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MARINE, RHEVIHW. HS Steel Forgings for Marine Engines, The Marine Journal of New York in a recent issue, gives a list of about a dozen large ocean vessels which have broken their shafts dur- ing the past twomonths. The list of casualties might be considerably augmented if information was at hand regarding all the similar but smaller breakages of which no record is kept. Lake vessel owners were reminded of the fact that there is a similar mortality of shafts, crank pins and other forged parts of marine engines on lake vessels by the paper read before the Lake Carriers' Association at Detroit in Jan- uary last, by Mr. H. F. J. Porter, western representative of the Bethlehem Iron Co., who had a long list of accidents of this kind which happened during the past year, and which had been compiled for him by some of his friends among the marine insurance agents. These accidents are occurring from time to time and we read of them casually, but as no one keeps a complete record of them we do not realize how important a duty forgings play among the component parts of marine engines. The character of vessels on the lakes is grad- ually changing and approaching rapidly the type of vessel which is built for ocean trade. Within a few years we have changed from small wooden vessels to vessels heavily strapped with iron; then to composite and iron vessels, and again to vessels entirely of steel, even as regards deck houses and spars. Weare now undergoing a final change from iron to steel forgings. In the paper read before the Lake Carriers' Association by Mr. Porter, the comparative merits of iron and steel forgings were very clearly shown and the advantages were pointed out of having lighter and stronger parts by using steel instead of iron. The importance of this subject to the vessel owners is apparent from the fact that they asked Mr. Porter to repeat' his address at their next annual meeting, and re- quested him to add to it any new information that he might be able to collect during the present year. Some extracts printed herewith, from a paper recently read by Mr. Porter before a scientific body in Chicago, are of interest in considering the subject. "Tt is the duty of the designing engineer to make the parts of his engines as light and as strong as possible, and it is for these reasons that the weaker and less reliable admixture known as wrought iron is gradually being replaced by the stronger metal, steel. In cases where economy in space and weight is required, the still stronger alloy, known as nickel steel, is rapidly coming intouse. Theold idea that wrought iron was more reliable than steel on account of its fibrous nature has given way now that we understand how to properly man- ufacture steel. The impression used to prevail among those who had not given the matter careful consideration that the characteristic dif- ference between wrought iron and steel was that the former was es- sentially fibrous, whereas the latter was crystalline in its structure; and that wrought iron, on account of its fibre, was tougher and more tenacious, whereas steel was apt to snap off suddenly. It was also sup- posed that it was only when wrought iron was subjected to sud- den shock and vibration its structure would assume a crystalline char- acter, and that it would then break like steel. We know that these ideas are very primitive; that all metals are by nature crystalline, wrought iron with the rest. All metals in cooling from a liquid toa solid state solidify by crystallization. This is the only period when crystallization can take place, and vibration and shock have nothing todo with making wrought iron crystalline, for it is already in that condition. As far back as twelve years ago, Prof. Thomas Egleston, of the School of Mines, Columbia College, New York city, in a dis- cussion of this subject ata meeting of the American Society of Mechanical Engineers, said: 'With regard to fibrous iron, there is no such thing. It is an appearance, not a quality. Etching with acid does not prove the fibrous structure, since all iron contains a consider- able amount of slag easily soluble in acids. This in a rolled bar will be distributed more or less uniformly in the direction in which the bar has been rolled, and when acted upon by acid will be eaten out in more or less parallel layers from the outside. When the action is con- tinued, this appearance of parallelism disappears, as it is only super- ficial. If thessame iron is submitted in a tube to a current of chlorine gas, the whole of the iron will be dissolved out and a mass of exactly the same shape as the iron will be left behind, which is exceedingly light and porous, and which is slag. If this be examined it will be seen to have a sort of pseudo-laminated structure running through its ~ mass, which brings long strings of it to the outside of the iron, giving the pseudo-fibrous appearance to the piece when itisetched. If the end of any fractured bar which has the pseudo-fibrous structure is examined with a glass, each so-called fibre will be seen to be the face of a crystal. It is the drawing out of the ends of these crystals which produces the change of color in the mass which gives the pseudo-fi- brous appearance. If the surface was highly magnified there would be no fibrous appearance.' "Mr. Bayles of the Iron Age said also: 'My opinion on this sub- ject was formed long ago, and has since been strengthened by observa- tion and experiment. Among the first questions which I was called upon to discuss under conditions imposing a professional responsi- bility was this very question of the crystallization of wrought iron. While seeking evidence on the subject I was invited by the manager of a rolling mill in Pennsylvania to witness some simple experiments, and from these I learned a great deal. In the blacksmith shop at- tached to the mill a number of test pieces of high quality merchant bar were tested. These pieces were nicked and turned over the horn of the anvil. They developed a fracture more like that of seasoned hickory wood than anything else to which I can compare it. The metal tore open with a long, silky fibrous fracture, showing a quality as good as had ever been attained in iron making up to that time. Six inches further along the same bar a second nick was made, and without any apparent difference in the manner of striking it, the iron was broken short off, showing a structure so apparently crystalline that one might imagine it was anything but good wrought iron. I found upon investigation that this was simply a blacksmith's trick, and that such results could be produced at pleasure, the character of the fracture depending entirely upon the manner in which the metal was struck after nicking. At first I was somewhat skeptical on this point, deeming it probable that the shocks and stresses of tear- ing the fiber apart in the first test had produced certain structural changes which accounted for the appearance of the fracture occasioned in breaking it short off. This, however, was disproved in a very few minutes, it being as easy for the blacksmith to produce the crystalline fracture first and fibrous fracture afterwards as to reverse the order. These facts have been touched upon by some of the gentlemen who have already spoken, but they do not seem to have given the fact that a piece of new iron can show both a fibrous and crystalline struc- ture within a space of two or three inches, as much weight as it seems to me entitled to as evidence with regard to the cold crystallization of iron. From such study of iron structure as T have had opportunity of making, I have reached the conclusion that talking about the crys- tallization of iron is much the same thing as talking about the crys- tallization of sugar and salt. It cannot pass from the plastic to the solid state in any other way than by crystallization. Whatever we may be able to do with it in the way of shop manipulation ,we can not give it -- a structure other than crystalline. In rolling iron important struct- ural changes are produced. Crystals are more or less distorted, and are so displaced that they form, with the aid of the cinder, what we commonly call the fibrous structure. The crystals remain, however, and I have never seen a piece of iron polished and etched with weak acid in which a well defined crystalline structure was not distinctly visible. If, therefore, we find in iron which is broken an appar- ently crystalline structure, there is no occasion for surprise. The ques- tion is not whether it has become crystalline as the result of shocks and stresses, but what changes have been produced by these means which render the metal more brittle than when first wrought into form. This is a question quite separate and distinct from that presented at present for discussion. No fact has ever been brought to my notice which has seemed to me to warrant the conclusion that any crystals -- had developed in cold iron which were not there before it had cooled.' "What is needed for our forgings is a metal free fromslag and such mechanically mixed impurities, so that the force of molecular attraction can act upon adjacent crystals and thus hold the mass together. Such a metal can be obtained by the melting process only, by which steel is produced, thus allowing all foreign substances to float to the top and be taken off. Steel in its mildest form is recognized as at least one-third stronger than wrought iron. Higher grades of steel are from twice to three times its strength. In these days of close competition, the carrying capacity of our lake vessels can be increased by reducing the size , and thereby the weight, of engine forgings, by making them of steel instead of iron. Or, if the original sizes of the wrought iron forgings be adhered to, as steel substitutes would be so much stronger, higher speed might be attempted and thus more car- goes be carried in a season. As steel will take a higher polish than iron, "friction will be less and less power will be required, As less breaks will occur, if the price is higher, this advance can be looked upon in the nature of insurance."'