Puddled steel, homogeneous iron, and steel iron
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_Puddled Steel, Homogeneous Iron, and Steel Iron. 255
been fractured in the experiments, and his own observations at pre- sent were unfavorable to rolling the several thicknesses together to form the plates, as not giving pressure enough to insure a thorough welding in all parts. Moreover, tile extent of surface to be welded, amounting to 3000 or 4000 square feet in the entire manufacture of a single plate, was so great, that it was difficult to conceive how a perfect weld could ever be obtained throughout, as it seemed impossi- ble to insur@ an entire exclusion of dirt from between the plates, and unless they were kept quite clean, they could not be welded into a single homogeneous plate. The difference in resisting power was very great between a really homogeneous material and one having any lamination of structure ; in the latter ease, all portions of the material did not take their share of the strain in resisting a blow, but some were more severely strained than the rest, causing them to give way sooner ; and a series of thinner plates, though making up a considera- bly greater total thickness, was inferior to a single homogeneous plate in resisting power. The ver~y best plates he had seen at present were some small forged plates, worked under a hammer at Portsmouth Dockyard; these were thoroughly sound in all parts, and free from impurities. What was wanted for the armor plates was a perfectly homogeneous material, and of soft texture; if they could be made, like the steel rails that had been described, from a single mass of thoroughly homogeneous metal, he thought there might be a good prospect of success. Ordinary east steel, however, he did not think would be so suitable as good wrought iron, on account of not being soft enough,
For forging the metal of the armor plates under the hammer, he considered the weight of the hammer was of the greatest importance ; and in reference to the use of a 4-ton hammer, with steam above the piston to increase the blow, it had to be borne in mind, that the steam increased only the velocity of the blow without adding to tim mass falling, which was not the result required ; he feared the effect would be, that the force of the blow would be spent on the surface of the material, and would not go through to the centre of the mass like the blow of a heavier weight falling with a proportionately smaller veloci- ty. This appeared to him a very important consideration in forging large masses, however effective that kind of steam hammer undoubt- edly was ibr lighter work.
Proceedings Insti. Mech. Engineers, July 31, 1861.
]Puddled Steel, Homogeneous Iron, and Steel Iron. From the Lend. Cir. Eng. and Arch. Journal~ February~ 1862.
The question of the mechanical properties of puddled steel, as also the less highly carbonized products of iron, is one of growing import- ance. Cheap and ready manufacture and a high degree of strength are advantages claimed for this class of material, and its field of ap- plication is becoming largely extended. An accurate acquaintance with the limits of strength and laws of elasticity becomes therefore increasingly desirable.
256 Mechanics, Physics, and Chemistry.
We ]lave before us a pamphlet by Mr. W. H. Barlow, :F. R.S., ~I. I. C. E., giving an account of some experiments which he has con- ducted by permission of the Royal Arsenal at Woolwich, for the pur- pose of obtaining some rail;ibis data upon this subject. The testing machine employed at Woolwich is a counterpart of that used by the United States Government for ascertaining the strength of cast iron. ]t records accurately the amounts of the ultimate resistances to rup- ture by tension, compression, transverse strain, and torsion, but is not ~ell arranged for exhibiting the progressive action of the three first named kinds of strain. Oonsequently, as Mr. Barlow states, although the experiments may be relied on as far as they go, and poin t out the more important properties of the materials tested, they do not afford all the data that could be wished ; as puddled steel rarely :yields to rupture in the testing machine except under tension.
":Puddled steel is made direct from cast iron by a process analo- gous to that used in obtaining common wrought iron, but instead of expelling all the carbon, such an amount is left contained as to impart the quality of the steel to the metal so treated. Considerable experi- ence is required in the selection of suitable qualities of metal, and also to know the precise moment at which to stop the process of decarbon- ization in the puddling furnace ; and other conditions have to be ob- served in order to secure the success of the operation; but it is now accomplished with great certainty, and the result is the production at a very low cost of steel, which, although not of high quality, is never- theless possessed of many valuable properties.
" In addition to the experiments on puddled steel, similar experi- ments were made on homogeneous metal and steel iron, and on pud- dled steel melted and cast into ingots. Steel iron is a condition of the metal when the process of decarbonization is carried further than in puddled steel ; its fi'acture is fibrous, and it approaches very nearly to wrought iron. The other materials above mentioned show a crystal- line fracture, the crystals being ver:y small, fine, and regular, like tha~ of gun metal. The steel possesses also similar properties of mallea- bility, although much harder and of much greater strength than gun metal."
The following table (I.) is an abridgment of Mr. Barlow's summary of the experiments on tension : - -
TABSE I.--Summary of Experiments on the Resistance to TenMon of Puddled Steel, ~c.
No. of J IN . . . . * f~Iaterial, - - - - - - [ __ . _per~sq. i , i e~h_~_ 1~I . . . . R . . . . . 'ks. )xperim't." Name of Maker. Ult imate Strain
~ -7 ,7 - f - - - - 52 to 56 [ Puddled steel, . . Mersey Iron Works~ I 84,152 to 109,lt7 95.233 ]~'racture crystalline.
l~irth & Co . . . . I 88.640 '. 115,133 100,99:L ] '~ ,. 19 " 23 ~ Uomo~eneous metal, I Naylor & Vickers, 1100,931 " 133.05~: 29 ~ 34 ]Pad,tied steel, . . 116,336 ~ " 57 " 61 |Puddled steel melted
| aml cast into ingots, Naylor & Vickers, I 84,652 .c 124,492 101,753 1 ~ 8 " 12 /Steel iron, . . . . Atlas Works, . . / 67,487 ~ 71,158 ] 69 456 [ ~ f ibrous
:From these results the author draws the following conclusions :-- " :From the above experiments it appears that the ultimate tensile
_Puddled Steel, Homogeneous Iron, and Steel Iron. 257
strength of puddled steel, homogeneous metal, and puddled steel melt- ed and cast into ingots, is nearly double that of wrought iron. Tho variation of strength in the different samples is not greater than is found to arise in wrought iron.
" Several specimens taken out and remeasured after receiving strain, indicate that permanent set first begins to be perceptible at 20,000 lbs. pc~ square inch.
" Puddled steel and homogeneous metal broke with a fracture pre- senting a minute crystalline appearance ; and there were two distinct forms of fracture, one being in a plane at right angles to the line ot~ strain, and the other a cup-shaped fracture more or less perfect.
" The material called ' steel iron' showed a fibrous fracture, and was of much less strength than puddled steel and homogeneous metal. In this material it was evident that the process of decarbonization had been carried too far, and that it differed but little from iron of good quality."
From the summary of experiments on compression we extract tho mean results (table I L ) : - -
TXBL~ II.--Summary of Experiments on the Resistance to Compression of Puddled Steel, ,~e.
NO. of experim't.
47 to 51 852'438
62 to 65
113,17, &18 ,
Name of Material.
Puddled steel (mean length, 1'323 ills.), Puddled steel (mean length, 1 368 ins.), Homogeneous metal (length, 1-295 ins.), Puddled steel melted and cast into ingots
(mean length, 1"4175 ins.), Steel iron (mean length, 1"102 ins),
Name of Maker.
Mersey Iron W'ks, Naylor & ickers, Firth & Co.,
Naylor & Yickers, Atlas Works,
Pressure Amount p,~r I of Com-
sq. In. pression.
los. I inch. 21,908 "0032 20,196 '00325 22,514 '003
21.998 '00575 23,574 "00533
Rate of Corn. pression per ton per sq.in in terms of
"000247 '000263 '000231
" The samples tested were all about 1 inches in length. The ap- proach of the steel pistons between which the samples were compress- ed was carefully measured, and the results as recorded are correct as showing the compressions of columns of the length employed. The amount of compression per ton per inch is however so great, and be- ing moreover inconsistent with that which may be inferred from tho experiments on transverse strain, it is to be presumed that the result is affected by the short length of the samples. The effect of the pres- sure is to enlarge the diameter at the centre of the sample.
"F ig. 1 represents the sample :No. 24 before Fig. 1. Fig. 2. pressure was applied, and fig. 2 is the same sam- ple after receiving a pressure of 51 tons per inch, ] - -~ and similar effects, though in a less degree, re- sult from smaller pressures. It is known that in long bars subjected to compression the centre portion is not proportionately expanded, and it follows that the decrease of length in short columns will not be propor- tional to that in long ones. It is evident, however, that the puddled steel and homogeneous metal are less compressible than cast puddled steel
258 $[echanics, Physics, and Chemistry.
and steel iron. Puddled steel, whether cast or otherwise, could not be crus