CN112846672A - Manufacturing method of pressure pipe tee joint - Google Patents
Manufacturing method of pressure pipe tee joint Download PDFInfo
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- CN112846672A CN112846672A CN202110106899.5A CN202110106899A CN112846672A CN 112846672 A CN112846672 A CN 112846672A CN 202110106899 A CN202110106899 A CN 202110106899A CN 112846672 A CN112846672 A CN 112846672A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention provides a manufacturing method of a pressure pipe tee joint, which comprises the following steps: after raw materials are subjected to rough smelting, a continuous casting billet is prepared by adopting an external refining method and a continuous casting process; manufacturing a construction forge piece as an extrusion blank by adopting a construction forming method on the continuous casting billet; manufacturing the extruded blank into a tee-shaped blank by adopting an extrusion forming process; and (3) demolding the tee-joint-shaped blank, and then sequentially carrying out rough machining, heat treatment and machining to obtain the finished product of the pressure pipe tee joint. The manufacturing method provided by the invention can ensure that the tee joint material has the characteristics of obdurability matching, uniform structure, intergranular corrosion resistance and high and low cycle fatigue, and meets the complex service environment and failure mode of the tee joint of the pressure pipe. In addition, the manufacturing method provided by the invention adopts a fast reactor integrated three-way forming process without welding seams for the first time, solves the problem of obvious size effect in the process of solidifying the large-section steel ingot of the forge piece with the complex structure, and overcomes the phenomena of segregation, looseness and coarse crystals of the steel ingot.
Description
Technical Field
The invention relates to the field of nuclear power main pipeline manufacturing, in particular to a method for manufacturing a pressure pipe tee joint.
Background
In the atomic energy fast reactor project, the pressure pipe is used for connecting a primary loop sodium pump supporting outlet and a large grid plate header, provides a flow channel for cooling sodium liquid, and is a part of a primary loop main cooling system flow channel.
The normal working temperature of the pressure pipe is 358 ℃, the highest accident temperature is 470 ℃, the safety level is 2 grade, the specification level is NC, the quality assurance level is QA1 grade, and the anti-seismic category is I grade. The design pressure is 0.638MPa, and the load comprises self weight, pressure, temperature, fluid load, pump induced vibration load and flow induced vibration load.
The pressure pipe part mainly comprises a tee joint, a three-dimensional bent pipe and the like, and the tee joint is similar to a pant shape. The tee joint is used as an important part of the pressure pipe, is large in size and complex in shape, and needs to break through the traditional blank forming technology to change rough forming into high-quality and high-precision forming technology in order to reduce machining amount, reduce machining difficulty and keep the integrity of a metal streamline.
The other difficulty of the tee joint part is the cavity processing, and because the inner cavity and the outer cavity of the pressure pipe have complex structures and are special-shaped complex curved surfaces, the processing and cutting parameters, the auxiliary tool and the clamping mode of the cavity need to be researched to determine the optimal machining process.
At present, in the field of manufacturing of nuclear power main pipelines, a scientific and reasonable complete manufacturing process of a nuclear power fast reactor pressure pipe tee joint does not exist.
Disclosure of Invention
Technical problem to be solved
In view of the above, the invention provides a manufacturing method of a pressure pipe tee aiming at the technical problem that the existing tee manufacturing process of a nuclear power fast reactor pressure pipe is lacked.
(II) technical scheme
The invention provides a manufacturing method of a pressure pipe tee joint, which comprises the following steps: after raw materials are subjected to rough smelting, a continuous casting billet is prepared by adopting an external refining method and a continuous casting process; manufacturing a construction forge piece as an extrusion blank by adopting a construction forming method on the continuous casting billet; manufacturing the extruded blank into a tee-shaped blank by adopting an extrusion forming process; and (3) demolding the tee-joint-shaped blank, and then sequentially carrying out rough machining, heat treatment and machining to obtain the finished product of the pressure pipe tee joint.
According to the embodiment of the present disclosure, in the step of manufacturing the continuous casting slab by using the external refining method and the continuous casting process, the external refining method includes: and refining the raw materials after the coarse smelting by adopting a vacuum oxygen blowing decarburization method, a ladle refining method and a vacuum degassing method in sequence.
According to an embodiment of the present disclosure, the refining the raw material after the rough refining by using the ladle refining method includes:
and refining steel by using a ladle refining furnace, and adding alloy to adjust the components of molten steel in the refining process so as to enable the smelted molten steel to meet the requirements of target components of steel grades.
According to the embodiment of the disclosure, in the step of manufacturing the construction forged piece by using the construction forming method for the continuous casting billet, the construction forming method sequentially comprises the following steps: sawing a continuous casting blank, milling and grinding the surface, cleaning and processing the surface, stacking, sealing and welding in vacuum and polishing welding seams.
According to the embodiment of this disclosure, wherein, the continuous casting billet is solid continuous casting round bar material, the continuous casting billet saw cuts including: and sawing the continuous casting blank to a preset blanking length.
According to an embodiment of the present disclosure, wherein the surface milling comprises: machining a blank sawed from the continuous casting blank into a flat and smooth surface by using a rotary milling cutter;
the surface cleaning treatment comprises: and carrying out surface treatment on the blank subjected to surface milling and grinding to ensure that the surface of the blank reaches the preset roughness and cleanliness.
According to an embodiment of the present disclosure, wherein the vacuum sealing comprises: and placing the stacked blanks in a vacuum environment integrally for vacuum electron beam sealing and welding.
According to an embodiment of the present disclosure, wherein the forming the extrusion billet into a three-way shaped billet by an extrusion forming process comprises:
the extrusion blank is a straight pipe blank, the extrusion blank is placed in an extrusion forming die, and an upsetting rod is driven by an extruder to perform extrusion upsetting on the extrusion blank, so that the extrusion blank is pulled out of the three-way branch pipe in the extrusion forming die.
According to the embodiment of the disclosure, the upsetting rod is composed of a solid cylindrical shaft and a cylindrical boss which is located at one end of the cylindrical shaft and has a diameter larger than that of the cylindrical shaft, the cylindrical shaft is used as an extrusion punch, the cylindrical boss is used for extrusion upsetting, and the diameter of the cylindrical boss is the same as that of the inner wall of the main pipe at the upper part of the extrusion forming die.
According to an embodiment of the present disclosure, before the placing the extrusion billet in the extrusion die, further comprises:
heating the extrusion billet to an austenite zone.
According to an embodiment of the present disclosure, before the placing the extrusion billet in the extrusion die, further comprises:
and uniformly smearing a lubricant on the inner wall of the extrusion forming die.
According to an embodiment of the present disclosure, after the extrusion billet is drawn out of the three-way branch pipe in the extrusion forming die, the method further comprises:
and reversely extruding the extrusion blank into the extrusion forming die by using the extrusion punch head at the other end of the upsetting rod until the extrusion blank is flush with the end part of the three-way main pipe of the extrusion forming die.
According to the embodiment of the disclosure, during the extrusion and inflation process of the main pipe, a circular extrusion pad is arranged on the upper part of the main pipe, and the diameter of the circular extrusion pad is between the design size of the main pipe and the inner size of the extrusion forming die.
According to an embodiment of the present disclosure, wherein the extruder is provided with a stroke switch to restrict the alignment of the central axis of the extrusion die and the central axis of the upset bar.
According to the embodiment of the disclosure, in the step of obtaining the finished product of the pressure pipe tee after the tee-shaped blank is subjected to demoulding, rough machining, heat treatment and machining in sequence, the rough machining comprises the following steps: and (3) finishing the end face, polishing, removing burrs and chamfering the groove.
According to the embodiment of the disclosure, in the step of obtaining the finished product of the pressure pipe tee after the tee-shaped blank is subjected to demoulding, rough machining, heat treatment and machining in sequence, the heat treatment comprises the following steps in sequence: solid solution heating and rapid water cooling.
According to an embodiment of the present disclosure, the solution heating and rapid water cooling process includes:
fully dissolving carbide in the tee-joint-shaped blank into an austenitic stainless steel matrix in a solid solution mode, and then rapidly cooling the steel matrix in a water cooling tank by water to avoid precipitation of the carbide.
According to the embodiment of the disclosure, in the step of obtaining the finished product of the pressure pipe tee after the tee-shaped blank is subjected to demoulding, rough machining, heat treatment and machining in sequence, the machining comprises the following steps: and performing finish machining and grinding, removing the allowance of each end part of the tee-joint-shaped blank, and performing groove cutting on each port until the design size of the finished pressure pipe tee-joint product is reached.
According to an embodiment of the present disclosure, wherein the machining further comprises, after the machining:
and carrying out nondestructive testing on the machined blank, and obtaining the finished product of the pressure pipe tee after the finished product is qualified.
According to an embodiment of the present disclosure, wherein the non-destructive testing comprises: penetration test and ultrasonic test.
According to the embodiment of the disclosure, the material of the finished pressure pipe tee is austenitic stainless steel, wherein the content of hydrogen in the chemical composition of the austenitic stainless steel is less than 2 ppm.
(III) advantageous effects
Compared with the prior art, the invention has at least the following beneficial effects:
firstly, the manufacturing method of the pressure pipe tee provided by the invention prepares the austenitic stainless steel used for the pressure pipe through the comprehensive application of smelting and continuous casting, construction forming method, extrusion forming process and heat treatment process of the fast reactor pressure pipe tee, wherein the content of hydrogen in the chemical components of the austenitic stainless steel is less than 2 ppm. The quality requirements of the high-purity tee finished product of the pressure pipe are difficult to achieve in the conventional electroslag smelting process, the tee material can be ensured to have the characteristics of obdurability matching, uniform structure, intergranular corrosion resistance and high and low cycle fatigue, and the complex service environment and failure mode of the tee of the pressure pipe are met.
Secondly, the manufacturing method of the pressure pipe tee joint provided by the invention covers the heat treatment deformation rule of large-scale complex austenitic stainless steel forgings, and accordingly, a complete heat treatment process flow is formed.
Thirdly, the manufacturing method of the pressure pipe tee joint provided by the invention adopts a fast reactor integrated tee joint forming process without welding seams for the first time, solves the problem of obvious size effect in the process of solidifying a large-section steel ingot of a forge piece with a complex structure, and overcomes the phenomena of segregation, looseness and coarse grains of the steel ingot.
Fourthly, the manufacturing method of the pressure pipe tee joint saves raw materials, shortens the manufacturing period and greatly improves the reliability of manufacturing the fast reactor integrated tee joint.
Drawings
Fig. 1 schematically shows a three-dimensional structure diagram of a fast reactor pressure pipe tee according to an embodiment of the invention.
Fig. 2 schematically shows a two-dimensional structure diagram of a fast reactor pressure pipe tee according to an embodiment of the invention.
Figure 3 schematically illustrates a flow chart of a method of making a pressure tube tee in accordance with an embodiment of the present invention.
FIG. 4 schematically illustrates a flow chart of operation of an out-of-furnace refining method of an embodiment of the present invention;
FIG. 5 schematically illustrates an operational flow diagram of a build shaping method of an embodiment of the invention;
fig. 6 schematically shows a schematic view of an extrusion process according to an embodiment of the present invention.
[ description of reference ]
1-a pressure pipe tee; 2-extruding and forming a die; 3-extruding the blank; 4-upsetting rod
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the atomic energy fast reactor project, the pressure pipe is used for connecting a primary loop sodium pump supporting outlet and a large grid plate header, provides a flow channel for cooling sodium liquid, and is a part of a primary loop main cooling system flow channel.
The function of the pressure pipe section is to feed the sodium output from the main sodium pump to the large grid header. When liquid sodium flows in the pressure pipe part, friction pressure drop, acceleration pressure drop and weight level pressure drop can be generated, and local pressure drop can be generated at the bent pipe and the joint of the pressure pipe and the large grid plate header.
The pressure pipe is subjected to complex working condition loads, including coolant pressure, temperature, fluid flow induced vibration load, load generated by pump rotation and the like; the design of the pressure pipe is greatly different from the conventional design of the common pipe due to the fact that the failure modes are multiple, including strength, low cycle fatigue, high cycle fatigue and the like.
The pressure pipe is a large-caliber thin-wall pipeline, and according to the working environment and load analysis, the material of the pressure pipe needs to be strong toughness matching, uniform in structure, resistant to intercrystalline corrosion and high and low cycle fatigue characteristics. In order to reduce the fracture risk of the main pipeline, the pressure pipe is required to have no longitudinal seam and few circular seams in the manufacturing process.
At present, in a nuclear power main pipeline, a pressure pipe part mainly comprises a tee joint, a bent pipe, a transition section, a sealing ring, a sealing assembly, a corrugated pipe assembly and the like, wherein the tee joint is positioned in an inlet cavity of a sodium pump and is welded with a pump joint sleeve.
Fig. 1 schematically shows a three-dimensional structure diagram of a fast reactor pressure pipe tee according to an embodiment of the invention. Fig. 2 schematically shows a two-dimensional structure diagram of a fast reactor pressure pipe tee according to an embodiment of the invention.
Referring to fig. 1 and 2, the pressure pipe tee 1 is a large-caliber thin-walled pipeline, and includes a main pipe and two branch pipes, wherein the main pipe and the branch pipes are respectively located at two ends of the pressure pipe tee 1. In the embodiment of the invention, the pressure pipe tee 1 is similar to a pant shape, is constructed by curved surfaces and has a complex shape.
The tee joint is used as an important part of the pressure pipe, is large in size and complex in shape, needs to obtain a high-performance forging piece in order to reduce machining amount, reduce machining difficulty and keep the integrity of a metal streamline, and breaks through the traditional blank forming technology through a near-net forging forming technology to change rough forming into a high-quality and high-precision forming technology.
The other difficulty of the tee joint part is the cavity processing, and because the inner cavity and the outer cavity of the pressure pipe have complex structures and are special-shaped complex curved surfaces, the processing and cutting parameters, the auxiliary tool and the clamping mode of the cavity need to be researched to determine the optimal machining process. The technical conditions for forming the pressure pipe are verified through the process of forming the tee joint.
FIG. 3 schematically illustrates a flow chart of a method of making a pressure tube tee of an embodiment of the present invention, the method comprising the steps of: step S1, after the raw materials are subjected to rough smelting, a continuous casting billet is manufactured by adopting an external refining method and a continuous casting process; step S2, manufacturing a construction forge piece as an extrusion blank by adopting a construction forming method on the continuous casting billet; step S3, manufacturing the extrusion blank into a tee-joint-shaped blank by adopting an extrusion forming process; and step S4, demolding the tee-shaped blank, and then sequentially carrying out rough machining, heat treatment and machining to obtain the finished product of the pressure pipe tee.
The steps of the method for manufacturing a pressure tube tee according to an embodiment of the present invention will be described in detail with reference to specific embodiments.
And step S1, after the raw materials are subjected to rough smelting, manufacturing a continuous casting billet by adopting an external refining method and a continuous casting process.
The coarse smelting comprises the following steps: the scrap steel is smelted by an electric furnace to produce crude steel.
Optionally, the electric furnace is an electric arc furnace or an oxygen converter, and the specific specification can be selected according to actual needs, for example, the electric furnace can adopt a 180t electric arc furnace.
FIG. 4 schematically illustrates a flow chart of the operation of the out-of-furnace refining method of an embodiment of the present invention.
As shown in fig. 4, according to an embodiment of the present disclosure, wherein the out-of-furnace refining method comprises, in order: vacuum Oxygen Decarburization (VOD), Ladle refining (LF), and Vacuum Degassing (VD).
Specifically, the vacuum oxygen decarburization method may include: blowing oxygen into the top of the molten steel surface in the vacuum tank for decarburization, blowing argon from the bottom of the steel ladle to promote the circulation of the molten steel so as to supplement the decarburization reaction near the nozzle, prevent the local oxidation of chromium, and simultaneously stirring the molten steel by argon in vacuum so as to promote the floating of nonmetallic inclusions.
The vacuum oxygen blowing decarbonization method comprises the following treatment processes: after the rough smelting, the molten steel smelted in an electric arc furnace or a converter is deslagged, poured into a ladle, and the ladle is placed into a vacuum tank, covered with a cover, and argon is blown in from a porous air brick arranged at the bottom of the ladle to stir the molten steel in the ladle. And simultaneously, starting a vacuum system, blowing oxygen from an oxygen lance arranged on the cover when the required vacuum degree is reached, carrying out vacuum decarburization until the C is less than 0.07%, adding ferroalloy, carrying out vacuum degassing, and finishing the whole treatment process. In addition, the VOD furnace not only can accurately control the blowing stop of the electric furnace or the converter to improve the productivity, but also can reduce the consumption of refractory materials and improve the recovery rate of chromium.
According to an embodiment of the present disclosure, wherein the ladle refining method may include: and (3) heating by graphite electrode submerged arc under reducing atmosphere, stirring and degassing by blowing argon through the air brick, and refining the high-alkalinity slag, thereby removing hydrogen, oxygen, sulfur and impurities in the steel.
Further, the ladle refining method may further include: and refining steel by adopting an LF furnace, and adding an alloy to adjust the components of molten steel in the refining process so as to ensure that the smelted molten steel reaches the target components required by steel grades.
It can be understood that LF refining is a technical means of external refining, and plays an important role in cleaning molten steel. Meanwhile, LF refining plays roles in buffer adjustment, stable production, smelting time shortening, production efficiency improvement, production cost reduction and the like between a converter and continuous casting.
By way of example of the present invention, among others, a vacuum degassing process may include: degassing of molten steel is realized under vacuum condition.
It can be understood that the vacuum degassing apparatus using the VD method is mainly composed of a ladle, a vacuum chamber and a vacuum system, and the basic function is to evacuate and degas molten steel. The VD type vacuum treatment furnace is used for blowing argon at the bottom of a steel ladle through vacuumizing, adding alloy material through an alloy feeding chamber on a furnace cover, and measuring temperature and sampling by using a temperature measuring and sampling device, so that degassing is effectively performed, and the content of hydrogen and nitrogen in molten steel is reduced. The VD method and the VOD method have the same processing procedures, but the difference is that the oxygen blowing pipe can be freely lifted from the upper cover of the vacuum tank, oxygen is blown into the molten steel in the vacuum tank for decarburization, and a large amount of carbon monoxide gas is generated, so the VOD method needs to be added with an exhaust function.
It should be noted that the VD type vacuum processing furnace does not have a heating function, and needs to be used in cooperation with an LF furnace.
According to the embodiment of the invention, in the continuous casting billet manufacturing process, the external refining method of VOD + LF + VD is comprehensively adopted, and the high-purity casting is obtained according to the smelting process routes of raw material rough smelting, VOD refining vacuum decarburization, LF furnace refining desulfurization, VD refining degassing and the like. The quality requirements of the prepared high-purity castings comprise: the casting defects such as slag inclusion, air holes, cracks and the like are avoided, and the secondary ultrasonic flaw detection and the performance detection are qualified.
Specifically, the specific treatment process of the external refining method in step S1 in the embodiment of the present invention is as follows:
firstly, vacuum oxygen decarburization is completed through VOD refining vacuum decarburization, and the mass fraction of carbon in steel is ensured to be lower than 0.01%. And then, after the refining and desulfuration of the LF furnace are finished, N, H, inclusions and the like in the steel are further reduced, so that the purity of the molten steel is improved. After VD refining and degassing are continuously carried out, the sulfur in the tapping can reach the requirement of 0.001 percent.
Further, after the above-mentioned external refining method, continuous casting and flame cutting processes are also required.
It can be understood that continuous casting is an important part of steel production, and the main process is that high-temperature molten steel is forced to cool in a crystallizer to form a billet shell with a certain thickness, and the inside of the billet shell is still liquid molten steel. And after the casting blank containing the liquid core from the crystallizer enters a secondary cooling zone, continuously cooling and reducing the temperature under the strong cooling of a water nozzle or a steam-water atomizing nozzle until the molten steel in the casting blank is completely solidified.
Because the production process of continuous casting is a molten steel continuous casting process, and a casting blank is continuously pulled out at the outlet of the fan-shaped section, in fact, the casting blank needs to be cut into a certain length according to the requirements of downstream processes, and therefore, a fire cutting process is also needed.
Specifically, the flame cutting process may include: and (3) rapidly burning the casting blank by using gas and oxygen to cut off the casting blank to obtain the casting blank with the required length.
The cast slab after the fire-cutting process, that is, the continuously cast slab finally manufactured at step S1.
And step S2, manufacturing a construction forge piece as an extrusion blank by adopting a construction forming method for the continuous casting billet.
FIG. 5 schematically illustrates a flow chart of the operation of a build shaping method of an embodiment of the present invention.
As shown in fig. 5, according to the embodiment of the present disclosure, wherein in step S2, the constructing a forming method may sequentially include, for example: sawing a continuous casting blank, milling and grinding the surface, cleaning and processing the surface, stacking, sealing and welding in vacuum and polishing welding seams.
In particular, the slab is a solid continuous casting round bar, and the slab sawing may include, for example: and sawing the continuous casting blank to a preset blanking length. The preset blanking length is a length set by preliminary design, and can be adjusted according to actual needs, and the invention is not limited in particular.
It should be noted that the extra stress added to the edge of the blank by the sawing and blanking is small, which is very beneficial to the stress control when the blank is subjected to vacuum sealing welding.
Specifically, the surface milling comprises: and processing the blank sawed by the continuous casting blank into a flat and smooth surface by adopting a rotary milling cutter.
It will be appreciated that after surface milling, the workpiece surface may be subjected to debris, residual oil, or other contaminants, and a surface cleaning process is required to facilitate subsequent stacking.
Based on this, the surface cleaning process may include, for example: and carrying out surface treatment on the blank subjected to surface milling and grinding to ensure that the surface of the blank reaches the preset roughness and cleanliness.
According to an embodiment of the present disclosure, wherein the stacking may comprise, for example: and stacking the blanks subjected to the surface cleaning treatment.
According to an embodiment of the present disclosure, among others, vacuum sealing may include, for example: and placing the stacked blanks in a vacuum environment integrally for vacuum electron beam sealing and welding.
It will be appreciated that vacuum sealing, as a more reliable welding process, requires that the workpiece be subjected to a vacuum environment. In particular, vacuum electron beam sealing welding utilizes an electron beam which moves at a high speed in a directional mode to impact a workpiece so that kinetic energy is converted into heat energy to melt the workpiece, and a welding seam is formed. Especially for the welding workpiece of large thick piece, compared with the common welding, the electron beam of the vacuum electron beam sealing welding can accurately determine the position of the welding seam, the precision and the repeatability error are almost zero, the welding seam is pure and smooth, the welding seam is a mirror surface, the defects of oxidization and the like are avoided, and the welding speed is higher.
Further, the weld grinding comprises: and further finishing and polishing the blank welding seam after vacuum sealing. Specifically, the weld grinding may include, for example: polishing the weld joint residual height, removing a surface scratch area, removing welding spatter, polishing a weld joint and polishing the weld joint. The grinding quality can be set according to actual needs, and can be, for example: the whole body after polishing has no burrs, pits and poor welding positions, and the surface has no obvious uneven polishing phenomenon.
And step S3, manufacturing the extrusion blank into a tee-joint-shaped blank by adopting an extrusion forming process.
In this embodiment of the present invention, step S3 further includes:
the extrusion blank is a straight pipe blank, the extrusion blank is placed in an extrusion forming die, and an upsetting rod is driven by an extruder to perform extrusion upsetting on the extrusion blank, so that the extrusion blank is pulled out of the three-way branch pipe in the extrusion forming die.
Fig. 6 schematically shows a schematic view of an extrusion process according to an embodiment of the present invention.
As shown in fig. 6, in the embodiment of the present invention, the upsetting bar 4 is composed of a solid cylindrical shaft as an extrusion punch and a cylindrical boss having a diameter larger than that of the cylindrical shaft and located at one end of the cylindrical shaft, and the cylindrical boss has a diameter identical to that of the inner wall of the main pipe at the upper part of the extrusion die 2 and is used for extrusion upsetting.
Specifically, in this step, the extruder is controlled to drive the upsetting rod 4 to move downwards, the extrusion blank 3 is a straight tube blank and is placed in the extrusion forming die 2, at this time, the upsetting rod 4 slowly enters the main tube position at the upper part of the extrusion forming die 2 to bear the extrusion blank 3, along with the slow operation of the upsetting rod 4, the pressure borne by the upper surface of the straight tube blank gradually increases, the straight tube blank is shunted along the branch tubes at two sides of the lower part of the extrusion forming die 2, so that the straight tube blank can be gradually filled into the branch tubes at two sides, after the branch tubes at two sides are completely filled, the press can be stopped, and the straight tube blank is press-formed into a special-shaped tube blank in a specific three-.
Further, after the extrusion billet 3 is drawn out of the three-way branch pipe in the extrusion die 2, the method further comprises the following steps:
and reversely extruding the extrusion blank 3 into the extrusion forming die 2 by using the extrusion punch at the other end of the upsetting rod 4 until the extrusion blank 3 is flush with the upper end part of the main pipe of the extrusion forming die 2.
It is understood that this step backward extrudes the upset bar 4 into the extrusion die 2 to avoid the upper main tube position of the extrusion die 2 failing to reach full shape due to the upset of the upset bar 4 on the extrusion billet 3 in the forward direction.
Specifically, referring to fig. 6, since the extrusion billet 3 fills the three-way branch pipe at the lower part of the extrusion die 2 during the above-mentioned upsetting, however, a large amount of gaps still exist between the main pipes at the upper part of the extrusion die 2 and are not yet filled, the present invention uses the extrusion punch to perform backward extrusion until the extrusion billet 3 is flush with the upper end of the main pipe of the extrusion die 2, so that the extrusion billet 3 fills the inner wall of the main pipe at the upper part of the extrusion die 2.
In the embodiment of the present invention, before the placing the extrusion billet 3 in the extrusion forming die 2, the method further includes: the extrusion billet 3 is heated to the austenite zone. Specifically, since the extrusion process of the present invention specifically employs hot extrusion, heating to the austenite region facilitates the deformation of the extrusion billet under pressure.
Further, before the extrusion billet 3 is placed in the extrusion die 2, the method further includes:
and uniformly smearing a lubricant on the inner wall of the extrusion forming die.
It can be understood that the quality and the upsetting work efficiency of upsetting the extrusion billet 3 can be improved by uniformly coating the lubricant on the inner wall of the extrusion die 2 and then placing the extrusion billet 3 on the extrusion die 2.
It should be noted that, in the three-way extrusion process, the deformation resistance is large, and the incomplete filling problem is easy to occur. The height of the die branch pipe is reasonably set before extrusion, so that the complete filling of the three-way branch pipe is ensured. For example, the internal dimension of the extrusion forming die 2 can be 1.1 to 1.3 times of the design dimension of the finished pressure pipe tee.
According to the embodiment of the disclosure, the pressure pipe tee 1 comprises a main pipe and two branch pipes, wherein a circular extrusion pad is arranged on the upper part of the main pipe in the extrusion and inflation process of the main pipe, and the diameter of the circular extrusion pad is positioned between the design size of the main pipe and the inner size of the extrusion forming die 2.
It can be understood that the extrusion pad is arranged on the upper portion of the main pipe of the tee joint, a smaller gap is reserved between the extrusion pad and the die due to the diameter design of the extrusion pad, the excessive growth of the flash is prevented, the upsetting rod 4 is prevented from being blocked, and the filling integrity of the main pipe of the tee joint is ensured.
In some embodiments, the extruder for extrusion is provided with a stroke switch to restrict the alignment of the central axis of the extrusion die 2 and the central axis of the upset bar 4.
Specifically, a travel switch is arranged below the extruder, and when the center position of the extrusion forming die 2 is aligned with the center position of the upsetting rod 4 above under the pushing action of the extruder, the travel switch sends a limit signal, so that the extruder drives the upsetting rod 4 to perform extrusion.
Alternatively, the design accuracy of the travel switch may be within ± 2 mm. It should be noted that, according to the embodiment of the present invention, the design accuracy may be adaptively adjusted according to actual needs, and the present invention is not particularly limited to this.
Because the extrusion forming die 2 is adopted, the product manufactured by adopting the extrusion forming process has less surface allowance and high material utilization rate. In addition, because the upsetting rod 4 and the extrusion punch at the other end of the upsetting rod are adopted to extrude the internal material of the constructed forging piece manufactured in the step S2, the constructed forging piece is compensated to the manufactured product body through metal flow, the material utilization rate is improved, and the heat treatment wall thickness of the product is greatly reduced. The method brings great benefits to formulation of a subsequent heat treatment process for constructing the forged piece, and can greatly reduce the internal defects of the material caused by large temperature difference between the inside and the outside of the material.
According to the embodiments of the disclosure, it can be known through measurement that the grain size of the tee-joint-shaped blank prepared in step S3 is ideal, the machining allowance is large, and the control of the external dimensions of the tee joint in the subsequent heat treatment and machining processes is facilitated.
Based on the above, the invention combines the construction forming method and the extrusion forming process, the construction forging is prepared by the construction forming method and is used as an extrusion blank, and the tee joint forming is carried out on the basis, so that the hydrogen content can be effectively controlled, and the technical requirements of the pressure pipe are further met. The chemical components, the mechanical property uniformity and the stability of the constructed forge piece are superior to those of the traditional forge piece, and the forge piece has great advantages when being used for extruding blanks.
And step S4, demolding the tee-shaped blank, and then sequentially carrying out rough machining, heat treatment and machining to obtain the finished product of the pressure pipe tee.
By an embodiment of the invention, wherein the rough machining comprises: and (3) finishing the end face, polishing, removing burrs and chamfering the groove.
The heat treatment comprises the following steps: solid solution heating and rapid water cooling.
Specifically, the solution heating and rapid water cooling process comprises:
fully dissolving carbide in the tee-joint-shaped blank into an austenitic stainless steel matrix in a solid solution mode, and then rapidly cooling the steel matrix in a water cooling tank by water to avoid precipitation of the carbide.
It should be noted that the solid solution heat treatment can re-dissolve the precipitated phase into austenite to form a supersaturated solution, thereby realizing the regulation and control of the structure and performance of the forging.
It can be seen that the heat treatment process of solid solution heating and rapid water cooling adopted by the application ensures the full solid solution of the hydrocarbon, the rapid water cooling process further avoids the precipitation of the carbide, and the obdurability matching and the high-temperature long-term performance of the material are ensured, thereby improving the intercrystalline corrosion resistance of the pressure pipe tee finished product.
Due to the fact that the wall thickness is thin and the shape is complex, deformation is prone to occurring under the action of thermal stress in the tee joint rapid water cooling process. Aiming at the deformation problem in the solution treatment, due to the subsequent organic processing procedure, in the embodiment of the invention, the size after processing can be ensured to meet the requirement by increasing the design allowance.
In an embodiment of the present invention, the machining includes: finish machining and grinding, removing the allowance of each end part of the tee-joint-shaped blank, and performing groove cutting on each port until the design size of the finished pressure pipe tee-joint product
Further, the machining process further comprises the following steps: and carrying out nondestructive testing on the machined blank, and obtaining the finished product of the pressure pipe tee after the finished product is qualified.
In the embodiment of the invention, the finished product of the pressure pipe tee is made of austenitic stainless steel, wherein the content of hydrogen in the chemical composition of the austenitic stainless steel is less than 2 ppm.
It should be noted that the chemical composition of the austenitic stainless steel used for manufacturing the pressure pipe tee finished product in the invention requires that the hydrogen content is less than 2ppm, and the conventional electroslag smelting process increases hydrogen and oxygen, so that the requirements are difficult to achieve.
The nondestructive testing comprises the following steps: penetration test and ultrasonic test. In addition, because the pressure pipe tee joint of the invention is applied to the nuclear power fast reactor, the nondestructive testing operation process is required to be carried out strictly according to relevant standard specifications.
In summary, embodiments of the present invention provide a method for manufacturing a pressure tube tee, in which an austenitic stainless steel used for a pressure tube is manufactured by comprehensive application of smelting and continuous casting, a construction forming method, an extrusion forming process, and a heat treatment process of the fast reactor pressure tube tee, wherein the content of hydrogen in chemical components of the austenitic stainless steel is less than 2 ppm. The quality requirement of the high-purity pressure pipe three-way finished product is difficult to achieve in the conventional electroslag smelting process.
It should be noted that the implementations not shown or described in the drawings are in a form known to those of ordinary skill in the art. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure. Additionally, while exemplifications of parameters including particular values may be provided herein, it is to be understood that the parameters need not be exactly equal to the respective values, but may be approximated to the respective values within acceptable error margins or design constraints.
It should be further noted that directional terms, such as "upper", "lower", "front", "back", etc., referred to in the embodiments are only directions referring to the drawings. Accordingly, the directional terminology used is intended to be in the nature of words of description rather than of limitation.
And the shapes and sizes of the respective components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.
Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (21)
1. A method of making a pressure tube tee, comprising:
after raw materials are subjected to rough smelting, a continuous casting billet is prepared by adopting an external refining method and a continuous casting process;
manufacturing a construction forge piece as an extrusion blank by adopting a construction forming method on the continuous casting billet;
manufacturing the extruded blank into a tee-shaped blank by adopting an extrusion forming process;
and (3) demolding the tee-joint-shaped blank, and then sequentially carrying out rough machining, heat treatment and machining to obtain the finished product of the pressure pipe tee joint.
2. The method for manufacturing a pressure tube tee as claimed in claim 1, wherein in the step of forming the continuous casting slab using an out-of-furnace refining method and a continuous casting process, the out-of-furnace refining method comprises: and refining the raw materials after the coarse smelting by adopting a vacuum oxygen blowing decarburization method, a ladle refining method and a vacuum degassing method in sequence.
3. The method of manufacturing a pressure tube tee as claimed in claim 2, wherein said refining the raw material after the rough refining by a ladle refining method comprises:
and refining steel by using a ladle refining furnace, and adding alloy to adjust the components of molten steel in the refining process so as to enable the smelted molten steel to meet the requirements of target components of steel grades.
4. The method for manufacturing the pressure pipe tee as claimed in claim 1, wherein in the step of manufacturing the construction forged piece by using the construction forming method for the continuous casting billet, the construction forming method sequentially comprises the following steps: sawing a continuous casting blank, milling and grinding the surface, cleaning and processing the surface, stacking, sealing and welding in vacuum and polishing welding seams.
5. The method for manufacturing the pressure pipe tee as claimed in claim 4, wherein the slab is a solid continuous cast round bar stock, and the slab sawing comprises: and sawing the continuous casting blank to a preset blanking length.
6. The method of making a pressure tube tee as claimed in claim 4, wherein said surface milling comprises: machining a blank sawed from the continuous casting blank into a flat and smooth surface by using a rotary milling cutter;
the surface cleaning treatment comprises: and carrying out surface treatment on the blank subjected to surface milling and grinding to ensure that the surface of the blank reaches the preset roughness and cleanliness.
7. The method of manufacturing a pressure tube tee as recited in claim 4, wherein the vacuum sealing comprises: and placing the stacked blanks in a vacuum environment integrally for vacuum electron beam sealing and welding.
8. The method of making a pressure tube tee as claimed in claim 1, wherein said forming said extrusion billet into a tee shaped billet using an extrusion process comprises:
the extrusion blank is a straight pipe blank, the extrusion blank is placed in an extrusion forming die, and an upsetting rod is driven by an extruder to perform extrusion upsetting on the extrusion blank, so that the extrusion blank is pulled out of the three-way branch pipe in the extrusion forming die.
9. The method for manufacturing the pressure pipe tee as claimed in claim 8, wherein the upsetting bar is composed of a solid cylindrical shaft and a cylindrical boss which is located at one end of the cylindrical shaft and has a diameter larger than that of the cylindrical shaft, wherein the cylindrical shaft is used as an extrusion punch, the cylindrical boss is used for extrusion upsetting, and the diameter of the cylindrical boss is the same as that of the inner wall of the main pipe at the upper part of the extrusion forming die.
10. The method of making a pressure tube tee as claimed in claim 8, wherein prior to placing the extrusion blank in the extrusion die, further comprising:
heating the extrusion billet to an austenite zone.
11. The method of making a pressure tube tee as claimed in claim 8, wherein prior to placing the extrusion blank in the extrusion die, further comprising:
and uniformly smearing a lubricant on the inner wall of the extrusion forming die.
12. The method of making a pressure tube tee as recited in claim 8, wherein the extrusion billet further comprises, after drawing the tee leg out of the extrusion die:
and reversely extruding the extrusion blank into the extrusion forming die by using the extrusion punch head at the other end of the upsetting rod until the extrusion blank is flush with the end part of the three-way main pipe of the extrusion forming die.
13. The method for making a pressure pipe tee as claimed in claim 12, wherein a circular extrusion pad is provided on the upper portion of the main pipe during extrusion and inflation of the main pipe, the circular extrusion pad having a diameter sized to be between the design size of the main pipe and the inner size of the extrusion die.
14. The method of manufacturing a pressure tube tee as claimed in claim 8, wherein the extruder is provided with a travel switch to limit the alignment of the central axis of the extrusion die and the central axis of the upset bar.
15. The method for manufacturing the pressure pipe tee as claimed in claim 1, wherein in the step of obtaining the finished pressure pipe tee after the tee-shaped blank is subjected to demoulding, rough machining, heat treatment and machining in sequence, the rough machining comprises the following steps: and (3) finishing the end face, polishing, removing burrs and chamfering the groove.
16. The method for manufacturing the pressure pipe tee as claimed in claim 1, wherein in the step of obtaining the finished pressure pipe tee after the tee-shaped blank is subjected to rough machining, heat treatment and machining in sequence after the step of demoulding, the heat treatment comprises the following steps in sequence: solid solution heating and rapid water cooling.
17. The method of manufacturing a pressure tube tee as claimed in claim 16 wherein the solution heating and rapid water cooling process comprises:
fully dissolving carbide in the tee-joint-shaped blank into an austenitic stainless steel matrix in a solid solution mode, and then rapidly cooling the steel matrix in a water cooling tank by water to avoid precipitation of the carbide.
18. The method for manufacturing the pressure pipe tee as claimed in claim 1, wherein in the step of obtaining the finished pressure pipe tee after the tee-shaped blank is subjected to the rough machining, the heat treatment and the machining in sequence after the demoulding, the machining comprises the following steps: and performing finish machining and grinding, removing the allowance of each end part of the tee-joint-shaped blank, and performing groove cutting on each port until the design size of the finished pressure pipe tee-joint product is reached.
19. The method of making a pressure tube tee as recited in claim 18, further comprising after said machining:
and carrying out nondestructive testing on the machined blank, and obtaining the finished product of the pressure pipe tee after the finished product is qualified.
20. The method of making a pressure tube tee as recited in claim 19, wherein the non-destructive testing comprises: penetration test and ultrasonic test.
21. The method for manufacturing a pressure tube tee as claimed in claim 1, wherein the material of the finished pressure tube tee is austenitic stainless steel, wherein the austenitic stainless steel has a chemical composition with less than 2ppm of hydrogen.
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