JPH0448060A - Alloying furnace for hot dip galvanizing - Google Patents

Abstract

PURPOSE:To decrease the change in the steel sheet temp. based on a change in operating conditions, etc., and to improve productivity by providing an auxiliary combustion chamber having a slit for ejecting a waste combustion gases diagonally downward in the steel sheet inlet of the alloying furnace. CONSTITUTION:The auxiliary combustion chamber 6 having auxiliary burners 9, etc., is provided to face both surfaces of the steel sheet 5 in the steel sheet 5 inlet part of the alloying furnace 7. The combustion gas of the above- mentioned burner 9 is ejected from the slit 8 provided on the steel sheet 5 side of the above-mentioned combustion chamber 6 at a downward angle with the steel sheet 5. A gaseous curtain is formed by the waste combustion gas having the downward momentum and the infiltration of the outdoor air in the inlet of the above-mentioned furnace 7 is prevented. The change in the sheet temp. by the change, etc., of the operating conditions is lessened and the productivity is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an alloy immersion furnace for hot-dip galvanized steel sheets, and more specifically, to prevent outside air from entering from the lower part of the furnace, and to prevent changes in operating conditions. The present invention also relates to an alloying furnace that maintains the alloying plate temperature at a predetermined value in response to the temperature change.

[Prior Art 1] Conventionally, as a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet in which part or all of the plating layer is an Fe-Zn alloy layer is known. Such alloying treatment is performed as shown in FIG. That is, the alloying furnace 7 is placed directly above the hot-dip galvanizing bath l, and the steel plate 5 that has entered the hot-dip galvanizing bath 2 changes its passing direction to the vertical direction by the zinc roll 3, and is pulled out from the hot-dip galvanizing bath 2. The wiping device 4 wipes off the zinc on the surface of the steel plate 5 to adjust the amount of zinc deposited.

Thereafter, the W4 treatment 5 is immediately heated in the alloying furnace 7 to diffuse iron into the zinc layer.

[Problem to be solved by the invention j A heating furnace with a long chimney shape has been used as an alloying furnace for alloying galvanized steel sheets, but there are problems with conventional furnaces from the viewpoints of energy saving and quality stability. was there.

For example, (1) In conventional furnaces, the short and large outlets were not sufficiently sealed, so a large amount of outside air entered the furnace due to the draft of high-temperature gas inside the furnace.
The amount of heat required to heat this outside air to the required furnace temperature is equivalent to approximately 20% of the total heat output (actual furnace measurement results), and since this intruding outside air prevents the furnace temperature from rising, production of the alloying furnace is limited. This poses a major hindrance to sexual improvement.

(2) The heating method of the alloying furnace is to heat the furnace wall by gas heating and heat the steel plate by radiation from the furnace wall.
The plate temperature response in plate temperature control according to load fluctuations was poor.

In order to solve this problem (1), a method has been adopted in which a partition wall is installed inside the furnace to reduce the draft of the atmosphere inside the furnace (Japanese Patent Application Laid-Open No. 149759/1983). In this method, the draft reduction effect is small because the distance between the steel plate and the partition wall cannot be made very small considering the vibration of the steel plate passing through the furnace.

Once the partition wall is installed, the draft reduction amount is uniquely determined by the combustion amount, so it is difficult to implement, for example, furnace pressure control and furnace atmosphere 02 control.

Regarding (2), although it is possible to improve plate temperature responsiveness by changing the heating method to an induction heating method, there is a problem in terms of cost and the like.

The present invention is intended to solve the above problems.

[Means for Solving the Problems 1] The present invention solves the above-mentioned problems, and consists of a hot-dip galvanizing bath, which is disposed directly above a hot-dip galvanizing bath, and which allows galvanized steel sheets to enter from the lower end and pass through to the upper end. It was applied to an alloying furnace for plating, and the following technical measures were adopted. Namely.

This is an alloying furnace for hot-dip galvanizing, characterized in that an auxiliary combustion chamber having a slit for ejecting combustion exhaust gas in a diagonal downward direction is provided in the steel plate entry section of the alloying furnace so as to face both sides of the steel plate.

In addition, ■ A plate thermometer that measures the temperature of the steel plate on the exit side of the alloying furnace; ■ Adjusts the amount of combustion exhaust gas in the auxiliary combustion chamber to control the amount of outside air entering the furnace, and adjusts the thermometer to a predetermined value. It is even more preferable to include a combustion control device for the auxiliary combustion chamber that maintains the combustion chamber.

[Operation 1 The operation of the present invention will be explained based on FIG. 1. The heat-treated steel plate 5 is immersed in a molten zinc bath 2 and curved lead adheres thereto. The jlli 5 coming out of the plating bath [1] is injected with gas by the wiping device 4 to wipe away excess curved lead and control the amount of zinc deposited to a predetermined level.

After that, the steel plate 5 enters an alloying furnace 7 and is heated by a direct-fired burner 10.
An auxiliary combustion chamber 6 equipped with an auxiliary burner 9 is installed at the entrance of the 9-alloying furnace 7, which undergoes alloying heat treatment. It is ejected from the jet 8 at a downward angle to the steel plate 5. A gas curtain is formed by the combustion exhaust gas having downward momentum, and it is possible to prevent outside air from entering the 1-alloy type igniter.

In addition, by changing the combustion amount of the auxiliary burner 9 based on the indicated value of the plate thermometer 12 on the outlet side of the alloying furnace 1, the amount of outside air entering is changed, and the indicated value of the i4 total 12 on the outlet side of the alloying furnace is kept constant. It is possible to control the Note that 13 is a one-item regulator.

[Example 1] FIG. 2 is a detailed explanatory diagram of FIG. 1. Heat treated fI
The filter 5 is immersed in a molten zinc bath 2 to adhere curved lead.

Thereafter, an auxiliary combustion chamber 6 is provided at the entrance of the zero-alloying furnace 7, in which the amount of zinc deposited is controlled by a wiping device 4. The auxiliary combustion chamber 6 includes an auxiliary burner 9, a baffle plate 11. It is composed of slits 8 and the like. The combustion exhaust gas from the auxiliary burner 9 is injected from the slit 8 and has a downward momentum relative to the steel plate 5, thereby preventing air from entering the alloying furnace 7.

The combustion amount of the auxiliary burner 9 is controlled so as to keep the indicated value of the plate thermometer 12 on the outlet side of the first alloying furnace constant.

In other words, the indicated value of the plate temperature meter 12 is controlled to be constant by adjusting the opening degree of the fuel gas flow rate regulating valve 15 via the plate temperature regulator 13.

Also, the air flow rate adjustment is performed using the fuel gas flow meter 14. This is done by adjusting the opening degree of the air flow rate control valve 20 using the ratio setter 16 and the air flow rate adjuster 18 while checking the indicated value of the air flow meter 19.

Further, the baffle plate 11 is for alleviating the influence of the dynamic pressure of the combustion exhaust gas ejected from the auxiliary burner 9. From this, the amount of intruding air can be adjusted in order to control the indicated value of the plate thermometer 12 on the outlet side of the alloying furnace to be constant.

Figure 3 shows a comparison graph between the case where the present invention is used in actual operation and the conventional example. According to this graph, the line speed is 70 m/min under the conditions of plate thickness of 0.7 mm and line speed of 80 m/min. When this happens, the difference in plate temperature was 39 seconds in the conventional method, but this was shortened to 8 seconds in the method of the present invention.

[Effect of the Invention 1] The present invention makes it possible to significantly reduce changes in plate temperature due to changes in operating conditions, etc., and has an excellent effect on improving productivity.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a longitudinal cross section of an embodiment of the present invention, Fig. 2 is a detailed explanatory diagram of Fig. 1, Fig. 3 is a graph showing the effects of the present invention, and Fig. 4 is a longitudinal cross section of a conventional example. FIG. 1... Plating bathtub 2... Molten zinc bath 3...
- Zin roll 4... Wiping device 5...
Steel plate 6 - Auxiliary combustion chamber 7 - Alloying furnace 8 - Slit 9 - Auxiliary burner l
O-...Direct fire burner 11...-Baffle plate 12...Plate thermometer 13...Plate temperature regulator 14
...Gas flow meter 15...Gas flow control valve 6.
... Ratio setting device 8 ... Air flow rate regulator 9 ... Air flow meter 0 ... Air current control valve 17 - ... Air fan application Kawasaki Steel Corporation

Claims (1)

[Scope of Claims] 1. In an alloying furnace for hot-dip galvanizing, which is disposed directly above a hot-dip galvanizing bath, and in which galvanized steel sheets enter from the lower end and pass through to the upper end, combustion exhaust gas is directed diagonally downward. 1. An alloying furnace for hot-dip galvanizing, characterized in that an auxiliary combustion chamber having a slit for spouting air is provided in the steel plate entry section of the alloying furnace, facing both sides of the steel plate. 2. A plate thermometer that measures the temperature of the steel plate on the outlet side of the alloying furnace;
2. A combustion control device for the auxiliary combustion chamber that adjusts the amount of combustion exhaust gas in the auxiliary combustion chamber, controls the amount of external air entering the furnace, and maintains the thermometer at a predetermined value. Alloying furnace for hot dip galvanizing.