JP6217671B2 - Thick steel plate with excellent wear resistance in high temperature environments - Google Patents

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 having excellent wear resistance in a high temperature 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.

  In particular, steel sheets that are exposed to wear environments that generate significant heat due to wear, such as when the earth and sand handled are high in hardness, and members that are used in high-temperature environments, the hardness decreases at high temperatures and wear resistance decreases. Therefore, a wear resistant steel material excellent in high temperature wear resistance is desired. Industrial machinery, transportation equipment, and the like are also expected to be used in a low temperature range of 0 ° C. or lower, and therefore, it is desired to have excellent low temperature toughness in addition to high temperature wear resistance. 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 a high temperature environment.

  Moreover, each technique described in Patent Literatures 1 to 4 requires tempering, and there is a problem that the manufacturing cost increases.

  The present invention has been made to solve such 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 high-temperature 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 high temperature wear resistance. As a result, it has been found that the high temperature 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 30 μm or less, excellent low temperature toughness can be ensured while ensuring excellent high temperature 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 30 μm or less; Furthermore, a thick steel plate having excellent wear resistance in a high-temperature environment, wherein the surface hardness is 400 or more in 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 is a content (% by mass), and an element not contained is 0.
(2)
Furthermore, in mass%,
N: 0.0015 to 0.0050%,
The thick steel plate having excellent wear resistance in a high-temperature environment as described in (1).
(3) 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%
A thick steel plate having excellent wear resistance in a high-temperature environment according to (1) or (2), comprising one or more selected from the group consisting of:
(4) 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 high-temperature environment according to any one of (1) to (3), comprising one or more selected from the group consisting of:

  According to the present invention, it has excellent low temperature toughness, and when it is used for a member exposed to a wear environment that generates significant heat due to wear, such as when the hardness of earth and sand to be handled is high, or a member used in a high temperature environment. A thick steel plate having the required high-temperature wear resistance is obtained, and has a remarkable industrial effect.

The wear-resistant steel sheet according to the present invention defines the component composition, microstructure, and surface hardness.
[Component 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 contributes to the improvement of high-temperature wear resistance by suppressing the decrease in high-temperature hardness by solid solution strengthening in an environment exposed to heat generation or high temperature due to wear. In order to acquire such an effect, 0.05% or more of content is required. If it is less than 0.05%, such an effect cannot be exhibited sufficiently. On the other hand, when it contains exceeding 2.00%, weldability will fall and manufacturing cost will rise. For this reason, Cr was limited to 0.05 to 2.00% of range. 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. TiN is an element that pins the austenite grain boundary and suppresses the coarsening of the austenite grain. 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. Also, in an environment where heat is generated due to wear or exposed to high temperatures, solid solution W is finely precipitated, and solid solution strengthening of solid solution W suppresses a decrease in high-temperature hardness, resulting in high-temperature wear resistance. Has the effect of improving. In order to acquire such an effect, 0.05% or more of content is required. If W is less than 0.05%, such an effect cannot be exhibited sufficiently. On the other hand, when it contains exceeding 1.00%, weldability will fall and manufacturing cost will rise. For this reason, W was limited to the range of 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. An example of an unavoidable impurity is N. N is an impurity, but if it is contained in an appropriate amount, it has a useful effect. Therefore, it is preferable to adjust the N content in the molten steel in the following range in the degassing treatment in the steel making process. 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.

N: 0.0015 to 0.0050%
N is an element that reacts with Ti and precipitates as TiN, contributing to the refinement of the austenite grain size. In order to acquire such an effect, it is necessary to contain 0.0015% or more. On the other hand, if the content exceeds 0.0050%, coarse nitrides precipitate and the toughness decreases, so the content is limited to the range of 0.0015 to 0.0050%. In addition, since excessive denitrification increases steelmaking cost, it is preferable to limit to 0.0020 to 0.0050% of range from a viewpoint of cost reduction.

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 0.10 to 0.20%.

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%. In addition, Preferably it is 0.020 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. If contained, the content is limited to the range of 0.0005 to 0.0080%. In addition, Preferably it is 0.0005 to 0.0030%.

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 sheet according to the present invention has the above-described composition, has a structure in which the martensite phase is the main phase as quenched and the prior austenite grain size is 30 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.

Old austenite grain size: 30 μm or less Even if the martensite phase fraction can be kept 90% or more in the area ratio, if the old γ grain size exceeds 30 μm and becomes coarse, the low temperature toughness decreases. The following. Preferably it is 25 micrometers or less, More preferably, it is 20 micrometers or less. 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, the preferable manufacturing method of the abrasion-resistant steel plate which concerns on this invention is demonstrated. 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. Even if it is any of a direct quenching process and a reheating quenching process, a tempering process is not performed after that.

  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 high temperature 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) High temperature wear resistance test Samples for high temperature hardness measurement are taken from the obtained steel sheet, the cross section of the steel sheet is polished to a mirror surface, and high temperature Vickers hardness is measured in accordance with the provisions of JIS Z 2252 (1991). did. The measurement position was 1 mm from the surface, and the test load was 1 kgf. The case where the high temperature Vickers hardness at 300 ° C. was 300 or more was evaluated as being excellent in “high temperature wear resistance”.

The obtained results are shown in Table 2. Each of the inventive examples has a high surface hardness of 400 HBW 10/3000 or higher, an excellent low temperature toughness of vE- ₄₀ : 30J or higher, and an excellent high temperature wear resistance of 300 or higher. On the other hand, in comparative examples that are outside the scope of the present invention, the surface hardness is low, the low-temperature toughness is reduced, the high-temperature hardness is low, or two or more of them are reduced.

Table 2 shows the manufacturing conditions and test results together. Each of the inventive examples (Nos. 1 to 11) has a high surface hardness of 400HBW10 / 3000 or more, an excellent low temperature toughness of vE- ₄₀ : 30J or more, and an excellent high temperature wear resistance of 300 or more. Have. 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 high temperature wear resistance.

  Steel sheets having the compositions shown in Table 3 were prepared in the same manner as in Example 1. Test pieces were collected from the obtained steel plates and subjected to structure observation, surface hardness test, Charpy impact test, and high temperature wear resistance test in the same manner as in Example 1.

Table 4 shows the obtained results. Each of the inventive examples has a high surface hardness of 400 HBW 10/3000 or higher, an excellent low temperature toughness of vE- ₄₀ : 30J or higher, and an excellent high temperature wear resistance of 300 or higher. On the other hand, in comparative examples that are outside the scope of the present invention, the surface hardness is low, the low-temperature toughness is reduced, the high-temperature hardness is low, or two or more of them are reduced.

Table 4 shows manufacturing conditions and test results together. Each of the inventive examples (Nos. 17 to 27) has a high surface hardness of 400 HBW 10/3000 or more, an excellent low temperature toughness of vE- ₄₀ : 30J or more, and an excellent high temperature wear resistance of 300 or more of high temperature hardness. Have. On the other hand, the comparative examples (Nos. 28 to 32) outside the scope of the present invention are inferior to the inventive examples in at least one of surface hardness, low temperature toughness, and high temperature wear resistance.

Claims (4)

% 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 30 μm or less; Furthermore, a thick steel plate having excellent wear resistance in a high-temperature environment, wherein the surface hardness is 400 or more in 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 is a content (% by mass), and an element not contained is 0. Furthermore, in mass%,
N: 0.0015 to 0.0050%,
The thick steel plate having excellent wear resistance in a high-temperature environment according to claim 1. The Si content is 0.34 to 1.00%;
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 high temperature environment according to claim 1 or 2, comprising one or more selected from the group consisting of: The Si content is 0.34 to 1.00%;
Furthermore, in mass%,
REM: 0.0005 to 0.0080% ,
M g: 0.0005~0.0050%,
The thick steel plate having excellent wear resistance in a high temperature environment according to any one of claims 1 to 3, wherein the steel plate contains one or more selected from the group consisting of: