A high-temperature resistant and low-cost 12Cr5Mo steel plate and its manufacturing method and application

Abstract

The present invention provides a high-temperature resistant, low-cost 12Cr5Mo steel plate, its manufacturing method, and application. The steel plate comprises C 0.10-0.13%, Si 0.05-0.15%, Mn 0.35-0.50%, P ≤ 0.015%, S ≤ 0.005%, Cr 4.00-4.20%, Mo 0.45-0.55%, Alt 0.010-0.040%, V 0.020-0.030%, N ≤ 0.0080%, (Alt+V) / (N)>5, and the remainder is Fe and unavoidable impurities. The present invention adopts the above composition and controls rolling and tempering to produce a 12Cr5Mo steel plate having a microstructure of bainite and a small amount of ferrite. Compared with conventional normalizing and tempering or full annealing processes, the steel of the present invention contains a small amount of ferrite, which improves the steel's low-temperature toughness and shortens the process flow. The steel plate can be used to manufacture steel pipes and meet the performance requirements of high-temperature resistant steel pipes.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal materials, and in particular relates to a high-temperature resistant and low-cost 12Cr5Mo steel plate and a manufacturing method and application thereof. Background Art

[0002] Grade 12Cr5Mo, specified in the GB / T20878-2007 standard, is suitable for use in rods, tubes, and billets. It is a ferritic heat-resistant steel with excellent oxidation and corrosion resistance. It is primarily used in chemical equipment and pipelines operating at temperatures between -40°C and 400°C and pressures between 10 MPa and 32 MPa, and is suitable for transporting media such as synthetic ammonia, urea, and methanol. The heat treatment process primarily involves full annealing, which involves heating to a temperature above Ac3, holding the temperature for a specified period, and then cooling the steel to room temperature.

[0003] The patent with publication number CN 113005276 A, published on June 22, 2021, discloses a new annealing heat treatment process for 12Cr5Mo seamless steel pipes for high-pressure fertilizer equipment. The round billet is pierced and rolled into pipes. The size of the pipes is limited, the full annealing time is long, and the manufacturing cost is high; and the performance of the patented product is relatively low.

[0004] In addition, 12Cr5Mo steel contains a large amount of alloy, especially Cr content of more than 4%. In order to improve welding performance and reduce the carbon content in the steel, it is in the peritectic reaction zone. During the entire process of alloy solidification, it shrinks violently, which can easily lead to cracks in the casting. The addition of more alloying elements destroys the regularity of the atomic arrangement of the steel, making heat conduction difficult. Therefore, this steel requires a longer heating time, and the thermal conductivity of high-chromium steel is poor.

[0005] Therefore, it is very necessary to provide a high-temperature resistant and low-cost 12Cr5Mo steel with low cost, shortened production cycle and excellent performance. Summary of the Invention

[0006] The present invention aims to provide a high-temperature resistant and low-cost 12Cr5Mo steel plate and a manufacturing method thereof. The 12Cr5Mo steel plate is produced by adopting low carbon, low silicon and low manganese, appropriately adding chromium and molybdenum elements, controlling the content of aluminum and vanadium as grain-refining elements, and controlling the rolling + tempering process to produce a 12Cr5Mo steel plate with a thickness of 6 to 12 mm. The 12Cr5Mo steel plate has the following properties: a transverse impact value of greater than 110 J at -20°C, a yield strength of 520 MPa or more, a tensile strength of 640 MPa to 680 MPa, an elongation of 33% or more, and a high-temperature yield strength of 440 MPa or more at 500°C.

[0007] Another object of the present invention is to provide a high-temperature, low-cost 12Cr5Mo steel plate for use in the manufacture of petroleum cracking tubes, high-pressure boiler superheater tubes with wall temperatures ≤500°C, headers, or steam pipes. This high-temperature, low-cost 12Cr5Mo steel plate exhibits a -20°C transverse impact strength greater than 110 J, a yield strength ≥520 MPa, a tensile strength of 640 MPa-680 MPa, an elongation ≥33%, and a 500°C yield strength ≥440 MPa. Through reeling and welding, it can produce steel pipes that meet the design requirements of high-pressure boiler superheater tubes, headers, and steam pipes for petroleum cracking or with wall temperatures ≤500°C.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following components in percentage by mass:

[0010] C: 0.10~0.13%, Si: 0.05~0.15%, Mn: 0.35~0.50%, P≤0.015%, S≤0.005%, Cr: 4.00~4.20%, Mo: 0.45~0.55%, Alt: 0.010~0.040%, V: 0.020~0.030%, N≤0.0080%, and the balance is Fe and unavoidable impurities.

[0011] The composition of the high temperature resistant and low cost 12Cr5Mo steel plate also satisfies: (Alt+V) / (N)>5;

[0012] When calculating the above formula, the symbol of each element represents its mass percentage content × 100;

[0013] The high-temperature resistant and low-cost 12Cr5Mo steel plate has a structure of bainite and a small amount of ferrite, wherein the area of ferrite accounts for 1% to 2%; the banded structure of the high-temperature resistant and low-cost 12Cr5Mo steel plate after heat treatment is not higher than level 0.5.

[0014] The high-temperature resistant and low-cost 12Cr5Mo steel plate has a transverse impact value of greater than 110J at -20°C, a yield strength of 520MPa or more, a tensile strength of 640MPa to 680MPa, an elongation of 33% or more, and a high-temperature yield strength of 440MPa or more at 500°C.

[0015] The design ideas of the present invention are as follows:

[0016] Carbon: The most effective element for increasing steel strength, forming carbides with chromium and molybdenum to ensure the strength of the steel plate. However, higher carbon content reduces weldability, impact toughness, and elongation, so this steel grade is designed with a carbon content of 0.10-0.13%.

[0017] Silicon: A residual element in molten iron, silicon dioxide reacts with chromium in steel at high temperatures under certain conditions to form high-melting calcium silicate, which affects the smelting process. This reaction can lead to increased corrosion and wear of furnace lining materials, increasing equipment maintenance costs. Therefore, this steel grade is selected to contain 0.05-0.15%.

[0018] Manganese: It is an important strengthening and toughening element. As the manganese content increases, the banded structure in the steel becomes more serious and segregation becomes more obvious, which affects the corrosion resistance. Therefore, the manganese content of this steel is selected to be 0.35-0.50%.

[0019] Chromium: It improves the strength of steel and has a positive impact on its corrosion resistance. However, as the chromium content increases, the steel plate's low-temperature impact toughness decreases, the tensile strength exceeds the standard, and the elongation fails to meet the requirements. Therefore, the chromium content of this steel is selected to be between 4.00-4.20%.

[0020] Molybdenum: It increases the strength of steel, helps to reduce the high temperature temper brittleness of steel, and improves the high temperature mechanical properties of steel. Therefore, the content of this steel is selected at 0.45-0.55%.

[0021] Aluminum: Fixes nitrogen in steel, forms second phase precipitation, refines grains, and improves the strength and toughness of steel plates, so the content of this steel grade is selected at 0.010-0.040%.

[0022] Vanadium: It delays austenite recrystallization, lowers the phase transition temperature, significantly refines grains, and improves low-temperature toughness. During tempering, precipitation strengthening increases the steel's strength. Therefore, the selected content for this steel is 0.020-0.030%.

[0023] P and S are unavoidable harmful impurity elements in steel. Impurity elements like S and P in steel tend to segregate at grain boundaries, forming network or flaky compounds, which reduces grain boundary strength. To minimize temper brittleness, this steel grade is designed with P ≤ 0.015% and S ≤ 0.005%.

[0024] The present invention provides a method for manufacturing a high-temperature resistant and low-cost 12Cr5Mo steel plate, which comprises steelmaking, billet heating, rolling and heat treatment.

[0025] The steelmaking process includes the following processes: converter smelting, LF refining, RH vacuum refining, continuous casting, and billet cleaning.

[0026] The converter smelting adopts slide plate slag blocking + slag blocking plug slag blocking, and requires P≤0.012% when tapping;

[0027] When 1 / 4 of the steel is tapped, add it in the order of "aluminum block-metallic manganese", and micro-carbon ferrochrome-ferromolybdenum are added during the refining process;

[0028] The LF refining process includes heating and slagging for 60 to 80 minutes, controlling [S] to be less than or equal to 0.005%. After the composition is uniform, 100 to 200 meters of seamless calcium wire is fed, and the soft blowing time is greater than or equal to 10 minutes.

[0029] During the continuous casting and pouring process, the amount of secondary cooling water is small to prevent rapid cooling of the billet and cracking of the slab. The superheat is controlled within the range of 10-30°C. A 210mm×1400mm cross-section casting machine is used, the casting speed is 1.3±0.05m / min, the secondary cooling water ratio is 0.8±0.05L / kg, and the crystallizer liquid level fluctuation is within the range of ±3mm.

[0030] The billet is heated and continuously cast, and the slab is cut as soon as possible. The temperature of the slab entering the heating furnace is 350-550°C.

[0031] During billet heating, the high alloy content in the steel reduces the heating temperature to prevent rapid heating of the slab, which can lead to large temperature differences between the inside and outside of the slab and cracking. The slab's time in the furnace is extended to allow for full and uniform diffusion of the alloying elements. The billet's preheating temperature is 700-900°C, the first heating stage is 1100-1200°C, the second heating stage is 1200-1250°C, and the soaking temperature is 1200-1240°C. The furnace time is (0.85-1.10) × H minutes, where H is the slab thickness in mm. After reaching temperature, rolling is performed.

[0032] The rolling is performed in one stage;

[0033] The one-stage rolling is specifically as follows: the starting rolling temperature of the rough rolling is greater than 1000°C, the roller speed is ≤2.5m / s, and the pass reduction rate is 10-12%; during rolling, high-pressure water is prevented from gathering to cool the surface of the steel plate, and at the same time, the cooling water between the stand rollers is reduced to 50%; the final rolling temperature is 850-880°C, air cooling or weak cooling is performed after rolling, and the red-return temperature is 780±20°C.

[0034] The heat treatment includes a tempering process;

[0035] The tempering process includes a tempering temperature of 750±10° C. and a furnace time of 1.5×H+60 minutes, where H is the thickness of the steel plate in mm.

[0036] The present invention adopts appropriate smelting and continuous casting processes to improve alloy yield and stabilize product quality. While ensuring the excellent mechanical properties of the steel plate, the heat treatment process is optimized, which not only shortens the production cycle but also reduces manufacturing costs.

[0037] Compared to existing technologies, the alloy content of the steel in this invention exceeds 4.5%. After tapping from the converter, a higher alloy content is added, and the refining heating and slagging time is controlled to 60 to 80 minutes, which helps control the nitrogen content absorbed into the steel. By adding aluminum and vanadium, the ω(Alt+V) / ω(N) requirement of >5 is achieved, which stabilizes the nitrogen content in the steel, inhibits nitrogen accumulation at grain boundaries, and improves the steel's high-temperature creep properties. The steel's recrystallization temperature is approximately 850°C. By controlling the final rolling temperature to 850 to 880°C, not only does it refine the austenite grains, but it also facilitates strain-induced precipitation, allowing the rolled steel to acquire a certain amount of ferrite, improving the impact toughness after tempering. The heat treatment method of this invention only requires tempering, with a controlled tempering process at a temperature below the austenitization temperature. The ferrite produced after rolling is retained, resulting in a microstructure composed of bainite and a small amount of ferrite. Compared to conventional processes involving normalizing and tempering or full annealing, the low ferrite content in this invention improves the steel's low-temperature toughness and shortens the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the structure of the steel plate after heat treatment in Example 3. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0041] Example 1

[0042] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following chemical components in percentage by mass: as shown in Table 1; the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0043] Example 1 A method for manufacturing a high-temperature resistant and low-cost 12Cr5Mo steel plate includes steelmaking, billet heating, rolling, and heat treatment. The specific process is as follows:

[0044] 1) Steelmaking process: The process includes converter smelting, LF refining and continuous casting. The converter smelting adopts slide plate slag blocking + slag plug slag blocking. The P content of converter steel is 0.012%. When 1 / 4 of the steel is tapped, it is added in the order of "aluminum block-metallic manganese". Micro-carbon ferrochrome-ferromolybdenum is added during the refining process. The heating and slag making time is 61 minutes, and the S content is 0.002%. 120 meters of seamless calcium wire are fed, and the soft blowing time is 12 minutes. The superheat during the casting process is 23°C. A 210mm×1400mm cross-section casting machine is used. The casting speed is 1.3m / min, the secondary cooling water volume is 0.8L / kg, the crystallizer liquid level fluctuation is 2mm, and the slab surface is defect-free.

[0045] 2) Billet heating process: The temperature of the thick billet of 210mm thickness entering the furnace is 380℃, the temperature of the preheating section is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 200 minutes, and rolling is carried out after reaching the temperature;

[0046] 3) Rolling process: adopt one-stage rolling, rough rolling start temperature 1058℃, high temperature, low speed and large reduction rolling, roller speed ≤ 2.5m / s, pass reduction rate 11%, avoid high pressure water accumulation to cool the steel plate surface during rolling, and reduce the cooling water between the stand rollers to 50%, final rolling temperature 856℃, rolling 6mm; air cooling after rolling, return to red temperature 768℃;

[0047] 4) Heat treatment process: The steel plate is tempered and kept at 755℃ in the furnace for 69 minutes, and then air-cooled after being taken out of the furnace.

[0048] Example 2

[0049] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following chemical components in percentage by mass: as shown in Table 1; the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0050] The method for manufacturing the high-temperature resistant and low-cost 12Cr5Mo steel plate includes the following processes:

[0051] 1) Steelmaking process: including converter smelting, LF refining and continuous casting; using slide plates and slag plugs to block slag, the converter tapping P is 0.012%, and aluminum blocks are added in the order of "metallic manganese" when 1 / 4 of the steel is tapped, and micro-carbon ferrochrome and ferromolybdenum are added during the refining process; the heating and slag-making time in the LF refining process is 65 minutes, and the S content is 0.002%; 130 meters of seamless calcium wire is fed, and the soft blowing time is 11 minutes; during the casting process, the superheat is 20°C, a 210mm×1400mm cross-section casting machine is used, the casting speed is 1.3m / min, the secondary cooling water volume is 0.8L / kg, the crystallizer liquid level fluctuation is 2mm, and the slab surface is defect-free.

[0052] 2) Billet heating process: The temperature of the thick billet of 210mm thickness is 400℃ when entering the furnace, the temperature of the preheating section is 750-850℃, the first heating section is 1150-1200℃, the second heating section is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 210 minutes, and rolling is carried out after reaching the temperature;

[0053] 3) Rolling process: adopt one-stage rolling, rough rolling starting temperature 1045℃, high temperature, low speed and large reduction rolling, roller speed ≤ 2.5m / s, pass reduction rate 12%, avoid high pressure water accumulation to cool the steel plate surface during rolling, and reduce the cooling water between the stand rollers to 50%, final rolling temperature 866℃, rolling 10mm; air cooling after rolling, return to red temperature 765℃;

[0054] 4) Heat treatment process: The steel plate is tempered and kept at 755℃ in the furnace for 75 minutes, and then air-cooled after being taken out of the furnace.

[0055] Example 3

[0056] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following chemical components in percentage by mass: as shown in Table 1; the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0057] The method for manufacturing the high-temperature resistant and low-cost 12Cr5Mo steel plate includes the following processes:

[0058] 1) Steelmaking process: The process includes converter smelting, LF refining and continuous casting; the converter tapping adopts slide plate + slag plug to block slag, the steel tapping P is 0.011%, and "aluminum block-metallic manganese" is added in the order of "aluminum block-metallic manganese" when 1 / 4 of the steel is tapped. Micro-carbon ferrochrome-ferromolybdenum is added during the refining process; the LF refining process heating and slag making time is 65 minutes, and the S content is 0.001%; 115 meters of seamless calcium wire is fed, and the soft blowing time is 13 minutes; during the casting process, the superheat is 20°C, a 210mm×1400mm cross-section casting machine is used, the casting speed is 1.3m / min, the secondary cooling water volume is 0.8L / kg, the crystallizer liquid level fluctuation is 2mm, and the slab surface is defect-free.

[0059] 2) Billet heating process: 210mm thick billet enters the furnace at a temperature of 395℃, the preheating section temperature is 750-850℃, the first heating section temperature is 1150-1200℃, the second heating section temperature is 1230-1250℃, the soaking temperature is 1220-1240℃, the furnace time is 205 minutes, and rolling is carried out after reaching temperature;

[0060] 3) Rolling process: adopt one-stage rolling, rough rolling start temperature 1050℃, high temperature, low speed and large reduction rolling, roll speed ≤ 2.5m / s, pass reduction rate 11%, avoid high pressure water accumulation to cool the steel plate surface during rolling, and reduce the cooling water between the stand rollers to 50%; final rolling temperature 870℃, rolling 12mm; weak cooling after rolling, return to red temperature 770℃;

[0061] 4) Heat treatment process: The steel plate is tempered and kept at 760℃ in the furnace for 78 minutes, and then air-cooled after being taken out of the furnace.

[0062] Comparative Example 1

[0063] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following chemical components in percentage by mass: as shown in Table 1; the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0064] The method for manufacturing the high-temperature resistant and low-cost 12Cr5Mo steel plate includes the following processes:

[0065] 1) Steelmaking process: The process flow includes converter smelting, LF refining, and continuous casting. The P content of the converter steel is 0.012%. When 1 / 4 of the steel is tapped, aluminum blocks are added in the order of "metallic manganese". Micro-carbon ferrochrome and ferromolybdenum are added during the refining process. In the LF refining process, the heating and slagging time is 61 minutes, and the S content is 0.002%. The seamless calcium wire is fed for 120 meters, and the soft blowing time is 12 minutes. The superheat is 23°C, the casting speed is 1.3 m / min, the secondary cooling water volume is 0.8 L / kg, the crystallizer liquid level fluctuation is 2 mm, and the slab surface is defect-free.

[0066] 2) Billet heating process: 210mm thick billet enters the furnace at a temperature of 380℃, preheating section temperature of 750-850℃, first heating section temperature of 1150-1200℃, second heating section temperature of 1230-1250℃, soaking temperature of 1220-1240℃, furnace time of 200 minutes, and rolling after reaching temperature;

[0067] 3) Rolling process: adopt one-stage rolling, rough rolling starting temperature 1058℃, high temperature, low speed and large reduction rolling, roll speed ≤ 2.5m / s, pass reduction rate 11%, final rolling temperature 856℃, rolling 6mm; air cooling after rolling, red-return temperature 768℃;

[0068] 4) Heat treatment process: steel plate tempering and insulation 730℃ The oven time was 69 minutes, and it was air-cooled after being taken out of the oven.

[0069] Comparative Example 2

[0070] A high-temperature resistant and low-cost 12Cr5Mo steel plate comprises the following chemical components in percentage by mass: see Table 1 below; the remainder is Fe and unavoidable impurities.

[0071] The method for manufacturing the high-temperature resistant and low-cost 12Cr5Mo steel plate includes the following processes:

[0072] 1) Steelmaking process: The process includes converter smelting, LF refining and continuous casting; the P content of converter steel is 0.012%, and aluminum block-metallic manganese is added in the order of 1 / 4 of the steel is tapped, and micro-carbon ferrochromium-ferromolybdenum is added in the refining process; in the LF refining process, When heating and slagging 90 minutes , S content 0.002%; feeding seamless calcium wire 118 meters, soft blowing time 13 minutes; superheat 24 ℃, using 210mm×1400mm section casting machine, casting speed 1.3m / min, secondary cooling water volume 0.8L / kg, crystallizer liquid level fluctuation 2mm, slab surface has no defects.

[0073] 2) Billet heating process: 210mm thick billet enters the furnace at a temperature of 389°C, the preheating section temperature is 750-850°C, the first heating section is 1150-1200°C, the second heating section is 1230-1250°C, the soaking temperature is 1220-1240°C, the furnace time is 205 minutes, and rolling is carried out after reaching temperature;

[0074] 3) Rolling process: adopt one-stage rolling, rough rolling starting temperature 1056℃, high temperature, low speed and large reduction rolling, roll speed ≤ 2.5m / s, pass reduction rate 11%, final rolling temperature 859℃, rolling 12mm; air cooling after rolling, red-return temperature 765℃;

[0075] 4) Heat treatment process: The steel plate is tempered and kept at 760℃ in the furnace for 78 minutes, and then air-cooled after being taken out of the furnace.

[0076] Table 1 Mass percentage of 12Cr5Mo steel plates in various embodiments and comparative examples (wt%)

[0077]

[0078]

[0079] The steel plates were tested for performance according to the GB / T228.1 tensile test, the GB / T229 impact test, and the GB / T4338 high-temperature tensile test. The mechanical properties of the high-temperature-resistant, low-cost 12Cr5Mo steel plates described in Examples 1-3 and Comparative Examples 1-2 are shown in Table 2. The banded structure of the high-temperature-resistant, low-cost 12Cr5Mo steel plates produced in the Examples and Comparative Examples after heat treatment was grade 0.5.

[0080] Table 2 Properties of high temperature resistant and low cost 12Cr5Mo steel plates in various embodiments and comparative examples

[0081]

[0082] The inventive steel plate meets the following performance requirements: tensile strength Rm: 640-663 MPa, yield strength Rel: 520-544 MPa, elongation A (L0 = 50 mm): 33.0-38.0%, and average transverse V-impact strength at -20°C ≥ 110 J. These characteristics meet the technical requirements for 12Cr5Mo steel plate: yield strength greater than 310 MPa, tensile strength 515-690 MPa, elongation greater than 18%, and transverse impact energy absorption greater than 47 J at 20°C. The steel plate also offers moderate strength, excellent low-temperature impact resistance, and a high-temperature yield strength of 446-461 MPa at 500°C. This fully meets the design requirements for superheater tubes, headers, and steam piping in high-pressure boilers used in petroleum cracking applications or with tube wall temperatures ≤ 500°C, contributing significantly to the development of the petrochemical industry.

[0083] The underlined data do not meet the requirements of the present invention.

[0084] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high temperature resistant and low cost 12Cr5Mo steel plate, characterized in that: The high temperature resistant and low cost 12Cr5Mo steel plate comprises the following components in percentage by mass: C: 0.10-0.13%, Si: 0.05-0.15%, Mn: 0.35-0.50%, P≤0.015%, S≤0.005%, Cr: 4.00-4.20%, Mo: 0.45-0.55%, Alt: 0.010-0.040%, V: 0.020-0.030%, N≤0.0080%, the balance is Fe and unavoidable impurities; The composition of the high temperature resistant and low cost 12Cr5Mo steel plate satisfies: (Alt+V) / (N)>5; The high-temperature resistant and low-cost 12Cr5Mo steel plate has a structure of bainite and ferrite, wherein the ferrite area accounts for 1% to 2%; the high-temperature resistant and low-cost 12Cr5Mo steel plate has a banded structure not higher than level 0.5 after heat treatment.

2. The high temperature resistant and low cost 12Cr5Mo steel plate according to claim 1, characterized in that: The high-temperature resistant and low-cost 12Cr5Mo steel plate has a transverse impact value of greater than 110J at -20°C, a yield strength of ≥520MPa, a tensile strength of 640MPa-680MPa, an elongation of ≥33%, and a high-temperature yield strength of ≥440MPa at 500°C.

3. A method for manufacturing the high-temperature resistant and low-cost 12Cr5Mo steel plate according to claim 1 or 2, characterized in that: The manufacturing method includes steelmaking, billet heating, rolling and heat treatment.

4. The manufacturing method according to claim 3, characterized in that The steelmaking includes LF refining, and the heating and slagging time is 60 to 80 minutes.

5. The manufacturing method according to claim 3, characterized in that The billet is heated with a preheating temperature of 700-900°C, a first heating temperature of 1100-1200°C, a second heating temperature of 1200-1250°C, an soaking temperature of 1200-1240°C, and a furnace time of (0.85-1.10) × H minutes, where H is the slab thickness in mm; and rolling is performed after reaching temperature.

6. The manufacturing method according to claim 3, characterized in that The rolling process is specifically as follows: the starting temperature of the rough rolling is greater than 1000°C, the roller speed is ≤2.5m / s, and the pass reduction rate is 10-12%; the final rolling temperature is 850-880°C, air cooling or weak cooling after rolling, and the red-return temperature is 780±20°C.

7. The manufacturing method according to claim 3, characterized in that The heat treatment includes a tempering process: a tempering temperature of 750±10°C, a furnace time of 1.5×H+60 minutes, where H is the thickness of the steel plate in mm.

8. An application of the high-temperature resistant and low-cost 12Cr5Mo steel plate according to claim 1 or 2, characterized in that: Used for the manufacture of petroleum cracking tubes, high-pressure boiler superheater tubes with wall temperature ≤ 500℃, headers or steam pipes.

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