CN116949260B - Steel ingot for P91 seamless steel tube and thermal deformation method thereof - Google Patents
Steel ingot for P91 seamless steel tube and thermal deformation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 103
- 239000010959 steel Substances 0.000 title claims abstract description 103
- 238000000034 method Methods 0.000 title claims abstract description 40
- 238000010438 heat treatment Methods 0.000 claims abstract description 117
- 238000005242 forging Methods 0.000 claims abstract description 72
- 238000009792 diffusion process Methods 0.000 claims abstract description 20
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 19
- 238000000265 homogenisation Methods 0.000 claims abstract description 12
- 238000000137 annealing Methods 0.000 claims abstract description 10
- 238000001816 cooling Methods 0.000 claims description 30
- 239000012535 impurity Substances 0.000 claims description 16
- 238000007599 discharging Methods 0.000 claims description 15
- 230000009467 reduction Effects 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 10
- 229910052745 lead Inorganic materials 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 6
- 230000008569 process Effects 0.000 abstract description 12
- 238000001514 detection method Methods 0.000 abstract description 7
- 238000012797 qualification Methods 0.000 abstract description 6
- 238000011161 development Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000004321 preservation Methods 0.000 description 6
- 229910052729 chemical element Inorganic materials 0.000 description 5
- 238000005336 cracking Methods 0.000 description 4
- 229910052718 tin Inorganic materials 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 241001330002 Bambuseae Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention belongs to the technical field of thermal deformation, and discloses a steel ingot for a P91 seamless steel tube and a thermal deformation method thereof, wherein the steel ingot comprises the steps of performing diffusion homogenization heat treatment on a P91 electroslag ingot to obtain a blank; heating the raw blank to obtain a steel blank; forging the steel billet to obtain a forging piece; and (5) annealing the forging to obtain a finished product. According to the invention, the diffusion homogenization heat treatment and the thermal deformation process are carried out on the P91 electroslag ingot, so that the delta ferrite area percentage in the manufactured steel ingot for the P91 seamless steel tube is reduced to below 1%, the surface quality of the steel ingot is good, the flaw detection qualification rate is above 92%, the quality of the steel ingot is effectively controlled, and a foundation is laid for smooth development of the P91 seamless steel tube manufacturing process.
Description
Technical Field
The invention belongs to the technical field of steel heat deformation, and particularly relates to a steel ingot for a P91 seamless steel tube and a heat deformation method thereof.
Background
The P91 seamless steel pipe is a main steam pipeline and is made of high alloy materials. P91 was successfully developed in the 80 s of the 20 th century by the American combustion engineering company and the American oak-ridge national laboratory, and belongs to martensitic heat-resistant steel, and elements (Mn, mo, cr, si, ni and the like) for improving the hardenability of the steel are added in the design process of the steel, so that the steel can also obtain martensite in air cooling. However, the P91 steel is in service in a high-temperature and high-pressure environment (welding, over-temperature and the like), the microstructure of a material part is changed, and the gamma and delta forms, the quantity, the size, the distribution and other factors influence the performance in service, so that the potential safety hazard of special equipment such as nuclear power, boilers, pressure pipelines and the like is increased.
The nuclear power is one of three world prop energy sources, and has the characteristics of cleanness, safety and high efficiency. The fourth generation high Wen Naleng fast reactor is a nuclear power technology developed by independent intellectual property rights of China, has better safety, higher nuclear fuel availability than pressurized water reactor technology, less nuclear waste and capability of effectively preventing nuclear diffusion, and represents the development trend and the technological front of an advanced nuclear power system.
Therefore, it is necessary to provide a thermal deformation method of a steel ingot before rolling a P91 seamless steel tube, which is suitable for the fourth generation nuclear power technology, and by homogenizing diffusion heat treatment and thermal deformation process of an electroslag ingot before thermal deformation, the delta ferrite area percentage in the steel ingot for the P91 seamless steel tube is controlled below 1%, the surface quality of the steel ingot is good, the flaw detection qualification rate is above 92%, and a foundation is laid for smooth development of the pipe manufacturing process of the P91 seamless steel tube.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide the steel ingot for the P91 seamless steel tube and the thermal deformation method thereof, which ensure that the delta ferrite area percentage of the steel ingot for the P91 seamless steel tube after thermal deformation is less than 1% through homogenizing diffusion heat treatment and thermal deformation process of an electroslag ingot, and the steel ingot does not generate cracking phenomenon, so that the flaw detection qualification rate is improved.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a method of hot deformation of a steel ingot for P91 seamless steel pipe, comprising:
performing diffusion homogenization heat treatment on the P91 electroslag ingot to obtain a blank;
heating the raw blank to obtain a steel blank;
forging the steel billet to obtain a forging piece;
and (5) annealing the forging to obtain a finished product.
Further, performing diffusion homogenization heat treatment on the P91 electroslag ingot, wherein the diffusion homogenization heat treatment comprises the following steps:
heating the P91 electroslag ingot for the first time, heating the P91 electroslag ingot to 490-510 ℃ at the speed of 70-90 ℃/h, and preserving the temperature for 1.5-2.0 hours;
heating the P91 electroslag ingot for the second time, heating the P91 electroslag ingot to 1020 ℃ at the speed of 60-80 ℃/h, and preserving heat for 8-12 hours;
and heating the P91 electroslag ingot for the third time, heating the P91 electroslag ingot to 1200 ℃ at the speed of 50-70 ℃/h, and preserving the heat for 10-15 hours.
Further, the diffusion homogenization heat treatment is carried out on the P91 electroslag ingot, and the method further comprises the following steps:
and (3) gradually cooling the P91 electroslag ingot heated for three times along with a furnace to be less than or equal to 150 ℃, and discharging the ingot for air cooling to obtain a raw blank.
Further, heating the blank, comprising:
heating the blank by adopting a continuous heating curve, heating the cold blank to 400-450 ℃ and preserving heat for 3-4 hours, continuously heating the blank to 800-850 ℃ at a heating speed of less than or equal to 100 ℃/h, preserving heat for 3-4 hours, continuously heating the blank to 1190-1210 ℃ at a heating speed of less than or equal to 150 ℃/h, preserving heat for 12-15 hours, and discharging to obtain the billet.
Further, forging the billet, comprising:
and forging the steel billet into a material by adopting a two-heading two-drawing method and an FM forging method.
Further, forging the billet, comprising:
heating the billet to 1220 ℃ before forging;
chamfering and rounding the heated billet, returning to the furnace, heating to 1210-1230 ℃, and preserving heat for 40-90 minutes;
carrying out double upsetting and double drawing on the steel billet after furnace return, wherein the height of the steel billet after the first upsetting is not more than half of the height of the original steel billet, the rolling reduction of the first drawing is not less than 150mm, the height of the steel billet after the second upsetting is not more than half of the height of the original steel billet, and the rolling reduction of the second drawing is not less than 100mm;
forging the two-headed and two-drawn billet into a square shape, and compacting the center;
and (3) re-forging the square, heating the square to 1210-1230 ℃ when the final forging temperature is less than or equal to 850 ℃, preserving the heat for 1.5-2 hours, and then drawing to the specification of a finished product to obtain the forged piece.
Further, annealing the forging, including:
heating the forging to 750-770 ℃ at a heating rate of 40-60 ℃/h and preserving heat for 10-12h;
and cooling the heated forging at a cooling rate of 30-60 ℃, and discharging and air-cooling to room temperature after the temperature is reduced to 150 ℃.
Further, the chemical components of the finished product are as follows by weight percent: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20 to 0.25 percent, pb less than or equal to 0.008 percent, bi less than or equal to 0.008 percent, the sum of Sn, as, sb and Pb is less than or equal to 0.020 percent, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
On the other hand, the invention discloses a steel ingot for a P91 seamless steel tube, which is prepared by adopting the method,
the steel ingot comprises the following chemical components in percentage by weight: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20 to 0.25 percent, pb less than or equal to 0.008 percent, bi less than or equal to 0.008 percent, the sum of Sn, as, sb and Pb is less than or equal to 0.020 percent, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
Further, the area percentage of delta ferrite of the steel ingot is less than or equal to 1 percent.
The invention has the technical effects and advantages that:
according to the invention, the diffusion homogenization heat treatment and the thermal deformation process are carried out on the P91 electroslag ingot, so that the delta ferrite area percentage in the manufactured steel ingot for the P91 seamless steel tube is reduced to be less than 1%, the steel ingot surface quality is good, the flaw detection qualification rate is more than 92%, the steel ingot quality is effectively controlled, and a foundation is laid for smoothly developing the P91 seamless steel tube manufacturing process.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Fig. 1 is a flowchart of a heat deformation method of a steel ingot for a P91 seamless steel tube according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, the present invention provides a heat deformation method of a steel ingot for a P91 seamless steel tube, comprising:
performing diffusion homogenization heat treatment on the P91 electroslag ingot to obtain a blank;
heating the raw blank to obtain a steel blank;
forging the steel billet to obtain a forging piece;
and (5) annealing the forging to obtain a finished product.
In some embodiments of the invention, the diffusion homogenizing heat treatment of the P91 electroslag ingot comprises:
heating the P91 electroslag ingot for the first time, heating the P91 electroslag ingot to 490-510 ℃ at the speed of 70-90 ℃/h, and preserving the temperature for 1.5-2.0 hours;
heating the P91 electroslag ingot for the second time, heating the P91 electroslag ingot to 1020 ℃ at the speed of 60-80 ℃/h, and preserving heat for 8-12 hours;
the purpose of the first two times of heating is to lead the large area delta ferrite distributed along the grain boundary in the P91 electroslag ingot to be changed into a long strip shape through diffusion and aggregation, and along with the extension of the heat preservation time, the long strip delta ferrite is changed into a bamboo joint shape due to the dissolution of part of chemical elements in the high temperature process;
and heating the P91 electroslag ingot for the third time, heating the P91 electroslag ingot to 1200 ℃ at the speed of 50-70 ℃/h and preserving heat for 10-15 hours, so that broken delta ferrite is diffused from high concentration to low concentration at high temperature due to chemical elements, and the delta ferrite is changed into small particles to be 'drip-shaped', thereby greatly reducing the area percentage of the delta ferrite.
The main cause of delta ferrite formation in heat-resistant steel is segregation of chemical elements. The purpose of the homogenizing heat treatment for the diffusion of the P91 electroslag ingot is to diffuse and homogenize the segregated chemical elements in the P91 electroslag ingot from high concentration to low concentration under the action of high temperature. Under the action of high temperature, the irregular delta ferrite formed on the grain boundary of the P91 electroslag ingot changes the large-area irregular delta ferrite into a long strip shape due to delta ferrite formation and diffusion of chemical elements along with the extension of heat preservation time, and finally becomes small-particle 'drip-shaped', so that the area percentage of the delta ferrite is greatly reduced.
In some embodiments of the invention, the diffusion homogenizing heat treatment of the P91 electroslag ingot further comprises:
and (3) gradually cooling the P91 electroslag ingot heated for three times to the temperature of less than or equal to 150 ℃ along with a furnace, discharging the ingot, and air-cooling to obtain a raw blank, wherein the purpose of gradually cooling to the temperature of less than or equal to 150 ℃ along with the furnace is to prevent cracking caused by the difference of internal and external cooling rates of high alloy steel.
In some embodiments of the invention, heating the blank comprises:
heating the blank by adopting a continuous heating curve, heating the cold blank to 400-450 ℃ and preserving heat for 3-4 hours, continuously heating the blank to 800-850 ℃ at a heating speed of less than or equal to 100 ℃/h, preserving heat for 3-4 hours, continuously heating the blank to 1190-1210 ℃ at a heating speed of less than or equal to 150 ℃/h, preserving heat for 12-15 hours, and discharging to obtain the billet.
The continuous heating curve is adopted for heating, so that the temperature of the inner surface and the outer surface of the raw blank is kept consistent, and meanwhile, stress cracks in the raw blank caused by too fast heating are prevented, the heating temperature is Wen Weizhun, and the temperature of a preheating section is not higher than the highest charging temperature required by the process.
In some embodiments of the present invention, forging a billet comprises:
forging the steel billet into a material by adopting a two-heading two-drawing method and an FM forging method, wherein,
the double upsetting and double drawing method is to upsett and draw a billet twice, upsetting adopts an upper arc tray and a lower arc tray, and a 500mm wide anvil is adopted up and down during drawing, so that the defects of looseness or holes and the like in the billet can be improved through upsetting and drawing processes, a homogeneous and compact microstructure is obtained, and the plasticity and mechanical properties of the billet are improved.
The FM forging method utilizes the asymmetric deformation of the upper flat anvil and the lower flat anvil during forging and the friction resistance of the lower flat anvil to the deformation of the forging, so that the steel billet is gradually deformed from top to bottom, the tensile stress is transferred to the contact surface of the steel billet and the flat anvil, the hydrostatic pressure stress of the central part is increased, and the stress state in the deformed body is improved.
In some embodiments of the present invention, forging a billet comprises:
chamfering and rounding the billet, returning to the furnace, heating to 1210-1230 ℃, and preserving heat for 40-90 minutes;
carrying out double upsetting and double drawing on the steel billet after furnace return, wherein the height of the steel billet after the first upsetting is not more than half of the height of the original steel billet, the rolling reduction of the first drawing is not less than 150mm, the height of the steel billet after the second upsetting is not more than half of the height of the original steel billet, and the rolling reduction of the second drawing is not less than 100mm;
forging the two-headed and two-drawn billet into a square shape, and compacting the center;
and (3) re-forging the square, heating the square to 1210-1230 ℃ when the final forging temperature is less than or equal to 850 ℃, preserving the heat for 1.5-2 hours, and then drawing to the specification of a finished product to obtain the forged piece.
The start of forging is to lightly press the billet to prevent cracking, and the reduction is determined by the heating temperature, but when the temperature is low, the reduction is reduced, and this is also to prevent cracking. If a forging crack is found, it should be immediately cleared to prevent propagation. When the mandrel is reamed, the rotation is uniform, the pressing amount is uniform every time, so that the deformation distribution is ensured to be uniform, and the mixed crystal phenomenon is reduced. When the temperature of the square is lower than the finish forging temperature, forging must be stopped.
In some embodiments of the invention, annealing the forging includes:
heating the forging to 750-770 ℃ at a heating rate of 40-60 ℃/h and preserving heat for 10-12h;
and cooling the heated forging at a cooling rate of 30-60 ℃, and discharging and air-cooling to room temperature after the temperature is reduced to 150 ℃.
After hot rolling or forging, the steel is subjected to annealing treatment to remove residual stress due to the fact that the residual stress is generated due to the difference in temperature difference between the inside and outside of the steel caused by different cooling speeds of the surface and the core in the cooling process.
In some embodiments of the present invention, the chemical composition of the finished product is as follows in weight percent: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20 to 0.25 percent, pb less than or equal to 0.008 percent, bi less than or equal to 0.008 percent, the sum of Sn, as, sb and Pb is less than or equal to 0.020 percent, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
On the other hand, the invention also discloses a steel ingot for the P91 seamless steel tube, which is prepared by adopting the method, and the steel ingot comprises the following chemical components in percentage by weight: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20 to 0.25 percent, pb less than or equal to 0.008 percent, bi less than or equal to 0.008 percent, the sum of Sn, as, sb and Pb is less than or equal to 0.020 percent, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
In some embodiments of the invention, the delta ferrite area percentage of the steel ingot is less than or equal to 1%.
For a better explanation of the present solution, the following examples are also provided.
Example 1
The embodiment provides a thermal deformation method of a steel ingot for a P91 seamless steel tube with the specification phi of 400mm, which comprises the following thermal deformation processes:
(1) Diffusion homogenization heat treatment of P91 electroslag ingot
Placing P91 electroslag ingots with phi 650mm and 2400mm in a chamber type heating furnace, heating to 500 ℃ at a heating speed of 90 ℃/h, and preserving heat for 1.5 hours; heating to 1020 ℃ at a heating speed of 80 ℃/h, and preserving heat for 8 hours; finally heating to 1200 ℃ at a heating rate of 70 ℃/h, preserving heat for 10 hours, slowly cooling to less than or equal to 150 ℃ along with a furnace after the heat preservation is finished, and discharging and air cooling to obtain a raw blank.
(2) Heating the blank
650mm x 2400mm Leng Yuan billets were heated to 400 ℃ and incubated for 3 hours; heating to 800 ℃ at a heating rate of 100 ℃/h, and preserving heat for 3 hours; finally heating to 1210 ℃ at a heating rate of 150 ℃/h, preserving heat for 12 hours, and discharging to obtain the billet.
(3) Forging a billet
The billet was heated to 1220 ℃ 30 minutes before the start of forging. Adopts a two-heading two-drawing (+ FM forging method) to form a material,
chamfering and rounding the billet, returning to the furnace and heating to 1220 ℃, and then burning for 65 minutes,
the first upsetting adopts an upper arc tray and a lower arc tray, the height of a billet after the first upsetting is 1200mm, the first drawing adopts a 500mm wide anvil from top to bottom, and the rolling reduction is 200mm.
The second upsetting adopts an upper arc tray and a lower arc tray, the height of a billet after the second upsetting is 1200mm, the upper anvil and the lower anvil are 500mm wide during the second drawing, and the rolling reduction is 150mm. Then forging into a square shape, and compacting the center.
And (3) re-forging the square, wherein in the re-forging process, if the final forging temperature is less than or equal to 850 ℃, the square is heated again, the heating temperature is 1220+/-10 ℃, and the forging is obtained after heat preservation for 1.5h and then is pulled to the specification of a finished product of phi 400 mm.
(4) Annealing the forging
Heating the forging to 770 ℃ at a heating rate of 60 ℃/h, preserving heat at the temperature for 10h, cooling at a cooling rate of 60 ℃/h, discharging from the furnace and cooling to room temperature after the temperature is reduced to 150 ℃ to obtain a finished product.
The chemical components of the finished product are as follows by weight percent: c:0.10%, si:0.26%, mn:0.41%, cr:8.75%, mo:0.92%, V:0.21%, pb 0.0001%, bi 0.002%, sn, as, sb and Pb in total: 0.010%, the balance being Fe and impurities, the impurities including: p is 0.006% and S is 0.008%.
Example 2
The embodiment provides a thermal deformation method of a steel ingot for a P91 seamless steel tube with the specification phi of 550mm, which comprises the following thermal deformation processes:
(1) Diffusion homogenization heat treatment of P91 electroslag ingot
Placing a P91 electroslag ingot with phi 730mm and 2600mm in a chamber type heating furnace, heating to 500 ℃ at a heating speed of 70 ℃/h, and preserving heat for 2.0 hours; heating to 1020 ℃ at a heating speed of 60 ℃/h, and preserving heat for 12 hours; finally, heating to 1200 ℃ at a heating speed of 50 ℃/h, preserving heat for 15 hours, slowly cooling to less than or equal to 150 ℃ along with a furnace after the heat preservation is finished, and discharging and air cooling to obtain a raw blank.
(2) Heating the blank
Heating a Leng Yuan blank with phi 730mm and 2600mm to 450 ℃, and preserving the heat for 4 hours; heating to 850 ℃ at a heating rate of 100 ℃/h, and preserving heat for 4 hours; finally heating to 1190 ℃ at a heating speed of 150 ℃/h, preserving heat for 15 hours, and discharging to obtain the billet.
(3) Forging a billet
Heating the steel billet to 1220 ℃ 30 minutes before forging, and forming the steel billet into a material by adopting a two-upsetting and two-drawing (+ FM forging method);
chamfering and rounding the billet, returning to the furnace and heating to 1220 ℃, and then burning for 90 minutes;
the first upsetting adopts an upper arc tray and a lower arc tray, the height of a billet after the first upsetting is 1300mm, the first drawing adopts a 500mm wide anvil from top to bottom, and the pressing amount is 150mm;
the second upsetting adopts an upper arc tray and a lower arc tray, the height of the second upsetted billet is 1300mm, the second upsetting adopts a 500mm wide anvil from top to bottom during the second drawing, and the rolling reduction is 100mm. Then forging into a square shape, and compacting the center;
and (3) re-forging the square, wherein in the re-forging process, if the final forging temperature is less than or equal to 850 ℃, the square is heated again, the heating temperature is 1220+/-10 ℃, and the forging is obtained after 2 hours of heat preservation and is drawn to the specification of a finished product of phi 550 mm.
(4) Annealing the forging
Heating the forging to 770 ℃ at a heating rate of 40 ℃/h, preserving heat at the temperature for 12h, cooling at a cooling rate of 30 ℃/h, discharging from the furnace and cooling to room temperature after the temperature is reduced to 150 ℃ to obtain a finished product.
The chemical components of the finished product are as follows by weight percent: c:0.09%, si:0.27%, mn:0.40%, cr:9.02%, mo:0.97%, V:0.20%, pb 0.0001%, bi 0.002%, sn, as, sb and Pb in total: 0.011%, the balance being Fe and impurities, the impurities including: p is 0.006% and S is 0.008%.
The area percentage of delta ferrite and the ultrasonic flaw detection qualification rate of the finished steel ingots prepared in the examples 1 and 2 are detected, the detection results are shown in table 1, the technical requirements of the steel ingots for the P91 seamless steel pipes are shown in table 2, and as can be seen from tables 1 and 2, the delta ferrite is controlled at an extremely low level, and the flaw detection qualification rate of the steel ingots for the P91 seamless steel pipes prepared by the method is greatly improved.
TABLE 1
TABLE 2
Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.
Claims (4)
1. A method for hot deformation of a steel ingot for P91 seamless steel tube, characterized by comprising:
performing diffusion homogenization heat treatment on the P91 electroslag ingot to obtain a blank;
heating the raw blank to obtain a steel blank;
forging the steel billet to obtain a forging piece;
annealing the forging piece to obtain a finished product;
the diffusion homogenization heat treatment for the P91 electroslag ingot comprises the following steps:
heating the P91 electroslag ingot for the first time, heating the P91 electroslag ingot to 490-510 ℃ at the speed of 70-90 ℃/h, and preserving heat for 1.5-2.0 hours;
heating the P91 electroslag ingot for the second time, heating the P91 electroslag ingot to 1020 ℃ at the speed of 60-80 ℃/h, and preserving heat for 8-12 hours;
heating the P91 electroslag ingot for the third time, heating the P91 electroslag ingot to 1200 ℃ at the speed of 50-70 ℃/h, and preserving heat for 10-15 hours;
slowly cooling the P91 electroslag ingot heated for three times along with a furnace to be less than or equal to 150 ℃, and discharging the ingot from the furnace for air cooling to obtain a blank;
the heating of the blank comprises the following steps:
heating the raw blank by adopting a continuous heating curve, heating a cold raw blank to 400-450 ℃ and preserving heat for 3-4 hours, continuously heating the raw blank to 800-850 ℃ at a heating speed of less than or equal to 100 ℃/h, preserving heat for 3-4 hours, continuously heating the raw blank to 1190-1210 ℃ at a heating speed of less than or equal to 150 ℃/h, preserving heat for 12-15 hours, and discharging to obtain a steel blank;
the forging of the steel billet comprises the following steps:
forging the steel billet into a material by adopting a two-heading two-drawing method and an FM forging method;
heating the steel billet to 1220 ℃ before forging;
chamfering and rounding the heated steel billet, returning to the furnace, heating to 1210-1230 ℃, and preserving heat for 40-90 minutes;
the billet after the furnace return is subjected to double upsetting and double drawing, the height of the billet after the first upsetting is not more than half of the height of the original billet, the rolling reduction of the first drawing is not less than 150mm, the height of the billet after the second upsetting is not more than half of the height of the original billet, and the rolling reduction of the second drawing is not less than 100mm;
forging the billet subjected to double upsetting and double drawing into a bloom, and compacting the center;
re-forging the bloom, heating the bloom to 1210-1230 ℃ when the final forging temperature is less than or equal to 850 ℃, preserving heat for 1.5-2 hours, and then drawing to a finished product specification to obtain a forging;
the annealing treatment of the forging comprises the following steps:
heating the forging to 750-770 ℃ at a heating rate of 40-60 ℃/h and preserving heat for 10-12h;
and cooling the heated forging at a cooling rate of 30-60 ℃, and discharging and air-cooling to room temperature after the temperature is reduced to 150 ℃.
2. A heat deformation method of steel ingot for P91 seamless steel tube as set forth in claim 1, wherein,
the chemical components of the finished product are as follows by weight percent: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20% -0.25%, pb less than or equal to 0.008%, bi less than or equal to 0.008%, sn, as, sb and Pb are less than or equal to 0.020%, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
3. A steel ingot for a P91 seamless steel pipe, which is characterized in that the steel ingot is prepared by the method of any one of claims 1-2,
the steel ingot comprises the following chemical components in percentage by weight: c:0.09% -0.12%, si:0.25% -0.50%, mn:0.35% -0.60%, cr:8.5% -9.5%, mo:0.90% -1.05%, V:0.20% -0.25%, pb less than or equal to 0.008%, bi less than or equal to 0.008%, sn, as, sb and Pb are less than or equal to 0.020%, and the balance is Fe and impurities, wherein the impurities comprise: p is less than or equal to 0.020%, S is less than or equal to 0.010%.
4. A steel ingot for a P91 seamless steel pipe according to claim 3,
the area percentage of delta ferrite of the steel ingot is less than or equal to 1 percent.
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