CN111378817B - Inner wall heating device and heat treatment method using same - Google Patents

Abstract

An inner wall heating device and a heat treatment method using the same relate to an inner wall heating device and a heat treatment method. The invention aims to solve the problems that the existing heat treatment method can not ensure that the internal residual stress after welding is fully released, the material structure can not be completely transformed, and further the expected material performance can not be obtained. A plurality of heating rod cores are inserted on a seat body in an annular array mode, a resistance wire is embedded in a ceramic chip insulating layer, a heat conduction layer is sleeved outside the ceramic chip insulating layer, and a power supply connector is connected with one end of the resistance wire. The invention adopts a mode of internal and external synchronous heating to carry out postweld heat treatment, the outer wall adopts a mode of medium-frequency induction heating as a main heating source to carry out heat treatment, and the inner wall adopts a mode of specially manufacturing a high-power resistance wire heater according to the structure size of a product to carry out stress relief heat treatment by adopting a heat radiation scheme. The invention is used for the postweld heat treatment of the large thick-wall reducing pipe orifice of the high main valve.

Description

Inner wall heating device and heat treatment method using same

Technical Field

The present invention relates to a wall heating apparatus and a heat treatment method, and more particularly, to an inner wall heating apparatus and a heat treatment method using the same.

Background

The diameter of a connecting weld area of a steam inlet transition section and a casting of a high-pressure main steam valve of a 660MW and 1000MW steam turbine is usually larger, the wall thickness is extremely thick (the conventional wall thickness is more than or equal to 190mm), the pipe orifice of the transition section is of a closing structure, namely the diameter of the pipe orifice is smaller than that of the weld area of the casting, for the condition, the conventional method of heating by an outer wall heat source for post-welding stress relief heat treatment cannot ensure that the heat treatment of the area near the inner wall meets the standard and the technical requirements, the internal stress cannot be fully released, and the material structure is completely transformed.

In summary, the conventional heat treatment method has the problems that the internal residual stress after welding cannot be fully released, the material structure cannot be completely transformed, and the expected material performance cannot be obtained.

Disclosure of Invention

The invention aims to solve the problems that the existing heat treatment method can not ensure that the internal residual stress after welding is fully released, the material structure can not be completely transformed, and further the expected material performance can not be obtained. Further provided are an inner wall heating apparatus and a heat treatment method using the same.

The technical scheme of the invention is as follows: the utility model provides an inner wall heating device includes pedestal and a plurality of heating rod core, and a plurality of heating rod cores are with annular array's mode cartridge on the pedestal, and every heating rod core all includes heat-conducting layer, potsherd insulating layer, resistance wire and power connection, and the resistance wire is embedded in potsherd insulating layer with the winding mode of spiral shell, and the heat-conducting layer suit is in potsherd insulating layer's outside, and power connection is connected with the one end of resistance wire.

Further, the pedestal includes lug, barrel and mounting panel, and the mounting panel horizontal installation is in the barrel, and the mounting panel is located barrel length direction's well lower part, and the lug is installed on the last edge of barrel.

Furthermore, a plurality of mounting holes are formed in the mounting plate.

Further, the pedestal still includes the baffle, and the baffle is installed on the mounting panel.

Preferably, the partition is a rectangular plate, a herringbone plate or a cross-shaped plate.

Further, the heat conduction layer is made of iron sheet.

Furthermore, a plurality of limiting blocks are arranged on the heat conduction layer on the same horizontal plane.

Further, the ceramic plate insulating layer is made of a filter screen-shaped ceramic plate.

The invention also provides a heat treatment method adopting the inner wall heating device, which comprises the following steps:

the method comprises the following steps: setting the length of a heating rod core of the inner wall heating device;

the method comprises the following steps: 4 heating rod cores are circumferentially and symmetrically arranged on the seat body;

the first step is: the positions of C1 and C2, D1 and D2, and E1 and E2 at the C1 point, C2 point, C1 point, D1 point of 50mm at the upper part of C2 point, D2 point and C1 point, and E1 point of 50mm at the lower part of C2 point, and E2 point on the inner side wall circumference of the large-thick-wall reducing pipe orifice welding seam of the high main valve are respectively arranged in a circumferential symmetry way, namely, the C1 and C2 form a 180 ℃ symmetry state, and similarly, the D1 and D2, and the E1 and E2 also form a 180 ℃ symmetry state to judge the temperature uniformity in the circumferential direction; in the vertical direction, six monitoring thermocouples H are respectively arranged at six points C1, C2, D1, D2, E1 and E2, the heating rod core is heated to 500 ℃, and heat preservation is carried out;

step one is three: the heating rod core is moved up and down through an external lifting device, so that the insertion depth of the heating rod core is adjusted; meanwhile, according to temperature data fed back by the monitoring thermocouple H at six points of C1, C2, D1, D2, E1 and E2, finding the optimal extending length of the heating rod core which enables the point positions of the C1 point and the C2 point to be the highest temperature point, and recording the position of the optimal extending length;

then, cooling the heating rod core, and installing a limiting block at a corresponding position of the optimal extending length, so that the extending length of the heating rod core is found;

step two: carrying out heat treatment formally;

step two, firstly: plugging and sealing the inner cavity A of the valve body by using a heat insulation material B;

step two: the method comprises the following steps of formally arranging an inner wall heating device at six points C1, C2, D1, D2, E1 and E2 in a large thick-wall reducing pipe orifice of a high main valve;

step two and step three: the method comprises the following steps that a plurality of temperature control thermocouples and a plurality of monitoring thermocouples are synchronously arranged on the casting and forging sides of the outer wall of the large-thick-wall reducing pipe orifice of the high main valve, wherein the temperature control thermocouples are used for controlling the output power of a heating rod core of the outer wall, so that the temperature of the casting and forging of the outer wall is controlled, and the monitoring thermocouples are used for monitoring and displaying the temperature of the casting and forging of the outer wall;

step two, four: wrapping an asbestos insulation layer with the thickness not less than 30mm on the outer wall of the large thick-wall reducing pipe orifice of the high main valve, installing a main heating source outside the insulation layer, setting a medium-frequency induction cable, and starting heat treatment after rated power output is set;

step two and step five: after the temperature of the inner wall and the outer wall is fed back to the rated temperature, accounting is carried out according to the wall thickness and related standards for heat preservation time, and heat preservation is carried out;

step three: detecting the heat treatment part;

after the heat treatment is finished, carrying out hardness inspection on the welding port and the base material areas of the casting and forging parts on the two sides, determining the hardness conditions of the inner wall and the outer wall, wherein the hardness values are close to each other and are all located in a reasonable temperature range required by the standard, selecting a sampling point on the outer wall to carry out metallographic structure inspection, determining the heat treatment effect according to the metallographic structure transformation condition, and further obtaining the high-main-valve large-thick-wall reducing pipe orifice material performance with qualified quality.

Further, the heat insulation material B in the second step and the third step is heat insulation asbestos.

Compared with the prior art, the invention has the following effects:

1. according to the invention, through the structural analysis of the large-thick-wall reducing pipe orifice of the high main valve and by combining a resistance heating and heat transfer principle, a high-power inner wall heating device is designed, so that the post-welding stress relief heat treatment effect and quality of the inner wall of the large-thick-wall special-shaped structure welded junction can be ensured, the internal heat treatment quality is ensured, and the damage to the material performance caused by the overtemperature of the outer wall and the workpiece core region or the overlong heat preservation time in the high-temperature heat treatment stage is avoided.

2. The invention verifies that the heat output effect of the inner wall heating device is good through actual operation in a feedback mode that the temperature of the inner wall heating device is higher than that of an external main heating heat source and the preset heat treatment temperature is preferentially reached. After heat treatment, hardness inspection is carried out on the inner wall welding meat, the requirements of relevant industry standards are met, and the method has good effect of carrying out local heat treatment on the inner wall of the special-shaped pipe orifice of the large thick-wall casting. The problems that internal stress cannot be fully released and material tissues cannot be completely changed are effectively avoided.

Drawings

FIG. 1 is a top view of an inner wall heating apparatus;

FIG. 2 is a schematic front view of FIG. 1;

FIG. 3 is a schematic view of the internal structure of the heater core 2;

fig. 4 is a schematic view of the installation of the inner wall heating apparatus at the time of heat treatment (the external heating during heat treatment is omitted), in which the arrow direction indicates the direction in which the heating rod core 2 moves.

Detailed Description

The first embodiment is as follows: the embodiment is described with reference to fig. 1 to 4, an inner wall heating device of the embodiment includes a base 1 and a plurality of heating rod cores 2, the plurality of heating rod cores 2 are inserted into the base 1 in an annular array, each heating rod core 2 includes a heat conduction layer 2-1, a ceramic insulating layer 2-2, a resistance wire 2-3 and a power connector 2-4, the resistance wire 2-3 is embedded in the ceramic insulating layer 2-2 in a manner of winding in a spiral, the heat conduction layer 2-1 is sleeved outside the ceramic insulating layer 2-2, and the power connector 2-4 is connected with one end of the resistance wire 2-3.

When the method is used practically, the length of the heating rod core 2 needs to be calculated, the position of a weld crater is guaranteed to be located at the highest temperature point in the middle of the rod core, resistance wires (with the diameter of 6mm) in thick specifications are used for heating, heat output power is guaranteed, insulation protection of filter screen-shaped ceramic pieces is used, potential safety hazards caused by current short circuit are prevented, the inner wall heating core is self-manufactured by combining the heat transfer principle, an external shell is designed to support and protect the inner wall, the method for carrying out large-scale heat output on the inner wall side meets the requirement of a heat treatment effect, internal stress is fully released, a weld joint tissue can be completely changed, and weld metal obtains expected material performance.

The second embodiment is as follows: the embodiment is described with reference to fig. 1 and 4, a seat body 1 of the embodiment comprises a lifting lug 1-1, a cylinder body 1-2 and a mounting plate 1-3, the mounting plate 1-3 is horizontally mounted in the cylinder body 1-2, the mounting plate 1-3 is located at the middle lower part of the length direction of the cylinder body 1-2, and the lifting lug 1-1 is mounted on the upper edge of the cylinder body 1-2. So set up, the lug is convenient for external hoist device and hoists. Other components and connections are the same as in the first embodiment.

The inner diameter of the cylinder 1-2 is matched with the size of the outer wall of the large-thick-wall reducing pipe orifice of the high main valve, so that the cylinder 1-2 can be seated on the outer wall of the large-thick-wall reducing pipe orifice of the high main valve when heat treatment is ensured. So as to fix the extending depth of the heating rod core 2.

The mounting plates 1 to 3 of the present embodiment are used to clamp the heater core 2.

The third concrete implementation mode: referring to fig. 1, the present embodiment will be described, and a plurality of mounting holes 1 to 4 are formed in a mounting plate 1 to 3 of the present embodiment. So set up, be convenient for install heating rod core 2. Other compositions and connections are the same as in the first or second embodiments.

The number of the mounting holes 1 to 4 of the present embodiment is set according to the number of the heater core 2.

The fourth concrete implementation mode: referring to fig. 1, the seat body 1 of the present embodiment further includes partition plates 1-5, and the partition plates 1-5 are mounted on the mounting plates 1-3. So set up, not only can separate heating rod core 2, can also increase the bulk strength of pedestal 1. Other compositions and connection relationships are the same as in the first, second or third embodiment.

The fifth concrete implementation mode: referring to fig. 1, the partition boards 1 to 5 of the present embodiment are rectangular boards, "herringbone boards" or "cross" boards. So set up, be convenient for select different baffle forms according to actual conditions, satisfy the requirement to heating rod core 2 quantity when the inner wall is thermal treatment. Other compositions and connection relationships are the same as those in the first, second, third or fourth embodiment.

The sixth specific implementation mode: in the present embodiment, the heat conductive layer 2-1 of the present embodiment is made of iron sheet, as described with reference to fig. 3. So set up, heat transfer effect is good. Other compositions and connection relationships are the same as in the first, second, third, fourth or fifth embodiment.

The seventh embodiment: in the present embodiment, a plurality of stoppers 2-5 are attached to the heat conductive layer 2-1 in the same horizontal plane, as described with reference to fig. 4. So set up, be convenient for after confirming the length of stretching into of heater rod core 2, the position that fixed heater rod core 2 stretched into. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The limiting blocks 2-5 of the embodiment are fixedly installed in a welding mode.

The specific implementation mode is eight: referring to fig. 3, the present embodiment will be described, in which the ceramic sheet insulating layer 2-2 is made of a filter-like ceramic sheet. So set up, prevent the potential safety hazard that the electric current short circuit caused. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The specific implementation method nine: the present embodiment is described with reference to fig. 1 to 4, and includes the following steps:

the method comprises the following steps: setting the length of a heating rod core of the inner wall heating device;

the method comprises the following steps: 4 heating rod cores are circumferentially and symmetrically arranged on the seat body;

the first step is: the positions of C1 and C2, D1 and D2, and E1 and E2 at the C1 point, C2 point, C1 point, D1 point of 50mm at the upper part of C2 point, D2 point and C1 point, and E1 point of 50mm at the lower part of C2 point, and E2 point on the inner side wall circumference of the large-thick-wall reducing pipe orifice welding seam of the high main valve are respectively arranged in a circumferential symmetry way, namely, the C1 and C2 form a 180 ℃ symmetry state, and similarly, the D1 and D2, and the E1 and E2 also form a 180 ℃ symmetry state to judge the temperature uniformity in the circumferential direction; in the vertical direction, six monitoring thermocouples H are respectively arranged at six points C1, C2, D1, D2, E1 and E2, the heating rod core is heated to 500 ℃, and heat preservation is carried out;

step one is three: the heating rod core is moved up and down through an external lifting device, so that the insertion depth of the heating rod core is adjusted; meanwhile, according to temperature data fed back by the monitoring thermocouple H at six points of C1, C2, D1, D2, E1 and E2, finding the optimal extending length of the heating rod core which enables the point positions of the C1 point and the C2 point to be the highest temperature point, and recording the position of the optimal extending length;

then, cooling the heating rod core, and installing a limiting block at a corresponding position of the optimal extending length, so that the extending length of the heating rod core is found;

step two: carrying out heat treatment formally;

step two, firstly: plugging and sealing the inner cavity A of the valve body by using a heat insulation material B;

step two: the method comprises the following steps of formally arranging an inner wall heating device at six points C1, C2, D1, D2, E1 and E2 in a large thick-wall reducing pipe orifice of a high main valve;

step two and step three: the method comprises the following steps that a plurality of temperature control thermocouples and a plurality of monitoring thermocouples are synchronously arranged on the casting and forging sides of the outer wall of the large-thick-wall reducing pipe orifice of the high main valve, wherein the temperature control thermocouples are used for controlling the output power of a heating rod core of the outer wall, so that the temperature of the casting and forging of the outer wall is controlled, and the monitoring thermocouples are used for monitoring and displaying the temperature of the casting and forging of the outer wall;

step two, four: wrapping an asbestos insulation layer with the thickness not less than 30mm on the outer wall of the large thick-wall reducing pipe orifice of the high main valve, installing a main heating source outside the insulation layer, setting a medium-frequency induction cable, and starting heat treatment after rated power output is set;

step two and step five: after the temperature of the inner wall and the outer wall is fed back to the rated temperature, accounting is carried out according to the wall thickness and related standards for heat preservation time, and heat preservation is carried out;

step three: detecting the heat treatment part;

after the heat treatment is finished, carrying out hardness inspection on the welding port and the base material areas of the casting and forging parts on the two sides, determining the hardness conditions of the inner wall and the outer wall, wherein the hardness values are close to each other and are all located in a reasonable temperature range required by the standard, selecting a sampling point on the outer wall to carry out metallographic structure inspection, determining the heat treatment effect according to the metallographic structure transformation condition, and further obtaining the high-main-valve large-thick-wall reducing pipe orifice material performance with qualified quality.

After the heat treatment is finished, carrying out hardness inspection on the welding port and the base material areas of the casting and forging parts on the two sides, determining the hardness conditions of the inner wall and the outer wall, wherein the hardness values are close to each other and are all located in a reasonable temperature range required by the standard, selecting a sampling point on the outer wall to carry out metallographic structure inspection, determining the heat treatment effect according to the metallographic structure transformation condition, and further obtaining the high-main-valve large-thick-wall reducing pipe orifice material performance with qualified quality.

The detailed implementation mode is ten: the present embodiment will be described with reference to fig. 4, and the heat insulating material B in step two and step three of the present embodiment is heat insulating asbestos. So set up, it is effectual to keep warm. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The working principle of the invention is explained in conjunction with fig. 1 to 4:

taking a post-welding heat treatment project of a transition section of a steam inlet of a high-pressure main steam valve of a thermal power steam turbine unit with a certain 660MW grade and a main steam temperature of 600 ℃ as an example:

in the application case, a valve shell casting is made of an E911 material (ZG1Cr10 MoWVNbN-II), a transition section is made of F92(1Cr9MoW2VNbNB), the thickness of a main welding seam area is about 200mm, the outer diameter phi Z of the welding seam area is about 800mm, the inner diameter phi X of the welding seam area is about 400mm, the welding method is argon arc welding bottoming 15mm, a cover surface is filled through manual electric arc welding, the used welding materials are ER90S-G (92) + E9015-G (92), the temperature of the planned heat treatment is 740 +/-5 ℃, and because the depth of a large welding seam and two sides of the welding seam are connected with a large-sized casting and forging piece, the heat dissipation is fast, the rated heat treatment temperature is high, and the heat treatment effect is difficult to guarantee through conventional local heat treatment.

In the case, an internal and external synchronous heating mode is adopted for post-welding heat treatment, an outer wall is used as a main heating source for heat treatment in a medium-frequency induction heating mode, and an inner wall is subjected to stress relief heat treatment by an inner wall auxiliary heating method through a heat radiation scheme in a mode of specially manufacturing a high-power resistance wire heater according to the structural size of a product.

The inner wall auxiliary heating method for the post-welding heat treatment of the large thick-wall reducing pipe orifice of the high main valve comprises the following specific processes:

the specially-made inner wall heating device is customized according to the structure size of a product, a simulated heating test is firstly carried out to determine the optimal heat penetration length, the highest point of the heating temperature of the inner wall is ensured to be positioned at the middle position of a welding seam, the specific measures are that 3 thermocouples are circumferentially and symmetrically arranged at the central position of the welding seam of the inner wall, 3 monitoring thermocouples are arranged on the 50mm upper part and the 50mm lower part of the weld joint at the periphery, the cylinder body of the inner wall heating device is hoisted by a hoisting device to carry out a heating test at 500 ℃, in the heating and test heat preservation stages, according to the temperature data fed back by the thermocouples at and above the welding seam, the insertion depth of the heating rod core is gradually changed by the hoisting device, the optimal extension length of the highest point of the heating temperature of the inner wall at the middle part of the welding seam is ensured by groping, and after cooling, a limiting block is manufactured according to the extending length, the extending length of the cylinder body is ensured to be the optimal extending length, and the highest point of the heating temperature of the inner wall is further ensured to be the center of a welding line.

When the heat treatment work is formally implemented, thermocouples are arranged at the position of a welding seam of the inner wall and in the 50mm areas of the upper part and the lower part of the welding seam of the inner wall, a certain number of thermocouples are synchronously arranged at the sides of the outer wall, a casting and a forging piece, the inner cavity of the valve body is plugged and sealed by heat-insulating materials such as heat-insulating asbestos and the like, an asbestos heat-insulating layer with the thickness not less than 30mm is wrapped on the outer wall of a product, a main heating source and a medium-frequency induction cable are arranged outside the heat-insulating layer, the auxiliary heating device is arranged on the inner wall, and the heat treatment work is started after the rated power output is set. And (3) after the temperature of the inner wall and the outer wall is fed back to the rated temperature, heat preservation is carried out for a certain time, and the specific heat preservation time is calculated according to the wall thickness and related standards, so that uniform and sufficient heat treatment is ensured. After the heat treatment is finished, carrying out hardness inspection on the welding port and the base material areas of the casting and forging pieces on two sides, determining the hardness conditions of the inner wall and the outer wall, wherein the results show that the hardness values are close to each other and are all positioned in a reasonable temperature range required by the standard, carrying out metallographic structure inspection on selected sampling points of the outer wall, determining the heat treatment effect aiming at the metallographic structure transformation condition, and further verifying the effectiveness of the inner wall auxiliary heating method for the heat treatment of the large-thick-wall reducing pipe port of the high main valve after welding.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (2)

1. The heat treatment method adopting the inner wall heating device comprises a base body (1) and a plurality of heating rod cores (2), wherein the plurality of heating rod cores (2) are inserted in the base body (1) in an annular array mode, each heating rod core (2) comprises a heat conduction layer (2-1), a ceramic plate insulation layer (2-2), a resistance wire (2-3) and a power connector (2-4), the resistance wire (2-3) is embedded in the ceramic plate insulation layer (2-2) in a spiral winding mode, the heat conduction layer (2-1) is sleeved outside the ceramic plate insulation layer (2-2), and the power connector (2-4) is connected with one end of the resistance wire (2-3), and the heat treatment method is characterized in that: the heat treatment method comprises the following steps:

the method comprises the following steps: setting the length of a heating rod core (2) of the inner wall heating device;

the method comprises the following steps: the 4 heating rod cores (2) are circumferentially and symmetrically arranged on the seat body (1);

the first step is: c1 and C2, D1 and D2, and E1 and E2 are respectively arranged in circumferential symmetry at C1 point, C2 point, C1 point, D1 point of 50mm at the upper part of C2 point, D2 point, C1 point, E1 point of 50mm at the lower part of C2 point and E2 point on the inner side wall circumference of the large-thick-wall reducing pipe mouth welding seam of the high main valve, namely C1 and C2 are in a 180 ℃ symmetrical state, and similarly D1 and D2, E1 and E2 are in a 180 ℃ symmetrical state to judge the temperature uniformity in the circumferential direction; in the vertical direction, six monitoring thermocouples (H) are respectively arranged at six points C1, C2, D1, D2, E1 and E2, the heating rod core (2) is heated to 500 ℃, and heat preservation is carried out;

step one is three: the heating rod core (2) is moved up and down through an external hoisting device, so that the insertion depth of the heating rod core (2) is adjusted; meanwhile, according to temperature data fed back by the monitoring thermocouple (H) at six points of C1, C2, D1, D2, E1 and E2, finding the optimal extending length of the heating rod core (2) which enables the position areas of the C1 point and the C2 point to be the highest temperature points, and recording the position of the optimal extending length;

then, cooling the heating rod core (2), and installing a limiting block (2-5) at a corresponding position of the optimal extending length, so that the extending length of the heating rod core (2) is found;

step two: carrying out heat treatment formally;

step two, firstly: the inner cavity (A) of the valve body is plugged and closed by a heat insulation material (B);

step two: the method comprises the following steps of formally arranging an inner wall heating device at six points C1, C2, D1, D2, E1 and E2 in a large thick-wall reducing pipe orifice of a high main valve;

step two and step three: a plurality of temperature control thermocouples and a plurality of monitoring thermocouples are synchronously arranged at the casting and forging sides of the outer wall of the large-thick-wall reducing pipe orifice of the high main valve, wherein the temperature control thermocouples are used for controlling the output power of the heating rod core (2) of the outer wall, so that the temperature of the casting and forging of the outer wall is controlled, and the monitoring thermocouples are used for monitoring and displaying the temperature of the casting and forging of the outer wall;

step two, four: wrapping an asbestos insulation layer with the thickness not less than 30mm on the outer wall of the large thick-wall reducing pipe orifice of the high main valve, installing a main heating source outside the insulation layer, setting a medium-frequency induction cable, and starting heat treatment after rated power output is set;

step two and step five: after the temperature of the inner wall and the outer wall is fed back to the rated temperature, accounting is carried out according to the wall thickness and related standards for heat preservation time, and heat preservation is carried out;

step three: detecting the heat treatment part;

after the heat treatment is finished, carrying out hardness inspection on the welding port and the base material areas of the casting and forging parts on the two sides, determining the hardness conditions of the inner wall and the outer wall, wherein the hardness values are close to each other and are all located in a reasonable temperature range required by the standard, selecting a sampling point on the outer wall to carry out metallographic structure inspection, determining the heat treatment effect according to the metallographic structure transformation condition, and further obtaining the high-main-valve large-thick-wall reducing pipe orifice material performance with qualified quality.

2. The heat treatment method according to claim 1, characterized in that: the heat insulation material (B) in the second step and the third step is heat insulation asbestos.

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