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Effects of steel - applied for large-dimension castings for the power engineering - refining in the ladle-furnace

Kalandyk B., Wojtal W

Archives of Metallurgy and Materials

2013

Vol. 58, iss. 3

779--783

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.

W pracy przedstawiono zmiany zawartosci siarki podczas rafinacji w czasie wytapiania stali nisko- i wysokostopowej (G17CrMoV5-10; GX12CrMoNiVNbN9-1) stosowanej na wielkogabarytowe odlewy dla energetyki. Badana stal wytopiono w technologii odzyskowo-tlenowej z zastosowaniem maksymalnie 70% złomu własnego. Dodatkowo, po wytopieniu stali w piecu łukowym (EAF) przeprowadzono obróbke pozapiecowa w pieco-kadzi (LF). Wykazano, ze zastosowanie obróbki pozapiecowej zuzlem syntetycznym w pieco-kadzi i argonowania kapieli metalowej prowadzi do uzyskania w analizie koncowej 0,0043-0,0046%S (zmniejszenie zawartosci S podczas rafinacji w LF siegało 40%). Uzyskaniu tak niskiej zawartosci siarki w stali sprzyja m.in. biezacy pomiar FeO w zuzlu i utrzymanie jego zawartosci ponizej 0,8%. Tak niski poziom stopnia utlenienia zuzla jest jednym z warunków koniecznym do dobrego odsiarczenia kapieli metalowej. Bez obróbki pozapiecowej zawartosc siarki w staliwie niskostopowym wynosiła 0,007%, natomiast dla staliwa wysokostopowego 0,01%. Kontrola zawartosci gazów (tlenu i azotu) w czasie wytapiania stali i dokonywana korekta ilosci wprowadzanych dodatków (np. odtleniaczy) doprowadziła do uzyskania niskiej zawartosci tlenu (ponizej 45 ppm dla dwóch badanych gatunków stali) i azotu (88 ppm dla stali niskostopowej, 330 ppm dla stali wysokostopowej) gwarantujaca dobra kombinacje własciwosci wytrzymałosciowych i plastycznych odlewów.

Application of cast nickel alloys for parts of electronics characterised by special magnetic properties

Uhl W., Pirowski Z., Kułak A.

Archives of Foundry Engineering

2008

Vol. 8, iss. 1 spec.

327--330

The theoretical part of the study highlights the origin of the idea to start investigations on alloys of high magnetic permeability, manufactured mainly by companies in the USA and Japan. The said materials are applied for various parts of electronics used by the military industry, e.g. satellite antennas for global communication with submarines, and for research instruments, e.g. ferromagnetic cores. They are characterised by very high magnetic permeability, resistivity and corrosion resistance which make them suitable for operation under extra-trying conditions. Nickel alloys of high magnetic properties are usually manufactured as rolled products. The ambition of the authors of this study is to manufacture them as cast products. The program of research included characteristic of nickel alloys with additions of molybdenum and iron satisfying the above mentioned requirements, with attention focussed on their application for magnetic parts of satellite antennas and ferromagnetic cores. Moulding and casting technologies were proposed to best suit the process of manufacture of these elements. The range of chemical compostion was selected to ensure the required magnetic, mechanical and anti-corrosive properties. A series of melts was prepared and castings of the above mentioned elements were made. The chemical composition of the alloys was analysed along with the structure examinations and quality assessment made by the non-destructive methods. Castings were subjected to the finishing treatment, followed by tests and examinations to enable their practical application.