The results of the modification of austenitic matrix in cast high-manganese steel containing 11÷19% Mn with additions of Cr, Ni and Ti were discussed. The introduction of carbide-forming alloying elements to this cast steel leads to the formation in matrix of stable complex carbide phases, which effectively increase the abrasive wear resistance in a mixture of SiC and water. The starting material used in tests was a cast Hadfield steel containing 11% Mn and 1.34% C. The results presented in the article show significant improvement in abrasive wear resistance and hardness owing to the structure modification with additions of Cr and Ti.

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The changes of a sulphur content during refining in melting low-alloy and high-alloy steels (G17CrMoV5-10; GX12CrMoNiVNbN9-1) applied for large-dimension castings for the power engineering are presented in the hereby paper. The investigated steel was melted in the oxygen-recovery melting technology with an application of maximum 70% of the process scrap. In addition, after steel melting in the electric arc furnace (EAF), the secondary metallurgy was performed in the ladle furnace (LF). It was shown that the application of the secondary metallurgy by a synthetic slag in the ladle furnace and argon bubbling of a metal bath leads to obtaining in the final analysis: 0.0043-0.0046% of sulphur (a decrease of S content during refining in LF reached 40%). Current measurements of FeO in the slag and maintaining its content below 0.8%, support obtaining such low sulphur content in steel. So low level of the slag oxidizing is one of the necessary conditions for a deep desulphurisation of the metal bath. Without the secondary metallurgy the sulphur content in low-alloy cast steel was 0.007%, while 0.01% in high-alloy cast steel.Controlling of the gas (oxygen, nitrogen) content during steel melting and correcting the amount of additions (e.g. deoxidants), allowed to obtain the low oxygen content (below 45 ppm for two investigated steel grades) and nitrogen content (88 ppm for low-alloy steel and 330 ppm for high-alloy steel), which warrants a good combination of strength and plastic properties.Keywords: Cast steel for power industry, Melting technology, Electric arc furnace, Ladle furnace, Desulphurisation W pracy przedstawiono zmiany zawartości siarki podczas rafinacji w czasie wytapiania stali nisko-i wysokostopowej (G17CrMoV5-10; GX12CrMoNiVNbN9-1) stosowanej na wielkogabarytowe odlewy dla energetyki. Badaną stal wytopiono w technologii odzyskowo-tlenowej z zastosowaniem maksymalnie 70% złomu własnego. Dodatkowo, po wytopieniu stali w piecu łukowym (EAF) przeprowadzono obróbkę pozapiecową w pieco-kadzi (LF). Wykazano, że zastosowanie obróbki pozapiecowej żużlem syntetycznym w pieco-kadzi i argonowania kąpieli metalowej prowadzi do uzyskania w analizie końcowej 0,0043-0,0046%S (zmniejszenie zawartości S podczas rafinacji w LF sięgało 40%). Uzyskaniu tak niskiej zawartości siarki w stali sprzyja m.in. bieżący pomiar FeO w żużlu i utrzymanie jego zawartości poniżej 0,8%. Tak niski poziom stopnia utlenienia żużla jest jednym z warunków koniecznym do dobrego odsiarczenia kąpieli metalowej. Bez obróbki pozapiecowej zawartość siarki w staliwie niskostopowym wynosiła 0,007%, natomiast dla staliwa wysokostopowego 0,01%. Kontrola zawartości gazów (tlenu i azotu) w czasie wytapiania stali i dokonywana korekta ilości wprowadzanych dodatków (np. odtleniaczy) doprowadziła do uzyskania niskiej zawartości tlenu (poniżej 45 ppm dla dwóch badanych gatunków stali) i azotu (88 ppm dla stali niskostopowej, 330 ppm dla stali wysokostopowej) gwarantująca dobrą kombinację właściwości wytrzymałościowych i plastycznych odlewów.

This paper discusses changes in the microstructure and abrasive wear resistance of G17CrMo5-5 cast steel modified with rare earth metals (REM). The changes were assessed using scanning microscopy. The wear response was determined in the Miller test to ASTM G75. Abrasion tests were supplemented with the surface profile measurements of non-modified and modified cast steel using a Talysurf CCI optical profilometer. It was demonstrated that the modification substantially affected the microstructure of the alloy, leading to grain size reduction and changed morphology of non-metallic inclusions. The observed changes in the microstructure resulted in a three times higher impact strength (from 33 to 99 kJ/cm 2 ) and more than two times higher resistance to cracking (from 116 to 250 MPa). The following surface parameters were computed: Sa: Arithmetic mean deviation of the surface, Sq: Root-mean-square deviation of the surface, Sp: Maximum height of the peak Sv: Maximum depth of the valley, Sz: Ten Point Average, Ssk: Asymmetry of the surface, Sku: Kurtosis of the surface. The findings also indicated that the addition of rare earth metals had a positive effect on the abrasion behaviour of G17CrMo5-5 cast steel.