KR101543463B1 - Method of manufacturing thick plate having high tensile strength - Google Patents

Abstract

The present invention relates to a steel sheet having improved toughness and high strength and excellent low temperature toughness and a method for producing the same. The steel sheet according to an embodiment of the present invention may contain 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% of molten Al, 0.01 to 0.03 of Ti %, N: 0.01 to 0.06%, Cr: 0.2 to 0.5%, Mo: 0.01 to 0.20%, B: 0.0003 to 0.005%, P: more than 0% to 0.015% And inevitably included impurities, but not Cu and Ni.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a steel plate having a high toughness,

More particularly, the present invention relates to a steel sheet having improved toughness and high strength and excellent low temperature toughness and a method for producing the steel sheet.

Generally, as architectural structures and bridge structures are becoming larger and larger, there is a growing demand for high strength in steel used in structures in order to withstand large loads of such structures. Also, as the weight of the steel is gradually decreased due to the demand for cost reduction, the demand for the strength of the steel itself constituting the structure is increasing more and more.

On the other hand, since strength and toughness tend to be inversely proportional, many high-strength structural steels show weak characteristics in toughness. However, low-temperature toughness suitable for construction steels is also required to be used in low-temperature regions such as extreme terrain. In addition, since not only the strength and toughness of the steel but also the weldability which is the most important in the use of the steel are also important, a low carbon equivalent (Ceq) is also required.

Conventionally, many alloying elements have been added in order to secure the strength and toughness of the steel, and therefore, it has had to have a high carbon equivalent. Accordingly, high strength steels having appropriate carbon equivalents are manufactured using control rolling (CR) and thermo mechanical control (TMCP) processes. However, in order to produce a high strength steel having a tensile strength of 600 MPa or more, expensive alloying elements are required to be added. In particular, Cu and Ni are added to increase strength and toughness at the same time, .

In high-strength steels with control rolling and thermal processing control processes, a large amount of Nb is added in order to secure the strength and maximize the control rolling effect. Such high Nb steels often exhibit abnormal grain growth, It can not be ensured.

This abnormal grain growth is known to be caused by diffusion of Nb solute atoms beyond the solubility limit and precipitation around the TiN, resulting in a coarse TiN grain, thereby reducing the pinning effect of suppressing grain growth. The diffusion of Nb solute atoms beyond the solubility limit and the coarsening of TiN particles due to precipitation around TiN are often caused by a long interval or a large temperature difference between the rolling passes of rough rolling and finishing rolling.

In addition, the lowering of the pass per pass at the recrystallization station also often causes abnormal lip growth. That is, coalescence and partial recrystallization of the austenite grains due to strain-induced grain boundary migration occur due to the reduction amount below the recrystallization critical strain amount. If partial recrystallization occurs once, recrystallization occurs only in the recrystallized grains repeatedly in subsequent rolling, So that it is difficult to disappear.

The presence of anisotropic growth or gigantic peaks as described above has a great problem in ensuring high toughness because the unit crack path is long and the crack propagation resistance is low in the impact toughness, which has a very bad influence.

In order to solve the above problems, a technical problem to be solved by the present invention is to provide a steel sheet with improved toughness, high strength and excellent low temperature toughness, and a method for producing the same.

In order to accomplish the above object, one embodiment of the present invention provides a method of manufacturing a semiconductor device, comprising: 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% of molten Al, 0.01 to 0.03% of Nb, 0.2 to 0.5% of Cr, 0.01 to 0.20% of Mo, 0.0003 to 0.005% of B, P of more than 0% and 0.015% or less, S of more than 0% and not more than 0.005% , The balance Fe and inevitably included impurities, but does not include Cu and Ni.

In one embodiment of the present invention, the steel sheet may have a tensile strength of 600 MPa or higher, a yield strength of 450 MPa or higher, and an impact energy of 100 J or higher at -20 캜.

In one embodiment of the present invention, the thickness of the backing sheet may be 80 mm or less.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, the method including the steps of: 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% P: 0.01 to 0.03% of Ti, 0.01 to 0.06% of Nb, 0.2 to 0.5% of Cr, 0.01 to 0.20% of Mo, 0.0003 to 0.005% of B, %, The remainder of Fe and inevitably included impurities, but does not contain Cu and Ni, at 1100 to 1200 占 폚; Continuously rolling the reheated slab, and terminating the rolling at a temperature of 850 캜 or more; And cooling the rolled slab at a cooling rate of 3 ° C / sec or more to terminate the cooling at a temperature of 300 to 550 ° C.

In one embodiment of the present invention, the continuous rolling includes a first rolling that rolls at a reduction rate of 15% or more at 1100-1200 ° C, a second rolling that rolls at a reduction ratio of 25% or higher at 1000-1080 ° C, And a third rolling which is rolled at 950 DEG C to a reduction ratio of 15% or more.

In one embodiment of the present invention, the second rolling may have a plurality of passes with a path reduction ratio of 10% or more.

According to an embodiment of the present invention, it is possible to obtain a high strength of not less than 450 MPa and a tensile strength of not less than 600 MPa while improving the economical efficiency because it does not contain expensive elements such as Ni and Cu, A steel sheet with excellent toughness can be obtained.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a photograph showing a microstructure of a high-toughness steel sheet produced by a method of manufacturing a high-toughness steel sheet according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A method of manufacturing a high-strength steel sheet according to an embodiment of the present invention includes a step of preparing a steel sheet having a composition of 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% of molten Al, 0.01 to 0.03% of Ti, 0.01 to 0.06% of Nb, 0.2 to 0.5% of Cr, 0.01 to 0.20% of Mo, 0.0003 to 0.005% of B, more than 0 to 0.015% of P, 0.005% or less, and the remainder Fe and inevitably included impurities, wherein the slab having a composition not containing Cu and Ni is reheated at 1100 to 1200 ° C; Continuously rolling the reheated slab, and terminating the rolling at a temperature of 850 캜 or more; And cooling the rolled slab at a cooling rate of 3 ° C / sec or more to terminate the cooling at a temperature of 300 to 550 ° C.

Accordingly, the high-toughness steel sheet according to an embodiment of the present invention may contain 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% of molten Al, Ti : 0.01 to 0.03%, Nb: 0.01 to 0.06%, Cr: 0.2 to 0.5%, Mo: 0.01 to 0.20%, B: 0.0003 to 0.005% Or less, and the remaining Fe and inevitably included impurities, but not including Cu and Ni. Such a post-hardened steel sheet may have a tensile strength of 600 MPa or higher, a yield strength of 450 MPa or higher, and an impact energy of 100 J or higher at -20 캜.

Hereinafter, the composition and the manufacturing conditions provided in the method of manufacturing a high-toughness steel sheet according to an embodiment of the present invention will be described.

C: 0.03 to 0.10 wt%

If C (carbon) is an effective element for increasing the strength, a desired strength can not be obtained when the content is less than 0.03 wt%. If the content is more than 0.10 wt%, the strength is increased but the toughness and ductility deteriorate. .

Si: 0.01 to 0.6 wt%

Si (silicon) is an element essential for deoxidation of steel, and is an element effective for increasing the strength. However, if the content is less than 0.01% by weight, desired high strength can not be obtained. In addition, when the content exceeds 0.6% by weight, toughness and ductility are deteriorated. Therefore, the Si content is preferably limited to a range of 0.01 to 0.6% by weight.

Mn: 1.0 to 2.5 wt%

Mn (manganese) has an effect of increasing the strength at the time of heat treatment, and it is also an element added for the compensation of the strength due to the limited amount of C added. However, when Mn is less than 1.0% by weight, the effect of improving the sinterability is hardly exhibited. When the content of Mn is more than 2.5% by weight, the weldability is lowered and the risk of cracks is increased. Therefore, the content of Mn is preferably limited to 1.0 to 2.5% by weight.

Molten Al (Sol.Al): 0.01 to 0.05 wt%

However, when the amount of the oxide inclusion exceeds 0.05 wt%, the amount of the oxide inclusion is large. When the content of the oxide inclusion exceeds 0.05 wt% And the impact toughness of the material is deteriorated. Therefore, it is preferable that the content is limited to 0.01 to 0.05 wt%.

Ti: 0.01 to 0.03 wt%

Ti (titanium) plays a key role in improving the low temperature toughness through grain refinement. Therefore, in order to sufficiently obtain the above effect, it is preferable to add at least 0.01 wt%, but if the amount is too large, the impact toughness at low temperature deteriorates. Therefore, the upper limit is preferably limited to 0.03 wt% or less. Therefore, the content of Ti is preferably limited to 0.01 to 0.03% by weight.

Nb: 0.01 to 0.06 wt%

Nb (niobium) is a very useful component for refining the crystal grains. At the same time, the strength of the base material and the welded part is improved. If the content is less than 0.01% by weight, the above effect can not be obtained. If the content is more than 0.06% , It is preferable to limit the content to 0.01 to 0.06% by weight.

Cr: 0.2 to 0.5 wt%

Cr (chromium) is an element required to improve strength. However, if the content is less than 0.2% by weight, the effect of improving the strength upon addition can not be obtained. If the content exceeds 0.5% by weight, the weldability and toughness of the welded heat affected zone (HAZ) Is limited to 0.2 to 0.5% by weight.

Mo: 0.01 to 0.20 wt%

Mo (molybdenum) is an element necessary for improving the hardenability and increasing the strength. However, when the content is less than 0.01% by weight, the above effect due to addition can not be obtained. When the content exceeds 0.20% by weight, It is preferable to limit the content to 0.01 to 0.20% by weight because the cost increases sharply due to the expensive elements.

B: 0.0003 to 0.005 wt%

B (boron) is an effective component for improving the strength of steel by significantly increasing the hardenability of the steel even with a small amount of addition. However, if the content is less than 0.0003% by weight, the above effects due to the addition can not be obtained. When the content exceeds 0.005% by weight, brittleness is caused and weldability is also deteriorated. Therefore, the content is preferably limited to 0.0003 to 0.005% by weight.

P: more than 0 wt% and not more than 0.015 wt%

P (phosphorus) is an impurity which deteriorates the weldability and hinders impact toughness, and it is desirable to suppress as much as possible. However, since it is an impurity inevitably contained in the manufacturing process, it is preferable to limit the content to more than 0 wt% and not more than 0.015 wt%.

S: more than 0% by weight and not more than 0.005% by weight

S (sulfur) is an element which deteriorates the ductility, impact toughness and weldability of steel, and is particularly preferably controlled to be as low as possible because it forms MnS inclusions in combination with Mn to lower the abrasion resistance of steel. % Or less.

The remainder other than the above-mentioned components are Fe and inevitably included impurities.

In addition, the high-toughness steel sheet according to an embodiment of the present invention may have a composition that does not include expensive elements Cu and Ni.

In the manufacturing method of the present invention, the slab thus formed is reheated at 1100 to 1200 ° C., the reheated slab is rolled in a plurality of stages, the rolled slab is cooled at a cooling rate of 3 ° C./sec or more, And the cooling is terminated at a temperature of -20 DEG C to a temperature of -20 DEG C, and a tensile strength of 600 MPa or more, a yield strength of 450 MPa or more, an impact energy of 100 J or more at -20 DEG C, It is possible to obtain a steel sheet after the toughness.

The detailed conditions for each step will be described below.

(1) Reheating slab: 1100 to 1200 ° C

The reheating process of the slab is a process necessary to smoothly carry out the subsequent rolling process and sufficiently obtain the physical properties of the target steel sheet.

When the reheating temperature of the steel is less than 1100 ° C, Nb and the like are difficult to be reused and it is difficult to secure the desired strength. Therefore, by keeping the reheating temperature of the steel at 1100 DEG C or higher, it is possible to promote the reuse of the precipitate and to uniformly form the austenite grains and render them highly dense. When the reheating temperature is higher than 1200 ° C, the austenite grains are excessively coarsened, and the grain size of the steel sheet is increased to lower the low-temperature toughness. Therefore, it is preferable that the appropriate reheating temperature range is 1100 to 1200 ° C.

(2) Rolling finish of continuous rolling: More than 850 캜

The continuous rolling is a process necessary to give the steel sheet excellent low temperature toughness and high strength by minimizing the size of the crystal grains inside the steel sheet. However, when the rolling finish temperature is less than 850 DEG C, it is not easy to maintain a high reduction rate per pass, and since the internal structure does not have a sufficient cooling range to transform into a hard phase, the yield strength and tensile strength are lower . Therefore, it is preferable that the finish temperature of continuous rolling is controlled to 850 DEG C or more.

(3) Constitution of continuous rolling: First rolling - a reduction rate of 15% or more at 1100 to 1200 ° C, a second rolling at a reduction rate of 25% or more at 1000 to 1080 ° C, a reduction at 1560 to 950 ° C % More than

In order to increase the toughness and strength of the steel, fine crystal grains must be formed inside the steel. For this purpose, it is desirable that the crystal grains after rolling are made finer. In the present invention, it is possible to optimize the pass schedule of the rough rolling and finishing the finish rolling in the high temperature region, thereby making the steel structure finer. For this purpose, in the present invention, the first rolling is performed at a reduction rate of 15% or more at 1100 to 1200 ° C., the second rolling is performed at a reduction rate of 25% or more at 1000 to 1080 ° C., % Or more. As described above, by reducing the temperature difference and the time difference between each rolling, it is possible to suppress the abnormal grain growth on the texture of the high Nb steel and to produce a steel material excellent in toughness even at low temperatures.

In the present invention, it is preferable that the reduction rate is controlled to 15% or more in the first rolling of continuous rolling. If the reduction rate is less than 15%, the effect of grain refinement by rolling is insufficient and improvement in low temperature toughness characteristics may be insignificant.

Further, in the present invention, by sufficiently rolling the steel material in the austenite recrystallization region, it is possible to make the structure formed through rolling more finely. If the reduction rate of the rolling in the austenite recrystallization region is too low, recrystallization occurs partially and the austenite grains become uneven and the satisfactory crack growth resistance can not be obtained. Therefore, in the second rolling, the reduction rate is set to 25% .

In addition, in the present invention, it is preferable to increase the pass reduction rate per pass by setting a plurality of passes in the second rolling and setting the pass reduction rate per pass to 10% or more, And the toughness can be ensured.

In the present invention, it is preferable that the reduction rate is controlled to be not less than 15% in the third rolling of continuous rolling. Unrecrystallized austenite grains having a reduction ratio of less than 15% become coarse and the ferrite grains The strength and toughness may be lowered.

(4) Cooling speed: 3 ° C / second or more

It is preferable that the rolled slab is cooled at a cooling rate of 3 DEG C / sec or more. When the cooling rate is less than 3 DEG C / sec, undesirable structures such as polygonal ferrite and the like cause a coarse grain size So that the strength and toughness may be significantly reduced to a level that does not satisfy the target value of the present invention.

The post-toughness steel sheet produced according to the embodiment of the present invention may have a tensile strength of 600 MPa or more, a yield strength of 450 MPa or more, and an impact energy of 100 J or more at -20 캜. Also, the post-toughness steel sheet produced according to the embodiment of the present invention may be manufactured to have a thickness of 80 mm or less.

Hereinafter, examples will be described in detail.

In the present invention, a slab having a range of alloy composition as described above was prepared, and Table 1 shows the alloy composition of the slab (unit: wt%).

division C Si Mn P S Al Ti Nb Cr Ni Cu Mo B Comparative Example 1 0.07 0.25 1.48 0.010 0.002 0.022 0.017 0.040 0.02 0.15 0.14 0.10 - Comparative Example 2 0.06 0.25 1.80 0.011 0.002 0.024 0.015 0.040 0.20 0.20 0.23 0.15 - Comparative Example 3 0.05 0.17 1.50 0.007 0.001 0.020 0.018 0.035 0.30 0.31 - 0.10 0.0016 Comparative Example 4 0.05 0.15 1.46 0.011 0.002 0.019 0.017 0.033 0.26 - - 0.09 0.0013 Comparative Example 5 0.04 0.16 1.50 0.009 0.002 0.021 0.016 0.034 0.26 - - 0.09 0.0014 Comparative Example 6 0.05 0.13 1.49 0.011 0.002 0.022 0.015 0.034 0.26 - - 0.08 0.0015 Example 1 0.05 0.13 1.48 0.010 0.002 0.020 0.016 0.034 0.29 - - 0.09 0.0014 Example 2 0.05 0.14 1.50 0.011 0.002 0.021 0.015 0.034 0.28 - - 0.08 0.0015

As shown in Table 1, Examples 1 and 2 satisfy all the conditions of the present invention, and Comparative Examples 1 through 3 are outside the conditions of the present invention. Specifically, in Comparative Example 1, the content of Cr was lower than that of the present invention, and Ni and Cu were included. Comparative Example 2 contained Ni and Cu, and Comparative Example 3 contained Cu. On the other hand, Comparative Examples 4 to 6 satisfied the conditions of the present invention, but did not satisfy the conditions of the present invention in continuous rolling, which will be described later.

The slabs of Comparative Examples 1 to 6 and the slabs of Examples 1 and 2 having the composition shown in Table 1 were produced under the following production conditions. Table 2 shows the manufacturing conditions of the slab.

division First rolling Second rolling Third rolling Third rolling Rolling
End
Temperature
(° C) Cooling
End
Temperature
(° C) Cooling
speed
(° C / sec) 1100 to 1200 ° C 1000 ~ 1080 ℃
860 ~ 950 ℃ 800 ~ 860 ℃ Reduction rate
(%) Reduction rate
(%) Pass reduction rate (%) Reduction rate
(%) Reduction rate
(%) Comparative Example 1 40 0 - 28 - 906 264 5 Comparative Example 2 41 0 - 0 28 832 232 4 Comparative Example 3 40 0 - 0 28 805 451 7 Comparative Example 4 40 0 - 0 29 821 552 7 Comparative Example 5 40 0 - 0 29 823 279 5 Comparative Example 6 41 0 - 0 23 816 610 7 Example 1 22 28 15.9
14.7
16.2 19 - 885 380 5 Example 2 22 27 19.6
10.1
10.3 20 - 892 364 5

As shown in Table 2, in Comparative Example 1, the first rolling was performed at a reduction rate of 15% or more at 1100 to 1200 ° C and the third rolling was performed at a reduction rate of 15% or more at 860 to 950 ° C. . In Comparative Examples 2 to 6, the first rolling was performed at a reduction ratio of 15% or more at 1100 to 1200 ° C, but the second rolling was not performed, and the third rolling was performed at 800 to 860 ° C . However, Examples 1 and 2 proceeded according to the production conditions of the present invention. Particularly, in Example 1, the second rolling was made of three passes, and the pass reduction rate per pass was 10% or more at 15.9%, 14.7%, and 16.2% at each pass. The reduction rate in the second rolling was 28%, which was 25% or more. Here, the reduction rate in the second rolling means the reduction rate in the section during the second rolling section. That is, the reduction rate in the second rolling means the final reduction ratio applied to the slab after passing through three passes made in the second rolling.

Also, in Example 2, the second rolling consisted of three passes, and the pass reduction rate per pass was 19.6%, 10.1%, and 10.3% in each pass, and the reduction rate was 27 % Was more than 25%. As described above, by setting a plurality of passes in the second rolling, the pass reduction rate per pass is set to 10% or more to increase the pass reduction rate per pass, and the reduction rate is kept at 25% It is possible to secure a high toughness.

Table 3 shows the results of measuring the physical properties of the steel sheet produced under the manufacturing conditions shown in Table 2. 1 is a photograph showing the microstructure of the steel sheet after the toughness of Example 1. Fig.

division thickness
(mm) Yield strength
(MPa) The tensile strength
(MPa) Elongation (EI.)
(%) CVN (-20 < 0 > C, J) One 2 3 Comparative Example 1 80 528 601 29.3 367 386 373 Comparative Example 2 83 584 661 27 308 285 275 Comparative Example 3 80 608 692 24.2 53 31 136 Comparative Example 4 80 561 669 25.1 33 29 27 Comparative Example 5 80 613 696 25.7 28 34 222 Comparative Example 6 80 521 658 23.9 35 23 61 Example 1 80 595 677 22.3 203 252 300 Example 2 80 624 691 23.4 309 313 295

As shown in Table 3, the slab satisfying the composition of the present invention was produced in accordance with the production method of the present invention, and Example 1 having a thickness of 80 mm had a tensile strength of 600 MPa or more at a tensile strength of 677 MPa, a yield strength of 450 MPa or more at a yield strength of 595 Ma, As a result of Charpy Impact Test (CVN Impack Test), impact strengths of 203J, 252J, and 300J at impact temperature of -20 ℃ were 100J or more, respectively. Example 2 having a thickness of 80 mm had a tensile strength of 600 MPa or more at a yield strength of 691 MPa and a yield strength of at least 450 MPa at a yield strength of 624 Ma, and as a result of a Charpy impact test, impact energy was measured at 30 J, 313 J and 295 J at 100 J Respectively.

On the other hand, both of Comparative Example 1 and Comparative Example 2 had a tensile strength of 600 MPa or more, a yield strength of 450 MPa or more, and a Charpy impact test in real time. Cu. In Comparative Examples 3 to 6, most of the Charpy impact test was carried out at -20 캜 for most of the real time results, and the impact energy was 100 J or less.

As such, the steel sheet according to an embodiment of the present invention does not include Ni and Cu, which are high-priced elements, so that the economical efficiency can be improved. Further, the steel sheet produced by the manufacturing method according to one embodiment of the present invention can have high strength and excellent low temperature toughness.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (6)

delete delete delete The steel sheet according to any one of the above items 1 to 3, wherein the steel contains 0.03 to 0.10% of C, 0.01 to 0.6% of Si, 1.0 to 2.5% of Mn, 0.01 to 0.05% of molten Al, 0.01 to 0.03% of Ti, 0.01 to 0.06% of Nb, And Fe and inevitably included impurities, wherein the content of Fe and at least one of Cu and Mo is 0.01 to 0.20%, Mo: 0.01 to 0.20%, B is 0.0003 to 0.005%, P is more than 0% and 0.015% Reheating the slab having a composition not containing Ni at 1100 to 1200 占 폚;
Continuously rolling the reheated slab, and terminating the rolling at a temperature of 850 占 폚 or higher; And
Cooling the rolled slab at a cooling rate of 3 DEG C / sec or more and terminating the cooling at a temperature of 300 to 550 DEG C,
The continuous rolling includes a first rolling that rolls at a reduction rate of 15% or more at 1100 to 1200 ° C, a second rolling that rolls at a reduction ratio of 25% or more at 1000 to 1080 ° C, and a reduction of 15% or more at 860 to 950 ° C And a third rolling process for rolling the steel sheet. delete 5. The method of claim 4,
And the second rolling has a plurality of passes with a path reduction ratio of 10% or more.

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