the quality of steel are sulphur, phosphorus, and copper. The amount of sulphur in steel of the best quality rarely exceeds ·012; within the limit of ·1 per cent. it is considered to render the metal more capable of being welded at a moderate heat, but to make it red short. Phosphorus also renders steel more capable of being welded, and at the same time makes its cold short when it amounts to ·1 per cent. The best steel rarely contains so much. Copper renders steel decidedly red short when present in very small amount, and for this reason iron smelted from ores containing copper pyrites is not suitable for making steel.”[195]
[195] Payen.
Within the last few years great attention has been paid to the investigation of the chemistry of steel. The researches of Despretz and Fremy tend to the conclusion that nitrogen exercises a very important influence over the phenomena of ‘steeling,’ and that carbon plays a less necessary part; while those of Caron and Deville still refer the formation of steel to the chemical combination of iron with carbon. There is no test of the value of steel beyond its elasticity and temper, and the fineness, equality, and smoothness of its grain.
Cast iron, wrought iron, and steel are all combinations of iron and carbon, differing in the amount they contain of the latter element. As cast iron contains a larger and wrought iron a smaller proportion of carbon than steel, it follows that to convert the cast iron into steel, its excess of carbon must be removed; whilst conversely, to make the wrought iron into steel, the requisite amount of carbon must be added to it.
Thus it is that the various processes for the manufacture of steel (with the exception of those which propose to obtain it direct from the ores) are directed to one or other of these ends, viz. the decarburation of cast or pig iron, and the carburation of wrought or malleable iron.
1. In the first, or decarburation method, the oxygen of the air plays an important part. Best carbon is heated with coal or charcoal, in some works on the refining hearth, in others upon the bed of the puddling furnace. The oxygen burnt off the excess of carbon from the iron and steel is left. Payen says that when the iron contains slag, the ferrous silicate present in this takes part in the reaction.
The steel obtained by this method is called natural steel. It is afterwards subjected to forging, and being of inferior quality is employed in the manufacture of springs for machinery, railway carriages, wheel tyres, ploughs, and other farming implements.
The following Table, from ‘Payen’s Industrial Chemistry’ gives the Composition of several kinds of Steel.
| Carbon. | ||||||
| Kind of Steel. | Locality. | Fe. | Mn. | Cu. | Combined. | Graphitic. |
| Natural Steel | Siegen | ... | ... | ·379 | 1·698 | ... |
| Ditto | Solingen | ... | ... | ... | 1·570 | ... |
| Puddled Steel | Hartz | ... | 0·12 | ... | 1·380 | ... |
| Cement Steel | English | ... | ... | ... | 1·807 | ... |
| Ditto | German | ... | ... | ... | ·416 | ·080 |
| Cast Steel | Sheffield | ... | ... | ... | ·950 | ·220 |
| Ditto | Ditto | ... | ... | ... | 1·758 | |
| Ditto | French | ... | ... | ... | ·65 | |
| Sword Steel | Damascus | ... | ·070 | ... | 1·089 | |
| Ditto | Ditto | ... | trace | ... | ·775 | |
| Wootz | Indian | ... | ... | ... | 1·500 | |
| Ditto | Ditto | 98·092 | ... | ... | 1·333 | ·312 |
| Cast Steel | German | ... | trace | ·300 | 1·180 | |
| Ditto | English | ... | ·024 | ·066 | 1·275 | |
| Bessemer Steel | Dowlais | ... | ·576 | ·025 | ·490 | |
| Ditto | Sweden | ... | trace | ... | ·085 | |
| Ditto | ... | ... | ·179 | ... | ·300 | |
| Ditto | ... | ... | ·256 | ... | ·700 | |
| Ditto | ... | ... | ·468 | ... | ·950 | |
| Ditto | ... | ... | ·355 | ... | 1·050 | |
| Wired | Barrow-in-Furness | ... | ·214 | ... | ·200 | |
| Rail Heads | German | ... | ·386 | ... | ·138 | |
| Rails | ... | ... | ·264 | ... | ·150 | |
| Ditto | ... | ... | ·638 | ... | ·046 | |
| Boiler Plates | ... | ... | ·136 | ... | ·250 | |
| Ditto | ... | ... | ·273 | ... | ·300 | |
| Kind of Steel. | Si. | S. | P. | Authority. |
| Natural Steel | ·038 | ... | ... | Karsten. |
| Ditto | ·020 | ... | ... | Lampadius. |
| Puddled Steel | ·006 | (at·12) | trace | Brauns. |
| Cement Steel | ·100 | ... | ... | Berthier. |
| Ditto | ... | ... | ... | Bromeis. |
| Cast Steel | ... | ... | ... | Ditto. |
| Ditto | ... | ... | ... | Karsten. |
| Ditto | ·040 | ... | ... | ... |
| Sword Steel | ... | (Ni·07 Wo·01) | ... | |
| Ditto | ... | (Ni·21 Co trace Wo trace) | ... | |
| Wootz | ·600 | ... | ... | ... |
| Ditto | ·045 | (as 037) | ... | Henry. |
| Cast Steel | ·330 | (Ni ·12) | ·020 | ... |
| Ditto | ·213 | (as·007) | ... | ... |
| Bessemer Steel | ·009 | ·003 | ·036 | ... |
| Ditto | ·008 | trace | ·025 | Brusewitz. |
| Ditto | ·044 | do. | ·033 | Ditto. |
| Ditto | ·032 | do. | ... | Ditto. |
| Ditto | ·047 | do. | ·032 | Ditto. |
| Ditto | ·067 | do. | ... | Ditto. |
| Wired | ·179 | ·030 | ·026 | Ditto. |
| Rail Heads | ·306 | ·040 | ·034 | Ditto. |
| Rails | ·091 | ·025 | ·032 | Ditto. |
| Ditto | ·634 | ·045 | ·093 | Ditto. |
| Boiler Plates | ·016 | ·010 | ... | Ditto. |
| Ditto | ·056 | ·040 | ·041 | Ditto. |