Which ever Chinese word we use after 单位耗钢, we can put Unit consumption of steel / steel consumption per unit in English to make understanding good/clear enough...though the word 强度 here is not of good wording here...

For your reference:
he effect of the unit consumption of aluminum on the quality of the surface of rolled prod- ucts made of structural steel St3sp delivered in the form of ...
http://www.springerlink.com/index/P852328557G4L611.pdf

AsiaInfo Services 08-04-2006 Energy Consumption Per Unit of GDP Rose 0.8 in H1...per unit of value-added at the steel industry, building material industry, ...
http://www.highbeam.com/doc/1P2-16133160.html