JP2002180222A - Immersion member for hot dip metal coating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion member for hot dip metal coating bath by which durability against thermal shock/repeated thermal fatigue can be improved and replacement at wear and breakage can be facilitated. SOLUTION: The immersion member for hot dip metal coating bath is provided to a pot roll device immersed in a hot dip metal coating bath. This immersion member is a silicon nitride type or silicon carbide type ceramic member fitted to a part or the whole of a sliding part at least of a pot-roll shaft sleeve member or a bearing member of the pot roll device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dipping member for a hot-dip metal plating bath in a continuous hot-dip metal plating apparatus for a steel plate or the like.

[0002]

2. Description of the Related Art As a method for obtaining a metal plated plate, as shown in FIG. 1, a metal plate heated and annealed in a heating furnace is led to a molten metal tank, and the molten metal is plated on the metal plate, and a pot roll and a guide roll are formed. And a method of continuously pulling up a metal-plated sheet by using a conventional method is widely used. More specifically, the plating method for a metal plate by a continuous hot-dip metal plating apparatus, when a steel plate is used as the metal plate, insert the steel plate whose surface has been cleaned and activated as a pretreatment into a molten metal bath,
After changing the direction with a pot roll in the bath, the steel sheet is passed between two guide rolls to suppress warpage in the width direction. Thereafter, the steel sheet is further lifted upward, and excess molten metal adhering to the steel sheet surface immediately above the plating bath is removed by wiping of a high-pressure gas or the like, and adjusted to a predetermined plating amount to produce a molten metal-plated steel sheet. Is what you do.

[0003] Generally, 24Cr-12Ni stainless steel having good corrosion resistance is used for a bearing member and a shaft portion sleeve member of a pot roll immersed in the molten metal plating bath. Stainless steel has low reactivity with molten metals such as molten zinc and molten aluminum, and has good corrosion resistance, but its wear resistance is not sufficient. In particular, the bearing member is extremely narrow with the shaft sleeve member. Since it is always in contact within the range (upper half), the amount of wear is larger than that of the shaft sleeve member, and the service life is as short as about 4 to 8 days. As the wear of the bearing members progresses,
Since the steel plate flaps or the like and good plating cannot be performed, the member must be pulled out of the molten metal plating bath and the bearing member must be replaced. Therefore, even if there is no abnormality in other members such as a pot roll immersed in the hot-dip metal plating bath, it is necessary to stop the operation and pull up the entire part immersed in the hot-dip metal plating bath. At this time, since the temperature is rapidly cooled from the bath temperature to room temperature, damage such as thermal shock damage may occur to other parts, and the whole part may be replaced at a time, resulting in a very large loss in production. . For this reason, various proposals have been made to extend the life of a roll used in a molten metal plating bath.

In JP-A-3-253547 and JP-A-5-44002, alumina or silicon nitride sialon is used for a bearing member and a shaft sleeve member in a molten zinc bath, and a rotating pot roll is externally mounted. Has been proposed for rotational drive. However, in this proposal, only zinc is used as the molten metal, and only the sliding wear amount and the wear coefficient are used as selection criteria, and heat shock resistance, wettability with the molten metal, and the like are not considered. Further, with respect to alumina or silicon nitride / sialon ceramics, there is no description of optimum conditions for various characteristics such as composition, firing conditions (density, structure), mechanical characteristics, and sliding surface roughness.

Further, it is known that monolithic silicon carbide and zirconia ceramics are inferior to silicon nitride and sialon in thermal shock resistance.

[0006] Based on the contents disclosed in the above prior art, a commercially available silicon nitride ceramic densified to a relative density ratio of 99% using yttria and alumina, which are general firing aids, is used in a molten aluminum bath. As a result of the sliding and thermal shock tests, the abrasion loss in the zinc bath was greatly exceeded, and it was broken only by performing air cooling from the molten aluminum bath three times.

[0007]

The above-mentioned technique relating to the plain bearing is characterized in that the surfaces of the bearing member and the shaft sleeve member that come into contact with each other have a better corrosion resistance in a molten metal bath and a higher hardness than stainless steel. It is intended to extend the life of the bearing by coating with ceramics or by using a cermet, a cemented carbide, a ceramic sintered body, or the like. However, the optimal combination of the bearing member and the shaft sleeve member for the molten metal plating bath member is
Considering the properties of the material, such as thermal shock resistance, high toughness, and poor wettability, is a much more important selection factor. It is indispensable to increase the durability against thermal shock and repeated thermal fatigue caused by air cooling when pulling a pot roll heated to several hundred degrees Celsius, and to control the wettability to molten aluminum, especially among molten metals.

[0008] Further, if the replacement work can be performed quickly, the opportunity loss in operation can be reduced. Therefore, it is also desired to provide a structure in which the members can be easily replaced.

Accordingly, an object of the present invention is to provide an immersion member for a hot-dip metal plating bath in which the durability against thermal shock and repeated thermal fatigue is greatly improved, and at the same time, the replacement work at the time of wear and breakage is remarkably simplified. It is in.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides an immersion member for a molten metal plating bath which can be used repeatedly and stably for a long time in a molten metal plating bath and can be easily replaced at the time of replacement work. (1) An immersion member attached to a pot roll device immersed in a molten metal plating bath, wherein the immersion member is at least a pot roll shaft portion of the pot roll equipment. A immersion member for a molten metal plating bath, wherein the immersion member is a silicon nitride-based or silicon carbide-based ceramic member fitted to a part or all of a sliding portion of a sleeve member and a bearing member. Immersion member, the immersion member for the molten metal plating bath according to (1), comprising a plurality of columnar members,
(3) The immersion member for a molten metal plating bath according to (2), wherein the columnar member is fitted in the axial direction of the bearing portion. (4) The sliding surface of the columnar member in the rotation direction is a flat surface or the immersion member. The immersion member for a hot-dip metal plating bath according to (3), which is an arc-shaped surface having a radius of curvature equal to or larger than the radius of curvature of the pot roll shaft sleeve member. (5) The columnar member is fitted in the pot roll shaft sleeve member in the axial direction. (2) The immersion member for a hot-dip metal plating bath according to (2), (6) the immersion member for a hot-dip metal plating bath according to (5), wherein the sliding surface of the columnar member is an arc-shaped surface having a radius of curvature equal to or less than the radius of curvature of the bearing member. (7) The axial sliding surface of the columnar member is uneven and / or corrugated, and the sliding surface height of the convex portion is uniform in the axial direction (3) or (5). (8) The immersion member for a hot-dip metal plating bath according to (8), wherein the ceramic member has a sintered body density of 95% or more of a theoretical density. (1) to (7), (9) the ceramic member is a silicon nitride sintered body containing a chromium compound in a volume fraction of 1 to 8%. (10) The chromium compound is chromium nitride.
(9) The immersion member for a hot-dip metal plating bath according to (9), wherein the ceramic member is a composite metal boride having a volume fraction of 20%.
The immersion member for a hot-dip metal plating bath according to (8), which is a silicon carbide sintered body containing about 70% to 70%, wherein the composite metal boride is a Ti-Zr-B solid solution and / or a Ti-Hf-B solid solution. (11)
A dipped member for a hot-dip metal plating bath as described above.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors reviewed the roll bearing in a molten zinc bath proposed in JP-A-3-253547 and JP-A-5-44402 and found that a molten aluminum bath having a higher melting point than zinc. Above all, it is possible to suppress defects such as sliding wear and chipping and cracking around the thermal fatigue portion, which were difficult with the conventional technology, mechanical shock when landing after pulling up the roll, and taking out from the bath and cooling by air. As a result, a structure, a shape and a material of a bearing member having excellent durability against thermal stress repeatedly applied have been found. These defects such as chipping and cracks are generated and propagated by thermal shock and mechanical shock, and when the member has many holes, low strength, low toughness, and good wettability with molten metal. , Low thermal conductivity, low thermal shock, when the sliding surface is rough, etc., and the sliding wear is remarkable when the sliding part is not a surface, but is in line contact or point contact. It was confirmed that it was suppressed.

The immersion member for a molten metal plating bath of the present invention comprises:
An immersion member attached to a pot roll device immersed in a molten metal plating bath, wherein the immersion member is at least part of a sliding portion of a pot roll shaft sleeve member or a bearing member of the pot roll equipment or A silicon nitride-based or silicon carbide-based ceramic member fitted to all. The immersion member for the hot-dip metal plating bath is preferably a silicon nitride-based or silicon carbide-based ceramic from the viewpoint of high thermal shock resistance, high toughness, and high wear resistance.

From the viewpoint of easy handling of the immersion member,
It is preferable to fit a plurality of columnar members. Regarding the embedding shape, a surface directly sliding on the pot roll is preferably a flat surface or an arc-shaped surface convex above the radius of curvature of the pot roll shaft sleeve member, but is not particularly limited.
The cross-sectional shape in the direction perpendicular to the axis may be a polygon, a semicircle, or a circle having a quadrangle or more. It is not preferable to arrange the columnar members in the rotation direction. In order to limit to the compressive stress load, it is recommended to arrange the line contact and point contact in the same direction as the rotation direction. In addition, a potion other than compressive stress is applied to the embedding material on an upwardly convex arc-shaped surface or a concave arc-shaped surface having a radius of curvature equal to or greater than the radius of curvature of the pot roll shaft sleeve member, and the probability of breakage is higher than compression. It is expected to be. Preferably, if a ceramic bearing piece having a lower side longer than the upper side and having an isosceles trapezoidal cross section is used, the positioning is easy without using a wedge (wedge) or an adhesive,
It is possible to apply only compressive stress. further,
As shown in iii) to iv) of FIG. 2, by sequentially providing irregularities or waveforms in a direction parallel to the rotation axis of the columnar embedding material, it is possible to change from line contact to point contact, so that the plating bath It is assumed that the rotation can be smoothed because the flow of the water can be promoted. Whether the concavo-convex pattern or the corrugated pattern with the adjacent embedding material is reversed or in-phase should be determined by the fluidity of the plating bath and the number of rotations of the pot roll. With such a shape, it becomes difficult for molten metal to collect in the bearing portion, and work efficiency such as repair work can be improved.

The sliding portion of the rotary shaft member of the pot roll may be made of the same ceramic material or ultra-hard particles as those of the bearing member dispersed in a binding metal (a binder such as copper, titanium or zinc). In this case as well, if the curvature on the bearing side is not greater than the curvature of the shaft as described above, a tensile stress for pushing and spreading is applied to the bearing member, which is completely unsuitable. If it is flat or arc-shaped, machining is easy, and if the curvature is large, it is easily expected that the stability of the rotating shaft on the pot roll side is slightly increased. Further, when fitting to the rotating shaft, if the curvature of the embedding material on the rotating shaft side becomes larger than the curvature of the bearing, the shape of the embedding material becomes extremely large or too thin, which is not preferable.

By forming this member into the above shape, the absolute value of the difference in expansion and contraction in the bath and in air cooling caused by the difference in thermal expansion coefficient between the member and the metal member to which the member is fitted can be reduced. In addition to reducing the compressive or tensile stress applied to the ceramic member, the effect of facilitating densification in manufacturing the ceramic member is brought about. The shape of the fitting member is preferably 5 mm or more and 20 mm or less, and it is preferable to use two or more columnar members. If the thickness is less than 5 mm, the compressive strength of the ceramic member is low, and wear marks formed on the sliding surface after use are polished, so that the total life is undesirably short when recycled. With only one columnar member, stability during rotation cannot be obtained at all, which is not appropriate. Further, the thickness is preferably in the range of 5 to 20 mm from the viewpoint of imparting strength against mechanical impact when handling the roll arm. The width depends on the diameter of the pot roll and the number of column members to be fitted, but is preferably 10 to 30 mm. Further, the length of the columnar member is uniquely determined by the length of the sleeve of the metal member to which the member is fitted. Generally, 80-200mm
The degree is often used.

As shown in FIG. 3, the compression or tensile stress caused by the difference in the coefficient of thermal expansion between the metal ring member and the molten metal used to hold the ceramic bearing is reduced. Therefore, it is preferable that the gap between the fitting portions between the ceramic member and the metal member be 1 mm or less.

Contrary to the above, it is also possible to fit a columnar member whose bearing portion is formed of a circular integral product and has an arc-shaped surface convex upwardly below the curvature of the bearing to the pot roll shaft portion sleeve. It is. However, care must be taken to obtain sufficient fixing strength when embedding in the bearing part.In order to reduce the frictional resistance when the bearing part comes into contact, the sliding part is not a flat surface but has a curvature smaller than the inner diameter of the bearing part. A small arcuate curved surface is most preferred. Further, it is necessary to fit over the entire circumference, two or more, preferably three or more, more preferably
Stable rotation can be obtained with 5 or more. If the number is less than two, the chance of sliding at portions other than the columnar member increases, the metal shaft sleeve material is selectively worn away from the columnar member, and the life extension cannot be expected.

As a method for simultaneously improving properties such as low wettability with molten metal, high thermal conductivity, high thermal shock resistance, and abrasion resistance, a sufficiently dense SiC or Si ₃ N ₄ sintered body is used.
It is effective to control the structure of the sintered body due to the formation of a phase (such as a Ti-Zr-B solid solution or a chromium compound represented by Cr ₂ N). Such a sintered body structure can also provide an effect of significantly improving chipping resistance, cracking and other chipping resistance as compared with the bearing made of monolithic silicon nitride and monolithic sialon described in the prior art. Ti _x Zr _y B
_The metal composite boride represented by No. 2 has the effect of increasing the toughness and the hardness by dispersing in the silicon carbide sintered body, and dramatically improves the fracture resistance and the wear resistance. Cr
_The chromium compound represented by 2N has the effect of increasing toughness by being dispersed in a silicon nitride-based sintered body, dramatically improving high-temperature strength, and exhibiting characteristics of excellent creep resistance and corrosion resistance. Give. On the other hand, it has the effect of reducing the wettability to the molten metal.

Regarding the surface roughness of the sliding portion, it is difficult to adhere the molten aluminum, and in order to reduce the dynamic friction coefficient, R _max ≤
It is effective to finish to 0.2 μm. If it exceeds 0.2 μm, even if the wettability with the molten aluminum is low, the mechanical adhesion ratio is increased and the dynamic friction coefficient is remarkably increased. In the case of contact on a flat surface or an upwardly convex arc surface, machining is relatively easy, so R _max ≤ 0.1 μm
Finishing is often cost effective.

Further, if the embedding material has a columnar member shape (FIG. 2), if it is a simple flat surface or an arcuate surface, or if it is irregular or corrugated in the longitudinal direction, it can be applied by simple grinding. The service life of the hot-dip metal plating bath member can be extended without increasing the finishing cost.

Silicon carbide (SiC) is a substance with strong covalent bonding
Sintering in inert gas at normal pressure (such as Ar)
It is difficult to densify with a theoretical density ratio of 95% or more.
Various additives may be added. 95% of theoretical density
Open pores almost disappear and closed pores dominate the sintered body structure.
To prevent the penetration of plating bath components,
Density range where wear rate can be significantly reduced
You. As sintering aids, for example, carbon black, various types
Borides, alumina, organic substances that can be carbon sources,
Luminium, aluminum nitride, etc. can be used
Wear. Silicon nitride (Si _ThreeN_Four) Is also cost-effective
Since sintering in pressurized nitrogen gas is difficult by itself,
95% or more densification, even if various additives are added
I do not care. As sintering aids, for example, silica, aluminum
Na, yttria, ferrous oxide, magnesia, AlN-Si_ThreeN_Four
-SiO_Two-Al_TwoO_ThreeEutectic, aluminum nitride, various rare earth acids
And the like can be used.

As a sintering method, a normal pressure (no pressure) sintering method,
Any of a gas pressure sintering method, a hot isostatic press sintering method, and a hot press method can be used, and one or more sintering methods can be combined.
Atmospheric pressure sintering is performed while flowing nitrogen gas or Ar gas.
A dense sintered body is easily obtained. In the molten metal bath member with a complicated shape, in order to achieve high density, after normal pressure sintering, further in a nitrogen gas or Ar gas pressurized atmosphere,
It is preferable to perform hot isostatic press sintering. Among them, the range of the maximum temperature during normal pressure sintering is 1550 to 1750 ° C for silicon nitride and 1900 to 2150 ° C for silicon carbide, and the holding time at the maximum temperature is 2 hours or more. It is desirable. In the case of silicon nitride, if the temperature is lower than 1550 ° C., a sufficiently high density cannot be obtained, it is difficult to form a high melting point crystalline phase in the grain boundary phase, and a high fracture toughness value cannot be obtained. At temperatures higher than 1750 ° C, some of the sintering aids
It decomposes and deterioration of the firing furnace is extremely unfavorable. As the holding time during normal pressure sintering, the crystal phase transition of silicon nitride as a main raw material used as a raw material sufficiently proceeds, and at least 2 hours in the above sintering temperature range for uniformization of a grain boundary phase. Must be maintained. In the case of silicon carbide, if it is lower than 1900 ° C., a sufficiently high density (relative density ≧ 95%) cannot be obtained, and the particle dispersing effect is not sufficiently exhibited, so that a high fracture toughness value cannot be obtained. Also, 2150 ° C
At higher temperatures, abnormal grain growth may occur, which is not preferable.

As for the silicon carbide ceramics, the metal composite boride is incorporated into the silicon carbide sintered body in a volume fraction of 20% by volume.
When the dispersion is less than 70%, the toughness is insufficient, and the volume fraction is 70 volumes.
If it exceeds%, it is difficult to densify to a relative density of 95% or more during normal-pressure sintering, and the inherent hardness and high-temperature strength of silicon carbide cannot be obtained. In addition, silicon carbide and Ti-Zr-B solid solution particles and / or Ti
Residual stress is generated in the vicinity of the dispersed Ti-Zr-B solid solution particles and / or Ti-Hf-B solid solution particles due to the difference in thermal expansion and the difference in Young's modulus from -Hf-B solid solution particles, Has the effect of dispersing the fracture energy upon fracture, has the effect of significantly improving toughness, and also has the effect of improving abrasion resistance; therefore, Ti-Zr-B solid solution particles and T
i-Hf-B solid solution particles are preferred.

The Ti-Zr-B solid solution particles and / or Ti-Hf-B
Solid solution particles are hard and oxidation-resistant high-melting compounds with an hcp structure that remain as dispersed particles in a silicon carbide-based sintered body after sintering and improve the hardness and fracture toughness of the entire sintered body. Has an action.

Ti-Zr-B solid solution particles and / or Ti-Hf-B solid solution
The composition of the body particles is Ti_1-xZr_xB _Two, Ti_1-xHf_xB_TwoIn table
The range of x is preferably 0.02 to 0.25, more preferably
Is 0.02 to 0.05. TiB_TwoTo ZrB_TwoAnd HfB_TwoSolid solution
And TiB_TwoHardness and fracture toughness increase as compared to a single substance. I
However, if x is smaller than 0.02, Zr, Hf TiB
_TwoThe effect of solid solution in the alloy is poor, and it is not possible to achieve sufficiently high hardness.
On the other hand, if x exceeds 0.25,
Rix's thermal expansion coefficient is far from silicon carbide
Therefore, it is difficult to densify during sintering, and sintering with low relative density
It is easy to become a body and the fracture toughness value is likely to decrease
You. The average particle diameter of the solid solution particles is 1 to 10 μm.
It is desirable. More preferably, it is 3 to 5 μm. average
If the particle size is less than 1 μm, it is difficult to obtain a contribution to toughness,
On the other hand, if it is larger than 10 μm, the hardness and fracture toughness decrease.
It is easy to invite.

On the other hand, regarding silicon nitride ceramics,
1 volume% chromium compound in silicon nitride sintered body by volume fraction
If the dispersion is less than 10, sufficient toughness and high-temperature high strength cannot be obtained, and if the dispersion exceeds 8% by volume, the creep resistance and the corrosion resistance decrease. Among the chromium compounds, chromium nitride (Cr ₂
N) It is effective to disperse the particles. In particular, chromium nitride (Cr ₂ N) particles, which are hard and have excellent oxidation resistance at 1200 to 1400 ° C. in an oxygen-containing atmosphere, provide physical and chemical stability, thermal stability, and mechanical stability to silicon nitride sintered bodies. It has excellent mechanical stability and can provide long-term durability. In particular, chromium nitride (Cr ₂ N) particles generate residual stress in the vicinity of dispersed particles after sintering due to a difference in thermal expansion or a difference in Young's modulus between the silicon nitride phase and the grain boundary phase. It has the effect of dispersing the fracture energy at the time of fracture, has the effect of increasing the fracture toughness, significantly improving the fracture resistance, and also improving the thermal shock resistance. The chromium nitride (Cr ₂ N) particles are hard and oxidation-resistant hcp
It is a high melting point compound having a structure and remains as dispersed particles in a silicon nitride sintered body after sintering, and has an effect of improving the hardness of the entire sintered body. The average particle size of chromium nitride (Cr ₂ N) particles is
Desirably, it is 0.5 to 10 μm. More preferably 5-8
μm. When the average particle size is smaller than 0.5 μm, it is difficult to obtain a contribution to toughness. On the other hand, when the average particle size is larger than 10 μm, hardness and thermal shock resistance are liable to be reduced.

[0027]

Next, examples of the present invention will be described together with comparative examples.

Examples 1 to 5 Silicon nitride (Si ₃ N ₄ ) powder (α type,
Chromium nitride (Cr ₂ N) powder with a purity of 99.7% and an average particle size of 0.3 μm)
(Average particle size 6.5 μm), yttria (Y ₂ O ₃ ) powder (average particle size 1 μm
m), magnesia (MgO) powder (average particle size 0.8 μm), alumina
(Al ₂ O ₃ ) powder (average particle size 0.3 μm), ferric oxide (Fe ₃ O ₄ ) powder
(Average particle size of 3.5 μm), and a polytype 21R composition powder as an example of the eutectic AlN-Si ₃ N ₄ -SiO ₂ -Al ₂ O ₃ (average particle size of 2.2 μm
m), silicon carbide (SiC) powder (α type, purity 98.5%, average particle size 0.4 μm) and titanium boride (TiB ₂ ) powder (average particle size 3.5 μm).
m), zirconium boride (ZrB ₂ ) powder (average particle size 5.5 μm),
Boron carbide (B ₄ C) powder (average particle size 1.5 μm), carbon black powder (average particle size 0.02 μm) predetermined amount shown in Table 1 (% by mass)
The resulting mixture was kneaded for 24 hours with a ball mill using purified water as a dispersion medium during kneading. The amount of purified water added was also 100 g with respect to 100 g of the whole ceramic powder material.

Next, the obtained mixed powder was molded and sintered. The molding conditions were a cold isostatic pressure of 150 MPa, and a 100 mm square, 22 mm high plate-like molded body was obtained. As the sintering conditions, under nitrogen gas or Ar gas flow, pressureless sintering of 4 to 8 hours at each temperature shown in Table 1, and hot isostatic press sintering were added as necessary .

From the obtained sintered body, 15 mm × 20 mm × length 80
The mm fixed-side bearing test material was ground and subjected to a bearing test in a molten aluminum bath (FIG. 4).

A test piece for evaluating mechanical properties was cut out from the remaining material obtained when cutting the test material having a size of 15 mm × 20 mm × 80 mm from the plate-like sintered body, and its characteristics were evaluated. Hardness was measured as Vickers hardness at an indentation load of 10 kg. Regarding toughness, the fracture toughness value K _IC was measured at room temperature by the SEPB method of JIS R1607. Further, the thermal shock resistance was evaluated by a quenching temperature difference ΔT in which a bending test piece was heated to a predetermined temperature in the atmosphere, then rapidly cooled in water, and the bending strength began to deteriorate. The sintered body density was measured as a relative density by the Archimedes method. The wettability was measured by a contact angle between a normal molten droplet and a horizontal plate.

Table 2 shows the Archimedes density and mechanical properties of each of the obtained sintered bodies, and the results of evaluation of the bearings in the aluminum bath shown in FIG. 4 for each compounding system. The test in the aluminum bath was performed under the following conditions. (1) Rotating side bearing test material: Carbide ring material φ90mm x height 60mm (2) Fixed side bearing test material: Ceramic test material 15mm
3 pieces of 20mm x 80mm length (3) Molten aluminum temperature: 680 ℃ (4) Pushing force: 30-50N (5) Sliding speed: 2-3m / sec (6) Sliding time: 1 Time (7) Finished surface roughness before test: R _max = 0.2 μm (approx. △△△△, see JIS B0031) (8) Repeated thermal fatigue test: After soaking in bath for 1 hour, pulling up from bath for 30 minutes Repeat air cooling (9) Wettability evaluation test: 50mm square x 10mm aluminum block
After melting at 680 ° C on a plate-like ceramic with a thickness, observe and measure through a viewing window from outside the furnace.As a method of obtaining the amount of wear under the conditions (1) to (7) above, the wear generated on the rotating side and the fixed side was determined. Trace depth h _r , h _s
Was measured with a surface roughness meter. Further, the presence or absence of damage around the wear mark, the chipping depth, and the crack depth were evaluated by a fluorescent flaw detection method or an optical microscope observation of the polished surface of the cross section. The required amount of grinding of the bearing rubbing surface during reuse is 1.2 times the wear mark depth h if no cracking or chipping damage is observed around the wear mark, and 1.2 times the chipping depth if chipping occurs. , And if cracks are occurring,
It is shown in Table 2 as 1.2 times the crack depth.

Comparative Examples 6 to 9 In Comparative Examples 6 to 8, when a commercially available sialon was used and a part of the ring was fitted into a bearing (Comparative Example 6), commercially available silicon nitride ceramics having different compositions were used. In the case of using a sialon-based material and manufacturing it with an all-around ring (Comparative Example 7), when using a commercially available sialon and fitting a part of the ring into a bearing (Comparative Example 8), using a known silicon carbide When the part is fitted into the bearing (Comparative Example
It is each comparative example of 9). The materials of these comparative examples are also described in Example 1.
The test was performed in a molten aluminum bath under the same conditions as in Examples 5 to 5, and the results are shown in Table 2.

[0034]

[Table 1]

[0035]

[Table 2]

As shown in Table 2, according to the embodiment of the present invention, the wear trace depth was 25 μm on both the fixed side and the rotating side.
Very little as below, and cracks and chipping defects are not observed in any case around the wear mark, and both the wear resistance and the chipping resistance are excellent, but each bearing of the comparative example is compared with the example of the present invention. The wear mark depth is as large as 60 μm or more, and either cracking or chipping has occurred.
It was confirmed that both of the fracture resistances were not achieved. The required grinding amount was found to be significantly larger than 72 μm in the comparative example, compared with 30 μm or less in the example.

Conditions for Evaluation Test of Bearing in Aluminum Bath
Table 3 shows the results based on (8) and (9).

[0038]

[Table 3]

Even when the bearing is repeatedly subjected to thermal fatigue, the material according to the present invention can be used 20 to 30 times, whereas each material of the comparative example is 5 to 10 times, which is less than half. Considering the processing cost at the time of re-grinding and the total life of the product including repeated use, it was confirmed that the bearing material made of the sintered body of the present invention was extremely advantageous. Also, in the evaluation of the wettability, it was found that the material according to the present invention was difficult to wet, at 105 to 135 °, and that the materials of Comparative Examples had a small contact angle of 40 to 50 ° and were easy to wet.
The effect of improving the corrosion resistance and reducing the tensile stress to the fixed side when heat shrinkage due to air cooling at the time of pulling up is sufficiently expected. For this reason, it is easily presumed that both the low wettability with the molten aluminum and the high durability of repeated thermal fatigue work in applications in the present molten aluminum bath, and the amount of wear is small, cracking and chipping occur. It is probable that it did not occur. From the evaluation results in the high-temperature aluminum bath, it is easily assumed that the thermal shock resistance in the lower-temperature zinc bath is also satisfied. Therefore, it can be determined that the present invention can be applied to a member for a hot-dip metal plating bath.

[0040]

According to the present invention, the life of the bearing member in the continuous hot-dip metal plating apparatus can be greatly extended. This makes it possible to stably produce a metal-plated steel sheet for a long time, and its industrial utility is very large.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a hot-dip plating bath.

FIG. 2 is a longitudinal sectional view and a rotating shaft sectional view of an embedding member.

FIG. 3 is a structural view of an assembly of a bearing unit.

FIG. 4 is a cross-sectional view of the apparatus when evaluating bearing wear according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Steel plate passing through plating process line 2 ... Pot roll 3 ... Guide roll 4 ... Bath with heating function 5 ... Rotating bearing test material (φ90mm x height 50mm) 6 ... Fixed bearing test material (15x20) X length 80mm) 7 ... Molten aluminum bath (680 ℃) 8 ... Thermocouple with thermowell

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shigeru Shibamoto 1-1 Futaba-cho, Tobata-ku, Kitakyushu-shi, Fukuoka F-term in Nippon Steel Corporation Yawata Works (reference) 4K027 AA02 AA22 AB48 AD17

Claims (12)

[Claims] An immersion member attached to a pot roll device immersed in a molten metal plating bath, wherein the immersion member slides at least a pot roll shaft sleeve member and a bearing member of the pot roll equipment. An immersion member for a molten metal plating bath, wherein the immersion member is a silicon nitride-based or silicon carbide-based ceramic member fitted to part or all of a part. 2. The immersion member for a molten metal plating bath according to claim 1, wherein the immersion member comprises a plurality of columnar members. 3. The immersion member for a molten metal plating bath according to claim 2, wherein the columnar member is fitted in an axial direction of the bearing portion. 4. The immersion member for a molten metal plating bath according to claim 3, wherein the sliding surface of the columnar member in the rotation direction is a flat surface or an arc-shaped surface having a radius of curvature equal to or greater than the radius of curvature of the pot roll shaft sleeve member. 5. The immersion member for a molten metal plating bath according to claim 2, wherein the columnar member is fitted in the pot roll shaft portion sleeve member in an axial direction. 6. The immersion member for a hot-dip metal plating bath according to claim 5, wherein the sliding surface of the columnar member is an arc-shaped surface having a radius of curvature equal to or less than a radius of curvature of the bearing member. 7. The columnar member according to claim 3, wherein the sliding surface in the axial direction of the columnar member is uneven and / or corrugated, and the sliding surface height of the convex portion is uniform in the axial direction. Immersion member for hot-dip metal plating bath. 8. The ceramic member having a theoretical density of 95%.
8. The immersion member for a hot-dip metal plating bath according to claim 1, which has a sintered body density of not less than 10%. 9. The immersion member for a molten metal plating bath according to claim 8, wherein the ceramic member is a silicon nitride sintered body containing a chromium compound in a volume fraction of 1 to 8%. 10. The immersion member for a molten metal plating bath according to claim 9, wherein the chromium compound is chromium nitride. 11. The immersion member for a molten metal plating bath according to claim 8, wherein the ceramic member is a silicon carbide sintered body containing a composite metal boride in a volume fraction of 20 to 70%. 12. The immersion member for a molten metal plating bath according to claim 11, wherein the composite metal boride is a Ti-Zr-B solid solution and / or a Ti-Hf-B solid solution.