JP2007197810A - Wear resistant steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wear resistant steel sheet having excellent weldability and wear resistance in a base metal part and a weld heat affected zone. <P>SOLUTION: The wear resistant steel sheet has a composition comprising 0.20 to 0.50% C, 0.1 to 1.0% Si, 0.1 to 2.0% Mn, ≤0.04% P, ≤0.04% S, 0.2 to 1.0% Ti, 0.2 to 2.0% Mo, 0.0003 to 0.01% B and ≤0.01% N, also satisfying Mo/Ti: ≥1.0, and the balance Fe with inevitable impurities, and has a structure where Ti carbide and Ti-Mo compound carbide with the average grain diameter of ≥0.5 μm are comprised in ≥400 pieces/mm<SP>2</SP>in total. Further, one or more kinds selected from Cu, Ni and Cr and/or Al may be incorporated therein. In this way, the wear resistant steel sheet having excellent weldability and excellent wear resistance in a base metal part and a weld heat affected zone can be produced without being accompanied by remarkable increase in hardness. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in construction, civil engineering, mining, etc., for industrial machines such as power shovels, bulldozers, hoppers, buckets, etc., carrying equipment, etc. The present invention relates to a wear-resistant steel plate suitable for a receiving member.

  Steel members having excellent wear resistance are used for members that are subjected to abrasive wear, sliding wear, impact wear, etc. due to rocks, sand, ore or 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, steel members that have been hardened by heat treatment such as quenching have been used for members that require a high level of wear resistance.

  For example, Patent Document 1 proposes a method of manufacturing a wear-resistant steel plate having good weldability. The technique described in Patent Document 1 includes C: 0.10 to 0.19%, containing appropriate amounts of Si and Mn, and Ceq limited to 0.35 to 0.44, directly quenched after hot rolling, or 900 to This is a method for producing a wear-resistant steel sheet that is reheated to 950 ° C. and then tempered and tempered at 300 to 500 ° C. to make the steel sheet surface hardness 300 HV or higher.

Patent Document 2 includes C: 0.10 to 0.20%, and Si, Mn, P, S, N, and Al are adjusted to appropriate amounts, or one of Cu, Ni, Cr, Mo, and B. Steel containing more than seeds is hardened directly after hot rolling, or cooled after rolling and then re-heated and quenched, and has a hardness of 340HB or more, and has excellent toughness and weld cold cracking resistance. Techniques for making thick steel plates have been proposed.
Patent Document 3 includes C: 0.07 to 0.17%, contains an appropriate amount of Si, Mn, V, B, and Al, or further contains one or more of Cu, Ni, Cr, and Mo. A method of manufacturing a wear-resistant steel sheet is proposed in which steel is quenched immediately after hot rolling, or once air-cooled and then reheated and quenched to obtain a steel sheet having a surface hardness of 321 HB or more and excellent bending workability. ing.

The techniques described in Patent Documents 1 to 3 add a large amount of alloy elements and utilize solid solution hardening, transformation hardening, precipitation hardening, and the like to remarkably increase hardness and improve wear resistance.
However, in recent years, the wear resistance required for steel sheets has become even more severe, and the current situation is that the method of simply increasing the hardness has not improved the wear resistance essentially. As in the techniques described in Patent Documents 1 to 3, when alloying elements are added in large quantities and solid solution hardening, transformation hardening, precipitation hardening, etc. are utilized to significantly increase the hardness, the result is In addition, there are problems that weldability and workability are lowered, and that the production cost is increased due to the high alloying. For this reason, it has been desired to improve the wear resistance without significantly increasing the hardness.

In response to such a request, for example, Patent Document 4 includes C: 0.10 to 0.45%, Si, Mn, P, S, and N are adjusted to appropriate amounts, and further Ti: 0.10 to 1.0% is contained. , 0.5 [mu] m or more the size of the TiC precipitates or TiC and TiN, includes a composite precipitate 400 / mm ² or more and TiS, wear of Ti * is excellent in surface properties is less than 0.4% 0.05% or more Steel has been proposed. According to the technique described in Patent Document 4, precipitates mainly composed of coarse TiC are generated during solidification, and wear resistance can be improved at low cost without significantly increasing hardness.
JP-A-62-142726 JP 63-169359 A Japanese Patent Laid-Open No. 1-142023 Japanese Patent No. 3089882

  Recently, in order to improve welding efficiency and reduce welding costs, it is required to reduce the preheating temperature and omit post-heating, and the wear-resistant steel sheets used are also required to improve weldability and weld heat affected zone characteristics. It has come to be. For example, in the wear-resistant steel sheet described in Patent Document 4, the wear resistance of the weld heat-affected zone tends to be slightly lower than the wear resistance of the base material, in order to ensure the desired wear resistance. It was necessary to perform overlay welding. Therefore, in the member using the abrasion-resistant steel plate described in Patent Document 4, there are problems such as a rise in welding construction cost and a reduction in member production efficiency.

  The present invention provides a wear-resistant steel sheet that has excellent weldability and excellent wear resistance of the base metal part and the weld heat-affected zone without significant increase in hardness in view of the problems of the prior art. For the purpose.

  In order to achieve the above-described object, the inventors of the present invention have a specific composition containing a large amount of Ti and coarse Ti carbide (TiC) in order to improve wear resistance without significantly increasing hardness. It has been found that it is effective to crystallize and precipitate. In addition, when the present inventors melt TiC during welding, the solid solution C increases and the weld cracking sensitivity is increased, which promotes low-temperature cracking during welding and is a factor that hinders improvement in welding efficiency. I also found out that it was one of the following. Then, the present inventors have conceived that by suppressing the dissolution of coarse Ti carbide during welding, the wear resistance of the weld heat-affected zone can be made the same as that of the base material, and Mo can be converted into Mo / Ti. Suppresses dissolution of coarse Ti carbides during welding by crystallizing and precipitating Ti and Mo composite carbides in which a certain amount or more of Mo is solid-dissolved in TiC. It was found that the wear resistance of the weld heat affected zone is significantly improved.

First, the experimental results on which the present invention is based will be described.
A steel material having a composition in which 0.31% C-0.40% Ti as a basic component and Mo was changed in a range of 0 to 0.77% was melted in a laboratory. Thermal cycle specimens were collected from these steel materials, and a thermal history simulating welding was added by energization heating. About these test pieces, the carbide | carbonized_material was extracted by the electrolytic extraction method, C amount which is a carbide | carbonized_material was measured, C amount | substance which became a carbide | carbonized_material was subtracted from the amount of total C, and solid solution C amount | quantity was calculated | required. The obtained results are shown in FIG. 1 in relation to the amount of solute C and Mo / Ti. In addition, the heat history that simulates welding has two types of maximum temperatures of 1250 ° C and 1350 ° C. It was set to ° C / s.

  From FIG. 1, when Mo / Ti is less than 1.0, the amount of solute C increases when the maximum temperature reached 1350 ° C. compared to when the maximum temperature reached 1250 ° C. When Mo / Ti is 1.0 or more, there is a tendency that the amount of dissolved C is almost equal between the case where the maximum temperature is 1250 ° C and the case where the maximum temperature is 1350 ° C. From FIG. 1, it can be seen that by setting Mo / Ti to 1.0 or more, dissolution of Ti carbide is remarkably suppressed even when heated to a temperature exceeding 1300 ° C. The reason for this is that TiC became a composite carbide of Ti and Mo in which Mo was dissolved in TiC by initially setting Mo / Ti to 1.0 or more from the analysis results of some precipitates. It was considered a thing. However, later, even if Mo / Ti is 1.0 or more and less than 1.0, a composite carbide of Ti and Mo will be observed, so that Mo / Ti affects the solubility of Ti carbide at a temperature of 1300 ° C or higher. It came to estimate. In other words, when Mo / Ti is 1.0 or more, the solubility of the composite carbide of Ti and Mo in which Mo is dissolved is as low as that at a lower temperature even when heated to a high temperature of 1300 ° C or higher. It seems that there is so far.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) By mass%, C: 0.20 to 0.50%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.0%, P: 0.04% or less, S: 0.04% or less, Ti: 0.2 to 1.0%, Mo: 0.2 -2.0%, B: 0.0003-0.01%, N: 0.01% or less, and Mo and Ti are represented by the following formula (1)
Mo / Ti ≧ 1.0 (1)
(Where Mo, Ti: content of each element (mass%))
And a composition comprising the balance Fe and inevitable impurities, and an average particle size: a Ti carbide of 0.5 μm or more and a composite carbide of Ti and Mo in total 400 pieces / mm ² or more Wear-resistant steel sheet characterized by.

(2) In (1), in addition to the above composition, in addition to mass, one or two selected from Cu: 0.1 to 2.0%, Ni: 0.1 to 10%, Cr: 0.1 to 3.0% A wear-resistant steel sheet characterized by having a composition including the above.
(3) In (1) or (2), in addition to the said composition, it is set as the composition containing Al: 0.08% or less by the mass% further, The abrasion-resistant steel plate characterized by the above-mentioned.

  According to the present invention, it is possible to easily and inexpensively manufacture a wear-resistant steel plate having excellent weldability and excellent wear resistance of the base metal part and the weld heat-affected zone without significantly increasing hardness. It has a remarkable industrial effect. In addition, according to the present invention, while ensuring the wear resistance of the weld heat-affected zone in the same level as the base metal part, it is possible to reduce the preheating work during welding and to omit the post heat treatment, thereby improving the welding efficiency and improving the welding work. There is also an effect that the cost can be reduced.

First, the reason for defining the composition range of the steel sheet of the present invention will be described. In addition, the following% display shows mass% altogether.
C: 0.20 ~ 0.50%
C is an essential element for forming a carbide (precipitate) mainly composed of TiC. If it is less than 0.20%, carbides (precipitates) mainly composed of TiC cannot be effectively formed. On the other hand, if the content exceeds 0.50%, excessive solute C remains, so that the weldability, workability, and the like decrease as the hardness increases. For this reason, C was specified in the range of 0.20 to 0.50%.

Si: 0.1-1.0%
Si is an effective element as a deoxidizing element, and in order to obtain the effect, it needs to contain at least 0.1% or more. In addition, Si is an effective element that contributes to high hardness by solid solution strengthening by solid solution strengthening. However, 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 0.1 to 1.0%. In addition, Preferably it is 0.1 to 0.5%.

Mn: 0.1-2.0%
Mn is an effective element for improving the hardenability, and in order to obtain the effect, the content needs to be 0.1% or more. On the other hand, if the content exceeds 2.0%, weldability decreases. For this reason, Mn was specified in the range of 0.1 to 2.0%. In addition, Preferably it is 0.5 to 1.6%.
P: 0.04% or less P is an element that lowers the ductility and toughness of steel and adversely affects the properties of the steel sheet. In the present invention, it is desirable to reduce it as an inevitable impurity, but excessive reduction increases the refining cost. Let From the viewpoint of preventing such an adverse effect and suppressing an excessive increase in the refining cost, P is specified to be 0.04% or less. In addition, Preferably it is 0.02% or less.

S: 0.04% or less S is an impurity element that causes a decrease in hot ductility and a decrease in ductility and toughness at room temperature, and it is desirable to reduce it as much as possible. However, excessive reduction increases the refining cost. For this reason, from the viewpoint of preventing such an adverse effect and suppressing an excessive increase in the refining cost, S is specified to be 0.04% or less. In addition, Preferably it is 0.02% or less.

Ti: 0.2-1.0%
Ti is the most important element together with C and Mo in the present invention, and is an essential element for stably producing TiC and a composite carbide of Ti and Mo. From the viewpoint of improving the wear resistance by forming such a carbide, the content of 0.2% or more is required. On the other hand, when it contains exceeding 1.0%, workability will fall and it will lead to the rise of material cost. For this reason, Ti was specified in the range of 0.2 to 1.0%. In addition, Preferably it is 0.3 to 0.8%.

Mo: 0.2-2.0%
In the present invention, Mo is the most important element together with C and Ti, and is an element that forms a composite carbide with Ti and improves wear resistance. In order to obtain such an effect, the content of 0.2% or more is required. On the other hand, if the content exceeds 2.0%, Mo cannot be dissolved in the composite carbide, so that the weldability is lowered and the material cost is increased. For this reason, Mo was specified in the range of 0.2 to 2.0%. In addition, Preferably it is 0.3 to 1.6%.

In the present invention, Mo and Ti are within the above-mentioned ranges, respectively, and the following formula (1)
Mo / Ti ≧ 1.0 (1)
(Where Mo, Ti: content of each element (mass%))
Is contained so as to satisfy. When Mo / Ti is less than 1.0, as is clear from FIG. 1, when heated to a high temperature during welding, Ti carbide dissolves, solute C increases, and wear resistance of the weld heat affected zone decreases. At the same time, the weld crack resistance decreases. For this reason, Mo / Ti was specified to be 1.0 or more. In addition, Preferably it is 2.0 or less.

B: 0.0003-0.01%
B is an element that enhances the hardenability by adding a small amount, but in order to exert this effect, the content of 0.0003% or more is required. On the other hand, the content exceeding 0.01% reduces weldability and hardenability. For this reason, B was specified in the range of 0.0003 to 0.01%. In addition, Preferably it is 0.0005 to 0.004%.

N: 0.01% or less N is an impurity element that lowers the ductility and toughness of steel, and it is desirable to reduce it as much as possible. However, excessive reduction leads to an increase in refining cost. For this reason, from the viewpoint of preventing such an adverse effect and suppressing an excessive increase in the refining cost, N is specified to be 0.01% or less. In addition, Preferably it is 0.006% or less.

The above-mentioned components are basic components. In addition to this basic component, if necessary, Cu: 0.1 to 2.0%, Ni: 0.1 to 10%, Cr: 0.1 to 3.0% 1 It can contain a seed | species or 2 or more types and / or Al: 0.08% or less.
Cu, Ni, and Cr are all elements that enhance the hardenability of the steel, and can be selected as necessary and contained in one or more.

Cu is an element that enhances hardenability, and is an element that works effectively to control the hardness according to the purpose, but 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%, the hot workability is lowered and the material cost is increased. For this reason, when it contains Cu, it is preferable to limit to 0.1 to 2.0% of range.
Ni is an element that enhances hardenability and improves low-temperature toughness, and such an effect becomes remarkable when the content is 0.1% or more. On the other hand, the content of expensive Ni exceeding 10% significantly increases the material cost. For this reason, when it contains, it is preferable to limit Ni to 0.1 to 10% of range.

Cr is an element that enhances hardenability and needs to be contained in an amount of 0.1% or more in order to obtain such an effect. On the other hand, if the content exceeds 3.0%, weldability deteriorates and material costs increase. For this reason, when it contains, it is preferable to limit Cr to 0.1 to 3.0% of range.
Al: 0.08% or less
Al is an element that acts as a deoxidizing agent and combines with N to contribute to refinement of crystal grains, and can be contained as necessary. Such an effect is recognized at a content of 0.01% or more, but a large content exceeding 0.08% reduces the cleanliness of the steel. For this reason, when it contains Al, it is preferable to limit to 0.08% or less.

Next, the reason for limiting the structure of the steel sheet of the present invention will be described.
The steel sheet of the present invention has a structure containing a total of 400 carbides / mm ² or more of Ti carbides having an average particle size of 0.5 μm or more and composite carbides of Ti and Mo.
In the steel sheet of the present invention, desired wear resistance is ensured by generating a large amount of coarse precipitates mainly composed of Ti carbide (TiC) and composite carbide of Ti and Mo. Fine precipitates having an average particle size of less than 0.5 μm cannot be expected to have a remarkable effect of improving wear resistance. For this reason, the size of precipitates mainly composed of Ti carbide and composite carbide of Ti and Mo was set to 0.5 μm or more in average particle size. In consideration of a decrease in wear resistance due to a shortage of precipitated composite carbide, the upper limit of the average particle size of the precipitate is preferably 50 μm.

The steel sheet of the present invention contains a total of 400 carbides / mm ² or more of Ti carbide and composite carbide of Ti and Mo having an average particle size of 0.5 μm or more. When the density of coarse precipitates mainly composed of coarse Ti carbide having an average particle size of 0.5 μm or more and composite carbide of Ti and Mo is less than 400 pieces / mm ² , the effect of improving wear resistance can hardly be expected. For this reason, the total number of Ti carbides and composite carbides of Ti and Mo having an average particle size of 0.5 μm or more was defined as 400 pieces / mm ² or more in total. There is no particular upper limit.

  In addition, the size and number of precipitates (Ti carbide and Ti and Mo composite carbide) are measured using an optical microscope or a scanning electron microscope (magnification: 400 times or more). (5 fields of view or more), and the size of each precipitate observed there and the number per unit area are measured using a technique such as image analysis. Moreover, it is preferable to perform identification of the composite carbide | carbonized_material of TiC or Ti and Mo among precipitates using the scanning electron microscope carrying an analyzer.

The “average particle size” here is obtained by measuring the area of each precipitate by a method such as image analysis, and calculating the equivalent circle diameter from each measured area as the diameter of each precipitate. The average value obtained by arithmetically averaging the diameters of the respective precipitates was defined as the average particle size of the precipitates on the steel sheet. In calculating the average particle size, at least 100 precipitates are measured.
In addition, the base structure of the structure | tissue which the above-mentioned carbide precipitates shall be a structure | tissue which has a martensite phase as a main component. In the case where the base structure is a structure mainly composed of a martensite phase, the effect of improving the wear resistance can be efficiently brought out by increasing the density and hardness of the carbide. On the other hand, when the base structure is not a structure mainly composed of martensite phase, by increasing the hardness and density of the carbide, the wear resistance is improved to some extent, but the effect of improving the wear resistance is saturated, and the carbide The effect commensurate with the increase in the hardness and density of can not be expected.

The “structure mainly composed of martensite phase” in the present invention refers to a structure having a martensite phase structure fraction of 70% or more. The balance may be a bainite phase, a pearlite phase, a ferrite phase, a retained austenite phase, or a mixed phase thereof other than the martensite phase.
In order to make the base structure a structure mainly composed of the martensite phase, it is preferable that the solid solution C amount of the base structure is more than 0.03% by mass. When the amount of solute C is 0.03% by mass or less, the base structure becomes a structure mainly composed of a ferrite phase even if any commonly used industrial heat treatment is performed.

Below, the preferable manufacturing method of the steel plate of this invention is demonstrated.
A steel material having a desired size and shape is obtained by using a known continuous casting method or ingot forming method with a molten steel adjusted to a composition within the above-described component range by a known melting method such as a converter, electric furnace or vacuum melting furnace. (Slab or ingot) is preferable.
When the continuous casting method is used, it is preferable to adjust the cooling so that the cooling rate in the temperature range of 1500 to 1200 ° C. on the surface of the slab having a thickness of 200 to 400 mm is in the range of 0.2 to 10 ° C./s. As a result, the precipitates (Ti carbide and composite carbide of Ti and Mo) have a desired size and number, that is, the total of Ti carbide and composite carbide of Ti and Mo having an average particle size of 0.5 μm or more, preferably 50 μm or less. Therefore, it is possible to adjust to 400 pieces / mm ² or more. Even in the case of using the ingot-making method, it is necessary to adjust the size and cooling conditions of the ingot so that the precipitates (Ti carbide and composite carbide of Ti and Mo) have the desired size and number. Needless to say.

  Next, the steel material is directly or reheated without cooling, and then hot-rolled to obtain a steel plate having a desired thickness. The hot rolling conditions are not particularly limited as long as the steel sheet can have a desired size and shape. After hot rolling, the steel sheet is cooled to near room temperature. After cooling, it is preferably reheated to a temperature of 900 ° C. or higher and then quenched to obtain a product (abrasion resistant steel plate). The quenching cooling is preferably water cooling and cooling to the Ms point or lower. If necessary, a tempering treatment may be performed after tempering in a temperature range of 700 ° C. or lower.

  Hereinafter, the present invention will be further described in detail based on examples.

  The molten metal having the composition shown in Table 1 was melted in a vacuum melting furnace to obtain a small steel ingot (50 kgf steel ingot). These small steel ingots were made into steel plates having a thickness of 15 mm by hot rolling. In addition, it was set as air cooling after hot rolling. These steel plates were then reheated to 900 ° C. and then quenched to 200 ° C. or lower. About the obtained steel plate, structure | tissue observation, abrasion resistance, weld cracking property, and also the solid solution C amount of the base structure were investigated. The survey method is as follows.

(1) Microstructure observation A specimen for microstructural observation is collected from the obtained steel plate, and the entire cross section perpendicular to the rolling direction is polished and subjected to nital corrosion, and a scanning electron microscope with an analyzer (magnification: 1000 times) is used. Used to image the tissue. For the enlarged 100 mm × 100 mm field of view (25 fields of view), the size and number of Ti carbide (TiC) and Ti, Mo composite carbide were measured using an image analyzer. As for the size of the carbide, the area of each carbide was measured, the equivalent circle diameter was calculated from the same area, the obtained equivalent circle diameter was arithmetically averaged, and the obtained average value was taken as the average particle diameter of the steel sheet. Further, among the obtained carbides (Ti carbide and composite carbide of Ti and Mo), the number of carbides having an average particle diameter of 0.5 μm or more was measured and converted to the number per 1 mm ² .

At the same time, the types of base organizations and their fractions were investigated. Note that the tissue fraction was evaluated using an image analysis device in the imaged range. In addition, the structure fraction of the martensite phase evaluated the ratio which occupies for the whole martensitic structure by the area ratio using the image analyzer.
(2) Abrasion resistance A test piece (size: t × 25 × 75mm) was taken from the obtained steel plate, and in accordance with ASTM G-65, using sand of SiO ₂ 90% or more as wear sand, A wear test was performed. A mild steel (SS400) plate was also tested in the same manner. The test was conducted on the base metal part and the weld heat affected zone.

The wear resistance of the base material portion of each steel plate was evaluated by the wear resistance ratio with the wear amount of the mild steel (SS400) plate as the standard (1.0). A larger wear resistance ratio means better wear resistance.
The wear resistance of the weld heat-affected zone is the same as that of the base metal, by performing hard build-up welding with a Vickers hardness of 600 class as the welding material on the test piece taken from each steel plate and grinding the build-up weld. The tests were conducted and evaluated. The wear resistance of the weld heat affected zone was evaluated by observing the appearance of the test piece after the wear test and comparing it with the test piece of the base metal part. ○ When the appearance of the specimen after the wear test shows no preferential wear in the weld heat affected zone and the damage is equivalent to that of the base metal, ○ When the damage was severe, it was set as x.

(3) Weld cracking property Test specimens were collected from each of the obtained steel plates, and a y-type weld cracking test was performed in accordance with the provisions of JIS Z 3158 to determine the crack stop temperature and the weld cracking property was evaluated.
(4) Solid solution C amount of base structure Collect specimens from each steel plate obtained, extract carbides by electrolytic extraction, measure the amount of carbon that has become carbides, and from the total C amount, The amount of C is subtracted to obtain the amount of dissolved C in the base tissue.

  The obtained results are shown in Table 2.

  Each of the inventive examples has a matrix structure mainly composed of a martensite phase in which the ratio of the martensite lath phase is 70% or more in area ratio, a solid solution C amount exceeding 0.03% by mass, and the base material part is Compared to mild steel (SS400), the wear ratio is 8 or more and excellent in wear resistance, and the weld heat affected zone is as excellent in wear resistance as the base metal. In the example of the present invention, the crack stop temperature is as low as 200 ° C. or less, and the weld crack resistance is also excellent. On the other hand, in comparative examples that are outside the scope of the present invention, the wear resistance of the base metal part is reduced, the wear resistance of the weld heat affected zone is lower than that of the base material part, or even at 200 ° C. preheating. The crack cannot be prevented and the weld crack resistance is low.

  The comparative example (steel plate No. 8) in which the Mo content deviated from the scope of the present invention was low because Mo / Ti was less than 1.0, and the Mo content was within the scope of the present invention, but Mo / Ti was less than 1.0. In the comparative example (steel plate No. 7), the wear resistance of the weld heat affected zone is lower than that of the base metal. Moreover, the comparative example (steel plates Nos. 7 and 8) also has a high cracking stop temperature of 200 ° C., and the weld crack resistance is low. In addition, in the comparative example (steel plate No. 9) in which Mo / Ti is out of the scope of the present invention, the wear resistance of the weld heat-affected zone is lower than that of the base material, and cracking cannot be prevented even at 200 ° C. preheating. Weld crack resistance is reduced. Further, the comparative examples (steel plates No. 10 and 11) in which the Mo amount or C amount is outside the scope of the present invention cannot prevent cracking even at 200 ° C. preheating, and the weld crack resistance is reduced.

It is a graph which shows the relationship between the amount of solute C and Mo / Ti.

Claims (3)

% By mass
C: 0.20 to 0.50%, Si: 0.1 to 1.0%,
Mn: 0.1 to 2.0%, P: 0.04% or less,
S: 0.04% or less, Ti: 0.2-1.0%,
Mo: 0.2-2.0%, B: 0.0003-0.01%,
N: containing 0.01% or less and containing Mo and Ti so as to satisfy the following formula (1), the balance consisting of Fe and unavoidable impurities, average particle size: Ti carbide of 0.5 μm or more, and Ti and Mo A wear-resistant steel sheet having a structure containing a total of 400 composite carbides of 400 pieces / mm ² or more.
Record
Mo / Ti ≧ 1.0 (1)
Here, Mo, Ti: Content of each element (mass%)   In addition to the above composition, the composition further includes one or more selected from Cu: 0.1 to 2.0%, Ni: 0.1 to 10%, and Cr: 0.1 to 3.0% by mass%. 2. The wear-resistant steel plate according to claim 1, wherein   The wear-resistant steel sheet according to claim 1 or 2, wherein in addition to the composition, the composition further includes, by mass%, Al: 0.08% or less.

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