KR101377786B1 - Cold-rolled steel sheet for enamel and method of manufacturing the same - Google Patents

Abstract

Disclosed is an enameled cold rolled steel sheet excellent in workability and fish scale resistance and a method of manufacturing the same.
Method for producing a cold rolled steel sheet for enamel according to the present invention in weight%, carbon (C): 0.001 ~ 0.01%, manganese (Mn): 0.05 ~ 0.25%, sulfur (S): 0.02 ~ 0.04%, nitrogen (N): Reheating the slab plate comprising 0.005 ~ 0.01% and tantalum (Ta): 0.05 ~ 0.3%, consisting of the remaining iron (Fe) and unavoidable impurities; Hot-rolling the reheated plate; After cooling the hot rolled plate, winding and air-cooled at 650 ~ 720 ℃; Cold rolling the unwinded sheet material; And continuously annealing the cold rolled sheet material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolled steel sheet for enamel,

More particularly, the present invention relates to a cold rolled steel sheet for an enamel excellent in workability and fish scale resistance and a method for producing the same.

Enamel is applied to glaze on the surface of steel sheet to give corrosion resistance, abrasion resistance, heat resistance, cleanliness, and is used in various fields.

In order to manufacture the enamel, the glaze is applied to the steel sheet and then fired.

Hydrogen dissolved during enamel firing is supersaturated during the cooling process, and hydrogen is released outside as it destroys the enamel layer, resulting in fish scales in the enamel layer.

This fish scale becomes a factor that hinders the surface properties of the enamel.

In addition, the enamel steel sheet is mainly used for flat enamel, because the workability of the normal enamel steel sheet is not good.

Background art related to the present invention is an enamel steel sheet without a bubble defect disclosed in Republic of Korea Patent Publication No. 10-2010-0070683 (published on June 28, 2010) and a manufacturing method thereof.

An object of the present invention is to provide an enameled cold rolled steel sheet excellent in workability and fish scale resistance through the alloy component and process control, and a manufacturing method thereof.

Method for producing a cold rolled steel sheet for enamel according to an embodiment of the present invention for achieving the above object by weight, carbon (C): 0.001 ~ 0.01%, manganese (Mn): 0.05 ~ 0.25%, sulfur (S): 0.02 Reheating the slab plate comprising 0.04%, nitrogen (N): 0.005% to 0.01%, and tantalum (Ta): 0.05% to 0.3%, and consisting of remaining iron (Fe) and unavoidable impurities; Hot-rolling the reheated plate; After cooling the hot rolled plate, winding and air-cooled at 650 ~ 720 ℃; Cold rolling the unwinded sheet material; And continuously annealing the cold rolled sheet material.

At this time, the reheating of the slab plate is preferably performed at 1200 ~ 1350 ℃.

In addition, the hot rolling is preferably carried out under the finish rolling temperature conditions of 850 ~ 950 ℃.

In addition, the cold rolling is preferably carried out at a reduction ratio of 75% or more.

In addition, the continuous annealing is preferably carried out at Ac3 ~ Ac3 + 100 ℃.

Cold rolled steel sheet for enamel according to an embodiment of the present invention for achieving the above object by weight, carbon (C): 0.001 ~ 0.01%, manganese (Mn): 0.05 ~ 0.25%, sulfur (S): 0.02 ~ 0.04 %, Nitrogen (N): 0.005 ~ 0.01% and tantalum (Ta): 0.05 ~ 0.3%, characterized in that consisting of the remaining iron (Fe) and inevitable impurities.

In this case, the cold rolled steel sheet may exhibit yield strength (YP): 8 to 12 Kgf / mm ² , tensile strength (TS): 25 to 30 Kgf / mm ^2, and elongation 50 to 60%.

Cold rolled steel sheet manufacturing method according to the present invention can exhibit a low yield strength and high elongation by controlling the carbon content to 0.01% by weight or less, and adding 0.05 ~ 0.3% by weight of tantalum (Ta), and also the precipitates in the steel The amount can be increased, and the hydrogen storage capacity can be improved.

Therefore, the application of glaze to the cold rolled steel sheet according to the present invention can suppress the generation of fish scale generated when hydrogen is penetrated through the enamel layer during enamel firing, and can produce enamel of complex shape through high formability or processability. .

1 is a flowchart showing a method for manufacturing a cold rolled steel sheet for enamel according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a cold rolled steel sheet for an enamel according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Cold rolled steel sheets for enamel

The cold rolled steel sheet for enamel according to the present invention in weight%, carbon (C): 0.001 ~ 0.01%, manganese (Mn): 0.05 ~ 0.25%, sulfur (S): 0.02 ~ 0.04%, nitrogen (N): 0.005 ~ 0.01% and tantalum (Ta): 0.05-0.3%.

In addition to the above components, the remainder consists of iron (Fe) and inevitable impurities.

Hereinafter, the role and content of each component included in the steel sheet according to the present invention will be described.

Carbon (C)

Carbon (C) is an element contributing to the increase in strength of steel.

The carbon is preferably added at 0.001 to 0.01 wt% of the total weight of the steel sheet. When the amount of carbon added is less than 0.001% by weight, it is difficult to secure desired strength. On the contrary, when the carbon addition amount exceeds 0.01% by weight, there is a problem that it is difficult to produce a complicated enamel by inhibiting workability.

Manganese (Mn)

Manganese (Mn) increases the strength and toughness of the steel, and serves to prevent redness brittleness.

The manganese is preferably added at 0.05 to 0.25% by weight of the total weight of the steel sheet. When the amount of manganese added is less than 0.05% by weight, the effect of adding manganese is insufficient. On the contrary, when the addition amount of manganese exceeds 0.25 weight%, there exists a problem which inhibits moldability.

Sulfur (S)

Sulfur (S) combines with manganese to form non-metallic inclusions, such as MnS, which contributes to preventing red brittleness.

The sulfur is preferably added in 0.02 ~ 0.04% by weight of the total weight of the steel sheet. If the amount of sulfur added is less than 0.02% by weight, the effect of addition is insufficient. On the contrary, when the amount of sulfur is more than 0.04% by weight, it may combine with iron other than manganese, causing red brittle brittleness.

Nitrogen (N)

Nitrogen (N) is combined with tantalum (Ta) to form a precipitate serves to suppress the formation of fish scale during enamel firing.

The nitrogen is preferably included in 0.005 ~ 0.01% by weight of the total weight of the steel sheet. When the content of nitrogen is less than 0.001% by weight, fish scale resistance may be lowered. On the contrary, when the content of nitrogen exceeds 0.01% by weight, the solid solution nitrogen may increase to decrease the impact characteristics and elongation of the steel sheet.

Tantalum (Ta)

Tantalum (Ta) forms precipitates and contributes to the improvement of hydrogen storage capacity.

The tantalum is preferably added at 0.05 to 0.3% by weight of the total weight of the steel sheet. When the addition amount of tantalum is less than 0.05% by weight, the addition effect is insufficient. On the contrary, when the addition amount of tantalum exceeds 0.3% by weight, a problem that greatly impairs workability may occur.

Cold rolled steel sheet for enamel according to the present invention through the composition containing less than 0.01% by weight of carbon and 0.05 ~ 0.3% by weight of tantalum and the process control described later, yield strength (YP): 8 ~ 12 Kgf / mm ² , tensile strength ( TS): 25 ~ 30 Kgf / mm ² and elongation 50 ~ 60%. Also, it can suppress the occurrence of fish scale during enamel firing after glaze application.

Manufacturing method of cold rolled steel sheet for enamel

Hereinafter, a method for manufacturing a cold rolled steel sheet for enamel according to the present invention having the above composition will be described.

1 is a flowchart showing a method for manufacturing a cold rolled steel sheet for enamel according to an embodiment of the present invention.

Referring to Figure 1, the enameled cold rolled steel sheet manufacturing method shown is a slab reheating step (S110), hot rolling step (S120), cooling / winding step (S130), cold rolling step (S140) and continuous annealing step (S150) It includes.

The slab reheating step (S110) re-uses the components and precipitates segregated during casting through reheating of the slab plate of the semi-finished state having the above-described composition.

The slab reheating is preferably carried out for about 1 to 3 hours at the slab reheating temperature (SRT) of 1200-1350 ° C. When the slab reheating is carried out at a temperature lower than 1200 캜, the effect of reusing the precipitate or making the homogenization effect may become insufficient. On the contrary, when the reheating is performed in excess of 1350 ° C., it may be difficult to secure the strength due to grain coarsening, and the economy may be lowered due to excessive heating.

Next, in the hot rolling step (S120) is hot rolled slab plate material reheated.

More specifically, hot rolling is preferably performed under a Finish Delivery Temperature (FDT) of 850 ° C to 950 ° C. Under the above-mentioned finish rolling temperature condition, the structure of the steel sheet prior to cooling may be an austenite phase. If the finishing rolling temperature exceeds 950 DEG C, it may become difficult to secure strength due to crystal grain coarsening. On the contrary, when the finish rolling temperature is less than 850 ° C., the steel sheet material may deteriorate due to the abnormal reverse rolling.

Next, in the cooling / winding step (S130), after cooling at an average cooling rate of about 5 ~ 50 ℃, it is wound at a coiling temperature (CT) of 650 ~ 720 ℃.

If the coiling temperature exceeds 720 ℃, it is difficult to secure sufficient strength. On the contrary, when the coiling temperature is lower than 650 ° C., the moldability may decrease.

Next, in the cold rolling step (S140) is cold-rolled while uncoiling the wound plate. A pickling process may be further included prior to cold rolling.

Cold rolling is preferably carried out at a reduction rate of 75% or more, more preferably 75 to 90% can be presented. If the reduction ratio in the cold rolling is less than 75%, there is a problem that the moldability is difficult to produce a difficult enamel of a complicated shape.

Next, in the continuous annealing step (S150) to continuously anneal the cold-rolled sheet material to adjust the strength and elongation of the final cold-rolled steel sheet.

The continuous annealing is preferably performed in an austenitic single-phase zone of Ac 3 to Ac 3 + 100 ° C. for about 30 seconds to 2 minutes, followed by air cooling or forced cooling. If the continuous annealing temperature is lower than the Ac3 temperature, cracks may occur during processing such as bending. On the contrary, when the continuous annealing temperature exceeds Ac 3 + 100 ° C., the austenite grain size may be greatly increased, thereby deteriorating physical properties of the cold rolled steel sheet.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

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

1. Preparation of cold rolled specimen

The slab sheet having the composition shown in Table 1 was reheated at 1250 ° C. for 2 hours, hot-rolled at 900 ° C. finish rolling temperature, cooled to 680 ° C. at an average cooling rate of 30 ° C./sec, and then wound up to room temperature. Air-cooled to prepare a hot rolled coil. Thereafter, the wound hot rolled coil was pickled and cold rolled at 80% reduction rate, and continuously annealed at 860 ° C. for 1 minute, followed by air cooling to room temperature, thereby preparing cold rolled specimens 1 to 4.

[Table 1] (unit:% by weight)

2. Evaluation of mechanical properties

Tensile strength (TS), yield strength (YS) and elongation (EL) were measured by the tensile test based on JIS No. 5 test piece.

Whether or not fish scale was generated was observed after visually enamel firing for 3 minutes in a firing furnace, where the dew point was 20 ° C. and 850 ° C. after applying glaze and drying.

Table 2 shows the tensile test results and fish scale evaluation results of specimens 1 to 4.

[Table 2]

Referring to Table 2, in the case of specimens 3 to 4 corresponding to the cold rolled steel sheet according to the embodiment of the present invention, yield strength (YP) of 8 to 12 Kgf / mm ² , tensile strength (TS): 25 to 30 Kgf / mm ² And elongation was 50 ~ 60% to satisfy the target mechanical properties, in particular the fish scale did not occur during enamel firing.

On the other hand, in the case of specimens 1 to 2 corresponding to the common enameled cold rolled steel sheet containing titanium, the carbon content was managed to be extremely low, but a certain amount of elongation could be exhibited, but fish scale occurred during enamel firing.

From these results, it can be seen that when adding 0.05 to 0.3% by weight of tantalum (Ta) than titanium (Ti), the moldability is excellent, and it is more effective in suppressing fish scale generation during enamel firing. This may be because tantalum (Ta) forms more sulfide-based or nitride-based precipitates than titanium (Ti) to improve hydrogen storage capacity.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Such changes and modifications are intended to fall within the scope of the present invention unless they depart from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

S110: Slab reheating step
S120: Hot rolling step
S130: cooling / winding step
S140: Cold rolling step
S150: continuous annealing step

Claims (7)

By weight, carbon (C): 0.001 to 0.01%, manganese (Mn): 0.05 to 0.25%, sulfur (S): 0.02 to 0.04%, nitrogen (N): 0.005 to 0.01%, and tantalum (Ta): 0.05 Reheating the slab plate comprising ˜0.3% and consisting of the remaining iron (Fe) and unavoidable impurities;
Hot-rolling the reheated plate;
After cooling the hot rolled plate, winding and air-cooled at 650 ~ 720 ℃;
Cold rolling the unwinded sheet material; And
And continuously annealing the cold rolled sheet material.
The method of claim 1,
The reheating of the slab plate
Enameled cold rolled steel sheet manufacturing method characterized in that carried out at 1200 ~ 1350 ℃.
The method of claim 1,
The hot rolling
Method for producing a cold rolled steel sheet for enamel, characterized in that carried out under the finish rolling temperature conditions of 850 ~ 950 ℃.
The method of claim 1,
The cold rolling
Method for producing a cold rolled steel sheet for enamel, characterized in that carried out at a rolling reduction of 75% or more.
The method of claim 1,
The continuous annealing is
Method for producing cold rolled steel sheet for enamel, characterized in that carried out at Ac3 ~ Ac3 + 100 ℃.
By weight, carbon (C): 0.001 to 0.01%, manganese (Mn): 0.05 to 0.25%, sulfur (S): 0.02 to 0.04%, nitrogen (N): 0.005 to 0.01%, and tantalum (Ta): 0.05 Enameled cold rolled steel sheet comprising ~ 0.3%, consisting of the remaining iron (Fe) and inevitable impurities.
The method according to claim 6,
The cold-
Yield strength (YP): 8 ~ 12 Kgf / mm ² , tensile strength (TS): 25 ~ 30 Kgf / mm ² and elongation cold rolled steel sheet, characterized in that 50 to 60%.

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