High-alloy heat-resistant steel and its continuous casting preparation method

Abstract

The present application discloses a high-alloy heat-resistant steel and a continuous casting preparation method therefor. The method includes providing molten steel and performing LF refining, adding microchromium and vanadium nitride alloy to the molten steel undergoing LF refining and melting same to obtain molten steel after LF refining; performing RH vacuum treatment on the molten steel after LF refining to obtain molten steel after RH vacuum treatment; performing continuous casting on the molten steel after RH treatment to obtain a continuous casting billet; using a peritectic steel protective slag during continuous casting, which includes components with the following contents: CaO, 35 wt% to 41 wt%; SiO2, 24 wt% to 39 wt%; Al2O3, 1.5 wt% to 4.5 wt%; F, 5 wt% to 8 wt%; R2O, 5.5 wt% to 9.5 wt%; MgO, ≤ 3.5 wt%; TC, 1.5 wt% to 5.5 wt%; wherein, m(CaO) / m(SiO2) = 1.1 to 1.4; Thalf, 1110 °C to 1170 °C; stacking and slowly cooling the continuous casting billet to room temperature to obtain a cooled billet; heating, solutionizing and continuously rolling the cooled billet to obtain rolled steel; cooling the rolled steel; performing normalizing and tempering heat treatments on the cooled rolled steel, with the normalizing temperature being maintained at 1040 °C to 1060 °C; cooling to room temperature after exiting the cooling bed and then tempering and holding at 760 °C to 780 °C, and cooling to < 100 °C to obtain the high-alloy heat-resistant steel.

Description

Technical Field

[0001] The present application belongs to the field of metallurgical technology, and in particular relates to a high-alloy heat-resistant steel and a continuous casting preparation method thereof. Background Art

[0002] Continuous casting is a method of continuously pouring molten metal into a mold from one end and then continuously pulling the solidified, crusted casting from the other end. Continuous casting can produce castings of specified or arbitrary lengths. In practice, the two fundamental requirements for steel are surface defects and minimal macrosegregation within the internal structure. However, existing continuous casting technology suffers from quality issues such as surface cracking, uneven internal structure, and excessive residual stress.

[0003] Taking high-alloy heat-resistant steel as an example, it suffers from uneven finished product properties, low yield, and high cutting and trimming losses. Therefore, how to effectively improve the quality of alloy continuous casting steel remains a challenge that must be faced and an issue that needs to be solved urgently. Summary of the Invention

[0004] An embodiment of the present application provides a continuous casting preparation method for high-alloy heat-resistant steel. By adding trace chromium and vanadium-nitrogen alloy to molten steel, and through appropriate rolling and heat treatment processes, the problems of surface cracking, uneven internal structure, and excessive residual stress existing in the production process of high-alloy heat-resistant steel can be solved.

[0005] In a first aspect, the present application provides a continuous casting method for preparing high-alloy heat-resistant steel, the method comprising:

[0006] Provide molten steel;

[0007] LF refining is performed on the provided molten steel, and micro-chromium and vanadium-nitrogen alloy are added to the LF-refined molten steel to melt the micro-chromium and vanadium-nitrogen alloy to obtain LF-refined molten steel;

[0008] The molten steel refined by LF is subjected to RH vacuum treatment to obtain molten steel subjected to RH vacuum treatment. The vacuum degree during the vacuum treatment is required to be ≤133MPa;

[0009] The molten steel treated by RH is subjected to continuous casting to obtain a continuous casting slab. The target superheat degree of the molten steel in the tundish used for continuous casting is 10°C to 25°C; during continuous casting, a peritectic steel protective slag is used. The peritectic steel protective slag includes components with the following contents: CaO, 35wt% to 41wt%; SiO2, 24wt% to 39wt%; Al2O3, 1.5wt% to 4.5wt%; F, 5wt% to 8wt%; R2O, 5.5wt% to 9.5wt%; MgO, ≤3.5wt%; TC, 1.5wt% to 5.5wt%; wherein, m(CaO) / m(SiO2) = 1.1 to 1.4; T half, 1110°C to 1170°C; the melting rate of the peritectic steel protective slag is 15 seconds to 35 seconds;

[0010] The continuous casting slab is successively subjected to stacking cooling and slow cooling to room temperature to obtain a cooled slab;

[0011] The cooled slab is heated, solutionized and continuously rolled to obtain rolled steel;

[0012] The rolled steel is cooled;

[0013] The cooled rolled steel is subjected to normalizing and tempering heat treatment. Among them, the normalizing temperature is 1040°C to 1060°C, and the holding time is 50 min to 70 min; after cooling to room temperature out of the cooling bed, tempering is carried out at 760°C to 780°C for 50 min to 70 min, and then cooled to <100°C to obtain a high-alloy heat-resistant steel.

[0014] In the method for continuously casting and preparing the high-alloy heat-resistant steel according to the embodiment of the present application, the steel plate is heat-treated by adopting the processes of high-temperature normalizing and high-temperature tempering in the heat treatment process. Among them, holding normalizing is carried out at 1040°C to 1060°C to ensure the formation of martensite, and tempering is carried out at 760°C to 780°C to produce tempered sorbite, and the structure is coarse, which can ensure the high-temperature performance of the steel.

[0015] In the present application, R2O refers to basic oxides, which is the sum of Na2O and K2O, and T half refers to the temperature at which the molten slag transforms from liquid state to solid state.

[0016] In an embodiment of the present application, the steps of providing the required molten steel include:

[0017] Desulfurization by the KR method, reducing the sulfur content in the hot metal to less than 0.010wt% to obtain hot metal with a sulfur content ≤0.010wt%;

[0018] Converter smelting, carrying out converter smelting on the hot metal with a sulfur content ≤0.010wt% and blowing argon through the ladle to obtain molten steel after converter smelting. The end control temperature of the molten steel at the argon station is greater than 1522°C.

[0019] In an embodiment of the present application, the steps of subjecting the provided molten steel to LF refining include adding micro-chromium and vanadium-nitrogen alloy accounting for 5% - 6% of the total mass of the molten steel to the molten steel undergoing LF refining.

[0020] In an embodiment of the present application, the steps of subjecting the provided molten steel to LF refining include that the LF refining time is ≥ 45 minutes, and the tapping temperature of the molten steel during LF refining is 1595°C - 1640°C.

[0021] In an embodiment of the present application, the steps of subjecting the molten steel refined by LF to RH vacuum treatment to obtain the molten steel after RH vacuum treatment include:

[0022] Open the main valve;

[0023] Open the first-stage pump, and after circulating for 2 minutes, open the circulation flow rate to the maximum;

[0024] After circulating for 10 minutes, retreat to the fourth-stage pump, and the RH treatment time is 20 minutes - 30 minutes.

[0025] In an embodiment of the present application, the steps of continuous casting the molten steel after RH treatment to obtain a continuous casting billet include continuous casting at a casting speed of 0.9 m / min - 1.1 m / min.

[0026] In an embodiment of the present application, the steps of successively subjecting the continuous casting billet to stacking cooling and slow cooling to room temperature to obtain a cooled billet include: successively subjecting the continuous casting billet to stacking cooling and slow cooling for at least 48 hours to room temperature to obtain a cooled billet.

[0027] In an embodiment of the present application, the steps of heating, solutionizing, and continuously rolling the cooled billet to obtain rolled steel include:

[0028] Heat the cooled billet, with the heating time being 150 minutes - 250 minutes and the solutionizing time being 30 minutes - 250 minutes, to obtain a heated billet, and the temperature of the billet is 1220°C - 1250°C;

[0029] Roll the heated billet to obtain rolled steel.

[0030] In an embodiment of the present application, the steps of rolling the heated billet to obtain rolled steel include:

[0031] First perform 3 - 5 passes of rough rolling on the heated billet, and then perform 5 - 7 passes of finish rolling.

[0032] In an embodiment of the present application, the process parameters for rough rolling the continuous casting billet need to meet: the rough rolling temperature is 1160°C - 1210°C; the process parameters for finish rolling need to meet: the finish rolling temperature is 1010°C - 1050°C, the finishing rolling temperature is 890°C - 950°C, and cooling is performed after finish rolling and finishing rolling.

[0033] In one embodiment of the present application, the steps of heating, solutionizing and continuously rolling the cooled ingot to obtain the rolled steel include:

[0034] The rolled steel is coiled to form a rolled steel;

[0035] The rolled steel in coil form is flattened to obtain a straight plate-shaped rolled steel product.

[0036] In one embodiment of the present application, the rolled steel is subjected to laminar cooling after finishing rolling, and is cooled to 780° C. to 850° C. without using boiling water before being coiled.

[0037] In one embodiment of the present application, the step of flattening the coiled rolled steel to obtain a straight plate-shaped rolled steel includes straightening the steel plate using a straightening force of 8500KN to 12000KN.

[0038] In the second aspect, the present application provides a high-alloy heat-resistant steel, comprising the following components: carbon 0.08wt%~0.12wt%, silicon 0.20wt%~0.50wt%, manganese 0.40wt%~0.60wt%, sulfur ≤0.005wt%, phosphorus ≤0.018wt%, Nb 0.060wt%~0.100wt%, titanium ≤0.01wt%, chromium 8.0wt%~9.5wt%, molybdenum 0.85wt%~1.05wt%, vanadium 0.18wt%~0.25wt%, aluminum ≤0.02wt%, nitrogen 0.03wt%~0.07wt%, hydrogen ≤0.0015wt%, and the remainder is Fe and impurity elements remaining during the smelting process.

[0039] In one embodiment of the present application, the yield strength of the high-alloy heat-resistant steel P91 is ≥415 MPa, the tensile strength is 620 MPa to 760 MPa, and the elongation A50 is greater than 20%.

[0040] The preparation method of high-alloy heat-resistant steel in the embodiment of the present application adds trace chromium and vanadium-nitrogen alloy to the molten steel to make the composition of the molten steel meet the requirements; and through appropriate continuous casting, rolling and heat treatment process steps, it can achieve stable slab drawing and continuous casting drawing speed with small fluctuations in continuous casting production, and the obtained high-alloy heat-resistant steel product has uniform performance. Compared with the effect of conventionally cast high-alloy heat-resistant steel, the yield rate is higher and the loss of cutting head and tail is less, which solves the problems existing in the production process of high-alloy heat-resistant steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0042] Figure 1 is a schematic flow chart of a continuous casting preparation method for a high-alloy heat-resistant steel provided by an embodiment of the present application;

[0043] Figure 2 is a macrostructure diagram of a high-alloy heat-resistant steel prepared by the continuous casting preparation method for a high-alloy heat-resistant steel provided by an embodiment of the present application;

[0044] Figure 3 is an electron microscope image of the high-alloy heat-resistant steel provided by an embodiment of the present application at a magnification of 100 times;

[0045] Figure 4 is an electron microscope image of the high-alloy heat-resistant steel provided by an embodiment of the present application at a magnification of 500 times. Detailed Embodiments

[0046] The features and exemplary embodiments of various aspects of the present application will be described in detail below. To make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0047] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, elements defined by the statement "comprising..." do not preclude the existence of additional identical elements in the process, method, article or device comprising the said elements.

[0048] The inventors found during the improvement of the present application that:

[0049] The metal flow and volume change (shrinkage rate) during the solidification of continuous casting steel largely determine the quality of the steel and subsequent processing techniques. Based on the above two basic requirements of the steel, improving the quality of the steel and developing and improving the process require research on the microstructure changes related to the expected solidification process as the basis.

[0050] To solve the problems of the prior art, an embodiment of the present application provides a continuous casting preparation method for high-alloy heat-resistant steel. First, the continuous casting preparation method for high-alloy heat-resistant steel provided by the embodiment of the present application will be introduced below.

[0051] Figure 1 The flow schematic diagram of the continuous casting preparation method for high-alloy heat-resistant steel provided by an embodiment of the present application is shown. As Figure 1 shown, the continuous casting preparation method for high-alloy heat-resistant steel includes:

[0052] S1. Provide molten steel;

[0053] S2. Perform LF refining on the provided molten steel, add micro-chromium and vanadium-nitrogen alloy to the molten steel undergoing LF refining to melt the micro-chromium and vanadium-nitrogen alloy, and the refining time ≥ 45 minutes to obtain the molten steel after LF refining;

[0054] S3. Perform RH vacuum treatment on the molten steel after LF refining to obtain the molten steel after RH vacuum treatment, and the required vacuum degree during vacuum treatment ≤ 133 MPa;

[0055] S4. Perform continuous casting on the molten steel after RH treatment to obtain a continuous casting billet. The target superheat of the tundish molten steel used for continuous casting is 10°C to 25°C; a peritectic steel protective slag is used during continuous casting. The peritectic steel protective slag includes components with the following contents: CaO, 35 wt% to 41 wt%; SiO2, 24 wt% to 39 wt%; Al2O3, 1.5 wt% to 4.5 wt%; F, 5 wt% to 8 wt%; R2O, 5.5 wt% to 9.5 wt%; MgO, ≤ 3.5 wt%; TC, 1.5 wt% to 5.5 wt%; wherein, m(CaO) / m(SiO2) = 1.1 to 1.4; T half, 1110°C to 1170°C; the melting rate of the peritectic steel protective slag is 15 seconds to 35 seconds;

[0056] S5. Stack-cool and slow-cool the continuous casting billet in sequence to room temperature to obtain a cooled billet;

[0057] S6. Heat, solutionize and continuously roll the cooled billet to obtain rolled steel;

[0058] S7. Cool the rolled steel;

[0059] S8. Perform normalizing and tempering heat treatment on the cooled rolled steel. Among them, the normalizing temperature is 1040°C to 1060°C, and the holding time is 50 min to 70 min; after cooling to room temperature on the cooling bed and then tempering at 760°C to 780°C for 50 min to 70 min and cooling to < 100°C, high-alloy heat-resistant steel is obtained.

[0060] The continuous casting preparation method of high-alloy heat-resistant steel according to the embodiments of the present application performs heat treatment on the steel plate by using the processes of high-temperature normalizing and high-temperature tempering in the heat treatment process. Among them, it is kept at 1040°C to 1060°C for normalizing to ensure the formation of martensite, and tempered at 760°C to 780°C to produce tempered sorbite. The structure is coarse, which can ensure the high-temperature performance of the steel.

[0061] In the present application, R2O refers to basic oxides, which is the sum of Na2O and K2O, and T half refers to the temperature at which the slag transforms from liquid state to solid state. The slag is the peritectic steel protective slag.

[0062] In the preparation method of high-alloy heat-resistant steel according to the embodiments of the present application, no calcium wire is added to the molten steel during LF refining. The time for LF refining using soft oxygen blowing is at least 60 minutes. Micro chromium and vanadium nitride alloys are added to the molten steel in batches. After adding micro chromium and vanadium nitride alloys, the condition of the slag surface is observed to ensure melting. It can only leave the station after the composition and temperature of the LF-refined molten steel are qualified. The calcium wire refers to the calcium wire containing a pure metal calcium core known to those skilled in the art for steel smelting.

[0063] In one embodiment of the present application, the steps of providing the required molten steel include:

[0064] Desulfurization by the KR method, reducing the sulfur content in the hot metal to less than 0.010 wt%, to obtain hot metal with a sulfur content ≤ 0.010 wt%;

[0065] Converter smelting, performing converter smelting on the hot metal with a sulfur content ≤ 0.010 wt% and blowing argon through the ladle to obtain the molten steel after converter smelting. The end control temperature of the molten steel at the argon station is greater than 1522°C.

[0066] In one embodiment of the present application, the steps of performing LF refining on the provided molten steel include adding micro chromium and vanadium nitride alloys accounting for 5% to 6% of the total mass of the molten steel to the molten steel undergoing LF refining.

[0067] In one embodiment of the present application, the steps of performing LF refining on the provided molten steel include that the LF refining time ≥ 45 minutes, and the tapping temperature of the LF-refined molten steel is 1595°C to 1640°C.

[0068] In one embodiment of the present application, the micro chromium alloy used for LF refining of the provided molten steel is FeCr 55 C 0.06 ; the vanadium nitride alloy is VN 16 . Among them, the numerical value of each element subscript represents the mass percentage of this element in the alloy. The content of the element without a displayed numerical value in the alloy is 100% minus the numerical value of the element with a subscript. All alloys meeting the above content can be used.

[0069] In an embodiment of the present application, the steps of subjecting the molten steel refined by LF to RH vacuum treatment to obtain the molten steel subjected to RH vacuum treatment include:

[0070] Open the main valve;

[0071] Open the first-stage pump, and after circulating for 2 minutes, increase the circulating flow rate to the maximum;

[0072] After circulating for 10 minutes, retreat to the fourth-stage pump, and the RH treatment time is 20 minutes to 30 minutes.

[0073] In an embodiment of the present application, the steps of continuous casting the molten steel subjected to RH treatment to obtain a continuous casting billet include continuous casting at a casting speed of 0.9 m / min to 1.1 m / min.

[0074] In an embodiment of the present application, the steps of successively stacking and slow-cooling the continuous casting billet to room temperature to obtain a cooled billet include:

[0075] In an embodiment of the present application, the steps of heating, solutionizing, and continuously rolling the cooled billet to obtain rolled steel include:

[0076] Heat the cooled billet for 150 minutes to 250 minutes, with a solutionizing time of 30 minutes to 250 minutes, to obtain a heated billet, and the temperature of the billet is 1220 °C to 1250 °C;

[0077] Roll the heated billet to obtain rolled steel.

[0078] In an embodiment of the present application, the steps of rolling the heated billet to obtain rolled steel include:

[0079] First perform 3 - 5 passes of rough rolling on the heated billet, and then perform 5 - 7 passes of finish rolling.

[0080] In an embodiment of the present application, the process parameters for rough rolling the continuous casting billet need to meet: the rough rolling temperature is 1160 °C to 1210 °C; the process parameters for finish rolling need to meet: the finish rolling temperature is 1010 °C to 1050 °C, the finishing rolling temperature is 890 °C to 950 °C, and cooling is performed after finish rolling.

[0081] In an embodiment of the present application, the steps of heating, solutionizing, and continuously rolling the cooled billet to obtain rolled steel include:

[0082] Coil the rolled steel to form coiled rolled steel;

[0083] Level the coiled rolled steel to obtain flat plate-shaped rolled steel.

[0084] In one embodiment of the present application, the rolled steel is subjected to laminar cooling after finishing rolling, and is cooled to 780° C. to 850° C. without using boiling water before being coiled.

[0085] In one embodiment of the present application, the step of flattening the coiled rolled steel to obtain a straight plate-shaped rolled steel includes straightening the steel plate using a straightening force of 8500KN to 12000KN.

[0086] Since the maximum straightening force at the beginning of rough straightening was about 12,000 kN, in order to prevent excessive reduction and resulting warping after flying shear shearing, the roll gap and work roll height were appropriately adjusted to reduce the straightening force to about 8,500 kN. After fine straightening, the middle part of the steel plate was basically straight.

[0087] The continuous casting preparation method of high-alloy heat-resistant steel in the embodiment of the present application includes a smelting step of providing molten steel, as well as process flows such as refining, continuous casting, rolling, controlled cooling, coiling, unrolling, and heat treatment.

[0088] In the second aspect, the present application provides a high-alloy heat-resistant steel, comprising the following components: carbon 0.08wt%~0.12wt%, silicon 0.20wt%~0.50wt%, manganese 0.40wt%~0.60wt%, sulfur ≤0.005wt%, phosphorus ≤0.018wt%, Nb 0.060wt%~0.100wt%, titanium ≤0.01wt%, chromium 8.0wt%~9.5wt%, molybdenum 0.85wt%~1.05wt%, vanadium 0.18wt%~0.25wt%, aluminum ≤0.02wt%, nitrogen 0.03wt%~0.07wt%, hydrogen ≤0.0015wt%, and the remainder is Fe and impurity elements remaining during the smelting process.

[0089] In one embodiment of the present application, the yield strength of the high-alloy heat-resistant steel P91 is ≥415 MPa, the tensile strength is 620 MPa to 760 MPa, and the elongation A50 is greater than 20%.

[0090] The microstructure of the high-alloy heat-resistant steel in the embodiment of the present application is tempered bainite, and can be used in boilers, electric power and other fields.

[0091] The technical solutions and beneficial effects of the present application are further described below through specific embodiments.

[0092] Example

[0093] High-alloy heat-resistant steels having the chemical compositions given in Examples 1 and 2 in Table 1 below were prepared. The high-alloy heat-resistant steels prepared in Examples 1 and 2 were calculated based on 100% of the total mass, wherein some components and contents of the molten steel are shown in Table 1 below, and the remainder is Fe and impurity elements remaining during the smelting process.

[0094] Table 1 Partial chemical compositions of the high-alloy heat-resistant steel prepared in Examples 1 and 2

[0095] Element / Content Example 1 Example 2 C 0.0908 0.0997 Si 0.2775 0.2445 Mn 0.461 0.4508 P 0.0122 0.0138 S 0.0021 0.0016 Cr 8.6231 8.4517 Mo 0.9119 0.9384 V 0.1859 0.2273 Nb 0.0694 0.0735 N 0.0394 0.0379 Alt 0.008 0.007

[0096] The continuous casting preparation method of the high-alloy heat-resistant steel in the above examples was carried out, wherein the continuous casting preparation method of the high-alloy heat-resistant steel includes:

[0097] The hot metal was desulfurized by the KR method, and the sulfur content in the hot metal was reduced to less than 0.010 wt%, obtaining hot metal with a sulfur content ≤ 0.010 wt%.

[0098] Converter smelting was carried out on the hot metal with a sulfur content ≤ 0.010 wt%, and the hot metal was blown with argon in the ladle to obtain molten steel after converter smelting. The end control temperature of the molten steel in the argon station was greater than 1522 °C;

[0099] LF refining was carried out on the provided molten steel after converter smelting, including adding micro-chromium and vanadium-nitrogen alloy to the molten steel after converter smelting to melt the micro-chromium and vanadium-nitrogen alloy. The LF refining time was 60 min; and calcium was not added to the molten steel during LF refining. The tapping temperature of the LF-refined molten steel was 1595 °C - 1640 °C to obtain LF-refined molten steel;

[0100] The LF-refined molten steel was subjected to RH vacuum treatment. The required vacuum degree during vacuum treatment was ≤ 133 MPa, including:

[0101] Open the main valve;

[0102] Open the first-stage pump. After circulating for 2 minutes, the circulation flow rate was opened to the maximum, which was 200 Nm 3 / h;

[0103] After circulating for 10 minutes, it was retreated to the fourth-stage pump to reduce the circulation flow rate. The RH treatment time was 30 minutes to obtain molten steel after RH vacuum treatment;

[0104] The molten steel after RH vacuum treatment was continuously cast to obtain a continuous casting billet of 230 mm. The target superheat of the tundish molten steel used during continuous casting was 25 °C; among them, the continuous casting process parameters were: this steel grade used peritectic steel powder, and the continuous casting casting speed was 1 m / min; when starting casting, 15 kg of starting slag was added to each strand, and a large-industry small-hole tundish nozzle was used for the submerged entry nozzle, and other refractories were used as required and used normally. During the production process, the liquid slag was measured to be about 10 mm - 12 mm, and the consumption of peritectic steel powder for the whole casting of two strands was calculated to be 0.4 kg / t. The indicators of the peritectic steel powder were good, and no sticking alarm occurred during the whole casting;

[0105] The continuous casting billet was successively subjected to stacking cooling and slow cooling for 48 hours to 30 °C room temperature to obtain a cooled billet;

[0106] Then the cooled billets are heated. The specific heating process is that the heating time in the furnace is 180 minutes and the solution time is 200 minutes, obtaining the heated billets. The billet furnace outlet temperature is 1235°C to 1240°C;

[0107] Next, the heated billets are subjected to thermo-mechanical controlled rolling and controlled cooling rolling by a 7-stand 2250 continuous rolling mill to obtain rolled steel. Among them, the first stage of rolling is rough rolling, with 5 rough rolling passes, and the rough rolling starting temperature is 1160°C to 1210°C; the second stage is finish rolling, with the starting temperature being 1010°C to 1050°C. Then, the rolled steel after finish rolling is subjected to laminar flow cooling, and water cooling is not turned on until it cools to 780°C to 850°C for coiling, obtaining coiled rolled steel. The coiled rolled steel is taken off the production line and placed in the steel coil storage for stacking and cooling until it reaches room temperature. The process parameters for thermo-mechanical controlled rolling and controlled cooling of the billets in Examples 1 and 2 are shown in Table 2 below:

[0108] Table 2 Process parameter table for rolling in Examples 1 and 2

[0109]

[0110] Then, the coiled rolled steel after temperature reduction is leveled with a straightening force of 8500 KN to obtain flat plate-shaped rolled steel;

[0111] Next, the flat plate-shaped rolled steel is heat-treated, and the heat-treated plate is cooled to 30°C to produce high-alloy heat-resistant steel plates with thickness specifications of 6 mm and 25 mm respectively. Among them, the process parameters for heat treatment of the rolled steel in Examples 1 and 2 are shown in Table 3 below for the specific process parameters of Examples 1 and 2:

[0112] Table 3 Process parameter table for heat treatment in Examples 1 and 2

[0113] Comparison Item Thickness / mm Normalizing Temperature / °C Normalizing Time / min Tempering Temperature / °C Tempering Time / min Example 1 6 1050±10 50 770±10 50 Example 2 25 1050±10 70 770±10 70

[0114] Finally, the high-alloy heat-resistant steels in Examples 1 and 2 are subjected to performance tests. The test items include:

[0115] 1. Yield strength test, and the test method is carried out in accordance with standards GB / T2975 and GB / T 228;

[0116] 2. Tensile strength test, and the test method is carried out in accordance with standards GB / T2975 and GB / T 228;

[0117] 3. Elongation test, which is carried out in accordance with standards GB / T2975 and GB / T 228;

[0118] 4. Transverse and normal temperature impact work test, which is carried out in accordance with standards GB / T2975 and GB / T 228.

[0119] Record the results of the above performance tests in Table 4 below:

[0120] Table 4 Test Results of Mechanical Properties of Examples 1 and 2

[0121]

[0122] Figure 2 Fig. shows the macrostructure diagram of the high-alloy heat-resistant steel prepared by the continuous casting preparation method of the high-alloy heat-resistant steel provided in the embodiment of the present application. The billet grade of the high-alloy heat-resistant steel shown in the macrostructure diagram reaches Class A level 1.5 and Class C level 1.5, and no obvious segregation and porosity are observed, indicating that the quality of the prepared high-alloy heat-resistant steel is relatively ideal; Figure 3 is the electron microscope image of the inclusions of the high-alloy heat-resistant steel provided in the embodiment of the present application at a magnification of 100 times. From Figure 3 it can be seen that the types and contents of the inclusions are B1.0, D1.0, and Ds1.0 respectively, indicating that the heat treatment steel plate produced by the continuous casting process of the present application has fewer inclusions; Figure 4 is the electron microscope image of the high-alloy heat-resistant steel provided in the embodiment of the present application at a magnification of 500 times. The structure therein is tempered sorbite, and the grain size is 10.0. The structure is coarse and uniform, indicating that the structure prepared by the continuous casting preparation method of the high-alloy heat-resistant steel of the present application is uniform and the surface has no cracks.

[0123] As described above, only the specific embodiments of the present application are provided. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes described above can refer to the corresponding processes in the foregoing method embodiments and will not be repeated here. It should be understood that the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application.

Claims

1. A continuous casting preparation method for a high-alloy heat-resistant steel, characterized in that, Including: Providing molten steel; Conducting LF refining on the provided molten steel, including that the LF refining time is ≥ 45 minutes, the tapping temperature of the molten steel after LF refining is 1595°C to 1640°C, and adding micro-chromium and vanadium-nitrogen alloy to the molten steel undergoing LF refining to melt the micro-chromium and vanadium-nitrogen alloy to obtain the molten steel after LF refining; Conducting RH vacuum treatment on the molten steel after LF refining to obtain the molten steel after RH vacuum treatment, and the required vacuum degree during vacuum treatment is ≤ 133 MPa; Conducting continuous casting on the molten steel after RH treatment to obtain a continuous casting billet, and the target superheat of the molten steel in the tundish used for continuous casting is 10°C to 25°C; during the continuous casting process, a peritectic steel protective slag is used, and the peritectic steel protective slag includes components with the following contents: CaO, 35wt% to 41wt%; SiO2, 24wt% to 39wt%; Al2O3, 1.5wt% to 4.5wt%; F, 5wt% to 8wt%; R2O, 5.5wt% to 9.5wt%; MgO, ≤ 3.5wt%; TC, 1.5wt% to 5.5wt%; wherein, m(CaO) / m(SiO2) = 1.1 to 1.4; T half, 1110°C to 1170°C; the melting rate of the peritectic steel protective slag is 15 seconds to 35 seconds; The continuous casting billet is successively subjected to stacking cooling and slow cooling to room temperature to obtain a cooled billet; Heating, solutionizing and continuously rolling the cooled billet, including: heating the cooled billet, the heating time is 150 minutes to 250 minutes, the solutionizing time is 30 minutes to 250 minutes, to obtain the heated billet, and the temperature of the billet is 1220°C to 1250°C; rolling the heated billet, including: first performing 3 - 5 passes of rough rolling on the heated billet, and then performing 5 - 7 passes of finish rolling; the process parameters for rough rolling of the continuous casting billet need to meet: the rough rolling temperature is 1160°C to 1210°C; the process parameters for finish rolling need to meet: the finish rolling temperature is 1010°C to 1050°C, the finishing rolling temperature is 890°C to 950°C, and cooling is performed after finish rolling to obtain the rolled steel; cooling the rolled steel; Normalize and temper the cooled rolled steel. Among them, the normalizing temperature is 1040°C to 1060°C, and the holding time is 50 min to 70 min; after cooling to room temperature out of the cooling bed, temper at 760°C to 780°C for 50 min to 70 min, and then cool to <100°C to obtain a high-alloy heat-resistant steel; the high-alloy heat-resistant steel includes the following components by content: carbon 0.08 wt% to 0.12 wt%, silicon 0.20 wt% to 0.50 wt%, manganese 0.40 wt% to 0.60 wt%, sulfur ≤0.005 wt%, phosphorus ≤0.018 wt%, Nb 0.060 wt% to 0.100 wt%, titanium ≤0.01 wt%, chromium 8.0 wt% to 9.5 wt%, molybdenum 0.85 wt% to 1.05 wt%, vanadium 0.18 wt% to 0.25 wt%, aluminum ≤0.02 wt%, nitrogen 0.03 wt% to 0.07 wt%, hydrogen ≤0.0015 wt%, and the balance is Fe and impurity elements remaining in the smelting process.

2. The preparation method according to claim 1, characterized in that, The step of providing the required molten steel includes: Desulfurize by the KR method to reduce the sulfur content in the hot metal to less than 0.010 wt% to obtain hot metal with a sulfur content ≤0.010 wt%. Converter smelting: Carry out converter smelting on the hot metal with a sulfur content ≤0.010 wt%, and blow argon through the ladle. The end control temperature at the argon station is greater than 1522°C to obtain molten steel after converter smelting.

3. The preparation method according to claim 1, characterized in that, The step of LF refining the provided molten steel includes adding micro-chromium and vanadium-nitrogen alloy accounting for 5% to 6% of the total mass of the molten steel to the molten steel undergoing LF refining.

4. The preparation method according to claim 1, characterized in that, The step of subjecting the molten steel after LF refining to RH vacuum treatment to obtain the molten steel after RH vacuum treatment includes: Open the main valve; Open the first-stage pump, and after circulating for 2 minutes, open the circulation flow rate to the maximum; After circulating for 10 minutes, retreat to the fourth-stage pump, and the RH treatment time is 20 minutes to 30 minutes.

5. The preparation method according to claim 1, characterized in that, The step of heating, solutionizing the cooled billet and continuously rolling to obtain rolled steel includes: Coil the rolled steel to make it into coiled rolled steel; Level the coiled rolled steel to obtain flat plate-shaped rolled steel.

6. The preparation method according to claim 5, wherein, The step of coiling the rolled steel to make it into coiled rolled steel includes: After finish rolling, carry out laminar flow cooling on the rolled steel to 780°C to 850°C and then coil it.

7. The preparation method according to claim 6, characterized in that, The step of leveling the coiled rolled steel to obtain flat plate-shaped rolled steel includes straightening the coiled rolled steel with a straightening force of 8500 KN to 12000 KN.

8. A high-alloy heat-resistant steel, characterized in that, Prepared by the continuous casting preparation method of the high-alloy heat-resistant steel according to any one of claims 1-7, the yield strength of the high-alloy heat-resistant steel ≥415 MPa, the tensile strength is 620 MPa to 760 MPa, and the elongation A50 is greater than 20%.

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