1、BRITISH STANDARD BS 6533:1984 Guide to Macroscopic examination of steel by etching with strong mineral acids UDC 669.14:620.183.255BS6533:1984 This British Standard, having been prepared under the directionof the Iron and SteelStandards Committee, waspublished under the authorityof the Board of BSIa
2、ndcomes into effect on 28 September 1984 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISE/72 Draft for comment 82/71885 DC ISBN 0 580 13995 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted b
3、y the Iron and Steel Standards Committee (ISE/-) to Technical Committee ISE/72 upon which the following bodies were represented: British Industrial Fasteners Federation British Railways Board British Steel Industry Ministry of Defence Stainless Steel Fabricators Association of Great Britain Amendmen
4、ts issued since publication Amd. No. Date of issue CommentsBS6533:1984 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Etching reagents 1 4 Sample 2 5 Preparation of sample 2 6 Etching procedure 2 7 Guidance for preservation of samples 3 8
5、Report 3 Table 1 Approximate times of application for etching reagents 3 Publications referred to Inside back coverBS6533:1984 ii BSI 09-1999 Foreword This British Standard has been prepared under the direction of the Iron and Steel Standards Committee. It is based on ISO 4969:1980 “Steel Macroscopi
6、c examination by etching with strong mineral acids”, published by the International Organization for Standardization (ISO). Additional mineral acids to those listed in ISO 4969 have been included in this British Standard; these acids are given in 3.2, 3.6 and 3.7. This standard does not purport to i
7、nclude all etching reagents suitable for the macroscopic etching of steel. For example, other suitable reagents widely used in industry include: a) acid mixtures containing ferric chloride; b) electrolytic etching reagents; c) ammonium persulphate solutions. Typical process solutions for the etching
8、 of steels and other metals for metallic materials and components for use in the aerospace industry are given in British Standard M 37. WARNING. This British Standard calls for the use of substances and procedures that may be injurious to health if adequate precautions are not taken. It refers only
9、to technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. This warning specifically refers to the use of strong mineral acids. It has been assumed in the drafting of this British Standard that the execution of its provisions is entruste
10、d to appropriately qualified and experienced people. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal o
11、bligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table
12、on the inside front cover.BS6533:1984 BSI 09-1999 1 1 Scope This British Standard gives guidance on and describes methods for the macroscopic examination of steel by etching with strong mineral acids. NOTEThe use of the methods, and the conditions for interpreting the results observed, depend on the
13、 particular case and details may be laid down in product standards or be subject to special agreement. The methods given have very wide application. Selection of the type and concentration of the reagent, the temperature of the reagent and the conditions of surface preparation of the test piece make
14、 it possible to achieve an informed description of the etched surface. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle 2.1 Macrographic etching with strong mineral acids reveals the macrostructure of a metal sample and may indicate cer
15、tain physical or chemical irregularities. 2.2 The reagent acts by dissolving different parts of the metal surface at unequal rates and thus produces differences in level which make observation possible. 2.3 Macroscopic examination after etching with mineral acids may reveal lack of chemical uniformi
16、ty (segregation of elements), lack of physical uniformity (cracks, porosity) and any structural variations such as those caused, for instance, by hardening, decarburization, and case hardening. NOTEDepending on the conditions of surface preparation of the test piece, and on the etching process, this
17、 macroscopic examination does not always make it possible to distinguish on the one hand porosities from segregations, and on the other hand cracks from lines of inclusions or segregations. 2.4 Very great sensitivity may be achieved by altering the conditions of preparation and attack. For instance,
18、 it is possible to reveal the dendritic structure of a metal or the presence of inclusions or very small defects. 2.5 Observation of the etched surface is carried out with the unaided eye or with a magnifying glass (magnification up to 10). 3 Etching reagents 3.1 General The reagents given are used
19、successfully for most routine examinations and for an extensive range of steel grades although other reagents are also permitted. Aqua regia is used for steels which are resistant to attack by the other acids. Depending on the objective, the type and concentration of the acid used may be varied, as
20、may the temperature and time of application. For very detailed examination, cold 1)dilute nitric acid solutions similar to reagents used for micrographic testing may be needed. WARNING. The acids listed in this standard CAUSE SEVERE BURNS. Prevent contact with skin and eyes. In addition, hydrochlori
21、c acid and nitric acid are irritating to the respiratory system and nitric acid may cause fire in contact with combustible materials. When making diluted acid solution, always cautiously add the acid to the water. Mix and cool if necessary, before making further additions of acid to the solution. At
22、tention should be paid to appropriate safety precautions, and the method should only be operated by trained personnel. 3.2 Hydrochloric acid (concentrated solution) ( 1.19 g/mL at 20 C). This solution is used cold. 3.3 Hydrochloric acid (dilute solution), having the following volumetric composition:
23、 a) HCI ( 1.19 g/mL at 20 C): 1 volume; b) H 2 O: 1 volume. This solution is used hot (60 C to 80 C). 3.4 Sulphuric acid (dilute solution), having the following volumetric composition: a) H 2 SO 4( 1.84 g/mL at 20 C): 15 volumes; b) H 2 O: 85 volumes. This solution is used either cold or hot (60 C t
24、o 80 C). 3.5 Sulphuric-hydrochloric acids solution, having the following volumetric composition: a) HCI ( 1.19 g/mL at 20 C): 38 volumes; b) H 2 SO 4( 1.84 g/mL at 20 C): 12 volumes; c) H 2 O: 50 volumes. This solution is used hot (60 C to 80 C). 3.6 Nitric acid solution, having the following volume
25、tric composition: a) HNO 3( 1.42 g/mL at 20 C): 1 volume; b) H 2 O: 1 volume. This solution is used cold. 3.7 Nitric acid (dilute solution), having the following volumetric composition: a) HNO 3( 1.42 g/mL at 20 C): 1 volume; b) H 2 O: 10 to 20 volumes. 1) For the purposes of this standard the term
26、cold means at ambient temperature.BS6533:1984 2 BSI 09-1999 This solution is used cold. NOTE 1This solution is especially suitable for examination of weldments. NOTE 2Water may be replaced by alcohol when good macrographs are required. 3.8 Aqua regia acid solution, having the following volumetric co
27、mposition: a) HCI ( 1.19 g/mL at 20 C): 3 volumes; b) HNO 3( 1.42 g/mL at 20 C): 1 volume. This solution is used either cold or up to 40 C. 4 Sample The examination is made on the product or on a sample cut from the product. NOTE 1The surface or section to be examined may be perpendicular or paralle
28、l to the principal direction of working depending upon the product and application, and the surface or section should be subject to agreement between the purchaser and the supplier. NOTE 2In the absence of requirements in the product standards, the number and position of the surfaces examined should
29、 be subject to agreement between the purchaser and the supplier. Locate the surfaces to be examined away from the cut faces when cutting has been carried out: a) by hot shearing, which deforms the fibres as well as the inclusions and may greatly offset the segregates; b) by flame cutting, which, in
30、the case of hardenable steels, may produce local hardening, shrinkage cracks or local tempering. 5 Preparation of sample 5.1 General The degree of surface preparation of the sample necessary depends upon the precision required for macroscopic examination by acid etching. 5.2 Machining Rough machinin
31、g, resulting in relatively coarse surfaces, may be sufficient in certain cases, e.g. in routine inspection to reveal shrinkage holes. However, more careful machining is generally required. The criteria to be observed when machining are as follows: a) cutting-tool marking should not be pronounced, e.
32、g. as the result of incorrect adjustment, excessively deep cuts or heavy feeds on the lathe or the shaping machine; good results are generally obtained with a final cut of approximately 0.1 mm; b) there should be as little cold working of the surface as possible, due for instance: 1) to a type of to
33、ol which is not suitable for the metal, or which is badly sharpened; 2) to the use of unsuitable grinding wheels. NOTE 1The main types of machining generally used are: a) grinding, with or without preliminary machining; b) shaping or turning. NOTE 2In general, it is recommended that a surface finish
34、 be obtained with an R avalue of: a) less than 6.3 4m for components; b) less than 12.5 4m for materials. This range of surface finish can be obtained by grinding, turning, boring, milling, shaping and planing (see BS 1134-2). 5.3 Polishing Where etching is used to reveal very fine defects or struct
35、ural irregularities (different welding zones for instance) careful polishing is necessary and the finer the polishing the better the definition. 5.4 Surface cleanliness The surface to be etched should be free of dirt and grease which might influence the result of the examination. 6 Etching procedure
36、 6.1 Method Immerse the sample in an acid bath, which may be heated. NOTEFor large samples, it may be useful to pre-heat them to the temperature of the bath. The volume of the bath should be adequate, at least of the order of 1 L of reagent per square decimetre of area of the sample. In addition, th
37、e bath should be sufficiently deep for the height of the liquid above the upper face of the sample to be at least 25 mm. When etching several samples in the same bath, ensure that there is no contact between them. The establishment of galvanic couples may cause an uneven and misleading etch. As an a
38、lternative to immersion and in the case of large samples or sections which cannot be immersed, swab the etching reagent over the surface to be examined. Ensure a uniform and constant distribution of the reagent over the surface. When the etching is considered satisfactory, remove the sample from the
39、 bath, wash it in running water, brush it carefully (with a non-metallic brush) to remove any residue, and then dry it. 6.2 Time of application For each type of etching reagent, the time of application depends upon the temperature of the etching reagent, the steel grade, the surface condition and th
40、e physical condition of the steel sample and the type of examination. It is preferable that the treatment be entrusted to an experienced operator who will supervise the process and end it when he considers the etch to be adequate.BS6533:1984 BSI 09-1999 3 Table 1 Approximate times of application for
41、 etching reagents Excessive etching may lead to an exaggerated relief which is difficult to interpret. For guidance, the approximate times of application are given in Table 1. The times given may be adjusted as necessary to suit individual applications. 7 Guidance for preservation of samples In orde
42、r to avoid subsequent corrosion of the surface of samples by see page of the reagent, which cannot always be eliminated completely by rinsing, two techniques are recommended: a) neutralization by immersion in a solution of10% ammonia in alcohol; b) passivation by brief immersion (approximately5 s) i
43、n concentrated nitric acid. (An additional advantage of passivation is that it whitens the etched surface and protects it to a certain extent against atmospheric corrosion.) After passivation, samples should be rinsed in hot water, brushed and dried. However, these two techniques permit preservation
44、 for only a short period. If it is wished to preserve the samples for a long period, it is necessary to protect the etched surfaces with a plastic film or a cellulose varnish or any similar product. 8 Report The report shall include the following information: a) the steel grade examined; b) the cast
45、 number or any other identification number; c) the position of the surface examined; d) the type of etch; e) the result of the examination (description of the etched surface, or photograph). Etching reagents Temperature of reagent Approximate time of application C Hydrochloric acid (concentrated sol
46、ution, see 3.2) Cold 4 h Hydrochloric acid (dilute solution, see 3.3) 60 to 80 30 min Sulphuric acid (dilute solution, see 3.4) a) Cold b) 60 to 80 a) 10 h b) 30 min Sulphuric-hydrochloric acids solution (see 3.5) 60 to 80 30 min Nitric acid solution a(see 3.6) Cold Up to 3 min Nitric acid (dilute s
47、olution, see 3.7) Cold 2 min Aqua regia acid solution (see 3.8) a) Cold b) Up to 40 a) 30 min b) A few min NOTEIt may be necessary to give consideration to hydrogen de-embrittlement of surface layers after etching. a Several applications may be necessary to obtain the desired results.4 blankBS6533:1
48、984 BSI 09-1999 Publications referred to BS 1134, Method for the assessment of surface texture. BS 1134-2, General information and guidance. BS M 37, Method for the etch inspection of metallic material and components 2) . 2) Referred to in the foreword only.BS 6533:1984 BSI 389 Chiswick High Road Lo
49、ndon W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inacc
