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    • 专利摘要:
    it is an abrasion-resistant steel plate that exhibits high hardness to the center of the plate in the thickness direction, although it has a plate thickness of 50 mm or more, and that can be produced at low cost. the abrasion-resistant steel sheet comprises specific components, has a constituent composition whereby the di * value defined by formula (1) is 120 or more, has a brinell hardness hb1 at a depth of 1 mm from surface from 360 to 490 hbw10 / 3000, has a hardness ratio, which is defined as the brinell hardness ratio hb1 / 2 at a position in the center of the plate in the direction of thickness in relation to hb1, 75% or more, and has a sheet thickness of 50 mm or more. formula (1): di * = 33.85 x (0.1 xc) 0.5 x (0.7 x si + 1) x (3.33 x min + 1) x (0.35 x cu + 1 ) x (0.36 x ni + 1) x (2.16 x cr + 1) x (3 x mo + 1) x (1.75 x v + 1) x (1.5 x w + 1).
    公开号:BR112019017699A2
    申请号:R112019017699-3
    申请日:2018-02-02
    公开日:2020-03-31
    发明作者:Takayama Naoki；Terazawa Yusuke；Murakami Yoshiaki；Hase Kazukuni；TAKEMURA Yusaku；Murota Yasuhiro
    申请人:Jfe Steel Corporation；
    IPC主号:
    专利说明:

    Invention Patent Descriptive Report for ABRASION-RESISTANT STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME.
    TECHNICAL FIELD [0001] The description refers to an abrasion resistant steel plate, in particular, an abrasion resistant steel plate that has high hardness in the intermediate thickness part of it, although the steel plate is thick and can be manufactured at low cost. The abrasion-resistant steel plate can be used appropriately for members of industrial machines and transportation devices that are used in fields such as construction, civil engineering and excavation such as mining. In addition, the description relates to a method for making the abrasion resistant steel plate.
    BACKGROUND [0002] It is known that the abrasion resistance of steel can be improved by increasing the steel's hardness. Therefore, high hardness steel has been widely used as abrasion resistant steel, and high hardness steel is obtained by subjecting alloy steel added with a large amount of alloying elements, such as Mn, Cr and Mo, to treatment. such as sudden cooling.
    [0003] For example, JP 4645306 B (PTL 1) and JP 4735191 B (PTL 2) propose an abrasion resistant steel plate that has a Brinell (HB) hardness of 360 to 490 in its surface layer. In the abrasion-resistant steel plate, high surface hardness is achieved by adding a predetermined amount of alloying elements and by abruptly cooling the steel plate to obtain a microstructure dominated by martensite.
    LIST OF QUOTES
    PATENT LITERATURES [0004] PTL 1: JP 4645306 B
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    2/33 [0005] PTL 2: JP 4735191 Β
    SUMMARY
    TECHNICAL PROBLEM [0006] In some operating environments of an abrasion resistant steel plate, a steel plate with a plate thickness as thick as tens of millimeters is used until it is worn close to the intermediate thickness part of the plate. Therefore, in order to prolong the service life of a steel plate, it is important that the steel plate has high hardness, not only in its surface layer, but also in its intermediate thickness part.
    [0007] The N documents 1 and PTL 2, however, do not consider the hardness in the intermediate position of a thick steel plate resistant to abrasion thick. Documents Nos PTL 1 and PTL 2 also has a cost increase problem due to the fact that a large amount of alloy elements must be added to ensure the hardness at the intermediate thickness of a sturdy steel plate with thick abrasion .
    [0008] The present description was made in view of the above, and an objective of the present description is to provide an abrasion resistant steel plate that has high hardness in the intermediate thickness part of it, although the steel plate has a thickness of plate as thick as 50 mm or more and can be manufactured at low cost. In addition, the purpose of the present description is to provide a method for making the abrasion resistant steel plate.
    SOLUTION TO THE PROBLEM [0009] In order to achieve the above objective, intensive studies were carried out on the various factors that affect the hardness in the intermediate thickness position of an abrasion resistant steel plate. As a result, it was found that when submitting a steel plate that
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    3/33 has a high carbon content with regular blast cooling treatment and then tempering under specific conditions, an abrasion resistant steel plate that has high hardness in the intermediate thickness part of it can be manufactured, although the steel plate has low content of alloy elements other than carbon.
    [0010] The description is based on the findings mentioned above and on additional studies. We provide the following.
    [0011] 1. An abrasion-resistant steel plate, which has a chemical composition that contains (consists of), in% by mass, [0012] C: 0.23% to 0.34%, [0013] Si: 0.05% to 1.00%, [0014] Mn: 0.30% to 2.00%, [0015] P: 0.020% or less, [0016] S: 0.020% or less, [0017] Al: 0.04% or less, [0018] Cr: 0.05% to 2.00%, [0019] N: 0.0050% or less, and [0020] O: 0.0050% or less, with the balance is Fe and unavoidable impurities, the chemical composition has a Dl * value of 120 or more, where Dl * is defined by the following Formula (1):
    [0021] Dl * = 33.85 x (0.1 x C) 0 5 x (0.7 x Si + 1) x (3.33 x Mn + 1) x (0.35 x Cu + 1) x (0.36 x Ni + 1) x (2.16 x Cr + 1) x (3 x Mo + 1) x (1.75 xV + 1) x (1.5 x W + 1) (1) where each element symbol in Formula (1) indicates a content, in% by mass, of a corresponding element and is taken to be 0 when the corresponding element is not contained, where the abrasion resistant steel plate has HBi 360 HBW10 / 3000 to 490 HBW10 / 3000, HBi being a Brinell hardness at a depth of 1 mm from an abrasion resistant steel plate surface,
    Petition 870190082861, of 26/08/2019, p. 19/54
    4/33 where the abrasion-resistant steel plate has a hardness ratio of 75% or more, the hardness ratio being defined as a ratio of HB1 / 2 to HB1, and where HB1 / 2 is a Brinell hardness in an intermediate thickness position of the abrasion resistant steel plate, and in which the abrasion resistant steel plate has a plate thickness of 50 mm or more.
    [0022] 2. The abrasion-resistant steel plate, according to 1, in which the chemical composition also contains, in% by mass, one or more selected from the group consisting of [0023] Cu: 0.01 % to 2.00%, [0024] Ni: 0.01% to 2.00%, [0025] Mo: 0.01% to 1.00%, [0026] V: 0.01% to 1.00 %, [0027] W: 0.01% to 1.00%, and [0028] Co: 0.01% to 1.00%.
    [0029] 3. The abrasion-resistant steel plate, according to 1 or
    2, where the chemical composition also contains, in% by mass, one or more selected from the group consisting of [0030] Nb: 0.005% to 0.050%, [0031] Ti: 0.005% to 0.050%, and [ 0032] B: 0.0001% to 0.0100%.
    [0033] 4. The abrasion-resistant steel plate, according to any one of 1 to 3, in which the chemical composition also contains, in% by mass, one or more selected from the group consisting of [0034] Ca: 0.0005% to 0.0050%, [0035] Mg: 0.0005% to 0.0050%, and [0036] REM: 0.0005% to 0.0080%.
    [0037] 5. A method for making an abrasion-resistant steel plate comprising:
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    5/33 heat a steel raw material to a heating temperature, the steel raw material having a chemical composition that contains, in% by mass, [0038] C: 0.23% to 0.34% , [0039] Si: 0.05% to 1.00%, [0040] Mn: 0.30% to 2.00%, [0041] P: 0.020% or less, [0042] S: 0.020% or less , [0043] Al: 0.04% or less, [0044] Cr: 0.05% to 2.00%, [0045] N: 0.0050% or less, and [0046] O: 0.0050% or less, the balance being Fe and impurities inevitable;
    hot-rolling the steel raw material heated on a hot-rolled steel plate with a plate thickness of 50 mm or more;
    subjecting the hot-rolled steel plate to sudden cooling, the sudden cooling being either direct sudden cooling or sudden reheating cooling, with the direct sudden cooling having a temperature of onset of sudden cooling of an Ars transformation point or higher, the reheat blast has an onset temperature of the blast chilling of a transformation point of Acs or higher; and subjecting the hot-rolled steel plate, after sudden cooling, to tempering under a condition such that a value of P is 1.20 x 10 4 to 1.80 x 10 4 , the value of P being defined by the following Formula (2):
    P = (T + 273) x (21.3 - 5.8 x C + log (60 x t)) (2), where, in Formula (2), C indicates the C content (in% in
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    6/33 mass) on the steel plate, T indicates the quenching temperature ( Q C) and t indicates the retention time (min.) In the quenching.
    [0047] 6. The method for making an abrasion-resistant steel plate, according to 5, in which the chemical composition also contains, in% by mass, one or more selected from the group consisting of [0048] Cu : 0.01% to 2.00%, [0049] Ni: 0.01% to 2.00%, [0050] Mo: 0.01% to 1.00%, [0051] V: 0.01% at 1.00%, [0052] W: 0.01% to 1.00%, and [0053] Co: 0.01% to 1.00%.
    [0054] 7. The method for making an abrasion-resistant steel plate, according to 5 or 6, in which the chemical composition also contains, in% by weight, one or more selected from the group consisting of [0055 ] Nb: 0.005% to 0.050%, [0056] Ti: 0.005% to 0.050%, and [0057] B: 0.0001% to 0.0100%.
    [0058] 8. The method for making an abrasion-resistant steel plate, according to any one of 5 to 7, in which the chemical composition still contains, in mass%, one or more selected from the group consisting of in [0059] Ca: 0.0005% to 0.0050%, [0060] Mg: 0.0005% to 0.0050%, and [0061] REM: 0.0005% to 0.0080%.
    ADVANTAGEOUS EFFECT [0062] It is possible to obtain an abrasion resistant steel plate that has high hardness in the intermediate thickness part of it at low cost, although the steel plate has a plate thickness as thick as 50 mm or more.
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    7/33
    DETAILED DESCRIPTION CHEMICAL COMPOSITION [0063] Next, a method for implementing the present description is described in detail below. It is important that an abrasion-resistant steel plate and a steel raw material used to manufacture the abrasion-resistant steel plate have the chemical composition described above. Therefore, the reasons for limiting the chemical composition of steel, as dictated above, are described first. In the chemical composition,% denotes% by mass, unless otherwise indicated.
    C: 0.23% to 0.34% [0064] C is an element that has an effect of increasing the hardness in a surface layer and an intermediate thickness position and improving the abrasion resistance. To achieve this effect, the C content is adjusted to be 0.23% or more. In order to further reduce the required amounts of other alloying elements and to manufacture the abrasion-resistant steel plate at a low cost, the C content is preferably 0.25% or more. On the other hand, when the C content exceeds 0.34%, the hardness of a surface layer is excessively increased during the blast cooling heat treatment to thereby increase the heating temperature necessary for the tempering heat treatment, thus increasing the costs of heat treatment. Consequently, the C content is 0.34% or less. To further decrease the temperature required for tempering, the C content is preferably 0.32% or less.
    Si: 0.05% to 1.00% [0065] Si is an element that works as a deoxidizer. It also has the effect of being dissolved in steel and increasing the hardness of a steel matrix by strengthening the solid solution. To obtain these effects, the Si content is adjusted to be 0.05% or more. O
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    8/33 Si content is preferably 0.10% or more, and more preferably 0.20% or more. On the other hand, if the Si content exceeds 1.00%, ductility and toughness are reduced, and, in addition, the amount of inclusions is increased. Consequently, the Si content is 1.00% or less. The Si content is preferably 0.80% or less, more preferably 0.60% or less, and still preferably 0.40% or less.
    Mn: 0.30% to 2.00% [0066] Mn is an element that has an effect of increasing the hardness in a surface layer and an intermediate thickness position and improving the abrasion resistance. To achieve this effect, the Mn content is adjusted to be 0.30% or more. The Mn content is preferably 0.70% or more, and more preferably 0.90% or more. On the other hand, if the Mn content exceeds 2.00%, weldability and toughness are reduced, and, in addition, alloy costs are excessively increased. Consequently, the Mn content is 2.00% or less. The Mn content is preferably 1.80% or less, and, more preferably, 1.60% or less.
    P: 0.020% or less [0067] P is an element contained as an unavoidable impurity, which causes an adverse effect such as a decrease in toughness in a base metal and a welded portion due to segregation to grain boundaries. Consequently, the P content is desirably as low as possible, but the P content of 0.020% or less is allowed. Thus, the P content is adjusted to be 0.020% or less. On the other hand, the P content can have any lower limit. The lower limit may be 0%, but in industrial terms, it may be more than 0% due to the fact that, typically, P is an element inevitably contained as a steel impurity. In addition, reducing the P content excessively leads to an increase in refining costs. Like this,
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    9/33 the Ρ content is preferably 0.001% or more.
    S: 0.020% or less [0068] S is an element inevitably contained as an unavoidable impurity, and exists in steel as a sulfide inclusion, such as MnS, which causes an adverse effect of generating the fracture origin. Consequently, the S content is desirably as low as possible, but the S content of 0.020% or less is permissible. Thus, the S content is adjusted to be 0.020% or less. On the other hand, the S content can have any lower limit. The lower limit may be 0%, but in industrial terms, it may be more than 0% due to the fact that, typically, S is an element inevitably contained as a steel impurity. Additionally, reducing the S content excessively leads to an increase in refining costs. Thus, the S content is preferably 0.0005% or more.
    Al: 0.04% or less [0069] Al is an element that works as a deoxidizer and has a refining effect on crystal grains. However, if the Al content exceeds 0.04%, an oxide-based inclusion is increased, thus reducing cleanliness. Consequently, the Al content is 0.04% or less. The Al content is preferably 0.03% or less, and more preferably 0.02% or less. On the other hand, the Al content can have any lower limit, but to further improve the Al addition effect, the Al content is preferably 0.01% or more.
    Cr: 0.05% to 2.00% [0070] Cr is an element that has an effect of increasing the hardness in a surface layer and an intermediate thickness position and improving the abrasion resistance. To achieve this effect, the Cr content is adjusted to be 0.05% or more. The Cr content is preferably 0.20% or more, and more preferably 0.25% or more. Per
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    10/33 on the other hand, if the C content exceeds 2.00%, the weldability is reduced. Consequently, the Cr content is 2.00% or less. The Cr content is preferably 1.85% or less, and more preferably 1.80% or less.
    N: 0.0050% or less [0071] N is an element inevitably contained as an unavoidable impurity, but the N content of 0.0050% or less is permissible. Consequently, the N content is 0.0050% or less, and preferably 0.0040% or less. On the other hand, the N content can have any lower limit. The lower limit may be 0%, but in industrial terms, it may be more than 0% due to the fact that, typically, N is an element inevitably contained as a steel impurity.
    O: 0.0050% or less [0072] O is an element inevitably contained as an unavoidable impurity, but an O content of 0.0050% or less is permissible. Consequently, the O content is 0.0050% or less, and preferably 0.0040% or less. On the other hand, the O content can have any lower limit. The lower limit may be 0%, but in industrial terms, it may be more than 0% due to the fact that, typically, O is an element inevitably contained as a steel impurity.
    [0073] An abrasion-resistant steel plate and a steel raw material in one of the modalities have the components mentioned above, the balance being Fe and inevitable impurities.
    [0074] In addition to the basic chemical composition described above, the chemical composition may optionally contain one or more selected from the group consisting of Cu: 0.01% to 2.00%, Ni: 0.01% to 2.00%, Mo: 0.01% to 1.00%, V: 0.01% to 1.00%, W: 0.01% to 1.00%, and Co: 0.01% to 1 , 00%.
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    11/33
    Cu: 0.01% to 2.00% [0075] Cu is an element that has an effect of improving the hardening of the cooling quench and can be optionally added to further improve the hardness of the interior of a steel plate. In the case of addition of Cu, to obtain this effect, the Cu content is adjusted to be 0.01% or more. On the other hand, when the Cu content exceeds 2.00%, the weldability is deteriorated and the costs with alloys are increased. Consequently, in the case of Cu addition, the Cu content is adjusted to be 2.00% or less.
    Ni: 0.01% to 2.00% [0076] Ni is an element that has an effect of improving the quenching hardness as well as with Cu, and can be optionally added to further improve the hardness of the inside of a plate. steel. In the case of adding Ni, to achieve this effect, the Ni content is adjusted to be 0.01% or more. On the other hand, when the Ni content exceeds 2.00%, the weldability is deteriorated and the costs with alloys are increased. Consequently, in the case of adding Ni, the Ni content is adjusted to be 2.00% or less.
    Mo: 0.01% to 1.00% [0077] Mo is an element that has an effect of improving the quenching temperability as well as with Cu, and can be optionally added to further improve the hardness of the interior of a plate. steel. In the case of addition of Mo, to obtain this effect, the Mo content is adjusted to be 0.01% or more. On the other hand, when the Mo content exceeds 1.00%, weldability is deteriorated and costs with alloys are increased. Consequently, in the case of addition of Mo, the Mo content is adjusted to be 1.00% or less.
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    12/33
    V: 0.01% to 1.00% [0078] V is an element that has an effect of improving the quenching hardness as well as with Cu, and can be optionally added to further improve the hardness of the interior of a plate. steel. In the case of adding V, to achieve this effect, the V content is adjusted to be 0.01% or more. On the other hand, when the V content exceeds 1.00%, weldability is deteriorated and costs with alloys are increased. Consequently, in the case of adding V, the V content is adjusted to be 1.00% or less.
    W: 0.01% to 1.00% [0079] W is an element that has an effect of improving the quenching hardness as well as with Cu and can be optionally added to further improve the hardness of the interior of a steel plate . In the case of adding W, to achieve this effect, the W content is adjusted to be 0.01% or more. On the other hand, when the W content exceeds 1.00%, the weldability is deteriorated and the costs with alloys are increased. Consequently, in the case of adding W, the W content is adjusted to be 1.00% or less.
    Co: 0.01% to 1.00% [0080] Co is an element that has an effect of improving the temperability of sudden cooling as well as with Cu, and can be optionally added to further improve the hardness of the interior of a plate steel. In the case of adding Co, to achieve this effect, the Co content is adjusted to be 0.01% or more. On the other hand, when the Co content exceeds 1.00%, weldability is deteriorated and costs with alloys are increased. Therefore, when Co is added, the Co content is adjusted to be 1.00% or less.
    [0081] In other modalities, the chemical composition may optionally contain one or more selected from the group that
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    13/33 consists of Nb: 0.005% to 0.050%, Ti: 0.005% to 0.050%, and B: 0.0001% to 0.0100%.
    Nb: 0.005% to 0.050% [0082] Nb is an element that additionally increases the hardness of a matrix and contributes to further improve the abrasion resistance. In the case of the addition of Nb, to obtain this effect, the Nb content is adjusted to be 0.005% or more. The Nb content is preferably 0.007% or more. On the other hand, when the Nb content exceeds 0.050%, a large amount of NbC is precipitated, thus reducing workability. Consequently, in the case of Nb addition, the Nb content is 0.050% or less. The Nb content is preferably 0.040% or less, and more preferably 0.030% or less.
    Ti: 0.005% to 0.050% [0083] Ti is an element that has a strong tendency to form nitride and has an N-fixing effect to decrease solute N. Therefore, the addition of Ti can improve the toughness of a base metal and a welded portion. Additionally, in the case of addition of both Ti and B, Ti fixes N to thereby prevent the precipitation of BN, thus improving an effect of B that increases the temperability of sudden cooling. To obtain these effects, in the case of Ti addition, the Ti content is adjusted to be 0.005% or more. The Ti content is preferably 0.012% or more. On the other hand, if the Ti content exceeds 0.050%, a large amount of TiC is precipitated, thus reducing workability. Consequently, when Ti is contained, the Ti content is adjusted to be 0.050% or less. The Ti content is preferably 0.040% or less, and more preferably 0.030% or less.
    B: 0.0001% to 0.0100% [0084] B is an element that has an effect of significant improvement in the temperability of sudden cooling even with an addition
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    14/33 of a trace amount of B. Therefore, the addition of B can facilitate the formation of martensite, further improving the abrasion resistance. To achieve this effect, in the case of the addition of B, the B content is adjusted to be 0.0001% or more. The B content is preferably 0.0005% or more, and more preferably 0.0010% or more. On the other hand, when the B content exceeds 0.0100%, weldability is reduced. Consequently, in the case of the addition of B, the B content is 0.0100% or less. The B content is preferably 0.0050% or less, and more preferably 0.0030% or less.
    [0085] In other modalities, the chemical composition may optionally contain one or more selected from the group consisting of Ca: 0.0005% to 0.0050%, Mg: 0.0005% to 0.0050% , and REM: 0.0005% to 0.0080%.
    Ca: 0.0005% to 0.0050% [0086] Ca is an element that combines with S and has an effect of preventing the formation of, for example, MnS that extends a lot in one lamination direction. Therefore, the addition of Ca can provide morphological control in sulfide inclusions so that the sulfide inclusions can be spherical in shape, further improving the toughness of a welded portion and the like. To achieve this effect, in the case of Ca addition, the Ca content is adjusted to be 0.0005% or more. On the other hand, when the Ca content exceeds 0.0050%, the cleaning of steel is reduced. The decrease in cleaning causes deterioration of surface characteristics due to an increase in surface defects and a decrease in bend workability. Consequently, in the case of Ca addition, the Ca content is 0.0050% or less.
    Mg: 0.0005% to 0.0050% [0087] Mg is an element that combines with S as well as Ca, and has an effect of preventing the formation of, for example, MnS that extends too much in a direction of lamination. Therefore, adding
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    15/33
    Mg can provide morphological control in sulfide inclusions so that the sulfide inclusions can be spherical in shape, further improving the toughness of a welded portion and the like. To achieve this effect, in the case of adding Mg, the Mg content is adjusted to be 0.0005% or more. On the other hand, when the Mg content exceeds 0.0050%, the cleaning of steel is reduced. The decrease in cleaning causes deterioration of surface characteristics due to an increase in surface defects and a decrease in bend workability. Consequently, in the case of adding Mg, the Mg content is 0.0050% or less.
    REM: 0.0005% to 0.0080% [0088] REM (rare earth metal) is an element that combines with S as well as Ca and Mg, and has an effect of preventing the formation of, for example, MnS that extends far in a rolling direction. Therefore, the addition of REM can provide morphological control in sulfide inclusions so that the sulfide inclusions can be spherical in shape, further improving the toughness of a welded portion and the like. To achieve this effect, in the case of adding REM, the REM content is adjusted to be 0.0005% or more. On the other hand, when the REM content exceeds 0.0080%, steel cleaning is reduced. The decrease in cleaning causes deterioration of surface characteristics due to an increase in surface defects and a decrease in bend workability. Consequently, in the case of adding REM, the REM content is 0.0080% or less.
    [0089] In other words, the abrasion-resistant steel plate and the steel raw material used to manufacture the abrasion-resistant steel plate may have the following chemical composition.
    [0090] In mass%, the chemical composition contains [0091] C: 0.23% to 0.34%, [0092] Si: 0.05% to 1.00%,
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    16/33 [0093] Μη: 0.30% to 2.00%, [0094] Ρ: 0.020% or less, [0095] S: 0.020% or less, [0096] Al: 0.04% or less, [0097] Cr: 0.05% to 2.00%, [0098] N: 0.0050% or less, [0099] O: 0.0050% or less, [00100] optionally, one or more selected from of the group consisting of Cu: 0.01% to 2.00%, Ni: 0.01% to 2.00%, Mo: 0.01% to 1.00%, V: 0.01% to 1, 00%, W: 0.01% to 1.00%, and Co: 0.01% to 1.00%, [00101] optionally, one or more selected from the group consisting of Nb: 0.005% to 0.050 %, Ti: 0.005% to 0.050%, and B: 0.0001% to 0.0100%, and [00102] optionally, one or more selected from the group consisting of Ca: 0.0005% to 0.0050 %, Mg: 0.0005% to 0.0050%, and REM: 0.0005% to 0.0080%, [00103] the balance being Fe and inevitable impurities.
    [00104] DF: 120 or more [00105] Dl * defined by the following Formula (1) is an index that indicates the sudden cooling temperability. As the value of Dl * is increased, the hardness is increased at the intermediate thickness position of a steel plate after abrupt cooling. To ensure central hardness in thick abrasion resistant steel, Dl * must be 120 or more. On the other hand, Dl * can have any upper limit, but when Dl * is too high, weldability is deteriorated. Therefore, D1 * is preferably 300 or less and, more preferably, 250 or less.
    Dl * = 33.85 x (0.1 x C) 0 5 x (0.7 x Si + 1) x (3.33 x Mn + 1) x (0.35 x Cu + 1) x (0, 36 x Ni + 1) x (2.16 x Cr + 1) x (3 x Mo + 1) x (1.75 x V + 1) x (1.5 x W + 1) (1)
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    17/33 where each element symbol in Formula (1) indicates a content, in mass%, of a corresponding element and is taken to be 0 when the corresponding element is not contained. SURFACE HARDNESS
    HBi: 360 HBW10 / 3000 to 490 HBW10 / 3000 [00106] The abrasion resistance of a steel plate can be improved by increasing the hardness in a surface layer of the steel plate. When the hardness on a surface layer of a steel plate is less than 360 HBW at Brinell hardness, sufficient abrasion resistance cannot be achieved. Therefore, the Brinell hardness at a depth of 1 mm from an abrasion resistant steel plate (HBi) surface is 360 HBW or more. On the other hand, when HBi is greater than 490 HBW, workability is deteriorated. Therefore, HBi is 490 HBW or less.
    REASON FOR HARDNESS
    HB1 / 2 / HB1: 75% or more [00107] As described above, so that a steel plate can exhibit excellent abrasion resistance in a harsh operating environment, in which a steel plate is worn close to its intermediate thickness part , and can have a long service life, the steel plate must have high hardness not only in its surface layer, but also in its intermediate thickness part. Therefore, our abrasion-resistant steel plate has a hardness ratio, HB1 / 2 to HBi, of 75% or more (HB1 / 2 / HB1> 0.75), where HB1 / 2 is a Brinell hardness in the intermediate thickness of the abrasion-resistant steel plate. As used in this document, the hardness ratio is HB1 / 2 / HB1 x 100 (%). The hardness ratio is preferably 80% or more. On the other hand, the hardness ratio can have any upper limit, but HB1 / 2 is typically HB1 or less, and thus the hardness ratio is 100% or less (HB1 / 2 / HB1 <1).
    Petition 870190082861, of 26/08/2019, p. 33/54
    18/33 [00108] Methods for achieving a hardness ratio of 75% or more, on an abrasion-resistant steel plate with a plate thickness of 50 mm or more, include a method in which a large amount of alloy is added to generate a large amount of martensite equally in a part of intermediate thickness, thus increasing the hardness. However, the method uses a large number of expensive alloying elements, thereby significantly increasing costs. Our abrasion-resistant steel plate can have a hardness ratio of 75% or more when subjecting a steel plate, which has the chemical composition mentioned above, to tempering heat treatment under the following specific conditions. The steel plate does not contain a large amount of alloying elements and is manufactured at low cost, but even so, as described above, it has a hardness ratio roughly equivalent to that yielded in the case where a large quantity of alloying elements is used.
    [00109] Brinell hardness (ΗΒι, HB1 / 2) is a value measured under a load of 3000 Kgf using a hard tungsten sphere with a diameter of 10 mm (HBW10 / 3000). Brinell's hardness can be measured by a method described in the Examples.
    PLATE THICKNESS
    Plate thickness: 50 mm or more [00110] The abrasion-resistant steel plate can guarantee hardness in an intermediate thickness part with a small amount of alloying elements, thus reducing the cost of the abrasion-resistant steel plate. When the plate thickness is less than 50 mm, however, conventional techniques can achieve sufficient internal hardness with a small amount of alloying elements. Therefore, our cost-saving effect is particularly noticeable when the plate thickness is 50 mm or more. So the plate thickness of the plate
    Petition 870190082861, of 26/08/2019, p. 34/54
    19/33 abrasion resistant steel is 50 mm or more. On the other hand, the plate thickness can have any upper limit, but in terms of manufacture, the plate thickness is preferably 100 mm or less. MANUFACTURING METHOD [00111] The following describes a method for making an abrasion resistant steel plate according to one of the modalities. The abrasion-resistant steel plate can be manufactured by heating a steel raw material that has the chemical composition mentioned above, hot rolling the steel raw material, and subsequently subjecting the steel raw material to treatment thermal which includes rough cooling and tempering under the following conditions.
    STEEL RAW MATERIAL [00112] The steel raw material can be manufactured by any method, but, for example, it can be manufactured from molten steel that has the chemical composition mentioned above through a conventional steelmaking process and when submitting casting steel. The steelmaking process can be carried out by any method using a converter steelmaking process, an electric steelmaking process, an induction heating process and the like. The casting is preferably carried out by continuous casting in terms of productivity, but it can also be carried out by ingot casting and roughing. As the raw material of steel, for example, a steel plate can be used.
    HEATING [00113] The steel raw material obtained is heated up to the heating temperature before hot rolling. The steel raw material obtained by a method such as casting can be cooled once before heating, or it can be directly heated without cooling.
    Petition 870190082861, of 26/08/2019, p. 35/54
    20/33 [00114] The heating temperature is not limited, but when the heating temperature is 900 ° C or more, the deformation resistance of the steel raw material is lowered to reduce a load on a rolling mill during cold rolling. hot, thus facilitating hot rolling. Therefore, the heating temperature is preferably 900 ° C or more, more preferably 950 ° C or more, and even more preferably 1100 ° C or more. On the other hand, when the heating temperature is 1250 ° C or less, oxidation of the steel is prevented to reduce the loss due to oxidation, resulting in further improvement in the throughput rate. Therefore, the heating temperature is preferably 1250 ° C or less, more preferably 1200 ° C or less, and even more preferably 1150 ° C or less.
    HOT LAMINATION [00115] The heated steel raw material is then hot rolled on a hot rolled steel plate with a plate thickness of 50 mm or more. Hot rolling has no particular conditions and can be carried out by a conventional method, but when the rolling temperature is 850 ° C or more, the deformation resistance of the steel raw material is lowered to reduce a load on a rolling mill during hot rolling, thereby facilitating hot rolling. Therefore, the lamination temperature is preferably 850 ° C or more and, more preferably, 900 ° C or more. On the other hand, when the rolling temperature is 1000 ° C or less, oxidation of the steel is prevented to reduce the loss due to oxidation, resulting in further improvement in the yield rate. Therefore, the laminating temperature is preferably 1000 ° C or less and, more preferably, 950 ° C or less.
    BRUSH COOLING [00116] The obtained hot-rolled steel plate is then cooled abruptly to a temperature of onset of cooling
    Petition 870190082861, of 26/08/2019, p. 36/54
    21/33 sudden for a final temperature of sudden cooling. The blast cooling can be direct blast cooling (DQ) or blast reheating cooling (RQ). Sudden cooling can be accomplished by any method of cooling, but sudden cooling is preferably performed with water. As used herein, the temperature of the start of the sudden cooling is a temperature of a surface of a steel plate at the beginning of the sudden cooling. The temperature of onset of sudden cooling can simply be referred to as the temperature of sudden cooling. In addition, the final temperature of sudden cooling is a temperature of a surface of a steel plate at the end of the sudden cooling. For example, when rough cooling is performed by means of water cooling, the temperature at the beginning of the water cooling is a temperature of the beginning of the sudden cooling, and the temperature at the end of the water cooling is a final temperature of the sudden cooling.
    DIRECT BRUSH COOLING [00117] When brisk cooling is direct brisk cooling, after hot rolling, the hot rolled steel plate is briskly cooled without reheating. At such an instant, the temperature of onset of sudden cooling is the transformation point Ars or higher. This is due to the sudden cooling being initiated from an austenite state to obtain a martensite structure. When the temperature of onset of sudden cooling is lower than the Ars transformation point, the hardening is insufficient so that the steel plate cannot be properly improved, thus reducing the abrasion resistance of a steel plate obtained finally. On the other hand, the temperature of the start of the sudden cooling may have any upper limit on the direct cooling, but the temperature of the beginning of the sudden cooling is preferably
    Petition 870190082861, of 26/08/2019, p. 37/54
    22/33
    950 ° C or less. The final temperature of sudden cooling will be discussed later.
    [00118] The Ar 3 transformation point is determined by the following Formula (3):
    Ar 3 ( Q C) = 910 - 273 x C - 74 x Mn - 57 x Ni - 16 x Cr - 9 x Mo - 5 x Cu (3) where each element symbol in Formula (3) indicates a content, in mass%, of a corresponding element and is taken to be 0 when the corresponding element is not contained. BREAKTHROUGH COOLING [00119] When rough cooling is sudden reheating cooling, after hot rolling is complete, the hot rolled steel plate is reheated and then abruptly cooled. At such an instant, the temperature of onset of sudden cooling is the transformation point Ac 3 or greater. This is due to the sudden cooling being initiated from an austenite state to obtain a martensite structure. When the temperature of the onset of sudden cooling is less than the transformation point Ac 3 , the hardening is insufficient so that the steel plate cannot have the hardness improved properly, thus reducing the abrasion resistance of a steel plate finally obtained. On the other hand, the starting temperature of the sudden cooling has any upper limit on the sudden cooling of reheating, but the starting temperature of the sudden cooling is preferably 950 ° C or less. The final temperature of sudden cooling will be discussed later.
    [00120] The transformation point Ac 3 is determined by the following Formula (4):
    Ac 3 ( q C) = 912.0 - 230.5 x C + 31.6 x Si - 20.4 x Mn - 39.8 x Cu - 18.1 x Ni - 14.8 x Cr + 16.8 x Mo (4)
    Petition 870190082861, of 26/08/2019, p. 38/54
    23/33 where each element symbol in Formula (4) indicates a content, in mass%, of a corresponding element and is taken to be 0 when the corresponding element is not contained. AVERAGE COOLING RATE [00121] Sudden cooling has no particular cooling rate. The cooling rate can be any value that allows a martensite phase to be formed. For example, the average cooling rate from the beginning of the blast cooling to the end of the blast cooling is preferably 20 ° C / s or more, and more preferably 30 ° C / s or more. In addition, the average cooling rate is preferably 70 ° C / s or less, and more preferably 60 ° C / s or less. The average cooling rate is determined by using a temperature of a steel plate surface.
    FINAL COOLING TEMPERATURE [00122] The sudden cooling process can have any final cooling temperature that generates martensite, but when the final cooling temperature is Mf or lower, the rate of a martensite structure is increased to further improve the hardness of the steel plate. Therefore, the final cooling temperature is preferably the temperature of Mf or less. On the other hand, the final cooling temperature can have any lower limit, but the final cooling temperature is preferably 50 ° C or more, due to the fact that an unnecessarily long cooling time decreases manufacturing efficiency. The Mf temperature can be determined from the following Formula (5)
    Mf ( Q C) = 410.5 - 407.3 x C - 7.3 x Si - 37.8 x Mn - 20.5 x Cu - 19.5 x Ni - 19.8 x Cr - 4.5 x Mo (5) where each element symbol in Formula (5) indicates a
    Petition 870190082861, of 26/08/2019, p. 39/54
    24/33 content, in mass%, of a corresponding element and is taken to be 0 when the corresponding element is not contained.
    TEMPERING [00123] After the sudden cooling is completed, the hot-rolled steel plate cooled down is reheated to a tempering temperature. The abruptly cooled steel plate is tempered by reheating. At such an instant, the quenching is carried out under conditions such that a value of P is 1.20 x 10 4 to 1.80 x 10 4 to obtain, in this way, the prescribed hardness in the surface layer and in the intermediate thickness part, the value of P being defined by the following Formula (2):
    P = (T + 273) x (21.3 - 5.8 x C + log (60 xt)) (2) where, C indicates the C content (in% by mass) in the steel plate, T indicates the quench temperature ( Q C), et indicates the retention time (min) in the quench.
    [00124] When the value of P is less than 1.20 x 10 4 , the quench is insufficient so that the hardness of one of the surface layer and the position of intermediate thickness, or both, cannot be in one desired track. On the other hand, when the value of P goes beyond 1.80 x 10 4 , the hardness in the surface layer is significantly reduced and, therefore, does not reach a prescribed value.
    [00125] When the heating temperature T is too low, manufacturing efficiency is decreased. Therefore, the heating temperature T is desirably 200 ° C or more. When the heating temperature T is too high, the heat treatment costs are increased. Therefore, the heating temperature T is preferably 600 ° C or less.
    [00126] In terms of manufacturing efficiency and heat treatment costs, the retention time t is preferably 180 minutes
    Petition 870190082861, of 26/08/2019, p. 40/54
    25/33 or less, more preferably 100 minutes or less and, even more preferably, 60 minutes or less. On the other hand, considering the uniformity of a microstructure, the retention time t is preferably 5 minutes or more.
    [00127] Tempering can be performed by any method, such as heating with a heat treatment oven, high frequency induction heating and electrical resistance heating.
    EXAMPLES [00128] Below, a more detailed description is given based on the Examples. The following Examples merely represent preferred examples, and the description is not limited to those Examples.
    [00129] Firstly, steel plates (steel raw material) that have the chemical composition listed in Table 1 were manufactured by continuous casting.
    [00130] Then, the obtained steel plates were subjected, sequentially, to heating, hot rolling, sudden cooling (direct sudden cooling or sudden reheating cooling) and tempering to obtain steel plates. Table 2 lists the treatment conditions for each process. The plate thickness listed in the Hot Rolling Column is a plate thickness of an abrasion resistant steel plate obtained at last.
    [00131] The blast cooling was direct blast cooling or blast reheating cooling. In direct blast cooling, the hot-rolled steel plate was directly subjected to blast cooling by water cooling. In the sudden reheat cooling, the hot-rolled steel plate was cooled with air, then heated to a prescribed reheat temperature and subsequently cooled down sharply by water cooling. The cooling with water in the sudden cooling was accomplished by passing the hot-rolled steel plate while it is sprayed
    Petition 870190082861, of 26/08/2019, p. 41/54
    26/33 a high rate of water flow on the front and back surfaces of the steel plate. The cooling rate in sudden cooling was an average cooling rate of 650 ° C to 300 ° C, which was determined by calculating heat transfer. Cooling was carried out to 300 ° C or less.
    [00132] In each of the steel plates obtained, the Brinell hardness and the microstructure in the 1 mm depth position from the surface of the steel plate and in the intermediate thickness position (position 1/2 t) of the steel plate steel were evaluated by the following method. The evaluation results are listed in Table 2.
    HARDNESS (BRINELL HARDNESS) [00133] As an index of resistance to abrasion, the hardness was measured in the surface layer and in the intermediate thickness part of each steel plate. Test pieces used for the measurement were taken from each steel plate obtained, as described above, so that the depth position of 1 mm from the surface of each steel plate and the position of intermediate thickness of it can be surfaces of test. The test surfaces of the test pieces were polished like mirrors, and then measured for Brinell hardness, according to JIS Z2243 (2008). The measurement used a hard tungsten sphere with a diameter of 10 mm under a load of 3,000 Kgf.
    MICROSTRUCTURE [00134] The test pieces for observation of the microstructure were taken from each steel plate obtained, and were polished and engraved (nital engraving solution). The microstructure was imaged at a position of 1 mm from the surface and from the position of intermediate thickness using an optical microscope (400 x magnification). The images obtained were submitted to image interpretation to identify each phase. At least five fields have been imagined. For
    Petition 870190082861, of 26/08/2019, p. 42/54
    27/33 the microstructure of the surface layer, a phase that accounts for 95% or more of the area fraction is listed as a main phase in Table 2.
    Petition 870190082861, of 26/08/2019, p. 43/54
    TABLE 1
    Steel SampleID Chemical composition (% by mass) * Dl * Ar3(° C) Ac3(° C) Mf(° C) Classification Ç Si Mn P s Al Cr N O Ass Ni Mo V w Co Nb You B Here Mg REM THE 0.28 0.25 1.55 0.011 0.0033 0.026 0.98 0.0027 0.0029 - - - - - - - - - - - - 128 703 809 217 Forming steel B 0.29 0.38 0.88 0.007 0.0024 0.021 1.03 0.0019 0.0019 0.55 1.55 - - - - - - - - - - 172 658 774 194 Forming steel Ç 0.27 0.55 1.92 0.007 0.0019 0.029 0.30 0.0030 0.0024 - - 0.38 - - - - 0.015 0.0012 - - - 201 686 830 216 Forming steel D 0.30 0.96 0.73 0.012 0.0033 0.015 0.78 0.0023 0.0019 - - 0.48 - - - - - - 0.0031 - - 220 757 855 236 Forming steel AND 0.33 0.19 0.33 0.015 0.0021 0.027 1.44 0.0021 0.0020 - 1.24 0.50 - - - - - - - - - 217 697 800 207 Forming steel F 0.26 0.56 1.67 0.012 0.0012 0.026 1.34 0.0025 0.0022 - - - 0.03 0.03 - - - - - - - 214 694 816 211 Forming steel G 0.28 0.63 1.38 0.005 0.0023 0.021 1.31 0.0020 0.0038 - 1.00 - - - 1.00 - - - - - - 238 653 802 194 Forming steel H 0.24 0.23 1.23 0.006 0.0007 0.028 1.97 0.0029 0.0022 - - - 0.03 0.03 - 0.012 0.015 0.0011 - - - 179 722 810 226 Forming steel 1 0.27 0.72 0.45 0.005 0.0030 0.031 1.39 0.0029 0.0020 0.31 0.34 0.39 - - - - - - - 0.0028 - 226 756 831 236 Forming steel J 0.28 0.17 1.28 0.015 0.0013 0.034 0.72 0.0019 0.0034 - - 0.48 - - - 0.013 0.013 0.0012 - - 0.0032 208 723 824 230 Forming steel K 0.36 0.42 1.46 0.012 0.0006 0.016 0.33 0.0023 0.0029 - 1.55 - - - - - 0.014 0.0013 - - - 130 610 780 169 Comparative steel L 0.20 0.78 1.98 0.007 0.0040 0.024 1.55 0.0021 0.0028 - - - - - - 0.011 0.012 0.0011 - - - 244 684 827 218 Comparative steel M 0.28 0.38 1.27 0.012 0.0023 0.019 0.48 0.0021 0.0019 - 0.23 0.13 - - - - 0.011 0.0012 - - - 115 718 824 231 Comparative steel N 0.23 0.25 1.02 0.006 0.0007 0.028 0.98 0.0029 0.0022 - 0.98 0.21 - - - - - - - - - 182 698 817 237 Forming steel 0 0.34 0.24 0.98 0.007 0.0008 0.027 1.03 0.0027 0.0019 - 1.02 0.22 - - - - - - - - - 227 668 791 192 Forming steel
    28/33 * The balance is Fe and unavoidable impurities
    Petition 870190082861, of 26/08/2019, p. 44/54
    TABLE 2
    No. Steel SampleID Manufacturing conditions Thickness ofSteel plate(mm) Heating Hot rolling Direct blast cooling TemperatureHeating° C) Lamination Finishing Temperature(° C) Plate Thicknessmm) Cooling Method Sudden cooling start temperature(° C) Final temperature of sudden cooling(° C) Cooling Rate(° C / s) 1 THE 250 1120 880 50 Air cooling - - - 2 THE 250 1120 880 50 Air cooling - - - 3 THE 250 1120 880 50 Air cooling - - - 4 THE 250 1120 880 50 Air cooling - - - 5 THE 250 1120 890 50 Air cooling - - - 6 B 250 1120 880 75 Water cooling 850 150 35 7 B 250 1120 890 75 Water cooling 850 190 40 8 B 250 1120 880 75 Water cooling 850 50 30 9 B 250 1120 880 75 Water cooling 850 170 35 10 B 250 1120 880 75 Water cooling 860 100 30
    29/33
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    TABLE 2 (Continued)
    No. Steel SampleID Manufacturing conditions Evaluation results Classification Abrupt cooling of reheating Hardening Depth 1 mm Average thickness Hardness ratio(%) Classification Reheat temperature(° C) Retention time(min) Cooling method Final temperature of sudden cooling(° C) Cooling rate(° C / s) Heating temperature(° C) Retention time(min) P / 10 4 HBi(HBW10/3000) Microstructure *(main phase) HBl / 2(HBW10/3000) Microstructure * 1 THE 900 10 Water cooling 150 40 450 10 1.62 399 TM 336 TB + TM 84 Example 2 THE 880 5 Water cooling 200 50 500 20 176 368 TM 304 TB + TM 83 Example 3 THE 910 10 Water cooling 50 40 300 1 1.23 489 TM 414 TB + TM 85 Example 4 THE 880 10 Water cooling 160 45 550 5 1.82 353 TM 289 TB + TM 82 Ex. Comp. 5 THE 900 5 Water cooling 130 45 250 10 1.17 502 TM 414 TB + TM 82 Ex. Comp. 6 B - - - - - 400 10 1.51 429 TM 354 TB + TM 83 Example 7 B - - - - - 500 20 175 373 TM 296 TB + TM 79 Example 8 B - - - - - 300 1 1.23 494 TM 394 TB + TM 80 Example 9 B - - - - - 550 10 1.84 352 TM 274 TB + TM 78 Ex. Comp. 10 B - - - - - 250 10 1.17 507 TM 394 TB + TM 78 Ex. Comp.
    30/33 * M: martensite, TM: tempered martensite, B: bainite, TB: tempered bainite
    Petition 870190082861, of 26/08/2019, p. 46/54
    TABLE 2 (Continued)
    No. Steel SampleID Manufacturing conditions Thickness ofSteel plate(mm) Heating Hot rolling Direct blast cooling TemperatureHeating° C) Lamination finish temperature (° C) Plate Thicknessmm) Cooling Method Sudden cooling start temperature(° C) Final temperature of sudden cooling(° C) Cooling Rate(° C / s) 11 Ç 300 1150 890 100 Air cooling - - - 12 D 300 1120 890 100 Air cooling - - - 13 AND 300 1120 880 100 Air cooling - - - 14 F 300 1120 890 100 Air cooling - - - 15 G 300 1120 890 100 Air cooling - - - 16 H 300 1180 880 100 Air cooling - - - 17 I 300 1120 890 100 Air cooling - - - 18 J 300 1180 890 100 Air cooling - - - 19 K 250 1150 890 50 Air cooling - - - 20 L 250 1180 890 50 Air cooling - - - 21 M 250 1150 880 100 Air cooling - - - 22 N 250 1120 880 50 Air cooling - - - 23 0 250 1120 880 50 Air cooling - - -
    31/33
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    TABLE 2 (Continued)
    No. Steel SampleID Manufacturing conditions Evaluation results Classification Abrupt cooling of reheating Hardening Depth 1 mm Average thickness Hardness ratio(%) Classification Reheat temperature(° C) Retention time(min.) Cooling method Final temperature of sudden cooling(° C) Cooling rate(° C / s) Heating temperature(° C) Retention time(min.) P / 10 4 HBi(HBW10/3000) Microstructure *(main phase) HBl / 2(HBW10/3000) Microstructure* 11 Ç 880 10 Water cooling 50 25 400 5 1.49 424 TM 336 TB + TM 79 Example 12 D 910 10 Water cooling 70 25 350 10 1.39 460 TM 374 TB + TM 81 Example 13 AND 850 10 Water cooling 160 30 500 5 1.69 403 TM 308 TB + TM 77 Example 14 F 880 10 Water cooling 110 30 400 30 1.55 408 TM 325 TB + TM 80 Example 15 G 910 10 Water cooling 190 30 450 10 1.62 399 TM 322 TB + TM 81 Example 16 H 900 10 Water cooling 180 30 500 5 1.73 359 TM 265 TB + TM 74 Example 17 I 910 10 Water cooling 80 25 450 5 1.61 399 TM 319 TB + TM 80 Example 18 J 900 5 Water cooling 130 30 400 20 1.53 420 TM 332 TB + TM 79 Example 19 K 900 5 Water cooling 180 50 300 10 1.26 514 TM 440 TB + TM 86 Ex. Comp. 20 L 860 5 Water cooling 120 40 500 5 1.75 339 TM 335 TB + TM 99 Ex. Comp. 21 M 900 5 Water cooling 110 40 500 5 1.71 378 TM 253 TB + TM 67 Ex. Comp. 22 N 910 10 Water cooling 50 50 250 20 1.21 475 TM 436 TB + TM 92 Example 23 0 910 10 Water cooling 50 50 250 20 1.17 526 TM 495 TB + TM 94 Ex. Comp.
    32/33 * M: martensite, TM: tempered martensite, B: bainite, TB: tempered bainite
    Petition 870190082861, of 26/08/2019, p. 48/54
    33/33 [00135] As can be seen from Tables 1 and 2, the Examples are abrasion-resistant steel plates with a plate thickness of 50 mm or more, which each have a Brinell hardness of 360 HBW10 / 3000 to 490 HBW10 / 3000 at a depth of 1 mm from a surface of the same, and have, in the intermediate thickness part, a Brinell hardness of 75% or more of the Brinell hardness at a depth of 1 mm from a surface. On the other hand, Comparative Examples that do not satisfy the tempering conditions are different from the Examples in the hardness of the surface layer or the interior. In addition, Comparative Examples that do not satisfy the conditions of the C content do not have a hardness of the surface layer that satisfies the conditions. In addition, steel plate sample No. 22 does not have Dl * within the scope of the description, and has a hardness ratio of 75% or less.
    权利要求:
    Claims (8)
    [1]
    1. Abrasion resistant steel plate characterized by the fact that it has a chemical composition that contains, in% by mass,
    C: 0.23% to 0.34%,
    Si: 0.05% to 1.00%,
    Mn: 0.30% to 2.00%,
    P: 0.020% or less,
    S: 0.020% or less,
    Al: 0.04% or less,
    Cr: 0.05% to 2.00%,
    N: 0.0050% or less, and
    O: 0.0050% or less, the balance being Fe and inevitable impurities, the chemical composition having a Dl * value of 120 or more, where Dl * is defined by the following Formula (1):
    Dl * = 33.85 x (0.1 x C) 0 5 x (0.7 x Si + 1) x (3.33 x Mn + 1) x (0.35 x Cu + 1) x (0, 36 x Ni + 1) x (2.16 x Cr + 1) x (3 x Mo + 1) x (1.75 xV + 1) x (1.5xW + 1) (1) where each element symbol in Formula (1) indicates a content, in% by mass, of a corresponding element and is taken to be 0 when the corresponding element is not contained, in which the abrasion resistant steel plate has HBi from 360 HBW10 / 3000 to 490 HBW10 / 3000, where HBi is a Brinell hardness at a depth of 1 mm from an abrasion resistant steel plate surface, where the abrasion resistant steel plate has a hardness ratio of 75% or more, where the hardness ratio is defined as a ratio of HB1 / 2 to HB1, and HB1 / 2 is a Brinell hardness in an intermediate thickness position of the abrasion resistant steel plate, and
    Petition 870190082861, of 26/08/2019, p. 50/54
    [2]
    2/4 where the abrasion resistant steel plate has a plate thickness of 50 mm or more.
    2. Abrasion-resistant steel plate, according to claim 1, characterized by the fact that the chemical composition also contains, in% by mass, one or more selected from the group consisting of
    Cu: 0.01% to 2.00%,
    Ni: 0.01% to 2.00%,
    Mo: 0.01% to 1.00%,
    V: 0.01% to 1.00%,
    W: 0.01% to 1.00%, and
    Co: 0.01% to 1.00%.
    [3]
    3. Abrasion-resistant steel plate according to claim 1 or 2, characterized by the fact that the chemical composition also contains, in% by mass, one or more selected from the group consisting of
    Nb: 0.005% to 0.050%,
    Ti: 0.005% to 0.050%, and
    B: 0.0001% to 0.0100%.
    [4]
    4. Abrasion-resistant steel plate according to any one of claims 1 to 3, characterized by the fact that the chemical composition also contains, in mass%, one or more selected from the group consisting of
    Ca: 0.0005% to 0.0050%,
    Mg: 0.0005% to 0.0050%, and
    REM: 0.0005% to 0.0080%.
    [5]
    5. Method for making an abrasion-resistant steel plate characterized by the fact that it comprises:
    heat a steel raw material to a heating temperature, the steel raw material having a composition
    Petition 870190082861, of 26/08/2019, p. 51/54
    3/4 chemistry that contains, in% by mass,
    C: 0.23% to 0.34%,
    Si: 0.05% to 1.00%,
    Mn: 0.30% to 2.00%,
    P: 0.020% or less,
    S: 0.020% or less,
    Al: 0.04% or less,
    Cr: 0.05% to 2.00%,
    N: 0.0050% or less, and
    O: 0.0050% or less, the balance being Fe and unavoidable impurities;
    hot-rolling the steel raw material heated on a hot-rolled steel plate with a plate thickness of 50 mm or more;
    subjecting the hot-rolled steel plate to sudden cooling, the sudden cooling being either direct sudden cooling or sudden reheating cooling, with the direct sudden cooling having a temperature of onset of sudden cooling of an Ars transformation point or higher, and the reheat blast has a temperature of onset of blast cooling from an Acs transformation point or higher; and subjecting the hot-rolled steel plate, after sudden cooling, to tempering under a condition such that a value of P is 1.20 x 10 4 to 1.80 x 10 4 , the value of P being defined by the following Formula (2):
    P = (T + 273) x (21.3 - 5.8 x C + log (60 xt)) (2), where, in Formula (2), C indicates a C content contained in the steel plate and expressed in mass%, T indicates a temperature
    Petition 870190082861, of 26/08/2019, p. 52/54
    4/4 quench expressed in ° C, and t indicates a quench retention time expressed in minutes.
    [6]
    6. Method for making an abrasion-resistant steel plate, according to claim 5, characterized by the fact that the chemical composition also contains, in% by mass, one or more selected from the group consisting of
    Cu: 0.01% to 2.00%,
    Ni: 0.01% to 2.00%,
    Mo: 0.01% to 1.00%,
    V: 0.01% to 1.00%,
    W: 0.01% to 1.00%, and
    Co: 0.01% to 1.00%.
    [7]
    7. Method for making an abrasion-resistant steel plate, according to claim 5 or 6, characterized by the fact that the chemical composition also contains, in mass%, one or more selected from the group consisting of
    Nb: 0.005% to 0.050%,
    Ti: 0.005% to 0.050%, and
    B: 0.0001% to 0.0100%.
    [8]
    8. Method for manufacturing an abrasion-resistant steel plate according to any one of claims 5 to 7, characterized by the fact that the chemical composition also contains, in mass%, one or more selected from the group that consisting of
    Ca: 0.0005% to 0.0050%,
    Mg: 0.0005% to 0.0050%, and
    REM: 0.0005% to 0.0080%.
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    公开号 | 公开日
    US11060172B2|2021-07-13|
    AU2018236313B2|2020-09-10|
    KR102250916B1|2021-05-11|
    EP3597784A4|2020-02-26|
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    KR20190113872A|2019-10-08|
    EP3597784B1|2021-03-31|
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    法律状态:
    2021-10-13| B350| Update of information on the portal [chapter 15.35 patent gazette]|
    优先权:
    申请号 | 申请日 | 专利标题
    JP2017047263|2017-03-13|
    JP2017-047263|2017-03-13|
    PCT/JP2018/003685|WO2018168248A1|2017-03-13|2018-02-02|Abrasion-resistant steel sheet and method for producing abrasion-resistant steel sheet|
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