GG-40 as-cast ductile iron accounts for about 70% of the total production of German ductile iron. In order to ensure that the as-cast state meets the required performance,it is not enough to only use low manganese content as a quality mark. More importantly,it is required to interfere with spheroidizing elements. The content of and stable pearlite elements is low and stable. The composition of special pig iron for ductile iron produced by German blast furnace is shown in Table 1,and its trace elements and their content are not more than the following quantities.
0.002%A1,0.002%As,0.001%B 0,0008% Bi.0.002%C 0.0.006%Cr,0.0008%Pb,0.001%Sb,0.001%Se,0.001%Sn.0.001%Te,0.035%Ti,0.003 %Cu.0.0009%Mo,0.004%Ni,0.010%V,0.001%W.0.002%Zn.
In the production of thick section ductile iron,it is necessary to pay special attention to the content of the spheroidizing elements Ti,Pb,Sb,Bi in the charge,the promotion of carbide elements B,V,Cr and the stable pearlite elements Mn,Gu,Sn. In Germany,the proportion of pig iron has fallen from 32% in 1960 to 16% in 1987. On the contrary,scrap steel has risen from 18% to 39%.