KR20040005453A - Method for grinding of roll at hot state - Google Patents

Abstract

PURPOSE: A warm grinding method for a rolling roll is provided to perform the grinding process even though after replacing the rolling roll, the difference of a center portion and peripheral portion in temperature is more than 10 degrees centigrade. CONSTITUTION: A warm grinding method for a rolling roll is composed of steps of: measuring the temperature at a center portion(24) and an edge portion(22) before grinding of the rolling roll and determining an initial temperature gradient; determining a thermal drop amount according to the temperature gradient of front and rear rolls; determining initial crown values of the front and rear rolls by substituting an initial crown reference for the thermal drop amount; and applying the initial crown valve into a numerical controller and grinding the rolling roll.

Description

Method for grinding of roll at hot state}

The present invention relates to a warm grinding method of a rolling roll for polishing a rolling roll in a warm state, and more particularly, to a warm grinding of a rolling roll, which allows the replaced rolling roll to be polished in a warm state without undergoing a separate cooling process. It is about a method.

In general, the hot rolling process for manufacturing hot rolled steel sheet is carried out by reheating and extracting slab to a temperature suitable for rolling in a heating furnace, and then performing width rolling and thickness rolling in a rough rolling mill, and suitable for the demands of demand in a finish rolling mill. After the final thickness rolling to the product of the thickness, it is wound in a coil form in the winder to produce the final product.

The work rolls used in the above hot rolling operations, in particular the work rolls used in finishing rolling mills, have a direct influence on the surface quality and thickness of the product depending on the surface condition.

Therefore, after rolling a certain amount of strips in consideration of fatigue and wear of the work roll, the work roll is replaced every fixed time.

The work roll replaced here is moved to the cooling station and cooled for a predetermined time, and then moved to a grinder (Roll Grinder) to polish the surface of the roll.

Meanwhile, before grinding the roll, the work roll contacts the strip, which is a hot rolled material during rolling, so that the heat of the strip is transferred to the work roll so that the temperature rises and thermal expansion occurs due to the temperature rise. As such, there is a temperature gradient in the longitudinal direction of the work roll.

Therefore, in order to minimize the temperature gradient in the longitudinal direction, the cooling water is intensively sprayed at the center of the highest rolling roll during rolling, but a temperature gradient of 20 ° C. to 30 ° C. still occurs between the center and the edge of the work roll.

As such, when the roll is polished in a temperature gradient state, heat is conducted from a high place to a low place as time passes, so that the central part of the work roll having the largest temperature change during cooling causes heat shrinkage. It is deformed into a shape different from that of the work roll.

In order to prevent such a change in shape of the work roll, after replacing the work roll, the roll was ground after cooling for a predetermined time.

As shown in FIG. 2, the shape of the target work roll is extremely changed in a thin layer of the work roll surface during rolling, and the temperature change decreases toward the inside of the rolling roll, so that it usually maintains about 72 ° C. at the center thereof. Able to know.

In addition, as shown in FIG. 3, it can be seen that the central crown and the edge of the rolling roll have a (+) crown more than a target crown due to thermal expansion due to a temperature difference.

As such, the (+) crown due to thermal expansion has a direct influence on the shape of the product.In order to compensate for this, the initial (-) calculated according to the rolling force, the sheeting ability, the material of the work roll, and the characteristics of each rolling stand The crown is attached to polish the work roll.

However, the initial (-) crown causes the thickness of the plate to increase until the thermal expansion occurs because the roll rises to a predetermined temperature during rolling, and the roll breaks due to thermal stress due to the temperature difference between the inside and the outside of the roll. There is a problem.

In addition, the cooling of the work roll through water cooling requires a separate cooling station, a large amount of water is required for the water cooling has a problem that the work process is complicated.

In addition, since the water present in the surface of the work roll is suddenly subjected to water cooling at a high temperature, the cracks are advanced and the depth of the roll to be polished is increased, thereby increasing the production cost.

As a method for solving the conventional problems as described above is published in Patent No. 293235.

However, according to the above-described prior art, various problems due to water cooling can be solved. However, in a method of obtaining a radius difference Δr of a central portion and an edge portion of a roll, an outer diameter must be measured and calculated for each roll. In order to set the target maximum temperature deviation (△ Ts), the target temperature difference (△ Ta) after polishing should be 3 ℃ or less. Therefore, polishing should be done only when the temperature difference before polishing is 10 ℃ or less. There is a problem that the constant (C) value to be set must always be constant.

In particular, after the replacement of the rolling roll, when the temperature difference between the center portion and the edge portion is more than 10 ℃ has to be slow cooling for a long time in order to reduce the temperature difference there is a problem that increases the waiting time caused by this.

Therefore, the present invention has been made in order to solve the above problems, after replacing the rolling roll, the rolling roll can be polished in the warm state by measuring the temperature of the center and the edge of the rolling roll immediately before polishing without additional cooling process It is an object of the present invention to provide a warm grinding method for rolling rolls.

1 is a longitudinal temperature distribution diagram of a rolling roll being rolled.

2 is a temperature distribution diagram of each part of the rolling roll after rolling for a predetermined time.

3 is a diagram showing the temperature difference caused by thermal expansion of each part of the rolling roll.

4 is a flowchart showing a warm polishing method of a rolling roll according to the present invention.

5 is a graph showing a temperature gradient change of the rolling roll during air cooling.

6 is a graph showing the change of the profile according to the temperature gradient of the rolling roll during air cooling.

7 is a graph showing the change of the crown according to the result of the air cooling profile and the temperature gradient.

8 is a graph showing a profile and a temperature change with time of the shear roll according to the first embodiment.

9 is a graph showing a profile and a temperature change with time of the after roll in accordance with the first embodiment.

10 is a graph showing a profile and a temperature change with time of a shear roll having a temperature of 55 ° C. or higher according to the second embodiment.

* Description of the symbols for the main parts of the drawings *

22: edge portion 24: center portion

In the present invention to achieve the above object in the warm grinding method of the rolling roll,

Obtaining an initial temperature gradient ΔT 1 by measuring the temperature of the center portion and the edge portion just before grinding of the rolling roll;

Obtaining an amount of thermal drop according to the temperature gradient of the front roll and the rear roll according to the following equations (1) and (2) calculated based on the profile data;

Thermal drop amount according to temperature gradient of shear roll = 3.1 X △ T1 ------- (1)

Thermal drop amount according to temperature gradient of rear roll = 3.6 X △ T1 ------- (2)

Deriving initial crown values of shear rolls and rear rolls by substituting an initial crown management criterion into a thermal drop according to a temperature gradient;

Initial crown value of shear roll = Initial crown management standard + Thermal drop amount according to temperature gradient of shear roll ------- (3)

Initial crown value of the after roll = Initial crown management standard + Thermal drop amount according to the temperature gradient of the after roll ------- (4)

It provides a warm grinding method of the rolling roll comprising the step of applying the initial crown value derived in the step of deriving the initial crown value to the numerical controller to polish the work roll.

Here, in the step of obtaining the thermal drop amount according to the temperature gradient of the front roll and the rear end roll, the step of obtaining the equations (1) and (2) from the profile data,

Obtaining a temperature gradient drop amount ΔT2 during rolling roll polishing using Equation (5) below;

(Grinding oil consumption per unit time × grinding time) ^0.521

△ T2 = ------------------------------------------- × 100- --- (5)

(Rolling roll cooling water x cooling time per unit time) ^0.521

Obtaining a temperature gradient drop (ΔT3) during rolling roll air cooling by using Equation (6) below;

ΔT3 = ΔT2 (1-0.4 ln (t + 1)) ----- (6)

(Where ΔT2 is the temperature difference between the center and the edge at the time of rolling roll air cooling, and t is the air cooling time)

Obtaining a total temperature gradient drop using Equation 7 below;

Total temperature gradient drop = Temperature gradient drop during grinding (△ T2) + Temperature gradient drop during air cooling ----- (7)

Obtaining a thermal drop amount of each of the front end roll and the rear end roll according to the temperature gradient drop by using Equations (8) and (9) below;

Thermal drop amount of shear roll according to temperature gradient = Total temperature gradient drop amount of shear roll X Thermal drop amount of temperature gradient per 1 ℃ --------------- (8)

Thermal drop amount of shear roll according to temperature gradient = total temperature gradient drop amount of shear roll X thermal drop amount of temperature gradient per 1 ℃ --------------- (9)

It is preferable that it consists of.

Further, after deriving the initial crown values of the formula (3) and the formula (4) in the step of deriving the initial crown values of the shear rolls and the rear end rolls, the initial crown value is added by adding a correction value for the rolling roll having a surface temperature of 55 ° C or higher. Further comprising the step of correcting the correction value is more preferably 15㎛.

Hereinafter, the warm grinding method of the rolling roll according to the present invention will be described with reference to the accompanying drawings.

Figure 4 shows a flow chart showing the warm grinding method of the rolling roll according to the present invention, when the rolling roll is drawn out to determine whether the polishing in the polishing standby state, when grinding the rolling roll in the center and the edge of the rolling roll The initial crown value is set by measuring the temperature. At this time, the initial crown value of the warm polishing is set by reflecting the occurrence of the temperature drop during polishing and the occurrence of the temperature drop after polishing.

The rolling roll is polished by giving the initial crown value set as described above, and the rolling roll, which has been polished, is put in the standby state and used again when used.

On the other hand, the initial crown grant criteria for warm polishing are the initial crown management criteria for each factory.The table below shows the point of time when the temperature of the center of the rolling roll 24 and the edge 22 is the same and the time until the reloading after the rolling roll is replaced. Set in consideration.

Table 1

Unit: μm

division Shear roll Trailing roll F1W F2W F3W F4W F5W F6W F7W Early Crown Hot Rolling Mill -100 -100 -100 -150 -150 -100 -100 Hot Rolling Mill -100 -100 -200 -200 -200 -200 3 Hot Rolling Mill -50 -100 -100 -100 -100 -100 -100

That is, it usually takes 6 hours to 9 hours to replace the rolling rolls after the rolling rolls are replaced, and about 10 hours may be required when the temperatures of the centers of the rolling rolls 24 and the edges 22 are the same when standing in the air-cooled state. Therefore, the time from the rolling roll replacement to polishing is regarded as 3 hours, and the crown value at the time point 6 hours after the rolling roll polishing is calculated to be the same as the initial crown management standard of Table 1.

Therefore, the initial crown value due to warm polishing becomes a difference between the initial crown management standard and the thermal drop amount due to the temperature gradient drop.

Here, in order to calculate the thermal drop amount by the temperature gradient drop amount, the temperature gradient drop amount at the time of rolling roll polishing is calculated, and the temperature gradient drop amount according to the time during air cooling is calculated, and then the rolling measured in advance with profile data. The amount of thermal drop per 1 ° C. of the temperature gradient should be calculated relative to the temperature gradient drop of the roll.

First, in order to calculate the temperature gradient drop in rolling roll polishing, the temperature drop in rolling roll polishing is calculated from the relationship between the temperature drop according to the rolling flow rate of the cooling roll in water cooling and the polishing flow rate of the rolling roll in polishing. Thermal conductivity is proportional to the coolant flow rate (W ^0.521 ).

Therefore, the temperature gradient drop amount ΔT2 during rolling roll polishing is calculated by the following equation (5).

(Grinding oil consumption per unit time × polishing time) ^0.521

△ T2 = ------------------------------------------- × 100- ------ (5)

(Roll cooling water amount x cooling time per unit time) ^0.521

Here, when the roll cooling and polishing conditions are as shown in Table 2 below, the temperature gradient drop amount (ΔT2) during rolling roll polishing is 48% of the gradient temperature (△ T1) before polishing in the case of the shear roll, and polishing in the case of the after roll. It becomes 53% of the total gradient temperature (ΔT1).

TABLE 2

division Roll Cooling Time Coolant flow rate Polishing time Grinding oil flow rate Shear Roll (F1W ~ F3W) 40 minutes 640 * 40 minutes = 25,600ℓ 33 minutes 190 * 33 minutes = 6,270ℓ Rear Roll (F4W ~ F7W) 35 minutes 640 * 35 minutes = 22,400ℓ 35 minutes 190 * 35 minutes = 6,650ℓ

Here, the roll cooling time is the time when the temperature gradient between the roll center part 24 and the edge part 22 becomes "0", and a grinding | polishing time means the time by which a roll is cooled by grinding oil.

Next, in calculating the temperature gradient drop amount according to the air cooling time until the roll is used after polishing, the working roll of the finishing mill is re-inserted 3 to 6 hours after the rolling roll polishing. This is the same result as air cooling for 3 to 6 hours until re-insertion after polishing, so to calculate the temperature gradient drop amount according to the air cooling time, the temperature gradient change according to the air cooling time is measured until the rolling roll is used after polishing. It should be.

Figure 5 shows the measurement of the temperature gradient change during the air-cooled, the front roll and the rear end roll shows a rapid decrease in the temperature gradient at the beginning, and then shows a gentle tendency to decrease, and decreases with a constant slope regardless of the magnitude of the initial temperature gradient It can be seen.

As shown in FIG. 5, the temperature gradient drop amount ΔT3 according to the air cooling time until the rolling roll is used is calculated by the following equation (6).

ΔT3 = ΔT2 (1-0.4 ln (t + 1)) ----- (4)

(Where T2 is the temperature difference between the center and the edge at the time of roll air cooling, and t represents the air cooling time.)

In addition, when the roll cooling and polishing conditions are as shown in Table 2 below, the temperature gradient drop amount (ΔT2) during rolling roll polishing was 48% of the gradient temperature (△ T1) before polishing for the shear roll, and before polishing for the after roll. Since it becomes 53% of the gradient temperature (ΔT1), the temperature gradient drop amounts at the time of air-cooling the rolls of the front roll and the rear roll are based on the following equations (10) and (11).

Temperature gradient drop at air cooling of shear roll = 0.48 ΔT1-0.48 ΔT1 (1-0.4 In (t + 1) ----- (10) (where shear roll is F1W ~ F3W)

Temperature gradient drop during air cooling of the rear roll = 0.53 ΔT1-0.53 ΔT1 (1-0.4 In (t + 1) ----- (11), where the rear roll is F4W ~ F7W)

That is, when the formulas (10) and (11) are calculated, they can be represented by the formulas (12) and (13).

Temperature gradient drop at air cooling of shear roll = 0.192 △ T1 In (t + 1) ----- (12)

Temperature gradient drop at air cooling of the after roll = 0.212 △ T1 In (t + 1) ----- (13)

Next, in calculating the thermal drop amount according to the roll temperature gradient, FIG. 6 shows the measured profile change according to the temperature gradient while air-cooling the roll to determine the thermal expansion amount according to the temperature gradient of the center and the edge of the rolling roll. The thermal expansion amount per 1 ° C. of the temperature gradient is calculated by using the measured profile data and comparing with the measured rolling roll temperature gradient.

In Figure 6, "a" shows the measured change in the profile of the shear roll, "I" shows the result shown by measuring the profile change of the rear roll.

In addition, in (a) of FIG. 6, (a-1) is the profile immediately after the roll change, (a-2) is the profile after 3 hours, and (a-3) is the profile after 7 hours after the roll change. .

Here, it can be seen that (a-2) and (a-3) are moved to the (-) side due to the decrease in thermal expansion amount due to the temperature gradient drop compared to (a-1) immediately after the replacement.

In Fig. 6, (b-1) is a profile immediately after roll change, (b-2) is a profile after 3 hours, and (b-3) is a profile after 7 hours after roll change. .

Here, too, it can be seen that (B-2) (B-3) moves the crown toward (-) due to the decrease in thermal expansion due to the temperature gradient drop compared to (B-1) immediately after the replacement.

FIG. 7 shows the crown change according to the temperature gradient with the profile result of FIG. 6.

In the case of the shear rolls, the crown change of the radius of the roll was 4.14㎛ / ℃ with respect to the temperature gradient 1 ℃ between the center and the edge of the roll, and the change of the crown was 4.37㎛ / ℃ for the trailing roll.

In the formulas (12) and (31), the thermal expansion amount value (diameter: shear roll 8.28 탆 / 캜, rear roll 8.74 탆 / 캜) according to t = 6 and temperature gradient is applied. And equation (13) can be represented by the following equation (1) and equation (2).

Thermal drop amount according to temperature gradient of shear roll = 3.1 × △ T1 ----- (1)

Thermal drop amount according to temperature gradient of rear roll = 3.6 × △ T1 ------ (2)

Therefore, the initial crown value of each of the front roll and the rear end roll values during warm polishing can be obtained by the following equations (3) and (4).

Initial crown value of shear roll = Initial crown management standard + Thermal drop amount according to temperature gradient of shear roll ------- (3)

Initial crown value of the after roll = Initial crown management standard + Thermal drop amount according to the temperature gradient of the after roll ------- (4)

However, it is preferable that a rolling roll having a surface temperature of 55 ° C. or higher adds a correction value of 15 μm in order to correct a polishing error of (−) relative to the target initial crown during warm polishing.

That is, after calculating an initial crown value by said Formula (1) and Formula (2) and said Formula (3) and Formula (4), roll surface temperature is 15 micrometers or more which is correction value about 55 degreeC or more rolls. It is preferable to set a value obtained by adding the initial crown target value.

Therefore, the corrected initial crown value can be obtained by the following equations (14) and (15).

Initial crown value of calibrated shear roll = Initial Crown Management Criteria + 3.1 △ T1 + α-(14)

Initial crown value of corrected rear roll = Initial crown management standard + 3.6 △ T1 + α-(15)

(Where α = 15 μm and the roll surface temperature is 55 ° C. or higher)

In the case where the polishing is to be performed after replacing the work roll by using the above formula, the temperature difference between the center portion and the edge portion of the roll is measured immediately before polishing, and the initial crown value (C) is obtained from the above formulas (13) and (14).

[First Embodiment]

In the first embodiment, the surface temperature of the roll is 55 ° C. or less. First, the shear roll will be described. FIG. 8 shows a change in the shear roll (initial crown management standard -100 μm) profile according to the first embodiment. , “A” is the profile and surface temperature before grinding, “B” is the profile and surface temperature after grinding according to the warm grinding standard, and “C” is the profile and surface temperature after a certain time.

When the work roll is pulled out and the polishing is determined, the temperature gradient (ΔT1) is obtained by checking the temperature at one center and two edges while the roll to be polished is set in the polishing machine.

Here, the center portion 24 is 49 degrees Celsius, and the edge portion 22 is 36 degrees Celsius, as shown in FIG. 8, so that the temperature gradient ΔT1 is 13 degrees Celsius.

Therefore, the calculation of the initial crown value is that the surface temperature of the rolling roll is not more than 55 ℃, applying the above formula (14) the corrected initial crown value of the shear roll is-0.060㎛.

The corrected initial crown value -0.060 mu m is applied to the numerical controller to polish the rolling roll.

Next, referring to the rear end roll, FIG. 9 shows a change in profile according to the first embodiment (initial crown management standard is -200 μm), and “a” in FIG. 9 is a profile and surface temperature before grinding, and Is the profile and surface temperature after polishing according to the warm polishing standard, and "c" is the profile and surface temperature after a certain time.

When the work roll is pulled out and the polishing is determined, the temperature gradient (ΔT1) is obtained by checking the temperature at one center and two edges while the roll to be polished is set in the polishing machine.

Here, as shown in “a” of FIG. 9, the center portion is 50 ° C. and the edge portion is 38 ° C., so the temperature gradient ΔT 1 is 12 ° C. FIG.

Therefore, the calculation of the initial crown value is that the surface temperature of the rolling roll is not more than 55 ℃, applying the above equation (15) is the corrected initial crown value of the rear end roll is-0.157㎛.

The corrected initial crown value -0.157 mu m is applied to the numerical controller to polish the rolling roll.

Second Embodiment

The second embodiment is a rolling roll surface temperature of 55 ℃ or more as shown in Figure 10 shows the change in the shear roll (initial crown management criteria is -100㎛) profile according to the second embodiment, "ga" is grinding The profile and surface temperature before, "b" is the profile and surface temperature after polishing by the warm polishing standard, and "d" is the profile and surface temperature after a certain time.

When the work roll is pulled out and the polishing is determined, the temperature gradient (ΔT1) is obtained by checking the temperature at one center and two edges while the roll to be polished is set in the polishing machine.

Here, as shown in “a” of FIG. 10, the center portion is 66 ° C. and the edge portion is 35 ° C., so the temperature gradient ΔT 1 is 31 ° C. FIG.

Therefore, the calculation of the initial crown value is that the surface temperature of the rolling roll is 55 ℃ or more, applying the above formula (15) the corrected initial crown value of the rear end roll is-0.011㎛.

The corrected initial crown value -0.011 mu m is applied to the numerical controller to polish the rolling roll.

As described above, according to the warm grinding method of the rolling roll according to the present invention, after the replacement of the rolling roll, polishing is possible even when the temperature difference between the center portion and the edge portion is 10 ° C. or more, thereby reducing the polishing waiting time, thereby improving productivity.

In addition, it is possible to shorten the work process, and because the rolling roll is put into the rolling mill in a state of maintaining a constant temperature, it is excellent in the flowability, and can prevent the roll breakage accident due to the rapid change in temperature.

Claims (4)

In the warm grinding method of the rolling roll, Obtaining an initial temperature gradient (ΔT1) by measuring the temperature of the center portion and the edge portion just before grinding of the rolling rolls; Obtaining a thermal drop amount according to the temperature gradients of the front end roll and the rear end roll according to the following equations (1) and (2) calculated based on the profile data; Thermal drop amount according to temperature gradient of shear roll = 3.1 X △ T1 ------- (1) Thermal drop amount according to temperature gradient of rear roll = 3.6 X △ T1 ------- (2) Deriving initial crown values of front and rear rolls by substituting an initial crown management criterion into the thermal drop according to the temperature gradient; Initial crown value of shear roll = Initial crown management standard + Thermal drop amount according to temperature gradient of shear roll ------- (3) Initial crown value of the after roll = Initial crown management standard + Thermal drop amount according to the temperature gradient of the after roll ------- (4) Warm grinding method of the rolling roll, comprising: applying the initial crown value derived in the step to the numerical controller to polish the rolling roll. The method of claim 1, In the step of calculating the thermal drop amount according to the temperature gradient of the front end and the rear end roll, the step of obtaining the above Equation (1) and Equation (2) based on the profile data, Obtaining a temperature gradient drop amount ΔT2 during rolling roll polishing using Equation (5) below; (Grinding oil consumption per unit time × grinding time) ^0.521 △ T2 = ------------------------------------------- × 100- --- (5) (Rolling roll cooling water x cooling time per unit time) ^0.521 Obtaining a temperature gradient drop (ΔT3) during rolling roll air cooling by using Equation (6) below; ΔT3 = ΔT2 (1-0.4 ln (t + 1)) ----- (6) (Where ΔT2 is the temperature difference between the center and the edge at the time of rolling roll air cooling, and t is the air cooling time) Obtaining a total temperature gradient drop using Equation 7 below; Total temperature gradient drop = Temperature gradient drop during grinding (△ T2) + Temperature gradient drop during air cooling ----- (7) Obtaining a thermal drop amount of each of the front end roll and the rear end roll according to the temperature gradient drop by using Equations (8) and (9) below; Thermal drop amount of shear roll according to temperature gradient = Total temperature gradient drop amount of shear roll X Thermal drop amount of temperature gradient per 1 ℃ --------------- (8) Thermal drop amount of shear roll according to temperature gradient = total temperature gradient drop amount of shear roll X thermal drop amount of temperature gradient per 1 ℃ --------------- (9) Warm grinding method of the rolling roll, characterized in that consisting of. The method of claim 1, After deriving the initial crown values of the formula (3) and the formula (4) in the step of deriving the initial crown value of the shear roll and the rear end roll, the initial crown value by adding a correction value for the rolling roll having a surface temperature of 55 ℃ or more The warm grinding method of the rolling rolls further comprising the step of correcting. The method of claim 3, wherein The correction value is a warm grinding method of the rolling roll, characterized in that 15㎛.