Stress and deformation of ceramic rolls to produce high quality zinc coated steel sheet

Several ceramic rolls can be used efficiently to produce high quality zinc coated steel sheet used for automobiles. Those ceramics rolls may provide a longer life and reduce the cost for the maintenance because of its large heat resistance and large wear resistance. One example may be seen in sink rolls used in molten zinc bath to manufacture zinc coated steel sheet. Since the rolls are subjected to large thermal stress and mechanical loading, care should be taken for the risk of fracture due to the ceramic brittleness. Moreover, since the sleeve and shafts can be connected only by using small shrink fitting ratio，another failure risk should be considered for the separation of those components [25, 26]. In this paper, therefore, the mechanical and thermal stress and separation condition will be investigated considering the separation of the connected portion. Here, by using the finite volume method the heat transfer coefficient is discussed and by using the finite element method the thermal stress is considered.12th International Conference on Damage Assessment of Structures 10–12 July 2017, Kitakyushu, Japa

Coming out prevention by stopper for the shrink fitted sandwiched shaft from the ceramic sleeve

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. The roller consists of sleeve and steel shaft connected only under a small shrink fitting ratio because of the brittleness. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated bending load. Therefore, how to prevent the coming out failure becomes an important issue. Based on the previous study, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Then, this research focuses on preventing the inner plate coming out from the outer plate by introducing a newly designed stopper on the outer plate. The simulation results shows that the coming out phenomenon can be prevented effectively due to the contact between the inter plate and the stopper installed on the outer plate. In order to evaluate the contact force between the inner plate and the stopper, the coming out mechanism is clarified. To prevent the coming out by stopper safely, the effects of the magnitude of repeated load and the friction coefficient upon the contact compressive force are investigated under large number of loading cycles by using 2D simulation.12th International Conference on Damage Assessment of Structures, 10–12 July 2017, Kitakyushu, Japa

Application of Large Ceramics Structures to Steel Manufacturing Machinery

Large ceramics structurers may be useful for several situations in steel manufacturing machinery because of their high abrasion and corrosion resistances. In this study, new roll structure is considered where a ceramics sleeve is connected with steel shafts at both ends by shrink gitting, which can be used in the continuous pickling line. Here, the ceramics sleeve may provide a longer lifetime and reduces the cost for the maintenance. However, attention should be paid to the maximum tensile stresses appearing between the ceramics sleeve, space rings and steel shafts because the fracture toughness, plasticity and fatigue strengths of ceramics are extremely lower than the values of steel. In this study, therefore, finite element method analysis is applied to the new structure, and the maximum tensile stress and stress ampliture have been investigated with varying the dimensions of the strucure. Both of static and fatigue strengths of ceramics are considered under several geometrical conditions. It is found that the large ceramics structures are suitable for several steel manufacturing rolls

Numerical simulation on interfacial creep generation for shrink-fitted bimetallic roll

The bimetallic work rolls are widely used in the roughing stands of hot rolling stand mills. The rolls are classified into two types; one is a single-solid type, and the other is a shrink-fitted assembled type consisting of a sleeve and a shaft. Regarding the assembled rolls, the interfacial creep sometimes appears between the shaft and the shrink-fitted sleeve. This interfacial creep means the relative displacement on the interface between the sleeve and the shaft. This creep phenomenon often causes damage to the roll such as shaft breakage due to fretting cracks. Although to clarify this creep mechanism is an important issue, experimental simulation is very difficult to be conducted. Since few studies are available, in this paper, the interfacial creep phenomenon is simulated by using the elastic finite element method (FEM) analysis. Here, the roll rotation is replaced by the road shift on the fixed roll surface. It is found that the interface creep can be explained as the accumulation of the relative circumferential displacement along the interface

Quasi-Equilibrium Stress Zone with Residual Displacement Causing Permanent Slippage in Shrink-Fitted Sleeve Rolls

Rolling back-up rolls require high fracture toughness, particularly in the shaft portion, and high-hardness in the sleeve portion. The rolls are classified into two types; one is an integrated type and the other is a shrink-fitted type consisting of a sleeve and a shaft. The shrink-fitted roll has several advantages, for example, suitable materials can be chosen and the shaft can be reused by replacing the damaged sleeve. However, during use if the residual permanent deflection occurs, the roll cannot be used anymore. In this paper, an elastic-contact finite element method FEM analysis is performed to explain the residual permanent deflection mechanism. It is found that the quasi-equilibrium stress zone with the residual displacement causes the permanent slippage in the axial direction. In a similar way, the interface creep in the circumferential direction can be also explained from the quasi-equilibrium stress zone with the residual displacement

Generation mechanism of driving out force of the shaft from the shrink fitted ceramic roll by introducing newly designed stopper

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. The roller consists of ceramic sleeve and steel shaft connected only under a small shrink fitting ratio because of the brittleness. However, the coming out of the shaft sometimes happens from the ceramic sleeve under repeated loading. Therefore, it is important to find out the driving out force to prevent the coming out failure. Based on the previous studies, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Then, the driving out force is focused in this study by introducing a newly designed stopper on the outer plate. The finite element simulation shows that the coming out phenomenon can be prevented due to the stopper installed on the outer plate. Then the mechanism of driving out force generation is clarified. Finally, the process of coming out is explained in terms of the residual displacement