CN112725572A - Main and auxiliary induction heating local heat treatment method - Google Patents
Main and auxiliary induction heating local heat treatment method Download PDFInfo
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- CN112725572A CN112725572A CN202011556840.8A CN202011556840A CN112725572A CN 112725572 A CN112725572 A CN 112725572A CN 202011556840 A CN202011556840 A CN 202011556840A CN 112725572 A CN112725572 A CN 112725572A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/42—Induction heating
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
The invention relates to the technical field of heat treatment, and provides a main and auxiliary induction heating local heat treatment method. The method combines main and auxiliary heating with induction heating, a thermocouple is welded in a main heating area and an auxiliary heating area, a heat preservation blanket and an induction cable are laid, the main heating area and the auxiliary heating area are heated by the induction power, the main heating area is subjected to heat treatment according to a main heating process curve, the induction cable and the heat preservation blanket in the main heating area are removed when the main heating area is cooled to room temperature, the auxiliary heating area is heated, the auxiliary heating area is subjected to heat treatment according to an auxiliary heating process curve, and local heat treatment of the main heating area and the auxiliary heating area is realized. The invention not only improves the mechanical property and microstructure of the welding seam area, but also greatly reduces the welding residual stress, generates smaller tensile stress and even compressive stress on the inner surface of the heat treatment object, realizes the quantitative regulation and control of the residual stress level of the heat treatment object, and effectively solves the problems of poor local heating temperature uniformity and difficult accurate temperature control of heavy equipment with super-diameter and super-wall thickness.
Description
Technical Field
The invention relates to the technical field of heat treatment, in particular to a main and auxiliary induction heating local heat treatment method.
Background
The heavy hydrogenation reactor and the overrun tower are used as core equipment in the petrochemical industry, the successful manufacture embodies the national overall technical level in a certain sense, and the heavy hydrogenation reactor and the overrun tower are the mark of a 'heavy equipment' in China. For the core equipment, the heat treatment method is required to eliminate the welding residual stress by domestic and foreign standards. At present, as the pressure vessel is developed in a large-scale direction, the pressure vessel cannot be subjected to overall heat treatment due to the limitation of the diameter and the length of the pressure vessel, and the pressure vessel needs to be manufactured by adopting a sectional assembly welding mode, a sectional heat treatment mode and an overall assembling mode, but a folding welding line is generated in the overall assembling process, and only local heat treatment can be performed. Through a large number of tests and calculation researches, the barrel can be subjected to waist-shrinking deformation by adopting a standard recommended local heat treatment method, and the inner surface generates new secondary tensile heat stress, so that the stress of the inner surface is not reduced and reversely increased, and the stress corrosion cracking is caused; secondly, the larger the diameter and the wall thickness of the hydrogenation reactor and the overrun tower are, the stronger the processing capacity of the hydrogenation reactor and the overrun tower is, and the equipment upsizing is a necessary way for improving economic benefits and is one of the development trends of the worldwide petrochemical industry. In 2007, the outer diameter of a heavy-duty hydrogenation reactor manufactured abroad has reached 5894 mm and the wall thickness has 347 mm, and the largest hydrogenation reactor in China at present has 6517 mm and 352 mm; for the container with the ultra-large diameter and the ultra-thick wall, the conventional heating modes such as flame heating, crawler-type ceramic wafer heating and the like are adopted, and the requirement on temperature uniformity of local heat treatment recommended by standard specifications is difficult to meet, so that a more advanced heating mode needs to be developed urgently, and the induction heating becomes the optimal heating mode of the container with the ultra-large diameter and the ultra-thick wall due to the advantages of high efficiency and accurate temperature control.
Disclosure of Invention
The invention provides a main and auxiliary induction heating local heat treatment method aiming at solving the problems that the residual stress of the inner wall of a container is difficult to eliminate by adopting the local heat treatment recommended by the current standard specification and the temperature uniformity is difficult to realize when an ultra-large diameter ultra-thick wall container is locally heated.
The invention specifically adopts the following technical scheme:
a main and auxiliary induction heating local heat treatment method is characterized in that a main heating area is arranged at a welding seam, and an auxiliary heating area is arranged at a position away from the main heating area, and specifically comprises the following steps:
Determining heat treatment process parameters of the main heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the width, the temperature rise and reduction rate, the heat preservation temperature and the heat preservation time of the main heating zone;
Determining heat treatment process parameters of the auxiliary heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the distance from the center position of the auxiliary heating zone to the center of the main heating zone, the width of the auxiliary heating zone, the highest heat preservation temperature of the auxiliary heating zone, the temperature rising and falling speed and the heat preservation time;
Determining the heating time of the main heating area and the auxiliary heating area based on the actual situation of the heat treatment object, and determining the heat treatment process of the main heating area and the auxiliary heating area of the heat treatment object;
for heat treatment objects with small radial deformation generated in the heat treatment and heat preservation process, simultaneously heating the main heating area and the auxiliary heating area to the heat preservation temperature of the main heating area, carrying out heat treatment on the main heating area according to a main heating process curve, cooling the temperature of the main heating area to room temperature, removing an induction cable and a heat preservation blanket arranged in the main heating area, heating the auxiliary heating area to the highest heat preservation temperature, and carrying out heat treatment on the auxiliary heating area according to an auxiliary heating process curve;
Before heat treatment, the thermocouple is welded on the outer surface of a heat treatment object and is in close contact with the outer surface of the heat treatment object, the thermocouple is connected with an induction power supply, one of the thermocouples is selected as a temperature control thermocouple, the other thermocouples are used as monitoring thermocouples, and a thermocouple lead is led out along the direction parallel to the magnetic line and is fixed by a glass fiber adhesive tape;
The heat-insulating blanket adopts a three-layer structure, the top layer and the bottom layer are both made of glass fiber fabrics, and the middle layer is made of ceramic fiber cotton or nano aerogel high-temperature-resistant materials;
laying heat preservation blankets on the outer surfaces of the heat treatment objects, symmetrically laying the heat preservation blankets left and right by taking the center line of a welding line as the center, wherein the thicknesses of the heat preservation blankets laid on the outer surfaces of the heat treatment objects are consistent, when a plurality of layers of heat preservation blankets need to be laid, the heat preservation blankets are tensioned and pressed to each layer, gaps between two adjacent layers of heat preservation blankets are eliminated, and the heat preservation blankets are bound and fixed by glass fiber tapes after the laying is finished;
for the inner surface of the heat treatment object, the heat preservation blanket can be paved by adopting the same method as the outer surface;
Selecting an air-cooled high-temperature-resistant alloy cable or a water-cooled heating cable as an induction cable;
determining the number of turns and the turn-to-turn distance of the induction cable according to the self characteristics of a heat treatment object and the heat treatment process requirement and in combination with the preset induction heating width;
the induction cables are symmetrically wound on the outer surface of the heat treatment object by taking the central line of the welding seam as a center, the induction cables are unevenly arranged, the induction cables close to the center of the welding seam are sparsely arranged, the induction cables far away from the center of the welding seam are densely arranged, the induction cables are fixed at the winding starting position and the winding ending position, the rest wires are twisted and led out in a double-stranded mode, the rest wires are overhead or wired from the cement ground by adopting glass fibers, refractory bricks or austenitic stainless steel, and are far away from the steel wall surface or the magnetic conductivity structural part;
Determining the power of an induction power supply according to thermal calculation, wherein the induction power supply has a working frequency quick automatic tracking function, an output loop leakage detection function, an abnormal state acousto-optic alarm function, a temperature difference protection function and a current attenuation demagnetization function;
Heating a heat treatment object by utilizing a hysteresis heat effect and an eddy heat effect of induction heating, realizing the uniformity of the temperature of the heat treatment object through heat conduction, setting an induction power supply operation mode into a constant power operation mode or a process operation mode, and presetting a heating curve, a heat preservation curve and a cooling control curve;
the induction heating temperature rise process is as follows: setting the heating rate of a heat treatment object according to a preset target temperature, comparing the set heating rate with the temperature of the heat treatment object measured by a thermocouple by using an induction power supply, adjusting the output power of the induction power supply by using PID (proportion integration differentiation) regulation control equipment in an induction power supply control system, enabling the output power of the induction power supply to meet the requirement of the heating rate of the heat treatment object, and heating the heat treatment object according to the set heating rate;
the induction heating and cooling process comprises the following steps: setting a cooling rate of a heat treatment object according to a preset target temperature, comparing the set cooling rate with the temperature of the heat treatment object measured by a thermocouple by using an induction power supply, adjusting the output power of the induction power supply by using PID (proportion integration differentiation) regulation control equipment in an induction power supply control system, enabling the output power of the induction power supply to meet the requirement of the cooling rate of the heat treatment object, and cooling the heat treatment object according to the set cooling rate;
According to the heat treatment process of the main heating area and the auxiliary heating area, the connecting wires are detected, the induction cable is connected with the induction power supply, the induction power supply is started, the operation mode of the induction power supply is set, the output power or the temperature curve is input into the induction cable control system, and the main induction heating and auxiliary induction heating local heat treatment is carried out.
Preferably, in the step 1, when the thickness of the weld joint of the heat treatment object does not exceed 50mm, the width of the main heating zone is determined according to GB/T30583 post-weld heat treatment regulation of pressure-bearing equipment, and when the thickness of the weld joint of the heat treatment object is greater than 50mm, the width of the main heating zone is determined according to the temperature uniformity requirement of the weld joint through process evaluation.
Preferably, in the step 2, the distance from the center position of the auxiliary heating zone to the center of the main heating zone is determined according to the thickness of the base material to be heat-treated, the thermal expansion coefficient and the correction coefficient;
determining the width of the auxiliary heating zone according to GB/T30583 post-welding heat treatment regulation of pressure-bearing equipment;
determining the highest heat preservation temperature of the auxiliary heating area according to the requirement of a heat treatment object on residual stress elimination in the service process, if the heat treatment object has strict requirement on residual stress elimination, setting the highest heat preservation temperature of the auxiliary heating area to be 40-60% of the heat preservation temperature of the main heating area, and if the heat treatment object has no strict requirement on residual stress elimination, setting the highest heat preservation temperature of the auxiliary heating area to be any temperature within 200-300 ℃;
and determining the heat preservation time of the auxiliary heating area according to the self characteristics of the heat treatment object and the service environment.
Preferably, in step 4, the thermocouple is a K-type thermocouple, and can be used as both a temperature control thermocouple and a monitoring thermocouple.
Preferably, in the step 5, when the main heating zone holding temperature is 500 ℃, the thickness of the heat preservation blanket is set to be not less than 50mm, and when the main heating zone holding temperature is 700 ℃, the thickness of the heat preservation blanket is set to be not less than 70 mm.
Preferably, in the step 6, an induction cable tool may be used to replace an induction cable, two sets of induction cable tools are used, a laying distance between the two sets of induction cable tools is determined according to a width of a main heating area, the induction cable tools are arranged in an open-close type, the induction cable tools are symmetrically laid on an outer surface of a heat treatment object by taking a welding seam as a center, heat treatment of the main heating area is performed, after the heat treatment of the main heating area is completed, the laying distance between the two sets of induction cable tools is determined according to a distance from a center position of an auxiliary heating area to a center of the main heating area, and the induction cable tools are moved outwards to a center position of the distance between the center of the main heating area and the center of the.
Preferably, in the step 6, if the object to be heat-treated is a cylinder, more than three mica or ceramic strips may be uniformly arranged at positions corresponding to twelve o ' clock positions on the outer wall of the cylinder to raise the induction cables by 10-20mm, or the induction cables may be sparsely arranged at positions corresponding to twelve o ' clock positions on the outer wall of the cylinder and densely arranged at positions corresponding to six o ' clock positions on the outer wall of the cylinder.
Preferably, in the step 7, the fast and automatic tracking function of the working frequency can fast track the resonant frequency when the induction heater is replaced and the number of turns of the induction coil or the load is changed, the resonant frequency of the induction power supply does not need to be adjusted, and the working frequency of the induction power supply is always the optimal working frequency;
the output loop leakage detection function sets an alarm value of an insulation resistor by embedding the output loop insulation resistor in the induction power supply, and if the resistance value of the insulation resistor is lower than the alarm value, the induction power supply is immediately cut off, so that the safety of the induction power supply is protected;
the abnormal state acousto-optic alarm function is used for carrying out acousto-optic alarm on the abnormal state of the induction power supply and displaying alarm information;
the temperature difference protection function is used for controlling the temperature difference between the inner surface and the outer surface of the heat treatment object, the induction power supply automatically reduces the output power when the temperature difference between the inner surface and the outer surface of the heat treatment object exceeds a limited range in the induction heating process, and the induction power supply automatically switches from uniform temperature power to heating power when the temperature difference between the inner surface and the outer surface of the heat treatment object is smaller than the limited range, so that the temperature difference between the inner surface and the outer surface of the heat treatment object in the induction heating process is ensured to be within;
the current-decaying demagnetization function is used to avoid leaving remanence on the heat-treated object.
Preferably, the induction power supply is a medium frequency induction heating power supply.
The invention has the following beneficial effects:
the invention adopts a main and auxiliary induction heating local heat treatment method, effectively solves the problems of poor local heating temperature uniformity and difficult accurate temperature control of the heavy equipment with the super-diameter and the super-wall thickness, quantitatively regulates and controls the residual stress level of the inner wall of the welding seam of the heat treatment object according to the service environment, the material and the like of the heat treatment object, and simultaneously combines the heat treatment process and the equipment to solve the local heat treatment problem of the heavy equipment with the super-diameter and the super-wall thickness.
Drawings
FIG. 1 is a diagram of the correction coefficient eta of the main and auxiliary heating intervals of a common material; wherein, fig. 1(a) is a diagram of the value of the main and auxiliary heating interval correction coefficient eta of carbon steel, fig. 1(b) is a diagram of the value of the main and auxiliary heating interval correction coefficient eta of stainless steel, and fig. 1(c) is a diagram of the value of the main and auxiliary heating interval correction coefficient eta of chromium molybdenum steel.
FIG. 2 is a main and auxiliary heating process curve.
FIG. 3 is a schematic view showing the arrangement of the heat insulating blanket inside and outside the cylinder and the induction cable according to the embodiment.
FIG. 4 is a diagram showing the arrangement of thermocouples on the inner and outer walls of the cylinder according to the embodiment; wherein the numbers 1-12 represent thermocouple numbers.
FIG. 5 is a graph showing axial stress and hoop stress of the inner wall of a vertical cylinder closure weld according to an embodiment; wherein, fig. 5(a) is a graph of axial stress of the inner wall of the vertical cylinder body folding welding seam, and fig. 5(b) is a graph of circumferential stress of the inner wall of the vertical cylinder body folding welding seam.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings:
taking a cylinder body folding seam of a pressure vessel as an example, the method for local heat treatment by main and auxiliary induction heating is explained, wherein a main heating area is arranged at a welding seam of the cylinder body, and an auxiliary heating area is arranged at a position which is a distance away from the main heating area, and the method specifically comprises the following steps:
Determining heat treatment process parameters of the main heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the width, the temperature rise and reduction rate, the heat preservation temperature and the heat preservation time of the main heating zone;
since the current standards for the width of the main heating zone for local heat treatment are inconsistent at home and abroad, the width of the main heating zone is determined according to GB/T30583 post-weld heat treatment specification of pressure-bearing equipment.
Determining heat treatment process parameters of the auxiliary heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the distance from the center position of the auxiliary heating zone to the center of the main heating zone, the width of the auxiliary heating zone, the highest heat preservation temperature of the auxiliary heating zone, the temperature rising and falling speed and the heat preservation time;
the width and the temperature rising and reducing rate of the auxiliary heating zone are determined according to GB/T30583 postweld heat treatment regulations of pressure-bearing equipment, and the width of the auxiliary heating zone meets the requirements of the uniform temperature zone in GB/T30583 postweld heat treatment regulations of pressure-bearing equipment;
calculating the distance from the center position of the auxiliary heating area to the center of the main heating area according to the thickness, the thermal expansion coefficient and the correction coefficient of the base material to be heat-treated, wherein the distance is expressed by the following formula (1):
the calculation formula of the distance between the main heating area and the auxiliary heating area is as follows:
in the formula, WDCBThe distance between the center position of the auxiliary heating area and the center of the main heating area is expressed in mm; wHBRepresents the width of the secondary heating zone in mm; eta represents a main heating interval correction coefficient and an auxiliary heating interval correction coefficient, and the correction coefficient integrates the radius and the wall thickness of the cylinder body, and the specific numerical value is shown in figure 1; delta represents the thickness of the cylinder in mm; alpha represents the coefficient of thermal expansion of the cylinder in mm/DEG C;
determining the highest heat preservation temperature of the auxiliary heating area according to the requirement of the cylinder on residual stress elimination in the service process, setting the highest heat preservation temperature of the auxiliary heating area to be 40-60% of the heat preservation temperature of the main heating area, and effectively improving the internal surface stress of the cylinder;
and setting the heat preservation time of the auxiliary heating zone to be half an hour according to the self characteristics of the cylinder and the service environment.
Determining the heating time of the main heating area and the auxiliary heating area based on the actual situation of the cylinder, and determining the heat treatment process of the main heating area and the auxiliary heating area of the cylinder;
because the radial deformation of the cylinder body generated in the heat treatment and heat preservation process is small, the main heating area and the auxiliary heating area are simultaneously heated to the heat preservation temperature of the main heating area, the main heating area is subjected to heat treatment according to the main heating process curve, after the temperature of the main heating area is cooled to the room temperature, the induction cable and the heat preservation blanket arranged in the main heating area are removed, the auxiliary heating area is heated to the highest heat preservation temperature, the auxiliary heating area is subjected to heat treatment according to the auxiliary heating process curve, and the main heating process curve and the auxiliary heating process curve are shown in fig. 2.
In the embodiment, the thermocouple adopts a K-type thermocouple, which can be used as a temperature control thermocouple and a monitoring thermocouple;
before heat treatment, the thermocouples are welded on the outer wall of the barrel body, the thermocouples are connected with an induction power supply and are tightly attached to the outer wall of the barrel body, one of the thermocouples is selected as a temperature control thermocouple, the other thermocouples are used as monitoring thermocouples, the temperature control thermocouple is used for feeding back temperature to the induction power supply so as to facilitate the induction power supply to control output power, the temperature control thermocouple is positioned in a heating area of the induction cable, a thermocouple lead is led out along a direction parallel to a magnetic line of force, and is fixed on the outer wall of the barrel body by using a glass fiber adhesive tape so; meanwhile, the thermocouple lead is led out along the direction parallel to the magnetic line of force, so that the induction sectional area of the thermocouple lead in a magnetic field is reduced, the temperature measurement error caused by extra electromotive force generated by electromagnetic induction when the thermocouple is placed in the magnetic field is avoided, and the temperature measurement precision of the thermocouple is ensured;
the thermocouple and the induction cable are arranged on the outer wall of the cylinder body, and when the induction cable is used for heating the cylinder body, the thermocouple can quickly measure the temperature of the outer wall of the cylinder body, so that the response speed is high; if the thermocouple and the induction cable are respectively arranged at two sides of the barrel, namely the induction cable is arranged on the inner wall of the barrel and the thermocouple is arranged on the outer wall of the barrel, at the moment, the heat generated by the induction cable in the barrel can be transmitted to the thermocouple arranged on the outer wall of the barrel through the wall thickness of the barrel only in a heat conduction mode, so that the temperature measurement of the thermocouple is seriously lagged, and the temperature measurement precision of the thermocouple is reduced;
in addition, the thermocouple can be sleeved in a shielding sleeve woven by metal wires, and the shielding sleeve is utilized to shield an electromagnetic field generated by an induction cable in the induction heating process, so that the interference of the electromagnetic field on the thermocouple is reduced, and the temperature measurement precision of the thermocouple is ensured.
The heat-insulating blanket in the embodiment adopts a three-layer structure, the top layer and the bottom layer are both made of glass fiber fabrics, the middle layer is made of ceramic fiber cotton, and the ceramic fiber cotton is not used independently because the ceramic fiber cotton is fragile and has holes with different sizes, the thickness of the heat-insulating layer is not uniform, the heat resistance is not uniform, and the heat-insulating effect is poor;
laying a heat preservation blanket on the outer surface of a heat treatment object, wherein the thickness of the heat preservation blanket determines the distance from an induction cable to the outer wall of a cylinder body, under the normal condition, the closer the induction cable is to the outer wall of the cylinder body, the higher the heating temperature of the induction cable to the outer wall of the cylinder body is, the better the heating effect is, the heat preservation blankets are symmetrically laid with the center line of a welding line as the center, the thickness of the heat preservation blankets laid at all positions on the outer wall of the cylinder body is ensured to be consistent, a plurality of layers of heat preservation blankets are laid, each layer of the heat preservation blanket wound on the cylinder body is tensioned, no gap is reserved between two adjacent layers of heat preservation blanket supports, the heat preservation blankets are bundled and fixed by using a glass fiber tape after the; for a large-diameter cylinder or pipeline, due to the action of gravity, the thermal insulation blanket may sag at the position of the outer wall of the cylinder corresponding to the 6 o 'clock position of the clock, and the sensing cable at the 6 o' clock position of the clock is added to the outer wall of the cylinder, so that the heating effect is poor, and the temperature is reduced, and special attention is needed when the thermal insulation blanket is laid;
in order to reduce heat loss and improve heat utilization efficiency, a heat insulation blanket is laid on the inner wall of the cylinder body in the same method as the outer wall of the cylinder body, the heat insulation blanket laid on the inner wall of the cylinder body can reduce convection heat transfer of the inner cavity of the cylinder body and improve the distribution uniformity of circumferential temperature and radial temperature of the cylinder body, and meanwhile, the openings at two ends of the cylinder body are also sealed by adopting the heat insulation blanket, so that the heat loss of the inner wall of the cylinder body is reduced, and the axial temperature of the cylinder body is uniformly distributed.
The induction cable can be an air-cooled high-temperature-resistant alloy cable or a water-cooled heating cable, the air-cooled high-temperature-resistant alloy cable can resist 450 ℃ and the temperature of the heat-insulating blanket cannot be higher than 200 ℃ when the water-cooled heating cable is adopted; in the embodiment, the air-cooled high-temperature-resistant alloy cable is selected as the induction cable, the high-temperature-resistant alloy cable adopts an air-cooled mode, the arrangement is convenient, the operation is flexible, the high-temperature-resistant alloy cable only generates a very small amount of resistance heat, the temperature rise mainly comes from the heat conduction and the heat radiation of the cylinder, and the heat-insulating blanket is laid between the induction cable and the outer wall of the cylinder, so that the working temperature of the induction cable is greatly reduced, and the heat damage to the induction cable is avoided;
the number of turns of the induction cable is determined according to the width of the main heating area and the width of the auxiliary heating area, the number of turns of the induction cable needs to meet the requirement of a uniform temperature area, then the turn pitch of the induction cable is determined by combining the width of the main heating area and the width of the auxiliary heating area according to the wall thickness, the material and the heat treatment process requirement of the cylinder body, so that the turn pitch of the induction cable meets the requirement of the uniform temperature area, if the turn pitch of the induction cable needs to be adjusted in the induction heating process, the turn pitch can be adjusted by an insulating non-metal deflector rod, the temperature distribution is improved, generally, the turn pitch of the induction cable;
the induction cables are symmetrically wound on the outer wall of the barrel by taking a welding line central line as a center, the welding line of the barrel is positioned at the position, corresponding to the twelve o ' clock, of the outer wall of the barrel, the induction cables are unevenly arranged, the induction cables are sparsely arranged at the position, corresponding to the twelve o ' clock, of the outer wall of the barrel (close to the center of the welding line of the barrel), the induction cables are densely arranged at the position, corresponding to the six o ' clock, of the outer wall of the barrel (far away from the center of the welding line of the barrel), the induction cables are fixed at the winding starting position and the winding ending position, the rest lines are led out.
And selecting a medium-frequency induction heating power supply with proper power according to thermal calculation, wherein the medium-frequency induction heating power supply has a working frequency quick automatic tracking function, an output loop leakage detection function, an abnormal state acousto-optic alarm function, a temperature difference protection function and a current attenuation demagnetization function.
Heating the cylinder by utilizing a hysteresis heat effect and an eddy heat effect of induction heating, realizing the uniformity of the temperature of the cylinder through heat conduction, setting the operation mode of the medium-frequency induction heating power supply into a constant-power operation mode, and presetting a heating curve, a heat preservation curve and a cooling control curve into a control system of the medium-frequency induction heating power supply;
wherein, the induction heating temperature rise process is as follows: setting the heating rate of the cylinder according to a preset target temperature, comparing the set heating rate with the temperature of the cylinder measured by a thermocouple by using a medium-frequency induction heating power supply, adjusting the output power of the medium-frequency induction heating power supply by using PID (proportion integration differentiation) regulation control equipment in a medium-frequency induction heating power supply control system, enabling the output power of the medium-frequency induction heating power supply to meet the requirement of the heating rate of the cylinder, and heating the cylinder according to the set heating rate;
the induction heating and cooling process comprises the following steps: the cooling rate of the cylinder is set according to the preset target temperature, the medium-frequency induction heating power supply compares the set cooling rate with the cylinder temperature measured by the thermocouple, and the PID adjusting and controlling equipment inside the medium-frequency induction heating power supply control system is used for adjusting the output power of the medium-frequency induction heating power supply, so that the output power of the medium-frequency induction heating power supply meets the requirement of the cylinder cooling rate, and the cylinder is cooled according to the set cooling rate.
According to the heat treatment process of the main heating area and the auxiliary heating area, the connecting wires are detected, the induction cable is connected with the medium-frequency induction heating power supply, the medium-frequency induction heating power supply is started, the operation mode of the medium-frequency induction heating power supply is set, and the output power or the temperature curve is input into the medium-frequency induction heating power supply control system to carry out local heat treatment of the main induction heating area and the auxiliary induction heating area.
Example of the implementation
The inner diameter of a cylinder of a certain hydrofining reactor is 5800mm, the wall thickness of the cylinder is 324mm +8mm, a low alloy steel base material with the thickness of 324mm is arranged in the wall thickness of the cylinder and is made of 21/4 Cr-1Mo-1/4V steel, stainless steel with the thickness of 8mm is welded on the inner surface of the cylinder in a surfacing mode, and a main induction heating local heat treatment method and an auxiliary induction heating local heat treatment method are used for treating a folding circumferential weld between cylinder sections.
Spot-welding a thermocouple on the surfaces of the inner wall and the outer wall of the cylinder body, and paving a heat-insulating blanket as shown in figure 3; according to thermal calculation, 5 200kw heating power supplies are adopted as induction power supplies, each power supply adopts 3 high-temperature-resistant induction cables with the length of 70m to wind for 3 circles side by side, the total winding is 45 circles, and the interval between the induction cables is 40-50 mm. The induction cable winding area comprises a main heating area and an auxiliary heating area, wherein the center of the auxiliary heating area is 1300mm away from the center of the welding seam (the auxiliary heating area is positioned at two sides of the welding seam), and the heating width of the auxiliary heating area is about 500 mm. Detecting various connecting wires, starting the induction power supply, selecting a constant power mode or a process mode, inputting output power or a temperature curve to the control panel, and switching on the induction power supply to start heating. And when the main heating area finishes heating, the temperature of the workpiece is reduced to room temperature, 4 200kw induction power supplies (2 200kw induction power supplies are adopted for each side of the welding line) for heating the main heating area are respectively connected to the induction cables positioned in the auxiliary heating areas at two sides of the welding line, heating is started to be heated to 300 ℃, heat preservation is carried out for 30 minutes, and heating and natural cooling are stopped.
The positions of the thermocouples on the inner wall and the outer wall of the cylinder are shown in fig. 4, the temperature of the thermocouples on the inner wall and the outer wall of the circumferential seam of the cylinder changes along with time in the heat treatment process, and the temperature rising trends of points in different directions are consistent in the induction heating process. In the heat preservation stage, the temperature of the uniform temperature zone is uniformly distributed, the maximum temperature difference is within 5 ℃, and the requirement of the uniform temperature zone of local heat treatment is met. FIG. 5 is a graph showing axial stress and hoop stress on the inner wall of a vertical cylinder body closure weld, with the abscissa indicating distance and the ordinate indicating axial stress and hoop stress, respectively. From fig. 5(a) and 5(b), the main and auxiliary induction heating local heat treatment method provided by the invention can effectively reduce the axial stress and the hoop stress near the weld joint, so that the stress of the inner surface is at a lower level, and the risk of stress corrosion generated in the service process can be inhibited. Compared with the traditional local heat treatment method, the method can quantitatively regulate and control the stress distribution level of the inner surface, and can better realize temperature uniformity and accurate temperature control by adopting induction heating, so that the heat treatment effect is better.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (9)
1. A main and auxiliary induction heating local heat treatment method is characterized in that a main heating area is arranged at a welding seam, and an auxiliary heating area is arranged at a distance from the main heating area, and specifically comprises the following steps:
step 1, determining heat treatment process parameters of a main heating area
Determining heat treatment process parameters of the main heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the width, the temperature rise and reduction rate, the heat preservation temperature and the heat preservation time of the main heating zone;
step 2, determining the heat treatment process parameters of the auxiliary heating area
Determining heat treatment process parameters of the auxiliary heating zone according to the self characteristics, the service environment and the welding process specification of the heat treatment object, wherein the heat treatment process parameters comprise the distance from the center position of the auxiliary heating zone to the center of the main heating zone, the width of the auxiliary heating zone, the highest heat preservation temperature of the auxiliary heating zone, the temperature rising and falling speed and the heat preservation time;
step 3, determining the heat treatment process of the main heating area and the auxiliary heating area
Determining the heating time of the main heating area and the auxiliary heating area based on the actual situation of the heat treatment object, and determining the heat treatment process of the main heating area and the auxiliary heating area of the heat treatment object;
for heat treatment objects with small radial deformation generated in the heat treatment and heat preservation process, simultaneously heating the main heating area and the auxiliary heating area to the heat preservation temperature of the main heating area, carrying out heat treatment on the main heating area according to a main heating process curve, cooling the temperature of the main heating area to room temperature, removing an induction cable and a heat preservation blanket arranged in the main heating area, heating the auxiliary heating area to the highest heat preservation temperature, and carrying out heat treatment on the auxiliary heating area according to an auxiliary heating process curve;
step 4, spot welding and arrangement of thermocouples
Before heat treatment, the thermocouple is welded on the outer surface of a heat treatment object and is in close contact with the outer surface of the heat treatment object, the thermocouple is connected with an induction power supply, one of the thermocouples is selected as a temperature control thermocouple, the other thermocouples are used as monitoring thermocouples, and a thermocouple lead is led out along the direction parallel to the magnetic line and is fixed by a glass fiber adhesive tape;
step 5, selecting and laying a heat preservation blanket
The heat-insulating blanket adopts a three-layer structure, the top layer and the bottom layer are both made of glass fiber fabrics, and the middle layer is made of ceramic fiber cotton or nano aerogel high-temperature-resistant materials;
laying heat preservation blankets on the outer surfaces of the heat treatment objects, symmetrically laying the heat preservation blankets left and right by taking the center line of a welding line as the center, wherein the thicknesses of the heat preservation blankets laid on the outer surfaces of the heat treatment objects are consistent, when a plurality of layers of heat preservation blankets need to be laid, the heat preservation blankets are tensioned and pressed to each layer, gaps between two adjacent layers of heat preservation blankets are eliminated, and the heat preservation blankets are bound and fixed by glass fiber tapes after the laying is finished;
for the inner surface of the heat treatment object, the heat preservation blanket can be paved by adopting the same method as the outer surface;
step 6, selecting and laying induction cables
Selecting an air-cooled high-temperature-resistant alloy cable or a water-cooled heating cable as an induction cable;
determining the number of turns and the turn-to-turn distance of the induction cable according to the self characteristics of a heat treatment object and the heat treatment process requirement and in combination with the preset induction heating width;
the induction cables are symmetrically wound on the outer surface of the heat treatment object by taking the central line of the welding seam as a center, the induction cables are unevenly arranged, the induction cables close to the center of the welding seam are sparsely arranged, the induction cables far away from the center of the welding seam are densely arranged, the induction cables are fixed at the winding starting position and the winding ending position, the rest wires are twisted and led out in a double-stranded mode, the rest wires are overhead or wired from the cement ground by adopting glass fibers, refractory bricks or austenitic stainless steel, and are far away from the steel wall surface or the magnetic conductivity structural part;
step 7, selecting an induction power supply
Determining the power of an induction power supply according to thermal calculation, wherein the induction power supply has a working frequency quick automatic tracking function, an output loop leakage detection function, an abnormal state acousto-optic alarm function, a temperature difference protection function and a current attenuation demagnetization function;
step 8, induction heating temperature control
Heating a heat treatment object by utilizing a hysteresis heat effect and an eddy heat effect of induction heating, realizing the uniformity of the temperature of the heat treatment object through heat conduction, setting an induction power supply operation mode into a constant power operation mode or a process operation mode, and presetting a heating curve, a heat preservation curve and a cooling control curve;
the induction heating temperature rise process is as follows: setting the heating rate of a heat treatment object according to a preset target temperature, comparing the set heating rate with the temperature of the heat treatment object measured by a thermocouple by using an induction power supply, adjusting the output power of the induction power supply by using PID (proportion integration differentiation) regulation control equipment in an induction power supply control system, enabling the output power of the induction power supply to meet the requirement of the heating rate of the heat treatment object, and heating the heat treatment object according to the set heating rate;
the induction heating and cooling process comprises the following steps: setting a cooling rate of a heat treatment object according to a preset target temperature, comparing the set cooling rate with the temperature of the heat treatment object measured by a thermocouple by using an induction power supply, adjusting the output power of the induction power supply by using PID (proportion integration differentiation) regulation control equipment in an induction power supply control system, enabling the output power of the induction power supply to meet the requirement of the cooling rate of the heat treatment object, and cooling the heat treatment object according to the set cooling rate;
step 9, implementing main and auxiliary induction heating
According to the heat treatment process of the main heating area and the auxiliary heating area, the connecting wires are detected, the induction cable is connected with the induction power supply, the induction power supply is started, the operation mode of the induction power supply is set, the output power or the temperature curve is input into the induction cable control system, and the main induction heating and auxiliary induction heating local heat treatment is carried out.
2. The main and auxiliary induction heating local heat treatment method as claimed in claim 1, wherein in step 1, when the thickness of the weld joint of the heat treatment object is not more than 50mm, the width of the main heating zone is determined according to GB/T30583 post-weld heat treatment regulation of pressure-bearing equipment, and when the thickness of the weld joint of the heat treatment object is more than 50mm, the width of the main heating zone is determined according to the temperature uniformity requirement of the weld joint through process evaluation.
3. The main and auxiliary induction heating local heat treatment method according to claim 1, wherein in the step 2, the distance from the center of the auxiliary heating zone to the center of the main heating zone is determined according to the thickness of the base material to be heat treated, the thermal expansion coefficient and the correction coefficient;
determining the width of the auxiliary heating zone according to GB/T30583 post-welding heat treatment regulation of pressure-bearing equipment;
determining the highest heat preservation temperature of the auxiliary heating area according to the requirement of a heat treatment object on residual stress elimination in the service process, if the heat treatment object has strict requirement on residual stress elimination, setting the highest heat preservation temperature of the auxiliary heating area to be 40-60% of the heat preservation temperature of the main heating area, and if the heat treatment object has no strict requirement on residual stress elimination, setting the highest heat preservation temperature of the auxiliary heating area to be any temperature within 200-300 ℃;
and determining the heat preservation time of the auxiliary heating area according to the self characteristics of the heat treatment object and the service environment.
4. The method of claim 1, wherein in step 4, the thermocouple is a type K thermocouple, and can be used as both a temperature control thermocouple and a monitoring thermocouple.
5. The main and auxiliary induction heating local heat treatment method according to claim 1, wherein in step 5, when the main heating zone holding temperature is 500 ℃, the thickness of the heat preservation blanket is not less than 50mm, and when the main heating zone holding temperature is 700 ℃, the thickness of the heat preservation blanket is not less than 70 mm.
6. The main and auxiliary induction heating local heat treatment method according to claim 1, wherein in step 6, an induction cable can be replaced by two sets of induction cable tools, the laying distance between the two sets of induction cable tools is determined according to the width of the main heating zone, the induction cable tools are arranged in an open-close type, the induction cable tools are symmetrically laid on the outer surface of a heat treatment object by taking a welding seam as a center, the heat treatment of the main heating zone is performed, after the heat treatment of the main heating zone is completed, the laying distance between the two sets of induction cable tools is determined according to the distance between the center position of the auxiliary heating zone and the center of the main heating zone, and the induction cable tools are moved outwards to the center position of the distance between the center of the main heating zone and the center of the auxiliary heating zone by taking the welding seam as a center.
7. The main and auxiliary induction heating local heat treatment method as claimed in claim 1, wherein in the step 6, if the heat treatment object is a cylinder, more than three mica or ceramic bars are uniformly arranged on the outer wall of the cylinder at the position corresponding to twelve o ' clock to raise the induction cables by 10-20mm, or the induction cables are sparsely arranged on the outer wall of the cylinder at the position corresponding to twelve o ' clock and densely arranged on the outer wall of the cylinder at the position corresponding to six o ' clock.
8. The main and auxiliary induction heating local heat treatment method according to claim 1, wherein in step 7, the fast automatic tracking function of the operating frequency can fast track the resonant frequency when the induction heater is replaced, the number of turns of the induction coil is changed, or the load is loaded, without adjusting the resonant frequency of the induction power supply, so as to ensure that the operating frequency of the induction power supply is always the optimal operating frequency;
the output loop leakage detection function sets an alarm value of an insulation resistor by embedding the output loop insulation resistor in the induction power supply, and if the resistance value of the insulation resistor is lower than the alarm value, the induction power supply is immediately cut off, so that the safety of the induction power supply is protected;
the abnormal state acousto-optic alarm function is used for carrying out acousto-optic alarm on the abnormal state of the induction power supply and displaying alarm information;
the temperature difference protection function is used for controlling the temperature difference between the inner surface and the outer surface of the heat treatment object, the induction power supply automatically reduces the output power when the temperature difference between the inner surface and the outer surface of the heat treatment object exceeds a limited range in the induction heating process, and the induction power supply automatically switches from uniform temperature power to heating power when the temperature difference between the inner surface and the outer surface of the heat treatment object is smaller than the limited range, so that the temperature difference between the inner surface and the outer surface of the heat treatment object in the induction heating process is ensured to be within;
the current-decaying demagnetization function is used to avoid leaving remanence on the heat-treated object.
9. The method as claimed in claim 8, wherein the induction power supply is a medium frequency induction heating power supply.
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| CN114182088A (en) * | 2021-12-08 | 2022-03-15 | 中国石油大学(华东) | Local heat treatment method for reducing stress corrosion cracking risk of welded joint of heat exchange tube and tube plate of shell-and-tube heat exchanger |
| CN114457232A (en) * | 2021-12-24 | 2022-05-10 | 燕山大学 | Heat treatment system and heat treatment method for heterogeneous welding strip |
| CN114760728A (en) * | 2022-04-13 | 2022-07-15 | 中国石油大学(华东) | Induction heating temperature-equalizing cable winding method |
| CN116219125A (en) * | 2023-02-09 | 2023-06-06 | 徐州尚航船舶配件有限公司 | Composite metal material heat treatment equipment |
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