US23139A - Improvement in the manufacture of steel - Google Patents

Description

UNITED STATES V PATENT OFFICE.

IaRANz ANTON LOHAGE, or UNNA, PRUSSIA, ASSIGNOR TO E. L. BENZON,

or BOSTON, MASSACHUSETTS.

IMPROVEMENT IN THEMANUFACTURE O F STEEL.

Specification forming part of Letters Patent No. 23,139, dated March 1, 1859.

To all whom it nlay-concern.-

Be it known that I, FRANZ ANTON LOHAGE, of Unna, in the Kingdom of Prussia, a subject of the King of Prussia, have invented Improvements in the Manufacture of Steel; and I do hereby declare that the following is a full and exact description of my said invention. W My invention of improvements in the manufacture of steel is based upon certain discoveriesllraye made in the behavior of pig or cast iron undf'iertain circumstances, such as l while being heated or boiled in a reverheratory \furnace; and it consists in the application of the knowledge of the scientificfacts so obtained to the treatment of crude pig or cast iron or refined metal, so that guided by a close observation of the behavior of such iron in a reverberatory or other melting furnace the workman may be enabled with certainty and precision to decarbonize the iron to a definite and determined extent, and leave or retain a proper amount or atomic proportion of carbon in chemical combination with the iron,and by this means be enabled to produce steel of any required temper or degree of hardness.

I am aware that many attempts have been made,with more orless success, to convert crude pig or cast iron into steel by decarbonizin g the former to a certain extent; but owing to the want of an accurate knowledge of thelaws upon which are based the chemical changes that take place in the iron while the process of decarbonization is proceeding these processes have heretofore been to a great extent uncertain, and the products obtained by them have not been uniform in quality, nor could the manufacturer with any certainty rely upon producing any predetermined and desired result.

Now, owing to the discoveries I have made of the behavior of fused iron in the paddling or reverberatory furnace I can detect and ascertain with accuracy the chemical changes which from time to time take place inthefurnace, and therefore I am enabled to conduct withprecision and certainty any process and operation connected with the conversion of pig or cast iron into steel; and I have found the ordinary puddlin g or reverberatory furnace to be best adapted for carrying out the improved process I have originated, because I can therein best control the chemical action of the cinder or slag upon the master pig iron, and lean also assist the process by the mechanical action of the puddlin'g-tool, and can guide myself by the eye to attain accuracy.

It has been long known to scientific men that the different physical properties of pigiron, steel, and wrought-iron depend upon the percentage of carbon they respectively contain, and that in making pig-iron into wrought-iron in the puddling-furnace the metal at some stage of the process must contain that atomic proportion or percentage of carbon which will constitute it the substance known as steel. Starting from this known fact I commenced studying the physical properties of pig-iron and steel,and after various careful experiments and observations I came to the conclusion, not only that the physical properties of pig-ironsuch as its non-malleability-and of various qualities or tempers of steel-.such as their malleability and welding propertyas well as the different degrees of hardness of steel, depended upon the proportion of carbon the different samples contained, but that during the process of manufacture the state of decarbonization re quired to impart these physical properties to the iron might be distinctly recognized.

In my practical experiments to ascertain at what point ofdearbonizatiou crude pig or cast iron first became a malleable metal I discovered that the particlesof the metal invariably at certain stages of the process assumed certain definite forms, and that such forms of the particles indicatedcertain definite degreesot' decarbonization and the possession of certain definite physical properties. I thus ascertained the form the particles of metal assumed when they possessed the physical properties of weldable steel, and from this I was enabled infallibly to determine at what stage ot' the process steel having such properties could be obtained. Having further determined by practical experiments the point at which pi g-iron first becomes malleable, and which is the point corresponding to the highest temper of steel, and

,having carefully watched every stage of the process of decarbonization, as hereinafter more fully described, I was enabled to determine at what point of decarbonization and at which corresponding form of particles crude pig or cast iron in the puddlin g or reverberatory furnace became first malleable and next weldable steel. This led to the discovery that by closely watching the various changes and controlling or regulating the process I could with certainty produce in the puddling-t'urnace every degree of temper of steel, from the hardest steel-so hard as only to be titfor meltinginto cast-steel down to the softest steel, which, in the form of German shear or cast steel,would not perceptibly harden at the highest heat it plunged into cold water.

I will now proceed to illustrate the practical application ofthe above-mentioned discoveries, and will, to do so more clearly, explain the manner in which it may be carried into effect in a puddling or reverberatory furnace.

I introduce into a reverberatory furnace of the usual construction (giving a preference to a furnace with a flat bottom) a convenient charge of crude pig-iron or of refined metalsay about three hundred and sixty pounds weight-and in the first stage of the puddling process I adopt the usual mode of operation, my object being to bring the mass to a perfect state of boiling. As the different descriptions of pig or cast iron vary in their nature, they require a somewhat different treatment, which is effected, as is well known, by opening or closing dampers, as may be required, or by adding a mixture of manganese and salt, or employing other known means for the purpose of securing perfect boiling and a good rising of the entire mass. This point having been attained, I make up a good fire, by means of an additional charge of coal, and work with an open damper in order to accumulate sufficient heat for the subsequent operations. During the boiling and raising of the mass, globular grains begin to appear on the surface of the melted cinder, and these will increase gradually in number as the process continues. The

grains, as long as they continue of a form which I call globular, will be found to be grains of cast-iron, having neither malleability nor a welding property, and in their motion through the cinderwill pass each other without any apparent attraction, and even if they touch each other will quickly separate. At this stage of the process the cinder acts very powerfully on the carbon of the pig-iron, the decarbonizat-ion of which goes on very rapidly, and it becomes important to watch the process with great care, when it will be seen that the particles of metal which break through the cinder will gradually losetheir globular form and will become pointed at one end, or of what I call a pear-like form. This form of particles will indicate the presence of that amount or proportion of carbon in the metal which constitutes the hardest kind of steel, which is ductile or malleable, but not weldable, and is fit only for melting into hard cast-steel. These pear-like grains, when they meet in their motion through the fluid cinder, mayperhaps come in contact with and touch each other, but will separate, having appar ently, as yet, no attraction for each other; but as the decarbonizat-ion continues the grains will become more and more pointed, and even elongated, and on touching each other during their motion through the fluid mass will not separate, as before, but will now adhere to each other, and on uniting will sink through; the cinder. This elongated form and adhesion or fusion of the particles together will indicate the presence of that percentage of carbon which constitutes the hardest weldable steel. This stage of the process having been attained, and which may also be recognized by the workman feeling greater resistance to the puddling-tool, it will form astarting-point for the workman, and will enable him to produce steel of the different degrees of temper and hardness required for various applications and purposes. If it be desired to produce a bloom of the hardest weldable steel,

the process of decarbonization is only to be continued long enough after the appearance of the indications just described to bring the entire mass into one uniform state, after which the further progress of decarbonization must be stopped, either by closing the damper or otherwise.

If it be desired to produce a milder temper of steel, the decarbonization of the mass in v the furnace must be allowed to continue for a shorter or longer time, according to the degree of temper required for the use or purpose to which the steel isintended to be applied. As soon as the proper amount of decarbonization has been effected and the further progress thereof stopped the metal is to be formed into balls, care being taken always to keep the metal as much as possible immersed in or covered by the cinder, and when the balls are made they may be removed from the furnace and forged into blooms at the welding-heat of steel.

What I claim as my invention, and desire to secure by Letters Patent, is-- The new or improved art of manufacturing steel of any desired'temper or hardness, according to the various purposes or uses for which the steel may be required, by arresting the decarbonization of the mass of metal 'in the furnace at certain points or stages thereof, ascertained and recognized by means of certain phenomena or external indications manifested by the material, substantially as described.

In witness whereot'I, the said FRANZ ANTON LOHAGE, have hereunto set my hand and seal the 2d day of October, .in the year of our Lord one thousand eight hundred and fifty-eight.

FRANZ ANTON LOHAGE. [L.S.]

Witnesses "KET WALKDEN, Clerk to Newton d; Son, 66 Chancery Lane, London.

Guns. 0. JONES, 24 Royal Exchange, London.