Abstract
The article addresses to distribution of loading between working and backup rolls of sheet levelling machines taking into account presence of initial gaps between them and heating that occurs during the straightening process, which is especially important in case of the high-temperature straightening. For levelling machines with a single row of backup rolls calculated dependencies were obtained to evaluate loads suffered by backup roll taking into account factors under this study and the analysis of results for the 9-roll straightening machine were carried out. The analysis showed a significant overload suffered by backup rolls.
Highlights
Operating practice of levelling machines at numerous iron making and non-ferrous metallurgy plants demonstrates that setting of roll-type levelling machines is quite a laborintensive procedure [1], since quality of the straightening process and subsequently quality of the finished product depends on many factors, part of which are rather variable and impossible to control in an unbiased manner what makes them hard to take into account
This challenge bears relevance especially for levelling machines intended for straightening of steel sheets under small series production conditions, which are typical for the plants manufacturing sheets from specialized steel grades or non-ferrous metals
The present research is aimed at identifying the heat strains of rolls during sheets straightening and evaluating the load distribution between working and backup rolls of RLM being exposed to straightening force
Summary
According to analyses of the obtained results, increase in temperature of the working roll up to 40°-80° makes the heat strain of the roll system compensate the initial gap Δ0, and force distribution between working and backup rolls is nearly equal to a theoretical value. For the steel grades used for manufacture of straightening machine rolls, values of mechanical properties according to the reference data [3, 5] at temperature range 20° up to 300°С are as follows: - Poisson’s ratio ν = 0.28...0.30; - elasticity modulus E = (2.11...1.90)·105 MPa. Should the gap between the rolls be equal nil (provided that we consider only bending torques), one shall obtain the force at the backup roll equal to 0.625 from the straightening force at the working roll, which gives a clear correspondence with the above mentioned classical solution of this task [2]. Together with that reaction of bearing supports shall have same tendency as that of the process load, increasing friction torque in the roll bearings
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