Austenitic stainless steel plate for fast neutron reactor and manufacturing method thereof
阅读说明：本技术 快中子反应堆用奥氏体不锈钢钢板及其制造方法 (Austenitic stainless steel plate for fast neutron reactor and manufacturing method thereof ) 是由 胡昕明 欧阳鑫 隋松言 王储 邢梦楠 冷松洋 孙殿东 贾春堂 王勇 黄松 于 2021-06-29 设计创作，主要内容包括：本发明提供了一种快中子反应堆用奥氏体不锈钢钢板及其制造方法,该钢板的成分按重量百分比计如下：C:0.04％～0.10％、Si:0.10％～0.60％、Mn:1.00％～2.0％、P≤0.035％、S≤0.010％、Ni:11.50％～12.50％、Cr:17.00％～18.00％、Mo:2.50％～2.70％、Cu≤0.10％、N:0.05％～0.15％、B≤0.0015％、Al≤0.03％、Sb≤0.002％、Pb≤0.001％、Se≤0.015％、Sn≤0.005％、V≤0.10％、Zn≤0.01％、As≤0.01％、Co≤0.06％、Zr≤0.015％、Nb≤1.50％、Ti≤1.00％、[O]≤30ppm、[H]≤5.0ppm；其余为Fe及不可避免的杂质。通过添加一定含量的氮元素,大幅提升了奥氏体不锈钢常温及高温强度；同时成品钢板中的铁素体含量＜1％,钢板具有均匀晶粒尺寸且晶粒度达到3～6级的同时具有优异的耐晶间腐蚀性能。(The invention provides an austenitic stainless steel plate for a fast neutron reactor and a manufacturing method thereof, wherein the steel plate comprises the following components in percentage by weight: 0.04 to 0.10 percent of C, 0.10 to 0.60 percent of Si, 1.00 to 2.0 percent of Mn, less than or equal to 0.035 percent of P, less than or equal to 0.010 percent of S, 11.50 to 12.50 percent of Ni, 17.00 to 18.00 percent of Cr, 2.50 to 2.70 percent of Mo, less than or equal to 0.10 percent of Cu, 0.05 to 0.15 percent of N, less than or equal to 0.0015 percent of B, less than or equal to 0.03 percent of Al, less than or equal to 0.002 percent of Sb, less than or equal to 0.001 percent of Pb, less than or equal to 0.015 percent of Se, less than or equal to 0.005 percent of Sn, less than or equal to 0.10 percent of V, less than or equal to 0.01 percent of Zn, less than or equal to 0.01 percent of As, less than or equal to 0.06 percent of Co, less than or equal to 0.015 percent of Zr, less than or equal to 1.50 percent of Nb, less than or equal to 1.00 percent of Ti, less than or equal to 30ppm of O, and less than or equal to 5.0ppm of H; the balance of Fe and inevitable impurities. By adding a certain content of nitrogen element, the normal temperature and high temperature strength of the austenitic stainless steel is greatly improved; meanwhile, the ferrite content in the finished steel plate is less than 1%, and the steel plate has uniform grain size, grain size reaching 3-6 grades and excellent intergranular corrosion resistance.)
1. The austenitic stainless steel plate for the fast neutron reactor is characterized by comprising the following components in percentage by weight: 0.04-0.10% of C, Si:0.10 to 0.60 percent of Mn, 1.0 to 2.0 percent of Mn, less than or equal to 0.035 percent of P, less than or equal to 0.010 percent of S, 11.50 to 12.50 percent of Ni, 17.00 to 18.00 percent of Cr, 2.50 to 2.70 percent of Mo, less than or equal to 0.10 percent of Cu, 0.05 to 0.15 percent of N, less than or equal to 0.0015 percent of B, less than or equal to 0.03 percent of Al, less than or equal to 0.002 percent of Sb, less than or equal to 0.001 percent of Pb, less than or equal to 0.015 percent of Se, less than or equal to 0.005 percent of Sn, less than or equal to 0.10 percent of V, less than or equal to 0.01 percent of Zn, less than or equal to 0.01 percent of As, less than or equal to 0.06 percent of Co, less than or equal to 0.015 percent of Zr, less than or equal to 1.50 percent of Nb, less than or equal to 1.00 percent of Ti, less than or equal to 30ppm of [ O ], [ 5.0ppm ]; the balance of Fe and inevitable impurities.
2. The austenitic stainless steel sheet for fast neutron reactor according to claim 1, wherein the steel sheet microstructure has a ferrite content of < 1%; the grain size of the full-thickness section of the steel plate is 3-6 grades.
3. A method for manufacturing the austenitic stainless steel plate for the fast neutron reactor of claim 1 or 2, comprising smelting, continuous casting, forging, homogenizing, heating, rolling, heat treating, straightening; the method is characterized in that:
(1) smelting and continuous casting: the temperature of the tundish molten steel is less than or equal to 1580 ℃, and the continuous casting adopts an electromagnetic stirring or continuous casting billet soft reduction process, wherein the soft reduction rate is controlled to be 8-12%;
(2) forging: heating the blank to 1230-1260 ℃, preserving the temperature for 15-20 h, and forging the accumulated deformation pass to 10-40 passes;
(3) homogenizing: homogenizing at 1230-1270 ℃, keeping the net temperature for 30-70 h, and then air-cooling at a cooling rate of 50-80 ℃/min;
(4) heating: the heating is divided into a preheating section, a heating section and a soaking section; wherein the temperature range of the heating section is 1190-1250 ℃; the temperature interval of the soaking section is 1200-1250 ℃; the total time in the furnace is 5-7 hours;
(5) rolling: two-stage rolling is adopted; the initial rolling temperature of the first stage is more than or equal to 1170 ℃, the first three single-pass reduction rate is more than or equal to 20 percent, the rolling temperature is more than or equal to 1120 ℃, the remaining single-pass reduction rate of the rolling is 7 to 15 percent, and the finishing temperature of the first stage is more than or equal to 1070 ℃; the thickness of the intermediate blank is 1.5-2 times that of the finished steel plate; the initial rolling temperature of the second stage is 970-1000 ℃, the final rolling temperature is 850-900 ℃, and the single-pass reduction rate is 5-8%; directly carrying out laminar cooling on the rolled steel plate, wherein the final cooling temperature is 650-700 ℃;
(6) and (3) heat treatment: when the thickness of the finished steel plate is less than or equal to 50mm, a stage heat treatment process is adopted, the heat treatment temperature of the steel plate is 1050-1100 ℃, the heat treatment time is 10-60 min, and the steel plate is cooled to room temperature after being taken out of the furnace;
when the thickness of the finished steel plate is larger than 50mm, a three-stage heat treatment process is adopted, the temperature of the first-stage heat treatment is 650-700 ℃, the heat preservation time is 60-120 min, then the temperature is increased to 980-1000 ℃, the second-stage heat treatment is started, the heat preservation time is 60-80 min, then the temperature is increased to 1050-1150 ℃, the third-stage heat preservation is started, the heat preservation time is 30-80 min, and the finished steel plate is cooled to the room temperature after being taken out of the furnace;
(7) straightening: the straightening deformation rate is 3-5%.
4. The method for manufacturing the austenitic stainless steel sheet for the fast neutron reactor according to claim 3, wherein: carrying out an electroslag remelting process before forging: the method is characterized in that continuous casting billets are used as electrodes to produce electroslag billets with the thickness of 200-550 mm, and an argon protection mode is adopted in the whole process of production, wherein the flow of argon is 20-40 m3H; the current in the electroslag remelting process is 6000-30000A, and the voltage is 70-120V.
5. The method for manufacturing the austenitic stainless steel sheet for the fast neutron reactor according to claim 3, wherein: in the heating process in the step (4), when the thickness of the plate blank is less than or equal to 200mm, the temperature range of the preheating section is 860-910 ℃; when the thickness of the plate blank is within the range of 200-400 mm, the temperature range of the preheating section is 810-860 ℃.
6. The method for manufacturing the austenitic stainless steel sheet for the fast neutron reactor according to claim 3, wherein: in the rolling process of the step (5), cooling water is not adopted for dephosphorization in the whole rolling process.
Technical Field
The invention belongs to the field of metal materials, and particularly relates to an austenitic stainless steel plate for a fast neutron reactor and a manufacturing method thereof.
Background
The fast neutron reactor (fast reactor for short) is the only practical breeder reactor at present, is a key reactor type for ensuring the large-scale development of nuclear power and the sustainable and safe supply of future energy sources in China, and the material for manufacturing the fast reactor is mainly austenitic stainless steel. The operating temperature range of the fast reactor is 250-650 ℃, so that the austenitic stainless steel serving at the temperature is required to have good high-temperature strength. The high-temperature strength of the steel plate can be effectively improved by increasing the carbon content in the steel, but the intercrystalline corrosion resistance of the steel plate is reduced by excessively increasing the carbon content, and particularly the intercrystalline corrosion resistance of the steel plate after sensitization treatment is rapidly deteriorated. Because austenitic stainless steel can form a certain amount of residual ferrite in the actual smelting process, and the residual ferrite is reduced or eliminated without adopting a special process, the steel plate runs at a long-term high-temperature service temperature, and the ferrite phase in the steel can decompose a brittle alpha phase to deteriorate the toughness of the steel plate. In addition, as the thickness of the austenitic stainless steel sheet increases, a mixed grain phenomenon, in which both coarse and fine grains are present, in which fine grains are distributed among the coarse grains, is formed to some extent in the inside thereof. The mixed crystal phenomenon has great harm to the mechanical property and the process property of the austenitic stainless steel. In view of the above, the austenitic stainless steel for fast reactor is required to have good high temperature performance and intergranular corrosion resistance, and simultaneously reduce residual ferrite in the steel to the maximum extent and avoid mixed crystals from forming in the steel.
Patent document "a method for controlling grain size uniformity of hot-rolled high-carbon austenitic stainless steel" (application number: 201911126633.6) discloses a three-stage heat treatment method, which performs segmented heat treatment at temperatures above 900-.
Patent document "grain size control method of high carbon austenitic stainless steel medium plate" (acceptance number CN111549276A) discloses a three-stage heat treatment method, the temperature of each stage is 600 ℃, 1010 ℃ and 1050 ℃, the heat treatment method not only ensures that the steel plate has uniform grains in the full thickness direction, but also has good intergranular corrosion resistance, but the invention does not relate to whether the heat treatment process is beneficial to eliminating residual ferrite in the steel.
In order to solve the above problems of the austenitic stainless steel for fast reactor, it is necessary to develop a stainless steel sheet having good high temperature strength and intergranular corrosion resistance, uniform crystal grains, and a single austenitic structure, and a method for producing the same.
Disclosure of Invention
The present invention has been made to overcome the above problems and disadvantages and to provide an austenitic stainless steel sheet for fast neutron reactor having good high temperature performance and intergranular corrosion resistance, and having uniform crystal grains throughout the thickness direction and no residual ferrite in the steel, and a method for manufacturing the same.
The purpose of the invention is realized as follows:
an austenitic stainless steel plate for a fast neutron reactor comprises the following components in percentage by weight: 0.04 to 0.10 percent of C, 0.10 to 0.60 percent of Si, 1.00 to 2.0 percent of Mn, less than or equal to 0.035 percent of P, less than or equal to 0.010 percent of S, 11.50 to 12.50 percent of Ni, 17.00 to 18.00 percent of Cr, 2.50 to 2.70 percent of Mo, less than or equal to 0.10 percent of Cu, 0.05 to 0.15 percent of N, less than or equal to 0.0015 percent of B, less than or equal to 0.03 percent of Al, less than or equal to 0.002 percent of Sb, less than or equal to 0.001 percent of Pb, less than or equal to 0.015 percent of Se, less than or equal to 0.005 percent of Sn, less than or equal to 0.10 percent of V, less than or equal to 0.01 percent of Zn, less than or equal to 0.01 percent of As, less than or equal to 0.06 percent of Co, less than or equal to 0.015 percent of Zr, less than or equal to 1.50 percent of Nb, less than or equal to 1.00 percent of Ti, less than or equal to 30ppm of O, and less than or equal to 5.0ppm of H; the balance of Fe and inevitable impurities.
The ferrite content in the steel plate microstructure is less than 1 percent; the grain size of the full-thickness section of the steel plate is 3-6 grades.
The steel plate of the invention has the following composition design reasons:
c is an important element of austenitic stainless steel, and the element C can enlarge an austenite region and inhibit the formation of ferrite in the steel. In addition, the C element exists in the form of solid solution or carbide precipitation in the steel, and the normal temperature and high temperature strength of the steel plate can be effectively improved. However, too high C content not only increases the hardness of the weld heat affected zone and the heat treatment cracks after welding, but also is not beneficial to the long-term high-temperature performance of the steel plate. Therefore, the C content is limited to 0.04 to 0.10%.
Si is a main deoxidizing element of austenitic stainless steel, can effectively reduce the oxygen content in the steel and improve the purity of the steel. However, too high a Si content promotes brittle sigma phase formation or silicon-rich G phase precipitation at grain boundaries. Therefore, the Si content is 0.10% to 0.60%.
Mn is an important element of austenitic stainless steel, and the Mn element can improve the strength performance of the steel while enlarging an austenite region. In particular, Mn element significantly improves the solubility of N in steel, and reduces the activity of N in austenite to stabilize the dissolved N in steel, thereby sufficiently exerting the effect of N element in improving the tensile strength of steel. However, too high Mn content affects the weldability of the steel sheet. Therefore, the Mn content is limited to 1.00 to 2.00%.
Ni is an important element of austenitic stainless steel, and Ni element can enlarge an austenite region and inhibit formation of ferrite in steel. Meanwhile, the steel plate is matched with Cr element for use to ensure that the steel plate has good oxidation and corrosion resistance. Since it is expensive, the Ni content is limited to 11.50% to 12.50%.
Cr is an important element of austenitic stainless steel, and the Cr element is a main element for improving the high-temperature oxidation resistance and the high-temperature corrosion resistance of the steel plate and is also an element for forming M23C6The key element of carbide. Then, the addition of excessive amount thereof causes coarsening of carbides, thereby causing a decrease in high-temperature strength and toughness of the steel sheet. Therefore, the Cr content is limited to 17.00% to 18.00%.
Mo is a main element for solid solution strengthening in austenitic stainless steel, can greatly improve the strength of the steel plate, and simultaneously, Mo is a pair of M23C6The carbides also act as strengthening. Therefore, the Mo content is limited to 2.50% to 2.70%.
N is an important element in austenitic stainless steels, and it does not significantly impair the toughness and plasticity of the steel in terms of stabilizing the austenitic structure, improving strength and corrosion resistance (in particular, localized corrosion resistance). In addition, the N element can form a fine and stable precipitated phase with the Nb and V elements, and the precipitated phase has good thermal stability and can improve the high-temperature strength of the steel plate. Therefore, the N content is 0.05 to 0.15 percent.
P, S is a harmful element in austenitic stainless steel, and theoretically, the lower the content, the better, but the excessive reduction will lead to a large increase in manufacturing cost. Therefore, the content of P is limited to be less than or equal to 0.035 percent, and the content of S is limited to be less than or equal to 0.015 percent.
Zr is a main strengthening element in the steel, and is precipitated in the form of carbide at grain boundaries, so that the grain boundaries are strengthened, and the normal temperature and high temperature performance of the steel plate is improved; meanwhile, because a large amount of Zr carbide is precipitated, the precipitation of Cr in a crystal boundary is inhibited, a chromium-poor area is prevented from appearing near the crystal boundary, and the intergranular corrosion resistance of the steel plate is improved. However, too high Zr content will cause the mechanical properties of the steel sheet to be degraded. Therefore, the Zr content is less than or equal to 0.015 percent.
Nb is precipitated in the form of carbide at the grain boundary, thereby inhibiting the precipitation of Cr at the grain boundary, preventing a chromium-poor area from appearing near the grain boundary and improving the intergranular corrosion resistance of the steel plate. In addition, the recrystallization temperature of the steel can be increased, the crystal grains of the steel are refined, and the tensile strength and the yield strength of the steel are improved. However, the Ti content is too high, so that the Ti content can cause embrittlement of a welding joint in the welding process and reduce the plasticity and the toughness of the material. Therefore, the Nb content is 1.50% or less.
Ti is precipitated in the form of carbide at the grain boundary, thereby inhibiting the precipitation of Cr at the grain boundary, preventing a chromium-poor area from appearing near the grain boundary and improving the intergranular corrosion resistance of the steel plate. However, the Ti content is too high, so that the Ti content can cause embrittlement of a welding joint in the welding process and reduce the plasticity and the toughness of the material. Therefore, the Ti content is less than or equal to 1.00 percent.
The Co element forms a radioisotope when irradiated by neutrons, which affects the service life of nuclear power plants. Therefore, the Co content is limited to 0.06% or less.
B: the toughness of the steel can be negatively influenced, so that the brittleness of the steel is increased; therefore, the B content of the invention is less than or equal to 0.0015 percent.
The V is ferrite forming element, and the excessive V element can cause abnormal growth of crystal grains and is not beneficial to controlling the size of the crystal grains, so the V is less than or equal to 0.10 percent.
Al; the deoxidizing element is mainly used for controlling the oxygen content in steel, but is also a ferrite forming element, the matrix phase of the alloy is changed into an austenite-ferrite dual-phase structure from an austenite phase along with the increase of the Al content, the control of the ferrite content is not facilitated, the Al is increased, nitrides can also appear, and the excessive Al can cause the gradual reduction of the toughness of the material, so the Al content is less than or equal to 0.03 percent.
Sb, Pb, Se, Sn, Zn and As are harmful elements in steel, and the content of Sb, Pb, Se, Sn, Zn and As in the steel can obviously reduce the high-temperature performance of the steel plate, increase the high-temperature brittleness of the steel and reduce the strength and the toughness of the steel when exceeding a certain content. Therefore, the content of Sb is limited to be less than or equal to 0.002 percent, the content of Pb is limited to be less than or equal to 0.001 percent, the content of Se is limited to be less than or equal to 0.015 percent, the content of Sn is limited to be less than or equal to 0.005 percent, and the content of As is limited to be less than or equal to 0.01 percent.
H and O in stainless steel can seriously affect the toughness of the material and must be strictly controlled. Therefore, the [ O ] content is limited to 30ppm or less and the [ H ] content is limited to 5.0ppm or less.
The second technical scheme of the invention is to provide a manufacturing method of an austenitic stainless steel plate for a fast neutron reactor, which comprises smelting, continuous casting, forging, homogenizing, heating, rolling, heat treatment and straightening;
(1) smelting and continuous casting processes: the smelting is carried out by adopting the processes of electric furnace smelting, VOD vacuum treatment and the like. A continuous casting process is adopted, the casting temperature is mainly controlled, the casting temperature of the molten steel in the tundish is less than or equal to 1580 ℃, and low-temperature casting is better so as to refine the original as-cast structure. In order to control the center segregation and the porosity of the continuous casting billet, an electromagnetic stirring process or a continuous casting billet soft reduction process is adopted, wherein the soft reduction rate is controlled to be 8-12%.
(3) The forging process comprises the following steps: heating the blank to 1230-1260 ℃, preserving heat for 15-20 h, controlling the deformation rate of each forging pass to be 4.5% -5.5%, forging the blank in the length direction, the width direction and the thickness direction, and accumulating the deformation in three directions for 10-40 passes until the forging process is completed.
(4) And (3) homogenizing: and (3) conveying the forged blank to a heating furnace for high-temperature homogenization heat treatment, wherein the heat treatment system is 1230-1270 ℃, the net heat preservation is carried out for 30-70 h, and the blank is taken out of the furnace after the heat preservation is finished and is cooled by air blowing, and the cooling rate is 50-80 ℃/min.
(5) A blank heating process: the blank is sent into a heating furnace for heating, and the heating of the plate blank is divided into a preheating section, a heating section and a soaking section; the temperature range of the heating section of the plate blank is 1190-1250 ℃; the temperature interval of the soaking section is 1200-1250 ℃; the total time of the plate blank in the heating furnace is controlled to be 5-7 hours.
(6) The rolling process comprises the following steps: two-stage rolling is adopted;
the initial rolling temperature of the first stage is more than or equal to 1170 ℃, the single-pass reduction rate of the first three passes is more than or equal to 20 percent, the rolling temperature is more than or equal to 1120 ℃, the residual single-pass reduction rate is controlled to be 7 to 15 percent, and the rolling termination temperature of the first stage is more than or equal to 1070 ℃; the thickness of the intermediate blank is determined according to the thickness of the finished product, and the thickness of the intermediate blank is 1.5-2 times that of the finished steel plate;
the initial rolling temperature of the second stage is 970-1000 ℃, the final rolling temperature is controlled to be 850-900 ℃, and the single-pass reduction rate is 5-8%; and (3) directly carrying out laminar cooling on the rolled steel plate, and controlling the final cooling temperature to be 650-700 ℃ on the surface layer of the steel plate.
(7) The heat treatment process comprises the following steps:
when the thickness of the finished steel plate is less than or equal to 50mm, a stage heat treatment process is adopted, the heat treatment temperature of the steel plate is 1050-1100 ℃, the heat treatment time is 10-60 mm, and the steel plate is cooled to room temperature after being taken out of the furnace;
when the thickness of the finished steel plate is larger than 50mm, a three-stage heat treatment process is adopted, the temperature of the first-stage heat treatment is 650-700 ℃, the heat preservation time is 60-120 min, after the heat preservation is finished, the temperature is rapidly increased to 980-1000 ℃, the second-stage heat treatment is started, the heat preservation time is 60-80 min, after the heat preservation time is finished, the temperature is increased to 1050-1150 ℃ again, the third-stage heat preservation is started, the heat preservation time is 30-80 min, after the heat preservation is finished, the steel plate is taken out of the furnace and cooled to the room temperature by water.
(8) Straightening process: and (3) straightening the steel plate after the steel plate is cooled to room temperature, wherein the deformation rate is 3% -5%. The purpose of straightening is to increase twin and special low angle grain boundaries near the surface of the steel sheet and to reduce the substructure ratio. The method is a key process for improving the intergranular corrosion resistance of the surface of the steel plate.
Further, the method comprises the following steps of; carrying out an electroslag remelting process before forging: : the method is characterized in that continuous casting billets are used as electrodes to produce electroslag billets with the thickness of 200-550 mm, and an argon protection mode is adopted in the whole process of production, wherein the flow of argon is 20-40 m3H is used as the reference value. The current in the electroslag remelting process is 6000-30000A, and the voltage is 70-120V.
Further, the method comprises the following steps of; in the heating process in the step (4), when the thickness of the plate blank is less than or equal to 200mm, the temperature range of the preheating section is 860-910 ℃; when the thickness of the plate blank is within the range of 200-400 mm, the temperature range of the preheating section is 810-860 ℃.
Further, the method comprises the following steps of; in the rolling process of the step (5), cooling water of a rolling mill is not adopted for dephosphorization in the whole rolling process, so that recrystallization stop caused by too fast temperature drop of the surface layer of the blank is prevented.
The invention has the beneficial effects that:
(1) in the aspect of component design, the normal temperature and high temperature strength of the austenitic stainless steel is greatly improved by adding a certain content of nitrogen element, wherein the yield strength at 450 ℃ is more than or equal to 160MPa, the tensile strength is more than or equal to 480MPa, the yield strength at 550 ℃ is more than or equal to 150MPa, the tensile strength is more than or equal to 450MPa, the yield strength at 650 ℃ is more than or equal to 130MPa, and the tensile strength is more than or equal to 380 MPa; in addition, the intergranular corrosion resistance of the high-carbon austenitic stainless steel is improved by adding a certain content of Nb, Ti and Zr elements.
(2) In the manufacturing process, the forging and homogenizing process is adopted and matched with staged rolling, straightening and multistage heat treatment, so that the ferrite content in the finished steel plate can be controlled to be less than 1%, the steel plate is ensured to have uniform grain size, the grain size reaches 3-6 grades, and the steel plate has excellent intergranular corrosion resistance. After being sensitized at 650 ℃ and kept warm for 2h, the steel plate still meets the requirements of the method E of GB/T4334-2018 'testing method for corrosion of metals and alloys between crystals'.
Drawings
FIG. 1 is a gold phase diagram of the microstructure of the steel of example 6 of the present invention.
FIG. 2 is a photograph showing intergranular corrosion bending of the steel of example 6 of the present invention.
Detailed Description
The present invention is further illustrated by the following examples.
According to the embodiment of the invention, according to the component proportion of the technical scheme, smelting, continuous casting- (electroslag remelting), forging, homogenizing, heating, rolling, heat treatment and straightening are carried out;
(1) smelting and continuous casting: the pouring temperature of the molten steel of the tundish is less than or equal to 1580 ℃, and the continuous casting adopts an electromagnetic stirring or continuous casting billet soft reduction process, wherein the soft reduction rate is controlled to be 8-12%;
(2) forging: heating the blank to 1230-1260 ℃, preserving the temperature for 15-20 h, wherein the deformation rate of each forging pass is 4.5-5.5%, and the cumulative deformation pass of the forging is 10-40 passes;
(3) homogenizing: homogenizing at 1230-1270 ℃, keeping the net temperature for 30-70 h, and then air-cooling at a cooling rate of 50-80 ℃/min;
(4) heating: the heating is divided into a preheating section, a heating section and a soaking section; wherein the temperature range of the heating section is 1190-1250 ℃; the temperature interval of the soaking section is 1200-1250 ℃; the total time in the furnace is 5-7 hours;
(5) rolling: two-stage rolling is adopted; the initial rolling temperature of the first stage is more than or equal to 1170 ℃, the first three single-pass reduction rate is more than or equal to 20 percent, the rolling temperature is more than or equal to 1120 ℃, the remaining single-pass reduction rate of the rolling is 7 to 15 percent, and the finishing temperature of the first stage is more than or equal to 1070 ℃; the thickness of the intermediate blank is 1.5-2 times that of the finished steel plate; the initial rolling temperature of the second stage is 970-1000 ℃, the final rolling temperature is 850-900 ℃, and the single-pass reduction rate is 5-8%; directly carrying out laminar cooling on the rolled steel plate, wherein the final cooling temperature is 650-700 ℃;
(6) and (3) heat treatment: when the thickness of the finished steel plate is less than or equal to 50mm, a stage heat treatment process is adopted, the heat treatment temperature of the steel plate is 1050-1100 ℃, the heat treatment time is 10-60 min, and the steel plate is cooled to room temperature after being taken out of the furnace;
when the thickness of the finished steel plate is larger than 50mm, a three-stage heat treatment process is adopted, the temperature of the first-stage heat treatment is 650-700 ℃, the heat preservation time is 60-120 min, then the temperature is increased to 980-1000 ℃, the second-stage heat treatment is started, the heat preservation time is 60-80 min, then the temperature is increased to 1050-1150 ℃, the third-stage heat preservation is started, the heat preservation time is 30-80 min, and the finished steel plate is cooled to the room temperature after being taken out of the furnace;
(7) straightening: the straightening deformation rate is 3-5%.
Carrying out an electroslag remelting process before forging: the method is characterized in that continuous casting billets are used as electrodes to produce electroslag billets with the thickness of 200-550 mm, and an argon protection mode is adopted in the whole process of production, wherein the flow of argon is 20-40 m3H; the current in the electroslag remelting process is 6000-30000A, and the voltage is 70-120V.
In the heating process in the step (4), when the thickness of the plate blank is less than or equal to 200mm, the temperature range of the preheating section is 860-910 ℃; when the thickness of the plate blank is within the range of 200-400 mm, the temperature range of the preheating section is 810-860 ℃.
In the rolling process of the step (5), cooling water is not adopted for dephosphorization in the whole rolling process.
The chemical compositions of the steels of the examples of the invention are shown in table 1. Main technological parameters of steel smelting and forging in the embodiment of the invention are shown in a table 2. The main process parameters of steel homogenization and heating in the inventive examples are shown in table 3. The main process parameters of the steel rolling of the embodiment of the invention are shown in Table 4. The main heat treatment parameters of the steels of the examples of the invention are shown in Table 5. The steel structure and properties of the inventive examples are shown in Table 6. The high temperature properties of the steels of the examples of the invention are shown in Table 7.
TABLE 1 chemical composition (wt%) of steels of examples of the present invention
Remarking: p in the steel is less than or equal to 0.035%, S is less than or equal to 0.010%, O is less than or equal to 30ppm, and H is less than or equal to 5.0 ppm.
TABLE 2 main process parameters of steel smelting and forging in the examples of the present invention
TABLE 3 main process parameters for steel homogenization and heating of examples of the invention
TABLE 4 Main Process parameters for steel rolling in the examples of the present invention
TABLE 5 Main Heat treatment parameters of the steels of the examples of the invention
TABLE 6 Steel compositions and Properties of examples of the invention
TABLE 7 high temperature Properties of steels of examples of the invention
The steel of the embodiment still meets the requirements of the method E of GB/T4334 & 2018 ' test method for intergranular corrosion of metal and alloy ' for intergranular corrosion of stainless steel ' after being sensitized at 650 ℃ and for 2h, and has good intergranular corrosion resistance.
In order to express the present invention, the above embodiments are properly and fully described by way of examples, and the above embodiments are only used for illustrating the present invention and not for limiting the present invention, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. made by the persons skilled in the relevant art should be included in the protection scope of the present invention, and the protection scope of the present invention should be defined by the claims.