WO2019132310A1 - Wear-resistant steel plate having excellent material uniformity and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a steel plate having a high degree of hardness, which is used in industry, construction machines, and the like and, more specifically, to a wear-resistant steel plate having excellent material uniformity and a manufacturing method therefor.

Description

Abrasion-resistant steel sheet excellent in uniformity of material and method of manufacturing the same

More particularly, the present invention relates to a wear-resistant steel sheet having excellent material uniformity and a method of manufacturing the steel sheet.

In the case of machines, apparatuses, etc. used in many industrial fields such as construction, civil engineering, mining industry, and cement industry, abrasion due to abrasion occurs severely during operation, and therefore it is necessary to apply materials having excellent abrasion resistance properties.

In general, the abrasion resistance of a steel is related to the hardness, and in order to improve abrasion resistance, it is necessary to increase the hardness of the steel. In order to ensure more stable abrasion resistance, it is required that the steel plate has a uniform hardness from the surface of the steel plate to the center of the plate thickness (t / 2, t: thickness), that is, there is no difference in hardness in the thickness direction of the steel plate.

Related prior arts are Patent Documents 1 and 2. The above Patent Documents 1 and 2 disclose a method of increasing the surface hardness and the hardness in the plate thickness by increasing the content of carbon (C) or adding a large amount of elements for improving hardenability such as chromium (Cr) and molybdenum (Mo) .

However, the conventional techniques including the above Patent Documents 1 and 2 focus only on securing a uniform hardness in the thickness direction from the surface of the steel sheet having a certain thickness or more. In the case of a steel sheet having a relatively small thickness of 15 mm or less, the hardness deviation at the center of the plate thickness at the surface is not significant, and the deviation of the hardness in the longitudinal direction or the width direction of the steel sheet is a problem. However, .

Therefore, there is an urgent need for a technique capable of ensuring a uniform hardness not only in the thickness direction of the steel sheet, but also in the longitudinal direction or the width direction.

(Patent Document 1) Japanese Laid-Open Patent Publication No. 1986-166954

(Patent Document 2) Japanese Laid-Open Patent Publication No. 1996-041535

One aspect of the present invention is to provide a steel sheet having excellent wear resistance and excellent material uniformity in the longitudinal direction and the width direction of the steel sheet and a method of manufacturing the steel sheet.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

One aspect of the present invention is a method of manufacturing a semiconductor device, comprising: 0.2 to 0.3% of C, 0.5 to 2.0% of Si (excluding 0), 0.5 to 2.0% of Mn, 0.03% (Excluding 0 is excluded), Al: not more than 0.05% (excluding 0), Cr: 0.1 to 1.0%, Mo: 0.01 to 0.3% ), Nb: not more than 0.05% (excluding 0), the remainder contains Fe and unavoidable impurities,

The present invention relates to an abrasion-resistant steel sheet having excellent uniformity of material having a main structure of martensite and an effective grain size (EGS) of 30 μm or less.

Another aspect of the present invention provides a method of manufacturing a semiconductor device, comprising: 0.2 to 0.3% of C, 0.5% or less of Si (excluding 0), 0.5 to 2.0% of Mn, Cr: 0.1 to 1.0%, Mo: 0.01 to 0.3%, B: not more than 50 ppm (excluding 0), Ti: not more than 0.02% (excluding 0) 0), Nb: not more than 0.05% (excluding 0), the remainder being Fe and unavoidable impurities, at 1100 to 1300 캜;

Subjecting the heated steel slab to hot rolling at a finish hot rolling temperature of 830 to 1000 占 폚;

Cooling at a cooling rate (CR) satisfying the following formula (1) from the finish hot rolling temperature to the coiling temperature (CT);

After cooling, winding at a coiling temperature (CT) satisfying the following formula (2);

Reheating the wound steel sheet at a temperature of 850 to 950 캜 for 20 to 60 minutes; And

And cooling the heated steel sheet to 100 DEG C or less at a cooling rate (CR) satisfying the relational expression (1) above.

[Relation 1]

Cr (° C./s) ≥ 69.6-56 [C] +2.1 [Si] -19.2 [Mn] -8.9 [Cr] +8.0 [Al] -26.9 [Mo]

[Relation 2]

(Ms + 30) 占 폚 CT? (Bs - 30) 占 폚

Ms = 539-423 [C] -30.4 [Mn] -17.7 [Ni] -12.1 [Cr]

Bs = 830-270 [C] -90 [Mn] -37 [Ni] -70 [Cr]

(Wherein each of [C], [Mn], [Ni], [Cr], [Mo], [Si], [Al], and [Mo]

According to the present invention, it is possible to provide a steel sheet having an excellent hardness and excellent material uniformity with a small deviation in the longitudinal and width directions of the steel sheet with respect to the steel sheet having a thickness of 15 mm or less.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the results of measurement of hardness and deviation of inventive examples and comparative examples in an embodiment of the present invention. FIG.

The inventors of the present invention have studied to produce a steel sheet having a thickness of 15 mm or less (preferably 3 to 15 mm) which is excellent in material uniformity by reducing the hardness deviation in the longitudinal direction and the width direction of the steel sheet, It is possible to produce a steel sheet excellent in material uniformity by managing the microstructure after hot rolling in the course of manufacturing, and came to the present invention.

Hereinafter, a steel sheet as an embodiment of the present invention will be described.

First, the alloy composition of the steel sheet of the present invention will be described in detail. Unless otherwise stated, the content of each component is expressed on a weight basis in advance.

The steel sheet according to the present invention contains 0.2 to 0.3% of C, 0.5 to 2.0% of Si (excluding 0), 0.5 to 2.0% of Mn, 0.03% or less of P (excluding 0) (Excluding 0), Al: not more than 0.05% (excluding 0), Cr: 0.1 to 1.0%, Mo: 0.01 to 0.3%, B: 50ppm or less ) And Nb: not more than 0.05% (excluding 0).

Carbon (C): 0.2 to 0.3%

C is the most economical and effective element in securing hardness. If the C content is excessively low, it may be difficult to secure the desired hardness. If the C content is excessively excessive, the toughness and weldability may be deteriorated due to excessive hardness increase. .

Silicon (Si): 0.5% or less (excluding 0)

Although Si usually contributes to increase in strength by deoxidation and solid solution strengthening of molten steel, it is not intentionally added in the present invention, and Si can not be prevented from the viewpoint of securing physical properties without addition of Si. If the content is excessively excessive, on the hot-rolled steel sheet surface, a proper scale due to Si may be formed to deteriorate the surface quality, and the quality of the plating may be deteriorated during plating. Therefore, the Si content is preferably 0.5% or less.

Manganese (Mn): 0.5 to 2.0%

The Mn is an element which suppresses ferrite formation and raises the hardness and toughness of the steel by effectively raising the incombustibility by lowering the Ar3 temperature, and is preferably contained in an amount of not less than 0.5% in order to secure an appropriate hardness. However, if the content thereof is excessively excessive, a center segregation part may occur in the performance process, so it is preferable that the content does not exceed 2.0%.

Phosphorus (P): 0.03% or less (excluding 0)

P is an impurity inevitably contained in the steel, and it is preferable to control the content as low as possible. In particular, when the content is excessive, the risk of deterioration of weldability and brittleness of steel increases, so that the content of P is preferably 0.03% or less.

Sulfur (S): 0.02% or less (excluding 0)

The above S is an impurity inevitably contained in the steel, and it is preferable to manage the content as much as possible. In particular, when the content thereof is excessive, a non-metallic inclusion can be formed by bonding with Mn or the like, and the risk of brittleness of steel is increased, so that the content of S is preferably controlled to be 0.02% or less.

Aluminum (Al): not more than 0.05% (excluding 0)

Although Al contributes to the deoxidation of molten steel, it is not intentionally included in the present invention, and even if the AL is not added, there is no problem in securing the physical properties. However, if the content thereof is excessive, clogging of nozzles may occur during performance, so that the content of Al in the present invention is preferably not more than 0.05%.

Cr (Cr): 0.1 to 1.0%

The Cr is advantageous in securing hardness by increasing the incombustibility, and therefore, it is preferable that Cr is contained in an amount of 0.1% or more in order to secure an appropriate hardness. However, when the content is excessively excessive, the weldability is poor and the manufacturing cost is increased, so it is preferable that the content is not more than 1.0%.

Molybdenum (Mo): 0.01 to 0.3%

The Mo is an element which is advantageous in securing hardness and improving toughness by increasing the incombustibility, and is preferably added in an amount of 0.01% or more for securing an appropriate hardness and toughness. However, if the content exceeds the above range and exceeds 0.3%, the weldability is poor and it may cause a rise in manufacturing cost, and therefore it is preferable that the content is not more than 0.3%.

Boron (B): 50ppm or less (excluding 0)

The B may be contained as an element capable of substituting for Si, and an extremely small amount can improve hardenability by enhancing hardenability and strengthening grain boundaries. However, when the content exceeds 50 ppm, excessive surface degradation due to BN precipitation and deterioration in toughness may be a problem, so that the content thereof is preferably not more than 50 ppm.

Titanium (Ti): 0.02% or less (excluding 0)

The Ti is present in the steel as TiN and has the effect of inhibiting the growth of the crystal grains during the heating process for hot rolling. In addition, it plays a role of removing N so that B does not react with N in boron added steel. If the Ti content is excessive, excessive TiN precipitation may cause nozzle clogging during performance.

Niobium (Nb): not more than 0.05% (excluding 0)

The Nb is dissolved in austenite to increase the hardenability of austenite and form carbonitride such as Nb (C, N), thereby being effective in increasing the strength of steel and suppressing the growth of austenite grains. However, when the Nb content exceeds 0.05%, a coarse precipitate is formed, which is a starting point of brittle fracture, which may be a problem of inhibiting toughness.

The steel sheet of the present invention may further contain, in addition to the above-described alloy composition, elements capable of ensuring favorable physical properties in the present invention. As a preferable example, it may include not more than 0.04% of cobalt (Co), not more than 0.1% of copper (Cu), not more than 0.02% of vanadium (V), and 2 to 100 ppm of calcium (Ca)

Cobalt (Co): not more than 0.04%

The Co is an element favorable for securing the hardness together with the strength of the steel by increasing the ingotability of the steel. However, if the content exceeds 0.04%, there is a fear that the ingot of the steel may be lowered due to segregation or the like, and the cost of manufacturing the steel is increased due to high-strength elements.

Copper (Cu): not more than 0.1%

The Cu improves the incombustibility of the steel and is an element which improves the strength and hardness of the steel by solid solution strengthening. When the content of Cu exceeds 0.1%, surface defects are generated and hot workability is deteriorated. Therefore, it is preferable that the content of Cu is not more than 0.1% when Cu is added.

Vanadium (V): not more than 0.02%

V is an element which is advantageous in suppressing the growth of austenite grains and enhancing the ingotability of steel by securing VC carbide upon reheating after hot rolling to secure strength and toughness. However, V is an expensive element, and if the content exceeds 0.02%, it increases the manufacturing cost, and therefore it is preferable that the V does not exceed 0.02%.

Calcium (Ca): 2 to 100 ppm

Ca has an effect of inhibiting the formation of MnS segregated in the central portion of the steel material by producing CaS because of its strong binding force with S. In addition, the CaS generated by the addition of Ca has an effect of increasing the corrosion resistance under a humid environment. For the above-mentioned effect, Ca is preferably added in an amount of 2 ppm or more, but if the content exceeds 100 ppm, it may cause clogging of the nozzle during steelmaking. Accordingly, in the present invention, the Ca content is preferably 2 to 100 ppm when Ca is added.

The steel sheet of the present invention is an iron (Fe) component in addition to the above-mentioned alloying elements. However, the impurities which are not intended from the raw material or the environment of caution can be inevitably incorporated in a normal manufacturing process, and therefore this can not be excluded. Since these impurities can be known to any ordinary technician, they do not fully exploit all of them.

The final microstructure of the inventive steel sheet preferably has an area fraction of 95% or more of martensite and 5% or less of the second phase. More preferably 97% or more of martensite and 3% or less of the second phase. Here, the second phase is not particularly limited, but may be ferrite, perlite, bainite or the like. In order to secure an excellent hardness, it is preferable that the martensite is uniformly formed. If the fraction of the second phase is high or if the second phase is formed in a large amount at a specific site, the homogeneous strength can not be secured. Therefore, it is preferable that the second phase is obtained at a minimum

Meanwhile, the effective grain size (EGS) of the martensite is preferably 30 탆 or less. More preferably not more than 20 mu m. As the effective grain size becomes finer, it is advantageous to obtain a homogeneous hardness, so that the effective grain size is 30 탆 or less, more preferably 20 탆 or less.

In the steel sheet of the present invention, it is preferable that the microstructure of the steel sheet after hot rolling and winding in the manufacturing process includes bainite as the main structure. It is preferable that the rolled steel sheet has an area fraction of bainite of 95% or more and a second phase of 5% or less. More preferably 97% or more of bainite, and 3% or less of the second phase. Here, the second phase includes ferrite, pearlite, and the like. Most preferably a bainite single phase.

Normally, in order to obtain desired hardness, reheating is followed by quenching to obtain a martensite structure. However, when the structure before reheating is made of ferrite or pearlite, or when these are contained in large amounts, there is a problem that the hardness of martensite obtained after quenching varies depending on ferrite or pearlite, and it is difficult to secure a homogeneous hardness. Accordingly, the present invention allows the microstructure before reheating and quenching to be formed into bainite fully bainite so that martensite can be uniformly produced after quenching.

The wear-resistant steel sheet of the present invention has a hardness of Hb 450 to 550, and a hardness deviation? HB across the longitudinal direction and the width direction of the steel sheet is 30 or less.

Hereinafter, a method for manufacturing a wear-resistant steel sheet, which is another aspect of the present invention, will be described in detail.

The steel sheet of the present invention is preferably prepared by preparing a steel slab satisfying the above-described alloy composition, and then subjecting the steel slab to heating, hot rolling, cooling, winding, reheating heat treatment and cooling. Each process will be described in detail below.

First, a steel slab having the above-described alloy composition is prepared and heated to 1100 to 1300 캜. If the heating temperature is lower than 1100 ° C, the rolling load in the subsequent hot rolling step may become excessively large. On the other hand, if the heating temperature exceeds 1300 ° C, partial microstructure due to abnormal growth of some austenite grains The grain size may not be homogeneous. On the other hand, in the present invention, the slab heating time is not particularly limited, and it may be a normal condition. As a non-limiting example, the slab heating time may be 100 to 400 minutes.

The heated slab is hot-rolled. Specifically, the hot-rolling process is a hot-rolled steel obtained by rough rolling a heated slab, followed by finish rolling at a reverse temperature of austenite. Means a series of rolling processes carried out prior to the rough rolling. The conditions of the rough rolling in the present invention are not particularly limited and may be any ordinary conditions. By way of example, the thickness of the rough-rolled slab relative to the slab thickness may be between 10 and 25%, and the rough-rolling temperature may be set at a sufficiently high temperature at which the finish rolling temperature can be ensured.

On the other hand, finish rolling is carried out at austenite single phase reverse temperature, in order to increase the uniformity of the texture. As an example, the finish rolling temperature may be 800 to 1000 占 폚. During the final hot rolling in the temperature range, the austenite structure of the hot rolled steel material having the finish rolling has an average grain size of 10 to 40 탆. If the finish rolling temperature is lower than 800 占 폚, coarse-grained structure due to subcooling of the edge of the steel sheet may occur and a uniform material can not be obtained. On the other hand, if it exceeds 1000 캜, a sand scale or the like, which is a high-temperature scale, may be formed on the surface of the steel sheet during hot rolling, and the surface quality of the final product may be poor.

After the hot rolling, the steel sheet is cooled from the finish hot rolling temperature to the coiling temperature (CT) at a cooling rate (CR) satisfying the following relational expression (1) It is preferable to take

[Relation 1]

Cr (° C./s) ≥ 69.6-56 [C] +2.1 [Si] -19.2 [Mn] -8.9 [Cr] +8.0 [Al] -26.9 [Mo]

[Relation 2]

(Ms + 30) 占 폚 CT? (Bs - 30) 占 폚

Ms = 539-423 [C] -30.4 [Mn] -17.7 [Ni] -12.1 [Cr]

Bs = 830-270 [C] -90 [Mn] -37 [Ni] -70 [Cr]

(Wherein each of [C], [Mn], [Ni], [Cr], [Mo], [Si], [Al], and [Mo]

If the coiling temperature (CT) is less than (Ms + 30) C, there is a risk of equipment accidents in subsequent processes due to poor shape after coiling. On the other hand, when the coiling temperature CT is higher than (Bs - 30) 占 폚, the microstructure of the steel sheet produced after coiling may be affected by the ferrite and the pearlite or coarse effective grain size (EGS) The hardness deviation in the direction can not be reduced. In addition, when the cooling rate does not satisfy the condition of the above-mentioned relational expression (1), ferrite or pearlite transformation occurs in the cooling process and ferrite or pearlite is formed in the microstructure after winding, It is difficult to secure characteristics.

The microstructure of the rolled steel sheet preferably has an area fraction of 95% or more of bainite and 5% or less of the second phase, more preferably 97% or more of bainite and 3% or less of the second phase. And most preferably formed of a bainite single phase.

The rolled hot-rolled steel sheet can be cut out. The steel plate may be cut out at a length of 3 to 20 m at the time of cutting. If the cut-off length is less than 3 m, the manufacturing cost may increase, and a facility accident may occur in the subsequent heat treatment process. On the other hand, when the cut-off length exceeds 20 m, it becomes difficult to secure a uniform cooling rate in the longitudinal direction in the subsequent cooling step after the heat treatment, resulting in an excessive hardness deviation.

The cut hot rolled steel sheet is subjected to reheating heat treatment at a temperature ranging from 850 to 950 DEG C for 20 to 60 minutes ashes. The reheating heat treatment is for reversely transforming the hot-rolled steel sheet composed of bainite into an austenite single phase. If the heat treatment temperature during reheating is less than 850 ° C, austenitization is not sufficiently performed and bainite remains, There is a problem that the hardness is lowered. On the other hand, when the temperature exceeds 950 DEG C, the austenite grains become coarse and the entanglement becomes large, but there is a problem that the toughness of the steel sheet is inferior. In addition, if the time is less than 20 minutes, the austenitization does not sufficiently take place in the above-mentioned temperature range, so that the phase transformation due to the subsequent rapid cooling, that is, the martensite structure, can not be obtained sufficiently. On the other hand, when the time exceeds 60 minutes, the effective grain size (EGS) of the final microstructure may be out of the range of the invention due to the coarsening caused by the abnormal growth of the austenite grains, and the material deviation may be weakened.

After the reheating heat treatment, it is preferable to cool to 100 DEG C or less at the cooling rate (CR) of the above-mentioned [Relation 1].

When the cooling rate during the cooling is less than the range of the formula 1, or when the cooling end temperature exceeds 100 ° C, the ferrite phase is formed during cooling or the bainite phase is excessively formed to obtain a desired hardness. And the hardness deviation? HB in the width direction exceeds 30.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the examples are only for the understanding of the present invention, and the present invention is not limited by the descriptions of the examples. And the scope of the present invention is determined by the matters described in the claims and the matters reasonably deduced therefrom.

(Example)

A steel slab satisfying the alloy composition shown in the following Table 1 was prepared and then the steel slab was heated at 1200 ° C for 1 hour and then subjected to hot rolling at the hot rolling temperature (FDT) shown in Table 2 to obtain a steel slab having a thickness of 5 mm Hot-rolled steel sheets were produced. After the finish rolling, the steel sheet was cooled at the cooling rate of CR1 from the water cooled stand (ROT) to the coiling temperature (CT) shown in Table 2. Next, the hot-rolled steel sheet was subjected to reheating heat treatment and then cooled to a temperature of 100 DEG C or lower at a cooling rate of CR2.

division	C	Si	Mn	P	S	Al	Nb	B	Cr	Mo	Ti	V
Comparative Example 1	0.07	0.2	1.8	0.008	0.0015	0.025	0	0.0017	0.4	0.15	0.02	0.005
Comparative Example 2	0.41	0.2	1.5	0.008	0.0015	0.01	0	0	0.1	0	0	0
Comparative Example 3	0.22	0.3	1.2	0.008	0.0015	0.03	0.015	0.002	0.2	0.2	0.02	0.005
Comparative Example 4	0.25	0.15	0.8	0.008	0.0015	0.03	0.015	0.0015	0.2	0.1	0.015	0
Comparative Example 5	0.25	0.15	0.8	0.008	0.0015	0.03	0.015	0.0015	0.2	0.1	0.015	0
Inventory 1	0.22	0.3	1.2	0.008	0.0015	0.03	0.015	0.002	0.2	0.2	0.02	0.005
Inventory 1	0.26	0.3	1.2	0.008	0.0015	0.03	0.015	0.002	0.3	0.25	0.015	0.005
Inventory 3	0.25	0.15	0.8	0.008	0.0015	0.03	0.015	0.0015	0.2	0.1	0.015	0

(Unit: wt%, balance Fe and inevitable impurities)

division	Ms + 30 (占 폚)	Bs - 30 (캜)	The value of equation (1)	FDT (占 폚)	CT (° C)	CR1 (占 폚 / s)	Relation 1 Satisfaction	Relation 2 Satisfaction	CR2 (° C / s)	Relation 1 Satisfaction
Comparative Example 1	479	579	24	880	550	35	○	○	45	○
Comparative Example 2	349	547	17	880	520	25	○	○	40	○
Comparative Example 3	436	602	28	880	620	35	○	X	50	○
Comparative Example 4	436	638	36	880	600	30	X	○	45	○
Comparative Example 5	436	638	36	880	610	40	○	○	30	X
Inventory 1	436	602	28	880	580	35	○	○	50	○
Inventory 2	417	580	23	880	560	30	○	○	45	○
Inventory 3	436	638	36	880	600	45	○	○	60	○

(In Table 2, FDT is the finish rolling temperature, CT is the coiling temperature, CR1 is the cooling rate after hot rolling, CR2 is the cooling rate after reheating heat treatment,

Ms = 539-423 [C] -30.4 [Mn] -17.7 [Ni] -12.1 [Cr]

Bs = 830-270 [C] -90 [Mn] -37 [Ni] -70 [Cr] -83 [Mo]

[Formula 1] is 69.6-56 [C] +2.1 [Si] -19.2 [Mn] -8.9 [Cr] +8.0 [Al] -26.9 [Mo]

[C], [Mn], [Ni], [Cr], [Mo], [Si], [Al], and [Mo]

The steel sheet thus prepared was measured for microstructure and mechanical properties, and the results are shown in Table 3 below

The brinell hardness (HB) was measured in the longitudinal direction and the width direction after milling 2 mm in the thickness direction from the surface, and when the maximum value was 100 and the minimum value was 0% % And 5% level of hardness were defined as hardness differences.

On the other hand, the effective grain size was obtained by EBSD (Electron Back Scatter Diffraction) measurement at 1/4 the thickness of the steel sheet. The EBSD measurement conditions were 2000 times as large as the area to be studied, 100 탆 x 100 탆, and step size of 0.05. Data analysis was performed using commercial version of TSL OIM Analysis 7.0. Therefore, raw data was first cleaned up, and KAM computed for CI> 0.1 data was selected.

division	Bainite fraction (area%) of steel sheet after winding	The martensite fraction of the final steel sheet (area%)	Effective Grain Size (탆)	Hardness (HB)	Hardness deviation (? HB)
Comparative Example 1	80	88	27	356	35
Comparative Example 2	85	89	25	638	63
Comparative Example 3	20	93	40	486	46
Comparative Example 4	30	92	45	511	51
Comparative Example 5	97	89	35	426	39
Inventory 1	97	98	14	486	22
Inventory 2	96	99	11	519	23
Inventory 3	98	97	12	511	24

(The second phase of the steel sheet after being wound is ferrite, pearlite, etc., and the second phase of the final steel sheet is ferrite, pearlite, bainite, etc.)

From the results of Table 3, it was confirmed that martensite of the final steel sheet had an area fraction of 95% or more, a high hardness, and a hardness deviation (? HB) of 30 or less in the inventive example satisfying the conditions of the present invention. On the other hand, the hardness and hardness deviations of Comparative Examples and Inventive Examples in Table 3 are shown in the graph in Fig.

On the other hand, in Comparative Example 1, the amount of carbon added was less than the range provided by the present invention, and the final hardness was also less than the present invention. But the area fraction of bainite and final martensite after winding was less than the range of the invention and the hardness deviation exceeded 30. In Comparative Example 2, the amount of carbon added exceeded the range provided by the present invention, and the final hardness exceeded the intended range of the present invention. But the area fraction of bainite and final martensite after winding was less than the range of the invention and the hardness deviation exceeded 30.

In the comparative example 3, although the component range is satisfied, the coiling temperature of the relational expression 2 exceeds the range of the present invention, resulting in a fraction of bainite of only 20% after winding, and the final martensite fraction is also less than 93% Hardness variation was severe.

The composition range of Comparative Example 4 is satisfactory, but the cooling rate to the coiling temperature after the finish rolling is insufficient, so that the fraction of bainite after winding is only 30%, and the martensite fraction of the final steel sheet is also 92% And the hardness deviation was severe.

Comparative Example 5 satisfied the conditions of the present invention at a content of 97% of bainite after the coiling, but the cooling rate during quenching after reheating was insufficient and the final martensitic structure fraction was 89% And has a low hardness.

Claims (12)

1. (Excluding 0), Mn: 0.5 to 2.0%, P: not more than 0.03% (excluding 0), S: not more than 0.02% (excluding 0) , Al: not more than 0.05% (excluding 0), Cr: 0.1-1.0%, Mo: 0.01-0.3%, B: 50ppm or less (excluding 0), Ti: 0.02% % Or less (excluding 0), the remainder contains Fe and unavoidable impurities,

   A wear-resistant steel sheet having excellent uniformity of material having a main structure of martensite and effective grain size (EGS) of 30 μm or less.
2. The method according to claim 1,

   Wherein the steel sheet further comprises at least one of Co: not more than 0.04%, Cu: not more than 0.1%, and V: not more than 0.02%.
3. The method according to claim 1,

   Wherein the steel sheet further comprises 2 to 100 ppm of Ca, and further has excellent material uniformity.
4. The method according to claim 1,

   Wherein the microstructure after the winding process is excellent in uniformity of material having an area fraction of 95% or more of bainite.
5. The method according to claim 1,

   Wherein the microstructure of the steel sheet has an area fraction of not less than 95% martensite and not more than 5% second phase and is excellent in material uniformity.
6. The method according to claim 1,

   The steel plate is excellent in uniformity of material in which the microstructure is the bainite main structure after the winding process.
7. The method according to claim 1,

   The abrasion-resistant steel sheet according to any one of claims 1 to 3, wherein the steel has a Brinell hardness (HB) of 450 to 550 and a hardness deviation (DELTA HB) of 30 or less.
8. (Excluding 0), Mn: 0.5 to 2.0%, P: not more than 0.03% (excluding 0), S: not more than 0.02% (excluding 0) , Al: not more than 0.05% (excluding 0), Cr: 0.1-1.0%, Mo: 0.01-0.3%, B: 50ppm or less (excluding 0), Ti: 0.02% Heating the steel slab containing Fe and unavoidable impurities at a temperature of 1100 to 1300 캜;

   Subjecting the heated steel slab to hot rolling at a final hot rolling temperature of 800 to 1000 占 폚;

   Cooling at a cooling rate (CR) satisfying the following formula (1) from the finish hot rolling temperature to the coiling temperature (CT);

   After cooling, winding at a coiling temperature (CT) satisfying the following formula (2);

   Reheating the wound steel sheet at a temperature of 850 to 950 캜 for 20 to 60 minutes; And

   Cooling the reheated steel sheet to a temperature of 100 DEG C or less at a cooling rate (CR) satisfying the relational expression 1

   Wherein the material is uniformly uniform.

   [Relation 1]

   Cr (° C./s) ≥ 69.6-56 [C] +2.1 [Si] -19.2 [Mn] -8.9 [Cr] +8.0 [Al] -26.9 [Mo]

   [Relation 2]

   (Ms + 30) 占 폚 CT? (Bs - 30) 占 폚

   Ms = 539-423 [C] -30.4 [Mn] -17.7 [Ni] -12.1 [Cr]

   Bs = 830-270 [C] -90 [Mn] -37 [Ni] -70 [Cr]

   (Wherein each of [C], [Mn], [Ni], [Cr], [Mo], [Si], [Al], and [Mo]
9. The method of claim 8,

   The method of manufacturing a wear-resistant steel sheet having excellent uniformity of material having an average grain size of 10 to 40 mu m after the hot-rolling.
10. The method of claim 8,

    Wherein the slab heating is excellent in material uniformity for 100 to 400 minutes.
11. The method of claim 8,

    And a step of cutting the steel sheet to a length of 3 to 20 m before the reheating treatment after the winding.
12. The method of claim 8,

    Wherein the microstructure after winding is excellent in material uniformity as a bainite main structure.

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