous, smooth, protective film with a uniform color that may range from yellow through bronze and olive-drab to brown and black and that may be dyed to a desired color. Bright dips that do not contain salts that yield films containing hexavalent chromium ions are not permitted as treatments for producing Type II coatngs 6.2.5.2 Waxes, lacquers, or other organic coatings may be used to improve lubricity, and the need for them shall be supplied in the purchase order or other governing document (see 4.1.1). supplemental lubrication treatments shall not be used to ensure conformance to the salt spray corrosion resistance requirements (see 8.5.4) 6.2.5.3 Lubrication of grade DH nuts processed in accordande with this specification and used with Specification A 325 High-strength bolts is a requirement of paragraph 6.5 of Specification A 325 and paragraph 4.8 of Specification A 563. Note 3—Although not included in specification A 194/A 194M, this provision should apply to mechanically galvanized A 194 2H NUTS WHEN SUPPLIED FOR use with specification A 325 bolts. Note 4—Specifications for structural joints using specification A 325 or A 490 bolts references the use of lubricants on nuts to be used with specification A 325 high-strength bolts and is found in the commentary on this RCSC (Research council on structural connections of the Engineering Foundation) Specification, within the paragraphs entitled “Effectof Galvanizing Upon Torque lnvolved in Tightening” and “shipping Requirements For Galvanized Bolts and nuts,” published November 1985, Page 30,” 6.2.6 Surface Defects—Defects and variations in appearance in the coating that arise from surface conditions of the substrate (scratches, roll marks, inclusions, etc.) and that persist in the finish despite the observance of good metal finishing practices shall not be cause for rejection. Note 5—Applied finishes generally perform better in service when the substrate over which they are applied is smooth and free of torn metal, inclusions, pores, and other defects. It is recommended that the specifications covering the unfinished product provide limits for these defects. A metal finisher can often remove blasting. Chemical in the treatment steps preceding the application of the finish. When desired they must be specified on the purchase order (4.1.2) 6.3 Thickness: 6.3.1 The thickness of the coating everywhere on the significant surfaces shall be at least that of the specified class as defined in 3.1. 6.3.2 Significant surfaces are defined as those normally visible (directly or by reflection) that are essential to the appearance or serviceability of the article when assembled in normal position; or that can be the source of corrosion products that deface visible surfaces on the assembled article. When necessary. The significant surfaces shall be indicated on the drawing for the article, or by the provision of suitably marked samples. Note 6—The thickness of mechanically-deposited coatings varies from point-to-point on the surface of a product, characteristically tending to be thicker on flat surfaces and thinner at exposed edges, sharp projections, shielded or recessed areas, interior corners and holes, with such thinner areas often being exempted from thickness requirements. 6.3.3 When significant surfaces are involved on which the specified thickness of deposit cannot readily be controlled, the purchaser and manufacturer should recognize the necessity for either thicker or thinner deposits. For example, to reduce buildup in thread roots, holes, deep recesses, bases of angles, and similar areas, the deposit thickness on the more accessible surfaces will have to be reduced proportionately. 6.4 Adhesion—The zinc coating shall be sufficiently adherent to the basis metal to pass the tests specified in 8.4. 6.5 Corrosion Resistance: 6.5.1 The presence of corrosion products visible to the unaided eye at normal teading distance at the end of the specified test periods stated in Table 1 shall constitute failure, except that corrosion products at edges of specimens shall not constitute failure. Slight “whisps” of white corrosion, as opposed to obvious accumulations, shall be acceptable. 6.5.2 On parts with Type II coatings, the greater number of bours for cither either white corrosion products or rust shall apply. For example, for Type II, Class 8, the test shall be continued until the 72-h requirement is met for white corrosion products; similarly, for Type II, class 25, if no white corrosion products appear before 72 h, test shall be continued until the 192-h requirement for basis metal corrosion is met(8.5.2). 6.6 Absence of hydrogen embrittlement—Springs and other high-strength parts subject to flexure shall by held for a minimum of 48 h at room temperature after coating before being loaded, flexed, or used. Such high-strength steel parts shall be free of hydrogen embrittlement. When specified in the purchase order, freedom from embrittlement shall be determined by the test specified herein (4.14 and 8.6). 7. Sampling 7.1 The purchaser and producer are urged to employ employ statistical process control in the coating process. Properly performed, statistical process control will assure coated products of satisfactory quality and will reduce the amount of acceptance inspection. The sampling plan used for the inspection of the quality coated article shall be agreed upon between the purchaser and producer. 7.1.1 when a collection of coated articles (inspection lot, see 7.2) is examined for compliance with the requirements placed on the articles. A relatively small number of the articles (sample) is selected at random and is inspected. The inspection lot is then classified as complying with the requirements based on the results of the inspection of the sample. The size of the sample and the criteria for compliance are determined by the application of statistics. The proceure is known as sampling inspection. Test Method B 602, Guide B697, and Method B 762 contain sampling plans that are designed for sampling inspection of coatings. TABLE1 Minimum Hours to Failure (white corrosion products and red red rust for mechanically deposited zinc coatings on lron and steel) Type white corrosion Class: 55-110 50 40 25 12 8 5 I A A A A A A A II 72 72 72 72 72 72 72 Red rust Class: 55-110 50 40 25 12 8 5 I no requirement 300 250 192 96 56 36 II no requirement 300 250 192 96 72 72 A No requirement. 7.1.2 Test Method B 602 contains four sampling plans, three for use with tests that are nondestructive and one when they are destructive.. Test Method B 602 Provides a default plan if one is not specified. 7.1.3 Guide B 697 provides a large number of plans and also gives guidance in the selection of a plan. Guide B 697 provides a default plan if one is not specified. 7.1.4 Test Method B 762 can be used only for coating requirements that have a numerical limit, such as coating thickness. The test must yield a numeric value and certain statistical requirements must be met. Test Method B 762 contains several plans and asso gives instructions for calculating plans to meet special needs. Test Method B 762 provides a default plan if one is not specified. 7.1.5 Guide F 1470 can be used for fasteners such as internally threaded, externally threaded and nonthreaded fasteners and washers. This guide provides for two plans: one designated the “detection process” and one designated the “prevention process.” The purchaser and producer shall agree on the plan to be used. 7.2 An inspection lot shall be defined as a collection of coated articles that are the same kind, that have been produced to the same specification, that have been coated by a single supplier at one time or approximately the same time. Under essentially identical conditions, and that are submitted for acceptance or rejection as a group. 8．Test Methods 8.1 Test specimens: 8.1.1 Test specimens may be used to represent the coated articles in a test if the articles are of a size, shape, or material that is not suitable for the test, or if it is preferred not to submit articles to a destructive test because, for example, the articles are expensive or few. The permission or the requirement to use test specimens, their number, the material from which they shall be made, and their shape and size shall be stated in the purchase order or other governing documernt. 8.1.2 The test specimen shall duplicate those characteristics of the article that influence the property being tested, and it shall be processed with the article through those process steps that influence the property. 8.1.2.1 the test specimen used to represent an article in an adhesion, corrosion resistance, or appearance test shall be made of the same material, shall be in the same metallurgical condition, and shall have the same surface condition as the article it represents, and it shall be placed in the production lot of, and be processed along with, the article it represents. 8.1.2.2 A test specimen used to represent an article in a coating thickness test shall be introduced into the process at the point where the coating or coatings are applied and it shall be carried through all steps that have a bearing on the coating thickness. 8.1.2.3 When a test specimen is used to represent a coated article in a thickness test, the specimen will not necessarily have the same thickness and thickness distribution as the article unless the specimen and the article are of the same general size and shape. Therefore, before coated articles may be accepted on the basis of a thickness test performed on representative test specimens the relationship between the thickness on the specimen and the thickness on the part shall be established. The criterion of acceptance shall be that thickness on the specimen that corresponds to the required thickness on the article. 8.2 Workmanship—Quality of workmanship shall be determined by the unaided eye at normal reading distance. 8.3 Thickness: 8.3.1 The thickness of the coating shall be determined by the microscopical method (test method B 487) or the magnetic method (test method B 499), as applicable. Other methods may be used if it can be demonstrated that the measurement uncertainty with these methods is less than 10%. 8.3.2 The thickness of the coating shall be measured at the location or loeations for both signifieant and nonsignifieant surfaces of the product where the coating would be expected to be the thinnest or at such locations as specified on the purchase order(4.1.3 and 6.3). 8.3.3 Theckness measurements of Type II deposits shall be made after application of the supplementary treatment. The Type II chromate conversion coatings shall be removed from the test area before the thickness is measured. Removal shall be done by using a very mild abrasive (such as a paste of levigated alumina or magnesium oxide) rubbed on gently with the finger. 8.4 Adhesion—Adhesion of the zinc deposit to the basis metal shall be tested in a manner that is consistent with the service requirements of the coated article. The ability to separate the coating from the substrate by peeling, as distinect from flaking caused by rupture of the deposit or of the basis metal, shall be evidence of failure. One of the following methods for determining adhesion shall be used: 8.4.1 The part shall be plastically deformed, if possible, to rupture as specified on the purchase order (4.1.4). 8.4.2 the surface of the coated article shall be scraped or sheared with a sharp edge, knife, or razor blade through the coating down to the basis metal and examined under 4 magnification. 8.5 Salt Spray Corrosion Resistance: 8.5.1 The 5%neutral salt spray (fog) test as defined in Practice B 117 shall be used. 8.5.2 If samples with Type II coatings are to be examined both for white corrosion products and for rust, separate samples may be used to determine the end point for white corrosion and ror rust. This is to permit uninterrupted exposure for the longer of the two test periods required without having to wash specimens for examination, in accordaned with Practice B 117. 8.5.3 Parts with Type II supplementary chromate film shall bc aged at room temperature for 24 h before subjection to the salt spray test . 8.5.4 parts with coatings of wax. Etc, shall not be used as samples for corrosion testing for conformance to the requirements of 6.5. 8.6 Absence fo Hydrogen Embrittlement: 8.6.1 Coated parts to be tested for the absence of embrittlement from cleaning shall be tested for brittle failure in accordance with a suitable method to be specified on the purchase order (4.1.4).The description of the method shall include the means of applying a load to the part the stress or load level to be applied, the duration of the test, the waiting time that must elapse between deposition of the zine and testing or use of the part, and testing or use of the part, and the criterion of failure. 86.2 Parts that must conform to U. S. Government requiremcnts shall be subjected to such loading conditions deseribed above for 200 h minimum. 9. Rejection and Rehearing 9.1 Materials that fail to conform to the requirements of this specification may be rejected. Rejection shall be reported to the producer or supplier promptly and A writing. In case of dissatisfaction with the results of a test, the producer or supplier may make a claim for rehearing, Finishes that show imperfections during subsequent manufacturing operations may be rejected. 10. Certification 10.1 The purchaser may require in the purchase order or contract that the producer or supplier give to the purchaser certification that the finish was produced and tested in accordance with this specification and found to meet the requirements. The purchaser may similarly require that a report of the test results be furnished. 11. Quality Assurance Provisions 11.1 For parts processed for U.S. Government procurement, the producer or supplier shall be responsible for the performance of all inspection and test requirements specified hercin. Except as otherwise specified in the contarct or order, the producer or supplier may use his own or any other suitable facilities for the performance of the inspection and test requirements specified herein, unless disapproved by the purchaser, The purchaser shall have the right to perform any of the inspections and tests set forth in this specification where such inspections are deemed necessary to assure that material conforms to prescribed requirements. APPENDIXES (Nonmandatory Information) X1. CHARACTERISTICS X1.1　Mechanical deposition in itself greatly teduces the risk of hydrogen embrittlement and is suitable for coating bores and recesses in many parts that cannot be conveniently electroplated (see Appendix x3). X1.2 Zinc coatings are usually applied to provide corrosion resistance. The performance of a zinc coating depends largely on its thickness, the supplementary treatment if any, and the kind of environment ot which it is exposed. The seven heaviest classes of coatings offer suitablc alternatives to hot-dip galvanizing. The following data, based on widespread testing, may be used to compare the behavior or zinc in various atmospheres. The values are only mdicative, bccause individual studies in various parts of the world have resulted in figures that vary widely from these averages. Atmosphere Mean Corrosion Rate Industrial 5.6 μm(0.22 mil)/year Urban nonindustrial or marine 1.5μm(0.06 mil)/year Suburban 1.3μm(0.05 mil)/year Rural 0.8μm(0.03 mil)/year Indoors considerably less than 0.5μm(0.01 mil)/year X2. SPECIFIC TYPES X2.1 Type I (plain zinc)is useful for lowest cost protection where early formation of white corrosion products is not detrimental. It is also used for higher temperature applications up to approximately 120℃ where the effectiveness of chromates is greatly reduced. X2.2 Type II (colored chromates)—Chromates that have a color (yellow, olive drab, bronze, etc.) are used to delay the appearance of white or red corrosion products on the plated article or to provide a color desired by a customer for a specific purpose. X3. HYDROGEN EMBRITTLEMENT X3.1 A major advantage of mechanical deposition is that it does not produce hydrogen embrittlement in hardened steel during the coating process. However, pronounced embrittlement can be produced in certain cleaning processes. The mild degree of embrittlement that might result from following proper procedures with clearing methods permitted in this specification normally is self-relieving within a day’s time at room temperature. The American Society for testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this starndard. Users of this standard are expressly advised that determination of the validity of any such patent righls, and the risk of 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 years and if not revised. either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additiona standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views down to the ASTM committee on standards. At the address shown below.