SHEET NON-FERROUS METALS 



763 



blocks from 40 to 60, 2| points; and for blocks over 60, \\ points. 

 Acceptance or rejection of blocks is based on these limits, except 

 where a minus reading results and in this case the 60-kg. load is 

 used. Blocks of this uniformity are calibrated for use with the 60, 

 100 and 150-kg. loads. 



Rockwell Scales Employed. — It has been found that the Rockwell 

 "B" scale employing the 100-kg. load, the i^-in. diameter ball and 

 reading the red figures, is satisfactory for rolled brass sheet; but in 

 the case of the nickel-silver and phosphor-bronze alloys it was found 

 that the Rockwell hardness-tensile strength curve became asymp- 

 totic, showing very little change in hardness for a large increase in 

 tensile strength in the harder tempers. A load of 150 kg. was sub- 

 stituted for the 100-kg. load and resulted in an improvement since 

 by using the larger load, a greater depth of penetration was obtained 

 and consequently better sensitivity in the higher tempers. The 

 curve, shown by Fig. 13, gives the Rockwell hardness-tensile strength 

 relationship employing the 100 and 150-kg. loads on the Rockwell 

 tester. The 150-kg. load has been adopted for nickel-silver and 



TABLE IV 

 Diameter ° of Average Grain for Annealed Brass and Nickel Silver 



" The method for determining the grain size of the material is the Jeffries method 

 as described in the note under Section 9 of the Society's Standard Rules Governing 

 the Preparation of Micrographs of Metals and Alloys (E 2-27), see 1927 Book of 

 A. S. T M. Standards, Part I, p. 778. 



