Post-weld local heat treatment method for welding structure of large pressure vessel nozzle

Abstract

The application discloses a post-welding local heat treatment method for a large pressure-bearing container pipe welding structure, which comprises the following steps: (1) determining the size parameters of the pressure-bearing container pipe structure; (2) determining the heating band width and the holding band width required by the local heat treatment; (3) determining the number of turns of the winding cable for the local heat treatment induction heating; (4) determining the local heat treatment temperature measuring points, and arranging the temperature measuring thermocouples and the temperature control thermocouples; (5) determining the local heat treatment process, including the heat treatment temperature, the holding time and the cooling process; and (6) implementing the heat treatment and recording the heat treatment temperature curve. According to the size parameters of the pressure-bearing container, the local heat treatment process parameters such as the heating band width and the number of turns of the cable and the holding band width are determined, the temperature uniformity in the local heat treatment process of the large pressure-bearing container pipe welding structure is realized, the post-welding residual stress regulation is realized, and the service life of the large pressure-bearing container is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a post-weld local heat treatment method for a welding structure of a large pressure vessel nozzle. BACKGROUND

[0002] Large pressure vessels produce large residual stress in the welding manufacturing process, which causes cracks and other defects in the welding joint area. Post-weld heat treatment can eliminate welding residual stress, improve fracture toughness, improve stress corrosion resistance, further release harmful gases in the weld metal, especially hydrogen, and prevent the occurrence of delayed cracks. Due to the huge structure of large pressure vessels, only local heat treatment method can be used to ensure its integrity. At present, the heating methods for local post-weld heat treatment of large pressure vessels in industry mainly include ceramic resistance heating sheet heating, flame heating and induction heating. Among them, the ceramic resistance heating sheet has poor heat penetration, and the maximum wall thickness of heating is 70mm, which cannot meet the current wall thickness requirement of large pressure vessels. The car-type furnace usually uses flame heating, which has huge energy consumption and low energy utilization rate, and does not meet the national requirements for energy saving and environmental protection. At the same time, the use of car-type furnace for heat treatment on site needs to re-arrange the natural gas pipeline, which is expensive. Compared with them, induction heating is energy saving and environmental protection, has high heating efficiency and is not easy to damage, and the heating is uniform, so the method of using induction heating for post-weld local heat treatment of large pressure vessel nozzle structure has more advantages. However, there are many influencing factors of post-weld heat treatment, and the process is complex. The heating band width and the number of cable turns, the width of the holding zone and other process parameters are important control parameters of local post-weld heat treatment, which will directly affect the heat treatment effect. Improper local heat treatment not only cannot reduce the welding residual stress, but also may cause additional residual stress. SUMMARY

[0003] To solve the above technical problems, the present application provides a post-weld local heat treatment method for a welding structure of a large pressure vessel nozzle.

[0004] The technical scheme adopted by the present application is:

[0005] The present application provides a post-weld local heat treatment method for a welding structure of a large pressure vessel nozzle, comprising the steps of:

[0006] (1) determining the size parameters of the pressure vessel nozzle structure, including the pressure vessel cylinder wall thickness δ1, the nozzle wall thickness δ2, the pressure vessel cylinder outer radius r1, and the nozzle outer radius r2;

[0007] (2) determining the heating band width and the holding zone width required for local heat treatment according to the size parameters of the pressure vessel nozzle structure determined in step (1);

[0008] (3) determining the number of turns of the cable wound for local heat treatment induction heating according to the size parameters of the pressure vessel nozzle structure determined in step (1);

[0009] (4) determining local heat treatment temperature measuring points and arranging temperature measuring thermocouples and temperature controlling thermocouples;

[0010] (5) determining a local heat treatment process, including heat treatment temperature, holding time and cooling process;

[0011] (6) implementing heat treatment and recording heat treatment temperature curve.

[0012] Further, the heating bands in step (2) include main heating bands arranged on the outer wall of the cylinder and the nozzle and auxiliary heating bands, the main heating bands are arranged on the weld and around the weld, and the auxiliary heating bands are arranged on the cylinder and located on one side of the main heating bands on the cylinder;

[0013] The width of the main heating band from the center of the weld to one side of the cylinder is:

[0014] The width of the main heating band from the center of the weld to one side of the nozzle is:

[0015] The width of the auxiliary heating band is: L3=k(L1+L2), wherein k is 0.5-1.

[0016] Further, the heat preservation bands in step (2) are arranged on the outer wall of the cylinder and the nozzle, and the main heating bands and the auxiliary heating bands are arranged outside the heat preservation bands;

[0017] The width of the heat preservation band from the center of the weld to one side of the cylinder is

[0018] The width of the heat preservation band from the center line of the weld to one side of the nozzle is

[0019] The width of the heat preservation band at the auxiliary heating band is

[0020] Further, the number of turns of the cable of the main heating band from one side of the cylinder to the center of the weld N1, the number of turns of the cable of the main heating band from one side of the nozzle to the center of the weld N2 and the number of turns of the cable of the auxiliary heating band N3 in step (3) are respectively:

[0021]

[0022] wherein K is a heat loss coefficient, C1 is the specific heat capacity of the cylinder, C2 is the specific heat capacity of the nozzle, kJ / (kg·℃), T1 and T2 are the heating starting temperature and the heating ending temperature respectively, ℃; t is the heating time, h; and p is the material density, kg / m 3; R1 is the resistance of the cylinder heating section, R2 is the resistance of the connecting pipe heating section, Ω; S1 is the cross-sectional area of the cylinder, S2 is the cross-sectional area of the connecting pipe, m 2 ; μ is the resistivity.

[0023] Further, the temperature measuring thermocouples in the step (4) are arranged at 3n, and n≥2, wherein n are arranged at one side end of the cylinder where the main heating band is arranged, n are arranged at one side end of the connecting pipe where the main heating band is arranged, and n are symmetrically arranged at both ends of the auxiliary heating band.

[0024] Further, the temperature control thermocouples in the step (4) are arranged at least 2, and the temperature control thermocouples are uniformly arranged around the center of the weld.

[0025] Further, the heat treatment temperature and the holding time in the step (5) are determined according to the heat treatment standard, the main heating band and the auxiliary heating band are heated at the same time in the heat treatment temperature rising process, and the heating speed of the cylinder and the connecting pipe is the same, in the heating process, the heating temperature is not required below 400 DEG C, and the heating speed is ℃ / h and not more than 220℃ / h above 400 DEG C.

[0026] Further, the cooling process in the step (5) is that a cooling fan is arranged outside the cylinder, the cylinder and the connecting pipe are cooled at the same cooling speed, when the center of the weld is cooled to below 400 DEG C, the auxiliary heating band is removed first, then the main heating band is removed, and finally the holding band is removed, and then the air cooling is performed to room temperature.

[0027] The beneficial effects of the present application are:

[0028] The present application provides a post-weld local heat treatment method for a connecting pipe welding structure of a large pressure vessel, process parameters such as the local heat treatment heating band width and the cable turn number, and the holding band width are determined according to the size parameters of the pressure vessel, the temperature uniformity in the local heat treatment process of the connecting pipe welding structure of the large pressure vessel is realized, the post-weld residual stress regulation is realized, and the service life of the large pressure vessel is improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The schematic diagram for arranging the main heating band and the auxiliary heating band of the pressure vessel connecting pipe welding structure is shown in the figure.

[0031] Figure 2A sectional view of a pressure vessel nozzle welding structure. DETAILED DESCRIPTION

[0032] The present application provides a post-weld local heat treatment method for a large pressure vessel nozzle welding structure. To make the purpose, technical solution and effects of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0033] The present application is described in detail below with reference to the accompanying drawings.

[0034] Referring to Figure 1 and Figure 2 , the present embodiment provides a post-weld local heat treatment method for a large pressure vessel nozzle welding structure, comprising the steps of:

[0035] (1) determining the size parameters of the pressure vessel nozzle structure, including the wall thickness of the pressure vessel cylinder, the nozzle wall thickness δ2, the outer radius of the pressure vessel cylinder r1, and the outer radius of the nozzle r2;

[0036] (2) determining the heating band width and the holding band width required for local heat treatment according to the size parameters of the pressure vessel nozzle structure determined in step (1);

[0037] The heating band in step (2) includes a main heating band and a secondary heating band arranged on the outer wall of the cylinder and the nozzle, the main heating band is arranged around the weld and the weld, and the secondary heating band is arranged on the cylinder and located on one side of the main heating band on the cylinder side;

[0038] The width of the main heating band from the center of the weld to one side of the cylinder is:

[0039] The width of the main heating band from the center of the weld to one side of the nozzle is:

[0040] The width of the secondary heating band is L3=k(L1+L2), wherein k is 0.5-1;

[0041] The holding band in step (2) is arranged on the outer wall of the cylinder and the nozzle, and the main heating band and the secondary heating band are arranged outside the holding band;

[0042] The width of the holding band from the center of the weld to one side of the cylinder is

[0043] The width of the holding band from the center line of the weld to one side of the nozzle is

[0044] The width of the holding band at the secondary heating band is

[0045] The heat preservation zone adopts a refractory ceramic fiber heat preservation blanket, and the thickness of the arranged heat preservation zone is uniform; the heat preservation zone is arranged by laying multiple layers of heat preservation blankets, and the joints between each layer of heat preservation blanket are staggered, and the overlap width between adjacent two heat preservation blankets is greater than 100 mm;

[0046] (3) determining the number of turns of the cable wound for local heat treatment induction heating according to the size parameters of the pressure-bearing container nozzle structure determined in step (1);

[0047] In step (3), the number of turns of the cable of the main heating zone from the side of the cylinder to the center of the weld N1, the number of turns of the cable of the main heating zone from the side of the nozzle to the center of the weld N2, and the number of turns of the cable of the auxiliary heating zone N3 are respectively:

[0048]

[0049] wherein K is a heat loss coefficient, C1 is the specific heat capacity of the cylinder, C2 is the specific heat capacity of the nozzle, kJ / (kg·℃), T1 and T2 are the heating starting temperature and the heating ending temperature respectively, ℃; t is the heating time, h; and p is the material density, kg / m 3 ; R1 is the resistance of the heating section of the cylinder, R2 is the resistance of the heating section of the nozzle, Ω; S1 is the cross-sectional area of the cylinder, and S2 is the cross-sectional area of the nozzle, m 2 ; and p is the resistivity;

[0050] (4) determining the local heat treatment temperature measuring points, and arranging the temperature measuring thermocouples and the temperature control thermocouples;

[0051] In step (4), 12 temperature measuring thermocouples are arranged, wherein 4 are arranged at the side end of the cylinder where the main heating zone is arranged, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock; 4 are arranged at the side end of the nozzle where the main heating zone is arranged, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock; and 4 are symmetrically arranged at the two end portions of the auxiliary heating zone, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock;

[0052] In step (4), 4 temperature control thermocouples are arranged, and the 4 temperature control thermocouples are uniformly arranged around the center of the weld, i.e. arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock;

[0053] (5) determining the local heat treatment process, including the heat treatment temperature, the holding time and the cooling process;

[0054] In step (5), the heat treatment temperature and the holding time are determined according to the heat treatment standard, the main heating zone and the auxiliary heating zone are heated at the same time in the heat treatment temperature rising process, and the heating speed of the cylinder is the same as that of the nozzle; in the heating process, the heating temperature is not required below 400℃, and the heating speed is °C / h and not more than 220 °C / h.

[0055] The cooling process in step (5) is that a cooling fan is arranged outside the cylinder, the cylinder and the connecting pipe are cooled at the same cooling rate, when the weld center is cooled to below 400 °C, the auxiliary heating belt is removed first, then the main heating belt is removed, and finally the insulation belt is removed, and then cooled to room temperature in air;

[0056] (6) Implementing heat treatment, and recording the heat treatment temperature curve.

[0057] Example 1

[0058] This example is to process the girth weld of the connecting pipe structure of the large pressure vessel.

[0059] The above workpiece related parameters are as follows: the material is 15CrMoR, the wall thickness of the pressure vessel cylinder is 89 mm, the wall thickness of the connecting pipe is 72 mm, the outer radius of the pressure vessel cylinder is 1500 mm, and the outer radius of the connecting pipe is 300 mm.

[0060] The workpiece is locally heat treated according to the following steps:

[0061] (1) The determined workpiece parameters are: the wall thickness of the pressure vessel cylinder is 89 mm, the wall thickness of the connecting pipe is 72 mm, the outer radius of the pressure vessel cylinder is 1500 mm, and the outer radius of the connecting pipe is 300 mm;

[0062] (2) The determined width of the main and auxiliary heating belts: the width of the insulation belt from the weld center to one side of the cylinder is L1 = 864 mm, the width of the insulation belt from the weld center line to one side of the connecting pipe is L2 = 402 mm, and the width of the insulation belt at the auxiliary heating belt is L3 = 633 mm;

[0063] (3) The determined width of the insulation belt: the width of the insulation belt from the weld center to one side of the cylinder is L1 ′ = 1595 mm; the width of the insulation belt from the weld center line to one side of the connecting pipe is L2 ′ = 696 mm; and the width of the insulation belt at the auxiliary heating belt is L3 ′ = 1893 mm;

[0064] (4) The determined number of turns of the arranged induction heating cable: the number of turns of the cable of the main heating belt from one side of the cylinder to the weld center is N1 = 30 turns, the number of turns of the cable of the main heating belt from one side of the connecting pipe to the weld center is N2 = 25 turns, and the number of turns of the cable of the auxiliary heating belt is N3 = 27 turns;

[0065] (5) Arranging temperature measuring thermocouples and temperature control thermocouples: 12 temperature measuring thermocouples are arranged, of which, 4 are arranged at the one side end of the cylinder where the main heating band is arranged, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock; 4 are arranged at the one side end of the connecting pipe where the main heating band is arranged, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock; 4 are respectively symmetrically arranged at the two end ends of the auxiliary heating band, and are arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock; 4 temperature control thermocouples are arranged, and are evenly arranged around the center of the weld, that is, arranged in the directions of 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock;

[0066] (6) Determining the heating rate and the cooling rate of the local heat treatment, arranging the cooling device, and implementing the heat treatment: no requirement is made below 400 DEG C, the heating rate is 50-80 DEG C / h above 400 DEG C, the heat treatment holding temperature is 690 DEG C, holding for 4 hours after reaching the set temperature, and then cooling to below 400 DEG C at a rate of 30-50 DEG C / h, and taking out to cool in air.

[0067] Comparative Example 1

[0068] The workpiece of the present comparative example 1 is the same as that of Example 1, and a traditional local heat treatment method is adopted, and the heating rate, the cooling rate and the holding rate of the heat treatment are unchanged. The present comparative example does not arrange the auxiliary heating band, the width of the heating band from the center of the weld to the one side of the cylinder is 1068 mm, the width of the holding band is 2136 mm, the width of the heating band from the center of the weld to the one side of the connecting pipe is 864 mm, and the width of the holding band is 1728 mm. It can be seen that the width of the heating band and the width of the holding band at the connecting pipe are obviously increased, which may affect the on-site implementation.

[0069] In the present comparative example, the thermocouples arranged by the auxiliary heating band are removed when arranging the temperature measuring thermocouples, and the arrangement of the remaining thermocouples is unchanged.

[0070] The residual stress of the workpiece in the as-welded state and the residual stress after the heat treatment of Example 1 and Comparative Example 1 are detected, the average reduction of the axial residual stress of Example 1 is increased by about 30% compared with Comparative Example 1, the average reduction of the circumferential residual stress of Example 1 is increased by about 50% compared with Comparative Example 1, the auxiliary heating area offsets the as-welded residual stress and the secondary stress generated by the “waisted deformation” of the main heating, so that the tensile residual stress of the inner surface is reduced.

[0071] It should be noted that the parts not mentioned in the present application can be realized by using or referring to the existing technology.

[0072] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples, and the changes, modifications, additions or replacements made by the person skilled in the art within the essential scope of the present application should also belong to the protection scope of the present application.

Claims

1. A method for post-weld local heat treatment of welded structures for nozzles of large pressure vessels, characterized in that, Including the following steps: (1) Determine the dimensional parameters of the pressure vessel nozzle structure, including the wall thickness of the pressure vessel cylinder. , pipe wall thickness outer radius of the pressure vessel cylinder Outer radius of the receiver ; (2) Determine the width of the heating band and the width of the insulation band required for local heat treatment based on the dimensional parameters of the pressure vessel nozzle structure determined in step (1); (3) Determine the number of turns of the cable wound for local heat treatment induction heating based on the dimensional parameters of the pressure vessel nozzle structure determined in step (1); (4) Determine the temperature measurement points for local heat treatment and arrange temperature measuring thermocouples and temperature control thermocouples; (5) Determine the local heat treatment process, including heat treatment temperature, holding time and cooling process; (6) Perform heat treatment and record the heat treatment temperature curve; In step (2), the heating band includes a main heating band and a secondary heating band disposed on the outer wall of the cylinder and the pipe. The main heating band is arranged on the weld and around the weld, and the secondary heating band is arranged on the cylinder and located on one side of the main heating band on the side of the cylinder. The width of the main heating band from the weld center to one side of the cylinder is: ; The width of the main heating band from the weld center to one side of the nozzle is: ; The width of the auxiliary heating band is: ,in, Take a value of 0.5 to 1; In step (2), the insulation tape is installed on the outer wall of the cylinder and the pipe, and the main heating tape and the auxiliary heating tape are installed on the outer layer of the insulation tape; The width of the insulation strip from the center of the weld to one side of the cylinder is: ; The width of the insulation strip from the weld centerline to one side of the nozzle is: ; The width of the insulation strip at the auxiliary heating zone is: ; The number of cable turns in the main heating band from one side of the cylinder to the center of the weld in step (3) The number of cable turns from one side of the pipe to the center of the weld. Number of turns of auxiliary heating cable They are respectively: ； ； ； in, The heat loss coefficient is... The specific heat capacity of the cylinder. To determine the specific heat capacity of the tube, kJ / (kg·℃), , These are the initial heating temperature and the final heating temperature, respectively, in °C; Heating time, in hours; The density of the material is kg / m³. The resistance of the heating section of the cylinder. The resistance of the heating section is measured in Ω. The cross-sectional area of ​​the cylinder is... The cross-sectional area of ​​the pipe is in m². is the resistivity.

2. The method for post-weld local heat treatment of a welded structure for a nozzle of a large pressure vessel according to claim 1, characterized in that, In step (4), 3n thermocouples are set, and n≥2. Among them, n are set at one end of the cylinder where the main heating belt is arranged, n are set at one end of the pipe where the main heating belt is arranged, and n are symmetrically set at both ends of the auxiliary heating belt.

3. The method for post-weld local heat treatment of a welded structure for a nozzle of a large pressure vessel according to claim 1, characterized in that, In step (4), at least two temperature control thermocouples are set up and evenly arranged around the center of the weld.

4. The method for post-weld local heat treatment of a welded structure for a nozzle of a large pressure vessel according to claim 1, characterized in that, In step (5), the heat treatment temperature and holding time are determined according to the heat treatment standard. During the heat treatment heating process, the main and auxiliary heating belts heat up at the same time, and the heating rate of the cylinder and the connecting pipe is the same.

5. The method for post-weld local heat treatment of a welded structure for a nozzle of a large pressure vessel according to claim 1, characterized in that, The cooling process in step (5) is as follows: a cooling fan is installed outside the cylinder, and the cylinder and the connecting pipe are cooled at the same cooling rate. When the temperature at the center of the weld drops below 400°C, the auxiliary heating belt is removed first, then the main heating belt is removed, and finally the insulation belt is removed. Then the cylinder is cooled to room temperature in the air.

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