Opportunities and dangers of using residual elements ... - Jernkontoret

Table 3 European scrap grading system.4. Residual elementsAn element can be regarded either as an alloying element or as a tramp element dependingon its content in steel and on the steel grade being produced.Residual elements in steel are usually defined as those elements left in the steel afterrefining which are not specifically required and in many cases are considered harmful tothe product properties when present in a too high concentration. The most importantresidual elements are: Cu, Sn, Zn, Pb, Bi, Sb, As, Ni, Cr, Mo and V. [10]There are 3 main mode of existence of residual elements in scrap: in pure state, as coatingmaterial and as alloying additions.[6]Some metallurgical phenomena related to an increase in the level of tramp elements areclearly unfavorable, but some may be beneficial, depending on the final application of theproduct.[3]In the following chapters, the modes of existence and effects of residual elements onprocessing and final properties of steels are treated, in a general matter and also throughsome more specified relevant case studies.Tables in chapter 7 are summarising the results presented in some general studies on theinfluence of residual elements.4.1 Sources of residual elementsReference [6] lists sources of the main tramp elements in steel scrap:The main sources of Cu are discarded passenger cars, structural steel with up to 0.5%Cu(mild resistance to corrosion and precipitation hardening), sheet.The main sources of Sn are post-consumer tinplate packaging and solders.The main sources of Zn is protective coating.9