81 V1.-On the connection between the Mechanica 2 Qualities of Malle-able Iron and Steel and the amount of P7kosphorus they contain. By B. H. PAUL,Ph.D. IThas been customary to consider the presence of veiy small amounts of phosphorus or sulphur in malleable iron and more especially in steel as being among the circumstances most pre- judicial to the qualityof the metal. This opinion is generally expressed in chemical text-bwks and metallurgical treatises ; but there appears to be much uncertainty as to the actual amounts of these substances which are sficient to cause dete- rioration of the quality of malleable iron or steel. Phosphorus is considered to render the metal weak and what is technically termed ‘‘(cold short.” As regards steel it has recently been stated by an eminent metallurgist* to be a fact at least as well established and as generally accepted as any relating to metallurgy that much less than about 0.3 per cent.of phos- phorus produces a decided and injurious effect. There is probably little reason to question the general ac- ceptance of the opinion that a very small amount of phosphorus exercises a prejudicial influence on the quality of steel but at the same time there does not appear to be any definite or satis- factory evidence that this opinion is well founded nor any sufficient- proof that the observed inferiority; in certain cases of the steel or malleable iron made from phosphuretted pig iron is really due to the presence of phosphorus in the metal ; still less is there any reasonable explanation to be met with either aB to the way in which phosphorus affects t,he qualities of the metal or as to the state in which it may exist.In fact the view held in regard to this subject though based to Bome extent on experience of a limited nature is unsupported by any scientific evidence and it rests mainly on the fact that certain celebrated varieties of malleable iron and steel of very high quality are known to be either free from phosphorus or to contain only infinitesimal amounts of that substance rarely exceeding 5+TT in malleable iron and s&a in steel. The opinion that the presence of phosphorus affects inju-iiously the qualities of steel and malleable iron has lately * Dr. Percy (‘Times,” 7th January 1869.VOL. XXII. H 82 ON THE CONNECTION BETWEEN THE MECHANICAL received considerable support from the experience gained in the application Gf the Bessemer method of converting pig-iron for it has been found to be a coincidence which so fa as I am aware is invariable that pig-iron containing as much as 0.1 per cent. of phosphorus is unsuitable for working by that method. As there is no elimination of phosphorus effecteih by the Bessemer method this amount of phosphorus hm conse-quently been regarded as the maximum proportion which steel can contain without its quality being deteriorated. This con- clusion appears to be a generalization much wider than is justified by the f‘dcts observed for it is still questionable whether the coiiicidence between the presence of‘ a certain amount of‘ phosphorus and the inferiority of the steel may not be purely accidental and whether the .inferiority of steel made fiom phosphuretted pig-iron may not be due to mme other circum- stance than the presence of phosphorus.The probability of this being the case occurred to me some years ago when I had occasion to give special attention to this subject and quite recently an opportunity has offered itgelf for testing the suffi- ciency of the received opinion. Some considerable surprise has been excited by the publication of an analysis by Dr. Miller of a sample of so-called ‘‘ steel iron,” which gave the proportion of phosphorus as amounting to 0.292 per cent. while the results obtained by Mr. Kirkaldy in testing a large number of samples of this metal showed that it gave indications of very excellent quality in regard to tensile strength and ductility These results taken together with the amount of phosphorus indicated by Dr.Miller’s analysis as Being present in the metal appeared to be so inconsistent with the general opinion as to the influence of phosphorus in rendering malleable iron weak and “cold short,” that I thought a further examination of other samples of this metal would be desirable; for if phosphorus were really the cause of weakness and if it were that substance which rendered iron (‘cold short,” it seemed to me that the tensile strength of the metal wds precisely the character that should be most prejudicially influenced by the presence of such an amount of phoaphorus.If therefore the analysis of several bars of thk “steel iron,” which had been tested as to their tensile strength and gave results showing that this was con-siderable should at the Bame time indicate the presence of phoaphorus to any great extent it appeared to me that there QUALITINS OF MALLEABLE IRON AND STEEL ETC. would at least be some ground for questioning the opinion hitherto held as to the influence of that substance on the quality of iron and Some evidence that in regard to the amount of phosphorus which might exist in malleable iron and steel with- out affecting its quality something yet remained to be learnt either as to the state in which the phosphorus existed or as to the conditions by which any prtjudicial effects of its presence might be counteracted.With this object I obtained through the kindness of Mr. No yes portions of several bars of "steel iron," produced from various kinds of pig-iron all of which bars had been tested by Mr. Kirkaldy as to their tensile strength and other mecha- nical qualities. These samples were examined for phosphorus quantitatively with the following results :-No. of bar. Tensile etrength in pounds per square inch sectional area. Permanent exteudon of bar per cent. Kind of pigironproduced from. Amount of phosphorus per cent. 1,090 1,091 51,671 51,181 25 '5 24 -5 Clay Lane No. 4 pig."Stanton forgepiq BBB.+ Clay Lane No. 4 pig.*Stanton forgepig BBB.t '206 -271 1,660 52,014 26 -6 *311 1,320 51,593 28 *6 -203 1,147 1,251 1,342 51,597 46,547 52,842 23 *7 21 .o 26 *6 Glengarnock,{ so.2 pig.§Round Oak11 ButterleyTI *170 0144 *286 These results are perfectly in accordance with the isolated result obtained by Dr. Miller and they indicate I believe an average amount of phosphoius much larger than would have been generally considered to exist in malleable iron presenting such a degree of tensile strength as that assigned to these bars and so far as this character gerves to indicate the quality of the * Cleveland iron. t Northamptonshire iron. $ Welsh iron. 9 Scotch iron. 11 .Staffordshire iron. 7 Derbyshire iron. H2 ON THE CONNEUTION BETWEEN THE MECHANICAL metal it would appear to be very good. According to the deter- minations of tensile strength of bar-iron by Fairbairn,* Kirkaldy,f Napier,-$ and others it amounts in the very best kinds of iron (Swedish and Lowmoor) to about 58,000 lbs.per square inch sectional area on the average and ranges from 47,855 lbs. to 66,390 lbs. while the average permanent extension or drawing out of the bars which furnishes an index of the ductility of the metal and its consequent power to resist the influence of a shock amounts to about 24 per cent. and ranges from 20 to 28 per cent. The number of analyses here given is of course much too small to admit of any general conclusion as to the amount of phosphorus which may be present in malleable iron without affecting its general quality and applicability for the various pur- poses to which it is applied; but in any case as tensile strength is one of the most important qualities of iron and as a high degree of that character appears to be compatible with the presence of a considerable amount of phosphorus in the metal this fact has an interest in reference to the manufacture of iron horn the very abundant iron ores of this country which have been considered inferior to a great extent by reason of the amount of phosphorus they contain.There are also other facts which tend to throw some doubt on the received opinion as to the influence of phoephorus. Thus for instance I can state as the result of my own observation that throughout the whole iron districts .of Belgium the ores smelted contain on the average a very large amount of phosphorus; but notwith- standing this fact some very good malleable iron is produced there although none of the Belgium pig-iron I have met with will answer for conversion into steel or malleable iron by the Bessemer method.In addition to the bars of ‘‘ steel iron ” above mentioned I also obtained portions of two bars of cast steel which were similarly tested by Mi*.Kirkaldy and on analysis I ascer-tained the presence of phosphorus in them in the following amounts :-* British Association Reports 1856. .t. Transactions of the Institution of Engineers in Scotland 1858-9. $ Ibid. QUALITIES OF MALLEABLE IRON AND STEEL ETC. Tensile strength Pemanent Amount of No.of bar. in pounds per extension Kind of pig-iron phOSphOrU6 square inch per cent.produced from. per cent. sectional area. ay Lane No. 4 1,077 80,916 3 -3 pig Stanton -240 p1 forge pig BBB. Clay Lane No. 4 1,082 106,602 13*7 pig Stanton *241 forge pig BBB. According to the observations of F nirbairn Kirkaldy and Napier the average tensile. strength of cast-steel bars and plates is about 100,000 lbs. per square inch of sectional area and it ranges from 75,594 lbs. to 132,909 lbs. according as the metal is hard or soft The corresponding permanent extension amounts on the average to 8.7 per cent. and ranges from 31 to 19-8per cent. In regard to mechanical qualities therefore the bars of cast steel here referred to come within the range of variation observed in high class steel. At the same time the amount of phosphorus in this cast steel is very much more in excess of’ the reputed maximum amount that can exist in steel of such quality as is indicated by these mechanical tests than it is in the case of the bars of ‘‘ steel iron,’’ and it is about tenfold -as much as is stated to be preseKt in the best kinds of steel.These results are therefore interesting in so .fax as they show that the presence of such an amount of phosphorus in steel does not ne’cessarily interfere with its possessing a high degree of tensile strength which is one of the most important qualities for many of the purposes to which steel is now being applied. It must be stated here that the samples of iron and steel analysed were produced by what is known as the Heaton method of converting pig-iron by means of alkaline nitrate.I am unable at present to give any results which wouldserve to indicate the state in which the phosphorus may exisrt in the samples of iron and steel above referred to; but this seems to be a question deserving of inquiry for as it is considered t80be an established fact that steel or ironmade by the Bessemer method cannot contain at the utmost. more than +&v part of phosphorus if its quality be good the existence of such a much larger amount in the samples I have analysed would seem to indicate the possibility that if phosphorus be injurious in some cases Kt5 MALLEABLE IRON AND STEEL ETC. still under certain coniiitions at least it may be present without any such effect. It is my intention to carry out a complete exaiiiination of theae samples with the object of elucidating if possible this question.The analytical method by which the separation of phosphorus was effected in these analyses; was that by means of molybdic acid and with the exception of the length of time required for the successful application of this method it is one-which I believe presents great advantages especially for the deter-mination of small amounts of phosphorus. The chief pre- cautioiis I have fwund necessary to be observed are to avoid the presence of any great excess of free acid in the solution to be tested; to haw this solution as concentrated as possible before adding the molybdic solution and then to give amply sufficient time for the perfect separation of the yellow precipitate.This separation is much facilitated by heating the liquid; but since arsenic acid reacts in the same manner as phosphoric acid and gives a similar yellow precipitate when the liqiiid is heated to near the boiling point it is desirable not to heat it much above 4OoC. At least 24 hours should be allowed for the separation of the precipitate and then it may be collected on a filter and washed with wat.er containing about 1 per cent. nitric acid and a mere trace of molybdate of ammonia in which the yellow pre- cipitate-containing only about 4 per cent. phosphoric acid-is 80 slightly soluble that the estimation of phosphorus is not sensibly affected. For the determinat3on of phosphorus 01-phosphoric acid the weighing of the yellow precipitate which may contain arsenic acid and silica is less to be depended upon than converting it into phosphate of magnesia arid ammonia by dissolving with ammonia and precipitating with a magnesia salt.The ammonia phosphate may either be weighed after drying at loPC. and then tested for silica and arsenic or ignited and the pyro- phosphate weighed as usual. This method of estimating phosphorus in iron and iron ore i%I believe much more to be depended on than any of the other methods hitherto adopted with some of which there is much iisk of an imperfect separation of t,he minute quantities of phosphoric acid from the disproportionately large quantity of iron.