JP5655356B2 - Wear-resistant steel plate with excellent low-temperature temper embrittlement cracking - Google Patents

Description

The present invention is used in the fields of construction, civil engineering, mining, for example, industrial machines such as power shovels, bulldozers, hoppers, buckets, etc., and wear caused by contact with earth and sand is a problem. suitable as a member, it relates to a wear-resistant steel plate, the steel plate in particular, gas cutting, heat fusing and plasma fusing etc., of the heat-affected zone by welding, to the improvement of low-temperature tempering embrittlement cracking resistance.

  Steel members having excellent wear resistance are used for members subjected to wear due to soil, sand, and the like in order to extend the life. Conventionally, it is known that the wear resistance of a steel material is improved by increasing the hardness. For this reason, for parts that require wear resistance, the steel is hardened by increasing the C content and adding a large amount of alloying elements such as Cr and Mo, and quenching and low-temperature tempering to increase the hardness. Steel has been used.

  In general, when such a hardened steel material is reheated to a low temperature temper embrittlement temperature range, delayed fracture may occur after cooling to room temperature. This delayed fracture is caused by the brittleness of the crystal grain boundaries. The fracture mode is grain boundary fracture, and the fracture surface exhibits a grain boundary fracture surface. In order to avoid such delayed fracture, it is only necessary to avoid reheating the steel material to the low temperature temper embrittlement temperature range, but when cutting the member, processing such as fusing or welding is essential. It is impossible to avoid reheating the steel material in the low temperature temper embrittlement temperature region at the fusing part or the welded part. Therefore, there is a demand for a wear-resistant steel sheet having excellent low-temperature temper embrittlement cracking resistance that can suppress delayed fracture even when reheated to a low-temperature temper embrittlement temperature range.

  In response to such a request, for example, in Patent Document 1, in mass%, C: 0.20 to 0.30%, Si: 0.05 to 1.0%, Mn: 0.45 to 1.2%, Nb: 0.005 to 0.024%, Ti: 0.005 to 0.05%, B: 0.0003-0.0030%, Al: 0.1% or less, P: 0.010% or less, S: 0.005% or less, Mo: 0.05-1.0%, W: 0.05-1.0% In addition, Cu: 0.1 to 1.0%, Ni: 0.1 to 2.0%, Cr: 0.1 to 1.0%, V: 0.005 to 0.10%, Ceq is 0.55% or less, DI * Low-temperature toughness and low-temperature temper embrittlement cracking with a composition consisting of the balance Fe and unavoidable impurities and a martensite phase with a prior austenite grain size of 30 μm or less as the base phase. An excellent wear resistant steel sheet is described.

  Moreover, in patent document 2, C: 0.20-0.35%, Si: 0.05-1.0%, Mn: Less than 0.45%, Ti: 0.005-0.05%, B: 0.0003-0.0030%, Al: 0.1% by mass% Hereinafter, P: 0.020% or less, S: 0.005% or less, Cu: 0.1-1.0%, Ni: 0.1-2.0%, Cr: 0.1-1.0%, Mo: 0.05-1.0%, V: 0.005-0.10% , W: 0.05-1.0% of one or more kinds are contained so that Ceq is 0.55% or less and DI * value is 45 or more, or Nb: 0.005-0.024% is contained, and the balance Fe A wear-resistant steel sheet having a composition composed of inevitable impurities and a structure having a martensite phase as a base phase and excellent in low temperature toughness and low temperature temper embrittlement cracking is described.

  Further, in Patent Document 3, in mass%, C: 0.20 to 0.30%, Si: 0.05 to 1.0%, Mn: 0.45 to 1.2%, Nb: 0.005 to 0.024%, Ti: 0.005 to 0.05%, B: 0.0003 -0.0030%, Al: 0.1% or less, P: 0.010% or less, S: 0.005% or less, Mo: less than 0.05%, W: less than 0.05%, Cu: 0.1-1.0%, Ni: 0.1-2.0% , Cr: 0.1 to 1.0%, V: 0.005 to 0.10%, Ceq is 0.55% or less, DI * value is 45 or more, and the remainder Fe and inevitable impurities And a wear-resistant steel sheet having a structure in which a martensite phase having a prior austenite grain size of 30 μm or less as a base phase and excellent gas cut surface properties and low-temperature temper embrittlement cracking properties are described.

JP 2009-30092 JP 2009-30093 JP 2009-30094

Recently, with the increase in size of members, there is a demand for a thicker wear-resistant steel plate. However, with the techniques described in Patent Documents 1 to 3, only wear-resistant steel plates having a thickness of up to about 32 mm can be produced.
The present invention advantageously solves such problems of the prior art, and is preferably a wear-resistant steel plate having excellent wear resistance and low-temperature temper embrittlement cracking resistance even when the thickness exceeds 32 mm. The purpose is to propose.

  In order to achieve the above-described object, the present inventors have further studied diligently on various factors affecting wear resistance and low temperature temper embrittlement cracking resistance. As a result, C: 0.25 to 0.35%, Mn: 0.80% or less, P: 0.010% or less, and by adjusting the carbon equivalent Ceq within the range of more than 0.55% and 0.60% or less, the plate thickness is reduced. Of course, even if it is thin, it is possible to make a steel plate with a thickness of more than 32 mm, with excellent wear resistance, and with improved resistance to low temperature temper embrittlement cracking. I came up with it.

First, basic experiments conducted by the present inventors will be described.
mass%, 0.30% C-0.25% Si-0.6-1.5% Mn-0.002-0.030% P-0.015% Nb-0.020% Ti-0.0012% B, and the following (1) formula Ceq = C + Mn / 6 + (Cu + Ni ) / 15 + (Cr + Mo + V) / 5 + W / 10 (1)
In order to keep the Ceq defined by the above constant at 0.60%, Ni, Cu, Mo, W is appropriately contained, molten steel having the composition of the remainder Fe is melted to form a steel slab, and then hot rolled. Plate thickness: 40 mm steel plate. These steel plates were reheated to 900 ° C. and quenched. Test materials were collected from the obtained steel plates and subjected to a T-shaped fillet weld cracking test. In the T-type fillet weld cracking test, the test material is assembled into a T-shaped fillet weld crack specimen as shown in Fig. 2, and the test weld (length: 200 mm) is welded with carbon dioxide gas with a heat input of 13 kJ / cm. Then, fillet welding of three layers and six passes was performed. After 48 hours from welding, the test weld was examined for the occurrence of delayed cracking. The investigation was performed by cutting and observing the cross section of the test specimen bead portion 5.

  The obtained results are shown in FIG. 1 due to the influence of the relationship between the Mn content and the P content on the occurrence of delayed fracture (cracking). As shown in FIG. 1, cracks occur in a region where Mn exceeds 0.80% and P exceeds 0.010%. It was determined that the fracture surface of the generated crack was a grain boundary fracture and a low-temperature tempered embrittlement crack. From Fig. 1, even if the Ceq is increased to 0.60%, the thickness of the steel plate exceeds 32mm. By adjusting Mn and P to Mn: 0.80% or less and P: 0.010% or less, cracking occurs. And the knowledge that low temperature tempering embrittlement cracking resistance is improved was obtained.

The present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.
(1) In mass%, C: 0.31 to 0.35%, Si: 0.05 to 1.0%, Mn: 0.80% or less, P: 0.010% or less, S: 0.005% or less, Ti: 0.005 to 0.05%, Nb: 0.005 to 0.024%, B: 0.0003 to 0.0030%, Al: 0.1% or less, further Cu: 0.1 to 1.0%, Ni: 0.1 to 2.0%, Cr: 0.1 to 1.0%, Mo: 0.05 to 1.0%, V: 0.005 to One or more selected from 0.10%, W: 0.05-1.0%, the following (1) formula Ceq = C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5 + W / 10 (1)
(Here, C, Si, Mn, Cu, Ni, Cr, Mo, V, W: content of each element (mass%))
The Ceq defined by is more than 0.55% and less than 0.60%, and the following equation (2)
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (2)
(Here, C, Si, Mn, Cu, Ni, Cr, Mo, V, W: content of each element (mass%))
The DI * value defined by the above is contained so as to satisfy 45 or more, and has a composition comprising the balance Fe and inevitable impurities, and a structure in which the matrix phase is a phase mainly composed of martensite phase, A wear-resistant steel sheet that is excellent in low temperature temper embrittlement cracking.

(2) In (1), in addition to the above composition, the composition further contains one or two kinds selected from mass: Ca: 0.0005 to 0.0050% and REM: 0.0005 to 0.0050%. Wear-resistant steel sheet characterized by.
(3) The wear-resistant steel sheet according to (1) or (2), wherein the structure has a prior austenite grain size of 15 μm or less.

  (4) The wear-resistant steel sheet according to any one of (1) to (3), wherein the surface hardness is 450 HBW10 / 3000 or more.

  According to the present invention, it has excellent wear resistance, and even when heated to a low temperature temper embrittlement region due to thermal effects during fusing and welding, delayed cracking (delayed fracture) is prevented and excellent. A thick wear-resistant steel sheet with a thickness of more than 32mm, which combines wear resistance and excellent low-temperature temper embrittlement cracking resistance, can be manufactured at low cost and easily, and has a remarkable industrial effect.

It is a graph which shows the influence of the relationship between Mn content and P content which has on the occurrence of delayed fracture (cracking). It is explanatory drawing which shows typically the shape dimension of the test body in the T-shaped fillet weld cracking test used in the Example, and the dimension shape of test welding.

First, the reasons for limiting the composition of the steel sheet of the present invention will be described. In the following, mass% is simply expressed as% unless otherwise specified.
C: 0.31 to 0.35%
C is an element that increases the hardness of the matrix and significantly improves the wear resistance. In order to obtain such an effect, the present invention needs to contain 0.25% or more. On the other hand, when it contains exceeding 0.35%, weldability will fall. In the present invention , C is limited to the range of 0.31 to 0.35% .

Si: 0.05-1.0%
Si is an effective element that acts as a deoxidizing agent, and in order to obtain such an effect, a content of 0.05% or more is required. Moreover, Si is an effective element that contributes to increasing the hardness of the steel sheet by solid solution strengthening by solid solution strengthening, but inclusion exceeding 1.0% decreases ductility and toughness, and further increases the amount of inclusions. Cause problems. For this reason, Si was specified in the range of 0.05 to 1.0%. In addition, Preferably it is 0.05 to 0.40%.

Mn: 0.80% or less
Mn is an effective element that contributes to increasing the hardness by solid solution strengthening. In order to obtain such an effect, it is desirable to contain 0.1% or more, but if it exceeds 0.80%, the P grain boundary Promotes segregation and facilitates delayed fracture. For this reason, Mn was specified to 0.80% or less. In addition, Preferably it is 0.60 to 0.80%.

P: 0.010% or less P is an element that segregates at the grain boundary and promotes the occurrence of delayed fracture. In the present invention, P is preferably reduced as much as possible, but excessive reduction leads to an increase in melting cost. % Was the upper limit. In addition, Preferably it is 0.007% or less.
S: 0.005% or less S forms MnS in steel, acts as a starting point for fracture occurrence, and causes a significant decrease in toughness. Therefore, it is desirable to reduce it as much as possible in the present invention. The upper limit was made 0.005%. In addition, Preferably it is 0.003% or less.

Ti: 0.005-0.05%
Ti binds to N to form TiN to fix N, suppress the formation of BN, and has the effect of effectively improving the hardenability of B. In order to obtain such an effect, the content of 0.005% or more is required. However, if the content exceeds 0.05%, TiC precipitates and the base metal toughness decreases. For this reason, Ti was specified in the range of 0.005 to 0.05%. In addition, Preferably, it is 0.005-0.020%.

Nb: 0.005-0.024%
Nb has the action of forming carbonitrides or carbides and refining the structure to suppress delayed fracture. In order to obtain such an effect, a content of 0.005% or more is required. However, if the content exceeds 0.024%, coarse carbonitride is precipitated and becomes a starting point of fracture, so that the toughness is lowered. For this reason, Nb was limited to 0.005 to 0.024% of range. In addition, Preferably, it is 0.005-0.018%.

B: 0.0003-0.0030%
B is an element that segregates at the grain boundary and significantly improves the hardenability when contained in a small amount. In order to acquire such an effect, 0.0003% or more needs to be contained. On the other hand, the content exceeding 0.0030% reduces weldability. For this reason, B was specified in the range of 0.0003 to 0.0030%. In addition, Preferably, it is 0.0005 to 0.0015%.

Al: 0.1% or less
Al is an element that acts as a deoxidizer and contributes to crystal grain refinement by combining with N. Such an effect is recognized at a content of 0.015% or more, but a large content exceeding 0.1% lowers the cleanliness of the steel. For this reason, Al was specified to be 0.1% or less.
Cu: 0.1-1.0%, Ni: 0.1-2.0%, Cr: 0.1-1.0%, Mo: 0.05-1.0%, V: 0.005-0.10%, W: 0.05-1.0% 2 or more types
Cu, Ni, Cr, Mo, V, and W are all elements that improve the hardenability of steel, and in the present invention, they are selected to contain one or more.

Cu: 0.1-1.0%
Cu is an element that improves the hardenability of steel by solid solution in steel, and in order to obtain such an effect, it needs to be contained in an amount of 0.1% or more. On the other hand, the content exceeding 1.0% decreases the hot workability. For this reason, when contained, Cu is specified in the range of 0.1 to 1.0%. In addition, Preferably it is 0.1 to 0.5%.

Ni: 0.1-2.0%
Ni is an element that improves the hardenability by forming a solid solution in steel, and such an effect becomes remarkable when the content is 0.1% or more. On the other hand, the content exceeding 2.0% significantly increases the material cost. For this reason, when Ni is contained, it is specified in the range of 0.1 to 2.0%. In addition, Preferably it is 0.1 to 1.0%.

Cr: 0.1-1.0%
Cr is an element that improves hardenability, and in order to obtain such an effect, it needs to be contained in an amount of 0.1% or more. On the other hand, the content exceeding 1.0% lowers the weldability. For this reason, when contained, Cr is specified in the range of 0.1 to 1.0%. In addition, More preferably, it is 0.1 to 0.40%.

Mo: 0.05-1.0%
Similarly, Mo is an element that improves the hardenability. In order to obtain such an effect, the content of 0.05% or more is necessary. On the other hand, the content exceeding 1.0% lowers the weldability. Therefore, when contained, Mo is specified in the range of 0.05 to 1.0%. In addition, Preferably, it is 0.05 to 0.40%.

V: 0.005-0.10%
V is an element that improves hardenability, and in order to obtain such an effect, a content of 0.005% or more is required. On the other hand, the content exceeding 0.10% reduces toughness and weldability. Therefore, when contained, V is specified in the range of 0.005 to 0.10%. In addition, Preferably, it is 0.010 to 0.090%.

W: 0.05-1.0%
Similarly, W is an element that improves the hardenability. In order to obtain such an effect, the content of 0.05% or more is required. On the other hand, the content exceeding 1.0% lowers the weldability. Therefore, when contained, W is specified in the range of 0.05 to 1.0%. In addition, Preferably, it is 0.05 to 0.40%.

In the present invention, the above-described components are contained in the above-mentioned range and the following formula (1): Ceq = C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5 + W / 10 (1)
(Here, C, Mn, Cu, Ni, Cr, Mo, V, W: content of each element (mass%))
The content of Ceq is adjusted so that it is in the range of more than 0.55% and not more than 0.60%. In addition, when not containing the element described in (1) Formula, the content of the element shall be calculated as zero.

Ceq: More than 0.55% and 0.60% or less When Ceq is 0.55% or less, the alloy element content is too small, making it difficult to secure the strength of the thick steel plate over 32mm thick and the wear resistance. descend. On the other hand, if it exceeds 0.60%, the weldability deteriorates too much and it becomes difficult to obtain a welded structure. For this reason, Ceq was limited to the range of more than 0.55% and not more than 0.60%.

Further, in the present invention, the above components are contained in the above range, in the above Ceq range, and in the following formula (2):
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (2)
(Here, C, Si, Mn, Cu, Ni, Cr, Mo, V, W: content of each element (mass%))
DI * value contains adjusted to be 45 or more in defined. In addition, when not containing the element described in (2) Formula, the content of the element shall be calculated as zero.

DI * value: 45 or more
The DI * value is related to wear resistance. If it is less than 45, the quenching depth from the steel sheet surface will be less than 10 mm, the wear resistance will be reduced, and the material will have the desired wear life. become unable. For this reason, the DI * value was limited to 45 or more. In addition, Preferably it is 60 or more.
Although the above-mentioned components are basic components, in the present invention, in addition to these basic compositions, one or two of Ca and REM may be further contained as selective elements.

One or two of Ca: 0.0005 to 0.0050%, REM: 0.0005 to 0.0050%
Both Ca and REM are elements having an action of suppressing the formation of coarse MnS, making the sulfide form into a spherical form, and improving the ductility and toughness of the steel, and can be contained as necessary. In order to obtain such an effect, it is preferable to contain Ca: 0.0005% or more, REM: 0.0005% or more, but if it contains more than Ca: 0.0050% and REM: 0.0050%, the inclusions will increase too much. Reduce the cleanliness of the steel sheet. For this reason, when it contains, it is preferable to limit to Ca: 0.0005-0.0050% and REM: 0.0005-0.0050%, respectively.

The balance other than the above components is Fe and inevitable impurities. Note that N: 0.010% or less is acceptable as an inevitable impurity.
The steel sheet according to the present invention has the above-described composition and a structure in which the matrix phase is mainly a martensite phase, and preferably has a surface hardness of 450 HBW10 / 3000 or more in terms of Brinell hardness. When the surface hardness is less than 450 HBW10 / 3000, the wear resistance is significantly reduced.

  The base phase of the steel sheet of the present invention is a phase mainly composed of a martensite phase. The phase mainly composed of the martensite phase here means martensite alone or a martensite containing a small amount of the second phase. When the second phase other than the martensite phase is generated in the base phase in excess of a predetermined amount, desired wear resistance cannot be ensured. Examples of the second phase include a bainite phase. In order to ensure desired wear resistance, the second phase is preferably limited to a total volume ratio of 10% or less.

  The base phase of the steel sheet of the present invention is preferably a phase having prior austenite grains (old γ grains) having an average crystal grain size of 15 μm or less. When the average crystal grain size of the old γ grains exceeds 15 μm, it may be difficult to suppress the occurrence of delayed fracture in the composition range of the present invention. For this reason, the base phase is preferably a phase mainly composed of a martensite phase having an old γ particle size of 15 μm or less.

Below, the preferable manufacturing method of this invention steel plate is demonstrated.
The steel sheet of the present invention is a hot rolling process in which a steel material is subjected to hot rolling to form a thick steel sheet, and immediately after completion of the hot rolling or after air cooling after completion of hot rolling, reheating, The thick steel plate is manufactured by subjecting it to a quenching treatment step for quenching.
In the production method of the present invention, a molten steel having the above composition is melted by a known melting method, and a steel material made into a slab having a desired size by a continuous casting method or an ingot-bundling rolling method is used as a starting material. It is preferable to use it.

  Next, the steel material is directly cooled without being cooled, or after being cooled and reheated to 950 to 1250 ° C., and then subjected to hot rolling to obtain a thick steel plate having a desired thickness. . The hot rolling condition is not particularly limited as long as it can be a thick steel plate having a desired size and shape. However, in the case of direct quenching in which a quenching process is performed immediately after completion of rolling, the rolling end temperature is 800 ° C. or higher. It is preferable to do. If the rolling end temperature is less than 800 ° C., a desired base phase cannot be secured.

  After the hot rolling is finished, the thick steel plate is immediately quenched, and is subjected to a quenching process for direct quenching. Or it is good also as a reheating quenching process which reheats and quenches after air-cooling after completion | finish of hot rolling. In addition, in the case of a reheating quenching process, it is preferable to set it as heating temperature: 850-950 degreeC. When the heating temperature is less than 850 ° C., sufficient quenching cannot be performed, and the base phase cannot be a phase mainly composed of the martensite phase. On the other hand, when the reheating temperature is higher than 950 ° C., the austenite grains become too coarse and it becomes difficult to suppress the occurrence of delayed fracture. For this reason, it is preferable to make the reheating temperature for a quenching process into the range of 850-950 degreeC.

Note that there is no problem even if a tempering treatment at 300 ° C. or lower is performed after the above-described quenching treatment.
The thick steel plate thus obtained has excellent wear resistance as a wear-resistant steel plate, and even when subjected to thermal effects such as fusing and welding, low temperature temper embrittlement cracking is not observed, It can be used as a steel plate excellent in temper embrittlement cracking.
Hereinafter, the present invention will be described in more detail based on examples.

  Molten steel having the composition shown in Table 1 was melted in a vacuum melting furnace to obtain a small steel ingot (150 kg) (steel material). These steel materials are heated to 1050 to 1250 ° C and then subjected to a hot rolling process in which the rolling end temperature is as shown in Table 2 and subjected to a direct quenching process (DQ) immediately after the end of the hot rolling. did. Note that some steel plates were air-cooled after the hot rolling was completed, and then reheated to 900 ° C. and subjected to quenching reheating and quenching (RQ).

Test pieces were collected from the obtained thick steel plates and subjected to structure observation, surface hardness test, and T-shaped fillet weld cracking test. The test method was as follows.
(1) Microstructure observation A specimen for microstructural observation is collected from the obtained thick steel plate, polished, and subjected to nital corrosion, and an optical microscope (magnification: 400 times) or scanning electron microscope is used for a 1/4 position in the thickness direction. (Magnification: 1000 times) was used to measure the type of base phase tissue and its tissue fraction.

In addition, the collected specimens for structure observation are polished, subjected to picric acid corrosion, revealing old austenite (γ) grain boundaries, imaged, and using an image analyzer, the average particle diameter of the old γ grains is determined. It was measured. The average grain size of the old γ grains is determined by measuring the area of each grain, calculating the equivalent circle diameter from the same area, arithmetically averaging the obtained equivalent circle diameters, and calculating the average value of the old γ grains in the steel sheet. The crystal grain size was used.
(2) Surface hardness test Using the 10mm diameter tungsten hard ball with a Brinell hardness tester (test force: 29.42kN) in accordance with the provisions of JIS Z 2243 for the obtained thick steel plate, The hardness HBW10 / 3000 was measured. The measurement positions were 5 points selected at random, and the average value of the 5 points was determined as the surface hardness of the steel sheet.

(3) T-shaped fillet weld crack test A test material was sampled from the obtained steel sheet, and a T-shaped fillet weld crack test was performed. The collected test material is assembled into a T-shaped fillet weld crack specimen as shown in Fig. 2, and the test weld (length: 200 mm) is welded with carbon dioxide gas with a heat input of 13 kJ / cm without preheating. Three-layer six-pass fillet welding was performed. After 48 hours from welding, the presence or absence of delayed cracking in the vicinity of the test weld was examined by cutting the cross section of the specimen 5.

  The obtained results are shown in Table 3.

Examples of the present invention (steel plates No. 4, 6, 8, 10) are all phases in which the base phase is mainly a martensite phase, and the former γ grain size is 15 μm or less. No cracking (delayed fracture) occurs in the weld cracking test, and the surface hardness is higher than 450 HBW10 / 3000, providing excellent wear resistance and low temperature temper embrittlement cracking resistance. It is an excellent steel plate.
On the other hand, the comparative examples (steel plates No. 11 to No. 15) outside the scope of the present invention have a surface hardness of less than 450 HBW10 / 3000 and low wear resistance, or a T-shaped fillet weld crack. Cracking (delayed fracture) occurred in the test, and the steel sheet has low-temperature tempering embrittlement cracking resistance.

Claims (4)

mass%
C: 0.31 to 0.35%, Si: 0.05 to 1.0%,
Mn: 0.80% or less, P: 0.010% or less,
S: 0.005% or less, Ti: 0.005-0.05%,
Nb: 0.005-0.024%, B: 0.0003-0.0030%,
Al: 0.1% or less, further Cu: 0.1-1.0%, Ni: 0.1-2.0%, Cr: 0.1-1.0%, Mo: 0.05-1.0%, V: 0.005-0.10%, W: 0.05-1.0% one or two or more species selected inner shell, the following (1) Ceq is less than or equal to 0.55% than 0.60%, which is defined by the equation, and the following (2) satisfies DI * value 45 or greater as defined in formula And having a composition comprising the balance Fe and inevitable impurities and a structure in which the matrix phase is mainly a martensite phase, and excellent in low-temperature tempering embrittlement cracking resistance Wear-resistant steel plate.
Ceq = C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5 + W / 10 (1)
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (2)
Here, C, Si, Mn, Cu, Ni, Cr, Mo, V, W: Content of each element (mass%)   The wear-resistant steel sheet according to claim 1, wherein in addition to the composition, the composition further includes one or two of mass%, Ca: 0.0005 to 0.0050%, and REM: 0.0005 to 0.0050%. .   The wear-resistant steel sheet according to claim 1 or 2, wherein the structure has a prior austenite grain size of 15 µm or less. The wear-resistant steel sheet according to any one of claims 1 to 3, wherein the surface hardness is 450 HBW10 / 3000 or more.

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