This study aims at finding ways to improve the service properties of state-of-the-art creepresistant Mg alloys for Thixomolding and minimise production problems. In doing so, microalloying with Si, Zn, Sr, Li, C, Ba and Bi, as well as the addition of rare earths is a viable solution.

Internal stresses or residual stresses remain in almost every part after manufacturing and/or further processing. Even if the entire stress state inside a system is in an equilibrium, single stresses due to their direction and strength may have positive or negative influences to the properties of a body. Especially in big parts, the residual stress state is relatively unknown, because it can only be determined by destructive methods as sectioning or slitting. The possibility of the use of non destructive measuring methods is only given for surface near regions or thin parts and not useful for the specification of the entire residual stress state inside a large compound work roll. This paper outlines an approach for the determination of residual stresses in centrifugal casted work rolls with an indefinite chill double poured or high speed steel shell. In several steps, different measurement techniques are tested and the results are to be presented. Beside the residual stress state, which is caused by manufacturing or heat treatment, these work rolls with different shell and core material differ in their thermophysical and elastic properties. These parameters in combination with the residual stress state and the thermal and load stresses, which arise during the hot rolling process, are causing a complex stress field that is presented by a combined model for work and backup rolls in operation.

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