Carbonitriding and deep hole anti-permeation method for thin-walled hollow long shaft part

Abstract

The application discloses a kind of thin-walled hollow long shaft part carbonitriding and deep hole anti-permeation method, including the outer surface of thin-walled hollow long shaft part both ends and inner hole end part copper plating protection;Iron oxide scrap preparation is carried out, and iron oxide scrap and diaspore sand are mixed and stirred uniformly to make anti-permeation agent;Water, diaspore, loess are mixed, fully stirred, and kneaded into dough clay to make sealing clay;Anti-permeation agent is filled in the inside of part and sealed with sealing clay;Part is placed in air furnace and dried, and the carburizing atmosphere in controllable atmosphere furnace is adjusted before loading furnace;After drying, the part is loaded into controllable atmosphere furnace, then the carburizing atmosphere is adjusted after loading furnace;Carburizing agent methanol and propane are introduced into the furnace for diffusion;The part after heat preservation is quenched;Then the part is ice cooled;Then tempering is carried out.The application avoids using toxic gas toluene, is more safe and environmentally friendly, and can be widely applied in inner hole anti-permeation process.

Description

Technical Field

[0001] This invention belongs to the field of chemical heat treatment technology, specifically to a method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts. Background Technology

[0002] 18Cr2Ni4WA steel, with a total alloy element content greater than 5%, is a commonly used low-carbon high-alloy structural steel. This steel has high hardenability and excellent comprehensive mechanical properties. In particular, the high Ni content gives the steel good strength, toughness, and hardenability, making it especially suitable for manufacturing various gears and splined shafts. These parts require high surface hardness and wear resistance, thus necessitating carbonitriding treatment. When carbonitriding the spline teeth on the outer surface of thin-walled hollow long shafts, non-carbonitriding protection is required. Conventional methods use copper plating for protection, but copper plating cannot be applied to the deep hollow interior of thin-walled hollow long shafts. This protection becomes a major challenge in the carbonitriding treatment of thin-walled hollow long shafts. Furthermore, carbonitriding requires high-temperature treatment, and deformation after high-temperature treatment is another problem hindering the use of thin-walled hollow long shafts. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts. This method avoids the use of toxic toluene gas, making it safer and more environmentally friendly, and can be widely applied in internal hole seepage prevention processes.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts includes the following steps:

[0006] Step 1: Apply copper plating to the outer surfaces of both ends and the inner hole ends of the thin-walled hollow long shaft part for protection.

[0007] Step 2: Prepare iron oxide chips and mix them with aluminum oxide sand at a mass percentage of 1:(2-4) to make an impermeable agent;

[0008] Step 3: Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay to make sealing clay;

[0009] Step 4: Fill the inside of the part with the anti-seepage agent and seal it with sealing clay;

[0010] Step 5: Place the parts from Step 4 into an air oven for drying at a temperature of 150-200℃ for 2-3 hours.

[0011] Step 6: Adjust the carburizing atmosphere in the controlled atmosphere furnace before loading; load the dried parts from Step 5 into the controlled atmosphere furnace, and then adjust the carburizing atmosphere after loading.

[0012] Step 7: Set the carbon potential inside the furnace to 1.0-1.2, introduce the carburizing agent methanol and propane into the furnace, with a methanol flow rate of 2-3 L / h, a propane flow rate of 2-3.5 L / min, and an ammonia flow rate of 1-2 L / h to bring the carbon potential inside the furnace to 1.0-1.2, hold for 0.5-2 h, and perform carbonitriding.

[0013] Step 8: Set the carbon potential inside the furnace to 0.8-1.0, and introduce the carburizing agent methanol and propane into the furnace. The flow rate of methanol is 1.5-2.5 L / h, the flow rate of propane is 1.5-3 L / min, and the flow rate of ammonia is 1-2 L / h, so that the carbon potential inside the furnace reaches 0.8-1.0. Hold the temperature for 20-40 min to allow diffusion.

[0014] Step 9: Quench and cool the parts after heat preservation in Step 8; then freeze the parts; then temper them.

[0015] Preferably, in step 1, the outer surface and the inner hole 10-20mm from the end of the thin-walled hollow long shaft part are protected by copper plating using electroplating.

[0016] Preferably, in step 2, the iron oxide chips are prepared by: heat-treating steel carbon steel or structural steel parts in an air resistance furnace to produce an oxide scale on the surface, and repeatedly rolling the oxide scale to produce iron oxide chips of 3-5mm.

[0017] Preferably, in step 4, stainless steel plates are selected and two rectangular gaskets are made. The width of the gaskets is equal to the outer diameter of the end face of the thin-walled hollow long shaft. A through hole is machined in the center of the gasket. Sealing clay is evenly applied to one gasket with a thickness of 4-6 mm. The gasket with the sealing clay is installed on one end of an M8 screw with a length greater than the thin-walled hollow long shaft by 50-100 mm, and a nut is installed on the side without sealing clay. The screw is passed through the inner hole of the thin-walled hollow long shaft with the sealing clay applied, and the end face is in contact with the gasket with the sealing clay. Then, an anti-seepage agent is filled into the inner hole until it is full. Then, sealing clay is evenly applied to the other gasket with a thickness of 4-6 mm. The gasket with the sealing clay is installed on the M8 screw, and the side with the sealing clay applied is in contact with the end face of the other end of the thin-walled hollow long shaft. Then, a nut is screwed on the screw to ensure that the gasket is tightly fitted to both ends of the thin-walled hollow long shaft.

[0018] Preferably, in step 6, before loading the furnace, the controlled atmosphere furnace is heated to 830-860℃ and the carbon potential inside the furnace is set to 0.6-0.8. The carburizing agent methanol and propane are introduced into the furnace, with a methanol flow rate of 1-2L / h and a propane flow rate of 1-3L / min. The furnace is kept at this temperature for 30-40min to bring the carbon potential inside the furnace to 0.6-0.8.

[0019] Preferably, in step 6, after loading the furnace, the parts are heated to (830-860)℃ along with the furnace, and the carbon potential (C%) in the furnace is set to 0.8-1.0. The carburizing agent methanol and propane are introduced into the furnace, with a methanol flow rate of 1.5-2.5L / h and a propane flow rate of 1.5-3L / min, so that the carbon potential (C%) in the furnace reaches 0.8-1.0, and the temperature is maintained for 5-15min.

[0020] Preferably, in step 9, during quenching and cooling, the part after heat preservation is directly quenched into quenching oil at 40-60℃ for cooling, and the cooling time is 30-40 minutes.

[0021] The quenched and cooled workpieces are cleaned and placed in a chiller within 2 hours. They are kept at -70-80℃ for 1-1.5 hours and then air-cooled for 0.5-1 hours after being taken out of the furnace.

[0022] The parts are then placed in a pit-type tempering furnace for tempering at a temperature of 150-170℃, held for 3-4 hours, and then air-cooled.

[0023] Preferably, in step 9, after tempering, a depth test is performed. The part is dissected and a sample is prepared. After the sample is polished, it is etched with nitric acid alcohol. The depth of the carbonitriding layer is detected using a 100x metallographic microscope.

[0024] Preferably, in step 9, after tempering, a hardness test is performed. The surface of the part is polished and a microhardness tester is used to test the hardness. The surface hardness of the carbonitriding layer is required to be ≥88HR15N, and the core hardness is 37-43HRC.

[0025] Preferably, in step 9, after tempering, warping deformation monitoring is performed, and a coordinate measuring machine is used to monitor the warping deformation of the thin-walled hollow long axis, with the deformation amount being less than or equal to 0.25 mm.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] This invention provides a carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts. A reasonable carbonitriding method is used to carbonitride thin-walled hollow long shaft parts made of 18Cr2Ni4WA material, improving hardness and wear resistance while reducing part deformation. Simultaneously, a self-made clay and stainless steel gasket are used to seal one end of the inner hole, which is then filled with a mixture of alumina sand and iron oxide as a seepage prevention agent. After filling, the other end of the inner hole is sealed with self-made clay and threaded gaskets to prevent seepage in the deep hole.

[0028] Thin-walled hollow long shaft parts made of 18Cr2Ni4WA alloy steel are typically carbonitrided using toluene and ammonia as the infiltrating agent, with non-infiltrated surfaces protected by copper plating or a residual method. This invention studies a carbonitriding method for 18Cr2Ni4WA alloy steel using methanol, propane, and ammonia as infiltrating agents. This method avoids the use of toxic toluene gas, making it safer and more environmentally friendly. Furthermore, this invention studies an internal hole seepage prevention method and a method for preparing sealing clay, which is simple to operate and has low cost, and can be widely applied in internal hole seepage prevention processes. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a thin-walled hollow long shaft part according to Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of a thin-walled hollow long shaft part according to Embodiment 2 of the present invention.

[0031] Figure 3 This is a schematic diagram of a thin-walled hollow long shaft part according to Embodiment 3 of the present invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0033] This invention discloses a carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts. A reasonable carbonitriding method is used to carbonitride thin-walled hollow long shaft parts made of 18Cr2Ni4WA material, improving hardness and wear resistance while reducing part deformation. Simultaneously, a self-made clay and stainless steel gasket are used to seal one end of the inner hole, and then a mixture of alumina sand and iron oxide as a seepage-proofing agent is filled into the hole. After filling, the other end of the inner hole is sealed with self-made clay and threaded gaskets to prevent seepage in the deep hole.

[0034] The present invention discloses a carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts, comprising the following steps: S1 Protection of the outer surface and the end of the inner hole.

[0035] Thin-walled hollow long shafts require carbonitriding of the spline teeth on the outer surface of both ends, while other parts are not carbonitrided. Copper plating is used to protect the outer surface and the inner hole 10-20mm from the end by electroplating.

[0036] Preparation of S2 iron oxide chips

[0037] When carbon steel or structural steel parts are heat-treated in an air resistance furnace, an oxide scale will be generated on the surface. This oxide scale is repeatedly rolled on a stainless steel platform to produce 3-5mm iron oxide chips.

[0038] S3 waterproofing agent preparation

[0039] The iron oxide chips prepared by S1 are mixed with 100-120 mesh aluminum oxide sand at a mass percentage of 1:(2-4) and stirred thoroughly.

[0040] S4 Sealing Clay Preparation

[0041] Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay.

[0042] S5 waterproofing agent filling and sealing

[0043] Select a 3mm thick stainless steel sheet and make two rectangular gaskets. The width of the gaskets is approximately equal to the outer diameter of the end face of the thin-walled hollow long shaft. Drill an Φ8 through hole in the center of each gasket. Apply the sealing clay prepared in S4 evenly to one gasket, with a thickness of 4-6mm. Install the gasket with the sealing clay on one end of an M8 screw that is 50-100mm longer than the thin-walled hollow long shaft. Attach a nut to the side without the sealing clay. Pass the screw through the inner hole of the thin-walled hollow long shaft with the sealing clay on the side, ensuring the end face is flush with the gasket. Then fill the inner hole with the anti-seepage agent prepared in S3 until it is full. Apply the sealing clay prepared in S4 evenly to the other gasket, with a thickness of 4-6mm. Install the gasket with the sealing clay on the M8 screw, ensuring the side with the sealing clay is flush with the other end face of the thin-walled hollow long shaft. Finally, screw on a nut to the screw, ensuring the gasket is tightly flush with both ends of the thin-walled hollow long shaft.

[0044] S6 tooling clamping

[0045] The workpiece, filled and sealed with S5, is placed into the fabricated flower stand fixture and hung vertically to prevent deformation.

[0046] S7 Sealing Clay Drying

[0047] The workpiece clamped in S6 is placed in an air oven for drying at a temperature of 150-200℃ for 2-3 hours.

[0048] S8 pre-charging carburizing atmosphere conditioning

[0049] The controlled atmosphere furnace is heated to (830-860)℃, and the carbon potential (C%) in the furnace is set to 0.6-0.8. Methanol and propane, which are carburizing agents, are introduced into the furnace. The flow rate of methanol is 1-2L / h, and the flow rate of propane is 1-3L / min. The furnace is held at this temperature for 30-40min to bring the carbon potential (C%) in the furnace to 0.6-0.8.

[0050] S9 post-charging carburizing atmosphere adjustment

[0051] After the workpiece and the flower stand fixture have been dried in S7, they are placed into the controlled atmosphere furnace with the carburizing atmosphere adjusted in S8. The furnace temperature is raised to (830-860)℃, and the carbon potential (C%) in the furnace is set to 0.8-1.0. Methanol and propane, the carburizing agents, are introduced into the furnace at a flow rate of 1.5-2.5L / h and a flow rate of 1.5-3L / min, so that the carbon potential (C%) in the furnace reaches 0.8-1.0. The furnace is then held at this temperature for 5-15 minutes.

[0052] S10 carbonitriding

[0053] After completing S9, set the carbon potential (C%) in the furnace to 1.0-1.2, and introduce the carburizing agent methanol and propane into the furnace. The flow rate of methanol is 2-3 L / h, the flow rate of propane is 2-3.5 L / min, and the flow rate of ammonia is 1-2 L / h to bring the carbon potential (C%) in the furnace to 1.0-1.2. Hold the furnace at this temperature for 0.5-2 hours.

[0054] S11 diffusion

[0055] After completing S10, set the carbon potential (C%) in the furnace to 0.8-1.0, and introduce carburizing agent methanol and propane into the furnace. The flow rate of methanol is 1.5-2.5 L / h, the flow rate of propane is 1.5-3 L / min, and the flow rate of ammonia is 1-2 L / h, so that the carbon potential (C%) in the furnace reaches 0.8-1.0, and hold for 20-40 min.

[0056] S12 quenching

[0057] After the S11 heat treatment is completed, the workpiece is directly quenched in quenching oil at 40-60℃ for cooling, with a cooling time of 30-40 minutes.

[0058] S13 Cold

[0059] After completing the S12 workpiece, clean it thoroughly and place it in a chiller within 2 hours. Keep it at -70-80℃ for 1-1.5 hours, then air-cool it for 0.5-1 hours.

[0060] S14 Tempering

[0061] After completing the S13 workpiece, it is placed in a pit-type tempering furnace for tempering at a temperature of 150-170℃. The workpiece is held at this temperature for 3-4 hours and then air-cooled.

[0062] S15 Depth Detection

[0063] After the sample was tempered in step S14, it was dissected and prepared. After polishing, the sample was etched with nitric acid alcohol and the depth of the carbonitriding layer was detected using a 100x metallographic microscope.

[0064] S16 Hardness Test

[0065] After tempering in step S14, the sample surface is directly polished and hardness is tested using a microhardness tester. The surface hardness of the carbonitriding layer is required to be ≥88HR15N and the core hardness is 37-43HRC.

[0066] S17 Warping Deformation Monitoring

[0067] For the completed S14 part, a coordinate measuring machine is used to monitor the warping deformation of the thin-walled hollow long shaft, and the deformation is less than or equal to 0.25mm.

[0068] This invention discloses a carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts, applied to thin-walled hollow long shaft parts made of 18Cr2Ni4WA alloy steel. Typically, carbonitriding uses toluene and ammonia as the infiltrating agent, with non-infiltrated surfaces protected by copper plating or a residual method. This invention studies a carbonitriding method for 18Cr2Ni4WA alloy steel using methanol, propane, and ammonia as infiltrating agents. This method avoids the use of toxic toluene gas, making it safer and more environmentally friendly. Simultaneously, this invention studies an internal hole seepage prevention method and a method for preparing sealing clay, which is simple to operate and has low cost, and can be widely applied in internal hole seepage prevention processes.

[0069] Example 1:

[0070] like Figure 1 As shown, the present invention provides a method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts, comprising the following steps:

[0071] S1 outer surface and inner hole end protection

[0072] Thin-walled hollow long shafts require carbonitriding of the spline teeth on the outer surface of both ends, while other parts are not carbonitrided. Copper plating is used to protect the outer surface and the inner hole 10-20mm from the end by electroplating.

[0073] Preparation of S2 iron oxide chips

[0074] When carbon steel or structural steel parts are heat-treated in an air resistance furnace, an oxide scale will be generated on the surface. This oxide scale is repeatedly rolled on a stainless steel platform to produce 3-5mm iron oxide chips.

[0075] S3 waterproofing agent preparation

[0076] The iron oxide chips prepared by S1 are mixed with 100-120 mesh aluminum oxide sand at a mass percentage of 1:(2-4) and stirred thoroughly.

[0077] S4 Sealing Clay Preparation

[0078] Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay.

[0079] S5 waterproofing agent filling and sealing

[0080] Select 3mm thick stainless steel sheet and fabricate two rectangular gaskets, one measuring 60×30×3mm and the other 60×50×3mm. Drill an 8mm through hole in the center of each gasket. Evenly apply the sealant clay prepared with S4 to the 60×50×3mm gasket to a thickness of 4mm. Attach the gasket with the sealant clay to one end of a 610mm long M8 threaded rod, and attach a nut to the unsealed side. Pass the threaded rod through the sealant clay-coated end of the threaded rod. The inner hole of the thin-walled hollow long shaft with a diameter of Φ52.5mm is made of soil. The end face is attached to the sealing clay gasket. Then, the anti-seepage agent prepared by S3 is filled into the inner hole until it is full. Then, the sealing clay prepared by S4 is evenly applied to the 60×35×3mm gasket with a thickness of 4mm. The gasket with the sealing clay is installed on the M8 screw, with the side with the sealing clay attached to the other end face of the thin-walled hollow long shaft. Then, the nut is screwed on the screw to ensure that the gasket is tightly attached to both ends of the thin-walled hollow long shaft.

[0081] S6 tooling clamping

[0082] The workpiece, filled and sealed with S5, is placed into the fabricated flower stand fixture and hung vertically to prevent deformation.

[0083] S7 Sealing Clay Drying

[0084] The workpiece clamped by S6 is placed in an air oven for drying at a temperature of 150°C for 3 hours.

[0085] S8 pre-charging carburizing atmosphere conditioning

[0086] The controlled atmosphere furnace was heated to 830±10℃, and the carbon potential (C%) in the furnace was set to 0.6. Methanol and propane, which are carburizing agents, were introduced into the furnace at a flow rate of 1L / h and a flow rate of 1L / min. The furnace was kept at this temperature for 30 minutes to bring the carbon potential (C%) in the furnace to 0.6.

[0087] S9 post-charging carburizing atmosphere adjustment

[0088] The workpiece and the flower stand fixture that have been dried in S7 are placed into the controlled atmosphere furnace with the carburizing atmosphere adjusted in S8. The furnace is heated to 830±10℃ and the carbon potential (C%) in the furnace is set to 0.8. Methanol and propane, the carburizing agents, are introduced into the furnace at a flow rate of 1.5L / h and a flow rate of 1.5L / min, so that the carbon potential (C%) in the furnace reaches 0.8. The furnace is then held at this temperature for 5 minutes.

[0089] S10 carbonitriding

[0090] After completing S9, set the carbon potential (C%) in the furnace to 1.0, and introduce carburizing agent methanol and propane into the furnace. The flow rate of methanol is 2L / h, the flow rate of propane is 2L / min, and the flow rate of ammonia is 1L / h to bring the carbon potential (C%) in the furnace to 1.0. Maintain the temperature for 0.5h.

[0091] S11 diffusion

[0092] After completing S10, set the carbon potential (C%) in the furnace to 0.8, and introduce carburizing agent methanol and propane into the furnace. The flow rate of methanol is 1.5 L / h, the flow rate of propane is 1.5 L / min, and the flow rate of ammonia is 1 L / h, so that the carbon potential (C%) in the furnace reaches 0.8, and hold for 20 min.

[0093] S12 quenching

[0094] After the S11 heat treatment is completed, the workpiece is directly quenched in 40℃ quenching oil for cooling for 30 minutes.

[0095] S13 Cold

[0096] After completing S12, clean the workpiece thoroughly, load it into the chiller after 1 hour, keep it at -70-80℃ for 1 hour, and then air-cool it for 0.5 hours.

[0097] S14 Tempering

[0098] The completed S13 workpiece is then placed in a pit-type tempering furnace for tempering at a temperature of 150℃. After holding at this temperature for 4 hours, the workpiece is removed from the furnace and air-cooled.

[0099] S15 Depth Detection

[0100] After the specimen was tempered in step S14, it was dissected and prepared. After polishing, the specimen was etched with nitric acid alcohol. The depth of the carbonitriding layer in the spline was measured to be 0.1-0.15 mm and the depth of the carbonitriding layer in the inner hole was 0 mm using a 100x metallographic microscope.

[0101] S16 Hardness Test

[0102] The surface of the sample after tempering in step S14 is directly polished, and the hardness is tested using a microhardness tester. The surface hardness of the carbonitriding layer is required to be 91.5HR15N, and the core hardness is required to be 42.5-43HRC.

[0103] S17 Warping Deformation Monitoring

[0104] For the completed S14 part, a coordinate measuring machine was used to monitor the warping deformation of the thin-walled hollow long shaft, with a deformation of 0.15mm.

[0105] Example 2:

[0106] like Figure 2 As shown, the present invention provides a method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts, comprising the following steps:

[0107] S1 outer surface and inner hole end protection

[0108] Thin-walled hollow long shafts require carbonitriding of the spline teeth on the outer surface of both ends, while other parts are not carbonitrided. Copper plating is used to protect the outer surface and the inner hole 10-20mm from the end by electroplating.

[0109] Preparation of S2 iron oxide chips

[0110] When carbon steel or structural steel parts are heat-treated in an air resistance furnace, an oxide scale will be generated on the surface. This oxide scale is repeatedly rolled on a stainless steel platform to produce 3-5mm iron oxide chips.

[0111] S3 waterproofing agent preparation

[0112] The iron oxide chips prepared by S1 are mixed with 100-120 mesh aluminum oxide sand at a mass percentage of 1:(2-4) and stirred thoroughly.

[0113] S4 Sealing Clay Preparation

[0114] Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay.

[0115] S5 waterproofing agent filling and sealing

[0116] Select 3mm thick stainless steel sheet and fabricate two rectangular gaskets, one measuring 60×26×3mm and the other 60×50×3mm. Drill an 8mm through hole in the center of each gasket. Evenly apply the sealant clay prepared with S4 to the 60×55×3mm gasket to a thickness of 4mm. Mount the gasket with the sealant clay onto one end of a 610mm long M8 threaded rod, and attach a nut to the uncoated side. Pass the threaded rod through the sealant clay-coated side. The inner hole of the thin-walled hollow long shaft with a diameter of Φ52.5mm is made of soil. The end face is attached to the sealing clay gasket. Then, the anti-seepage agent prepared by S3 is filled into the inner hole until it is full. Then, the sealing clay prepared by S4 is evenly applied to the 60×35×3mm gasket with a thickness of 4mm. The gasket with the sealing clay is installed on the M8 screw, with the side with the sealing clay attached to the other end face of the thin-walled hollow long shaft. Then, the nut is screwed on the screw to ensure that the gasket is tightly attached to both ends of the thin-walled hollow long shaft.

[0117] S6 tooling clamping

[0118] The workpiece, filled and sealed with S5, is placed into the fabricated flower stand fixture and hung vertically to prevent deformation.

[0119] S7 Sealing Clay Drying

[0120] The workpiece clamped in S6 is placed in an air oven for drying at 180℃ for 2.5 hours.

[0121] S8 pre-charging carburizing atmosphere conditioning

[0122] The controlled atmosphere furnace was heated to 840±10℃, and the carbon potential (C%) in the furnace was set to 0.7. Methanol and propane, which are carburizing agents, were introduced into the furnace at a flow rate of 1.5L / h and a flow rate of 1.5L / min. The furnace was held at this temperature for 35 minutes to bring the carbon potential (C%) in the furnace to 0.7.

[0123] S9 post-charging carburizing atmosphere adjustment

[0124] The workpiece and the flower stand fixture that have been dried in S7 are placed into the controlled atmosphere furnace with the carburizing atmosphere adjusted in S8. The furnace is heated to 840±10℃ and the carbon potential (C%) in the furnace is set to 0.9. Methanol and propane, the carburizing agents, are introduced into the furnace at a flow rate of 2L / h and a flow rate of 2.5L / min, so that the carbon potential (C%) in the furnace reaches 0.9. The furnace is then held at this temperature for 10min.

[0125] S10 carbonitriding

[0126] After completing S9, set the carbon potential (C%) in the furnace to 1.1, and introduce carburizing agent methanol and propane into the furnace. The flow rate of methanol is 2.5 L / h, the flow rate of propane is 2.5 L / min, and the flow rate of ammonia is 1.5 L / h to bring the carbon potential (C%) in the furnace to 1.1. Hold the furnace at this temperature for 1 hour.

[0127] S11 diffusion

[0128] After completing S10, set the carbon potential (C%) in the furnace to 0.9, and introduce the carburizing agent methanol and propane into the furnace. The flow rate of methanol is 2L / h, the flow rate of propane is 2L / min, and the flow rate of ammonia is 1.5L / h, so that the carbon potential (C%) in the furnace reaches 0.9, and hold for 30 minutes.

[0129] S12 quenching

[0130] After the S11 heat treatment is completed, the workpiece is directly quenched in 50℃ quenching oil for cooling for 30 minutes.

[0131] S13 Cold

[0132] After completing S12, clean the workpiece thoroughly, load it into the chiller after 1.5 hours, keep it at -70-80℃ for 1.5 hours, and then air-cool it for 0.5 hours.

[0133] S14 Tempering

[0134] The workpieces that have been completed to S13 are then placed in a pit-type tempering furnace for tempering at a temperature of 160℃ and held for 3.5 hours before being air-cooled.

[0135] S15 Depth Detection

[0136] After the specimen was tempered in step S14, it was dissected and prepared. After polishing, the specimen was etched with nitric acid alcohol. The depth of the carbonitriding layer in the spline was measured to be 0.25-0.30 mm and the depth of the carbonitriding layer in the inner hole was 0 mm using a 100x metallographic microscope.

[0137] S16 Hardness Test

[0138] After tempering in step S14, the sample surface is directly polished and hardness is tested using a microhardness tester. The surface hardness of the carbonitriding layer is required to be 90-90.5HR15N, and the core hardness is required to be 40-41HRC.

[0139] S17 Warping Deformation Monitoring

[0140] For the completed S14 part, a coordinate measuring machine was used to monitor the warping deformation of the thin-walled hollow long shaft, with a deformation of 0.2 mm.

[0141] Example 3:

[0142] like Figure 3As shown, the present invention provides a method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts, comprising the following steps:

[0143] S1 outer surface and inner hole end protection

[0144] Thin-walled hollow long shafts require carbonitriding of the spline teeth on the outer surface of both ends, while other parts are not carbonitrided. Copper plating is used to protect the outer surface and the inner hole 10-20mm from the end by electroplating.

[0145] Preparation of S2 iron oxide chips

[0146] When carbon steel or structural steel parts are heat-treated in an air resistance furnace, an oxide scale will be generated on the surface. This oxide scale is repeatedly rolled on a stainless steel platform to produce 3-5mm iron oxide chips.

[0147] S3 waterproofing agent preparation

[0148] The iron oxide chips prepared by S1 are mixed with 100-120 mesh aluminum oxide sand at a mass percentage of 1:(2-4) and stirred thoroughly.

[0149] S4 Sealing Clay Preparation

[0150] Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay.

[0151] S5 waterproofing agent filling and sealing

[0152] Select 3mm thick stainless steel sheet and fabricate two rectangular gaskets, one measuring 60×26×3mm and the other 60×50×3mm. Drill an 8mm through hole in the center of each gasket. Evenly apply the sealant clay prepared with S4 to the 60×55×3mm gasket to a thickness of 4mm. Mount the gasket with the sealant clay onto one end of a 610mm long M8 threaded rod, and attach a nut to the uncoated side. Pass the threaded rod through the sealant clay-coated side. The inner hole of the thin-walled hollow long shaft with a diameter of Φ52.5mm is made of soil. The end face is attached to the sealing clay gasket. Then, the anti-seepage agent prepared by S3 is filled into the inner hole until it is full. Then, the sealing clay prepared by S4 is evenly applied to the 60×35×3mm gasket with a thickness of 4mm. The gasket with the sealing clay is installed on the M8 screw, with the side with the sealing clay attached to the other end face of the thin-walled hollow long shaft. Then, the nut is screwed on the screw to ensure that the gasket is tightly attached to both ends of the thin-walled hollow long shaft.

[0153] S6 tooling clamping

[0154] The workpiece, filled and sealed with S5, is placed into the fabricated flower stand fixture and hung vertically to prevent deformation.

[0155] S7 Sealing Clay Drying

[0156] The workpiece clamped by S7 is placed in an air oven for drying at a temperature of 150℃ for 2 hours.

[0157] S8 pre-charging carburizing atmosphere conditioning

[0158] The controlled atmosphere furnace was heated to 860±10℃, and the carbon potential (C%) in the furnace was set to 0.8. Methanol and propane, which are carburizing agents, were introduced into the furnace at a flow rate of 2L / h and a flow rate of 2L / min. The furnace was kept at this temperature for 40min to bring the carbon potential (C%) in the furnace to 0.8.

[0159] S9 post-charging carburizing atmosphere adjustment

[0160] The workpiece and the flower stand fixture that have been dried in S7 are placed into the controlled atmosphere furnace with the carburizing atmosphere adjusted in S8. The furnace is heated to 860±10℃ and the carbon potential (C%) in the furnace is set to 1.0. Methanol and propane, the carburizing agents, are introduced into the furnace at a flow rate of 2.5L / h and a flow rate of 3L / min, so that the carbon potential (C%) in the furnace reaches 1.0. The furnace is then held at this temperature for 15min.

[0161] S10 carbonitriding

[0162] After completing S9, set the carbon potential (C%) in the furnace to 1.2, and introduce the carburizing agent methanol and propane into the furnace. The flow rate of methanol is 3L / h, the flow rate of propane is 3.5L / min, and the flow rate of ammonia is 2L / h, so that the carbon potential (C%) in the furnace reaches 1.2, and keep it at that temperature for 2 hours.

[0163] S11 diffusion

[0164] After completing S10, set the carbon potential (C%) in the furnace to 1.0, and introduce carburizing agent methanol and propane into the furnace. The flow rate of methanol is 2.5 L / h, the flow rate of propane is 3 L / min, and the flow rate of ammonia is 2 L / h, so that the carbon potential (C%) in the furnace reaches 1.0, and hold for 40 min.

[0165] S12 quenching

[0166] After the S11 heat treatment is completed, the workpiece is directly quenched in quenching oil at 60℃ for cooling, with a cooling time of 40 minutes.

[0167] S13 Cold

[0168] After completing the S12 workpiece, clean it thoroughly and place it in a chiller within 2 hours. Keep it at -70 to -80℃ for 1.5 hours, then air-cool it for 1 hour after removing it from the furnace.

[0169] S14 Tempering

[0170] The completed S13 workpiece is then placed in a pit-type tempering furnace for tempering at a temperature of 170℃. After holding at this temperature for 3 hours, the workpiece is removed from the furnace and air-cooled.

[0171] S15 Depth Detection

[0172] After the specimen was tempered in step S14, it was dissected and prepared. After polishing, the specimen was etched with nitric acid alcohol. The depth of the carbonitriding layer in the spline was measured to be 0.35-0.4 mm and the depth of the carbonitriding layer in the inner hole was 0 mm using a 100x metallographic microscope.

[0173] S16 Hardness Test

[0174] After tempering in step S14, the sample surface is directly polished and hardness is tested using a microhardness tester. The surface hardness of the carbonitriding layer is required to be 89-89.5HR15N, and the core hardness is required to be 39-40HRC.

[0175] S17 Warping Deformation Monitoring

[0176] For the completed S14 part, a coordinate measuring machine was used to monitor the warping deformation of the thin-walled hollow long shaft, with a deformation of 0.2 mm.

Claims

1. A method for carbonitriding and deep-hole seepage prevention of thin-walled hollow long shaft parts, characterized in that, Includes the following steps, Step 1: Apply copper plating to the outer surfaces of both ends and the inner hole ends of the thin-walled hollow long shaft part for protection. Step 2: Prepare iron oxide chips and mix them with aluminum oxide sand at a mass percentage of 1:(2-4) to make an impermeable agent; Step 3: Mix water, 100-120 mesh aluminum oxide, and loess in a mass percentage ratio of 1:(2-3):(3-5), stir thoroughly, and knead into a dough-like clay to make sealing clay; Step 4: Fill the inside of the part with the anti-seepage agent and seal it with sealing clay; Step 5: Place the parts from Step 4 into an air oven for drying at a temperature of 150-200℃ for 2-3 hours. Step 6: Adjust the carburizing atmosphere in the controlled atmosphere furnace before loading. Load the dried parts from Step 5 into the controlled atmosphere furnace, and then adjust the carburizing atmosphere after loading. Before loading, heat the controlled atmosphere furnace to 830-860℃ and set the carbon potential inside the furnace to 0.6-0.

8. Introduce carburizing agents methanol and propane into the furnace at a flow rate of 1-2 L / h and 1-3 L / min, and hold for 30-40 minutes to achieve a carbon potential of 0.6-0.

8. After loading, heat the parts to 830-860℃ with the furnace, and set the carbon potential inside the furnace to 0.8-1.

0. Introduce carburizing agents methanol and propane into the furnace at a flow rate of 1.5-2.5 L / h and 1.5-3 L / min, and hold for 5-15 minutes. Step 7: Set the carbon potential inside the furnace to 1.0-1.2, introduce the carburizing agent methanol and propane into the furnace, with a methanol flow rate of 2-3 L / h, a propane flow rate of 2-3.5 L / min, and an ammonia flow rate of 1-2 L / h to bring the carbon potential inside the furnace to 1.0-1.2, hold for 0.5-2 hours, and perform carbonitriding. Step 8: Set the carbon potential inside the furnace to 0.8-1.0, and introduce the carburizing agent methanol and propane into the furnace. The flow rate of methanol is 1.5-2.5 L / h, the flow rate of propane is 1.5-3 L / min, and the flow rate of ammonia is 1-2 L / h, so that the carbon potential inside the furnace reaches 0.8-1.

0. Hold the temperature for 20-40 min to allow diffusion. Step 9: Quench and cool the parts after heat preservation in Step 8; then freeze the parts; then temper them; during quenching and cooling, immerse the parts after heat preservation directly in quenching oil at 40-60℃ for 30-40 minutes. The quenched and cooled workpieces are cleaned and placed in a chiller within 2 hours. They are kept at -70-80℃ for 1-1.5 hours and then air-cooled for 0.5-1 hours after being taken out of the furnace. The parts are then placed in a pit-type tempering furnace for tempering at a temperature of 150-170℃, held for 3-4 hours, and then air-cooled.

2. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 1, the outer surface and the inner hole 10-20mm from the end of the thin-walled hollow long shaft part are protected by copper plating using electroplating.

3. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 2, the preparation process of the iron oxide chips is as follows: steel carbon steel or structural steel parts are heat-treated in an air resistance furnace to produce oxide scale on the surface. The oxide scale is repeatedly rolled to produce iron oxide chips of 3-5mm.

4. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 4, stainless steel plates are selected and two rectangular gaskets are made. The width of the gaskets is equal to the outer diameter of the end face of the thin-walled hollow long shaft. A through hole is machined in the center of the gasket. The sealing clay is evenly applied to one gasket with a thickness of 4-6 mm. The gasket with the sealing clay is installed on one end of an M8 screw with a length greater than the thin-walled hollow long shaft by 50-100 mm. A nut is installed on the side without the sealing clay. The screw is passed through the inner hole of the thin-walled hollow long shaft with the sealing clay applied, and the end face is in contact with the gasket with the sealing clay. Then, the inner hole is filled with an anti-seepage agent until it is full. Then, the sealing clay is evenly applied to the other gasket with a thickness of 4-6 mm. The gasket with the sealing clay is installed on the M8 screw, and the side with the sealing clay applied is in contact with the end face of the other end of the thin-walled hollow long shaft. Then, a nut is screwed on the screw to ensure that the gasket is tightly fitted to both ends of the thin-walled hollow long shaft.

5. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 9, after tempering, a depth test is performed. The part is dissected and a sample is prepared. After the sample is polished, it is etched with nitric acid alcohol. The depth of the carbonitriding layer is detected using a 100x metallographic microscope.

6. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 9, after tempering, a hardness test is performed. The surface of the part is polished and a microhardness tester is used to test the hardness. The surface hardness of the carbonitriding layer is required to be ≥88HR15N, and the core hardness is 37-43HRC.

7. The carbonitriding and deep-hole seepage prevention method for thin-walled hollow long shaft parts according to claim 1, characterized in that, In step 9, after tempering, warping deformation is monitored. A coordinate measuring machine is used to monitor the warping deformation of the long axis of the thin-walled hollow core. The deformation is less than or equal to 0.25 mm.

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