JP4147515B2 - Roll for continuous molten metal plating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a roll for continuous molten metal plating such as a sink roll and a support roll used by being immersed in a molten metal bath when metal plating such as galvanization is applied to a steel sheet.
[0002]
[Prior art]
The continuous molten metal plating apparatus performs continuous plating while immersing and running a steel plate having a cleaned and activated surface in a molten metal bath such as zinc. At that time, rolls for continuous molten metal plating such as sink rolls and support rolls are used by being immersed in a molten metal bath. In the case of molten zinc, the temperature in the bath is about 480 ° C. A sink roll is arrange | positioned at the bottom part in a molten metal bath, and changes the advancing direction of the steel plate sent in the bath to the upper bath surface side. Usually, the driving torque is applied to the rotational power of the sink roll by the traveling movement of the steel plate. The support roll consists of a pair of rolls and is provided at a position close to the bath surface after passing through the sink roll. The support roll is driven by an external motor via a spindle, sandwiches the steel plate, maintains the pass line of the steel plate, and sinks. Corrects the warpage of the steel sheet that occurs when it passes through the roll.
[0003]
Steel materials such as stainless steel and chromium heat-resistant steel having excellent corrosion resistance have been used for conventional rolls for continuous molten metal plating. However, when the roll was immersed in a molten metal bath for a long time, the surface was eroded and easily worn. Furthermore, in order to improve the corrosion resistance and wear resistance, the surface of the roll base made of steel material was welded with a corrosion-resistant Co-based alloy, or a ceramic such as WC-Co cemented carbide or Al ₂ O ₃ was sprayed. Although there are some, the difference in the thermal expansion coefficient between the base material and the thermal sprayed coating caused cracks in the thin coating, and eroded from there, so wear was unavoidable.
[0004]
If the wear becomes remarkable, the roundness and cylindricity of the roll cannot be maintained, and the roll and the steel plate are vibrated, so that a steel plate having uniform plating characteristics cannot be obtained. For this reason, conventionally, after continuous use for 1 to 2 weeks, it was necessary to stop the plating operation and replace the worn roll. This significantly reduces productivity and increases the cost of the product due to an increase in roll replacement costs.
[0005]
Therefore, in order to solve this problem, there is known a continuous hot metal plating roll in which a roll body portion (through plate portion) in contact with a steel plate is made of ceramics having excellent corrosion resistance, heat resistance, and wear resistance. For example, in Japanese Patent Laid-Open No. 5-271877 as a conventional example, a brass retaining ring for holding a sialon ceramic sleeve is inserted into a shaft made of heat resistant steel of SUH309, and then a heat resistant steel presser is inserted from both ends of the shaft. A support roll is described in which a ring is fitted and a shaft and a ceramic sleeve are fixed.
[0006]
[Problems to be solved by the invention]
Rolls for continuous molten metal plating such as sink rolls and support rolls need to rotate at the same speed as the steel sheet because they are in contact with the steel sheet. For this reason, it is desired that the roll for continuous molten metal plating is as easy to rotate as possible and can easily follow the start-up and changes in the running speed of the steel sheet. However, in the case of the conventional example, the roll has its own weight because it has a solid shaft made of heat-resistant steel, and there is a problem that it is difficult to rotate following the traveling steel plate.
[0007]
In addition, when the molten metal has entered the gap between the roll shaft and the ceramic sleeve and the roll is lifted from the bath, the molten metal is retained in the gap and solidifies as the temperature decreases. On the other hand, the roll that has been thermally expanded during use in the bath starts to cool and shrink due to a drop in temperature. Therefore, there has been a problem that the ceramic sleeve is subjected to a compression action by the metal solidified in the gap and cracks.
[0008]
In the above conventional example, only the roll body is made of ceramics, and the roll shaft and presser ring are made of heat-resistant steel, and the retaining ring is made of brass, so the corrosion resistance and wear resistance to the molten metal bath are still insufficient. It was. Therefore, it is sufficient that the entire roll can be made of ceramics. However, sintered ceramics are manufactured by, for example, putting ceramic raw material powders in a mold, forming them with a cold isostatic press, and then firing them. There is a limit in size and shape. In particular, in the case of a long product such as a roll, in order to manufacture the entire roll integrally with ceramics, there have been many restrictions on the length dimension.
[0009]
In response to this problem, the inventor made a hollow roll body part and a roll shaft part separately from ceramics having excellent corrosion resistance, heat resistance, and wear resistance, and then formed one piece at one end of the roll body part. There has already been proposed a support roll for continuous molten metal plating in which a roll shaft portion is assembled by screwing another roll shaft portion to the other end portion of the roll body portion.
[0010]
However, in the proposed support roll, when the shape of the screw made of ceramics is such that the crests 12 and the troughs 13 of the screw 11 as shown in FIG. There is a problem that the screw is easily contacted, the stress acting on the screw portion becomes extremely high, and the screw is easily broken.
[0011]
Therefore, the present invention aims to solve such problems, and is excellent in corrosion resistance, heat resistance, and wear resistance, and is easy to rotate by reducing the weight of the roll, preventing cracking when the roll is lifted from the bath. It is an object of the present invention to provide a roll for continuous molten metal plating that can lengthen the entire roll with ceramics and prevent screw breakage during screw joining.
[0012]
[Means for Solving the Problems]
The roll for continuous molten metal plating of the present invention is used by continuously immersing it in a molten metal bath in which a roll body and a roll shaft are formed hollow with ceramics, and the roll shaft is screwed to the inner surface of the roll body. A roll for molten metal plating, characterized in that flat portions are formed at the crest and trough of the screw to be joined. Secondly, a buffer material is interposed between the screws to be joined. Third, the surface of the screw to be joined is plated. Fourth, the surface of the screw to be joined is sprayed.
[0013]
[Action]
In the roll for continuous molten metal plating according to the present invention, the shape of the screw made of ceramics is formed flat on the crest and trough of the screw as shown in FIG. 3, thereby improving the rigidity of the screw and making it difficult to break. . It is preferable to avoid the stress concentration by processing the crest and trough corners of the screw into a curved shape.
[0014]
Further, by interposing a buffer material between the screws to be joined, local contact between the screws is suppressed and stress concentration is avoided. The buffer material is preferably a heat-resistant inorganic adhesive having a thermal expansion coefficient close to that of ceramics, and is applied to the screw surface or filled between a male screw and a female screw.
[0015]
Further, by applying plating or thermal spraying to the surfaces of the screws to be joined, local contact between the screws is suppressed and stress concentration is avoided. The plating applied to the surface of the screw is preferably excellent in heat resistance and wear resistance, such as nickel-phosphorous plating, and the plating thickness is desirably 50 μm or less. The thermal spraying applied to the surface of the screw is preferably excellent in heat resistance and wear resistance, and the thermal spraying thickness is preferably 200 μm or less by a known method such as plasma spraying. In the present invention, it is further desirable to combine the formation of flat portions at the crests and troughs of the screw and interposing a buffer material, plating the surface of the screw, or spraying the surface of the screw.
[0016]
Since the roll body part and the roll shaft part are made of ceramics, the roll for continuous molten metal plating of the present invention has sufficient corrosion resistance, heat resistance, and wear resistance for the molten metal bath. Among ceramics, silicon nitride ceramics such as silicon nitride and sialon are preferable because they have a small thermal expansion coefficient of about 3 × 10 ⁻⁶ / ° C., excellent thermal shock resistance, and high temperature and strength.
[0017]
Since each of the roll body and the roll shaft is a hollow body having a through hole in the direction of the rotation axis, the entire weight of the roll becomes light. Accordingly, the rotational inertia force of the roll is reduced, and the roll can be rotated following the start-up of the operation and the change in the traveling speed of the steel sheet.
[0018]
In the present invention, there is only a portion where there is a possibility that a molten metal invades, and the roll barrel portion and the roll shaft portion are joined, and when the roll is lifted out of the bath, a hollow roll barrel is formed. Since the molten metal is smoothly discharged from the openings at both ends of the through-hole formed by the portion and the roll shaft portion, it is possible to prevent the roll from cracking due to the molten metal remaining in the gap and solidifying. In addition, it is desirable to provide holes such as circles, ellipses, and squares for discharging molten metal on the outer periphery of the roll shaft, and it is equally divided on the circumference of the roll shaft or in a staggered arrangement. May be drilled.
[0019]
In addition, after the roll body and the roll shaft are separately manufactured, one roll shaft is screwed into one end of the roll body and another roll shaft is screwed into the other end of the roll body. A roll made entirely of ceramics can be easily elongated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example in which sialon ceramics is applied to a support roll of a continuous molten metal plating apparatus will be described. FIG. 1 shows an outline of a continuous molten metal plating apparatus. In FIG. 1, a steel sheet 1 delivered from an annealing furnace passes through an antioxidant snout 2 and is immersed in a molten metal bath 3 of zinc. The traveling direction of the steel plate 1 is changed by the sink roll 4 suspended at the bottom of the molten metal bath 3 and is raised to the bath surface side. Next, the steel plate 1 is sandwiched between the support rolls 5 composed of a pair of rolls immersed and supported near the bath surface to prevent warpage and vibration of the steel plate 1. Subsequently, high-speed gas is sprayed by the gas wiping 6 above the surface of the molten metal bath 3, and the thickness of the adhesion plating is uniformly adjusted by the gas pressure and spray angle. In this way, the plated steel plate 1 is sent to the next step. This continuous molten metal plating apparatus was equipped with a support roll 5 having the features of the present invention.
[0021]
FIG. 2 shows a cross-sectional view of a support roll 5 which is an example of the present invention. In FIG. 2, the support roll 5 is configured by screwing a roll shaft part 8 and a tightening ring 9 to both ends of the roll body part 7. The support roll 5 was formed of sialon ceramics having excellent corrosion resistance, thermal shock resistance, and high temperature and high strength characteristics with respect to the molten metal bath.
[0022]
In this example, the roll body 7 of the support roll 5 was produced as follows. First, α-Si ₃ N ₄ powder having an average particle diameter of 0.8 μm: 87 wt%, Al ₂ O ₃ powder having an average particle diameter of 0.5 μm: 5 wt%, AlN solid solution powder having an average particle diameter of 0.5 μm: 3 A mixture obtained by blending 5% by weight of Y ₂ O ₃ powder having an average particle size of 1.0 μm: 5% by weight, adding 0.5% by weight of polyvinyl butyral as a binder per 100 parts by weight of the raw material powder, and stirring the mixture, CIP molding was performed at a pressure of 1000 kg / cm ² . Next, sintering was performed at 1750 ° C. for 5 hours under normal pressure and nitrogen atmosphere to obtain a sialon ceramic sintered body.
[0023]
The obtained sialon ceramic sintered body had a density of 99.1% of the theoretical density, Vickers hardness Hv at room temperature, 1580, and bending strength by three-point bending at room temperature was 100 kgf / mm ² . The sintered body was machined into a predetermined shape to produce a hollow cylindrical roll body 7. The roll shaft portion 8 and the fastening ring 9 were also made of a sialon ceramic sintered body in the same manner as the roll body portion 7.
[0024]
The roll body 7 is a hollow cylindrical body having an outer diameter of 210 mm, an inner diameter of 165 mm, and a length of 1500 mm. The outer peripheral surface of the roll body portion 7 is a surface through which the steel plate 1 comes into contact. A stepped portion 71 having a different thickness was provided on the inner surface of the roll body portion 7. A screw groove 72 used for joining with the roll shaft portion 8 is provided on the center side of the roll body portion 7 with the stepped portion 71 interposed therebetween. Here, the tightening direction of the thread groove 72 is referred to as a positive direction. Further, a thread groove 73 used for joining with the tightening ring 9 is provided on the end surface side of the roll body portion 7 with the stepped portion 71 interposed therebetween. The thread groove 73 was formed so that the tightening direction was negative.
[0025]
The roll shaft portion 8 is formed of a hollow body and is rotated through a spindle (not shown) by a drive motor (not shown) provided outside the molten metal bath. On the outer surface of the roll shaft portion 8, a convex protrusion 81 serving as a fitting portion with the roll body portion 7 was provided. A thread groove 82 used for joining to the roll body 7 is provided on the end face side of the roll shaft portion 8 in the vicinity of the protrusion 81. One roll shaft portion 8 (right shaft portion in FIG. 2) is a drive shaft, and a clutch member (not shown) for coupling with the spindle is attached to the end portion of the small diameter shaft. In this case, the clutch member was also made of a sialon ceramic sintered body. The other roll shaft portion 8 is a driven-side shaft portion supported by a slide bearing.
[0026]
The tightening ring 9 is a ring body, and a thread groove 91 used for joining to the roll body 7 is provided on the outer surface thereof.
[0027]
After preparing such roll body 7, roll shaft 8, and tightening ring 9, the support roll 5 of the present invention was assembled. First, the roll shaft portion 8 is screwed to the inner surface of the roll body portion 7 so that the end surface of the protrusion 81 of the roll shaft portion 8 is in contact with the stepped portion 71 of the roll body portion 7 at the center side of the roll body portion 7. The roll shaft portion 8 was positioned in the roll axis direction. The roll shaft portion 8 and the roll body portion 7 were screw-joined so as to be tightened with respect to the rotation direction of the roll. On the other hand, a gap was provided between the outer surface of the roll shaft portion 8 and the inner surface of the roll barrel portion 7 on the end surface side of the roll barrel portion 7, and the tightening ring 9 was inserted into this gap. Then, the tightening ring 9 was screwed to the inner surface of the roll body portion 7 so that the front end surface of the tightening ring 9 was in contact with the protrusion 81 of the roll shaft portion 8. The tightening ring 9 and the roll body portion 7 are screw-joined in a reverse screw direction that is a tightening rotation direction opposite to the screw joint of the roll shaft portion 8 and the roll drum portion 7.
[0028]
In joining the roll body portion 7 and the roll shaft portion 8, screw joining shown in FIG. 3 was performed. In FIG. 3, the crest 12 and the trough 13 of the screw 11 have a flat portion 14, and the corner 15 is processed into a curved shape. In addition, a heat resistant adhesive was filled in the gap 16 between both screws. Also in the joining of the roll body 7 and the tightening ring 9, the same joining structure as that of the screw joining of the roll body 7 and the roll shaft portion 8 was adopted.
[0029]
In the continuous molten metal plating apparatus shown in FIG. 1, the SUS300 type stainless steel plate having a plate thickness of 2 mm and a plate width of 1300 mm is galvanized in the continuous hot metal plating apparatus shown in FIG. After that, the support roll 5 was hardly eroded and worn, and the service life was remarkably improved, and the screws provided on the roll body, the roll shaft and the fastening ring were not broken during use. In addition, since the roll weight is light, it is easy to rotate, and it follows the changes in the starting speed and the running speed of the steel plate well. Further, the occurrence of vibration of the roll and steel plate due to wear can be suppressed, so a steel plate with high quality plating characteristics was obtained. .
[0030]
As mentioned above, although the Example of the support roll was described, it cannot be overemphasized that this invention is applicable to various rolls for continuous molten metal plating, such as a sink roll.
[0031]
【The invention's effect】
The roll for continuous molten metal plating of this invention can prevent that the screw formed in each member breaks during use. In addition, it has excellent corrosion resistance, heat resistance, wear resistance and the like, and has a long service life. Since the roll weight is light, it rotates following the change in the running speed of the steel plate. When the roll is lifted from the bath, it is difficult for the molten metal to enter the gap and cracking of the roll can be prevented. Therefore, it is possible to stably produce a steel plate having high quality plating characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic view of a continuous molten metal plating apparatus.
FIG. 2 is a cross-sectional view of a support roll as an example of the present invention.
FIG. 3 is a schematic cross-sectional view of a screw shape according to the present invention.
FIG. 4 is a schematic cross-sectional view of a conventional screw shape.
[Explanation of symbols]
1 steel plate, 2 snout, 3 molten metal bath, 4 sink roll,
5 Support roll, 6 Gas wiping, 7 Roll body,
8 Roll shaft, 9 Clamping ring, 11 Screw, 12 Crest,
13 valley part, 14 flat part, 15 corner part, 16 gap

Claims (5)

This is a roll for continuous molten metal plating that is used by immersing it in a molten metal bath in which the roll body and roll shaft are formed hollow with ceramics and the roll shaft is screwed to the inner surface of the roll body. A roll for continuous molten metal plating, characterized in that flat portions are formed at the crest and trough of a screw. This is a roll for continuous molten metal plating that is used by immersing it in a molten metal bath in which the roll body and roll shaft are formed hollow with ceramics and the roll shaft is screwed to the inner surface of the roll body. A roll for continuous molten metal plating, characterized in that a buffer material is interposed between the screws. This is a roll for continuous molten metal plating that is used by immersing it in a molten metal bath in which the roll body and roll shaft are formed hollow with ceramics and the roll shaft is screwed to the inner surface of the roll body. A roll for continuous molten metal plating, wherein the surface of a screw is plated. This is a roll for continuous molten metal plating that is used by immersing it in a molten metal bath in which the roll body and roll shaft are formed hollow with ceramics and the roll shaft is screwed to the inner surface of the roll body. A roll for continuous molten metal plating characterized by spraying the surface of a screw. The roll for continuous molten metal plating used by being immersed in the molten metal bath according to any one of claims 1 to 4, wherein the ceramic is a silicon nitride ceramic.

Images