Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B17/00—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling
  • B21B17/02—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling with mandrel, i.e. the mandrel rod contacts the rolled tube over the rod length
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B25/00—Mandrels for metal tube rolling mills, e.g. mandrels of the types used in the methods covered by group B21B17/00; Accessories or auxiliary means therefor ; Construction of, or alloys for, mandrels or plugs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B25/00—Mandrels for metal tube rolling mills, e.g. mandrels of the types used in the methods covered by group B21B17/00; Accessories or auxiliary means therefor ; Construction of, or alloys for, mandrels or plugs
  • B21B25/06—Interchanging mandrels, fixing plugs on mandrel rods or cooling during interchanging mandrels

Definitions

• the invention relates to pipe production, namely to the production of pipes on a continuous tube mill and the design of the mandrel assembly.
• Continuous tube rolling mills with a floating long cylindrical mandrel have been known since 1885 (patent CA N ° 24956, publ. 13.09.1886).
• a floating mandrel is used, which is introduced into the tube stock (sleeve), and during rolling, the mandrel moves together with the roll outside the continuous mill, then the mandrel is removed from the roll using a chain type mandrel.
• the mandrel is made monolithic, containing a guide cone at the front end, a cylindrical part and a tail part in the form of an annular groove for which the gripper of the mandrel extractor is engaged.
• a mandrel unit with controlled movement during the rolling process is used for rolling tube billets (sleeves).
• the holding speed of the mandrel assembly during rolling can be in the range from 500 to 2000 mm / s. Removing the mandrel from the roll is carried out using a mill-extractor, which is located in line with a continuous rolling mill.
• the mandrel assembly consists of a cylindrical mandrel with a guide cone section at the front end, which is connected to the extension by a nipple connection with the opposite end, and the extension is likewise connected to the shank to hold the mandrel assembly in the grip during rolling (US Pat. No. JSTs 3120139, B21B 25 / 04, published on 02/04/1964).
• the billet In the process of rolling using a mandrel assembly, the billet is deformed on a cylindrical mandrel, the remaining elements of the mandrel assembly are accessories and may include one or more extensions, a shank, plugs, various inserts, bushings and nozzles.
• the working part of the mandrel assembly is operated in the production process under difficult temperature conditions and is subject to constant cyclic alternating loads, as a result of which its wear is intensified, the quality of the finished pipes depends on the degree of which.
• a significant problem in the production of pipes on units with a continuous rolling mill is the low operational life and high cost of mandrels, acquired mainly from import purchases.
• the critical value of the wear of the mandrel refers to the mismatch of the geometric parameters and the surface condition of the mandrel with the specified requirements.
• the critical wear of the mandrel is regulated in the technological instructions of pipe manufacturers.
• the mandrels are taken out of service when the critical wear value is exceeded, which includes various indicators, for example: the presence of sections with the outer diameter wear value higher than the regulated one, the presence on the surface of the mandrel of numerous surface mismatches in the form of “comets”, mechanical damage, rough cracking, and also surface roughness of the mandrel exceeding the specified critical values.
• the average specific consumption of mandrels is from 0.1 to 4.0 kg / t. Specific consumption is the difference between the weight of a worn mandrel before regrinding and the weight of the mandrel after regrinding, related to the number of rolled tons of products.
• the disadvantage of the method of producing pipes on a continuous mill using a prefabricated mandrel assembly is that during the rolling process, the wear of the mandrel occurs at a distance of 200-7500 mm from the front end, while the opposite part of the mandrel practically does not wear out.
• the mandrel reaches a critical value of wear, it enters the regrind, during which metal is removed over the entire surface of the mandrel, which significantly reduces its operational life.
• the closest technical solution adopted as a prototype for the method and the mandrel assembly is the production of pipes on a continuous tube mill using a mandrel assembly (RF patent No. 2486976, B21B 25/00, publ. 07/10/2013), in which a cylindrical mandrel is used. At the ends of the cylindrical part of the mandrel, blind holes are made for alternately articulating the cylindrical part with an extension and a conical part of the mandrel.
• the rolling metal flows into the gap between the conical and cylindrical parts of the mandrel, defects of various types form on the inner surface of the pipes.
• emergencies may occur on a continuous charging mill and extraction mill, such as a stop rolling process due to equipment breakdown, failure of fuses, full mandrel shackles with metal roll, formation of a shortage.
• the prototype also does not regulate the amount of wear of the mandrel, at which it is necessary to change the end joint of the mandrel with the equipment of the reference unit, which can lead to premature termination of operation of the mandrel.
• the technical problem solved by the invention is to increase the operational life of the mandrel by increasing the number of rolled pipes on one mandrel, improving the quality of the surface of the pipes and eliminating emergencies during the rolling process.
• the problem is solved due to the fact that in the method of continuous rolling of pipes, including the deformation of the tube stock using a cylindrical mandrel, made at the ends with identical coaxial blind holes, for alternating articulation of the mandrel with tooling assembly and deformation of the tube stocks at work sites from different the sides of the mandrel, the control of the dimensions of the mandrel and the regrinding of the mandrel, according to the invention, the deformation of the pipe blanks is carried out up to the wear of the working section op on the one hand, constituting at least 25% of the critical value, while the mandrel is re-sharpened after changing the end joint of the mandrel with the snap-in of the mandrel assembly, followed by deformation of pipe billets and wear of the working section on the other side of the mandrel is not less than 25% of the critical value.
• the problem is also solved due to the fact that in the mandrel assembly of a continuous tube mill, including a cylindrical mandrel made at one end with a beveled side surface, identical coaxial blind threaded holes for alternating articulation are made at the ends of the mandrel by connecting the mandrel to the tooling of the mandrel assembly, according to of the invention, the opposite end of the mandrel is made with a beveled side surface, the angle forming the beveled surfaces with the longitudinal axis of the mandrel on both their ends is the same and ranges from 10 to 70 degrees, while in the working position the hole at the front end of the mandrel is muffled.
• the invention is illustrated by the drawing, which schematically shows a mandrel assembly for implementing the method of continuous rolling of pipes.
• the mandrel assembly includes a cylindrical mandrel 1, made at both ends with a beveled side surface 2 and snap in the form of an extension 3 and a shank 4.
• identical blind threaded holes 5 are made for alternately joining the mandrel with the extension 3 by means of, for example, a nipple connection .
• a plug 6 In working the position of the hole on the front end of the mandrel is muffled using a plug 6 to provide protection from external influences and prevent clogging with scale and lubricants during the rolling process.
• the mandrel assembly may also be coupled to the shank 4 by means of a nipple joint.
• the wear value does not exceed 25% of the critical value, the satisfactory condition of the surface of the mandrels and the operating life are maintained, and when such mandrels are removed from the continuous rolling mill mandrel circulation system and regrind to a smaller diameter, a significant metal volume is grinded and the average specific consumption increases mandrels from 2 to 40 times.
• the premature decommissioning of mandrels significantly increases the cost of the tool and negatively affects the performance of the pipe rolling unit as a whole.
• the rolling process occurs on the unworn working section of the mandrel until the wear of the section on the other side of the mandrel is also not less than 25% of the critical value.
• the mandrel can be re-machined along the entire length to another outer diameter, which will increase the life of the mandrel taking into account the regulation of its wear and improve the quality of the finished pipes.
• the magnitude of the wear of the mandrels is regulated in the technological documentation of the enterprise and for different pipe sizes depends, in particular, on the deformation modes of the continuous rolling mill, the power parameters of the process, the grade and grade of steel of the rolled pipes, the temperature of the rolling mill and rolling tool, the properties of lubricants and antioxidants.
• the mandrel is made in such a way that the angle of the generatrix of the chamfered surfaces 2 with the longitudinal axis of the mandrel at both ends is the same and ranges from 10 to 70 degrees, which ensures unimpeded entry of the mandrel into the sleeve before rolling in a continuous rolling mill and helps to reduce the number of defects on the inner surface of the pipes during insertion and removal of the mandrel, as well as during the rolling process. If the angle of the generatrix is less than 10 degrees, then it is difficult to enter the mandrel into the sleeve and to remove the rough pipe by the extraction mill, while defects on the inner surface of the roll form in the form of patterns and prints.
• the angle of the generatrix is more than 70 degrees, the likelihood of cracking at the ends of the mandrel and in the area of blind holes designed to connect with snap-in increases, which reduces the reliability of the connection.
• the angle of the generatrix of the chamfered surfaces remains in the specified range, there are no obstacles when entering the mandrel into the sleeve and practically no defects form on the inner surface of the sleeve.
• the hole at the front end of the mandrel is plugged with a plug 6 to provide protection from external influences and prevent clogging with scale and lubricants during the rolling process.
• the threaded connections of all elements of the mandrel assembly are made similar to the connection of casing pipes and have a tapered trapezoidal thread or, for example, a thread of the Butress type. Before screwing, a lubricant is applied to the threads.
• Such a constructive implementation of the mandrel assembly allows to increase the service life of the mandrels, the quality of the inner surface of the pipes and prevent accidents during the rolling process.
• the proposed method for continuous rolling of pipes using a mandrel assembly is as follows. During the rolling process, the mandrel assembly is inserted into the sleeve and then, together with the sleeve, is set into a continuous rolling mill. The deformation of the sleeve into the rough pipe occurs strictly on the cylindrical part of the mandrel, located between two sections with beveled side surfaces. The wear of the portion of the cylindrical part of the mandrel is formed mainly closer to the front end, and the portion of the mandrel adjacent to the opposite end practically does not wear out.
• a plug is removed from the hole on the front end of the mandrel, the mandrel is disconnected from the tooling, articulated with another tooling end face, and the plug is inserted into the hole on the other end of the mandrel.
• the operations of connecting and disconnecting the components of the mandrel assembly can be carried out on a machine for screwing and unscrewing the mandrels. After that, in the next cycle, the rolling process is carried out on the unworn portion of the mandrel also until it reaches a critical wear level of at least 25%.
• the mandrel After wear of the cylindrical mandrel over almost the entire length by at least 25% of the critical, the mandrel can be re-machined along the entire length to another outer diameter, which increases the service life of the mandrel and improves the quality of the finished pipes.
• pipe rolling provides unhindered entry of the mandrel into the sleeve and its extraction, which leads to a significant reduction in the number of defects on the inner surface of the roll.
• the mandrel operating life is significantly reduced, since in this case the average specific consumption of mandrels increases from 2 to 40 times .
• the service life increases due to the possibility of using a plug made without thread, which reduces thread wear in the threaded holes due to fewer screwing and unscrewing operations.
• Using the proposed method for continuous rolling of pipes using a mandrel assembly can reduce tool costs by increasing its life, reduce the formation of various types of defects on the inner surface of pipes, and also eliminate the risks associated with emergencies during the rolling process.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)
• Metal Extraction Processes (AREA)

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Citations (10)

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• 2017
  • 2017-05-05 US US16/610,739 patent/US20200156127A1/en not_active Abandoned
  • 2017-05-10 JP JP2020513481A patent/JP2020519452A/ja active Pending
  • 2017-05-10 EA EA201800621A patent/EA036775B1/ru not_active IP Right Cessation
  • 2017-05-10 WO PCT/RU2017/000296 patent/WO2018208184A1/ru unknown
  • 2017-05-10 MX MX2019013406A patent/MX2019013406A/es unknown
  • 2017-05-10 EP EP17909616.9A patent/EP3623066A4/en not_active Withdrawn
  • 2017-05-10 RU RU2018134751A patent/RU2707052C1/ru active
  • 2017-05-10 CA CA3052867A patent/CA3052867A1/en not_active Abandoned
  • 2017-05-10 CN CN201780088139.8A patent/CN110382126A/zh active Pending
• 2019
  • 2019-11-04 ZA ZA2019/07301A patent/ZA201907301B/en unknown

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