JP2015193873A - Thick steel plate excellent in abrasion resistance in corrosive environment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thick steel plate excellent in abrasion resistance in corrosive environment and used for members to which abrasion resistance is required in industrial machinery, transfer device or the like.SOLUTION: There is provided a thick steel plate having a composition consisting of, by mass%, 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%, one or more kind of Mo, Cu, Ni, V, B, REM, Ca, Mg if needed, DI* of 45.0 or more and the balance Fe with inevitable impurities, a structure containing an as-quenched martensite phase having old austenite grain size of 25 μm as a main phase and surface hardness of 400 or more in Brinell hardness HBW 10/3000.

Description

  The present invention relates to a thick steel plate used for a member that requires wear resistance in industrial machinery, transportation equipment, and the like, and particularly relates to a steel plate excellent in wear resistance in a corrosive environment.

  For example, industrial machines such as excavators, bulldozers, hoppers, buckets, and dump trucks, and transportation equipment used in construction, civil engineering, and mining sites are subject to wear due to earth and sand. For this purpose, steel materials having excellent wear resistance are used.

  Sediment and the like are in various states such as dry and wet, but wear due to the soil and the like in a wet state may be wear in an environment containing a corrosive substance, so-called corrosive wear.

  In addition, since industrial machines, transportation equipment, and the like are expected to be used in a low temperature range of 0 ° C. or lower, it is desired that they have excellent low temperature toughness, and various techniques have been proposed for wear-resistant steel.

  For example, in Patent Document 1, by mass%, C: 0.30 to 0.50%, Cr: 0.10 to 0.50%, Mo: 0.05 to 1.00%, appropriate amounts of Si, Mn After hot-rolling a steel slab containing Al, N, Ti, Nb, and B, it is quenched from a temperature not lower than the Ar3 transformation point and subsequently tempered to obtain a high-hardness wear-resistant steel with excellent low-temperature toughness. A manufacturing method has been proposed, and it is described that by containing a large amount of Cr and Mo, hardenability is improved, grain boundaries are strengthened, low temperature toughness is improved, and tempering is further improved. .

  In patent document 2, it is the mass%, C: 0.18-0.25%, Si: 0.10-0.30%, Mn: 0.03-0.10%, Cr: 1.00-2. A high toughness wear-resistant steel sheet excellent in toughness and delayed fracture resistance after water quenching and tempering treatment containing 00%, Mo: more than 0.50 to 0.80%, and appropriate amounts of Nb, Al, N, B Proposed to keep the Mn content low and to contain a large amount of Cr and Mo, the hardenability is improved, the predetermined hardness can be secured, the toughness and delayed fracture resistance are improved, and the tempering treatment is performed. It is described that the low temperature toughness is improved.

  In patent document 3, C: 0.30-0.45%, Si: 0.10-0.50%, Mn: 0.30-1.20%, Cr: 0.50-1. 40%, Mo: 0.15-0.55%, B: 0.0005-0.0050%, sol. Al: 0.015 to 0.060% and a high toughness wear-resistant steel containing an appropriate amount of Nb and / or Ti has been proposed. By containing a large amount of Cr and Mo, the hardenability is improved and the grain boundary is increased. Is strengthened and low temperature toughness is improved.

  In Patent Document 4, by mass%, C: 0.05 to 0.40%, Cr: 0.1 to 2.0%, Si, Mn, Ti, B, Al, and N as appropriate components as essential components, If necessary, a steel having a composition containing one or more of Cu, Ni, Mo, and V is hot-rolled at a cumulative reduction of 50% or more in an austenite non-recrystallized region at 900 ° C. or lower, and Ar 3 A method of manufacturing a wear-resistant steel that is quenched from above and then tempered is proposed, and a structure in which austenite grains are expanded is directly quenched and tempered to obtain a tempered martensite structure in which old austenite grains are expanded. Thus, it is described that the low temperature toughness is remarkably improved.

  In Patent Document 5, by mass%, C: 0.23 to 0.35%, Si, Mn, Nb, Ti, B contains an appropriate amount as an essential component, and if necessary, further Cu, Ni, Cr, A wear-resistant steel sheet containing one or more of Mo and V has been proposed, the components are adjusted to predetermined values, and the steel slab is heated to 1200 to 1250 ° C., so that the wear resistance after reheating and quenching is improved. It is ensured and the low temperature toughness is further improved.

  In patent document 6, C: 0.10-0.30%, Si: 0.05-1.0%, Mn: 0.1-2.0%, W: 0.10-1. 40%, B: 0.0003-0.0020%, Ti: 0.005-0.10% and / or Al: 0.035-0.1% as an essential component, if necessary Furthermore, a wear-resistant steel sheet having a composition containing at least one of Cu, Ni, Cr, V, Ca, and REM has been proposed, and has high surface hardness, excellent wear resistance, and low temperature toughness. It is said to be excellent.

  In patent document 7, C: 0.05-0.30% and Ti: 0.1-1.2% are contained by the mass%, and the amount of solid solution C is 0.03% or less, as needed. Furthermore, it has a composition containing one or more of Nb, V, Mo, W, Si, Mn, Cu, Ni, B, and Cr, the matrix is a ferrite phase, and the hard phase is in the matrix A wear-resistant steel sheet having a dispersed structure is described, and both wear resistance against earth and sand wear and bending workability are improved without a significant increase in hardness.

Japanese Patent Laid-Open No. 08-41535 Japanese Patent Laid-Open No. 02-179842 JP-A 61-166554 JP 2002-20837 A JP 2004-270001 A JP 2007-92155 A JP 2007-197813 A

  Each technique described in Patent Documents 1 to 6 is intended to have low-temperature toughness and wear resistance, and the technique described in Patent Document 7 combines bending workability and wear resistance. No study has been made on wear in an environment containing corrosive substances, such as soil in a wet state.

Moreover, each technique described in Patent Documents 1 to 4 has a requirement that tempering is performed, and there is a problem that the manufacturing cost increases.
The present invention has been made to solve the problems of the prior art, and an object thereof is to provide a thick steel plate that is inexpensive, has excellent low-temperature toughness, and has excellent wear resistance in a corrosive environment.

  In order to achieve the above object, the present inventors have conducted extensive studies on the influence of various factors on low temperature toughness and corrosion wear resistance. As a result, it was found that the corrosion wear resistance is remarkably improved by using a composition containing an appropriate amount of W.

  Furthermore, the hardenability is improved, and the hardened martensite phase is the main phase, the surface hardness is 400 or more with Brinell hardness HBW10 / 3000, and the old austenite (γ) of the martensite phase as quenched. It has been found that by reducing the particle size to 25 μm or less, excellent low temperature toughness can be ensured while ensuring excellent corrosion wear resistance.

The present invention has been completed with further studies based on the above findings.
(1) In mass%,
C: 0.18 to 0.25%,
Si: 0.05-1.00%,
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: 0.05-1.00%,
A composition comprising DI * defined by the following formula (1) of 45.0 or more, the balance Fe and inevitable impurities, and a structure having a martensite phase as a main phase as-quenched with a prior austenite grain size of 25 μm or less; Furthermore, a thick steel plate having excellent wear resistance in a corrosive environment, characterized in that the surface hardness is 400 or more according to Brinell hardness HBW10 / 3000.
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (1)
In the formula, each alloy element has a content (mass%).
(2) Furthermore, in mass%,
Mo: 0.05-1.00%,
Cu: 0.03-1.00%,
Ni: 0.03-2.00%,
V: 0.005-0.100%,
B: 0.0003 to 0.0030%
The thick steel plate having excellent wear resistance in a corrosive environment according to (1), comprising one or more selected from the group consisting of:
(3) Furthermore, in mass%,
REM: 0.0005 to 0.0080%,
Ca: 0.0005 to 0.0050%,
Mg: 0.0005 to 0.0050%,
A thick steel plate having excellent wear resistance in a corrosive environment as described in (1) or (2), comprising one or more selected from the group consisting of:

  According to the present invention, a thick steel plate having excellent low-temperature toughness and excellent wear resistance in a corrosive environment under a wet earth and sand wear environment can be obtained, which has a remarkable industrial effect.

The wear-resistant steel sheet according to the present invention defines the component composition, microstructure, and surface hardness.
[Ingredient composition]
In the following description, “%” means “mass%”.
C: 0.18 to 0.25%
C is an important element for increasing the hardness of the steel sheet and improving the wear resistance. If C is less than 0.18%, sufficient hardness cannot be obtained. On the other hand, a large content exceeding 0.25% is limited to a range of 0.18 to 0.25% in order to reduce weldability, low temperature toughness and workability. In addition, Preferably it is 0.20 to 0.23%.

Si: 0.05-1.00%
Si is an effective element that acts as a deoxidizer for molten steel, and is an element that contributes effectively to improving the strength of the steel sheet by solid solution strengthening. In order to ensure such an effect, the content of 0.05% or more is required. On the other hand, when it contains more than 1.00%, ductility and toughness are lowered and inclusions are increased, so the content is limited to 0.05 to 1.00%. In addition, Preferably it is 0.15-0.45%.

Mn: 0.10 to 2.00%
Mn is an element that improves hardenability. In order to ensure such an effect, it is necessary to contain 0.10% or more. On the other hand, if the content exceeds 2.00%, high-strength steel containing Cr and Mo causes temper embrittlement and also increases the hardness of the weld heat affected zone and decreases weldability. It was limited to a range of ˜2.00%. In addition, Preferably it is 0.40 to 1.70%, More preferably, it is 0.50 to 1.00%.

P: 0.020% or less Since P causes a decrease in low temperature toughness when contained in a large amount in steel, the upper limit is 0.020%. Although it is desirable to reduce as much as possible, excessive reduction leads to an increase in refining cost, so it is desirable to make it 0.005% or more.

S: 0.0050% or less When S is contained in a large amount in steel, it precipitates as MnS, becomes a starting point of occurrence of fracture, and causes deterioration of toughness, so 0.0050% is made the upper limit. Although it is desirable to reduce as much as possible, excessive reduction leads to an increase in refining cost, so it is desirable to make it 0.0005% or more.

Al: 0.005 to 0.100%
Al is an effective element that acts as a deoxidizer for molten steel, and contributes to improvement of low-temperature toughness by refining crystal grains. In order to acquire such an effect, 0.005% or more of content is required. On the other hand, if the content exceeds 0.100%, the weldability decreases, so the content is limited to the range of 0.005 to 0.100%. In addition, Preferably it is 0.015-0.035%.

Cr: 0.05-2.00%
Cr has the effect of improving the low temperature toughness by increasing the hardenability and refining the martensite phase. Cr has an effect of improving corrosion wear resistance by being eluted as Cr acid ions by an anodic reaction and suppressing corrosion by an inhibitor effect in a corrosive wear environment such as wet earth and sand. In order to acquire such an effect, 0.05% or more of content is required. On the other hand, if the content exceeds 2.00%, the weldability deteriorates and the manufacturing cost increases, so the content is limited to the range of 0.05 to 2.00%. In addition, Preferably it is 0.07 to 1.00%, More preferably, it is 0.20 to 0.90% of range.

Nb: 0.005 to 0.100%
Nb is an element that precipitates as carbonitride and contributes effectively to improving toughness through refinement of the structure. In order to acquire such an effect, 0.005% or more of content is required. On the other hand, if the content exceeds 0.100%, weldability decreases, so the content is limited to a range of 0.005 to 0.100%. In addition, from a viewpoint of refinement | miniaturization of a structure, it is preferable to set it as 0.012 to 0.030% of range.

Ti: 0.005 to 0.100%
Ti is an element that precipitates as TiN and contributes to improvement of toughness through fixation of solute N. In order to acquire such an effect, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.100%, coarse carbonitrides precipitate and the toughness decreases, so the content is limited to the range of 0.005 to 0.100%. In addition, it is preferable to limit to 0.005 to 0.030% of range from a viewpoint of cost reduction.

W: 0.05-1.00%
W is an important element in the present invention. W has the effect of improving the low temperature toughness by increasing the hardenability and making the martensite phase fine. In addition, in a corrosive wear environment due to wet earth and sand, etc., it is eluted as W acid ions by the anode reaction, and has the effect of improving the corrosion wear resistance by suppressing the corrosion by the inhibitor effect. By containing an appropriate amount of W, even when exposed to wet earth and sand, etc., the eluted W forms a complex oxide with Fe in the vicinity of the interface of the iron core, and suppresses the corrosion reaction. It is presumed to be because it is present as W acid ions and suppresses the arrival of corrosion promoting factors to the ground iron.

  In order to acquire such an effect, 0.05% or more of content is required. On the other hand, if the content exceeds 1.00%, the weldability is lowered and the manufacturing cost is increased, so the content is limited to 0.05 to 1.00%. In addition, Preferably, it is 0.10 to 0.50%, More preferably, it is 0.20 to 0.40%.

DI *: 45.0 or more When DI * is less than 45.0, the quenching depth from the steel sheet surface layer is less than 10 mm, and the life as a wear-resistant steel sheet is shortened. Therefore, DI * is limited to 45.0 or more. In addition, Preferably it is 75.0 or more. DI * is obtained by the following equation (1).
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (1)
(Here, C, Si, Mn, Cu, Ni, Cr, Mo, V, W: The content (mass%) of each element, and the elements not contained are calculated as zero.)
The above components are the basic component composition, and the balance is Fe and inevitable impurities. Furthermore, when improving a characteristic, 1 type, or 2 or more types of Mo, Cu, Ni, V, B, REM, Ca, and Mg can be contained as a selection element.

Mo: 0.05-1.00%
Mo has the effect of improving the low temperature toughness by increasing the hardenability and refining the martensite phase. In order to obtain such an effect, 0.05% or more is required. On the other hand, when it contains exceeding 1.00%, weldability will fall and manufacturing cost will rise, Therefore When it contains, it is set as 0.05 to 1.00% of range. In addition, Preferably, it is 0.10 to 0.50%, More preferably, it is 0.20 to 0.40%.

Cu: 0.03-1.00%,
Cu is an element that contributes to improving hardenability. In order to acquire such an effect, it is necessary to contain 0.03% or more. On the other hand, when it contains exceeding 1.00%, hot workability will fall and manufacturing cost will also rise, and when it contains, it is preferable to limit to 0.03 to 1.00% of range. In addition, it is more preferable to limit to 0.03 to 0.50% of range from a viewpoint of cost reduction.

Ni: 0.03-2.00%,
Ni is an element that improves the hardenability and contributes to the improvement of low temperature toughness. In order to obtain such an effect, a content of 0.03% or more is required. On the other hand, the content exceeding 2.00% increases the production cost, so when it is contained, it is limited to the range of 0.03 to 2.00%. In addition, it is more preferable to limit to 0.03 to 0.50% of range from a viewpoint of cost reduction.

V: 0.005-0.100%,
V is an element which precipitates as carbonitride and contributes to improvement of toughness through the effect of refining the structure. In order to acquire such an effect, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.100%, the weldability is lowered. Therefore, when it is contained, the content is limited to the range of 0.005 to 0.100%.

B: 0.0003 to 0.0030%
B is an element that contributes to improving the hardenability when contained in a small amount. In order to acquire such an effect, it is necessary to contain 0.0003% or more. On the other hand, when it contains exceeding 0.0030%, toughness falls, and when it contains, it limits to 0.0003 to 0.0030% of range. Incidentally, from the viewpoint of suppressing cold cracking in the low heat input welds such as CO ₂ weld preferably limited to a range of 0.0003 to 0.0015%.

  Any of REM, Ca, and Mg can be contained in one or more types because it is an element that combines with S to generate sulfide inclusions and suppresses the generation of MnS.

REM: 0.0005 to 0.0080%,
REM fixes S and suppresses the production | generation of MnS which causes a toughness fall. In order to acquire such an effect, it is necessary to contain 0.0005% or more. On the other hand, if the content exceeds 0.0080%, the amount of inclusions in the steel increases, leading to a decrease in toughness. When contained, the content is limited to the range of 0.0005 to 0.008%. In addition, Preferably it is 0.0005 to 0.0020%.

Ca: 0.0005 to 0.0050%,
Ca fixes S and suppresses the generation of MnS that causes a decrease in toughness. In order to acquire such an effect, it is necessary to contain 0.0005% or more. On the other hand, if the content exceeds 0.0050%, the amount of inclusions in the steel increases, which leads to a decrease in toughness. For this reason, when it contains, it limits to 0.0005 to 0.0050% of range. In addition, Preferably it is 0.0005 to 0.0030%.

Mg: 0.0005 to 0.0050%
Mg fixes S and suppresses the production | generation of MnS which causes a toughness fall. In order to acquire such an effect, it is necessary to contain 0.0005% or more. On the other hand, if the content exceeds 0.0050%, the amount of inclusions in the steel increases, leading to a decrease in toughness. When contained, the content is limited to the range of 0.0005 to 0.0050%. In addition, Preferably it is 0.0005 to 0.0040%.

[Microstructure]
The wear-resistant steel plate according to the present invention has the above-described composition, has a structure in which the martensite phase is the main phase as it is quenched, and the prior austenite grain size is 25 μm or less. The “main phase” is a phase having an area ratio of 90% or more.

Quenched martensite phase: 90% or more by area ratio Quenched martensite phase, if the area fraction is less than 90%, it does not become the main phase, can not secure the desired hardness, wear resistance It is reduced, and sufficient low temperature toughness cannot be ensured, so 90% or more. The area ratio is preferably 95% or more. The remaining phases are not specified.

  Tempered martensite is martensite as quenched because Cr and Mo form carbides with Fe when cementite is produced by tempering, and the amount of solid solution Cr and Mo effective for ensuring corrosion resistance decreases.

Former austenite grain size: 25 μm or less Even when the martensite phase fraction can be 90% or more in area ratio, if the former γ grain size exceeds 25 μm and becomes coarse, the low temperature toughness decreases. The following. The old γ particle diameter is a value obtained by observing the structure corroded with picric acid corrosive solution with an optical microscope (magnification: 400 times) and complying with JIS G 0551.

[Surface hardness]
The surface hardness is 400 or more with Brinell hardness HBW10 / 3000. When the surface hardness is Brinell hardness HBW10 / 3000 and less than 400, the life as a wear-resistant steel sheet is shortened, so 400 or more. In addition, Brinell hardness shall be measured based on prescription | regulation of JISZ2243.

  Next, a preferred method for producing the wear-resistant steel sheet of the present invention will be described. When the steel material having the above component composition is maintained at a predetermined temperature after casting, it is not cooled as it is or is cooled and then reheated to obtain a steel plate having a desired size and shape by hot rolling.

  The method for producing the steel material is not particularly limited, but the molten steel having the above composition is melted by a known melting method such as a converter, and a slab having a predetermined size is obtained by a known casting method such as a continuous casting method. It is preferable to use a steel material such as Needless to say, the steel material may be obtained by the ingot-making and ingot rolling method.

Heating temperature: 950-1200 ° C
When the heating temperature is less than 950 ° C., the deformation resistance is high, the rolling load becomes excessive, and hot rolling cannot be performed. On the other hand, at a high temperature exceeding 1200 ° C., the coarsening of crystal grains becomes remarkable, and desired toughness cannot be ensured. For this reason, it is preferable to limit heating temperature to the range of 950-1200 degreeC.

  The heated steel material, or the steel material that maintains a predetermined temperature without being heated after casting, is hot-rolled to obtain a steel plate having a desired size and shape. Hot rolling conditions are not limited. It is preferable to perform a direct quenching process immediately after the hot rolling.

  The quenching start temperature is preferably set to a temperature equal to or higher than the Ar3 transformation point. In order to set the quenching start temperature to a temperature equal to or higher than the Ar3 transformation point, the hot rolling end temperature is preferably set to 800 ° C or higher, which is a temperature equal to or higher than the Ar3 transformation point. Moreover, since a crystal grain will coarsen when hot rolling completion temperature is too high, it is preferable to set it as 950 degrees C or less. The Ar3 transformation point can be measured from a thermal expansion curve when cooling from austenite.

  The quenching cooling rate is equal to or higher than the cooling rate at which the martensite phase is formed. In order to prevent the martensite phase from being self-tempered (auto-tempered), the cooling stop temperature is preferably 300 ° C. or lower. More preferably, it is 200 degrees C or less.

  The direct quenching process may be a reheat quenching process. The reheating temperature is preferably 850 to 950 ° C. The quenching cooling rate and the cooling stop temperature after reheating are in accordance with the direct quenching process. In any of the direct quenching process and the reheating quenching process, the tempering process is not performed thereafter.

  Molten steel having the composition shown in Table 1 was melted in a vacuum melting furnace and cast into a mold to obtain a 150 kg steel ingot (steel material). These steel materials were subjected to a direct quenching process (DQ) in which the steel materials were heated and hot-rolled, and were quenched (directly quenched) immediately after the hot rolling was completed. Some steel plates were air-cooled after hot rolling was completed, re-heated, and then re-heated and quenched (RQ) for quenching.

Test pieces were sampled from the obtained steel plates and subjected to structure observation, surface hardness test, Charpy impact test, and corrosion wear resistance test.
(1) Microstructure observation A specimen for microstructural observation was collected from a position where the thickness of the obtained steel sheet was ¼ so that the observation surface had a cross section parallel to the rolling direction. Corrosion caused the old γ grains. Observed with an optical microscope (magnification: 400 times), the equivalent circle diameter of 100 old γ grains was measured, the obtained values were arithmetically averaged, and the average value was taken as the old γ grain diameter of the steel sheet.

Similarly, a thin film specimen (transmission electron microscope structure observation specimen) is taken from a position that is 1/4 of the thickness of the obtained steel sheet, and the thin film is obtained by grinding and polishing (mechanical polishing, electrolytic polishing). And 20 fields of view with a transmission electron microscope (magnification: 20000 times), the area where cementite is not precipitated is the martensite phase area, the area is measured, and the ratio is expressed as a percentage (%) of the entire structure. The site fraction (area ratio) was used. In addition, about the phase in which cementite precipitated, the kind was also determined.
(2) Surface hardness test A test piece for measuring the surface hardness was collected from the obtained steel sheet, and the surface hardness HBW10 / 3000 was measured in accordance with the provisions of JIS Z 2243 (1998). For the hardness measurement, a tungsten hard ball of 10 mm was used, and the load was 3000 kgf.
(3) Charpy impact test V-notch test specimens were taken from the direction perpendicular to the rolling direction (C direction) at a quarter of the plate thickness of the obtained steel sheet, and conformed to the provisions of JIS Z 2242 (1998). A Charpy impact test was conducted. The test temperature calculated | required absorption energy vE- ₄₀ (J) in _-40 degreeC. Note that the number of test pieces was three each, and the arithmetic average was the absorbed energy vE- _{40 of the} steel sheet. A steel plate having a vE- ₄₀ of 30 J or more was evaluated as a steel plate excellent in the low temperature toughness of the base material.
(4) Corrosion-resistant wear test Abrasion test piece (size: 10mm thickness x 25mm width x 75mm length) was sampled from a position 1mm below the surface layer of the obtained steel sheet, mounted on a wear tester, and subjected to a wear test. did. The wear test piece is attached so that the surface of the test machine rotor is perpendicular to the rotation axis of the test machine rotor and the surface of 25 mm × 75 mm is in the circumferential tangent direction of the rotation circle, and then the test piece and the rotor are covered with an outer tub, Wear material was introduced inside. The wear material used was a mixture of cinnabar sand having an average particle diameter of 0.65 mm and an aqueous NaCl solution prepared to a concentration of 15000 ppm so that the weight ratio was 3: 2.

  The test conditions were such that the rotor was rotated at 600 times / minute and the outer tank was rotated at 45 times / minute. The rotor was rotated until the total number of rotations reached 10800 times. After completion of the test, the weight of each test piece was measured.

  The difference between the weight after the test and the initial weight (= weight reduction amount) is calculated, and the wear reduction ratio (= (reference value) / (test) The weight reduction amount of the piece)) was calculated. The case where the wear resistance ratio was 1.5 or more was evaluated as “excellent in wear resistance in a corrosive environment”.

Table 2 shows the manufacturing conditions and test results together. Examples of the present invention (Nos. 1 to 11) all have a high surface hardness of 400 HBW 10/3000 or more, an excellent low temperature toughness of vE- ₄₀ : 30 J or more, and an excellent corrosion resistance of 1.5 or more. It has sex. On the other hand, the comparative examples (Nos. 12 to 16) outside the scope of the present invention are inferior to the inventive examples in at least one of surface hardness, low temperature toughness, and corrosion wear resistance.

Claims (3)

% By mass
C: 0.18 to 0.25%,
Si: 0.05-1.00%,
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: 0.05-1.00%,
A composition comprising DI * defined by the following formula (1) of 45.0 or more, the balance Fe and inevitable impurities, and a structure having a martensite phase as a main phase as-quenched with a prior austenite grain size of 25 μm or less; Furthermore, a thick steel plate having excellent wear resistance in a corrosive environment, characterized in that the surface hardness is 400 or more according to Brinell hardness HBW10 / 3000.
DI * = 33.85 × (0.1 × C) ^0.5 × (0.7 × Si + 1) × (3.33 × Mn + 1) × (0.35 × Cu + 1) × (0.36 × Ni + 1) × (2.16 × Cr + 1) × (3 × Mo + 1) × (1.75 × V + 1) × (1.5 × W + 1) (1)
In the formula, each alloy element has a content (mass%). Furthermore, in mass%,
Mo: 0.05-1.00%,
Cu: 0.03-1.00%,
Ni: 0.03-2.00%,
V: 0.005-0.100%,
B: 0.0003 to 0.0030%
The thick steel plate having excellent wear resistance in a corrosive environment according to claim 1, comprising one or more selected from the group consisting of: Furthermore, in mass%,
REM: 0.0005 to 0.0080%,
Ca: 0.0005 to 0.0050%,
Mg: 0.0005 to 0.0050%,
The thick steel plate having excellent wear resistance in a corrosive environment according to claim 1 or 2, comprising one or more selected from the group consisting of: