JP2000129416A - Method for preheating roll in bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To halve the preheating time for a roll to be newly dipped into a pot and to uniformize the temp. distribution by in5erting a roll inside heating means different from a heating means for the roll surface from the opening of the roll and controlling both heating means with a good balance. SOLUTION: The outer surface of a sink roll 4 is fitted with a flexible electric heater 6. The electric heater 6 has a two-pieces divided structure and has heater capacitance of about 100 KW in total, and whose back face is coated with a heat insulating layer. A simplified gas burner 11 is inserted into the inside face of the sink roll 4 from the opening 10 of the roll edge face. Or, a radiant tube or a rod-shaped electric heater executing gas burning at the inside is used instead of the gas burner. The set temp. of the electric heater 6 is set to the preheating objective temp., and the set temp. of the simplified gas burner 11 at the inside is highly set to the preheating objective temp. While the roll surface temp. is measured, the sink roll 4 is heated from the inside and outside faces, and the roll surface temp. is raised to the objective temp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for extending the life of a roll in a continuous galvanizing line.

[0002]

2. Description of the Related Art FIG. 2 illustrates the construction of equipment around a pot in a continuous galvanizing line. Strip 1 enters zinc pot 2 holding zinc bath 3 and sink roll 4
, And changes direction and rises, and is supported by the support roll 5 and transported above the bath. The sink roll 4 and the support roll 5 are collectively called a roll in the bath.

It has been known that preheating is required when a roll in a bath of a continuous galvanizing line is newly immersed in a pot.

The purpose of preheating is to preheat the roll to a temperature equivalent to that of the molten zinc bath, thereby preventing a change in bath components due to a local and rapid change in the temperature of the bath when the roll is immersed, and stabilizing the plating quality. It is to plan. In addition, dross deposited on the low-temperature roll surface adheres to the roll surface and grows on rolls with insufficient preheating, causing a problem that the roll surface is roughened in a short time and the roll needs to be replaced. There is.

[0005] Conventional roll preheating, as shown in FIG.
The heating is performed by winding an electric heater 6 around the surface of the roll 4 or heating the roll 4 in a preheating furnace 7 as shown in FIG. The former is heating only from the roll surface, and the latter is also accompanied by internal heating when the roll has a hollow structure, but heating from the roll surface is dominant.

[0006]

Generally, in the bath, the surface of the roll is sprayed with metal or ceramic of various materials in order to prevent dross from adhering, and the preheating means from the roll surface shown in FIG. If the preheating is attempted, the durability of the thermal sprayed layer may be deteriorated due to a temperature difference or a thermal expansion difference from the base material, or in extreme cases, the thermal sprayed layer may be cracked and become unusable. Furthermore, even if the surface once rises to the set temperature by heating only from the surface, the temperature immediately drops as soon as the heating is stopped.For uniform heating, it is necessary to preheat slowly with a heating source as low as possible. there were.

The technique shown in FIG. 4 can also be uniformly heated if sufficient time is taken, but in order to actually adopt this method, the structure of a furnace for surrounding only the rolls after setting the rolls on the frame becomes complicated. If it is not realistic, and the roll is preheated by itself without setting the roll on the frame, it is difficult to set the high-temperature roll on the frame, which is not practical. In addition, when a sudden change of the roll is required, it is necessary to preheat the roll in a short time, which is not possible.
In addition, the long-time preheating work hinders the efficiency of the maintenance work, and the short-time uniform preheating has been a problem.

An object of the present invention is to provide a method for preheating a roll in a bath which has solved the above-mentioned problems.

[0009]

The present invention has a structure in which a large-diameter bath roll is generally hollow, and furthermore, a face plate provided with shafts at both ends has an opening and the inside and outside of the roll are open. Paying attention to this, if the inside of the roll other than the heating means of the roll surface is inserted into the roll from this opening and heating is performed while controlling the inside and outside heating means in a well-balanced manner, it can be compared with heating only from the surface And the preheating time is halved,
It was created from the viewpoint that the temperature distribution can be made uniform.

That is, in the method of the present invention, in a roll preheating operation for immersing a roll in a bath immersed in a zinc pot of a continuous hot-dip galvanizing line in a new pot, independently controllable heating means can be used. A method for preheating a roll in a bath, wherein the roll is heated simultaneously from the outside and the inside of the roll by using a roll.

Here, the independently controllable heating means may be any heating means capable of independently controlling the temperature, and the types of the heating means themselves may be the same and different. The content does not matter.

In the above preheating method, the heating source temperature outside the roll is set to a preheating target temperature or a temperature slightly lower than the preheating target temperature.
By setting the heating temperature of the internal heating source to be equal to or higher than the preheating target temperature, the temperature outside the roll can be suppressed to the preheating target temperature, and dross can be prevented from adhering to the roll surface after use.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, since the shell of the roll in the bath is heated from both the inside and outside, the heating efficiency is good and the surface temperature can be controlled so as not to be higher than necessary. Uniform preheating can be performed in a short time without damaging the thermal sprayed layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example in which the present invention is applied to a sink roll, which is a roll in the bath. FIG. 1A is a front view, and FIG.
Is a side view.

In this embodiment, the sink roll 4 is
Preheating was carried out in a state where it was set on the support frame 8 via.

A flexible electric heater 6 was attached to the outer peripheral surface of the roll. This electric heater 6 has a heater capacity of 100 KW in total in a split structure, and the back surface is covered with a heat insulating layer, so that a large-scale heat insulating box or the like is unnecessary.

On the other hand, the inner surface of the roll is
A simple gas burner 11 was inserted into the roll. The burner used this time was a premix type and the gas used was propane gas. The nozzle used was a nozzle having φ3 × 20 nozzles arranged in a line on a φ20 pipe. Instead of a gas burner, it is also possible to use a radiant tube for performing gas combustion inside, or to use a rod-shaped electric heater.

Next, the set temperature of the external electric heater 6 was set to 400 ° C., which is the preheating target temperature. The set temperature of the internal heater (gas burner 11) was set to 450 ° C. with respect to the preheating target temperature of 400 ° C. If this temperature is set at a temperature of 500 ° C. (heat-resistant temperature of the roll) or less, there is no problem at all.

As a result of heating from the inside and outside of the roll while measuring the roll surface temperature with a contact thermometer every 10 minutes,
In about 3 hours, the surface temperature of the roll reached the target temperature, and the preheating was completed. After stopping the heating, the roll surface temperature is about 20.
The preheat target temperature was able to be maintained for a minute.

[0021]

When the roll is immersed in the galvanizing bath, the preheating time, which conventionally took 7 hours or more, can be reduced to 3 hours by heating from both the inside and outside of the roll. Was completed.

Further, the temperature of the external heater can be suppressed to the preheating target temperature by heating from the inside of the roll, and no trouble caused by the high temperature has occurred.

Further, after the completion of the preheating, the roll surface temperature could be maintained at the target preheating temperature until the roll was transported to the zinc pot and dipped. Further, dross adhesion to the roll surface after use was reduced, and the roll could be reused only by simple cleaning.

[Brief description of the drawings]

FIG. 1A is a front view and FIG. 1B is a side view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an equipment configuration around a pot in a continuous galvanizing line.

3A and 3B are a front view and a side view, respectively, showing an example of conventional roll preheating.

FIG. 4 is an explanatory view showing an example of conventional roll preheating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Strip 2 Zinc pot 3 Zinc bath 4 Sink roll 5 Support roll 6 Electric heater 7 Preheating furnace 8 Sink roll support frame 9 Bearing 10 Roll end face opening 11 Simple gas burner

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K027 AA03 AA05 AB42 AD15 4K042 AA20 BA13 BA14 DA06 DB07 DB08 DC05

Claims (2)

[Claims] 1. In a roll preheating operation for immersing a roll in a bath which is immersed in a zinc pot of a continuous hot-dip galvanizing line and newly immersed in a pot, the roll is heated by independently controllable heating means. A method for preheating a roll in a bath, comprising simultaneously heating from outside and inside. 2. The method for preheating a roll in a bath according to claim 1, wherein the temperature of the heating source outside the roll is set to a target preheating temperature, and the temperature of the internal heating source is set to be equal to or higher than the target preheating temperature.