JP2617592B2 - Hot dip galvanizing alloying equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an alloying apparatus for subjecting a steel strip to continuous hot-dip galvanizing and then subjecting the steel strip to a heat alloying treatment.

[Conventional technology]

A conventional alloying method after galvanizing will be described with reference to FIG.

The steel strip 1 to be galvanized is first subjected to reduction annealing in a pretreatment furnace 2 and cooled to about 450 ° C., and then introduced into a molten zinc tank 3 without being exposed to the atmosphere. , And is led out from the zinc tank 3. During this time, the surface of the steel strip is galvanized.

The plated steel strip taken out of the zinc tank 3 is removed by an air knife 5 to remove excess molten zinc on the surface, and the plated layer is controlled to an appropriate thickness. Thereafter, the heater is heated to a predetermined temperature by an induction heating device 6 provided immediately above, and then heated to a predetermined temperature in a heating furnace 7 provided with a gas burner provided above. Next, the zinc-plated layer is sent to the heat insulation furnace 8 directly above, where it is heated and diffused to be alloyed with the base material iron. Thereafter, it is sent to the quenching zone 9 and cooled, and the alloyed plating layer on the surface is cooled and solidified.
Approximately 320 where the alloyed plating layer does not adhere to the roll
The plated steel strip cooled to ° C. reaches the top roll 10 at this stage, turns its direction horizontally, and is further cooled to a low temperature in the cooling chamber 11.

Generally, a cool air prevention plate is provided between the air knife 5 and the induction heating device 6.

[Problems to be solved by the invention]

In the conventional alloying apparatus, it is necessary to keep the distance between the lower sink roll 4 and the upper top roll 10 within about 60 m in terms of suppressing the vibration of the plated steel strip and building construction costs. Therefore, as a condition for heating and diffusing the plating layer to form an alloy by heating, it is necessary to perform heating in a short time of about 20 seconds, so that a heat treatment at a high temperature is required. In other words, high-temperature and short-time heating must be employed as the alloying condition. However, the correlation between the alloying time, the alloying temperature, and the amount of powder leave is shown in FIG. 3, and it can be seen from FIG.
It is necessary to heat and maintain at ℃, but the powdering (Poudering) property, which is an index of the workability of the alloyed plating layer, is not good at about 5 mg. This is because brittle δ ₁ phase and ζ phase increase instead of ζ phase with good workability as the alloying temperature becomes higher.

The present invention has been made in view of the above-mentioned state of the art, and aims to solve the problems of the conventional equipment of this kind and to provide a galvanizing apparatus for alloying at a relatively low temperature so as to reduce the amount of powdering. Things.

[Means for solving the problem]

The present invention relates to a hot dip galvanizing tank for galvanizing a steel strip, a vertically extending heating furnace provided above the hot dip galvanizing tank for heating a galvanized steel strip, and a heated galvanized steel. A floater provided above the heating furnace for changing the traveling direction of the strip, a heating furnace for further heating the redirected heated galvanized steel strip, and a heating furnace for cooling the heated galvanized steel strip. A quenching chamber provided, a top roll provided subsequent to the quenching chamber, a cooling tower provided subsequent to the top roll, and a water cooling tank.

That is, in the present invention, instead of the top roll 4 of the conventional alloying apparatus described in FIG. 2, a gas floater, an electromagnetic floater or a floater of a combination of both, which can change the direction of the plated steel strip in a non-contact manner, is installed. At the same time, the quenching zone 9 of the conventional apparatus was removed, the heat insulation furnace was extended to the vicinity of the floater and installed, and immediately after the direction change floater,
A heating device is provided for continuously heating the plated steel strip.

The heating device may be a system combining induction heating and gas heating, or may be gas heating alone, and it is preferable to provide a heating and soaking facility in the direction changing section so that heating and soaking can be performed for about 5 seconds or more. Thereafter, it is preferable to provide a quenching chamber for cooling the alloyed plated steel strip, cool the steel strip to about 320 ° C. or lower, and then turn the direction downward, for example, by a deflector roll serving as a top roll.

[Action]

By installing a floater capable of turning the direction of the plated steel strip in a non-contact manner in place of the conventional top roll, the plating layer for alloying may still be in a molten or semi-molten state when passing through the floater. In the past, the alloyed plated steel strip was quenched just before the top roll and the temperature when passing through the top roll was reduced to about 320 ° C or less, but there is no need for this quenching, so the plated steel strip is continued even when passing through the floater Can be heated. Further, in the direction changing part after passing through the floater, for example, in the horizontal part, the heating and the soaking are continued, so that sufficient alloying time can be taken. By using a high-temperature gas such as a high-temperature gas for the floater, alloying heating can be applied even during the passage of the floater.

Assuming that the alloying apparatus of the present invention is operated at the same line speed as the conventional alloying furnace, the alloying heating is performed for 7 to 10 seconds compared to the conventional alloying furnace in the section up to the upper turning floater.・ The soaking time can be extended, and the horizontal part can be heated after turning 90 °. ・ It can be heated and soaked for about 20 seconds in the soaking chamber. Total heating and soaking time 20 seconds + (7 to 10 seconds) + 20 seconds = 47 to
The alloying time can be longer than 50 seconds, twice as long as the conventional 20 seconds.

Therefore, from the correlation of alloying time-temperature-powdering amount in FIG. 3, the alloying apparatus of the present invention should be alloyed at about 500 ° C., and the powdering property is reduced from the conventional 5 mg to about 3 mg. And the workability can be remarkably improved.

〔Example〕

Next, FIG. 1 showing an embodiment of the present invention will be described in detail.

In FIG. 1, reference numerals 1 to 7 indicate the same components as those of the conventional apparatus shown in FIG. That is, 1 is a steel strip, 2 is a pretreatment furnace, and a reduction annealing furnace or an air atmosphere furnace is used. 3 is a molten zinc tank, 4 is a sink roll, 5 is an air knife, 6 is an induction heating device, 7 is a burner type heating furnace, and the function is the same as that of the conventional device.

A gas floater 20 is provided at a height corresponding to the position of a conventional top roll, so that the furnace 7 of the heating furnace 7 can have a longer length. That is, since the direction of the plated steel strip can be changed by the gas floater 20 in a non-contact state, the plated layer on the surface of the plated steel strip when passing through the gas floater 20 has no problem even in the heat-melted state.

21 is an induction heating device, 22 is a burner type heating device,
Each is for heating for alloying the plating layer. With the additional heating device in the horizontal portion, the alloying time can be sufficiently increased. Accordingly, since the alloying temperature can be kept low, the powdering property of the alloy layer can be suppressed from the correlation between the alloying time, the temperature and the amount of powdering shown in FIG.

23 is a temperature at which the alloy layer is not mechanically damaged even when the alloyed plated steel strip comes into contact with the roll after the alloying heating, that is, about 23 ° C.
This is a quenching chamber for cooling to 320 ° C or lower, and is usually cooled by blowing cold air. Reference numeral 24 denotes a deflector roll (top roll) for turning the plated steel strip downward. The alloyed galvanized steel strip turned down by the rolls 24 is sequentially sent to a gas cooling tower 25 and a water cooling tank 26 for further cooling, and cooled to room temperature to be an alloyed galvanized steel strip.

27 is an electromagnetic type floater, which can reduce the power of the gas floater 20 if used in combination with the gas floater 20. Further, a duct 28 is provided when a high-temperature gas is used as a working fluid of the gas floater 20, and there is an advantage that thermal efficiency can be increased. In this case, the induction heating device 21 may be omitted.

The following table shows the effect of the embodiment of the present invention in the case where low carbon steel, aluminum killed steel and titanium killed steel are used as the raw steel strip for plating, respectively, in comparison with the case where the conventional apparatus is used.

 The plating conditions are the same in each case.

As can be seen from the results, the alloying time can be set to 40 seconds in the apparatus of the present invention for any steel type (raw steel strip), so that the alloying temperature can be kept low, and therefore the amount of powdering of the product can be reduced. Can be significantly reduced to about half, and the workability of the alloyed plated steel sheet can be greatly increased.

[Effects of the Invention] According to the present invention, it is possible to perform a heat treatment at a relatively low temperature and for a long time at the time of alloying hot-dip galvanized coating, greatly reduce powdering of products, and improve workability of alloyed galvanized steel sheets. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic view of a galvanizing alloying apparatus according to one embodiment of the present invention, FIG. 2 is a schematic view of one embodiment of a conventional galvanizing alloying apparatus, and FIG. 3 is a galvanizing alloying apparatus. time-
4 is a table showing a correlation between a temperature and a powdering amount.

Claims (1)

(57) [Claims] 1. A hot-dip galvanizing tank for galvanizing a steel strip, a vertically extending heating furnace provided above the hot-dip galvanizing tank for heating the galvanized steel strip, A floater provided above the heating furnace for changing the traveling direction of the galvanized steel strip, a heating furnace for further heating the reversed heated galvanized steel strip, and a heating furnace for cooling the heated galvanized steel strip A galvanizing apparatus for hot-dip galvanizing, comprising: a quenching chamber provided following the quenching chamber; a top roll provided following the quenching chamber; a cooling tower provided subsequent to the top roll; and a water cooling tank.