Steel plate

Abstract

To provide a steel plate with excellent resistance to corrosion and wear as well as excellent ductility.SOLUTION: A steel plate comprises, in mass%, C: 0.10% or more and less than 0.24%, Si: 0.05% or more and 1.00% or less, Mn: 0.10% or more and 2.00% or less, P: 0.030% or less (excluding 0%), S: 0.0300% or less (excluding 0%), Al: 0.005% or more and 0.100% or less, Cr: 3.00% or more and 11.50% or less, with the balance being Fe and inevitable impurities, where its surface hardness is 370 or more and 475 or less, measured by Brinell hardness HBW10 / 3000.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a steel plate. In particular, the present invention relates to a steel plate used for members that require wear resistance in industrial machines, transportation equipment, etc., and more particularly to a steel plate having excellent corrosion and wear resistance in an acidic corrosive environment such as a coal mining environment.

Background Art

[0002] Members of industrial machines such as power shovels, bulldozers, hoppers, buckets, dump trucks, conveyors, and transportation equipment are worn by contact with earth and sand, ore, coal, etc. For this reason, thick steel plates having excellent wear resistance are used for the purpose of extending the life of the members. The actual use environments of industrial machines, transportation equipment, etc. are in various states such as dry and wet, and when used in a wet state, they often contain corrosive substances. It is known that corrosion wear in such an environment is very severe. In particular, in a coal mining environment, the leachate from coal may be acidic, and in such a case, the corrosion wear becomes even more severe. Therefore, there has been a demand for a steel plate having excellent corrosion and wear resistance with both corrosion resistance and wear resistance.

[0003] In response to such demands, for example, in Patent Document 1, a thick steel plate having excellent wear resistance in a corrosive environment having a composition of C: 0.18 to 0.25%, Si: 0.05 to 1.00%, Mn: 0.10 to 2.00%, P: 0.020% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.05 to 2.00%, Nb: 0.005 to 0.100%, Ti: 0.005 to 0.100%, W: 0.05 to 1.00% by mass, and containing one or more of Mo, Cu, Ni, V, B, REM, Ca, Mg as required is disclosed. In Patent Document 1, the wear resistance is evaluated using an aqueous NaCl solution as the corrosive environment.

[0004] In addition, Patent Document 2 discloses a wear-resistant steel plate with excellent corrosion-resistant wear resistance, having a composition containing, by mass%, C: more than 0.20% and 0.35% or less, Si: 0.02 to 1.00%, Mn: 0.1 to 2.0%, P: 0.020% or less, S: 0.005% or less, Al: 0.005 to 0.100%, Sb: 0.005 to 0.20%, B: 0.0003 to 0.0030%, further containing at least one selected from Cr: 0.05 to 2.0% and Mo: 0.05 to 1.0%, and satisfying 0.05 ≦ (Crsol + 2.5Mosol) ≦ 2.0 (where Crsol is the amount of Cr dissolved in the steel (mass%), and Mosol is the amount of Mo dissolved in the steel (mass%)). In Patent Document 2, the wear resistance is evaluated using an NaCl aqueous solution as the corrosion environment.

[0005] In addition, Patent Document 3 discloses a corrosion-resistant steel having excellent corrosion resistance, wear resistance, and high toughness when placed in a specific environment, with a component composition containing, by mass%, C: 0.01 to 0.25%, Si: 0.01 to 0.50%, Mn: 0.1 to 2.0%, P: 0.035% or less, S: 0.035% or less, Al: 0.003 to 0.10%, Cu: 0.05 to 0.35%, Ni: 0.02 to 0.40%, Sb: 0.01 to 0.2%, W: 0.005 to 0.5%, Nb: 0.003 to 0.025%, Cr: 0.1% or less, N: 0.0010 to 0.0080%, the balance being Fe and inevitable impurities, and the Vickers hardness at a position 2 mm from the surface in the depth direction being 140 or more.

[0006] In addition, Patent Document 4 discloses a composition containing, by mass%, C: 0.10 to 0.35%, Si: more than 1.00% and 2.00% or less, Mn: 0.10 to 2.00%, P: 0.0200% or less, S: 0.0100% or less, Cr: more than 0.05% and 2.00% or less, Al: 0.010 to 0.100%, N: 0.0020 to 0.0100%, B: 0.0003 to 0.0030%, the balance being Fe and impurities, and H ≧ 235 + 706[C](1 - 0.3[C] 2(In the formula, H represents the surface hardness (HV) of the corrosion-resistant and wear-resistant steel plate, and [C] represents the content (% by mass) of C). By satisfying this, a corrosion-resistant and wear-resistant steel plate is disclosed that has excellent toughness and combines corrosion resistance and wear resistance. In Patent Document 4, wear resistance is evaluated using artificial seawater as the corrosion environment.)

[0007] Further, in Patent Document 5, in mass%, C: 0.01 to 0.15%, Si: 0.05 to 1.00%, Mn: 0.10 to 2.00%, Cr: more than 0.05% and 3.00% or less, Al: 0.01 to 0.10%, B: 0.0003 to 0.0020%, N: 0.0020 to 0.0100% are contained, and the following formula (Ceq (%) = [C] + [Mn] / 6 + [Si] / 24 + [Ni] / 40 + [Cr] / 5 + [Mo] / 4 + [V] / 4) (where [X] represents the content in mass% of element X) is used to obtain a carbon equivalent Ceq (%) of 0.20% or more, the area ratio of the lath-like structure in the surface layer is 90% or more, and the average value of the major axis / minor axis ratio of the cementite present in the lath-like structure is 2.00 or more. By having a metal structure and a surface hardness of 200 or more (HV5), a steel suitable for the hold of a coal-only ship or a coal-ore dual-purpose ship and having excellent corrosion resistance and wear resistance is disclosed.)

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in Patent Documents 1, 2, and 4, since the corrosion environment to be improved in corrosion resistance is an NaCl aqueous solution or artificial seawater, there is a problem that the corrosion-resistant wear resistance in an acidic environment such as a coal mining environment cannot be improved. Further, Patent Documents 3 and 5 have a problem that the hardness of the steel material is as low as 365 or less in Vickers hardness and the wear resistance is low, so they are not suitable for industrial machines, transportation equipment, etc. Further, industrial machines, transportation equipment, etc. need to have appropriate toughness due to the severity of their use environment.

[0010] In view of such circumstances, an object of the present invention is to provide a steel plate excellent in corrosion-resistant wear resistance and toughness.

Means for Solving the Problems

[0011] In order to solve the above problems, various factors were intensively studied from the viewpoint of corrosion-resistant wear resistance. As a result, in order to improve the wear resistance and corrosion resistance of the steel material at the same time, it was found that by simultaneously satisfying the following (1) and (2), the corrosion-resistant wear resistance in an acidic environment such as a coal mining environment is improved.

[0012] In order to improve the wear resistance, (1) Increase the hardness. In order to improve the corrosion resistance in an acidic environment, (2) In an acidic corrosion environment, add Cr which elutes as ions by an anodic reaction and is effective in improving the corrosion-resistant wear resistance by suppressing corrosion by an inhibitor effect.

[0013] That is, in order to solve the above problems, it was found that it is necessary to increase the hardness so that the wear resistance and corrosion resistance are improved at the same time and add Cr.

[0014] The gist of the present invention is as follows. [1] By mass%, C: 0.10% or more and less than 0.24%, Si: 0.05% or more and 1.00% or less, Mn: not less than 0.10% and not more than 2.00%, P: not more than 0.030% (excluding 0%), S: not more than 0.0300% (excluding 0%), Al: not less than 0.005% and not more than 0.100%, Cr: contains not less than 3.00% and not more than 11.50%, with the balance consisting of Fe and inevitable impurities, having a component composition, and a surface hardness of not less than 370 and not more than 475 in terms of Brinell hardness HBW10 / 3000 A steel sheet characterized by the above. [2] Further, in mass%, Mo: not more than 1.000%, Nb: not more than 0.100%, Ti: not more than 0.100%, V: not more than 0.200%, Zr: not more than 0.100%, Sn: not more than 0.200%, Sb: not more than 0.200%, Cu: not more than 2.00%, Ni: not more than 2.00%, Co: not more than 2.00%, W: not more than 1.000%, B: not more than 0.0030%, REM: not more than 0.0100%, Ca: not more than 0.0100%, Mg: not more than 0.0100%, The steel sheet according to [1], characterized by containing one or more selected from the above.

Advantages of the Invention

[0015] According to the present invention, a steel sheet excellent in corrosion and wear resistance and toughness can be obtained.

Modes for Carrying Out the Invention

[0016] The present invention will be described in detail below. Note that “%” regarding the component composition means “mass%” unless otherwise specified.

[0017] C: More than 0.10% and less than 0.24% C is an element that increases the hardness of steel. To ensure the desired hardness, it is necessary to contain 0.10% or more of C. If the C content is less than 0.10%, the desired surface hardness cannot be obtained, and sufficient corrosion and wear resistance cannot be obtained. On the other hand, if it is 0.24% or more, the hardness becomes too high and the target surface hardness cannot be ensured. Therefore, the C content shall be more than 0.10% and less than 0.24%. Preferably, it is 0.11% or more and 0.22% or less. More preferably, it is 0.12% or more and 0.21% or less.

[0018] Si: 0.05% or more and 1.00% or less Si is an effective element that acts as a deoxidizer for molten steel. To ensure such an effect, it is necessary to contain 0.05% or more of Si. On the other hand, if a large amount of Si exceeding 1.00% is contained, the ductility decreases and the inclusions increase. Therefore, the Si content shall be 0.05% or more and 1.00% or less. Preferably, it is 0.10% or more and 0.40% or less.

[0019] Mn: 0.10% or more and 2.00% or less Mn is an element that improves hardenability, and it is necessary to contain 0.10% or more of Mn to ensure the desired hardness. If the Mn content is less than 0.10%, the desired surface hardness cannot be obtained, and sufficient corrosion and wear resistance cannot be obtained. On the other hand, if it is contained in excess exceeding 2.00%, the weldability deteriorates. Therefore, the Mn content shall be 0.10% or more and 2.00% or less. Preferably, it is 0.15% or more and 1.80% or less. More preferably, it is 0.20% or more and 1.80% or less.

[0020] P: 0.030% or less (excluding 0%) When a large amount of P is contained in steel, the weldability deteriorates. Therefore, the upper limit is 0.030%. The P content is desirably reduced as much as possible, preferably 0.015% or less. However, excessive reduction leads to an increase in refining cost, so the P content is preferably 0.001% or more.

[0021] S: Below 0.0300% (excluding 0%) When S is contained in a large amount in steel, it precipitates as MnS, leading to deterioration of gas cutting properties. Therefore, it is desirable to reduce it as much as possible and it is necessary to set it to 0.0300% or less. However, excessive reduction causes an increase in refining cost, so the S content is preferably 0.0001% or more.

[0022] Al: 0.005% or more and 0.100% or less Al is an element necessary for deoxidation during steelmaking, and has the effect of forming nitrides, reducing the austenite grain size, and improving toughness. To obtain these effects, it is necessary to contain 0.005% or more as the Al content. On the other hand, if it exceeds 0.100%, the cleanliness of the steel material and steel plate decreases, and as a result, the toughness decreases. Therefore, the Al content is set to 0.005% or more and 0.100% or less. Preferably it is 0.070% or less, more preferably 0.050% or less. Preferably it is 0.010% or more.

[0023] Cr: 3.00% or more and 11.50% or less Cr is an important requirement in the present invention and has the effect of significantly improving corrosion and wear resistance, especially in an acidic corrosion environment such as a coal mining environment. Cr is an element that improves hardenability and has the effect of increasing hardness. Also, in an acidic corrosion environment such as a coal mining environment, it elutes as Cr ions by an anodic reaction and has the effect of improving corrosion and wear resistance by suppressing corrosion by an inhibitor effect. To ensure the desired surface hardness and obtain sufficient corrosion and wear resistance in an acidic corrosion environment such as a coal mining environment, it is necessary to contain 3.00% or more of Cr. On the other hand, if it exceeds 11.50%, the weldability decreases and the manufacturing cost increases. Furthermore, the hardness becomes too high and the target surface hardness cannot be ensured. Therefore, the Cr content is limited to the range of 3.00% or more and 11.50% or less. Note that the Cr content is preferably more than 5.00%. Also, the content of Cr is preferably 11.00% or less, more preferably 10.00% or less.

[0024] The basic components (essential components) in the steel sheet of the present invention have been described above. Among the component compositions of the steel sheet of the present invention, the components other than the above (the balance) can be Fe and inevitable impurities. Here, as the inevitable impurities, for N and O respectively, N: 0.0100% or less and O: 0.0100% or less are allowable.

[0025] By having the above component composition, the characteristics aimed at in the present invention can be obtained.

[0026] The component composition of the steel sheet of the present invention can further contain, as selected elements as needed, one or more selected from the following elements within the following content ranges respectively.

[0027] Mo: 1.000% or less Mo is an element effective for improving hardenability and has the effect of increasing hardness. In order to obtain such an effect, it is preferable to contain Mo at 0.001% or more. On the other hand, if it exceeds 1.000%, it will cause an increase in cost due to an increase in Mo consumption. Therefore, when Mo is contained, the Mo content is 1.000% or less, preferably 0.800% or less. Also, when Mo is contained, the Mo content is preferably 0.100% or more.

[0028] Nb: 0.100% or less Nb is an element effective for increasing strength. In order to fully obtain this effect, it is preferable to contain Nb at 0.001% or more. On the other hand, if it exceeds 0.100%, the effect will saturate. Therefore, when Nb is contained, the Nb content is 0.100% or less. Also, when Nb is contained, the Nb content is preferably 0.001% or more.

[0029] Ti: 0.100% or less Ti is an element effective for enhancing strength. To fully obtain this effect, it is preferable to contain Ti at 0.001% or more. On the other hand, when it exceeds 0.100%, the effect saturates. Therefore, when containing Ti, the Ti content should be 0.100% or less. Also, when containing Ti, the Ti content is preferably 0.001% or more.

[0030] V: 0.200% or less V is an element effective for enhancing strength. To fully obtain this effect, it is preferable to contain V at 0.001% or more. On the other hand, when it exceeds 0.200%, the effect saturates. Therefore, when containing V, the V content should be 0.200% or less. Also, when containing V, the V content is preferably 0.001% or more.

[0031] Zr: 0.100% or less Zr is an element effective for enhancing strength. To fully obtain this effect, it is preferable to contain Zr at 0.001% or more. On the other hand, when it exceeds 0.100%, the effect saturates. Therefore, when containing Zr, the Zr content should be 0.100% or less. Also, when containing Zr, the Zr content is preferably 0.001% or more.

[0032] Sn: 0.200% or less Sn is an element effective for improving the weather resistance of steel by suppressing the anodic reaction of the steel and also suppressing the hydrogen generation reaction which is the cathodic reaction in an acidic corrosion environment such as a coal mining environment. To fully obtain such an effect, it is preferable to contain Sn at 0.001% or more. On the other hand, even when Sn is contained in excess of 0.200%, the effect saturates. Therefore, when containing Sn, the Sn content should be 0.200% or less. Also, when containing Sn, the Sn content is preferably 0.001% or more.

[0033] Sb: 0.200% or less Sb is an effective element for improving the weather resistance of steel by suppressing the anodic reaction of the steel and the hydrogen generation reaction that is the cathodic reaction in acidic corrosion environments such as coal mining environments. In order to fully obtain such an effect, it is preferable to contain Sb at 0.001% or more. On the other hand, even if the content of Sb exceeds 0.200%, the effect saturates. Therefore, when containing Sb, the Sb content should be 0.200% or less. Also, when containing Sb, the Sb content is preferably 0.001% or more.

[0034] Cu: 2.00% or less Cu makes the corrosion product dense and suppresses the permeation of water, oxygen, sulfate ions, chloride ions, etc., which are corrosion promoting factors, into the steel, thereby suppressing the corrosion reaction. Due to this effect, the corrosion and wear resistance is improved. To obtain such an effect, it is preferable to contain Cu at 0.01% or more. On the other hand, when the Cu content exceeds 2.00%, the hot workability deteriorates and the manufacturing cost increases. Therefore, when containing Cu, the Cu content should be 2.00% or less, preferably 1.50% or less, and even more preferably 1.20% or less. Also, when containing Cu, the Cu content is preferably 0.01% or more, more preferably 0.10% or more, and even more preferably 0.60% or more.

[0035] Ni: 2.00% or less Ni is an effective element for improving hardenability. To obtain such an effect, it is preferable to contain Ni at 0.01% or more. On the other hand, a content exceeding 2.00% increases the manufacturing cost. Therefore, when containing Ni, the Ni content is limited to 2.00% or less, preferably 1.50% or less, and more preferably 0.60% or less. Also, when containing Ni, the Ni content is preferably 0.01% or more, more preferably 0.10% or more, and even more preferably 0.30% or more.

[0036] Co: 2.00% or less Co is an element effective for improving hardenability. To obtain this effect, it is preferable to contain Co at 0.01% or more. On the other hand, containing more than 2.00% increases the manufacturing cost. Therefore, when Co is contained, the Co content is limited to 2.00% or less. Also, when Co is contained, the Co content is preferably 0.01% or more.

[0037] W: 1.000% or less W is an element effective for improving hardenability and has the effect of increasing hardness. To obtain such an effect, it is preferable to contain W at 0.001% or more. On the other hand, exceeding 1.00% causes a cost increase associated with an increase in W consumption. Therefore, when W is contained, the W content is 1.000% or less, preferably 0.800% or less. Also, when W is contained, the W content is preferably 0.001% or more, more preferably 0.100% or more.

[0038] B: 0.0030% or less B is an element effective for improving hardenability. To obtain this effect, it is preferable to contain B at 0.0001% or more. On the other hand, when exceeding 0.0030%, the effect saturates. Therefore, when B is contained, the B content is 0.0030% or less. Also, when B is contained, the B content is preferably 0.0001% or more.

[0039] REM: 0.0100% or less REM is effective for fixing S and suppressing the formation of MnS which causes cracking. In order to obtain such an effect, it is preferable to contain REM at 0.0005% or more. On the other hand, if it is contained in excess of 0.0100%, the amount of inclusions in the steel increases, leading to cracking. Therefore, when REM is contained, the REM content is limited to 0.0100% or less, preferably 0.0035% or less, more preferably 0.0020% or less. Further, when REM is contained, the REM content is preferably 0.0005% or more. Note that REM is a general term for Sc, Y, and 15 elements from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71, and the REM content referred to here is the total content of these elements.

[0040] Ca: 0.0100% or less Ca is an element effective for fixing S in the steel and improving the toughness of the heat-affected zone of welding. In order to sufficiently obtain this effect, it is preferable to contain Ca at 0.0001% or more. On the other hand, if it exceeds 0.0100%, the amount of inclusions in the steel increases, causing cracking. Therefore, when Ca is contained, the Ca content is 0.0100% or less. Further, when Ca is contained, the Ca content is preferably 0.0001% or more.

[0041] Mg: 0.0100% or less Mg is an element effective for fixing S in the steel and improving the toughness of the heat-affected zone of welding. In order to sufficiently obtain this effect, it is preferable to contain Mg at 0.0001% or more. On the other hand, if it exceeds 0.0100%, the amount of inclusions in the steel increases, causing cracking. Therefore, when Mg is contained, the Mg content is 0.0100% or less. Further, when Mg is contained, the Mg content is preferably 0.0001% or more.

[0042] Further, the steel plate of the present invention has a surface hardness of 370 or more and 475 or less in terms of Brinell hardness HBW10 / 3000. The "surface hardness" referred to here means the value (Brinell hardness) measured in accordance with the provisions of JIS Z 2243 (2008) at a position 0.5 mm in the plate thickness direction from the surface.

[0043] Surface hardness: Brinell hardness HBW10 / 3000 of 370 or more and 475 or less If the surface hardness is less than 370 in HBW10 / 3000, the surface hardness is low and it does not show sufficient corrosion and wear resistance. Therefore, in an acidic corrosion environment such as a coal mining environment where the wear environment is severe and higher corrosion and wear resistance is required, the desired wear life cannot be ensured. For this reason, in the steel plate of the present invention, the surface hardness is limited to 370 or more in Brinell hardness HBW10 / 3000. On the other hand, when the surface hardness exceeds 475 in HBW10 / 3000, the bend processability deteriorates. For this reason, the surface hardness is set to 475 or less in Brinell hardness HBW10 / 3000.

[0044] [Manufacturing method of steel plate] The molten steel having the above-described component composition is melted by a known method such as a converter or an electric furnace, and made into a steel material such as a slab or a billet by a known method such as a continuous casting method or an ingot method. Needless to say, treatments such as ladle refining and vacuum degassing may be added to the molten steel. In hot rolling, in order to ensure strength, it is preferable to optimize the heating temperature of the steel material, the finishing temperature at the time of hot rolling, and the cooling rate. That is, from the viewpoint of ensuring the hot finishing rolling end temperature, preferably, after heating the steel material to a temperature of 1000 to 1250 ° C, hot rolling it into a desired dimensional shape, or when the temperature of the steel material is high enough to be hot rolled, without heating, or immediately after soaking to a desired dimensional shape of the steel material. It is preferable to hot roll.

[0045] In hot rolling, in order to ensure strength, it is preferable to optimize the finish temperature of hot finish rolling and the cooling rate after hot rolling. Hot rolling is terminated at a temperature of 770°C or higher, air-cooled to 700°C or lower, reheated to 850°C to 1000°C, and then immediately or after a certain holding time (for example, a holding time of 10 to 60 s), cooling (for example, water cooling) is carried out at a cooling rate of 0.5°C / s or more and 100°C / s or less starting from a cooling start temperature of 750°C or higher, and it is preferable to terminate the cooling at a cooling stop temperature of 200°C or lower. Further, after hot rolling, immediately or after a certain holding time (for example, a holding time of 10 to 60 s), accelerated cooling (for example, water cooling) is carried out at a cooling rate of 0.5°C / s or more and 100°C / s or less starting from a cooling start temperature of 750°C or higher (in the case of water cooling, the water cooling start temperature). The accelerated cooling may be terminated at a cooling stop temperature of 200°C or lower.

Examples

[0046] Steel (the balance being Fe and inevitable impurities) having the component composition shown in Table 1 was melted in a vacuum melting furnace, cast into a mold, and used as a steel material. Then, these steel materials were hot rolled, air-cooled immediately after the hot rolling was completed, and after air-cooling, they were reheated and then water-cooled. Test pieces were taken from the obtained steel plates, and surface hardness tests, corrosion wear tests, and Charpy tests were carried out.

[0047] (1) Surface hardness test A test piece for surface hardness measurement was taken so that the position 0.5 mm from the surface of the obtained steel plate was the measurement surface, and the surface hardness HBW10 / 3000 was measured in accordance with the provisions of JIS Z 2243 (2018). The hardness measurement was carried out using a 10 mm tungsten carbide hard ball and a load of 3000 kgf. In addition, three-point measurement was carried out at a position 0.5 mm from the surface, and the arithmetic mean of the obtained measured values was obtained, and the mean value was taken as the surface hardness of the steel plate.

[0048] (2) Corrosion wear test A wear test piece (size: 10 mm φ × 75 mm length) was taken from the 1 / 4t part in the thickness direction of the obtained steel plate (t indicates the plate thickness). The test piece was mounted on a wear testing machine and a wear test was carried out. Three wear test pieces were attached at an angle of 120 degrees at a position 150 mm from the rotation axis parallel to the rotation axis of the test machine rotor. Then, the test pieces were placed in the test tank and wear materials were introduced into the interior. As the wear materials, silica sand with an average particle size of 0.7 mm and dilute sulfuric acid with a pH of 2 were used, which were mixed so that the weight ratio of silica sand to dilute sulfuric acid was 5:3. The test conditions were a rotation speed of 500 rpm and a number of rotations of 60,000. After the test, the weight of each test piece was measured. Then, the difference between the weight after the test and the initial weight (= weight reduction amount) was calculated. As a conventional example, a test piece taken from hot-rolled steel for general structure SS400 (JIS G3101) was similarly subjected to a wear test to obtain the weight reduction amount of the test piece. The corrosion-resistant wear resistance was evaluated by the ratio of the weight reduction amount of each test piece to the weight reduction amount of SS400. According to the following criteria, if it was ○ or ◎, it was determined that it had sufficient corrosion-resistant wear resistance. The results are shown in Table 2. ◎ (qualified, particularly excellent in corrosion-resistant wear resistance): The ratio of the weight reduction amount is less than 0.60 ○ (qualified, excellent in corrosion-resistant wear resistance): The ratio of the weight reduction amount is 0.60 or more and 0.75 or less × (unqualified): The ratio of the weight reduction amount exceeds 0.75 In all of the inventive examples, excellent corrosion-resistant wear resistance was obtained. Furthermore, among the inventive examples, steel grades 1 to 2, 4 to 8, 10 to 12, and 14 to 16 containing more than 5.00% of Cr obtained particularly excellent corrosion-resistant wear resistance (judgment was ◎).

[0049] (3) Charpy test The toughness by the Charpy test (JIS Z 2242 (2018)) was evaluated as good if the absorbed energy was 27.0 J or more on average per set (n = 3) at -40 °C using a V-notch standard test piece taken from the above steel plate. Note that an absorbed energy of 30.0 J or more is more preferable.

[0050] The evaluation results of (1) and (2) and the toughness values measured by the Charpy test are shown together in Table 2.

[0051] As shown in Table 2, all of the inventive examples have both the desired surface hardness and excellent corrosion-resistant wear properties. Furthermore, they are also excellent in toughness. On the other hand, for steel grades 18 to 22 of the comparative examples, sufficient properties are not obtained for at least one of the surface hardness or the corrosion-resistant wear properties. Also, for steel grades 23 and 24 of the comparative examples, sufficient properties are not obtained for toughness.

[0052]

Table 1

[0053]

Table 2

Industrial Applicability

[0054] As described above, according to the present invention, there is provided a steel sheet for use in members that require wear resistance in industrial machines, transportation equipment, etc., and in particular, a steel sheet excellent in corrosion-resistant wear properties in an acidic corrosion environment such as a coal mining environment.

Claims

1. by mass percentage, C: 0.10% or more and less than 0.24%, Si: 0.05% or more and 1.00% or less, Mn: 0.10% or more and 2.00% or less, P: 0.030% or less (excluding 0%), S: 0.0300% or less (excluding 0%), Al: 0.010% or more and 0.070% or less, containing Cr: 3.00% or more and 11.50% or less, with the balance consisting of Fe and unavoidable impurities, having a component composition, the surface hardness being 370 or more and 475 or less in Brinell hardness HBW10 / 3000, a steel sheet characterized by the above.

2. Furthermore, by mass percentage, Mo: 1.000% or less, Nb: 0.100% or less, Ti: 0.100% or less, V: 0.200% or less, Zr: 0.100% or less, Sn: 0.200% or less, Sb: 0.200% or less, Cu: 2.00% or less, Ni: 2.00% or less, Co: 2.00% or less, W: 1.000% or less, B: 0.0030% or less, REM: 0.0100% or less, Ca: 0.0100% or less, Mg: 0.0100% or less, the steel sheet according to Claim 1, characterized by containing one or more selected from the above.

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