JP3067985B2 - Method for setting gap of backup roll rolling bearing of rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting a gap in a backup roll rolling bearing of a rolling mill. In particular, the present invention relates to a setting method suitable for setting a gap between a roller of an oil mist lubricated rolling bearing and an outer periphery of a bearing inner ring.

[0002]

2. Description of the Related Art For example, a process line in which a continuous heat treatment facility and a rolling mill are connected, a rolled steel strip is heat-treated to impart workability, and then the shape is corrected by rolling to produce a product line. Rolling speed is about 800m / min or higher, so that the steel strip is rolled, so the rolling bearing of the backup roll that backs up the work roll of the rolling mill,
Due to the heat generated due to the agitation resistance of the bearing lubricating oil due to the high rolling force applied to the entire rolling load, especially in the case of dry rolling using no rolling oil, the bearing may seize due to oil film breakage due to high temperature. Further, when the lubrication method of the bearing is changed from the conventional mogoil lubrication to the oil mist lubrication to improve the rolling accuracy, the problem of heat generation in the bearing becomes particularly remarkable. In order to prevent the seizure of the backup roll bearing in this manner, Japanese Patent Laid-Open Publication No. Sho 61-53002 discloses that the entire periphery of the roll chock is water-cooled.

[0003]

As described above, when the internal bearing is cooled via the roll chock by water cooling, the clearance (clearance) of the bearing is a combination of various thermal deformations, and the setting conditions are complicated. It is. That is,
The bearing lubricating oil is agitated by the high-speed rotation of the rolls and generates heat, and it is extremely difficult to grasp (estimate) the relationship between the thermal expansion of the bearing inner ring due to the generated heat and the heat shrinkage of the outer ring due to roll chock cooling. It has been difficult to properly set the gap between the rolling bearings. If the gap between the rolling bearings of the backup rolls is narrower than appropriate, the outer ring of the bearing tightens the inner ring of the bearing with the rollers in between, so the outer shaft of the bearing spalls early and needs to be replaced, The operation rate of the rolling mill decreases. If the rolling bearing gap is wider than appropriate,
Oscillation of the bearing inner ring makes it difficult to apply an accurate rolling load to the rolled steel strip, which causes problems such as making high-precision rolling impossible. The method of the present invention has been made to advantageously solve such a problem, and provides a method of appropriately setting a gap of a backup roll rolling bearing (particularly, an oil mist lubricated rolling bearing) of a rolling mill. It is the purpose.

[0004]

The feature of the method of the present invention is that the gap between the backup roll rolling bearings of the rolling mill is set based on the following equation: Setting method. Cp = K · (Vn · L · W _L · ν) ^a・ D _b ^b・ exp [−1
/ ｛L · N _p · (Q / D _p ) ^ab ｝] where K = 10 ⁶ to 10 ⁷ , a = 1/3 to 2/3, b = 4/3 to 5/3 Cp: Set gap, K : Correction constant, Vn: Shaft rotation speed, L: Bearing width,
W _L : Bearing load, ν: Lubricating oil viscosity, D _b : Average bearing diameter, Q: Cooling water flow rate, Dp: Cooling pipe hole diameter, Np: Number of cooling pipe holes, a, b: Coefficient by bearing material.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of the method of the present invention will be described with reference to the drawings. In FIG. 1, a steel strip 1 is connected to an upper work roll 2,
Lower work roll 2a, upper intermediate roll 3, lower intermediate roll 3
a, upper backup roll 4, lower backup roll 4
a 6Hi rolling mill 5 comprising upper and lower backup rolls 4, 4 by upper and lower backup roll chocks 6, 6a.
a is subjected to a rolling load, and is continuously annealed (heat treatment) by upper and lower work rolls 2 and 2a via upper and lower intermediate rolls 3 and 3a.
A rolling load is applied to the steel strip 1 after the heat treatment by equipment (not shown) to perform continuous rolling. As shown in FIG. 2, the backup rolls 4 and 4a of the rolling mill 5 are provided with rollers 8 on the bearing outer ring 7 with respect to the upper and lower backup roll chocks 6 and 6a, and the rollers 8 and the outer circumference 9a of the bearing inner ring (solid line). Is set as follows. The bearing inner ring outer periphery 9a is the position of the bearing inner ring outer periphery 9a when the rolling load of the backup roll is applied (during rolling).
b (two-dot chain line) is the position of the outer circumference of the bearing inner ring when the backup roll is not loaded.

The set gap as described above is set in a range in which the life of the bearing outer ring 7 and the risk of seizure of the roller 8 are balanced. From the measured data, it has been found that the appropriate gap is set by the above formula. Things. As actual measurement data, for example, cooling water temperature ≦ 50 ° C., outside air temperature ≦ 50 ° C.
in the case of. Shaft speed _Vu = 374 (rpm), bearing average diameter _Db =
750 (mm), bearing width L = 400 (mm), bearing load W _L = (rolling load) / 2 = 600 (t), cooling water quantity Q = 40 (l / min), lubricating oil viscosity at 40 ° C = 460 (cst), cooling pipe diameter D _p = 40 (m
m), when the coolant pipe Bolt N _p = 8 of (the), set gap Cp
= 500 (μm), the bearing outer ring life can be rolled over 500,000 tons. At this time, the values of the coefficients a and b according to the bearing material in the bearing gap setting formula according to the method of the present invention were a = 1/2 and b = 1527.

Next, as described above, the backup roll chock 6 in which the gap between the roller 8 and the outer periphery 9a of the bearing inner ring is set.
2, when the rolling load is applied to the backup roll 4, as shown in FIG. 2, the upper and lower roll chocks 6, 6a rotate as a part of the roller 8 of the bearing outer ring 7 so that the bearing inner ring outer periphery 9a (solid line) contacts and rotates within an angle θ range. The roller 8 in the θ portion generates heat due to friction and lubricating oil stirring resistance, and becomes high temperature, and seizure occurs. On the other hand, the roller 8 in non-contact with the outer periphery 9a of the bearing inner ring hardly generates heat and is of the order of heat transfer, and has a lower temperature than the θ portion.

Therefore, by cooling only the bearing outer ring 7 of the upper and lower roll chocks 6, 6a in a range where the contact rotation of the roller 8 occurs, the contact rotation of the bearing outer ring 7 of the upper and lower roll chocks 6, 6a in contact with the bearing outer ring 7 is achieved. In addition to cooling only the high-temperature rollers 8 to prevent seizure, the bearing outer ring 7 in the non-contact portion of the bearing inner ring outer periphery 9a (solid line)
By reducing the temperature difference between the roller 8 and the outer circumference 9 of the bearing, the thermal distortion of the entire circumference of the bearing outer ring 7 is eliminated.
Rolling can be performed while maintaining the gap 10 with the set gap a.

As a mechanism for performing such cooling, for example, as shown in the figure, a cooling pipe 11 is disposed on a roll chock 6a near the bearing outer ring 7 in a range where the contact rotation of the roller 8 occurs, and the cooling pipe 11 is cooled. The bearing outer ring 7 can be cooled through the medium, and water (normal temperature) is optimal as the cooling medium. The cooling temperature of the bearing outer ring 7 to be cooled varies slightly depending on the material of the roller 8 and the like. However, if a commonly used material is cooled to 120 ° C. or less, the material hardness of the bearing outer ring 7 is reduced. It is possible to prevent the lubricating oil from dropping due to a decrease in the viscosity of the lubricating oil at a high temperature without being reduced in plastic deformation. As a lower limit, it can be cooled to the limit that can be cooled by water cooling.

By cooling the bearing outer ring 7 in this manner, seizure of the roller 8 is prevented, thermal distortion of the entire outer periphery of the bearing outer ring 7 is eliminated, and the roller 8 and the outer periphery 9 of the bearing inner ring are removed.
Rolling can be performed while maintaining the gap 10 with the gap a at the set gap, and the steel strip can be rolled with high precision.

[0011]

Next, examples of the method of the present invention will be described together with comparative examples.

[Table 1]

Note 1: The gap between the bearing inner ring and the roller was set based on the above formula. Note 2: Rolling is a continuous process line consisting of continuous annealing equipment and a temper rolling mill.
mm and a sheet width of 1000 mm) were continuously rolled as described above. Note 3: Rolling roll diameter BUR diameter is backup roll, BU
The R axis is the backup roll shaft diameter, the IMR diameter is the intermediate roll diameter, and the WR diameter is the work roll diameter. Note 4: The cooling range is the ratio of the contact rotation generation range of the roller to the entire circumference of the roll chock. Note 5: The set gap is the gap between the outer circumference of the bearing inner ring and the rollers. Note 6: The life of the bearing outer ring is as follows: ○: Rolled 500,000 tons or more, Δ: Rolled from 100,000 to less than 500,000 tons, ×: Rolled to less than 100,000 tons. Note 7: Rolling accuracy is good: ± 0.001mm or less of target rolled thickness, bad: more than ± 0.001mm of target rolled thickness.

[0013]

According to the method of the present invention, the life of the backup roll bearing can be significantly extended, and the operation rate of the rolling mill can be prevented from being lowered by replacing the bearing outer ring, thereby increasing the productivity. In addition, the life of the bearing outer ring can be extended, and the repair cost can be greatly reduced. Further, excellent effects such as improvement of the rolling accuracy of the steel strip can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing an outline of a rolling mill.

FIG. 2 is a front view of a main part of a backup roll bearing.

──────────────────────────────────────────────────続 き Continued on the front page (56) References Japanese Utility Model 1-84802 (JP, U) Japanese Utility Model 1-60025 (JP, U) Japanese Utility Model 63-85304 (JP, U) Japanese Utility Model 1962 29802 (JP, U) Actually open 60-1720 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 31/07 B21B 31/02 F16C 37/00

Claims (1)

(57) [Claims] 1. A method for setting a gap between backup roll rolling bearings of a rolling mill, wherein the gap between the backup roll rolling bearings of the rolling mill is set based on the following equation. Cp = K · (Vn · L · W _L · ν) ^a・ D _b ^b・ exp [−1
/ ｛L · N _p · (Q / D _p ) ^ab ｝] where K = 10 ⁶ to 10 ⁷ , a = 1/3 to 2/3, b = 4/3 to 5/3 Cp: Set gap, K : Correction constant, Vn: Shaft rotation speed, L: Bearing width,
W _L : Bearing load, ν: Lubricating oil viscosity, D _b : Average bearing diameter, Q: Cooling water flow rate, Dp: Cooling pipe hole diameter, Np: Number of cooling pipe holes, a, b: Coefficient by bearing material.