la Verne W. Spring

“ We have several times referred to the debt which civilization owes to iron and steel structural materials, machinery and tools and particularly to those tools which have hardened cutting edges. Almost every one knows that hardened cutting edges are imparted to tools by sudden cooling in water or oil from a good red heat. Probably most of us, too, know that the blacksmith can again soften such tools by reheating to the same red heat and allowing them to cool slowly. ”

“ THE ALLOY STEELS We have learned that steel, fundamentally, is an alloy of iron with carbon, i.e., carbon is the characteristic element. We are now to note what often seem to be exceptions to this rule. While in reality steel is just this iron-carbon alloy, there are alloys known as steels to which such strong characteristics are given by elements other than carbon, that carbon seems not to be the defining constituent at all. ”

“ What can compare with thirty thousand pound lots of steel turned out from one Bessemer converter each seventeen minutes during the 24 hours in the day, that is, a total of 1300 tons or 2,600,000 pounds, in which not only the main controlling element, carbon, but also four lesser ones, silicon, manganese, sulphur, and phosphorus, are held within extremely narrow limits; or the modern blast furnace which produces a million pounds each 24 hours, run with the same certainty of control? ”

“ As the material for wire gauze and cloth, wire rope, cable, piano strings, springs of all sorts, pins, needles, nails, fence, barbed wire, and the myriad of other things, wire really is one of our great products.
It was mentioned that piano wire had been made which had a tensile strength as high as 400,000 pounds per square inch, which is six or seven times the strength of an equivalent cross-section of steel rail or plate. Wire is undoubtedly the strongest product which is made from steel. This is why wire rope or cable is so strong. ”

“ The incessant quiver of the iron plates beneath our feet with the rumbling and groaning from the inside of this monster are disquieting and the thought constantly recurs: “What if this powerful creature should just now rebel, as quite occasionally occurred in the old days when all of its moods had not been so well understood?” ”

“ While no one can desire to cast the slightest disparagement on the product of that period, much of which was excellent, astonishingly so considering the period, a moment’s consideration will convince one that modern products not only do not suffer in comparison but in reality are immensely superior. The ancients had little or no knowledge of the reason for the proper qualities of their tools and they made the metal from variable materials in a crude way in such small quantities that little uniformity was possible. ”

“ Unlike puddling furnace and open-hearth no burning out of the silicon, manganese and carbon is desired, though, of course, some occurs and has to be allowed for in calculating the mixture. The intention is simply to melt together with the least possible loss a mixture of such materials as will give the average final composition which long experience has shown to give the proper qualities to the finished product. ”

“ Steel has no fiber and for this reason it cannot be split as was the wrought iron bar shown in the illustration of page 92.
It will have been noticed that only small amounts of iron can be refined at one time. This, indeed, has been the unfortunate part of wrought iron manufacture, for it may readily be seen that production of any such material in lots as small as a quarter ton results in labor costs which are almost prohibitive in these days of machine-made goods. Not only is the output of a furnace small but much skill and judgment are necessary for the production of a high grade product. ”

“ Parts that do not have to be machined can be of “harder” iron; i. e., made of iron having lower silicon content.
Manipulation of the silicon content is not the only method by which the hardness of cast iron can be influenced. Graphite can “precipitate” (i.e., separate throughout the casting) only if sufficient time is given it to do so. That is, the cooling of the casting after pouring must be sufficiently slow. In a sand mold the iron remains molten for a time, and after solidification it cools slowly enough that the greater portion of the carbon separates as graphite. ”

“ One naturally wonders how it is possible to mine and carry these ores to the shipping ports of Duluth, Superior, Two Harbors, Marquette, Ashland, Escanaba, etc., put them aboard ore carrying boats, transport them by steam power to Milwaukee, Chicago, Gary, Detroit, Cleveland, Pittsburg, Buffalo, and the many other iron centers and convert them into iron and steel at a profit. This, of course, is only possible because of the inventive genius of man. For every operation ingenious machinery has been constructed which has brought the cost of such operations to its lowest terms. ”

“ Unlike the modern Bessemer, open-hearth, and other steel products which are reworked, i.e., rolled, forged, etc., cast iron is a comparatively old alloy dating back over several centuries. It cannot be rolled, forged, or otherwise reshaped, so its final form must be given to it at once by pouring or “casting” the molten metal into a mold. Its castings serve exceedingly well in the hundreds of places for which they are adapted. They are comparatively cheap, can be readily duplicated in small or large quantities, and those from the softer grades of cast iron may be machined easily. ”

“ As the open-hearth elimination of carbon is slower and under so much better control, the furnace usually is tapped when the carbon has been reduced to the percentage desired in the finished steel. When it is necessary to add carbon it is done sometimes by adding pig iron to the bath and sometimes by throwing a weighed amount of coal or coke in the ladle as the steel is going in. Molten iron and steel have strong appetites for carbon and dissolve it very readily. Ferro-manganese is used to prevent red-shortness and to deoxidize the metal. ”

“ Almost every civilized country has ore enough that it does pretty well. With many the trouble is that the ore has objectionable constituents or that supply of cheap fuel is not available. Germany has large deposits of iron ore, but until the invention of the basic Bessemer process about 1870 she was handicapped because of the high phosphorus content of her ore. The basic processes, both Bessemer and open-hearth, allow of the removal of this phosphorus during the conversion into steel, and they therefore brought Germany to the front as an iron producer. ”

“ Now the mills’ own inspectors are commonly more severe in their rejections of products than are the representatives which the customers themselves send. Not only does the mill laboratory make careful and accurate analysis of each heat or batch of steel made, but, after its application to orders, pieces of plate, shapes or rails rolled from it are examined, gauged, and test bars of the steel are pulled in the physical testing laboratory. ”

“ A trip through one of the large steel plants with its furnaces, its blooming and slabbing mills, its rail, plate, structural and rod mills is one of the most interesting that can be taken. If the visitor is not afraid of smoke or dust or of what seems to him an uncomfortable heat 276on a warm day he will discover new worlds. No particular attention is paid to the casual visitor to the plant, but, for those who show real interest, steel men have a warm welcome, from manager to the sample boys. ”

“ Largely because of the great size of the open-hearth furnace solid fuel, such as coal which can be used for puddling furnaces, is not adaptable.
As far back as 1839 attempts were made to gasify coal by burning it to ash and utilizing the gaseous products for industrial purposes. These attempts succeeded and the process has been brought to quite a high state of development. There are to-day a large number of efficient types of “gas producers” which furnish gas for general industrial use and it is with this “producer gas” that a great deal of the steel nowadays is made. ”

“ In cooling through Ar3, i.e., from gamma to beta iron, some rearrangement of its molecules produces the dilatation or expansion and the change in conductivity which was noted above.
From the fact that by chemical analysis any certain steel must have the same composition in its hardened that it has in its unhardened condition, it will readily be seen how futile it would be to expect chemical analysis to give us complete information regarding it. Too, tensile strength and the other usual physical tests can hardly tell us all that we wish to know. ”

“ Too, the metal for valves and fittings and other more or less complicated castings for high steam, air, ammonia, water, etc., must be uniform, of close grain, strong, yet soft enough to machine easily at the extremely high speeds which modern efficient tools and methods demand. The production of the best metal for such work requires the use of properly selected materials, judicious mixing, and clever operation of the cupola furnace, that the molten metal delivered to the foundry for the pouring of the molds may be hot and fluid and of the right composition for the particular work in hand. ”

“ When he thinks the steel should be molten, the expert attendant known as the “melter” quickly removes the tight fitting cover of the crucible and with an iron rod determines whether any unmelted pieces remain.
After complete melting the steel must be “killed,” else it will boil up in the mold upon pouring and leave a spongy or insufficiently solid “ingot” or block of steel. This “killing” of steel is a rather peculiar phenomenon. It is accomplished by allowing the steel to remain quiet in the furnace for another half hour or so. ”

“ With the latter the metal at the top of the bath is hotter than that underneath, and, through action of the flame and air, silicon is somewhat lowered before all of the heat can be poured, especially with air furnaces of large size. The metal can easily be “burnt” unless extreme care is taken. In the cupola we can get very hot iron continuously so that it is unnecessary to prolong the heat with the danger of burning that occurs with the air furnace.
Air furnace iron anneals rather more readily than does the product of the cupola, and the strength and malleability are usually greater. ”

“ Another constituent which is of great interest scientifically, though not at all commercially, is “austenite.” By quenching very high carbon steels from a very high temperature very suddenly and completely, we can fasten the “austenite” structure, which exists only at temperatures higher than martensite, i.e., austenite is our gamma iron with the carbon of the alloy in solid solution, perhaps as iron carbide, while martensite is thought to be the beta iron solid solution, perhaps with some gamma iron mixed with it. ”

“ The newly devised electric furnace process is the only possible competitor in sight. Of course for quantity and for lower cost the Bessemer and the open-hearth processes are the only available ones, but crucible steel has been the mighty factor in the commercial development of the world—at least until the latter half of the last century when the two other processes last mentioned began to acquire honor of their own without, however, detracting much from the importance of crucible steel as the steel of “quality.” ”

“ The excellence of Sweden’s iron and steel has long been known the world over. Sweden produces approximately one per cent of the world’s total production of iron and steel, but her ore has been of such high grade that iron made 35from it has maintained its position as a standard for use in the manufacture of highest grade crucible steels. The very finest steels for cutlery and tools, and even the softer grades of steel of northwestern Europe, have been made from Swedish iron as a base. ”

“ When taking heavy cuts a tool of to-day may exert as much as ten tons’ pressure against the metal it is cutting and the advent of this wonderful material for tools necessitated the building of immensely heavier and stronger lathes and other machines, which, alone, were capable of giving them power to do their work. The high-speed steels, therefore, have revolutionized metal-cutting practice and shop methods and have very largely aided efficiency. ”

“ Undoubtedly the best preservative against corrosion for iron and steel is what is known as “hot galvanizing.” Much wire is hot galvanized. In this process the wire is “pickled” in weak acid to remove scale, given a soft red coating by dipping in weak muriatic acid and drying. The strands of wire 20 or 30 abreast are run through a kettle of molten zinc. The wires are wiped smooth and free from excess zinc by pulling them through asbestos pads. A continuous coating of zinc is thus permanently left upon the surfaces of the wires which very effectively keeps them from rusting. ”

“ Consider the power plants of our factories, of gas and electric lighting plants, the pumping machinery and distribution systems of water works, mines, etc. Would the electric current which supplies so much of our power and light be known to-day or even be possible but for the magnetic properties of iron? ”

“ The melter has become very proficient in judging the composition of the metal of the bath from the fracture of these broken test pieces. By means of the samples taken he watches the elimination of the metalloids. When he thinks the reactions have progressed far enough he takes a last sample which is rushed to the chemist who makes a hurried “control” analysis for carbon and phosphorus, the metal being held in the furnace meanwhile. If the results of this analysis show the bath to have the desired composition the steel is poured. ”

“ So during ordinary cooling from the molten alloy or the slower cooling of the steel during the annealing process, the martensitic structure breaks down at the recalescent temperature into pearlite and ferrite (soft iron) if the carbon content of the steel is lower than about .90%, or pearlite and the other and very hard constituent, “cementite,” if the steel has more than .90% of carbon. If the carbon content happens to be just .90%, or thereabouts, there is exactly sufficient pearlite to make up the total area of the field shown under the microscope. ”