A correlation between the friction coefficient and the roughness of rolls in a hot flat rolling
The principal factors affecting spread in hot flat rolling are geometric (initial width and height, roll radius) and tribological (roll roughness, friction coefficient, rolling temperature). The factors affecting the frictional conditions in the contact zone are very important also for the design of the rolling mill. In particular, in order to calculate, by analytical formulae and FEM simulation, the rolling power and the maximum contact angle, the value of the friction coefficient is necessary. The aim of this work is the evaluation of the friction coefficient starting from the knowledge of the values of rolls roughness. The influence of this parameter on lateral spread in flat rolling has been evaluated by experimental tests. The tests have been conducted at high temperature (1000°C) using steel and cast iron rolls, for different values of the area reduction and of the rolls roughness. In order to determine the value of the frictional coefficient for different conditions, a series of FEM simulations has been conducted. By FEM results, obtained setting the value of friction coefficient, the spread has been evaluated and compared with the values measured in experimental tests. In this way, the value of the friction coefficient has been correlated to the value of the rolls roughness.
Dear Dr. Brousseau,
regarding your remarks, I’d like to make it clear that in FEM analysis no material was set for rolls because only mechanical properties could be assigned; so, the FEM simulation are independent of rolls material and the correlation between spread and friction coefficient was obtained apart from this one.
But, in experimental data, the correlation between the spread and roughness was carried out for the two different rolls materials.
So we have preferred to consider the correlation between friction coefficient and rolls roughness for the two rolls materials.
FEM analysis Spread Steel rolls Cast iron rolls
F1 ----> b1 <--- R1
F2 ----> b2 <----------------------- R2
F3 ----> b3 <--- R3
F4 ----> b4 <---------------- ------ R4
With F friction coefficient, b workpiece width, R rolls roughness
I was wondering if you have a full reference for the coefficient of friction temperature dependence equations you specified in your presentation entitled: A correlation between the friction coefficient and the roughness of rolls in a hot flat rolling .
I am working on citing some references in my literature review of my master of science. Thanks, Farley
Dear author, in the pdf file, section 4 (FEM analysis), it is stated: "the roll was assumed to be a rotating rigid surface, so it is not necessary to assign the material properties". In addition: you also mentioned that: "From the comparison between the spread values obtained by experimental data and by simulation, a correlation between the parameter Ra and the friction coefficient is possible, both for steel and for cast iron rolls." Could you explain further how this correlation can be established for both rolls given that no particular material is assigned in the FEM analysis?