TREATMENT OF ALLOY STEEL 71 



so-called cheap pyrometer that I tested departed from the 

 truth over 100 in a month, and another was 50 off when 

 installed. In a lot of six couples tested after being in use 

 some time, three were all right and three all wrong and by 

 varying amounts. If you are going to use pyrometers by 

 all means see that you have good ones and then see that they 

 are systematically tested. Many people buy high priced 

 alloy steels and get no better results from them than could 

 be had from a carbon steel properly handled. If you can- 

 not afford a good pyrometer stick to the trained eye of a 

 skilled man; and if you have a good pyrometer employ a 

 skilled man, anyway, and consider the pyrometer as an aid. 

 With it you can at least give orders in temperatures rather 

 than in heat colors, and the laboratory and works can meet 

 on an intelligent basis. Pyrometers, like "smoke consum- 

 ers/' are all right if carefully watched and intelligently 

 used. Too often both fail after about thirty days' use. 



Heat treatment operations depend upon a solid scientific 

 basis. And by this is not meant that steel essentially of 

 inferior quality can be made to pass muster by heat treat- 

 ment. 



On the other hand, however, it might be said that alloy 

 steel in its so-called natural state, as it comes from the rolls, 

 hammer or drop forge, is almost unfit for automobile con- 

 struction. Steel which depends upon alloys for a high 

 elastic limit in its natural condition will have much less 

 elongation than the same steel oil tempered and annealed. 

 For example, a chrome steel gave in its rolled condition 

 158,000 pounds elastic limit and 5 per cent, elongation, with 

 9.4 per cent, reduction of area. The same steel oil tempered 

 and annealed gave 153,000 pounds elastic limit, 14 per cent, 

 elongation and 52 per cent, reduction of area. In other 

 words, the material was transformed from brittle to tough, 

 from treacherous to safe, without materially affecting its 

 elastic limit. A nickel steel similarly treated had its elas- 

 tic limit raised 20 per cent., with the reduction in area 

 improved and its elongation unchanged. 



