JPH02303606A - Hertz pressure reducing method and rolling device at hot rolling - Google Patents

Abstract

PURPOSE:To reduce the Hertz pressure generated at barrel ends and to prevent the damage of rolls by providing a taper at the barrel ends of the back-up rolls on the recessing crown side of work rolls of a bottle shape having a projecting crown in the half part on one side of the roll barrels and recessing crown in the half part on the other side. CONSTITUTION:The work roll 3 of the bottle shape in the axial section having the projecting crown in the half part on the operating side or driving side of the work roll barrel and the recessing crown on the other side is used. The crowns of the bottle shape and disposed to the upper and lower work rolls 3, 3 point-symmetrically with each other. The taper 7 is provided at the barrel end on the side imparted with the crowns of the work rolls 3, 3 of the barrel ends of the upper and lower back up rolls 1, 1 for supporting the upper and lower work rolls 3, 3 of such multiplex hot rolling which controls the crown of sheets by axially shifting the work rolls 3, 3 in the directions to each other. The Hertz pressure generated at the barrel ends is reduced in this way and the generation of the roll damages, such as spalling, is obviated and the sheet crown control of a high range is executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has a bottle-shaped profile with a convex tarun on one half of the roll barrel and a concave crown on the other half, and the profile of the upper and lower rolls is In hot rolling in which temporary crown is controlled by shifting work rolls that are point symmetrical to each other in the axial direction in the opposite direction to vertical pressure, Hertzian pressure between the work rolls and the reinforcing rolls that support the work rolls is applied. The present invention relates to a method and apparatus for reducing.

(Prior Art) In recent years, there has been a demand for higher precision and higher quality of product dimensions in hot rolling, and in response to these needs, plate crown and shape control have become very important. On the other hand, from an operational perspective, there is a trend toward schedule-free production in order to achieve short delivery times and high efficiency. To achieve these objectives, a hot rolling mill with great sheet crown control capability is required, and a number of new rolling mills with sheet crown and shape control functions have been developed.

For example, as a method that has low equipment cost, can be easily modified, and has a large plate crown control ability,
3-62283 and Japanese Patent Application Laid-Open No. 63-84713, the upper and lower bottle-shaped work rolls are moved relative to each other in the axial direction to create a temporary crown of the rolled material by 1Il.
There is a method of li7B (hereinafter referred to as the CvC method).

As shown in FIG. 1, according to the CvC method, the work roll 3 has a bottle-shaped cross section, and the upper and lower work rolls 3
．． 3 is arranged so that the roll gap profile is point symmetrical. The plate crown of the rolled material 4 is adjusted by a work roll bender 5 and by shifting upper and lower work rolls, which will be described later.

Here, regarding the plate crown control method using the CvC method,
This will be explained using FIG. 2 f8+, fbl, and fcl. Second
As shown in Figure fa+, when the upper and lower rolls are not shifted and placed in the neutral position, the gap profile in the width direction is constant, resulting in rolling that is close to rolling with flat rolls without crowns. On the other hand, if the upper roll is shifted to the right and the lower roll is shifted to the left in this figure, as shown in Figure 2 (
The gear profile shown in b) is narrow at the center of the sheet width, wide at the ends of the sheet width, and the crown of the sheet is small, as in the case of rolling with a top and bottom convex crown roll. Conversely, when the upper roll is shifted to the left and the lower roll is shifted to the right, the gap profile is wide at the center of the board width and narrow at the ends of the board width, resulting in a vertically concave shape, as shown in Figure 2 fcl. The crown of the plate becomes larger as in the case of rolling with a crown roll.

This plate crown control method using a work roll with a bottle-shaped profile is effective because if the bottle shape given to the work roll is appropriately selected, a very large temporary crown control ability can be obtained in proportion to the amount of shift. This is considered to be a means of controlling the plate crown.

(Problem to be Solved by the Invention) However, since the CvC method uses a work roll provided with a bottle-shaped crown as described above, in a multiple rolling mill, there is a gap between the reinforcing roll that supports the work roll and the work roll. The Hertzian pressure distribution in the barrel direction that occurs in the barrel direction becomes a bottle-shaped distribution where the part where the work roll diameter is large is high, and the Hertzian pressure distribution becomes uneven compared to a normal rolling mill, especially in the region where the roll diameter increases at the end of the barrel. Pressure increases. For this reason, especially when rolling is carried out under a high load such as hot rolling, there is a problem in that reinforcing roll damage such as spalling occurs. If the reinforcing roll is damaged, the surface of the work roll is naturally damaged and product quality is adversely affected, so the roll must be replaced immediately, which reduces production efficiency. Furthermore, if the reinforcing roll is damaged to a large extent due to spalling, it cannot be ground and reused, and a new reinforcing roll must be manufactured, resulting in very high running costs.

Therefore, an object of the present invention is to reduce the local high Hertz pressure generated at the end of the roll when using a work roll with a bottle-shaped crown, prevent roll damage such as spalling of the reinforcing roll, and improve stability. The object of the present invention is to provide a rolling method and device that can perform rolling.

(Means for solving the problem) When using a work roll with a bottle-shaped crown, it is expected that the Hertzian pressure will be high at the part where the work roll diameter is large, but until now it has not been possible to quantify it systematically. It has not been studied in detail, and it is unclear how much Hertzian pressure changes depending on various rolling conditions.

Therefore, the inventor conducted a numerical analysis by varying the conditions that affect the rolling load such as the steel type, reduction amount, rolling temperature, rolling speed, and strip width, as well as the strip crown control conditions such as work roll bender force and work roll shift position. When we examined the Hertzian pressure distribution in the barrel direction, we found the following.

(2) When rolling with a work roll exhibiting a bottle-shaped crown, the Hertzian pressure is high in areas A and B shown in FIG. 1, but the maximum Hertzian pressure occurs in area B under most rolling conditions.

(2) As shown in Fig. 2 fc), the plate crown shifts in the direction of increasing, and the Hertzian pressure in region B becomes maximum when a work roll bender is further applied.

■The maximum Hertz pressure in this region B is 20 kgf compared to a normal rolling mill with a quadratic crown on the work roll.
For example, when rolling a wide material of 1,500 mm or more in the first stand of a hot rolling finishing mill row, the Hertzian pressure limit value of 200 kgf is required to ensure stable operation without causing the conventionally known spalling. /wm".

For the above reasons, when rolling is performed using a work roll provided with a bottle-shaped crown, it is presumed that roll damage such as spalling occurs in region B of the reinforcing roll. Therefore, it is necessary to reduce the Hertzian pressure in region B.

Therefore, the inventor conducted further studies and found that
By tapering region B of the reinforcing roll and reducing the amount of contact between the work roll and the reinforcing roll, the Hertzian pressure generated in region B can be reduced, and by tapering, the Hertzian pressure in region B can be reduced. However, it was found that the Hertzian pressure in the AeI region, which is the other high Hertzian pressure region, hardly increases.

Furthermore, if the taper length and taper angle given to the reinforcing roll are set to optimal values according to the bottle-shaped crown of the work roll, the pressure can be increased to the same level as the maximum Hertzian pressure during normal rolling.
That is, it has been found that it is possible to reduce the Hertzian pressure to 200 kgf/w+m'' or less, which does not cause roll damage such as spalling of the reinforcing roll, leading to the present invention.

The gist of the present invention is to use a work roll having a bottle-shaped axial cross section with a convex crown on the operating side half or the driving side half of the work roll barrel and a concave crown on the other side. The crown of the bottle shape is point symmetrical with respect to the upper and lower work rolls;
In multiple hot rolling, which involves shifting the upper and lower work rolls in opposite directions in the axial direction to control the temporary crown, the barrel ends of the upper and lower reinforcing rolls that respectively support the upper and lower work rolls are attached to the work rolls. According to a preferred embodiment of the present invention, a method for reducing Hertzian pressure during hot rolling between a work roll and a reinforcing roll is characterized in that the end of the barrel on the side to which a concave crown is provided is tapered. The length of the taper provided on the roll should be 50% or more of the maximum shift amount of the work roll, and the angle of the taper should have a change gradient corresponding to the increase in roll radius at the end of the work roll barrel provided with the concave crown. When the amount is α, it is preferably 0.8α or more.

From a further aspect, the gist of the present invention is that the upper and lower work rolls have a bottle-shaped axial cross section with a convex crown on the operation side half or the drive side half of the work roll barrel and a concave crown on the other side. multiple hot rolling, in which the bottle-shaped crown is arranged in point symmetry with respect to the upper and lower rolls, and the plate crown can be controlled by shifting the upper and lower work rolls in opposite directions in the axial direction; The Hertzian pressure during hot rolling is characterized in that among the barrel ends of the upper and lower reinforcing rolls that support the upper and lower work rolls, a taper is provided at the barrel end on the side where the work roll is provided with a concave crown. This is a reduction rolling equipment.

(Operation) Next, the present invention will be described in detail in comparison with a conventional example with reference to the accompanying drawings.

Figure 3 shows the reinforcing rolls with the dimensions shown in Figure 1 (unit: m+o) when hot rolling is carried out in a 4-type rolling mill consisting of a reinforcing roll 1 without a crown and a work roll 3 with a bottle-shaped crown. This is an example in which the distribution of the Hertzian pressure generated between the work roll 1 and the work roll 3 in the barrel direction is examined.

However, the work roll crown was a bottle-shaped crown represented by a cubic curve with the origin at the barrel center, as shown in FIG.

In Figure 4, the cubic equation (y
) coefficients were a=0.461, b-0,365. Maximum work roll shift is ±δ steel = ±150 w
+m. Rolling load is 1.5 ton/ffiIw
Met.

Figure 3 (8) shows the effect of sheet width on the distribution of Hertzian pressure in the barrel direction during hot rolling under such conditions.
bl shows the influence of work roll shift, and C1 shows the influence of work roll bending force. From the results of these graphs, it can be seen that the wide material is on the - side (in the direction where the plate crown becomes larger). The greater the shift and the greater the work roll bending force, the higher the Hertzian pressure in area B in Figure 1 (the rightmost part of each graph in Figure 3 corresponds to area B), and when all these conditions are combined, In this case, the maximum Hertzian pressure is 200 kgf/m+112
It will exceed.

It goes without saying that the Hertzian pressure will increase as the load increases, but in order to increase the plate crown control ability, the bottle-shaped crown should be made larger (maximum work roll,
If the difference in the minimum diameter is enlarged), the Hertzian pressure in region B becomes even higher. That is, depending on the rolling conditions, the ability to control the plate crown must be restricted due to Hertzian pressure limitations, so reducing the Hertzian pressure at the barrel end is important.

Therefore, in the present invention, as shown in FIG. 4, a tapered part 7 is provided at the barrel end of the upper and lower reinforcing rolls 1 corresponding to the above-mentioned region B. In Figure 4, upper reinforcing roll 1
Show only about.

Although not particularly limited thereto, in terms of -C, it is sufficient if the taper length in the present invention is about 100 to 200 mm and the taper angle is about 0.03 to 0.15 degrees.

FIG. 5 is a graph showing the effect of the Hertzian pressure reduction method of the present invention. As shown in FIG. The graph shows the Hertzian pressure reduction rate at the barrel end when the barrel is tapered at an angle θ. These data were obtained from a rolling test when the taper shown in Fig. 4 was provided on a type 4 rolling mill with the dimensions shown in Fig. 1.
Figure ta+ shows the effect of the taper length L) when θζα, and figure ta+ shows the effect of the taper angle (θ) when L=δ−.

Here, in order to perform stable operation without roll damage such as spalling, it is necessary to reduce the Hertzian pressure by 10% or more. The maximum shift amount (6 m
) is required. Also, the taper angle (
If θ) is small, there is little effect of Hertzian pressure reduction;
In order to obtain a Hertzian pressure reduction effect of 10% or more, 0.
It can be seen that it is preferable to set the taper angle (θ) to 8α or more.

That is, it is preferable that the taper angle (θ) given to the reinforcing roll substantially match the amount of increase in the radius of the work roll (this corresponds to the gradient α of change in the radius of the work roll).

Note that tapered slopes are also provided on the reinforcing rolls of ordinary rolling mills, but these are all 100 mva in length.
Hereinafter, the angle is 0.3° or more, which can be called a chamfer, and is shorter and steeper than that of the present invention. Also, the chamfering of conventional reinforcing rolls is applied to the drive and operating side barrel ends and has an essentially different purpose from the taper applied to the reinforcing roll according to the present invention.

EXAMPLE Next, an example in which the present invention is applied to an upstream stand of a row of hot rolling finishing mills will be described.

The hot rolling finishing mill row of this example consisted of seven rolling stands, and the rolling mills in the four upstream stands were quadruple rolling mills similar to those shown in FIG. As for the plate crown control means of these upstream stands, the coefficients of the equation (y) defining the cubic curve shown in FIG. 4 are a = 0.461, b =
Bottle-shaped crown of 0.365 and maximum shift amount ±δ
It was equipped with a CVC method of - = 150 + lIl and an increase work roll bender of up to 250 tons per chonke.

As a conventional example, there is a case where hot finish rolling is performed only with the above-mentioned plate crown control means, and a case where the upper and lower reinforcing rolls are tapered in accordance with the present invention in the above-mentioned 4 upstream stands.
The results were compared with those obtained when hot finish rolling was performed using a heavy rolling mill.

Here, the taper provided in the example of the present invention had a length L'' of 150 mm and 10 km, and a taper angle θ=0.06°, as indicated by the symbol shown in FIG.

FIG. 6 is a graph showing the Hertzian pressure reduction effect according to the present invention under the above-mentioned conditions in the first finishing stand as an example. In other words, in the first stand of the finishing mill row, a hot-rolled steel plate with a thickness of 3 o 111 I and a plate width of 165° is transferred to a work roll shift position of -1501, a work roll bending position of 100 tons/inch, and a thickness of
It shows the Hertzian pressure distribution in the barrel direction when rolling to a diameter of 16.5+am.

As is clear from the results shown in the graph of Figure 6, 1.
By tapering the reinforcing roll according to the invention, the maximum Hertzian pressure at the end of the barrel is 200 k
gf/s+w" or less. As a result, roll damage such as spalling of the reinforcing roll did not occur, and stable operation became possible.

In other words, the reinforcing roll of a normal hot rolling finishing mill is 2
If the reinforcing roll is used continuously for more than a week and the work to change the reinforcing roll is several hours, which is extremely long, and if the CVC method is used in the conventional method without tapering the reinforcing roll, the first stand of the finishing mill The second stand has the same load as the first stand, but requires more roll transfers than the first stand.
There was a problem that spalling of the reinforcing roll occurred at the third stand, and the continuous use period was halved compared to the conventional method that does not use the CVC method, but with the present invention, the driving roll By providing a taper in the reinforcing roll, the maximum Hertzian pressure can be significantly reduced, and the number of spalling incidents during continuous use has become zero. It has also become possible to increase the amount of bottle-shaped crown applied to the work roll by about 20%, making it possible to improve the crown control ability.

(Effects of the Invention) As a result of the present invention, the Hertzian pressure generated at the end of the barrel can be reduced, and roll damage such as spalling does not occur.
By shifting the work rolls provided with bottle-shaped crowns, stable operation is possible while implementing a wide range of temporary crown control. This makes it possible to increase yield by improving plate thickness accuracy and shorten delivery times by expanding schedule-free rolling.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of roll arrangement in the conventional CVC method;
Figures ta+, crest) and (C) are schematic diagrams explaining the plate crown control method using the conventional CVC method; A graph explaining an example of examining the behavior of the Hertzian pressure occurring between; FIG. 4 is a schematic diagram explaining the Hertzian pressure reduction mechanism in the present invention; and FIGS. It is a graph showing the effect of the present invention.

Claims (3)

[Claims] (1) Use a work roll whose axial cross section is bottle-shaped, with a convex crown on the operation side half or drive side half and a concave crown on the other side, and the crowns exhibiting the bottle shape are the upper and lower work rolls. In the multiple hot rolling method, the upper and lower reinforcing rolls supporting the upper and lower work rolls respectively support the upper and lower work rolls in the multiple hot rolling method, in which the plate crown is controlled by shifting the upper and lower work rolls in opposite directions in the axial direction. A method for reducing Hertzian pressure during hot rolling between a work roll and a reinforcing roll, characterized by providing a taper at the barrel end on the side where the work roll is provided with a concave crown. (2) The length of the taper provided to the reinforcing roll is 50% or more of the maximum shift amount of the work roll, and the angle of the taper is set by the increase in roll radius at the end of the work roll barrel provided with the concave crown. The amount of change gradient corresponding to α
2. The Hertzian pressure reduction method according to claim 1, wherein the Hertzian pressure reduction method is set to 0.8α or more. (3) Consisting of upper and lower work rolls whose axial cross section is bottle-shaped, with a convex crown on the operation side or drive side half of the work roll barrel and a concave crown on the other side, and the bottle-shaped crown is the upper and lower rolls. A multi-layer hot rolling mill in which the upper and lower work rolls are arranged point-symmetrically with respect to each other and the plate crown can be controlled by shifting the upper and lower work rolls in opposite directions in the axial direction, the upper and lower work rolls supporting the upper and lower work rolls A rolling device for reducing Hertzian pressure during hot rolling, characterized in that, among the barrel ends of the reinforcing roll, the barrel end on the side where the work roll is provided with a concave crown is tapered.