| 摘要 |
<p>A method of reducing temper brittleness in low alloy steels (i.e. containing a total of 0.5 to 10% by weight of chromium, nickel, molybdenum, vanadium, manganese, titanium, cobalt or niobium) comprises adding to the steel at least one rare earth metal in a proportion within the range 0.8 to 2.0 times the weight percentage given by the formula: RE = 8.7S + 2.3Sn + 4.5P wherein S, Sn and P represent the weight percentages of sulphur, tin and phosphorus respectively and RE represents the weight percentage of the rare earth metal expressed as its lanthanum equivalent. The rare earth metal is preferably lanthanum, but may be cerium or a mixture of rare earth metals. After addition the steel is preferably maintained at an elevated temperature for long enough to permit precipitation of the compounds formed. A temperature of 1100 DEG C maintained for 1-2 hours is usually suitable. Following this the steel may be tempered. The invention therefore provides a convenient method of reprocessing steel scrap containing otherwise deleterious amounts of these impurities.</p> |
