|
|
|
|
RD-OV Pass Design Help Document
Width, Height, Top Radius, Side Radius
If the stock is a perfect round, use diameter as Width and Height, and round
radius as Top Radius and Side Radius.
In real pass design practice, usually entry stock is not a perfect round.
The Top Radius should be the side radius of the previous pass, and the Side
Radius is the Top radius of the previous pass. For any pass, the side radius is
usually the free radius, and the top radius in hot state equals to groove
radius of the previous pass. 
Oval Pass
Oval groove is considered as a single radius circle with the Pass Radius
(R), Depth Of Groove (DOG) and Width Of Face (WOF) as primary parameters. Other
parameters are explained as follows.
Roll Work Dia.: Roll Collar Diameter minus the loss of diameter due to the
existence of groove.
Roll Effective Dia.: Work diameter plus the gain of diameter due to
the forward slip.
Spread factor (DB/DH): ratio of width change to height change, i.e.
(B1-B0)/(H0-H1).
Friction angle (FricAng): TAN(FricAng) = FricCoeff (Friction coefficient). It
specifies the maximum value of the bite angle.
Free Radius: The radius formed for the free portion of the stock that has no
contact with the groove.
Width/Height: Also called Aspect Ratio, an important factor critical for the
smooth entry into round groove. When this value is over 2.2 (or even 2.1 in
some mills), it could be hard for such a oval stock to enter a round
groove without rotation. Suggested maximum value for the Aspect Ratio is
1.9-2.2.
Mean Hm and Mean Wm: Are from the equivalent rectangle with the same
cross-sectional area, while the Width/Height ratio is kept.
Round Pass
RD-SL and RD-2R. To avoid over fill, the lower portion of the RD groove (near
the roll gap) are either straight lines or double-radius circles (circles
with radius of 2R, R is the groove top radius). The RD groove with
straight lines as its lower portion is referred to as RD-SL, and that with
double-radius circles is called RD-2R in the design program. The groove
with the double-radius circles is used for finish passes, while those grooves
with straight lines are for non-finish groove. The length of the straight
line is specified with the Open Angle A (deg.). For rolling block
(No-Twist Mill, the Open Angle uses 15-20 deg. Passes before NTM use
20-30 deg as the Open Angle. Similarly, the length of a double-radius
circle in a finish groove is specified by the open angle Q (see the figure
below). The Q value is usually 120-145 deg. The big value 145 deg. is often
used for last and second last round passes of a rolling block (No-Twist Mill,
or NTM).
Other parameters in the report are explained below.
Width of Face: Width of face corresponding to a groove containing either
straight lines, or double-radius circles.
Pass Radius: R in the figures.
Release Radius: R2 in the figures.
Other terms used in the report, such as Spread factor, Friction angle,
etc., follow the definition mentioned above (in Oval Pass).
|
|