IRON. 



313 



lion. 



PL Alt 



*<*+ 1", 

 17. 





The carbon becomes gradually dissipated at the ex- 

 pence of the oxygen, which is afforded by the blast, 

 and its fusibility is gradually diminished. It then be- 

 comes pulpy, and ultimately is obtained in rude shape- 

 lea* lump*. In this state they are taken with tongs 

 from the fire, and placed under a large hammer, which 

 is raised by machinery, called a stamping hammer. 

 The anvil is broad, and is surrounded with tray- like 

 tides, to keep the small fragments from falling off, which 

 are apt to fly in all directions by the action of the ham* 

 mer. The workman, with a rake, continues to push 

 the pieces under the hammer so long as they keep 

 their heat. These flatted and shapeless masses are cal- 

 led stampings. These pieces are then piled upon round 

 pieces of fire-stone (labs, and placed in a reverberatory 

 furnace, called a boiling furnace, and heated to a full 

 welding heat. These balls are then placed under a 

 forge-hammer, where they are drawn into ban about 

 three inches square, and cut into lengths of half a yard 

 in length. These pieces are called blooms. Each of 

 these are heated a second time, and drawn by the forge- 

 hammer into ban. for sale. This is the old method of 

 working, and is still practised by some, who have an 

 idea that the iron is of better quality. It is attended 

 with great waste, and, in the principal iron districts, is 

 superseded by the puddling process, which we shall 

 next describe. 



The process of converting pig-iron into the malleable 

 state, by the puddling method, is commenced by the 

 operation called refining, which is performed in a for- 

 nace called a refining, and by some a run-out, furnace : 

 this is represented in Plate CCCXI.. and Fig*. 16. and 

 4 17. The recess, or trough A, is made of cast metal, the 

 bottom consisting of fire-stone or brick. It is surround- 

 ed on three tide* by a cavity, through which water is 

 constantly passing from the cistern C. pp are two pipes 

 from a blowing machine, inserted into the conical 

 opening!, and kept cool by water from the pipe t, 

 which runs off at the pipe U. These are to blow the 

 fire which occupies the recess A. The fire being made in 

 thj trough, and filled with cokes, the pigs of iron are 

 thrown into the midst of it, and coke* heaped up 

 around them, the blast being kept up, and toe out- 

 sides of the trough being kept cool by the water. The 

 metal first melts, and the blast, instantly acting upon 

 it, separates a quantity of its carbon, but not nearly 

 to the extent to which it is carried in the old method 

 already described, as the metal still remains liquid. 

 In this state it receives the action of the blast for three 

 or four hour*. It is now run out at the bottom of the 

 trough through an opening o, temporarily stopped w itb 

 sand. The melted mass is received into the shallow 

 recess DE. A Urge quantity of the vitreous oxide of 

 iron also runs on, which is formed by the blast, and 

 floats on the surface of the melted metal Indeed, it is 

 through the medium of this vitreous oxide that the me- 

 tal below is deprived of its carbon. The blast first de- 

 stroys a portion of carbon on the surface, and then oxy - 

 dates the iron thus deprived of its carbon. This forms 

 the vitreous oxide which floats upon the carbonated 

 mass. The oxygen, therefore, of the floating oxide is 

 constantly in contact with the carbon of the metal be- 

 low. The stratum immediately below gives its carbon 

 to that deprived of its carbon above, and thus the 

 change is effected to the bottom of the trough. 



The cake of metal, as run out, U then broken into 

 _ piece*. It* fracture is white, and apparently crystalli- 

 sed, very different from it* original fracture. This an. 



vou xw. FAIT i. 





sea from its loss of carbon. These pieces are now in- Ito!; - 

 troduced into the puddling furnace, which is repre- 

 sented in Plate CCCXL. Figs. 18. and 19. A is 

 the ash pit ; G the grate ; D the door for the fuel ; 

 C the hollow cavity where the prepared metal is laid, 

 The flame passes over it, and then up the chimney F ; 

 H is a door for the introduction of the pieces of me- 

 tal. It is a cast-iron shell lined with fire-brick. In 

 the bottom of this door is a square hole h for the in- 

 troduction of the rake, and other tools used for working 

 the metal. The workman, at the same time, can see 

 the mass exposed, during the process, through the same 

 aperture. Without this door the intense heat would pre- 

 vent him from approaching the work, for the purpose of 

 agitating it. Even with this guard against the heat, it 

 is almost too great to be borne without great inconveni- 

 ence, As soon as the metal is melted, the puddler begins 

 to rake it about, occasionally throwing water upon it 

 with a small iron dish. This water is decomposed by the 

 iron and carbon ; the hydrogen escaping, and the oxy* 

 gen uniting with the iron, forming the vitreous oxide. 

 This latter being constantly agitated with the melted 

 metal, continues to dissipate the remaining carbon. 

 The fusibility of the mass gradually diminishes, till at 

 length it loses all cohesion, and appears a loose granu- 

 lated mass. During the time of this change bubbles 

 of gas are seen to bunt from the melted mass with a 

 blue flame. This is the carbonic oxide. Soon after 

 the metal has assumed the granular form, and the heat 

 is raised, the fragments begin to adhere, and the whole 

 forms a number of balls of an irregular shape. These 

 consist of the iron deprived of its carbon, mixed with 

 the vitreous oxide. These balls are made as compact 

 as possible by beating them on the hollow hearth, with 

 a very heavy iron rod shaped like a club. In this 

 state they are brought out ot the furnace with a pair of 

 large tongs, and passed through rollers similar to thote Rollers. 

 represented in Plate CCCXL. Figs, 20. and 22. first pass- J* , 

 ing through the widest gates, and then in succession 

 till the pieces become about three feet long, six or se- 

 ven inches broad, and a little more than half an inch 

 thick. In the finishing gate of the rollers, there is a 

 protuberant part crossing the gate, which makes inden- 

 tures across the bar, at intervals of about one foot each. 

 This is for the purpose of breaking the ban into pieces 

 of regular lengths when cold. It has, in this stage of 

 the process, a certain degree of malleability while hot, 

 but when cold is very brittle. 



U lien the bars above mentioned are broken into 

 lengths, they are laid one upon another five or six in 

 depth, and aie bound together with bands of rod-iron. 

 They are now heated in a reverberatory furnace similar to 

 the puddling furnace, but having a flat hearth. As soon 

 as these bundles are heated to a full welding heat, they 

 arc separately brought out and passed again through 

 the successive gates of the rollers. If the iron is not 

 intended to be of the best quality, this rolling would 

 finish the bars for sale ; but if it is to be of a superior 

 kind, the second rolling is carried only to the extent of 

 the first, and the bars broken up into bundles a second 

 time. Every time this is repeated, the quality of the 

 iron is improved, as well as its tenacity, as being freer 

 from specks, which consist of the small bits of vitreous 

 oxide worked up with the iron. It has been observed 

 by some, that, in the rolling process, where the hammer 

 15 not used, the iron is liable to abound with more vi- . 

 treous oxide, which, when polished, is very conspicu- 

 ous in small specks. It is believed that the hammer 

 2 R 



