1、BRITISH STANDARD BS 6200-3.33.2: 1992 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section3.33 Determination of tungsten Subsection 3.33.2 Steel: spectrophotometric methodBS6200-3.33.2:1992 This British Standard, having been prepared under the directionof
2、the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15June1992 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment91/44346DC ISBN 0 580 20802 8 Committees
3、responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/18, upon which the following bodies were represented: BCIRA British Steel Industry Department of Trade and Industry (Labora
4、tory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.33.2:1992 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Appa
5、ratus 1 5 Sampling 1 6 Procedure 1 7 Calculation and expression of results 3 8 Test report 4 Table 1 Calibration data 2 Table 2 Precision data 3 Table 3 Values for inter-laboratory agreement(2.83s, P =95%) 4 Publication(s) referred to Inside back coverBS6200-3.33.2:1992 ii BSI 09-1999 Foreword This
6、Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method2 for the determination of tungsten in BSI Handbook No.19, to which it is technically equivalent. BS6200 is a multipart British Standard, covering all aspects of the sampl
7、ing and analysis of iron, steel and other ferrous metals. A list of contents, together with general information, is given in Part1. 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. Com
8、pliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have
9、had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6200-3.33.2:1992 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a spectrophotometric method for the determination of tungsten in steel. It is suitable for contents of0.02%(m/m) to3.0%(m/
10、m) but is not recommended for steels with tungsten exceeding3%(m/m) or more than1.5% (m/m) molybdenum. For these the method given in BS6200-3.33.1 is more suitable. A correction is required if vanadium is present. NOTEThe titles of the publications referred to in this Subsection of BS6200 are listed
11、 on the inside back cover. 2 Principle Tungsten is converted to the yellow-coloured thiocyanate in phosphoric-sulfuric acid solution to which tin(II) and titanium(III) chlorides have been added to reduce the tungsten and to prevent the formation of iron(III) thiocyanate. The determination is complet
12、ed spectrophotometrically. 3 Reagents During the analysis use only reagents of recognized analytical grade and only grade3 water as specified in BS3978. 3.1 Ammonium thiocyanate,250g/l solution. Dissolve25g of ammonium thiocyanate in water, dilute to100ml and mix. 3.2 Hydrochloric acid, density =1.1
13、6g/ml to1.18g/ml. 3.3 Iron, of high purity, free from tungsten. 3.4 Nitric acid, =1.42g/ml. 3.5 Orthophosphoric acid, =1.75g/ml. 3.6 Orthophosphoric-sulfuric acid mixture. To600ml of water add cautiously, with cooling and stirring,150ml of orthophosphoric acid(3.5), and150ml of sulfuric acid, =1.84g
14、/ml. Cool, dilute to1l and mix. 3.7 Sodium hydroxide,100g/l solution. In70ml of water, dissolve cautiously, with cooling and stirring,10g of sodium hydroxide. Cool, dilute to100ml and mix. Prepare this solution in a polyethylene beaker and store in a stoppered polyethylene bottle. 3.8 Sulfuric acid,
15、 =1.84g/ml, diluted1+99. To400ml of water, add cautiously10ml of sulfuric acid, =1.84g/ml. Mix, cool, dilute to1l and mix. 3.9 Tin(II) chloride,5g/l solution. Dissolve5g of tin(II) chloride, SnCl 2 .2H 2 O, in500ml of hydrochloric acid(3.2), dilute to1l with water and mix. 3.10 Titanium(III) chlorid
16、e solution. Dissolve1g of titanium metal in25ml of hydrochloric acid(3.2), warm until solution is complete, cool, dilute to100ml and mix. Store in a stoppered bottle. 3.11 Tungsten, standard solution, equivalent to2mg of tungsten per millilitre. Dissolve2.522g of high purity tungsten trioxide, previ
17、ously ignited at approximately800 C to constant weight, in25ml of sodium hydroxide(3.7). Cool, transfer to a1l volumetric flask, dilute to the mark and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS846, BS1583 or BS1792, as appropriate. 4
18、.3 Spectrophotometer, suitable for measuring absorbance at a wavelength of415nm. 4.4 Cells, having optical path lengths of2cm,1cm or0.5cm. 5 Sampling Carry out sampling in accordance with BS1837. NOTEBS6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsecti
19、on will be amended to include sampling in accordance with BS6200-2. 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of1.0g. 6.2 Blank test The differential measurement used in the procedure renders the use of a blank test unnecessary. 6.3 Procedure 6.3.1 Preparation of the t
20、est solution Place the test portion in a250ml conical beaker. For readily soluble steels add40ml of orthophosphoric-sulfuric acid(3.6), cover the beaker and heat until solvent action ceases. Add6ml of orthophosphoric acid(3.5), oxidize with nitric acid(3.4) and evaporate to fuming. For steels that d
21、o not dissolve readily, or which leave a residue of acid-resistant carbides, make the initial dissolution with15ml of hydrochloric acid(3.2) and5ml of nitric acid(3.4). Cover the beaker and when solvent action ceases add40ml of orthophosphoric-sulfuric acid(3.6),6ml of orthophosphoric acid(3.5) and
22、evaporate to fuming. Allow to cool, add20ml of water, heat to redissolve salts, repeat the evaporation to fuming and cool. In either case, add50ml of water and heat until soluble salts are dissolved.BS6200-3.33.2:1992 2 BSI 09-1999 Irrespective of the choice of solvent acids, after fuming the soluti
23、on shall contain the equivalent of12ml of orthophosphoric acid(3.5) and6ml of sulfuric acid, =1.84g/ml and no nitric acid. Filter through a paper-pulp pad into a100ml volumetric flask, washing the filter with sulfuricacid(3.8). Cool, dilute to the mark and mix. 6.3.2 Development of the colour Transf
24、er a5ml aliquot into each of two50ml volumetric flasks. Make this transfer and all subsequent reagent additions using a pipette, or safety pipette when appropriate, or burette. To one aliquot add40ml of tin(II) chloride solution(3.9), mix, add3ml of ammonium thiocyanate solution(3.1), mix again, the
25、n add1ml of titanium(III) chloride solution(3.10). Mix, dilute to the mark and allow to stand for5min at20 1 C. In the case of steels containing2% (m/m) of copper or more, copper(I) thiocyanate may be precipitated. Remove the precipitate by filtration through a dry sintered glass filter. To the othe
26、r aliquot add40ml of tin(II) chloride solution(3.9), dilute to the mark and mix. Allow to stand for5min at20 1 C. 6.3.3 Spectrophotometric measurement Measure the absorbance of each solution at a wavelength of415nm and20 1 C, using cells of the same optical path length for the test portion and its c
27、ompensating solution. Record the absorbance readings and the optical path length used. 6.4 Preparation of the calibration graph Weigh nine1.0g portions of high purity iron(3.3) and place in separate250ml conical beakers. Make additions of tungsten solution(3.11) as shown in Table 1, and according to
28、 the concentration of tungsten expected. Treat the calibration solutions exactly as described in6.3.1 to6.3.3. Prepare calibration graphs by plotting the differences of the absorbance readings of the tungsten standard solutions and their compensating solutions against the equivalent tungsten percent
29、age by mass. NOTEVanadium gives a positive error which varies slightly with the tungsten content, the magnitude of the correction being approximately0.19% to be deducted for each1% of vanadium present (see footnotes to Table 2). For test portions containing less than0.3% (m/m) vanadium, no significa
30、nt error will be introduced by assuming the correction to be independent of tungsten content. Make appropriate corrections by means of a vanadium interference graph. For the highest accuracy with test portions containing more than0.3%(m/m) vanadium, the correction should be made from a graph prepare
31、d from vanadium calibration solutions containing approximately the same amount of tungsten as the test portion. Table 1 Calibration data 2.0cm cell 1.0cm cell 0.5cm cell Tungsten solution Tungsten equivalent Tungsten solution Tungsten equivalent Tungsten solution Tungsten equivalent ml 0.0 0.5 1.0 1
32、.5 2.0 2.5 3.0 3.5 4.0 % (m/m) nil 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ml 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 % (m/m) nil 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 ml 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 % (m/m) nil 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2BS6200-3.33.2:1992 BSI 09-1999 3 7 Calculation and expression of
33、 results 7.1 Calculation From the difference in the absorbance of the test solution and its compensating solution, read the tungsten% (m/m) from the calibration graph corresponding to the optical path length of the cell used. 7.2 Precision 7.2.1 Precision data Planned trials of this method were carr
34、ied out by six to10analysts, each from a different laboratory, and using10steels. The mean results for each laboratory in the original reports (see Table 2) have been examined statistically to obtain values of between-laboratory agreement. In the absence of individual results it is not possible to c
35、alculate repeatability r and reproducibility R, as defined in BS5497-1. From the results reported, for probability P =95%, the statistical limits(2.83s) for agreement between laboratory means have been calculated and are given in Table 2. The difference between the mean results of two laboratories f
36、ound on identical test material will exceed the95% probability level, on average, not more than once in20cases in the normal and correct operation of the method. 7.2.2 Regression data Statistical analysis of the results showed an approximately linear relationship between tungsten content W and the v
37、alue of the standard deviation of the laboratory means s, expressed by the following equation: s%(m/m)=0.0131W%(m/m)+0.007 correlation coefficient=0.972 Table 2 Precision data Sample Number Ref. Alloy type Element Tungsten content W Between- laboratory agreement 2.83s C Cr Mo Ni Co V 1 2 3 4 5 6 7 8
38、 9 10 a b a a a b a a b b b a % (m/m) 1.1 0.6 0.5 0.9 0.3 0.9 % (m/m) 18 18 0.5 1.5 1.8 6.0 1.3 4.6 % (m/m) 1.5 nil 0.04 4.2 % (m/m) 8 8 0.3 0.2 3.5 % (m/m) 35 0.7 % (m/m) 0.2 0.2 1.4 % (m/m) 0.020 0.028 0.185 0.350 0.554 0.537 0.658 2.18 2.21 4.71 5.31 6.65 0.0138 0.0020 0.0151 0.0094 0.0084 0.0177
39、 0.0220 0.0316 0.0290 0.0517 0.087 0.098 a Methods of Analysis Committee. Absorptiometric determination of tungsten in steel. Journal of the Iron and Steel Institute 172, December 1952,413415. b Methods of Analysis Committee. Improvements in the absorptiometric determination of tungsten. Journal of
40、the Iron and Steel Institute 178, November 1954,267269.BS6200-3.33.2:1992 4 BSI 09-1999 The predicted values for the statistical limits of agreement between laboratory means at probability P =95% calculated from the above equation are given in Table 3. Table 3 Values for inter-laboratory agreement(2
41、.83s, P =95%) 8 Test report The test report shall include the following information: a) all information necessary for the identification of the sample, the laboratory and the date of analysis; b) the method used, by reference to this Subsection of BS6200; c) the results, and the form in which they a
42、re expressed; d) any unusual features noted during the determination; e) any operation not specified in this BritishStandard or any optional operation which may have influenced the results. Tungsten 2.83s % (m/m) 0.02 0.05 0.10 0.20 0.50 1.0 2.0 3.0 0.021 0.022 0.024 0.027 0.038 0.057 0.094 0.131BS6
43、200-3.33.2:1992 BSI 09-1999 Publication(s) referred to BS846, Specification for burettes. BS1583, Specification for one-mark pipettes. BS1792, Specification for one-mark volumetric flasks. BS1837, Methods for the sampling of iron, steel, permanent magnet alloys and ferro-alloys. BS3978, Specificatio
44、n for water for laboratory use. BS5497, Precision of test methods. BS5497-1, Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. BS6200, Sampling and analysis of iron, steel and other ferrous metals. BS6200-1, Introduction and conten
45、ts 1) . BS6200-2, Methods of sampling and sample preparation 2) . BS6200-3, Methods of analysis. BS6200-3.33, Determination of tungsten. BS6200-3.33.1, Steel: gravimetric method. BSI Handbook No.19, Methods for the sampling and analysis of iron, steel and other ferrous metals 1) . 1) Referred to in
46、the foreword only. 2) In preparation.BS 6200-3.33.2: 1992 BSI 389 Chiswick High Road London 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 inco
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