Extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons

Abstract

The invention discloses an extrusion production method of a boron-containing seamless steel pipe for shielding nuclear power fuel neutrons. The extrusion production method comprises blank extrusion preparation procedures such as blank outer diameter selection and surface treatment, saw cutting, deep hole, horn mouth and arc machining. The heating temperature and the heating time of a preheating section, a heating section and a soaking section of the annular furnace are set; induction furnace heating: setting the heating temperature, the heating power and the heating time of a primary induction furnace and a secondary induction furnace; the deformation process comprises chambering and extruding, and chambering deformation is a pre-chambering process of extruding deformation. A newly designed tool and die participating in deformation comprises the design of a broaching cone, and the diameter, the cone angle and other key dimensions of the broaching cone are stipulated; design contents such as the diameter of a working belt of the shearing ring and tolerance fit of the outer diameter of the shearing ring are stipulated in the shearing ring design. Through the steps and the design of tools and dies, the seamless steel pipe with the quality meeting the standard requirement is successfully produced on an extruding machine through the material.

Description

Technical Field

[0001] The invention relates to the technical field of seamless steel pipe preparation, in particular to an extrusion production method of a 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons. Background Art

[0002] Boron-containing steel has a high boron content of 1.5%-1.7%. The boron element is diffusely distributed at the grain boundaries in the form of borides, which blocks the alpha and gamma rays emitted by nuclear fuel and other materials, as well as microscopic particles such as neutrons, effectively reducing the transmittance of nuclear radiation. It is a good nuclear fuel storage container. This material is mainly used in the application scenarios of radiation shielding in third-generation nuclear power plants.

[0003] However, due to the high boron content of this stainless steel, most of the boron is formed on the grain boundaries in the form of borides, which are hard and brittle compounds. As a result, the plasticity and toughness of the material are very poor, and its processing is very difficult. The main problem in production is that this steel is prone to internal and external surface cracks, resulting in a very high scrap rate during the production process.

[0004] In order to solve some or all of the technical problems existing in the above-mentioned prior art, the present invention provides an extrusion production method of 13Cr type boron-containing seamless steel pipe. By studying the material properties, especially the existence form of boron element and its compounds at high temperature, and its mechanical properties, a corresponding process scheme is formulated, and a 13Cr type boron-containing seamless steel pipe for neutron shielding function of the core component of the third-generation nuclear power is successfully developed. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems and provide a method for extruding a 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons.

[0006] The object of the present invention is achieved in this way: an extrusion production method of a 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons, comprising the following steps: step one: selection of outer diameter of billet and surface treatment: selecting a series of sizes, turning the surface of the billet, and ensuring the smoothness of the outer surface after turning; step two: sawing: determining the length of the billet, and sawing it to the required size, sawing flat heads at both ends, and finally using an angle grinding wheel to grind the burrs clean; step three: deep hole: a through deep hole is drilled in the center of the billet through a deep hole drill to ensure the surface roughness of the deep hole and the deep hole and Quality requirements for the concentricity of the outer cylindrical surface; Step 4: Bell mouth and arc processing: Machine the bell mouth and arc surface on the same end face of the blank according to the process requirements; Step 5: Ring furnace heating: Heat the processed blank in a ring furnace, and divide it into three sections according to the different temperature ranges of the furnace, namely preheating section, heating section and soaking section; Step 6: Primary induction furnace heating: After the ring furnace is heated, the blank is induction heated once before the hole is expanded, and the heating temperature, heating power and capacitor selection are set according to the material properties; Step 7: Expanding cone design: The expansion cone The design content includes the diameter of the expansion cone, the width of the shear circle working plane, the angle between the two lines of the cone surface axial section, the radius of the smooth transition connection between the shear circle working plane and the cone surface, the nose diameter, the nose cone angle, the radius of the smooth transition connection between the nose cone surface and the working cone surface, the expansion cone reverse cone angle, the two-section connection angle, the axial length, and the surface machining finish; Step 8: Shear ring design: The design content of the shear ring includes the shear ring working band diameter, working surface length, guide section diameter, shear ring thickness, shear ring outer diameter, shear ring outer diameter and shear ring support fit, shear ring The concentricity of the cutting ring working circle and the outer diameter circle; Step nine: Hole expansion: Use glass powder lubrication first during the hole expansion process, determine the glass powder model and the lubrication method of the glass powder, determine the preheating temperature of the hole expansion barrel, and set the hole expansion force level; Step ten: Secondary induction furnace heating: After hole expansion, the blank is subjected to secondary induction heating, and its heating temperature, heating power and capacitor are set according to the material properties; Step eleven: Extrusion: Set the preheating temperature of the extrusion barrel, select glass powder in a suitable temperature range, select the pressure level of the extruder, and determine the cooling method of the extruded rough tube after extrusion molding.

[0007] In step one, the machining outer diameter tolerance is -2mm-0mm, and the surface roughness after outer circle finishing is Ra≤1.6um; in step two, the sawing length of the blank is 800mm-850mm, both ends are flush, the sawing length tolerance is ±2mm, and the sawing slope is <2mm; in step three, the deep hole diameter is φ100mm-φ110mm, the deep hole eccentricity is ≤1mm, and the deep hole surface roughness is ≤3.2um.

[0008] In step four, the bell mouth is turned and processed. The diameter of the cone bottom on one side of the end face of the blank is φ290mm-φ310mm, and a R10mm-R15mm smooth transition is used between the cone surface and the end face. The angle between the cone surface and the center axis of the blank is 30°-35°. A R15mm-R25mm smooth transition is used between the top of the cone and the deep hole. The processing arc of the connection between the end face of the blank and the outer cylindrical surface is R25mm-R35mm.

[0009] In step five, the heating is divided into three sections according to the different temperature ranges of the furnace, namely preheating section, heating section and soaking section. The temperature of the preheating section is ≤750℃, heating section one is 900±15℃, heating section two is 930±15℃, heating section three is 950±15℃, soaking section is 930±15℃, furnace outlet temperature is 910±20℃, heating time is 6h-6.5h, soaking time is 0.5h-0.6h.

[0010] In step six, the temperature of the induction furnace is set to 1030°C-1060°C, capacitors No. 3 and No. 4 are selected, the power is set to 250kw-280kw, and the heating and insulation time is 30min-40min.

[0011] In step seven, the diameter of the expansion cone is 290±0.1mm, the width of the shear circle working plane is 30mm-35mm, the angle between the two lines of the cone surface axial section is 42°-45°, the shear circle working plane and the cone surface are connected with a R3mm-R6mm smooth transition, the nose diameter is 50mm-60mm, the nose cone angle is 8°-12°, the nose cone surface and the working cone surface are connected with a R4mm-R6mm smooth transition, the two sections of the expansion cone reverse cone angle connection angle are 18°-23° and 27°-32°, the axial lengths are 5mm-8mm and 12mm-15mm respectively, and the surface roughness is ≤0.8um.

[0012] In step eight, the working band diameter of the shear ring is 290.5mm-290.8mm, the working surface length is ≤10mm, the guide section diameter is 295.5mm-295.7mm, the shear ring thickness is 49.9mm-50mm, the outer diameter of the shear ring is 330mm-340mm, the outer diameter of the shear ring takes p6 interference tolerance fit, and the concentricity of the shear ring working circle and the outer diameter circle is ≤0.03mm.

[0013] In step nine, the outer surface is lubricated by platform rolling and dyeing, the external coating powder uses GW7 model, the inner hole is blocked with glass wool, and glass powder is poured into the bell mouth. The glass powder uses 844-7 (80-120) model. The preheating temperature of the expansion tube before production is 200℃-400℃, the expansion force level is set to 25MN-28MN, the actual maximum expansion force is ≤15MN, and the average expansion force is ≤12MN.

[0014] In step ten, the temperature of the induction furnace is set to 1080°C-1110°C, capacitors No. 2 and No. 4 are selected, the power is set to 500kw-550kw, and the heating and insulation time is ≤20min.

[0015] In step eleven, the preheating temperature of the extrusion barrel is 300°C-350°C, the inner surface is free of sticky steel and pits, the melting point temperature range of the glass mat is 1050°C-1080°C, the pressure level of the extruder is 55MN-60MN, and after extrusion molding, air cooling is selected to cool to ≤40°C.

[0016] The beneficial effects of the present invention are as follows: 13Cr type boron-containing steel is a container for storing nuclear fuel in the third generation nuclear power technology. The material effectively shields neutrons emitted during nuclear radiation. The successful production of the material is innovative in China and has great significance.

[0017] The production of boron-containing steel makes the storage of nuclear power fuel safer, reduces the radiation dose to humans, and greatly reduces the thickness of radiation protection materials, thereby reducing the weight of related equipment. In addition to the above outstanding properties, 13Cr boron-containing steel is also corrosion-resistant and prevents rust in the atmospheric environment. Its martensitic structure makes the material have very high hardness and strength, and its load-bearing capacity is even better. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the embodiments of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 The present invention is a schematic diagram of an expansion cone for an extrusion production method of a 13Cr type boron-containing seamless steel tube for shielding nuclear power fuel neutrons. Figure 2 The present invention is a top view of a shear ring in an extrusion production method of a 13Cr type boron-containing seamless steel tube for shielding nuclear power fuel neutrons. Figure 3 The present invention is a left view of a shear ring in an extrusion production method of a 13Cr type boron-containing seamless steel tube for shielding nuclear power fuel neutrons. DETAILED DESCRIPTION

[0019] Boron is a key element for absorbing radiation, so the concentration of boron in the material must reach the required value to effectively protect against radiation. Since the boron content of this steel is as high as 1.7%, the increase in the content of non-metallic elements will make the plasticity and impact toughness at room temperature very poor, and the control of supercooling is crucial. In addition, high boron content will significantly reduce the melting point of metal materials. At this time, it is necessary to test the lowest temperature based on the bearing capacity of hole expansion and extrusion. The heating temperature, heating power and heating time must ensure that the boride in the metal material is fully dissolved in the lattice from the grain boundary to ensure the high-temperature plasticity of the material. In terms of lubrication, the low temperature of this steel must be fully considered. Since the average suitable temperature of glass powder is above 1100℃, the selection of the particle size, composition and model of glass powder is very important to ensure its good lubrication state.

[0020] In order to achieve the final outer diameter and wall thickness requirements, the diameter of the expansion cone reaches 290mm, and the expansion coefficient reaches above 1.55, which exceeds the current maximum expansion diameter of 280mm. Based on the above situation, it is necessary to redesign the expansion cone and the matching shear ring mold, and formulate corresponding process parameters such as expansion and induction heating.

[0021] The present invention provides an extrusion production method of a 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons. The technical scheme of the invention is as follows: 1. The outer diameter of the incoming material is selected to be extruded in the 450 series, which is the largest series in extrusion, so as to meet the process requirements of the outer diameter of the rough pipe being above 300, thereby providing a sufficient extrusion ratio to ensure the quality requirements of the inner and outer surfaces of the rough pipe. The outer diameter after turning is 432mm, and the tolerance is -2mm-0mm. The selection of the turning outer diameter and its tolerance range are finally determined based on the expansion amount of the material production process temperature and the expansion amount at the working temperature of the expansion tube. The surface of the blank has no defects such as cracks and scars, and the surface roughness Ra≤1.6um after the outer circle is finely turned. The quality requirements of the outer surface fully guarantee the uniform adhesion of the outer surface glass lubricant on the surface of the blank during the extrusion process. In order to prevent expansion cracks during the expansion process, it is required that the center of the blank has no defects such as looseness and shrinkage.

[0022] 2. The sawing length of the billet is 830mm, and the sawing length tolerance is ±1mm. The design of the billet length must ensure the final required length of the rough pipe and the length after expansion is ≤1300mm. The two ends are flush, and the outer diameter must be measured before marking. The sawing is carried out according to the standards of the process card. After sawing, the material information is clearly marked on the billet. The sawing slope is ≤1mm. The cutting slope tolerance ensures the verticality of the induction furnace, so as to ensure that the billet keeps a distance from the induction furnace lining when entering and exiting the induction furnace, and the billet and the induction furnace lining will not be scratched. The edge chain or adhered sawdust formed after sawing should be polished clean with tools such as angle grinding wheels. The unevenness of the sawing end face will cause the outer surface quality of the pipe end to have wavy patterns after the final extrusion breakthrough. The adhered sawdust will form extrusion-induced crushing injuries on the inner and outer surfaces of the rough pipe.

[0023] 3. Drill a through deep hole in the center of the blank. The diameter of the deep hole drilled is φ100mm, and the tolerance of the deep hole diameter is 0mm-2mm. The size of the deep hole diameter is closely related to the size of the final expanded hole and the diameter of the blank. The two together determine the expansion coefficient of the hole expander. For materials with poor plasticity, it is necessary to select a suitable expansion coefficient to ensure the specifications of the rough pipe while ensuring that no cracks are generated on the surface of the inner hole after expansion. The eccentricity of the deep hole is ≤1mm. The eccentricity requirement makes the inner hole and the outer circle as concentric as possible after expansion, and ultimately ensures that the extruded rough pipe does not produce a skewed wall. The surface roughness of the deep hole is ≤3.2um. After drilling, check the inner surface of the deep hole, remove the oil and iron filings from the inner hole, and the standard of the finish of the inner surface of the deep hole allows the molten glass powder to adhere evenly to the inner hole, which is directly related to the quality of the inner surface after expansion.

[0024] 4. Turning the bell mouth, the diameter of the cone bottom on one side of the blank end face is φ300mm, the diameter of the expansion cone is 290mm, the diameter of the bell mouth should ensure that the expansion cone can enter the bell mouth smoothly, and a gap must be left to ensure the accommodation of glass powder to ensure sufficient lubrication of the inner hole. R10mm smooth transition is used between the cone surface and the end face. This transition ensures the uniformity of the edges of the expansion blank during the extension process, prepares for the subsequent extrusion of the rough pipe, and minimizes the occurrence of wall deviation. The angle between the cone surface and the center axis of the blank is 33.5°, which is greater than the corresponding expansion cone half angle. The expansion cone surface and the bell mouth cone surface of the blank form a certain angle. This design not only meets the stress characteristics of the expansion hole, reduces the stress and ensures the uniform lubrication of the glass powder. R20mm smooth transition is used between the top of the cone and the deep hole, and the arc is more evenly stressed, minimizing the possibility of tearing the inner hole. The processing arc of the connection between the end face and the outer cylindrical surface of the blank is R35mm. This large arc design is more closely matched with the arc of the extrusion die sleeve, which reduces the extrusion breakthrough force and reduces the probability of wall deflection and tearing at the end of the extruded rough pipe.

[0025] 5. Heating is divided into three sections according to the different temperature ranges of the furnace, namely preheating section, heating section and soaking section. The heating section is divided into one section, two sections and three sections. The temperature of the preheating section is ≥750℃, one section is 900±15℃, two sections are 930±15℃, three sections are 950±15℃, soaking section is 930±15℃, and the furnace discharge temperature is 910±20℃. The setting of the temperature of each section needs to consider the microstructure of the material at high temperature. First of all, it is necessary to ensure that the transformation from martensite structure to austenite structure is completed within the temperature range. Secondly, the titanium boride compound in the material must be melted from the grain boundary into the austenite face-centered cubic structure within the temperature range. Finally, the heating time is 6h-6.5h, and the soaking time is 0.5 h-0.6h, the heating time and the soaking time are determined according to the diameter of the billet and its thermal conductivity, which not only ensures that the billet is evenly burned from the outer surface to the core, but also has enough time for compounds such as titanium boride to be fully melted into the lattice, ultimately ensuring the uniformity of the billet's structure from the time it comes out of the ring furnace to the time it enters the primary induction furnace.

[0026] 6. The temperature of the induction furnace is set to 1050℃, which is a temperature parameter formulated according to the material characteristics and high-temperature mechanical properties. On the one hand, the temperature must reach the point where compounds such as titanium boride are fully dissolved, but not so high that the material melts between crystals and causes overburning. Capacitors No. 3 and No. 4 are selected to maintain the frequency in the range of 40HZ-50HZ. This range ensures the depth of the skin effect of the induction furnace and avoids the temperature stratification range of the billet, thereby ultimately reducing the possibility of stratification defects in the extruded rough pipe. The power is set to 260kw, and the heating and holding time is 30min-40min. Considering the conduction speed of the material temperature, the power setting value must be in a suitable range, which not only ensures the realization of the billet heating temperature, but also avoids the difference in heating levels of the billet.

[0027] 7. The diameter of the expansion cone is 290±0.1mm. The size of the expansion cone must meet the limit requirements of the expansion coefficient. After the expansion cone is expanded, the inner diameter of the billet must match the extrusion needle, which not only ensures that the extrusion needle can enter the inner hole smoothly, but also makes the gap between the extrusion needle and the inner diameter of the expansion hole within the process requirements. The tolerance range of the expansion cone must meet the matching requirements of the shear ring working belt, so that the expansion surplus and the original billet can be sheared and separated smoothly. The width of the working circular plane is 32mm. This width ensures the shearing length of the expansion cone and the shear ring working belt, making the shearing fully clean, reducing the expansion surplus length, and improving the yield rate. Through the force analysis of the expansion process, the angle between the two lines of the cone surface axial section is designed to be 44°, and the working circular plane and the cone surface are connected with R5mm smooth transition. This design is uniform in force and will not make the expansion cone too long. The nose diameter is 56mm, the nose cone angle is 10°, the nose cone surface and the working cone surface are connected by R5 smooth transition. The design of the nose diameter and nose cone angle should match the deep hole diameter and can play a guiding role in the expansion of the hole. The two-section connection angle of the expansion cone reverse cone angle is 20° and 30°, and the axial length is 7mm and 13mm respectively. This reverse cone design allows the expansion cone and the expansion surplus to be separated smoothly. The surface roughness of the entire surface in contact with the inner hole of the blank is ≤0.8um, which can reduce the friction between the expansion cone and the inner hole of the blank.

[0028] 8. The working band diameter of the shear ring is 290.3mm-290.5mm, and the working surface length is ≤10mm. The diameter of the shear ring should match the working band of the reamer cone, so that the shear ring and the reamer cone form shearing, and finally the expansion and shear ring are separated smoothly, which is crucial to effectively reduce the expansion size. In order to ensure that the expansion can be smoothly exported after shearing, the guide section diameter is set to 295.5mm-295.7mm, and the shear ring thickness is 49.9mm-50mm. The outer diameter of the shear ring should have an interference fit with the shear ring support, and the outer diameter of the shear ring is designed to be 328-333mm, and the outer diameter of the shear ring is p6 tolerance. The concentricity of the shear ring working circle and the outer diameter circle is ≤0.03mm, which ensures the concentricity during the shearing process, so that the shear force is more uniform.

[0029] 9. The outer surface lubrication adopts the platform rolling dyeing method, and the outer coating powder uses the GW7 model. The outer coating method and the selection of the outer coating glass powder are to ensure the uniform coating of the glass powder and to ensure the formation of a uniform molten lubrication mold on the outer surface, reduce the extension friction between the blank and the reaming tube during the reaming process, and ensure the outer surface quality of the pre-extruded blank after reaming. The inner hole is plugged with glass wool, and glass powder is poured into the bell mouth. The glass powder uses the 844-7 (80-120) model. The inner hole lubrication method and the selection of the inner hole lubrication glass powder are to ensure that the expansion cone forms uniform lubrication during the expansion of the inner hole of the blank, so that the glass powder on the inner surface of the expansion hole is evenly covered to ensure the quality of the inner surface of the expansion hole. Due to the thermal expansion of the material, in order to reduce the temperature difference between the blank and the reaming tube, the preheating temperature of the reaming tube before production is 200℃-400℃. Considering the bearing capacity of the tooling and the protection of the tooling and related equipment, the expansion force level is set to 28MN, the actual maximum expansion force does not exceed 15MN, and the average expansion force does not exceed 12MN.

[0030] 10. The setting of the temperature, frequency and heating time of the secondary induction furnace should take into account the inherent characteristics of boron-containing steel, ensure that the boron compound enters the unit cell from the grain boundary in the form of boron element, and ensure its sufficiency without causing grain growth and plasticity deterioration. The temperature of the secondary induction furnace is set to 1050℃, the power is set to 550kw, and the heating and holding time is ≤20min. Capacitors No. 2 and No. 4 are selected. The selection of capacitors determines the heating frequency, thereby determining the depth of the skin effect and ensuring the uniformity of the heating temperature of the outer and inner surfaces.

[0031] 11. In order to reduce the temperature difference between the billet and the extrusion barrel after hole expansion, the preheating temperature of the extrusion barrel is 300℃-350℃. By preheating the extrusion barrel, the life of the tooling can be increased and brittle cracks caused by thermal expansion and contraction can be prevented. Before production, check that there is no sticky steel or pits on the inner surface of the extrusion barrel to ensure the surface quality of the billet. Since the hot working temperature of the billet is lower than that of conventional austenitic stainless steel, the melting point temperature range of the glass pad is 1050℃-1090℃ to ensure the inner and outer surface quality of the extruded rough tube. The extruded rough tube of this specification is the 450 series, which is the largest series among the 7 series of extruders, and the pressure level of the extruder is selected as 60MN. Since the material is 13Cr type, its normal temperature is martensitic structure, and the supercooling required for quenching is low. Air cooling is selected after extrusion molding.

[0032] A method for extruding a 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons comprises the following steps: S1, selection of billet outer diameter and surface treatment: selecting a series of sizes, turning the billet surface, and ensuring the smoothness of the outer surface after turning.

[0033] S2. Sawing: Determine the length of the blank and saw it to the required size, saw flat ends at both ends, and finally use an angle grinding wheel to grind the burrs clean.

[0034] S3. Deep hole: A deep hole is drilled through the center of the blank to ensure the quality requirements such as the surface roughness of the deep hole and the concentricity of the deep hole and the outer cylindrical surface.

[0035] S4. Bell mouth and arc processing: Machine the bell mouth and arc surface on the same end face of the blank according to the process requirements.

[0036] S5. Ring furnace heating: The processed blanks are heated in a ring furnace and divided into three sections according to the different temperature ranges of the furnace, namely the preheating section, the heating section and the soaking section.

[0037] S6. Primary induction furnace heating: After heating in the annular furnace, the blank is subjected to one induction heating before hole expansion, and the heating temperature, heating power and capacitance are set according to the material properties.

[0038] S7. Design of hole expansion cone: The design contents of hole expansion cone include the diameter of hole expansion cone, the width of shear circle working plane, the angle between two lines of cone surface axial section, the radius of smooth transition connection between shear circle working plane and cone surface, nose diameter, nose cone angle, the radius of smooth transition connection between nose cone surface and working cone surface, the connection angle of two sections of hole expansion cone reverse cone angle, the length in the axial direction, and the finish of surface machining.

[0039] S8. Shear ring design: The design contents of the shear ring include the shear ring working band diameter, working surface length, guide section diameter, shear ring thickness, shear ring outer diameter, fit between the shear ring outer diameter and the shear ring support, and the concentricity between the shear ring working circle and the outer diameter circle.

[0040] S9. Hole expansion: During the hole expansion process, glass powder is first used for lubrication. The glass powder model and lubrication method of the glass powder are determined, the preheating temperature of the hole expansion tube is determined, and the hole expansion force level is set.

[0041] S10, secondary induction furnace heating: After hole expansion, the blank is subjected to secondary induction heating, and the heating temperature, heating power and capacitance are set according to the material properties.

[0042] S11. Extrusion: Set the preheating temperature of the extrusion barrel, select glass powder in a suitable temperature range, select the pressure level of the extruder, and determine the cooling method of the extruded rough tube after extrusion molding.

[0043] In step S1, the machining outer diameter tolerance is -2mm-0mm, and the surface roughness after outer circle finishing is Ra≤1.6um.

[0044] In step S2, the sawing length of the blank is 800mm-850mm, both ends are flush, the sawing length tolerance is ±2mm, and the sawing slope is <2mm.

[0045] In step S3, the diameter of the deep hole is φ100mm-φ110mm, the eccentricity of the deep hole is ≤1mm, and the surface roughness of the deep hole is ≤3.2um.

[0046] In step S4, the bell mouth is turned, the diameter of the cone bottom on one side of the blank end face is φ290mm-φ310mm, the cone surface and the end face are smoothly transitioned by R10mm-R15mm, the angle between the cone surface and the central axis of the blank is 30°-35°, and the top of the cone and the deep hole are smoothly transitioned by R15mm-R25mm. The arc of the connection between the blank end face and the outer cylindrical surface is processed to be R25mm-R35mm.

[0047] In step S5, the heating is divided into three sections according to the different temperature ranges of the furnace, namely, preheating section, heating section and soaking section. The temperature of the preheating section is ≤750℃, heating section one is 900±15℃, heating section two is 930±15℃, heating section three is 950±15℃, soaking section is 930±15℃, furnace outlet temperature is 910±20℃, heating time is 6h-6.5h, and soaking time is 0.5h-0.6h.

[0048] In step S6, the temperature of the induction furnace is set to 1030°C-1060°C, capacitors No. 3 and No. 4 are selected, the power is set to 250kw-280kw, and the heating and insulation time is 30min-40min.

[0049] In step S7, the diameter of the reaming cone is 290±0.1mm, the width of the shear circle working plane is 30mm-35mm, the angle between the two lines of the conical surface axial section is 42°-45°, the shear circle working plane and the conical surface are connected with a R3mm-R6mm smooth transition, the nose diameter is 50mm-60mm, the nose cone angle is 8°-12°, the nose cone surface and the working conical surface are connected with a R4mm-R6mm smooth transition, the two connection angles of the reaming cone reverse cone angle are 18°-23° and 27°-32°, the axial lengths are 5mm-8mm and 12mm-15mm respectively, and the surface roughness is ≤0.8um.

[0050] In step S8, the working belt diameter of the shear ring is 290.5mm-290.8mm, the working surface length is ≤10mm, the guide section diameter is 295.5mm-295.7mm, the shear ring thickness is 49.9mm-50mm, the outer diameter of the shear ring is 330mm-340mm, the outer diameter of the shear ring takes p6 interference tolerance fit, and the concentricity of the shear ring working circle and the outer diameter circle is ≤0.03mm.

[0051] In step S9, the outer surface is lubricated by rolling and dyeing on the platform, the outer coating powder is GW7 model, the inner hole is plugged with glass wool, and the glass powder is poured into the bell mouth. The glass powder is 844-7 (80-120) model. The preheating temperature of the expansion tube before production is 200℃-400℃, the expansion force level is set to 25MN-28MN, the actual maximum expansion force is ≤15MN, and the average expansion force is ≤12MN.

[0052] In step S10, the temperature of the induction furnace is set to 1080°C-1110°C, capacitors No. 2 and No. 4 are selected, the power is set to 500kw-550kw, and the heating and insulation time is ≤20min.

[0053] In step S11, the preheating temperature of the extrusion barrel is 300℃-350℃, the inner surface is free of sticky steel and pits, the melting point temperature range of the glass mat is 1050℃-1080℃, the pressure level of the extruder is 55MN-60MN, and after extrusion molding, air cooling is selected to cool to ≤40℃.

[0054] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] The technical solution provided by the embodiments of the present invention is described in detail below with reference to the accompanying drawings. Example 1

[0056] (1) Selection of the outer diameter of the blank and its quality parameters: The outer diameter of the incoming material is selected from the extrusion 450 series. The outer diameter after turning is 430 mm. There are no defects such as cracks and scars on the surface of the blank. The surface roughness Ra after outer circle fine turning is 1.2 um. There are no defects such as looseness and shrinkage holes in the center of the blank.

[0057] (2) Sawing: The sawing length of the blank is 830mm, and both ends are flush. The outer diameter must be measured before marking. Sawing is carried out according to the standards of the process card. After sawing, the material information is clearly marked on the blank. The sawing slope is 1.5mm. The edge chain or attached sawdust formed after sawing should be polished clean with an angle grinding wheel or other tools.

[0058] (3) Deep hole: A through deep hole is drilled in the center of the blank. The diameter of the deep hole drilled is φ102mm, the eccentricity of the deep hole is 0.6mm, and the surface roughness of the deep hole is 2.8um. ​​After drilling, check the inner surface of the deep hole and remove the oil and iron filings in the inner hole.

[0059] (4) Bell mouth, arc: Bell mouth is machined by turning. The diameter of the cone bottom on one side of the blank end face is φ305mm. The cone surface and the end face are smoothly transitioned by R12mm. The angle between the cone surface and the center axis of the blank is 33.5°. The top of the cone and the deep hole are smoothly transitioned by R20mm. The arc of the connection between the end face of the blank and the outer cylindrical surface is R35mm.

[0060] (5) Ring furnace heating: The heating is divided into three sections according to the different temperature ranges of the furnace, namely the preheating section, the heating section and the soaking section. The heating temperature and heating time of each section are shown in the following table.

[0061]

[0062] (6) Primary induction heating: The induction furnace temperature is set to 1050°C, capacitors No. 3 and No. 4 are selected, the power is set to 260kw, and the heating and holding time is 30min.

[0063] (7) Design and selection of reaming tools: 7.1 Design of reaming cone: The diameter of the reaming cone is 290.1 ​​mm, the width of the shear circle working plane is 32 mm, the angle between the two lines of the cone surface axial section is 44°, the shear circle working plane and the cone surface are connected by R5mm smooth transition, the nose diameter is 56 mm, the nose cone angle is 10°, the nose cone surface and the working cone surface are connected by R5 smooth transition, the two sections of the reaming cone anti-cone angle are 20° and 30°, and the axial lengths are 7 mm and 13 mm respectively. The surface roughness is 0.8 um.

[0064] 7.2 Shear ring design: The working band diameter of the shear ring is 290.3mm, the working surface length is 10mm, the guide section diameter is 295.7mm, the shear ring thickness is 49.9mm, the outer diameter of the shear ring is 330mm, the outer diameter of the shear ring takes p6 interference tolerance fit, and the concentricity of the shear ring working circle and the outer diameter circle is 0.02mm.

[0065] (8) Hole expansion process control: The outer surface is lubricated by platform rolling and dyeing, the outer coating powder is GW7 model, the inner hole is plugged with glass wool, and glass powder is poured into the bell mouth. The glass powder is 844-7 (80-120) model. The preheating temperature of the hole expansion tube before production is 270℃, the hole expansion force level is set to 28MN, the actual maximum hole expansion force does not exceed 15MN, and the average hole expansion force does not exceed 12MN.

[0066] (9) Secondary induction heating: The induction furnace temperature is set to 1090°C, capacitors No. 2 and No. 4 are selected, the power is set to 550kw, and the heating and holding time is 20min.

[0067] (10) Extrusion process control: The preheating temperature of the extrusion barrel is 320℃, there is no sticky steel or pits on the inner surface, the melting point temperature range of the glass pad is 1060℃, the extruder pressure level is 60MN, and air cooling is selected after extrusion molding. Example 2

[0068] (1) Selection of the outer diameter of the blank and its quality parameters: The outer diameter of the incoming material is selected from the extrusion 450 series. The outer diameter after turning is 431 mm. The surface of the blank has no defects such as cracks and scars. The surface roughness Ra after outer circle fine turning is 1.0 um. There is no looseness, shrinkage hole and other defects in the center of the blank.

[0069] (2) Sawing: The sawing length of the blank is 815mm, and both ends are flush. The outer diameter must be measured before marking. Sawing is carried out according to the standards of the process card. After sawing, the material information is clearly marked on the blank. The sawing slope is 1.7mm. The edge chain or attached sawdust formed after sawing should be polished clean with an angle grinding wheel or other tools.

[0070] (3) Deep hole: A through deep hole is drilled in the center of the blank. The diameter of the deep hole drilled is φ100mm, the eccentricity of the deep hole is 0.9mm, and the surface roughness of the deep hole is 3.0um. After drilling, check the inner surface of the deep hole and remove the oil and iron filings in the inner hole.

[0071] (4) Bell mouth, arc: Bell mouth is machined by turning. The diameter of the cone bottom on one side of the blank end face is φ300mm. The cone surface and the end face are smoothly transitioned by R13mm. The angle between the cone surface and the center axis of the blank is 33.5°. The top of the cone and the deep hole are smoothly transitioned by R22mm. The arc of the connection between the end face of the blank and the outer cylindrical surface is R30mm.

[0072] (5) Ring furnace heating: The heating is divided into three sections according to the different temperature ranges of the furnace, namely the preheating section, the heating section and the soaking section. The heating temperature and heating time of each section are shown in the following table.

[0073]

[0074] (6) Primary induction heating: The induction furnace temperature is set to 1030°C, capacitors No. 3 and No. 4 are selected, the power is set to 255kw, and the heating and holding time is 35min.

[0075] (7) Design and selection of reaming tools: 7.1 Design of reaming cone: The diameter of the reaming cone is 290 mm, the width of the shear circle working plane is 34 mm, the angle between the two lines of the cone surface axial section is 42.5°, the shear circle working plane and the cone surface are connected by R4mm smooth transition, the nose diameter is 55 mm, the nose cone angle is 11°, the nose cone surface and the working cone surface are connected by R5 smooth transition, the two sections of the reaming cone anti-cone angle are 22° and 32°, and the axial lengths are 6 mm and 13 mm respectively. The surface roughness is 0.6 um.

[0076] 7.2 Shear ring design: The working band diameter of the shear ring is 290.4mm, the working surface length is 8mm, the guide section diameter is 295.5mm, the shear ring thickness is 50mm, the outer diameter of the shear ring is 335mm, the outer diameter of the shear ring takes the p6 interference tolerance fit, and the concentricity of the shear ring working circle and the outer diameter circle is 0.03mm.

[0077] (8) Hole expansion process control: The outer surface is lubricated by platform rolling and dyeing, the outer coating powder is GW7 model, the inner hole is plugged with glass wool, and glass powder is poured into the bell mouth. The glass powder uses 844-7 (80-120) model. The preheating temperature of the hole expansion tube before production is 290℃, the hole expansion force level is set to 26MN, the actual maximum hole expansion force does not exceed 12MN, and the average hole expansion force does not exceed 11MN.

[0078] (9) Secondary induction heating: The induction furnace temperature is set to 1080°C, capacitors No. 2 and No. 4 are selected, the power is set to 520kw, and the heating and insulation time is 22min.

[0079] (10) Extrusion process control: The preheating temperature of the extrusion barrel is 300℃, there is no sticky steel or pits on the inner surface, the melting point temperature range of the glass pad is 1050℃, the extruder pressure level is 60MN, and air cooling is selected after extrusion molding.

[0080] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. Extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons, characterized in that: The following steps are involved: Step 1: Selection of billet outer diameter and surface treatment: Select a series of sizes, turn the billet surface, and ensure the smoothness of the surface after turning; Step 2: Sawing: Determine the length of the blank and saw it to the required size, cut the ends flat, and finally use an angle grinding wheel to grind the burrs clean; Step 3: Deep hole: The blank is drilled with a deep hole through the center to ensure the surface roughness of the deep hole and the concentricity of the deep hole and the outer cylindrical surface. Step 4: Bell mouth and arc processing: Machine the bell mouth and arc surface on the same end face of the blank according to the process requirements; Step 5: Ring furnace heating: The processed blank is heated in a ring furnace and divided into three sections according to the different temperature ranges of the furnace, namely the preheating section, the heating section and the soaking section; Step 6: Primary induction furnace heating: After the annular furnace is heated, the blank is induction heated once before the hole is expanded, and the heating temperature, heating power and capacitance are set according to the material characteristics; Step 7: Design of the reamer cone: The design of the reamer cone includes the diameter of the reamer cone, the width of the shear circle working plane, the angle between the two lines of the cone surface axial section, the radius of the smooth transition connection between the shear circle working plane and the cone surface, the nose diameter, the nose cone angle, the radius of the smooth transition connection between the nose cone surface and the working cone surface, the connection angle of the two sections of the reamer cone reverse cone angle, the length in the axial direction, and the finish of the surface machining; Step 8: Shear ring design: The design of the shear ring includes the shear ring working band diameter, working surface length, guide section diameter, shear ring thickness, shear ring outer diameter, shear ring outer diameter and shear ring support fit, and the concentricity of the shear ring working circle and outer diameter circle; Step 9: Hole expansion: During the hole expansion process, glass powder is first used for lubrication, the glass powder model and lubrication method of the glass powder are determined, the preheating temperature of the hole expansion cylinder is determined, and the hole expansion force level is set; Step 10: Secondary induction furnace heating: After hole expansion, the blank is subjected to secondary induction heating, and the heating temperature, heating power and capacitance are set according to the material properties; Step 11: Extrusion: Set the preheating temperature of the extrusion barrel, select glass powder in a suitable temperature range, select the pressure level of the extruder, and determine the cooling method of the extruded blank tube after extrusion molding.

2. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step one, the machining outer diameter tolerance is -2mm-0mm, and the surface roughness after outer circle finishing is Ra≤1.6um; in step two, the sawing length of the blank is 800mm-850mm, both ends are flush, the sawing length tolerance is ±2mm, and the sawing slope is <2mm; in step three, the deep hole diameter is φ100mm-φ110mm, the deep hole eccentricity is ≤1mm, and the deep hole surface roughness is ≤3.2um.

3. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step four, the bell mouth is turned and processed. The diameter of the cone bottom on one side of the end face of the blank is φ290mm-φ310mm, and a R10mm-R15mm smooth transition is used between the cone surface and the end face. The angle between the cone surface and the center axis of the blank is 30°-35°. A R15mm-R25mm smooth transition is used between the top of the cone and the deep hole. The processing arc of the connection between the end face of the blank and the outer cylindrical surface is R25mm-R35mm.

4. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step five, the heating is divided into three sections according to the different temperature ranges of the furnace, namely preheating section, heating section and soaking section. The temperature of the preheating section is ≤750℃, heating section one is 900±15℃, heating section two is 930±15℃, heating section three is 950±15℃, soaking section is 930±15℃, furnace outlet temperature is 910±20℃, heating time is 6h-6.5h, soaking time is 0.5h-0.6h.

5. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step six, the temperature of the induction furnace is set to 1030°C-1060°C, capacitors No. 3 and No. 4 are selected, the power is set to 250kw-280kw, and the heating and insulation time is 30min-40min.

6. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step seven, the diameter of the expansion cone is 290±0.1mm, the width of the shear circle working plane is 30mm-35mm, the angle between the two lines of the cone surface axial section is 42°-45°, the shear circle working plane and the cone surface are connected with a R3mm-R6mm smooth transition, the nose diameter is 50mm-60mm, the nose cone angle is 8°-12°, the nose cone surface and the working cone surface are connected with a R4mm-R6mm smooth transition, the two sections of the expansion cone reverse cone angle connection angle are 18°-23° and 27°-32°, the axial lengths are 5mm-8mm and 12mm-15mm respectively, and the surface roughness is ≤0.8um.

7. The method for preparing a type 13 boron-containing seamless steel pipe according to claim 1, characterized in that: In step eight, the working band diameter of the shear ring is 290.5mm-290.8mm, the working surface length is ≤10mm, the guide section diameter is 295.5mm-295.7mm, the shear ring thickness is 49.9mm-50mm, the outer diameter of the shear ring is 330mm-340mm, the outer diameter of the shear ring takes p6 interference tolerance fit, and the concentricity of the shear ring working circle and the outer diameter circle is ≤0.03mm.

8. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step nine, the outer surface is lubricated by platform rolling and dyeing, the external coating powder uses GW7 model, the inner hole is blocked with glass wool, and glass powder is poured into the bell mouth. The glass powder uses 844-7 (80-120) model. The preheating temperature of the expansion tube before production is 200℃-400℃, the expansion force level is set to 25MN-28MN, the actual maximum expansion force is ≤15MN, and the average expansion force is ≤12MN.

9. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step ten, the temperature of the induction furnace is set to 1080°C-1110°C, capacitors No. 2 and No. 4 are selected, the power is set to 500kw-550kw, and the heating and insulation time is ≤20min.

10. The extrusion production method of 13Cr type boron-containing seamless steel pipe for shielding nuclear power fuel neutrons according to claim 1 is characterized in that: In step eleven, the preheating temperature of the extrusion barrel is 300°C-350°C, the inner surface is free of sticky steel and pits, the melting point temperature range of the glass mat is 1050°C-1080°C, the pressure level of the extruder is 55MN-60MN, and after extrusion molding, air cooling is selected to cool to ≤40°C.

Images