The remelting behavior of the hot-work tool steel X37CrMoV5-1 is investigated with several experimental melts on a lab-scale ESR-plant. The investigated parameters comprise a variation of the slag compositions and the use of a protective nitrogen atmosphere. Variations of the slag composition include slags with different contents of CaF 2 , CaO, and Al 2 O 3 as well as a variation of the SiO 2content in the slag. The remelted ingots are forged and analyzed regarding their chemical composition. The distribution and composition of the non-metallic inclusions (NMI) is studied by an automated SEM-EDX method. Additionally, the chemical composition of the slag after remelting is analyzed. The results show clearly an equilibrium reaction between Si and Al in the steel with SiO 2 and Al 2 O 3 in the slag as well as the effect of oxygen in open ESR operation. A protective atmosphere reduces the Si-losses during remelting, but has no major effect on the number or composition of NMI compared to open remelting. The content of NMI, especially the larger ones, is reduced significantly in all remelting experiments. The majority of the NMI are MA-spinel type except for the CaO-free slag, where alumina inclusions prevail. In general, remelting leads to an almost complete removal of sulfides, a reduction of oxisulfides, and a slight increase of oxides.

The service life of roller bearings is extremely sensitive to large and hard nonmetallic inclusions (NMIs), requesting the highest standards in their production. To determine the metallurgical possibilities, the effect of Al2O3 contents between 0 and 33 pct in the remelting slag was investigated by remelting a roller bearing steel in an experimental electroslag remelting (ESR) plant. Thereby, changes in the chemical composition of the materials (electrode vs ingots) and in the remelting slag during remelting, as well as the amount and composition of the NMIs prior to and after remelting, were investigated. Changes in the chemical composition can largely be explained by equilibrium reactions between the slag and the metal, thereby low Al contents in the remelted materials could only be achieved with the lowest Al2O3 contents in the slag. Furthermore, higher Al2O3 contents in the slag also lead to higher oxygen and sulfur contents in the steel as well as higher amounts of NMIs after remelting. The composition of the NMIs changed from alumina type for high Al2O3 contents to spinel type and other mixed MgO-SiO2 oxides for low Al2O3 contents. The results indicate solutions for the production of bearing steels with the lowest amounts of undesired large and hard NMIs.

The service life of roller bearings strongly depends on nonmetallic inclusions (NMIs). Therefore, these steels request highest metallurgical standards in their production. To determine the effect of the Al2O3 content and a protective atmosphere (N2) on the electroslag remelting (ESR) behavior, laboratory scale experiments are conducted. Changes in the composition of the remelted materials and in the slag are determined. In addition, the amount and composition of the NMI prior and after remelting are investigated, and thermodynamic simulations on the formation of NMI are conducted. Changes in the chemical composition can largely be explained by well‐known equilibrium reactions between the slag and the metal. Lowest Al contents in the remelted steel can only be achieved with the Al2O3‐free slag. Higher Al2O3 contents in the slag lead to higher oxygen and sulfur contents in the steel and corresponding higher amounts of NMI after remelting. The use of a protective gas mainly reduced the loss of Si and led to lower O and S contents after remelting with the Al2O3‐free slag. The composition of the NMI changed from alumina type to MgO–Al2O3 (MA)‐spinel type and finally mixed MgO–SiO2 oxides with decreasing Al2O3 contents. These results are confirmed by thermodynamic calculations.

The remelting behavior of the tempering steel 50CrMo4, was investigated with several experimental melts on a lab-scale ESR-plant. The investigated parameters included a variation of the slag compositions and the use of a protective nitrogen atmosphere. Variations of the slag composition comprised slags with different contents of CaF2, CaO and Al2O3 as well as a variation of the SiO2-content. The remelted ingots were forged and analyzed regarding their chemical composition as well as their distribution and composition of the non-metallic inclusions (NMI) by automated SEM-EDX method. The chemical composition of the slag after remelting was analyzed as well. The results clearly show a relationship mainly of Si and Al in the steel with the process parameters. NMI changed in their total amount, type and size distribution. The protective atmosphere reduced the Si-losses during remelting. The majority of the NMI were of the Al2O3- & MnS-type. In general, remelting lead to an almost complete removal of sulfides, a reduction of oxisulfides and a shift towards more oxides. The total amount of NMI was most strongly reduced by the high CaF2-containing remelting slag.