WO2021232618A1 - Heating and temperature equalization method for local induction heat treatment performed on thick-walled high-pressure apparatus after welding - Google Patents

Abstract

A heating and temperature equalization method for local induction heat treatment performed on a thick-walled high-pressure apparatus after welding, comprising the following steps: step 1: spot-welding multiple temperature measurement thermocouples (1) to an inner wall and an outer wall of a circumferential weld (11) of a thick-walled high-pressure cylinder (8); step 2: respectively laying ceramic fiber thermal insulation blankets (7, 9) on an inner wall and an outer wall of the cylinder; step 3: wrapping a flexible water-cooled cable (10) around the ceramic fiber thermal insulation blanket (9) on the outer wall of the cylinder to form a heating coil, wherein an electric circuit of the flexible water-cooled cable (10) is connected to an induction heating power supply (3), and a water circuit of the flexible water-cooled cable (10) is connected to an industrial water chiller (5); and step 4: using the temperature measurement thermocouple (1) to monitor respective temperatures of the inner wall and the outer wall of the thick-walled cylinder (8), and using a maximum temperature difference T between the inner wall and the outer wall of the cylinder and a maximum temperature difference P in a circumferential direction of the outer wall to control temperature uniformity of a heating region. The method uses an induction heating process and heating characteristics thereof, thereby improving an energy utilization rate, improving the accuracy of temperature measurement, and reducing process preparation time for the local heat treatment.

Description

Heating and temperature equalization method for local induction heat treatment after welding of thick-walled pressure-bearing equipment Technical field

The invention belongs to the technical field of post-weld heat treatment of thick-wall pressure-bearing equipment, and specifically relates to a heating and temperature equalization method for local induction heat treatment of thick-wall pressure-bearing equipment after welding.

Background technique

Thick-walled pressure-bearing equipment is widely used in the chemical industry, pressure vessels, power stations, heat exchangers, oil and gas transportation, nuclear power and other industrial fields. The structure of thick-walled pressure-bearing equipment is generally cylinder or pipeline, usually short cylinder or pipeline. The manufacturing method of girth butt welding. According to different industry standards, national standards and international standards, the welded joints (circumferential weld zone) of thick-walled pressure-bearing equipment require post-weld heat treatment to dissolve the harmful phases formed in the weld and its surrounding area during the welding process. Solution heat treatment), reduce welding residual stress (stress relief heat treatment) and improve the stability of chromium in austenite (stabilization heat treatment), etc. According to the size of the pressure-bearing equipment, there are currently two methods of overall heat treatment and local heat treatment. The overall heat treatment is to put the pressure-bearing equipment into the furnace as a whole, and the heat treatment process is carried out in accordance with the heat treatment process in both the welding area and the non-welding area. Local heat treatment means that only the weld and adjacent areas are heat treated, and other parts are not heat treated. Obviously, local heat treatment is not affected by the size of the equipment, and can be carried out regardless of the size of the equipment; the equipment and labor costs used, and the energy consumed are far less than the overall heat treatment, which has very important process and cost advantages.

The post-weld local heat treatment of thick-wall pressure equipment has a high heating temperature. According to the heat treatment process requirements of different materials, the maximum heating temperature can reach 650-900°C. The heat treatment process is required to be carried out in strict accordance with the heat treatment process curve, and there are strict requirements on the temperature rise and fall speed, the holding temperature and time, the width of the welding seam uniform temperature zone, the width direction of the uniform temperature zone, the temperature difference in the circumferential direction and the temperature difference between the inner and outer walls. Among them, the welding seam uniform temperature zone refers to the welding seam and its surrounding area. The biggest difference between the local heat treatment and the overall heat treatment is that the local heat treatment requires the temperature of all parts of the uniform temperature zone to be basically the same, and the temperature distribution satisfies a certain temperature range ( Temperature difference range, such as 900±20℃). Different local heat treatment process standards have different uniform temperature and distribution requirements, but generally include the temperature distribution in the axial direction of the cylinder (transverse temperature difference), the temperature distribution in the circumferential direction of the outer wall (circumferential temperature difference), and the temperature distribution between the inner and outer walls. (Radial temperature difference) and other three indicators.

The post-weld local heat treatment of thick-walled pressure-bearing cylinders commonly used in engineering generally uses ceramic sheet resistance heating. The specific process is to first surround the heating ceramic sheet array around the butt joint of the cylinder and its adjacent area, then wrap the insulation blanket outside the ceramic sheet, and finally heat the cylinder with electricity. The preparation time of this heating process is long, and the temperature distribution in the uniform temperature zone of the weld is uneven, which cannot meet the standard requirements of the local heat treatment of the thick-walled cylinder welded joint after welding.

CN110564946A discloses a post-weld heat treatment non-cooling induction heater for a small-diameter pipe welded joint and a manufacturing method thereof. The patent mainly proposes an induction heater for the post-weld heat treatment of the welded joints of small diameter pipes and its manufacturing process, but does not propose a post-weld local induction heating heat treatment method and a uniform temperature process for the welded joints of thick-walled pressure equipment.

CN107598332A discloses a new type of CB2 heat-resistant steel medium and large diameter pipeline welding and heat treatment process. The heat treatment process is to use flexible ceramic heaters (ceramic sheet resistance heaters) on the outer wall of the pipeline, and use built-in argon-filled heating and heat preservation integrated tooling to heat the inside of the pipeline. Since the heat transfer of the gas flow in the axial direction of the pipeline is eliminated, this process mode can improve the circumferential temperature difference and the radial temperature difference to a certain extent. However, due to the convection of gas in the closed cavity inside the pipe, the temperature of the inner wall of the pipe cross section at 6 o'clock is the lowest, and the temperature at 12 o'clock is the highest. The result of this process is that there is still a large temperature difference in the circumferential direction of the pipeline, and the temperature uniformity in the circumferential direction of the pipeline cannot meet the process requirements. Moreover, the inner wall of the pipeline is not insulated, and the radial temperature difference is very large. In addition, in this process method, the flexible ceramic heater is an external heat source compared to the pipeline, relying on the heat conduction between the flexible ceramic heater and the pipeline (when the two are in contact with each other) or heat radiation (when the two are not in contact with each other). Time) heat conduction and low energy utilization rate. Since the temperature measuring thermocouple is arranged on the outer surface of the pipe and is in contact with the flexible ceramic heating plate and the pipe at the same time, it is impossible to determine whether the measured temperature is the temperature of the ceramic heating plate or the pipe temperature, and the accuracy of temperature measurement is poor.

CN110592362A discloses a post-weld heat treatment method for 304L welded parts of liquid nitrogen storage tanks, which is mainly used to eliminate residual stress on welded parts of 304L material of liquid nitrogen storage tanks. The heat treatment method is divided into two steps: firstly heat the welded parts to 570°C, the heating rate is 55-220°C/h, and the holding time is at least to ensure uniform heat penetration of the welded parts; secondly, the temperature is reduced at 55-280°C/h, when the furnace temperature After the temperature is lower than 400°C, the welded parts are taken out of the furnace and cooled in still air. The invention only proposes the temperature-time process curve of the post-weld stress relief heat treatment, but does not clarify the heat treatment heating method used and how to ensure the uniform temperature process of heat penetration inside and outside the storage tank.

In summary, the post-weld local heat treatment of welded joints of thick-walled pressure equipment urgently requires a heat treatment technology with convenient process, precise temperature control, and uniform temperature distribution in the heating zone to ensure the mechanical and mechanical properties of thick-walled pressure equipment after welding. Chemical properties.

Summary of the invention

In order to overcome the shortcomings of the prior art, the present invention provides a heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding. The technical scheme of the present invention is:

A heating and temperature equalization method for local induction heat treatment of thick-wall pressure-bearing equipment after welding, including the following steps:

(1) Spot weld several thermocouples on the inner and outer walls of the girth weld of the thick-walled pressure-bearing cylinder placed horizontally. The thermocouple wire is drawn along the wall of the thick-walled pressure-bearing cylinder and connected to induction heating through the thermocouple extension wire power supply;

(2) Laying ceramic fiber insulation blankets on the inner and outer walls of the thick-walled pressure-bearing cylinder;

(3) Wrap a flexible water-cooled cable outside the ceramic fiber insulation blanket on the outer wall to form an induction heating coil. The circuit of the flexible water-cooled cable is connected to the induction heating power supply, and the water circuit is connected to the industrial chiller;

(4) The induction heating power supply outputs medium and high frequency alternating current to the flexible water-cooled cable to heat the thick-walled cylinder;

(5) The temperature of the inner and outer walls of the thick-walled cylinder is monitored by a temperature measuring thermocouple, and the allowable temperature difference between the inner and outer walls of the thick-walled cylinder during the heating, heat preservation and cooling process is set to T, and the circumferential direction of the outer wall of the thick-walled cylinder The allowable temperature difference is P; when the actual temperature difference between the inner and outer walls of the thick-walled cylinder exceeds T or the actual circumferential temperature difference between the outer wall of the thick-walled cylinder exceeds P, the output power of the induction heating power supply is reduced; when the actual temperature between the inner and outer walls of the thick-wall cylinder When the temperature difference does not exceed T and the actual circumferential temperature difference of the outer wall of the thick-walled cylinder does not exceed P, the induction heating power supply continues to output power to heat the thick-walled cylinder; this is repeated until the entire post-weld heat treatment process is completed.

The thick-walled pressure-bearing cylinder is a horizontal cylinder or pipe with an outer diameter greater than or equal to 300 mm and a wall thickness greater than or equal to 24 mm.

The arrangement of spot welding thermocouples on the inner and outer walls of the thick-walled cylinder is as follows: at least two thermocouples are arranged on the inner wall of the thick-walled cylinder and at least three are arranged on the outer wall of the thick-wall cylinder; A thermocouple is arranged at the highest point and lowest point of the inner wall and outer wall of the cross section respectively; the temperature measuring thermocouple is a cheap metal thermocouple; the thermocouple is fixed on the inner and outer walls of the thick-walled cylinder by spot welding; The thermocouple wire drawn along the wall of the thick-walled pressure-bearing cylinder means that the thermocouple wire is drawn from the cylinder wall parallel to the axial direction of the thick-walled pressure-bearing cylinder.

The ceramic fiber insulation blanket is a sandwich structure ceramic fiber insulation blanket with a thickness of at least 50 mm. The inner and outer layers of the sandwich structure ceramic fiber insulation blanket are glass fiber cloth, and the middle layer is ceramic fiber cotton.

The laying of ceramic fiber insulation blankets on the inner and outer walls of the thick-walled pressure-bearing cylinder means that ceramic fiber insulation blankets are placed on the inner and outer walls of the pressure-bearing cylinder, and the ceramic fiber insulation blanket is symmetrical with the centerline of the weld bead. Lay symmetrically; the length of the cylinder covered by the ceramic fiber insulation blanket on the outer wall of the thick-walled cylinder is at least 10 times the thickness of the cylinder, and the length of the cylinder covered by the ceramic fiber insulation blanket on the inner wall of the thick-walled cylinder is the thickness of the cylinder. At least 10 times.

The nominal cross-sectional area of the flexible water-cooled cable is not less than 50 mm ² , and the cross-sectional area of the cooling water pipe is not less than 20 mm ² .

The flexible water-cooled heating cable is symmetrically wound on both sides of the center line of the circumferential weld of the thick-walled cylinder, and the flexible water-cooled heating cable at the center line of the circumferential weld is sparsely arranged, and the flexible water-cooled heating cable away from the center of the weld bead is densely arranged; In the axial direction of the thick-walled pressure-bearing cylinder, the heating width of the flexible water-cooled cable winding is not less than 6 times the thickness of the thick-walled cylinder.

In the process of heating, holding and cooling, the allowable temperature difference between the inner and outer walls of the thick-walled cylinder is T, which refers to the highest temperature measured by all thermocouples on the outer wall of the thick-walled cylinder and that measured by all the thermocouples on the inner wall of the thick-walled cylinder. The difference between the lowest temperatures.

The allowable temperature difference P in the circumferential direction of the outer wall of the thick-walled cylinder refers to the difference between the highest temperature and the lowest temperature measured by all thermocouples on the outer wall of the thick-walled cylinder.

The T value does not exceed 40°C, and the P value does not exceed 20°C.

The invention has the advantages that the method utilizes the induction heating process and its heating characteristics to increase the energy utilization rate, improve the temperature measurement accuracy, and reduce the process preparation time of the local heat treatment. The use of thermocouples in different positions for temperature measurement, insulation of the inner and outer walls of the cylinder, and special winding methods of water-cooled flexible cables have improved the uniformity of temperature distribution in the local heat treatment uniform temperature zone. It solves the shortcomings of long preparation time for local heat treatment heating process after ceramic resistance welding, low energy utilization, and substandard temperature distribution in the uniform temperature zone.

Description of the drawings

Fig. 1 is a schematic diagram of the structure adopted by the heating and temperature equalization method of the local induction heat treatment of the present invention.

Fig. 2 is a schematic diagram of the arrangement of flexible water-cooled cables of the present invention.

Figure 3 is a schematic diagram of the thermocouple arrangement on the outer wall of the cylinder of the present invention.

Among them, 1- Thermocouple for temperature measurement; 2- Thermocouple extension cord; 3- Induction heating power supply; 4- Extension cable; 5- Industrial chiller; 6-Water pipe; 7- Inner wall insulation blanket; 8- Thick-walled cylinder; 9-Outer wall insulation blanket; 10-Flexible water-cooled cable; 11-Girth weld.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, these embodiments are only exemplary, and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solution of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements fall within the protection scope of the present invention.

Example 1: The present invention provides a heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding, which is used for an evaporator cylinder with an outer diameter of 1450mm, wall thickness of 142mm, and SA508-3 material after welding, up to 610± The stress relief heat treatment at 15°C includes the following steps:

(1) Spot welding multiple thermocouples 1 on the inner and outer walls of the cylinder girth weld 11; the thick-walled cylinder 8 is a pressure-bearing cylinder with an outer diameter of 1450mm and a wall thickness of 142mm;

(2) Lay 50mm thick ceramic fiber insulation blankets on the inner and outer walls of the thick-walled cylinder 8, which are the inner wall insulation blanket 7 and the outer wall insulation blanket 9 respectively;

(3) Wrap a flexible water-cooled cable 10 on the outer wall insulation blanket 9 on the outer wall of the thick-walled cylinder 8 to form an induction heating coil. Industrial chiller 5;

(4) The induction heating power supply 3 outputs medium and high frequency alternating current to the flexible water-cooled cable to heat the thick-walled cylinder 8; the temperature of the inner and outer walls of the thick-walled cylinder is monitored by the temperature measuring thermocouple 1, which is set during the heating and cooling process The allowable temperature difference between the inner wall and the outer wall of the medium-thick wall cylinder 8 is T, and the allowable temperature difference between the outer wall of the thick-wall cylinder 8 is P, where the value of T is 30°C and the value of P is 20°C.

(5) When the actual temperature difference between the inner wall and the outer wall of the thick-walled cylinder 8 exceeds T or the actual circumferential temperature difference between the outer wall of the thick-walled cylinder 8 exceeds P, the output power of the induction heating power supply 3 is reduced; When the actual temperature difference does not exceed T and the actual circumferential temperature difference of the outer wall of the thick-walled cylindrical body 8 does not exceed P, the induction heating power supply 3 continues to output power to heat the cylindrical body 8. This is repeated until the entire post-weld heat treatment process is completed.

As shown in Figure 3, the arrangement of the multiple temperature measuring thermocouples 1 is: 4 pieces are arranged on the inner wall of the thick-walled cylinder, and 7 pieces are arranged on the outer wall of the cylinder (respectively 1# temperature measuring thermocouple, 2# temperature measuring thermoelectric Couple, 3# temperature measuring thermocouple, 4# temperature measuring thermocouple, 5# temperature measuring thermocouple, 6# temperature measuring thermocouple, 12# temperature measuring thermocouple); among them, there are 8 ring welds 11 in the thick-walled cylinder A temperature measuring thermocouple 1 (12# temperature measuring thermocouple and 6# temperature measuring thermocouple respectively) is arranged at the highest point and the lowest point of the cross section; the temperature measuring thermocouple 1 is a cheap metal thermocouple; The temperature measuring thermocouple 1 is fixed on the inner wall and the outer wall of the thick-walled cylinder 8 by spot welding; the temperature measuring thermocouple 1 is connected to the induction heating power supply 3 through the thermocouple extension cord 2.

The ceramic fiber insulation blanket (inner wall insulation blanket 7 and outer wall insulation blanket 9) is a sandwich structure ceramic fiber insulation blanket with a thickness of 50 mm. The inner and outer layers of the sandwich structure ceramic fiber insulation blanket are glass fiber cloth, and the middle layer is ceramic Fiber cotton.

The inner wall insulation blanket 7 and the outer wall insulation blanket 9 are laid symmetrically with the centerline of the weld bead (circular weld 11) as the symmetric center; the length of the cylinder covered by the ceramic fiber insulation blanket 9 on the outer wall of the thick-walled cylinder 8 is The length of the cylinder covered by the ceramic fiber insulation blanket 7 on the inner wall of the thick-walled cylinder is 1.6 m; the nominal cross-sectional area of the flexible water-cooled cable 10 is 70 mm ² , and the cross-sectional area of the cooling water pipe is 40 mm ² .

As shown in Figure 2, the flexible water-cooled heating cable 10 is symmetrically arranged on both sides of the center line of the thick-walled cylinder girth weld 11, and the flexible water-cooled heating cable 10 is sparsely arranged with 2 turns at the center line of the girth weld 11. The flexible water-cooled heating cable 10 far from the center of the weld bead is densely arranged with 9 turns.

In the axial direction of the thick-walled cylinder 8, the heating width of the flexible water-cooled cable 10 is 900 mm.

Wherein, the allowable temperature difference T between the inner and outer walls of the thick-walled cylinder 8 refers to the maximum temperature measured by all thermocouples on the outer wall of the thick-walled cylinder 8 and the lowest temperature measured by all the thermocouples on the inner wall of the thick-walled cylinder 8 The difference.

The peripheral allowable temperature difference value P of the outer wall of the thick-walled cylinder 8 refers to the difference between the highest temperature and the lowest temperature measured by all the thermocouples on the outer wall of the thick-walled cylinder 8.

After heating for 20 hours and 30 minutes, the temperature distribution in the uniform temperature zone is shown in Table 1. Table 1 shows the temperature distribution in the uniform temperature zone in the last 4 hours of heat treatment (unit: ℃)

Table 1

Example 2: The present invention provides a heating and temperature equalization method for local induction heat treatment of thick-wall pressure-bearing equipment after welding, which is used for a petrochemical pipeline with an outer diameter of 500mm, a wall thickness of 50mm, and a TP347 material to stabilize the maximum 880±20℃ after welding. Chemical heat treatment, including the following steps:

(1) Spot welding multiple thermocouples 1 on the inner and outer walls of the cylinder girth weld 11; the thick-walled cylinder 8 is a cylinder with an outer diameter of 500mm and a wall thickness of 50mm;

(2) On the inner wall and outer wall of the thick-walled cylinder 8, 50 and 70mm thick ceramic fiber insulation blankets are respectively laid, which are the inner wall insulation blanket 7 and the outer wall insulation blanket 9 respectively;

(3) Wrap a flexible water-cooled cable 10 on the outer wall insulation blanket 9 on the outer wall of the thick-walled cylinder 8 to form an induction heating coil. Industrial chiller 5;

(4) The induction heating power supply 3 outputs medium and high frequency alternating current to the flexible water-cooled cable to heat the thick-walled cylinder 8; the temperature of the inner and outer walls of the thick-walled cylinder is monitored by the temperature measuring thermocouple 1, which is set during the heating and cooling process The allowable temperature difference between the inner wall and the outer wall of the medium-thick wall cylinder 8 is T, and the allowable temperature difference between the outer wall of the thick-wall cylinder 8 is P. Wherein, the T value is 40°C, and the P value is 20°C.

(5) When the actual temperature difference between the inner wall and the outer wall of the thick-walled cylinder 8 exceeds T or the actual circumferential temperature difference between the outer wall of the thick-walled cylinder 8 exceeds P, the output power of the induction heating power supply 3 is reduced; When the actual temperature difference does not exceed T and the actual circumferential temperature difference of the outer wall of the thick-walled cylindrical body 8 does not exceed P, the induction heating power supply 3 continues to output power to heat the cylindrical body 8. This is repeated until the entire post-weld heat treatment process is completed.

As shown in Figure 3, the arrangement of the multiple temperature measuring thermocouples 1 is: 4 pieces are arranged on the inner wall of the thick-walled cylinder, and 7 pieces are arranged on the outer wall of the cylinder (respectively 1# temperature measuring thermocouple, 2# temperature measuring thermoelectric Couple, 3# temperature measuring thermocouple, 4# temperature measuring thermocouple, 5# temperature measuring thermocouple, 6# temperature measuring thermocouple, 12# temperature measuring thermocouple); among them, there are 8 ring welds 11 in the thick-walled cylinder A thermocouple 1 (12# temperature measuring thermocouple and 6# temperature measuring thermocouple respectively) is arranged at the highest point and the lowest point of the cross section; said thermocouple 1 is a cheap metal thermocouple; temperature measuring thermocouple 1 is fixed on the inner wall and outer wall of the thick-walled cylinder 8 by spot welding; the temperature measuring thermocouple 1 is connected to the induction heating power supply 3 through the thermocouple extension cord 2.

The ceramic fiber insulation blanket (inner wall insulation blanket 7 and outer wall insulation blanket 9) is a sandwich structure ceramic fiber insulation blanket with a thickness of 50 and 70 mm. The inner and outer layers of the sandwich structure ceramic fiber insulation blanket are glass fiber cloth, and the middle layer It is ceramic fiber cotton.

The ceramic fiber insulation blankets 7 and 9 are laid symmetrically with the centerline of the weld bead (circumferential weld 11) as the symmetric center; the length of the cylinder covered by the ceramic fiber insulation blanket 9 on the outer wall of the thick-walled cylinder 8 is 6m, The length of the cylinder covered by the ceramic fiber insulation blanket 7 on the inner wall of the thick-walled cylinder is 2 m; the nominal cross-sectional area of the flexible water-cooled cable 10 is 50 mm ² , and the cross-sectional area of the cooling water pipe is 20 mm ² .

As shown in Fig. 2, the flexible water-cooled heating cable 10 is arranged symmetrically on both sides of the center line of the thick-walled cylindrical body girth weld 11. At the center line of the girth weld 11, the flexible water-cooled heating cable 10 is sparsely arranged with 6 turns. The flexible water-cooled heating cables 10 away from the center of the weld bead are densely arranged with 10 turns each. In the axial direction of the thick-walled cylinder 8, the heating width of the flexible water-cooled cable 10 is 600 mm.

Wherein, the allowable temperature difference T between the inner and outer walls of the thick-walled cylinder 8 refers to the maximum temperature measured by all thermocouples on the outer wall of the thick-walled cylinder 8 and the lowest temperature measured by all the thermocouples on the inner wall of the thick-walled cylinder 8 The difference.

The peripheral allowable temperature difference value P of the outer wall of the thick-walled cylinder 8 refers to the difference between the highest temperature and the lowest temperature measured by all the thermocouples on the outer wall of the thick-walled cylinder 8.

After 20 hours and 30 minutes of heating, the temperature distribution in the uniform temperature zone is shown in Table 2. Table 2 The temperature distribution in the uniform temperature zone throughout the heat treatment process (unit: °C).

Heating time/Min		Outer wall 12#		Outer wall 3#		Outer wall 6#		Inner wall 12#		Inner wall 3#		Inner wall 6#		Outer wall 5#
0	14	14	11	11	12	11	14
15	53	54	44	45	47	45	51
35	111	110	95	96	101	96	114

55	180	175	159	160	160	159	175
75	236	231	220	215	222	214	239
95	308	302	288	286	294	285	305
115	334	325	318	316	322	313	342
135	365	357	351	349	355	346	377
155	394	393	402	379	385	376	401
175	443	437	439	406	412	404	440
195	477	477	479	440	444	436	476
205	505	505	507	469	474	466	511
225	543	533	534	510	514	496	534
245	550	557	555	536	541	533	553
265	566	562	565	561	565	557	568
285	585	589	586	571	575	567	581
305	606	597	593	600	605	596	603
325	635	625	628	629	633	624	630
345	671	664	664	662	666	657	666
365	705	691	692	691	693	684	706
385	725	717	711	714	713	705	718
405	743	736	730	736	732	723	740
425	755	746	744	749	743	733	750
445	765	756	754	761	754	746	752
465	768	759	758	765	755	748	766
485	835	825	821	820	820	812	835
505	872	861	855	855	853	848	875
535	886	877	871	870	868	863	889

Table 2

It can be seen from Table 2 that the temperature rise trend of the outer wall and inner wall uniform temperature zone during the heating and temperature rise stage is the same. When the temperature is below 300°C, it is about 180°C/h, and when it is above 400°C, it is about 78°C/h. The temperature rise control. In the heat preservation stage, the maximum lateral temperature difference in the uniform temperature zone is 18°C, which is less than the set value of 20°C; the radial temperature difference is maximum 26°C, which is less than the set value of 40°C. The uniform temperature zone of the circumferential weld meets the technical requirements of temperature distribution.

From the above description, it can be seen that the above-mentioned examples implemented in this aspect achieve the following technical effects:

(1) The present invention realizes the heating and temperature equalization process of the local induction heat treatment of the thick-walled pressure-bearing equipment after welding, reduces the process preparation time, reduces the heat treatment cost, and reasonably controls the allowable temperature difference parameters in the circumferential and radial directions of the cylinder , The maximum temperature difference obtained meets the requirements of the heat treatment process, ensuring the process quality of the post-weld heat treatment.

(2) The present invention simultaneously spot-welds thermocouples on the inner and outer walls of the cylinder, and simultaneously lays a thermal insulation blanket, which improves the temperature measurement accuracy, improves the uniformity of the cylinder's temperature distribution in the circumferential and lateral directions, and reduces the maximum temperature difference.

(3) The present invention uses a special water-cooled flexible cable winding method and temperature control strategy to improve the uniformity of the temperature distribution of the cylinder in the radial direction, so that the temperature difference between the inner and outer walls of the cylinder meets the standard requirements or even exceeds the standard requirements. It is a ceramic chip resistor. The heating process cannot be achieved.

Industrial applicability

The method utilizes the induction heating process and its heating characteristics to increase the energy utilization rate, improve the temperature measurement accuracy, and reduce the process preparation time of the local heat treatment. The use of thermocouples in different positions for temperature measurement, insulation of the inner and outer walls of the cylinder, and special winding methods of water-cooled flexible cables have improved the uniformity of temperature distribution in the local heat treatment uniform temperature zone. It solves the shortcomings of long preparation time for local heat treatment heating process after ceramic resistance welding, low energy utilization, and substandard temperature distribution in the uniform temperature zone.

Claims (10)

1. A heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding is characterized in that it comprises the following steps:

   (1) Spot weld several thermocouples on the inner and outer walls of the girth weld of the thick-walled pressure-bearing cylinder placed horizontally. The thermocouple wire is drawn along the wall of the thick-walled pressure-bearing cylinder and connected to induction heating through the thermocouple extension wire power supply;

   (2) Laying ceramic fiber insulation blankets on the inner and outer walls of the thick-walled pressure-bearing cylinder;

   (3) Wrap a flexible water-cooled cable outside the ceramic fiber insulation blanket on the outer wall to form an induction heating coil. The circuit of the flexible water-cooled cable is connected to the induction heating power supply, and the water circuit is connected to the industrial chiller;

   (4) The induction heating power supply outputs medium and high frequency alternating current to the flexible water-cooled cable to heat the thick-walled cylinder;

   (5) The temperature of the inner and outer walls of the thick-walled cylinder is monitored by a thermocouple. The allowable temperature difference between the inner and outer walls of the thick-walled cylinder is T during the heating, heat preservation and cooling process, and the outer wall of the thick-walled cylinder is around The allowable temperature difference in the direction is P; when the actual temperature difference between the inner and outer walls of the thick-walled cylinder exceeds T or the actual circumferential temperature difference between the outer wall of the thick-walled cylinder exceeds P, the output power of the induction heating power supply is reduced; When the actual temperature difference does not exceed T and the actual circumferential temperature difference between the outer wall of the thick-walled cylinder does not exceed P, the induction heating power supply continues to output power to heat the thick-walled cylinder; repeat this process until the entire post-weld heat treatment process is completed.
2. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding according to claim 1, wherein the thick-walled pressure-bearing cylinder has an outer diameter greater than or equal to 300 mm, and a wall thickness greater than or equal to 24 mm. A cylinder or pipe placed horizontally.
3. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding according to claim 1, wherein the arrangement of the thermocouple for spot welding on the inner and outer walls of the thick-walled cylinder is: At least two are arranged on the inner wall of the thick-walled cylinder, and at least three are arranged on the outer wall of the cylinder; among them, at least one thermocouple is arranged at the highest point and the lowest point of the inner wall and the outer wall of the cross section where the girth weld of the thick-walled cylinder is located; The temperature measurement thermocouple is a cheap metal thermocouple; the thermocouple is fixed on the inner and outer walls of the thick-walled cylinder by spot welding; the thermocouple wire is drawn along the wall of the thick-walled pressure-bearing cylinder, which means that the thermocouple wire is parallel to the thick wall. The axial direction of the wall bearing cylinder is drawn from the cylinder wall.
4. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure equipment after welding according to claim 1, wherein the ceramic fiber insulation blanket is a sandwich structure ceramic fiber insulation blanket with a thickness of at least 50 mm. The inner and outer layers of the ceramic fiber insulation blanket are glass fiber cloth, and the middle layer is ceramic fiber cotton.
5. The heating and temperature equalization method for local induction heat treatment of thick-wall pressure-bearing equipment after welding according to claim 1, characterized in that, laying ceramic fiber insulation blankets on the inner and outer walls of the thick-walled pressure-bearing cylinder means that Ceramic fiber insulation blankets are placed on the inner and outer walls of the pressure-bearing cylinder. The ceramic fiber insulation blankets are laid symmetrically with the center line of the weld bead as the center of symmetry; the length of the cylinder covered by the ceramic fiber insulation blanket on the outer wall of the thick-walled cylinder is The wall thickness of the barrel is at least 10 times, and the length of the barrel covered by the ceramic fiber insulation blanket on the inner wall of the thick-walled barrel is at least 10 times the wall thickness of the barrel.
6. A heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding according to claim 1, wherein the nominal cross-sectional area of the flexible water-cooled cable is not less than 50 mm ² , and the cross-sectional area of the cooling water pipe is not less than 50 mm 2. Less than 20mm ² .
7. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure equipment after welding according to claim 1, wherein the flexible water-cooled heating cable is symmetrical on both sides of the center line of the thick-walled cylinder girth weld Winding, the flexible water-cooled heating cables at the center line of the girth weld are sparsely arranged, and the flexible water-cooled heating cables away from the center of the weld bead are densely arranged; in the axial direction of the thick-walled pressure-bearing cylinder, the heating width of the flexible water-cooled cable is not less than 6 times the wall thickness of the thick-walled cylinder.
8. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding according to claim 1, wherein the allowable temperature difference between the inner wall and the outer wall of the thick-walled cylinder during the heating, heat preservation and cooling process is T It refers to the difference between the highest temperature measured by all the thermocouples on the outer wall of the thick-walled cylinder and the lowest temperature measured by all the thermocouples on the inner wall of the thick-walled cylinder.
9. The heating and temperature equalization method for local induction heat treatment of thick-walled pressure-bearing equipment after welding according to claim 1, wherein the allowable temperature difference in the circumferential direction of the outer wall of the thick-walled cylinder is P means that the outer wall of the thick-walled cylinder The difference between the highest temperature and the lowest temperature measured by all thermocouples.
10. The heating and temperature equalization method for local induction heat treatment of thick-wall pressure-bearing equipment after welding according to claim 9, wherein the T value does not exceed 40°C, and the P value does not exceed 20°C.

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