JPS639568B2 - - Google Patents

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to a hearth roll installed in a vertical continuous annealing furnace, and more specifically, to a hearth roll installed in a vertical continuous annealing furnace used for heat treatment of strip-shaped metal materials. The present invention relates to a hearth roll used for conveying the above-mentioned band-shaped metal material in high-temperature processing zones such as heating zones and soaking zones.

[Background of the Invention] A continuous annealing furnace is comprised of heating, soaking, and cooling zones from the upstream side, and the strip-shaped metal material is subjected to appropriate heat treatment according to the purpose while passing through these zones in sequence.

Operational problems with such equipment include:
There are meandering of the band-shaped metal material in the width direction and buckling that occurs within the band-shaped metal material.

As a means of preventing meandering of the above-mentioned belt-shaped metal material, this problem is avoided by adopting a hearth roll shape with a medium-high crown, which applies the same principle as conventionally used to prevent meandering in so-called belt wheels. .

Hearth rolls with such a shape have the function of preventing meandering of the band-shaped metal material, but when using a hearth roll with a tapered taper at both ends, if the inclination angle of the taper is excessive,
When a round ground roll is used and the radius of curvature of the curved crown is too small, or when the tension in the longitudinal direction of the metal strip is increased, compression is induced by uneven tension within the surface of the metal strip. Stress is generated and this stress causes a new problem in that the strip of metal material buckles.

In order to prevent meandering and buckling that occur in strip metal materials that vary in size, size, material, heat treatment conditions, etc., optimize the shape of the hearth roll, such as the width of the parallel part of a tapered hearth roll, the inclination angle of the taper, etc. However, it has been extremely difficult to prevent both of the above defects at the same time with strip metal materials that have a wide width, a small thickness, and require high-temperature annealing. Ta.

[Summary of the Invention] An object of the present invention is to provide a hearth roll having a shape that prevents meandering and buckling of a strip-shaped metal material in a vertical continuous annealing furnace.

The present invention solves the above problems by adding new ideas to the conventional optimal roll shape.

The present inventors conducted experiments and analyzes in which the longitudinal tension of the strip metal material and the shape of the hearth roll were systematically varied. As a result, if the tapered shoulder of the hearth roll is given an appropriate roundness, even if a large longitudinal tension is applied to the strip metal material to prevent it from meandering, the problematic buckling will not occur, and the strip metal material will not meander. It was discovered that this method is extremely effective in preventing both meandering and buckling of the material, and based on this knowledge, the present invention was completed.

[Detailed Description of the Invention] The appearance of buckling that occurs in a band-shaped metal material differs depending on the shape of the hearth roll. As shown in FIG. 5, buckling 9 occurs at a portion of the band-shaped metal material 8 that corresponds to the tapered shoulder of the hearth roll. When the hearth roll 2 provided with the curved crown shown in FIG. 2 is used, as shown in FIG. occurs. These buckling occurrence locations coincide with locations where the band-shaped metal material is subjected to non-uniform tension and the compressive stress induced thereby is greatest.

Meandering and buckling are phenomena that occur under contradictory conditions. Buckling is likely to occur when using a hearth roll with a large taper or crown amount that has excellent meandering prevention function, or when applying a large tension to the band metal material to prevent meandering, but there are conditions in which buckling does not occur. Meandering is likely to occur when Under appropriate conditions in between, neither meandering nor buckling occurs.

FIG. 4 is a diagram schematically showing the above. The shaded area on the lower left side of the figure indicates the area where meandering occurs, and in severe cases, this is an area where there is a danger that the band-shaped metal material may come off the hearth roll and the end thereof may rub against the furnace wall. On the other hand, the diagonally shaded area in the upper right corner of Fig. 4 is the area where buckling occurs.
This buckling not only causes the band-shaped metal material to lose its value as a product, but in severe cases, this buckling can cause the band-shaped metal material to break in the furnace. There is a region between these two regions where neither of these occurs. That is, it can be seen that under the same hearth roll shape, there is a limited narrow appropriate tension range that prevents both meandering and buckling.

In general, in a continuous annealing furnace, the dimensions (plate thickness, plate width) and material (high temperature strength, heat treatment conditions) of the strip metal material are
As the values vary considerably, the proper tension shown in FIG. 4 will vary accordingly. The shape of the hearth roll is determined at the time of facility construction, and converting the roll to change this requires a very large amount of work and a long period of time.

If the longitudinal tension of the strip-shaped metal material is small, buckling will not occur, but if the tension is gradually increased, buckling will begin to occur at a certain tension. The tension at this time is defined as the buckling limit tension (Tcr).

We will explain the results of an experimental investigation of the critical buckling stress Tcr of each hearth roll when using hearth rolls of various shapes. The rolls used were the tapered roll 1 shown in FIG. 1, the round crown roll 2 shown in FIG. 2, and the roll 3 shown in FIG. 3. Roll 3 is the first
The radius of the tapered shoulder of tapered roll 1 in the figure is 60000.
It has a roundness of 10 mm.

The maximum roll diameter (Dmax) at the center of the width of the three rolls mentioned above is 600 mm, the minimum roll diameter (Dmin) at the end part is 598 mm, and the total roll width (L) is 2000 mm. Further, the width (H) of the central parallel portion of the tapered hearth roll 1 is 500 mm. In FIG. 7, the horizontal axis shows the roll types (1 to 3), and the vertical axis shows the buckling limit tension Tcr of the band-shaped metal material.

From FIG. 7, the buckling limit tension Tcr of the round crown roll 2 is the smallest, the buckling limit tension Tcr of the roll 3 with rounded tapered shoulders is the largest, and the buckling limit tension Tcr of the tapered roll 2 is the lowest for both. It can be seen that it is located in the middle.

That is, it is clear that the roll 3 with rounded tapered shoulders does not buckle even when a high tension is applied to the band-shaped metal material 8 compared to the other two rolls.

Next, the influence of the roll shape on the meandering of the band-shaped metal material will be explained.

The widthwise shape, plate thickness, temperature distribution, and longitudinal tension applied to the strip metal material 8 transported through the continuous annealing furnace are not necessarily symmetrical;
Therefore, the center of the width of the hearth roll and the center of the material do not coincide with each other, and the material is generally conveyed with some deviation in the width direction. The mid-height hearth roll has the function of correcting the deviation of the band-shaped metal material in the width direction and moving the band-shaped metal material to the center of the hearth roll.

The above-mentioned meandering correction ability of the hearth roll can be evaluated by the speed at which the shifted band-shaped metal material is transferred to the center of the roll. An experiment conducted to investigate how much this meandering correction ability differs depending on the shape of the hearth roll will be described.

When a 1000 mm wide strip of metal material is wound in advance with the center shifted 200 mm from the center of the hearth roll and conveyed with a constant tension in the longitudinal direction, the amount of movement (Mx) of the strip of metal material toward the center of the hearth roll and the rotation of the hearth roll. The relationship with the number (N) is shown in FIG. The hearth rolls used in the experiment were a tapered roll 1 similar to that shown in FIG. 7, a round crown roll 2, and a tapered roll 3 of the present invention having rounded tapered shoulders. As shown in FIG. 8, the rolls shown in each roll type (1 to 3) have a rotation speed N
As increases, the amount of movement Mx of the strip metal material toward the center of the roll increases, and when Mx reaches 200 mm, that is, when the center of the strip metal material moves to the center of the roll, Mx becomes saturated. The smaller the number of roll rotations N until Mx is saturated, or the larger dMx/dN, the better the hearth roll can be said to have the ability to correct the meandering of the band-shaped metal material.

From FIG. 8, it can be seen that the meandering correction ability of the round crown roll 2 is the poorest, and that of the tapered roll 1 is the best. It was found that the roll 3 with rounded tapered shoulders according to the present invention has almost the same meandering correction ability as the tapered roll 1. It was confirmed that Roll No. 3 has excellent buckling prevention ability and has the same meandering correction ability as the conventional tapered hearth roll 1.

The present invention has been completed based on the above knowledge, and has a cylindrical portion at the center of the width, and a truncated cone-shaped taper portion of the same shape on both end surfaces of the cylindrical portion, whose trapezoidal end surfaces are brought into contact with the end surfaces of the cylinder portion. This hearth roll has a basic shape in which the rolls are connected in series, and the boundary between the cylindrical part and the tapered part is rounded.

What is important in rounding the boundary between the tapered part and the cylindrical part of the tapered hearth roll is to provide an arc 6 that smoothly connects the tapered part 4 and the parallel part 5, as shown in FIG. Yes, it includes the 9th
As shown in the figure, a circular arc 6 inscribed in the tapered portion 4 and the parallel portion 5 is best. The radius R of a circle inscribed in the tapered portion 4 with a taper angle θ is geometrically given by the following equation, with a point of contact located 1 mm from the cylindrical end toward the center of the roll.

R×{sinθ/(1+cosθ)}=l...(1) To find the optimal R, set θ to 1.33×10 ^-3
(rad) and vary l variously to obtain the above
A large number of rolls with varying R determined by equation (1) were created, and using these rolls, the effects on buckling and meandering of the band-shaped metal material 8 were investigated through experiments. The results will be explained below. The horizontal axis in Figure 10 is the value obtained by dividing the above equation (1) by the width (H) of the parallel part of the hearth roll, making it dimensionless, (R/H) {sinθ/(1+cosθ)}, and this value is zero. In the case of , it means that the roll is the same as the conventional tapered roll 1 shown in FIG. The scale on the left side of the vertical axis is the buckling limit tension Tcr, and the curve 40 in the figure corresponds to this. The scale on the right side of the vertical axis indicates the time required for the strip metal material 8 to return to the center of the hearth roll when the strip metal material 8 is intentionally shifted from the center of the hearth roll by 200 mm at the initial stage. Hearth roll rotation speed N
The curve 50 in the figure corresponds to this. The larger the buckling limit tension Tcr is, the less buckling occurs, and the smaller the rotational speed N is, the higher the ability of the roll to correct meandering of the band-shaped metal material.

From Fig. 9, N is constant in the range of (R/H) {sinθ/(1+cosθ)}≦0.1, and when the above value exceeds that value, N increases and the meandering correction ability gradually deteriorates. I know what's going on.

On the other hand, if we focus on buckling of the material, we can see that Tcr increases as (R/H) {sinθ/(1+cosθ)} increases, but when it becomes larger than 0.1, Tcr gradually decreases. . However, even with 0.2, a higher Tcr of 20% or more than the conventional one can be obtained.

When (R/H) {sin θ/(1+cos θ)}=0.5, a buckling pattern similar to that when the round crown roll 2 shown in FIG. 6 was used was observed.

From the above experiments, in order to simultaneously prevent buckling and meandering of the strip metal material, an arc with a radius R that satisfies 0.03≦(R/H) {sinθ/(1+cosθ)}≦0.2 should be used as the cylindrical part of the tapered hearth roll. It is effective to apply it to the boundary with the tapered part. In FIG. 10, the above region is shown with diagonal lines.

In addition, in the range of (R/H) {sinθ/(1+cosθ)}≦0.2, buckling as shown in Figures 5 and 6 hardly occurs, but in rare cases buckling 9 in Figure 6 occurs. This may occur. Therefore, the diameter of at least a part of the central part of the cylindrical part of the tapered hearth roll of the present invention is formed to be slightly smaller than the diameter of the large diameter end face of the tapered part, so that the buckling 9 of the strip metal material makes the roll. It is more desirable that the material is allowed to pass through the rolls while remaining in an elastic region without being crushed by the rolls. This makes it possible to prevent deterioration in the quality of the band-shaped metal material as a product.

[Example] Next, the results of confirming the effects of the present invention using an actual machine will be described. Two upper hearth rolls on the outlet side of the heating zone 7 and two upper hearth rolls on the input side of the soaking zone 8 shown in FIG. It was replaced with the provided tapered hearth roll 3.

The hearth roll 3 of the example has an outer diameter: 600 mm, an inclination angle θ of the taper portion: 0.33×10 ^-3 (rad), and a cylindrical portion width H: 500 mm.

The band-shaped metal material 8 is Plate thickness: 0.7mm Board width: 1320mm Using ultra-low carbon steel, Soaking zone temperature: 810℃ Threading speed: 200m/min heat treated with

The material tension T is gradually increased from 0.2Kg/ ^mm2 ,
The critical tension at which buckling occurs was determined.

The results are shown in FIG.

The diagonally shaded area on the lower side of FIG. 12 is the area where the band-shaped metal material meanderes, and both the conventional device and the device equipped with the hearth roll of the embodiment of the present invention have T.
Meandering occurs when ≦0.22Kg/ ^mm2 . Therefore, in order to prevent meandering of the band-shaped metal material, it is necessary to operate at T > 0.22 Kg/mm ² . If the tension T of the band-shaped metal material is increased, meandering will no longer occur, but problematic buckling will occur in the band-shaped metal material.

The open circles (◯) shown in FIG. 12 indicate conditions where buckling does not occur, and the x's indicate conditions where buckling occurs. In the case of conventional rolls, the tension range in which meandering and buckling do not occur is 0.22Kg/mm ² < T < 0.26Kg/mm ² , forcing them to operate in a narrow tension range of only 0.04Kg/mm ² I understand.

On the other hand, when using the roll according to the present invention, the range of 0.22Kg/mm ² < T < 0.32Kg/mm ² is the tension range in which neither meandering nor buckling occurs, and the operating conditions are significantly relaxed, resulting in less defects. It has become possible to manufacture products that do not already exist.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional tapered hearth roll, FIG. 2 is a front view of a conventional round crown hearth roll, and FIG. 3 is a front view of an embodiment of the present invention.
Figure 4 is a graph schematically showing the influence of the taper angle and curvature of the hearth roll on meandering and buckling of the material, and Figure 5 shows the appearance of buckling that occurs in a strip of metal material in contact with the tapered hearth roll. FIG. 6 is a front view showing the appearance of buckling occurring in the band-shaped metal material in contact with the round crown hearth roll;
Fig. 7 is a graph showing the buckling limit tension at which buckling begins to occur, Fig. 8 is a graph explaining the state in which the meandering of the material is corrected by the hearth roll, and Fig. 9 is a graph showing how the cylindrical part and the tapered part are smoothed. Fig. 10 is a graph showing the effect of the roundness on the tapered shoulder of the hearth roll on the buckling limit tension and meandering correction ability, and Fig. 11 is a graph showing the effect of the roundness on the tapered shoulder of the hearth roll when the hearth roll of the present invention is installed. Schematic vertical cross-sectional view of a vertical continuous annealing furnace, 1st
FIG. 2 is a graph showing the effect of expanding operating conditions by the hearth roll according to the present invention. 1...Conventional tapered hearth roll, 2...Round crown hearth roll, 3...Tapered hearth roll of the embodiment of the present invention, 4...Tapered portion of tapered hearth roll, 5...Tapered hearth roll cylindrical part, 6... circular arc, 7... heating zone, 8...
...Soaking zone, 9...Buckling wrinkles, 10...Rounding of tapered shoulder.

Claims (1)

[Claims] 1. In a hearth roll used in a high-temperature treatment zone in a continuous annealing furnace, the width center part is a cylindrical part, and the large diameter end faces are provided with truncated conical tapered parts of the same shape on both end faces of the hearth roll. It has a basic shape that is connected to and in contact with the end surface of the cylindrical part, and at the boundary between the cylindrical part and the tapered part, the following formula 0.03≦(R/H) {sin θ/(1+cos θ)} ≦0.2 (however, the upper In the formula, H: Width of the central cylindrical part of the roll (mm) θ: Inclination angle of the tapered part (degrees) R: Radius of the circle inscribed in the cylindrical part and the tapered part (mm)
are shown respectively. ) A hearth roll for heat treatment characterized by being rounded with a radius R that satisfies the following. 2. The hearth roll for heat treatment according to claim 1, wherein the diameter of at least a portion of the cylindrical portion is smaller than the diameter of the large-diameter end surface of the tapered portion.