Punching core rod for supercritical or ultra-supercritical steel pipe machining and slag removing device of punching core rod

Abstract

The utility model relates to a punching core rod for supercritical or ultra-supercritical steel pipe processing and a slag removing device thereof, a core rod body of the punching core rod is provided with a through hole which extends from the head part of the core rod body to the tail part of the core rod body along the axial direction of the core rod body and allows the center of a continuous casting billet to pass through, the head part of the through hole is provided with a coaxial guide hole, and the guide hole is communicated with the core rod body from the head part to the tail part of the core rod body. The hole diameter of the guide hole is gradually reduced, residues of center cracks of the continuous casting billet in the punching process can be guided into the through hole along the guide hole to be discharged, and steel slag can be pushed out of the through hole to remove residual steel after being cooled through the slag removal device. The method thoroughly solves the problem of steel pipe inner defects caused by large center cracks of P91, P92 and other low-carbon high-alloy steel or high-alloy stainless steel continuous casting billets, breaks through the bottleneck that the continuous casting billets replace die casting steel ingots, is suitable for machining large-wall-thickness steel pipes, effectively reduces the single-side turning amount of the steel pipes, and greatly improves the yield and qualified rate of the steel pipes.

Description

Technical Field

[0001] The utility model belongs to the technical field of punching mandrels for pipe processing, and specifically relates to a punching mandrel for processing supercritical or ultra-supercritical steel pipes and a slag cleaning device thereof, including large-walled thick steel pipe processing for P91 and P92 continuous casting billets. Background Art

[0002] Supercritical and ultra-supercritical units are a type of power generation technology that uses high-temperature and high-pressure steam to drive steam turbines. They are characterized by high efficiency, low energy consumption, and high environmental performance, and are of great significance in meeting energy needs and promoting sustainable development. At present, the main steam pipelines of supercritical and ultra-supercritical units are developing in the direction of large specifications and large wall thickness. The solidification speed of the raw material, the die-cast steel ingot, is slow. Although the center is relatively dense, the die-cast steel ingot needs to be cut off, resulting in a yield rate of about 70% to 80%. There are problems such as low production efficiency, long delivery time, and low yield rate. With the continuous advancement of continuous casting technology, the yield rate of continuous casting round billets is above 90%, and the yield rate has been greatly improved. China hopes to gradually adopt continuous casting round billets P91 and P92 to replace die-cast steel ingots, but there are still the following bottlenecks in using continuous casting round billets to replace die-cast steel ingots:

[0003] When the main steam pipe has a larger size and thicker wall, a larger size of continuous casting round billet is required. However, steels such as P91 and P92 belong to the low-carbon high-alloy series. The violent peritectic reaction and the well-developed columnar crystals can easily cause bridging during the solidification process and produce axial intergranular cracks. Taking a φ800mm P92 continuous casting round billet as an example, its longitudinal section is as follows: Figure 1 As shown, the length of the central crack is within φ115mm. The traditional pipe making process is "cutting → heating → punching → forging pipe". The punching process diagram is as follows Figure 2 As shown, a flat-bottomed core rod 1 is used as a punching core rod. After the heated continuous casting round billet 2 is placed in a mold 3, the flat-bottomed core rod 1 is aligned with the center of the head section of the continuous casting round billet 2, and then the flat-bottomed core rod 1 is squeezed toward the bottom of the continuous casting round billet 2 and punched into the continuous casting round billet 2. The punching is stopped when the distance from the bottom end of the continuous casting round billet 2 to 200 mm is stopped, and the punching core rod is replaced, and then forged into a steel pipe; during the punching process, the center crack residue 4 caused by the axial intergranular crack of the continuous casting round billet 2 will gradually accumulate with the increase of the stroke of the flat-bottomed core rod 1, resulting in the center crack remaining on the inner wall of the steel pipe, as shown in FIG. Figure 3 As shown, such defects are often concentrated at the end of the steel pipe, forming inner wall defects, which seriously affect the final product qualification rate. At the same time, the single-side turning amount of the steel pipe is large, about 10 to 15 mm, which also affects the processing efficiency and production cost. Utility Model Content

[0004] The utility model aims to solve at least one of the above-mentioned technical problems to a certain extent. The utility model provides a punching mandrel and a slag cleaning device for supercritical or ultra-supercritical steel pipe processing, which can effectively solve the problem of inner wall defects of the steel pipe caused by the center defects of the continuous casting billet during punching, and is conducive to using the continuous casting billet to replace the die-cast steel ingot to manufacture large-wall supercritical or ultra-supercritical steel pipes, thereby greatly improving the processing yield rate.

[0005] The technical solution adopted by the utility model to solve its technical problems is:

[0006] A punching mandrel for processing a supercritical or ultra-supercritical steel pipe comprises a mandrel body, wherein the mandrel body is provided with a through hole extending from the head of the mandrel body to the tail along the axial direction of the mandrel body, and the head of the through hole is provided with a coaxial guide hole, and the aperture of the guide hole gradually decreases from the head to the tail of the mandrel body.

[0007] Preferably, the aperture of the through hole decreases gradually from the head to the tail of the core rod body.

[0008] Preferably, the cross-section of the inner wall of the guide hole is an arc-shaped structure convex toward the center of the guide hole.

[0009] Preferably, a guide ring is provided at the head of the core rod body, and the inner hole of the guide ring also serves as a guide hole.

[0010] Preferably, the guide ring is a high-temperature alloy ring.

[0011] Preferably, the outer diameter of the guide ring is consistent with the outer diameter of the core rod body.

[0012] Preferably, an openable and closable rear cover is provided at the rear of the core rod body, and the rear cover can block the through hole.

[0013] Preferably, it includes a support frame that cooperates with the tail of the core rod body.

[0014] The slag cleaning device for punching mandrel for processing supercritical or ultra-supercritical steel pipes according to any one of the above items comprises a cooling device and a push rod, wherein the cooling device is used for cooling the mandrel body, and the push rod can extend into the through hole from the tail end of the through hole.

[0015] Preferably, the cooling device comprises a plurality of water cooling nozzles facing the outside of the core rod body.

[0016] Compared with the prior art, the beneficial effects of the utility model are:

[0017] (1) After the punching mandrel of the utility model is pressurized and punched into the continuous casting billet, the residue of the center crack of the continuous casting billet can be introduced into the through hole through the guide hole, and the center crack part is removed by pressurization. After the finished steel pipe is tested, no abnormal reflection wave is found on the inner wall, which greatly improves the qualified rate of the steel pipe, and completely solves the problem of internal defects in the steel pipe caused by large center cracks in the continuous casting billet of low-carbon high-alloy steel such as P91 and P92, thereby breaking through the bottleneck link of continuous casting billets replacing die-cast steel ingots.

[0018] (2) Since the head and tail of the die-cast steel ingot need to be cut off, the yield rate is about 70% to 80%, while the yield rate of the continuous casting billet is above 90%. It is possible to use continuous casting billets instead of die-cast steel ingots to manufacture large-walled supercritical or ultra-supercritical steel pipes, which greatly improves the yield rate.

[0019] (3) For steel pipes of the same specification, by using the punching mandrel of the utility model, the single-side turning amount of the steel pipe can be reduced from the original 10-15 mm to 1-2 mm, which is beneficial to improving processing efficiency and reducing production costs.

[0020] (4) For continuous casting round billets or high alloy stainless steel with large central defects, this punching mandrel can also be used to process them into steel pipes.

[0021] (5) After the slag cleaning device cools the core rod body, a push rod can be inserted into the through hole from the rear end of the through hole to push the cooled and condensed slag in the through hole out of the guide hole, thereby achieving a rapid slag cleaning effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0023] Figure 1 This is a longitudinal section sample of the central defect of a P92 continuous casting round billet;

[0024] Figure 2 It is a schematic diagram of punching of an existing flat bottom mandrel;

[0025] Figure 3 This is a photo of the inner wall defects of P92 steel pipe;

[0026] Figure 4 This is a cross-sectional structural diagram of the core rod body of Example 1 of the utility model;

[0027] Figure 5 It is a punching schematic diagram of Example 1 of the utility model;

[0028] Figure 6 This is a cross-sectional structural diagram of the core rod body of Example 2 of the utility model;

[0029] Figure 7It is a left view of the mandrel body of Embodiment 2 of the present utility model;

[0030] Figure 8 It is a top view of the mandrel body of Example 2 of the utility model;

[0031] Fig. 9 It is a punching schematic diagram of Embodiment 2 of the present utility model;

[0032] Fig.10 This is a schematic diagram of slag removal in Example 3 of the utility model;

[0033] Fig.11 This is a record diagram of the steel pipe flaw detection process of Example 4 of the utility model;

[0034] Fig.12 This is a record diagram of the steel pipe flaw detection process of the comparative example of the utility model;

[0035] Fig.13 This is a photo of the inner wall defect of the P92 steel end face of the comparative example of the utility model.

[0036] Markings in the figure: flat-bottomed core rod 1, continuous casting round billet 2, mold 3, center crack residue 4;

[0037] Mandrel body 5, through hole 501, guide hole 502, guide ring 6, rear cover 7, support frame 8, steel slag 9;

[0038] Cooling device 10 , water cooling nozzle 101 , cooling water 102 , push rod 12 . DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0040] In the description of the present invention, it should be understood that the terms "center", "thickness", "head", "tail", "axial", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] Embodiment 1:

[0043] In view of the problem of internal defects in steel pipes caused by large central cracks in continuous casting billets when continuous casting billets are used to replace die-cast steel ingots to manufacture large-walled supercritical or ultra-supercritical steel pipes in the prior art, Figure 4 As shown, a preferred embodiment of the punching mandrel for processing supercritical or ultra-supercritical steel pipes of the utility model is shown, the punching mandrel includes a mandrel body 5, which is used for punching continuous casting billets, the mandrel body 5 is provided with a through hole 501 extending along the axial direction of the mandrel body 5 from the head of the mandrel body 5 to the tail for the center of the continuous casting billet to pass through, the head of the through hole 501 is provided with a guide hole 502 coaxial with the through hole 501 and for the center of the continuous casting billet to pass through, and the aperture of the guide hole 502 gradually decreases from the head to the tail of the mandrel body 5.

[0044] like Figure 5 As shown, when used, after the heated continuous casting billet is placed in the mold 3, the head of the core rod body 5 is placed close to the head of the continuous casting billet to be punched, so that the guide hole 502 and the through hole 501 are aligned with the center of the continuous casting billet, and the core rod body 5 is pressed and moved toward the tail of the continuous casting billet to gradually punch into the continuous casting billet. When the core rod body 5 is a certain distance away from the tail of the continuous casting billet, the aperture of the guide hole 502 gradually decreases from the head to the tail of the core rod body 5, so that the residue of the crack in the center of the continuous casting billet can be introduced into the through hole 501 through the guide hole 502, and the steel attached to the inside of the through hole 501 is extracted from the processed continuous casting billet along with the punching core rod, and then further The punching core rod can be reused by cleaning the steel slag 9 in the through hole 501. Compared with the existing flat-bottomed solid core rod, the central crack part can be removed by pressurization, which effectively reduces the residual accumulation of the central crack residue 4 of the continuous casting billet at the end of the steel pipe, thereby improving the inner wall defect problem of the steel pipe caused by the axial intergranular cracks of the continuous casting billet. This structure is simple, which is conducive to reducing the transformation cost based on the existing flat-bottomed core rod 1, and then the continuous casting billet with a yield rate greater than that of the die-cast steel ingot can be used to replace the die-cast steel ingot to manufacture steel pipes, and the qualified rate of the continuous casting billet to manufacture steel pipes is greatly improved, and the single-side grinding amount can also be reduced, thereby breaking through the bottleneck of the continuous casting billet replacing the die-cast steel ingot.

[0045] Preferably, the inner wall cross-section of the guide hole 502 is an arc-shaped structure convex toward the center of the guide hole 502, which is beneficial to increase the thickness of the core rod body 5 at the guide hole 502 and improve the strength. At the same time, the arc-shaped structure can quickly reduce the aperture of the guide hole 502, making it easier for the steel flow to flow.

[0046] Embodiment 2:

[0047] like Figures 6 to 8 As shown, it is another preferred embodiment of the punching mandrel for processing supercritical or ultra-supercritical steel pipes described in the utility model, which differs from Example 1 in that: a guide ring 6 is provided at the head of the mandrel body 5, and the inner hole of the guide ring 6 also serves as a guide hole 502, and the guide hole 502 is a tapered hole structure. The guide ring 6 is a high-temperature alloy ring. The ring made of high-temperature alloy material has the characteristics of high temperature resistance and high strength and hardness compared with the mandrel body 5. Compared with the one-piece structure of Example 1, a high-temperature alloy ring is used as the guide ring 6 to be combined with the mandrel body 5, which can improve the tolerance of the head during the punching process of the punching mandrel, reduce the wear on the mandrel body 5, and thus improve the overall life of the punching mandrel. The high-temperature alloy ring can be fixedly connected to the mandrel body 5 by welding to improve the connection strength. The high-temperature alloy ring can also be detachably connected to the mandrel body 5 by threaded matching or the like, which is convenient for replacing the high-temperature alloy ring that is damaged or of unsuitable specifications after the guide ring 6 is used, thereby improving the flexibility of use and reducing the replacement cost compared with the overall replacement.

[0048] Preferably, the aperture of the through hole 501 gradually decreases from the head to the tail of the core rod body 5. For example, the through hole 501 can adopt a conical hole structure. On the one hand, it can facilitate the steel flow in front of the through hole 501 to move backward, thereby improving the removal effect of the central crack residue 4. On the other hand, the steel slag 9 solidified in the through hole 501 can be in a truncated cone structure, which is more convenient to push the steel slag 9 out from the tail of the through hole 501 for cleaning.

[0049] Preferably, the outer diameter of the guide ring 6 is consistent with the outer diameter of the core rod body 5, which is convenient for maintaining the punching roundness and consistency of the continuous casting billet. Compared with the guide ring 6 with a larger outer diameter than the core rod body 5, the pressure bearing capacity is increased. The consistent outer diameter can reduce the impact wear on the guide ring 6.

[0050] Preferably, the tail of the mandrel body 5 is provided with an openable and closable rear cover 7, for example: the rear cover 7 can be detachably connected to the tail of the mandrel body 5 by threaded cooperation, or one side of the rear cover 7 is hinged to the mandrel body 5, and the other side is connected to the mandrel body 5 by a movable connection structure such as a lock, so as to achieve opening and closing. The rear cover 7 can block the through hole 501. The purpose of adding the rear cover 7 is to prevent the high-temperature steel flow from flowing along the through hole 501 and out of the tail of the mandrel body 5 during the punching process, thereby polluting the working environment or damaging mechanical equipment close to the punching mandrel.

[0051] Preferably, a support frame 8 is included which cooperates with the tail of the mandrel body 5. The support frame 8 can be used to connect the mandrel body 5 or to abut against the tail of the mandrel body 5, and its function is to assist in the connection or support of the mandrel body 5 and its pressurizing drive mechanism.

[0052] The processing technology of the punching mandrel described in Example 1 or Example 2 includes:

[0053] (1) Cutting: Cut the continuous casting billet into a certain length after cutting, and heat the continuous casting billet to the target temperature;

[0054] (2) Punching: Fig. 9 As shown, the heated continuous casting billet is placed in the mold 3, and then a punching mandrel is used to punch holes from one end of the continuous casting billet to the other end. The guide hole 502 and the through hole 501 are aligned with the axis of the continuous casting billet, and the punching mandrel is pressed toward the center of the continuous casting billet, so that the central crack residue 4 of the high-temperature continuous casting billet flows along the guide hole 502 to the through hole 501 with the steel flow to perform punching.

[0055] (3) Removing residual steel: The through hole 501 after punching is filled with steel slag 9. The punching mandrel is pulled out from the continuous casting billet after punching, and the residual steel in the through hole 501 is cleaned. The punching mandrel in Example 2 can be cleaned by disassembling or opening the back cover 7, and the punching mandrel can be reused after cleaning. The continuous casting round billet 2 or high-alloy stainless steel with large central defects can also be processed into steel pipes by this process.

[0056] Embodiment 3:

[0057] like Fig.10 As shown, according to a preferred embodiment of the slag cleaning device for the punching core rod for processing supercritical or ultra-supercritical steel pipes described in Example 2, the slag cleaning device includes a cooling device 10 and a push rod 12, the cooling device 10 is used for cooling the core rod body 5, the push rod 12 can be extended into the through hole 501 from the tail end of the through hole 501, for example: the push rod 12 can be an iron rod, which can make the steel slag 9 in the through hole 501 condense with each other after cooling, and the steel slag 9 will not adhere to the inner wall of the through hole 501, and the iron rod is extended into the through hole 501 from the tail end of the through hole 501 to push the condensed steel slag 9 out of the guide hole 502 at the same time, so as to achieve a rapid slag cleaning effect, and the slag cleaning device has a simple structure and is easy to use.

[0058] Preferably, the cooling device 10 includes a plurality of water cooling nozzles 101 facing the outside of the core rod body 5. For example, a plurality of spaced water cooling nozzles 101 can be provided on both sides of the core rod body 5, and cooling is performed by spraying cooling water 102 onto the outer wall of the core rod body 5. The structure is simple and uniform cooling can be achieved.

[0059] Embodiment 4:

[0060] A method for processing a steel pipe with an outer diameter of φ596 mm and an inner diameter of φ126.5 mm using a P92 continuous casting round billet 2 with a specification of φ800 mm, the method comprising:

[0061] (1) Cutting: The P92 continuous casting round billet 2 with a size of φ800 mm is 2.3 m long and weighs about 9.13 tons. After the continuous casting round billet 2 is heated to 1250-1280°C in a ring furnace and kept warm for a certain period of time, the length of the central crack of the continuous casting round billet 2 is within φ120 mm.

[0062] (2) Punching + forging: The punching mandrel described in Example 2 is used, the outer diameter of the punching mandrel is φ575 mm, the diameter of the first end of the through hole 501 is φ100 mm, and the diameter of the tail end of the through hole 501 is φ80 mm. The continuously cast round billet 2 after being heated is placed in the mold 3, and then the punching mandrel is used to punch holes from one end of the continuously cast round billet 2 to the other end. The guide hole 502 is aligned with the through hole 501 and the axis of the continuously cast round billet 2. The punching mandrel is pressed toward the continuously cast round billet 2. The core of the billet 2 is squeezed to make the central crack residue 4 of the high-temperature continuous casting round billet 2 flow along the guide hole 502 to the through hole 501 with the steel flow, and punching is performed. The punching is stopped when the punching mandrel is 200mm away from the bottom; the punching mandrel is replaced, and the continuous casting round billet 2 is forged into a steel pipe. The steel pipe is subjected to normalizing + tempering heat treatment, and the inner wall of the steel pipe is ground on one side with a 3mm margin, and the outer wall is turned with a 8mm margin. After turning, flaw detection is performed, and it is seen Fig.11 As shown, no abnormal reflection waves were found on the inner wall.

[0063] (3) Removing residual steel: After the punching core rod is withdrawn, the slag cleaning device described in Example 3 is used to flush the punching core rod with water to cool it. The through hole 501 after punching is filled with steel slag 9. Then, the rear cover 7 is opened, and the steel slag 9 is pushed out with the push rod 12 to clean the residual steel in the through hole 501.

[0064] Embodiment 5:

[0065] A method for processing a steel pipe with an outer diameter of φ711 mm and an inner diameter of φ150 mm using a P92 continuous casting round billet 2 with a specification of φ900 mm, the method comprising:

[0066] (1) Cutting: The P92 continuous casting round billet 2 with a size of φ900 mm is 2.2 m long and weighs about 10.88 tons. After the continuous casting round billet 2 is heated to 1250-1280°C in a ring furnace and kept warm for a certain period of time, the length of the central crack of the continuous casting round billet 2 is within φ140 mm.

[0067] (2) Punching + forging: The punching mandrel described in Example 2 is used. The outer diameter of the punching mandrel is φ525 mm. The diameter of the through hole 501 at the head end is φ110 mm. The diameter of the through hole 501 at the tail end is φ80 mm. The continuously cast round billet 2 after being heated is placed in the mold 3. Then, the punching mandrel is used to punch holes from one end of the continuously cast round billet 2 to the other end. The guide hole 502 is aligned with the through hole 501 and the axis of the continuously cast round billet 2. The punching mandrel is pressed into the center of the continuously cast round billet 2. The central crack residue 4 of the high-temperature continuous casting round billet 2 is pressed to flow along the guide hole 502 to the through hole 501 with the steel flow, and punching is performed. The punching is stopped when the punching mandrel is 200 mm away from the bottom. The punching mandrel is replaced, and the continuous casting round billet 2 is forged into a steel pipe. The steel pipe is subjected to a normalizing + tempering heat treatment, and the inner wall of the steel pipe is ground on one side with a 2 mm margin, and the outer wall is turned with a 6 mm margin. After turning, flaw detection is performed, and no abnormal reflection wave of the inner wall is found.

[0068] (3) Removing residual steel: After the punching core rod is withdrawn, the slag cleaning device described in Example 3 is used to flush the punching core rod with water to cool it. The through hole 501 after punching is filled with steel slag 9. Then, the rear cover 7 is opened, and the steel slag 9 is pushed out with the push rod 12 to clean the residual steel in the through hole 501.

[0069] Embodiment 6:

[0070] A method for processing a steel pipe with an outer diameter of φ811 mm and an inner diameter of φ160 mm using a P92 continuous casting round billet 2 with a specification of φ1000 mm, the method comprising:

[0071] (1) Cutting: The P92 continuous casting round billet 2 with a size of φ1000 mm is 2.4 m long and weighs about 14.26 tons. After the continuous casting round billet 2 is heated to 1250-1280°C in a ring furnace and kept warm for a certain period of time, the length of the central crack of the continuous casting round billet 2 is within φ150 mm.

[0072] (2) Punching + forging: The punching mandrel described in Example 1 is used, the outer diameter of the punching mandrel is φ585 mm, the through hole 501 is a tapered hole, the diameter of the first end of the through hole 501 is φ120 mm, and the diameter of the tail end of the through hole 501 is φ90 mm. The continuously cast round billet 2 after being heated is placed in the mold 3, and then the punching mandrel is used to punch holes from one end of the continuously cast round billet 2 to the other end, the guide hole 502 is aligned with the through hole 501 and the axis of the continuously cast round billet 2, and the punching mandrel is pressed toward the continuously cast round billet. The core of the billet 2 is squeezed so that the central crack residue 4 of the high-temperature continuous casting round billet 2 flows along the guide hole 502 to the through hole 501 with the steel flow, and punching is performed. The punching is stopped when the punching mandrel is 200 mm away from the bottom. The punching mandrel is replaced, and the continuously cast round billet 2 is forged into a steel pipe. The steel pipe is subjected to normalizing + tempering heat treatment, and the inner wall of the steel pipe is ground on one side with a 2 mm allowance, and the outer wall is turned with a 6 mm allowance. After turning, flaw detection is performed, and no abnormal reflection wave of the inner wall is found.

[0073] (3) Removing residual steel: After the punching mandrel is withdrawn, the slag cleaning device described in Example 3 is used to flush the punching mandrel with water to cool it. The through hole 501 after punching is filled with steel slag 9, and the steel slag 9 is pushed out by the push rod 12 to clean the residual steel in the through hole 501.

[0074] Comparative Example:

[0075] A method for processing a steel pipe using a flat-bottomed mandrel 1, the method comprising:

[0076] (1) Cutting: The P92 continuous casting round billet 2 with a size of φ800 mm is 2.3 m long and weighs about 9.13 tons. After the continuous casting round billet 2 is heated to 1250-1280°C in a ring furnace and kept warm for a certain period of time, the length of the central crack of the continuous casting round billet 2 is within φ120 mm.

[0077] (2) Punching + forging: Figure 2 As shown, a flat-bottomed core rod 1 is used as a punching core rod, and the outer diameter of the flat-bottomed core rod 1 is φ575mm. The continuously cast round billet 2 after being heated is placed in a mold 3, and then the flat-bottomed core rod 1 is used to punch holes from one end of the continuously cast round billet 2 to the other end. The flat-bottomed core rod 1 is pressed toward the core of the continuously cast round billet 2, and the punching is stopped when the flat-bottomed core rod 1 is 200mm away from the bottom. The punching core rod is replaced, and the continuously cast round billet 2 is forged into a steel pipe, and the steel pipe is subjected to normalizing + tempering heat treatment, and the inner wall of the steel pipe is ground on one side with a 9mm allowance, and the outer wall is turned with a 8mm allowance. After turning, flaw detection is performed, as shown in FIG. Fig.12 As shown in Figure 1, abnormal reflection waves were found on the inner wall at a distance of 0 to 300 mm from the end of end B. Fig.13 As shown, upon inspection, there are obvious defects inside.

[0078] It can be seen from the comparison results of Examples 4 to 6 with the comparative example that the use of the punching mandrel described in the utility model completely solves the problem of internal defects in the steel pipe caused by large central cracks in the continuous casting round billet 2 of low-carbon high-alloy steel such as P91 and P92, thereby breaking through the bottleneck link of the continuous casting round billet 2 replacing the die-cast steel ingot, greatly improving the yield rate, significantly reducing the single-side grinding amount, and greatly improving the qualified rate of the steel pipe. It is suitable for processing the continuous casting round billet 2 with large central defects or high-alloy stainless steel into steel pipes.

[0079] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the utility model. They are not intended to limit the protection scope of the utility model. All equivalent embodiments or changes that do not deviate from the technical spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A punching mandrel for processing supercritical or ultra-supercritical steel pipes, characterized in that: The invention comprises a mandrel body (5), wherein the mandrel body (5) is provided with a through hole (501) extending from the head of the mandrel body (5) to the tail along the axial direction of the mandrel body (5), and a coaxial guide hole (502) is provided at the head of the through hole (501), and the aperture of the guide hole (502) gradually decreases from the head to the tail of the mandrel body (5).

2. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 1, characterized in that: From the head to the tail of the core rod body (5), the aperture of the through hole (501) gradually decreases.

3. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 1, characterized in that: The inner wall cross section of the guide hole (502) is in an arc-shaped structure that bulges toward the center of the guide hole (502).

4. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 1, characterized in that: The head of the core rod body (5) is provided with a guide ring (6), and the inner hole of the guide ring (6) also serves as a guide hole (502).

5. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 4, characterized in that: The guide ring (6) is a high-temperature alloy ring.

6. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 4, characterized in that: The outer diameter of the guide ring (6) is consistent with the outer diameter of the core rod body (5).

7. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 1, characterized in that: The rear part of the core rod body (5) is provided with an openable and closable rear cover (7), and the rear cover (7) is capable of blocking the through hole (501).

8. The punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 1, characterized in that: It comprises a support frame (8) matched with the tail of the core rod body (5).

9. The slag cleaning device for punching mandrel for processing supercritical or ultra-supercritical steel pipe according to any one of claims 1 to 8, characterized in that: It comprises a cooling device (10) and a push rod (12), wherein the cooling device (10) is used for cooling the core rod body (5), and the push rod (12) can extend from the rear end of the through hole (501) into the interior of the through hole (501).

10. The slag cleaning device for punching mandrel for processing supercritical or ultra-supercritical steel pipe according to claim 9, characterized in that: The cooling device (10) comprises a plurality of water cooling nozzles (101) facing the outside of the core rod body (5).

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