JPH0338322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for coating iron strands comparable to the method described in Australian Patent No. 481508.

Although the melt plating method described in the above-mentioned prior patent specification is almost satisfactory in terms of use, this method has at least
It is relatively expensive and somewhat complicated to implement, as it requires the use of gas heated to 750 degrees F (390 degrees C). Furthermore, the invention described in the prior patent specification aims to provide a strand coating free of the defects of pinholes and bare spots, and in comparison with earlier coating methods, has largely achieved that objective. However, according to experiments, it was found that the earlier invention was not completely successful in preventing the occurrence of pinholes and the like. In fact, we question whether pinholes and the like can be completely eliminated.

Another drawback of the earlier prior invention is that zinc and zinc oxide are deposited on the inner surface of the hood (indicated by 16 in the drawing of the earlier prior patent specification), so that they are removed on a relatively frequent and regular basis (e.g. monthly). This means that the deposits must be removed. Heating elements are also used to heat the strands in the annealing furnace located upstream of the hood, but they are usually electrically heated. Another drawback is therefore that early deposits often short-circuit the heating element, necessitating its repair.

The object of the present invention is to overcome or improve the disadvantages of the prior inventions by a simple method, namely:
It is an object of the present invention to eliminate the need for the use of high-temperature reducing gases, reduce the amount of gas required, and reduce defects such as pinholes as compared to the results obtained by practicing the prior invention; It is an object of the present invention to provide a strand coating method and apparatus that can completely or nearly completely avoid the formation of zinc and other deposits on the inner surface of a hood.

The present invention comprises: (a) advancing the strand in the longitudinal direction of the hood through a hood having an exit end of the strand which is immersed in a bath of a metallizing agent made of an aluminum-zinc alloy in a molten state so as to surround a portion of its surface; (b) introducing a reducing gas into an outlet conduit of a strand heating furnace located upstream of said hood and through which the strands pass as they proceed to the hood; (c) reducing within said hood; In order to maintain the gas stationary at least at the strand outlet, the diffusion rate of reducing gas from the outlet conduit into the hood is lower than the rate required to maintain substantially constant the amount and composition of the reducing gas in the hood. A method of coating a furnace-heated iron strand with a metal coating consisting of an aluminum-zinc alloy, characterized in that the strand is limited so as not to be substantially large.

The invention also resides in an apparatus for carrying out the method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The accompanying drawings showing embodiments of the apparatus according to the present invention will be described below.

In FIG. 1, 3 refers to the strand to be coated. The strand 3 enters from the furnace outlet conduit 4 through a hood 5 into a bath 6 of molten coating consisting of an aluminum-zinc alloy. It then advances into the stripping area 7 where excess coating material is removed by conventional methods such as gas wiping. The strand outlet end 5A of the hood 5 enters the molten coating bath 6.

While the strand is in the outlet conduit 4 (furnace not shown, but of conventional construction),
Exposure to reducing gas atmosphere. This reducing gas is
A gas mixture consisting primarily of nitrogen, but may contain hydrogen in an amount not exceeding 15% by volume of the gas mixture. This reducing gas is usually dehumidified. This reducing gas is introduced into the outlet conduit 4 in any suitable manner. For example, it is fed from a supply header 9 through a series of inlet nozzles 8 . The used or excess reducing gas is removed from the outlet conduit 4 in any suitable manner, for example via a series of outlets 10 leading to a take-off header 11. The reducing gas is introduced into the outlet conduit 4 at a suitable temperature, which temperature is sufficient to be at ambient temperature.

The outlet conduit 4 has a plurality of perforated internal septa, as indicated at 12, 13, 14. The strands proceeding from the furnace to the molten coating bath pass through holes in the perforated bulkhead. The holes in the septum are sized to be sufficient for the passage of the strands, but to leave as little space as possible between them and the strands passing through. Although some backflow loss of gas occurs through the partitions 12, 13, this loss is not significant.

The reducing gas also diffuses into the hood 5 through the holes in the septum 14 and acts as a make-up gas to maintain the gas content and gas composition within the hood 5 approximately constant. It also goes without saying that some reducing gas is lost along with the strands leaving the hood, and there is also very little gas loss within the hood due to oxidation.

The reducing gas entering the furnace outlet conduit 4 is normally at a pressure slightly above atmospheric pressure sufficient to maintain a positive pressure within the outlet conduit. The supply and discharge of reducing gas is always controlled to be sufficient to provide the initial positive pressure while at the same time replenishing gas losses due to leakage of reducing gas into the hood, etc.

The amount of gas supplied into the hood 5 should be the minimum flow rate that achieves the required replenishment function within the hood while maintaining a static state of the gas within the hood, at least near the hood outlet. For this purpose, the reducing gas which wishes to enter the hood 5 from the outlet conduit 4 is normally supplied in a suitable manner, e.g.
This is accomplished by the use of a conventional sealing roller as indicated at 5, or by the use of a stopper placed in the outlet conduit 4 near the strand outlet of the furnace.

The device of FIG. 2 is substantially the same as the previous device, except for the stationary member placed near the connection between the outlet conduit 4A and the hood 5A.

Trial implementation of the invention has shown that the gas within the hood is effectively maintained at the required conditions. In particular, if the strand to be treated is in the form of a continuous band and its width is approximately close to the width of the inside of the hood,
It has been shown that a pair of restraints, such as those labeled 16 and 17, effectively maintain the gas within the hood at the desired condition.

The restraining member 16 is a built-in wall of refractory material that extends across the hood entrance and upwardly from the hood floor to a level just below the strand 3A.

The restraining member 17 has a beam shape and is made of ceramic fiber or other refractory material. This restraining member is
Although it may be built-in, it is usually rotated to the position shown by dotted line 17A to facilitate insertion of the tip of the strand into the hood.
It is attached to the rotation shaft 18. A care port 19 is usually provided in the hood for a similar purpose. During use of the device, the cleaning port is closed by a removable lid designated by 20.

[Brief explanation of drawings]

FIG. 1 shows the outlet conduit 4 of the strand treatment furnace;
Figure 3 is a side sectional view showing the hood attached to the outlet conduit 4 and the molten coating bath. FIG. 2 is a modified enlarged view of the right end portion of FIG. 1. 3: Strand, 4: Outlet conduit, 5: Hood,
6: molten coating bath; 7: stripping zone;
8: Entrance nozzle, 10: Outlet, 15: Sealing roller, 16, 17: Stopping member, 18: Rotating shaft.

Claims (1)

[Scope of Claims] 1 (a) A strand is passed through a hood having an outlet end immersed in a bath of a metal coating made of an aluminum-zinc alloy in a molten state so as to surround a portion of the surface of the strand, along the length of the hood. (b) introducing a reducing gas into an outlet conduit of a strand heating furnace located upstream of said hood and through which the strands pass as they advance into the hood; (c) said hood. a diffusion flow rate of the reducing gas from the outlet conduit into the hood to maintain a substantially constant amount and composition of the reducing gas in the hood to maintain the reducing gas in the hood stationary at least near the strand outlet end; A method for coating furnace-heated iron strands with a metal coating consisting of an aluminum-zinc alloy, characterized in that the flow rate is limited to no substantially greater than the required flow rate. 2. The method of claim 1, wherein the reducing gas is a dehumidified mixture of nitrogen and hydrogen containing not more than 15% hydrogen by volume. (a) a strand heating furnace having one end connected to a strand outlet conduit connected to the other end of a hood immersed in a molten metal coating bath; and (b) a strand heating furnace having an outlet conduit, a hood and a molten metal coating from the strand heating furnace; (c) a device for supplying a reducing gas into the outlet conduit to maintain a positive pressure in the outlet conduit; (d) a hood; Apparatus for coating iron strands with a metallization agent, characterized in that it has a stopper located near the connection of the outlet conduit and the hood to control the reducing gas entering therein. 4. The outlet conduit has a plurality of internal partitions arranged transversely of the outlet conduit, each of the fusing walls having one hole through which the strand can freely pass. Apparatus according to scope 3. 5. The apparatus of claim 4, wherein the stop member comprises a pair of sealing rollers through which the strand passes as it advances toward the hood, and one of the partition walls. 6. said restraining member comprises a fire-resistant wall disposed transversely to the hood and extending from the floor of the hood to a height proximate to just below the strands traveling within the hood; 5. The apparatus of claim 4, further comprising a refractory beam extending to a height immediately above and adjacent to the strand traveling through the hood. 7. Claim 6, wherein the fire-resistant beam is attached to a pivot axis arranged transversely of the hood, thereby increasing the distance between the fire-resistant beam and the strands traveling in the hood. Apparatus described in section. 8. The device according to claim 7, wherein a cleaning port is provided in a portion of the hood adjacent to the fireproof beam, and a removable lid is attached to the cleaning port.