WO2008146929A9

WO2008146929A9 - Abrasion-resistant steel sheet having excellent processability, and method for production thereof

Info

Publication number: WO2008146929A9
Application number: PCT/JP2008/060096
Authority: WO
Inventors: 室田康宏; 石川操; 渡邉好紀; 鈴木伸一; 鹿内伸夫
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2007-05-29
Filing date: 2008-05-26
Publication date: 2009-11-12
Also published as: KR20090123006A; JP2009007665A; AU2008255706A1; CL2008001542A1; BRPI0812277A2; CA2685710C; CN101688283A; CA2685710A1; JP5380892B2; AU2008255706B2; PE20090342A1; CN101688283B; WO2008146929A1; EP2154262B1; US20100147424A1; EP2154262A4; EP2154262A1; MX2009012820A; KR101165654B1

Abstract

Disclosed is an abrasion-resistant steel sheet which is suitable for a member that contacts with dirt such as a power shovel and has excellent processability in bending. Also disclosed is a method for producing the steel sheet. Specifically disclosed is a steel sheet which comprises the following components (by mass): C: 0.05 to 0.35%, Si: 0.05-1.0%, Mn: 0.1 to 2.0%, Ti: 0.1 to 1.2% and Al: 0.1% or less, further comprises at least one member selected from 0.1 to 1.0% of Cu, 0.1 to 2.0% of Ni, 0.1 to 1.0% of Cr, 0.05 to 1.0% of Mo, 0.05 to 1.0% of W and 0.0003 to 0.0030% of B (by mass), has a DI* value represented by the formula below of less than 60, and optionally comprises one or two members selected from 0.005 to 1.0% of Nb and 0.005 to 1.0% of V (by mass), with the remainder being Fe and inevitable impurities: DI* = 33.85x(0.1xC*)^0.5x(0.7xSi+1)x(3.33xMn+1)x (0.35xCu+1)x(0.36xNi+1)x(2.16xCr+1)x(3xMo*+1)x(1.5xW*+1) (1) [wherein C* = C-1/4x(Ti-48/14N); Mo* = Mox(1-0.5x(Ti-48/14N)); and W* = Wx(1-0.5x(Ti-48/14N))].

Description

Specification

Abrasion-resistant steel plate with excellent workability and manufacturing method thereof

The present invention is used in the fields of construction, civil engineering, mining, etc., for example, power shovels, bulldozers, hoppers, buckets. Suitable for materials such as industrial machines such as buckets and transporting machines where wear or abrasion due to contact with earth and sand is a problem. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to abrasion resistant steel and a method for producing the same, and particularly to a material having excellent bending formability.

For materials subject to wear due to soil, sand, etc., steel materials with excellent wear resistance are used to extend the service life. It is known that the abrasion resistance property of steel is improved by increasing the hardness, and a large amount of alloying elements such as Cr and Mo are required for parts that require wear resistance. Steel materials that have been hardened by heat treatment such as quenching have been used.

For example, Japanese Patent Application Laid-Open No. Sho 62-1-4 2 7 2 6 contains C: 0.1 0-0.19%, contains appropriate amounts of Si and Mn, and C eq is 0.3. The steel limited to 5 to 0.44% is directly quenched after hot rolling, or re-heated to 90 to 95 ° C and then quenched, at 300 to 500 ° C. There has been proposed a method for producing a wear-resistant steel sheet having a tempering and steel sheet surface hardness of 300 HV (Vickers hardness) or more.

JP-A-6 3-1 6 9 3 5 9 includes C: 0.1 0 to 0.20% and adjusts Si, Mn, P, S, N, and A 1 to appropriate amounts. , Or further to steel containing one or more of Cu, Ni, Cr, Mo, B after hot rolling and directly quenching, or after rolling and allowing to cool, then reheating and quenching 340HB (Brinell hardness) A method of manufacturing a wear-resistant thick steel plate that imparts the above hardness has been proposed.

Japanese Patent Laid-Open No. 1 1 4 2 0 2 3 includes C: 0.07 to 0.17%, and adjusts Si, Mn, P, S, N, and A1 to appropriate amounts, Alternatively, steel containing one or more of Cu, Ni, Cr, Mo, and B is either quenched immediately after hot rolling, or once cooled to room temperature and then reheated and quenched. A method for producing a wear-resistant steel sheet having a surface hardness of 3 2 1 HB or more and a bending workable steel sheet has been proposed.

The techniques described in Japanese Patent Application Laid-Open Nos. Sho 6 2-1 4 2 7 2 6, Japanese Patent Application Laid-Open No. 6 3-1 6 9 3 5 9, and Japanese Patent Application Laid-Open No. 1-14 20 2 3 By adding a large amount of elements, solid solution ¾Sig, so 丄 id solution hardening), transformation ■ (匕 (transformation hardening), precipitation hardening (precipitation hardening), etc. are used to increase the hardness. However, when a large amount of alloying elements are added and solid solution hardening, transformation hardening, precipitation hardening, etc. are used to increase the hardness, weldability (voidability) and processing are improved. As a result, the formability deteriorates and the manufacturing cost increases.

By the way, in the case of a member that requires wear resistance, depending on the usage conditions, it may be necessary to increase the hardness of only the surface and the vicinity of the surface to improve the wear resistance. It is not necessary to add a large amount of alloying elements such as Cr, Mo, etc. to the steel used in the steel, and it is possible to apply a heat treatment such as quenching to form a hardened structure only on the surface and the vicinity of the surface. Conceivable.

However, in order to increase the hardness of the hardened structure, it is generally necessary to increase the amount of solute C in the steel material. However, an increase in the amount of solute C causes a decrease in weldability, bending workability, etc. In particular, a decrease in bending workability restricts the bending work required as a member and limits the use conditions.

For this reason, there is a demand for a wear-resistant steel sheet that can improve the wear resistance without excessively increasing the hardness. Japanese Patent No. 3 0 8 9 8 8 2 discloses C: 0. 1 to 0 to 0.4 5%, Si, Mn, P, S, and N are adjusted to appropriate amounts, and Ti: 0.1 to 1.0 to 1.0%, with an average particle size of 0.5 / zm or more T i C precipitates or T i C and T i N, the composite precipitates with T i S includes a 40 0 / mm ² or more, T i * Ca 0.0 A wear-resistant steel having an excellent surface property of 5% or more and less than 0.4% has been proposed.

Furthermore, Japanese Patent Laid-Open No. 4 1 6 1 6 discloses that C: 0.05 to 0.4: 5%, S i: 0.1 to 1.0%, Mn: 0.1 to 1. Manufacture of wear-resistant steel plates with improved bending workability by containing 0%, T i: 0.05 to 1.5%, and having a surface hardness of 40 1 or less in terms of Brinellhardness A method has been proposed.

According to the techniques described in Japanese Patent No. 3 0 8 9 8 8 2 and Japanese Patent Application Laid-Open No. 4 -4 1 6 16, a precipitate mainly composed of coarse Ti C is generated during solidification, and excessively It is possible to improve the wear resistance at low cost without increasing the hardness.

However, in the technology described in Japanese Patent No. 3 0 8 9 8 8 2, quenching heat treatment is performed and the structure is made into a martensitic structure as it is quenched. Since deformation resistance at the time of bending increases, it is difficult to say that bending is easy, leaving a problem in bending workability.

In the technique described in Japanese Patent Laid-Open No. 4 1 6 1 6, the surface hardness is regulated to 401 or less in terms of Brinell hardness in order to ensure bending workability, but the amount of alloying elements added is large. Therefore, the tensile strength exceeds 7 8 OMPa, and sufficient bending workability is not achieved from the viewpoint of reducing the load during processing.

In addition, Japanese Patent Laid-Open Nos. 62-14-272 6, Japanese Patent Laid-Open No. 63-1 693 559, Japanese Patent Laid-Open No. 1-14 2 023, Japanese Patent Laid-Open No. Hei 4 1 4 1 6 1 6 It is essential to perform heat treatment on the wear-resistant steel described in No. 6 publication, leaving problems in terms of production period and production cost.

Therefore, the present invention provides a method for producing a wear-resistant steel plate that can be produced without being subjected to heat treatment while being hot-rolled, and that has excellent wear resistance and bendability. Objective. Disclosure of the invention

In order to achieve the above-mentioned objectives, the inventors have an influence on wear-resistant plugs and bending workability. As a result of diligent research on various factors, it has a component system containing Ti and C, and has a microstructure of base metal force. S Ferrite and pearlite structure as-rolled ) Is a complex structure (base phase), and a hard second phase (hard phase _: Ti-based carbide) in the matrix. It has been found that by dispersing, it is possible to reduce the processing load during bending while maintaining wear resistance, that is, it is possible to improve bending workability.

The present invention has been made on the basis of the further findings based on the obtained knowledge.

1. Mass ⁰ /. C: 0.05 to 0.35%, S i: 0.05 to 1.0%, Mn: 0.1 to 2.0%, T i: 0.1 to 1.2% , AI: 0.1% or less, Cu: 0.1-1.0%, Ni: 0.1-2.0%, Cr: 0.1-1.0%, Mo: 0.0%, 1.0%, W: 0.05 ~; 1.0%, B: 0. 0 0 0 3 to 0.0 0 3 0% 1 type or 2 types or more A wear-resistant steel sheet having an excellent workability consisting of the balance Fe and inevitable impurities, wherein DI * represented by the formula (1) is less than 60.

DI * = 3 3. 8 5 X (0. 1 XC *) ° " ⁵ X (0. 7 XS i + 1) X (3. 3 3 XMn + 1) X (0. 3 5 XC u + 1) X (0. 3 6 XN i + 1) X (2.1

6 XC r + 1) X (3 ΧΜο * + 1) X (1.5 XW * + 1) (1) However, C * = C— 1Z4 X (T i— 4 8/1 4 N), Mo * = Mo X (1—0.5 X (T i-4 8/1 4 N)), W * = WX (1 1 0.5 X (T i 1 4 8/1 4N)) C, S i, Mn, C, Ni, Cr, Mo, W, Ti, and N are contained (mass%) 2. Further, mass% is Nb: 0. 0 0 5 to 1.0%, V: 0. 2. The wear-resistant steel plate according to 1, which contains 1 or 2 types of 0 0 to 1.0%.

3. The wear-resistant steel sheet according to 1 or 2, wherein the metallographic structure has a ferrite phase as a matrix phase and a hard phase is dispersed in the matrix phase.

4. The wear-resistant steel sheet according to 3, wherein the hard phase has a dispersion density of 400 pieces / mm ² or more. 5. After hot rolling a steel slab having the composition described in 1 or 2, it is cooled to 400 ° C or less at a cooling rate of ₃ or less in 2 to produce a wear-resistant steel plate with excellent workability. Manufacturing method.

6. Further, in hot rolling, the rolling reduction at 920 ° C. or lower is set to 30% or more, and the rolling end temperature is set to 900 or lower, and wear resistance with excellent workability according to 5, Steel manufacturing method.

Here, the hard phase is preferably a Ti-based carbide such as T i C, and is contained in T i C, (Nb T i) C, (VT i) C, or T i C. An example is a solution in which Mo and W are dissolved.

According to the present invention, a wear-resistant steel sheet having improved bending workability without degrading the wear resistance can be obtained after hot rolling without being subjected to heat treatment. Reasonable production, such as shortening the production period, is possible and has a remarkable industrial effect. Brief Description of Drawings

Figure 1: A graph showing the effect of Ti addition on wear resistance.

Fig. 2: Diagram showing the effect of Ti addition on tensile properties (yield strength: Y S, tensile strength: T S).

Figure 3: Diagram showing the effect of D I * on wear resistance.

Figure 4: Diagram showing the effect of D I * on tensile properties (yield strength: YS, tensile strength: TS). BEST MODE FOR CARRYING OUT THE INVENTION

The reason why the component composition and the metal structure are defined in the wear-resistant steel sheet according to the present invention will be described.

(Ingredient composition) All percentages below are massy. And

C: 0.05-0.35%

C improves the wear resistance by improving the hardness of Matritas in the metal structure At the same time, Ti carbide is formed as a hard second phase (hereinafter also referred to as a hard phase), and is an effective element for improving wear resistance. 0 Containing 5% or more is required.

On the other hand, ◦ When C content exceeds 35%, the carbide as the hard phase becomes coarse, and cracking occurs starting from the carbide during bending. For this reason, C is specified in the range of 0.05 to 0.35%. In addition, Preferably it is 0.15 to 0.32%.

T i: 0.1 to 1.2%

Ti, together with C, is an important element in the present invention, and is an essential element that forms carbides as a hard phase that contributes to improved wear resistance. In order to obtain such an effect, a content of 0.1% or more is required.

Fig. 1 shows the effect of Ti addition on wear resistance, and Fig. 2 shows the effect of Ti addition on tensile properties (yield strength: Y S, tensile strength: TS). In Fig. 1, the vertical axis shows the wear resistance ratio of the rubber wheel abrasion test compared to the abrasion weight loss of mild steel (S S 400).

When the Ti addition amount is 0.1% or more, the wear resistance is as high as that of general wear-resistant steel, and TS is reduced to 80 OMPa or less. In other words, it is possible to improve workability while having the same wear characteristics as the conventional wear-resistant steel plate subjected to quenching heat treatment.

The test steel in the rubber wheel wear test is massy. 0.3% 3% C— 0.35% S i-0.82% Mn-0.05-1. After rolling a steel slab containing 2% T i to 19 mm t, cooling rate: It was produced by air cooling at 0.5 ° CZ _S.

The obtained steel sheet was subjected to a tensile test and an abrasion test. In the tensile test, J I S 5 test specimens were collected and subjected to a tensile test in accordance with the provisions of J I S Z 2201, and the tensile properties (tensile strength: TS, yield strength: YS) were obtained.

The abrasion test is performed by a rubber wheel abrasion test in accordance with ASTM G 65, and the test result is determined by the ratio of the wear amount of mild steel (SS 400) to the wear amount of each test steel plate. Organized as wear ratio. The larger the wear resistance ratio, the better the wear characteristics. As a comparative test, the same test as described above was performed for wear-resistant steel sheets produced by general heat treatment. The results obtained are shown in Fig. 1 and Fig. 2 for conventional steel. Here, the general wear-resistant steel sheet is: 0.15 mass¾C— 0.35raass% Si— 1.50 mass% Mn— 0.13 mass% Cr-0.13 mass% Mo-0.01 mass% Ti-0.0010 mass% B This steel is a material that has been hot-rolled and then reheated to 900 ° C and then subjected to a quenching heat treatment, and it has a Brinell hardness of about 400 HB.

On the other hand, if the Ti content exceeds 1.2%, the hard phase (Ti carbide) becomes coarse, and cracks occur starting from the coarse hard phase during bending. Therefore, it is limited to the range of Τ ΗΐΟ. 1 to 1.2%, preferably 0.1 to 0.8%.

S i: 0.0 5 to 1.0%

Si is an effective element as a deoxidizing element, and in order to obtain such an effect, it needs to be contained in an amount of 0.05% or more. In addition, Si is an effective element that contributes to high hardness by solid solution strengthening by solid solution strengthening, but inclusion exceeding 1.0% lowers ductility and toughness. In addition, problems such as an increase in inclusion content occur. For this reason, 1 is preferably limited to a range of 0.05 to 1.0%. More preferably, it is 0.05 to 0.40%.

M n: 0.1 to 2.0%

Mn is an effective element that contributes to high hardness by solid solution strengthening, and in order to obtain such an effect, it needs to contain 0.1% or more. On the other hand, if the content exceeds 2.0%, weldability is lowered. For this reason, Mn is preferably limited to a range of 0.1 to 2.0%. More preferably, it is 0.1 to 1.6%.

A 1: 0.1% or less

A 1 acts as a deoxidizing element, and such an effect is recognized at a content of 0.0 20% or more, but a large content exceeding 0.1% is the cleanliness of steel. Reduce (cleanness). For this reason, A 1 is limited to 0 .. 1% or less. It is preferable.

C u: 0. ~ 1.0%, Ni: 0.1 ~ 2.0%, Cr: 0.1 ~ :; .0%, Mo: 0.05 ~; I. 0%, W: 0.0 5 to 1.0%, B: 0.0003 to 0.0003%, 1 type or 2 or more types

C u: 0.1 to 1.0%.

Cu is an element that improves hardenability by dissolving in solid solution. To obtain this effect, Cu must be contained in an amount of 0.1% or more. On the other hand, if the content exceeds 1.0%, hot workability is lowered. For this reason, Cu is preferably limited to the range of 0.1 to 1.0%. More preferably, the content is 0.1 to 0.5%.

N i: 0.1 to 2.0%

Ni is an element that improves the hardenability by dissolving it in a solid solution, and such an effect becomes remarkable when it is contained in an amount of 1% or more. On the other hand, if the content exceeds 2.0%, the material cost increases remarkably. Therefore, Ni is preferably limited to a range of 0.1 to 2.0%. More preferably, the content is 0.1 to 1.0%.

C r: 0.1 to 1.0%

Cr has the effect of improving hardenability. To obtain such an effect, it needs to be contained in an amount of 0.1% or more. However, if it exceeds 1.0%, the weldability is lowered. Let For this reason, it is preferable that O is limited to the range of 0.1 to 1.0%. More preferably, the content is 0.1 to 0.8%. More preferably, it is 0.4 to 0.7%.

Mo: 0.05-; L. 0%

Mo is an element that improves hardenability. In order to obtain such an effect, the content of 0.05% or more is required. On the other hand, if it exceeds 1.0%, the weldability is lowered. Therefore, Mo is preferably limited to the range of 0.05 to 1.0%. More preferably, it is 0.05 to 0.40%.

W: 0.05-: L. 0% w is an element that improves hardenability. In order to obtain such an effect, the content of 0.05% or more is required. On the other hand, if the content exceeds 1.0%, the weldability is lowered. Therefore, W is preferably limited to a range of 0.05 to 1.0%. More preferably, it is 0.05 to 0.40%. Since Mo and W are dissolved in TiC, they also have the effect of increasing the amount of hard phase.

B: 0. 0 0 0 3 to 0.0 0 3 0%

B is an element that segregates at the grain boundary and strengthens the grain boundary to effectively contribute to the improvement of toughness. In order to obtain such an effect, 0.000% or more Must be included. On the other hand, if it exceeds 0.0 0 30%, the weldability is lowered. For this reason, B is preferably limited to the range of 0.0 0 0 3 to 0.0 0 30%. More preferably, it is 0.0 0 0 3 to 0.0 0 15%.

D I * <6 0

In the present invention, DI * (hardenability index value) is DI * = 33.85 X (0.1 XC *) ° · ⁵ X (0.7 XS i + 1) X (3. 3 3 XMn + 1) X (0.35 XC u + 1) X (0.36 XN i + 1) X (2. 16 XC r + 1) X (3 XM o * + 1) X ( 1.5 XW * + 1), where C * = C 1/4 X (T i-4 8/1 4 N), M o * = M o X (1 — 0.5.5 X (T i- 4 8/1 4 Ν)) W * = W (1 — 0.5. 5 (T i — 4 8/1 4 N)). Here, C, Si, Mn, Cu, Ni, Cr, Mo, W, Ti, and N are contents (mass%). Fig. 3 shows the effect of DI * on wear resistance, and Fig. 4 shows the effect of DI * on tensile properties (yield strength: YS, tensile strength: TS). In Fig. 3, the vertical axis shows the wear resistance ratio comparing the amount of wear in the rubber wheel wear test with the amount of wear of mild steel (SS 400). The higher the wear resistance ratio, the better the wear characteristics. From Fig. 3 and Fig. 4, when DI * force is less than S 60, tensile strength: Despite the low strength of TS of less than 800 MPa, wear amount is generally wear resistant steel It is recognized that

-On the other hand, when DI * is 60 or more, the wear resistance is excellent, but the tensile strength is 80 Above OMP a, workability is inferior. If DI * is greater than 60, it is presumed to be a ferrite and bainite structure.

In the rubber wheel wear test, the test steel is 0.34% C— 0.22% S i-0.55% Mn-0.22% T i in addition to Cu, Ni, Cr, Mo. A steel piece containing one or more of W and having a DI * of 40 to 120 was rolled to 8 mm t and then air-cooled (cooling rate: 1.2 ° CZs).

The obtained steel sheet was subjected to a tensile test and an abrasion test. In the tensile test, in accordance with the provisions of JISZ2201, JIS5 test specimens were collected and subjected to a tensile test to determine tensile properties (tensile strength TS, yield strength YS).

The rubber wheel wear test was conducted in accordance with AS TMG 65, and the test results were organized as the wear resistance ratio of the ratio of wear of mild steel (S S 400) to that of each steel plate.

The above-mentioned components are basic components, and excellent wear resistance can be obtained. In the present invention, in order to further improve the wear resistance, a hard second phase is formed, which contributes to the wear resistance. Nb and V can be contained as selective elements.

N b: 0.005 ~: L. 0%,

When Nb is added in combination with T i, it forms a composite carbide of T i and Nb ((N b T i) C), which is dispersed as a hard second phase and is effective in improving wear resistance. It is an element that contributes to In order to obtain such an effect of improving wear resistance, a content of 0.005% or more is required. On the other hand, if the content exceeds 1.0%, the hard second phase (Ti, Nb composite carbide) becomes coarse and cracks starting from the hard second phase (Ti, Nb composite carbide) during bending. Will occur. For this reason, when Nb is added, Nb is preferably limited to a range of 0.005 to 1.0%. More preferably, the content is 0.1 to 0.5%.

V: 0.005 to 1.0%

When added in combination with T i, V, like Nb, forms a composite carbide of T i and V ((VT i) C), disperses it as a high-quality second phase, It is an element that contributes to effective wear resistance. In order to obtain such an effect of improving wear resistance, 0.0 0 Containing 5% or more is required.

On the other hand, if the content exceeds 1.0%, the hard second phase (Ti, V composite carbide) coarsens, and the second phase (Ti, V composite carbide) is the starting point during bending. Cracking occurs. For this reason, when V is added, V is preferably limited to a range of 0.05 to 1.0%. More preferably, the content is 0.1 to 0.5%.

When Nb and V are added in combination, only the hard second phase becomes (N b VT i) C, which has the same effect of improving wear resistance. When N is contained, carbonitrides may be formed in addition to carbides, but similar effects can be obtained.

However, when the amount of N added exceeds 0.01%, the ratio of N in the carbonitride increases and the hardness of the hard second phase decreases, but there is a concern that the wear resistance may deteriorate. The Therefore, it is preferable that the amount of N added is not more than 0.0. 1%.

(Metal structure)

In the wear-resistant steel sheet according to the present invention, the metal structure is a structure in which the ferrite phase is a base phase and a hard phase (hard second phase) is dispersed in the base phase. The base phase means 90% or more by volume ratio, and in the steel sheet according to the present invention, the two phases of ferrite and perlite occupy 90% or more of the whole.

Further, among them, the ferrite phase preferably has a volume fraction of 70% or more and a ferrite phase with an equivalent circle diameter and an average particle diameter of 20 μη. In consideration of workability, it is preferable that the base phase has a Brinell hardness of 300 or less.

The hard phase is preferably a Ti carbide such as TiC, and Mo and W are solid in TiC, (NbTi) C, (VTi) C, or TiC. The melted material can be exemplified.

The size of the hard phase is not particularly limited, but is preferably about 0.5 μm or more and 50 μm or less from the viewpoint of wear resistance. Further, the dispersion density of the hard phase is preferably 400 pieces / "mm ² or more from the viewpoint of wear resistance.

For the size of the hard phase, measure the area of each hard phase and calculate the equivalent circle diameter from the same area. The average equivalent diameter of the obtained circle-equivalent diameters is taken as the size of the hard phase (average particle size) in the steel sheet.

(Production method)

The wear-resistant steel sheet according to the present invention is obtained by melting a molten steel having the above-described composition by a known melting method, and by using a continuous forging method or an ingot-disintegrating rolling method, It is preferable to use a material.

In order to adjust the number of hard phases to a predetermined size, for example, when the continuous forging method is used, 1 5 0 0 to 1 2 0 of a piece having a thickness of 200 to 400 mm It is preferable to adjust the cooling so that the cooling rate in the temperature range of 0 ° C is in the range of 0.2 to 10 ° CZ s.

Even when using the ingot-making method, it is necessary to adjust the ingot size and cooling conditions so that the desired number of hard phases can be obtained. Not too long.

Next, the steel material is immediately hot-rolled without being cooled, or after being cooled, re-heated to 9500-125 ° C and then hot-rolled to obtain a steel plate having a desired thickness. . After hot rolling, it is cooled at an average cooling rate of 2 ° C / s or less without heat treatment.

When the cooling rate is 2 and exceeds Z s, a ferrite-perlite structure cannot be obtained, the tensile strength becomes 80 OMPa or more, the processing load during steel plate bending increases, and the workability deteriorates. Therefore, it should be 2 ° CZ s or less.

The hot rolling conditions are not particularly limited as long as the steel sheet can have a desired size and shape. However, considering the toughness, which is a performance to be provided as a steel sheet, the surface temperature of the steel sheet is 9 2 0. It is necessary that the rolling reduction at 30 ° C. or less is 30% or more and the rolling end temperature is 90 ° C. or less.

The wear-resistant steel sheet according to the present invention does not need to be heat-treated after hot rolling, and can be used for various applications that require bending while hot rolling. Example Molten steel with the composition shown in Table 1 is melted in a vacuum melting furnace to form a small steel ingot (50 kg) (steel material), then heated to 1 0 50 0 to 1 2 5 0 and hot rolled To give a test steel plate with a thickness of 6 to 100 mm. Each steel plate was subjected to microstructure observation, tensile test, wear test, Charpy impact test, and bend test.

(Tissue observation)

After polishing, the specimens for tissue observation were corroded by nital, and at a position 1 mm below the surface layer, an optical microscope (magnification ratio: 400 times) was used. Identification, ferrite grain diameter, and the size and number of hard phases were measured. In the observation field of view, the structure occupying 90% or more was the base phase, and the size of the hard phase was the average particle size obtained by the method described above.

(Tensile test)

In accordance with the provisions of JISZ 2 201, JIS No. 5 test specimens were collected and subjected to a tensile test in accordance with the provisions of JISZ 2 24 1, tensile properties (yield strength: YS, tensile strength: TS). Tensile strength (T S) <80 OMPa and yield strength (Y S) <60 0 MPa are within the scope of the present invention.

(Abrasion test)

The test piece was t (plate thickness) X 20 X 7 5 (mm), and the rubber wheel abrasion test was performed using abrasive sand in accordance with the regulations of AS TM G 65. After the test, the amount of wear of the test piece was measured.

The test results were evaluated using the wear resistance ratio = (abrasion amount of mild steel plate) / (abrasion amount of each steel plate) with the wear amount of mild steel (S S 400) as the standard (1.0). The larger the wear resistance ratio, the better the wear resistance, and the scope of the present invention was set to 4.0 or more.

(Charby impact test)

Conforms to the JISZ 2202 standard, from the position of the plate thickness direction 1Ζ4 to the L direction Notch impact test specimens were collected and subjected to a Sha / Repe impact test at a test temperature of 0 in accordance with JISZ 2 24 2 to determine Charpy absorbed energy. The number of tests was three, and the average value was obtained.

(Bending test)

If the width is 50 mm and the thickness of the test steel plate is 45 mm or more, the test piece that has been ground from one side and reduced to a thickness of 25 mm is used. When the thickness of the test steel plate was less than 45 mm, a specimen with the same thickness was taken and a bending test was performed in accordance with the provisions of JISZ 2 24 8. The bending test was carried out by the push bending method with the bending radius set to r = 1.5 t.

Table 2 shows the results of microstructure observation, tensile test, and wear test. Examples of the present invention (steel plate Nos. 1 to 6, steel plates No. 8, 9) have a tensile strength (TS) <80 OMPa and a yield strength (YS) <60 OMPa, It is a steel plate with excellent wear resistance. The Charpy absorbed energy was 27 J or more when the rolling finishing temperature was 900 ° C or lower. On the other hand, the comparative example is inferior in bending workability as compared with the present invention example, or even if the wear resistance is equivalent, YS and TS are high, so that the bending workability is inferior.

Note 1: * mark outside the scope of the present invention

Note 2: Wear resistance ratio (abrasion amount of mild steel sheet) / (abrasion amount of each steel sheet) (Invention scope: wear resistance ratio of 4.0 or more)

(Invention scope: wear resistance ratio of 4.0 or more)

Note 2: vEo (J): Test temperature 0. Charbi in C-Shock absorption I Nerki '-(J)

Claims

The scope of the claims

1. Mass ⁰ /. C: 0.05 to 0.35%, Si: 0.05 to L; 0%, Mn: 0.1 to 2.0%, Ti: 0.1 to 1.2 %, A 1: 0.1% or less, C u: 0.1 to 1.0%, N i ': 0.1 to 2.0%, C r: 0.1 to 1.0%, Mo: 0.05 to 1.0%, W: 0.05 to 1.0%, B: 0.0 0 0 3 to 0.0 0 3

A wear-resistant steel sheet containing 1% or 2 or more of 0%, wherein D I * represented by the formula (1) is less than 60, and the balance is Fe and inevitable impurities.

DI * = 3 3. 8 5 X (0. 1 XC *). ⁵ X (0. 7 XS i + 1) X (3.3 3 XMn + 1) X (0. 3 5 XC u + 1) X (0. 3 6 XN i + 1) X (2.1

6 XC r + 1) X (3 XMo * + 1) X (1.5 XW * + 1) (1) However, C * = C-1/4 X (Τ Ϊ-4 8/1 4 Ν), Mo * = M o X (1-0 0 5 X (T i --4 8Z l 4 N)), W * = WX (1-0.5.5 X (T i-4 8/1 4 N)), here in, C, S i, Mn, C u, N i, C r, Mo, W, T i, N content (mass ^_0/0)

2. The abrasion resistance according to claim 1, further comprising one or two of Nb: 0.05 to 1.0% and V: 0.05 to 1.0% in mass%. Worn steel sheet.

3. The wear-resistant steel sheet according to claim 1 or 2, wherein the metallographic structure has a ferrite phase as a matrix phase, and a hard phase is dispersed in the matrix phase.

4. The wear-resistant steel plate according to claim 3, wherein the dispersion density of the hard phase is 400 pieces / mm ² or more.

5. A method for producing a wear-resistant steel sheet, wherein a steel slab having the composition according to claim 1 or 2 is hot-rolled and then cooled to 400 ° C. or lower at a cooling rate of 2 ° C / s or lower.

6. Further, in hot rolling, the rolling reduction at 9 20 or less is 30% or more, and the rolling end temperature is 90 or less and the wear resistance is excellent in workability according to claim 5. A method for producing worn steel.