Investigations on Materials Used for Manufacturing the Rolling Rolls in Few Durability Experiments

Introduction

Hot rolling mill rolls are the parts most subjected to wear in the rolling trains because the incandescent rolled material is deformed between the water cooled rolls, at temperatures of 1100…1150 ⁰C. They represent a consumption of 0.8 kg/tone of rolled steel. It is noticeable that approximately 1 from 10 rolling rolls are removed from exploitation because of the thermal shock caused breakings, which cause accidental damage and stoppage, and the losses expand over the rolls cost, as well as production losses, disturbing the entire technological flux (Kiss, 2005, Toader, Pinca-Bretotean, & Plesa, 2004).

Up to this moment, there is no reference publication to minutely deal with the theoretical and experimental aspects of this theme of research (Kiss, 2005, 2008; Pinca-Bretotean, Kiss, Josan, & Tirian, 2005). Poverty of detailed research, theoretical and experimental, about the thermo-mechanical processes take place during the plastic deformation between the rolling mills rolls, represents a factor that reduces the possibility of rational exploitation of rolling mills (Werquin & Caillaud, 1990; Lundberg, 1993; Kato, Yamamoto, Ataka, & Nakajima, 1992; Toader, Pinca-Bretotean, & Plesa, 2004). In the context of market economy is necessary a new evolution in the area of scientific researches, in the purpose of modernization of the equipment and metallurgical plants, using the most efficient solutions for obtaining aggregates with performances to the level of world technique (Kiss2005, 2008).

The durability in exploitation of the rolling mill rolls is little approached in the reference literature, both in Romania and worldwide. Up to this moment, there is no reference publication to minutely deal with the theoretical and experimental aspects of this theme of research (Kiss, 2005, 2008; Kiss, Alexa, Cioata, & Ratiu, 2011; Pinca-Bretotean, Kiss, Josan, & Tirian, 2005; Pinca-Bretotean & Tirian, 2006).

The lack of detailed theoretical and experimental research upon the mechanic and thermal process taking place during plastically deformation between the rolls constitutes a factor to reduce the possibilities of rational mill exploitation (Kiss, 2005, 2008; Kiss, Cioata, & Alexa, 2010; Toader, Pinca-Bretotean, & Plesa, 2004). In the context of present day market an evolution is necessary in the field of scientific research in order to modernize the metallurgical equipment, using the most efficient solutions to obtain performing aggregates on world level (Kiss, 2008; Schroder, 2000, 2003).

Currently, many aspects of the thermal regime of lamination are still not enough studied, and also, there are no efficient methods for the determination and adjustment of the rolling rolls temperatures from the industrial rolling mills. The intensification of the lamination process directly influences the rolls durability, these being the most solicited organs of machines from whole ensemble of the lamination equipment. The technological processes of the rolling rolls manufacture, as well as the quality of used materials have a quick extension, materialized in worldwide market competition, through exceptional qualities of rolls. The different high alloy ferrous products currently used in the manufacture of these rolls define an important chapter from the quality assurance of the industrial products (Kiss, 2005, 2008, 2009, 2010; Kiss, Cioata, & Alexa, 2010; Kiss, Cioata, Alexa, & Ratiu, 2010).

The research of durability in the exploitation of rolling rolls define experimentally an important chapter from the thermal fatigue of the organs of machines in the movement of rotation, in variable temperature mediums (Kiss, 2005, 2008; Toader, Pinca-Bretotean, & Plesa, 2004). The researches on the durability in exploitation of hot rolling mill rolls represent an important scientific and economical issue.