JP5888593B2 - Roll for hot metal plating bath - Google Patents

Description

  The present invention relates to a roll for a molten metal plating bath used by being immersed in a molten metal plating bath such as zinc, aluminum, or an alloy thereof.

  An example of the invention relating to the above technical field is disclosed in Patent Document 1 below. The roll for hot metal plating disclosed in Patent Document 1 is made of “a ceramic made of a fitting portion and a support portion respectively connected to a driven side and a driving side at an end portion of a cylindrical body portion made of ceramics. In the molten metal plating roll having the shaft portion, at least one of the shaft portions penetrates the plurality of through holes penetrating from the support portion to the fitting portion and the fitting portion around the support portion. A hot-dip metal plating roll having at least one of the through holes.

JP 2010-255043 A

  The roll for hot metal plating baths (hereinafter, sometimes simply referred to as roll) of Patent Document 1 is an assembly-type hot metal plating bath roll fitted to a separate body and shaft. The problem will be described with reference to FIG. 6, which is an enlarged cross-sectional view of the fitting portion between the body portion and the shaft portion of the roll of Patent Document 1.

  That is, the roll 9 of Patent Document 1 has a tubular body portion 9 having a hollow portion 9n, and a fitting portion 9a is fitted to the inner circumferential surface of the end portion so that the outer circumferential surface is in close contact with the shaft portion. 9d is fixed. When this roll 9 is immersed in a hot molten metal plating bath (hereinafter sometimes simply referred to as a plating bath), the body portion 9b and the shaft portion 9d heated in the plating bath start to thermally expand for a certain period of time. After the lapse of time, the thermal expansion of both converges and stabilizes. Here, immediately after the roll 9 is immersed in the plating bath, the end surface of the body portion 9b where the fitting portion 9a exists and the end region shown in the figure B in the vicinity thereof are heated earliest and the amount of heat input is large. On the other hand, since the fitting portion 9a that is in close contact with the inner peripheral surface of the body portion 9b in the end region B does not directly touch the plating bath, the amount of heat input immediately after immersion is small. As a result, immediately after immersion in the plating bath, the amount of thermal expansion of the region B of the body portion 9b is larger than that of the fitting portion 9a, and there is a gap between the two in the radial direction due to the time difference between the two thermal expansions. Will occur. Due to the gap formed immediately after immersion in the plating bath, the shaft portion 9d moves in the horizontal direction or is inclined to be eccentric, or in a significant case, the shaft portion 9d is detached from the body portion 9b. There was a possibility. In order to solve this problem, when the tightening allowance for fitting the shaft portion 9d to the body portion 9b is increased, the tightening force by the body portion 9b is increased. Then, there is a possibility that the end portion of the body portion 9b that acts by superimposing the tightening force and the pressing force from the shaft portion 9d indicated by the arrow C in the drawing may be damaged.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a roll for a molten metal plating bath in which the fitting between the body portion and the shaft portion is not loosened immediately after immersion in the plating bath. Yes.

To achieve the above object, one aspect of the present invention has the appearance with the axis and a barrel member of a cylindrical shape and a shaft member fixed to the end of the barrel member, the barrel member , in axial direction, that a large-diameter hole portion arranged in the body member coaxially with an opening in the end face, which is disposed the to the large-diameter hole portion coaxially also inwardly from the large-diameter hole portion It includes a fitting hole portion and a small-diameter hole portion, the shaft member, the fitted in the large diameter hole section and a large diameter portion having a larger diameter than the small diameter portion is fitted into the small-diameter hole portion And it is a roll for hot metal plating bath provided with the fitting part which has a small diameter part whose diameter is smaller than a large diameter part.

Incidentally, in the molten metal plating bath rolls, a connecting member is a separate member from the said barrel member fixed to an end of said barrel member, the shaft member via the connecting member is fixed to the barrel member, the fitting portion may be formed on the connecting member instead of the shaft member.

Further, in the state of the body member and the shaft member is separate, the inner diameter of the large diameter hole portion D1, the outer diameter of the large-diameter portion D2, the inner diameter of the small-diameter hole portion D3, the diameter When the outer diameter of the part is D4, it is desirable that the relationship is (D2-D1) / D1 <(D4-D3) / D3.

  In addition, it is desirable that the large-diameter portion has a groove or a hole formed along the axial direction.

In addition, the connecting member is in the axial direction, and a large-diameter hole portion arranged in the body member coaxially with an opening in its end face, the large-diameter inward of said large diameter portion and a small-diameter hole portion arranged in the hole coaxial with said shaft member is fitted into the large-diameter hole portion of the connecting member, and large diameter is larger than the small diameter portion of the connecting member parts and, fitted into the small-diameter hole portion of the connection member, and it is desirable to have a small diameter portion having a smaller diameter than the large diameter portion of the connecting member. Hereinafter, in the embodiment according to the present invention, the body portion 1b indicates a body member, the shaft portion 1d indicates a shaft member, and the connection portion 2w indicates a connection member.

  According to the present invention, the object can be achieved.

It is a side view which shows the structure of the molten metal plating apparatus with which the roll of 1st Embodiment concerning this invention was integrated. It is a front view which shows a part which expanded the roll of FIG. 1, and the bearing which supports the said roll in the cross section. It is a right view of the roll of FIG. It is the elements on larger scale of the A section of FIG. It is a partial expanded sectional view of the trunk | drum, connection part, and axial part of the roll of 2nd Embodiment concerning this invention. It is the elements on larger scale of the trunk | drum and axial part of the roll of 3rd Embodiment concerning this invention. It is the elements on larger scale of the trunk | drum and axial part of the roll of patent document 1 which is a prior art.

  Hereinafter, the present invention will be described based on the first and second embodiments with reference to the drawings. In addition, each element of each embodiment described below can be used singly or in appropriate combination, and can be appropriately modified and used without departing from the gist of the present invention.

[Molten metal plating equipment]
First, a molten metal plating apparatus incorporating a roll according to the present invention will be described with reference to FIG.

As shown in FIG. 1, the molten metal plating apparatus 80 prevents the oxidation of the steel plate introduced into the plating bath 81 by being immersed in the bath 82 containing the plating bath 81 and the surface layer portion of the plating bath 81. And a pair of hot metal plating bath rolls positioned above the sink roll 1 in the plating bath 81. There are support rolls 7 and 7 and a gas wiping nozzle 86 located slightly above the surface of the plating bath 81. The sink roll 1 itself is not applied with an external driving force, and is driven by contact with the traveling steel plate. The support rolls 7 and 7 are usually provided with one support roll 7 connected to an external motor (
The other support roll 7 is a non-drive roll. The support roll 7 may be a non-driving type to which no external driving force is applied. The sink roll 1 and the pair of support rolls 7 and 7 which are rolls for a molten metal plating bath are rotatably supported by bearings 87 and 88 attached to the frames 84 and 85, respectively. Soaked in.

  The traveling steel plate P enters the plating bath 81 from the oblique direction via the snout 83 and is changed in the traveling direction upward via the sink roll 1. The steel plate P rising in the plating bath 81 is sandwiched between the pair of support rolls 7 and 7 so that the pass line is maintained and warpage and vibration are prevented. The gas wiping nozzle 86 sprays a high-speed gas onto the steel plate P <b> 1 coming out from the plating bath 81. The thickness of the molten metal plating adhering to the steel plate P1 is uniformly adjusted by the gas pressure and spray angle of the high-speed gas. Thus, the steel plate P1 to which the molten metal plating is applied is obtained.

[First Embodiment]
FIG. 2 is a front view showing a part of the configuration of the sink roll 1 of the first aspect incorporated in the molten metal plating apparatus 80 of FIG. 1 and a right side view of FIG. ), And will be described with reference to FIG. Note that the same applies to the configurations of the sink rolls of the following second and third modes, but basically the configuration described using the sink roll as an example can also be applied to the support roll.

  As shown in FIG. 2, the roll 1 has a barrel portion 1 b that is a cylindrical body having a substantially columnar appearance with an axis I, and a shaft portion 1 d that is fixed to both ends of the barrel portion 1 b. The shaft portion 1d is disposed coaxially with the body portion 1b and extends from both ends of the body portion 1b in a direction along the axis I of the body portion 1b (hereinafter, this direction is referred to as an axial direction). It is rotatably supported by a bearing (slide bearing) 87 disposed at the end. And the fitting hole part 1a to which the axial part 1d is connected is arrange | positioned at the edge part of the trunk | drum 1b which has the hollow part 1n. Hereinafter, although the structure of the trunk | drum 1b and the axial part 1d is demonstrated, the structure of the two axial parts 1d arrange | positioned at the both ends of the trunk | drum 1b and the fitting hole part 1a, and the relationship between these and the trunk | drum 1b are the same. Therefore, only the right shaft portion 1d and the fitting hole portion 1a will be described, and the description of the left shaft portion 1d and the fitting hole portion 1a will be omitted.

[Body]
As shown in FIGS. 2 and 3, the body portion 1 b preferably made of ceramic is formed so that the outer peripheral surface with which the steel plate P to be plated is in direct contact has a predetermined outer diameter. The body portion 1b of this embodiment has a substantially cylindrical shape having a substantially cylindrical hollow portion 1n having a substantially circular cross-sectional shape along a direction orthogonal to the axis I (hereinafter, this direction is referred to as a radial direction). I am doing. The body portion 1b shown in the figure has the same thickness in the axial direction of the portion other than the fitting hole portion 1a, but the thickness thereof may be changed. The thick portion and the thin portion May be arranged as appropriate.

  As shown in FIG. 3 (b), the fitting hole 1a disposed at the end of the body 1b opens in the right end surface of the body 1b in the axial direction and is coaxial with the axis I of the body 1b. A large-diameter hole 1i disposed on the left side and a small-diameter hole 1j disposed coaxially with the large-diameter hole 1i on the left side (inward) of the large-diameter hole 1i. The large-diameter hole portion 1i and the small-diameter hole portion 1j of the fitting hole portion 1a of this aspect both have end surfaces 1k and 1L extending in the radial direction, and the outer peripheral surface of the small-diameter hole portion 1j is the large-diameter hole portion 1i. It arrange | positions continuously so that it may connect directly to the end surface 1k. The cross-sectional shapes in the radial direction of the large-diameter hole portion 1i and the small-diameter hole portion 1j are both substantially circular, but the cross-sectional shape is not limited to this, and is fitted into and fixed to the fitting hole portion 1a. What is necessary is just to form corresponding to the shaft part 1d. The large-diameter hole portion 1i and the small-diameter hole portion 1j are both substantially disk-shaped with the same diameter in the axial direction, but may be inclined holes that reduce inward from the end face side of the body portion 1b.

[Shaft]
As shown in FIG. 2 and FIG. 3 (a), the shaft portion 1d, preferably made of ceramics, has a hollow, substantially cylindrical shape, and has a large-diameter fitting portion 1e fitted to the body portion 1b, and a slip. A small-diameter support portion 1g supported by the bearing 87 and a connecting portion 1f that connects the large-diameter portion 1e and the small-diameter portion 1g are provided. The shaft portion 1d may be solid. In addition, the shape of the outer peripheral edge of the shaft portion 1d in the cross section along the radial direction does not need to be substantially circular, and may be triangular, quadrangular, other polygonal or elliptical, but the roll 1 rotates. From the viewpoint of suppressing the occurrence of vibrations occurring at the time, it is desirable to have a substantially circular shape that can ensure a rotational balance. Further, when the shaft portion 1d is made of ceramics, corrosion wear due to the plating bath is suppressed, but it is desirable that the ceramics have poor toughness, and if there is an acute angle portion, it becomes a starting point of fracture. Therefore, the connecting portion 1f, the fitting portion 1e and the bearing are supported. It is desirable to form the connecting portions of the portions 1g with smooth curves in a sectional view along the axial direction.

  In FIG. 2, reference numeral 1h denotes a thrust receiving portion that supports the roll 1 in the axial direction. The thrust receiving portion 1h preferably made of ceramic is inserted into the end opening of the support portion 1g, and is configured so that the area in contact with the bearing is reduced in consideration of the rotation of the roll 1. The cross-sectional view along the radial direction of the right end surface has an arc shape that is convex in the right direction. Further, in FIG. 3A, reference numeral 1p denotes a plating bath flow hole that communicates with the hollow portion 1n of the body portion 1b. The circulation holes 1p formed at an equal angle around the shaft center at a pitch of 60 ° are formed by a plurality of grooves formed on the outer peripheral surface of the fitting portion 1e and extending in the axial direction and the inner peripheral surface of the fitting hole portion 1a. This is a defined through-hole, and when the roll 1 is immersed, a plating bath is introduced into the hollow portion 1n of the body portion 1b to prevent breakage due to thermal shock, and when the roll 1 is pulled up from the plating bath, The plating bath is discharged from the hollow portion 1n, and the plating bath remaining in the hollow portion 1n is solidified to prevent the roll 1 from being damaged. Further, by introducing a plating bath into the hollow portion 1n through the through hole 1p and discharging the air inside the roll 1, the shaft portion of the roll 1 that has been lifted by buoyancy comes into contact with the bearing with excessive force, and the wear is reduced. Progress can be suppressed.

  In addition, the structure of the flow hole 1p is not limited to the illustration which is a preferable embodiment, and a plurality of flow holes 1p having different hole diameters may be provided, and the angular pitch at which the flow holes 1p are arranged is not necessarily the same, There is no need to provide them on the same circumference. Furthermore, in order to make the introduction and discharge of the plating bath smoother, when viewed from the axial direction, the left end portion of the circulation hole 1p formed in the right end portion of the cylinder shown in FIG. You may arrange | position both so that the formed through-hole 1p may become a position shifted | deviated.

  As shown in FIG. 3B, the fitting portion 1e of the shaft portion 1d includes a large-diameter portion 1m fitted into the large-diameter hole portion 1i and a small-diameter portion 1o fitted into the small-diameter hole portion 1j. And have. Specifically, the substantially cylindrical small-diameter portion 1o is formed on the left end side of the fitting portion 1e in the axial direction, and the large-diameter portion 1m formed coaxially with the small-diameter portion 1o is the small-diameter portion 1o. It is arranged on the right (outside). And the shaft part 1d is fixed to the trunk | drum 1b by fitting the fitting part 1e in which the large diameter part 1m and the small diameter part 1o were formed as mentioned above to the fitting hole part 1a. As described above, in the roll according to this aspect, the large-diameter portion 1m is fitted into the large-diameter hole portion 1i, the first-stage fitting portion is provided in the axial direction, and the small-diameter portion 1o is fitted into the small-diameter hole portion 1j. Since the second stage fitting part is provided and the shaft part 1d is fixed to the body part 1b at the two stage fitting part, the first stage fitting is performed by thermal expansion immediately after immersion in the plating bath. Even when the large-diameter hole portion 1i and the large-diameter portion 1m are loosely fitted, the small-diameter hole portion 1j and the small-diameter portion that are the second-stage fitting portions formed inward in the axial direction Since the fitting with 1o is maintained, it is possible to maintain the fixation between the body portion 1b and the shaft portion 1d. In addition, a fitting part is not limited to two steps, You may form three or more steps along an axial direction.

  The fitting method between the fitting portion 1e and the fitting hole portion 1a is a fixed fastening margin between the large diameter hole portion 1i and the large diameter portion 1m and between the small diameter hole portion 1j and the small diameter portion 1o. These inner diameters or outer diameters may be adjusted so as to exist and fixed by shrink fitting or cold fitting. In addition, it is preferable that the fitting rate which is the value which remove | eliminated the allowance by the internal diameter of the large diameter hole part 1i and the small diameter hole part 1j is in the range of 0.01 / 1000-0.5 / 1000. When the fitting rate is less than 0.01 / 1000, the tightening force of the fitting portion 1e is insufficient, and the shaft portion 1d may be detached from the trunk portion 1b. On the other hand, if the fitting rate exceeds 0.5 / 1000, the tightening force becomes excessively large, and the body 1b or the shaft 1d may be damaged. A more preferable fitting rate is 0.2 / 1000 to 0.3 / 1000.

  In addition, it is desirable that the tightening margin between the small diameter hole portion 1j and the small diameter portion 1o is larger than the tightening margin between the large diameter hole portion 1i and the large diameter portion 1m. That is, FIG. 3B is a view of the state where the shaft portion 1d is fixed to the body portion 1b, but in a state where the shaft portion 1d is detached from the body portion 1b and each is separated, FIG. As shown, when the diameter of the large-diameter hole portion 1i is D1, the diameter of the large-diameter portion 1m is D2, the diameter of the small-diameter hole portion 1j is D3, and the diameter of the small-diameter portion 1o is D4, (D2-D1) / D1 < It is desirable that the relationship is (D4-D3) / D3. As described above, the invention intends to solve the problem by suppressing the tightening force by reducing the tightening margin between the large-diameter hole portion 1i and the large-diameter portion 1m which are the first-stage fitting portions. It is possible to avoid the breakage of the end portion of the body portion 1b described above. On the other hand, since the tightening margin between the small-diameter hole portion 1j and the small-diameter portion 1o, which is the second-stage fitting portion, is large, the small-diameter hole portion 1j and the small-diameter portion 1o are fitted even immediately after immersion in the plating bath. Is maintained, and the body 1b and the shaft 1d can be kept fixed.

  Furthermore, as shown in FIGS. 3A and 3B, it is desirable that a groove 1c formed along the axial direction is formed on the outer peripheral surface of the large-diameter portion 1m of the fitting portion 1e. . When the groove 1c is provided in the large diameter portion 1m as described above, a space defined by the groove 1c and the inner peripheral surface of the large diameter hole portion 1i when the large diameter portion 1m and the large diameter hole portion 1i are fitted. Is formed in the large diameter portion 1m. And if the roll 1 in which the said space was formed in the large diameter part 1m is immersed in a plating bath, a plating bath will infiltrate into the said space immediately after immersion, and the large diameter part 1m will be heated. Thereby, the large diameter portion 1m thermally expands almost simultaneously with the end portion of the trunk portion 1b in which the large diameter hole portion 1i is formed, and the generation of a gap due to the time difference between the two thermal expansions is suppressed. In addition, as shown to Fig.3 (a), it is preferable to provide the groove | channel 1c in the outer peripheral surface of the fitting part 1e preferably at multiple strips, More preferably at an equal angle.

  Furthermore, as shown in FIG. 3B, at least one of the left end surface of the large diameter portion 1m and the left end surface of the small diameter portion 1o is in contact with the end surface 1k of the large diameter hole portion 1i or the end surface 1L of the small diameter hole portion 1j. It is desirable that This is because, when bending is applied to the shaft portion 1d, it is possible to suppress the concentration of force on the end surface of the body portion 1b by receiving bending at the contacting end surface, and it is possible to suppress damage to the body portion 1b.

[Second Embodiment]
The sink roll 2 of the 2nd aspect concerning this invention is demonstrated referring FIG. In the sink roll 2 shown in FIG. 4, the same reference numerals are given to the same elements as those of the sink roll 1, and a detailed description thereof will be omitted (hereinafter, the third aspect of the sink roll described with reference to FIG. 5). The same applies to rolls.)

  The roll 2 of the second aspect has a connection portion 2w fixed to the end of the body portion 1b, the shaft portion 1d is fixed to the body portion 1b via the connection portion 2w, and the fitting portion 2e is It differs from the roll 1 of the first aspect in that it is formed in the connecting portion 2w instead of the shaft portion 1d. Hereinafter, the configuration of the connection unit 2w will be described in detail.

[Connection]
As shown in FIG. 4, the connecting portion 2w having a substantially annular shape is coaxial with the small-diameter portion 1o formed on the left side in the axial direction and on the right side (outside) of the small-diameter portion 1o. And a large-diameter portion 1m. By fitting the fitting portion 2e formed with the large diameter portion 1m and the small diameter portion 1o into the fitting hole portion 1a, the connection portion 2w is fixed to the trunk portion 1b. In addition, the code | symbol 2p in a figure is a through-hole of the plating bath formed in the through-hole shape.

  As described above, the shaft portion 1d is fixed to the connecting portion 1w fitted to the body portion 1b. Here, as a preferable aspect, the shaft portion 1d of this aspect is fitted and fixed to the connection portion 2w by the same configuration as the fitting between the connection portion 2w and the trunk portion 1b. That is, in the axial direction, the connecting portion 2w has an opening at its end face and a large-diameter hole portion 1q arranged coaxially with the body portion 1b, and the large-diameter hole portion 1q inside the large-diameter hole portion 1q. And a small diameter hole 1r arranged coaxially. On the other hand, the shaft portion 1d has a large diameter portion 1s fitted into the large diameter hole portion 1q of the connection portion 2w and a small diameter portion 1t fitted into the small diameter hole portion 1r of the connection portion 2w. . The shaft portion 1d is fixed to the connecting portion 2w by fitting the large diameter portion 1m into the large diameter hole portion 1q of the connecting portion 2w and the small diameter portion 1o into the small diameter hole portion 1r. The fitting between the body portion 1b and the connecting portion 2w and the fitting between the connecting portion 2w and the shaft portion 1d may be performed in the same manner as in the case of the roll 1 of the first aspect.

[Third Embodiment]
The sink roll 3 of the 3rd aspect concerning this invention is demonstrated referring FIG. The roll 3 of the first aspect is the roll 1 of the first aspect in that the large-diameter hole part and the small-diameter hole part of the fitting hole part provided in the body part are not continuously arranged in the axial direction. Is different.

  That is, as shown in FIG. 5, the fitting hole portion 3a of this aspect includes a large diameter hole portion 1i and a small diameter hole portion 1j formed inward of the large diameter hole portion 1i in the axial direction. In addition, there is an inclined hole portion 3u interposed between the large diameter hole portion 1i and the small diameter hole portion 1j and reducing the diameter from the large diameter hole portion 1i toward the small diameter hole portion 1j. As described above, by providing the inclined hole portion 3u, it is possible to suppress an excessive thermal stress generated in the suddenly changing portion of the wall thickness, and it is particularly suitable when the body portion 1b is made of ceramic which is a brittle material. As shown in FIG. 5, the fitting portion 3e of the shaft portion 1d fitted into the fitting hole portion 3a of the trunk portion 1b is also inclined between the large diameter portion 1m and the small diameter portion 1o. 3v may be provided.

[Material composition]
The case where the trunk | drum 1b, the shaft part 1d, and the connection part 2w of the rolls 1-3 of the said 1st-3rd aspect are preferably comprised with ceramic is demonstrated. Ceramics include alumina, zirconia, silica and other oxide ceramics, zirconium boride, titanium boride, boride depending on the thermal shock resistance and corrosion resistance required by the operating conditions of the rotating body and other operating conditions. Boron and other boride ceramics, silicon carbide / boron carbide and other carbide ceramics, or inorganic materials such as carbon may be used. And the sink roll of this aspect needs to be excellent in thermal shock resistance since it is rapidly heated and rapidly cooled when immersed in the plating bath and taken out. Therefore, as the ceramic constituting the body portion 1b, the shaft portion 1d and the connection portion 2w, silicon nitride / aluminum nitride or other nitride ceramics having high thermal conductivity is preferable, and high resistance to erosion with respect to molten metal as a plating bath. A silicon nitride-based ceramics that has excellent properties and wear resistance and is excellent in high-temperature strength is particularly preferable. Hereinafter, although silicon nitride ceramics suitable for constituting the trunk portion 1b, the shaft portion 1d, and the connecting portion 2w will be described in detail, the silicon nitride ceramics themselves may be the same as those described in JP-A-2001-335368.

  Aluminum and oxygen present in the silicon nitride ceramic serve as a phonon scattering source and reduce the thermal conductivity. Silicon nitride ceramics are composed of silicon nitride particles and surrounding grain boundary phases, and aluminum and oxygen are contained in these phases. Since aluminum has an ionic radius close to that of silicon, it easily dissolves in silicon nitride particles. Due to the solid solution of aluminum, the thermal conductivity of the silicon nitride particles themselves is lowered, and the thermal conductivity of the silicon nitride ceramics is significantly lowered. Therefore, it is desirable to reduce the aluminum content in the silicon nitride ceramics as much as possible.

  Most of the oxygen in the oxide added as a sintering aid is present in the grain boundary phase. In order to achieve high thermal conductivity of silicon nitride ceramics, it is necessary to reduce the amount of grain boundary phase having lower thermal conductivity than silicon nitride particles. The lower limit of the addition amount of the sintering aid is such an amount that a sintered body having a relative density of 8.5% or more can be obtained. It is desirable to reduce the amount of oxygen in the grain boundary phase by making the addition amount of the sintering aid as small as possible within this range.

When silicon nitride powder with a small amount of oxygen is used as a raw material, the amount of oxygen in the grain boundary phase can be reduced, so the amount of grain boundary phase itself can be reduced, and high thermal conductivity of the sintered body can be achieved. It becomes difficult to sinter due to a decrease in the amount of SiO ₂ produced in the process. However, when MgO, which is superior in sinterability to other oxides, is used as a sintering aid, the amount of sintering aid added can be reduced and a dense sintered body can be obtained. As a result, the thermal conductivity of the sintered body is dramatically increased.

  Moreover, as a sintering auxiliary agent which can be added together with magnesium, periodic table group 3 of Y, La, Ce, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, etc. ( (Described later). Among these, Y, La, Ce, Gd, Dy, and Yb are preferable in that the sintering temperature and pressure do not become too high.

  The thermal conductivity at normal temperature of the silicon nitride ceramic used in the present invention is 50 W / (m · K) or more, more preferably 60 W / (m · K) or more. Accordingly, the oxygen content in the silicon nitride ceramic is 5% by weight or less to obtain a thermal conductivity of 50 W / (m · K) or more, and a thermal conductivity of 60 W / (m · K) or more. Is 3% by weight or less. The oxygen content in the silicon nitride particles is 2.5% by weight or less for obtaining a thermal conductivity of 50 W / (m · K) or more, and a thermal conductivity of 60 W / (m · K) or more. Is 1.5% by weight or less. Furthermore, the aluminum content in the silicon nitride ceramic is 0.2% by weight or less for obtaining a thermal conductivity of 50 W / (m · K) or more, and a thermal conductivity of 60 W / (m · K) or more. Is 0.1% by weight or less.

  The total amount of magnesium oxide (MgO) and Group 3 element oxides in the silicon nitride ceramics is preferably 0.6 to 7% by weight. When the total amount is less than 0.6% by weight, the relative density of the sintered body is less than 95%, which is insufficient. On the other hand, if it exceeds 7% by weight, the amount of the grain boundary phase having a low thermal conductivity becomes excessive, and the thermal conductivity of the sintered body becomes less than 50 W / (m · K). The MgO + Group 3 element oxide is more preferably 0.6 to 4% by weight.

The weight ratio of MgO / Group 3 element oxide is preferably 1 to 70, more preferably 1 to 10, and most preferably 1 to 5. If the MgO / Group 3 element oxide is less than 1, the ratio of the rare earth oxide in the grain boundary phase is too high, and it becomes difficult to sinter and a dense sintered body cannot be obtained. MgO /
If the Group 3 element oxide exceeds 70, the diffusion of Mg during sintering cannot be suppressed, and color unevenness occurs on the surface of the sintered body. When the Mg / Group 3 element oxide is in the range of 1 to 70, the thermal conductivity is significantly increased by sintering at 1650 to 1850 ° C. When the sintered body is heat-treated at 1800 to 2000 ° C., the thermal conductivity is further increased. The increase in thermal conductivity by heat treatment is due to the growth of silicon nitride particles and volatilization of MgO having a high vapor pressure.

  The total amount of aluminum, magnesium, and Group 3 elements in the periodic table in the silicon nitride particles is preferably 1.0% by weight or less.

  Of the β-type silicon nitride particles in the silicon nitride sintered body, when the proportion of β-type silicon nitride particles having a minor axis diameter of 5 μm or more exceeds 10% by volume, the thermal conductivity of the sintered body is improved. Since the coarse particles introduced into the film act as a starting point of fracture, the fracture strength is remarkably lowered, and a bending strength of 700 Mpa or more cannot be obtained. Therefore, the ratio of β-type silicon nitride particles having a minor axis diameter of 5 μm or more in the β-type silicon nitride particles in the silicon nitride sintered body is preferably 10% by volume or less. Similarly, the β-type silicon nitride particles preferably have an aspect ratio of 15 or less in order to prevent the coarse particles introduced into the structure from acting as a starting point of fracture.

The silicon nitride ceramic that forms the body portion 1a in the sink roll 1 needs to have sufficient resistance to rapid temperature changes. The resistance to sudden temperature changes is the following formula (1):
R = αc (1−ν) / Eα (1)
(However, αc: Four-point bending strength (MPa) at normal temperature, ν: Poisson's ratio at normal temperature, E: Young's modulus (MPa) at normal temperature, α: Average thermal expansion coefficient from normal temperature to 800 ° C)
The coefficient R represented by the coefficient represented by is preferably 600 or more, and more preferably 700 or more. If the coefficient R is less than 600, the shaft portion 1d and the connecting portion 1j may be broken. The coefficient R is a four-point bending strength αc (MPa) at room temperature measured for a test piece cut out from the shaft portion 1d and the connecting portion 1j.
, Poisson's ratio ν at room temperature, Young's modulus E (MPa) at room temperature, and average coefficient of thermal expansion α from room temperature to 800 ° C.

1 (2, 3) sink roll 1a fitting hole 1b trunk 1c groove 1d shaft 1e fitting 1i large diameter hole 1j small diameter hole 1m large diameter 1o small diameter 1p flow hole 2w connection 7 support roll

Claims (5)

And the body member of cylindrical appearance with the axis, and a shaft member fixed to the end of the barrel member, the barrel member, in the axial direction, with an opening at its end face a large-diameter hole portion arranged in the body member coaxially provided with a fitting hole having said large diameter hole small-diameter hole portion is also disposed on the large diameter portion coaxially inwardly from the unit, the shaft member has said fitted in the large diameter hole section and a large diameter portion having a larger diameter than the small diameter portion, wherein fitted in the small-diameter hole portion, and the diameter than the large diameter portion is smaller diameter portion A roll for a hot-dip metal plating bath comprising a fitting part having A connecting member is a separate member from the said barrel member fixed to an end of said barrel member, the shaft member is fixed to the barrel member via said connecting member, the fitting portion, the molten metal plating bath roll according to claim 1, which is formed on the connecting member instead of the shaft member. In the state of the shaft member and is separate from the said body member, the inner diameter of the large diameter hole portion D1, the outer diameter of the large-diameter portion D2, the inner diameter of the small-diameter hole portion D3, of the small-diameter portion The roll for molten metal plating baths according to claim 1 or 2, wherein the outer diameter is D4, and the relationship is (D2-D1) / D1 <(D4-D3) / D3.   The hot metal plating bath roll according to any one of claims 1 to 3, wherein the large-diameter portion has grooves or holes formed along the axial direction. The connecting member is in the axial direction, and a large-diameter hole portion arranged in the body member coaxially with an opening in its end face, coaxial with the large diameter hole the large-diameter hole portion inward from the unit and a arranged small diameter hole portion, the shaft member is fitted into the large-diameter hole portion of the connecting member, and a large diameter portion diameter is larger than the small diameter portion of the connecting member, wherein fitted in the small diameter hole portion of the connecting member, and the molten metal plating bath roll according to claim 2 having a small diameter portion diameter than the large diameter portion smaller of the connecting member.

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