CN111893367B - Method for producing 5CrNi2MoV hot-work die steel plate by using continuous casting slab - Google Patents
Method for producing 5CrNi2MoV hot-work die steel plate by using continuous casting slab Download PDFInfo
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Abstract
The invention relates to a method for producing a 5CrNi2MoV hot-work die steel plate by using a continuous casting plate blank, which comprises the steps of (1) smelting molten steel; (2) producing a continuous casting blank with the thickness of 150-400 mm; (3) annealing the continuous casting plate blank; (4) reheating of continuous casting slabs: homogeneous solid melting to make the structure completely austenitized; (5) descaling: removing scale on the surface by high-pressure water, and controlling the temperature of the descaled plate blank to be 980-; (6) rolling: the steel plate is rolled in two stages, namely rough rolling and finish rolling, wherein the rough rolling is uncontrolled rolling, direct rolling, high-temperature rolling reduction, finish rolling at high temperature, small reduction and multi-pass rolling process are carried out to the greatest extent, the steel plate is rolled to the target thickness, and the rolled steel plate is slowly cooled; (7) and (3) heat treatment: complete annealing, air cooling quenching and high temperature tempering. The grain size of the steel plate after heat treatment is more than or equal to 7.0 grade, the structure is uniform, and the steel plate has better tempering softening resistance.
Description
Technical Field
The invention relates to a production method of die steel, in particular to a method for producing a 5CrNi2MoV hot-work die steel plate by using a continuous casting billet.
Background
The 5CrNi2Mo die steel is a high-wear-resistance hot forging die steel, and is produced into a steel ingot by an Electric Arc Furnace (EAF), refining (LF), Vacuum (VD) and forging. The national standard (GB/T1299-.
The 5CrNi2Mo die steel belongs to high-end die steel, the production difficulty is large, and the method for producing the 5CrNi2Mo die steel plate in batches with high quality is rarely reported at present.
Disclosure of Invention
According to the invention, the 5CrNi2MoV steel plate with the thickness of 8-50mm is produced by using a continuous casting plate blank and a heavy and medium plate mill, the steel plate has no white spots and fine cracks on the core part, the plate shape is good, and the 5CrNi2MoV die steel with the thickness of 8-50mm can be produced in a large scale and high quality.
The invention relates to a specific technical scheme which comprises the following steps: a steel plate for producing 5CrNi2MoV hot work die steel by a continuous casting billet is characterized in that the element components of the steel plate are designed according to the requirements of national standard (GB/T1299-: c: 0.50% -0.60%, Si: 0.10-0.40%, Mn: 0.60% -0.90%, Ni: 1.50% -1.80%, Cr: 0.80% -1.20%, Mo: 0.35% -0.55%, V: 0.05% -0.15%, P: less than or equal to 0.025 percent, S: less than or equal to 0.010 percent and less than or equal to 0.25 percent of Cu, wherein the requirements of P and S are in accordance with the strictest requirements in the standard, and the requirements can be generally achieved only by an expensive production mode of electric arc furnace, electroslag remelting and vacuum arc remelting at present.
The requirements on P, S and Cu are further improved, P is less than or equal to 0.013%, S is less than or equal to 0.003%, and Cu is less than or equal to 0.05%, and harmful element P, S and segregation-prone element Cu are reduced to improve the purity of the material and slow down the segregation of the material, so that the structure is continuous and homogeneous.
In the invention, elements except for the standard requirements are further strictly required, and Al: 0.02% -0.05%, residual element Ti: less than or equal to 0.003 percent; sb: less than or equal to 0.003 percent, Sn: less than or equal to 0.005 percent, As: less than or equal to 0.008 percent, H: less than or equal to 0.0002 percent, O: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent. The purpose of adding a proper amount of Al is to control the grain size of the material; the purpose of strictly controlling Ti is to prevent the occurrence of Ti (C, N) inclusions in steel and influence the service life of the material; the strict control of harmful elements Sb, Sn and As is beneficial to improving the toughness of the material; the content of the material H is strictly controlled, white spots in the material are prevented from being generated, and the generation of fine microcracks at the core part in the cooling process of the sheet is avoided; the content of O in the material is controlled to control the content of inclusions in the material, and the fatigue life of the material can be effectively prolonged by reducing the content of the inclusions; the N has stronger aging effect, is helpful for improving the hardness and the strength of the material, but has negative effect on the plasticity and the toughness of the material, and the N content is controlled at a lower level by comprehensive consideration.
The invention continuously casts the molten steel into 150-400mm 5CrNi2MoV continuous casting blank, and requires that the low-power quality requirement meets the requirement that the segregation is not more than class B1.0 level and the porosity is not more than 1.0 level. Selecting blank types with different thicknesses according to the final plate thickness, carrying out annealing, rolling and multi-pass heat treatment on the continuous casting blank, finishing and sampling inspection after the flaw detection is qualified, and warehousing after the qualified flaw detection is carried out. The production process flow roughly comprises the following steps: BOF → LF → RH → CCM → slab annealing → steel rolling → heat treatment → flaw detection → finishing → inspection → warehousing.
The main steps are as follows:
(1) smelting: by adopting a clean steel smelting mode, thermodynamic conditions which are low in temperature in the early stage and beneficial to dephosphorization are fully utilized during converter steelmaking, and slagging treatment is carried out in the later stage of converter smelting, so that rephosphorization is reduced. In the refining process, the content of P, S in the steel slag mixing technology can be effectively controlled by using the high-alkalinity white slag refining and steel tapping, in addition, the content of other residual elements is further controlled on the basis that P is less than or equal to 0.013 percent and S is less than or equal to 0.003 percent, and the content of inclusions is strictly controlled, so that the sum of the grades of A, B, C, D inclusions in the molten steel is required to be less than or equal to 3.5 grade. RH vacuum degassing is adopted, molten steel is stirred by argon, the flow rate of the argon is 850-: less than or equal to 0.0002 percent, O: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent.
(2) Continuous casting: the arc roll gap of the sector section of the continuous casting machine is ensured to be within +/-0.5 mm, dynamic soft reduction is used in the horizontal section of the sector section of the continuous casting machine, the soft reduction is 5-10mm, and center segregation and looseness are effectively improved. Argon protective casting is carried out in the whole process, a low-drawing-speed weak water-cooling continuous casting process is adopted, the thickness of a produced blank is 150-400mm, and the low power segregation of the plate blank is required to be not more than class B1.0 level and the porosity is not more than 1.0 level.
(3) Annealing of the plate blank: and (3) carrying out stress relief annealing treatment on the continuous casting plate blank by using a trolley furnace, wherein the heating temperature is 780 +/-10 ℃, the heat preservation time is 2.5-3.5 min/mm, and the continuous casting plate blank is cooled to 200 ℃ along with the furnace and taken out of the furnace.
(4) Heating the plate blank: the heating is carried out by adopting a vehicle bottom furnace or a soaking furnace, the heating rate is controlled to be 8-12 ℃/min, and the heating temperature of the slab is controlled to be 1100-1250 ℃.
(5) Descaling: and (3) taking the heated blank out of the furnace, and then carrying out high-pressure water descaling treatment to remove surface oxide scale, wherein the temperature of the descaled plate blank is controlled at 980-.
(6) Rolling: a staged rolling process is adopted. The rough rolling stage adopts large rolling reduction, the rolling temperature is more than or equal to 1000 ℃, the maximum pass rolling reduction in the rough rolling stage is between 15 and 25 percent, the rolling reduction of 2 to 3 passes in the rough rolling stage is ensured to be between 40 and 100mm, and the rolling reduction of at least one pass is more than 60 mm; rough rolling is carried out when the thickness of the steel plate is 2-4 times of the target thickness, finish rolling is carried out, the start rolling temperature of finish rolling is more than or equal to 920 ℃, a small reduction rolling process is adopted in the finish rolling stage, the single-pass reduction rate is controlled to be 8-12%, cumulative rolling is carried out for 5-10 passes, the steel plate is rolled to the target thickness, and the rolled steel plate is slowly cooled for more than 48 hours. The rough rolling principle is a high-temperature uncontrolled rolling and high-reduction process, the rolling penetration deformation to the steel plate core part is realized by utilizing the maximum capacity of a rolling mill, and the finish rolling principle is a high-temperature small-reduction and multi-pass rolling process as far as possible, so that the rolling difficulty caused by the temperature reduction in the sheet rolling process is avoided, and the occurrence of fine cracks of the material core part caused by overlarge deformation can be avoided. The total compression ratio of the rolled steel plate is more than or equal to 5.
(7) And (3) heat treatment: carrying out 'complete annealing, air cooling quenching and high temperature tempering' heat treatment on the steel plates in sequence, carrying out complete annealing treatment by using a trolley furnace, preferably stacking the steel plates, paving other steel plates with the thickness of more than or equal to 100mm on the lowest layer to ensure the plate shape, carrying out annealing heating at 850-900 ℃, carrying out annealing heat preservation for 2.0-2.5 min/mm, and taking the steel plates out of the furnace and carrying out air cooling after the steel plates are cooled to 300 ℃ along with the furnace, wherein the calculated thickness of the heat preservation time is the accumulated stacking thickness of the steel plates and the thickness of the steel plates including the bedding steel plates; quenching treatment is carried out by using a continuous furnace, the quenching heating temperature is 850-880 ℃, the quenching heat preservation time is 1.8-2.0 min/mm, air cooling is carried out after discharging, and the annealing and slow cooling are carried out when the temperature is 150-; and (3) tempering and heating at the temperature of 600-660 ℃, tempering and heat preservation for 3.5-5.0 min/mm, and cooling in the air after discharging to obtain a steel plate finished product.
The invention has the following characteristics:
the invention realizes that the 5CrNi2MoV medium plate with the thickness of 8-50mm is obtained by producing the die steel plate by the continuous casting plate blank, has good plate shape, high toughness, high hardenability, high wear resistance and the like.
In order to realize the production of the 5CrNi2MoV medium plate with the thickness of 8-50mm, in the molten steel smelting stage, the content of other residual elements is controlled on the basis that P is less than or equal to 0.013 percent and S is less than or equal to 0.003 percent, the vacuum degree is reduced and the vacuum treatment time is prolonged to float inclusions in the molten steel through vacuum treatment, the content of the inclusions is strictly controlled, the sum of the grades of A, B, C, D types of inclusions is required to be less than or equal to 3.5 grade, RH vacuum degassing is adopted, and the molten steel H is ensured: less than or equal to 0.0002 percent, O: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent.
According to the invention, the continuous casting slab is used for forming materials, various blank models with the thickness of 150-400mm are utilized to match the thickness of a steel plate finished product with the thickness of 8-50mm, the rolling pass of the steel plate is favorably controlled, the situation that a forged product with the thickness is heated and forged for many times in the forging process is avoided, in addition, the continuous casting slab is used for forming materials, the appearance of the steel plate is greatly improved compared with that of a steel ingot, especially the steel plate with the thickness of 8mm, the realization of large-scale production is more favorably realized by the continuous casting slab, and the production cost is reduced.
The steel plate manufactured by the invention has extremely high requirements on the working state of a continuous casting machine, requires the arc roll gap of a sector section of the continuous casting machine to be within +/-0.5 mm, and adopts a continuous casting process of low drawing speed and weak water cooling, so that the purpose of preventing surface cracks in batches is achieved; the horizontal section of the sector section of the continuous casting machine is used for dynamic soft reduction equipment, so that the segregation and loosening conditions of the core of the blank are improved in a key mode, the low power segregation of the plate blank is not more than class B1.0 level, and the loosening is not more than 1.0 level.
The rolling process of the invention adopts the basic principle of high temperature and uncontrolled rolling in the rough rolling stage, the continuous casting billet is directly rolled after being reheated and discharged, and the process of high reduction utilizes the maximum capability of a rolling mill to realize the rolling and permeation deformation to the core part of a steel plate, and aims to realize the grain refinement of the core part, the shrinkage cavity closure and the performance improvement. The principle of finish rolling is a high-temperature, small-reduction and multi-pass rolling process as far as possible, the finish rolling is high-temperature multi-pass rolling, the traditional controlled rolling is not adopted, the rolling difficulty caused by temperature reduction in the sheet rolling process is avoided, and the occurrence of core fine cracks caused by overlarge material deformation can be avoided.
The heat treatment process of the hot work die steel plate manufactured by the invention adopts a unique process of complete annealing, air cooling quenching and high temperature tempering, achieves the purpose of reducing segregation and uniform components through a complete annealing process, has high content of 5CrNi2MoV carbon and alloy components with the thickness of 8-50mm, finishes martensite transformation during quenching and air cooling, obtains uniform martensite structure, and then carries out corresponding tempering process on steel plates with different thicknesses so as to ensure that the steel can obtain uniform hardness in the full thickness direction. Because the material has extremely strong crack sensitivity, and fine cracks of a core part are easily caused if the material is improperly cooled in the annealing and quenching processes, the pretreatment process of completely annealing the material aims to realize the sufficient diffusion of alloy elements and avoid stress cracking caused by abnormal tissues due to partial segregation of the elements.
The 5CrNi2MoV medium plate with the thickness of 8-50mm manufactured by the invention has good steel plate profile, the material hardness is 38-42HRC, and the hardness difference of the whole plate is controlled within 15 HBW; the inclusion surface scan index is less than or equal to 7.0; the flaw detection of the steel plate can meet the II-grade requirements of the NB/T47013.3 forging part and the harsh requirements on the quality of the hot-working die steel core part with high performance requirements; the grain size of the steel plate after heat treatment is more than or equal to 7.0 grade, the structure is uniform, and the steel plate has better tempering softening resistance. In addition, compared with a forged piece, the corresponding preparation method has the advantages of low cost and short production period, and is convenient to popularize and apply.
Drawings
FIG. 1 shows a 500-fold metallographic structure at 1/2 thick after complete annealing and air-cooled quenching of 5CrNi2MoV with a thickness of 50 mm;
FIG. 2 shows a 500-fold metallographic structure at 1/2 thick after "full annealing + air-cooled quenching + high-temperature tempering" of 5CrNi2MoV with a thickness of 50 mm.
Detailed Description
The present invention will be described in further detail below with reference to the embodiments of the drawings, which are illustrative and intended to be illustrative of the present invention and are not to be construed as limiting the present invention.
Example 1
The thickness of the 5CrNi2MoV hot work die steel plate related to the embodiment is 15mm, and the steel plate comprises the following chemical components in percentage by mass: c: 0.55%, Si: 0.30%, Mn: 0.80%, P: 0.010%, S: 0.002%, Ni: 1.65%, Cr: 1.10%, Mo: 0.45%, V: 0.12%, Al: 0.035%, and the balance of Fe and inevitable impurity elements.
The manufacturing process of the steel plate with the thickness of 15mm and suitable for the 5CrNi2MoV hot-working die comprises the following steps of preparing smelting raw materials according to chemical components of a finished steel plate product, and sequentially carrying out KR molten iron pretreatment, converter smelting, LF refining and RH vacuum degassing to obtain molten steel with higher purity, wherein the RH ultimate vacuum time is 25min, continuously casting a continuous casting slab with the thickness of 150mm by a straight arc continuous casting machine through the molten steel, ensuring the operation at the constant drawing speed at the low superheat temperature of 10-20 ℃ in the continuous casting process, and adopting a soft reduction technology, wherein the continuous casting slab is low-powered and reaches the following level: the center segregation C is 0.5 grade, the center is loose by 0.5 grade, no other defects exist, the continuous casting blank is put into a trolley furnace with the temperature for annealing and stress relief treatment, the heating temperature is 780 ℃, the heat preservation coefficient is 2.6min/mm, and the continuous casting blank is taken out of the furnace after being cooled to 200 ℃ along with the furnace. Heating the annealed plate blank in a continuous heating furnace at a heating rate of 10 ℃/min to 1230 ℃, and keeping the temperature for 3 hours; and (4) removing scale by high-pressure water of 20MPa after discharging. The rolling adopts a staged rolling process, the rolling reduction of two passes before the rough rolling stage is respectively 60mm and 40mm, the strip temperature thickness of the rough rolled plate blank is 30mm, the strip temperature is 930 ℃, the finish rolling is carried out until the target thickness is reached, and the rolled steel plate is subjected to offline stack slow cooling for 50 hours. The rolled steel plates are sequentially subjected to complete annealing, air cooling quenching and high-temperature tempering heat treatment, the steel plates are subjected to stacking annealing by using a trolley furnace, the lowest layer is paved with other steel plates with the thickness of 100mm, the annealing heating temperature is 880 ℃, the heat preservation time is 2.0min/mm, the calculated thickness of the heat preservation time is the accumulated stacking thickness of the steel plates and the thickness of the steel plates including the paved steel plates, and the steel plates are taken out of the furnace and cooled to 300 ℃ along with the furnace; quenching treatment is carried out by using a continuous furnace, the quenching heating temperature is 870 ℃, the quenching heat preservation time is 2.0min/mm, air cooling is carried out after discharging, and the lower line stack is slowly cooled when the air cooling is carried out to 180 ℃; the tempering heating temperature is 650 ℃, the tempering heat preservation time is 4.0min/mm, and the steel plate finished product is obtained after the steel plate is taken out of the furnace and cooled in the air.
The hot-work die steel plate with the thickness of 15mm, which is prepared by the manufacturing process, has the advantages of good appearance plate shape, uniform performance, less harmful elements, low inclusion level and uniform hardness, and the main performance is detailed in table 1.
Example 2
The thickness of the 5CrNi2MoV hot work die steel plate related to the embodiment is 35mm, and the steel plate comprises the following chemical components in percentage by mass: c: 0.56%, Si: 0.30%, Mn: 0.79%, P: 0.011%, S: 0.003%, Ni: 1.67%, Cr: 1.08%, Mo: 0.46%, V: 0.12%, Al: 0.030%, and the balance of Fe and inevitable impurity elements.
The manufacturing process of the steel plate with the thickness of 35mm and suitable for the 5CrNi2MoV hot-working die comprises the following steps of preparing smelting raw materials according to chemical components of a finished steel plate product, and sequentially carrying out KR molten iron pretreatment, converter smelting, LF refining and RH vacuum degassing to obtain molten steel with higher purity, wherein the RH ultimate vacuum time is 25min, continuously casting a continuous casting plate blank with the thickness of 370mm by a straight arc continuous casting machine through the molten steel, ensuring low superheat degree and constant drawing speed operation in the continuous casting process, and adopting a light reduction technology, wherein the continuous casting blank is low-powered and reaches the following power: the center segregation C is 0.5 grade, the center is loose by 0.5 grade, no other defects exist, the continuous casting blank is put into a trolley furnace with the temperature for annealing and stress relief treatment, the heating temperature is 780 ℃, the heat preservation coefficient is 2.9min/mm, and the continuous casting blank is taken out of the furnace after being cooled to 200 ℃ along with the furnace. Heating the annealed plate blank in a continuous heating furnace at the heating rate of 11 ℃/min to 1240 ℃, and preserving heat for 6 hours; and (4) removing scale by high-pressure water of 20MPa after discharging. The rolling adopts a staged rolling process, the rolling reduction of three passes before the rough rolling stage is respectively 60mm, 60mm and 40mm, the thickness of the rough-rolled plate blank is 90mm, the strip temperature is 930 ℃, the finish rolling is carried out until the target thickness is reached, and the rolled steel plate is subjected to the offline stack slow cooling for 50 hours. The rolled steel plates are sequentially subjected to complete annealing, air cooling quenching and high-temperature tempering heat treatment, the steel plates are subjected to stacking annealing by using a trolley furnace, the lowest layer is paved with other steel plates with the thickness of 100mm, the annealing heating temperature is 880 ℃, the heat preservation time is 2.0min/mm, the calculated thickness of the heat preservation time is the accumulated stacking thickness of the steel plates and the thickness of the steel plates including the paved steel plates, and the steel plates are taken out of the furnace and cooled to 300 ℃ along with the furnace; quenching treatment is carried out by using a continuous furnace, the quenching heating temperature is 870 ℃, the quenching heat preservation time is 2.0min/mm, air cooling is carried out after discharging, and the lower line stack is slowly cooled when the air cooling is carried out to 180 ℃; the tempering heating temperature is 640 ℃, the tempering heat preservation time is 3.8min/mm, and the steel plate finished product is obtained after the steel plate is taken out of the furnace and cooled in the air.
The steel plate of the hot-work die steel with the thickness of 35mm, which is prepared by the manufacturing process, has the advantages of good appearance plate shape, uniform performance, less harmful elements, low inclusion level and uniform hardness, and the main performance is detailed in table 1.
Example 3
The thickness of the 5CrNi2MoV hot work die steel plate related to the embodiment is 48mm, and the steel plate comprises the following chemical components in percentage by mass: c: 0.54%, Si: 0.30%, Mn: 0.72%, P: 0.009%, S: 0.003%, Ni: 1.63%, Cr: 1.15%, Mo: 0.50%, V: 0.13%, Al: 0.035%, and the balance of Fe and inevitable impurity elements.
The manufacturing process of the steel plate with the thickness of 48mm and suitable for the 5CrNi2MoV hot-working die comprises the following steps of preparing smelting raw materials according to chemical components of a finished steel plate product, and sequentially carrying out KR molten iron pretreatment, converter smelting, LF refining and RH vacuum degassing to obtain molten steel with higher purity, wherein the RH ultimate vacuum time is 30min, continuously casting a continuous casting slab with the thickness of 370mm by a straight arc continuous casting machine through the molten steel, ensuring that the continuous casting is operated at the constant drawing speed at the low superheat temperature of 8-15 ℃ in the continuous casting process, and adopting a soft reduction technology, wherein the continuous casting slab is low-powered and reaches the following power: the center segregation C is 0.5 grade, the center is loose by 0.5 grade, no other defects exist, the continuous casting blank is put into a trolley furnace with the temperature for annealing and stress relief treatment, the heating temperature is 780 ℃, the heat preservation coefficient is 2.8min/mm, and the continuous casting blank is taken out of the furnace after being cooled to 200 ℃ along with the furnace. Heating the annealing plate blank in a continuous heating furnace at a heating rate of 11 ℃/min to 1235 ℃, and keeping the temperature for 6 hours; and (4) removing scale by high-pressure water of 20MPa after discharging. The rolling adopts a staged rolling process, the rolling reduction of three passes before the rough rolling stage is respectively 60mm, 60mm and 40mm, the thickness of the rough-rolled plate blank is 120mm, the strip temperature is 930 ℃, the finish rolling is carried out until the target thickness is reached, and the rolled steel plate is subjected to the offline stack slow cooling for 50 hours. The rolled steel plates are sequentially subjected to complete annealing, air cooling quenching and high-temperature tempering heat treatment, the steel plates are subjected to stacking annealing by using a trolley furnace, the lowest layer is paved with other steel plates with the thickness of 100mm, the annealing heating temperature is 880 ℃, the heat preservation time is 2.0min/mm, the calculated thickness of the heat preservation time is the accumulated stacking thickness of the steel plates and the thickness of the steel plates including the paved steel plates, and the steel plates are taken out of the furnace and cooled to 300 ℃ along with the furnace; quenching treatment is carried out by using a continuous furnace, the quenching heating temperature is 860 ℃, the quenching heat preservation time is 2.0min/mm, air cooling is carried out after discharging, and the lower line stack is slowly cooled when the air cooling is carried out to 180 ℃; the tempering heating temperature is 630 ℃, the tempering heat preservation time is 3.5min/mm, and the steel plate finished product is obtained after the steel plate is taken out of the furnace and cooled in the air.
The steel plate of the hot-work die steel with the thickness of 48mm and the thickness of 5CrNi2MoV prepared by the manufacturing process has the advantages of good appearance plate shape, uniform performance, less harmful elements, low inclusion level and uniform hardness, and the main performance is detailed in table 1.
TABLE 1 hardness and flaw detection of the steel sheets produced in the examples
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for producing a 5CrNi2MoV hot-work die steel plate by using a continuous casting slab is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
(1) smelting molten steel: the molten steel is based on Fe, and comprises the following components in parts by weight: 0.50% -0.60%, Si: 0.10-0.40%, Mn: 0.60% -0.90%, Ni: 1.50% -1.80%, Cr: 0.80% -1.20%, Mo: 0.35% -0.55%, V: 0.05% -0.15%, P: less than or equal to 0.025 percent, S: less than or equal to 0.010 percent and less than or equal to 0.25 percent of Cu; and further controlling Ti: less than or equal to 0.003 percent; sb: less than or equal to 0.003 percent, Sn: less than or equal to 0.005 percent, As: not more than 0.008 percent, not more than 0.05 percent of Cu, and adding a proper amount of Al: 0.02% -0.05%;
(2) continuous casting: producing continuous casting blanks with the thickness of 150-400mm, wherein the low power segregation of the plate blanks is not more than class B1.0 level, and the porosity is not more than 1.0 level;
(3) annealing of the continuous casting slab: performing stress relief annealing treatment on the plate blank;
(4) reheating of continuous casting slabs: then heating to 1100-1250 ℃, homogenizing and solid-melting to completely austenitize the structure;
(5) descaling: removing scale on the surface by high-pressure water, and controlling the temperature of the descaled plate blank to be 980-;
(6) rolling: the method comprises the following steps of carrying out rolling in two stages, namely rough rolling and finish rolling, wherein the initial rolling temperature of the rough rolling is more than or equal to 1000 ℃, the rough rolling is direct rolling without controlled rolling, the maximum pass reduction in the rough rolling stage is 15-25%, the finish rolling is carried out when the steel plate is rolled to be 2-4 times of the target thickness, the initial rolling temperature of the finish rolling is more than or equal to 920 ℃, the single pass reduction rate in the finish rolling stage is 8-12%, the steel plate is rolled for 5-10 passes in an accumulated mode to reach the target thickness, and the rolled steel plate is slowly cooled in a pile;
(7) and (3) heat treatment: and (2) carrying out complete annealing, air cooling quenching and high-temperature tempering on the steel plates in sequence, wherein the complete annealing treatment is to stack the steel plates or lay other steel plates with the thickness of more than or equal to 100mm on the lowest layer of the stacked steel plates, putting the whole steel plate stack into a furnace for heating, the annealing heating temperature is 850-900 ℃, the annealing heat preservation time is 2.0-2.5 min/mm, the calculated thickness of the heat preservation time is the total thickness of the accumulated stacked steel plates and the laid steel plates, and taking out of the furnace for air cooling after the steel plates are cooled to 300 ℃ along with the furnace.
2. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: the step (1) of smelting molten steel comprises converter steelmaking, refining and vacuum degassing,
during converter steelmaking, by utilizing thermodynamic conditions that the temperature is low in the early stage of steelmaking and dephosphorization is facilitated, slagging-off treatment is carried out in the later stage of steelmaking so as to reduce rephosphorization;
during refining, impurity removal and P, S content control are carried out, P, S of molten steel is controlled to be less than or equal to 0.013 percent of P and less than or equal to 0.003 percent of S, and the content of inclusions is controlled to meet the requirement that the sum of the grades of A, B, C, D inclusions is less than or equal to 3.5 grade;
RH vacuum degassing is adopted, argon stirring is combined, the flow rate of the argon is controlled to be 850-1250NL/min, the vacuum treatment time is more than or equal to 20min, the vacuum degree is controlled to be 1KPa-0.01KPa, H in molten steel is less than or equal to 0.0002%, O is less than or equal to 0.0010%, and N is less than or equal to 0.0040%.
3. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: and (3) during continuous casting in the step (2), controlling the machine arc roll gap of the fan-shaped section of the continuous casting machine within +/-0.5 mm, and using dynamic soft reduction on the horizontal section of the fan-shaped section of the continuous casting machine, wherein the soft reduction is 5-10mm, so that the center segregation and the porosity are effectively improved.
4. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: and (3) during continuous casting in the step (2), argon protection casting is carried out in the whole process, a low-drawing-speed weak water-cooling continuous casting process is adopted, and the casting superheat degree is controlled at 8-24 ℃.
5. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: and (4) annealing the continuous casting plate blank in the step (3), wherein the annealing heating temperature is 780 +/-10 ℃, the heat preservation time is 2.5-3.5 min/mm, and the continuous casting plate blank is discharged after being cooled to 200 ℃ along with a heating furnace.
6. The method for producing the 5CrNi2MoV hot-work die steel plate by the continuous casting slab according to claim 1, characterized in that: and (4) reheating the continuous casting slab in the step (4), and setting the heating rate at 8-12 ℃/min.
7. The method for producing the 5CrNi2MoV hot-work die steel plate by the continuous casting slab according to claim 1, characterized in that: and (6) in the rough rolling stage, ensuring that the rolling reduction of 2-3 passes is between 40 and 100mm, wherein the rolling reduction of at least one pass is over 60 mm.
8. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: the total compression ratio of the rolling in the step (6) is more than or equal to 5.
9. The method for producing a 5CrNi2MoV hot-work die steel plate from a continuous cast slab according to claim 1, wherein: air cooling quenching in the step (7), wherein the quenching heating temperature is 850-880 ℃, the quenching heat preservation time is 1.8-2.0 min/mm, air cooling is carried out after discharging, and the line is discharged and slowly cooled when the temperature is 150-;
and (4) tempering in the step (7), wherein the tempering heating temperature is 600-660 ℃, the tempering heat preservation time is 3.5-5.0 min/mm, and the steel is cooled in the air after being discharged from the furnace.
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