Preparation method of large-size special-shaped thin-wall front casing of new engine

Abstract

The present invention belongs to the processing and manufacturing technology of large-sized stainless steel new engine front casing, and relates to the preparation method of large-sized special-shaped thin-walled front casing of new engine. The present invention adopts vacuum induction + electroslag remelting to produce homogenized, large-sized rods with a diameter of φ350mm without delta ferrite control, and adopts die forging forming process to manufacture front casing forgings for the first time. First, it is the best heat treatment process to obtain casing performance indicators that meet the design indicator requirements; second, it is a shot peening process that significantly improves the fatigue life of the casing; third, it is a surface protection process that further improves the corrosion resistance of the material. The dimensions and performance of the 1Cr12Ni3Mo2VN steel front casing prepared by the present invention meet the design indicator requirements, and are installed in large aircraft engines and commercial engines in batches.

Description

Technical Field

[0001] The invention belongs to the processing and manufacturing technology of a large-size stainless steel new engine front casing, and relates to a preparation method of a large-size special-shaped thin-walled front casing of a new engine. Background Art

[0002] The material selection and preparation technology of the front casing of large aircraft engines and commercial engines (development of large-size bars, development of forgings and preparation of large-size special-shaped thin-walled casings) plays a very critical role in the development of new engines. The front casing of the engine is usually made of titanium alloy. Large aircraft engines and commercial engines are large turbofan engines with high thrust. The operating temperature of the front casing is high. If the front casing is made of titanium alloy, "titanium fire" will occur. In order to prevent the occurrence of "titanium fire", in response to the demand for long life and reliability of new materials for the casing of large aircraft engines and commercial engines, the front casing of large aircraft engines and commercial engines is made of 1Cr12Ni3Mo2VN steel for the first time. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing an engine front casing whose dimensions and performances meet the design index requirements, which is applied to large aircraft engines and commercial engines.

[0004] The technical solution of the present invention is: a method for preparing a large-sized, special-shaped, thin-walled front casing of a new engine, and the preparation steps are as follows:

[0005] 1.1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm;

[0006] 1.1.1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1480℃~1530℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 4h~5h; demolding and annealing of the steel ingot after casting, annealing process: 650~680℃, 4h~5h, air cooling; then electroslag remelting; arcing and slag removal, arcing current 10,000A~13,000A, voltage 58~68V, current: 11000~13000A, casting φ550mm steel ingots, demolding and slow cooling of the steel ingots;

[0007] 1.1.2. Upset and draw the steel ingot into bars; Upset and draw the φ550mm steel ingot into steel bars with a diameter of φ350mm;

[0008] 1.2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings;

[0009] 1.2.1. Cutting: Cut the φ350mm diameter steel bar into bars with a length of 535-540mm;

[0010] 1.2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm;

[0011] 1.2.3. Annealing: annealing the forged slab;

[0012] 1.2.4. Final forging: Forge the slab into a semicircular arc-shaped forging with a die on a forging machine, with a size of Ф760mm (outer diameter) × 565mm (height);

[0013] 1.2.5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 900±10℃ insulation for 60min, air cooling; 680±10℃ insulation for 240min, air cooling;

[0014] 1.3. Front Receiver Manufacturing

[0015] 1.3.1. Rough machining of the shape and front and rear ends; rough milling of the semi-circular arc forgings, the surface finish after rough machining reaches Ra3.2μm;

[0016] 1.3.2. Heat treatment: heat treatment is performed on the casing parts after rough machining;

[0017] 1.3.3. Finish the appearance and front and rear ends; the surface finish after finishing reaches Ra0.8μm;

[0018] 1.3.4. Shot peening: Shot peening is performed on the outer surface of the finely machined casing parts to achieve 100% coverage;

[0019] 1.3.5. Surface protection: Use chemical passivation process to protect the surface of the casing;

[0020] 1.3.6 Drying: Dry in a drying oven at a temperature not higher than 70°C until the parts are dry; you can also use compressed air to blow dry.

[0021] The electroslag remelting in step 1.1.1 adopts CaF2:Al2O3:MgO slag system.

[0022] The specific upsetting and drawing process of step 1.1.2 is as follows: the φ550mm steel ingot is subjected to three upsetting and four drawing on a fast forging machine, the upsetting and drawing temperatures are all 1120℃~1140℃, the final forging temperature is ≥850℃, and it is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.5~2.5, the forging ratio of the second upsetting and drawing is 6~8, and the forging ratio of the third upsetting and drawing is 7~9, and the last fire drawing is for lengthening and forming, and the deformation amount is not less than 30%.

[0023] The pre-forging process in step 1.2.2 is as follows: preheating at 900±10°C for 180 minutes, and then at 1150±10°C for 100 minutes, and the final forging temperature is ≥850°C, followed by air cooling.

[0024] Annealing process described in 1.2.3: keep at 680±℃ for 240min, and air cool.

[0025] The final forging process described in 1.2.4 is as follows: preheating at 850±10℃ for 100min, keeping at 1150±10℃ for 80min, final forging temperature ≥850℃, air cooling.

[0026] The 1.3.1 rough machining process: v = 90m / min, fz = 0.15min / z, ap = 2mm.

[0027] The heat treatment process described in 1.3.2 is: 1025-1050°C, 90 min, oil cooling; 565±10°C, more than 180 min, air cooling.

[0028] The 1.3.3 finishing process: v = 100 m / min, fz = 0.05 min / z, ap = 0.5 mm, cutting speed v = 250 r / min, f = 30 mm / min.

[0029] The shot peening process described in 1.3.4: steel shot S110, shot peening distance 13-15mm, nozzle pressure 0.33-0.35MPa, flow rate 0.36-4kg / min. Shot peening intensity 0.15mmA-0.20mmA; shot peening method is that the part moves in a circle, the nozzle moves up and down, one up and down movement of the nozzle is one cycle, and the part nozzle moves up and down 12 cycles.

[0030] The advantages of the present invention are as follows: the present invention adopts vacuum induction + electroslag remelting to produce homogenized, δ-ferrite-free large-size rods with a diameter of φ350mm. In order to save costs and improve the quality of forgings, the die forging process is used for the first time to manufacture the front casing forgings to achieve the refined forming of the forgings; because the design requirements of the front casing not only have high requirements on strength, toughness, plasticity and durability performance indicators, but also have huge parts size, complex structure, thin wall, and very high precision requirements, in order to prepare a large-size special-shaped thin-wall front casing with performance and life that meet the design index requirements, first, the best heat treatment process is obtained to obtain the casing performance index that meets the design index requirements; second, the shot peening process is significantly improved for the fatigue life of the casing; third, the surface protection process is further improved for the corrosion resistance of the material. The size and performance of the front casing manufactured by the method of the present invention all meet the design index requirements. The design requires the impact performance index to be not less than 41J, and the impact performance of the front casing reaches more than 262J. The design requires the section shrinkage index to be not less than 30%, and the section shrinkage of the front casing reaches more than 73.0%. The high temperature lasting fracture time under 595℃ and 240MPa is greater than 400h, which is much higher than the design index requirement of ≥30h. The dimensions and performance of the 1Cr12Ni3Mo2VN steel front casing prepared by the present invention meet the design index requirements and are installed in large aircraft engines and commercial engines in batches. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the embodiments. The preparation method of large aircraft engine and commercial engine large-scale special-shaped thin-walled front casing, the manufacturing steps are as follows:

[0032] 1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm;

[0033] 1.1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1480℃~1530℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 4h~5h; demolding and annealing of the steel ingot after casting, annealing process: 650℃~680℃, 4h~5h, air cooling; then electroslag remelting; electroslag remelting uses CaF2:Al2O3:MgO slag system; arcing slag, arcing current 10,000A~13,000A, voltage 58V~68V, current: 11000~13000A, casting φ550mm steel ingot, demolding and slow cooling of the steel ingot;

[0034] 1.2. Upset and draw the steel ingot into bars; perform three upsetting and four drawing on the φ550mm steel ingot on the fast forging machine, the upsetting and drawing temperature is 1120℃~1140℃, the final forging temperature is ≥850℃, and the steel ingot is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.5~2.5, the forging ratio of the second upsetting and drawing is 6~8, and the forging ratio of the third upsetting and drawing is 7~9. The deformation of the last fire drawing is not less than 30%. After upsetting and drawing, the steel ingot becomes a steel bar with a diameter of φ350mm;

[0035] 2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings;

[0036] 2.1. Cutting: Cut the φ350mm diameter steel bar into bars with a length of 535-540mm on a sawing machine;

[0037] 2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm; Pre-forging process: preheat at 900±10℃ for 180min, keep at 1150±10℃ for 100min, final forging temperature ≥850℃, air cooling;

[0038] 2.3 Annealing: Anneal the forged slab. Annealing process: 680±10℃ for 240min, air cooling.

[0039] 2.4. Final forging: Forge the slab into a semicircular arc-shaped forging on a forging bed with a die, with a size of φ760mm (outer diameter) × 565mm (height); Final forging process: preheat at 850±10℃ for 100min, keep at 1150±10℃ for 80min, final forging temperature ≥850℃, air cooling;

[0040] 2.5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 900±10℃ insulation for 60min, air cooling; 680±10℃ insulation for 240min, air cooling.

[0041] 3. Manufacturing of the Receiver

[0042] 3.1. Rough machining of the shape and front and rear ends; rough milling of the semicircular arc forgings, the surface finish after rough machining reaches Ra3.2μm, process: v=90m / min, fz=0.15min / z, ap=2mm.

[0043] 3.2. Heat treatment: heat treatment of the casing parts after rough machining. Heat treatment process: 1025-1050℃, 90min, oil cooling; 565±10℃, more than 180min, air cooling.

[0044] 3.3. Finish the appearance and front and rear ends, and the surface finish after finishing reaches Ra0.8μm; process: v=100m / min, fz=0.05min / z, ap=0.5mm. Cutting speed v=250r / min, f=30mm / min.

[0045] 3.4. Shot peening: Shot peening is performed on the outer surface of the finely processed casing parts. The shot peening process is: steel shot S110, shot peening distance 13-15mm, nozzle pressure 0.33-0.35MPa, flow rate 0.36-4kg / min. The shot peening intensity is 0.15mmA-0.20mmA. The shot peening method is that the parts move in a circular motion, and the nozzle moves up and down. One up and down movement of the nozzle is one cycle, and the part nozzle moves up and down 12 cycles. Take out the parts and observe whether the parts have reached 100% coverage.

[0046] 3.5. Surface protection: Use chemical passivation process to protect the surface of the casing. The chemical passivation process is as follows: chemical degreasing → chemical passivation → neutralization → drying.

[0047] Chemical degreasing: sodium hydroxide (NaOH), 5-15 g / L

[0048] The temperature is 50-70℃ until all the water is removed. The casing is cleaned in running warm water at 40-60℃. Then clean it in running cold water. The surface of the parts should be completely wetted by water, that is, the water film should be continuous for 30 seconds.

[0049] Chemical passivation; chemical passivation solution components and process parameters are as follows:

[0050] Phosphoric acid (H3PO4, ρ = 1.70 g / mL), 23-35 mL / L

[0051] Chromic anhydride (CrO3), 150~250g / L

[0052] Temperature, 45-55°C

[0053] Time: 10-20 minutes

[0054] Neutralization; process parameters and formula:

[0055] Sodium carbonate (Na2CO3 10H2O), 30~50g / L

[0056] Temperature, room temperature

[0057] Time: 0.5 to 2 minutes

[0058] Drying: Dry in a drying oven at a temperature not higher than 70°C until the parts are dry; you can also blow dry with compressed air. Avoid scratching the parts when removing them from the fixture.

[0059] The processed front receiver parts meet the requirements of the design drawings.

[0060] Example 1

[0061] 1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm;

[0062] 1.1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1500℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 4.5h; demolding and annealing of the steel ingot after casting, annealing process: 660℃, 5h, air cooling; then electroslag remelting; electroslag remelting uses CaF2:Al2O3:MgO slag system; arcing slag, arcing current 12,000 amperes, voltage 62V, current: 12000A, casting φ550mm steel ingots, demolding and slow cooling of the steel ingots;

[0063] 1.2. Upset and draw the steel ingot into bars; perform three upsetting and four drawing on the φ550mm steel ingot on the fast forging machine, the upsetting and drawing temperature is 1130℃, the final forging temperature is ≥850℃, and the steel ingot is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.8, the forging ratio of the second upsetting and drawing is 6.7, and the forging ratio of the third upsetting and drawing is 7.4. The last fire drawing has a deformation amount of 40%. After upsetting and drawing, the steel ingot becomes a steel bar with a diameter of φ350mm;

[0064] 2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings;

[0065] 2.1. Cutting: Cut the φ350mm diameter steel bar into 540mm long bars on a sawing machine;

[0066] 2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm; Pre-forging process: preheat at 905℃ for 180min, keep at 1150℃ for 100min, final forging temperature ≥850℃, air cooling;

[0067] 2.3. Annealing: Anneal the forged slab. Annealing process: 680℃ for 240min, air cooling.

[0068] 2.4. Final forging: Forge the slab into a semicircular arc-shaped forging with a die on a forging bed, with a size of φ760mm (outer diameter) × 565mm (height); Final forging process: preheat at 850℃ for 100min, keep at 1150℃ for 80min, final forging temperature ≥850℃, air cooling;

[0069] 2.5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 900℃ insulation for 60min, air cooling; 680℃ insulation for 240min, air cooling.

[0070] 3. Manufacturing of the Receiver

[0071] 3.1. Rough machining of the shape and front and rear ends; rough milling of the semicircular arc forgings, the surface finish after rough machining reaches Ra3.2μm, process: v=90m / min, fz=0.15min / z, ap=2mm.

[0072] 3.2. Heat treatment: heat treatment is performed on the casing parts after rough machining. Heat treatment process: 1030℃, 90min, oil cooling; 565℃, 180min, air cooling.

[0073] 3.3. Finish the appearance and front and rear ends, and the surface finish after finishing reaches Ra0.8μm; process: v=100m / min, fz=0.05min / z, ap=0.5mm. Cutting speed v=250r / min, f=30mm / min.

[0074] 3.4. Shot peening: Shot peening is performed on the outer surface of the finely processed casing parts. The shot peening process is: steel shot S110, shot peening distance 13mm, nozzle pressure 0.34MPa, flow rate 4kg / min. The shot peening intensity is 0.18mmA. The shot peening method is that the parts move in a circular motion, and the nozzle moves up and down. One up and down movement of the nozzle is one cycle, and the part nozzle moves up and down 12 cycles. Take out the parts and observe whether the parts have reached 100% coverage.

[0075] 3.5. Surface protection: Use chemical passivation process to protect the surface of the casing. The chemical passivation process is as follows: chemical degreasing → chemical passivation → neutralization → drying.

[0076] Chemical degreasing; sodium hydroxide (NaOH), 10g / L

[0077] The temperature is 60℃ until all the water is removed. The casing is cleaned in running warm water at 50℃. Then cleaned in running cold water. The surface of the parts should be completely wetted by water, that is, the water film is continuous for 30s.

[0078] Chemical passivation; chemical passivation solution components and process parameters are as follows:

[0079] Phosphoric acid (H3PO4, ρ = 1.70 g / mL), 30 mL / L

[0080] Chromic anhydride (CrO3), 200g / L

[0081] Temperature, 50°C

[0082] Time: 15 minutes

[0083] Neutralization; process parameters and formula:

[0084] Sodium carbonate (Na2CO3 10H2O), 40g / L

[0085] Temperature, room temperature

[0086] Time, 1min

[0087] Drying: Dry in a drying oven at 60°C until the parts are dry. Avoid scratching the parts when removing them from the fixture.

[0088] The performance of the front receiver is as follows:

[0089] Mechanical properties of 1Cr12Ni3Mo2VN steel

[0090]

[0091] Example 2

[0092] 1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm;

[0093] 1.1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1450℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 5h; demolding and annealing the steel ingot after casting, annealing process: 670℃, 5h, air cooling; then electroslag remelting; electroslag remelting uses CaF2:Al2O3:MgO slag system; arcing slag, arcing current 13,000 amperes, voltage 65V, current: 12500A, casting Φ550mm steel ingots, demolding and slow cooling of the steel ingots;

[0094] 1.2. Upset and draw the steel ingot into bars; perform three upsetting and four drawing on the φ550mm steel ingot on the fast forging machine, the upsetting and drawing temperature is 1140℃, the final forging temperature is ≥850℃, and the steel ingot is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.85, the forging ratio of the second upsetting and drawing is 6.76, and the forging ratio of the third upsetting and drawing is 7.68. The deformation of the last fire drawing is 45%. After upsetting and drawing, the steel ingot becomes a steel bar with a diameter of φ350mm;

[0095] 2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings;

[0096] 2.1. Cutting: Cut the φ350mm diameter steel bar into 538mm long bars on a sawing machine;

[0097] 2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm; Pre-forging process: preheat at 900℃ for 180min, keep at 1152℃ for 100min, final forging temperature ≥850℃, air cooling;

[0098] 2.3. Annealing: Anneal the forged slab. Annealing process: 670℃ for 240min, air cooling.

[0099] 2.4. Final forging: Forge the slab into a semicircular arc-shaped forging with a die on a forging bed, with a size of φ760mm (outer diameter) × 565mm (height); Final forging process: preheat at 855℃ for 100min, keep at 1150℃ for 80min, final forging temperature ≥850℃, air cooling;

[0100] 2.5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 905℃ insulation for 60min, air cooling; 675℃ insulation for 240min, air cooling.

[0101] 3. Manufacturing of the Receiver

[0102] 3.1. Rough machining of the shape and front and rear ends; rough milling of the semicircular arc forgings, the surface finish after rough machining reaches Ra3.2μm, process: v=90m / min, fz=0.15min / z, ap=2mm.

[0103] 3.2. Heat treatment: heat treatment is performed on the casing parts after rough machining. Heat treatment process: 1025℃, 90min, oil cooling; 565℃, 180min, air cooling.

[0104] 3.3. Finish the appearance and front and rear ends, and the surface finish after finishing reaches Ra0.8μm; process: v=100m / min, fz=0.05min / z, ap=0.5mm. Cutting speed v=250r / min, f=30mm / min.

[0105] 3.4. Shot peening: Shot peening is performed on the outer surface of the finely processed casing parts. The shot peening process is: steel shot S110, shot peening distance 15mm, nozzle pressure 0.35MPa, flow rate 4kg / min. The shot peening intensity is 0.15mmA. The shot peening method is that the parts move in a circular motion, and the nozzle moves up and down. One up and down movement of the nozzle is one cycle, and the part nozzle moves up and down 12 cycles. Take out the parts and observe whether the parts have reached 100% coverage.

[0106] 3.5. Surface protection: Use chemical passivation process to protect the surface of the casing. The chemical passivation process is as follows: chemical degreasing → chemical passivation → neutralization → drying.

[0107] Chemical degreasing; sodium hydroxide (NaOH), 8g / L

[0108] The temperature is 55℃ until all the water is removed. The casing is cleaned in running warm water at 50℃. Then clean it in running cold water. The surface of the parts should be completely wetted by water, that is, the water film is continuous for 30s.

[0109] Chemical passivation; chemical passivation solution components and process parameters are as follows:

[0110] Phosphoric acid (H3PO4, ρ = 1.70 g / mL), 25 mL / L

[0111] Chromic anhydride (CrO3), 180g / L

[0112] Temperature, 45°C

[0113] Time: 16 minutes

[0114] Neutralization; process parameters and formula:

[0115] Sodium carbonate (Na2CO3 10H2O), 45g / L

[0116] Temperature, room temperature

[0117] Time, 1.5min

[0118] Drying: Dry in a drying oven at 65°C until the parts are dry. Avoid scratching the parts when removing them from the fixture.

[0119] The performance of the front receiver is as follows:

[0120] Mechanical properties of 1Cr12Ni3Mo2VN steel

[0121]

[0122] Example 3

[0123] 1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm;

[0124] 1.1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1500℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 5h; demolding and annealing of the steel ingot after casting, annealing process: 675℃, 5h, air cooling; then electroslag remelting; electroslag remelting uses CaF2:Al2O3:MgO slag system; arcing slag, arcing current 11,000 amperes, voltage 68V, current: 13000A, casting φ550mm steel ingots, demolding and slow cooling of the steel ingots;

[0125] 1.2. Upset and draw the steel ingot into bars; perform three upsetting and four drawing on the φ550mm steel ingot on the fast forging machine, the upsetting and drawing temperature is 1140℃, the final forging temperature is ≥850℃, and the steel ingot is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.75, the forging ratio of the second upsetting and drawing is 6.79, and the forging ratio of the third upsetting and drawing is 8.1. The deformation of the last fire drawing is 45%. After upsetting and drawing, the steel ingot becomes a steel bar with a diameter of φ350mm;

[0126] 2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings;

[0127] 2.1. Cutting: Cut the φ350mm diameter steel bar into a 536mm long bar on a sawing machine;

[0128] 2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm; Pre-forging process: preheat at 900℃ for 180min, keep at 1150℃ for 100min, final forging temperature ≥850℃, air cooling;

[0129] 2.3. Annealing: Anneal the forged slab. Annealing process: 680℃ for 240min, air cooling.

[0130] 2.4. Final forging: Forge the slab into a semicircular arc-shaped forging with a die on a forging bed, with a size of φ760mm (outer diameter) × 565mm (height); Final forging process: preheat at 850℃ for 100min, keep at 1150℃ for 80min, final forging temperature ≥850℃, air cooling;

[0131] 2.5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 900℃ insulation for 60min, air cooling; 670℃ insulation for 240min, air cooling.

[0132] 3. Manufacturing of the Receiver

[0133] 3.1. Rough machining of the shape and front and rear ends; rough milling of the semicircular arc forgings, the surface finish after rough machining reaches Ra3.2μm, process: v=90m / min, fz=0.15min / z, ap=2mm.

[0134] 3.2. Heat treatment: heat treatment is performed on the casing parts after rough machining. Heat treatment process: 1030℃, 90min, oil cooling; 565℃, 180min, air cooling.

[0135] 3.3. Finish the appearance and front and rear ends, and the surface finish after finishing reaches Ra0.8μm; process: v=100m / min, fz=0.05min / z, ap=0.5mm. Cutting speed v=250r / min, f=30mm / min.

[0136] 3.4. Shot peening: Shot peening is performed on the outer surface of the finely processed casing parts. The shot peening process is: steel shot S110, shot peening distance 15mm, nozzle pressure 0.35MPa, flow rate 4kg / min. The shot peening intensity is 0.20mmA. The shot peening method is that the parts move in a circular motion, and the nozzle moves up and down. One up and down movement of the nozzle is one cycle, and the part nozzle moves up and down 12 cycles. Take out the parts and observe whether the parts have reached 100% coverage.

[0137] 3.5. Surface protection: Use chemical passivation process to protect the surface of the casing. The chemical passivation process is as follows: chemical degreasing → chemical passivation → neutralization → drying.

[0138] Chemical degreasing; sodium hydroxide (NaOH), 10g / L

[0139] The temperature is 60℃ until all the water is removed. The casing is cleaned in running warm water at 50℃. Then cleaned in running cold water. The surface of the parts should be completely wetted by water, that is, the water film is continuous for 30s.

[0140] Chemical passivation; chemical passivation solution components and process parameters are as follows:

[0141] Phosphoric acid (H3PO4, ρ = 1.70 g / mL), 20 mL / L

[0142] Chromic anhydride (CrO3), 220g / L

[0143] Temperature, 48°C

[0144] Time: 17 minutes

[0145] Neutralization; process parameters and formula:

[0146] Sodium carbonate (Na2CO3 10H2O), 46g / L

[0147] Temperature, room temperature

[0148] Time, 0.5min

[0149] Drying: Dry in a drying oven at 50°C until the parts are dry. Avoid scratching the parts when removing them from the fixture.

[0150] The performance of the front receiver is as follows:

[0151] Mechanical properties of 1Cr12Ni3Mo2VN steel

[0152]

Claims

1. A method for preparing a new type of large-sized, special-shaped, thin-walled front casing of an engine, characterized in that the preparation steps are as follows: 1.

1. Manufacture 1Cr12Ni3Mo2VN stainless steel bars with a diameter of φ350mm; 1.1.

1. Melting and casting steel ingots; using vacuum induction furnace to smelt and cast φ300mm1Cr12Ni3Mo2VN electrode rods, melting temperature: 1480℃~1530℃; vacuumizing the furnace, vacuum degree ≤1Pa, melting for 4h~5h; demolding and annealing of the steel ingot after casting, annealing process: 650~680℃, 4h~5h, air cooling; then electroslag remelting; arcing and slag removal, arcing current 10,000A~13,000A, voltage 58~68V, current: 11000~13000A, casting φ550mm steel ingots, demolding and slow cooling of the steel ingots; 1.1.

2. Upset and draw the steel ingot into bars; perform three upsetting and four drawing on a fast forging machine for a φ550mm steel ingot, the upsetting and drawing temperature is 1120℃~1140℃, the final forging temperature is ≥850℃, and the steel ingot is slowly cooled after forging; the forging ratio of the first upsetting and drawing is 1.5~2.5, the forging ratio of the second upsetting and drawing is 6~8, and the forging ratio of the third upsetting and drawing is 7~9. The deformation of the last fire drawing is not less than 30%. After upsetting and drawing, the steel ingot becomes a steel bar with a diameter of φ350mm; 1.

2. Manufacture of 1Cr12Ni3Mo2VN stainless steel large die forgings; 1.2.

1. Cutting: Cut the φ350mm diameter steel bar into bars with a length of 535-540mm; 1.2.2 Pre-forging: Forge the bar into a slab on a forging bed with a size of 165mm×365mm×915mm; Pre-forging process: preheat at 900±10℃ for 180min, keep at 1150±10℃ for 100min, final forging temperature ≥850℃, air cooling; 1.2.3 Annealing: Anneal the forged slab. Annealing process: 680±10℃ for 240min, air cooling. 1.2.

4. Final forging: Forge the slab into a semicircular arc-shaped forging with a die on a forging bed, with the size of outer diameter 760mm×height 565mm; Final forging process: preheat at 850±10℃ for 100min, keep at 1150±10℃ for 80min, final forging temperature ≥850℃, air cooling; 1.2.

5. Normalizing + high temperature tempering: normalizing + high temperature tempering of the semicircular arc forgings; normalizing + high temperature tempering process: 900±10℃ insulation for 60min, air cooling; 680±10℃ insulation for 240min, air cooling; 1.

3. Front Receiver Manufacturing 1.3.

1. Rough machining of the shape and front and rear ends; rough milling of the semicircular arc forgings, the surface finish after rough machining reaches Ra3.2μm; 1.3.

2. Heat treatment: heat treatment of the casing parts after rough machining; heat treatment process: 1025-1050℃, 90min, oil cooling; 565±10℃, more than 180min, air cooling; 1.3.

3. Finish the appearance and front and rear ends; the surface finish after finishing reaches Ra0.8μm; 1.3.4, Shot peening; Shot peening is performed on the outer surface of the finely machined casing parts to achieve 100% coverage; the shot peening process is: steel shot S110, shot peening distance 13-15mm, nozzle pressure 0.33-0.35MPa, flow rate 0.36-4kg / min; shot peening intensity is 0.15mmA-0.20mmA; the shot peening method is that the parts move in a circular motion, the nozzle moves up and down, the nozzle moves up and down one round as one cycle, and the part nozzle moves up and down 12 times; 1.3.

5. Surface protection: Use chemical passivation process to protect the surface of the casing; Chemical passivation process: chemical degreasing → chemical passivation → neutralization → drying; Chemical degreasing: Sodium hydroxide (NaOH) 5-15g / L; temperature 50-70℃, until all oil is removed; the casing is cleaned in flowing warm water at 40-60℃, and then in flowing cold water, the surface of the parts is completely wetted by water, that is, the water film is continuous for 30s; Chemical passivation; chemical passivation solution components and process parameters are as follows: Phosphoric acid H3PO4: ρ = 1.70 g / mL, 23-35 mL / L; Chromic anhydride CrO3: 150~250g / L; Temperature: 45-55°C; Time: 10-20 minutes; Neutralization; process parameters and formula: Sodium carbonate Na2CO3·10H2O: 30~50g / L; Temperature: room temperature; Time: 0.5-2 minutes; 1.3.6 Drying: Dry in a drying oven at a temperature not higher than 70°C until the parts are dry; or blow dry with compressed air.

2. The method for preparing a novel large-sized, special-shaped, thin-walled front casing of an engine as claimed in claim 1, characterized in that: The electroslag remelting in step 1.1.1 adopts CaF2:Al2O3:MgO slag system.

3. The method for preparing a novel large-sized, special-shaped, thin-walled front casing of an engine as claimed in claim 1, characterized in that: The 1.3.1 rough machining process: v = 90m / min, fz = 0.15min / z, ap = 2mm.

4. The method for preparing a novel large-sized, special-shaped, thin-walled front casing of an engine as claimed in claim 1, characterized in that: The 1.3.3 finishing process: v = 100m / min, fz = 0.05min / z, ap = 0.5mm, cutting speed v = 250r / min, f = 30mm / min.

Images