CN111411213B - Simultaneous electric induction heat treatment process for inner and outer walls of butt weld of plug valve - Google Patents
Simultaneous electric induction heat treatment process for inner and outer walls of butt weld of plug valve Download PDFInfo
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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
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- C—CHEMISTRY; METALLURGY
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- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/22—Martempering
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- C—CHEMISTRY; METALLURGY
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- 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
A simultaneous electric induction heat treatment process for the inner and outer walls of a butt weld of a plugging valve is characterized in that a valve body and a steel pipe of the plugging valve are forged from high-alloy heat-resistant steel, and the inner and outer walls are simultaneously heated by electric induction; adopting a medium-frequency induction heat treatment construction process for the connecting welding seam of the P92 steel pipe and the F92 valve body, wherein the inner wall and the outer wall have different heating temperatures; the outer wall adopts electric induction heating for the valve body, and adopts a medium-frequency electric induction heating method for the connecting welding seam of the steel pipe and the forging. The invention ensures the heat permeability and the weld quality of the weld in the heat treatment process, effectively improves the heat treatment quality and avoids the overtemperature at the welding joint.
Description
Technical Field
The invention relates to a heat treatment process for a plugging valve.
Background
When each ultra-supercritical high-temperature high-pressure coal-fired thermal power plant is installed, two blocking valves special for the hydraulic pressure test are installed for the convenience of the control of the hydraulic pressure test, and are generally provided by special valve manufacturers. This block valve is activated only during the hydrostatic test, as a gate valve that withstands a test pressure of about 10 Map. After the hydrostatic test is qualified, the valve core is lifted out of the valve, so that the blocking valve is in a normally open state and is used as a part of a high-temperature reheating section steam pipeline. Forging the overall dimension of the plug valve: the length, width and height are respectively: 1200 × 1000 × 900mm, valve weight: about 5000 Kg. The sizes of the pipe orifices at the two ends of the valve are as follows: phi 836 x 55 mm; the valve body is an irregular forged cuboid, and the thickest part of the valve body is 110 mm; the thickness of the transition section is as follows: 95 mm; whereas the thickness to the nozzle is only 55mm, this specification is exactly the same as the size of the reheat section and: Φ 836X 55 mm.
The reheat steam hydrostatic test block valve is made of SA355-F92 steel and has the specification of phi 836 multiplied by 55mm, and the shape and the thickness of two sides of a welding opening are greatly different because the actual situation on site is not considered when a manufacturer supplies materials.
The valve manufacturer does not consider that the distance between the groove and the valve body is only 50mm, and the construction of heat treatment after welding is difficult.
Following the heat treatment protocol: the heating width at the time of heat treatment cannot satisfy the requirement. The transition section near the valve side is extremely short, the difference between each side of the thickness of the valve and a welded junction is close to 25mm, great technical difficulty is brought to field heat treatment work, the welded joint is easily over-heated, and the temperature of a welded joint near the valve side is too low, so that the tempering is insufficient. The structural shape is difficult to ensure the heat treatment quality after welding, and improper heat treatment heating can cause the hardness of a welding joint at the position to exceed the standard, thereby influencing the safe operation of a high-temperature high-pressure reheating section of a power plant.
The material of the stop valve is forged F92 steel, and because of the forging structure, the reduction of the valve body is large, and large welding residual stress exists during welding, and F92 steel contains about 2% of alloy element W and is very sensitive to the heat treatment temperature after welding. The temperature of the postweld heat treatment is 750-770 ℃, and the temperature range is narrow.
Disclosure of Invention
In order to overcome the defects that the overtemperature and poor heat treatment quality at the welding joint are easily caused by insufficient tempering of the existing heat treatment process of the plugging valve, the invention provides the electric induction heat treatment process for the inner and outer walls of the butt welding line of the plugging valve, which effectively improves the heat treatment quality and avoids the overtemperature at the welding joint.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a simultaneous electric induction heat treatment process for the inner and outer walls of a butt weld of a plugging valve comprises the following steps:
1) selecting three different temperature control areas, and respectively controlling the temperature; two different electrical heating methods were used:
the connecting weld joint of the F92 valve body and the P92 steel pipe is a main control object of heat treatment, and an intelligent medium-frequency induction heat treatment machine is adopted for heating, keeping constant temperature and cooling in the whole process; different heating temperatures are adopted for the inner wall and the outer wall; the temperature of the valve body is increased by adopting high-power electric induction auxiliary heating for the valve body; auxiliary electric heating is carried out in the valve body according to the structural characteristics;
2) before opening, hardness detection is carried out on the steel pipe at two sides of the welding seam and the valve body, MT inspection is carried out on the opening and the pipe opening of the valve body, and the hardness of the valve body of the plugging valve is determined to be in a qualified range; the valve body opening and the pipe opening have no sand hole, interlayer and crack defects;
3) carrying out isothermal martensite transformation on a weld joint of the steel pipe and the valve body; the isothermal martensite transformation treatment is carried out at the following time: after the welding is completely finished; isothermal martensite transformation process: cooling to 80-100 ℃, and keeping the temperature for 1.5-2.5 hours;
4) selecting a short pipe in the pipe, arranging a heating block on the short pipe, and performing auxiliary electric heating on the inner wall of the valve body;
5) the temperature of a welding seam of the straight pipe section is a main control object of the temperature, and a medium-frequency intelligent induction electric heater is adopted for heating;
6) when the inner wall and the outer wall of the valve body are subjected to heat treatment, the temperature of the outer wall is controlled to be 720-730 ℃, and the temperature is kept for 6-7 hours; in order to prevent the over-temperature of the sealing material in the valve, the temperature of the auxiliary heating of the inner wall of the valve body is controlled at 625-635 ℃, and the temperature is kept for 6.5-7.5 h; the butt welding seam of the F92 valve body and the P92 steel pipe is a main control welding seam, an intelligent intermediate frequency electric heating process is adopted, the welding seam temperature is controlled to be 750-770 ℃, and the constant temperature is kept for 6-7 hours;
further, the width of straight tube section heat preservation is about 500mm, and the cotton thickness of heat preservation is 60mm, thickens the one deck heat preservation cotton again near the stop valve side, and the width of thickening layer is about 300mm, and thickness also is 60mm, and two-layer heat preservation cotton all must hug closely stop valve vertical edge.
In order to ensure that the hardness of the welding seam can reach a qualified range, a piece of heat insulation cotton with the width of 300mm is added at the welding seam, a layer is wrapped along the welding seam, and the highest temperature is kept at the center of the welding seam during heat treatment. The hardness and the performance of the welding seam of the special-shaped pipe fitting after welding heat treatment meet the requirements of the specification.
Still further, in the step 4), a short tube with a length of 550 and a diameter of 530 × 8mm is selected, and three heating blocks with heating powers of 10kW and 550 × 450mm are arranged on the short tube.
Furthermore, in the step 5), the length of the medium-frequency heating wire is about 28m, the number of the medium-frequency heating wire is 11, the output power is 35kW, and the frequency is 1200 Hz. The intelligent medium-frequency induction electric heating welding seam has good heat penetration, the heat penetration of the welding seam improves the comprehensive mechanical property of the joint, and the hardness index of the welding seam can be better controlled.
The technical conception of the invention is as follows: the valve body and the steel pipe of the high-alloy heat-resistant steel plug valve are forged, and the inner wall and the outer wall are simultaneously heated by electric induction; adopting a medium-frequency induction heat treatment construction process for the connecting welding seam of the P92 steel pipe and the F92 valve body, wherein the inner wall and the outer wall have different heating temperatures; the outer wall adopts electric induction heating for the valve body, and adopts a new heating method of medium-frequency electric induction for the connecting welding seam of the steel pipe and the forging, thereby ensuring the heat permeability and the welding seam quality of the welding seam in the heat treatment process.
The invention has the following beneficial effects: effectively improve the heat treatment quality and avoid the overtemperature at the welding joint.
Drawings
FIG. 1 is a schematic structural diagram of simultaneous electric induction heat treatment of inner and outer walls of a butt weld of a plugging valve, wherein 1 is a valve core, 2 is an F92 valve body, 3 is a P92 steel pipe, 4 is a thermocouple, 5 is medium-frequency electric heating, and 6 is a valve core; reference numeral 7 denotes far infrared heating and valve body auxiliary heating, and the arrow on the right side indicates the moving direction of the auxiliary heating in the pipe.
FIG. 2 is a heat treatment curve diagram of the welding seam of the F/P92 steel plug valve.
Wherein, the first stage is manual argon tungsten-arc welding at 150-200 ℃; the second stage is manual electric arc welding, and the temperature is 200-250 ℃; the third stage is martensite isothermal transformation, and the temperature is 80-100 ℃ for 2 h; the fourth stage is heating up, 113 ℃/h; the fifth stage is constant temperature, 750-770 ℃, 6 h; sixthly, cooling to 250 ℃ at 113 ℃/h; the seventh stage is cooling in still air.
Fig. 3 is a graph of the external heat treatment of the F92 valve body.
Wherein, the first stage is heating up, 113 ℃/h; the second stage is constant temperature, 720-730 ℃, and 6.5 hours; the third stage is cooling, 113 ℃/h, to 250 ℃; the fourth stage is cooling in still air.
Fig. 4 is a graph of internal supplemental heating of the valve body of F92.
Wherein, the first stage is heating up, 113 ℃/h; the second stage is constant temperature, namely 625-635 ℃ for 7 hours; the third stage is cooling, 113 ℃/h, to 250 ℃; the fourth stage is cooling in still air.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1 to 4, the simultaneous electric induction heat treatment process for the inner wall and the outer wall of the butt weld of the plugging valve comprises the following steps:
1) selecting three different temperature control areas, and respectively controlling the temperature; two different electrical heating methods were used:
the connecting welding line of the steel pipe and the valve body is a main control object of heat treatment, and an intelligent intermediate frequency induction heat treatment machine is adopted for heating, keeping constant temperature and cooling in the whole process; different heating temperatures are adopted for the inner wall and the outer wall; the temperature of the valve body is increased by adopting high-power electric induction auxiliary heating for the valve body; auxiliary electric heating is carried out in the valve body according to the structural characteristics;
2) before opening, hardness detection is carried out on the steel pipe at two sides of the welding seam and the valve body, MT inspection is carried out on the opening and the pipe opening of the valve body, and the hardness of the valve body of the plugging valve is determined to be in a qualified range; the valve body opening and the pipe opening have no sand hole, interlayer and crack defects;
3) carrying out isothermal martensite transformation on a weld joint of the steel pipe and the valve body; the isothermal martensite transformation treatment is carried out at the following time: after the welding is completely finished; isothermal martensite transformation process: cooling to 80-100 ℃, and keeping the temperature for 1.5-2.5 hours;
4) selecting a short pipe in the valve body, arranging a heating block on the short pipe, and performing auxiliary electric heating on the inner wall of the valve body;
5) the temperature of a welding seam of the straight pipe section is a main control object of the temperature, and a medium-frequency intelligent induction electric heater is adopted for heating;
6) when the inner wall and the outer wall of the valve body are subjected to heat treatment, the temperature of the outer wall is controlled to be 720-730 ℃, and the temperature is kept for 6-7 hours; in order to prevent the over-temperature of the sealing material in the valve, the temperature of the auxiliary heating of the inner wall of the valve body is controlled at 625-635 ℃, the constant temperature is 6.5-7.5 hours, the butt welding seam of the F92 valve body and the P92 steel pipe is a main control welding seam, the intelligent intermediate frequency electric heating process is adopted, the welding seam temperature is controlled at 750-770 ℃, and the constant temperature is 6-7 hours;
further, the width of straight tube section heat preservation is about 500mm, and the cotton thickness of heat preservation is 60mm, thickens the one deck heat preservation cotton again near the stop valve side, and the width of thickening layer is about 300mm, and thickness also is 60mm, and two-layer heat preservation cotton all must hug closely stop valve vertical edge.
In order to ensure that the hardness of the welding seam can reach a qualified range, a piece of heat insulation cotton with the width of 300mm is added at the welding seam, a layer is wrapped along the welding seam, and the highest temperature is kept at the center of the welding seam during heat treatment. The hardness and the performance of the welding seam of the special-shaped pipe fitting after welding heat treatment meet the requirements of the specification.
Still further, in the step 4), a short tube with a length of 550 and a diameter of 530 × 8mm is selected, and three heating blocks with heating powers of 10kW and 550 × 450mm are arranged on the short tube.
Furthermore, in the step 5), the length of the medium-frequency heating wire is about 28m, 11 turns are needed, the output power is 35kW, the frequency is 1200Hz, the heat penetration of the intelligent medium-frequency induction electric heating to the welding seam is good, the heat penetration performance of the welding seam improves the comprehensive mechanical performance of the joint, and the hardness index of the welding seam can be better controlled.
Preheating in the welding process: because the transition section of the connecting pipe of the block valve in the hydrostatic test is too short, the parent metal at two sides of the groove and the forged valve body are subjected to hardness detection before the opening is checked, and the hardness of the P92 steel pipe and the hardness of the forged F92 valve body are confirmed to meet the requirements; meanwhile, MT inspection is carried out on the valve body opening and the pipe opening, and the hardness of the F92 valve body is determined to be in a qualified range; the valve body opening and the pipe opening have no defects of sand holes, interlayers, cracks and the like. When welding is preheated, two sides of a welding seam are respectively heated by 20kW crawler-type ceramic heating blocks, and at least two thermocouples are arranged on each side for temperature control. Considering that the heat dissipation of the valve side is fast, the whole valve is wrapped by heat-preservation cotton at the valve. When the stop valve is welded, two end welding openings are welded at the same time as much as possible, if the welding openings cannot be welded at the same time, the welded welding openings are subjected to isothermal dehydrogenation, the isothermal temperature is that after the welding is finished, the welded welding openings are cooled to 80-100 ℃, the temperature is kept for 2 hours, and then the temperature is increased to 300-350 ℃ at the rate of 200 ℃ per hour, and the temperature is kept for 2 hours.
The temperature of the welding preheating; the preheating temperature of the argon arc welding bottom is 150-180 ℃, and the interlayer preheating temperature of the electric arc welding is 200-250 ℃. The interlayer temperature of the welding is not higher than 250 ℃. Welding according to a welding process card until the whole welding seam is welded, cooling to 80-100 ℃, keeping the temperature for 2 hours, and carrying out martensite transformation on the welding seam according to requirements, wherein the martensite transformation temperature is as follows: keeping the temperature at 80-100 ℃ for 2 hours.
Arrangement of thermocouple and heating block: after preheating, welding and martensite isothermal transformation are finished, immediately arranging thermocouple temperature measuring points when the temperature of a welding seam is about 100 ℃; the temperature of the welding seam of the straight pipe section is used as a main control point of the temperature, and a medium-frequency intelligent induction electric heater is adopted for heating. The length of the medium-frequency heating wire is about 28m, the number of the medium-frequency heating wire is 11, the average output power is about 35kW, the frequency is 1200Hz, and 3 thermocouples are arranged for temperature monitoring. The welding seam is a main control point of heat treatment, and the temperature is controlled to be 750-770 ℃.
The valve body adopts 1600 x 170 mm's 4 blocks of crawler-type ceramic heating blocks to carry out the auxiliary heating, and every heating block power is 10kW, and valve body auxiliary heating power totals: 40 kW. 2 thermocouples were arranged for temperature monitoring, with the temperature controlled between 720 ℃ and 730 ℃.
When the valve body is heated outside, in consideration of the difference between the wall thickness of the valve body and the wall thickness of a welding seam, a short pipe with the diameter of 530 multiplied by 8mm and the length of 550 is used in the valve body, three crawler-type ceramic heating blocks with the diameter of 550 multiplied by 450mm are arranged on the short pipe, the power of each heating block is 10kW, 3 thermocouples are arranged for temperature monitoring, and the inner wall of the valve body is subjected to auxiliary heating. Two ends of the short pipe are blocked by heat insulation cotton, then the short pipe is arranged at the center of the welding line to form a small chamber, the internal space of the valve body is heated, and the temperature of the inner wall is controlled at 625-635 ℃. In order to effectively control the temperature in the valve body, a thermocouple is arranged in each heating block for controlling the temperature. The total power of such a single valve body weld heat treatment arrangement is about 105 Kw.
The constant temperature of the welded junction heat treatment of the valve body is 765 ℃, the upper deviation and the lower deviation range are smaller, the temperature control precision of the spot welding fixed thermocouple is higher than that of the iron wire binding thermocouple, and the energy storage spot welding machine is adopted for spot welding and fixing the thermocouple during the heat treatment of the welded junction. The thermocouple is spot-welded on the edge of the welding seam, a circular flat surface with the diameter of about 5mm is ground at the position needing spot welding by a file or a polishing machine, and the distance between two poles of the thermocouple is about 5-6 mm. The discharge current of the spot welder is set between 40 and 45A. After spot welding is finished, spot welding seams should be carefully checked to prevent a cold joint phenomenon, and a thermocouple subjected to spot welding is fastened and fixed by two front and rear iron wires.
And (3) weld crater heat preservation measures during heat treatment: because the distance length of welding seam two sides differs too greatly, so can not keep warm according to the heat preservation width of rule, otherwise can cause the parent metal hardness of straight tube section to descend greatly, the width of straight tube section heat preservation is about 500mm, and the cotton thickness of heat preservation is 60mm, thickens the one deck heat preservation cotton again near the stop valve side, and the width of thickening layer is about 300mm, and thickness is 60mm also. Both layers of heat preservation cotton are required to be tightly attached to the edge of the vertical surface of the stop valve. In addition, in order to ensure that the hardness of the welding seam can not reach the qualified range, a piece of heat preservation cotton with the width of 300mm is added at the welding seam, and a layer is wrapped along the welding seam, so that the hardness of the welding seam can be controlled within the qualified range, and the hardness of the base material can be better ensured.
The technical characteristics of the medium-frequency induction heating DZWK-80 kW intelligent heat treatment machine are as follows: input voltage range: 315VAC-445VAC, input power frequency: 50-60HZ, input current: 120A, output power: 80kW, output current: 180A, coil L value: 80-100uh, temperature control precision: within + -10 ℃.
The equipment has a protection function: input overvoltage protection, input undervoltage protection, input open-phase protection, input overcurrent protection, output overcurrent protection, induction coil short-circuit protection, open-circuit protection, start short-circuit protection, lightning protection and leakage protection.
Adjusting the function of the power panel key; menu key: the menu switching of parameter mode, monitoring mode, default mode, input mode and power adjusting mode, the parameter can be changed into return key, and the confirm key: the enter power is modified and the enter power is modified, and the enter power is not modified.
Heat insulation measures are required to be made between the induction cable and the workpiece, the induction cable is prevented from being damaged by the workpiece, heat dissipation of the workpiece is effectively reduced, and heating efficiency is improved. The heat insulation cotton with the thickness of 50mm is adopted, the heating width (the winding width of the coil) is at least 3 times of the wall thickness, the heat insulation width is at least 2 times of the heating width, the high temperature resistance of the induction coil is 300 ℃, and the heat insulation is realized by adopting the aluminum silicate fiber heat insulation cotton. The outside of the induction cable is not covered with heat insulation cotton, and the outer surface of the induction cable needs to be fully contacted with air for heat dissipation.
The post-welding heat treatment of the high-temperature high-pressure stop valve adopts the following steps: the length of the medium-frequency heating wire is about 28m, the number of the medium-frequency heating wire is 11, the average output power is about 35kW, the frequency is 1200Hz, and 3 thermocouples are arranged for temperature monitoring.
In this embodiment, the heat treatment process at the weld: starting to heat at the speed of 113 ℃/h after isothermal temperature (80-100 ℃) and martensite transformation are finished, starting to keep the temperature at 765 ℃, keeping the temperature for 7 hours, then cooling to 250 ℃ at the speed of 113 ℃/h, and cooling in static air.
The key steps of different temperature control of internal and external heating in heat treatment are as follows:
1) selecting three different temperature control areas, and respectively controlling the temperature; two different heating methods were used. Wherein: the connecting weld of the steel pipe and the valve body is a main control object for heat treatment. The heating, constant temperature and cooling of the whole process by adopting an intelligent intermediate frequency induction heat treatment machine are main control points; different heating temperatures are adopted for the inner wall and the outer wall according to the technical requirements; the temperature of the valve body is increased by adopting high-power electric induction auxiliary heating for the valve body; and auxiliary electric heating is carried out in the valve body according to the structural characteristics.
2) Before opening, firstly, carrying out hardness detection on base materials of steel pipes on two sides of a welding seam and a valve body, carrying out MT (MT) inspection on an opening and an opening of the valve body, and determining that the hardness of the F92 valve body is in a qualified range; the valve body opening and the pipe opening have no defects of sand holes, interlayers, cracks and the like.
3) Carrying out isothermal martensite transformation on a weld joint of the steel pipe and the valve body; the isothermal martensite transformation treatment is carried out at the following time: after the welding is completely finished; isothermal martensite transformation process: cooling to 80-100 ℃, and keeping the temperature for 1.5-2.5 hours.
4) A short pipe with the diameter of 530 mm multiplied by 8mm and the length of 550 is selected in the valve body, three heating blocks with the heating power of 10kW respectively with the diameter of 550 mm multiplied by 450mm are arranged on the short pipe, and auxiliary electric heating of the inner wall of the valve body is carried out.
5) The temperature of a connecting welding line of the valve body and the straight pipe section is a main control point of the temperature, and a medium-frequency intelligent induction electric heater is adopted for heating. The length of the medium-frequency heating wire is about 28m, the number of the medium-frequency heating wire is 11, the output power is 35kW, and the frequency is 1200 Hz; the heat treatment temperature of the outer wall welding seam is controlled at 750-770 ℃, and the constant temperature is kept for 6 h. The intelligent medium-frequency induction electric heating welding seam has good heat penetration, the heat penetration of the welding seam improves the comprehensive mechanical property of the joint, and the hardness index of the welding seam can be better controlled.
6) When the inner wall and the outer wall of the valve body are subjected to heat treatment, the temperature of the outer wall is controlled to be 720-730 ℃, and the temperature is kept for 6.5 hours; the temperature of the inner wall of the valve body is controlled at 625-635 ℃, and is kept constant for 7 hours, so that the overtemperature of the sealing material of the valve body on the inner wall is prevented.
In order to ensure that the hardness of the welding seam can reach the qualified range, a piece of heat insulation cotton with the width of 300mm is added at the welding seam, and the highest temperature is kept at the center of the welding seam during heat treatment. The hardness and the performance of the welding seam of the special-shaped pipe fitting after welding heat treatment meet the requirements of the specification.
Claims (5)
1. The simultaneous electric induction heat treatment process for the inner wall and the outer wall of the butt weld of the plug valve is characterized by comprising the following steps of:
1) selecting three different temperature control areas, and respectively controlling the temperature; two different electrical heating methods were used:
the connecting weld joint of the F92 valve body and the P92 steel pipe is a main control object of heat treatment, and an intelligent medium-frequency induction heat treatment machine is adopted for heating, keeping constant temperature and cooling in the whole process; different heating temperatures are adopted for the inner wall and the outer wall; the temperature of the valve body is increased by adopting high-power electric induction auxiliary heating for the valve body; auxiliary electric heating is carried out in the valve body according to the structural characteristics;
2) before the F92 valve body and the P92 steel pipe are aligned, hardness detection is firstly carried out on the steel pipe at two sides of the welding seam and the valve body, MT inspection is carried out on the opening and the pipe opening of the valve body, and the hardness of the valve body of the stop valve is determined to be in a qualified range; the valve body opening and the pipe opening have no sand hole, interlayer and crack defects;
3) carrying out isothermal martensite transformation on a welded junction of the welded steel pipe and a connecting weld joint of the valve body; the isothermal martensite transformation treatment is carried out at the following time: after the welding is completely finished; isothermal martensite transformation process: cooling to 80-100 ℃, and keeping the temperature for 1.5-2.5 hours;
4) after the isothermal martensite transformation is finished and during heat treatment heating, selecting a short pipe in the pipe, arranging a heating block on the short pipe, and performing auxiliary electric heating on the inner wall of the valve body; meanwhile, the outer wall of the valve body adopts 4 crawler-type ceramic heating blocks with the size of 1600 mm multiplied by 170mm for auxiliary heating;
5) while heating by heat treatment, the temperature of a connecting weld joint of the valve body and the straight pipe section is a main control object of the temperature, and a medium-frequency intelligent induction electric heater is adopted to heat the outer wall of the weld joint;
6) when the inner wall and the outer wall of the valve body are subjected to heat treatment, controlling the temperature of the outer wall of the valve body to be 720-730 ℃ and keeping the temperature for 6-7 h; in order to prevent the over-temperature of the sealing material in the valve, the temperature of the auxiliary heating of the inner wall of the valve body is controlled at 625-635 ℃, and the temperature is kept for 6.5-7.5 h; the butt welding seam of the F92 valve body and the P92 steel pipe is a main control welding seam, an intelligent intermediate frequency electric heating process is adopted, the welding seam temperature is controlled to be 750-770 ℃, and the constant temperature is kept for 6-7 hours.
2. The simultaneous electric induction heat treatment process for the inner and outer walls of the butt weld of the stop valve according to claim 1, wherein the width of the heat-insulating layer of the straight pipe section is 500mm, the thickness of the heat-insulating cotton is 60mm, a layer of heat-insulating cotton is thickened on the side close to the stop valve, the width of the thickening layer is 300mm, the thickness of the thickening layer is 60mm, and both layers of heat-insulating cotton must be tightly attached to the edge of the vertical surface of the stop valve.
3. The simultaneous electric induction heat treatment process for the inner and outer walls of the butt weld of the plugging valve according to claim 2, wherein a piece of heat preservation cotton with the width of 300mm is added at the weld, and a layer is wrapped along the weld.
4. The simultaneous electric induction heat treatment process for the inner and outer walls of the butt weld of the plugging valve according to any one of claims 1 to 3, characterized in that in the step 4), a short tube with a length of 550 mm phi 530 x 8mm is selected, and three heating blocks with heating power of 10kW and respectively with a length of 550 x 450mm phi are arranged on the short tube.
5. The simultaneous electric induction heat treatment process for the inner and outer walls of the butt weld of the plugging valve according to any one of claims 1 to 3, wherein in the step 5), the length of the medium-frequency heating wire is 28m, the total number of the medium-frequency heating wire is 11, the output power is 35kW, and the frequency is 1200 Hz.
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| CN202010180924.XA CN111411213B (en) | 2020-03-16 | 2020-03-16 | Simultaneous electric induction heat treatment process for inner and outer walls of butt weld of plug valve |
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