| 46 | ECONOMICS OF BRIDGEWORK | Chapter V |
Chrome Steel
| 99 lbs. Steel | @ 8.5¢ = $8.42 |
| 1 lb. Chromium | @ 25¢ = .25 |
| 100 lbs. Alloy | @ 8.67¢=$8.67 |
|
Chromol Steel |
| Working tensile stress for heat-treated steel | = 50,300 lbs. |
| Ditto untreated (approximately) | = 39,000 lbs. |
| Average= 1/3 (2 X 39,000 + 50,300) | = 42,800 lbs. |
Chrome Steel
| Working tensile stress for heat-treated steel | = 46,300 lbs. |
| Ditto untreated (assumed) | = 33,000 lbs. |
| Average= 1/3 (2 X 33,000 + 46,300) | = 37,400 lbs. |
|
and r r' = 1.082 X 0.87 = 0.94 |
|
As this is lower than nearly all the values of r r' in Figs. 5a and 5b, it may be concluded that it is almost always economic to add molybdenum to chrome steel; or, in other words, chromol steel is preferable to chrome steel for bridgework on account of both cost and toughness. Nicmol Steel versus Nickel SteelUnfortunately, the records in "Molybdenum Commercial Steels" do not give any tests for the untreated Nickel Steel; but as the author once made some tests on a 4 1/4% nickel steel for eye-bars, he will use the results thereof in this crude investigation. Referring to Table 5h, and employing averages, we have the following: Nicmol Steel |
| 94.92 lbs. Steel | @8.5¢ =$8.07 |
| 4.50lbs. Nickel | @ 43¢ = 1.94 |
| 0.58 lb. Molybdenum | @ $2.53 = 1.47 |
| 100.00 lbs. Alloy | @ 11.48¢ = $11.48 |