KR102020381B1 - Steel having excellent wear resistnat properties and method for manufacturing the same - Google Patents

Abstract

It is an object of the present invention to provide a steel and a method of manufacturing the same, which are excellent in strength, elongation and impact toughness, as well as excellent in internal quality and wear resistance.
According to the present invention, in weight%, carbon (C): 0.55 to 1.4%, manganese (Mn): 12 to 23%, chromium (Cr): 5% or less (excluding 0%), copper (Cu): 5 % Or less (excluding 0%), Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%), phosphorus (P): 0.04 Steels containing less than% (including 0%), residual Fe and unavoidable impurities, and having a fine structure and abrasion resistance containing less than 10% (including 0%) of carbides and residual austenite in an area%, and a manufacturing method thereof Is provided.

Description

Steel material with excellent wear resistance and manufacturing method thereof {STEEL HAVING EXCELLENT WEAR RESISTNAT PROPERTIES AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to austenitic steels used in industrial machinery, structural materials, steel for slurry pipes, sour steels, etc. in the oil and gas industries such as mining, transportation, and storage, and manufacturing methods thereof. In more detail, the present invention relates to an austenitic steel having excellent internal quality and wear resistance and a method of manufacturing the same.

Austenitic steels are used for various purposes due to their excellent work hardening properties, low temperature toughness and nonmagnetic properties. Particularly, as carbon steel mainly composed of ferrite or martensite, which has been mainly used, shows its limitation in its characteristics, its application is increasing as an alternative material to overcome these disadvantages.

In particular, with the growth of the mining industry, oil and gas industries (Oil and Gas Industries), wear of the steel used in the mining, transportation, refining and storage process is a major problem. In particular, with the recent development of oil sands as a fossil fuel to replace petroleum, steel wear caused by slurry containing oil, rock, gravel, sand, etc. is pointed out as an important cause of the increase in production cost. Accordingly, the demand for the development and application of steel having excellent wear resistance is increasing.

In the existing mining and machinery parts industry, the hard-wearing Hadfield steel has been mainly used.In order to increase the abrasion resistance of the steel, a high content of carbon and a large amount of manganese are added to increase austenite structure and wear resistance. Efforts have been made steadily. However, in the case of the headfield steel, the high carbon content rapidly generates network-shaped carbides along the austenite grain boundaries at high temperatures, thereby drastically lowering the properties of the steel, particularly the ductility.

In order to suppress the precipitation of network type carbide, a method of manufacturing high manganese steel by solution treatment at high temperature or by quenching to room temperature after hot processing has been proposed. However, when the thickness of the steel is thick, or when the manufacturing conditions are not easily changed, such as when welding is essential, it is difficult to suppress the precipitation of the network type carbide, which causes a problem of rapid deterioration of the properties of the steel. Done.

In addition, ingots or slabs of high manganese steel inevitably generate segregation due to impurity elements such as P and S in addition to alloying elements such as manganese and carbon during solidification. Coarse carbides are formed along the segregated sedimentary zones, which leads to non-uniformity of microstructures and deterioration of physical properties.

In addition, there may be a result of generating a center crack caused by heat or stress generated during processing.

In order to improve the wear resistance, it is necessary to increase the carbon content, and to increase the manganese content in order to prevent the deterioration of the property due to carbide precipitation, it may be a general method, but this leads to an increase in the amount of alloy and manufacturing cost. do.

In order to solve this problem, research on addition of an element effective in suppressing carbide formation compared to manganese is required. In addition, research on brittleness problems caused by segregation, which is common in high-alloy products, is continuously required.

Republic of Korea Patent Application Publication No. 2016-0077558

One preferred aspect of the present invention is to provide a steel having excellent strength, elongation and impact toughness as well as excellent internal quality and wear resistance.

Another preferred aspect of the present invention is to provide a method for producing a steel having excellent strength, elongation and impact toughness as well as excellent internal quality and wear resistance.

According to a preferred aspect of the present invention, in weight%, carbon (C): 0.55 ~ 1.4%, manganese (Mn): 12-23%, chromium (Cr): 5% or less (excluding 0%), copper ( Cu): 5% or less (excluding 0%), Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%), phosphorus ( P): less than 0.04% (including 0%), remainder Fe and unavoidable impurities; fine structure, abrasion resistant steels containing up to 10% (including 0%) carbides and residual austenite in area% Is provided.

The steel material may have a component segregation index (S) represented by the following Formula (1) of 3.0 or less.

[Relationship 1]

Component segregation index (S) = (rolling material center C component / molten steel C component) / 1.25 + (rolling material center Mn component / molten steel Mn component) / 1.15 + (rolling material center P component / molten steel P component) / 3.0

(In this case, the central component means a component in the range of 50 µm or less in the upper and lower portions of the portion where the highest component is measured in the microstructure analysis at the 1/2 thickness position of the rolled material )

The steel may have a yield strength of 350 MPa or more, a uniform elongation of 20% or more, and an impact toughness of 40 J or more .

According to another preferred aspect of the present invention, in weight%, carbon (C): 0.55 ~ 1.4%, manganese (Mn): 12-23%, chromium (Cr): 5% or less (excluding 0%), copper (Cu): 5% or less (excluding 0%), Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%), phosphorus (P): preparing molten steel containing 0.04% or less (including 0%), residual Fe and inevitable impurities;

A continuous casting step of obtaining slabs by continuously casting the molten steel under conditions of a molten steel temperature (T _C ) satisfying the following formula (2) and a casting speed (V) satisfying the following formula (3);

[Relationship 2]

K≤T _C ≤K + 60

(K value in said Formula (2) shows the value determined by following formula (4).)

[Relationship 4]

K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])

(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)

[Relationship 3]

V (m / min) ≥ 0.025 [T _C -K]

(K value in said Formula (3) shows the value determined by following formula (4).)

[Relationship 4]

K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])

(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)

Reheating the slab below a reheating temperature (T _R ) obtained by the following equation (5);

[Relationship 5]

T _R = 1453-165 [C]-4.5 [Mn]-414 [P]

[T _R: reheat temperature (° C.); [C] and [Mn] each means the content (% by weight) of the element.]

Hot-rolling the slab reheated as described above to have a finish rolling temperature of 850 to 1050 ° C. to obtain a hot rolled steel; And

Provided is a method for producing steel having excellent wear resistance, including cooling the hot rolled steel to 600 ° C. or less at 5 ° C./sec or more.

According to the present invention, in the oil and gas industry where the wear resistance is high due to the high wear resistance, it can be applied to the field where the wear resistance is required in the mining, transportation, storage, or industrial machinery fields in general, and internal defects that may occur during the production process It can dramatically reduce the incidence rate and can provide steel materials that can extend the scope of application to areas requiring internal quality.

1 is a photograph showing a defect in the thickness of the steel sheet in Comparative Steel 4;

The inventors of the present invention while studying the steel having excellent strength and wear resistance compared to the existing steel used in the technical field requiring wear resistance, in the case of high manganese steel can not only secure the excellent strength and elongation peculiar to the austenitic steel, In the case of improving the work hardening rate, the present invention has been completed by recognizing that hardness is increased due to work hardening of the material itself in a wear environment, thereby ensuring excellent wear resistance.

The present invention not only has excellent strength and elongation characteristic of austenitic steels, but also provides austenitic steels having excellent abrasion resistance due to work hardening of the material itself in abrasion environment, and a method of manufacturing the same.

Furthermore, the present invention optimizes the casting conditions and reheating conditions to control the internal embrittlement problems caused by impurities such as P and a large amount of carbon and manganese, which are problems of conventional austenitic abrasion resistant steels. Provided is an improved austenitic wear resistant steel and a method of manufacturing the same.

Hereinafter, the steel material excellent in the wear resistance which concerns on one preferable aspect of this invention is demonstrated.

According to the preferred aspect of the present invention, the steel having excellent wear resistance is% by weight, carbon (C): 0.55 to 1.4%, manganese (Mn): 12 to 23%, and chromium (Cr): 5% or less (excluding 0%). ), Copper (Cu): 5% or less (excluding 0%), Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%) ), Phosphorus (P): contains 0.04% or less (including 0%), residual Fe and inevitable impurities, and contains 10% or less (including 0%) of carbides and residual austenite in a microstructure.

Hereinafter, the component and the component range will be described.

C: 0.55-1.4 wt% (hereinafter also referred to as "%")

Carbon (C) is an austenite stabilizing element that not only plays a role of improving the uniform elongation, but is also an element that is very advantageous for improving the strength and the work hardening rate. If the content of such carbon is less than 0.55%, it is difficult to form stable austenite at room temperature, and it is difficult to secure sufficient strength and work hardening rate. On the other hand, if the content exceeds 1.4%, carbides may be precipitated in large quantities, thereby reducing uniform elongation, which may make it difficult to obtain excellent elongation, and may cause wear resistance and premature fracture.

Therefore, the content of C is preferably limited to 0.55 ~ 1.4%.

Mn: 12-23%

Manganese (Mn) is a very important element that plays a role of stabilizing austenite, and improves uniform elongation. In the present invention, in order to obtain austenite as the main tissue, Mn is preferably contained 12% or more.

If the Mn content is less than 12%, the austenite stability may be lowered to form martensite structure, which may make it difficult to secure sufficient uniform elongation if the austenite structure is not sufficiently secured. On the other hand, if the Mn content exceeds 23%, not only the manufacturing cost increases, but also the problems such as deterioration of corrosion resistance and difficulty in the manufacturing process due to the addition of manganese.

Therefore, the content of Mn is preferably limited to 12 to 23%.

Cr: 5% or less (except 0%)

Chromium (Cr) stabilizes austenite up to the range of an appropriate amount of addition, thereby improving impact toughness at low temperatures, and solid-solution in austenite increases the strength of steel. In addition, chromium is also an element for improving the corrosion resistance of steel materials. However, when the Cr content exceeds 5%, carbides are excessively formed at the austenite grain boundary, which may greatly reduce the toughness of the steel, which is not preferable.

Cu: 5% or less (except 0%)

Copper (Cu) has a very low solid solubility in carbides and a slow diffusion in austenite, concentrating at the austenite and nucleated carbide interface, thereby interfering with the diffusion of carbon, which effectively slows carbide growth, eventually leading to carbide production. It has a suppressing effect. However, when the content of Cu exceeds 5%, there is a problem of lowering the hot workability of the steel, so the upper limit of the content is preferably limited to 5%.

Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%)

Aluminum (Al) and silicon (Si) are added to the deoxidizer during the steelmaking process, the upper limit of the aluminum (Al) content is preferably limited to 0.5%, the upper limit of the silicon (Si) content is preferably limited to 1.0%. .

S: 0.02% or less (including 0%)

It is preferable to suppress S as an impurity as much as possible, and it is preferable to manage the upper limit to 0.02%.

P: 0.04% or less (including 0%)

In general, P is well known as an element causing segregation at grain boundaries and causing high temperature embrittlement. Especially, high alloy steels containing a large amount of C and Mn, such as the steel of the present invention, are severe in slabs and products when added to P segregation. May cause brittleness. Moreover, since the segregation rate is sharply increased when P exceeds a certain content, the content is preferably limited to 0.04% or less.

In addition to the balance Fe and unavoidable impurities. However, in the conventional manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, not all of them are specifically mentioned in the present specification. In addition, addition of an effective component other than the said composition is not excluded.

Steel having excellent abrasion resistance according to a preferred aspect of the present invention is a microstructure, including an area%, less than 10% (including 0%) of carbide and the remainder austenite.

If the fraction of the carbide is 10% by area, it may cause rapid impact toughness deterioration. The austenite improves ductility and toughness.

It is preferable that the component segregation index (S) of the said steel material represented by following formula (1) is 3.0 or less.

[Relationship 1]

Component segregation index (S) = (rolling material center C component / molten steel C component) / 1.25 + (rolling material center Mn component / molten steel Mn component) / 1.15 + (rolling material center P component / molten steel P component) / 3.0

(In this case, the central component means a component in the range of 50 µm or less in the upper and lower portions of the portion where the highest component is measured in the microstructure analysis at the 1/2 thickness position of the rolled material)

If the component segregation index (S) represented by the above formula (1) exceeds 3.0, the probability of cracking along the segregation zone at the 1 / 2t (t: steel thickness) position during machining, for example, during cutting, is high. It can rise sharply.

The steel may have a yield strength of 350 MPa or more, a uniform elongation of 20% or more, and an impact toughness of 40 J or more.

Hereinafter, a method for producing steel having excellent wear resistance according to another preferred aspect of the present invention will be described in detail.

According to another preferred aspect of the present invention, a method for producing steel having excellent wear resistance is% by weight, carbon (C): 0.55 to 1.4%, manganese (Mn): 12 to 23%, and chromium (Cr): 5% or less ( 0% excluding), Copper (Cu): 5% or less (excluding 0%), Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (Including 0%), phosphorus (P): preparing molten steel containing 0.04% or less (including 0%), balance Fe and inevitable impurities;

A continuous casting step of obtaining slabs by continuously casting the molten steel under conditions of a molten steel temperature (T _C ) satisfying the following formula (2) and a casting speed (V) satisfying the following formula (3);

[Relationship 2]

K≤T _C ≤K + 60

(K value in said Formula (2) shows the value determined by following formula (4).)

[Relationship 4]

K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])

(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)

[Relationship 3]

V (m / min) ≥ 0.025 [T _C -K]

(K value in said Formula (3) shows the value determined by said Formula (4).)

[Relationship 4]

K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])

(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)

Reheating the slab below a reheating temperature (T _R ) obtained by the following equation (5);

[Relationship 5]

T _R = 1453-165 [C]-4.5 [Mn]-414 [P]

[T _R: reheat temperature (° C.); [C] and [Mn] each means the content (% by weight) of the element.]

Hot-rolling the slab reheated as described above to have a finish rolling temperature of 850 to 1050 ° C. to obtain a hot rolled steel; And

Cooling the hot rolled steel to 600 ° C or less at 5 ° C / sec or more.

Continuous casting stage

The molten steel formed as described above is continuously cast under the conditions of the molten steel temperature (T _C ) satisfying the following formula (2) and the casting speed (V) satisfying the following formula (3) to obtain a steel slab.

[Relationship 2]

K≤T _C ≤K + 60

(K value in said Formula (2) shows the value determined by following formula (4).)

[Relationship 4]

K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])

(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)

[Relationship 3]

V (m / min) ≥ 0.025 [T _C -K]

(K value in said Formula (3) shows the value determined by said Formula (4).)

In the present invention, in order to suppress excessive segregation in the slab structure that can easily occur in high-carbon high-manganese wear-resistant steel, casting conditions according to the component change, such as the formula (2) ~ (4) is derived. This can suppress the internal quality (center quality) defects that occur frequently in the final steel.

If the slab is not manufactured under the above casting conditions, excessive segregation zone may be formed in the slab, and the slab brittleness may occur, and excessive segregation zone may remain even after reheating and rolling, causing quality defects.

Slab reheating stage

The slab obtained by continuous casting as described above is reheated.

The slab reheating is preferably performed at a reheating temperature (T _R ) or less obtained by the following formula (5).

[Relationship 5]

T _R = 1453-165 [C]-4.5 [Mn]-414 [P]

[T _R: reheat temperature (° C.); [C] and [Mn] each means the content (% by weight) of the element.]

In the present invention, in order to suppress the central embrittlement due to partial melting of the segregation zone during reheating that can easily occur in high carbon high manganese wear-resistant steel, the reheating temperature limitation condition according to the component change as shown in Equation (5) . This can suppress the internal quality (center quality) defects that occur frequently in the final steel.

If the slab reheating temperature exceeds the T _R temperature, partial melting may occur in the segregation zone in the slab, which results in core embrittlement leading to the product, causing the core segregation index of the rolled material to exceed 3.0, causing core failure.

Hot rolled steel  Getting steps

The slab reheated as above is hot rolled to obtain a finish rolling temperature of 850 ° C to 1050 ° C to obtain a hot rolled steel.

When the finish rolling temperature is less than 850 ℃, carbides may be precipitated to lower the uniform elongation, and microstructures may be pancake to cause nonuniform stretching due to tissue anisotropy. When the finish rolling temperature exceeds 1050 ° C, grain growth may be active and coarse crystal grains may easily cause a problem that the strength is lowered.

Of hot rolled steel  Cooling stage

The hot rolled steel is cooled to 600 ° C. or less at 5 ° C./sec or more.

If the cooling rate is less than 5 ℃ / sec, or if the cooling stop temperature exceeds 600 ℃ may be a problem that the carbide is precipitated elongation is reduced. Rapid cooling processes help to ensure high solubility of the C and N elements in the matrix. Therefore, the cooling is preferably carried out to 5 ° C / sec or more to 600 ° C or less. The cooling rate is more preferably 10 ° C / sec or more, and even more preferably 15 ° C / sec or more.

The upper limit of the cooling rate is not particularly limited, and may be limited in consideration of the cooling capacity of the equipment. Cooling of the thermal steel material may be made up to room temperature.

According to a method for producing steel having excellent wear resistance according to another preferred aspect of the present invention, for example, a steel having a yield strength of 350 MPa or more, a uniform elongation of 20% or more, and an impact toughness of 40 J or more can be manufactured.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, it should be noted that the following embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and the matters reasonably inferred therefrom.

(Example)

The molten steel that satisfies the components and component ranges as shown in Table 1 was continuously cast under the conditions of Table 2, and then the slabs were reheated, hot rolled, and cooled under the conditions of Table 3 to produce hot rolled steel.

The microstructure, component segregation index, cutting crack incidence (%), wear resistance (g), yield strength (MPa) and uniform elongation (%) of the hot rolled steel prepared as described above were measured, and the results are shown in Table 4 below. It was . Here, the wear resistance is evaluated by measuring the reduced weight after abrasion by contacting the specimen to the rotating roll while spraying a certain amount of sand in the sand wear test according to the ASTM 65 test method.

In addition, -29 ℃ impact toughness [impact energy (J)] for the hot rolled steel was measured, and the results are shown in Table 4 together.

On the other hand, the comparative steel 4 was photographed to confirm the occurrence of defects in the thickness of the steel sheet thickness, the results are shown in FIG.

Steel grade Steel composition (% by weight) C Mn P Cr Cu Al Si S Inventive Steel 1 0.58 22.1 0.031 4.3 2.1 0.035 0.43 0.006 Inventive Steel 2 0.65 16.6 0.022 3.4 3.9 0.078 0.017 0.011 Inventive Steel 3 0.83 14.9 0.019 1.2 0.33 0.044 0.21 0.007 Inventive Steel 4 1.11 18.4 0.015 2.1 0.06 0.121 0.015 0.005 Inventive Steel 5 1.32 12.6 0.011 0.08 1.2 0.264 0.085 0.012 Comparative Steel 1 0.36 16.1 0.018 3.1 0.02 0.055 0.07 0.01 Comparative Steel 2 1.44 17.2 0.012 2.3 0.3 0.049 0.12 0.007 Comparative Steel 3 0.59 11.6 0.015 0.8 1.2 0.078 0.15 0.005 Comparative Steel 4 1.17 17.1 0.045 0.4 0.2 0.043 0.11 0.008 Comparative Steel 5 1.21 18.9 0.016 1.0 0.9 0.039 0.21 0.007 Comparative Steel 6 0.98 15.8 0.015 3.3 2.3 0.046 0.098 0.004 Comparative Steel 7 0.89 18.3 0.015 2.1 1.3 0.039 0.046 0.006 Comparative Steel 8 1.09 21.3 0.022 0.01 1.2 0.063 0.15 0.011 Comparative Steel 9 0.99 17.8 0.018 0.05 0.044 1.2 0.8 0.009

Steel grade Continuous casting condition Molten steel temperature (T _C ) of Equation 2 (℃) Casting Speed (V) (m / min) Actual steel temperature (℃) Actual casting speed (m / min) Inventive Steel 1 1425 0.2 1434 0.5 Inventive Steel 2 1447 0.3 1459 0.4 Inventive Steel 3 1445 0.6 1467 One Inventive Steel 4 1415 0.5 1433 One Inventive Steel 5 1430 0.8 1462 0.9 Comparative Steel 1 1465 0.5 1486 0.7 Comparative Steel 2 1403 0.8 1435 One Comparative Steel 3 1473 1.1 1517 1.2 Comparative Steel 4 1416 0.2 1425 0.5 Comparative Steel 5 1407 1.0 1446 1.2 Comparative Steel 6 1433 1.4 1489 1.5 Comparative Steel 7 1427 0.8 1460 One Comparative Steel 8 1402 0.7 1431 One Comparative Steel 9 1424 0.7 1453 0.2

In Table 2, the casting speed V is V (m / min) = 0.025 [T _C -K].

Steel grade Reheating, Hot Rolling and Cooling Conditions Reheating temperature (T _R ) of Equation 5 (℃) Reheating Temperature (℃) Finish rolling temperature (℃) Cooling rate (℃ / sec) Cooling stop temperature (℃) Inventive Steel 1 1245 1212 870 44 540 Inventive Steel 2 1262 1205 875 25 390 Inventive Steel 3 1241 1185 903 19 320 Inventive Steel 4 1181 1170 980 61 250 Inventive Steel 5 1174 1162 990 41 270 Comparative Steel 1 1314 1220 1020 21 560 Comparative Steel 2 1133 1130 905 19 440 Comparative Steel 3 1297 1196 898 28 280 Comparative Steel 4 1164 1152 885 30 370 Comparative Steel 5 1162 1187 913 29 380 Comparative Steel 6 1214 1195 829 25 385 Comparative Steel 7 1218 1207 908 3 420 Comparative Steel 8 1168 1179 950 16 690 Comparative Steel 9 1202 1156 945 22 420

division Microstructure ingredient
Segregation Index 1) Breaking crack incidence (%) 2) Wear resistance
(g) Yield strength
(MPa) Uniform elongation
(%) Impact Toughness (-29 ℃)
(J) Inventive Steel 1 γ + carbide 10% or less 2.85 0 1.88 363 51 193 Inventive Steel 2 γ + carbide 10% or less 2.58 0 1.74 451 53 233 Inventive Steel 3 γ + carbide 10% or less 2.51 0 1.54 412 60 265 Inventive Steel 4 γ + carbide 10% or less 2.45 0 1.43 499 53 247 Inventive Steel 5 γ + carbide 10% or less 2.27 0 1.41 522 49 122 Comparative Steel 1 γ + carbide 10% or less 2.45 0 2.69 270 49 99 Comparative Steel 2 γ + carbides 15.8% 2.31 0 1.56 581 18 33 Comparative Steel 3 γ + α - 12 2.98 378 36 20 Comparative Steel 4 γ + carbide 10% or less 3.56 83 - 505 22 60 Comparative Steel 5 γ + carbide 10% or less 3.59 68 - 514 27 69 Comparative Steel 6 γ + carbides 12.1% 2.39 0 2.11 418 28 33 Comparative Steel 7 γ + carbide 13.2% 2.31 0 2.17 432 25 29 Comparative Steel 8 γ + carbides 14.2% 2.55 0 2.34 519 33 35 Comparative Steel 9 γ + carbide 10% or less 3.9 85 - 508 29 55

1) Component Segregation Index (S) = (C center component / molten steel C component) / 1.25 + (Mn component / molten steel Mn component) / 1.15 + (P component / molten steel P component) /3.0

* Center component: It means the component in the upper and lower 50㎛ range of the part where the highest component is measured in the microstructure analysis at 1/2 thickness of the rolled material.

2) Cutting crack incidence: (center crack incidence length / total cutting length) × 100

As shown in Table 1 to Table 4, the invention steel (1-5) that satisfies both the steel composition and manufacturing conditions of the present invention is not only excellent in abrasion resistance, yield strength, impact toughness and uniform elongation but also cutting crack The rate is also low.

On the other hand, in the case of the comparative steel (1 -9) that does not meet at least one of the steel composition and manufacturing conditions of the present invention, the physical properties of at least one of the wear resistance, yield strength, impact toughness and uniform elongation is insufficient or the cutting crack rate It can be seen that this is high.

In the case of Comparative Steel 4 having a central component segregation index of more than 3.0, the cutting crack incidence is high, and as shown in FIG. 1, it can be seen that a defect in the thickness of the steel core is generated. It can be seen that the crack occurred in the weakest center due to the thermal stress generated during the cutting process, and the crack propagated along the center.

Claims (4)

By weight%, carbon (C): 0.55 to 1.4%, manganese (Mn): 12 to 23%, chromium (Cr): 5% or less (excluding 0%), copper (Cu): 5% or less (0% Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%), phosphorus (P): 0.04% or less (0%) ), Including the balance Fe and inevitable impurities, the microstructure includes less than 10% (including 0%) of carbides and residual austenite in area%,
Steel material excellent in abrasion resistance whose component segregation index represented by following formula (1) is 3.0 or less.
[Relationship 1]
Component segregation index (S) = (rolling material center C component / molten steel C component) / 1.25 + (rolling material center Mn component / molten steel Mn component) / 1.15 + (rolling material center P component / molten steel P component) / 3.0
(In this case, the central component means a component in the range of 50 µm or less in the upper and lower portions of the portion where the highest component is measured in the microstructure analysis at the 1/2 thickness position of the rolled material)
delete The steel according to claim 1, wherein the steel has a yield strength of 350 MPa or more, a uniform elongation of 20% or more, and an impact toughness of 40 J or more.
By weight%, carbon (C): 0.55 to 1.4%, manganese (Mn): 12 to 23%, chromium (Cr): 5% or less (excluding 0%), copper (Cu): 5% or less (0% Al: 0.5% or less (excluding 0%), Si: 1.0% or less (excluding 0%), S: 0.02% or less (including 0%), phosphorus (P): 0.04% or less (0%) Comprising) preparing a molten steel comprising the balance Fe and inevitable impurities;
A continuous casting step of obtaining slabs by continuously casting the molten steel under conditions of a molten steel temperature (T _C ) satisfying the following formula (2) and a casting speed (V) satisfying the following formula (3);
[Relationship 2]
K≤T _C ≤K + 60
(K value in said Formula (2) shows the value determined by following formula (4).)
[Relationship 4]
K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])
(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)
[Relationship 3]
V (m / min) ≥ 0.025 [T _C -K]
(K value in said Formula (3) shows the value determined by following formula (4).)
[Relationship 4]
K (° C) = 1536-(69 [C] + 4.2 [Mn] + 39 [P])
(Wherein each of [C], [Mn], and [P] means the content (% by weight) of the corresponding element)
Reheating the slab below a reheating temperature (T _R ) obtained by the following equation (5);
[Relationship 5]
T _R = 1453-165 [C]-4.5 [Mn]-414 [P]
[T _R: reheat temperature (° C.); [C] and [Mn] each means the content (% by weight) of the element.]
Hot-rolling the slab reheated as described above to have a finish rolling temperature of 850 to 1050 ° C. to obtain a hot rolled steel; And
Cooling the hot rolled steel to 600 ° C or less at 5 ° C / sec or more,
The manufacturing method of the steel material excellent in the wear resistance which satisfy | fills 3.0 or less of the component segregation index represented by following formula (1).
[Relationship 1]
Component segregation index (S) = (rolling material center C component / molten steel C component) / 1.25 + (rolling material center Mn component / molten steel Mn component) / 1.15 + (rolling material center P component / molten steel P component) / 3.0
(In this case, the central component means a component in the range of 50 µm or less in the upper and lower portions of the portion where the highest component is measured in the microstructure analysis at the 1/2 thickness position of the rolled material)

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