JP2002088457A - Galvanizing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a galvanizing apparatus in which the uniformity of temperature distribution in a galvanizing bath is improved and the unevenness of galvanized thickness is not developed by facilitating the maintenance control of the temperature of the galvanizing bath, and the problems in galvanizing work and in galvanization quality, or the like, are dissolved. SOLUTION: This galvanizing apparatus is provided with a combustion chamber, a preheating cylinder above the chamber and a crucible laid in the combustion chamber and having a molten metal tapping hole, and is constituted of a crucible furnace for heating and melting zinc in the crucible, a tapping trough and a galvanizing bath vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hot dip galvanizing apparatus.

[0002]

2. Description of the Related Art Hot-dip galvanizing is used for plating various metal products such as guardrails, bridges, power transmission radio towers, railway overhead wires, hardware, valves, bolts, nuts, steel wires, steel pipes, and the like.
Widely used. Hot-dip galvanizing is generally performed by pre-treating these metal products, such as degreasing, pickling, and fluxing, and then immersing them in a hot-dip galvanizing bath at a plating temperature of about 450 ° C. This is done by lifting, "dripping" excess molten zinc and then cooling. The resulting galvanized coating consists of an alloy layer formed by the reaction between molten zinc and a metal product and a pure zinc layer on the alloy layer.The thickness of the alloy layer and the pure zinc layer is deeply dependent on the temperature of the molten zinc bath. For this reason, it is desirable that the temperature of the molten zinc bath can be easily maintained at a predetermined temperature during the plating process.

Conventionally, as a hot-dip galvanizing apparatus, an iron pot furnace, a reverberatory furnace and an immersion furnace are generally used.

FIG. 1 is a cross-sectional view showing an example of a conventional iron pot furnace. In FIG. 1, a molten metal 2 is provided at the center of a combustion chamber 1 of a furnace.
Solid zinc is supplied to the iron pan 3 placed as a container, and the iron pan is heated from the outer periphery by the combustion burner 4 to melt the zinc, which is used as a plating bath. In FIG. 1, 5 indicates a bright flame protection brick, 6 indicates an exhaust port, and 7 indicates a furnace wall.

FIG. 2 is a longitudinal sectional view showing an example of a conventional reverberatory furnace. In FIG. 2, solid zinc is supplied to a molten metal container 9 lined with refractory brick, and is heated from the surface of the molten metal by a combustion burner 11 in a combustion chamber 10 provided above the molten metal container 9 to melt the zinc. This is used as a plating bath. In FIG. 2, reference numeral 8 denotes a molten metal, and reference numeral 12 denotes an exhaust port.

FIG. 3 is a longitudinal sectional view showing an example of a conventional immersion furnace. In FIG. 3, solid zinc is supplied to a molten metal container 14 lined with refractory brick, and heated by an immersion heater 15 immersed in the molten metal container 14 to melt the solid zinc from the inside of the molten metal and increase the temperature. To melt the zinc, which is used as a plating bath. Incidentally, in FIG.
Indicates molten metal.

[0007] However, the conventional hot-dip galvanizing apparatuses all dissolve and raise the temperature of zinc in a molten metal vessel, and directly charge solid zinc into a plating bath (hereinafter referred to as "cold charge"). Therefore, there were the following problems. That is, in the cold charge, it is impossible to avoid a drop in the molten metal temperature and an uneven temperature distribution. In addition, it is necessary to adjust the injection amount and the injection interval in order to minimize the drop of the molten metal temperature and the unevenness of the temperature distribution,
Nevertheless, in order to maintain the temperature of the plating bath and ensure the uniformity of the temperature distribution, it is necessary to heat and raise the temperature again with a burner, depending on the use and purpose of the plating.

Further, during the cold charge operation, solid zinc is accidentally dropped into a plating bath to scatter molten zinc, and steam explosion occurs due to insufficient removal of moisture mixed in solid zinc. In addition, turbulence of the molten metal, spilling of the molten metal, etc., increase the generation of zinc oxide etc. in the molten metal and reduce the yield, and solid zinc that has not completely melted and settled down Such as reducing the properties of the plating film by diffusing the dross,
There are problems in work, plating yield and plating quality.

Further, in the conventional hot-dip galvanizing apparatus, since the heating is performed by ON-OFF control, a temperature difference of the molten metal easily occurs, so that the temperature adjustment of the molten metal is not always easy. In addition, in an iron pot furnace, the heat transfer area is small, the temperature at the bottom is high, etc., so the uniformity of the temperature distribution of the bath water is poor, the heat efficiency is low, dross is generated frequently, metal loss is large, There is also a problem that there is a great deal of anxiety about perforation due to the damage of the steel. In addition, in the reverberatory furnace, since the heating is performed from the surface of the molten metal, the surface of the molten metal becomes higher than the inside of the molten metal, and the uniformity of the temperature distribution of the molten metal is poor, and zinc oxide and metal fume are frequently generated. There is also a problem. On the other hand, in an immersion furnace, zinc is melted and heated only by the immersion heater, so the thermal load on the ceramic tube, which is the protective tube of the heater, is large, and the heating power of the heater must be increased or long-time heating is required. Also, there are problems such as the need to use more heaters.

[0010]

SUMMARY OF THE INVENTION According to the present invention, the uniformity of the temperature distribution of a hot-dip galvanizing bath is improved, the temperature of the bath is easily maintained, and there is no variation in plating thickness. An object of the present invention is to provide a hot-dip galvanizing apparatus in which problems in work and plating quality have been solved.

[0011]

Means for Solving the Problems The present inventor has conducted intensive studies to achieve the above object, and as a result, has found that a specific crucible furnace, hot water gutter, and hot dip galvanizing for heating and melting zinc in a crucible having a tap hole. According to a hot-dip galvanizing apparatus constituted of a bath, the subject can be achieved by being able to continuously supply hot-dip zinc which is separately melted and brought to a temperature near the melting point of zinc, in a hot-dip galvanizing bath. The present invention was completed based on this.

That is, the present invention comprises a crucible having a combustion chamber, a material preheating cylinder above the crucible, and a taphole placed in the combustion chamber, in which the zinc is heated and melted in the crucible, a tapping gutter, and The present invention relates to a hot dip galvanizing apparatus comprising a hot dip galvanizing bath.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION
The crucible furnace, tapping gutter and hot-dip galvanizing bath are essential. Preferably, the apparatus of the present invention further comprises a dipping heater or /
And a combustion burner.

Hereinafter, one embodiment of a hot-dip galvanizing apparatus according to the present invention will be described with reference to FIG.

FIG. 4 is a longitudinal sectional view showing an example of an embodiment of the hot-dip galvanizing apparatus of the present invention. In the hot-dip galvanizing apparatus of this embodiment, the crucible furnace 21 includes a combustion chamber 22 and a material preheating cylinder 23 provided above the combustion chamber 22, and the combustion chamber 22 includes a combustion burner 24 on a part of the furnace wall. A crucible 25 is placed on a crucible base 26 at substantially the center of the combustion chamber. The horizontal moving device 2
7 is attached. The crucible 25 has a tap hole 28, and a hot-dip galvanizing bath 29
A hot water gutter 30 and a hot water gutter opening 31 are provided in the direction of.
Solid zinc 32 is introduced from the upper part of the material preheating cylinder 23,
It is heated and melted in the crucible 25. The molten zinc flows from the tap hole 26 through the tap hole 30 into the molten metal 33 through the tap hole 31. An immersion heater 35 having a ceramic tube 34 is provided in the galvanizing bath 29.

The material preheating cylinder 23 preheats the solid zinc 32 and serves as an exhaust flue for the combustion gas emitted from the heating burner 24. Further, since the horizontal movement device 27 is attached to the material preheating cylinder 23, maintenance such as replacement of the crucible 25 can be easily performed.

In the combustion chamber 22, the crucible 25 on the crucible base 26 is externally heated by the combustion burner 24, descends, and the solid zinc 32 charged into the crucible is melted. Solid zinc melts at about 420 ° C. Part of the heat generated by heating from the outside of the crucible is the heat of fusion of zinc (24.09).
Kcal / Kg), the temperature of the molten metal in the crucible is kept almost constant near the melting point of zinc (419.5 ° C.).

The molten zinc is supplied from the tap 28 to the tapping gutter 3.
0, and flows into the hot-dip galvanizing bath 29 through the hot water outlet 31 (hereinafter referred to as “hot charge”). The tap 28 is usually provided in the body of the crucible 25. An immersion heater 34 is provided in the plating bath 29, and thereby the temperature of the molten zinc is raised. In this embodiment,
Although an immersion heater is provided, a combustion burner may be used instead or together with it.

In the apparatus of the present invention, the width of the above-mentioned temperature rise can be reduced by hot charging the plating bath. Therefore, compared with the conventional combustion burners of iron pot furnaces and reverberatory furnaces and immersion heaters of immersion furnaces. , Can greatly reduce the thermal power. In addition, the durability of the ceramic tube of the immersion heater is improved, and the number of immersion heaters used can be reduced.

The crucible is preferably excellent in thermal shock resistance, corrosion resistance, oxidation resistance and the like. For example, a graphite crucible for non-ferrous metals can be suitably used. Graphite crucibles are usually
A crucible-like refractory container made by mixing raw materials such as graphite and silicon carbide with an organic binder and firing at a high temperature in a reducing atmosphere. The outer surface is oxidized to prevent oxidation by air during heating. It is coated with an inhibitor.

The tapping gutter is used by being integrally formed with the crucible or by being separately formed and joined to the crucible. As the material, a material mainly composed of graphite, silicon carbide, or the like, which is excellent in heat resistance, corrosion resistance, and the like, is preferable.

The immersion heater directly heats the molten metal by a combustion burner or an electric heater built in a ceramic tube, and is used in a state of being immersed in the molten metal from above a hot-dip galvanizing bath. The ceramic tube preferably has excellent thermal shock resistance, corrosion resistance, oxidation resistance, and the like. For example, a sintered body containing graphite, silicon carbide, or the like as a main component can be suitably used.

In the hot dip galvanizing apparatus of the present invention,
While the solid zinc is supplied into the crucible and solid zinc is present in the molten metal, molten zinc having a temperature near the melting point of zinc (about 420 ° C.) is supplied from a tap provided in the crucible to a tapping gutter and a tapping gutter. Through the hot-dip galvanizing bath. That is, it is hot charged. On this occasion,
Since the solid zinc is melted without being overheated, clean zinc of the same quality as the used solid zinc is supplied to the plating bath. In the plating bath, an immersion heater or / and a combustion burner are used to reduce the plating temperature to about 45 ° C.
The temperature is raised to 0 ° C. In this case, since the heating by the immersion heater or the combustion burner is not for melting zinc but for reheating for raising the temperature of the molten metal, the heating power may be small. Therefore, as a result of preventing excessive temperature rise, dross is less generated, energy is saved, and the life of the plating bath is improved. Next, hot-dip galvanizing is performed according to a conventional method.

As described above, according to the plating apparatus of the present invention, unnecessary overheating of molten zinc can be avoided without directly charging solid zinc into the galvanizing bath, and clean zinc As a result, solid zinc is dropped into a plating bath to scatter molten zinc,
The danger of causing a steam explosion due to moisture contained in the solid zinc is eliminated, the metal loss is reduced, and the plating quality is further improved.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 A hot-dip galvanizing bath was prepared using the hot-dip galvanizing apparatus of the present invention shown in FIG. That is, the graphite crucible 2
5, the solid zinc 32 was charged, the combustion burner 24 was ignited, and the outer surface of the graphite crucible was heated to melt the solid zinc. The molten zinc flowed from a tap hole 28 provided in the body of the graphite crucible, through a tapping gutter 30 and a tapping gutter port 31 to a hot-dip galvanizing bath 29 provided with an immersion heater 34. Here, six immersion heaters were fired with city gas and used at an immersion depth of 450 mm. The bathtub dimensions are width 1,
It was 700 mm long, 4,000 mm long and 1,000 mm deep.

In the hot dip galvanizing apparatus, the temperature of the molten metal was 420 ° C. and the temperature of the hot dip galvanizing bath was 450 ° C. due to hot charging. Therefore, as compared with the case of the cold charge, the temperature rise width was small and the temperature control was easy.

When hot-dip galvanizing was performed using a steel wire as a processed product, the processed amount was 0.5 tons / Hr. The resulting product has less variation in plating thickness,
The properties of the plating film were good. Further, the energy consumption was 130,000 Kcal / ton / Hr, and the energy consumption was significantly reduced as compared with 300,000 to 500,000 Kcal / ton / Hr of the related art.

[0029]

According to the hot-dip galvanizing apparatus of the present invention, the following remarkable effects can be obtained.

(1) The hot charge improves the uniformity of the temperature distribution in the hot-dip galvanizing bath, facilitates the control of the bath temperature, reduces variations in plating thickness, and greatly reduces defective products. it can.

(2) Since the material is preheated in the material preheating cylinder and melted in the crucible, high thermal efficiency and energy saving can be achieved.

(3) Since clean molten zinc is supplied and there is almost no overheating of the plating bath, dross generation is reduced,
Metal loss is reduced.

(4) The service life of the plating bath is improved and maintenance is reduced.

(5) Since solid zinc is not directly introduced into the plating bath, the danger of scattering of molten zinc and explosion of steam is eliminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an iron pot furnace which is a conventional hot-dip galvanizing apparatus.

FIG. 2 is a longitudinal sectional view showing an example of a reverberatory furnace which is a conventional galvanizing apparatus.

FIG. 3 is a longitudinal sectional view showing an example of an immersion furnace which is a conventional hot-dip galvanizing apparatus.

FIG. 4 is a longitudinal sectional view showing one example of a hot-dip galvanizing apparatus of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 combustion chamber 2 molten metal 3 iron pan 4 combustion burner 5 bright flame protection brick 6 exhaust port 7 furnace wall 8 molten metal 9 molten vessel 10 combustion chamber 11 combustion burner 12 exhaust port 13 molten metal 14 molten metal vessel 15 immersion heater 21 crucible furnace 22 combustion chamber 23 Material Preheating Cylinder 24 Combustion Burner 25 Crucible 26 Crucible Stand 27 Horizontal Moving Device 28 Outlet 29 Hot Dip Galvanizing Bathtub 30 Outlet Gutter 31 Outlet Gutter 32 Solid Zinc 33 Molten Metal 34 Ceramic Tube 35 Immersion Heater

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideo Yoshikawa 1-21-3 Ebisu, Shibuya-ku, Tokyo Japan Crucible Co., Ltd. Furnace Construction Division (72) Inventor Mankin Ikuzawa 3 Inada Shinmachi, Higashi Osaka City, Osaka Prefecture No. 11-40, Nihon Crucible Co., Ltd., Furnace Division (72) Inventor Yuhiro Ueda 3-11-40, Inada Shinmachi, Higashi-Osaka, Osaka Pref., Nihon Crucible Co., Ltd. 3-11-32 Inada Shinmachi, Higashiosaka City, Japan Crucible Co., Ltd. Osaka Plant (72) Inventor Kakei Nishihira 3-11-32 Inadashinmachi, Higashi Osaka City, Osaka Japan Crucible Co., Ltd. 4K027 AA01 AA22 AB42 AD04 AD08 AD25 AE06

Claims (2)

[Claims] 1. A crucible furnace having a combustion chamber, a material preheating cylinder thereabove, and a taphole placed in the combustion chamber, wherein the crucible heats and melts zinc in the crucible, a tapping gutter, and a hot-dip galvanizing bath. A hot-dip galvanizing apparatus characterized by comprising: 2. The hot dip galvanizing apparatus according to claim 1, wherein the hot dip galvanizing bath is provided with an immersion heater and / or a combustion burner.