KR20120032992A - Manufacturing method of hot rolled steel sheet having excellent adhesiveness with scale layer - Google Patents

Abstract

PURPOSE: A method for manufacturing a hot-rolled steel plate with superior adhesion to a scale layer is provided to prevent the delamination of a scale layer from a base material of a hot-rolled steel plate and minimize dust. CONSTITUTION: A method for manufacturing a hot-rolled steel plate with superior adhesion to a scale layer comprises the steps of: reheating slab to 1100-1300°C, rough rolling the slab(S110), removing scale from the rolled plate(S120), finish rolling the scaled plate(S130), and cooling and coiling the plate at a CT(Coiling Temperature) of 570-620°C(S140). The slab comprises sulfur of 0.005-0.010 weight%.

Description

MANUFACTURING METHOD OF HOT ROLLED STEEL SHEET HAVING EXCELLENT ADHESIVENESS WITH SCALE LAYER}

The present invention relates to a method for manufacturing a hot rolled steel sheet, and more particularly, to a method for manufacturing a hot rolled steel sheet excellent in adhesion to a scale layer which can prevent processing equipment defects due to powder dust in advance.

In general, hot rolled steel sheet is produced by heating the slab to a predetermined temperature in a heating furnace, rolling the heated slab to a predetermined thickness in a rolling mill, and winding the rolled slab sheet while cooling by a cooling device.

Formation of high temperature oxide scale is inevitable in the manufacturing process of such a hot rolled steel sheet. Although it is removed by the descaling process, it is difficult to remove it completely.

An object of the present invention is to provide a method for producing a hot rolled steel sheet having excellent adhesion to the scale layer by minimizing the peeling phenomenon by reducing the thickness of the scale layer by controlling the temperature of the finishing rolling and the impurity content in the steel.

Another object of the present invention is to produce a hot-rolled steel sheet as a plated steel sheet or a cold rolled steel sheet without removing the scale layer through providing a hot rolled steel sheet excellent in adhesion with the scale layer.

The method for manufacturing a hot rolled steel sheet having excellent adhesion to a scale layer according to an embodiment of the present invention includes a rough rolling step of roughly rolling a slab plate; Descaling to remove the scale of the roughly rolled sheet; A finishing rolling step of finishing the descaled sheet material; And a winding step of cooling the finishing rolled plate, and winding it at a coiling temperature (CT): 570 to 620, wherein the finishing rolling start temperature of the finishing rolling step is 1000 to 1080 ° C, and the finishing rolling end temperature is It is characterized by being 860 degrees C or less.

According to another embodiment of the present invention, a method for manufacturing a hot rolled steel sheet having excellent adhesion to a scale layer may include carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), iron, and other unavoidable materials. A slab reheating step of reheating the slab plate formed of impurities; A rough rolling step of roughly rolling the reheated plate; Descaling the rough rolled sheet using a finishing scale braker (FSB); A finishing rolling step of finishing the descaled sheet material; And a winding step of cooling the filament-rolled sheet material, coiling temperature (CT): 570 to 620, and limiting the content of the silicon (Si) to form the slab plate to 0.03 to 0.20 wt%. And, the content of sulfur (S) is characterized in that it is limited to 0.005% by weight or less.

Since the manufacturing method of the hot rolled steel sheet according to the present invention is excellent in adhesion with the scale layer, the peeling phenomenon that the scale layer is separated from the base material of the hot rolled steel sheet does not occur, and the effect of minimizing the generation of powdery dust is effective. have.

Through this, the method for manufacturing a hot rolled steel sheet using the hot rolled steel sheet according to the present invention can be produced as a plated steel sheet or cold rolled steel sheet without removing the scale layer because no powder dust is generated on the surface of the hot rolled steel sheet. As a result, powder dust does not occur on the surface of the hot-rolled steel sheet, thereby preventing the problem of equipment failure.

1 is an image showing a state in which the powdery dust generated on the surface of the hot-rolled steel sheet.
2 is a process flowchart showing a method of manufacturing a hot rolled steel sheet having excellent adhesion with a scale layer according to the present invention.
Figure 3 briefly shows the tissue changes according to the oxygen content and temperature of the hot rolled steel sheet produced by each process of FIG.
4 and 5 are graphs and schematic diagrams showing whether cracks occur according to the scale layer thickness.
6 is an image showing the final structure of the hot rolled steel sheet excellent in scale adhesion according to the present invention.
7 is an image showing the adhesion of the scale layer according to the winding temperature.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims.

Hereinafter, a method of manufacturing a hot rolled steel sheet excellent in adhesion with the scale layer according to the present invention will be described in detail.

The hot rolled steel sheet homogenizes the slab at 1100 to 1300 ° C, finishes hot rolling in the Ar3 to Ar3 + 100 ° C range, and then winds up at 500 to 700 ° C, preferably 550 to 650 ° C to produce a hot rolled coil.

In the manufacturing process of such a hot-rolled steel sheet, a scale layer is inevitably generated by a high temperature oxidation scale.

Subsequently, when fabricating a plated steel sheet or a cold rolled steel sheet using the hot rolled steel sheet thus manufactured, the scale layer generated on the surface of the hot rolled steel sheet must be removed through a pickling process, but the process of removing the scale layer for manufacturing cost reduction. It can also be used by omitting and processing after coating.

In this case, when the scale layer is easily peeled off from the surface of the hot-rolled steel sheet, the scale layer is powdered to cause dust, which may cause shortening of the repair and maintenance cycle of the processing equipment.

1 is an image showing a state in which powdery dust is generated on the surface of a hot rolled steel sheet.

Referring to Figure 1, it can be seen that the scale layer is powdered on the surface of the hot-rolled steel sheet to generate dust. Such dust may not only act as a factor to deteriorate the surface quality during the manufacturing process of the hot rolled steel plated or cold rolled steel sheet, but also cause the dust to be scattered into the processing equipment, causing malfunction or shortening the equipment replacement cycle. Can cause problems.

The present invention is to reduce the thickness of the scale layer to 15㎛ or less in order to minimize the generation of powder dust of the scale layer after descaling the FSB (Finishing Scale Braker), by configuring the composition of the scale layer of Fe + Fe ₃ O ₄ , The adhesiveness between the surface of a steel plate and a scale layer can be improved.

Through this, even without removing the scale layer, even if manufactured using a hot-rolled steel sheet or a cold-rolled steel sheet, it is possible to prevent the problem of equipment failure due to the generation of powder dust on the hot-rolled steel sheet surface.

Hot rolled steel

Hot rolled steel sheet excellent in adhesion to the scale layer according to an embodiment of the present invention is composed of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S) and iron and other unavoidable impurities A slab reheating step of reheating the slab sheet to be reheated, a rough rolling step of roughly rolling the reheated plate, a descaling step of removing the scale using the finishing scale braker (FSB), and the descaled plate The finishing rolling step of finishing rolling and cooling the finishing rolled plate, CT (Coiling Temperature): can be produced by performing a winding step of winding to 570 ~ 620 ℃.

 At this time, it is preferable to limit the content of the silicon (Si) to form the slab plate to 0.03 ~ 0.20% by weight, and limit the content of the sulfur (S) to 0.005% by weight or less.

First, the steel composition of the slab sheet is as follows.

Carbon (C)

Carbon (C) in the present invention is added to secure the strength of the hot rolled steel sheet.

The carbon (C) is preferably added in a content ratio of 0.05 to 0.08% by weight of the total weight of the hot rolled steel sheet.

If the carbon (C) is added less than 0.05% by weight, there is a problem that the strength of the steel sheet is lowered, it is uneconomical to add a relatively large amount of other alloy elements in order to exhibit the same strength.

On the contrary, when the carbon (C) exceeds 0.08% by weight, the strength of the steel sheet is increased, but there is a problem that low-temperature impact toughness and weldability are lowered.

Silicon (Si)

Silicon (Si) plays a role of deoxidation to remove oxygen from steel in the steelmaking process, and also contributes to solid solution strengthening effect to help secure strength. Silicon (Si) is a strong oxidizing element and is concentrated at the interface between the scale and the base metal during the rolling process and suppresses the growth of the scale layer.

In the present invention, silicon (Si) is preferably limited to 0.03 to 0.20% by weight.

If the content of silicon (Si) is less than 0.03% by weight, the interface thickening is not dense, and the effect of inhibiting scale layer growth is insignificant. Conversely, if the content of silicon (Si) exceeds 0.20% by weight, it is possible to form powdery scale dust on the surface of the steel sheet.

Manganese (Mn)

Manganese (Mn) in the present invention is very effective as a solid solution strengthening element, is an element effective in securing the strength by improving the hardenability of the steel.

The manganese (Mn) may be added at 0.15 to 0.25 wt% of the total weight of the hot rolled steel sheet.

The manganese (Mn) increases the hardenability to increase the strength, and as mentioned above combined with silicon (Si) in a content ratio within a certain range contributes to the solid solution strengthening, at least 0.15% by weight or more is preferably added. .

Otherwise, if the content of the manganese (Mn) is added in excess of 0.25% by weight may deepen segregation in the center of the slab plate, and may act as a cause of lowering the impact toughness.

Phosphorus (P)

Phosphorus (P) is a component which suppresses the formation of impurity elements and cementite in steel, and is advantageous in improving strength and corrosion resistance.

However, when the phosphorus (P) is excessively added to the hot-rolled steel sheet can greatly impair the impact toughness, it may cause variation in the final material by the slab center segregation.

For this reason, it is advantageous to keep the content ratio of phosphorus (P) as low as possible.

Therefore, in the present invention, the content of such phosphorus (P) is limited to 0.02% by weight or less of the total weight of the hot rolled steel sheet.

Sulfur (S)

Sulfur (S), like silicon (Si), is concentrated at the interface between the scale and the base metal during the rolling process, and serves to improve the toughness and strength of the steel.

In the present invention, the content of sulfur (S) is preferably limited to 0.005% by weight or less of the total weight of the steel.

If the content of sulfur (S) exceeds 0.005% by weight, an emulsion-based inclusion (eg, MnS) may be formed to significantly inhibit the toughness and strength of the steel, and may cause cracking during processing of the steel.

In addition to the above-mentioned materials, aluminum (Al): 0.01 to 0.05% by weight, titanium (TI): 0.015 to 0.030% by weight, nitrogen (N): 0.008% by weight or less may be further included as necessary for strength reinforcement. And, may further include other unavoidable impurities, the remainder is made of iron (Fe).

Method of manufacturing hot rolled steel sheet

2 is a process flowchart showing a method of manufacturing a hot rolled steel sheet having excellent adhesion with a scale layer according to an embodiment of the present invention.

Referring to Figure 2, the method of manufacturing a hot rolled steel sheet having excellent adhesion to the scale layer according to the present invention is a rough rolling step (S110) for roughly rolling the slab plate, using the FSB (Finishing Scale Braker) Descaling step (S120) to remove the scale, the finishing rolling step 130 for finishing the rough-rolled sheet material and cooling the finishing rolled sheet material, CT (Coiling Temperature): winding to 570 ~ 620 ℃ It may include a winding step (S140).

At this time, the finishing rolling start temperature during the finishing rolling step 130 is 1000 ~ 1050 ℃, limit the finishing rolling temperature to 860 ℃ or less, preferably 840 ~ 860 ℃, the scale layer thickness is 15㎛ or less, preferably Preferably it is reduced to 13 ~ 15㎛ characterized in that the final structure of the scale layer composed of Fe + Fe ₃ O ₄ .

If the finishing rolling start temperature after descaling the FSB exceeds 1080 ° C., scale growth occurs after descaling to increase the scale layer thickness of the hot-rolled steel sheet, thereby facilitating the peeling phenomenon and generating powdery dust. have.

On the contrary, when the finishing rolling start temperature is less than 1000 ° C., problems of increased rolling load and lowered sheet flow due to the lowered rolling temperature occur.

On the other hand, when the finishing rolling end temperature exceeds 860 ° C, the thickness of the scale layer grows to 15 µm or more, so the finishing rolling end temperature is preferably limited to 860 ° C or less.

The take-up temperature is high-temperature safety merchant FeO after the take-up is not present in the scale layer after the winding Fe + Fe ₃ O to ₄ to completely transformed into Fe0 → Fe + Fe ₃ O ₄ to be a transformation temperature of more than 570 ℃, opposed to the take-up If the temperature exceeds 620 ℃ there is a problem that the thickness of the scale layer becomes thick. Therefore, in the present invention, the winding temperature is preferably limited to 570 ~ 620 ℃.

Although not shown in the drawings, a slab reheating step of reheating the slab plate at 1100 to 1300 ° C. before the rough rolling may be further included.

On the other hand, Figure 3 is a simplified view of the oxygen content and the temperature change according to the temperature of the hot rolled steel sheet produced by each process of Figure 2, Figures 4 and 5 is a graph and a schematic diagram showing the occurrence of cracking according to the scale layer thickness. 6 is an image showing the final structure of the hot rolled steel sheet excellent in adhesion with the scale layer according to the present invention.

In this case, in FIG. 3, w represents a wustite (FeO) region, m represents a magnetite region, and h represents a hematite region.

Meanwhile, referring to FIG. 4, it can be seen that as the thickness of the scale layer increases, the probability that cracks exist in the scale increases. That is, it turns out that uniformity exists in a scale in the area | region whose thickness of a scale layer is 14 micrometers or more. In this case, as shown in Figure 5, the thicker the thickness of the scale layer, it can be seen that the possibility of cracking in the scale due to the stress acting on the base material of the hot-rolled steel sheet during the winding and unwinding process.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

1. Manufacturing of hot rolled steel sheet

The compositions of the hot rolled steel sheets applied to Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, 5, and 6 are shown in Table 1 below.

(Chemical composition: wt%) division C Si Mn P S Al TI Al N sample 0.07 0.03 0.20 0.02 0.01 0.03 0.020 0.03 0.08

2. Characterization

Table 2 shows the characteristics of Examples 1, 2 and 3 and Comparative Examples 1, 2, 3, 4, 5 and 6.

division Sasang Rolling
Start temperature
(° C) Finish rolling end temperature
(° C) Coiling temperature
(° C) Scale layer
Thickness (㎛) Scale layer
Furtherance scale
Exfoliation Comparative Example 1 1066 855 500 16.07 FeO / Fe ₃ O ₄ Peeling Comparative Example 2 1052 842 545 17.04 FeO / Fe ₃ O ₄ Peeling Comparative Example 3 1105 853 583 18.05 Fe ₃ O ₄ / Fe + Fe ₃ O ₄ Peeling Example 1 1061 851 601 14.08 Fe + Fe ₃ O ₄ Unpeeled Example 2 1055 847 617 13.20 Fe + Fe ₃ O ₄ Unpeeled Example 3 1067 854 593 13.78 Fe + Fe ₃ O ₄ Unpeeled Comparative Example 4 1087 880 609 16.78 Fe + Fe ₃ O ₄ Peeling Comparative Example 5 1055 877 640 20.78 Fe + Fe ₃ O ₄ Peeling Comparative Example 6 1099 851 643 21.21 Fe + Fe ₃ O ₄ Peeling

Referring to Tables 1 and 2, it can be seen that a significant difference occurs in the thickness of the scale layer under the control of the finishing rolling start temperature, the finishing rolling end temperature, and the winding temperature.

According to the above test, it can be seen that, unlike Comparative Examples 1, 2, 3, 4, 5, and 6, the thickness of the scale layer in Examples 1, 2, 3 was significantly reduced.

In addition, in Comparative Examples 1, 2, 3, 4, 5, and 6, the peeling phenomenon of the scale layer was generated, whereas in Examples 1, 2, and 3, the peeling phenomenon was not generated.

On the other hand, Figure 6 is an image showing the final structure of the hot rolled steel sheet excellent in scale adhesion according to the present invention, Figure 7 is an image showing the adhesion of the scale layer according to the winding temperature.

As shown in Figure 6, it can be confirmed that the final structure of the hot rolled steel sheet excellent in adhesion with the scale layer according to the present invention is Fe + Fe ₃ O ₄ .

On the other hand, referring to Figure 7, although the dust is generated in Comparative Example 1 carried out at the winding temperature 500 ℃, in Examples 1 and 2 carried out at the coiling temperature 580 ℃ and 620 ℃ confirmed that the powder dust did not occur Can be.

According to the test results described above, the hot rolling start temperature is 1000 ~ 1080 ℃, the finishing rolling end temperature is adjusted to 560 ℃ or less and the winding temperature is limited to 570 ~ 620 ℃ hot rolled steel sheet to reduce the thickness of the scale layer to 15 ㎛ or less When it is prepared, since adhesion to the scale layer can be excellent, the peeling phenomenon that the scale layer is separated from the base material of the hot-rolled steel sheet does not occur, thereby minimizing the occurrence of powdered dust.

Therefore, even if the hot rolled steel sheet is used as a plated steel sheet or a cold rolled steel sheet without removing the scale layer, it is possible to prevent the problem of equipment defects caused by the generation of powder dust on the surface of the hot rolled steel sheet.

The foregoing embodiments are to be understood in all respects as illustrative and not restrictive, the scope of the invention being indicated by the following claims rather than the foregoing description, and the meaning and scope of the claims and All changes or modifications that can be derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

S110: Rough Rolling Step
S120: Descaling Step
S130: finishing rolling stage
S140: winding step

Claims (10)

A rough rolling step of roughly rolling the slab plate;
Descaling to remove the scale of the roughly rolled sheet;
A finishing rolling step of finishing the descaled sheet material; And
And a winding step of cooling the filament-rolled sheet material and winding it in CT (Coiling Temperature): 570 to 620.
The finishing rolling starting temperature of the finishing rolling step is 1000 ~ 1080 ℃, finishing finishing temperature is 860 ℃ or less, characterized in that the hot rolled steel sheet excellent in adhesion with the scale layer.
The method of claim 1,
Before the rough rolling step
A method of manufacturing a hot rolled steel sheet having excellent adhesion with a scale layer, further comprising a slab reheating step of reheating the slab plate material at 1100 to 1300 ° C.
The method of claim 1,
The slab plate is
Method for producing a hot rolled steel sheet excellent in adhesion with the scale layer, characterized in that the silicon (Si) content is 0.05 ~ 0.20% by weight.
The method of claim 1,
The slab plate is
Sulfur (S) content of 0.005 ~ 0.010% by weight of the hot rolled steel sheet excellent in adhesion with the scale layer, characterized in that the manufacturing method.
The method of claim 1,
After the descaling step
The thickness of the scale layer is 15㎛ or less method for producing a hot rolled steel sheet excellent in adhesion with the scale layer.
The method of claim 1,
The scale layer is
Fe + Fe ₃ O _{4 A} method for producing a hot rolled steel sheet excellent in adhesion with the scale layer, characterized in that the composition.
The method of claim 1,
In the descaling step
A method for producing a hot rolled steel sheet having excellent adhesion with a scale layer, characterized by using FSB (Finishing Scale Braker).
A slab reheating step of reheating a slab plate composed of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S) and the remaining iron (Fe) and unavoidable impurities;
A rough rolling step of roughly rolling the reheated plate;
Descaling the rough rolled sheet using a finishing scale braker (FSB);
A finishing rolling step of finishing the descaled sheet material; And
And a winding step of cooling the filament-rolled sheet material and winding it in CT (Coiling Temperature): 570 to 620.
Hot rolled sheet excellent in adhesion to the scale layer, characterized in that to limit the content of the silicon (Si) to form the slab plate to 0.03 ~ 0.20% by weight, and the content of the sulfur (S) to 0.005% by weight or less. Method of manufacturing steel sheet.
The method of claim 8,
In the finishing rolling step
Finish rolling temperature is 1000 ~ 1080 ℃, finishing rolling temperature is 860 ℃ or less, characterized in that the hot rolled steel sheet excellent in adhesion with the scale layer.
The method of claim 8,
The slab plate is
The content of the carbon (C) is 0.05 to 0.08% by weight, the content of the manganese (Mn) is 0.15 to 0.25% by weight, the content of the phosphorus (P) with the scale layer, characterized in that less than 0.02% by weight Method for producing hot rolled steel sheet with excellent adhesion.

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