41S 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Dkokmbkr, 



PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF CIVIL ENGINEERS. 

 June 21. — fconiinued.J 



" On Kome peculiar Changes in the Internal Structure of Iron, intlependenl 

 of, ami subsequent to, the several processes of its manufacture." By 

 Charles Hood, F.R.A.S., &e. 



The singular and important changes in the structure of iron, which it is 

 the ohject of this Paper to explain, arc those which arise in the conversion 

 of the quality of iron, known by the name of " red short iron," which is 

 tough and fibrous, into the brittle and highly crystallized qnality known hy 

 the name of " cold short iron." This change the author considers has never 

 been attributed (as it ought to be) to the operation of any definite and 

 ascertained law, but has generally, when observed, been supposed to arise 

 from some accidental cause, and been considered as an isolated fact. 



The fracture of railway axles, by which some of the most lamentable ac- 

 cidents liave occurred, arises from this molecular change in the structure of 

 iron, by which the axles lose a vast proportion of their strength. 



The principal causes which produce this change are percussion, heat, and 

 magnetism, and the author traces through a great number of practical cases 

 of ordinary occurrence the joint, as well as the separate effect of these three 

 causes; showing that the rapidity of the change is proportional to the com- 

 bined action of these several causes, and that in some cases where all the 

 three causes are in operation at the same time, the change of structure is 

 almost instantaneous ; while in other cases, where this united operation does 

 not occur, the change is extremely slow, extending over several years before 

 it becomes sensible. Among the examples given, and of which the causes 

 are explained, are the conversion by means of heat, as in the case of wrought- 

 iron furnace-bars, and other analogous cases, particularly when any vapour is 

 present : the operation of the tilt hammer in the planishing of iron, by 

 which both vibration and magnetism of the bar is produced, when the tem- 

 perature is within a certain Hniit, beyond which limit the bar loses its mag- 

 netic power, and no crystallization occurs ; and the instance of piston-rods 

 and other cases, where from any accidental circumstance a peculiar jar or 

 vibration has been given to particular parts. The effect of the continual jar 

 or vibration upon the axles of common road carriages is a case of the oppo- 

 posite kind, where, notwithstanding the continual vibration, this molecular 

 change does not take place u-lien the a.rle is insulated from the effects of 

 magnetism. In railway axles, however, the case is very different. The rapid 

 rotation of the axle produces powerful magnetic action, while the friction 

 causes much lieat ; and these effects, added to the constant percussion which 

 is prod\iced by the peculiar motion of railway wheels, causes the crystal- 

 lization to be produced with extreme rapidity; the effect being probably 

 further increased in the axles of locomotive engines by the magnetising 

 power of the electricity generated hy the effluent steam. The crystaUized 

 structure being the natural condition of iron, as well as of several other 

 metals, the author considers that in these changes we observe a constant 

 effort to return from the artificial to the natural and primal condition of the 

 metal, and the conclusion arrived at is, that this crystaUization is not neces- 

 sarily dependent upon time for its development, but is determined by other 

 circumstances of which the principal is undoubtedly vibration: that heat, al- 

 though it assists, is not essential to it, but that magnetism, whether induced 

 by percussion or otherwise, is an essential accompaniment of the phenomena. 

 The paper concludes by pointing out the increased effects likely to result 

 from the rigidity of the springs, the looseness of the brasses, and other 

 causes which increase the vibration on tlie axles of railway carriages. 



Several samples of broken railway axles were exhibited ; some of them 

 being cut from different parts of the same axles, showed that at the journals, 

 where the vibration was the most intense, the crystallization was increased 

 to a great extent beyond what occurred in other parts of the same axle. 



Kemarks. — Mr. Moreland had frequently noticed that pins for chains, and 

 pump-rods, although made of the best iron, would, if subjected to concus- 

 sion, after a certain time break suddenly, and that the fracture would exhibit 

 a large crystallized texture. This was also frequently observed in the broken 

 axles of road-carriages, although they were generally made of iron of the 

 finest quality. 



Mr. E. Woods had observed the crystallized fracture in all the broken 

 axles on railways which be had seen. 



Mr. Hood exhibited some specimens of broken axles, all of which showed 

 a large crystallized fracture : he believed that the iron from which the ma- 

 jority of them had been made was of the best qnality, and in the p.irts not 

 immediately subjected to concussion the fracture was quite different. One 

 of them had been in use only three months, and had become so brittle that, 

 on attempting to break it, it jarred off at the shoulder of the journal, al- 

 though an incision was made all round at the spot where it was intended to 

 be broken. 



Mr York would account for the tendency of the axles to break at the 

 journal, by that part being subjected during the process of forging to more 

 hammering than the body. 



,Mr. Hood agreed that such might be the case, but he conceived that it 

 was more probably produced by cold hammering. He had taken a sample 

 frimi the body of a hrolicn cranked axle, from the (irand Junction Itailway, 

 the iron of which was evidently of the best quality, but at tlie point of frac- 



ture, which was certainly at that part where it had been most hammered, the 

 fracture presented a large crystallized texture. 



A large anchor, which had been in store for more than a ccnturv', at 

 Woolwich Dock-yard, and was sujiposed to be made of extremely good iron, 

 had been recently tested as an experiment, and had broken instantly with a 

 comparatively small strain ; the fracture presented very large crystals : in 

 this case he believed the length of time which the anchor had remained in 

 the same position had produced the same effects as magnetism and vibration. 



Mr. Lowe stated that at the gas-works under his direction wrought-irou 

 fire-bars, although more expensive, were generally preferred ; a pan of water 

 was kept beneath them, the steam from which woidd speedily cause them to 

 become magnetic: he had frequently seen these bars, when throw down, 

 break into three pieces with a large crystallized fracture. 



Mr. Miller had frequently seen in manufactories, that when the smiths had 

 forged parts of engine-work which from their intricate forms had required 

 to be much hammered, the ends were jarred off while they were being 

 worked upon. He instanced particularly the side rods of the engine for the 

 " Lord iMelville " steamer, of which, while shutting up the middle, one of 

 the ends of each rod was jarretl off, and presented large crystals in the 

 fracture ; being well assured of the good quality of the iron in the rods, he 

 had the same ends welded on again, and although the circnmstancc had oc- 

 curred 20 years since, they were still at work, and had not shown any symp- 

 tom of weakness. It must be evident that iu this case, the fracture and the 

 crystallized appearance of the metal must have been produced by the cold 

 hammering to which it had been subjected. 



Mr. York agreed with Mr. Hood in the fact of a change taking place in 

 the texture of the iron, but he was of opinion that it more frequently oc- 

 curred during than after manipulation ; he alluded more particularly to rail- 

 way axles, in which he believed the injury to be done by tlje cold hammering 

 or planishing after they were faggoted; he had frequently seen one end of 

 an axle fall off while the other was being hammered : in all such cases, 

 and those of accidental breakage, such as recently occurred on the Versailles 

 Railway, and in other places, the fracture always presented a crystallized 

 appearance. 



He then exhibited and described a railway axle, which he stated to possess 

 the combined advantages of rigidity and toughness, and avoiding entirely the 

 crystallization of the iron during the process of manufacture ; this he des- 

 cribed to be effected by maintaining the axle in a hollow state during the 

 whole operation of hammering, thereby avoiding the vibration and concus- 

 sion, to which cause he attributed the crystallization of the iron in solid 

 axles, being of opinion that the repeated blows of the hammer on a solid 

 mass, particularly during the process of " planishing," were the chief, if 

 not the only cause of the ductile quality of the iron being destroyed. He 

 stated, that he had made numerous experiments for the purpose of ascertain- 

 ing this fact, and in every instance when the axle was sound, the iron pre- 

 sented the same crystallized fracture, although the bars, previous to their 

 being welded together, were of the most fibrous quality, but if the axle was 

 not quite sound, and the bars not perfectly welded to the centre, then the 

 fracture was somewhat fibrous, the axle being partially hollow and thereby 

 avoiding the vibration to a considerable extent. This fact suggested to him 

 the propriety of keeping the axle hollow ; and the mode of manufacture he 

 described to be by taking two dished half-cylindrical bars of iron, of the 

 entire length of the axle, putting them together and welding them under a 

 hammer in swages, by which means the particles are not driven asunder by 

 the heavy blows and the axle of faggot lengthened, but are driven together 

 and towards the centre. The axles produced by this means, he stated to be 

 as perfectly ductile as the bars in the first instance. A further advantage, 

 he stated to consist, in being able to make half the whole length of the axle 

 at one heat, thereby avoiding to a considerable extent the danger of burning 

 the iron by repeatedly heating it ; the iron in the axle he described, as being 

 a uniform cylinder in thickness, and consequently requiring a uniform lieat, 

 whereas the external bars of a faggot for a common axle were liable to be 

 burnt, before the centre was heated to a welding state. The diameter of the 

 hollow axle was increased from 3^ in. (the general size of a solid axle) to 

 4 in. in order to give a proper degree of rigidity, but without increasing the 

 weight. 



The usual proof to which solid railway axles were subjected, was by al- 

 lowing a weight of C cwt. to fall upon them from a height of 9 ft. ; with 

 that force they were frequently brol.en at the second blow, and sometimes 

 by the first — he had tried some of tiie hollow axles, by letting fall upon 

 them a weight of 10 cwt. from a height of 15 ft., without breaking one of 

 them. 



Mr. Simpson expressed the obligation of the Institution to .Mr. Hood, for 

 bringing before the nieetiug such an interesting communication, upon a sub- 

 ject which it is of the utmost importance to railways, should be carefully 

 examined. It was to be regretted, that the late period of the Session had 

 prevented the attendance of those members whose attention had been more 

 particularly directed to railways ; but on the renewal of the subject next 

 Session, upon the production of the report upon the projected experiments, 

 promised by Mr. Hood, a very useful discussion might be anticipated. 



June 28. — The Preside.\t in the Chair. 

 " An Account of the Uridyl- over the Thames, at Kingston, Surrey." I!y 

 John lirannis Birch, Crad. Inst. C. E. 



Previous to the vear 1828, when the present bridge was opened to tlie 



