JPH07116522B2 - In-furnace roll of continuous annealing furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-furnace roll installed in a continuous annealing furnace for metal strips and used for passing the strip.

[0002]

2. Description of the Related Art In-furnace rolls provided in a continuous annealing furnace are provided with crowns for the purpose of achieving stable in-furnace stripping while avoiding in-furnace meandering and drawing.

A mechanical crown (m
The meandering correction capability of the in-furnace roll given in c), that is, the correction amount Δx per rotation and the centering force F are expressed by the following equations. Δx = αθmπD (1) α: Meandering correction coefficient [α∝f (μ), μ: Roll surface friction coefficient] θm: Average inclination angle D: Roll diameter F = 2δμγT / W ……… (2 ) δ: meandering amount μ: roll surface friction coefficient γ: winding angle T: metal band tension W: metal band width

Here, to impart a crown to the roll means to impart an inclination angle θ to the roll surface, which means that when the metal band meanders, the meandering angle enhances the meandering correction ability. Therefore, if the crown is small, the meandering correction amount will be small and the centering force will be small, and therefore the meandering cannot be corrected well. Buckling in the width direction in the plane causes a so-called drawing phenomenon. Therefore, the crown amount is set so that neither meandering nor drawing occurs in each continuous annealing furnace, and then it is applied to each in-furnace roll.

[0005]

However, in the furnace roll of the continuous annealing furnace, a so-called heat crown occurs due to the difference in roll thermal expansion in the cylinder length direction due to the difference between the temperature of the metal strip and the furnace temperature. Due to the influence of this heat crown, the amount of crown of the actual roll fluctuates, causing meandering and drawing.

The present invention was devised in view of the above problems of the prior art. To prevent the occurrence of meandering / throttle in the furnace in a continuous annealing furnace, a mechanical crown is set in consideration of this roll heat crown. To do.

[0007]

Means for Solving the problems] furnace rolls Therefore the present invention includes a 15 ≦ Rz ≦ 25 roughness Rz of each roll surface
And, it is basically characterized by further has a total crown tc is the sum of the mechanical crown and the heat crown and 0.2 mm ≦ tc ≦ 0.4 mm.

[0008] furnace roll of the second invention, the roughness Rz of 15 ≦ Rz ≦ 25 of each roll surface and the ratio W and the distance L between the inflection point of the width W and the roll crown of the metal strip / With regard to L
1.3 ≦ W / L ≦ 2.4, and the total crown tc , which is the sum of mechanical crown and heat crown, is 0.2 mm ≦ tc
It is characterized in that a ≦ 0.4 mm.

The above-described structure of the present invention was devised from the results of the investigation by the inventors of the present invention regarding the cause of the meandering and throttling in the furnace due to the heat crown, and the details thereof will be described below.

[0010] The above-described heat crown (hc) is generated by a roll thermal expansion difference of the body length direction due to the difference in the temperature of the metal strip and (T ₁₎ RoAtsushi and (T _2), as follows Represented. hc = D (T ₁ −T ₂ ) ・ β / 2 ………… (3) β: linear expansion coefficient of roll

Therefore, in the continuous annealing furnace, in the treatment zone (for example, cooling zone) where the metal zone temperature T ₁ is higher than the furnace temperature T ₂ (T ₁ > T ₂ ), this heat crown becomes a positive crown, and conversely. The furnace temperature T ₂ is higher than the metal band temperature T ₁ (T ₂ >
T ₁ ) In the treatment zone (for example, the heating zone), a minus crown is obtained. Therefore, if the furnace rolls with the same mechanical crown are used for both heating and cooling zones,
Considering the heat crown, the meandering correction capability becomes small in the heating zone and the throttling phenomenon tends to occur in the cooling zone.

Therefore, it is necessary to consider the influence of the heat crown (hc) on the mechanical crown (mc) applied to the rolls in the actual amount of roll crown in each furnace of the continuous annealing furnace. As shown, the total crown (tc), which is the sum of the mechanical crown (mc) and the heat crown (hc), should be set to the range where no meandering or throttling occurs in the furnace. The total crown amount is obtained from The total crown (tc) is 0.2mm in this experimental result.
When it is less than 0.4 mm, meandering is likely to occur, and when it exceeds 0.4 mm, it is clarified that constriction frequently occurs.

However, the setting of the total crown as described above is effective when the roll surface roughness Rz is within the range of 15≤Rz≤25. That is, the roll surface roughness Rz is related to the meandering correction coefficient α and the friction coefficient μ in the equations (1) and (2) [α
When Rz is less than 15, the roll life is short and clogging occurs, and the meandering correction ability is significantly reduced. On the other hand, when the roughness Rz exceeds 25, the metal band, especially the strip, is prominently prone to scratches, and there is a concern that biting flaws may occur due to a defective convex portion of the roughness. Therefore, the total crown amount is set on condition that the roll surface roughness Rz is within the above range.

Further, the meandering correction ability of the mechanical crown (mc) of the roll is mainly determined by the inclination angle θ as described above, but in addition, the width W of the metal strip and the crown inflection point shown in FIG. Between CP ₁ and CP ₂ (corresponding to the straight part)
It is also affected by the ratio W / L with the distance L of. According to the experiments by the present inventors, when the value of W / L is less than 1.3, the metal strip comes into contact with the roll in a substantially planar manner (that is, the amount of mechanical crown becomes small), and the thread is wound by the crown roll. The effect cannot be obtained and the meandering easily occurs. Especially the heat crown (hc) is a minor
In the treatment zone that becomes a crown, the meandering due to the planar contact
To prevent the roll from being given a mechanical crown
It is necessary to keep this W / L value above 1.3 on the floor.
On the other hand, when the value of W / L exceeds 2.4, the mechanical crown becomes large and the occurrence rate of the diaphragm increases.
Especially, heat crown (hc) is a positive crown
In the band, the increase in the crown due to the increase in the crown amount increases the
This W / at the stage of giving a mechanical crown to the roll
The value of L must be 2.4 or less. Therefore, in the second aspect of the invention, the W / L range (1.3 ≦ W / L ≦ 2.4) is set as the second condition to set the total crown amount.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0016] Each furnace roll having the specifications shown in Table 1 below was installed in an experimental furnace consisting of a heating zone, soaking zone, slow cooling zone and quenching zone. Strips of 610 to 1100 mm were threaded.

[0017]

[Table 1]

In this experiment, it was confirmed that meandering was generated in the heating zone and throttling was generated in the slow cooling zone and the rapid cooling zone. Therefore, the present inventors also investigated the heat crown amount of the roll in each furnace.

As a result, it was found that the heat crown distribution as shown in FIG. 2 was obtained in each furnace, and the heat crown of the furnace roll in each furnace was obtained by the following equation. Heating zone: hc = −9.53 × 10 ⁻⁴ (T ₁ −T ₂ ) −0.025 Soaking zone: hc = −1.40 × 10 ⁻³ (T ₁ −T ₂ ) +0.002 Slow cooling zone / quenching zone: hc = -1.65 x 10 ^-3 (T ₁ -T ₂ ) -0.00
6

Furthermore, the total crown (tc) amount of the rolls in the furnace in the slow cooling zone of these furnaces and the occurrence rate of the strip drawing were examined, and the results shown in FIGS. 3 and 4 were obtained.

FIG. 3 shows the relationship between the total crown of the rolls in the furnace and the plate temperature. According to the figure, the total crown amount of all rolls exceeds 0.2 mm.
Many were over 0.4 mm [In Fig. 3, the amount below the dashed-dotted line is the amount of heat crown (hc), and above that is the amount of mechanical crown (mc), and the total amount of crown (tc) is the sum of them. I have been told].

Further, in FIG. 4, the strip occurrence rate of the strip is shown in relation to the strip width W (a polygonal line), but at the same time, the correspondence relation between the strip width W and the strip thickness when the strip is produced is also shown. Yes (part surrounded by a frame). As described above, in the slow cooling zone including the in-furnace roll having the total crown (tc) amount exceeding 0.4 mm (the thinner the plate thickness and the larger the plate width W are), the strip occurrence rate becomes high. I understand.

On the other hand, the inventors of the present invention changed the rolls in the furnace in the experimental furnace (provided that the changed rolls had the same material and diameter as those of the rolls before the change, and had the same heat crown as that of the roll before the change). The amount of heat crown was obtained), and a mechanical crown was applied to each roll so that the total crown of the rolls in each furnace was within the range of 0.2 to 0.4 mm as shown in FIG. The mechanical crown was set based on the amount obtained by subtracting the heat crown amount shown in Fig. 2 from the desired total crown amount. Therefore, the hatched portion in Fig. 5 corresponds to the mechanical crown amount). .

At this time, neither meandering nor throttling of the strip was confirmed in any of the furnaces, but the present inventors have found that among these furnaces, the total crown amount of the rolls in the furnace, especially in the above-mentioned slow cooling zone, The squeezing rate of the strip was examined, and the results shown in FIGS. 6 and 7 were obtained. Even if it is not shown in Fig. 6, the total crown of the furnace rolls in this slow cooling zone is set within the range of 0.2 to 0.4 mm as described above, and unlike the case before the rolls are reassembled, the strip drawing occurs. The rate was 0 as shown in FIG. 7.

[0025]

As described above in detail, according to the in-furnace roll of the present invention, the roll having the surface roughness Rz adjusted within a specific range is used.
On the other hand, the mechanical crown is set in consideration of the heat crown caused by the difference between each furnace temperature of the continuous annealing furnace and the temperature of the metal strip, and therefore, the meandering and throttling in the furnace are prevented.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a total crown of a roll in a furnace.

FIG. 2 is a graph showing the amount of heat crown generated in each furnace roll of the experimental furnace.

FIG. 3 is a graph showing the relationship between the plate temperature in the slow cooling zone of the experimental furnace and the total crown amount of the in-furnace rolls.

FIG. 4 is a graph showing a strip occurrence rate in the slow cooling zone.

FIG. 5 is a graph showing the total crown amount of each roll when the roll inside the experimental furnace is recombined with the roll having the constitution of the present invention.

FIG. 6 is a graph showing the relationship between the plate temperature in the slow cooling zone of this experimental furnace and the total crown amount of the in-furnace rolls.

FIG. 7 is a graph showing the rate of occurrence of squeezing of strips in the slow cooling zone.

FIG. 8 is an explanatory view showing a schematic configuration of a furnace roll of a continuous annealing furnace.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Sansegawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (56) Bibliographic Publication Sho 60-9574 (JP, B2) Sho 63-30369 (JP, B2)

Claims (2)

[Claims] 1. An in-furnace roll installed in a continuous annealing furnace for metal strips and provided with a crown, the roughness Rz of each roll surface is set to 15 ≦ Rz ≦ 25, and the sum of the mechanical crown and the heat crown is used. a certain total crown tc
Furnace roll continuous annealing furnace, characterized in that it has a 0.2mm ≦ tc ≦ 0.4mm. 2. An in-furnace roll installed in a continuous annealing furnace for metal strips and provided with a crown, has a surface roughness Rz of 15 ≦ Rz ≦ 25 and a width W of the metal strip and a roll crown. Ratio to the distance L between the inflection points: 1.3 per W / L
≤ W / L ≤ 2.4, and the total crown tc , which is the sum of the mechanical crown and the heat crown, is 0.2 mm ≤ tc ≤
In-furnace roll for continuous annealing furnace characterized by 0.4mm.