JPS6332860B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hollow immersion roll of a continuous molten metal plating device that has grooves on its barrel surface and rotates in contact with a material to be plated in a molten metal plating bath. Immersion rolls of the type described above serve to pass the plated material through a bath of molten metal for a certain period of time for reaction between the plated material and the molten metal. For this reason, the surface of the immersion roll body is in contact with the material to be plated, so the immersion roll must always rotate at the same speed as the material to be plated. In this case, as for the rotational power of the immersion roll, due to the structure of the molten metal bath of the continuous molten metal plating apparatus, driving torque is applied to the immersion roll mostly by utilizing the movement of the material to be plated. That is, the dipping roll is driven by the contact between the plated material and the surface of the dipping roll body. However, in a molten metal bath, molten metal is always present between the surface of the immersion roll body and the material to be coated, making it extremely difficult to obtain the contact resistance necessary to drive the immersion roll. Another point to consider is that since the immersion roll is always in a molten metal bath, an alloy layer is formed on the surface of the immersion roll body due to reaction with the molten metal, resulting in an uneven state commonly referred to as "roll roughness." This is because the plated material is heated to almost the same temperature as the molten metal, so its tensile strength is reduced. For this reason, simply increasing the surface pressure between the coated material and the immersion roll will cause the coated material to be affected by "roll roughness" and the roll roughness will be transferred to the coated material. However, this is unfavorable for the quality of the plated product. Furthermore, even if "roll roughness" does not occur, if the tensile strength of the plated material is lower than the rotational force of the immersion roll, the plated material will be deformed. In this case, the phenomenon most likely to occur is called "squeezing", which is a state in which wrinkles occur in a portion of the material to be plated. The reason for this is that when the material to be plated and the dipping roll come into contact, an uneven force is applied in the width direction of the material to be plated, and a resistance that exceeds the tensile strength is generated in a part of the material to be plated. It is thought that a part of the plating material is deformed and becomes "squeezed." In order to deal with the above-mentioned problems, it has been conventional practice to form grooves or holes on the surface of the immersion roll body. The effects of such groove machining and hole machining will be explained below using examples shown in the drawings. In FIG. 1, the material to be plated 1 passes through a pretreatment device 2 and enters a molten metal bath 3. A dipping roll 4 is placed in the molten metal bath, and a plated material 1 is placed in the molten metal bath.
is wound around this dipping roll 4 and directed upward, the amount of plating is adjusted by the plating amount adjusting device 5, and it becomes a plated product 6 and runs outside. When the material to be plated 1 starts to come into contact with the dipping roll 4, the advancement of the material to be plated and the rotation of the dipping roll 4 causes the molten metal to flow in the direction of contact between the material to be plated and the dipping roll, and the material to be plated flows. The pressure of the molten metal acts in a direction that prevents contact between the plating material and the immersion roll. This pressure effect becomes larger as the plated material is operated at higher speeds, and in general, the thinner the plated material is, the more easily it is subjected to the above pressure effect and deforms. In order to prevent such inconveniences, a grooved dipping roll shown in FIG. 2 has already been proposed. Grooves 7 and holes 8 are formed on the body surface 4a of the dipping roll 4 shown in FIG. In this case, the hole 8 is
As best shown in FIG. 3, it is located between the grooves. The grooves allow the molten metal between the plated material and the immersion roll to flow out toward both edges of the plated material, thereby reducing the contact resistance between the plated material and the immersion roll. That's what you're trying to get. The wider the groove and the smaller the pitch,
Although the above effects are great, if the contact resistance per unit area is too large, the material to be plated will be affected by the unevenness of the surface of the immersion roll cylinder, so it is necessary to design the optimum conditions. Generally, the groove is formed in a spiral shape extending left and right from the center of the body surface of the dipping roll, and its dimensions are as follows. Width: 3 to 10 mm Depth: 0.5 to 20 mm Groove pitch: 3 to 60 mm The holes serve as passageways for the molten metal between the material to be plated and the dipping roll to flow into the hollow part inside the dipping roll. The material adheres to the dipping roll,
It has the effect of facilitating rotation of the dipping roll. The center of the hole is located approximately centrally between the grooves and extends through the hollow portion of the dipping roll. Its dimensions are generally as follows. Hole diameter: 25 to 60 mm Hole spacing: 50 to 100 mm The larger the holes 8, the greater the effect of flowing molten metal into the inner hollow part of the immersion roll. The edges of the plated material affect the plated material, which becomes a "transfer mark" of the hole and has an undesirable effect on the quality of the plated product. Also, the larger the total area of the holes and the total area of the grooves, the easier it is for the molten metal between the plated material and the immersion roll to escape, making it easier to obtain contact resistance.
However, since the contact resistance per unit area increases, even slight irregularities on the surface of the dipped roll cylinder are transferred to the plated material, which also has an unfavorable effect on the quality of the plated product. For the above-mentioned reasons, there is a strong demand for improvements in dipping rolls, and the present invention has been made in response to this demand. The invention will now be described with reference to the embodiments shown in FIGS. 4 and 5. In FIG. 4, grooves 7 are provided on the body surface 4a of the dipping roll 4, and these grooves extend from the center of the body of the dipping roll 4 to the left and right sides, as in the conventional dipping roll shown in FIG. It is formed in a spiral shape. Holes 9 are machined in the bottom of this groove at appropriate intervals, and the holes 9 penetrate through the body of the dipping roll and reach the inner hollow part thereof, as shown in FIG. The conditions for hole machining vary depending on the plating speed and tensile strength of the material to be plated, but the maximum hole diameter must be within the width of the groove, and the larger the hole, the greater the effect. When the hole diameter exceeds the groove width, a phenomenon occurs in which the hole-processed portion protruding from the groove portion is transferred to the plated material, depending on the extent of the excess, the tensile strength of the plated material, contact resistance, etc. If the pore diameter is small, the effect will be small, and if the pore diameter is too small, the pores may become clogged and lose their effectiveness altogether. For example, when a hole with a diameter of 1 mm was formed for a groove width of 5 mm using a hot-dip galvanizing device, an iron-zinc alloy formed in the hole, resulting in the hole being clogged. Therefore, the hole diameter must be within a range that will not clog the hole during operation. The distance between the holes is narrow, and therefore the effect is greater as the number of holes increases, but the processing cost increases accordingly. Taking these points into consideration, the following methods can be considered for designing the hole spacing. The first step is to place holes at the bottom of the trench at intervals of approximately 20 times the hole diameter. If the effect is not satisfactory, operate with a spacing of about 10 times the hole diameter, and if there are further problems, operate with a spacing of about 5 times, then 2.5 times. If the problem still exists even after increasing the spacing by 2.5 times, double the groove width, double the hole diameter, and increase the spacing by 20%.
The system will be operated twice and its effectiveness will be confirmed. In this way, the same process as described above is repeated and the investigation is carried out to find an appropriate hole spacing. If the hole spacing is too narrow, the only problem is the economical efficiency of hole machining, but as the groove width becomes larger and the pitch of the groove becomes smaller, the total area of the groove becomes larger.
The contact resistance per unit area between the plated material and the immersion roll increases. As a result, the unevenness on the surface of the body of the dipping roll is likely to be transferred to the plated material, so it is necessary to select the groove width and the total area of the grooves to be as small as possible. Below, examples are shown in which the immersion roll of the present invention was operated.

[Table] The continuous hot-dip galvanizing equipment and continuous hot-dip aluminum plating equipment shown in the table have a service life of 7 to 10 days when conventional immersion rolls are used, especially when the material to be plated is thin and wide. The possible number of days for soaking was limited to 3 to 4 days after the dipping roll was replaced. When the dipping roll according to the present invention was used, the performance of the pore diameter of 1 mm was significantly lower than that of the conventional dipping roll, but other dipping rolls according to the present invention were less likely to cause squeezing or transfer of the roll body surface. Also, since there is no transfer of holes, the lifespan can be extended several times compared to conventional dip rolls. In conventional dip rolls, grooves and holes are separately machined on the surface of the body, but in the present invention, holes are machined at the bottom of the grooves, so the effects of both the grooves and holes are synergized, and the plated material It is presumed that the molten metal interposed between the roller and the immersion roll will easily escape, resulting in a significant increase in contact resistance. In the present invention, since the holes are located at the bottom of the groove, the contact area between the plated material and the immersion roll is not reduced due to the holes, so the contact resistance per unit area is small, and the immersion roll body It is also less susceptible to the negative effects of surface irregularities. Furthermore, one of the problems with conventional dipping rolls is that
Hot hole "transfer marks" are completely prevented in the present invention. As mentioned above, the dipping roll according to the present invention has great effects in extending its life, saving maintenance costs, and improving product quality.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a continuous molten metal plating device, Figure 2 is a front view of a conventional dip roll, and Figure 3 is a
FIG. 4 is a front view of the dipping roll according to the present invention, and FIG. 5 is a partial sectional view thereof. 3... Molten metal bath, 4... Dipping roll, 7...
Groove, 9...hole.

Claims (1)

[Claims] 1. In a hollow dipping roll of a continuous molten metal plating device that has grooves on its body surface and rotates in contact with the material to be plated in a molten metal plating bath, A dipping roll characterized in that holes are provided at appropriate intervals and these holes reach an inner hollow part. 2. The dipping roll according to claim 1, wherein the diameter of the hole is not larger than the width of the groove.