Full-process induction heat treatment device and method for steel pipe mandrel

Abstract

The present invention discloses a full-process induction heat treatment device and method for a steel pipe mandrel, the method comprising: transferring a mandrel (1) at room temperature from one end of a horizontal conveyor roller to the other end, heating the mandrel to a first quenching temperature through an induction heating furnace (2), and cooling through a cooler (4); transferring the mandrel in the reverse direction, heating the mandrel to a first tempering temperature through an induction heating furnace, cooling after heating; transferring the mandrel in the reverse direction again, heating the mandrel to a second quenching temperature through an induction heating furnace, cooling after heating; performing several consecutive tempering processes, heating the mandrel to a second tempering temperature through an induction heating furnace, cooling after heating. The present invention uses a conveyor roller to reciprocately transfer the mandrel, and uses induction heating to complete preliminary quenching, quenching and tempering, formal quenching and multiple tempering processes, thereby improving the heat treatment quality of the mandrel, and improving the heat treatment efficiency and the performance of the mandrel.

Description

Technical Field

[0001] The present invention relates to a steel pipe production device and method, and in particular to a full-process induction heat treatment device and method for a steel pipe mandrel. Background Art

[0002] The mandrel is one of the main deformation tools for hot rolling of seamless steel pipes. It is required to have good resistance to thermal shock and cold shock to prevent thermal cracking when the surface temperature changes drastically periodically; it is also required to have sufficient toughness to avoid fracture after multiple local bending deformations; it is also required to have sufficient hardness and wear resistance to make the mandrel have longer durability. The mandrel in the prior art is produced by using H13 type tool steel through the process of blank making → annealing → finishing → surface induction quenching → tempering, among which the surface induction quenching is carried out in a dedicated induction quenching line, and the annealing and tempering are carried out in a gas-fired heating furnace.

[0003] The final hardness of the working layer on the surface of the mandrel in the prior art is 40-50HRC, the hardening depth is about 10mm, and the core maintains an annealed hardness of 20-30HRC. During rolling, the mandrel often has defects such as excessive wear and surface cracks, and needs to be taken offline for periodic re-machining and re-heat treatment. If the mandrel breaks, it will not only directly lead to the scrapping of the mandrel, but also affect the forming of the steel pipe, making it difficult to remove the rod, greatly increasing the production and rolling costs of the steel pipe. The existing mandrel preparation process has the following shortcomings:

[0004] 1. The purpose of annealing the mandrel is to facilitate straightening, peeling, rough turning, grinding, head and tail processing, etc., but the pearlite formed by annealing is generally coarse, which is not conducive to the acquisition of high-quality surface quenching structure for subsequent grain refinement.

[0005] 2. After the core rod is induction hardened on the surface, for the sake of production efficiency, it is usually only tempered in a low-temperature furnace for a long time, which fails to give full play to the "secondary tempering hardening" effect of tool steel.

[0006] 3. Annealing and tempering are both carried out in a gas-fired heating furnace, and the heating time often takes more than ten hours, which may cause various risks or problems such as surface decarburization and furnace gas pollution.

[0007] Chinese invention patent application CN201910822595.1 discloses a heat treatment process for large die-casting mold steel with high toughness and low deformation. Its "temperature difference speed control + three-step step cooling" quenching process is: slowly heat up to 500-600℃ at 1.5-2℃ / min, and when the core temperature reaches 5-10℃ lower than the set furnace temperature, keep warm for 150-200 minutes; heat up to 800-850℃ at 2℃ / min, and when the core temperature reaches 5-10℃ lower than the set furnace temperature, keep warm for 200-240 minutes; then raise the furnace temperature to the Austenitic temperature of the mold steel within 40 minutes. austenitizing temperature, when the core temperature reaches 5-10℃ lower than the set austenitizing temperature, keep it warm for 30-35 minutes; first stage cooling: use slow cooling with the furnace, wait for the mold surface temperature to drop to 800-850℃; second stage cooling: under a cooling pressure of not less than 7-8Bar, control the cooling rate ≥40℃ / min, quench the mold surface temperature to 500-550℃, and start the isothermal process; when the difference between the core temperature and the surface temperature is ≤100℃, end the isothermal process; third stage cooling: control the cooling rate to 7-8℃ / min, reduce the furnace temperature to 200℃, and air cool out of the furnace. The tempering process is as follows: wait for the mold surface temperature to drop to 50-60℃, and then temper immediately; after quenching, the mold should be tempered at least three times, and the furnace temperature before tempering is 100-200℃; the first tempering temperature is selected to be 20-30℃ higher than the peak temperature of the mold steel secondary hardening tempering. When the core temperature reaches 5-10℃ lower than the set value, start timing, and the tempering time is based on the effective thickness of 30-40mm / h. After being taken out of the furnace, the fan is used to accelerate cooling, and the mold surface temperature is reduced to 50-60℃; the second tempering is to 590-600℃, the hardness gradually decreases, and the core temperature is When the temperature is 5-10℃ lower than the set value, the timing starts, and the tempering time is 30-40mm / h. After the mold is taken out of the furnace, the fan is used to accelerate the cooling, and the mold surface temperature is reduced to 50-60℃; the mold surface tempering hardness is detected, and the third tempering temperature is adjusted to 580-600℃ according to the target hardness of 44-46HRC; large die-casting molds need to add a fourth tempering, and the tempering temperature is the same as the third tempering temperature. When the temperature reaches 5-10℃ lower than the set value, the timing starts, and the tempering time is 30-40mm / h. The last tempering is air-cooled out of the furnace. If a large die-casting mold is quenched and heat-treated on the basis of the cast or even annealed state structure, because this type of structure is generally coarse and some other possible inclusions, composition segregation and other casting defects are easy to cause the so-called quenching cracks in the mold quenching heating and cooling process, the heat treatment adopts a complex graded heating (cooling) process, which is slow and takes dozens of hours. Moreover, in this heat treatment process, large molds need to be quenched and tempered in the furnace from the outside to the inside. The workpiece has a large heat storage capacity and a corresponding cooling load, making it difficult to implement continuous and efficient surface induction heat treatment.At the same time, this heat treatment belongs to the traditional heating furnace heat treatment, which has many inherent disadvantages such as decarburization, environmental pollution, low efficiency, complex production organization, and difficulty in achieving timely tempering. Summary of the invention

[0008] One of the purposes of the present invention is to provide a full-process induction heat treatment device for a steel pipe mandrel, which can provide a variety of uniform heating and cooling processes for the horizontally transmitted mandrel, so as to improve the heat treatment quality of the mandrel during the induction heat treatment process, avoid the problem of excessive pollution during the heat treatment process, improve the heat treatment efficiency of the mandrel, and reduce the cost of steel pipe rolling.

[0009] The second object of the present invention is to provide a full-process induction heat treatment method for a steel pipe mandrel, which can improve the heat treatment quality of the mandrel through preliminary quenching and tempering processes, and at the same time give full play to the secondary hardening effect of H13 steel through 2-3 timely tempering processes, effectively improve the performance of the mandrel, and reduce the mandrel consumption during the steel pipe rolling process.

[0010] The present invention is achieved in that:

[0011] A full-process induction heat treatment device for a steel pipe mandrel comprises an induction heating furnace, a conveying roller, a cooler and a temperature measuring instrument; a plurality of conveying rollers are arranged in sequence along a horizontal plane to form a horizontal conveying roller for reciprocatingly conveying the mandrel; the induction heating furnace and two coolers are arranged along the horizontal conveying roller respectively, and the two coolers are respectively located on the outsides of the two inlets and outlets of the induction heating furnace, and the mandrel passes through one of the coolers, the induction heating furnace and the other cooler in sequence when being conveyed along the horizontal conveying roller; temperature measuring instruments are respectively provided between the two inlets and outlets of the induction heating furnace and the two coolers.

[0012] The induction heating furnace comprises a heating furnace shell, a coil copper tube and a rotating assembly; the coil copper tube is a circular ring structure, the coil copper tube is installed in the rotating assembly through a support, and rotates in the heating furnace shell through the rotating assembly, and the core rod coaxially penetrates the coil copper tube; a refractory lining is provided on the inner wall of the coil copper tube; the power supply power of the induction heating furnace is 400-1000kW.

[0013] The cooler comprises a cooler shell, a cooling nozzle and a rotating assembly; the cooling nozzle is a circular ring structure, and nozzles facing the surface of the core rod are evenly distributed on the cooling nozzle; the cooling nozzle is installed in the rotating assembly through a support, and rotates in the cooler shell through the rotating assembly, and the core rod coaxially passes through the cooling nozzle; the cooling water flow rate of the cooler is 30-60m 3 / h, pressure 0.4-0.8MPa.

[0014] The rotating assembly includes a ring gear, a gear and a driver; the gear is coaxially connected to the output shaft of the driver and rotates synchronously, the ring gear is meshed with the gear, and the ring gear can swing back and forth around the center of the ring gear through the gear; the center of the ring gear is located on the central axis of the core rod; the swing angle range of the ring gear is [-180°, 180°], and the swing frequency is 10-30 times / minute.

[0015] A full-process induction heat treatment method for a steel pipe mandrel is implemented based on the full-process induction heat treatment device, and the full-process induction heat treatment method comprises the following steps:

[0016] Step 1: Place the mandrel on a horizontal conveyor roller and enable it to reciprocate horizontally through the horizontal conveyor roller;

[0017] Step 2: Preliminary quenching process: The mandrel at room temperature is transferred from one end of the horizontal conveyor roller to the other end. During the transfer process, the mandrel is heated to the first quenching temperature by the induction heating furnace, and after the induction heating, it is cooled by the cooler at the outlet side of the induction heating furnace to reduce the temperature of the mandrel to below 180°C.

[0018] Step 3: Tempering process: The core rod is transferred from the other end of the horizontal conveyor roller to one end. During the transfer process, the core rod is heated to the first tempering temperature by the induction heating furnace, and after induction heating, it is cooled by the cooler on the outlet side of the induction heating furnace to reduce the temperature of the core rod to below 180°C;

[0019] Step 4: Formal quenching process: The mandrel is transferred from one end of the horizontal conveyor roller to the other end. During the transfer process, the mandrel is heated to the second quenching temperature by the induction heating furnace, and after induction heating, it is cooled by the cooler on the outlet side of the induction heating furnace to reduce the temperature of the mandrel to below 180°C.

[0020] Step 5: The tempering process is performed several times continuously. The process of each tempering process is as follows: the core rod is transported through a horizontal conveyor roller, the core rod is heated to a second tempering temperature by an induction heating furnace during the transportation process, and after the induction heating, the core rod is cooled by a cooler on the outlet side of the induction heating furnace to reduce the temperature of the core rod to below 180°C.

[0021] The first quenching temperature is 950-1050° C., the power of the induction heating furnace is 850-950 kW, the frequency is 500-2000 Hz, and the transmission speed of the mandrel is 1-1.5 m / min.

[0022] The first tempering temperature is 650-700° C., the power of the induction heating furnace is 500-600 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod is 0.1-0.5 m / min.

[0023] The second quenching temperature is 1000-1100° C., the power of the induction heating furnace is 900-1000 kW, the frequency is 500-2000 Hz, and the transmission speed of the mandrel is 1-1.5 m / min.

[0024] The tempering process is performed 2-3 times, the transmission direction of the mandrel in the first tempering process is opposite to the transmission direction of the mandrel in step 4, and the transmission directions of the mandrel in two adjacent tempering processes are opposite;

[0025] In each of the tempering processes, the second tempering temperature is 550-600° C., the power of the induction heating furnace is 400-500 kW, the frequency is 500-2000 Hz, and the transmission speed of the mandrel is 0.1-0.5 m / min.

[0026] During the quenching and tempering process, the power of the induction heating furnace is linearly adjusted from small to large according to the temperature of the core rod before entering the induction heating furnace, and the cooling water flow of the cooler is linearly adjusted from large to small according to the temperature of the core rod before entering the cooler.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The full-process induction heat treatment device of the present invention adopts medium-frequency electromagnetic induction heating, which avoids problems such as decarbonization, three wastes emission and pollution compared with the heating methods such as gas furnaces in the prior art, and is energy-saving and environmentally friendly; at the same time, the temperature uniformity of the induction heating and cooling process is ensured by adjusting the rotating components and equipment parameters, reducing the cost of heat treatment, improving the quality and efficiency of heat treatment, and can be promoted and applied to the heat treatment processing and manufacturing fields of various slender workpieces such as rods, bars, tubes, rollers, etc.

[0029] 2. The full-process induction heat treatment device of the present invention adopts a horizontal roller that can reciprocate to transport the core rod, so that the heating and cooling equipment are arranged very compactly, which is conducive to the continuous implementation of multiple processing steps in the full-process induction heat treatment method and meets the requirements of timely tempering, thereby achieving the effect of improving the quality of heat treatment, reducing the turnover time and improving the heat treatment efficiency, and eliminating the gas emissions and pollution problems of traditional heating furnaces to the greatest extent.

[0030] 3. The full-process induction heat treatment method of the present invention adopts preliminary quenching and tempering processes, so that the surface of the core rod is in a state of troostite structure with extremely fine grains before quenching, and reduces or eliminates the band segregation defects that often exist inside the core rod blank, so as to prepare the structure for the subsequent formal quenching process; at the same time, the present invention performs 2-3 tempering treatments after formal quenching, fully exerts the secondary hardening effect of H13 type tool steel, further improves the stability of the core rod quenching martensitic structure, and effectively improves the tempering hardness and wear resistance of the core rod, and timely tempering avoids cracking of the core rod due to excessive residual quenching stress after quenching, which is beneficial to improving the heat treatment quality of large workpieces such as core rods.

[0031] 4. The full-process induction heat treatment method of the present invention adopts mist cooling. The cooling process of the core rod after induction heating adopts mist cooling with an adjustable air-water ratio, which can increase the cooling rate of the core rod surface to obtain a higher content of martensitic structure with high hardness and high wear resistance, while preventing the core rod from cracking due to excessive quenching stress, reducing the cooling process time and improving the heat treatment efficiency.

[0032] 5. The full-process induction heat treatment method of the present invention can largely eliminate the head-to-tail temperature difference caused by the different natural cooling time experienced by the core rod on the conveying roller during the conveying process due to the automatic adjustment of the cooling intensity and the induction heating power, so as to improve the uniformity of the axial temperature of the core rod before entering the heating furnace and after leaving the heating furnace. At the same time, the swinging action of the heating furnace and the cooler improves the uniformity of the circumferential temperature of the core rod, thereby fundamentally ensuring the uniformity and stability of the heat treatment performance of the core rod.

[0033] The present invention uses a conveyor roller to reciprocately transfer the mandrel, and utilizes induction heating to complete preliminary quenching, tempering, formal quenching and multiple tempering processes, which can fundamentally improve the microstructure of the mandrel surface working layer (radial depth 0-10mm), improve the heat treatment quality and performance of the mandrel, and improve the heat treatment efficiency by more than 50%. The mandrel has a long service life, and the manufacturing cost and consumption in the steel pipe rolling process are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a sectional front view of the full-process induction heat treatment device of the steel tube mandrel of the present invention;

[0035] Figure 2 It is a side cross-sectional view of an induction heating furnace in a full-process induction heat treatment device for a steel pipe mandrel of the present invention;

[0036] Figure 3 It is a side cross-sectional view of a cooler in a full-process induction heat treatment device for a steel tube mandrel of the present invention;

[0037] Figure 4It is a flow chart of the full process induction heat treatment method of the steel tube mandrel of the present invention;

[0038] Figure 5 It is a diagram of the adjustment method between heating power, cooling flow and mandrel position in the full-process induction heat treatment method of a steel pipe mandrel of the present invention. In the figure, the arrow indicates the transmission direction of the mandrel, the dotted line indicates the cooling water flow of the cooler, and the solid line indicates the power supply power of the induction heating furnace.

[0039] In the figure, 1 is a core rod, 2 is an induction heating furnace, 21 is a heating furnace shell, 22 is a coil copper tube, 23 is a refractory furnace lining, 3 is a conveying roller, 4 is a cooler, 41 is a cooler shell, 42 is a cooling nozzle, 5 is a temperature measuring instrument, 6 is a gear ring, 7 is a gear, 8 is a driver, and 9 is a support. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0041] Please see attached Figure 1 A full-process induction heat treatment device for a steel pipe mandrel comprises an induction heating furnace 2, a conveying roller 3, a cooler 4 and a thermometer 5; a plurality of conveying rollers 3 are arranged in sequence along a horizontal plane to form a horizontal conveying roller for reciprocatingly transmitting the mandrel 1; the induction heating furnace 2 and two coolers 4 are arranged along the horizontal conveying roller, respectively, and the two coolers 4 are respectively located on the outside of the two inlets and outlets of the induction heating furnace 2, and the mandrel 1 passes through one of the coolers 4, the induction heating furnace 2 and the other cooler 4 in sequence when being transmitted along the horizontal conveying roller; thermometers 5 are respectively provided between the two inlets and outlets of the induction heating furnace 2 and the two coolers 4.

[0042] Please see attached Figure 2 The induction heating furnace 2 comprises a heating furnace shell 21, a coil copper tube 22 and a rotating assembly; the coil copper tube 22 is a circular ring structure, the coil copper tube 22 is installed in the rotating assembly through the support 9, and rotates in the heating furnace shell 21 through the rotating assembly, and the core rod 1 coaxially penetrates the coil copper tube 22. Preferably, the power supply of the induction heating furnace 2 is 400-1000kW, the frequency is 500-2000Hz, and the power supply power can be linearly adjusted from small to large according to the temperature of the core rod 1.

[0043] The coil copper tube 22 is arranged in a spiral shape, and the two electrode ends of the coil copper tube 22 are connected to the induction heating power supply. When the medium frequency alternating current is turned on during operation, a strong alternating electromagnetic field is formed in the center of the coil copper tube 22, which then induces a large amount of eddy current on the surface layer of the core rod 1. The eddy current flows in the steel and there is an ohmic heating effect, thereby rapidly increasing the temperature of the surface layer of the core rod within the skin effect depth. In order to prevent self-heating, the inside of the coil copper tube 22 needs to be cooled by circulating water.

[0044] The inner wall of the coil copper tube 22 is provided with a refractory lining 23, which plays the role of protecting the coil copper tube 22 from the radiant heat of the high-temperature workpiece, preventing the electrical insulation layer on the surface of the coil copper tube 22 from being over-baked by the high-temperature workpiece, which may cause discharge and ignition accidents between adjacent coil copper tubes 22, and preventing the irregular movement of the workpiece during the actual transportation process from directly damaging or scratching the coil copper tube. The refractory lining 23 can be made of a mixture of corundum Al2O3 powder and silica sol, or a prefabricated tubular lining. The thickness of the refractory lining 23 is based on the principle of being able to fully protect the coil copper tube 22 without increasing the distance between the coil copper tube 22 and the core rod 1 to avoid reducing the induction heating effect. The thickness of the refractory lining 23 is preferably 5-20 mm.

[0045] Please see attached Figure 3 The cooler 4 comprises a cooler housing 41, a cooling nozzle 42 and a rotating assembly; the cooling nozzle 42 is a circular ring structure, and the cooling nozzle 42 is evenly distributed with nozzles facing the surface of the core rod 1; the cooling nozzle 42 is installed in the rotating assembly through the support 9, and rotates in the cooler housing 41 through the rotating assembly, and the core rod 1 coaxially passes through the cooling nozzle 42. Preferably, the cooling water flow rate of the cooler 4 is 30-60m 3 / h, pressure 0.4-0.8MPa, the cooling water flow rate can be linearly adjusted from large to small according to the temperature of the core rod 1. The cooler 4 can be an aerosol cooler, and its water-gas ratio can be adjusted according to the actual cooling needs. For example: a high water-gas ratio during quenching can increase the cooling rate and increase the content of quenched martensite; a low water-gas ratio during tempering can reduce the cooling rate and avoid the generation of excessive tempering stress.

[0046] Please see attached Figure 2 and attached Figure 3 The rotating assembly includes a ring gear 6, a gear 7 and a driver 8; the gear 7 is coaxially connected to the output shaft of the driver 8 and rotates synchronously, the ring gear 6 is meshed with the gear 7, and the ring gear 6 can swing back and forth around the center of the ring gear 6 through the gear 7; the center of the ring gear 6 is located on the central axis of the core rod 1.

[0047] The swing angle range of the gear ring 6 is [-180°, 180°], and the reciprocating swing frequency of the gear ring 6 is 10-30 times / minute. The swing of the gear ring 6 can reduce the circumferential temperature non-uniformity that may occur during the actual heating and cooling process of the mandrel 1 along the circumference, ensuring that the mandrel 1 is uniformly heated or cooled circumferentially during the transmission process.

[0048] Please see attached Figure 4 , a full-process induction heat treatment method for a steel tube core rod, the full-process induction heat treatment method is implemented based on the above-mentioned full-process induction heat treatment device.

[0049] The full-process induction heat treatment method of the steel tube mandrel comprises the following steps:

[0050] Step 1: Place the mandrel 1 on a horizontal conveyor roller, and enable the mandrel 1 to reciprocate horizontally through the horizontal conveyor roller.

[0051] The material of the mandrel 1 is usually H13 steel, the diameter of the mandrel 1 is usually 50-250 mm, and the length of the mandrel 1 is usually 10-30 m.

[0052] In each transmission process of the mandrel 1, that is, in each unidirectional transmission process of the mandrel 1 along the horizontal conveyor roller, the mandrel 1 first enters from one side of the induction heating furnace 2, which is defined as the inlet side of the induction heating furnace 2; after being heated, the mandrel 1 is output from the other side of the induction heating furnace 2, which is defined as the outlet side of the induction heating furnace 2. The end of the mandrel 1 that first enters the induction heating furnace 2 is defined as the head end, and the other end of the mandrel 1 is defined as the tail end. The mandrel 1 passes through one of the coolers 4 (defined as the cooler 4 on the inlet side of the induction heating furnace 2), one of the thermometers 5 (defined as the thermometer 5 on the inlet side of the induction heating furnace 2), the induction heating furnace 2, another thermometer 5 (defined as the thermometer 5 on the outlet side of the induction heating furnace 2), and another cooler 4 (defined as the cooler 4 on the outlet side of the induction heating furnace 2).

[0053] Step 2: Preliminary quenching process: The core rod 1 at room temperature is transferred from one end of the horizontal conveyor roller to the other end. During the transfer process, the core rod 1 is heated to the first quenching temperature by the induction heating furnace 2, and after induction heating, the core rod 1 is cooled by the cooler 4 at the outlet side of the induction heating furnace 2, so that the temperature of the core rod 1 drops below 180°C. The first quenching temperature can be measured by the thermometer 5 at the outlet side of the induction heating furnace 2, and the temperature after cooling can be measured by the thermometer 5 at the outlet side of the induction heating furnace 2 during the next transfer process. The thermometer 5 can be an infrared thermometer.

[0054] The first quenching temperature is 950-1050° C., the power of the induction heating furnace 2 is 850-950 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod 1 is 1-1.5 m / min.

[0055] Step 3: Tempering process: The core rod 1 is transferred from the other end to the one end of the horizontal conveyor roller (i.e., the transfer direction of the core rod 1 in step 3 is opposite to the transfer direction of the core rod 1 in step 2). During the transfer process, the core rod 1 is heated to the first tempering temperature by the induction heating furnace 2, and after the induction heating, it is cooled by the cooler 4 on the outlet side of the induction heating furnace 2, so that the temperature of the core rod 1 drops below 180°C.

[0056] During the quenching and tempering process, before the core rod 1 enters the induction heating furnace 2 for induction heating, the core rod 1 can be cooled by the cooler 4 located at the inlet side of the induction heating furnace 2 in the transmission direction of the core rod 1. The cooling water flow rate of the cooling nozzle 42 in the cooler 4 at the inlet side can be linearly adjusted from large to small according to the temperature of the core rod 1. Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 is eliminated. The first tempering temperature can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2, and the temperature after cooling can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2 during the next transmission process.

[0057] The first tempering temperature is 650-700°C, the power of the induction heating furnace 2 is 500-600kW, the frequency is 500-2000Hz, and the transmission speed of the core rod 1 is 0.1-0.5m / min. The power of the induction heating furnace 2 can be adjusted linearly from small to large according to the temperature of the core rod 1, as shown in the attached figure. Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 can be further eliminated.

[0058] Through the preliminary quenching process and the quenching and tempering process, the surface layer of the core rod 1 is in a state of sorbite structure with refined grains before the formal quenching, reducing the degree of banded segregation and preparing for the subsequent formal quenching process. Moreover, the surface layer is a depth range of 10-15mm greater than the thickness of the working layer from the surface of the core rod 1, so as to improve the metallographic structure and performance of the transition zone at the bottom of the surface hardened layer.

[0059] Step 4: Formal quenching process: The core rod 1 is transferred from one end to the other end of the horizontal conveyor roller (i.e., the transfer direction of the core rod 1 in step 4 is the same as the transfer direction of the core rod 1 in step 2). During the transfer process, the core rod 1 is heated to the second quenching temperature by the induction heating furnace 2, and after the induction heating, it is cooled by the cooler 4 on the outlet side of the induction heating furnace 2, so that the temperature of the core rod 1 drops below 180°C.

[0060] During the formal quenching process, before the core rod 1 enters the induction heating furnace 2 for induction heating, the core rod 1 can be cooled by the cooler 4 located at the inlet side of the induction heating furnace 2 in the transmission direction of the core rod 1. The cooling water flow rate of the cooling nozzle 42 in the cooler 4 at the inlet side can be linearly adjusted from large to small according to the temperature of the core rod 1, as shown in the attached figure. Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 is eliminated. The second quenching temperature can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2, and the temperature after cooling can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2 during the next transmission process.

[0061] The second quenching temperature is 1000-1100°C, the power of the induction heating furnace 2 is 900-1000kW, the frequency is 500-2000Hz, and the transmission speed of the core rod 1 is 1-1.5m / min. The power of the induction heating furnace 2 can be linearly adjusted from small to large according to the temperature of the core rod 1, as shown in the attached figure. Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 can be further eliminated.

[0062] Step 5: The tempering process is performed several times continuously. The process of each tempering process is as follows: the core rod 1 is transported through a horizontal conveyor roller. During the transportation process, the core rod 1 is heated to a second tempering temperature by the induction heating furnace 2. After the induction heating, the core rod 1 is cooled by the cooler 4 at the outlet side of the induction heating furnace 2 to reduce the temperature of the core rod 1 to below 180°C.

[0063] During each tempering process, before the core rod 1 enters the induction heating furnace 2 for induction heating, the core rod 1 can be cooled by the cooler 4 located at the inlet side of the induction heating furnace 2 in the transmission direction of the core rod 1. The cooling water flow rate of the cooling nozzle 42 in the cooler 4 at the inlet side can be linearly adjusted from large to small according to the temperature of the core rod 1. Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 is eliminated. The second tempering temperature can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2, and the temperature after cooling can be measured by the temperature measuring instrument 5 at the outlet side of the induction heating furnace 2 during the next transmission process.

[0064] During each tempering process, the second tempering temperature is 550-600°C, the power of the induction heating furnace 2 is 400-500kW, the frequency is 500-2000Hz, and the transmission speed of the core rod 1 is 0.1-0.5m / min. The power of the induction heating furnace 2 can be linearly adjusted from small to large according to the temperature of the core rod 1, as shown in the attached Figure 5 As shown, the axial temperature difference caused by the different natural cooling of the head and tail ends of the core rod 1 can be further eliminated.

[0065] In the step 5, the heating temperature of each tempering can be the same or different according to the specific material and process conditions, and the corresponding power supply power is adjusted accordingly, while the frequency and speed can remain unchanged.

[0066] The tempering process is performed 2-3 times, and the transmission direction of the mandrel 1 in the first tempering process is opposite to the transmission direction of the mandrel 1 in step 4, and the transmission directions of the mandrel 1 in two adjacent tempering processes are opposite. Through 2-3 consecutive tempering processes, the secondary hardening effect of H13 steel can be fully exerted, the hardness and performance of the tempered martensite structure of the mandrel 1 can be improved, and the heat treatment quality of the mandrel 1 can be improved.

[0067] The first quenching temperature, the first tempering temperature, the second quenching temperature, the second tempering temperature and the temperature after cooling are all the surface temperatures of the core rod 1, which can be measured by two temperature measuring instruments 5. The surface temperature of the core rod 1 is substantially consistent with the internal temperature of the skin layer.

[0068] Since the above temperatures are all the surface temperatures of the core rod 1 measured by the temperature measuring instrument 5, and in order to eliminate the problem that the core rod 1 has an axial temperature difference due to the different actual residence time of the head end and the tail end of the core rod 1 in the natural cooling section on the conveying roller during the continuous reciprocating transmission, the core rod 1 has a different temperature drop under the natural cooling of the surrounding air, which may affect the temperature uniformity of the induction heating (that is, the basic temperature is high at the front and low at the back), the cooling water flow rate of the cooler 4 is set to 30-60m 3 / h, the pressure is set to 0.4-0.8MPa. Figure 5 , during each transfer of the mandrel 1 (except for the transfer of the mandrel 1 in the pre-quenching process, since the head and tail of the mandrel 1 are already at a uniform basic temperature state of room temperature during the pre-quenching process, there is no need to adjust the cooling flow), the cooling water flow of the cooler 4 can be linearly adjusted from large to small according to the temperature of the mandrel 1 to keep the overall temperature of the mandrel 1 uniform before heating. Alternatively, during each transfer of the mandrel 1 (except for the transfer of the mandrel 1 in the pre-quenching process, since the head and tail of the mandrel 1 are already at a uniform basic temperature state of room temperature during the pre-quenching process, there is no need to adjust the power), the power of the induction heating furnace 2 can be linearly adjusted from small to large according to the temperature of the mandrel 1 to keep the overall temperature of the mandrel 1 uniform after heating. Alternatively, during each transfer of the mandrel 1 (except for the transfer of the mandrel 1 during the preliminary quenching process, since the head and tail of the mandrel 1 are at a uniform basic temperature state of room temperature during the preliminary quenching process, there is no need to adjust the cooling flow or power), the cooling water flow of the cooler 4 and the power of the induction heating furnace 2 can be adjusted simultaneously according to the temperature of the mandrel 1 to keep the overall axial temperature of the mandrel 1 uniform after heating. The power of the induction heating furnace 2 can also further form a closed-loop control with the temperature signal of the temperature measuring instrument 5.

[0069] The preliminary quenching process, the quenching and tempering process, the formal quenching process, and several tempering processes constitute the whole process of induction heat treatment, and the whole process of induction heat treatment takes 4-6 hours. Compared with the heat treatment process in the prior art which takes 10 hours (excluding the turnover time of the core rod being transported and hoisted between the gas furnace and the induction quenching line), the heat treatment time of the present invention can be reduced by about 50%, which greatly improves the heat treatment efficiency of the core rod 1, improves the heat treatment quality of the core rod 1, and does not have the problems of decarburization, three wastes discharge and pollution.

[0070] Embodiment 1:

[0071] The core rod 1 is made of H13 steel, has a diameter of 200 mm and a length of 30 m.

[0072] Please see attached Figure 1 , the mandrel 1 is placed on the horizontal transmission roller of the full-process induction heat treatment device, and the mandrel 1 is horizontally reciprocated by the transmission roller 3. The induction heating furnace 2 is arranged in the middle of the horizontal transmission roller, and the coolers 4 are arranged outside the two inlets and outlets of the induction heating furnace 2, and the temperature measuring instruments 5 are arranged between the two coolers 4 and the two inlets and outlets of the induction heating furnace 2. The swing angle range of the gear ring 6 of the rotating assembly in the induction heating furnace 2 and the cooler 4 is [-180°, 180°], and the reciprocating swing frequency is 20 times / minute.

[0073] The cooler 4 on the right side of the induction heating furnace 2 is recorded as the first cooler, and the cooler 4 on the left side of the induction heating furnace 2 is recorded as the second cooler; the thermometer 5 on the right side of the induction heating furnace 2 is recorded as the first thermometer, and the thermometer 5 on the left side of the induction heating furnace 2 is recorded as the second thermometer.

[0074] The whole process of induction heat treatment of core rod 1 is as follows:

[0075] Preliminary quenching process: The core rod 1 at room temperature is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1 m / min. During the transfer process, the core rod 1 is heated to a first quenching temperature of 1000°C (measured by a first temperature meter) by an induction heating furnace 2. The power of the induction heating furnace 2 is 900 kW and the frequency is 1000 Hz. After induction heating, the core rod 1 is cooled to 160°C by aerosol through a first cooler (i.e., cooler 4 at the outlet side of the induction heating furnace 2).

[0076] Tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the mist cooling in the preliminary quenching process is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the first tempering temperature of 680°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 580 kW and the frequency is 1000 Hz. After the induction heating, the core rod 1 is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0077] Formal quenching process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1m / min. When the core rod 1 passes through the second thermometer, the surface temperature of the core rod 1 after the aerosol cooling during the tempering process is measured by the second thermometer. During the transmission process, the core rod 1 is heated to the second quenching temperature of 1050°C (measured by the first thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 950kW and the frequency is 1000Hz. After induction heating, it is aerosol cooled to 160°C through the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0078] The first tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the formal quenching process mist cooling is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the second tempering temperature of 600°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 500 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0079] Second tempering process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the second thermometer, the surface temperature of the core rod 1 after the mist cooling in the first tempering process is measured by the second thermometer. During the transmission process, the core rod 1 is heated to the second tempering temperature of 600°C (measured by the first thermometer) by the induction heating furnace 2. The power of the induction heating furnace 2 is 500 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C by the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0080] In this embodiment, the preliminary quenching process is 30 minutes, the tempering process is 60 minutes, the formal quenching process is 30 minutes, the first tempering process is 60 minutes, and the second tempering process is 60 minutes. The total time of the whole process of induction heat treatment is 4 hours. Compared with the traditional technology, this embodiment adopts the full process of induction heat treatment, and timely tempering is achieved by reciprocating the core rod. There is no turnaround time between each process, and the production efficiency and core rod quality are improved at the same time. The final hardness of the core rod 1 produced in this embodiment is about 45HRC, the tensile strength is about 1600MPa, and the grains are refined, the segregation is reduced, and the comprehensive properties such as toughness, wear resistance, and resistance to cold and hot shocks are improved.

[0081] Embodiment 2:

[0082] The core rod 1 is made of H13 steel, has a diameter of 200 mm and a length of 30 m.

[0083] Please see attached Figure 1 , the mandrel 1 is placed on the horizontal transmission roller of the full-process induction heat treatment device, and the mandrel 1 is horizontally reciprocated by the transmission roller 3. The induction heating furnace 2 is arranged in the middle of the horizontal transmission roller, and the coolers 4 are arranged outside the two inlets and outlets of the induction heating furnace 2, and the temperature measuring instruments 5 are arranged between the two coolers 4 and the two inlets and outlets of the induction heating furnace 2. The swing angle range of the gear ring 6 of the rotating assembly in the induction heating furnace 2 and the cooler 4 is [-180°, 180°], and the reciprocating swing frequency is 20 times / minute.

[0084] The cooler 4 on the right side of the induction heating furnace 2 is recorded as the first cooler, and the cooler 4 on the left side of the induction heating furnace 2 is recorded as the second cooler; the thermometer 5 on the right side of the induction heating furnace 2 is recorded as the first thermometer, and the thermometer 5 on the left side of the induction heating furnace 2 is recorded as the second thermometer.

[0085] The whole process of induction heat treatment of core rod 1 is as follows:

[0086] Preliminary quenching process: The core rod 1 at room temperature is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1 m / min. During the transfer process, the core rod 1 is heated to a first quenching temperature of 1000°C (measured by a first temperature meter) by an induction heating furnace 2. The power of the induction heating furnace 2 is 900 kW and the frequency is 1000 Hz. After induction heating, the core rod 1 is cooled to 160°C by aerosol through a first cooler (i.e., cooler 4 at the outlet side of the induction heating furnace 2).

[0087] Tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.3 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the mist cooling in the preliminary quenching process is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the first tempering temperature of 680°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 550 kW and the frequency is 1000 Hz. After the induction heating, the core rod 1 is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0088] Formal quenching process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1m / min. When the core rod 1 passes through the second thermometer, the surface temperature of the core rod 1 after the aerosol cooling during the tempering process is measured by the second thermometer. During the transmission process, the core rod 1 is heated to the second quenching temperature of 1050°C (measured by the first thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 950kW and the frequency is 1000Hz. After induction heating, it is aerosol cooled to 160°C through the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0089] The first tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.3 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the formal quenching process mist cooling is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the second tempering temperature of 580°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 420 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0090] Second tempering process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 0.3 m / min. When the core rod 1 passes through the second thermometer, the second thermometer measures the surface temperature of the core rod 1 after the mist cooling in the first tempering process. During the transmission process, the core rod 1 is heated to the second tempering temperature of 600°C (measured by the first thermometer) by the induction heating furnace 2. The power of the induction heating furnace 2 is 430 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C by the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0091] In this embodiment, the preliminary quenching process is 30 minutes, the tempering process is 100 minutes, the formal quenching process is 30 minutes, the first tempering process is 100 minutes, and the second tempering process is 100 minutes. The total time of the whole process of induction heat treatment is 6 hours. Compared with the traditional technology, this embodiment adopts the full process of induction heat treatment, and timely tempering is achieved by reciprocating transportation of the core rod. There is no turnaround time between each process, and the production efficiency and core rod quality are improved at the same time. The final hardness of the core rod 1 produced in this embodiment is about 45HRC, the tensile strength is about 1600MPa, and the grains are refined, the segregation is reduced, and the comprehensive properties such as toughness, wear resistance, and resistance to cold and hot shocks are improved. At the same time, compared with Example 1, due to the slower tempering speed, this embodiment can make the tempering process more sufficient, which can effectively reduce the risk of rapid tempering cracking of the core rod.

[0092] Embodiment 3:

[0093] The core rod 1 is made of H13 steel, has a diameter of 200 mm and a length of 30 m.

[0094] Please see attached Figure 1 , the mandrel 1 is placed on the horizontal transmission roller of the full-process induction heat treatment device, and the mandrel 1 is horizontally reciprocated by the transmission roller 3. The induction heating furnace 2 is arranged in the middle of the horizontal transmission roller, and the coolers 4 are arranged outside the two inlets and outlets of the induction heating furnace 2, and the temperature measuring instruments 5 are arranged between the two coolers 4 and the two inlets and outlets of the induction heating furnace 2. The swing angle range of the gear ring 6 of the rotating assembly in the induction heating furnace 2 and the cooler 4 is [-180°, 180°], and the reciprocating swing frequency is 20 times / minute.

[0095] The cooler 4 on the right side of the induction heating furnace 2 is recorded as the first cooler, and the cooler 4 on the left side of the induction heating furnace 2 is recorded as the second cooler; the thermometer 5 on the right side of the induction heating furnace 2 is recorded as the first thermometer, and the thermometer 5 on the left side of the induction heating furnace 2 is recorded as the second thermometer.

[0096] The whole process of induction heat treatment of core rod 1 is as follows:

[0097] Preliminary quenching process: The core rod 1 at room temperature is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1 m / min. During the transfer process, the core rod 1 is heated to a first quenching temperature of 1000°C (measured by a first temperature meter) by an induction heating furnace 2. The power of the induction heating furnace 2 is 900 kW and the frequency is 1000 Hz. After induction heating, the core rod 1 is cooled to 160°C by aerosol through a first cooler (i.e., cooler 4 at the outlet side of the induction heating furnace 2).

[0098] Tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the mist cooling in the preliminary quenching process is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the first tempering temperature of 680°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 580 kW and the frequency is 1000 Hz. After the induction heating, the core rod 1 is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0099] Formal quenching process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 1m / min. When the core rod 1 passes through the second thermometer, the surface temperature of the core rod 1 after the aerosol cooling during the tempering process is measured by the second thermometer. During the transmission process, the core rod 1 is heated to the second quenching temperature of 1050°C (measured by the first thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 950kW and the frequency is 1000Hz. After induction heating, it is aerosol cooled to 160°C through the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0100] The first tempering process: the core rod 1 is transferred from the right end to the left end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the first thermometer, the surface temperature of the core rod 1 after the formal quenching process mist cooling is measured by the first thermometer. During the transmission process, the core rod 1 is heated to the second tempering temperature of 600°C (measured by the second thermometer) through the induction heating furnace 2. The power of the induction heating furnace 2 is 500 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C through the second cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0101] Second tempering process: the core rod 1 is transferred from the left end to the right end of the horizontal conveyor roller at a speed of 0.5 m / min. When the core rod 1 passes through the second thermometer, the surface temperature of the core rod 1 after the mist cooling in the first tempering process is measured by the second thermometer. During the transmission process, the core rod 1 is heated to the second tempering temperature of 600°C (measured by the first thermometer) by the induction heating furnace 2. The power of the induction heating furnace 2 is 500 kW and the frequency is 1000 Hz. After induction heating, it is mist cooled to 150°C by the first cooler (i.e., the cooler 4 on the outlet side of the induction heating furnace 2).

[0102] In each transmission process (except the preliminary quenching process), before the core rod 1 enters the induction heating furnace 2 for induction heating, it can be cooled by the cooler 4 on the inlet side of the induction heating furnace 2 along the transmission direction of the current process to eliminate the axial temperature difference between the head and tail ends of the core rod 1. The cooling method is: when the head end of the core rod 1 enters the cooler 4, the flow rate of cooling water is 50m 3 / h linearly decreases to 30m3 when the tail end of the core rod 1 leaves the cooler 4 3 / h.

[0103] In this embodiment, the preliminary quenching process is 30 minutes, the tempering process is 60 minutes, the formal quenching process is 30 minutes, the first tempering process is 60 minutes, and the second tempering process is 60 minutes. The total time of the whole process of induction heat treatment is 4 hours. Compared with the traditional technology, this embodiment adopts the full process of induction heat treatment, and timely tempering is achieved by reciprocating the transportation of the core rod. There is no turnaround time between each process, and the production efficiency and core rod quality are improved at the same time. The final hardness of the core rod 1 produced in this embodiment is about 45HRC, the tensile strength is about 1600MPa, and the grains are refined, the segregation is reduced, and the comprehensive properties such as toughness, wear resistance, and resistance to cold and hot shocks are improved. At the same time, compared with Example 1, this embodiment adjusts the aerosol cooling intensity according to the temperature difference between the head and tail of the core rod, which can improve the uniformity of the basic temperature of the core rod before induction heating, so that the induction quenching or tempering heating temperature can reach the set target value more accurately.

[0104] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A full-process induction heat treatment device for a steel pipe mandrel, characterized by: Including induction A heating furnace (2), a conveying roller (3), a cooler (4) and a temperature measuring instrument (5); a plurality of conveying rollers (3) are arranged in sequence along a horizontal plane to form a horizontal conveying roller for reciprocatingly conveying a core rod (1); the induction heating furnace (2) and two coolers (4) are arranged along the horizontal conveying roller, respectively, and the two coolers (4) are respectively located outside two inlets and outlets of the induction heating furnace (2), and the core rod (1) passes through one of the coolers (4), the induction heating furnace (2) and the other cooler (4) in sequence when being conveyed along the horizontal conveying roller; and temperature measuring instruments (5) are respectively provided between the two inlets and outlets of the induction heating furnace (2) and the two coolers (4).

2. The full-process induction heat treatment device for a steel pipe mandrel according to claim 1 is characterized in that: The induction heating furnace (2) comprises a heating furnace shell (21), a coil copper tube (22) and a rotating assembly; the coil copper tube (22) is a circular ring structure, the coil copper tube (22) is installed in the rotating assembly through a support (9), and rotates in the heating furnace shell (21) through the rotating assembly, and the core rod (1) coaxially penetrates the coil copper tube (22); a refractory furnace lining (23) is provided on the inner wall of the coil copper tube (22); the power supply power of the induction heating furnace (2) is 400-1000kW.

3. The full-process induction heat treatment device for a steel pipe mandrel according to claim 1 is characterized in that: The cooler (4) comprises a cooler housing (41), a cooling nozzle (42) and a rotating assembly; the cooling nozzle (42) is a circular ring structure, and nozzles facing the surface of the core rod (1) are evenly distributed on the cooling nozzle (42); the cooling nozzle (42) is installed in the rotating assembly through a support (9), and rotates in the cooler housing (41) through the rotating assembly, and the core rod (1) coaxially passes through the cooling nozzle (42); the cooling water flow rate of the cooler (4) is 30-60m 3 / h, pressure 0.4-0.8MPa.

4. The full-process induction heat treatment device for a steel pipe mandrel according to claim 2 or 3, characterized in that: The rotating assembly comprises a ring gear (6), a gear (7) and a driver (8); the gear (7) is coaxially connected to an output shaft of the driver (8) and rotates synchronously, the ring gear (6) is meshingly connected to the gear (7), and the ring gear (6) can swing back and forth around the center of the ring gear (6) through the gear (7); the center of the ring gear (6) is located on the central axis of the core rod (1); the swing angle range of the ring gear (6) is [-180°, 180°], and the swing frequency is 10-30 times / minute.

5. A full-process induction heat treatment method for a steel pipe mandrel, characterized in that: The full-process induction heat treatment method is implemented based on the full-process induction heat treatment device according to claim 1, and the full-process induction heat treatment method comprises the following steps: Step 1: placing the mandrel (1) on a horizontal conveyor roller, and enabling the mandrel (1) to reciprocate horizontally through the horizontal conveyor roller; Step 2: Preliminary quenching process: The core rod (1) at room temperature is transferred from one end of the horizontal conveyor roller to the other end. During the transfer process, the core rod (1) is heated to a first quenching temperature by the induction heating furnace (2). After the induction heating, the core rod (1) is cooled by a cooler (4) at the outlet side of the induction heating furnace (2) so that the temperature of the core rod (1) drops to below 180° C.; Step 3: Tempering process: the core rod (1) is transferred from the other end to the one end of the horizontal conveyor roller, and during the transfer process, the core rod (1) is heated to a first tempering temperature by the induction heating furnace (2), and after the induction heating, the core rod (1) is cooled by a cooler (4) at the outlet side of the induction heating furnace (2), so that the temperature of the core rod (1) is reduced to below 180° C.; Step 4: Formal quenching process: the core rod (1) is transferred from one end of the horizontal conveyor roller to the other end. During the transfer process, the core rod (1) is heated to a second quenching temperature by the induction heating furnace (2). After the induction heating, the core rod (1) is cooled by the cooler (4) at the outlet side of the induction heating furnace (2) so that the temperature of the core rod (1) drops to below 180° C.; Step 5: The tempering process is continuously performed for several times, and the process of each tempering process is as follows: the core rod (1) is transported by a horizontal conveyor roller, and during the transportation process, the core rod (1) is heated to a second tempering temperature by an induction heating furnace (2), and after the induction heating, the core rod (1) is cooled by a cooler (4) at the outlet side of the induction heating furnace (2) to reduce the temperature of the core rod (1) to below 180°C.

6. The full-process induction heat treatment method for a steel tube mandrel according to claim 5, characterized in that: The first quenching temperature is 950-1050° C., the power of the induction heating furnace (2) is 850-950 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod (1) is 1-1.5 m / min.

7. The full-process induction heat treatment method for a steel tube mandrel according to claim 5, characterized in that: The first tempering temperature is 650-700° C., the power of the induction heating furnace (2) is 500-600 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod (1) is 0.1-0.5 m / min.

8. The full-process induction heat treatment method for a steel tube mandrel according to claim 5, characterized in that: The second quenching temperature is 1000-1100° C., the power of the induction heating furnace (2) is 900-1000 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod (1) is 1-1.5 m / min.

9. The full-process induction heat treatment method for a steel tube mandrel according to claim 5, characterized in that: The tempering process is performed 2-3 times, the transmission direction of the core rod (1) in the first tempering process is opposite to the transmission direction of the core rod (1) in step 4, and the transmission directions of the core rod (1) in two adjacent tempering processes are opposite; During each tempering process, the second tempering temperature is 550-600° C., the power of the induction heating furnace (2) is 400-500 kW, the frequency is 500-2000 Hz, and the transmission speed of the core rod (1) is 0.1-0.5 m / min.

10. The full-process induction heat treatment method for a steel pipe mandrel according to claim 5, characterized in that: During the quenching and tempering process, the formal quenching process and the tempering process, the power of the induction heating furnace (2) is linearly adjusted from small to large according to the temperature of the core rod (1) before it enters the induction heating furnace (2), and the cooling water flow of the cooler (4) is linearly adjusted from large to small according to the temperature of the core rod (1) before it enters the cooler (4).

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