JPS59156506A - Cooling method of work roll in hot rolling - Google Patents

Abstract

PURPOSE:To improve cooling efficiency and to reduce driving power for cooling water by increasing a cooling area in proportion to a pressure fluctuating ratio simultaneously with reducing the pressure of the cooling water to be sprayed to work rolls from a high to low pressure thereby maintaining specified cooling power. CONSTITUTION:Cooling water from a water storage source 6 is sprayed and supplied via plural spray nozzles 4a-d disposed on the inlet and outlet sides for a rolling material 10 and in a barrel direction to work rolls 1 of a rolling mill to cool said work rolls 1. A specified pressure P1 in a range of 8-30kg/cm<2> is reduced to a pressure P2 in a range of 1-7kg/cm<2> and at the same time a specified direct cooling area on the barrel surface of the rolls 1 is increased in proportion to the pressure fluctuating ratios of both pressures P1 and P2 and the flow of the cooling water is decreased in flow rate density at approximately a specified rate to maintain specified cooling power in the case of spraying said water under the pressure P1 in said direct cooling area and obtaining the specified cooling power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling mill cooling method for effectively cooling work rolls when rolling a steel plate in a hot rolling mill.

Traditionally, this type of mill roll cooling has often been carried out by using a high-pressure spray nozzle to spray a cooling medium such as water very locally onto the surface of the roll to be cooled, which is the so-called Nupure one-way method. In order to improve their cooling performance, emphasis is placed on increasing the injection pressure and increasing the amount of cooling water, both of which require a high injection pressure and a large amount of cooling medium. However, the cooling effect of the rolling rolls is not always sufficient, which affects the formed shape of the rolled material.
Further, there were drawbacks such as surface roughness occurring on the rolling rolls and shortening their lifespan.

In order to eliminate the drawbacks of the above-mentioned conventional example, the present invention effectively cools this type of rolling roll by expanding the direct cooling area with a cooling medium operated with relatively small driving energy, and also uses the cooling medium. The present invention aims to provide a new roll cooling method that can simplify the guiding structure.

That is, the roll cooling method of the present invention includes jetting and supplying cooling water to a work roll during hot rolling through a plurality of nozzles arranged in the barrel direction on the inlet and outlet sides of the rolled material of the work roll. At least cooling is performed, and the injection pressure P2 of each nozzle is set to 1 to 7 Kg/aA,
The water density W2 on the cooling surface by each nozzle is w2=(Pl/P2)""X5X10'[J/""
(However, Pl is the injection pressure of conventionally used roll cooling water. P1 = 8 to 30 kg/i), and the direct cooling area by the cooling water of the nozzle is the work roll cylinder. A wide-angle jet is applied so that it covers more than 20% of the surface, and the amount of cooling water is reduced per unit rolling amount.
2. jm3/jan stand or less, and in a more preferred embodiment, the work roll is backed up by a backup roll and rotates in one direction, rolling the rolled material. A pair of drain plates are strategically installed above and behind the area that comes into contact with the rolled material, and a fixed amount of water is sprayed from multiple nozzles onto the surface of the work roll on the back-up roll side, which is isolated from the rolled material by the drain plates. Each nozzle is used to spray water at a wide angle so that the direct cooling area in which water is directly applied to the work roll μ from all nozzles is 20% or more of the cooling area on the surface of the work roll body, and The direct cooling area of each nozzle is made continuous in the direction of the barrel of the work roll, and the density of the amount of water injected by all nozzles is decreased as the total area of the direct cooling area increases, so that the total water amount is approximately constant (per unit rolling Weight: 2.5m3/lon
・At the same time, the amount of water jetted in the cooling area from the drain plate on the exit side of the rolled material to the backup roll is lower than the amount of water jetted in the cooling area from the backup roll to the drain plate on the input side of the rolled material on the opposite side. Become greater or equal.

By the work roll cooling method in hot rolling of the present invention, a good cooling effect of the rolling rolls and a normal rolling effect of the rolled material can be expected. .

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

In FIG. 1, 1 is a work roll rotated in one direction by a known drive mechanism, 2 is a backup roll that backs up the work roll 1, and 3a.

3b is a pair of draining plates provided close to the outer peripheral surface of the work row /l/1 so as to partition each of the left and right surfaces of the work row/l/1;
4a, 4b, 4C24d are the above-mentioned work rows.
A plurality of water injection nozzles 5 provided around the periphery are pumps that pump water from a water storage source 6 to each nozzle. As is conventionally known, a rolling material 10 is sandwiched between a pair of upper and lower work rolls 1 and rolled to a constant thickness. Now, when the outer peripheral surface of the work roll 1 is expanded at 360° as shown in Fig. 2, the rolled material 1
0 first at point A, then separated from the rolled material 10 at point B, and then faces the draining plate 3 on the rolled material exit side at point 0, and the draining plate 3a
In this method, from point 0 to point D before coming into contact with the backup roll 2, it is cooled by the jet water from the jet water nozzles 4a and 4b, and then it comes into contact with the backup roll 2 from the point after that to the point F. After that, from point E to point F until it faces the drain plate 3b on the rolling gain side, it is cooled by the jet water from the jet water nozzle ν4C, and after leaving the drain plate, it returns to point A. It returns to contact with the rolled material 10.

As shown in Fig. 2, the temperature of each surface of the work roll 1 between the circumferences is 60°C at the processed part of the rolled material (points A and B).
The temperature rises to nearly 0°C, but when it leaves the rolled material,
The heat on the surface is absorbed inside the roll, and the temperature drops below 200°C at the drain plate on the exit side of the rolled material (point 0), and 100°C at the drain plate on the input side of the rolled material (point F). It can be seen that it has fallen below C. Therefore, regarding cooling of such a rolling roll, it is sufficient to consider the cooling performance when the surface temperature is 200° C. or less.

In a rolling mill as shown in Fig. 1, the surface temperature of the work roll 1 is 15.
The third figure shows the cooling ability of cooling water at 0°C.
As shown in the figure, the horizontal axis shows the cooling water flow rate density W (the amount of cooling water colliding per unit area, per unit time), and the vertical axis shows the heat flux 9 (the amount of cooling water taken per unit area, unit time). amount of heat)
Looking at the relationship, it becomes approximately a -order function in a log-logarithmic graph, that is, a sloping straight line. Note that the cooling capacity when a thin heated steel plate passes through still water at high speed for a short time (C) and the cooling capacity (C) during immersion cooling are expressed parallel to the horizontal axis in Figure 3 because the flow rate density cannot be defined. It is indicated by a line.

As is clear from Figure 3, the cooling capacity, that is, the cooling heat flux Q
(Kcal 7'm hr) and flow density w (17f
n mtn ) is expressed by q from the angle of inclination of the straight line.
It can be seen that the father WO, 49, 6 is approximately expressed as Qcst wo・5. The inventors considered this result and
'If the same amount of cooling water is used, the flow density is reduced and the cooling area where the cooling water jets directly collide (named the direct cooling area)
Effective cooling is possible by increasing the area of . We have discovered one of the basic concepts of the present invention. In other words, efforts to improve the cooling capacity of conventional methods have focused on increasing the injection pressure or increasing the amount of cooling water, but have not taken into consideration the direct cooling area (described later). , the present inventors focused on the direct cooling area, which had not been considered in the past.

For example, consider the case where the flow rate density W is halved and the direct cooling area is doubled when the amount of cooling water used is constant.
Since the flow rate density W is halved, the cooling capacity is (1 zo 5 = 0.
71, or about 29%, but the direct cooling area is 2
Since the time to pass through the direct cooling zone on the roll surface is doubled, the amount increases by ~1.41, that is, about 41%, so the cooling capacity improves by about 41%.

Looking at the development in the axial direction of the roll, the direct cooling surface of the roll is the cooling from water jet nozzles provided in a row in the axial direction of the roll, corresponding to the cooling surface of the roll, as shown in Figure 4 (a). This refers to the surface that is cooled by water, but due to the thermal crown, the cooling capacity is high in the center of the roll and the cooling capacity is low at both ends of the roll, so that the central part is cooled more. When viewed in the axial direction, each block is divided into specific areas at fixed distances, and each divided area can be regarded as having approximately the same direct cooling surface and providing approximately the same cooling effect. still,
If we look at the direct cooling surface of the roll in the circumferential direction of the roll, as shown in Fig. This refers to the surface that is cooled by the cooling water from the nozzle.The distribution of the cooling water is highest in the center of the spray, and the cooling capacity is lower on both sides of the spray pattern.Therefore, the cooling capacity is particularly low in the central area. It is necessary to use the cooling capacity effectively.

Note that the actual roll surface is cooled even in areas other than the direct cooling area by reflection or parallel flow of jet-like cooling water that once collides with the direct cooling area. Although the behavior of the cooling water in this indirect cooling region is unknown, the inventors investigated the cooling water behavior in this indirect cooling region in order to estimate the cooling capacity in this region.
As a result of an experiment in which a steel plate (thickness 2 mm) was passed through still water at high speed (5 to 10 m/5 ec) for a short time (80 m 5 ec), the cooling capacity was approximately 4 x 10' Kcal.
/rn2hr It was cute to have te. In addition, in the conventional cooling method, the direct cooling force on the work roll accounts for about 10% of the total cooling surface area, and the flow density there is 4 to 5 X'
fO'J, A+2m1n (2.8
107Kcal/fn2hr). Now, to estimate the cooling capacity of the direct cooling area of this type of work roll, we will use the relationship between the cooling capacity Q and the flow rate density W shown in Figure 3, and the average cooling when changing the direct cooling area with the cooling water amount as constant. The capacity (Kcal/lr1.hr) can be increased by directly increasing the cooling area. It can be seen that the cooling capacity is significantly increased.

In other words, the average cooling capacity in the conventional cooling method is 4'X10
Xo, 9+2.8X10 Xo, 1~6.4X 1
0 Kca17tn hr or 10 Xo
, 9+2.8X10Xo, 1=3.7X106Kc
a17tn hr, whereas in the present invention, (0
,5=(8,3~'6.9)X10Kca
l/rn hr (when direct cooling area is 50%)
It is estimated that the cooling capacity of the method of the present invention is large.

In order to further confirm the effects of the present invention, the present inventors
We conducted an experiment to measure the cooling effect of the cooling plate by changing only the nozzle jet pattern (the area of the direct cooling area).

That is, as shown in FIG. 5(a), cooling water was injected onto the surface of the cooling plate passing at a constant speed using a full cone nozzle and a flight spray nozzle, and the temperature change of each cooling plate was determined. The experimental conditions were: cooling plate: 5N#It x 80 x 500, material: pure copper, cooling plate passing speed: 3m/
sec, injection pressure: 3 Kg/c1A, amount of cooling water (amount of water supplied in order of width 80 of the test piece): 271/min
, Distance between nozzle and cooling plate: 90” + Cooling start temperature: 1
It is 80°C.

As a result of conducting a cooling experiment under the above conditions, the temperature of the specimen decreased by 30.4°C when the direct cooling area was large (when a full cone nozzle was used) as shown in Figure 5(a). In contrast, when the direct cooling area is small (in Figure 5) (when using a flat spray nozzle), it is 14.7°.
Only C decreased. Therefore, from this experimental result, it was confirmed that the cooling capacity could be increased by increasing the direct cooling area.

Similar experiments were conducted by varying the amount of cooling water and injection pressure.

In addition, the flow density of the direct cooling area was determined from each direct cooling area. As a result, the cooling capacity of the indirect cooling area is 1Q5Kc
It was found that al/rn2hr. The results of the cooling capacity of the direct cooling area are shown in Figures 6, 7, and 9. Figure 6 shows the case where the cooling surface temperature of the cooling plate is 180°C, and Figure 7 shows the case where the cooling surface temperature of the cooling plate is 90°C. Water flow density w
(J/m2-m1n) and heat flux q (Kcal', A
Looking at the relationship between
・4, Figure 7 is q# 5.8 X 10' Wo
・It becomes 6. , but these figures also show that increasing the direct cooling area significantly improves the cooling capacity.

According to the relationship between Figures 6 and 7, the absolute value of the cooling capacity is greater on the high temperature side (180'C) than on the low temperature side (90°C), so from the drain plate on the outlet side of the rolled material to the backup roll. It is preferable that the amount of water injected into the cooling area is set to be larger than the amount of water injected into the cooling area from the backup roll on the opposite side where the rolled material enters to the drain plate.

In the present invention, the direct cooling area refers to the area where the injected cooling water spreads out at the center when viewed from the cooling water density curve when the cooling water is injected from the spray nozzle in Fig. 11 and collides with the surface of the roll. As shown in Figure 12, in the conventional method, the direct cooling area is narrow, so the direct cooling area is discontinuous when viewed from the barrel direction of the work roll, and there are many places that do not fall into the direct cooling area. However, according to the method of the present invention, as shown in Figs. Since the direct cooling area of the cooling water sprayed onto the surface of the wrinkled roll is expanded, the work roll can be cooled with a better cooling effect. In addition, in such a direct cooling zone, more effective cooling can be achieved by performing greater cooling on the side where the rolled material enters the cooling zone via a drain plate on the outlet side. In other words, even if a large amount of cooling water is used in the cooling area between the entrance side of the rolled material and before exiting the drain plate, a very good cooling effect cannot be obtained.

The wider the direct cooling area for cooling this type of roll, the greater the cooling effect.However, in order to obtain a sufficient average cooling capacity, the direct cooling area must be placed in the cooling area of the surface of the work roll body. It is preferable to make it 20% or more. That is,
The cooling capacity of the indirect cooling area of the work roll is IQ5Kcal.
/rrI2-hr constant, the ratio (%) of the direct cooling area to the entire cooling area and the average cooling capacity (Kcal,
ztn2·hr) is as shown in FIG. 8 for the rolling mill outlet side (high temperature side).

In Fig. 8, the solid line indicates a cooling water injection pressure of 8 h/- and a cooling water flow rate density of 4 Q l/m1n-cvi, and the dotted line indicates a cooling water injection pressure of 8 KiI/crA and a cooling water flow rate density of 201/kn. In the case of an i n-saw, the dashed line indicates the cooling water injection pressure of 8 kg/- and the cooling density I Q l /fnin
-cm, the two-dot chain line indicates the cooling water injection pressure of 16h/-
The cases where the cooling density is 401/min-α are shown respectively, and it can be seen that in each case, when the direct cooling area exceeds 20% or more, the average cooling capacity increases dramatically. For example, the ratio of the direct cooling area to the total cooling area in the conventional method is 10
%, but if this is expanded to 20% or more as in the present invention, it can be seen that the average cooling capacity increases by approximately 35%. Also, for example, if the indirect cooling area is 4×l Q6Kcal/
This is an estimate assuming fn2hr (the upper limit of the cooling capacity of the indirect cooling area), but even in this case, by increasing the direct cooling area, the cooling capacity will be reduced by 30% (8,
3X106/6.4X106 = 1.30). Furthermore, since the cooling capacity Q and the cooling density (flow rate) W are approximately in the relationship QQlw, by directly increasing the cooling area, the cooling capacity can be improved without changing the cooling capacity.
For example, increase the amount of cooling water by 10% to 20% of the direct cooling area.
When the cooling density W increases to approximately (1/1..3
5) 2-0.549, which can be reduced by 45.1%.

The relationship between the cooling capacity in such a direct cooling region is expressed as the injection pressure P
Then, the injection pressure P (Kg/i) and heat flux q (K
ca17tn2-hr) is the relationship when the cooling water flow rate density W is set to the lower chamber (here W-101/m2・m1n)
, as shown in FIG. 9, becomes sloped or linear at a constant angle on the logarithmic graph. In Figure 9, the solid line indicates that the cooling surface temperature is 1.
At 80°C, q' = 2.2 Xl 07 Po
・174 relationships 1. The cooling surface temperature of the bride line is 90°C.
In the case of 9″=f9×10 P, approximately q
If considered as cc po・2, as mentioned above, the cooling capacity Q has a relationship with the flow rate density W of QQCwo・4″″6,
It can be seen that the cooling effect of the cooling water on the work rolls, that is, the cooling capacity, is more dependent on the water volume density than on the injection pressure. From this result, even if the injection pressure of the cooling water is significantly lowered, by slightly increasing the amount of cooling water, it is possible to obtain the desired cooling effect without reducing the cooling capacity.
Therefore, it is possible to save labor by reducing the driving power for injecting the cooling water. Looking at the relationship between low injection pressure and QocP” wo・5OyoU WcX:P
W I) Use relationships. However, Q is the cooling capacity, P is the injection pressure, W is the flow rate density, and W is the power consumption. The injection pressure of conventionally used roll cooling water is Pl, and the flow rate density is Wl.
The cooling capacity at this time is 91, and the power consumption is Wl.

Further, when the injection pressure is lowered to P2, the flow rate density is W2, the cooling capacity is 92, and the power consumption is W2. When Q1=Q2, Pl wl =P2 w2 In order to improve the cooling capacity slightly, 1ν2 = (Pi/P2
)”6W1・・・・・・(3), then W2−(P2
/P1)0・4 Wl・・・・・・(4) Q2-
(P2 /P1) 0.2 (W2/Town) 0.5 Ql
......(5).

These relationships are shown in FIG. (]) in Figure 10.

The curves (2), (3), and (4) correspond to (1), (2), and (3) in each of the above equations.

Corresponding to (4), the upper curve (5) is Q2/Ql
shows the ratio of As Pl 7P2 increases, W2 /W
1 increases almost linearly, but the rate of decrease in required power is Pl
It can be seen that when /P2≦4, it is very large, and when P1/P2 and 4, it gradually decreases. As a specific example, Pl = 15 Kg/ Cm-+P2 =
41 (g 10.4 to 0.6 pieces, w2 = (15/4) Xwl =
(~2.21)0・” Q1=Q, ~1.14 Ql
, W2 = (-L-)5 0°6''-'Wl = (0,45~0°59)Wl
becomes. Therefore, the injection pressure was reduced from 15Kg/ctA to 4Kg/ltA, and the amount of cooling water was reduced from 1.7 to 2.2Kg/ltA.
By doubling the cooling capacity, the current cooling capacity or 14
%, while power consumption is 55-41%
% can be reduced. As shown in FIG. 10, in order to reduce the required power without unnecessarily increasing the amount of cooling water, Pi/P2 is preferably about 2 to 7.

The injection pressure of roll cooling water in a conventional hot rolling mill is 10 kg.
/CJA or more, the effective injection pressure is 1 to 7 kg/era.

Note that below IKg/ctA, a large amount of cooling water is required, which increases the cost of adding piping systems, pumps, pits, cooling towers, etc.

In addition, cooling water is used by circulating pump reroll cooling → pit → pump → cooling tower → pump, but for example, the feeding pressure to the cooling tower needs to be at least IKg/-, It is conceivable that the power does not decrease even if the injection pressure of the roll cooling reservoir is extremely reduced.

Furthermore, if we consider Figures 6, 7, and 9 together, we can see that even with the same amount of cooling water, the cooling capacity on the high-temperature cooling surface is much greater. It turns out that it is more effective.

As described in detail in the above embodiments, the roll cooling method for a rolling mill according to the present invention involves rolling a hot steel plate at the front and rear of the work roll in contact with the rolled material while the work roll is backed up by a backup roll and rotates in one direction. A pair of drain plates are provided in the plate, and a number of nozzles are used to cool the surface of the work roll on the backup roll side isolated from the rolled material by spraying cooling water to the surface of the work roll. The direct cooling area in which the nozzles are sprayed at a wide angle to direct the propellant water onto the work roll is made to be 20% or more of the cooling area on the surface of the work roll body, and the direct cooling area of each nozzle is The injection pressure of each nozzle should be kept approximately uniform continuously in the barrel direction of the work roll, and the injection pressure should be 1 to 7 kg.
/- and the water injection volume pot w2-(P1
/P2) 0.29.8×W1 (However, injection pressure P1.P2
The amount of water injected at the time of w1. w2), and the amount of water injected by all nozzles is increased by increasing the total area of the direct cooling zone and decreasing the flow rate density, so that the total water amount is approximately constant (2.5 m per unit rolling amount). ” / ton
・In addition to maintaining the amount of water jetted in the cooling area from the drain plate on the outlet side of the rolled material to the backup roll to the cooling area from the backup roll to the drain plate on the input side of the rolled material on the opposite side. It is characterized by being larger or equal,
This is a method of cooling by dispersing the coolant onto the roll cooling surface and colliding the cooling medium jets over the entire surface of the cooling surface to the extent possible, so instead of colliding locally with the cooling surface as in the conventional method, it is uniformly distributed. This method uses a large amount of cooling medium on the hot part of the roll cooling surface, and uses a large amount of cooling medium on the surface of the rolled material exit roll where the surface temperature is higher. When cooling the surface, the distribution should be improved so that a large amount of cooling medium collides with the higher temperature roll surface, and the cooling medium should be distributed evenly. Furthermore, on the roll surface on the exit side of the rolled material, a large amount of cooling medium should be cooled on the surface near the drain plate. A large amount of the cooling medium collides with the surface near the backup roll on the entry side roll surface, and the cooling water injection pressure is lowered and the amount of cooling water is slightly increased. It reduces the power for injection, so it is possible to efficiently cool the reeds and therefore the rolls of the rolling mill, and it is possible to reduce the electricity cost required for supplying roll cooling water.
As a result, it has the advantage of reducing the thermal crown of the roll, improving the shape of the product, preventing roll roughness, and extending the life of the roll.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the main parts of a rolling mill to which the roll cooling method of the present invention is applied, Figure 2 is a diagram showing the relationship between the developed position of the roll surface and surface temperature, and Figure 3 is the relationship between flow rate density and heat flux. Figure 4 (a) I (b) is a developed diagram of the direct cooling area, Figure 5
Figures (a) and (b) are illustrations of the cooling experiment, Figures 6 and 7.
The figure shows the relationship between cooling water flow rate density and heat flux, Figure 8 shows the relationship between direct cooling area and average cooling capacity, Figure 9 shows the relationship between cooling water injection pressure and heat flux, and Figure 10 shows the relationship between injection pressure ratio. Relationship diagram between required power ratio, cooling water flow rate ratio, and cooling capacity ratio, Figure 11 (a) l
(b) and (C) are explanatory diagrams of the direct cooling area, and Fig. 12 (
c) and (to) are explanatory diagrams of the injection state of the conventional injection nozzle;
FIGS. 13(B) to 16(5) (2) are explanatory diagrams of the injection state of the injection nozzle used in the present invention. 1... Work roll, 3a, 3b... Draining plate, 4"
+4b, 4c, 4d... Water jet nozzle, Death... Pump, 10... Rolled material. Patent applicant: Agent of Kobe Steel, Ltd.
Patent attorney Aobai Ao and 2 others Fig. 3 1 + 闊 Quantity sub) t 1v (Q /m2rninl Fig. 4 (
a) Figure 5 (a) Figure 5 (b) (JLI2u
17. . , :,, )-9 evacuation threat Figure 9 Injection p (''/am2) Figure 8 fL axis C%) Figure 2 (A) Figure 12 (8) Figure 1z (B) (Procedural Amendment Form C) March 29, 1980 Commissioner of the Japan Patent Office ■Case Description 1982 Patent Application No. 185451 2 Title of Invention Method for Cooling Work Rolls in Hot Rolling 3 Person Who Makes Amendment Case Relationship between patent applicant 4 and agent

Claims (1)

[Claims] (1) A work roll during hot rolling of a steel plate is cooled by injecting cooling water to a plurality of holes arranged in the nozzle direction on the inlet and outlet sides of the rolled material of the work roll. Water is sprayed from a nozzle onto the work roll at a constant pressure within the range of 8 to 30 kg/cTA (
Pl) is injected onto a certain direct cooling area (A1) on the surface of the work roll cylinder to obtain a certain cooling capacity, the above pressure (Pl) is reduced to within the range of 1 to 7 Kg/aA (P2 ) Sult and the above area at the same time as both the above pressures (pl
) A work roll cooling method in hot rolling, characterized in that the cooling capacity increases in proportion to the pressure fluctuation ratio of (P2) and maintains the constant cooling capacity.