KR101696733B1

KR101696733B1 - Cold-rolled ferritic stainless steel sheet having excellent surface quality and method of manufacturing the same

Info

Publication number: KR101696733B1
Application number: KR1020150078914A
Authority: KR
Inventors: 최가영; 박수호; 박미남
Original assignee: 주식회사 포스코
Priority date: 2015-06-04
Filing date: 2015-06-04
Publication date: 2017-01-17
Also published as: KR20160143900A

Abstract

A ferritic stainless steel cold-rolled steel sheet and a method for manufacturing the same. According to the ferritic stainless steel cold-rolled steel sheet and the method for producing the same according to the present invention, the ferritic stainless steel sheet is subjected to the annealing heat treatment, the shot blast treatment is omitted, and the cold- And the average roughness is rough-rolled to work rolls of # 1,000 or more. Therefore, the surface of the ferritic stainless steel cold-rolled steel sheet has a fine crack fraction of 1.1% or less and a surface roughness of 96 or more.

Description

FIELD OF THE INVENTION The present invention relates to a ferritic stainless steel cold-rolled steel sheet having excellent surface quality and a method for manufacturing the same.

The present invention relates to a ferritic stainless steel cold rolled steel sheet excellent in surface quality and a method of manufacturing the same, and more particularly to a ferritic stainless steel cold rolled steel sheet excellent in surface quality, To a ferritic stainless steel cold-rolled steel sheet having improved gloss and distinctiveness, and a method of manufacturing the same.

Ferritic stainless steel cold rolled steel sheets are mainly used for household or automotive exterior decoration trim applications. For this reason, a ferritic stainless steel cold-rolled steel sheet is an important product with a beautiful surface, and is required to have excellent surface quality with high gloss, in particular, a gloss of 1,050 or more.

Such a ferritic stainless steel cold-rolled steel sheet is obtained by temper rolling of a brass annealed sheet material. In the conventional manufacturing method, however, a fine scratch is present even at a high gloss of 1,050 or more, and surface tackiness is observed during visual observation, There was a problem. That is, even if the glossiness is 1,050 or more, if the minute scratch percentage is high, the gloss appears to be dull during visual observation. Fine scratches, which are the cause of such turbidity, cause the lubricating oil to remain in the grooves without being easily removed during cold rolling.

In addition, when the surface roughness of the ferritic stainless steel cold-rolled steel sheet is inferior, the degree of linearity is lowered. Therefore, in order to obtain a high-gloss ferritic stainless steel cold-rolled steel sheet having excellent gloss and linearity, it is essential to reduce the surface flaws of the material before cold rolling to remove the main cause of fine scratches. , Lubricating oil conditions, and so on. In addition, the manufacturing process parameters such as cold annealing conditions and temper rolling conditions should be managed.

Japanese Patent Application Laid-Open No. 10-2000-005801

Embodiments of the present invention can control the parameters in the manufacturing process of the ferritic stainless steel cold-rolled steel sheet to optimize the factors affecting the gloss and the linearity, for example, the hot-rolled annealing process, the temper rolling process, To provide a ferritic stainless steel cold-rolled steel sheet excellent in strength.

The ferritic stainless steel cold-rolled steel sheet according to an embodiment of the present invention includes 0.10% or less of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn) (S) of not more than 0.020%, nickel (Ni) of not more than 2.0%, chromium (Cr) of 8 to 30%, nitrogen (N) of 0.050% or less and the balance of iron (Fe) and other unavoidable impurities . The surface of the ferritic stainless steel cold-rolled steel sheet has a fine crumb fraction of 1.1% or less, and a linearity of 96 or more.

According to an embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: a step of forming a metal layer containing Al in an amount of 0.10% or less, molybdenum (Mo) of 1.0% or less, copper (Cu) of 1.0% ), 0.01 to 0.50% of vanadium (V), 0.01 to 0.30% of vanadium (V), 0.01 to 0.30% of zirconium (Zr), and 0.0010 to 0.0100% of boron (B).

According to an embodiment of the present invention, the gloss (GS 20 ° C) of the surface of the ferritic stainless steel cold-rolled steel sheet may be 1,050 or more.

According to an embodiment of the present invention, the gloss (GS 20 ° C) / fine scratch percentage of the surface of the ferritic stainless steel cold-rolled steel sheet may be 1,100 or more.

A method of manufacturing a ferritic stainless steel cold-rolled steel sheet according to an embodiment of the present invention includes the steps of annealing a ferritic stainless steel sheet, then performing a pickling treatment without omitting a shot blast treatment, And subjecting the cold-rolled steel sheet to temper rolling to a work roll having an average roughness of # 1,000 or more. The surface of the ferritic stainless steel cold-rolled steel sheet has a fine crumb fraction of 1.1% or less, and a linearity of 96 or more.

According to an embodiment of the present invention, the ferritic stainless steel sheet may contain 0.10% or less of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn) (Fe) and other inevitable impurities are contained in an amount of 0.050% or less, 0.020% or less of sulfur, 0.020% or less of sulfur, 2.0% or less of nickel (Ni), 8 to 30% .

According to an embodiment of the present invention, the gloss (GS 20 ° C) of the surface of the ferritic stainless steel cold-rolled steel sheet may be 1050 or more.

Further, according to an embodiment of the present invention, the temper rolling may be performed in two to five cycles.

According to an embodiment of the present invention, the cold rolling includes a primary cold rolling which is rolled at a reduction ratio of 60% or more and a secondary cold rolling which is performed at a reduction ratio of 65% or more, and the total reduction is 85 % &Lt; / RTI >

Further, according to an embodiment of the present invention, after the primary cold rolling, a polishing process may be performed, and the polishing process may be performed one to two times.

Embodiments of the present invention are directed to a method of manufacturing a ferrite stainless steel cold-rolled steel sheet in which a shot blast process is omitted from a ferritic stainless steel sheet subjected to heat-annealing in a hot- It is possible to minimize the minute scratches in the final cold-rolled steel sheet by the marks.

Further, the ferritic stainless steel sheet subjected to annealing after cold rolling can be rough-rolled to a work roll having an average roughness of # 1,000 or more to improve the gloss of the final cold-rolled steel sheet.

FIG. 1 is a graph showing the gloss / fine scratches of a steel sheet produced by a method of manufacturing a stainless steel cold-rolled steel sheet according to Comparative Examples and Examples. FIG.
FIG. 2 is a graph showing the linearity of a steel sheet produced according to the method of manufacturing a stainless steel cold-rolled steel sheet according to Comparative Examples and Examples. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

Ferritic Stainless steel cold rolled steel plate

According to an embodiment of the present invention, a ferritic stainless steel cold-rolled steel sheet comprises 0.10% or less of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn) (S) of not more than 0.020%, nickel (Ni) of not more than 2.0%, chromium (Cr) of 8 to 30% and nitrogen (N) of 0.050% or less and the balance of iron (Fe) and other unavoidable impurities do.

Carbon (C) is present as an intercalation element as an element forming a carbide, and if it is contained excessively, the strength is increased but it causes impact toughness, corrosion resistance and moldability to be deteriorated. Therefore, the content thereof is preferably 0.10% by weight or less.

Silicon (Si) is an effective element for improving oxidation resistance and corrosion resistance, and if it is increased, oxidation resistance is improved, but the elongation is lowered and the moldability is lowered. Therefore, the content thereof is preferably 1.0 wt% or less.

When Mn content is high, MnS is eluted and corrosion resistance is deteriorated. Therefore, it is preferable that Mn content is 1.0 wt% or less.

As the content of phosphorus (P) and sulfur (S) increases, the pitting resistance and hot workability are lowered, so that phosphorus (P) is preferably 0.050 wt% or less and sulfur (S) is preferably 0.020 wt% or less.

Nickel (Ni) is an element for improving corrosion resistance, and when added in a large amount, not only hard but also stress corrosion cracking may occur.

When the content of chromium (Cr) is small, the corrosion resistance is deteriorated. When the content of chromium (Cr) is large, the corrosion resistance is improved, but the elongation is decreased and the formability is deteriorated, and therefore its content is preferably from 8.0 wt% to 30.0 wt%.

Nitrogen (N) is present as an element which forms a nitride and is present in an interstitial form. If it is contained excessively, the strength is increased, but the impact toughness, corrosion resistance and moldability are deteriorated. Therefore, the content thereof is preferably 0.050 wt% or less.

Aluminum (Al) is an element to be added as a deoxidizing agent, and when it is added in a large amount, it causes surface defects, so it is preferable to limit it to 0.10 wt% or less.

Molybdenum (Mo) is an element added to improve corrosion resistance, particularly pitting resistance. However, if it is added in a large amount, the workability is deteriorated. Therefore, it is preferable to add 1.0 wt% or less.

Copper (Cu) is preferably contained in an amount of more than 0 to 1.0% by weight for improving the corrosion resistance. However, when the content exceeds 1.0% by weight, the workability is deteriorated.

Titanium (Ti) and niobium (Nb) are elements that are effective in improving corrosion resistance and moldability by precipitating solid carbon (C) and nitrogen (N) with carbonitride. However, when added in a large amount, appearance defects and toughness due to inclusions are lowered. Therefore, it is preferable to add 0.01 to 0.50% by weight.

Vanadium (V) and zirconium (Zr) are elements added for fixing carbon (C) and nitrogen (N). In particular, it is an element to be added when the precipitation of chromium carbonitride in the welded portion is suppressed to improve the corrosion resistance and when the high temperature strength is required. However, since they are expensive, it is preferable to add them by 0.01 to 0.30 wt%.

Boron (B) is segregated in grain boundaries to enhance the grain boundary strength, thereby improving secondary workability. However, when added in a large amount, 0.0010 to 0.0100% by weight is preferably added in order to lower the hot workability.

Ferritic Manufacturing method of stainless steel cold rolled steel sheet

The ferritic stainless steel cold-rolled steel sheet is produced by subjecting a ferritic stainless steel sheet to a heat treatment after annealing, followed by pickling treatment without a shot blast treatment, cold-rolling the pickled steel sheet, And can be produced by temper rolling an average roughness to a work roll of # 1,000 or more.

Generally, a shot blast process is performed in the hot-rolled annealing and pickling process in order to facilitate the removal of the scale from the stainless hot-rolled and annealed sheet. In this process, And causes surface turbidity, and thus the gloss of the surface of the final cold-rolled steel sheet is lowered. Here, the fine scratches are flaws formed on the surface of the steel sheet, which means scratches having a length of 50 to 100 탆 and a depth of 1 to 5 탆.

Therefore, the ferritic stainless steel cold-rolled steel sheet according to an embodiment of the present invention may be subjected to pickling treatment in a pickling bath after the annealing heat treatment by omitting the shot blasting treatment. Accordingly, it is possible to omit the shot blasting treatment, which is a cause of the fine scratches in the final cold-rolled steel sheet, to minimize the minute scratches.

Thereafter, the pickled steel sheet can be cold rolled. For example, the cold rolling may be carried out twice as a primary cold rolling and a secondary cold rolling.

For example, the primary cold rolling can be rolled at a reduction ratio of 60% or more. Thereafter, the primary cold-rolled steel sheet can be annealed at a temperature of 850 to 1050 占 폚. For example, the secondary cold rolling can be rolled at a reduction ratio of 65% or more. Thereafter, the secondary cold-rolled steel sheet can be annealed at a temperature of 850 to 1050 ° C. Accordingly, the secondary cold-rolled steel sheet may have a total reduction ratio of 85% or more.

The primary cold-rolled steel sheet may be subjected to a polishing process to remove fine scratches on the surface of the steel sheet before secondary cold rolling and to improve the linearity. The polishing step is preferably performed one to two times, and when the polishing step is carried out three times or more, the polishing cost is increased and the productivity is lowered because it causes a burden on the process.

In order to improve the gloss of the surface of the ferritic stainless steel cold-rolled steel sheet, temper rolling may be carried out. The temper rolling can be carried out with a work roll having an average roughness of # 1,000 or more. When the average roughness of the work roll is less than # 1,000, the work roll is too coarse to reduce the gloss of the steel sheet surface, and it is difficult to obtain a desired level of gloss, for example, a gloss of 1,050 or more.

For example, the temper rolling may be carried out in two to five cycles. When the temper rolling is performed only once, sufficient glossiness is difficult to obtain. If the temper rolling is performed six times or more, the process cost increases and the productivity is lowered because the process is burdened.

The surface of the ferritic stainless steel cold-rolled steel sheet has a gloss (GS 20 ° C) / fine scratch fraction of 1100 or more and a saturation degree of 96 or more. For example, the gloss (GS 20 ° C) / fine scratch fraction may be greater than or equal to 1100 and less than 2000.

For example, the surface of the ferritic stainless steel cold-rolled steel sheet may have a fine crack fraction of 1.1% or less.

For example, the gloss of the surface of the ferritic stainless steel cold-rolled steel sheet may be 1,050 or more.

If the final cold-rolled steel sheet has a high percentage of fine scratches, even if the gloss is high, surface turbidity may be detected during visual observation. Therefore, in order to ensure the excellent surface quality of the final cold-rolled steel sheet, it is necessary to secure both high gloss and a low micro-flaw fraction at the same time.

Therefore, when the gloss value / fine scratch fraction value is compared with the visual observation result, when the gloss / fine scratch fraction value is less than 1,100, the surface scratch can be detected by visual inspection. Therefore, in order to secure an excellent surface quality, it is preferable that the gloss / fine-brittle fraction value is 1,100 or more.

Generally, the gloss / fine crack fraction value of the steel sheet produced according to the prior art is about 100 to 1,050, and when the fine scratch fraction is more than 1.1% even if the gloss is higher than the standard of gloss of 1,050 or more, Most of the flaw fraction values are less than 1,100. For example, in the case where the fine brittle fraction exceeds 1.1%, in order to have a gloss / fine brittle fraction of 1,100 or more, the gloss should be 1,221 or more, and it is somewhat difficult to obtain a glossiness of 1,221 or more in the present process.

Therefore, even if the final cold-rolled steel sheet exhibits high gloss overall, if the fine scratch area ratio exceeds 1.1%, it is recognized as a surface roughness due to minute scratches during visual observation.

However, in the ferritic stainless steel cold-rolled steel sheet produced according to the manufacturing method of the present invention, even if the gloss and the minute crumb fraction are optimized, the value of gloss / fine crumb ratio is 2,000 or more It is difficult to secure.

division Shot ball projection Work roll average roughness (#) Glossiness Fine flaw fraction (%) Sun Young Lee Gloss / fine flaw fraction Comparative Example 1 projection 600 1,019 5.50 95.45 185 Comparative Example 2 projection 600 1,030 4.61 95.95 223 Comparative Example 3 projection 600 1,036 2.61 95.55 397 Comparative Example 4 projection 600 1,040 4.44 95.2 234 Comparative Example 5 projection 600 1,031 5.08 96.1 203 Comparative Example 6 projection 1,000 1,082 4.28 97.2 253 Comparative Example 7 Medicine Projection 1,000 1,183 1.11 96.7 1,065 Comparative Example 8 projection 1,000 1,175 2.37 96.45 496 Comparative Example 9 Medicine Projection 1,000 1,164 1.01 95.21 1,152 Example 1 No projection 1,000 1,206 1.06 96.55 1,137 Example 2 No projection 1,000 1,152 1.00 96.1 1,152 Example 3 No projection 1,000 1,158 0.89 96.76 1,301

The glossiness is the amount of light reflected by the reflection angle on the surface of the object, and is measured using a gloss meter. The area of fine scratches was measured by using an optical microscope to maximize the light source, to prolong the exposure time, to magnify 50 times, and then to measure the area ratio by using an image analyzer. Sunyoungdo is also referred to as resolution and is a measure of the degree of sharpness of the material, measured using a Doryong II measuring instrument.

In Table 1, whether or not the shot ball is projected is represented by 'projection' when the projection amount is large, 'drug projection' when the projection amount is small, and 'no projection' when the projection ball is not projected according to the projection degree of the shot ball during the shot blasting process .

Referring to Table 1, FIG. 1 and FIG. 2, it can be seen that when shot balls are shot through a shot blasting process, fine scratches are generated with a fine scratch percentage of 2% or more, Is generated. In the shot blasting process, even if the shot ball is projected lightly, the fine defect fraction is found to be 1% or more.

The ferritic stainless steel cold-rolled steel sheet produced according to Examples 1 to 3 had a gloss (GS 20 ° C) / fine scratch percentage of 1,100 or more and a surface glossiness of 96 or more, The surface quality of the ferritic stainless steel cold rolled steel sheet is improved due to the excellent linearity and excellent surface smoothness.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited thereto. Those skilled in the art will readily obviate modifications and variations within the spirit and scope of the appended claims. It will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

Claims

(P), 0.020% or less of sulfur (S), 2.0% or less of nickel (Ni), 0.1% or less of silicon (C) Of a ferritic stainless steel cold-rolled steel sheet containing 8 to 30% of chromium (Cr) and 0.050% or less of nitrogen (N) and containing the balance of Fe and other unavoidable impurities,
The surface of the ferritic stainless steel cold-rolled steel sheet has a fine crumb fraction of 1.1% or less and a linearity of 96 or more.

The method according to claim 1, further comprising the steps of: providing an alloy containing not more than 0.10% of aluminum, not more than 1.0% of molybdenum, not more than 1.0% of copper, 0.01 to 0.50% of titanium, 0.01 to 0.50% of niobium, , 0.01 to 0.30% of vanadium (V), 0.01 to 0.30% of zirconium (Zr), and 0.0010 to 0.0100% of boron (B).

The ferritic stainless steel cold-rolled steel sheet according to claim 1, wherein the surface of the ferritic stainless steel cold-rolled steel sheet has a gloss (GS 20 ° C) of 1,050 or more.

The ferritic stainless steel cold-rolled steel sheet according to claim 3, wherein the surface of the ferritic stainless steel cold-rolled steel sheet has a gloss (GS 20 ° C) / fine scratch percentage of 1,100 or more.

A step of subjecting the ferritic stainless steel sheet to a heat treatment for annealing, followed by pickling treatment without omitting the shot blast treatment;
Cold rolling the pickled steel sheet; And
And subjecting the cold-rolled steel sheet to temper rolling to a work roll having an average roughness of at least # 1,000, the method comprising the steps of:
Wherein the surface of the ferritic stainless steel cold-rolled steel sheet has a fine crumb fraction of 1.1% or less and a linearity of 96 or more.

The ferritic stainless steel sheet according to claim 5,
(P), 0.020% or less of sulfur (S), 2.0% or less of nickel (Ni), 0.1% or less of silicon (C) By mass or less of chromium (Cr) and 0.050% or less of nitrogen (N), and the balance of iron (Fe) and other unavoidable impurities.

The method of manufacturing a ferritic stainless steel cold-rolled steel sheet according to claim 5, wherein the surface of the ferritic stainless steel cold-rolled steel sheet has a gloss (GS 20 ° C) of 1,050 or more.

The method of manufacturing a ferritic stainless steel cold-rolled steel sheet according to claim 7, wherein the surface of the ferritic stainless steel cold-rolled steel sheet has a gloss (GS 20 ° C) / fine scratch percentage of 1,100 or more.

6. The method of manufacturing a ferritic stainless steel cold-rolled steel sheet according to claim 5, wherein the temper rolling is performed two to five times.

The cold rolling method according to claim 5,
Primary cold rolling which is rolled at a reduction ratio of 60% or more; And
And a second cold rolling which is rolled at a reduction ratio of 65% or more,
Wherein the total reduction ratio is 85% or more.

11. The method of claim 10, further comprising, after the primary cold rolling,
Wherein the polishing step is carried out one to two times. 2. The method of manufacturing a ferritic stainless steel cold-rolled steel sheet according to claim 1,