Metallurgy (Orowan Egon könyvtárából) [antikvár]

INTRODUCTION By professor c. h. desch, f.r.s. Of the Department of Metallurgy, Sheffield University The need of somé metallurgical knowledge on the part of the engineer becomes more evident each year, as the metals and alloys used in engineering construction become more numerous and more varied, and as the conditions under which they are employed become more onerous. Not so many years ago mild steel, wrought iron, and cast iron, with a few non-ferrous alloys, were all that were required, but a far wider field is needed at the present day. The aeroplane and automobilé industries have been largely responsible for the development of metals having a high resistance to fatigue, whilst the needs of the chemical industry have had to be met by the production of alloys which retain a large part of their strength at elevated temperatures, leading in turn to the construction of steam boilers for use at high pressures and temperatures. The attempt to lessen losses by corrosion has brought about the invention of many alloys, ferrous and non-ferrous, which are highly resistant to atmospheric corrosion and to attack by such agents as sea-water. These newer materials have as a rule to be subjected to heattreatment before use, and unless the best treatment be applied, the metál cannot develop the full qualities which distinguish it from other and less costly varieties. Somé knowledge of the effects of heat-treatment is therefore essential to the engineer, and this involves a study of the means, such as microscopical examination, by which the correctness of the treatment may be determined. vii