CN115896624B - Nitriding steel 31CrMoV9 annealed material and production method thereof - Google Patents
Nitriding steel 31CrMoV9 annealed material and production method thereof Download PDFInfo
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Abstract
The invention relates to a nitriding steel 31CrMoV9 annealing material and a production method thereof, wherein the steel comprises the chemical components of 0.27-0.33% of C, 0.28-0.36% of Si, 0.63-0.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 2.43-2.53% of Cr, less than or equal to 0.10% of Ni, 0.17-0.23% of Mo, 0.10-0.16% of V, less than or equal to 0.10% of Cu, 0.015-0.045% of Alt, and the balance of Fe and impurities. The 31CrMoV9 steel produced by the invention can meet the requirement that the steel delivery hardness is not more than 248HBW; tensile strength after quenching and tempering is 1000-1200 MPa, and yield strength is more than or equal to 800MPa; the depth of the total decarburized layer at each side of the steel is not more than 1.0% of the nominal diameter, so that the material has good processing performance.
Description
Technical Field
The invention relates to the technical field of nitrided steel production, in particular to a nitrided steel 31CrMoV9 annealed material and a production method thereof.
Background
31CrMoV9 is a typical grade of nitrided steel, also in European Union Standard EN 10085. After the 31CrMoV9 is subjected to quenching and tempering nitriding treatment, the surface hardness of the product can reach more than 1000 Vickers hardness, and the product has high hardenability, excellent toughness, wear resistance, anti-seizing property and corrosion resistance, and is used for manufacturing precise hydraulic pistons, hydraulic piston rods, connecting shafts, heavy-duty large parts, couplings, wind power gear box gear rings, engine transmission shafts and other important deep nitriding parts. However, the hot rolling structure of the 31CrMoV9 steel is complex due to the special component composition, and under the actual production condition, the hot rolling state of the 31CrMoV9 steel is in a structure of 'B+P+M+a small amount of F', so that the hardness is higher (more than 300 HBW), and the subsequent processing and manufacturing are not facilitated.
At present, aiming at the related technology for providing the processing performance of 31CrMoV9 nitriding steel, less data can be found at home and abroad.
The chinese patent application with publication number CN109402350a discloses a "heat treatment process for a steel material" selected from one of 42CrMo4, 42CrMo, 34CrNiMo6 and 31CrMoV 9. The heat treatment process comprises the following steps: 1) Quenching: the temperature is 880-940 ℃, the heat preservation time is 1-7h, and then the mixture is cooled to 500-600 ℃ in 35-135 s; 2) Tempering: the temperature is 590-630 ℃, the heat preservation time is 3-8h, and then the mixture is cooled to room temperature. The steel after heat treatment can effectively improve the tensile strength and the yield strength of the steel, and can further effectively improve the impact energy of the steel; but it does not consider workability of the steel.
Chinese patent application publication No. CN106086671a discloses "an alloy nitrided steel for shafts", containing, in weight percentage, C:0.25 to 0.35 percent of Si:0.2 to 0.5 percent of Mn:0.5 to 1 percent of Cr:1.5 to 2.5 percent of Mo:0.40 to 0.60 percent, V:0.15 to 0.25 percent, S: 0.001-0.030%, al:0.1 to 0.5 percent of Ti:0.6 to 1.2 percent of Ni:0.05 to 0.2 percent, and the rest part comprises Fe and unavoidable impurities; and limits the following elements to: p: less than 0.02%, O: less than 0.06%. The preparation method comprises the following steps: smelting: smelting by adopting an electric arc furnace, wherein ingredients comprise molten iron with the weight percentage of more than or equal to 40% and scrap steel with the weight percentage of 40% -60%, the control end point C is more than or equal to 0.25%, P is less than or equal to 0.020%, the content of residual elements meets the design requirement, the tapping temperature of molten steel is 1600 ℃ -1650 ℃, and the pre-deoxidization alloying is carried out in a ladle, and Al is added in the tapping process; then, carrying out LF external refining, and blowing argon in the whole refining process, wherein the white slag time is kept between 20 and 30 minutes; vacuum treatment is carried out after refining, the vacuum degree is less than 67Pa, the holding time is 20-25 min, and the soft argon blowing time after the vacuum treatment is more than 12 min; pouring: adopting continuous casting whole-process protection casting, and adopting electromagnetic stirring in continuous casting; rolling: slowly cooling the continuous casting billet, and then rolling, wherein the soaking temperature of a heating furnace is controlled to be 1200-1240 ℃, the heating time is controlled to be 2.5-3 hours, the initial rolling temperature is 1100-1110 ℃, and the final rolling temperature is 860-960 ℃; after rolling, piling up and cooling to room temperature; annealing: heat preservation is carried out in the annealing furnace for 12-15 hours at 700-720 ℃, and then the annealing furnace is cooled to 520-550 ℃ along with the furnace and is discharged. But the technical problems solved by the method are as follows: the high aluminum content in the traditional nitriding steel causes more inclusions in the steel, the surface quality of the steel is poor, and the nitriding layer is brittle after nitriding heat treatment. The traditional nitriding steel 38CrMoAl has high production difficulty and few continuous casting furnaces, so that many steel factories still adopt a die casting process for production, and the quality and cost of the steel are difficult to control. The 31CrMoV9 belongs to aluminum-free nitriding steel, and the Alt in the steel is only 0.015% -0.045%, which is far lower than the Al content (0.1% -0.5%) in the patent application, so that the technical problem described in the patent application does not exist.
The Chinese patent application with the application publication number of CN102443740A discloses an alloy nitriding steel and a manufacturing method thereof, wherein the alloy nitriding steel comprises the following chemical elements in percentage by mass: carbon: 0.30 to 0.36 weight percent; silicon: 0.60 to 0.80 weight percent; manganese: 0.60 to 0.90 weight percent; chromium: 2.90 to 3.40 weight percent; molybdenum: 0.40 to 0.60 weight percent; vanadium: 0.15 to 0.25 weight percent; niobium: 0.02 to 0.06 weight percent; sulfur: less than or equal to 0.015wt%; phosphorus: less than or equal to 0.020wt%; copper: less than or equal to 0.15wt%; nickel: less than or equal to 0.15wt%; the balance being Fe and other unavoidable impurities. The manufacturing method comprises the following steps: (1) smelting: after vacuum induction smelting and electroslag remelting, casting the raw materials into steel ingots; (2) The steel ingot is heated to 1280-1290 ℃ at the heating rate of 180-200 ℃/h and then is kept for 160-180 minutes after being kept at the temperature of 800-820 ℃ for 80-100 minutes at the heating rate of 80-90 ℃/h in a soaking pit; (3) after blooming and cogging, slowly cooling the steel ingot, and then finishing the surface; (4) Rolling heating temperature 1180-1220 ℃, soaking temperature 1160-1200 ℃ and total heating time 135-150 minutes; the final rolling temperature is more than or equal to 850 ℃, and after rolling, stacking cooling to room temperature is carried out; (5) annealing: preserving heat in an annealing furnace for 10-15 hours at 700-720 ℃, cooling to 500-550 ℃ along with the furnace, and discharging. The technical problems which are mainly solved by the utility model are as follows: 1. the strength and the thermal stability of the quenched and tempered 38CrMoAl steel cannot meet the requirement of the supporting strength of a matrix; 2. the nitriding time is too long, so that the cost is high, and the supporting strength of the matrix is reduced due to the long-time nitriding treatment. In addition, 38CrMoAl steel has the following disadvantages: the hardenability is not high, the part can be completely quenched in oil when the interface diameter is smaller than 30mm, and the hardness difference between the surface and the center can reach about 60HB after the part with the size diameter of 60mm is subjected to oil quenching; the critical point of the steel is higher, so that the normalizing and quenching temperatures are correspondingly higher; because the aluminum-containing ferrite has high stability and is not easy to dissolve into austenite, the heat preservation time is about 1.5 times longer than that of the common alloy structural steel. In addition, 38CrMoAl steel has the following problems in metallurgical manufacture: because the aluminum content in the steel is high, the aluminum element is easy to oxidize during smelting, so that the yield is unstable, and the reject ratio is extremely high; the problem of low-power punctiform segregation of 38CrMoAl steel is more serious. The alloy nitriding steel produced by the patent application has higher hardenability and good toughness after heat treatment; compared with aluminum-containing nitriding steel after nitriding, the depth of a permeation layer and the hardness of the core part of the steel are higher than those of the aluminum-containing nitriding steel, and the steel has heat resistance superior to that of the existing nitriding steel; in addition, the alloy nitrided steel should also have good economy. It can be seen that the technical problem addressed by this patent application is totally different from the present invention.
Disclosure of Invention
The invention provides a nitriding steel 31CrMoV9 annealing material and a production method thereof, and the produced 31CrMoV9 steel can meet the requirement that the steel delivery hardness is not more than 248HBW; tensile strength after quenching and tempering is 1000-1200 MPa, and yield strength is more than or equal to 800MPa; the total decarburized layer depth (ferrite + transition layer) of each side of the steel is not more than 1.0% of the nominal diameter, so that the material is ensured to have good processing performance.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the steel comprises, by mass, 0.27% -0.33% of C, 0.28% -0.36% of Si, 0.63% -0.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 2.43% -2.53% of Cr, less than or equal to 0.10% of Ni, 0.17% -0.23% of Mo, 0.10% -0.16% of V, less than or equal to 0.10% of Cu, 0.015% -0.045% of Alt, and the balance of Fe and unavoidable impurities.
The production method of the nitriding steel 31CrMoV9 annealed material comprises the following steps of sequentially smelting raw materials by an EBT electric furnace, refining by an LF furnace, refining by a VD furnace, continuous casting, heat preservation, heating, rolling, slow cooling and annealing to obtain a product steel, wherein the specific steps are as follows:
1) Smelting by an EBT electric furnace: smelting temperature 1640-1680 ℃, smelting end point C:0.05 to 0.10 percent, P is less than or equal to 0.013 percent, and the content of residual elements meets the design requirement; 2.0-3.0 kg/t aluminum powder is added for pre-deoxidation before tapping, a pre-deoxidizer, a slag-forming material, an alloy and a carburant are added in the tapping process, steel is reserved, slag is reserved, and the tapping time is controlled to be 3-6 min;
2) Refining in an LF furnace: stirring by bottom blowing argon in the whole process, and controlling the pressure of the argon to be 0.2-0.3 MPa; refining white slag in LF furnace, controlling slag alkalinity R not less than 3.5, and controlling A1 in slag 2 O 3 25% -30% FeO+MnO content less than 1.0%; the operation and holding time of the white slag is more than or equal to 20min;
3) Refining by a VD furnace: the argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started; maintaining for more than 10min after the vacuum degree reaches 100Pa, and adjusting the argon pressure to 0.3-0.5 MPa; finally deoxidizing after breaking vacuum, and feeding Al wires to adjust the Al content in the steel to be 0.025% -0.035%; feeding Ca-Si wire 100-120 m to regulate aluminum nitride inclusion; after breaking vacuum, static argon blowing is carried out for 10-35 min, and the argon pressure is regulated to be 0.1-0.3 MPa; after the static argon blowing is finished, adding 30-80 kg of heat preservation agent into the furnace;
4) Continuous casting: adopting a three-machine three-stream arc continuous casting machine, wherein the temperature of a continuous casting head furnace ladle is 1589-1594 ℃, the temperature of a 2 nd furnace ladle is 1577-1587 ℃, and the temperature of a 3 rd furnace to a tail furnace ladle is 1567-1577 ℃, and carrying out argon protection casting;
5) Heating: the furnace temperature of the preheating section is 500-750 ℃, and the heating time is 45-50 min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 140-170 ℃/h, the furnace temperature is 1220-1230 ℃, and the heating time is 55-60 min; heating the second stage at a heating speed of 300-330 ℃/h, a furnace temperature of 1060-1080 ℃ and a heating time of 60-65 min; furnace temperature of the soaking section is 1200-1220 ℃, and soaking time is 60-90 min; the billet tapping temperature is 1180-1200 ℃, and the total heating time is 220-265 min;
6) Rolling: the initial rolling temperature is 1100-1200 ℃, the final rolling temperature is 850-1000 ℃, and the steel is immediately put into a pit for heat preservation or cold piling after being put into a cooling bed;
7) Annealing: an isothermal annealing process is adopted; firstly, heating the steel to 760-780 ℃ at a heating rate of 70-100 ℃/h, then homogenizing the temperature and preserving the heat for more than 3 hours, then cooling the steel to 690-710 ℃ in a furnace, homogenizing the temperature and preserving the heat for more than 2 hours, cooling the steel to below 500 ℃ along with the furnace, discharging the steel, and cooling the steel to room temperature in an air.
Further, in the step 1), scrap steel and molten iron are adopted as raw materials, firstly scrap steel is filled, molten iron is added after the well is penetrated to the bottom and a molten pool is formed, and the temperature of the molten iron is more than 1150 ℃ when the molten iron is added; decarburization, dephosphorization and temperature adjustment are carried out through oxygen supply, slag formation and electrifying.
Further, the molten iron comprises the following components in percentage by mass: c is more than or equal to 3.5%, mn is less than or equal to 0.80%, si is 0.20% -1.00%, P is less than or equal to 0.070%, and S is less than or equal to 0.070%.
Further, in the step 4), the crystallizer M-EMS and the solidification end F-EMS are adopted to be jointly stirred, and the electric stirring current is 360-400A.
Furthermore, the step 6) adopts high-pressure water to remove scales before rolling, and the scale removal pressure is 28-30 MPa.
Further, in the step 6),the steel is put into a furnace for heat preservation, the pit outlet temperature is less than or equal to 300 ℃, and the heat preservation time is more than or equal to 24 hours; />Is cooled by stacking.
Further, the hardness of the produced 31CrMoV9 steel is less than or equal to 248HBW; the tensile strength after quenching and tempering is 1000-1200 MPa, and the yield strength is more than or equal to 800MPa.
Further, the total decarburized layer depth of each side of the 31CrMoV9 steel produced is not more than 1.0% of the nominal diameter.
Compared with the prior art, the invention has the beneficial effects that:
the 31CrMoV9 steel produced can meet the requirement that the steel delivery hardness is not more than 248HBW; tensile strength after quenching and tempering is 1000-1200 MPa, and yield strength is more than or equal to 800MPa; the total decarburized layer depth (ferrite + transition layer) of each side of the steel is not more than 1.0% of the nominal diameter, so that the material is ensured to have good processing performance.
Drawings
FIG. 1 is a graph of the heat treatment process of nitrided steel 31CrMoV9 according to the present invention.
FIG. 2 is a photograph of a rolled metallographic structure (structure B+P+M+F) of a nitrided steel 31CrMoV9 according to the present invention.
FIG. 3 is a photograph showing a metallographic structure of an annealed state of a nitrided steel 31CrMoV9 according to the present invention (the structure is a granular P structure).
Detailed Description
The invention relates to a 31CrMoV9 nitriding steel annealing material, which comprises, by mass, 0.27% -0.33% of C, 0.28% -0.36% of Si, 0.63% -0.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 2.43% -2.53% of Cr, less than or equal to 0.10% of Ni, 0.17% -0.23% of Mo, 0.10% -0.16% of V, less than or equal to 0.10% of Cu, 0.015% -0.045% of Alt, and the balance of Fe and unavoidable impurities.
The invention relates to a production method of a nitriding steel 31CrMoV9 annealing material, which comprises the following steps of smelting raw materials sequentially through an EBT electric furnace, LF furnace refining, VD furnace refining, continuous casting, heat preservation, heating, rolling, slow cooling and annealing to obtain a product steel material:
1) Smelting by an EBT electric furnace: smelting temperature 1640-1680 ℃, smelting end point C:0.05 to 0.10 percent, P is less than or equal to 0.013 percent, and the content of residual elements meets the design requirement; 2.0-3.0 kg/t aluminum powder is added for pre-deoxidation before tapping, a pre-deoxidizer, a slag-forming material, an alloy and a carburant are added in the tapping process, steel is reserved, slag is reserved, and the tapping time is controlled to be 3-6 min;
2) Refining in an LF furnace: stirring by bottom blowing argon in the whole process, and controlling the pressure of the argon to be 0.2-0.3 MPa; refining white slag in LF furnace, controlling slag alkalinity R not less than 3.5, and controlling A1 in slag 2 O 3 25% -30% FeO+MnO content less than 1.0%; the operation and holding time of the white slag is more than or equal to 20min;
3) Refining by a VD furnace: the argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started; maintaining for more than 10min after the vacuum degree reaches 100Pa, and adjusting the argon pressure to 0.3-0.5 MPa; finally deoxidizing after breaking vacuum, and feeding Al wires to adjust the Al content in the steel to be 0.025% -0.035%; feeding Ca-Si wire 100-120 m to regulate aluminum nitride inclusion; after breaking vacuum, static argon blowing is carried out for 10-35 min, and the argon pressure is regulated to be 0.1-0.3 MPa; after the static argon blowing is finished, adding 30-80 kg of heat preservation agent into the furnace;
4) Continuous casting: adopting a three-machine three-stream arc continuous casting machine, wherein the temperature of a continuous casting head furnace ladle is 1589-1594 ℃, the temperature of a 2 nd furnace ladle is 1577-1587 ℃, and the temperature of a 3 rd furnace to a tail furnace ladle is 1567-1577 ℃, and carrying out argon protection casting;
5) Heating: the furnace temperature of the preheating section is 500-750 ℃, and the heating time is 45-50 min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 140-170 ℃/h, the furnace temperature is 1220-1230 ℃, and the heating time is 55-60 min; heating the second stage at a heating speed of 300-330 ℃/h, a furnace temperature of 1060-1080 ℃ and a heating time of 60-65 min; furnace temperature of the soaking section is 1200-1220 ℃, and soaking time is 60-90 min; the billet tapping temperature is 1180-1200 ℃, and the total heating time is 220-265 min;
6) Rolling: the initial rolling temperature is 1100-1200 ℃, the final rolling temperature is 850-1000 ℃, and the steel is immediately put into a pit for heat preservation or cold piling after being put into a cooling bed;
7) Annealing: an isothermal annealing process is adopted; firstly, heating the steel to 760-780 ℃ at a heating rate of 70-100 ℃/h, then homogenizing the temperature and preserving the heat for more than 3 hours, then cooling the steel to 690-710 ℃ in a furnace, homogenizing the temperature and preserving the heat for more than 2 hours, cooling the steel to below 500 ℃ along with the furnace, discharging the steel, and cooling the steel to room temperature in an air.
Further, in the step 1), scrap steel and molten iron are adopted as raw materials, firstly scrap steel is filled, molten iron is added after the well is penetrated to the bottom and a molten pool is formed, and the temperature of the molten iron is more than 1150 ℃ when the molten iron is added; decarburization, dephosphorization and temperature adjustment are carried out through oxygen supply, slag formation and electrifying.
Further, the molten iron comprises the following components in percentage by mass: c is more than or equal to 3.5%, mn is less than or equal to 0.80%, si is 0.20% -1.00%, P is less than or equal to 0.070%, and S is less than or equal to 0.070%.
Further, in the step 4), the crystallizer M-EMS and the solidification end F-EMS are adopted to be jointly stirred, and the electric stirring current is 360-400A.
Furthermore, the step 6) adopts high-pressure water to remove scales before rolling, and the scale removal pressure is 28-30 MPa.
Further, in the step 6),the steel is put into a furnace for heat preservation, the pit outlet temperature is less than or equal to 300 ℃, and the heat preservation time is more than or equal to 24 hours; />Is cooled by stacking.
Further, the hardness of the produced 31CrMoV9 steel is less than or equal to 248HBW; the tensile strength after quenching and tempering is 1000-1200 MPa, and the yield strength is more than or equal to 800MPa.
Further, the total decarburized layer depth of each side of the 31CrMoV9 steel produced is not more than 1.0% of the nominal diameter.
The main functions and the design corresponding to each element in the chemical components of the nitriding steel 31CrMoV9 are as follows:
nitriding, also called nitriding, is one of the important processes in chemical heat treatment. The steel grades suitable for nitriding processes are called nitriding steels, also called nitriding steels. The product can be used for manufacturing machine parts, and after nitriding treatment, the product can obtain higher surface hardness, good wear resistance, high fatigue strength, lower notch sensitivity, certain corrosion resistance and high thermal stability.
31CrMoV9 belongs to aluminum-free nitriding steel, and the addition of the element forming nitride to the steel can improve the nitrogen absorption capacity of the steel and enable the nitride surface layer to have good adhesiveness. Such elements have a strong affinity for nitrogen and form stable and highly dispersed nitrides, thereby increasing hardness, and include chromium, vanadium, molybdenum, titanium, and the like.
Chromium is an excellent nitride promoting element and is also the main alloying element in nitrided steels. In the steel free of aluminium nitriding, chromium is the most important element, and is matched with vanadium or molybdenum to further optimize the performance. Chromium is favorable for improving the hardenability, strength and surface hardness of steel, but when the content is too high, the volume expansion of the steel is gradually remarkable after nitriding, so that the deformation of parts is increased, and the surface layer is easy to fall off when serious.
Vanadium can form stable nitride, is a common element in aluminum-free nitriding steel, plays a role in improving the hardness of a nitriding layer, has good toughness although the surface hardness is high in the aluminum-free nitriding steel, and is quite suitable for parts which are worn and subjected to a certain impact load.
The important function of molybdenum in nitriding steel is to avoid temper embrittlement during nitriding.
Carbon is an element that is detrimental to nitriding and reduces the diffusion coefficient of nitrogen, thereby reducing the nitriding rate. Carbon also has an adverse effect on the carburized layer surface hardness and its distribution. However, carbon is an essential element for ensuring the strength of steel, and insufficient core strength adversely affects the properties of the nitrided layer, particularly fatigue strength, so that the carbon content should not be too low for ensuring the core strength of the transmission shaft.
The different roles of the alloy elements are considered from the mechanical property perspective. Silicon not only increases the hardenability of the steel, but also increases the tempering resistance of the steel after quenching. Manganese and iron form solid solutions, so that the strength and hardness of ferrite and austenite in steel are improved, and manganese plays a role in refining pearlite in steel due to reduction of critical transition temperature, and indirectly plays a role in improving the strength of pearlite steel. Aluminum is used to refine the grains of the steel, fix nitrogen and oxygen in the steel, thereby reducing the sensitivity of the steel to chipping, reducing or eliminating the aging phenomenon of the steel, and improving the impact toughness of the steel. Molybdenum has solid solution strengthening effect on ferrite and improves carbide stability, so that the strength of steel is beneficial, and the addition of a proper amount of molybdenum into quenched and tempered steel can improve the hardenability of the steel, so that the strength and ductility of the steel are improved, and the impact toughness of the steel is greatly facilitated because the molybdenum can eliminate or lighten the tempering brittleness caused by other alloy elements. The influence of vanadium on the mechanical properties of annealed low-carbon steel is: when the content is low and the steel is dissolved in ferrite in a solid way, the strength of the steel is slightly increased, and the plasticity and toughness of the steel are slightly reduced; if present as aggregated carbides, the strength of the steel is rather reduced as it fixes a portion of the carbon. Chromium is added into steel, the strength and toughness of the steel can be improved within a certain content, but the mechanical property of the carbon steel after normalizing or tempering is not obviously improved by independently adding chromium, and meanwhile, better performance can be shown by improving or adding other alloy elements such as manganese, molybdenum and the like.
The invention determines that the smelting control component requirements of the nitriding steel 31CrMoV9 are that C is 0.27-0.33%, si is 0.28-0.36%, mn is 0.63-0.70%, P is less than or equal to 0.025%, S is less than or equal to 0.025%, cr is 2.43-2.53%, ni is less than or equal to 0.10%, mo is 0.17-0.23%, V is 0.10-0.16%, cu: less than or equal to 0.10 percent, alt is 0.015 to 0.045 percent. The balance being Fe and unavoidable impurities.
The production process of the nitriding steel 31CrMoV9 annealed material comprises the following steps: high-quality molten iron and scrap steel, an EBT electric furnace, an LF refining furnace, a VD vacuum treatment furnace, a 235 multiplied by 265mm medium billet continuous casting machine, an end-in end-out walking beam type heating furnace, a 1150BD rolling mill and 850 bar continuous rolling unit, a high-precision finishing line, physical and chemical organization and other inspection, and a finished product packaging payment warehouse. The main control procedure is as follows:
scrap steel and molten iron are adopted as raw materials for electric furnace smelting, wherein the molten iron is required to contain more than or equal to 3.5% of C, less than or equal to 0.80% of Mn, 0.20% -1.00% of Si, less than or equal to 0.070% of P and less than or equal to 0.070% of S. Firstly, scrap steel (active lime is filled on the bottom of a furnace before charging to lighten the impact on the bottom of the furnace, form a molten pool in advance, stabilize electric arc and dephosphorize early), and after the well is penetrated to the bottom and a certain molten pool is formed, molten iron is added (the temperature of the molten iron is less than or equal to 1150 ℃ and cannot be added). Decarburizing, dephosphorizing and adjusting the temperature by means of oxygen supply, slagging and electrifying. Smelting temperature is 1640-1680 ℃, and chemical composition C:0.05 to 0.10 percent, P is less than or equal to 0.013 percent, and the residual elements meet the requirements and can be tapped. 2.0-3.0 kg/t aluminum powder is added before tapping to carry out pre-deoxidation. And adding a pre-deoxidizer, a slag-forming material, an alloy, a carburant and the like in the tapping process. The steel tapping needs to pay attention to steel and slag, and oxidizing slag is prevented from entering the steel ladle. The tapping time is controlled to be 3-6 min.
In the LF refining process, bottom argon blowing stirring is carried out in the whole process (argon is controlled to fluctuate the slag surface during refining, and molten steel is not exposed). When the steel ladle is in a receiving position, firstly, switching on argon gas to blow off a slag surface for temperature measurement, taking a primary sample for analyzing all components, and after the primary sample analysis result is reported back, carrying out coarse adjustment on the components according to the lower limit of the requirement; the ladle is put into an LF station, high-current heating slag melting is adopted, once power supply is adopted, the temperature is raised to a target value (1580-1620 ℃), white slag refining is carried out in the LF furnace, the slag alkalinity R is controlled to be more than or equal to 3.5, w (A12O 3) =25-30% in the slag, w (FeO+MnO) is less than 1.0% (preferably less than 0.5%), the diffusion deoxidation of the slag to molten steel is realized, and meanwhile, the desulfurization task is completed. Taking a secondary sample after the slag is white, analyzing the total components, continuously adjusting slag by using a diffusion deoxidizer after the secondary sample is taken, keeping proper slag alkalinity and good fluidity, keeping white slag operation in the whole process, reporting back the secondary sample result, feeding Al wires, and adjusting the Al content in steel to be more than 0.020%; and performing component fine adjustment according to the target component. The white slag holding time is more than or equal to 20min, and the argon pressure is controlled to be 0.2-0.3 MPa in the whole process.
When VD refining, the argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started, and the slag surface micro-motion molten steel is not exposed. When the vacuum degree reaches 100Pa, starting timing, keeping the time not less than 10min, and adjusting the argon pressure to 0.3-0.5 MPa. Finally deoxidizing after breaking vacuum, feeding Al wire, controlling Al content of molten steel to be 0.025% -0.035%, feeding Ca-Si wire to adjust aluminum nitride inclusion by 100-120 m, and ensuring castability of steel; after breaking vacuum, argon is blown for 10-35 min, and the argon pressure is 0.1-0.3 MPa, so that the slag surface micro-motion molten steel is not exposed. After the static argon blowing is finished, 30-80 kg of heat preservation agent is added per furnace, and the heat preservation agent is added when the liquid level of molten steel still fluctuates at the end of the static argon blowing of each furnace, and the uniform coverage of the liquid level is ensured.
The continuous casting adopts a three-machine three-stream arc continuous casting machine to cast steel billets continuously, the temperature of a continuous casting head furnace ladle is 1589-1594 ℃, the temperature of a 2 nd furnace ladle is 1577-1587 ℃, and the temperature of a 3 rd furnace to tail furnace ladle is 1567-1577 ℃, and argon protection casting is carried out; the electronic stirring adopts a crystallizer (M-EMS) and a solidification end (F-EMS) to jointly stir, and the electronic stirring current is set to be 380-420A.
In the heating stage, setting the furnace temperature of the preheating section to be 500-750 ℃ and the heating time to be 45-50 min; the heating section is divided into a first heating section and a second heating section according to different requirements of the heating speed of the billet, wherein the heating speed of the first heating section is 140-170 ℃/h, the furnace temperature is 1220-1230 ℃, and the heating time is 55-60 min; heating the second stage at a heating speed of 300-330 ℃/h, a furnace temperature of 1060-1080 ℃ and a heating time of 60-65 min; furnace temperature of the soaking section is 1200-1220 ℃, and soaking time is 60-90 min. The billet tapping temperature is 1180-1200 ℃, and the total heating time is 220-265 min.
In the rolling stage, high-pressure water is adopted for descaling before rolling, the descaling pressure is 28-30 MPa, the initial rolling temperature is 1100-1200 ℃, the final rolling temperature is 850-1000 ℃, and the steel is immediately put into a pit for heat preservation or cold stacking after being put into a cooling bed. The method specifically comprises the following steps:the steel materials are subjected to pit entering heat preservation, the pit exiting temperature is less than or equal to 300 ℃, and the heat preservation time is more than or equal to 24 hours; />The steel products of (2) are cooled by stacking. A photograph of a rolled metallographic structure of the nitrided steel 31CrMoV9 is shown in FIG. 2, and the structure is B+P+M+F.
In the annealing stage, based on the composition and performance characteristics of the 31CrMoV9 steel, an isothermal annealing process is designed on the basis of principle analysis of isothermal annealing heating temperature, heating time, isothermal temperature and isothermal time, and an isothermal annealing process curve is shown in figure 1. The photograph of the metallographic structure of the annealed state of the nitrided steel 31CrMoV9 is shown in FIG. 3, and the structure is a granular P structure.
The following examples are given by way of illustration of detailed embodiments and specific procedures based on the technical scheme of the present invention, but the scope of the present invention is not limited to the following examples.
[ example 1 ]
In the embodiment, the 31CrMoV9 nitriding steel annealed material is manufactured by adopting the method, and the steel comprises the following chemical components in percentage by mass: 0.29%, si:0.33%, mn:0.67%, P:0.011%, S:0.002%, cr:2.49%, ni:0.02%, mo:0.19%, cu:0.03%, alt:0.026%, 0.13% V, the balance being Fe and unavoidable impurities.
The production process is controlled as follows:
1. EBT electric furnace smelting
The electric furnace is filled with scrap steel for 17t, molten iron is added after 20min of power transmission, the temperature of the molten iron ranges from 1250 ℃ to 1350 ℃, and the weight is 35.8t. Oxygen is oxidized and boiled vigorously, the oxidation temperature is 1679 ℃, high alkalinity, large slag quantity and low temperature slag are formed in the early stage of oxidation to strengthen dephosphorization effect, when the furnace burden is melted by more than 70%, an electric furnace foaming agent is blown into the slag, and after the steel is melted, C, mn, P, S and residual elements are sampled and analyzed. The C content is 0.05% and the P content is 0.008% during tapping, and the tapping temperature is 1678 ℃. When the electric furnace is tapped for 1/4, a proper amount of slag is added, 102kg of pre-deoxidizer aluminum iron, 201kg of alloy silicon manganese and 1000kg of low chromium are added.
2. LF furnace refining
When the steel ladle is in a receiving position, firstly, switching on argon gas to blow off a slag surface for temperature measurement, taking a primary sample for analyzing all components, and after the primary sample analysis result is reported back, carrying out coarse adjustment on the components according to the lower limit of the requirement; and (3) performing bottom argon blowing stirring in the whole LF refining process, adding 499kg of active lime, 10kg of coke powder carburant and 50kg of fluorite briquetting for slagging, and adding 200kg of alumina balls for diffusion deoxidation after liquid slag is formed. Taking a secondary sample to analyze the total composition after the slag white and the temperature meet the requirements; and after the secondary sample is taken out, slag is continuously regulated by using a diffusion deoxidizer, proper slag alkalinity and good fluidity are kept, white slag operation is kept in the whole process, a secondary sample result is reported back, and component fine adjustment is carried out according to target control components. The white slag holding time is more than or equal to 20min. The argon pressure is controlled to be 0.2-0.3 MPa in the whole process, so that secondary oxidation caused by the naked molten steel is prevented. The temperature of the hanging bag is 1690 ℃.
3. Refining in VD furnace
The temperature of molten steel entering the VD furnace is 1677 ℃. The argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started, and the slag surface micro-motion molten steel is not exposed. When the vacuum degree reached 100Pa, the timing was started and maintained for 15min. After breaking the vacuum, ca-Si wire is fed 100m. Argon is blown from the wire feeding end, the static argon blowing is carried out for 20-35 min, the argon pressure is regulated to be 0.1-0.3 MPa, and the slag surface micro-motion molten steel is not exposed. And after the static argon blowing is finished, adding 80kg of carbonized rice husk serving as a heat preservation agent, uniformly covering, and hanging the bag at the temperature of 1604 ℃.
4. Continuous casting
Adopting a three-machine three-stream arc continuous casting machine to continuously cast billets, wherein the temperature of a continuous casting head furnace ladle is 1598 ℃, and argon protection pouring is carried out; baking the middle ladle for 4 hours; immersion nozzle depth of insertion: 85mm from the crystallizer liquid level; the pulling speed is 0.80m/min, the superheat degree of the continuous casting head furnace is 31 ℃, and the water flow of the crystallizer is 160m 3 And/h, the specific water quantity of the secondary cooling water is 0.30L/kg, and the electric stirring current is 360A.
5. Heating
The furnace temperature of the preheating section is 600 ℃, and the heating time is 50min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 150 ℃/h, the furnace temperature is 1230 ℃, and the heating time is 60min; heating the second stage at a heating speed of 320 ℃/h and a furnace temperature of 1060 ℃ for 60min; the furnace temperature of the soaking section is 1220 ℃, and the soaking time is 70min; the billet tapping temperature is 1180 ℃, and the total heating time is 240min.
6. Rolling
High-pressure water descaling before rolling, the descaling pressure is 28-30 MPa, the initial rolling temperature is 1150 ℃, the final rolling temperature is 910 ℃, and the rolling specification is thatAnd (5) cooling the steel immediately after the steel is cooled down in a cooling bed.
7. Annealing
The isothermal annealing process is adopted, steel is firstly put into a heating furnace with the furnace temperature of 300 ℃, the temperature is raised to 770 ℃ at the heating rate of 80 ℃/h, the total heating is carried out for 6h, the temperature is kept for 8h, the furnace is cooled to 700 ℃ and then kept for 3h, and then the steel is discharged after being cooled to below 500 ℃ along with the furnace and is cooled to the room temperature by air. At oven time 23h.
The steel product prepared in this example was examined and the results were as follows:
| yield strength of | Tensile strength of | Face shrinkage | Elongation percentage | Hardness of | Decarburized layer |
| 1022MPa | 1149MPa | 62％ | 20％ | 237HB | 0.15mm |
[ example 2 ]
In the embodiment, the 31CrMoV9 nitriding steel annealed material is manufactured by adopting the method, and the steel comprises the following chemical components in percentage by mass: 0.31%, si:0.34%, mn:0.68%, P:0.011%, S:0.004%, cr:2.52%, ni:0.02%, mo:0.19%, cu:0.01%, alt:0.024%, 0.14% V, the balance being Fe and unavoidable impurities.
The production process is controlled as follows:
1. EBT electric furnace smelting
The electric furnace is filled with scrap steel for 18t, molten iron is added after 20min of power transmission, the temperature of the molten iron ranges from 1250 ℃ to 1350 ℃, and the weight is 35.5t. Oxygen is oxidized and boiled vigorously, the oxidation temperature is 1683 ℃, high alkalinity, large slag quantity and low temperature slag are formed in the early stage of oxidation to strengthen dephosphorization effect, when the furnace burden is melted by more than 70%, an electric furnace foaming agent is blown into the slag, and after the steel is melted, C, mn, P, S and residual elements are sampled and analyzed. The C content is 0.08% and the P content is 0.008% during tapping, and the tapping temperature is 1678 ℃. When the electric furnace is tapped for 1/4, adding a proper amount of slag, and adding 103kg of pre-deoxidizer aluminum iron, 203kg of silicon-manganese alloy and 1009kg of low-chromium steel ball.
2. LF furnace refining
When the steel ladle is in a receiving position, firstly, switching on argon gas to blow off a slag surface for temperature measurement, taking a primary sample for analyzing all components, and after the primary sample analysis result is reported back, carrying out coarse adjustment on the components according to the lower limit of the requirement; and (3) performing bottom argon blowing stirring in the whole LF refining process, adding 500kg of active lime, 20kg of coke powder carburant and 80kg of fluorite briquetting for slagging, and adding 200kg of alumina balls for diffusion deoxidation after liquid slag is formed. Taking a secondary sample to analyze the total composition after the slag white and the temperature meet the requirements; and after the secondary sample is taken out, slag is continuously regulated by using a diffusion deoxidizer, proper slag alkalinity and good fluidity are kept, white slag operation is kept in the whole process, a secondary sample result is reported back, and component fine adjustment is carried out according to target control components. The white slag holding time is more than or equal to 20min. The argon pressure is controlled to be 0.2-0.3 MPa in the whole process, so that secondary oxidation caused by the naked molten steel is prevented. The temperature of the hanging bag is 1680 ℃.
3. Refining in VD furnace
The temperature of molten steel entering the VD furnace is 1663 ℃. The argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started, and the slag surface micro-motion molten steel is not exposed. When the vacuum degree reached 100Pa, the timing was started and maintained for 15min. After breaking the vacuum, ca-Si wire is fed 100m. Argon is blown from the wire feeding end, the static argon blowing is carried out for 20-35 min, the argon pressure is regulated to be 0.1-0.3 MPa, and the slag surface micro-motion molten steel is not exposed. And after the static argon blowing is finished, adding 80kg of carbonized rice husk serving as a heat preservation agent, uniformly covering, and hanging at 1570 ℃.
4. Continuous casting
Adopting a three-machine three-stream arc continuous casting machine to continuously cast steel billets, and casting under the protection of argon at the temperature of 1561 ℃ for continuous casting and ladle hanging; baking the middle ladle for 4 hours; immersion nozzle depth of insertion: 85mm from the crystallizer liquid level; the pulling speed is 0.85m/min, the superheat degree of the continuous casting head furnace is 26 ℃, the water flow rate of the crystallizer is 160m3/h, the specific water flow rate of secondary cooling water is 0.30L/kg, and the electric stirring current is 380A.
5. Heating
The furnace temperature of the preheating section is 600 ℃, and the heating time is 50min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 150 ℃/h, the furnace temperature is 1230 ℃, and the heating time is 60min; heating the second stage at a heating speed of 320 ℃/h and a furnace temperature of 1060 ℃ for 60min; the furnace temperature of the soaking section is 1220 ℃, and the soaking time is 70min; the billet tapping temperature is 1190 ℃ and the total heating time is 240min.
6. Rolling
High-pressure water descaling before rolling, the descaling pressure is 28-30 MPa, the initial rolling temperature is 1150 ℃, the final rolling temperature is 910 ℃, and the rolling specification is thatAnd (5) cooling the steel immediately after the steel is cooled down in a cooling bed.
7. Annealing
The isothermal annealing process is adopted, steel is firstly put into a heating furnace with the furnace temperature of 300 ℃, the temperature is raised to 770 ℃ at the heating rate of 90 ℃/h, the total heating is carried out for 6h, the temperature is kept for 8h, the furnace is cooled to 690 ℃ and then kept for 3h, and then the steel is discharged after being cooled to below 500 ℃ along with the furnace and is cooled to the room temperature by air. At oven time 23h.
The steel product prepared in this example was examined and the results were as follows:
| yield strength of | Tensile strength of | Face shrinkage | Elongation percentage | Hardness of | Depth of decarburized layer |
| 1018MPa | 1147MPa | 64％ | 18％ | 229HB | 0.14mm |
[ example 3 ]
21C5351 this example uses the method of this invention to make 31CrMoV9 annealed steel, according to the weight percentage content, the chemical composition in steel includes C:0.29%, si:0.32%, mn:0.67%, P:0.015%, S:0.001%, cr:2.47%, ni:0.02%, mo:0.19%, cu:0.03%, alt:0.022 percent, 0.12 percent of V, and the balance of Fe and unavoidable impurities.
The production process is controlled as follows:
1. EBT electric furnace smelting
The electric furnace is filled with scrap steel for 18t, molten iron is added after 20min of power transmission, the temperature of the molten iron is 1250-1350 ℃, and the weight is 25.9t. Oxygen is oxidized and boiled vigorously, the oxidation temperature is 1678 ℃, high alkalinity, large slag quantity and low temperature slag are formed in the early stage of oxidation to strengthen dephosphorization effect, when the furnace burden is melted by more than 70%, an electric furnace foaming agent is blown into the slag, and after the steel is melted, C, mn, P, S and residual elements are sampled and analyzed. The C content is 0.05% and the P content is 0.0012% during tapping, and the tapping temperature is 1676 ℃. When the electric furnace is tapped for 1/4, a proper amount of slag is added, 102kg of pre-deoxidizer aluminum iron, 201kg of alloy silicon manganese and 1000kg of low chromium are added.
2. LF furnace refining
When the steel ladle is in a receiving position, firstly, switching on argon gas to blow off a slag surface for temperature measurement, taking a primary sample for analyzing all components, and after the primary sample analysis result is reported back, carrying out coarse adjustment on the components according to the lower limit of the requirement; in the whole LF refining process, argon bottom blowing stirring is carried out, 452kg of active lime and 45kg of coke powder carburant are added, and 200kg of alumina balls are added for diffusion deoxidation after liquid slag is formed. Taking a secondary sample to analyze the total composition after the slag white and the temperature meet the requirements; and after the secondary sample is taken out, slag is continuously regulated by using a diffusion deoxidizer, proper slag alkalinity and good fluidity are kept, white slag operation is kept in the whole process, a secondary sample result is reported back, and component fine adjustment is carried out according to target control components. The white slag holding time is more than or equal to 20min. The argon pressure is controlled to be 0.2-0.3 MPa in the whole process, so that secondary oxidation caused by the naked molten steel is prevented. The temperature of the hanging bag is 1682 ℃.
3. Refining in VD furnace
The temperature of molten steel entering the VD furnace is 1660 ℃. The argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started, and the slag surface micro-motion molten steel is not exposed. When the vacuum degree reached 100Pa, the timing was started and maintained for 15min. After breaking the vacuum, ca-Si wire is fed 100m. Argon is blown from the wire feeding end, the static argon blowing is carried out for 20-35 min, the argon pressure is regulated to be 0.1-0.3 MPa, and the slag surface micro-motion molten steel is not exposed. And after the static argon blowing is finished, adding 80kg of carbonized rice husk serving as a heat preservation agent, uniformly covering, and hanging at 1568 ℃.
4. Continuous casting
Adopting a three-machine three-stream arc continuous casting machine to continuously cast steel billets, and casting under the protection of argon at 1563 ℃ in a continuous casting head furnace ladle; baking the middle ladle for 4 hours; immersion nozzle depth of insertion: 85mm from the crystallizer liquid level; the pulling speed is 0.85m/min, the superheat degree of the continuous casting head furnace is 27 ℃, and the water flow of the crystallizer is 160m 3 And/h, the specific water quantity of the secondary cooling water is 0.30L/kg, and the electric stirring current is 380A.
5. Heating
The furnace temperature of the preheating section is 600 ℃, and the heating time is 50min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 150 ℃/h, the furnace temperature is 1230 ℃, and the heating time is 60min; heating the second stage at a heating speed of 320 ℃/h and a furnace temperature of 1060 ℃ for 60min; the furnace temperature of the soaking section is 1220 ℃, and the soaking time is 70min; the billet tapping temperature is 1200 ℃, and the total heating time is 240min.
6. Rolling
High-pressure water descaling before rolling, descaling pressure of 28MPa, initial rolling temperature of 1150 ℃, final rolling temperature of 910 ℃ and rolling specification ofAnd (5) cooling the steel immediately after the steel is cooled down in a cooling bed.
7. Annealing
The isothermal annealing process is adopted, steel is firstly put into a heating furnace with the furnace temperature of 300 ℃, the temperature is raised to 770 ℃ at the heating rate of 85 ℃/h, the total heating is carried out for 6 hours, the temperature is kept for 8 hours, the furnace is cooled to 690 ℃ and then kept for 3 hours, and then the steel is discharged after being cooled to below 500 ℃ along with the furnace and is cooled to the room temperature by air. At oven time 23h.
The steel product prepared in this example was examined and the results were as follows:
| yield strength of | Tensile strength of | Face shrinkage | Elongation percentage | Hardness of | Depth of decarburized layer |
| 1015MPa | 1129MPa | 65％ | 18％ | 239HB | 0.12mm |
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (7)
1. A production method of a nitriding steel 31CrMoV9 annealing material is characterized in that the steel comprises, by mass, 0.27% -0.33% of C, 0.28% -0.36% of Si, 0.63% -0.70% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 2.43% -2.53% of Cr, less than or equal to 0.10% of Ni, 0.17% -0.23% of Mo, 0.10% -0.16% of V, less than or equal to 0.10% of Cu, 0.015% -0.045% of Alt, and the balance of Fe and unavoidable impurities;
the raw materials sequentially pass through an EBT electric furnace smelting, an LF furnace refining, a VD furnace refining, continuous casting, heat preservation, heating, rolling, slow cooling and annealing to obtain the product steel, and the specific steps are as follows:
1) Smelting by an EBT electric furnace: smelting temperature 1640-1680 ℃, smelting end point C:0.05 to 0.10 percent, P is less than or equal to 0.013 percent, and the content of residual elements meets the design requirement; 2.0-3.0 kg/t aluminum powder is added for pre-deoxidation before tapping, a pre-deoxidizer, a slag-forming material, an alloy and a carburant are added in the tapping process, steel is reserved, slag is reserved, and the tapping time is controlled to be 3-6 min;
2) Refining in an LF furnace: stirring by bottom blowing argon in the whole process, and controlling the pressure of the argon to be 0.2-0.3 MPa; refining white slag in LF furnace, controlling slag alkalinity R not less than 3.5, and controlling A1 in slag 2 O 3 25% -30% FeO+MnO content less than 1.0%; the operation and holding time of the white slag is more than or equal to 20min;
3) Refining by a VD furnace: the argon pressure is controlled to be 0.1-0.3 MPa before the vacuum pump is started; maintaining for more than 10min after the vacuum degree reaches 100Pa, and adjusting the argon pressure to 0.3-0.5 MPa; finally deoxidizing after breaking vacuum, and feeding Al wires to adjust the Al content in the steel to be 0.025% -0.035%; feeding Ca-Si wire 100-120 m to regulate aluminum nitride inclusion; after breaking vacuum, static argon blowing is carried out for 10-35 min, and the argon pressure is regulated to be 0.1-0.3 MPa; after the static argon blowing is finished, adding 30-80 kg of heat preservation agent into the furnace;
4) Continuous casting: adopting a three-machine three-stream arc continuous casting machine, wherein the temperature of a continuous casting head furnace ladle is 1589-1594 ℃, the temperature of a 2 nd furnace ladle is 1577-1587 ℃, and the temperature of a 3 rd furnace to a tail furnace ladle is 1567-1577 ℃, and carrying out argon protection casting;
5) Heating: the furnace temperature of the preheating section is 500-750 ℃, and the heating time is 45-50 min; the heating section is divided into a first heating section and a second heating section according to the difference of the heating speeds of the billets, the heating speed of the first heating section is 140-170 ℃/h, the furnace temperature is 1220-1230 ℃, and the heating time is 55-60 min; heating the second stage at a heating speed of 300-330 ℃/h, a furnace temperature of 1060-1080 ℃ and a heating time of 60-65 min; furnace temperature of the soaking section is 1200-1220 ℃, and soaking time is 60-90 min; the billet tapping temperature is 1180-1200 ℃, and the total heating time is 220-265 min;
6) Rolling: the initial rolling temperature is 1100-1200 ℃, the final rolling temperature is 850-1000 ℃, and the steel is immediately put into a pit for heat preservation or cold piling after being put into a cooling bed;
7) Annealing: an isothermal annealing process is adopted; firstly raising the temperature of steel to 760-780 ℃ at a heating rate of 70-100 ℃/h, then homogenizing the temperature and preserving the heat for more than 3 hours, then cooling the steel to 690-710 ℃ in a furnace, homogenizing the temperature and preserving the heat for more than 2 hours, cooling the steel to below 500 ℃ along with the furnace, discharging the steel, and cooling the steel to room temperature in an air;
the hardness of the produced 31CrMoV9 steel is less than or equal to 248HBW; the tensile strength after quenching and tempering is 1000-1200 MPa, and the yield strength is more than or equal to 800MPa.
2. The method for producing the nitriding steel 31CrMoV9 annealed material according to claim 1, wherein in the step 1), scrap steel and molten iron are adopted as raw materials, the scrap steel is firstly filled, molten iron is added after the steel is fed through a well to form a molten pool, and the temperature of the molten iron is more than 1150 ℃ when the molten iron is added; decarburization, dephosphorization and temperature adjustment are carried out through oxygen supply, slag formation and electrifying.
3. The production method of the nitrided steel 31CrMoV9 annealed material according to claim 2, wherein the molten iron composition is as follows: c is more than or equal to 3.5%, mn is less than or equal to 0.80%, si is 0.20% -1.00%, P is less than or equal to 0.070%, and S is less than or equal to 0.070%.
4. The method for producing a nitrided steel 31CrMoV9 annealed material according to claim 1, characterized in that in the step 4), a crystallizer M-EMS and a solidification end F-EMS are used for combined stirring, and an electric stirring current is 360-400A.
5. The method for producing a 31CrMoV9 annealed steel sheet according to claim 1, wherein the step 6) is performed with high-pressure water for descaling before rolling, and the descaling pressure is 28-30 MPa.
6. The method for producing a 31CrMoV9 annealed steel sheet according to claim 1, wherein in the step 6), the steel sheet with a specification of not less than 85mm is subjected to heat preservation by entering a furnace, the pit outlet temperature is not more than 300 ℃, and the heat preservation time is not less than 24 hours; for steel with the specification of < 85mm, heap cooling is adopted.
7. The method of producing a 31CrMoV9 annealed steel as set forth in claim 1, wherein the total decarburized depth of each side of the 31CrMoV9 steel to be produced is not more than 1.0% of the nominal diameter.
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| CN102443740A (en) * | 2010-10-14 | 2012-05-09 | 宝山钢铁股份有限公司 | Alloy steel nitride and manufacture method thereof |
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| CN106086671A (en) * | 2016-06-16 | 2016-11-09 | 安庆市吉安汽车零件锻轧有限公司 | A kind of axle alloy steel nitride |
| CN109402350A (en) * | 2018-11-27 | 2019-03-01 | 中车北京南口机械有限公司 | A kind of heat treatment process of steel |
| CN112828536A (en) * | 2020-12-29 | 2021-05-25 | 无锡鹰贝精密液压有限公司 | Method for machining plunger of hydraulic plunger pump |
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2022
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| CN102443740A (en) * | 2010-10-14 | 2012-05-09 | 宝山钢铁股份有限公司 | Alloy steel nitride and manufacture method thereof |
| CN103088349A (en) * | 2012-11-27 | 2013-05-08 | 龙工（上海）桥箱有限公司 | Heating processing technology for material of plunger of plunger pump |
| CN106086671A (en) * | 2016-06-16 | 2016-11-09 | 安庆市吉安汽车零件锻轧有限公司 | A kind of axle alloy steel nitride |
| CN109402350A (en) * | 2018-11-27 | 2019-03-01 | 中车北京南口机械有限公司 | A kind of heat treatment process of steel |
| CN112828536A (en) * | 2020-12-29 | 2021-05-25 | 无锡鹰贝精密液压有限公司 | Method for machining plunger of hydraulic plunger pump |
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| CN115896624A (en) | 2023-04-04 |
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