Cyclic temperature changes in the working layer of a roll during hot rolling cause thermal stress which leads to damage on the surface layer of the roll due to thermal fatigue. The pre-conditions of crack initiation are described. The intensity of crack propagation could be influenced by optimizing the chemical composition and physical-mechanical properties of the material on the working layer. This reduces the tendency of the material with respect to damage due to thermal fatigue and extends the lifetime of the rolls. The microstructure as well as the operational characteristics of the developed HSS working rolls resistant to thermal fatigue are presented.
Numerous FEM calculation models for load introduction onto rolling mill rolls have been developed. The stress that can arise during heat treatment as well as during roller use was calculated. This has made it possible to optimize roll use conditions and to develop new roll qualities. The following results are described: stress in the heat treatment of rolls, the calculation of large work rolls of a heavy plate mill, the counter-bending of rolls whose body length is greater than 6,000 mm, von Mises stress in roll necks, contact stress at the edge region of working and back-up rolls, stress distribution in pre-stressed composite profile rolls in use
Fatigue strength of cyclically stressed components can be affected by various sub-microdefects such as dislocations, vacancy and micropores. An interaction of dislocations and non-metallic inclusions, the formation of pores and various cracking mechanism have been described.
The resistance of a modern ceramic material -silicon nitride -was examined by cyclical high temperature and compressive loads by the use of warm upsetting tests at cylindrical molybdenum and wolfram samples. Furthermore, flow curves of these samples were determined for different temperatures.
The causes of a composite roll fracture were investigated. The result of an FEM analysis showed that the occurrent stress could not have led to this fracture. Metallographic investigations in the area of the crack start site clearly showed non-metallic inclusions. These affect structural weak points and activate malfunctions. They significantly accelerated the cracking process due to the local notch effect which significantly reduced the performance of the material and thus the service life of the roll shaft.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.