STEEL.
Steel, we are frequently and emphatically reminded, is the material of the future. Passing from assertions respecting the time to come, let us concern ourselves with the present and the past of the material, and inquire why and wherefore steel should be held up so prominently as destined to make its mark in the future. Every age has stamped for its own not only a certain style of architecture or a peculiar class of construction, but it has also impressed into its service different materials, by means of which it has carried out those designs to which it has given birth. As formerly wood gave place to iron, so now, slowly yet surely, is the use of iron waning before the enhanced advantages accruing from steel in large constructive works. As ductile as iron, and possessed in a superior degree of tenacity, more uniform and compact, it is not a matter of surprise that steel should have largely usurped the position formerly occupied by iron in the engineering and constructive world, or that engineers and architects should gladly avail themselves of such a material in their designs, more especially when they desire to combine the maximum of strength and security with the minimum of weight and mass. So slight is the difference in appearance between rolled iron and rolled steel, that the casual observer will be unable to distinguish between the two substances. A certain amount of experience and skill is requisite before the eye becomes sufficiently educated to appreciate the appearance presented by each material. Nor should we omit to notice a method both simple and expeditious by which all doubts may be set at rest. A drop of diluted nitric acid placed on a piece of steel will at once separate the carbon in the steel, producing a black stain on its surface. On iron, no such effect will result.
The extensive works for manufacturing steel in England, Wales, Scotland, and on the continent, amply testify to the growth and vigour of the industry; and if further proof is wanted, it is supplied by the fact of the conversion of their plant by existing ironworks, to enable them to turn out steel. Such steps—though frequently producing financial distress, happy if only temporary—show the direction in which the commerce of the present day is moving.
That steel should so speedily overcome the initial difficulties incident to the introduction of every new material, adduces important evidence in its favour. In shipbuilding, for example, the inconvenience and delay occasioned by employing steel side by side with iron presented a formidable barrier to its use, the alternate demand for iron and steel built vessels causing no small confusion in the yards. The gradual and, before long, probable abandonment of iron in this class of constructions, is rapidly enabling shipbuilders to lay themselves out for steel, and steel only. We should not omit to notice the employment of steel plates, one-sixteenth of an inch in thickness, for the ‘skin’ of torpedo launches, a use to which the lightness and tenacity of such plates eminently adapt them.
The effective and systematic manner in which it is now customary in large works to test all steel previous to its despatch, has aided in no small degree to remove the feeling of doubt and uncertainty which was attached to the material on its introduction. There hung around steel an insecurity and a novelty, which, until dissipated, caused a feeling of distrust that might have proved fatal to its extended use, had not precautions been taken by its manufacturers to demonstrate the consistency and reliability of the article they sought to bring into the market. For the purpose of making these tests, a special machine is provided, usually driven by steam. A strip from the plate to be tested is placed in ‘jaws’ at each end; the machine is then set in motion, the strain on the test-piece being gradually increased until its ultimate tensile strength is reached, and it breaks—a travelling pointer indicating the pressure exerted by the machine on the steel test-piece at the moment of fracture. Thus the ultimate tensile strength per square inch and also the elasticity of the plate under manipulation are ascertained.
In order to check these and similar tests, one or more inspectors are stationed at the manufacturers’ works by the government, the company, or the engineer in whose designs the steel is to be employed. The Admiralty employ a number of men to watch the tests of all the steel destined for the royal dockyards; a similar class of inspectors perform a like task, under Lloyd’s rules, for the private yards and the vessels of our merchant service; whilst every engineer under whose directions steel is being made places his assistants—their number varying with the importance and extent of the work—to see that these tests are faithfully carried out, that they duly fulfil the conditions he has laid down, and to report to him the quality, quantity, and progress of the material under their charge.
Accurate records are made of every test to which the steel has been subjected, and the results of the behaviour of the material are carefully noted. Hence, should any event occur to call special attention to any particular bar, its history can be traced from the very first to the moment it took up its position in the finished structure for which it was destined.
So rigid and well checked a system of testing cannot fail to command the favour of all engaged in the design of vessels, roofs, or bridges, and to inspire the general public with confidence in and reliance on this comparatively young member of the material world, daily increasingly impressed into its service, and tending to promote the general well-being and comfort of the civilised world.