TREATMENT OF MANUFACTURED IRON AND STEEL. 267 
radius is one and a-half times the thickness of the plate, and 
similar pieces must stand the same test after having been heated 
uniformly to a low cherry red, and cooled in water having a 
temperature of eighty-two degrees Fahr. 
Some engineers, instead of the first bending test described, 
stipulate a ‘punch test,” and in the case of an ordinary locomo- 
tive boiler plate, require strips to be cut from it, three and a-half 
inches wide, having a five-eighth inch hole drilled in it equidistant 
from the three edges at one end, which must withstand being 
drifted to one and five-eighth inches without fracture. 
For steel boiler flues the same bending tests are required, but 
the ultimate tensile strength is kept between twenty-four and 
twenty-seven tons per square inch. 
The tests of iron for boilers are omitted, as the requirements of 
engineers, with regard to the strength, ductility, and brands of 
material used, vary considerably, but it may be mentioned that 
three classes of iron are frequently adopted, namely: “ Best 
Yorkshire,” for the furnaces, “ Flanging Plates,” for the ends, 
and a less expensive quality for the shells. 
Many locomotive boilers are still manufactured entirely of best 
Yorkshire iron, which material can certainly have the holes made 
in it by punching, and the forged portions can be safely dealt with 
by workmen who have not the special knowledge of the proper 
treatment required by steel during and after forging ; but this 
knowledge is now very general, and it is becoming the practice of 
most of the highest locomotive authorities to make boiler shells of 
mild steel, costing about one-half the amount of Yorkshire iron, 
and as it is at the same time, of a more uniformly strong character 
and free from laminations, it is believed, that in the near future, 
steel for locomotive boilers will be universally adopted. 
When specifying tests for material, it is most usual to state 
the “ultimate tensile strength” and “elongation ” required, but 
in some cases the “ tensile strength” and “reduction of area” are 
stipulated. It is not advisable to state the tensile strength per 
