JP4487844B2 - Method and apparatus for hot-dip plating of steel strip - Google Patents

Description

  The present invention relates to a method and apparatus for hot-dip plating (eg, hot-dip galvanizing) of steel strip. The hot-dip plating method and apparatus of the present invention can improve the uniformity of the plating adhesion amount by suppressing the vibration of the support roll provided on the outlet side (downstream side of the sink roll) in the plating bath.

  In hot dip galvanizing of steel strip, the steel strip annealed in a continuous annealing furnace is allowed to penetrate downward into a plating bath holding molten plating metal (zinc, but may contain a small amount of other elements) The direction of the steel strip is changed upward by a sink roll installed in the bath, and the excess plating is removed by a gas wiping device installed immediately above the plating bath surface to adjust to a predetermined amount of plating, thereby plating. Is done.

  Recently, as the demand for hot dip galvanized steel sheets has increased, the level of quality required has become more advanced than ever before, and the uniform coating coverage is especially important for the corrosion resistance and welding of hot dip galvanized steel sheets. It is regarded as very important because it has a dominant influence on the properties and adhesion of the plating layer.

  FIG. 1 is an explanatory view showing an outline of the periphery of a plating bath in a continuous hot dip galvanizing line. As described above, the steel strip 4 annealed by a continuous annealing furnace (not shown) penetrates the hot dip galvanizing bath 1 downward and is immersed in the plating bath 1. The steel strip 4 that has entered the plating bath 1 is turned upward by the sink roll 2 installed inside the plating bath, and exits the plating bath 1 upward via the support rolls 3a and 3b. Then, a surplus plating metal adhering to the steel strip 4 is removed by a gas wiping device (not shown) installed immediately above the plating bath surface, and adjusted to a predetermined plating adhesion amount.

  The support rolls 3a and 3b are used to stabilize the shape of the steel strip (mainly the warp in the width direction) and the pass line of the steel strip, and their positions can be moved in the horizontal direction and contact the steel strip 4. It can be pushed in the horizontal (horizontal) direction to change the amount of pushing. As shown in FIG. 1, there are actually many plating lines with two support rolls, but there are also lines with only one or three or more support rolls. The warp in the width direction and the instability of the pass line are the main causes of locally uneven plating deposition in the gas wiping apparatus.

  As shown in FIG. 2A, each support roll 3 includes a roll body (roll body) and roll shafts 5 on both sides thereof. Although the roll shaft 5 can be formed integrally with the roll body portion, the roll shaft as a separate member is usually fixed to the roll body portion by welding or the like. The roll shafts 5 on both sides are respectively inserted into bearings 11 provided on the bearing support 10 and supported so as to be able to roll (rotate) using the inner surface of the bearing as a rolling surface. Although FIG. 1 shows the roll shaft 5 and the bearing 11 only for the support roll 3a, the support roll 3b has the same configuration. The bearing 11 may not be a through hole as shown, but may be a hole closed on the side not facing the roll.

The roll shaft 5 needs to rotate in synchronism with the plate feed speed of the steel strip 4 (the rotation speed of the sink roll 2) in the bearing 11. The rotation method of each support roll 3 is a non-driving method in which the support roll 3 is rotated by friction with the steel strip accompanying the passing plate of the steel strip 4 without rotating the roll shaft 5 (for example, Patent Document 1, There are a patent document 2 and a patent document 4), and an external drive method (for example, patent document 3) in which the support roll 3 is rotationally driven by forcibly rotationally driving the roll shaft 5 from the outside. In the present invention, the former is called a non-driving roll and the latter is called an external driving roll. The non-driving support roll has an advantage that the plating adhesion amount is easily uniformed because vibration of external driving such as a motor is not transmitted to the support roll.
JP-A-6-128711 JP-A-6-184717 JP-A-5-70916 Utility Model Registration No. 2565736

  In both cases of the externally driven roll and the non-driven roll, vibration of the support roll 3 results in vibration of the pass line of the steel strip 4 (sometimes called fluttering, chattering, etc.), and the amount of plating adhesion is stable. Therefore, the plating quality is deteriorated.

  In the case of an external drive roll, the main cause of vibration of the support roll is that the transmission mechanism of the drive system vibrates and pulsates. On the other hand, the mechanism in which vibration occurs even when the support roll is a non-driving roll can be explained as follows.

  As shown in FIGS. 3 (a) and 3 (b), the diameter of the hole of the bearing 11 that supports the roll shaft 5 of the support roll 3a is larger than the diameter of the support roll shaft 5 inserted into this, and there is play between the two. There is. This play is necessary for smoothly rolling the support roll shaft 5 in the bearing 11 without driving. 3A and 3B, the difference (play) between the diameter of the bearing 11 and the diameter of the roll shaft 5 is greatly exaggerated for convenience of explanation.

  Fig.3 (a) shows the time when the steel strip 4 and the roll trunk | drum of the support roll 3a are not contacting. The roll shaft 5 of the support roll 3a is located at the bottom of the bearing 11 by gravity 8 due to the mass of the support roll 3a. In this state, the lower end of the roll shaft 5 is in contact with the lower end of the bearing 11.

  Next, when the roll shaft 5 is moved in the horizontal direction in the direction approaching the steel strip 4 and the support roll 3a (the body portion) is pushed into the steel strip 4 as shown by the arrows in FIG. The pressing force 9 acts on the roll shaft 5 of the support roll as shown in FIG. 3A by the tension 15 of the steel band 4 and the pressing amount 14 of the support roll 3a with respect to the steel band 4 shown in FIG. Therefore, the combined load vector 6 of the gravity 8 and the pushing force 9 of the support roll 3 a acts on the roll shaft 5. The angle between this combined load vector 6 and the vertical direction is 12. By the action of the composite load 6, the support roll rises in the direction opposite to the pushing direction along the rolling surface of the bearing 11, and theoretically the bearing 11 of the roll shaft 5 is shown in FIG. When the contact position reaches the position where the combined load vector 6 and the bearing 11 intersect, the position becomes stable. The roll position at this time [position shown in FIG. 3B] is hereinafter referred to as a stable position. When the roll shaft is in this stable position, the direction (angle 12) of the composite load vector 6 does not change, but its starting point changes, compared to when the roll shaft is in the position where there is no indentation shown in FIG.

  During the operation of the hot dipping line, the non-driven support roll 3 a rotates following the plate of the steel strip 4. The support roll 3a is made lighter by making the inside of the roll hollow in order to make it easy to rotate following the through plate of the steel strip 4 especially in the case of no drive. Many. In that case, the gravity 8 due to the weight of the support roll in FIG. As a result, the support roll does not always stay in the above-mentioned stable position and does not rotate, but slightly swings while rotating, resulting in vibration of the steel strip pass line, and vibration and pulsation of the support roll are generated. .

  Patent Document 1 and Patent Document 2 propose changing the position of the non-driving support roll up and down, which is intended to mainly correct C warpage of the steel strip due to the support roll. No mention is made of the vibration of the support roll itself.

  Patent Document 4 discloses that in order to avoid a roll rotation failure due to friction in a non-driven roll, a contact resistance is reduced by reducing a contact area with a bearing by forming a groove in a roll shaft, thereby improving lubricity. is doing. This patent document also considers that in order to reduce the contact resistance with the bearing, the axial cross section of the bearing may be L-shaped with the upper part and one side open, and in that case, stability is considered. Thus, it has been proposed to attach a pressing member to the exposed roll shaft portion of the upper open portion. However, there is no disclosure about the pressing method. In addition, the purpose of the press of the roll shaft part is to prevent the roll from dropping from the open bearing, not the roll vibration, because the roll press is applied only in the case of an L-shaped bearing having an open top. it is conceivable that.

  The present invention relates to hot-dip galvanizing and other hot-dip metal plating, and can suppress the vibration of a support roll in a plating bath, particularly a non-driven roll, thereby ensuring the uniformity of the amount of plating. It is an object of the present invention to provide a method for manufacturing a steel strip and a hot dipping apparatus.

  According to the present invention, vibrations of the support roll (particularly the non-driving roll) in the metal plating bath are applied from the outside in an appropriate direction and load so that the roll axis of the support roll is stabilized at the above-described stable position. The above-mentioned problem can be solved by holding down.

  In one aspect, the present invention provides at least one support roll in a method for producing a hot dipped steel strip in which a steel strip is passed through a sink roll and one or more support rolls disposed in order in a plating bath. A hot-dip galvanized steel strip manufacturing method is characterized in that a pressing load is applied to the roll axis of the steel sheet, and the size and direction of the pressing load is controlled to suppress vibration of the support roll.

A preferred embodiment of this method is as follows:
Controlling the magnitude and direction of the presser load with reference to the minimum steel strip tension when no presser load is applied and the position of the support roll at that time; and / or the at least one support roll is The non-driving roll has no driving means, and the size of the pressing load is set so as not to cause the support roll to slip.

  From another aspect, the present invention relates to a hot dipping apparatus in which a sink roll and one or more support rolls downstream thereof are disposed in a plating bath, wherein the hot roll plating apparatus includes at least one support roll roll axis. And a roll shaft pressing means capable of applying a pressing load so that the size and direction can be controlled.

A preferred embodiment of this device is as follows:
The roll shaft pressing means is composed of a bar whose direction can be adjusted, a roll shaft pressing pad attached to one end of the bar, and a pressing means that can controlably apply a pressing force to the other end of the bar. ;
-The at least one support roll is a non-driving roll.

  In addition to hot dip galvanizing (including alloyed hot dip galvanizing in which alloying heat treatment is performed after plating), the hot dip galvanized steel strip manufacturing method and hot dip plating apparatus of the present invention include tin, aluminum, and tin-lead alloys (turn metal). It can be applied to the production of various hot dip galvanized steel strips.

  By using the method of the present invention and / or the apparatus of the present invention, there is no surface flaws and excellent plating adhesion uniformity without causing vibration or rotation failure of the support roll and slip in the case of a non-driven roll. High quality hot dip galvanized steel strip can be mass-produced at low cost.

The present invention will be described below based on the embodiments shown in the accompanying drawings. However, the examples shown in the drawings are merely examples and do not limit the present invention.
In FIG. 4, 1 is a molten metal plating bath, 2 is a sink roll installed near the bottom of this plating bath, and changes the direction of the steel strip 4 that is continuously fed, 3a, 3b, It is a pair of support rolls installed above the sink roll 2. Both the sink roll 2 and the support rolls 3 a and 3 b are located inside the molten metal plating bath 1. Below, although the vibration suppression means by this invention is demonstrated about the lower side support roll 3a, when using a some support roll, the same means can be employ | adopted for each support roll. All the support rolls may be subjected to vibration suppression measures according to the present invention, or only some of the support rolls may be applied with the roll presser according to the present invention. In the case of only some of the support rolls, it is preferable to apply a pressing load to the roll shaft of the lower support roll.

In the present invention, the roll shaft 5 of the support roll 3 a is pressed by the roll shaft pressing means 22 installed outside the plating bath 1 to suppress vibration. The presser load applied to the roll shaft 5 and the presser direction are changed according to factors such as the tension applied to the steel strip 4 (upward tensile force 15 shown in FIG. 1), the positions of the sink roll 2 and the support roll 3a. For example, if the tension is changed in response to changes in the steel strip thickness or steel strip width during operation, it is necessary to adjust the presser means and presser load accordingly. For this purpose, the roll shaft pressing means 22 can apply a presser load to the roll shaft 5 so that the size and direction can be controlled. However, on the basis of the minimum steel strip tension when the plate is passed without using the presser means and the support roll position at that time, the minimum necessary presser load and its Knowing the direction makes it easier to operate.

  In addition, if the presser load applied to the roll shaft is too large, the support roll is difficult to rotate and surface flaws due to slippage due to the non-driven roll are likely to occur. It is preferable to obtain a presser foot load and operate with a presser foot load that is about the same or slightly higher.

The roll shaft pressing means used in the present invention is not particularly limited as long as the pressing direction of the roll shaft and the size of the pressing load can be adjusted, but some specific examples will be described.
The roll shaft pressing means 22 shown in FIGS. 4 and 5 (a) has a presser pad 16 having an arc-shaped cross section (an arc having an inner diameter substantially equal to the outer diameter of the roll shaft) for pressing the roll shaft at one end of the presser bar 23. By providing the press pad 16 to the roll shaft, a press load is applied to the roll shaft 5 of the support roll 3a through the pad 16.

  The other end of the presser bar 23 is connected to a spring 21 that is a pressing means capable of applying a controllable load to the presser bar 23. The vicinity of the end portion of the presser bar 23 on the side connected to the spring 21 can be constituted by another connecting member. The front side portion of the presser bar 23 is bent so that the end is horizontal, and the presser bar 23 is a vertical part having a rotatable pin 20 and a long hole 19 at a portion immediately before the bent part. It is supported by the plate 18. The vertical plate 18 and the pin 20 are fixed to a horizontal pedestal (platform) 17 that can move horizontally back and forth. With this structure, as the horizontal pedestal 17 moves back and forth, the presser bar 23 changes its angle with the pin 20 as a fulcrum. In this way, the pressing direction of the roll shaft 5 can be controlled. The presser load of the roll shaft 5 can be controlled by adjusting the load (pressing force) applied to the presser bar by the spring 21. The spring 21 can control a load to be applied by adjusting its length.

  Of course, the separate presser bar 23 is each arrange | positioned so that the steel strip 4 may be pinched | interposed into the roll axis | shaft 5 of the both sides of the roll trunk | drum of the support roll 3a. However, the portion of the pressing means 22 on the near side from the pin 20 (from the pin 20 to the spring 21) may be a single member common to both sides. Thereby, it is possible to reliably apply a pressing load to the presser bars on both sides with the same load and direction. Or the member of this part can also be separately installed in the both sides of a roll trunk | drum.

  The presser load and presser direction of the roll shaft 5 by the presser bar 23 are based on the minimum steel strip tension when the plate is passed without using the presser and the support roll position at that time. The minimum steel strip tension is the tension indicated by 15 in FIG. 1, and the support roll position at that time is the position shown in FIG. 3B, that is, the tensile force of the steel strip (15 in FIG. 1). ) And gravity 8 due to the weight of the support roll, and the amount of pushing of the steel strip by the support roll (14 in FIG. 1).

  Therefore, the direction of the presser bar 23 is a direction that keeps the support roll at this stable position. Specifically, as shown in FIG. 5A, the pressing direction is the same as the direction of the combined load vector 6 of the pressing force 9 acting on the roll shaft 5 of the support roll and the gravity 8 due to the weight of the support roll. Direction (or a direction as close as possible to this direction, for example, within 5 ° from the same direction). Thereby, it can suppress that a support roll moves from the stable position shown in FIG.3 (b), and vibrates.

  If the presser load by the presser bar is too weak, the vibration suppressing effect of the support roll cannot be sufficiently exhibited. On the other hand, if the strength is too strong, the rotation of the non-driven support roll associated with the plate through the steel strip is hindered, causing slippage of the steel strip and generating surface defects due to slip on the plating surface. Therefore, it is only necessary to set the presser load within a range that is effective for vibration suppression and that does not generate slip. The minimum presser load that effectively suppresses vibrations is the steel plate 4 passing speed, the pushing amount of the steel strip 4 by the support roll 3, the surface condition of the support roll 3 (or the support roll and steel strip in the hot dipping bath) It can be calculated from the data at the time of plating operation with no presser. By applying the remaining load (or a slightly larger load) obtained by subtracting the load applied by the above-described composite vector from the minimum presser load to the presser bar 23, the vibration of the support roll is generated without generating a slit. Can be effectively suppressed.

  The position where the press pad 16 pushes the roll shaft 5 is, for example, as shown in FIG. 2B, the position of the roll shaft 5 between the roll body portion of the support roll 3 and the bearing 11 (that is, the inner side of the bearing). The position of the roll shaft 5). In this case, as shown in FIG. 2B, it is preferable to provide a presser receiver 27 on the side facing the pad 16 across the roll shaft. In the illustrated example, the presser receiver 27 is supported by a chock 26, and this is welded and fixed to the bearing support 10. The position to be pushed in by the presser pad 16 is not limited to the inside from the bearing 11. For example, the roll shaft 5 may be pushed by the press pad 16 outside the bearing 11. Alternatively, the bearing 11 may have a substantially semicircular shape with an open top, and the roll shaft 5 may be pushed into the bearing 11 with the presser pad 16. Furthermore, presser pads may be arranged at two or more positions on the roll shaft.

  As shown in FIG. 5B, the presser 22 includes two pressers such that the roll shaft 5 is pressed by the presser pad 16 at the same position in the axial direction and at two different positions in the circumferential direction of the roll shaft. Means may be provided. In this case, since the combined force of the pressing forces loaded through the two pads becomes the presser direction, the combined presser direction is applied to the two presser pads 16 so that the combined presser direction matches the aforementioned combined load vector 6. Apply indentation force.

  Furthermore, as shown in FIG. 6, the holding means 22 can be installed on the support roll 3 a side from the pass line of the steel strip 4. The presser load can be applied by a method using the cylinder 24 (FIG. 7) or a method using the counterweight 25 (FIG. 8).

The presser pad 16 and the presser bar 23 are made of a material that exhibits corrosion resistance and wear resistance in a hot dipping bath. For example, a stainless steel material in which a carbide such as WC, a boride such as ZrB ₂ , a Co—Cr—W alloy, or the like is thermally sprayed or deposited is used.

  Generally, the presser bar 23 is preferably configured so that the presser load can be adjusted in a range of 10 to 100 kg, and the presser direction can be adjusted in a range from vertically downward to approximately 90 ° (substantially horizontal).

  In the above, the non-driving roll has been mainly described. The present invention is particularly effective in the non-driving roll as described above, but can also be applied to a support roll of an external driving system. Even in that case, vibration of the support roll can be suppressed by applying a presser load having an appropriate direction and size to the roll shaft. In this case, it may be necessary to increase the external driving force against the pressing load, and to use a high-strength material for each member for that purpose. The upper limit of the presser load may be set.

  An example of production of a hot dip galvanized steel strip according to the present invention using a hot dip galvanizing bath having a roll arrangement shown in FIG. 1 and an Al content of 0.15% by mass at a temperature of about 500 ° C. or lower will be described. . Although not shown in FIG. 1, the presser receiver shown in FIG. 2 (b) was also used.

  The tensile tension of the steel strip was 1400 kg, and the support rolls 3a and 3b had a mass in the bath of 80 kg, a roll diameter (the diameter of the body) of 300 mm, and a roll shaft diameter of 65 mm. Hereinafter, the simple support roll means the lower support roll 3a.

  When the pushing amount 14 of the support roll 3a is about 6 mm in distance from the vertical extension line (dotted line vertical line in FIG. 1) of the outer surface of the sink roll 2, and the height of the roll center is about 320 mm from the center of the sink roll When the friction coefficient is set to 0.1, the combined load vector 6 of the weight 8 and the reaction force 9 of the support roll 3a is about 18 kg, and the angle 12 with respect to the vertical line is calculated to be about 60 °. On the other hand, under this condition, the minimum load for suppressing roll shaft vibration was 57 kg and the angle was 60 ° as above, based on the data during the conventional operation.

  4 and 5 (a) is used to adjust the presser bar 23 by adjusting the length of the spring 21 to a load difference of 39 kg between the combined load 6 and the minimum load that suppresses roll shaft vibration. The load was applied to the roll shaft 5 of the support roll 3a. The bearing, presser bar, presser pad, and presser foot were all made of WC-sprayed stainless steel (SUS316L), and the other components in the plating bath were mainly SUS316L.

  As a result, the plating surface flaws did not occur due to the rotation of the support roll 3 and the plating surface flaws due to slip, and the variation in the amount of plating did not push the roll shaft by the pressing means 22, as shown by the solid line in FIG. Compared to the case (dotted line), it was reduced by about 47%, and the uniformity of the plating adhesion amount was remarkably improved.

  In this example, the pressing load is applied only to the lower support roll 3a. However, if the pressing load is applied to the upper support roll 3b in the same manner, it is expected that the variation in the adhesion amount is further improved.

It is a figure which shows roll arrangement | positioning in a hot dipping bath. FIG. 2A is an exploded explanatory view showing a configuration example of a support roll, its roll shaft and a bearing, and FIG. 2B is an explanatory view showing an application example of a presser bar and a presser pad according to the present invention. is there. FIGS. 3A and 3B are views showing the positional relationship between the roll shaft and the bearing before contacting the steel strip and after pushing the steel strip, respectively. It is the schematic of the hot dipping apparatus provided with the roll axis pressing means of the support roll which concerns on this invention. 5A and 5B are explanatory diagrams in the vicinity of the support roll shaft, showing different arrangements of presser pads for pressing the roll shaft. It is the schematic of the hot dipping apparatus which shows another example of the pressing means of the support roll axis | shaft of this invention. It is the schematic of the hot dipping apparatus which shows another example of the pressing means of the support roll axis | shaft of this invention. It is the schematic of the hot dipping apparatus which shows another example of the pressing means of the support roll axis | shaft of this invention. It is a graph which shows the result of the Example of this invention.

Explanation of symbols

1: molten metal plating bath; 2: sink roll; 3, 3a, 3b: support roll; 4: steel strip; 5: roll shaft, 6: composite load vector; 8: roll gravity; 9: pushing force; 11: Bearing; 14: Pushing amount by support roll; 15: Steel strip tensile force; 16: Press pad; 17: Horizontal base; 18: Vertical plate; 19: Long hole; 20: Pin; 22: Roll shaft presser means; 23: Presser bar; 24: Cylinder; 25: Counterweight; 26: Chock;

Claims (6)

  In a manufacturing method of a hot dipped steel strip in which a steel strip is passed through a sink roll and one or more support rolls arranged in order in a plating bath, a pressing load with respect to a roll axis of at least one support roll The method of manufacturing a hot-dip galvanized steel strip is characterized by suppressing vibration of the support roll by controlling the size and direction of the presser load.   The hot-dip galvanized steel strip manufacturing method according to claim 1, wherein the size and direction of the presser load are controlled on the basis of a minimum steel strip tension when no presser load is applied and a position of the support roll at that time. Method.   The said at least 1 support roll is a non-driving roll which does not have a drive means, The magnitude | size of the said pressing load is set so that it may not cause the slip of this support roll. Manufacturing method of hot dipped steel strip.   A hot dipping apparatus in which a sink roll and one or more support rolls on the downstream side thereof are arranged in a plating bath, and the size and direction of the roll axis of at least one support roll can be controlled in a controllable manner. A hot dipping apparatus comprising roll shaft pressing means capable of applying a load.   The roll shaft pressing means is composed of a bar whose direction can be adjusted, a roll shaft pressing pad attached to one end of the bar, and a pressing means capable of applying a pressing force to the other end of the bar in a controllable manner. The hot dipping apparatus according to claim 4.   The hot dipping apparatus according to claim 4 or 5, wherein the at least one support roll is a non-driven roll.

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