JPH01283352A - Galvanealing furnace - Google Patents

Abstract

PURPOSE:To enhance the heating efficiency of the title furnace and to produce an alloyed steel sheet with stable quality by providing gas sealing devices respectively to the respective zone inlet sides and outlet sides of an induction heating zone, etc. CONSTITUTION:The gas sealing device 3 which prevents the air intruding from the inlet aperture part of the induction heating zone 4 is provided to said heating zone so that the draft in the furnace is prevented by the gas sealing device 5 in the juncture of the heating zone 4 and a direct heating zone 6 after the strip 2 emitted from a pot 1 is rapidly heated in the heating zone 4. The strip 2 is heated to the final heating temp. in the heating zone 6 and the gas sealing device 7 in the juncture to a holding zone 8 on the outlet side of the heating zone 6 prevents the draft in the furnace and prevents the intrusion of a high-temp. exhaust gas directly into the holding zone 8 and the temp. rise of the holding zone 8. The gas sealing device 9 on the outlet side of the holding zone 8 prevents the draft in the furnace and prevents the inflow of the relatively high-temp. exhaust gas into a cooling zone 10 and the decrease of the cooling efficiency by parting the flow of the gases in the holding zone 8 and the cooling zone 10. The heating efficiency is thereby enhanced and the alloyed steel sheet having high quality is stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an alloying heat treatment furnace, that is, a galvanil furnace, in which an alloyed layer is formed by heating and heat-retaining a strip immediately after hot-dip galvanizing.

<Prior Art> In recent years, alloyed steel sheets have been increasingly used in automobiles, home appliances, etc., and high-quality steel sheets are required.

The conventional alloying furnace has a direct heating zone and a holding zone arranged in series above the plating pot (Japanese Patent Application Laid-Open No. 60-149759).
No.), or one in which an induction heating zone, a direct flame heating zone, and a holding zone are arranged in series above the plating pot (Japanese Patent Laid-Open No. 61-207
No. 564) is known. This latter method, in which an induction heating zone, a direct flame heating zone, and a holding zone are arranged in series, can be said to be the result of considering the advantages and disadvantages of direct flame heating and induction heating, and incorporating the advantages of each.

However, since these types have a long chimney shape, a large amount of air enters due to the draft effect of high-temperature gas inside the furnace, which not only reduces thermal efficiency but also causes uneven heating and deteriorates quality. It also leads to a decline.

In conventional alloying furnaces, the amount of intruding air due to draft is about six times that of combustion air, and about 60% of the input fuel is used to heat this intruding air.

In addition, although the structure is arranged as shown in Figure 2, if the strip comes into contact with the top roll 16 before being completely cooled after being heated and held, zinc may adhere to the roll. This causes surface flaws, leading to a decline in quality.

On the other hand, if the direction is changed after complete cooling, a long cooling zone is required above the holding zone, which increases the height of the entire alloying furnace and the cost including the building.

<Problems to be Solved by the Invention> The present invention provides a galvanyl furnace that suppresses drafts in the alloying furnace, prevents air from entering, increases heating efficiency, performs uniform heating, and enables optimal heating and optimal holding. It provides:

The present invention also provides a galvanil furnace in which the heated and held strip is transported and cooled to a temperature below a certain level without contacting rolls, etc., and surface flaws are also prevented.

<Means for Solving the Problems> The present invention provides a galvaneal furnace in which an induction heating zone, a direct flame heating zone, a holding zone, and a cooling zone are arranged in series on the upper part of a hot-dip galvanized pot, at the entrance side of the induction heating zone.

A galvaneal furnace is characterized in that a gas sealing device is provided at the joint between the induction heating zone and the direct-fired heating zone, at the joint between the direct-fired heating zone and the retention zone, and at the exit side of the retention zone. The gas seal device on the inlet side is equipped with piping to introduce the exhaust gas from the direct-fired heating zone, and the direction of conveyance of the strip can be changed using a non-contact method at the top of the holding zone or the top of the cooling zone. It is equipped with a gas pad.

<Function> Next, the present invention will be explained based on FIG. 1, which is an embodiment.

The strip 2 leaving the plating pot 1 is heated to a predetermined temperature in a heating zone 13 consisting of an induction heating zone 4 and a direct flame heating zone 6, and after being kept in a holding zone 8 for a certain period of time, it is cooled in cooling zones 10 and 12. 14 is a wiping nozzle for adjusting the zinc coating amount. In the heating step 1113, a gas sealing device W3 is first installed to prevent air from entering through the inlet opening of the induction heating zone 4. It is desirable to use hot air (450 to 600° C.) obtained by diluting the exhaust gas from the direct-fired heating zone 6 with air at room temperature in the gas sealing device 3 because the strip 2 is preheated and the thermal efficiency of the furnace is increased. Although this embodiment shows a fluid pad tights gas seal device, an air curtain type gas seal device may also be used.

The strip is then rapidly heated in induction heating zone 4. This induction heating zone 4 can compensate for the excessive or insufficient heating of the direct-fired heating zone, which does not have good response, with its quick response during unsteady conditions such as during temporary jointing.

The gas sealing device 5 at the connection part to the direct-fired heating zone 6 on the exit side of the induction heating zone 4 prevents drafts in the furnace, and also prevents the high-temperature exhaust gas from the direct-fired heating zone 6 from flowing into the induction heating zone 4, causing induction heating. Prevent overheating of the coil (not shown). The gas used here is preferably hot air obtained by diluting the exhaust gas from the open heating zone 6 with air in order to prevent the strip temperature from decreasing.

In the open heating zone 6 the strip 2 is heated to the final alloying temperature (500-700'C) by an open burner (not shown).

The gas seal device 7 at the connection to the holding zone 8 on the outlet side of the direct-fired heating zone 6 not only prevents drafts in the furnace, but also prevents high-temperature exhaust gas (900 to 1200°C) from directly entering the holding zone 8. , it also prevents the retention zone temperature from increasing. Therefore, in this gas sealing device 7, cold air is used so that the rising exhaust gas from the open heating zone 6 reaches a holding temperature (500 to 700°C), or the exhaust gas led from the open heating zone 6 is diluted with air. Use hot air at a holding temperature. In this example, the temperature of the exhaust gas flowing into the holding zone is controlled to the holding temperature by performing gas sealing with cold air.

The gas seal device 9 on the outlet side of the retention zone prevents drafts in the furnace, and also separates the gas flow between the retention zone 8 and the cooling zone 10, allowing relatively high temperature exhaust gas to flow into the cooling IF 10 and improving cooling efficiency. prevent deterioration.

In addition, a gas pad 11 is placed above the cooling zone 10 to change the direction of the high-temperature strip after alloying in a non-contact manner, thereby eliminating the occurrence of surface flaws due to smearing of the zinc onto the roll surface, which conventionally occurs with the top roll 16. In this example, the gas pad 11 is placed above the cooling zone 10, but it can also be placed directly above the holder 4iF via the gas seal device 9.

In this case, the height of the furnace can be further reduced, making it more economical.

Incidentally, the structure of each gas seal may be either a known fluid pad or a gas curtain.

<Effects of the Invention> As described above, in the present invention, since a gas seal device is used on each inlet side and outlet side, intrusion air can be almost completely prevented, and the strip can also be preheated, so the heating efficiency is higher than that of the conventional one. This increases from about 20% to about 40%.

In addition, by installing gas seal devices on the inlet and outlet sides of each zone, it is possible to control the gas flowing in from the front and rear zones, and the unique temperature control of each zone can be performed with good responsiveness and high precision, making it possible to perform various Alloyed steel sheets can be manufactured with stable quality.

By using a gas pad, which is a non-contact direction changing device, in place of the top roll, surface flaws caused by the top roll that have occurred up until now are completely eliminated.

In addition, this setup (RW arrangement) allows the entire alloying furnace to be made lower in height, and high-quality alloyed plated steel sheets can be produced stably at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the galvaneal furnace of the present invention, and FIG. 2 is a cross-sectional view of a conventional galvaneal furnace. 1... Plating pot, 2... Strip, 3
...Gas seal device, 4...Induction heating zone, 5...
・Gas seal device, 6...Direct fire heating zone, 7...Gas seal device, 8...Insulation zone, 9...Gas seal device, 10...Cooling zone, 11...Gas pad ,
12... Cooling zone, 13... Heating zone,
14... Wiping nozzle, 15... Blower, 16
...Top roll. Patent Applicant Kawasaki Steel Corporation Figure 1 "Figure 2 111 IR

Claims (1)

[Claims] 1. In a galvaneal furnace in which an induction heating zone, a direct flame heating zone, a holding zone, and a cooling zone are arranged in series on the upper part of a hot-dip galvanized pot, the induction heating zone entry side and the induction heating zone and A galvaneal furnace characterized in that a gas sealing device is provided at each of the connecting portion of the fire heating zone, the connecting portion of the direct flame heating zone and the holding zone, and the exit side of the holding zone. 2. A galvaneal furnace, characterized in that the gas seal device at the entrance side of the induction heating zone according to claim 1 is provided with piping so that exhaust gas from the direct-fired heating zone can be introduced. 3. A galvaneal furnace, characterized in that a gas pad is provided above the holding zone or above the cooling zone according to claim 1, for changing the direction of conveyance of the strip in a non-contact manner.