Die forging pumped storage water turbine guide vane manufacturing process

Abstract

The invention discloses a die forging pumped storage water turbine guide vane manufacturing process, and belongs to the technical field of die forging processes. 2, prefabricating a blank; (3) die forging of the guide vane valve body and the flange; 4, cleaning and detecting; and fifthly, tempering treatment is conducted. The guide vane base body manufactured through the technical scheme is high in compactness, grains are refined, and the grain size grade reaches 5-7 grades. Under the condition that the material strength is similar, the toughness is obviously improved by more than 40%, the internal quality is good, the nondestructive flaw detection grade is improved, and the highest grade requirement of flaw detection can be met, so that the service life and the use safety of the guide vane are guaranteed and improved, and the quality requirement of the pumped storage stainless steel guide vane can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of die forging processes, and particularly to a die forging manufacturing process for a guide vane of a pumped storage hydroturbine. Background Art

[0002] With the improvement of the design level of hydroturbines, the owners of hydropower stations have put forward higher requirements for the quality and use safety of the guide vanes of pumped storage high-head hydroturbines. The stainless-steel guide vanes of hydroturbines produced by existing casting processes can no longer meet the actual use requirements for safety and quality. The existing stainless-steel guide vanes are made by two casting processes, namely sand casting and electroslag remelting. The inevitable disadvantages of the casting process are numerous casting defects, such as slag inclusions, sand inclusions, shrinkage porosity, etc., low density, and coarse grains (grain size is 2 - 4 grades). The toughness of the guide vane products is low, the wear resistance and corrosion resistance are poor, the anti-fatigue failure performance is poor, and there are many non-destructive testing defects. As a result, the quality of the guide vanes is low, the service life is short, the use safety is poor, and it cannot meet the requirements for the material toughness and the internal quality of the product in the design and use of high-head pumped storage guide vanes. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a die forging manufacturing process for a guide vane of a pumped storage hydroturbine, which can refine the grains of the guide vane material and greatly improve the toughness, wear resistance, corrosion resistance, and non-destructive testing quality of the guide vane products.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] A die forging manufacturing process for a guide vane of a pumped storage hydroturbine includes the following steps:

[0006] Step 1: Vacuum refining of a stainless-steel ingot: The stainless-steel molten steel melted by an intermediate-frequency furnace or an electric arc furnace is vacuum refined to adjust the content of elements in the stainless-steel molten steel, remove the gas and impurities in the molten steel, and reduce the sulfur content, so as to obtain pure molten steel meeting the composition requirements, and then the pure molten steel is poured into an ingot;

[0007] Step 2: Preparing a preform: The ingot in Step 1 is heat-treated at a high temperature and then forged by three upsetting and three drawing processes to obtain a preform; the width of the petal part of the preform is L2;

[0008] Step 3: Die forging of the guide vane petal and flange: Before die forging, the whole preform is heated and kept at a high temperature. After the high-temperature heat preservation of the preform is completed, the petal part of the blank is put into the die cavity for die forging. After die forging, the preform becomes a whole guide vane blank, and the width of the petal of the whole guide vane blank is C;

[0009] Step 4: Cleaning and inspection: After die forging, wait for the whole guide vane blank to cool to room temperature, and then clean and check the dimensions of the whole guide vane blank;

[0010] Step 5 Tempering treatment: Inspect the dimensions of the integral guide vane blank after cleaning. After passing the inspection, reheat it in the furnace. After heating is completed, perform high-temperature heat preservation. After heat preservation ends, perform slow cooling. After slow cooling to room temperature, the production of the integral guide vane blank is completed.

[0011] Further, in the high-temperature treatment process of the ingot in Step 2 of the preformed blank, the ingot is heated as a whole to 980°C - 1050°C. The heating and temperature-rising speed is free temperature-rising before the ingot temperature ≤ 600°C, and the temperature-rising speed ≤ 80°C / hour when the ingot temperature ≥ 600°C. The high-temperature heat preservation time ≥ the maximum thickness of the ingot ÷ 50 + 2 hours ± 1 hour, and the measurement unit of the maximum thickness of the ingot is millimeters.

[0012] Further, in the overall heating of the preformed blank in Step 3 of the guide vane petal body and flange die forging, the specific process is as follows: Heat the preformed blank to 1000°C - 1080°C. When the temperature of the preformed blank ≤ 600°C, the temperature-rising speed < 100°C / hour. When the temperature of the preformed blank ≥ 600°C, the temperature-rising speed < 70°C / hour. The high-temperature heat preservation time is > the maximum thickness of the preformed blank ÷ 50 + 2 hours ± 1 hour, and the measurement unit of the maximum thickness of the preformed blank is millimeters. During the die forging process of the preformed blank, the final pressing temperature > 880°C, and the final forging holding time > 3 minutes.

[0013] Further, in Step 5 of the tempering treatment, the heating and temperature-rising speed of the integral guide vane blank ≤ 80°C / hour, the maximum heating temperature of the integral guide vane blank is 550 - 620°C, the high-temperature heat preservation time of the integral guide vane blank is the maximum thickness of the integral guide vane blank ÷ 50 + 4 hours ± 1 hour, the measurement unit of the maximum thickness of the integral guide vane blank is millimeters, the slow cooling standard is to drop 50 - 70 degrees per hour, and when slow cooling to ≤ 100 degrees, air-cool to room temperature.

[0014] Further, the total weight of the preformed blank > 105% of the mass of the integral guide vane blank, and the width L2 of the blank petal body < the dimension of the petal body width C by 6 mm - 14 mm.

[0015] Further, in Step 3 of the guide vane petal body and flange die forging, the mold material is 5CrMnMo. The mold includes two parts: the upper mold and the lower mold. After the upper mold and the lower mold are closed, a die forging cavity is formed in the middle. The mold takes the center line of the guide vane axis as the longitudinal positioning reference and the maximum longitudinal section of the petal body as the parting surface. Extrusion flash edges F are reserved on both sides of the parting surface of the upper mold and the lower mold cavity; the designed mold shrinkage is 1.5%; the height of the extrusion flash reserved on both sides of the parting surface of the upper mold and the lower mold is 4 - 6 millimeters.

[0016] Advantages of the present invention:

[0017] The internal matrix of the guide vane material produced by the technical solution of the present invention has a high density, refined grains, and the grain size grade reaches 6-7 levels. Under the same material strength, the toughness is significantly improved, with a toughness increase of more than 40%. The internal quality is good, the non-destructive testing grade is improved, and the highest level of testing requirements can be met, thus ensuring and improving the service life and safety of the guide vane, and fully meeting the quality requirements of the stainless steel guide vane for pumped storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a preform drawing completed after forging a stainless steel ingot provided by the present invention through three upsetting and three drawing processes;

[0019] Figure 2 (a) is the front view of the finished guide vane completed after die forging of the preform provided by the present invention;

[0020] Figure 2 (b) is the transverse sectional view of the petal body of the finished guide vane completed after die forging of the preform provided by the present invention;

[0021] Figure 3 It is a schematic diagram of the internal structure of the die cavity of the die forging die provided by the present invention;

[0022] Figure 4 It is a schematic diagram of the structure of the guide vane provided by the present invention;

[0023] Figure 5 It is a metallographic diagram of the grain size of the guide vane of Example 1 provided by the present invention at 200 times magnification;

[0024] Figure 6 It is a metallographic diagram of the grain size of the guide vane of Example 2 provided by the present invention at 200 times magnification;

[0025] Figure 7 It is a metallographic diagram of the grain size of the guide vane of Example 3 provided by the present invention at 200 times magnification;

[0026] Figure 8 It is a metallographic diagram of the grain size of the guide vane of Example 4 provided by the present invention at 200 times magnification.

[0027] The reference numerals in the accompanying drawings of the specification include:

[0028] L1 - the length of the long axis of the preform, φ1 - the diameter of the long axis of the preform, L2 - the width of the petal body of the preform, φ2 - the diameter of the petal body of the preform, L3 - the length of the short axis of the preform, φ3 - the diameter of the short axis of the preform, A - the length of the long axis, B - the width of the long axis flange of the overall guide vane blank, C - the width of the petal body of the overall guide vane blank, D - the width of the short axis flange of the overall guide vane blank, F - the reserved extrusion flash area, E - the length of the short axis. DETAILED DESCRIPTION OF THE INVENTION

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0030] Embodiment 1:

[0031] As Figures 1 to 4 shown, a manufacturing process for a die-forged guide vane of a pumped-storage hydroturbine includes the following steps:

[0032] Step 1: Vacuum refining of stainless steel ingots: The stainless steel molten steel melted in an electric arc furnace is vacuum refined to adjust the contents of alloying elements such as Cr, Ni, Mo, etc. in the stainless steel molten steel, reduce the carbon content, remove the gases and impurities in the molten steel and reduce the sulfur content, so as to obtain pure molten steel that meets the composition requirements, and then the pure molten steel is poured into a stainless steel ingot with a diameter of 250 mm. The material of the stainless steel ingot is 04Cr13Ni5Mo.

[0033] Step 2: Preparing blanks: The ingot in Step 1 is heat-treated at a high temperature. The high-temperature treatment process of the ingot is to heat the whole ingot to 1020°C - 1040°C. The heating and temperature-rising speed is free temperature-rising before the ingot temperature ≤ 600°C, and the temperature-rising speed is 60°C / hour after the ingot temperature > 600°C. The high-temperature holding time is 7.5 hours. After the high-temperature treatment, it is forged by three upsetting and three drawing processes to obtain the preform blanks; the length of the long axis of the preform blank after forging is L1, the diameter of the long axis of the preform blank is φ1; the width of the petal body of the preform blank is L2, and the diameter of the petal body of the preform blank is φ2; the length of the short axis of the preform blank is L3, and the diameter of the short axis of the preform blank is φ3;

[0034] Step 3: Die forging of guide vane petal body and flange: Before die forging, the preform blank is heated as a whole and held at a high temperature. The specific requirements for the whole heating are to heat the preform blank to 1010°C - 1030°C. When the temperature of the preform blank ≤ 600°C, the temperature-rising speed is 80°C / hour. When the temperature of the preform blank > 600°C, the temperature-rising speed is 60°C / hour. The maximum thickness of the preform blank is 300 mm, and the high-temperature holding time is 8.2 hours. After the high-temperature holding of the preform blank is completed, the petal body part of the blank is put into the die cavity of the mold for die forging. After the die forging is completed, the whole guide vane blank is made. The final forging temperature during the die forging process of the preform blank is 916°C, and the final forging pressure holding time is 3.5 minutes. The length of the long axis is A, the width of the long-axis flange of the whole guide vane blank is B, the width of the petal body of the whole guide vane blank is C, the width of the short-axis flange of the whole guide vane blank is D, and the length of the short axis is E.

[0035] Step 4: Cleaning and inspection: After the die forging is completed, wait for the whole guide vane blank to cool to room temperature, and clean and check the dimensions of the whole guide vane blank;

[0036] Step 5 Tempering treatment: Perform ultrasonic non-destructive testing and dimensional inspection on the machined integral guide vane blank according to the national standard and the highest grade of ASTM. After passing the inspection, reheat the integral guide vane blank in the furnace. The heating rate of the integral guide vane blank is 70 °C / h, and the maximum heating temperature of the integral guide vane blank is 600 - 620 °C. After heating, perform high-temperature heat preservation. The maximum thickness of the integral guide vane blank is 325 mm, and the heat preservation time is 10 hours. After the heat preservation is completed, cool down at a rate of 60 degrees per hour. When cooling slowly to 90 degrees, air-cool to room temperature. After cooling slowly to room temperature, perform mechanical property testing, non-destructive testing, and dimensional inspection. The manufacturing of all blanks of the guide vane is completed.

[0037] The total weight of the preform is 106% of the weight of the integral guide vane blank. The width L2 of the blank segment is 10 mm less than the dimension C of the integral guide vane blank segment.

[0038] In the die forging of the guide vane segment and flange in Step 3, the die forging die material is 5CrMnMo. The die includes an upper die and a lower die. After the upper die and the lower die are closed, a die forging cavity is formed in the middle. The die uses the center line of the guide vane shaft as the longitudinal positioning reference and the maximum longitudinal section of the segment as the parting surface. The die cavities of the upper die and the lower die reserve an extrusion flash zone F on both sides of the parting surface; the designed die shrinkage is 1.5%; the height of the extrusion flash reserved between the two sides of the parting surface of the upper die and the lower die is 5 mm.

[0039] The guide vane made by the technical solution of the present invention is made of 04Cr13Ni5Mo stainless steel, with a dense matrix, fine grains, and a grain size of grade 7. The metallographic structure of the grain size is shown in Figure 5 .

[0040] In Example 1, the mechanical properties of the guide vane made by the technical solution of the present invention are compared with the national standard, the highest enterprise standard, and the American standard of the mechanical properties of the guide vane made by the existing technical specifications of the same material in Tables 1 and 2. The material of the guide vane is 04Cr13Ni5Mo stainless steel:

[0041] Example 2:

[0042] Step 1 Vacuum refining of stainless steel ingot: Vacuum refine the stainless steel molten steel melted in the electric arc furnace to adjust the content of alloy elements such as Cr, Ni, and Mo in the stainless steel molten steel, reduce the carbon content, remove the gas and impurities in the molten steel, and reduce the sulfur content, so as to obtain pure molten steel that meets the composition requirements. Then, pour the pure molten steel into a stainless steel ingot with a material of 04Cr13Ni5Mo and a diameter of 200 mm.

[0043] Step 2: Preformed blank: The ingot in Step 1 is heat-treated at high temperature. The high-temperature treatment process of the ingot is to heat the whole ingot to 990°C - 1010°C. The heating and temperature-rising speed is free temperature-rising before the ingot temperature ≤ 600°C, and the temperature-rising speed is 75°C per hour after the ingot temperature > 600°C. The high-temperature holding time is 6.2 hours. After high-temperature treatment, it is forged by three upsetting and three drawing processes to obtain a preformed blank; the major-axis length of the forged preformed blank is L1, and the major-axis diameter of the preformed blank is φ1; the petal width of the preformed blank is L2, and the petal diameter of the preformed blank is φ2; the minor-axis length of the preformed blank is L3, and the minor-axis diameter of the preformed blank is φ3.

[0044] Step 3: Die forging of guide vane petal and flange: Before die forging, the preformed blank is heated as a whole and held at high temperature. The specific requirements for the whole heating are to heat the preformed blank to 1020°C - 1040°C. When the preformed blank temperature ≤ 600°C, the temperature-rising speed is 85°C per hour. When the preformed blank temperature > 600°C, the temperature-rising speed is 65°C per hour. The maximum thickness of the preformed blank is 315 mm, and the high-temperature holding time is 8.2 hours. After the high-temperature holding of the preformed blank is completed, the petal part of the blank is put into the die cavity of the mold for die forging. After die forging is completed, the whole guide vane blank is made. The final forging temperature during the die forging process of the preformed blank is 925°C, and the final forging pressure-holding time is 4.0 minutes. The major-axis length is A, the major-axis flange width of the whole guide vane blank is B, the petal width of the whole guide vane blank is C, the minor-axis flange width of the whole guide vane blank is D, and the minor-axis length is E.

[0045] Step 4: Cleaning and inspection: After die forging, wait for the whole guide vane blank to cool to room temperature, and then clean and check the dimensions of the whole guide vane blank.

[0046] Step 5: Tempering treatment: The whole guide vane blank after cleaning is subjected to ultrasonic non-destructive testing and dimension inspection according to the highest grades of national standards and ASTM. After passing the inspection, it is re-heated in the furnace. The heating and temperature-rising speed of the whole guide vane blank is 75°C per hour, and the highest heating temperature of the whole guide vane blank is 570 - 590°C. After heating is completed, high-temperature holding is carried out. The maximum thickness of the whole guide vane blank is 322 mm, and the holding time is 10.0 hours. After the holding is completed, it cools down by 60 degrees per hour, and is slowly cooled to 90 degrees and then air-cooled to room temperature. After being slowly cooled to room temperature, mechanical properties, non-destructive testing, and dimension inspection are carried out. The manufacturing of all blanks of the guide vane is completed.

[0047] The total weight of the preformed blank is 108% of the weight of the whole guide vane blank. The petal width L2 of the blank is 10 mm less than the petal width C dimension of the whole guide vane blank.

[0048] In the third step of die forging the guide vane lobe body and flange, the die forging die material is 5CrMnMo. The die includes an upper die and a lower die. After the upper die and the lower die are closed, a die forging cavity is formed in the middle. The die takes the center line of the guide vane shaft as the longitudinal positioning reference and the largest longitudinal section of the lobe body as the parting surface. Extrusion flash edges F are reserved on both sides of the parting surface of the upper die and the lower die cavities. The designed die shrinkage is 1.5%. The height of the extrusion flash reserved on both sides of the parting surface of the upper die and the lower die is 4.3 mm.

[0049] The guide vane made by adopting the technical solution of the present invention is made of 04Cr13Ni5Mo stainless steel. The matrix is dense, the grains are fine, the grain size is 6.5 levels, and the metallographic structure of the grain size is shown in Figure 6 .

[0050] In Example 2, the mechanical properties of the guide vane made by adopting the technical solution of the present invention are compared with the national standard, the highest enterprise standard, and the American standard of the mechanical properties of the guide vane made by the existing technical specifications of the same material in Tables 1 and 2. The guide vane materials are all 04Cr13Ni5Mo stainless steel:

[0051] Example 3:

[0052] Step 1: Vacuum refining of stainless steel ingot: The stainless steel water melted in the electric arc furnace is vacuum refined to adjust the contents of alloy elements such as Cr, Ni, Mo, etc. in the stainless steel water, reduce the carbon content, remove the gases and impurities in the steel water and reduce the sulfur content, so as to obtain pure steel water meeting the composition requirements, and then the pure steel water is poured into a stainless steel ingot with a diameter of 230 mm and a material of 04Cr13Ni5Mo.

[0053] Step 2: Preparing the preform: The ingot in Step 1 is heat-treated at high temperature. The process of heat-treating the ingot at high temperature is to heat the whole ingot to 1040°C - 1060°C. The heating and temperature-rising speed is free temperature-rising before the ingot temperature ≤ 600°C, and the temperature-rising speed is 78°C / hour after the ingot temperature > 600°C. The high-temperature holding time is 6.0 hours. After the high-temperature treatment, it is forged by three upsetting and three drawing to obtain the preform; the length of the long axis of the preform after forging is L1, the diameter of the long axis of the preform is Φ1; the width of the lobe body of the preform is L2, the diameter of the lobe body of the preform is Φ2; the length of the short axis of the preform is L3, and the diameter of the short axis of the preform is Φ3;

[0054] Step 3: Die forging of the guide vane lobe body and flange: Before die forging, the preformed blank is heated as a whole and kept at a high temperature. The specific requirements for the overall heating are to heat the preformed blank to 1015°C - 1035°C. When the temperature of the preformed blank is ≤600°C, the heating rate is 78°C per hour; when the temperature of the preformed blank is >600°C, the heating rate is 65°C per hour. The maximum thickness of the preformed blank is 300 mm, and the high-temperature holding time is 7.5 hours. After the high-temperature holding of the preformed blank is completed, the lobe body part of the blank is placed into the die cavity of the mold for die forging. After die forging is completed, the overall guide vane blank is manufactured. During the die forging process of the preformed blank, the final forging temperature is 930°C, and the final forging pressure holding time is 3.0 minutes. The length of the long axis is A, the width of the long-axis flange of the overall guide vane blank is B, the width of the lobe body of the overall guide vane blank is C, the width of the short-axis flange of the overall guide vane blank is D, and the length of the short axis is E.

[0055] Step 4: Cleaning and inspection: After die forging, wait for the overall guide vane blank to cool to room temperature, and then clean and check the dimensions of the overall guide vane blank.

[0056] Step 5: Tempering treatment: The cleaned overall guide vane blank is subjected to ultrasonic non-destructive testing and dimensional inspection according to the highest grades of national standards and ASTM. After passing the inspection, it is re-furnaced for heating the overall guide vane blank. The heating rate of the overall guide vane blank is 70°C per hour, the maximum heating temperature of the overall guide vane blank is 565 - 585°C. After heating is completed, high-temperature holding is carried out. The maximum thickness of the overall guide vane blank is 320 mm, and the holding time is 10.5 hours. After the holding is completed, it cools down by 65 degrees per hour. When it cools slowly to 90 degrees, it is air-cooled to room temperature. After cooling slowly to room temperature, mechanical properties, non-destructive testing, and dimensional inspection are carried out. The manufacturing of all blanks of the guide vane is completed.

[0057] The total weight of the preformed blank is 107% of the weight of the overall guide vane blank. The width L2 of the lobe body of the blank is 11 mm less than the width C of the lobe body of the overall guide vane blank.

[0058] In step 3 of the die forging of the guide vane lobe body and flange, the material of the die forging die is 5CrMnMo. The die includes two parts: the upper die and the lower die. After the upper die and the lower die are closed, a die forging cavity is formed in the middle. The die uses the center line of the guide vane shaft as the longitudinal positioning reference and the largest longitudinal section of the lobe body as the parting surface. Extrusion flash edges F are reserved on both sides of the parting surface of the upper die and the lower die cavity; the designed die shrinkage is 1.5%; the height of the extrusion flash reserved on both sides of the parting surface of the upper die and the lower die is 4.5 mm.

[0059] The guide vane made by using the technical solution of the present invention is made of 04Cr13Ni5Mo stainless steel, with a dense matrix, fine grains, and the grain size is 7 levels. The grain size metallographic structure is shown in Figure 7 .

[0060] In Example 3, the mechanical properties of the guide vane manufactured using the technical solution of the present invention are compared with the national standard, the highest enterprise standard, and the American standard of the mechanical properties of the guide vane manufactured according to the existing technical specifications of the same material in Table 1 and Table 2. The material of the guide vane is 04Cr13Ni5Mo stainless steel:

[0061] Example 4:

[0062] Step 1: Vacuum refining of the stainless steel ingot: The molten stainless steel from the electric arc furnace is vacuum refined to adjust the contents of alloying elements such as Cr, Ni, and Mo in the molten stainless steel, reduce the carbon content, remove the gases and impurities in the molten steel, and reduce the sulfur content, so as to obtain pure molten steel that meets the composition requirements. Then, the pure molten steel is cast into a stainless steel ingot with a diameter of 185 mm and a material of 04Cr13Ni5Mo.

[0063] Step 2: Preparing the preform: The ingot in Step 1 is heat-treated at high temperature. The process of heat-treating the ingot is to heat the whole ingot to 1015°C - 1035°C. The heating and temperature-rising speed is free temperature-rising before the ingot temperature ≤ 600°C, and the temperature-rising speed is 60°C / hour after the ingot temperature > 600°C. The high-temperature holding time is 6.3 hours. After the high-temperature treatment, it is forged by three upsetting and three drawing processes to obtain the preform; the length of the long axis of the preform after forging is L1, the diameter of the long axis of the preform is Φ1; the width of the lobe of the preform is L2, the diameter of the lobe of the preform is Φ2; the length of the short axis of the preform is L3, and the diameter of the short axis of the preform is Φ3;

[0064] Step 3: Die forging of the guide vane lobe and flange: Before die forging, the preform is heated as a whole and held at high temperature. The specific requirements for the whole heating are to heat the preform to 1020°C - 1040°C. When the temperature of the preform ≤ 600°C, the temperature-rising speed is 90°C / hour. When the temperature of the preform > 600°C, the temperature-rising speed is 66°C / hour. The maximum thickness of the preform is 290 mm, and the high-temperature holding time is 8.3 hours. After the high-temperature holding of the preform is completed, the lobe part of the blank is placed in the die cavity of the mold for die forging. After the die forging is completed, the production of the whole guide vane blank is completed. The final forging temperature during the die forging process of the preform is 940°C, and the final forging pressure holding time is 3.0 minutes. The length of the long axis is A, the width of the long-axis flange of the whole guide vane blank is B, the width of the lobe of the whole guide vane blank is C, the width of the short-axis flange of the whole guide vane blank is D, and the length of the short axis is E.

[0065] Step 4: Cleaning and inspection: After the die forging is completed, wait for the whole guide vane blank to cool to room temperature, and clean and check the dimensions of the whole guide vane blank;

[0066] Step 5 Tempering treatment: The cleaned integral guide vane blank is subjected to ultrasonic non-destructive testing and dimensional inspection according to the national standard and the highest grade of ASTM. After passing the inspection, it is re-furnaced for heating the integral guide vane blank. The heating rate of the integral guide vane blank is 75 °C per hour, and the maximum heating temperature of the integral guide vane blank is 585 - 605 °C. After heating, high-temperature heat preservation is carried out. The maximum thickness of the integral guide vane blank is 327 mm, and the heat preservation time is 9.8 hours. After the heat preservation ends, it cools down by 65 degrees per hour. When it cools slowly to 95 degrees, it is air-cooled to room temperature. After cooling slowly to room temperature, mechanical properties, non-destructive testing, and dimensional inspection are carried out. The manufacture of all blanks of the guide vane is completed.

[0067] The total weight of the preform is 106% of the weight of the integral guide vane blank. The width L2 of the blank segment is 12.4 mm less than the dimension C of the integral guide vane blank segment.

[0068] In the die forging of the guide vane segment and flange in Step 3, the die forging die material is 5CrMnMo. The die includes two parts: the upper die and the lower die. After the upper die and the lower die are closed, a die forging cavity is formed in the middle. The die takes the center line of the guide vane shaft as the longitudinal positioning reference and the maximum longitudinal section of the segment as the parting surface. Extrusion flash zones F are reserved on both sides of the parting surface of the upper die and the lower die cavities; the designed die shrinkage is 1.5%; the height of the extrusion flash reserved on both sides of the parting surface of the upper die and the lower die is 5.2 mm.

[0069] The guide vane made by adopting the technical scheme of the present invention is made of 04Cr13Ni5Mo stainless steel. The matrix is dense, the grains are fine, the grain size is 6.5 levels, and the grain size metallographic phase is shown in Figure 8 .

[0070] In Example 4, the mechanical properties of the guide vane made by adopting the technical scheme of the present invention are compared with the national standard, the highest enterprise standard, and the American standard of the mechanical properties of the guide vane made by the existing technical specifications of the same material in Tables 1 and 2. The guide vane material is 04Cr13Ni5Mo stainless steel:

[0071] Table 1: Comparison table of standard strength indexes between the present invention and existing guide vanes

[0072]

[0073]

[0074] Table 2: Comparison table of standard toughness indexes between the present invention and existing guide vanes

[0075]

[0076] In Tables 1 and 2, GB / T 6967-2009 is the standard for medium and high strength stainless steel castings for engineering structures; ASTM A743 is the standard of the American Society for Testing and Materials; QJ / CTG 03.02-2013 is the enterprise standard of China Three Gorges Corporation, which is currently the highest standard for this material in the world.

Claims

1. A manufacturing process for a die-forged guide vane of a pumped storage hydro turbine, characterized in that, It includes the following steps: Step 1: Vacuum refining of stainless steel ingot: The molten stainless steel in an intermediate frequency furnace or an electric arc furnace is vacuum refined to adjust the elemental composition content in the molten stainless steel, remove the gas and impurities in the molten steel and reduce the sulfur content, so as to obtain pure molten steel meeting the composition requirements, and then the pure molten steel is cast into an ingot; Step 2: Preparing a preform: The ingot in Step 1 is heat-treated at a high temperature and then forged by three upsetting and three drawing processes to obtain a preform; The high-temperature treatment process is to heat the whole ingot to 980°C - 1050°C, with a free heating rate before ≤600°C and a heating rate ≤80°C / h when ≥600°C, and the high-temperature holding time ≥ the maximum thickness of the ingot ÷ 50 + 2 hours ± 1 hour, and the unit of measurement for the maximum thickness of the ingot is millimeters; the width of the preform petal body is L2; Step 3: Die forging of the guide vane petal body and flange: Before die forging, the preform is heated as a whole and held at a high temperature. The preform is heated to 1000°C - 1080°C. When the temperature of the preform ≤600°C, the heating rate ≤100°C / h; when the temperature of the preform ≥600°C, the heating rate ≤70°C / h, and the high-temperature holding time is ≥ the maximum thickness of the preform ÷ 50 + 2 hours ± 1 hour, and the unit of measurement for the maximum thickness of the preform is millimeters. After the high-temperature holding of the preform is completed, the petal body part of the blank is put into the die cavity of the mold for die forging. During the die forging process of the preform, the final forging temperature > 880°C and the final forging pressure holding time > 3 minutes. After die forging, the preform becomes an integral guide vane blank, and the width of the petal body of the integral guide vane blank is C; Step 4: Cleaning and inspection: After die forging, wait for the integral guide vane blank to cool to room temperature, and clean and check the dimensions of the integral guide vane blank; Step 5: Tempering treatment: Check the dimensions of the integral guide vane blank after cleaning. After passing the inspection, it is reheated in the furnace. During the tempering treatment, the heating rate of the integral guide vane blank ≤80°C / h, the maximum heating temperature of the integral guide vane blank is 550 - 620°C. After heating is completed, high-temperature holding is carried out. The high-temperature holding time of the integral guide vane blank is the maximum thickness of the integral guide vane blank ÷ 50 + 4 hours ± 1 hour, and the unit of measurement for the maximum thickness of the integral guide vane blank is millimeters. After the holding is completed, slow cooling is carried out. After slow cooling to room temperature, the production of the integral guide vane blank is completed. The slow cooling standard is a decrease of 50 - 80 degrees per hour, and when it cools to ≤100 degrees, it is air-cooled to room temperature.

2. The manufacturing process of a die-forged guide vane of a pumped storage hydroturbine according to claim 1, characterized in that, The total weight of the preform > 105% of the mass of the integral guide vane blank, and the width L2 of the petal body of the preform < the width C of the petal body of the integral guide vane blank by 6mm - 14mm.

3. The manufacturing process of a die-forged guide vane of a pumped storage hydroturbine according to claim 1, characterized in that, In Step 3, for the die forging of the guide vane petal body and flange, the material of the mold is 5CrMnMo. The mold includes two parts, an upper mold and a lower mold. After the upper mold and the lower mold are closed, a die forging cavity is formed in the middle. The mold takes the center line of the guide vane shaft as the longitudinal positioning reference and the maximum longitudinal section of the petal body as the parting surface. Extrusion flash zones F are reserved on both sides of the parting surface of the upper mold and the lower mold cavity; the designed mold shrinkage is 1.5%; the height of the extrusion flash reserved on both sides of the parting surface of the upper mold and the lower mold is 4 - 6 millimeters.

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