JPH0545667B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical field> The present invention relates to a method and apparatus for manufacturing single-sided alloyed galvanized steel sheets in which the thinner side is alloyed by heat-treating differentially-thickness plated steel sheets using heating rolls in a plating line in vacuum evaporation galvanizing. Regarding. Compared to normal galvanized steel sheets that are not alloyed, alloyed galvanized steel sheets have (a) good continuous operability in spot welding, and (b) good paint adhesion in electrodeposition coating, so they are easier to use after electrodeposition coating. It is widely used because of its good corrosion resistance. Conventionally, the following method is known as a method for manufacturing an alloyed galvanized steel sheet. (a) A method of heat-treating and alloying the plated zinc immediately after hot-dip galvanizing before it solidifies. (b) A method of reheating and alloying electrogalvanized steel sheets. However, since method (a) uses melt plating, it has the disadvantage that it is difficult to obtain a uniform thin plating of 30 g/m ² or less per side, and it is extremely difficult to obtain plating on one side. have In addition, method (b) is mainly a method in which electrogalvanized coils are subjected to long-term heat treatment in a batch-type annealing furnace at a temperature range of 250 to 350°C to form an alloy. (i) Since a batch-type annealing furnace is used, the process is complicated and the manufacturing time is long. Furthermore, (ii) the quality varies widely and quality control is troublesome. It has problems such as:
Furthermore, since method (b) uses electrogalvanized steel sheet as the material, the amount of coating is usually limited to 40 g/m ² or less. This is because if the coating weight exceeds 40 g/m ² , manufacturing by electrogalvanizing is not preferable in terms of cost. On the other hand, in addition to the hot-dip plating and electroplating described above, vapor deposition plating is at the stage of practical use, and a method for manufacturing a vapor deposited galvanized steel sheet in which one side is alloyed in vapor deposition plating is known. In this method, a differentially plated steel plate is heat treated in a batch annealing furnace, or an in-line annealing furnace is provided and one side is alloyed by post-heating. However, batch processing is a complicated process, and because the temperature is non-uniform, unevenness of alloying is likely to occur.Additionally, when an annealing furnace is provided in the line, the equipment becomes very large. <Means for solving the problem> The inventor of the present invention utilizes the rise in steel strip temperature due to heat of condensation during vacuum evaporation galvanizing, and heat-treats the plating layer on the thinner side with a heating roll, thereby developing the alloy layer on the thicker side. We obtained the knowledge that only the plating layer on the thinner side can be alloyed to the surface. The present invention is based on the above findings and has achieved a manufacturing method and an apparatus for performing alloying treatment in vacuum evaporation galvanizing without providing an annealing furnace in the line. According to the present invention, after plating both sides of a steel sheet with differential thickness of vacuum-deposited zinc, the plating surface on the thinner coating side is wrapped around a heating roller and heat-treated to alloy the surface. A method of manufacturing an alloyed galvanized steel sheet is provided. Further, according to the present invention, the pretreatment furnace, the pressure chamber, the first
A seal roll chamber, a first vacuum deposition chamber, a second vacuum deposition chamber, a second seal roll chamber, and a cooling chamber are successively provided, and a steel strip is further provided between the second seal roll chamber and the cooling chamber. Provided is an apparatus for producing a single-sided alloyed, vapor-deposited galvanized steel sheet, characterized in that a heated roll chamber for winding the thinner side of the sheet is provided. Hereinafter, the present invention will be described with reference to embodiments and drawings. Several types of continuous vacuum evaporation plating equipment have been proposed, but the one shown in Figure 1 has two evaporation chambers for double-sided plating, and is equipped with a pretreatment furnace 2, a gas An exhaust cooler 3, a pressure chamber 4, first and second seal roll chambers 5a and 5b having a large number of seal rolls, a first vacuum deposition plating chamber 6a for vacuum plating both sides of the steel strip, and a second vacuum plating chamber. It is equipped with a vapor deposition plating chamber 6b and a cooling chamber 7 for cooling the steel strip after plating.
Incidentally, a winding roll 8 is provided in the vapor deposition plating chambers 6a and 6b.
a, 8b and a zinc evaporation tank (not shown). As shown in FIG. 2, the apparatus for carrying out the present invention further includes a heating roll chamber 9 interposed between the second sealing roll chamber 5b and the cooling chamber 7, and the heating roll chamber 9 is provided with a plated steel plate. A heating roll 9a around which the light weight side is wound and a cooling roll 9b around which the thick weight side is wound are provided. The cold-rolled steel strip 1 is continuously introduced into a pretreatment furnace 2, and is subjected to pretreatment by gas reduction simultaneously with annealing. There are differences depending on the steel type, but in order for a steel strip to be annealed, it must be heated at a temperature range of 600 to 900℃ for 20 to 20 minutes.
A holding time of 180 seconds is required. The steel strip is cooled in the latter half of the pretreatment furnace 2, further cooled by the gas jet cooler 3, and then passed through the pressure chamber 4 and the first seal roll chamber 5a to the first vacuum evaporation chamber 6a. will be introduced in Zinc vapor introduced from the evaporation tank adheres to the opposite surface of the winding roll 8a in the vapor deposition chamber. Next, the steel strip 1 is guided to the second vacuum deposition chamber 6b, and is wound around the winding roll 8b with the upper surface and lower surface reversed, and zinc vapor is deposited on the other surface of the steel strip in the same manner as described above. It will be marked. As mentioned above, in the present invention, the winding rolls 8a and 8b are provided in the vacuum deposition chamber, and the steel strip to be plated is passed through, and steam is applied from the opposite side of the rolls, so that the contact surface between the winding roll and the steel strip is No metal vapor deposition is performed on the plate, and as shown in Table 2 below, the amount of metal deposited is uniform on both sides, including the width edges of the plate. The plated steel strip 1 is then led to the heating roll chamber 9 via the second vacuum sealing roll chamber 5b. In the heating roll chamber 9, the thinner side of the steel strip 1 is wound around a heating roll 9a and heat treated. The temperature of the vacuum-deposited steel strip increases due to the condensation heat of the zinc and the heat transfer from the wrapping rolls in the deposition chamber, and the heating roll 9a heat-treats the plated layer on the thinner side. It is possible to alloy up to the surface. For example, when performing vacuum evaporation galvanizing under the following operating conditions, the plate temperature increase ΔT of the steel strip after plating is proportional to the amount of zinc deposited, and the amount of deposited zinc is 10/10.
g/m ² and about 137° C. when the adhesion amount is 100/100 g/m ² . Steel strip: 0.6 mm thick x 300 mm wide low carbon steel Threading speed: 15 m/min Pressurizing gas: N ₂ Vacuum degree: 0.01 to 0.1 Torr Vapor deposited zinc: Commercially available electrolytic zinc Meanwhile, the vapor deposited galvanized steel sheet was recycled. The conditions for heating and alloying treatment vary depending on the amount of zinc plating deposited. For example, if the coating amount on one side is 10g/ ^m2, the temperature is 340
If the holding time is 60 seconds or more at ℃ and 5 seconds or more at 420℃, alloying will be completed to the outermost layer of galvanization, and an alloyed galvanized steel sheet with a uniform and beautiful skin will be obtained. Similarly, when the coating weight on one side is 100 g/m ² , an alloyed galvanized steel sheet with a uniform and beautiful skin can be obtained if the holding time is at least 60 seconds at 420°C and at 500°C for at least 5 seconds. In the present invention, reheating after plating is performed using a heating roll 9a. That is, the thin side of the plated steel plate is wound around a heating roll 9a and heat treated. As a means for heating the heating roll, sheath heaters are evenly distributed within the roll shell, and electricity is applied to heat the roll surface by electrical resistance heat generation. In this case, since only the light weight side is heated by contacting the heating roll 9a, an alloy layer does not develop on the thick weight side, and only the thin weight side can be alloyed to the surface. Further, since the heat treatment is performed by contact with a heating roll, a uniform alloy layer can be obtained. During the heat treatment using the heating roll, as shown in FIG. 2, it is preferable to provide a cooling roll 9b that wraps the thick side continuously around the heating roll 9a. In this case, cooling of the thick side is promoted and alloying is reliably prevented. The steel strip heat-treated in the heating roll chamber 9 is conveyed to the outside of the system via the cooling chamber 7. The single-sided alloyed galvanized steel sheet produced in this manner has a uniform and beautiful skin with galvanization on one side and alloy on the other side, and the workability of the plating layer is also good. <Example> Continuous vacuum evaporation galvanizing was carried out under the following operating conditions. The results are shown in Table 1. Pretreatment furnace: Gas reduction annealing furnace Heating roll diameter: 2m Roll wrapping angle: 180 degrees

【table】

[Table] (Note) Alloying state: × means non-alloyed to the surface
◯ indicates alloying up to the surface Table 2 shows an example of the amount of plating and the average Fe content rate in the plating layer of the single-sided alloyed vapor-deposited galvanized steel sheet according to the present invention, which was conducted under the above conditions. Samples for measuring the plating amount were taken at the sample positions shown in FIG.

[Table] Table 3 also shows the powdering resistance test results of the alloyed vapor-deposited galvanized layer and the alloyed hot-dip galvanized layer. Powdering resistance was tested using the method shown in Figure 4.

【table】

[Table] As is clear from the results, according to the method of the present invention, only one side of the double-sided plated steel plate is selectively alloyed. <Effects of the Invention> Since the present invention is configured as described above, in a continuous vacuum evaporation galvanizing line,
It is possible to perform single-sided alloying treatment by heat-treating one side of a double-sided plated steel plate using a heating roll installed in the line.The equipment is simple and the heat treatment is uniform, resulting in an alloy layer and a plated plate. The layer is beautiful and has good adhesion, making it extremely useful industrially.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a continuous vacuum evaporation galvanizing apparatus according to the present invention, Fig. 2 is a schematic diagram of a cooling roll chamber, and Fig. 3 is a sample for measuring the amount of plating deposited and the average Fe content rate in the plating layer. A perspective view of the sampled steel plate and FIG. 4 are explanatory diagrams showing the order of the powdering resistance test. In the drawings, 1... steel plate, 2... pretreatment furnace, 3...
Gas jet chamber, 4... Pressure chamber, 5a, 5b...
Vacuum seal roll chamber, 6a, 6b... Vacuum deposition chamber, 7... Cooling chamber, 8a, 8b... Wound roll,
9...Heating roll chamber, 9a...Heating roll, 9b
...Cooling roll.

Claims (1)

[Claims] 1. After plating both sides of a continuous steel sheet with differential thickness of vacuum-deposited galvanizing, the plating surface on the thinner coating side is wrapped around a heating roll and heat-treated to alloy the surface. A method for producing a single-sided alloyed galvanized steel sheet. 2. The method for manufacturing a single-sided alloy vapor-deposited galvanized steel sheet according to claim 1, wherein a roll for winding a steel strip is provided in a vacuum deposition chamber, and a vapor deposition source is installed on the opposite side of the roll for plating. 3. When the plating surface on the thinner coating side is wound around a heating roll and heat treated, the plating surface on the thicker coating side is wound around a cooling roll to prevent alloying of the plating layer on the thicker coating side. A method for producing a single-sided alloyed vapor deposited galvanized steel sheet according to item 1 or 2. 4. A pretreatment furnace, a pressure chamber, a first seal roll chamber, a first vacuum deposition chamber, a second vacuum deposition chamber, a second seal roll chamber, and a cooling chamber are successively provided, and the second seal roll An apparatus for manufacturing a continuous single-sided alloyed galvanized steel sheet, characterized in that a heating roll chamber for winding the light weight side of the steel strip is interposed between the chamber and the cooling chamber. 5. The apparatus for manufacturing a continuous single-sided alloyed and vapor-deposited galvanized steel sheet according to claim 4, wherein a roll for winding a steel strip is provided in the vacuum deposition chamber, and a vapor deposition source is provided on the opposite side of the roll.