Defects in metal forming processes

Tehnologija oblikovanja deformiranjem podrazumijeva izradu proizvoda deformacijom materijala, bez odvajanja čestica. U radu je, uz pomoć znanja stečenog tokom studija i dodatne literature, proučen mehanizam deformacije metala, faktori koji utječu na pojavu pogreški i tipične pogreške kod klasičnih postupaka obrade deformiranjem. Deformacija metala objašnjava se na dva načina. Prvi način jest deformacija monokristala, a drugi deformacija polikristala, odnosno realnog slučaja. Iako u stvarnosti metal nije građen kao monokristal, ovakav način proučavanja bitan je za razumijevanje procesa koji se odvijaju unutar jedinice građe metala tijekom deformacije. Prikazan je pregled faktora koji igraju važnu ulogu kod oblikovanja deformiranja te kakav utjecaj ima pojedini faktor tijekom obrade. Određeni faktori mogu pozitivno utjecati na pojedina svojstva, ali negativno na druga pa je potrebno pažljivo određivanje parametara obrade. Nadalje, napravljen je pregled grešaka ovisno o vrsti postupka sa naglaskom na valjanje koji prethodi brojnim drugim obradama. Naime, valjanje je najrasprostranjenija tehnologija obrade deformiranjem te će se greške koje nastanu kod valjanja zasigurno zadržati na gotovom proizvodu. Kod grešaka su navedeni uzroci nastanka te smjernice kako spriječiti pojavu takvih grešaka.Metal forming technology implies metal part production only by material deformation, without cutting. This thesis gives a study of deformation mechanism, factors that influence the occurrence of material defects and typical defects in basic deformation processes, collected from the knowledge gained during the study and from the literature review. Metal deformation is explained in two ways. The first way is the simplified case - deformation of the monocrystalline, and the second one presents the real case - deformation of the polycrystal. Although metal is not built as a monocrystal, this way of study is essential for understanding the processes that take place within the metal structure unit during deformation. The thesis gives an overview of the factors that play an important role in deformation process and explains the impact of a particular factor during material processing. Certain factors can have a positive effect on individual properties, but negatively on others, so careful determination of processing parameters is required. Furthermore, an overview of defects was made depending on the type of forming process with focus on rolling which precedes many other types of processes. Namely, rolling is the most widespread metal forming technology and defects that are made when rolling will surely be kept on the finished product. Causes of defects are given and guidelines for preventing such defects