KR900004853B1 - Making process for steel plate for galvanization - Google Patents

Abstract

The method is characterised by heating steel slab to above 1200 deg.C, hot-rolling at a finish temperature of 870-920 deg.C, coiling at 580-720 deg.C, cold-rolling to reduction of 60-85%, and holding a dipping temperature to 480-500 deg.C. The steel slab comprises up to 0.1 wt.% C, up to 0.3 wt.% Mn, up to 0.02 wt.% Si, up to 0.015 wt.% P. up to 0.015 wt.% S, 0.03-0.07 wt.% sol. Al, and the balance Fe.

Description

Manufacturing method of galvanized steel sheet with good adhesion

1 is a graph showing the adhesion index according to the plating bath temperature.

2 is a graph showing the Al content in the plating layer according to the plating bath temperature.

The present invention relates to a method for producing a galvanized steel sheet, in particular, to a method for producing a hot-dip galvanized steel sheet having excellent adhesion to a material Al-Killed steel.

As the performance ratio in the steelmaking process increases, the usage of Al-Killed steel sheet is increasing in cold rolled steel sheets and galvanized steel sheets. Various surface-treated steel sheets, including those for plating materials, are not a product value when the plating layer is peeled off even in the harsh processing conditions after manufacture, so the plating adhesion as well as the material of the steel sheet material becomes an important problem.

Therefore, in order to manufacture hot-dip galvanized steel sheet having good adhesion with Al-Killed steel as a material, methods such as component change, high temperature winding after hot rolling, adjustment of Al content in the melting tank and reduction heat treatment cycle adjustment have been proposed. .

First, the method of changing the component is a method of improving the adhesion of Si: 0.02 wt% (hereinafter referred to as%) and Sol.Al to 0.02% or less for increasing the Fe-Zn reactivity, but the adhesion of the level of Capped steel is improved. Not only does not have a Sol.Al is less than 0.02% there is a problem that can not produce a steel sheet for processing and high processing.

On the other hand, the method of hot winding after hot rolling is known to improve the Fe-Zn reactivity during hot dip galvanizing due to the combination of high-strength Al (Sol.Al) and N to form a large amount of AlN. As a result, it is not possible to effectively precipitate the solid solution Al and N into the total amount of AlN. In addition, the reduction heat treatment cycle adjustment method improves the plating adhesion by grain coarsening by increasing the annealing temperature during the reduction heat treatment, but this also does not reach the level of the capped steel.

Therefore, the present invention is to provide a method for producing a galvanized steel sheet having excellent adhesion to the material Al-Killed steel.

Hereinafter, the present invention will be described in detail.

In the present invention, in producing a galvanized steel sheet, C: 0.1 wt% or less (hereinafter referred to as%), Mn: 0.3% or less, Si: 0.02% or less, P, S: 0.015% or less, and Sol.Al: The present invention relates to a method for producing a galvanized steel sheet having excellent adhesion, characterized in that the slab of steel composed of 0.03-0.07% is hot rolled, pickled and cold rolled to maintain the bathing temperature at 480-500 ° C.

In the above, since C is deteriorated in cold forming when 0.1% or more, 0.1% or less is preferable. When Mn is 0.3% or more, the plating adhesion is deteriorated by Mn compound formation during heat treatment, so 0.3% or less is preferable.

Si is the most active element on the surface of the steel sheet during the reduction heat treatment, and when it is 0.02% or more, the adhesion is rapidly deteriorated due to the decrease in Fe / Zn reactivity due to the compound formation, and therefore 0.02% or less is preferable.

Sol.Al means solid Al (Soluble Al), that is, Al ₂ O ₃ in the total Al added to the steel, and means Al except Al. Since the steel sheet cannot be manufactured and the surface quality is deteriorated when it is 0.07% or more, 0.03-0.07% is preferable.

When the plating bath temperature is below 480 ° C and above 500 ° C, the Fe-Al layer is shortened and the Fe-Al layer breaks in a short time. Therefore, Fe reacts directly with Zn, causing the Fe-Zn layer to react. As adhesion is degraded as it is produced, 480-50 ° C. is preferred.

On the other hand, the usual hot rolling preferably applied to the present invention is to be heated to 1200 ° C or higher, hot rolled to a finish rolling temperature of 870-920 ° C, and wound up at 580-720 ° C, and 10% hydrochloric acid by the pickling method. The method of immersing in a solution and pickling is mentioned, It is preferable to cold-roll cold-roll at a reduction ratio of 60-85%.

In the present invention configured as described above, Fe-Al has a larger enthalpy than Fe-Zn, so that more Al is extracted from the galvanizing bath, and Fe-Al bonds are preferentially formed in comparison with Fe-Zn, so that the Al content in the plating layer is increased. Since the plating process is increased by the diffusion action of the Fe-Zn reaction after being increased and concentrated directly on the material surface, a galvanized steel sheet having excellent adhesion is provided.

Hereinafter, the present invention will be described in detail through examples.

Example 1

After hot rolling the slab of the steel composition according to the following Table 1 is subjected to normal pickling, and then cold rolled to prepare a steel sheet having a final thickness of 0.7mm. Continuous melt plating operation, as shown in Table 2, is fixed to the preheating temperature 630 ℃ reduction heating temperature 700 ℃, steel plate temperature (F / S) before plating bath is deposited and changed from 460 ℃ to 520 ℃.

On the other hand, the temperature of the melting bath is 460 ° C, Al content is 0.18%, and Fe content is 0.097%.

TABLE 1

TABLE 2

The adhesion test on the galvanized steel sheet manufactured under the above conditions, that is, the adhesion index and the Al content in the plating layer were measured, and the results are shown in FIGS. 1 and 2. Value is an average value for each steel sheet shown in Table 1). As can be seen in FIGS. 1 and 2, when the plating bath temperature is manufactured at 480-500 ° C. and the melting pot temperature 460 ° C. Excellent plating adhesion on the same level as steel.

Accordingly, the present invention provides an Al-Killed steel sheet having excellent plating adhesion.

Claims (1)

In manufacturing the galvanized steel sheet, in wt%, C: 0.1% or less, Mn: 0.3% or less, Si: 0.02% or less, P and S: 0.015% or less and Sol.Al: 0.03-0.07%, respectively The steel slab was heated to 1200 ° C. or higher, hot rolled to a finish rolling temperature of 870-920 ° C., wound up at a temperature of 580-720 ° C., and cold rolled to a reduction ratio of 60-85%, and then the bathing temperature was increased to 480 ° C. A method for producing a galvanized steel sheet with excellent adhesion, characterized in that it is maintained at -500 ℃.

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