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1、BRITISH STANDARD BS 6200-3.33.2: 1992 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.33 Determination of tungsten Subsection 3.33.2 Steel: spectrophotometric method Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Un
2、controlled Copy, (c) BSI BS 6200-3.33.2:1992 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 June 1992 BSI 09-1999 The following BSI references relat
3、e to the work on this standard: Committee reference ISM/18 Draft for comment 91/44346 DC ISBN 0 580 20802 8 Committees 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,
4、upon which the following bodies were represented: BCIRA British Steel Industry Department of Trade and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun
5、 sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 BSI 09-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3Reagents1 4Apparatus1 5Sampling1 6Procedure1 7Calculation and expression of results3 8Test report4
6、Table 1 Calibration data2 Table 2 Precision data3 Table 3 Values for inter-laboratory agreement (2.83s, P = 95 %)4 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 ii BSI 09-1999
7、 Foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method 2 for the determination of tungsten in BSI Handbook No. 19, to which it is technically equivalent. BS 6200 is a multipart British Standard, covering all a
8、spects of the sampling and analysis of iron, steel and other ferrous metals. A list of contents, together with general information, is given in Part 1. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corr
9、ect application. Compliance 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, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyr
10、ight date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 BSI 09-19991 1 Scope This Subsection of BS 6200
11、 describes a spectrophotometric method for the determination of tungsten in steel. It is suitable for contents of 0.02 % (m/m) to 3.0 % (m/m) but is not recommended for steels with tungsten exceeding 3 % (m/m) or more than 1.5 % (m/m) molybdenum. For these the method given in BS 6200-3.33.1 is more
12、suitable. A correction is required if vanadium is present. NOTEThe titles of the publications referred to in this Subsection of BS 6200 are listed 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
13、titanium(III) chlorides have been added to reduce the tungsten and to prevent the formation of iron(III) thiocyanate. The determination is completed spectrophotometrically. 3 Reagents During the analysis use only reagents of recognized analytical grade and only grade 3 water as specified in BS 3978.
14、 3.1 Ammonium thiocyanate, 250 g/l solution. Dissolve 25 g of ammonium thiocyanate in water, dilute to 100 ml and mix. 3.2 Hydrochloric acid, density = 1.16 g/ml to 1.18 g/ml. 3.3 Iron, of high purity, free from tungsten. 3.4 Nitric acid, = 1.42 g/ml. 3.5 Orthophosphoric acid, = 1.75 g/ml. 3.6 Ortho
15、phosphoric-sulfuric acid mixture. To 600 ml of water add cautiously, with cooling and stirring, 150 ml of orthophosphoric acid (3.5), and 150 ml of sulfuric acid, = 1.84 g/ml. Cool, dilute to 1 l and mix. 3.7 Sodium hydroxide, 100 g/l solution. In 70 ml of water, dissolve cautiously, with cooling an
16、d stirring, 10 g of sodium hydroxide. Cool, dilute to 100 ml and mix. Prepare this solution in a polyethylene beaker and store in a stoppered polyethylene bottle. 3.8 Sulfuric acid, = 1.84 g/ml, diluted 1 + 99. To 400 ml of water, add cautiously 10 ml of sulfuric acid, = 1.84 g/ml. Mix, cool, dilute
17、 to 1 l and mix. 3.9 Tin(II) chloride, 5 g/l solution. Dissolve 5 g of tin(II) chloride, SnCl2.2H2O, in 500 ml of hydrochloric acid (3.2), dilute to 1 l with water and mix. 3.10 Titanium(III) chloride solution. Dissolve 1 g of titanium metal in 25 ml of hydrochloric acid (3.2), warm until solution i
18、s complete, cool, dilute to 100 ml and mix. Store in a stoppered bottle. 3.11 Tungsten, standard solution, equivalent to 2 mg of tungsten per millilitre. Dissolve 2.522 g of high purity tungsten trioxide, previously ignited at approximately 800 C to constant weight, in 25 ml of sodium hydroxide (3.7
19、). Cool, transfer to a 1 l volumetric flask, dilute to the mark and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with class A of BS 846, BS 1583 or BS 1792, as appropriate. 4.3 Spectrophotometer, suitable for measuring absorbance at a wavelength of 415 n
20、m. 4.4 Cells, having optical path lengths of 2 cm, 1 cm or 0.5 cm. 5 Sampling Carry out sampling in accordance with BS 1837. NOTEBS 6200-2, which will supersede BS 1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS 6200-2.
21、6 Procedure 6.1 Test portion Weigh, to the nearest 0.001 g, a test portion of 1.0 g. 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 test solution Place the test portion in a 250 ml conical beaker.
22、For readily soluble steels add 40 ml of orthophosphoric-sulfuric acid (3.6), cover the beaker and heat until solvent action ceases. Add 6 ml of orthophosphoric acid (3.5), oxidize with nitric acid (3.4) and evaporate to fuming. For steels that do not dissolve readily, or which leave a residue of aci
23、d-resistant carbides, make the initial dissolution with 15 ml of hydrochloric acid (3.2) and 5 ml of nitric acid (3.4). Cover the beaker and when solvent action ceases add 40 ml of orthophosphoric-sulfuric acid (3.6), 6 ml of orthophosphoric acid (3.5) and evaporate to fuming. Allow to cool, add 20
24、ml of water, heat to redissolve salts, repeat the evaporation to fuming and cool. In either case, add 50 ml of water and heat until soluble salts are dissolved. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 2 BSI 09-199
25、9 Irrespective of the choice of solvent acids, after fuming the solution shall contain the equivalent of 12 ml of orthophosphoric acid (3.5) and 6 ml of sulfuric acid, = 1.84 g/ml and no nitric acid. Filter through a paper-pulp pad into a 100 ml volumetric flask, washing the filter with sulfuric aci
26、d (3.8). Cool, dilute to the mark and mix. 6.3.2 Development of the colour Transfer a 5 ml aliquot into each of two 50 ml volumetric flasks. Make this transfer and all subsequent reagent additions using a pipette, or safety pipette when appropriate, or burette. To one aliquot add 40 ml of tin(II) ch
27、loride solution (3.9), mix, add 3 ml of ammonium thiocyanate solution (3.1), mix again, then add 1 ml of titanium(III) chloride solution (3.10). Mix, dilute to the mark and allow to stand for 5 min at 20 1 C. In the case of steels containing 2 % (m/m) of copper or more, copper(I) thiocyanate may be
28、precipitated. Remove the precipitate by filtration through a dry sintered glass filter. To the other aliquot add 40 ml of tin(II) chloride solution (3.9), dilute to the mark and mix. Allow to stand for 5 min at 20 1 C. 6.3.3 Spectrophotometric measurement Measure the absorbance of each solution at a
29、 wavelength of 415 nm and 20 1 C, using cells of the same optical path length for the test portion and its compensating solution. Record the absorbance readings and the optical path length used. 6.4 Preparation of the calibration graph Weigh nine 1.0 g portions of high purity iron (3.3) and place in
30、 separate 250 ml conical beakers. Make additions of tungsten solution (3.11) as shown in Table 1, and according to the concentration of tungsten expected. Treat the calibration solutions exactly as described in 6.3.1 to 6.3.3. Prepare calibration graphs by plotting the differences of the absorbance
31、readings of the tungsten standard solutions and their compensating solutions against the equivalent tungsten percentage by mass. NOTEVanadium gives a positive error which varies slightly with the tungsten content, the magnitude of the correction being approximately 0.19 % to be deducted for each 1 %
32、 of vanadium present (see footnotes to Table 2). For test portions containing less than 0.3 % (m/m) vanadium, no significant 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 high
33、est accuracy with test portions containing more than 0.3 % (m/m) vanadium, the correction should be made from a graph prepared from vanadium calibration solutions containing approximately the same amount of tungsten as the test portion. Table 1 Calibration data 2.0 cm cell1.0 cm cell0.5 cm cell Tung
34、sten solutionTungsten equivalent Tungsten solutionTungsten equivalent Tungsten solutionTungsten equivalent ml 0.0 0.5 1.0 1.5 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
35、 12.0 14.0 16.0 % (m/m) nil 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 BSI 09-19993 7 Calculation and expression of results 7.1 Calculation From the difference in the absorbance of the
36、 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 carried out by six to 10 analysts, each from a different laboratory, and
37、 using 10 steels. 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 calculate repeatability r and reproducibility R, as defined in BS
38、 5497-1. 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 found on identical test material will exceed the 95 % probabi
39、lity level, on average, not more than once in 20 cases 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 value of the standard deviation of the laboratory means s
40、, expressed by the following equation: s % (m/m) = 0.0131 W % (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 CCrMoNiCoV 1 2 3 4 5 6 7 8 9 10 a b a a a b a a b b b a % (m/m) 1.1 0.6 0.5 0
41、.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 0.0220 0.0316 0.0290 0.0517 0.087 0.098 a Methods
42、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 the Iron and Steel Institute 178, November 1954, 2
43、67269. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 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 giv
44、en in Table 3. Table 3 Values for inter-laboratory agreement (2.83s, 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 S
45、ubsection of BS 6200; c) the results, and the form in which they are expressed; d) any unusual features noted during the determination; e) any operation not specified in this British Standard or any optional operation which may have influenced the results. Tungsten2.83s % (m/m) 0.02 0.05 0.10 0.20 0
46、.50 1.0 2.0 3.0 0.021 0.022 0.024 0.027 0.038 0.057 0.094 0.131 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2:1992 BSI 09-1999 Publication(s) referred to BS 846, Specification for burettes. BS 1583, Specification for one-mar
47、k pipettes. BS 1792, Specification for one-mark volumetric flasks. BS 1837, Methods for the sampling of iron, steel, permanent magnet alloys and ferro-alloys. BS 3978, Specification for water for laboratory use. BS 5497, Precision of test methods. BS 5497-1, Guide for the determination of repeatabil
48、ity and reproducibility for a standard test method by inter-laboratory tests. BS 6200, Sampling and analysis of iron, steel and other ferrous metals. BS 6200-1, Introduction and contents1). BS 6200-2, Methods of sampling and sample preparation2). BS 6200-3, Methods of analysis. BS 6200-3.33, Determi
49、nation of tungsten. BS 6200-3.33.1, Steel: gravimetric method. BSI Handbook No. 19, Methods for the sampling and analysis of iron, steel and other ferrous metals1). 1) Referred to in the foreword only. 2) In preparation. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.33.2: 1992 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on stan