Cr-W-Cu martensite heat-resistant steel and preparation method thereof

Abstract

The invention belongs to the field of heat-resistant steel casting, and relates to Cr-W-Cu martensite heat-resistant steel and a preparation method thereof. By optimizing the content of the tungsten (W) element and introducing the copper (Cu) element to replace cobalt (Co), the high-temperature strength and durability of the material are remarkably improved, and the production cost is greatly reduced. Tungsten serves as a solid solution strengthening element, the high-temperature strength of the steel is improved, meanwhile, uniform distribution of a Cu-rich phase in the steel is promoted, and the stability of Cr23C6 carbide is enhanced; and copper effectively inhibits generation of delta ferrite, is separated out along a grain boundary in a Cu-rich phase form, pinns the grain boundary and hinders martensite lath migration, so that the structure stability and the high-temperature strength are enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of heat-resistant steel casting, and relates to a Cr-W-Cu martensitic heat-resistant steel and a preparation method thereof. Background Art

[0002] Energy shortage and environmental pollution have become major problems restricting the economic development of countries around the world. With the acceleration of the global industrialization process, the demand for energy is increasing continuously. At the same time, the consumption of traditional energy has brought serious environmental problems, such as greenhouse gas emissions, acid rain, and air pollution. Ultra-supercritical thermal power generation technology, as an efficient and environmentally friendly power production method, can alleviate the above dilemmas to a great extent. By significantly improving the thermal efficiency, this technology reduces fuel consumption and corresponding pollutant emissions, and has become one of the key ways to solve the dual challenges of energy and environment.

[0003] During the operation of ultra-supercritical thermal power generating units, they need to withstand extremely high temperatures and pressures, which pose stringent requirements on the materials of their internal components. These materials not only need to be able to withstand high-temperature and high-pressure environments, but also possess corrosion resistance to ensure the safe and stable operation of the units. 9-12% Cr martensitic heat-resistant steels stand out due to their excellent thermophysical properties, oxidation resistance, corrosion resistance, high creep strength, and good heat-resistant fatigue characteristics, and have become an indispensable material choice for constructing ultra-supercritical thermal power generating units.

[0004] Currently, there are mainly three typical commercial martensitic heat-resistant steels on the market: First is the 9Cr-1Mo steel, which is a basic type of steel defined in the American ASME SA-213 standard and is applicable to working temperatures up to 500°C; second is the T / P91 steel, which is improved on the basis of 9Cr-1Mo. By adding trace elements such as nitrogen, vanadium, and niobium to form MX-type carbonitrides for precipitation strengthening, the strength of the steel is greatly improved; finally is the T / P92 steel, which is the product of the improvement of T / P91 in Japan and Europe. Using tungsten to replace molybdenum realizes composite solid-solution strengthening, further increasing the allowable stress of the steel.

[0005] With the continuous improvement of the steam parameters of ultra-supercritical units, the requirements for material properties are also constantly strengthening. To meet higher working conditions, researchers at home and abroad are exploring the research and development of a new generation of martensitic heat-resistant steels. For example, new steels such as SAVE12, MARBN, and G115 improve the high-temperature stability and creep strength by increasing the tungsten content and introducing cobalt. However, excessive use of tungsten may lead to excessive precipitation of δ-ferrite, affecting the long-term stability of the material and possibly causing early failure; while insufficient tungsten content is not enough to guarantee the high-temperature strength of the material. In addition, although the addition of cobalt can enhance the material properties, it will also significantly increase the cost, restricting its wide application. Summary of the Invention

[0006] The object of the present invention is to address the above problems existing in the prior art, and a Cr-W-Cu martensitic heat-resistant steel is proposed. By optimizing the content of element W and synergistically acting with element Cu, the strength and creep properties of the martensitic heat-resistant steel are improved, so that it can be applied to ultra-supercritical units.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A Cr-W-Cu martensitic heat-resistant steel, the composition and mass percentage content of the heat-resistant steel are as follows: 0.10-0.14% C, 10-12% Cr, 0.2-0.3% Si, 0.4-0.5% Ni, 0.5-0.8% Mn, 0.5-1.0% Mo, 1.0-1.5% W, 0.04-0.05% Nb, 0.18-0.23% V, 0.03-0.05% N, 0.008-0.012% B, 0.5-2.0% Cu, P≤0.02%, S≤0.02%, and the balance is Fe.

[0009] In the present invention, carbon forms carbides of types such as M23C6 and MX with alloying elements. These carbides can pin grain boundaries, improving the strength, tissue stability, and service life of the material. However, too high a carbon content will cause the aggregation and growth of carbides, thereby reducing the toughness and strength of the material. Therefore, the carbon content in the steel of the present invention is strictly controlled between 0.10-0.14% to ensure the best performance.

[0010] As the most important alloying element in martensitic heat-resistant steel, chromium not only improves oxidation resistance and corrosion resistance but also enhances high-temperature strength. However, too high a chromium content will cause the formation of δ-ferrite, thereby reducing creep strength and toughness. To balance these properties, the present invention selects to set the Cr content to 10-12%.

[0011] Silicon can enhance the ability of steel to resist high-temperature oxidation corrosion, but too much silicon will promote the precipitation of δ-ferrite and Laves phase, affecting tissue stability. Therefore, the content of silicon is controlled at 0.2-0.3% to maintain appropriate corrosion resistance and tissue stability.

[0012] In the present invention, the addition amount of nickel is controlled at 0.4-0.5% to achieve the best comprehensive performance. Nickel is an austenite-forming element, having a solid-solution strengthening effect and inhibiting the formation of δ-ferrite.

[0013] 0.5-0.8% of manganese in the present invention can improve hardenability, reduce the precipitation of carbides at grain boundaries, reduce the sensitivity to intergranular corrosion, and enhance corrosion resistance.

[0014] The molybdenum content is controlled at 0.5-1.0%, because molybdenum is an important ferrite-forming element, which can promote the formation of a dense surface oxide film, enhance the pitting resistance, and improve the performance through secondary hardening effect and solid solution strengthening.

[0015] The tungsten content is controlled at 1.0-1.5% to ensure the best performance of the material, because tungsten significantly improves the high-temperature strength of the steel, but excessive tungsten leads to the formation of δ-ferrite and reduces the comprehensive performance.

[0016] In the present invention, the niobium content is controlled at 0.04-0.05%. The Nb(C,N) precipitates formed at high temperature can inhibit the growth of austenite grains. At the same time, fine MX secondary phases are formed in the temperature range of 600-800 °C, further enhancing the strengthening effect. Vanadium and niobium act together to form Nb(C,N) precipitates to achieve precipitation strengthening. The addition amount of vanadium is controlled at 0.18-0.23% to obtain the best precipitation strengthening effect.

[0017] The addition amount of nitrogen is controlled at 0.03-0.05% can inhibit the formation of δ-ferrite and form stable carbonitrides with elements such as V and Nb, enhancing the tissue stability and creep strength.

[0018] The boron content is controlled at 0.008-0.012% can stabilize the grain boundaries and improve the strength, but excessive boron will form BN inclusions and deteriorate the performance.

[0019] In the present invention, 0.5-2.0% of Cu element is introduced as an alternative to Co element. It can not only effectively inhibit the formation of δ-ferrite, but also precipitate in the form of Cu-rich phase, pinning the grain boundaries, inhibiting the recovery and growth of martensite laths, enhancing the high-temperature strength and tissue stability, while improving the performance of martensitic heat-resistant steel and maintaining a relatively low cost.

[0020] In the above-mentioned Cr-W-Cu martensitic heat-resistant steel, 1.5wt% ≤ Cu + W ≤ 3.0wt%, 0.5 ≤ Cu / W ≤ 2.0. By setting the total content of Cu + W between 1.5wt% and 3.0wt%, the present invention ensures sufficient solid solution strengthening effect, which helps to improve the high-temperature strength of the steel. At the same time, an appropriate ratio of Cu / W (0.5 to 2.0) can balance the influence of the two elements on the material performance, avoiding negative effects caused by excessive content of a certain element, such as the formation of δ-ferrite or the reduction of material toughness.

[0021] The present invention also provides a preparation method of the above-mentioned Cr-W-Cu martensitic heat-resistant steel, and the method comprises the following steps:

[0022] S1. Configure raw materials according to the above components;

[0023] S2. Smelt the raw materials, remove the slag and deoxidize, and then tap the steel.

[0024] S3. After tapping the steel, cover the molten steel with a covering agent, and then pour it after cooling down.

[0025] S4. After pouring is completed, cool it, and then perform normalizing treatment.

[0026] S5. After normalizing treatment, perform tempering treatment, and finally air-cool to room temperature to obtain heat-resistant steel.

[0027] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, the smelting temperature in step S2 is 1600 - 1650 °C.

[0028] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, the covering agent in step S3 is a CaO-Al2O3-SiO2 basic covering agent.

[0029] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, after cooling down to 1550 - 1580 °C in step S3, perform pouring.

[0030] The present invention uses a CaO-Al2O3-SiO2 basic covering agent to protect the surface of the molten steel from oxidation. At the same time, maintaining an appropriate temperature (cooling down to 1550 - 1580 °C) helps to control the fluidity during the pouring process and prevent defects caused by excessive cooling.

[0031] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, after pouring is completed in step S4, cool it to 150 - 250 °C.

[0032] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, the normalizing treatment in step S4 is specifically: heat up to 950 - 1050 °C, hold for 1 - 3 h, and then air-cool to room temperature.

[0033] In the above preparation method of a Cr-W-Cu martensitic heat-resistant steel, the tempering treatment in step S5 is specifically: heat up to 650 - 750 °C, hold for 1 - 3 h.

[0034] In the present invention, after cooling to 150 - 250 °C, perform normalizing treatment (heat up to 950 - 1050 °C, hold for 1 - 3 h). This step optimizes the mechanical properties of the material by adjusting the grain structure, making the steel more uniform and stronger. The tempering treatment (heat up to 650 - 750 °C, hold for 1 - 3 h) further adjusts the internal structure of the steel, eliminates stress and improves toughness, and the final air-cooling process is to stabilize the organizational structure of the material and ensure its good comprehensive performance.

[0035] In the above preparation method of the Cr-W-Cu martensitic heat-resistant steel, in step S5, the high-temperature tensile strength of the heat-resistant steel at 600 °C is ≥556 MPa, the yield strength is ≥498 MPa, and under the conditions of 600 °C and 200 MPa, the creep rupture time is ≥174 h.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. Based on the 10-12% Cr martensitic heat-resistant steel and combined with the actual situation of industrial production, the present invention has developed an 11Cr-W-Cu martensitic heat-resistant steel that is particularly suitable for long-term service in a high-temperature environment of 600 °C.

[0038] 2. By optimizing the content of tungsten (W) element and introducing copper (Cu) element to replace cobalt (Co), the present invention not only significantly improves the high-temperature strength and creep properties of the material, but also greatly reduces the production cost. As a solid solution strengthening element, tungsten improves the high-temperature strength of the steel, promotes the uniform distribution of the Cu-rich phase in the steel, and enhances the stability of the Cr23C6 carbide; while copper effectively inhibits the formation of δ-ferrite, precipitates along the grain boundaries in the form of Cu-rich phase, pins the grain boundaries and hinders the migration of martensite laths, thereby enhancing the tissue stability and high-temperature strength.

[0039] 3. By utilizing the synergistic effect among solid solution strengthening, precipitation strengthening and dislocation strengthening, the prepared Cr-W-Cu martensitic heat-resistant steel realizes the effective improvement of room-temperature strength, high-temperature strength and creep properties.

[0040] 4. The Cr-W-Cu martensitic heat-resistant steel of the present invention fully meets the application conditions of ultra-supercritical units, can operate stably for a long time in a harsh environment of 600 °C, and provides strong support for a cleaner and more efficient energy utilization mode. Description of the Drawings

[0041] Figure 1 is the metallographic structure photograph of Examples 1-4; (a) Example 1; (b) Example 2; (c) Example 3; (d) Example 4;

[0042] Figure 2 is the tensile strength and yield strength of Examples 1-4 and Comparative Examples 1-7 at room temperature;

[0043] Figure 3 is the tensile strength and yield strength of Examples 1-4 and Comparative Examples 1-7 at 600 °C;

[0044] Figure 4 is the short-term creep rupture time of Examples 1-4 and Comparative Examples 1-7 under the conditions of 600 °C and 200 MPa. Detailed Embodiments

[0045] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0046] Embodiment 1

[0047] S1. Configure raw materials according to the following components: 0.12% C, 11.45% Cr, 0.25% Si, 0.43% Ni, 0.66% Mn, 0.86% Mo, 1.0% W, 0.05% Nb, 0.23% V, 0.037% N, 0.010% B, 0.5% Cu, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe;

[0048] S2. Melt the raw materials at 1620°C, remove slag and deoxidize, and then tap the steel.

[0049] S3. After tapping the steel, cover the molten steel with a CaO-Al2O3-SiO2 basic covering agent, and pour when the temperature drops to 1580°C.

[0050] The CaO-Al2O3-SiO2 basic covering agent is purchased from Zhengzhou Shengyuan Foundry Materials Co., Ltd.

[0051] S4. After the casting cools to 200°C, open the box, clean the burrs and flash.

[0052] S5. Normalize the casting: Put the casting into a heat treatment furnace, heat it up to 1000°C with the furnace, hold for 2 hours, and finally take out the casting and air-cool it to room temperature.

[0053] S5. Temper the casting: Put the casting into a heat treatment furnace, heat it up to 700°C with the furnace, hold for 2 hours, and finally take out the casting and air-cool it to room temperature.

[0054] Embodiment 2

[0055] S1. Configure raw materials according to the following components: 0.12% C, 11.45% Cr, 0.25% Si, 0.43% Ni, 0.66% Mn, 0.86% Mo, 1.24% W, 0.05% Nb, 0.23% V, 0.037% N, 0.010% B, 1.0% Cu, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe;

[0056] S2. Melt the raw materials at 1620°C, remove slag and deoxidize, and then tap the steel.

[0057] S3. After tapping the steel, cover the molten steel with a CaO-Al2O3-SiO2 basic covering agent, and pour when the temperature drops to 1580°C.

[0058] Among them, the CaO-Al2O3-SiO2 basic covering agent was purchased from Zhengzhou Shengyuan Foundry Materials Co., Ltd.;

[0059] S4. After the casting is cooled to 200 °C, it is taken out of the box, and the burrs and flash are removed;

[0060] S5. Normalize the casting: Put the casting into the heat treatment furnace, heat it up to 1000 °C with the furnace, hold for 2 h, and finally take out the casting and air-cool it to room temperature;

[0061] S5. Temper the casting: Put the casting into the heat treatment furnace, heat it up to 700 °C with the furnace, hold for 2 h, and finally take out the casting and air-cool it to room temperature.

[0062] Example 3:

[0063] S1. Configure raw materials according to the following composition: 0.13% C, 11.28% Cr, 0.26% Si, 0.41% Ni, 0.65% Mn, 0.81% Mo, 1.26% W, 0.05% Nb, 0.20% V, 0.036% N, 0.014% B, 1.5% Cu, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe;

[0064] S2. Melt the raw materials at 1620 °C, remove slag and deoxidize, and then tap the steel;

[0065] S3. After tapping the steel, cover the molten steel with a CaO-Al2O3-SiO2 basic covering agent, and pour when the temperature drops to 1580 °C;

[0066] Among them, the CaO-Al2O3-SiO2 basic covering agent was purchased from Zhengzhou Shengyuan Foundry Materials Co., Ltd.;

[0067] S4. After the casting is cooled to 200 °C, it is taken out of the box, and the burrs and flash are removed;

[0068] S5. Normalize the casting: Put the casting into the heat treatment furnace, heat it up to 1000 °C with the furnace, hold for 2 h, and finally take out the casting and air-cool it to room temperature;

[0069] S5. Temper the casting: Put the casting into the heat treatment furnace, heat it up to 700 °C with the furnace, hold for 2 h, and finally take out the casting and air-cool it to room temperature.

[0070] Example 4:

[0071] S1. Configure raw materials according to the following composition: 0.14% C, 12.0% Cr, 0.30% Si, 0.50% Ni, 0.80% Mn, 1.0% Mo, 1.0% W, 0.04% Nb, 0.18% V, 0.03% N, 0.008% B, 2.0% Cu, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe;

[0072] S2. Melting the raw materials at 1620 °C, removing slag and deoxidizing, and then tapping the steel.

[0073] S3. After tapping, covering the molten steel with a CaO - Al2O3 - SiO2 covering agent, and pouring when the temperature drops to 1580 °C.

[0074] The CaO - Al2O3 - SiO2 basic covering agent is purchased from Zhengzhou Shengyuan Foundry Materials Co., Ltd.

[0075] S4. After the casting cools to 200 °C, open the box, clean the burrs and flash.

[0076] S5. Normalizing the casting: Put the casting into a heat treatment furnace, heat it up to 1000 °C with the furnace, hold for 2 h, and finally take out the casting and air - cool it to room temperature.

[0077] S5. Tempering the casting: Put the casting into a heat treatment furnace, heat it up to 700 °C with the furnace, hold for 2 h, and finally take out the casting and air - cool it to room temperature.

[0078] Comparative Example 1:

[0079] The difference from the example is only that Cu is not added to the raw materials, and the addition amount of W is 0.5 wt%.

[0080] S1. Prepare the raw materials according to the following composition: 0.11% C, 11.31% Cr, 0.22% Si, 0.41% Ni, 0.66% Mn, 0.78% Mo, 0.5% W, 0.04% Nb, 0.22% V, 0.032% N, 0.010% B, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe.

[0081] S2. Melting the raw materials at 1620 °C, removing slag and deoxidizing, and then tapping the steel.

[0082] S3. After tapping, covering the molten steel with a CaO - Al2O3 - SiO2 covering agent, and pouring when the temperature drops to 1580 °C. The CaO - Al2O3 - SiO2 basic covering agent is purchased from Zhengzhou Shengyuan Foundry Materials Co., Ltd.

[0083] S4. After the casting cools to 200 °C, open the box, clean the burrs and flash.

[0084] S5. Normalizing the casting: Put the casting into a heat treatment furnace, heat it up to 1000 °C with the furnace, hold for 2 h, and finally take out the casting and air - cool it to room temperature.

[0085] S5. Tempering the casting: Put the casting into a heat treatment furnace, heat it up to 700 °C with the furnace, hold for 2 h, and finally take out the casting and air - cool it to room temperature.

[0086] Comparative Example 2:

[0087] The difference from the example is only that Cu is not added to the raw materials, and the addition amount of W is 1.0 wt%.

[0088] Comparative Example 3:

[0089] The difference from the example is only that Cu is not added to the raw materials, and the addition amount of W is 1.5 wt%.

[0090] Comparative Example 4:

[0091] The difference from the example is only that W is not added to the raw materials, and the addition amount of Cu is 0.5 wt%.

[0092] Comparative Example 5:

[0093] The difference from the example is only that W is not added to the raw materials, and the addition amount of Cu is 1.0 wt%.

[0094] Comparative Example 6:

[0095] The difference from the example is only that W is not added to the raw materials, and the addition amount of Cu is 1.5 wt%.

[0096] Comparative Example 7:

[0097] The difference from the example is only that W is not added to the raw materials, and the addition amount of Cu is 2.0 wt%.

[0098] Table 1: Detection Results of Heat-Resistant Steels Prepared in Examples 1-4 and Comparative Examples

[0099]

[0100]

[0101] In the present invention, the Cu and W contents of Examples 1-4 and Comparative Examples 1-7 are significantly different. Microstructure observation and mechanical property tests are carried out on Examples 1-4 and Comparative Examples 1-7. The microstructures of Examples 1-4 are as Figure 1 shown, the room-temperature tensile test results are as Figure 2 shown, the 600°C tensile test results are as Figure 3 shown, and a short-term creep rupture test is carried out under the conditions of 600°C and 200 MPa, and the test results are as Figure 4 shown.

[0102] I. The microstructures of the examples and comparative examples are as Figure 1 , 2 shown:

[0103] From Figure 1It can be seen that as the Cu content increases, the content of δ-ferrite gradually decreases. In particular, the content of δ-ferrite in Example 4 is the least. The Cu / W values of Examples 1-4 are 0.5, 0.8, 1.2, and 2.0 respectively. The higher the Cu / W value, the less the content of δ-ferrite. This shows that Cu can inhibit the formation of δ-ferrite in steel, and Cu can offset the adverse effects of W, playing a role in synergistic strengthening.

[0104] II. The test results of the room-temperature tensile test are as Figure 2 shown:

[0105] It can be seen from the figure that the tensile strength and yield strength of the examples at room temperature are higher than those of the comparative examples. At the same time, the tensile strength and yield strength of Example 4 are significantly higher than those of other examples. The strengthening effect of the combined addition of Cu and W is stronger than that of the individual addition of Cu and W. As the total content of Cu and W increases, the strengthening effect becomes more obvious. The Cu+W value of Example 4 is the largest, and it exhibits higher strength at room temperature.

[0106] III. The test results of the 600°C tensile test are as Figure 3 shown:

[0107] It can be seen from the figure that at 600°C, the tensile strength and yield strength of the examples are higher than those of the comparative examples, and the tensile strength and yield strength of Example 4 are significantly higher than those of other examples. The strengthening effect of the combined addition of Cu and W is stronger than that of the individual addition of Cu and W. The higher the total content of Cu and W, the more obvious the strengthening effect. The martensitic heat-resistant steel prepared in Example 4 (containing 2.0% Cu and 1.0% W) has higher high-temperature strength.

[0108] IV. The test results of the short-term creep rupture test under the conditions of 600°C and 200 MPa are as Figure 4 shown:

[0109] It can be seen from the data in the figure that under the conditions of 600°C and 200 MPa, the creep rupture time of the examples is longer than that of the comparative examples, and the creep rupture time of Example 4 is longer, showing more excellent creep rupture performance.

[0110] The above test results show that the 11Cr-W-Cu martensitic heat-resistant steel of the present invention greatly reduces the production cost by optimizing the content of W element and introducing Cu element to replace Co element. By utilizing the synergistic effect of W element and Cu element, the room-temperature strength, high-temperature strength and creep rupture performance of the martensitic heat-resistant steel are effectively improved.

[0111] In the embodiments herein, the new technical solutions formed by the unexhausted midpoint values in the technical scope claimed by the present invention and the equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed by the present invention; at the same time, in all the listed or unlisted embodiments of the present invention, each parameter in the same embodiment only represents an example (i.e., a feasible solution) of its technical solution, and there is no strict cooperation and limitation relationship between the parameters. Among them, the parameters can be replaced with each other without violating the axioms and the requirements of the present invention, except as otherwise specifically stated.

[0112] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed by the above technical means, but also include the technical solutions formed by any combination of the above technical features. The above is the specific implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

[0113] The specific embodiments described herein are only illustrative of the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A Cr-W-Cu martensitic heat-resistant steel, characterized in that, The composition of the heat-resistant steel and its mass percentage content are as follows: 0.10 - 0.14% C, 10 - 11% Cr, 0.2 - 0.3% Si, 0.4 - 0.5% Ni, 0.5 - 0.8% Mn, 0.5 - 1.0% Mo, 1.0 - 1.5% W, 0.04 - 0.05% Nb, 0.18 - 0.22% V, 0.03 - 0.05% N, 0.008 - 0.012% B, 0.5 - 2.0% Cu, P ≤ 0.02%, S ≤ 0.02%, and the balance is Fe.

2. The martensitic heat-resistant steel Cr-W-Cu according to claim 1, characterized in that, 1.5wt% ≤ Cu + W ≤ 3.0wt%, 0.5 ≤ Cu / W ≤ 2.

0.

3. A preparation method of the Cr-W-Cu martensitic heat-resistant steel as described in claim 1, characterized in that, The method includes the following steps: S1. Configure raw materials according to the composition described in Claim 1; S2. Melt the raw materials, remove slag and deoxidize, and then tap the steel; S3. After tapping, cover the molten steel with a covering agent, and then pour after cooling; S4. After pouring, cool, and then perform normalizing treatment; S5. After normalizing treatment, perform tempering treatment, and finally air-cool to room temperature to obtain the heat-resistant steel.

4. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, The melting temperature in Step S2 is 1600 - 1650°C.

5. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, The covering agent in Step S3 is a CaO - Al2O3 - SiO2 basic covering agent.

6. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, In Step S3, pour after cooling to 1550 - 1580°C.

7. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, In Step S4, cool to 150 - 250°C after pouring.

8. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, The specific normalizing treatment in Step S4 is: heat up to 950 - 1050°C, hold for 1 - 3 h, and then air-cool to room temperature.

9. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, The specific tempering treatment in Step S5 is: heat up to 650 - 750°C, hold for 1 - 3 h.

10. The preparation method of a Cr-W-Cu martensitic heat-resistant steel according to claim 3, characterized in that, The heat-resistant steel in Step S5 has a high-temperature tensile strength ≥ 556 MPa at 600°C, a yield strength ≥ 498 MPa, and a creep rupture time ≥ 296 h under the conditions of 600°C and 200 MPa.

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