KR101382833B1 - Steel sheet for oil sands slurry pipe having excellent erosion resistance and method for manufacturing the same - Google Patents

Abstract

One aspect of the present invention is an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, balance Fe and other unavoidable impurities, and the microstructure includes ferrite and pearlite.
Another aspect of the present invention is a method for producing an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% Or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, heating a steel slab containing residual Fe and other unavoidable impurities, wherein the heated steel slab is Finishing hot rolling with a residual reduction ratio of 50% or more in the temperature range of Ar3 + 200 ° C. and cooling the hot rolled steel at a cooling rate of 0.5˜5 ° C./sec.

Description

STEEL SHEET FOR OIL SANDS SLURRY PIPE HAVING EXCELLENT EROSION RESISTANCE AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a steel sheet for an oil sand slurry pipe excellent in corrosion resistance and a method of manufacturing the same.

Among the steel materials used in the oil sands industry, especially pipe steels used for transporting oil sand slurry, wear is caused by sand particles of 200 ~ 300㎛, and the replacement life is about one year. It is costly and time consuming.

Oil sand mining is largely divided into open pit mining and underground mining. In open pit mining, the application of slurry pipe systems is essential for the post-treatment of mining ore. The ground mining mixed with water has the form of a slurry, containing about 35% by weight of sand, and about 500 ppm of salt, and is transported at a speed of 3.5 to 5.5 m / sec. When transporting the slurry, sand particles move along the inner lower end of the pipe to erode the material (with abrasion and corrosion), so the pipe is rotated about two to four times a year to increase the service life of the material. .

In addition, the inside of the slurry pipe is not only abrasion by the moving sand, but also corrosion due to water and salt, which is more problematic, the corrosion product generated by the corrosion stably lowers the corrosion rate of the material Rather, it is immediately removed by the moving sand. In particular, erosion of these materials occurs much faster in environments that occur with corrosion and wear, such as in the use of the oil sand slurry pipes, than in environments where corrosion and wear exist separately.

In order to delay the erosion and extend the life of the pipe, carbide coating or surface heat treatment may be applied to the inside of the pipe. However, since the cost of the reprocessing process exceeds the replacement cost of the material, it may be applied to the slurry without the above reprocessing process. There is a demand for development of a material having excellent resistance to erosion.

In general, the wear resistance of the material is known to increase with the increase in hardness, but it is impossible to apply high hardness martensite because the increase in the hardness of the material should have the strength and ductility that can be corrugated due to the characteristics of the pipe material.

In addition, in order to reduce the corrosion rate of the steel in the salt atmosphere, the oxide rust forming elements such as Cr or Al are generally used, but the surface rust layer is almost impossible in carbon steel due to the characteristics of the oil sand slurry pipe.

Currently used oil sand slurry pipe steel is API grade line pipe steel, ferritic TMCP steel is used to increase the strength at the level that can be commercially piped in order to increase the wear resistance of the material, the wear resistance is currently used Examine the superior pipe steel technology.

First, Patent Literature 1 proposes a method of securing a wear resistance by installing a ceramic plate inside a steel pipe, and Patent Literature 2 uses a tungsten carbide or high chromium powder on the inner surface of a pipe to form a hardened growth welding layer to prevent wear. A method of manufacturing pipes is proposed.

However, both Patent Document 1 and Patent Document 2 are a kind of reprocessing process using high hardness materials to secure wear resistance on the surface of existing pipes. Due to this, the reprocessing layer may fall off, and thus there is a disadvantage in that it does not guarantee long term wear resistance.

In addition, Patent Document 3 provides a method for producing steel having excellent wear resistance for use in storage oil pipes of crude oil tanks, in-board light distribution, etc., and the steel material provided in Patent Document 3 is in weight%, C: 0.03 to 0.1. %, Si: 0.1-0.3%, Mn: 0.05-1.2%, P: 0.05% or less, S: 0.035% or less, Al: 0.03% or less, Cr: 0.8-1.1%, Cu: 0.1-0.3%, Ni: Re-heat the steel controlled to 1000 ~ 1200 ℃ by adding Ca-Si in wire form and degassing to molten steel composed of 0.1 ~ 0.3%, remaining Fe and other unavoidable impurities. And then hot rolling at a temperature of Ar3 or higher.

However, the invention of Patent Document 3 improves the wear resistance and corrosion resistance by improving the density of the rust layer by utilizing Cr, Cu, Ni, Ca and the like, but the rust layer is used in a harsh wear environment such as an oil sand slurry pipe. There is a problem that it is impossible to secure the wear resistance and corrosion resistance.

Therefore, the demand for steel plate for oil sand slurry pipe having excellent corrosion resistance and excellent economic efficiency and production efficiency even in severe abrasion and corrosive environment such as the use environment of oil sand slurry pipe is increasing rapidly.

Korean Patent Publication No. 1987-0010217 Korean Patent Publication No. 2000-0046429 Korean Patent Publication No. 2004-0059177

One aspect of the present invention provides a steel sheet for oil sand slurry pipes and a method of manufacturing the same, which can be conduited as a pipe and has excellent erosion resistance even in the harsh wear environment of the oil sand slurry pipe, and has excellent economic efficiency and production efficiency.

One aspect of the present invention is an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, balance Fe and other unavoidable impurities, and the microstructure includes ferrite and pearlite.

Another aspect of the present invention is a method for producing an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% Or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, heating a steel slab containing residual Fe and other unavoidable impurities, wherein the heated steel slab is Finishing hot rolling with a residual reduction ratio of 50% or more in the temperature range of Ar3 + 200 ° C. and cooling the hot rolled steel at a cooling rate of 0.5˜5 ° C./sec.

In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.

According to the present invention, by appropriately controlling the alloying components and manufacturing conditions, it is possible to pipe, but also have excellent wear resistance in the harsh wear environment of the oil sand slurry pipe, and also excellent in corrosion resistance, economical and production Steel plate for oil sand slurry pipe which is excellent in efficiency can be obtained.

1 is a diagram showing a change in erosion resistance according to the change of the ferrite and pearlite fraction.

The inventors have found that wear of steel material is caused by surface deformation and dropping of the strained layer regardless of the microstructure, and that erosion occurring in the material is caused by wear rather than corrosion in the atmosphere of the oil sand slurry pipe environment. Therefore, as a result of the research to derive the steel plate for oil sand slurry pipe having excellent corrosion resistance, it has the hardness and toughness of the level not to be destroyed even though the collided abrasive particles are thrown out, and the deformation capacity is improved to eliminate the deformation layer. By having a microstructure that can increase the deformation capacity of the, it was confirmed that the steel sheet excellent in corrosion resistance can be produced and led to the present invention.

Hereinafter, the steel sheet for oil sand slurry pipe which is excellent in corrosion resistance which is one side of this invention is demonstrated in detail.

One aspect of the present invention is an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, balance Fe and other unavoidable impurities, and the microstructure includes ferrite and pearlite.

Carbon (C): 0.25-0.35 wt%

C is an element added to form a ferrite matrix structure by forming perlite on the base structure of the ferrite. When the content of C is less than 0.25% by weight, it is difficult to secure wear resistance due to insufficient pearlite. On the other hand, if the content of C exceeds 0.35% by weight, the amount of pearlite increases while the amount of ferrite decreases, the hardness value increases, and at the same time, the deformation capacity for wear decreases and wear resistance decreases. Therefore, the content of C is preferably limited to 0.25 to 0.35% by weight. Moreover, in order to improve corrosion resistance more, it is more preferable to control the said carbon to 0.28 weight% or more.

Silicon (Si): 0.1 to 0.5 wt%

The Si not only acts as a deoxidizer of the steelmaking process but also serves to increase the strength of the steel. When the content of Si is less than 0.1% by weight, the above effects cannot be sufficiently obtained, and the manufacturing cost increases. On the other hand, when the content of Si is more than 0.5% by weight, the impact toughness of the material is worsened, the weldability is inhibited, and scale peelability is induced during rolling. Therefore, the content of Si is preferably limited to 0.1 to 0.5% by weight.

Manganese (Mn): 1.4-1.8 wt%

Mn is an element that increases the amount of pearlite without impairing impact toughness. In order to exhibit such an effect in the present invention, it is preferable to add 1.4% by weight or more. However, when the content exceeds 1.8% by weight, central segregation may occur, thereby reducing impact toughness, forming bainite or martensite other than pearlite, and deteriorating weldability. Therefore, the content of Mn is preferably limited to 1.4 to 1.8% by weight.

Aluminum (Al): 0.05% by weight or less (excluding 0%)

Al is an element that acts as a deoxidizer to remove oxygen by reacting with oxygen present in molten steel, but when the amount is added too much, a large amount of oxide inclusions are formed, which impairs the impact toughness of the material. It is preferable to limit the weight percentage.

Chromium (Cr): 0.4 wt% or less (excluding 0%)

Cr, like Mn, is an element that serves to lower the transformation temperature of steel and increase the amount of pearlite. Cementite is changed from Fe ₃ C to hard (Fe, Cr) ₃ C, thereby increasing the corrosion resistance of the material. However, when Cr exceeds 0.4% by weight, the amount of cementite in pearlite increases and hardness increases adversely to erosion resistance, but also forms a structure such as bainite or martensite with Mn. Therefore, the chromium is preferably included in 0.4% by weight or less.

The remainder of the present invention is iron (Fe). However, in the ordinary manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably incorporated, so that it can not be excluded. These impurities are not specifically mentioned in this specification, as they are known to any person skilled in the art of manufacturing.

However, since nitrogen, phosphorus, and sulfur are generally referred to as impurities, they will be briefly described as follows.

Nitrogen (N): not more than 0.01% by weight

N is unavoidably contained impurity. Forming a nitride in combination with Al, Ti, Nb, V, etc., hinders the growth of austenite grains, thereby improving toughness and strength, but if the content is too high, there is a solid solution of N. Since it adversely affects toughness, the upper limit of the content is preferably limited to 0.01% by weight.

Phosphorus (P): 0.03% by weight or less

P is unavoidably an impurity, and is preferably controlled as low as possible because weldability is lowered and impact toughness is degraded. Theoretically, it is preferable to limit the phosphorus content to 0%, but it is inevitably contained inevitably in the manufacturing process. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the phosphorus content is preferably limited to 0.03 wt%.

Sulfur (S): 0.03 wt% or less

S is an inevitable impurity, and combines with Mn to form a non-metallic inclusion and thus greatly impairs the low temperature impact toughness of the steel. In addition, there is a problem of deteriorating ductility, impact toughness and weldability of steel. Theoretically, it is advantageous to limit the content of sulfur to 0%, but it is inevitably contained inevitably in the manufacturing process. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the sulfur content is preferably limited to 0.03% by weight.

According to an aspect of the present invention, by satisfying the above component system, it is possible to provide a steel sheet for oil sand slurry pipe excellent in corrosion resistance. In addition, the microstructure of the steel sheet is preferably made of 50% by area or more of pearlite, 20 to 40% by area of ferrite, the balance bainite and martensite.

Although the pearlite has a high hardness of the entire material, cementite reflects wear particles, and soft ferrite serves to accommodate deformation caused by wear particles. Therefore, the optimization of the pearlite fraction due to the C content change plays an important role in improving the erosion resistance. In addition, when the fraction of pearlite is less than 50 area%, cementite is not sufficiently formed, and thus it is difficult to secure corrosion resistance. Therefore, it is preferable to contain pearlite of 50 area% or more.

In addition, the ferrite serves to improve the corrosion resistance by the deformation acceptance by the wear particles and to keep the strength of the steel low to the observable level. In addition, when the ferrite fraction is less than 20 area%, the deformation capacity and the strength of the steel are rapidly increased. If the ferrite fraction is more than 40 area%, the strength is decreased, but the corrosion resistance is deteriorated due to the decrease in the amount of pearlite. do. Therefore, it is preferable to contain 20-40 area% ferrite. In view of improving corrosion resistance and strength, it is more preferable to limit the pearlite to 60 area% or more and 20-30% by ferrite.

The hardness of the pearlite and ferrite phases is influenced by the composition of the steel, the lamellar cementite fraction and distribution, and the like. This change in hardness also changes the erosion resistance of the steel sheet. In the present invention, the hardness of the pearlite is preferably controlled to 240 ~ 260Hv, the hardness of ferrite 150Hv or more. When the hardness of the pearlite phase is less than 240 Hv, deformation due to wear particles is severely generated, and corrosion resistance is lowered. When it exceeds 260 Hv, the ability to accept deformation is reduced, and corrosion resistance is rather deteriorated. Therefore, in this invention, it is preferable to control the hardness of a pearlite phase to 240-260 Hv.

In addition, when the ferrite hardness value is 150Hv or more, the ferrite phase itself accommodates deformation to improve erosion resistance, and at the same time has some effect of improving erosion resistance by reflection of collision particles, so that the hardness of the ferrite structure is limited to 150Hv or more. do. However, when the ferrite hardness value is more than 190Hv, the deformation capacity of the ferrite is reduced to reduce the erosion resistance rather than limit the hardness range of the ferrite to more than 150 ~ 190Hv.

Hereinafter, another aspect of the present invention will be described in detail a method for producing an oil sand slurry pipe steel plate excellent in corrosion resistance.

Another aspect of the present invention is a method for producing an oil sand slurry pipe having excellent corrosion resistance in weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% Or less, P: 0.03% or less, S: 0.03% or less, N: 0.01% or less, Cr: 0.4% or less, heating a steel slab containing residual Fe and other unavoidable impurities, wherein the heated steel slab is Finishing hot rolling with a residual reduction ratio of 50% or more in the temperature range of Ar3 + 200 ° C. and cooling the hot rolled steel at a cooling rate of 0.5˜5 ° C./sec.

Hot rolling

First, after heating the steel slab having the composition as described above under normal conditions, it is preferable to finish hot rolling at a residual pressure reduction rate of 50% or more in the temperature range of Ar3 to Ar3 + 200 ° C. If the finish rolling temperature is less than the Ar3 point, bainite is likely to be formed because the concentration of the alloying elements on the austenite phase increases due to the formation of the superfine ferrite and the hardenability increases. On the other hand, if Ar3 + 200 ° C., even if cooling is started in the austenitic single-phase zone, the number of ferrite and pearlite phase transformation initiation points decreases, and thus the quenchability increases. In addition, it may be difficult to have a residual pressure drop of more than 90% due to process constraints.

Cooling stage

In the steel slab applied to the present invention, since a large amount of hardenable elements such as C, Mn, or Cr are added, bainite or martensite structures may be formed without controlling the cooling conditions, thereby obtaining a mixed structure of ferrite and pearlite. . Therefore, it is very important to secure the erosion resistance suitable for the use environment of the oil sand slurry pipe by controlling the cooling conditions to obtain the mixed structure of the present invention.

It is preferable to start cooling the hot-rolled steel as described above in the temperature range of Ar3 ~ Ar3 + 200 ℃ to terminate the cooling at 500 ℃ or less. If the cooling start temperature is less than the Ar3 point, cooling starts in a state in which phase transformation to austenite is not sufficiently performed, and thus, the structure to be obtained in the present invention cannot be secured, and the cooling start temperature exceeds Ar3 + 200 ° C. If it means that the rolling is made in excess of Ar3 + 200 ℃, there is a big problem that the crystal grains are very coarse, it is preferable to limit the cooling start temperature to a temperature range of Ar3 ~ Ar3 + 200 ℃.

In addition, it is preferable to limit the cooling end temperature to 500 ° C. or less. If the cooling end temperature exceeds 500 ° C., all tissues are not transformed from austenite to pearlite / ferrite mixed tissues, but the tissues remain as austenite without transformation. Because of this, a problem may arise in that the pearlite fraction cannot be sufficiently secured. Therefore, it is desirable to limit the cooling end temperature to 500 ° C or lower.

Moreover, it is preferable to cool steel materials at the speed | rate of 0.5-5 degree-C / sec. When the cooling rate is less than 0.5 ° C / sec, not perlite is formed but carbides are spheroidized to form a structure in which spheroidized carbides are present together in the ferrite. In this case, sufficient hardness cannot be secured and wear particles may collide directly with the ferrite. On the other hand, when the temperature exceeds 5 ° C / sec, low temperature transformation tissues such as bainite and martensite may be generated, making it difficult to obtain a mixed structure of pearlite and ferrite. Therefore, the cooling rate is preferably limited to 0.5 ~ 5 ℃ / second.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

(Example)

To prepare a molten steel having a composition as shown in Table 1 below to prepare a steel slab using a continuous casting. The cast slabs were heated under the conditions shown in Table 2, followed by rolling and cooling to prepare steel sheets. In addition, Table 3 below shows the fraction and hardness of the microstructures of the inventive examples and comparative examples, and additionally measured and measured the erosion resistance and yield strength. In addition, the erosion resistance was evaluated by simulating the oil sand flowing environment.

C Si Mn P S Al N Cr Honor Inventory 1 0.26 0.21 1.65 0.008 0.003 0.035 0.005 0.09 Inventory 2 0.28 0.19 1.71 0.009 0.007 0.037 0.008 0.29 Inventory 3 0.29 0.32 1.59 0.008 0.004 0.029 0.007 0.03 Honorable 4 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Inventory 5 0.33 0.27 1.73 0.006 0.004 0.033 0.009 0.15 Comparative Example Conventional Example 1 0.041 0.23 1.21 0.006 0.006 0.037 0.005 0.1 Comparative Example 1 0.38 0.22 1.75 0.009 0.003 0.043 0.008 0.12 Comparative Example 2 0.21 0.21 1.48 0.006 0.004 0.037 0.008 0.13 Comparative Example 3 0.28 0.16 2.1 0.005 0.003 0.029 0.007 0.22 Comparative Example 4 0.26 0.18 1.1 0.008 0.007 0.033 0.009 0.18 Comparative Example 5 0.27 0.22 1.47 0.009 0.004 0.043 0.008 0.55 Comparative Example 6 0.29 0.18 1.53 0.007 0.003 0.032 0.004 0.43 Comparative Example 7 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Comparative Example 8 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Comparative Example 9 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Comparative Example 10 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Comparative Example 11 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18 Comparative Example 12 0.3 0.19 1.66 0.007 0.006 0.041 0.005 0.18

Ar3
(° C) Heating temperature
(° C) Cooling start temperature
(° C) Cooling end temperature
(° C) Cooling rate
(° C / sec) Residual pressure drop rate (%) at Ar3 ~ Ar3 + 200 ℃ Honor Inventory 1 700 1160 837 494 0.9 70 Inventory 2 686 1148 803 485 3.2 70 Inventory 3 696 1186 880 473 1.9 60 Honorable 4 685 1160 788 456 2.8 70 Inventory 5 671 1148 776 477 1.6 55 Comparative Example Conventional Example 1 803 1154 825 355 15.8 70 Comparative Example 1 654 1154 825 355 3.1 70 Comparative Example 2 728 1159 872 465 2.8 75 Comparative Example 3 656 1147 802 358 2.6 75 Comparative Example 4 743 1175 777 379 2.8 65 Comparative Example 5 704 1165 785 458 2.7 65 Comparative Example 6 695 1143 798 443 0.4 70 Comparative Example 7 685 1144 910 462 3.5 65 Comparative Example 8 685 1163 633 421 3.6 65 Comparative Example 9 685 1167 842 647 2.1 70 Comparative Example 10 685 1150 833 455 6.3 70 Comparative Example 11 685 1167 815 433 0.12 65 Comparative Example 12 685 1165 827 416 4.2 40

Erosion resistance
(Area% compared to Conventional Example 1) Yield strength
(MPa) Ferrite fraction
(area%) Perlite fraction
(area%) Bainite / Martensite fraction (area%) Ferrite Hardness
(Hv) Pearlite Hardness
(Hv) Honor Inventory 1 183 459 36 56 8 158 245 Inventory 2 185 483 35 59 6 169 259 Inventory 3 201 478 33 60 7 163 255 Honorable 4 204 480 30 61 9 166 255 Inventory 5 189 496 28 63 9 165 258 Comparative Example Conventional Example 1 100 473 93 5 2 143 225 Comparative Example 1 151 585 12 83 5 166 257 Comparative Example 2 144 423 50 46 4 159 243 Comparative Example 3 138 602 11 52 37 171 251 Comparative Example 4 129 430 53 42 5 158 249 Comparative Example 5 139 656 16 43 41 166 278 Comparative Example 6 165 433 32 59 9 169 269 Comparative Example 7 166 505 29 46 25 165 253 Comparative Example 8 152 512 33 21 46 161 243 Comparative Example 9 148 451 48 46 6 163 241 Comparative Example 10 173 652 15 22 63 169 256 Comparative Example 11 144 411 46 48 6 152 229 Comparative Example 12 165 521 31 47 22 156 255

As can be seen in Table 3, Inventive Examples 1 to 5 can be confirmed to have the same or higher erosion resistance than conventional Example 1, which is a low carbon steel conventionally used as steel for oil sand slurry pipe.

In the case of Comparative Example 1 is a steel sheet exceeding 0.35% by weight, the maximum of the C content limited in the present invention, the C content is higher than the Inventive Examples 1 to 5, but the pearlite fraction satisfies the range proposed by the present invention, but the ferrite fraction is Deformation capacity is reduced to less than the limit in the present invention can be confirmed that the erosion resistance is poor. Comparative Example 2 is a case where C is added to less than 0.25% by weight, the ferrite fraction is increased and the pearlite fraction is reduced it can be seen that the erosion resistance is reduced.

Comparative Example 3 and Comparative Example 4 are steels of components outside the range of 1.4 to 1.8% by weight of Mn, which is limited in the present invention, and Comparative Example 3 having an Mn content of 2.1% by weight increases the bainite fraction to increase yield strength. And it can be confirmed that the erosion resistance is reduced, Comparative Example 4 can be confirmed that the Mn content of 1.1% by weight of Mn decreases the fraction of the pearlite and ferrite outside the range limited in the present invention, the corrosion resistance is reduced.

In Comparative Example 5, the content of Cr is 0.55% by weight and exceeds the upper limit of 0.4% by weight, which can be confirmed that the yield strength is rapidly increased and the erosion resistance decreases due to the increase in the bainite fraction. Comparative Example 6 is a case in which the Cr content exceeds 0.4% by weight, which is the upper limit as in Comparative Example 5, and is manufactured outside the cooling rate of 0.5 to 5 ° C / sec provided by the present invention. As shown in Table 3, although the fraction of ferrite and pearlite is within the range defined by the present invention, it is confirmed that the corrosion resistance is decreased due to the high hardness of the pearlite phase.

In Comparative Example 7, the cooling start temperature exceeds the upper limit of the present invention, and it can be seen that the bainite fraction is increased due to the increase in hardenability due to grain coarsening, thereby increasing the strength and decreasing the erosion resistance. Comparative Example 8 is a case where the cooling start temperature is below Ar3, the quenchability of austenite is increased in the ideal zone, the fraction of bainite is increased, the strength increases and the erosion resistance decreases.

Comparative Example 9 is a case where the cooling end temperature exceeds 500 ° C. or less, which is limited by the present invention, and the ferrite fraction exceeds the range limited by the present invention, and the erosion resistance decreases.

Comparative Example 10 and Comparative Example 11 is the case that the cooling rate is out of the range of 0.5 ~ 5 ℃ / sec prescribed in the present invention, Comparative Example 10 with a high cooling rate was increased in strength with the increase in the bainite phase fraction and erosion resistance It can also be seen that the decrease. Comparative Example 11 having a low cooling rate can be seen that the ferrite fraction is formed beyond the range specified in the present invention, the strength is low but the hardness of the pearlite is low and the corrosion resistance is low.

In Comparative Example 12, the finish rolling cumulative reduction rate did not satisfy 50%, which is the lower limit defined in the present invention, and it was confirmed that the austenite grains were coarse to increase the bainite fraction and to reduce erosion resistance.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (6)

By weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% or less (excluding 0), P: 0.03% or less (excluding 0), S: 0.03 % Or less (excluding 0), N: 0.01% or less (excluding 0), Cr: 0.4% or less (excluding 0), balance Fe and other unavoidable impurities, and the microstructure includes pearlite and ferrite, , Perlite is 50% or more by area fraction, ferrite is 20 to 40% by area fraction, the steel plate for oil sand slurry pipe excellent in corrosion resistance.
delete The method according to claim 1,
The hardness of the pearlite is 240 ~ 260Hv, ferritic hardness of 150Hv or more excellent corrosion resistance oil sand slurry pipe steel sheet.
By weight%, C: 0.25-0.35%, Si: 0.1-0.5%, Mn: 1.4-1.8%, Al: 0.05% or less (excluding 0), P: 0.03% or less (excluding 0), S: 0.03 Heating a steel slab comprising up to% (excluding 0), N: 0.01% or less (excluding 0), Cr: 0.4% or less (excluding 0), residual Fe and other unavoidable impurities; Finishing hot rolling the heated steel slab to a residual reduction ratio of 50% or more in a temperature range of Ar 3 to Ar 3 + 200 ° C .; And cooling the hot rolled steel at a cooling rate of 0.5 to 5 ° C./sec.
5. The method of claim 4,
The cooling method of producing a steel plate for oil sand slurry pipe excellent in corrosion resistance to start cooling in the temperature range of Ar3 ~ Ar3 + 200 ℃ to terminate the cooling at 500 ℃ or less.
5. The method of claim 4,
The steel sheet includes a microstructure of pearlite and ferrite, the microstructure is
A method for producing an oil sand slurry pipe having excellent corrosion resistance of an area fraction of 50% or more perlite and 20% to 40% ferrite.

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