Pyongyang says its torpedoes are made of steel alloys .

平壤说，它的鱼雷是由合金钢做的。

Molybdenum and vanadium are used as alloys for steel to prevent corrosion .

钼和钒用于各种合金，帮助钢铁防止腐蚀。

Super alloys cobalt , titanium and chrome are used in such specialised engineering manufacturing as jet engines .

而超合金钴、钛和铬则用于飞机引擎等特种工程制造行业。

The aluminium alloys that are used for their strength and lightness in aircraft construction are just the opposite .

由于它们的强度和亮度而被使用在飞机结构中的铝合金却恰恰相反。

But steel alloys subjected to cyclic stress levels below their endurance limit rarely fail as a result of fatigue .

但是在钢铁合金的耐用度限制下，作为疲劳的结果，它们经受周期压力级别很少失灵。