Machining method of seamless thick-wall conical pipe for chemical equipment

Abstract

According to the machining method of the seamless thick-wall conical pipe for the chemical equipment, zirconium alloy raw materials are accurately controlled, the seamless thick-wall conical pipe is manufactured through a series of machining steps such as vacuum melting, cogging, saw cutting, blank manufacturing and rolling on the basis of the zirconium alloy raw materials, multiple heat treatment processes are executed in the machining process, the mechanical internal stress of products is effectively reduced, and the product quality is improved. Particularly, the design of a reaming die mandrel and a driving rotating shaft is adopted after forging in the machining process, so that the large head and the small head of the conical workpiece rotate at the same angle and speed in the reaming process, and finally better roundness and uniform wall thickness are obtained; and a product with a uniform structure is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical equipment processing and manufacturing, and specifically relates to a processing method of a seamless thick-walled tapered pipe for chemical equipment. Background Art

[0002] With the continuous advancement of science and technology, chemical production has increasingly higher requirements for the physical and chemical properties of chemical equipment materials. Typically, chemical equipment needs to have stable chemical properties, including corrosion resistance, acid resistance, and alkali resistance. It also needs to have stable physical properties and maintain structural integrity in high-temperature and high-pressure reaction environments to ensure long-term safe and reliable operation of the equipment. On this basis, conical tubes are used in many application scenarios. For example, in the production of fertilizers, resins, plastics, acids, etc., they are often used as key components of heat exchangers or container linings.

[0003] The traditional processing method of conical tubes is usually welded from rolled plates, but the production efficiency and yield rate of both rolling and welding processes are very low, and welds are still inevitably produced in the finished products, which affects the service life of conical tubes in the high temperature, high pressure and high corrosion environment of chemical equipment. With the development of technology, seamless conical tubes have gradually been more widely used. There are two main technical routes for their processing methods: one is forging with a conical punch through a hydraulic press; the other is machining through a forging machine to form a ring blank, but for thick-walled conical tubes, the machining allowance of the conical tube obtained by the first processing method is large, it is difficult to obtain accurate dimensional parameters, and it is impossible to obtain the size of the large-diameter conical tube mouth. The second processing method requires more raw materials, has a low yield rate, and has a high machining cost. In addition, it is difficult to evenly distribute the force during the processing, and the internal stress of the product is large, which is prone to deformation during use. Summary of the invention

[0004] In view of this, the present invention provides a processing method for seamless thick-walled tapered tubes for chemical equipment, which can reduce the loss of raw materials as much as possible while meeting the requirements of chemical equipment for high temperature resistance, high pressure resistance, and high corrosion resistance, reduce machining allowances and costs, and obtain products with more uniform structure by virtue of more uniform force, thereby greatly improving the yield rate and service life of seamless thick-walled tapered tubes.

[0005] The present invention provides a method for processing a seamless thick-walled tapered tube for chemical equipment, comprising the following steps:

[0006] S1. Raw material preparation, select sponge zirconium raw material, the mass fraction of Zr and Hf in the sponge zirconium raw material is not less than 99.4%, and the mass fraction of Hf is not more than 3%, the mass fraction of Cl in the remaining impurity elements is not more than 0.13%, the mass fraction of Mg is not more than 0.06%, the mass fraction of C and Al is not more than 0.03%, the mass fraction of Cr is not more than 0.02%, the mass fraction of H is not more than 0.0125%, the mass fraction of Si, Mn, Ni, N and O is not more than 0.01%, and the mass fraction of Ti, V and Pb is not more than 0.005%;

[0007] S2. Vacuum melting, melting the sponge zirconium raw material and a predetermined amount of zirconium dioxide powder and iron powder in a vacuum consumable arc furnace to obtain a zirconium ingot with a diameter of 600 mm, and making the mass fraction of the Zr element in the zirconium ingot not less than 99.0%, the mass fraction of the Hf element not more than 4.5%, and the total mass fraction of the Fe element and the Cr element in the impurity elements not exceeding 0.20%, wherein the mass fraction of the Fe element is between 0.08% and 0.13%, the mass fraction of the O element is between 0.11% and 0.15%, the mass fraction of the H element is not more than 0.005%, the mass fraction of the N element is not more than 0.15%, and the mass fraction of the C element is not more than 0.03%;

[0008] S3. Opening the blank, heating the zirconium ingot to 1020°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform three-pier and three-draw to obtain a rough round blank with a final size of 520mm in diameter, wherein the lower pier ratio of each of the three-pier and three-draw is controlled between 2.0 and 2.3, grinding the rough round blank and heating it to 860°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform two-pier and two-draw to obtain a rectangular material with a cross-sectional size of 300mm×300mm;

[0009] S4. Sawing, unloading the rectangular material on a horizontal belt saw and sawing a long billet with a height of 500±5mm, while accurately controlling the mass of the long billet to be 293kg;

[0010] S5. Blank making, the long blank is heated to 850℃±10℃ by a resistance heating furnace, and after being taken out of the furnace, a 800T hydraulic press is used to press the height of 500mm down to about 350mm, and then the 300mm×300mm square cross-section circular surface is rounded to a diameter of 400mm, thereby obtaining a round cake with a height of 350mm, and the round cake is returned to the furnace for heat preservation for 1.5h, and then a punch with a diameter of 150mm is used to punch a ring blank; then, the long blank is heated to 840℃±10℃ by a resistance heating furnace, and the round cake is kept for 150min, and after being taken out of the furnace, an 800T hydraulic press is used to expand the inner hole to a diameter of 290mm, and then a tapered punch is used to punch a tapered hole to obtain a tapered ring blank with an inner hole diameter of 300mm at the small end and an inner hole diameter of 400mm at the large end;

[0011] S6. rolling, heating the conical ring blank obtained by blank making to 830℃±10℃ by using a resistance heating furnace, keeping the temperature for 120min, and expanding the conical hole to the finished product size by using an 800KN reamer after taking out of the furnace, wherein the reamer has an opposing reaming die mandrel and an active rotating and pressing shaft, the wall surface of the conical ring blank is clamped between the reaming die mandrel and the active rotating and pressing shaft, and the active rotating and pressing shaft is driven to rotate so that the large end and the small end of the conical ring blank have the same rotation angular velocity, thereby expanding the hole to a preset roundness and wall thickness;

[0012] S7. Heat treatment: the rolled product is kept at 650°C in a trolley-type resistance furnace for 120 minutes and then air-cooled to room temperature.

[0013] The present invention provides a processing method for a seamless thick-walled tapered tube for chemical equipment. First, the composition of raw materials is precisely controlled to ensure that the product has excellent chemical properties and has acid, alkali and corrosion resistance. Secondly, a series of processing steps such as vacuum melting, blanking, sawing, blanking and rolling are selected on the basis of strict control of raw materials, so that the seamless thick-walled tapered tube has excellent physical properties while meeting the size standards, and the high pressure and high temperature resistance are greatly enhanced. Thirdly, multiple heat treatment processes are strictly performed in the above-mentioned processing steps to reduce the internal stress of the product during the mechanical processing process and improve the strength and toughness of the product. Fourthly, after forging, the core shaft of the hole expansion die and the active rotating and pressing shaft are designed so that the large and small heads of the tapered workpiece can rotate at the same angle and speed during the hole expansion process, and finally a better roundness and uniform wall thickness are obtained, and a product with uniform structure is obtained by making the workpiece evenly stressed during the rolling process. In summary, the present invention can realize the mass production of large-diameter seamless thick-walled tapered tubes, greatly save raw materials, reduce costs, have a smaller machining allowance than traditional ring blanks, improve machining efficiency, reduce residual stress of products after processing, prevent micro-deformation of products during long-term chemical production processes, and improve the dimensional accuracy of products during long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide a further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application, but do not constitute a limitation on the technical solution of the present application.

[0015] Figure 1 A schematic diagram of the structure of a horse-bar expansion and punching device used in a method for processing a seamless thick-walled tapered tube for chemical equipment provided by the present invention;

[0016] Figure 2 A schematic diagram of a tapered hole punching process used in a method for processing a seamless thick-walled tapered tube for chemical equipment provided by the present invention;

[0017] Figure 3 A schematic structural diagram of a tapered hole expanding device used in a method for processing a seamless thick-walled tapered tube for chemical equipment provided by the present invention;

[0018] Reference numerals:

[0019] 1-ring blank, 2-hammer, 3-core rod, 4-bracket, 5-conical ring blank, 6-punch, 7-active rotating and pressing shaft, 8-reaming machine core shaft. DETAILED DESCRIPTION

[0020] Various exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is not intended to be any limitation on the present invention and its application or use. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present invention clear and complete and to fully express the scope of the present invention to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the components and steps described in these embodiments should be interpreted as being merely exemplary and not as a limitation.

[0021] The present invention provides a method for processing a seamless thick-walled tapered tube for chemical equipment, comprising the following steps:

[0022] S1. Raw material preparation, select sponge zirconium raw material, the mass fraction of Zr and Hf in the sponge zirconium raw material is not less than 99.4%, and the mass fraction of Hf is not more than 3%, the mass fraction of Cl in the remaining impurity elements is not more than 0.13%, the mass fraction of Mg is not more than 0.06%, the mass fraction of C and Al is not more than 0.03%, the mass fraction of Cr is not more than 0.02%, the mass fraction of H is not more than 0.0125%, the mass fraction of Si, Mn, Ni, N and O is not more than 0.01%, and the mass fraction of Ti, V and Pb is not more than 0.005%;

[0023] S2. Vacuum melting, melting the sponge zirconium raw material and a predetermined amount of zirconium dioxide powder and iron powder in a vacuum consumable arc furnace to obtain a zirconium ingot with a diameter of 600 mm, and making the mass fraction of the Zr element in the zirconium ingot not less than 99.0%, the mass fraction of the Hf element not more than 4.5%, and the total mass fraction of the Fe element and the Cr element in the impurity elements not exceeding 0.20%, wherein the mass fraction of the Fe element is between 0.08% and 0.13%, the mass fraction of the O element is between 0.11% and 0.15%, the mass fraction of the H element is not more than 0.005%, the mass fraction of the N element is not more than 0.15%, and the mass fraction of the C element is not more than 0.03%;

[0024] Through S1 raw material preparation and S2 vacuum melting, the present invention accurately controls the chemical composition of the seamless thick-walled tapered tube, which together form the basis for the excellent physical and chemical properties of the Zr alloy.

[0025] The Zr alloy ingot configured by the present invention has extremely strong corrosion resistance: in an acidic environment, the corrosion resistance of zirconium is better than that of titanium and various steels, and even close to that of tantalum, a rare and expensive metal; more strikingly, zirconium also shows extremely high stability in alkaline solutions, and it is difficult to corrode it, whether it is an alkaline solution at room temperature or an alkali in a molten state. For example, in a strong alkaline medium such as sodium hydroxide, the corrosion resistance of zirconium is equivalent to that of nickel, but the cost is more economical, and in some cases, its performance is even better than tantalum and precious metals. This characteristic makes Zr alloy ingots an ideal choice for manufacturing key components such as heat exchangers and container linings in chemical equipment.

[0026] In addition to excellent corrosion resistance, the Zr alloy ingot configured in the present invention also has excellent mechanical properties and high temperature resistance: under extreme working conditions, such as high temperature and high pressure environment, the Zr alloy ingot can maintain stable structural strength and toughness, ensuring the safe and reliable operation of the equipment, which makes it suitable for manufacturing key components in chemical equipment. In addition, the Zr alloy ingot configured in the present invention also has a higher melting point, which can be better applied to various application scenarios in high temperature environments.

[0027] In the application field of the seamless thick-walled conical tube of the present invention, taking factories producing fertilizers, resins, plastics, acids and other chemicals as an example, these production processes often involve the treatment of a large amount of corrosive media, which places extremely high demands on equipment materials. Based on the above-mentioned raw material preparation and vacuum melting process, the Zr alloy ingot configured in the present invention can be successfully applied to the key parts of these equipment with its excellent corrosion resistance, mechanical properties and high temperature resistance, effectively extending the service life of the equipment, reducing maintenance costs, and improving production efficiency and safety.

[0028] Although Zr alloy ingots have many advantages, they also face certain challenges during the processing. The processing of Zr alloy ingots requires specific equipment and processes to ensure that the performance of the material is not destroyed during the processing. In view of this, the present invention provides subsequent mechanical processing steps.

[0029] S3. Opening the blank, heating the zirconium ingot to 1020°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform three-pier and three-draw to obtain a rough round blank with a final size of 520mm in diameter, wherein the lower pier ratio of each of the three-pier and three-draw is controlled between 2.0 and 2.3, grinding the rough round blank and heating it to 860°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform two-pier and two-draw to obtain a rectangular material with a cross-sectional size of 300mm×300mm;

[0030] S4. Sawing, unloading the rectangular material on a horizontal belt saw and sawing a long billet with a height of 500±5mm, while accurately controlling the mass of the long billet to be 293kg;

[0031] S5. Blank making, the long blank is heated to 850℃±10℃ by a resistance heating furnace, and after it comes out of the furnace, a 800T hydraulic press is used to press the height of 500mm down to about 350mm, and then the 300mm×300mm square cross-section circular surface is rounded to a diameter of 400mm, so as to obtain a round cake with a height of 350mm, and the blank is returned to the furnace for insulation for 1.5h, and then a punch with a diameter of 150mm is used to punch a ring blank; then, the long blank is heated to 840℃±10℃ by a resistance heating furnace, and the blank is heat-insulated for 150min and then taken out of the furnace and the blank is pressed down to about 350mm in height by a 800T hydraulic press, and then the round cake with a height of 350mm is rounded to a diameter of 400mm, and the blank is returned to the furnace for insulation for 1.5h, and then a punch with a diameter of 150mm is used to punch a ring blank; then, the long blank is heated to 840℃±10℃ by a resistance heating furnace, and the blank is heat-insulated for 150min and then taken out of the furnace and the blank is pressed down to about 350mm in height by a 800T hydraulic press, ... Figure 1 The 800T hydraulic press shown in the figure is used to expand the horse bar to an inner hole diameter of 290mm, and then the Figure 2 The tapered punch shown punches a tapered hole to obtain a tapered ring blank with a small end inner hole diameter of 300 mm and a large end inner hole diameter of 400 mm;

[0032] S6. Rolling: The conical ring blank obtained by billet making is heated to 830℃±10℃ in a resistance heating furnace, kept warm for 120min, and then taken out of the furnace and treated as follows: Figure 3 The 800KN reaming machine shown is used to expand the tapered hole to the finished product size, wherein the reaming machine has an opposing reaming die mandrel and an active rotating and pressing shaft, the wall surface of the tapered ring blank is clamped between the reaming die mandrel and the active rotating and pressing shaft, and the active rotating and pressing shaft is driven to rotate so that the large end and the small end of the tapered ring blank have the same rotation angular velocity, thereby reaming the hole to a preset roundness and wall thickness;

[0033] S7. Heat treatment: the rolled product is kept at 650°C in a trolley-type resistance furnace for 120 minutes and then air-cooled to room temperature.

[0034] On the basis of strict control of raw materials, the present invention selects a series of processing steps such as vacuum melting, blanking, sawing, blanking, rolling, etc., so that the seamless thick-walled tapered tube has excellent physical properties while meeting the size standards, and the high pressure and high temperature resistance are greatly enhanced. In addition, multiple heat treatment processes are strictly implemented in each of the above processing steps to reduce the internal stress of the product during the mechanical processing process and improve the strength and toughness of the product.

[0035] In particular, the present invention uses a hole expanding machine equipped with a hole expanding die mandrel and an active rotating and pressing shaft to further expand the hole after the conical ring blank is forged. Figure 3 On the processing section shown, the active rotating and pressing shaft is controlled to remain relatively parallel to the reaming machine mandrel during its own rotation and the approach amount is accurately controlled during the reaming process. On the one hand, the large and small ends of the tapered workpiece are driven to rotate at the same angle and speed, so that the workpiece is evenly stressed during the rolling process. On the other hand, the reaming force is controlled to prevent local deformation of the workpiece. Finally, better roundness and uniform wall thickness are obtained, and a product with uniform structure is obtained.

[0036] In summary, the present invention can realize the mass production of large-diameter seamless thick-walled tapered tubes, greatly save raw materials, reduce costs, have a smaller machining allowance than traditional ring blanks, improve machining efficiency, reduce residual stress of products after processing, prevent micro-deformation of products during long-term chemical production processes, and improve the dimensional accuracy of products during long-term use.

[0037] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for processing a seamless thick-walled tapered tube for chemical equipment, characterized in that: The following steps are involved: S1. Raw material preparation, select sponge zirconium raw material, the mass fraction of Zr and Hf in the sponge zirconium raw material is not less than 99.4%, and the mass fraction of Hf is not more than 3%, the mass fraction of Cl in the remaining impurity elements is not more than 0.13%, the mass fraction of Mg is not more than 0.06%, the mass fraction of C and Al is not more than 0.03%, the mass fraction of Cr is not more than 0.02%, the mass fraction of H is not more than 0.0125%, the mass fraction of Si, Mn, Ni, N and O is not more than 0.01%, and the mass fraction of Ti, V and Pb is not more than 0.005%; S2. Vacuum melting, melting the sponge zirconium raw material and a predetermined amount of zirconium dioxide powder and iron powder in a vacuum consumable arc furnace to obtain a zirconium ingot with a diameter of 600 mm, and making the mass fraction of the Zr element in the zirconium ingot not less than 99.0%, the mass fraction of the Hf element not more than 4.5%, and the total mass fraction of the Fe element and the Cr element in the impurity elements not exceeding 0.20%, wherein the mass fraction of the Fe element is between 0.08% and 0.13%, the mass fraction of the O element is between 0.11% and 0.15%, the mass fraction of the H element is not more than 0.005%, the mass fraction of the N element is not more than 0.15%, and the mass fraction of the C element is not more than 0.03%; S3. Opening the blank, heating the zirconium ingot to 1020°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform three-pier and three-draw to obtain a rough round blank with a final size of 520mm in diameter, wherein the lower pier ratio of each of the three-pier and three-draw is controlled between 2.0 and 2.3, grinding the rough round blank and heating it to 860°C±10°C by a resistance heating furnace and keeping it warm for 360min, and after being taken out of the furnace, using a 5000T hydraulic press to perform two-pier and two-draw to obtain a rectangular material with a cross-sectional size of 300mm×300mm; S4. Sawing, unloading the rectangular material on a horizontal belt saw and sawing a long billet with a height of 500±5mm, while accurately controlling the mass of the long billet to be 293kg; S5. Blank making, the long blank is heated to 850℃±10℃ by a resistance heating furnace, and after being taken out of the furnace, a 800T hydraulic press is used to press the height of 500mm down to about 350mm, and then the 300mm×300mm square cross-section circular surface is rounded to a diameter of 400mm, thereby obtaining a round cake with a height of 350mm, and the round cake is returned to the furnace for heat preservation for 1.5h, and then a punch with a diameter of 150mm is used to punch a ring blank; then, the long blank is heated to 840℃±10℃ by a resistance heating furnace, and the round cake is kept for 150min, and after being taken out of the furnace, an 800T hydraulic press is used to expand the inner hole to a diameter of 290mm, and then a tapered punch is used to punch a tapered hole to obtain a tapered ring blank with an inner hole diameter of 300mm at the small end and an inner hole diameter of 400mm at the large end; S6. rolling, heating the conical ring blank obtained by blank making to 830℃±10℃ by using a resistance heating furnace, keeping the temperature for 120min, and expanding the conical hole to the finished product size by using an 800KN reamer after taking out of the furnace, wherein the reamer has an opposing reaming die mandrel and an active rotating and pressing shaft, the wall surface of the conical ring blank is clamped between the reaming die mandrel and the active rotating and pressing shaft, and the active rotating and pressing shaft is driven to rotate so that the large end and the small end of the conical ring blank have the same rotation angular velocity, thereby expanding the hole to a preset roundness and wall thickness; S7. Heat treatment: the rolled product is kept at 650°C in a trolley-type resistance furnace for 120 minutes and then air-cooled to room temperature.

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