| 50 | ECONOMICS OF BRIDGEWORK | Chapter V |
Class C
| Average analysis, Carb. 0.18, Mang. 0.37, |
| Chrom. 1.05, Moly., 0.73, |
| E. L. = 150,000 lbs., Ult. =170,000 lbs., Elong. = 18%, Red. = 58%. |
Class A
| 99.00 lbs. Steel | @ 8.5¢ = $8.42 |
| 0.72 lb. Chromium | @ 25¢ = 0.18 |
| 0.28 lb. Molybdenum | @ $2.53 = 0.71 |
| 100.00 lbs. Alloy | @ 9.31¢ = $9.31 |
Class C
| 98.22 lbs. Steel | @ 8.5¢ = $8.35 |
| 1.05 lbs. Chromium | @ 25¢ = 0.26 |
| 0.73lb. Molybdenum | @ $2.53 = 1.85 |
| 100.00 lbs. Alloy | @ 10.46¢= $10.46 |
|
Class A |
| Working tensile stress for heat-treated steel | = 43,300 lbs. |
| Ditto untreated (assumed) | = 37,000 lbs. |
| Average= 1/3 (2 X 37,000 + 43,300) | = 39,100 lbs. |
Class C
| Working tensile stress for heat-treated steel | = 56,700 lbs. |
| Ditto untreated (assumed) | = 48,500 lbs. |
| Average= 1/3 (2 X 48,500 + 56,700) | = 51,200 lbs. |
|
and r r' = 1.124 X 0.763 = 0.858
From Figs. 5a and 5b we find that this is lower than those recorded there for very short spans, from which it is evident that increasing the molybdenum content up to three quarters of one per cent is in the line of economy, provided that the resulting alloy be not too brittle. The writer of "Molybdenum Commercial Steels" states that there is an advantage in using molybdenum up to a limit of one per cent; but whether this can |
