Steel 100Cr6 belongs to a group of hardened steels, which are applicable for production of rolling element parts. Because of specific working conditions, a proper chemical composition is required with a minimum content of nonmetallic inclusion. In this paper, the research results of presence the nonmetallic inclusions and their chemical composition are presented for the steel produced in vacuum and open induction electric furnace and their influence on the prescribed properties for this steel. The optical and scanning electronic microscope are used to identify presence and the chemical compositions of nonmetallic inclusions.Čelik 100Cr6 pripada grupi prokaljivih čelika koji su prvenstveno našli primjenu u proizvodnji dijelova kotrljajućih ležajeva. Glede posebnih uvjeta rada za ovu vrstu čelika se zahtijeva propisani kemijski sastav sa minimalnim prisustvom nemetalnih uključaka. U ovom radu su predstavljeni rezultati ispitivanja prisustva nemetalnih uključaka i njihov kemijski sastav za čelik 100Cr6 proizveden u vakuumskoj i otvorenoj indukcionoj elektro peći te njihov uticaj na svojstva propisane normom za ovu vrstu čelika. Ispitivanje prisustva nemetalnih uključaka kao i analiza kemijskog sastava urađena je primjenom optičkog i skening elektronskog mikroskopa

A. Gigović-Gekić

B. Vujičić

I. Vitez

M. Oruč

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A. GIGOVI]-GEKI], M. ORU^, I. VITEZ, B. VUJI^I]ANALYSE AND RESEARCHOF NONMETALLIC INCLUSIONS FOR STEEL 100Cr6Received – Prispjelo: 2007-11-08Accepted – Prihva}eno: 2008-05-20Preliminary Note – Prethodno priop}enjeINTRODUCTIONThe steel 100Cr6 is mainly used for production ofrolling element parts like balls, cylinders and rings forbearings having a diameter up to 30 mm. The bearings areused as machine parts that are stressed by reversed com-pression, tension and shear loads during an exploitation1, 2. The presence of nonmetallic inclusions plays veryimportant role in determination of the material properties,especially when aim is improvement of the mechanicalproperties. Investigation of the nonmetallic inclusions in-fluence on a steel quality is based on their dimension,shape, chemical and mineralogical composition andphysical characteristic (melting temperature, deforma-bility, hardness etc.). Above mentioned nonmetallic in-clusions properties mainly depend on way of productionand casting of steel and they can vary from charge tocharge. In order to extend the working life of bearings thefollowing is necessary: high and uniformly spaced hard-ness, wear resistance, fatigue resistance, high strengthand elasticity and good machinability. Accordingly, thesmallest defects in the materials like inclusions or differ-ent microstructure have harmfull effects on propertiesand exploitation of the steel 1, 2, 3, 4.EXSPERIMENTAL PROCEDUREA plan of experimental work was carried out as fol-lows:– production of steel 100Cr6– plastic processing– heat treatment– metalographical investigation.PRODUCTION OF STEEL 100Cr6Experimental melts of 100Cr6 steel are produced inopen and vacuum induction electrical furnaces at Metal-lurgical Institute „Kemal Kapetanovi}“ in Zenica. A steelscrap (bars and sheets) was used as a raw material in openinduction electrical furnace. Raw materials prepared inopen induction furnace were used as a charge for the vac-uum induction electrical furnace. The chemical composi-tion of produced samples is given in Figure 1.METALURGIJA 48 (2009) 1, 29-32 29Steel 100Cr6 belongs to a group of hardened steels, which are applicable for production of rolling elementparts. Because of specific working conditions, a proper chemical composition is required with a minimum con-tent of nonmetallic inclusion. In this paper, the research results of presence the nonmetallic inclusions and theirchemical composition are presented for the steel produced in vacuum and open induction electric furnace andtheir influence on the prescribed properties for this steel. The optical and scanning electronic microscope areused to identify presence and the chemical compositions of nonmetallic inclusions.Key words: steel 100Cr6, nonmetallic inclusions, optical and scanning electronic microscope, vacuum and in-duction electric furnaceAnaliza i ispitivanje nemetalnih uklju~aka za ~elik 100Cr6. ^elik 100Cr6 pripada grupi prokaljivih ~elikakoji su prvenstveno na{li primjenu u proizvodnji dijelova kotrljaju}ih le`ajeva. Glede posebnih uvjeta rada zaovu vrstu ~elika se zahtijeva propisani kemijski sastav sa minimalnim prisustvom nemetalnih uklju~aka. U ovomradu su predstavljeni rezultati ispitivanja prisustva nemetalnih uklju~aka i njihov kemijski sastav za ~elik 100Cr6proizveden u vakuumskoj i otvorenoj indukcionoj elektro pe}i te njihov uticaj na svojstva propisane normom zaovu vrstu ~elika. Ispitivanje prisustva nemetalnih uklju~aka kao i analiza kemijskog sastava ura|ena je primje-nom opti~kog i skening elektronskog mikroskopa.Klju~ne rije~i: ~elik 100Cr6, nemetalni uklju~ci, opti~ki i skening elektronski mikroskop, vakuumska i indukcijskaelektro pe}ISSN 0543-5846METABK 48(1) 29-32 (2009)UDC – UDK 669.14.018.24:620.153.086=111A. Gigovi}-Geki}, University of Zenica, Faculty of Metallurgy and Mate-rials Science, Zenica, BiHM. Oru~, Metallurgical Institute “Kemal Kapetanovi}”, Zenica, BiHI. Vitez, University of Osijek, Faculty of Mechanical Engineering,Slavonski Brod, CroatiaB. Vuji~i}, University of Osijek, Polytehnic, Slavonski Brod, CroatiaPLASTIC PROCESSING– Plastic processing by hammering (with dimension120x120 mm on 34 x 34 mm)– Rolling with dimension 34 x 34 mm on ø 26 mm.Heat treatmentThe samples of the steel 100Cr6 are heat treated asfollows:– heating to a temperature 800 °C in the furnacewithout protection atmosphere– holding at that temperature for about 4 hours– cooling in the furnace– heating to a temperature 820 °C in the furnacewithout protection atmosphere– holding at that temperature for about 20 minutes– quenching in water– heating to a temperature 180 °C in the furnacewithout protection atmosphere– holding at that temperature for about 1 hour and30 minutes– cooling.Metalographical investigationAfter heat treatment, an optical microscope was usedfor investigating and identification of nonmetallic inclu-sions. The analyse of chemical compostions observednonmetallic inclusion was done by a scanning electronicmicroscope.RESULTS AND DISCUSIONChemical analyseThe achieved and prescribed chemical compositionaccording to standards ASTM A 295/94 and DIN17230/80 for 100Cr6 steel is given in Table 1 5, 6.Table 1. Chemical compositionElement/ %ASTMA 295/94DIN17230/80B 7611 C 1302C 0,98/1,10 0,9/1,05 0,98 0,95Si 0,15/0,35 0,15/0,35 0,29 0,35Mn 0,25/0,45 0,25/0,45 0,41 0,43P max.0,025 max.0,030 0,013 0,007S max.0,025 max.0,025 0,029 0,016Cr 1,30/1,60 1,35/1,65 1,52 1,60Ni max.0,25 max.0,30 0,20 0,22Mo max. 0,10 - 0,03 0,03Cu max.0,35 max.0,30 0,23 0,19Analyse of non-metallic inclusions by theoptical microscopeA results of the analyse of nonmetallic inclusionswere done according to standard ASTM E 45, methodA, the worst field 7. The samples were tested inquenched and tempered state. The metallographic ana-lyse shows a presence of oxide, oxide-sulphide, alumi-nates and sulphide inclusions in all melts, Figure 2. In-creasing of the deformation degree during the plasticprocessing increases deformation of observed thesulphides. After the plastic processing new arrange ofthe sulphide inclusions was observed forming strings.The sulphide inclusions in the vacuum melts are moreplastic because they are pure sulphides in comparingwith the oxide-sulphide inclusions in the case from theopen induction furnace. The presence of silicates is notnoticed. The nonmetallic inclusions are distributed byprimary grain border and grouped in small nest by lowerdeformation degrees and they are arranged formingstrings in case of higher deformation degrees.Analyse of non-metallic inclusions by thescanning electronic microscopeAs addition to the analyse of nonmetallic inclusionsby optical microscope, the investigation of presence andchemical composition of nonmetallic inclusions wasdone at the Institute for materials and technology inLjubljana-Slovenia. The samples in annealing state of30 METALURGIJA 48 (2009) 1, 29-32A. GIGOVI]-GEKI] et al.: ANALYSE AND RESEARCH OF NONMETALLIC INCLUSIONS FOR STEEL 100Cr6Figure 1. Chemical compositions of 100Cr6 steel produ-ced in open induction furnace a) and vacuum in-duction furnace b)a)b)100Cr6 steel from both types of melts were investigated.The chemical composition and the inclusions shape forthe melts from the open induction furnace are given inFigure 3.The chemical composition and the inclusions shapefor the melts from the vacuum induction furnace aregiven in Figure 4.The analyse of nonmetallic inclusions by the scan-ning electronic microscope indicated a presence ofAl2O3, MnS, (FeMn)S inclusions and rarely TiN inclu-sions. It is possible to see a characteristic shape for somesort of inclusions by different magnification, describedin a literature 8, 9. The oxide inclusions Al2O3 arespherical in shape, TiN inclusions have irregular shapeand sharp edges and MnS inclusions have deformedshape. The analyse of chemical composition indicated apresence of (FeMn)S inclusions but they are visible onlyby higher magnification.Determination of JK inclusion ratingJK inclusion rating is presented in Table 2. for steel100Cr6.Table 2. JK inclusion rating (A-sulfide, B-aluminate,C-silicate, D-globular oxide)Inclu-sionsMeltThin series Heavy seriesAchieved JK Achieved JKAB7611 1½-22 ½1½-2½1½C1302 1½-2 1-2BB7611 ½-221-2½1C1302 1-2 1-2CB7611 -½-½C1302 - -DB7611 ½-11½-11C1302 1 1CONCLUSIONS– From the chemical analysis of produced steel wecan see the higher content of sulphur according tothe standard ASTM 295 in the melts produced inthe open induction electrical furnace. The highercontent of sulphur in the raw materials is reasonfor that and if we want to reduce it the proper se-lection of raw materials is necessary.METALURGIJA 48 (2009) 1, 29-32 31A. GIGOVI]-GEKI] et al.: ANALYSE AND RESEARCH OF NONMETALLIC INCLUSIONS FOR STEEL 100Cr6Figure 2. Distribution of presented nonmetallic inclusions for steel 100Cr6, 50xa.) Melt B 7611, 80x80 mm.Oxide-sulphide inclusionsb.) Melt B 7611, 80x80 mm.Sulphide inclusionsc.) Melt C1302, 80x80 mm.Sulphide inclusionsd.) Melt C1302, 34 x34 mm.Aluminates inclusions– Higher content of the sulphide inclusions in themelts is a result of increased level of sulphur.There is the increased content of oxides in the meltfrom open induction furnace, what was expectedbecause the influence of atmosphere. The SEManalyse indicated a presence of the complex ox-ide-sulphide and sulphide nonmetallic inclusions.Harmfully effects of inclusions is reduced by in-creasing the deformation degree.– The proper selection of raw materials is very im-portant and vacuum furnace should be used formelting, in the case of the industrial productionhigher grades of bearing steel 10, 11.– It is necessary to investigated as next step, openinduction furnace can be used for production ofsome grades of bearing steels and selection of rawmaterials what is very important too 12.REFERENCES1 Verein Deutscher Eisenhüttenleute Steel: A Handbook forMaterials Research and Engineering, Vol.2: Applications,Springer-Verlag, Verlag Stahleisen mbH, 1993, p.584-592.2 P. Pavlovi}: Materijal ~elik, SKTH/ Kemija u industriji, Za-greb, 1990, str.246.3 T. Filetin, F. Kova~i~ek, J. Indof, Svojstva i primjena mate-rijala, Fakultet strojarstva i brodogradnje, Zagreb, 2002, str.96.4 F. Begovac: Osobine ~elika, Univerzitet u Sarajevu, Fakultetza metalurgiju i materijale u Zenici, Zenica, 2000, str. 201.5 *** Standard DIN 17230/1980.6 *** Standard ASTM A 295/1994.7 *** Standard ASTM E 45/1997.8 R. Kiessling N.Lange, Non-metallic inclusions in steel, TheMetal Society, London, 1976, p. 50-110.9 E.Kratina, B.Faki}, Osvajanje proizvodnje ~elika 100Cr6,Metalur{ki institut “Kemal Kapetanovi}”, Zenica, 2006,str.13.10 *** Propisi FAG PL1.901A/2001.11 *** Propisi FAG PL1.203/2002.12 A. Gigovi}, Prilog izu~avanju uticaja nemetalnih uklju~akana kvalitet ~elika 100Cr6 proizvedenog u vakuumskoj i ot-vorenoj indukcionoj elektro pe}i, magistarski rad, Univerzi-tet u Zenici, Fakultet za metalurgiju i materijale. Zenica,2007, str. 83-84.Note: English language lecturer: Dijana Hasanica, Zenica, Bosnia andHerzegovina32 METALURGIJA 48 (2009) 1, 29-32A. GIGOVI]-GEKI] et al.: ANALYSE AND RESEARCH OF NONMETALLIC INCLUSIONS FOR STEEL 100Cr6Figure 3. Chemical compositions a) and shape b) of re-presentative sample inclusions 84-5 (Melt B7611)-1, 9500xa)b)Figure 4. Chemical composition a) and shape b) of re-presentative sample inclusions 144-5 (Melt C1302)-2, 8500xa)b)

Analiza i ispitivanje nemetalnih uključaka za čelik 100Cr6

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