JPS5852445B2 - Oil film bearing for rolling rolls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil film bearing for a rolling roll.

Currently, in continuous rolling of plate materials, whether hot or cold rolling, automatic plate thickness control (hereinafter simply referred to as AGC) is performed to make the thickness of the rolled plate uniform in the longitudinal direction.

AGC in this plate rolling is mostly BISR
Method A, as shown in Figure 1, estimates the plate thickness at that point from the rolling position and rolling load, compares this with the target plate thickness, and detects deviations in the plate thickness. When this happens, the plate thickness is controlled by adjusting the rolling position so that the deviation becomes zero.

That is, in FIG. 1, if the entrance plate thickness of the plate material is H10 and the set gap is S, the plastic characteristic curve of the material and the elastic characteristic curve of the rolling mill are generally a in the figure.

b, and the thickness of the outlet plate at this time is the double opening line a
, b is indicated by the intersection m.

When performing AGC with this h as the target plate thickness, for example, if the entrance side plate thickness changes by △H, the rolling load will be △P
, and the exit side plate thickness becomes h, resulting in a plate thickness deviation of Δh with respect to h.

Therefore, the roll gap is changed to 8-)S so that △h=o.
Only S is changed.

In this way, the BISRA type AGC reads the change in the thickness of the rolled plate from the change in the rolling load, and automatically adjusts the roll gap to the specified thickness according to the degree of this change, but unlike the normal multi-stage AGC, In rolling mills, the eccentricity of the center of rotation of the rolling rolls, generally known as roll eccentricity, is a large variation in the roll gap that does not appear on the detector, and if the rolling load changes due to this roll eccentricity, it may interfere with AGC. This results in the deterioration of the shape quality of the rolled plate.

In other words, as shown in Fig. 2, if the change in the roll gap due to the eccentricity of the rolls is △E, the roll gap is actually shown by the curve g, as opposed to the apparent elastic characteristic curve of the rolling mill. The rolling load changes from P to Pl by ΔPe.

However, what is detected as the roll gap is only S, so in reality the load change caused by roll eccentricity △
Pe is measured in the control device as a result of a change in the thickness of the inlet plate △". Therefore, assuming that the deviation of the plate thickness on the outlet side is △h', the roll gap is adjusted △ to make this △h' zero.
Only S' is changed.

For this reason, what was actually the outlet side plate thickness h1 becomes thinner than h2 due to AGC.

The curve indicated by g' in the figure is a rolling mill elastic characteristic curve that further changes due to roll eccentricity when the roll gap is changed by ΔS'.

As described above, in the BISRA type AGC, roll eccentricity is a large disturbance, and together with the responsiveness of the rolling device, it causes various reports.

Therefore, roll eccentricity must be kept as small as possible.

Conventionally, this roll eccentricity was thought to be caused by the machining accuracy of rolling rolls such as work rolls and reinforcing rolls, but it was previously disclosed in Japanese Patent Application Laid-Open No. 112760/1983,
Further, subsequent research by the inventors revealed that most of the causes were due to the oil film bearings of the rolling rolls, especially the reinforcing rolls.

That is, a tapered neck bearing is a typical bearing for a reinforcing roll, and an example thereof is shown in cross section of a main part in FIG.

In the figure, 1 is a rolled material, 2 is a work roll, and 3 is a reinforcing roll.

Also, 4 is the tapered neck of the reinforcing roll 3, 5 is the key, and 6
is a keyway, and the bushing 8 and the sleeve 7 tightly fitted to the tapered neck 4 of the reinforcing roll 3 to form a journal constitute an oil film bearing.

Here, the sleeve 7 is locked with the key 5 to prevent it from rotating relative to the tapered neck 4.
The key groove 6'' carved in the taper hole is made slightly deeper than the height of the key 5 protruding from the taper neck 4, taking into consideration the thermal expansion of the key 5, etc., so that there is a gap between the bottom of the key groove 6' and the key 5. There is a gap.

Now, when rolling is carried out in a rolling mill in which the rolling rolls are pivoted by such oil film bearings, the sleeve 7 has an oil film (the third
The rolling load is received by the bushing 8 via the bushing 8 (section B in the figure), and a rolling blade of q (θ) as shown in FIG. When the keyway portions (section C in FIG. 4) coincide, the keyway portion of the sleeve 7 deforms as shown, and the roll gap increases by an amount corresponding to the deformation.

Note that the above-mentioned deformation of the keyway portion is mainly due to plastic deformation, but some elastic deformation also occurs.

Thus, each time the keyway portion rotates toward the pressure receiving surface (the surface receiving the rolling blade q(θ)), a large roll gap change occurs other than the roll gap change related to the processing accuracy of the rolling roll 3, and due to this, the rolling The load drops rapidly.

Here, using an ordinary four-high rolling mill as a representative example, FIG. 5 shows a comparison of the change in the roll gap for each rotation of the rolls when the work roll and the reinforcing roll are used alone and when they are combined.

In the figure, 12 graphs indicate the degree of roll eccentricity caused only by the machining accuracy of the work roll and the reinforcing roll, and the curve j shown in C is a composite of the 42 curves i.

Therefore, if the cause of roll eccentricity is only due to the processing accuracy of the rolling rolls, the change in the roll gap of a four-high rolling mill that combines these rolling rolls should follow the curve j in C, but the actual measurement It changed as shown in the curve.

The position indicated by the arrow in the upper part of FIG. 5 is a state in which the key groove portions of the upper and lower trunk reinforcing rolls are aligned with the pressure receiving surface.

That is, the hatched portion in FIG. 5 is the change in the roll gap caused by the deformation of the keyway portion of the sleeve, and this amount may amount to 70 to 80% of the total eccentricity.

In the tapered neck bearing disclosed in JP-A-51-112760, this problem was solved by providing a detent for fixing the sleeve to the rolling roll, away from the fitting area between the two. Even if there were no problems when manufacturing a new rolling mill, there were various difficulties when applying it to an existing rolling mill because the scope of modification was large.

Therefore, this invention can be easily applied to existing rolling mills.
Furthermore, the present invention attempts to propose an oil film bearing for rolling rolls that advantageously solves the problem of sudden changes in rolling load caused by keyways.

The inventors believed that the sudden change in rolling load caused by the keyway was caused by the size of the key stop, and in order to solve the problem by reducing the size of the key stop, they first investigated the shear stress that actually acts on the key.

An example of the results is shown in FIG.

FIG. 6 shows a case where kiss roll operation and normal rolling operation are performed using an existing key (305 x 100 x 75 mm).

From this result, it was found that the shear stress acting on the key during rolling is slight, and that the above-mentioned key dimensions have a pressure-receiving area of 9 times the applied load, taking into account the safety factor.

Therefore, the inventors created a roll and a sleeve that did not have a keyway in a part of the taper, and set the key stop on them sequentially larger over the range of X from the end of the taper fitting area as shown in Figure 7. The amount of load fluctuation in the kiss roll during hot rolling was investigated.

For comparison, we also conducted a similar investigation using an existing oil film bearing.

The results are shown in FIG. 8 in comparison.

In the same figure, the horizontal axis shows the ratio x/L of the set length X of the key stop and the length L of the bearing pressure receiving area, and the vertical axis shows the load fluctuation amount ΔPo according to the present invention when using an existing bearing. Ratio △P/△P of load fluctuation amount △P when using a bearing.

It is shown by .

As is clear from the figure, the ratio of load fluctuations △P/△Po increases rapidly when x/L is between 0.15 and 0.25, and vertically when x/L is 0. 2 or less, that is, by setting the set length of the key stop to 0.2 times or less, more preferably 0.15 times or less, of the bearing pressure area length, it was found that the amount of variation in rolling load can be significantly reduced. .

The shear strength of the key is determined from the shear area (width x length) of the key and the strength of the material, but from the measurement results of the shear stress acting on the key during rolling mentioned above, the length of the key is x/ It was also confirmed that if L was 0.1 or more, there would be no problem in normal use.

Thus, in normal rolling, there is no sudden change in rolling load caused by the keyway, and stable operation can be performed under accurate AGC.

However, the role of the key used in oil film bearings is not limited to simply preventing the rotation of the sleeve and roll during rolling. It also protects the rolls by withstanding the maximum torque until safety devices such as overload clutches installed on the spindle start, preventing slippage and seizing accidents between the rolls and sleeves.

For this reason, the dimensions of keys currently in use have been determined based on numerous accident cases with this point in mind, and usually the ratio of the overall length of the key l to the outer diameter of the sleeve is l/D.
is set to be approximately 0.3.

Therefore, even when using a key with a reduced length, it is necessary to provide the same shear strength as in the conventional key, but this problem was solved by setting a plurality of key stops.

In other words, oil film bearings (D=
1115mm).
FIG. 9 shows the results of an investigation into the number of key stops required to obtain a conventional level of shear strength (l/D 0.3) when L was varied over a range of 0.05 to 0.4.

As is clear from the figure, when l/L is 0.1 to 0.2, the number of reduction keys may be 2 to 3, and if they are arranged at equal intervals along the circumference of the edge of the fitting area. More preferred.

Furthermore, the oil film bearing of this invention is extremely easy to apply to existing rolling mills; all that is required is a new sleeve, and the conventional keyway carved into the tapered neck of the roll can be replaced by padding. It suffices to fill in the key grooves using the method described above, and then carve new key grooves according to the present invention.

Furthermore, the present invention is applicable to all multi-high rolling mills that use oil film bearings such as moboil bearings and mesta bearings as rolling roll bearings.

As described above, according to the present invention, the sudden change in the rolling blade caused by the keyway of the sleeve can be significantly reduced without reducing the shear strength of the key, so that the AGC can properly correct the following of the plate thickness. Therefore, the thickness accuracy of rolled plate products is significantly improved.

Note that when this invention is applied particularly to hot rolling, A
Improvements in GC will enable low-temperature extraction of rolled material from the heating furnace, which can also be expected to save energy.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the structure of the BISRA point AGC, Fig. 2 is a diagram illustrating the adverse effect that roll eccentricity has on the BISRA type AGC, Fig. 3 is a longitudinal cross-sectional view of a conventional tapered neck oil film bearing, Figure 4 is a view taken along arrow A-A in Figure 3, and Figure 5 A2 and C show the degree of roll eccentricity due only to the roll machining accuracy for each roll rotation of the work roll and reinforcing roll, and the degree of roll eccentricity of both rolls. FIG. 6 is a graph showing the relationship between rolling load and shear stress acting on the key. FIG. 7 is a graph showing the relationship between the rolling load and the shear stress acting on the key. FIG. Figure 8 shows the installed state. Figure 8 is a graph showing the relationship between key installation length and rolling load variation. Figure 9 shows the set length and number of keys required to obtain the specified shear strength. This is a graph showing the relationship between 0, 1...rolled material, 2...work roll,
3... Reinforcement roll, 4... Taper neck, 5... Key, 6, 6'... Keyway, 7... Sleeve 8...Bushing.

Claims (1)

[Claims] 1. In an oil film bearing for a roll roll consisting of a bushing of a roll chock bearing box and a sleeve tightly fitted to the tapered neck of a roll to form a journal, a plurality of bushings are used to fix this sleeve to the roll. The length of the bearing pressure area is 0 from the end of the tapered fitting area between the sleeve and roll neck.
．． An oil film bearing for a rolling roll, characterized in that it is provided in a range of 2 times or less.