A production process for hot-rolled seamless copper tube

Abstract

The invention discloses a production process of hot-rolled seamless copper tube, which is characterized by comprising the following steps: heating of blank: opening a heating furnace, raising the furnace temperature in the heating furnace to a temperature 40°C to 60°C higher than the temperature required for rolling, and loading the blank into the heating furnace; heat preservation: after the blank is heated to the furnace temperature, the blank is kept warm for a required time, and after the heat preservation time is over, the blank is discharged; perforation: the blank is perforated into a hollow rough tube by a perforator; tube rolling: the thick-walled rough tube after perforation is pressed into a thin-walled rough tube to achieve the thermal size and uniformity required by the finished tube; sizing: the rough tube is shaped to the required outer diameter accuracy and roundness by a sizing machine, and during the heating process, the temperature of the blank after entering the heating furnace can quickly cross the range of 550°C to 800°C, so that the blank nucleation rate is high, and the grain growth rate is slow, the coarse grain phenomenon is reduced, and defects on the tube body surface are prevented.

Description

Technical Field

[0001] The invention relates to the technical field of hot rolling manufacturing, in particular to a production process of hot rolled seamless copper pipes. Background Art

[0002] In the prior art, the billets used to make copper tubes are mostly forged billets, and steel tubes are formed from the forged billets by hot extrusion. However, the forged billets are generally not dense enough. To avoid this phenomenon, the forged billets are replaced with continuous casting billets. However, the continuous casting billets cannot reach the billet diameter used by domestic hot extruders, and there are microcracks on the surface of the continuous casting billets. If the extrusion process is used (first punching holes, heating, and extruding by an extruder), cracks are likely to appear on the surface of the finished tube. For the production of seamless pipe fittings, there is also a hot rolling production process in the prior art. For example, patent document CN102513360A discloses a seamless steel pipe hot rolling manufacturing process, including: (1) heating the tube blank; (2) perforating; (3) continuous rolling; (4) concentrating the rough tube after perforation and rolling in a reheating furnace for reheating; (5) arranging a 5-stand tube stripping machine after the 8-stand continuous rolling unit to strip the rough tube after the 8-stand continuous rolling from the mandrel and enter the next process 20-stand tension reduction process; (6) configuring a 20-stand three-roller tension reduction stand after the 5-stand tube stripping unit, and the rough tube after the stripping enters (7) The hot finished steel pipe is finished by finishing the hot finished steel pipe. However, during the heating process, the tube blank is directly heated to 1290-1400°C, i.e., the temperature required for rolling. Firstly, the preparation of seamless copper tubes basically does not involve hot rolling. If the hot rolling manufacturing process disclosed in patent document CN102513360A is applied to the production of copper tubes, surface quality defects of the tube body are likely to occur. In addition, since the copper blank is relatively soft, it is inevitably easy to deform and bend during the heating process, which further affects the quality of the tube body. Summary of the invention

[0003] The purpose of the present invention is to provide a hot-rolled seamless copper tube production process to solve the problems existing in the above-mentioned prior art, and to prevent the coarse grain phenomenon that is easy to occur during the heating process of the copper billet, thereby preventing the surface quality defects of the tube body caused by the coarse grain, and ensuring the high quality of the finished product of the hot-rolled copper tube.

[0004] To achieve the above object, the present invention provides the following solution: The present invention provides a hot-rolled seamless copper tube production process, comprising the following steps:

[0005] Heating the billet: turning on the heating furnace, raising the temperature in the heating furnace to 40°C to 60°C higher than the temperature required for rolling, and loading the billet into the heating furnace;

[0006] Insulation: After the blank is heated to the furnace temperature, the blank is kept warm for a required time, and after the insulation time is over, the blank is discharged;

[0007] Perforation: the blank is perforated into a hollow rough tube by a perforator;

[0008] Pipe rolling: Press the perforated thick-walled rough pipe into a thin-walled rough pipe to achieve the thermal size and uniformity required by the finished pipe;

[0009] Sizing: Use a sizing machine to shape the rough pipe to the required outer diameter accuracy and roundness.

[0010] Preferably, before the blank heating step, a centering hole is opened at the end of the blank.

[0011] Preferably, in the blank heating step, a plurality of heat-resistant bricks are arranged at the bottom of the heating furnace, the blank is placed on each of the heat-resistant bricks, and the heat-resistant bricks are evenly distributed along the axial direction of the blank, and the heating temperature of the upper and lower surfaces of the blank is consistent.

[0012] Preferably, in the blank heating step, the blank reaching the furnace temperature is observed until the surface of the blank is uniformly red.

[0013] Preferably, before the punching step, the punching machine is used to roll a number of plain carbon steels for trial rolling, and after the trial rolling is correct, the blank is punched.

[0014] Preferably, before the punching step, glass powder for lubricating the plug is placed in the centering hole, and the glass powder is wrapped with a paper ball and fixed in the centering hole by the paper ball.

[0015] Preferably, in the heat preservation step, the heat preservation time is more than 120 minutes.

[0016] Preferably, in the sizing step, the sizing machine is equipped with a sizing frame, and the sizing frame adopts a thick-walled tube frame, and the thermal expansion coefficient of the thick-walled tube frame is 1.0178%.

[0017] Preferably, in the sizing step, a caliper is used to measure the diameter of the rough pipe, and the diameter of the rough pipe is adjusted by the sizing machine.

[0018] Preferably, after the sizing step, the finished pipe is placed on a cooling bed for cooling.

[0019] Compared with the prior art, the present invention has achieved the following technical effects:

[0020] First, turn on the heating furnace, raise the furnace temperature to 40℃ to 60℃ higher than the temperature required for rolling, and load the billet into the heating furnace. On the one hand, consider the temperature difference when the billet leaves the furnace during the rolling process to avoid the temperature of the billet from decreasing and falling below the temperature required for rolling. Therefore, the atmosphere temperature in the heating furnace is raised by 40℃ to 60℃ to the temperature required for rolling to ensure effective rolling of the billet. On the other hand, since the billet is cold when loaded into the furnace, the billet will cause the atmosphere temperature in the heating furnace to drop below 550℃. Then the furnace temperature is raised to 40℃ to 60℃ higher than the temperature required for rolling. First, the atmosphere temperature in the furnace drops to a certain temperature after the billet enters the furnace. However, even after dropping to a certain temperature, it is still higher than 550℃. Then the temperature is restored to the preset atmosphere of the heating furnace. The ambient temperature is increased, the temperature span is shortened, and the time required to heat up to the preset temperature is reduced, so that the billet temperature can quickly cross 550°C to 800°C, and after the billet is loaded into the heating furnace, due to the high preset temperature in the heating furnace, the billet heats up faster, and can quickly cross the range of 550°C to 800°C, so that the billet nucleation rate is high, and the grain growth rate is slow, reducing the coarse grain phenomenon, thereby preventing defects on the surface of the tube body; after the billet is heated to the furnace temperature, the billet is kept warm for the required time, and after the holding time is over, the material is discharged, and the billet is fully heated through the insulation effect to avoid insufficient heating effect in the middle position, which affects the subsequent piercing and rolling process, and ensures the rolling effect of the billet.

[0021] Secondly, before the billet heating step, a centering hole is opened at the end of the billet, and the plug is accurately positioned through the centering hole to ensure the uniformity of billet rolling and improve the quality of billet rolling.

[0022] Third, in the billet heating step, a number of heat-resistant bricks are arranged at the bottom of the heating furnace, and the billet is placed on each heat-resistant brick, and each heat-resistant brick is evenly distributed along the axial direction of the billet, and the heating temperature of the upper and lower surfaces of the billet is consistent. Since the copper billet is relatively soft, during the billet heating process in the heating furnace, if the billet is directly placed on the bottom of the inner side of the heating furnace, the heating temperature of the upper and lower surfaces of the billet will be different, the upper side will be heated faster, and the lower side will be heated slower, which will inevitably cause the heated and softened billet to deform. Furthermore, by arranging heat-resistant bricks, the upper and lower surfaces of the billet are heated at the same speed, thereby ensuring the coaxiality of the billet during rolling and improving the quality of the product.

[0023] Fourth, in the billet heating step, observe the billet that has reached the furnace temperature until the surface of the billet is uniformly red. By observing the state of the billet, the uniformity of heating of the billet can be determined. If the middle of the billet is white, it means that the heating is uneven, which can easily affect the subsequent rolling quality. The uniform red surface of the billet ensures that the billet is heated evenly, thereby improving the quality of billet rolling. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 The figure is a flow chart of the overall process of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The purpose of the present invention is to provide a hot-rolled seamless copper tube production process to solve the problems existing in the above-mentioned prior art, and to prevent the coarse grain phenomenon that is easy to occur during the heating process of the copper billet, thereby preventing the surface quality defects of the tube body caused by the coarse grain, and ensuring the high quality of the finished product of the hot-rolled copper tube.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Please refer to Figure 1 , wherein this embodiment provides a hot-rolled seamless copper tube production process, comprising the following steps:

[0030] Billet heating: Turn on the heating furnace, preferably an electric heating furnace, raise the furnace temperature in the heating furnace to 40°C to 60°C higher than the temperature required for rolling, and load the billet into the heating furnace; on the one hand, consider the temperature difference when the billet leaves the furnace during the rolling process, and avoid the billet temperature from decreasing and falling below the temperature required for rolling, so the atmosphere temperature in the heating furnace is raised by 40°C to 60°C to the temperature required for rolling, so as to ensure effective rolling of the billet; on the other hand, since the billet is cold when loaded into the furnace, the billet will cause the atmosphere temperature in the heating furnace to drop below 550°C, so the furnace temperature is raised to 40°C to 60°C higher than the temperature required for rolling, so that the atmosphere temperature in the furnace drops to a certain temperature after the billet enters the furnace, but even if the temperature is lowered to a certain level, the billet will not be heated. After the temperature reaches 550℃, it is higher than 550℃, and then it is restored to the preset atmosphere temperature of the heating furnace from this temperature. The temperature span is shortened, and the time required to heat up to the preset temperature is reduced, so that the billet temperature can quickly cross 550℃ to 800℃, and after the billet is loaded into the heating furnace, due to the high preset temperature in the heating furnace, the billet temperature rises faster, and can quickly cross the range of 550℃ to 800℃, so that the billet nucleation rate is high, and the grain growth rate is slow, reducing the coarse grain phenomenon, thereby preventing defects on the surface of the tube body; preferably, the rolling temperature of the rolled piece is required to be 830℃, the furnace temperature is heated to 870℃, and the heating furnace temperature is loaded when the furnace temperature rises to 870℃, and quickly crosses the 550-800℃ range. The reason for setting it to 870℃ is also to limit the preset temperature within a controllable range and reduce costs.

[0031] Insulation: After the billet is heated to the furnace temperature, it is kept warm for the required time. After the insulation time is over, the billet is discharged. The billet is fully heated by the insulation to avoid insufficient heating in the middle, which affects the subsequent piercing and rolling process, and ensures the rolling effect of the billet.

[0032] Punching: The blank is punched into a hollow tube by a punching machine. Specifically, during the punching process, the requirements for the punching process are: (1) the wall thickness of the punched tube must be uniform, the ovality must be small, and the geometric dimension accuracy must be high; (2) the inner and outer surfaces of the tube must be smooth, without defects such as scarring, folding, and cracks; (3) there must be a corresponding punching speed and rolling cycle to adapt to the production rhythm of the entire unit so that the final rolling temperature of the tube can meet the requirements of the tube rolling mill; and no water is turned on during the punching process, that is, cooling water is generally not added to the copper parts, the guide plate is not lubricated with glass powder, the guide plate has a good sealing of the hole type, and the length of the guide plate can be designed according to the length of the deformation zone;

[0033] Pipe rolling: the thick-walled rough pipe after perforation is pressed into a thin-walled rough pipe to achieve the thermal size and uniformity required by the finished pipe; that is, the wall thickness of the rough pipe in this process is determined according to the diameter reduction amount and empirical formula of the subsequent process, and the wall thickness is processed. This equipment is called a pipe rolling mill. Rolling is a material processing method that uses the friction of the rotating rollers to drag the workpiece into the roller space, and relies on the pressure exerted by the rollers to cause the workpiece to be compressed and deformed between two or more rollers. In the rolling deformation process, compression in the thickness direction is the dominant deformation. When the workpiece is compressed by the rollers in the thickness direction, the metal will flow longitudinally and transversely. The hot rolling process will refine the grains and make it less likely to crack on the surface;

[0034] The requirements for the tube rolling process are: (1) when converting thick-walled rough tubes into thin-walled rough tubes (reducing the wall and extending the tube), the rough tube must first have a high uniformity of wall thickness; (2) the rough tube has good internal and external surface quality. The selection of the tube rolling mill and the reasonable matching of the deformation between it and the perforation process are the key to determining the product quality, output and technical and economic indicators of the unit;

[0035] Sizing: The rough pipe is shaped to the required outer diameter accuracy and roundness by a sizing machine. The main function of sizing is to eliminate the uneven outer diameter of the rough pipe caused by the previous rolling process, so as to improve the outer diameter accuracy and roundness of the hot-rolled finished pipe. The requirements for the sizing process are: (1) to achieve the sizing purpose under a certain total diameter reduction rate and a smaller single-frame diameter reduction rate; (2) to achieve the task of using one specification of pipe blank to produce finished pipes of various specifications; (3) to further improve the outer surface quality of the steel pipe; and no water is turned on during the sizing process;

[0036] Before the billet heating step, a centering hole is opened at the end of the billet, and the plug is accurately positioned through the centering hole to ensure the uniformity of billet rolling and improve the quality of billet rolling.

[0037] Furthermore, in the billet heating step, a plurality of heat-resistant bricks are arranged at the bottom of the heating furnace, the billet is placed on each heat-resistant brick, and each heat-resistant brick is evenly distributed along the axial direction of the billet, and the heating temperature of the upper and lower surfaces of the billet is consistent. Since the copper billet is relatively soft, during the billet heating process in the heating furnace, if the billet is directly placed on the inner bottom of the heating furnace, the heating temperature of the upper and lower surfaces of the billet will be different, the upper side will be heated faster, and the lower side will be heated slower, which will inevitably cause the heated and softened billet to deform. Furthermore, by arranging the heat-resistant bricks, the upper and lower surfaces of the billet are heated at the same speed, thereby ensuring the coaxiality of the billet during rolling and improving the quality of the product.

[0038] Moreover, in the billet heating step, the billet that reaches the furnace temperature is observed until the surface of the billet is uniformly red. By observing the state of the billet, the uniformity of heating of the billet can be clearly determined. If the middle of the billet is white, it means that the heating is uneven, which can easily affect the subsequent rolling quality. The uniform red surface of the billet ensures that the billet is heated evenly, thereby improving the quality of billet rolling.

[0039] Before the punching step, a puncher is used to roll several pieces of ordinary carbon steel for trial rolling. After the trial rolling is correct, the billet is punched to avoid errors and defects in the rolling of copper billets.

[0040] Furthermore, before the punching step, glass powder for lubricating the plug is placed in the centering hole. The glass powder is wrapped with a paper ball and fixed in the centering hole by the paper ball. The paper ball wrapping ensures that the glass powder can be accurately placed in the centering hole to avoid scattering. In addition, by setting the glass powder, the plug can be fully lubricated to ensure the flexibility of the billet during rolling.

[0041] Moreover, in the heat preservation step, the heat preservation time is more than 120 minutes. The sufficient heat preservation effect allows the billet to be fully heated to avoid insufficient heating effect in the middle position, which affects the subsequent perforation and rolling process, thereby ensuring the rolling effect of the billet.

[0042] Among them, in the sizing step, the sizing machine is equipped with a sizing frame, and the sizing frame adopts a thick-walled tube frame. The thermal expansion coefficient of the thick-walled tube frame is 1.0178%, so that the expansion of the sizing frame is limited to a certain range, avoiding excessive thermal expansion of the sizing frame, which affects the sizing effect of the blank.

[0043] Furthermore, in the sizing step, a caliper is used to measure the diameter of the rough pipe, and the diameter of the rough pipe is adjusted by a sizing machine, thereby improving the accuracy of sizing the rough pipe and improving product quality.

[0044] Furthermore, after the sizing step, the finished pipe is placed on a cooling bed for cooling. The finished pipe can be gradually cooled down according to the required process through the cooling bed, thereby ensuring its product quality. The rolled products are conveyed into the cooling bed through a roller conveyor, and then the workpieces arranged on the cooling bed are gradually moved to the top of the cooling bed by rack stepping tooth extraction and other forms, thereby achieving the cooling effect of the workpieces. The cooling bed is composed of a mechanical transmission system, a water cooling system, a cooling bed work surface, a fixed bracket and other aspects. The cooling beds mainly include tooth extraction cooling beds, rack stepping cooling beds, claw cooling beds, carrier chain cooling beds, roller cooling beds and the like.

[0045] Further, as another embodiment of the present invention, the billet is a continuous casting tube billet, the material purity is 99.99% copper, the size of the continuous casting tube billet is Φ197, and the length is divided into 1.5m and 3m. The finished product is required to be processed into 162.5*18.75 times the length of 2000mm; the inner diameter tolerance is + / -0.5; the wall thickness deviation is less than 1mm; the total length curvature is less than 1.5mm. It is planned to be processed into 168*24, the outer circle processing amount is 2.75mm on one side; the inner hole processing is 2.5mm on one side; the centering hole at the end of the cast tube billet is φ30mm and the depth is 100mm; the on-site heating process: the heating furnace is raised to 870℃, the continuous casting tube billet begins to enter the furnace, and the temperature drops to 570℃ after entering the furnace; the temperature starts to rise after ten minutes until it rises to 870℃, and the heat preservation begins. Two hours later, the first one starts to be produced, and after it is finished, the next one is produced after an interval of 30 minutes. The perforator uses a 3-degree roller with a roller diameter of φ734mm; the sizing rough rolling mill is produced with a thick-walled pipe rack, and the thermal expansion coefficient is selected at 1.0178%. At this time, the outer diameter of the pipe is 171mm; 3. The outer diameter after sizing is 170mm, and the hot state is measured with a caliper. The temperature before sizing is 740-760℃, and the temperature after sizing is 720-740℃.

[0046] In the prior art, the tube billet is directly heated to the required temperature for rolling, such as 1290-1400°C. Due to the high temperature, the copper billet has several defects:

[0047] a. Overheating. When copper billets are heated at high temperatures for a long time, they are prone to overheating. The overheating of copper billets is mainly manifested in the excessive growth of copper grains into coarse-grained structures, which reduces the bonding force between grains and reduces the plasticity of copper. Overheated copper is prone to cracking during rolling, especially at the corners. When slightly overheated, cracks appear on the surface of the copper material, affecting the surface quality and mechanical properties of the copper material. In order to avoid overheating defects, the heating temperature and heating time must be strictly controlled.

[0048] b. Overburning: When copper billets are heated at high temperatures for a long time, they will become coarse crystalline structures. At the same time, the low-melting-point non-metallic compounds on the grain boundaries will oxidize and destroy the crystalline structures, causing the copper to lose its strength and plasticity. This phenomenon is called overburning. Overburned copper will produce serious cracks during rolling. Therefore, overburning is a more serious heating defect than overheating. Overburned copper cannot be saved except by re-smelting. The way to avoid overburning is to reasonably control the heating temperature and the oxidizing atmosphere in the furnace, strictly implement the correct heating system and waiting system, and avoid excessive temperature.

[0049] The present invention solves the problems existing in the above-mentioned prior art, can prevent the coarse grain phenomenon that is easy to occur during the heating process of the copper billet, and further prevent the surface quality defects of the tube body caused by the coarse grain, thereby ensuring the high quality of the finished product of the hot-rolled copper tube.

[0050] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0051] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0052] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A hot-rolled seamless copper tube production process, characterized in that: The steps include: Heating the billet: turning on the heating furnace, raising the temperature in the heating furnace to 40°C to 60°C higher than the temperature required for rolling, and loading the billet into the heating furnace; Insulation: After the blank is heated to the furnace temperature, the blank is kept warm for a required time, and after the insulation time is over, the blank is discharged; Perforation: the blank is perforated into a hollow rough tube by a perforator; Pipe rolling: Press the perforated thick-walled rough pipe into a thin-walled rough pipe to achieve the thermal size and uniformity required by the finished pipe; Sizing: Use a sizing machine to shape the rough pipe to the required outer diameter accuracy and roundness; Heating process: The heating furnace is heated to 870℃, and the continuous casting billet begins to enter the furnace. After entering the furnace, the temperature drops to 570℃; after ten minutes, the temperature begins to rise until it reaches 870℃, and then insulation begins. After two hours, the first billet is produced, and after it is produced, the next billet is produced after an interval of 30 minutes.

2. The hot-rolled seamless copper tube production process according to claim 1, characterized in that: Prior to the billet heating step, a centering hole is opened at the end of the billet.

3. The hot-rolled seamless copper tube production process according to claim 2, characterized in that: In the blank heating step, a plurality of heat-resistant bricks are arranged at the bottom of the heating furnace, the blank is placed on each of the heat-resistant bricks, and the heat-resistant bricks are evenly distributed along the axial direction of the blank, and the heating temperature of the upper and lower surfaces of the blank is consistent.

4. The hot-rolled seamless copper tube production process according to claim 3, characterized in that: In the blank heating step, the blank reaching the furnace temperature is observed until the surface of the blank is uniformly red.

5. The hot-rolled seamless copper tube production process according to any one of claims 2 to 4, characterized in that: Before the punching step, the punching machine is used to roll a number of ordinary carbon steels for trial rolling, and after the trial rolling is correct, the blank is punched.

6. The hot-rolled seamless copper tube production process according to claim 5, characterized in that: Before the perforating step, glass powder for lubricating the plug is placed in the centering hole. The glass powder is wrapped with a paper ball and fixed in the centering hole by the paper ball.

7. The hot-rolled seamless copper tube production process according to claim 6, characterized in that: In the heat preservation step, the heat preservation time is 120 minutes or more.

8. The hot-rolled seamless copper tube production process according to claim 7, characterized in that: In the sizing step, the sizing machine is equipped with a sizing frame, and the sizing frame adopts a thick-walled tube frame, and the thermal expansion coefficient of the thick-walled tube frame is 1.0178%.

9. The hot-rolled seamless copper tube production process according to claim 8, characterized in that: In the sizing step, a caliper is used to measure the diameter of the rough pipe, and the diameter of the rough pipe is adjusted by the sizing machine.

10. The hot-rolled seamless copper tube production process according to claim 9, characterized in that: After the sizing step, the finished tube is placed on a cooling bed for cooling.

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