the parts which have been cast from spheroidal cast alloys preferably have , in addition to great mechanical strengths of 500 to 850 mpa , high yield strengths of 350 to 550 mpa and , at the same time , high degrees of ductility of up to 12 %. furthermore , according to a particular refinement of the invention , the spheroidal cast alloy contains not only the main component fe but also the non - iron constituents c , si , p , mg , cr , al , s , cu and mn with the conventional impurities , according to the following examples : the chemical composition is 3 . 34 % by weight c , 2 . 92 % by weight si , 0 . 62 % by weight cu , 0 . 17 % by weight mn , 0 . 038 % by weight mg , 0 . 025 % by weight p , 0 . 021 % by weight cr , 0 . 01 % by weight al , 0 . 001 % by weight s , remainder fe and the conventional impurities . the number of spherulites is 400 spherulites per mm 2 . the graphite content is 9 . 7 %. the graphite form in accordance with din en iso 945 is 97 . 9 % of the form vi . the size distribution in accordance with din en iso 945 is 45 % of size 8 , 42 % of size 7 and 13 % of size 6 . the pearlite content is 84 %. the brinell hardness is 248 hb . in the tensile test , the following values were established : yield strength r p 0 . 2 = 474 mpa , tensile strength rm = 778 mpa , elongation at rupture a5 up to 11 . 4 % and modulus of elasticity e = 165 to 170 kn / mm 2 . the chemical composition is 3 . 5 % by weight c , 2 . 65 % by weight si , 0 . 77 % by weight cu , 0 . 26 % by weight mn , 0 . 038 % by weight mg , 0 . 026 % by weight p , 0 . 029 % by weight cr , 0 . 004 % by weight al , 0 . 001 % by weight s , remainder fe and the conventional impurities . in the tensile test , the following values were established : yield strength r p 0 . 2 = 405 mpa , tensile strength rm = 639 mpa , elongation at rupture a5 up to 9 . 6 % and modulus of elasticity e = 165 to 170 kn / mm 2 . the brinell hardness is 238 hb . the chemical composition is 3 . 43 % by weight c , 3 . 38 % by weight si , 0 . 71 % by weight cu , 0 . 2 % by weight mn , 0 . 037 % by weight mg , 0 . 047 % by weight p , 0 . 043 % by weight cr , 0 . 012 % by weight al , 0 . 004 % by weight 5 and 0 . 0008 % by weight b , remainder fe and the conventional impurities . in the tensile test , the following values were established : yield strength r p 0 . 2 = 558 mpa , tensile strength rm = 862 mpa and elongation at rupture a5 up to 6 . 1 %. the brinell hardness is 288 hb . the number of spherulites in the microstructure was determined as 455 spherulites per mm 2 . an example of an axle stub is shown in the single figure . the advantages associated with the invention are , in particular , that the axle stub can be produced at lower cost compared to the known solution by forging . it is distinguished by a reduced weight . in addition , the machining is improved considerably . since two materials are combined in one component , the main advantages of each individual material are utilized optimally in the bearing journal which is subjected to high levels of loading . high strength on the outside , high elongation on the inside . the composite casting effects advantageous stress distribution ( modulus of elasticity ) and thereby increases the service life of the bearing journal which is loaded to reverse bending . owing to the composite casting , delayed component failure rather than abrupt component failure occurs in the event of excessive loading , with correspondingly high deformation of the bearing journal . this makes it possible to detect the initial damage and to prevent total failure . the steel insert has a very positive effect on the cooling conditions and the microstructure formation of the cast material . a very fine - grained pearlite / ferrite microstructure with a high number of spherulites is formed . the outer side of the steel insert may be coated before it is inserted . the coating may be applied by chemical deposition , for example phosphatizing .