Modeliranje reparaturnog i proizvodnog navarivanja radnih delova građevinske mehanizacije

Abstract

U ovom radu (disertaciji) razmatraju se savremene metode obnavljanja oštećenih radnih delova građevinske mehanizacije, nastalih pod dejstvom različitih procesa habanja i korozije. Reč je uglavnom o navarivanju koje nalazi sve širu primenu pri nanošenju metalnih prevlaka, otpornih na habanje i koroziju. Izbor odgovarajućeg postupka i propisivanje optimalne tehnologije navarivanja, bilo da je reč o reparaturnom ili proizvodnom navarivanju, od izuzetnog je značaja, zbog produženja radnog veka i smanjenja troškova održavanja građevinske mehanizacije. Da bi se odredila optimalna tehnologija navarivanja, odnosno modeliranje procesa navarivanja radnih delova građevinske mehanizacije, neophodno je bilo izvesti istraživanja na većem broju navarenih fizičkih modela i realnih radnih delova, izrađenih od različitih vrsta čelika. Takođe, neophodno je bilo odrediti neka petrografska, fizička, mehanička i tehnološka svojstva građevinskog materijala, odnosno kamena. Izbor postupka navarivanja i određivanje najpovoljnije tehnologije navarivanja u velikoj meri zavisi od svojstava osnovnih materijala. Svojstva osnovnog materijala i zahtevana svojstva navara su ulazni parametri procesa navarivanja, a izlazni parametri su svojstva čistog metala navara. Da bi se dobio zahtevan kvalitet navara, najčešće nije dovoljno samo pravilno izabrati postupak navarivanja i dodatni materijal, već pravilno propisati parametre navarivanja i odgovarajuću tehniku nanošenja navara. Izborom različitih postupaka navarivanja, više vrsta dodatnih materijala, varijacijom parametara navarivanja i primenom različitih tehnika, stvoreni su uslovi za optimizaciju procesa navarivanja i dobijanje zahtevanih izlaznih svojstava navara. Kod osnovnih materijala uglavnom je određivan hemijski sastav, najvažnija mehanička svojstva, ocenjivana njihova zavarljivost i otpornost na habanje. Provera kvaliteta navara može se izvesti prema različitim kriterijumima, merenjem tvrdoće, ispitivanjem mikrostrukture i proverom otpornosti na habanje. Brojna eksperimentalna istraživanja na modelima dovela su do uspostavljanja veze između ulaznih i izlaznih parametara procesa navarivanja. Polazna tehnologija navarivanja odabrana je na osnovu rezultata modelskih ispitivanja. Za proveru, odnosno verifikaciju primenjene tehnologije, poslužili su rezultati ispitivanja na realnim radnim delovima i pri realnim uslovima eksploatacije. Iako je izvođenje svakog procesa navarivanja gotovo unikatan posao, jer zahteva tehnologiju prilagođenu svakom radnom delu, ustanovljena je opšta procedura, odnosno model navarivanja za grupe sličnih delova građevinske mehanizacije. Osnovni cilj ovih istraživanja je, da se na konkretnim primerima reparaturnog ili proizvodnog navarivanja, odredi procedura i optimalna tehnologija, koja će obezbediti dobijanje navarenih radnih delova zahtevanog kvaliteta uz minimalne troškove. Kako se to može ostvariti pokazuju rezultati teorijskih i eksperimentalnih istraživanja prikazanih u ovom radu (disertaciji). Dobijeni rezultati ukazuju na opravdanost primene reparaturnog ili proizvodnog navarivanja kod velikog broja radnih delova građevinske mehanizacije, pri čemu se ostvaruju značajne uštede na njenom održavanju, jer se znatno produžava radni vek i smanjuju gubici usled zastoja za vreme eksploatacije. Obimna teorijska i eksperimentalna istraživanja, i složena procedura provere kvaliteta nanetih metalnih prevlaka, ukazuju da se reparaturni radovi mogu izvoditi samo u pogonima koji raspolažu adekvatnom opremom i odgovarajućim stručnim kadrom, i da na ovim poslovima mogu uspešno raditi samo oni kojima je održavanje tehničkih sistema profesija, a ne usputno zanimanje.

In this paper (dissertation) are considered contemporary methods of reparation of the damaged working parts of the civil engineering mechanization, where the damaged was caused due to action of various wear and corrosion processes. The subject is mainly hard-facing, which is all the more widely applied in metals coatings deposition, resistant to wear and corrosion. The selection of the appropriate procedure and prescribing the optimal hard-facing technology, whether one speaks about reparatory or manufacturing hard-facing, are of the utmost importance, due to extended working life and reduced maintenance costs of civil engineering mechanization. In order to determine the optimal hard-facing technology, namely to model the hard-facing process, it was necessary to perform hard-facing and research on a larger number of physical models as well as of the real machine parts, made of different types of steels. It was also necessary to determine certain petrographic, physical and technological properties of the building materials, namely stones and rocks. The hard-facing selection procedure and determination of the optimal hard-facing technology depend, to the great extent, on the properties of the base metals. The base metals properties and the required properties of the hard-faced layers are the input parameters of the welding process, while the output parameters are properties of the pure weld metal. In order to obtain the hard-faced layer of the required quality, it is not sufficient, most frequently, just to adequately select the hard-facing procedure and the filler metals, but it is also necessary to prescribe parameters of the hard-facing process and the appropriate technology of hard-faced layers deposition. Through selection of different hard-facing processes, several filler metals, variation of hard-facing parameters and application of various welding techniques, the conditions were created for optimization of the hard-facing process and obtaining of the required output properties of the hard-faced layers. For the base metals, mainly the chemical compositions were determined, as well as the most important mechanical properties, their weldability and wear resistance were evaluated. The hard-faced layer quality checking can be performed according to various criteria, by measuring hardness, investigating the microstructure and by testing the wear resistance. Numerous experimental investigations led to establishing the relationship between the input and the output hard-facing process parameters. Determination of the initial technology of hard-facing was done based on results of the model investigations. For checking, namely verification of the applied technology, served results of investigation on the real working parts and in the real operating conditions. Though the conducting of each hard-facing process is a unique task, since the technology adjusting to each working part is required, the general procedure was established, namely the model of hard-facing for groups of similar part of the civil engineering mechanization. The fundamental goals of these investigations is to determine, on concrete examples of reparatory or manufacturing hard-facing, the procedure and optimal technology, which would guarantee obtaining of the hard-faced working parts with required quality and with minimal costs. How that is possible to achieve is shown by results of theoretical and experimental research performed within this paper (dissertation). Results obtained thus far point to validity of application of the reparatory or manufacturing hard-facing for numerous parts of the civil engineering mechanizations, where the significant savings were realized in maintenance costs, since the working life of components was extended and losses due to down-times during exploitation were reduced . Voluminous theoretical and experimental research, and the complex verification procedure of deposited metal coatings quality, suggest that the reparatory tasks can be performed only in plants that are have at their disposal the adequate equipment as well as the expert staff, and that on these tasks can work only personnel to whom maintenance of the technical systems is a profession and not just casual interest.