1、BRITISH STANDARD BS 6200-3.26.5: 1985 ISO4158:1978 Sampling and analysis of iron, steel and other ferrous metals Part3: Methods of analysis Section3.26 Determination of silicon Subsection3.26.5 Ferrosilicon, ferrosilicomanganese and ferrosilicochromium: gravimetric method UDC 669.1:543.21:546.28BS62
2、00-3.26.5:1985 This British Standard, having been prepared under the directionof the Iron and Steel Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 28 February1985 BSI09-1999 The following BSI references relate to the work on this standard: Committee
3、 reference ISM/18 Draft for comment77/79236 DC ISBN0 580 14270 1 National foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Committee. It is identical with ISO4158:1978 “Ferrosilicon, ferrosilicomanganese and ferrosilicochromium Determination of
4、 silicon content Gravimetric method” published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventi
5、ons are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard”
6、appear, referring to this standard, they should be read as “British Standard”. Cross-reference. At present, there is no corresponding British Standard for ISO3713 which is still at draft stage. Appropriate procedures from ISO3713 will be incorporated in BS6200-2 “Methods of sampling and sample prepa
7、ration”, which will be published in due course. 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 obliga
8、tions. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and 2, 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 on the
9、inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS6200-3.26.5:1985 BSI 09-1999 i Contents Page National foreword Inside front cover 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sample 1 7 Procedure 1 8 Expression o
10、f results 2 9 Reproducibility 2 10 Test report 2 Publication referred to Inside back coverii blankBS6200-3.26.5:1985 BSI 09-1999 1 1 Scope and field of application This International Standard specifies a gravimetric method for the determination of the silicon content of ferrosilicon, ferrosilicomang
11、anese and ferrosilicochromium. The method is applicable to alloys containing from8 to95%(m/m) of silicon. 2 Reference ISO3713, Ferroalloys Sampling and preparation of samples General rules 1) . 3 Principle Transformation of the silicon in a test portion into silicate by oxidizing fusion with sodium
12、peroxide and taking up with acid. Double dehydration of the silicate by evaporation in a perchloric acid medium, and weighing of the impure silica. Double hydrofluoric-sulphuric volatilization of the silica, weighing of the residue, and determination, by difference, of the pure silica. 4 Reagents Du
13、ring the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 4.1 Sodium peroxide 4.2 Sodium carbonate (anhydrous). 4.3 Ammonia solution, 0,91g/ml. 4.4 Perchloric acid 2) , 1,61g/ml. 4.5 Hydrofluoric acid, 1,14g/ml. 4.6 Hydrochloric acid
14、, 1,19g/ml. 4.7 Sulphuric acid, 1,83g/ml. 4.8 Hydrochloric acid, 1,19g/ml, diluted1+9. 4.9 Sulphuric acid, 1,83g/ml, diluted1+1. 4.10 Silver nitrate, 10g/lsolution. 5 Apparatus Usual laboratory equipment, and in particular: 5.1 Crucible, capacity40ml, of silicon-free iron, vitreous carbon, nickel or
15、 zirconium. 5.2 Beakers, for melt dissolution, of polytetrafluoroethylene, stainless steel or high purity nickel. 5.3 Platinum dish, capacity40ml. 5.4 Fluted glass funnel, diameter75mm. 5.5 Glass beaker, capacity600ml or800ml. 5.6 Muffle furnace 5.7 Desiccator 6 Sample Use powder which will pass thr
16、ough a sieve with a mesh size of160 4m, prepared in accordance with ISO3713. 7 Procedure 7.1 Test portion For silicon contents less than or equal to50% (m/m), take a test portion of0,50 0,0002g. NOTEFor silicon contents less than25%(m/m), it is possible to use a test portion of1g. For silicon conten
17、ts more than50%(m/m), take a test portion of0,25 0,0002g. 7.2 Blank test Carry out a blank test in parallel with the determination, following the same procedure and using the same quantities of all the reagents. 7.3 Determination 7.3.1 Transfer the test portion(7.1) to the crucible(5.1) containing10
18、 to12g of the sodium peroxide(4.1). Mix carefully and then, to prevent any loss of the test portion, cover with3g of the sodium peroxide(4.1) or3g of the sodium carbonate(4.2). Heat the crucible containing the test portion and flux on an electric hot-plate at350 to400 C until the melt blackens. Hold
19、ing the crucible in tongs, swirl it over a flame, heating gently at first to avoid deflagration, and then more strongly until the attack is complete. Maintain the product of fusion at red heat for approximately5min. Allow the crucible to cool. 7.3.2 Dissolve the melt as specified in either7.3.2.1 or
20、7.3.2.2. 7.3.2.1 Alternative I Place the crucible in a beaker(5.2), containing200ml of water. Cover with a watch glass. When effervescence has ceased, remove the crucible and wash it with hot water, collecting the washings in the same beaker. Transfer the alkaline solution to a glass beaker(5.5), co
21、ntaining30ml of the hydrochloric acid(4.6). Stir to mix the solution, wait for the salts to dissolve and add100ml of the perchloric acid(4.4). Proceed as specified in7.3.3. 1) At present at the stage of draft. 2) Attention is drawn to the hazards associated with perchloric acid when heated to fuming
22、.BS6200-3.26.5:1985 2 BSI 09-1999 7.3.2.2 Alternative II Cover the crucible and tap it on a hard surface to loosen the cake. Transfer the cake to a clean glass beaker(5.5), containing100ml of the perchloric acid(4.4). Fill the crucible with hot water and, after effervescence has ceased in the beaker
23、, add the contents of the crucible to the beaker. Transfer any residue from the crucible to the beaker using a rubber-tipped stirring rod and a minimum of water. Add30ml of the hydrochloric acid(4.6). Proceed as specified in7.3.3. 7.3.3 Place the beaker on a strongly heated hot-plate until white per
24、chloric fumes are evolved. Continue heating until the fuming residue begins to crystallize and acquires a pasty consistency. Remove from the hot-plate and allow to cool. Take up with20ml of the hydrochloric acid(4.6), added gently down the wall of the beaker, and a few millilitres of hot water. Stir
25、 and dilute with250ml of boiling water. Mix well and allow to settle. Filter the silica on a125mm flat ashless filter paper placed on the fluted glass funnel(5.4). Retain the filtrate. Rinse the beaker with warm water, using a rubber-tipped stirrer. Wash the filter with warm hydrochloric acid(4.8) u
26、ntil the yellow colour due to iron salts disappears, then finally wash several times with hot water until chloride ions are no longer present verify by means of a spot test with the silver nitrate solution(4.10). The filter shall be thoroughly washed, so as to remove any trace of perchloric acid, wh
27、ich would cause flaming up during incineration. Transfer the filtrate and the washings to the beaker used for the initial dehydration. Evaporate to a volume of about250ml. Add20ml of the perchloric acid(4.4) and carry out a second dehydration as described in the first paragraph of7.3.3. Take up, fil
28、ter (using a fresh filter paper) and wash the precipitate as before, but carrying out the final washing with cold water instead of hot water. 7.3.4 Place the two filters containing the silica precipitates in the platinum dish(5.3). Add4drops of the ammonia solution(4.3) to the filters 3) . Dry to re
29、move excess moisture and incinerate in the muffle furnace(5.6), initially at400 C maximum. Allow to cool. Add1ml of the sulphuric acid(4.9). Evaporate to dryness until sulphuric fumes cease to be evolved and then calcine at1100 C to constant mass. Allow to cool in a desiccator and weigh the dish con
30、taining the impure silica. 7.3.5 Moisten the impure silica with a few drops of water. Add about10ml of the hydrofluoric acid(4.5) and2 or3drops of the sulphuric acid(4.7). Evaporate to dryness until sulphuric fumes cease to be evolved. Carry out a second volatilization under the same conditions, but
31、 decreasing the quantity of hydrofluoric acid to2ml. Calcine in the muffle furnace(5.6) at1100 C to constant mass. Allow to cool in a desiccator and weigh the dish containing the impurities. 8 Expression of results The silicon content, expressed as a percentage by mass of the sample, is given by the
32、 formula where m 0is the mass, in grams, of the test portion(7.1); m 1is the mass, in grams, of the dish and impure silica obtained in the determination(7.3.4); m 2is the mass, in grams, of the dish and impurities obtained in the determination(7.3.5); m 3is the mass, in grams, of the dish and impure
33、 silica obtained in the blank test; m 4is the mass, in grams, of the dish and impurities obtained in the blank test; 0,4674 is the conversion factor from silica to silicon. 9 Reproducibility Experience has shown that the95% confidence limits for an experienced operator are: 0,30% for silicon content
34、s exceeding50% (m/m); 0,20% for silicon contents less than50% (m/m). 10 Test report The test report shall include the following particulars: a) the reference of the method used; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation
35、 not included in this International Standard or regarded as optional. 3) This reduces the hazard of volatile perchlorates spitting some of the silica from the crucible. m 1 m 2 ()m 3 m 4 () 0,467 4 100 m 0 - 46,74 m 1 m 2 ()m 3 m 4 () m 0 - =BS6200-3.26.5:1985 BSI 09-1999 Publication referred to See
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