KR101356877B1 - Continuous manufacturing device of ferritic stainless steel and Continuous manufacturing method of using the same - Google Patents

Abstract

The present invention includes a first continuous rolling mill having two or more stands that are sequentially aligned; A second continuous mill connected to the first continuous mill and having two or more stands sequentially aligned; A bright annealing furnace connected to the second continuous mill; And a tempered rolling mill connected to the bright annealing furnace and having a finishing roll. The present invention relates to a continuous production apparatus of ferritic stainless steel and a method of continuously manufacturing ferritic stainless steel.

Description

TECHNICAL FIELD The present invention relates to a ferritic stainless steel and a continuous manufacturing method using the ferritic stainless steel,

The present invention relates to a continuous continuous manufacturing apparatus of ferritic stainless steel and a manufacturing method using the same, and more particularly, by using a novel apparatus and method including one or more continuous rolling mill and bright annealing furnace, excellent productivity and surface quality The present invention relates to a continuous production apparatus for ferritic stainless steel and a manufacturing method using the same.

In general, ferritic stainless steels, which have high deformation resistance and require excellent surface gloss, are rolled by reversibly reciprocating several times using a reversible rolling mill such as a small-size Zhenmier mill, and then annealed in a bright annealing furnace, which is a reducing gas atmosphere. It is common to manufacture the materials by fitting them and finishing rolling for final hardness, shape and surface gloss using a temper mill.

After the reversible rolling mill prepares the material to be rolled in advance on the winding rolls arranged before and after the rolling mill, the thickness is sequentially reduced while reciprocating the material, and the surface of the material is made flat. In accordance with the target thickness and surface quality of the material to replace the operation roll used in the reversible rolling mill from time to time to produce a ferritic stainless steel having a predetermined surface quality. Since the reversible rolling mill is rolled using a small diameter working roll, fine control of the rolling conditions is possible, while the rolling time is relatively long and replacement of the operating roll during the rolling process reduces production efficiency. Therefore, it is mainly used for a steel sheet having high deformation resistance such as a stainless steel sheet, a battery steel sheet or a titanium steel sheet, or a steel sheet requiring a strict surface quality.

Unlike the reversible rolling mill, the continuous rolling mill has a very high productivity compared to the reversible rolling mill, while the operation roll diameter is relatively large, which makes it difficult to finely control the thickness of the wood, and the rolling oil used has a high viscosity. Surface quality is relatively inferior. Since the plurality of stands having the operating rolls are sequentially arranged, the continuous rolling mill is excellent in terms of productivity and work efficiency since the rolling can be performed by passing the work through once to have a predetermined thickness. On the other hand, since the number of stands that can be arranged is limited, rolling under high pressure must be performed in order to produce a ferritic stainless steel having a predetermined thickness. Therefore, it is possible to use a continuous rolling mill in the case of relatively softness such as carbon steel, but it may be a problem in case of other high strength or in case of requiring fine surface quality.

An object of the present invention devised to solve the above problems is to provide a continuous continuous production apparatus of ferritic stainless steel, including a novel continuous rolling mill, and having an excellent surface quality.

In addition, another object of the present invention is a method for producing a ferritic stainless steel using a continuous rolling mill, a method of producing a continuous continuous ferritic stainless steel not only improves productivity, but also has a surface quality similar to that of a conventional reversible rolling mill. To provide.

According to a feature of the present invention for achieving the object as described above, the present invention is a continuous continuous production apparatus of ferritic stainless steel rolling the ferritic stainless steel, the first continuous rolling mill having two or more stands sequentially aligned ; A second continuous mill connected to the first continuous mill and having two or more stands sequentially aligned; A bright annealing furnace connected to the second continuous mill; And a temper rolling mill connected to the bright annealing furnace and having a finishing roll.

Each of the first continuous mill and the second continuous mill may include first to fourth stands, and each of the first to fourth stands may include one or more operation rolls.

In addition, the operation roll may include a diameter is in the range of 130mm to 150mm.

In this case, in the first continuous rolling mill, the operating roll of the first stand has a surface roughness (Ra) of 0.8 μm to 1.0 μm, and the operating rolls of the second and third stands have a surface roughness (Ra) of 0.4 μm to 0.6 μm. , The working roll of the fourth stand may have a surface roughness (Ra) of 0.2 μm to 0.4 μm.

Preferably, in the second continuous mill, the operating rolls of the first to third stands have a surface roughness (Ra) of 0.2 μm to 0.4 μm, and the operating rolls of the fourth stand have a surface roughness (Ra) of 0.1 μm to 0.8. May be μm.

The first continuous rolling mill and the second continuous rolling mill may further include rolling oil, and the rolling oil may include mineral oil-based knit oil having a viscosity of 15 cSt to 25 cSt.

In addition, the rolling oil may have a saponification degree of 40 mgKOH / g or more and a flash point of 210 ° C. or more.

In this case, the injection amount of the rolling oil in the second continuous mill may be 40% to 60% of the injection amount of the rolling oil in the first continuous mill. Preferably, the rolling oil injection amount in the second continuous mill may be 50% of the rolling oil injection amount in the first continuous mill.

The bright annealing furnace may include reducing hydrogen gas.

The temper rolling mill includes a finishing rolling roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm, and may be lubricated without introducing rolling oil.

In addition, according to another feature of the present invention, the present invention is a method for rolling a ferritic stainless steel, the first continuous rolling step of rolling a ferritic stainless steel with a first continuous rolling mill having two or more stands that are arranged in sequence ; A second continuous rolling step of rolling the ferritic stainless steel passed through the first continuous rolling step into a second continuous mill having two or more stands which are sequentially aligned; An annealing step of annealing the ferritic stainless steel that has undergone the second continuous rolling step using a bright annealing furnace; And a temper rolling step of rolling the ferritic stainless steel that has undergone the annealing step into a temper rolling mill having a finishing rolling roll.

In the first continuous rolling step, the first continuous rolling mill includes first to fourth stands each having one or more working rolls, and in the second continuous rolling step, the second continuous rolling mills respectively include one or more working rolls. It includes a first to fourth stand provided, wherein the ferritic stainless steel may sequentially pass through the first to fourth stand of the first continuous mill and the first to fourth stand of the second continuous mill.

In the first continuous rolling step and the second continuous rolling step, respectively, the stainless steel is rolled by using rolling oil, and the rolling oil injection amount in the second continuous rolling step is 40% to 60% of the rolling oil injection amount in the first continuous rolling step. May be%. Preferably, the rolling oil injection amount in the second continuous rolling step may be 50% of the rolling oil injection amount in the first continuous rolling step.

In the first continuous rolling step, the ferritic stainless steel may be rolled at a reduction ratio of 50% to 70%, and in the second continuous rolling step, the ferritic stainless steel may be rolled at a reduction ratio of 30% to 50%.

In the first continuous rolling step, the ferritic stainless steel may be rolled at a reduction ratio of 60% to 67%, and in the second continuous rolling step, the ferritic stainless steel may be rolled at a reduction ratio of 33% to 40%.

In the annealing step, the ferritic stainless steel may be annealed in a bright annealing furnace in a reducing hydrogen gas atmosphere.

In the temper rolling step, the ferritic stainless steel may be rolled with a finishing roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm, but without lubrication of rolling oil.

According to the present invention as described above, it is possible to provide a continuous continuous production apparatus of ferritic stainless steel comprising a novel continuous rolling mill, which can produce a ferritic stainless steel having excellent surface quality.

In addition, according to the present invention is a method for producing a ferritic stainless steel using a continuous rolling machine, not only to improve the productivity, but also to provide a method for producing a continuous continuous ferritic stainless steel having a surface quality similar to that of using a conventional reversible rolling mill. can do.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of an apparatus for continuously manufacturing a ferritic stainless steel according to a preferred embodiment of the present invention. Fig.
FIG. 2 is a flowchart showing a continuous continuous manufacturing method of a ferritic stainless steel according to a preferred embodiment of the present invention. FIG.

The details of other embodiments are included in the detailed description and drawings.

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. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. In the following description, it is assumed that a part is connected to another part, But also includes a case in which other elements are electrically connected to each other in the middle thereof. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic view of an apparatus for continuously manufacturing a ferritic stainless steel according to a preferred embodiment of the present invention; FIG.

Continuous continuous production apparatus 10 of ferritic stainless steel according to a preferred embodiment of the present invention includes a first continuous rolling mill (100) having two or more stands (110) sequentially aligned; A second continuous mill (200) connected to the first continuous mill (110) and having two or more stands (210) sequentially arranged; A bright annealing furnace (300) connected to the second continuous mill (200); And a temper mill 400 connected to the bright annealing furnace 300 and having a finishing roll 410.

In addition, each of the first continuous mill 100 and the second continuous mill 200 includes first to fourth stands 110 and 210, and each of the first to fourth stands 110 and 210 is one. The above operation rolls 120 and 220 may be included. At this time, the operation roll (120, 220) is preferably in the range of 130mm to 150mm in diameter.

The first continuous mill 100 and the second continuous mill 200 are provided with first to fourth stand (110a, 110b, 110c, 110d, 210a, 210b, 210c, 210d) sequentially provided, respectively, The first to fourth stands 110a, 110b, 110c, 110d, 210a, 210b, 210c, and 210d may each have one or more operation rolls 120 and 220. The operation rolls 120 and 220 are rolled by applying pressure at upper and lower portions of the ferritic stainless steel provided in a sheet form in order to control the thickness of the ferritic stainless steel. In this case, the ferritic stainless steel is the first continuous rolling mill by using the winding rolls 130 and 230 provided at the entrance and exit sides of the first and fourth stands 110a, 110d, 210a, 210b, 210c, and 210d. Pass through the first to fourth stand (110a, 110b, 110c, 110d) of (100), and then through the first to fourth stand (210a, 210b, 210c, 210d) of the second continuous mill 200. can do.

When rolling ferritic stainless steel using a rolling mill like the first and second continuous mills, it is necessary to control the rolling conditions in order to secure surface quality and high-speed rolling. For example, in the rolling process using only the first and second continuous rolling mills, it is difficult to secure the surface quality when rolling rolling conditions such as working rolls, rolling speeds, rolling oils, and the like using ordinary conditions. Therefore, this invention rolls a ferritic stainless steel by the novel continuous manufacturing apparatus of the ferritic stainless steel which uses rolling conditions as follows.

The operation rolls 120 and 220 for rolling the ferritic stainless steel may have a diameter of 130 mm to 150 mm. When the diameter of the operation roll (120, 220) is less than 130mm, the pressure by the operation roll (120, 220) applied to the ferritic stainless steel is not sufficient, to compress the ferritic stainless steel to a predetermined thickness A supplementary force must be added in order to increase the process cost. In addition, when the diameter of the operation roll (120, 200) is more than 150mm, the pressure applied to the ferritic stainless steel is increased, the surface of the ferritic stainless steel is not flat, may cause surface defects. In addition, by increasing the volume and weight of the first and second continuous mill (100, 200) can be a problem in managing the device.

In the first continuous mill 100, the operation roll 120a of the first stand 110a has a surface roughness Ra of 0.8 μm to 1.0 μm, and the operation rolls of the second and third stands 110b and 110c. 120b and 120c may have surface roughness (Ra) of 0.4 μm to 0.6 μm, and the operation roll 120d of the fourth stand 110d may have surface roughness (Ra) of 0.2 μm to 0.4 μm. The working rolls 220a, 220b, 220c of the first to third stands 210a, 210b, and 210c of the second continuous mill 200 have surface roughness Ra of 0.2 μm to 0.4 μm, and the fourth stand ( The operating roll 220d of 210d) may have a surface roughness (Ra) of 0.1 μm to 0.8 μm.

The actuating roll 120 is a member for directly rolling the ferritic stainless steel to face the ferritic stainless steel, the surface roughness of the actuating roll 120 may directly affect the surface quality of the ferritic stainless steel. In addition, the rolling performed in the preceding stand 110 may affect the rolling in the subsequent stand 110, and also in the first to fourth stands 110a, 110b, 110c, 110d and The surface quality of the ferritic stainless steel according to the transfer can be transferred to affect the subsequent process. Therefore, the surface roughness of the operation rolls 120 and 220 provided in the stands 110 and 210 of the first and second continuous mills 100 and 200 may be correlated and influenced.

For example, in the first continuous mill 100, the operation roll 120a of the first stand 110a has a surface roughness (Ra) of less than 0.8 μm or more than 1.0 μm, and the second and third stands 110b, The operating rolls 120b and 120c of 110c have a surface roughness (Ra) of less than 0.4 μm or more than 0.6 μm, and the operating rolls 120d of the fourth stand 110d have a surface roughness of less than 0.2 μm of Ra. If it exceeds 0.4 mu m, it may cause surface defects in the rolled ferritic stainless steel, which may not be cured by the subsequent process, which may be a problem for the surface quality of the final product.

In addition, in the second continuous mill 200, the operation rolls (220a, 220b, 220c) of the first to third stands (210a, 210b, 210c) has a surface roughness (Ra) of less than 0.2㎛, or more than 0.4㎛ In addition, when the working roll 220d of the fourth stand 210d has a surface roughness (Ra) of less than 0.1 μm or more than 0.8 μm, surface defects are similarly induced in the ferritic stainless steel, so that the second continuous mill ( The surface annealing of the ferritic stainless steel is also not cured by the bright annealing furnace 300 and the temper rolling mill 400 connected to the 200, which may cause quality problems.

The first continuous mill 100 and the second continuous mill 200 may further include rolling oil, and the rolling oil may include mineral oil-based knit oil having a viscosity of 15 cSt to 25 cSt. In this case, the rolling oil may have a saponification degree of 40 mgKOH / g or more and a flash point of 210 ° C. or more.

When the ferritic stainless steel is rolled by using the first and second continuous mills 100 and 200, the ferritic stainless steel is rolled under high pressure so that friction occurs between the operating rolls 120 and 220 and the ferritic stainless steel. This part may be peeled off and transferred to the operation rolls 120 and 220. Since the operating rolls 120 and 220 roll continuously the ferritic stainless steel while rotating, the ferritic stainless steel transferred to the surface of the operating rolls 120 and 220 acts as an uneven surface to subsequently roll the ferritic stainless steel. It may cause a defect. Therefore, in order to prevent the use of the rolling oil, the rolling oil may require a predetermined viscosity, saponification degree and flash point by the diameter and the reduction ratio, the reduction speed of the operation roll (120, 220). When the operation rolls 120 and 220 according to the present invention are about 150 mm, mineral oil-based knit oil having a viscosity of 15 cSt to 25 cSt may be used. In addition, the rolled oil has a saponification degree of 40 mgKOH / g or more, the flash point is preferably 210 ℃ or more.

When the viscosity of the rolled oil is less than 15 cSt, the thickness of the oil film formed on the surface of the ferritic stainless steel may not be sufficient, causing heat streaks under high pressure, which may cause problems in surface quality. In addition, when the viscosity of the rolling oil is greater than 25 cSt, the rolling oil may not be easily introduced between the ferritic stainless steel and the operation roll, thereby making it difficult to secure surface gloss. In addition, when the degree of saponification of the rolling oil is less than 40mgKOH / g, the strength of the oil film provided on the surface of the ferritic stainless steel is a problem, and when the flash point of the rolling oil is less than 210 ℃ is provided with a process for washing the rolling oil separately. In the subsequent bright annealing furnace, the rolled oil may remain in the ferritic stainless steel without being removed.

The rolling oil injection amount in the second continuous mill 200 may be 40% to 60% of the rolling oil injection amount in the first continuous mill 100. Preferably, the rolling oil injection amount in the second continuous mill 200 may be 50% of the rolling oil injection amount in the first continuous mill 100.

Usually, the surface gloss of ferritic stainless steel is largely determined by the rolling conditions of the final rolling mill, and in the final rolling mill, rolling is carried out with a small diameter working roll, a low viscosity rolling oil and a low speed rolling condition. On the other hand, in the case of the first and second continuous mills as in the present invention, only the final rolling conditions, that is, the rolling speed of the second continuous mill cannot be independently controlled. Therefore, in order to secure the surface quality of the ferritic stainless steel, it is preferable to spray the rolling oil injection amount in the second continuous mill in a smaller amount than the rolling oil injection amount in the first continuous mill.

When the amount of rolled oil sprayed in the second continuous mill 200 is less than 40%, the amount of rolled oil is not sufficient to maintain the surface quality of the ferritic stainless steel. Difficult to maintain film thickness In addition, when the rolling oil injection amount in the second continuous mill (200) is more than 60% of the rolling oil injection amount in the first continuous mill (100), the viscosity of the rolling oil in the final step is high, the surface quality of high-gloss ferritic stainless steel Difficult to secure. In particular, the rolling oil injection amount in the second continuous rolling mill 200 may be preferably 50% of the rolling oil injection amount in the first continuous rolling mill 100. When the rolling oil injection amount is 50%, the use of unnecessary rolling oil is reduced. In addition, since unnecessary losses for removing the rolled oil can be reduced in a subsequent process, production costs can be reduced and process efficiency can be improved.

As described above, in the case of rolling the ferritic stainless steel using only the first and second continuous mills, the above-described rolling mill can relatively shorten the rolling time, while the first and second continuous mills are continuously processed. It is difficult to control the surface defects of ferritic stainless steel that can occur during high accuracy. In addition, even if controlled, the process must be stopped in the middle can greatly reduce the process efficiency. That is, for this reason, continuous rolling of the ferritic stainless steel using only the first and second continuous mills makes it difficult to secure the surface quality of the ferritic stainless steel. Surface defects, such as heat strips, can also affect subsequent processes, adversely affecting the quality of the final product. On the other hand, in the case of using the continuous continuous production apparatus of ferritic stainless steel according to the present invention, high-speed rolling is possible to increase the process efficiency, it is also possible to easily ensure the surface quality of the rolled ferritic stainless steel.

The brass annealing furnace 300 may include a reducing hydrogen gas. In the present invention, pickling can be omitted using a brass annealing furnace 300 using a reducing hydrogen gas, and ferritic stainless steels passing through a brass annealing furnace 300 can be rolled in a temper rolling machine 400. The ferritic stainless steel is annealed in the brass annealing furnace 300, and the rolling oil and the like remaining on the surface of the ferritic stainless steel can be removed.

The temper rolling mill 400 includes a finishing rolling roll 410 having a surface roughness (Ra) of 0.01 μm to 0.02 μm, and may be lubricated without introducing rolling oil.

For example, the finishing rolling roll 410 in the temper rolling mill 400 is preferably a surface roughness (Ra) of 0.01㎛ to 0.02㎛, the surface roughness (Ra) of the finishing rolling roll 410 is less than 0.01㎛ In this case, it is difficult to flatten the concave shape occurring on the surface of the ferritic stainless steel. In addition, when the roughness Ra of the finishing rolling roll 410 is more than 0.02 µm, the glossiness of the ferritic stainless steel is hardly obtained above a predetermined target. Since lubrication-free rolling is performed in the temper rolling mill 400, the glossiness decrease due to the rolling oil can be prevented, thereby ensuring a high gloss surface quality.

FIG. 2 is a flowchart illustrating a continuous continuous manufacturing method of a ferritic stainless steel according to a preferred embodiment of the present invention.

Referring to Figure 2, the present invention is a method for continuously manufacturing a ferritic stainless steel, the first continuous rolling step of rolling a ferritic stainless steel by a first continuous rolling mill having two or more stands that are sequentially aligned (S1) ); A second continuous rolling step (S2) of rolling the ferritic stainless steel which has undergone the first continuous rolling step into a second continuous mill having two or more stands which are sequentially aligned; Annealing step (S3) of annealing the ferritic stainless steel which has undergone the second continuous rolling step using a bright annealing furnace; And a temper rolling step (S4) of rolling the ferritic stainless steel that has undergone the annealing step into a temper rolling mill having a finishing rolling roll (S4).

In the first continuous rolling step (S1), the first continuous rolling mill includes first to fourth stands each having at least one working roll, and in the second continuous rolling step (S2), the second continuous rolling mill is A first to fourth stand each having one or more operation rolls, wherein the ferritic stainless steel includes first to fourth stands of the first continuous mill and first to fourth stands of the second continuous mill. Can be rough sequentially. In the first and second continuous rolling mill, the first to fourth stands each include one or more operating rolls having a diameter in the range of 130 mm to 150 mm, and can continuously roll ferritic stainless steel by the operating rolls. .

In the first and second continuous rolling step (S1, S2) it can be continuously rolled through each of the first to fourth stand through the take-up roll. In this case, the rolling oil may be injected into the ferritic stainless steel at the entrance and exit sides of the first continuous mill and the second continuous mill. In addition, a welder, a looper, or the like may be arranged between the first and second continuous mills to continuously roll the ferritic stainless steel.

The operating roll of the first stand in the first continuous rolling step (S1) has a surface roughness (Ra) of 0.8 μm to 1.0 μm, and the operating rolls of the second and third stands have a surface roughness (Ra) of 0.4 μm to 0.6 It is a micrometer and the operation roll of a 4th stand can use the thing whose surface roughness (Ra) is 0.2 micrometer-0.4 micrometer. In addition, in the second continuous rolling step (S2), the operating rolls of the first to third stands have a surface roughness (Ra) of 0.2 μm to 0.4 μm, and the operating rolls of the fourth stand have a surface roughness (Ra) of 0.1 μm. To 0.8 μm can be used.

In the first continuous rolling step (S1) and the second continuous rolling step (S2), respectively, the stainless steel is rolled using rolling oil, and the injection amount of the rolling oil in the second continuous rolling step (S2) is the first continuous rolling step. 40% to 60% of the rolling oil injection amount in (S1), preferably, the rolling oil injection amount in the second continuous rolling step (S1) is 50% of the rolling oil injection amount in the first continuous rolling step (S1). Can be. In addition, the rolled oil may be a mineral oil-based knit oil having a viscosity of 15 cSt to 25 cSt, a saponification degree of 40 mgKOH / g or more, and a flash point of 210 ° C. or more may be used.

In the first continuous rolling step S1, the ferritic stainless steel may be rolled at a rolling reduction rate of 50% to 70%, and the second continuous rolling step S2 may be performed to roll the ferritic stainless steel at a rolling reduction rate of 30% to 50%. have. Preferably, the first continuous rolling step (S1) is to roll the ferritic stainless steel at 60% to 67% reduction rate, the second continuous rolling step (S2) is 33% to reduce the ferritic stainless steel To 40%.

When the reduction ratio in the first continuous rolling step (S1) is less than 50%, it is difficult to roll the ferritic stainless steel to a predetermined thickness even by the second continuous rolling step (S2), which is a subsequent rolling process. When the reduction ratio in the first continuous rolling step (S1) is greater than 70%, heat streaks may occur on the surface of the ferritic stainless steel. In addition, when the reduction rate in the second continuous rolling step (S2) is less than 30%, it is difficult to control the thickness of the final product of the ferritic stainless steel thinly, the reduction rate in the second continuous rolling step (S2) is 50% If exceeded, it may be difficult to produce a high gloss ferritic stainless steel by causing a surface defect. Therefore, in the first continuous rolling step (S1), after the ferritic stainless steel is rolled to a thickness about half the final target thickness and the initial thickness, the second continuous rolling step (S1) subsequent to the first continuous rolling step (S1) It may be rolled further in S2).

In addition, the rolling reduction rate of the first continuous rolling step (S1) may be 60% to 67%, the second continuous rolling step (S2) may be preferably the reduction rate of the ferritic stainless steel is 33% to 40%. . The reduction ratio in the first and third continuous rolling steps (S1, S2) is to make the ferritic stainless steel to have the optimum surface quality, and at the same time can be efficiently controlled to the target thickness.

The annealing step (S3) can anneal the ferritic stainless steel in a brass annealing furnace in a reducing hydrogen gas atmosphere. The ferritic stainless steel passed through the second continuous rolling step (S2) may be annealed in the bright annealing furnace to remove the rolling oil remaining on the surface.

In the temper rolling step (S4), the ferritic stainless steel is rolled with a finishing roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm, but without lubrication of rolling oil. Ferritic stainless steel, which has undergone the first and second continuous rolling steps S1 and S2 and the annealing step S3, may have low toughness instead of increasing strength. Therefore, in the temper rolling step (S4) it is possible to refine the crystal grains of the ferritic stainless steel from which the internal stress is removed in the preceding annealing step (S3). In the temper rolling step (S4), it is possible to improve the glossiness of the ferritic stainless steel by using a finishing roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm. In addition, in the temper rolling step (S4) it is possible to ensure a high gloss surface quality by lubrication-free rolling without using rolling oil.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the scope of the present invention is not limited by the following examples.

Various embodiments of the ferritic stainless steel of STS430 were fabricated by the continuous continuous manufacturing apparatus of the ferritic stainless steel according to the above-mentioned FIG. 1 and the continuous continuous manufacturing method according to FIG. Hereinafter, results of examining physical properties and surface qualities of Comparative Examples and Examples are examined.

The ferritic stainless steel, STS430, was rolled using various conditions of reduction ratio (%) using the first and second continuous mills. The rolled ferritic stainless steel was annealed in a bright annealing furnace, and then surface roughness (Gs20) was confirmed after temper rolling. In the bright annealing furnace, the plate speed was 40mpm, the annealing temperature was 820 ° C, and the dew point was -60 ° C. In the table below, when heat streaks occurred, the surface glossiness was expressed as NG. When heat streaks did not occur and excellent surface quality was shown, the surface glossiness was expressed as OK. The surface gloss (Gs20) was measured in a direction perpendicular to the GS20 rolling direction.

First continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 3.0 2.00 33.3 113 1.0 Second stand 2.00 1.40 30.0 150 0.4 NG Third stand 1.40 1.00 28.6 196 0.4 NG Fourth stand 1.00 0.80 20.0 250 0.2 NG Second continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 0.8 0.70 12.5 167 0.4 NG Second stand 0.70 0.62 11.4 195 0.4 NG Third stand 0.62 0.55 11.3 227 0.4 NG Fourth stand 0.55 0.50 9.1 250 0.1 NG

Table 1 is for Comparative Example 1, using a STS430 having a thickness of 3.0t and a length of 1290mm to perform rolling (3.0t → 0.8t) with a first continuous mill, followed by rolling with a second continuous mill (0.8 After t → 0.5t), annealing was carried out in the bright annealing furnace, followed by temper rolling to check the surface glossiness. The reduction rate in the first continuous mill was 73.3%, exceeding 70%, and the reduction rate in the second continuous mill was 37.5%. As described above, since the reduction ratios of the first and second continuous mills are complementary to each other, the reduction in the first continuous mills even if the reduction ratio in the second continuous mill is within the range of 30% to 50%. If the rate does not satisfy the 50% to 70% it could be confirmed that the heat strip occurs.

First continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 3.0 2.26 24.7 113 1.0 Second stand 2.26 1.92 15.0 150 0.4 NG Third stand 1.93 1.64 15.0 196 0.4 NG Fourth stand 1.66 1.40 15.7 250 0.2 NG Second continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 1.40 1.10 21.4 167 1.40 NG Second stand 1.10 0.76 30.9 195 1.10 NG Third stand 0.76 0.61 19.7 227 0.76 NG Fourth stand 0.61 0.50 18.0 250 0.61 NG

Table 2 is for Comparative Example 2, using the STS430 having a thickness of 3.0t and a length of 1290mm to perform rolling (3.0 → 1.4t) with a first continuous mill, followed by rolling with a second continuous mill (1.4t → 0.5t) was annealed in a bright annealing furnace and temper rolled to check the surface glossiness. The reduction rate in the first continuous mill was 53.3%, and the reduction rate in the second continuous mill was 64.2%. Since the reduction rates of the first and second continuous mills complementary to each other, even if the reduction rate in the first continuous mill is within the range of 50% to 70%, the reduction rate in the second continuous mill is 30% to If 50% is not satisfied, it can be confirmed that heatstrip occurs.

First continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 3.0 2.20 26.7 113 1.0 Second stand 2.20 1.55 29.5 150 0.4 OK Third stand 1.55 1.15 25.8 196 0.4 OK Fourth stand 1.15 0.90 21.7 250 0.2 OK Second continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 0.9 0.74 17.8 167 0.4 OK Second stand 0.74 0.62 16.2 195 0.4 OK Third stand 0.62 0.55 11.3 227 0.4 OK Fourth stand 0.55 0.50 9.1 250 0.1 OK

Table 3 is for Example 1, performing rolling (3.0 → 0.9t) with a first continuous mill using STS430 having a thickness of 3.0t and a length of 1290mm, followed by rolling with a second continuous mill (0.9t → 0.5t) was annealed in the bright annealing furnace and temper rolled to check the surface glossiness. The rolling reduction in the first continuous mill was 70%, the rolling reduction in the second continuous mill was 44.4%, and it was confirmed that no heat streaks occurred on the surface.

First continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 3.0 2.26 24.7 113 1.0 Second stand 2.26 1.60 29.2 150 0.4 OK Third stand 1.60 1.20 25.0 196 0.4 OK Fourth stand 1.20 1.00 16.7 250 0.2 OK Second continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 1.0 0.80 20.0 167 0.4 OK Second stand 0.80 0.66 17.5 195 0.4 OK Third stand 0.66 0.56 15.2 227 0.4 OK Fourth stand 0.56 0.50 10.7 250 0.1 OK

Table 4 is for Example 2, performing rolling (3.0 → 1.0t) with a first continuous mill using STS430 having a thickness of 3.0t and a length of 1290mm, followed by rolling with a second continuous mill (1.0t → 0.5t) was annealed in a bright annealing furnace and temper rolled to check the surface glossiness. The rolling reduction in the first continuous mill was 66.7%, the rolling reduction in the second continuous mill was 50%, and it was confirmed that no heat streaks occurred on the surface.

First continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 3.0 2.26 24.7 113 1.0 Second stand 2.26 1.80 20.4 150 0.4 OK Third stand 1.80 1.45 19.4 196 0.4 OK Fourth stand 1.45 1.20 17.2 250 0.2 OK Second continuous rolling mill Mouth thickness
(t) Thickness
(t) Reduction rate
(%) Rolling speed
(mpm) Operating roll
Surface roughness
(탆) Surface gloss
(Gs20) 1st stand 1.2 0.95 20.8 167 0.4 OK Second stand 1.0 0.76 24.0 195 0.4 OK Third stand 0.82 0.61 25.6 227 0.4 OK Fourth stand 0.68 0.50 26.5 250 0.1 OK

Table 5 is for Example 3, performing rolling (3.0 → 1.2t) with a first continuous mill using STS430 having a thickness of 3.0t and a length of 1290mm, followed by rolling with a second continuous mill (1.2t → 0.5t) was annealed in a bright annealing furnace and temper rolled to check the surface glossiness. The rolling reduction in the first continuous mill was 60%, the rolling reduction in the second continuous mill was 58.3%, and it was confirmed that no heat streaks occurred on the surface.

Referring to Tables 1 to 5, Comparative Example 1 and Comparative Example 2 and Examples 1 to 3 are compared as follows. In Examples 1 to 3 (Tables 3 to 5), the reduction ratio in the first rolling mill satisfies 50% to 70%, and the reduction ratio in the second continuous mill satisfies 30% to 50%. And, it was confirmed that no heat streaks occurred on the surface. On the other hand, in the case of Comparative Example 1 (Table 1), which satisfies only the reduction rate of the second continuous mill, or in Comparative Example 2 (Table 2), which satisfies only the reduction rate of the first continuous mill, heat streaks occurred. I could confirm it. That is, since the reduction ratios in the first and second continuous mills are complementary to each other, it can be confirmed that the predetermined surface quality cannot be secured when only one of them is satisfied.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalents thereof are included in the scope of the present invention Should be interpreted.

100: first continuous rolling mill 200: second continuous rolling mill
300: brass annealing furnace 400: temper rolling mill

Claims (16)

A first continuous mill having two or more stands sequentially aligned;
A second continuous mill connected to the first continuous mill and having two or more stands sequentially aligned;
A bright annealing furnace connected to the second continuous mill; And
Including; the temper rolling mill connected in the bright annealing furnace having a finishing roll roll;
The first continuous rolling mill and the second continuous rolling mill each have first to fourth stands, the first to fourth stands each including one or more operating rolls, and the operating rolls have a diameter ranging from 130 mm to 150 mm. ,
The working roll of the first stand in the first continuous rolling mill has a surface roughness (Ra) of 0.8 μm to 1.0 μm, and the operating rolls of the second and third stands have a surface roughness (Ra) of 0.4 μm to 0.6 μm, 4, the operation roll of the stand is a continuous production apparatus of ferritic stainless steel, characterized in that the surface roughness (Ra) is 0.2㎛ to 0.4㎛. delete delete The method of claim 1,
The operating rolls of the first to third stands in the second continuous rolling mill has a surface roughness (Ra) of 0.2 μm to 0.4 μm, and the operating rolls of the fourth stand have a surface roughness (Ra) of 0.1 μm to 0.8 μm. Continuous production apparatus of ferritic stainless steel. A first continuous mill having two or more stands sequentially aligned;
A second continuous mill connected to the first continuous mill and having two or more stands sequentially aligned;
A bright annealing furnace connected to the second continuous mill; And
Including; the temper rolling mill connected in the bright annealing furnace having a finishing roll roll;
The first continuous rolling mill and the second continuous rolling mill further comprises rolling oil, wherein the rolling oil is a continuous continuous production apparatus of ferritic stainless steel comprising a mineral oil-based knit oil having a viscosity of 15cSt to 25cSt. The method of claim 5,
The rolling oil has a saponification degree of 40 mgKOH / g or more, the flash point is a continuous continuous production apparatus of ferritic stainless steel, characterized in that 210 ℃ or more. The method of claim 5,
Rolling oil injection amount in the second continuous mill is 40% to 60% of the rolling oil injection amount in the first continuous mill, characterized in that the continuous continuous production apparatus of stainless steel. The method of claim 1,
The bright annealing furnace continuous continuous production apparatus of ferritic stainless steel, characterized in that it comprises a reducing hydrogen gas. A first continuous mill having two or more stands sequentially aligned;
A second continuous mill connected to the first continuous mill and having two or more stands sequentially aligned;
A bright annealing furnace connected to the second continuous mill; And
Including; the temper rolling mill connected in the bright annealing furnace having a finishing roll roll;
The temper rolling mill comprises a filamentous rolling roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm, and continuously lubrication-free rolling without introducing rolling oil. A first continuous rolling step of rolling the ferritic stainless steel with a first continuous rolling mill having two or more stands which are sequentially aligned;
A second continuous rolling step of rolling the ferritic stainless steel passed through the first continuous rolling step into a second continuous mill having two or more stands which are sequentially aligned;
An annealing step of annealing the ferritic stainless steel that has undergone the second continuous rolling step using a bright annealing furnace; And
And a temper rolling step of rolling the ferritic stainless steel subjected to the annealing step with a temper rolling mill having a finishing rolling roll,
In the temper rolling step, the ferritic stainless steel is continuously rolled with a finishing roll having a surface roughness (Ra) of 0.01 μm to 0.02 μm, but without lubrication of rolling oil. . The method of claim 10,
In the first continuous rolling step, the first continuous rolling mill includes first to fourth stands each having one or more working rolls, and in the second continuous rolling step, the second continuous rolling mills respectively include one or more working rolls. And a first to fourth stand provided, wherein the ferritic stainless steel sequentially passes through the first to fourth stands of the first continuous mill and the first to fourth stands of the second continuous mill. Continuous production method of ferritic stainless steel. A first continuous rolling step of rolling the ferritic stainless steel with a first continuous rolling mill having two or more stands which are sequentially aligned;
A second continuous rolling step of rolling the ferritic stainless steel passed through the first continuous rolling step into a second continuous mill having two or more stands which are sequentially aligned;
An annealing step of annealing the ferritic stainless steel that has undergone the second continuous rolling step using a bright annealing furnace; And
And a temper rolling step of rolling the ferritic stainless steel subjected to the annealing step with a temper rolling mill having a finishing rolling roll,
The first continuous rolling step and the second continuous rolling step are each rolling the stainless steel using a rolling oil, the rolling oil comprises a mineral oil-based knit oil having a viscosity of 15cSt to 25cSt, rolling oil in the second continuous rolling step Injection amount is a continuous production method of ferritic stainless steel, characterized in that 40% to 60% of the injection amount of the rolling oil in the first continuous rolling step. The method of claim 10,
In the first continuous rolling step, the ferritic stainless steel is rolled at a reduction ratio of 50% to 70%, and the second continuous rolling step is performed in the ferritic stainless steel at a reduction ratio of 30% to 50%. Continuous production method of stainless steel. The method of claim 10,
In the first continuous rolling step, the ferritic stainless steel is rolled at a reduction ratio of 60% to 67%, and in the second continuous rolling step, the ferritic stainless steel is rolled at a reduction ratio of 33% to 40%. Continuous production method of ferritic stainless steel. The method of claim 10,
In the annealing step, the ferrite stainless steel is continuously annealed in a bright annealing furnace in a reducing hydrogen gas atmosphere. delete

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