Reducer butt joint assembly heat treatment method

Abstract

The embodiment of the invention provides a reducing pipe butt joint assembly heat treatment method. The reducing pipe butt joint assembly comprises a first straight pipe section, a slope welding seam and a second straight pipe section which are sequentially connected, and the outer diameter of the first straight pipe section is smaller than that of the second straight pipe section. The method comprises the steps that thermocouples are arranged at a plurality of preset positions on the surfaces of the first straight pipe section, the bevel weld joint and the second straight pipe section correspondingly; sheet-shaped heaters are arranged on the surfaces of the first straight pipe section and the second straight pipe section in the circumferential direction, and a rope-shaped heater is arranged on the surface of the slope welding seam; the sheet-shaped heater and the rope-shaped heater are wrapped with heat preservation cotton; and heat treatment parameters are set, and heat treatment is conducted on the assembly. According to the embodiment of the invention, a mode of combining the sheet-shaped heater and the rope-shaped heater is adopted, so that scientific configuration of heating power of pipelines with different pipe diameters and accurate zoning temperature control of weld heat treatment of reducing pipes are realized, the technical requirements are met, and the effect and the quality of postweld heat treatment are ensured.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of heat treatment of reducer butt-joint assemblies, and specifically relate to a heat treatment method of reducer butt-joint assemblies. Background Art

[0002] One side is a straight pipe component, and the other side is a valve, tee, elbow, etc., with inconsistent structural dimensions at both ends, especially different diameter components with unequal inner and outer wall dimensions and significant thickness differences. Components formed by welding are widely used in engineering practice. For such components, national standards and industry standards have certain regulations on how to transition them, but due to limited manufacturing and processing capabilities or actual production, there are a large number of special-shaped welded joints with sudden changes in knot shape and wall thickness in engineering practice. These welded joints need to be subjected to on-site post-weld heat treatment after on-site construction or welding repair. In order to improve the welding process performance of the workpiece, the metallographic structure, mechanical properties and stress state of the weld.

[0003] On-site heat treatment processes are divided into electric heating and flame heating. Flame heating is generally used in situations where process quality requirements are low and other heating methods are difficult to use, and it is not suitable for high-alloy materials. In comparison, the electric heating process has the advantages of stable heat source and easy measurement and control of heating temperature, and has been widely used in on-site installation and maintenance.

[0004] Relevant welding heat treatment regulations such as DL / T819-2019 "Technical Regulations for Welding Heat Treatment of Thermal Power Plants" have the following requirements for heat treatment processes: the heating center of the pipeline weld should be located at the center of the weld, and measures should be taken to reduce the circumferential and radial temperature differences; the heating width should be selected according to the heating method and the ratio of the outer diameter (D) to the wall thickness (δ). When induction heating is used, the single-side heating width is 5 to 6 times the wall thickness. When flexible ceramic resistance heating or far-infrared radiation heating is used, the single-side heating width is 6 to 9 times the wall thickness. How to combine the above-mentioned principled regulations with actual pipeline components to achieve the expected effect, realize the technical requirements of the regulations for heating width, heating center located at the center of the weld, and reducing circumferential and radial temperature differences, and ensure the weld heat treatment effect and quality is a current technical problem. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a heat treatment method for a reducer butt-joint assembly.

[0006] The reducer butt joint assembly comprises a first straight pipe section, a bevel weld and a second straight pipe section connected in sequence, wherein the outer diameter of the first straight pipe section is smaller than that of the second straight pipe section; the method comprises: Thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section; A sheet heater is arranged circumferentially on the surface of the first straight pipe section and the second straight pipe section, and a rope heater is arranged on the surface of the inclined weld; Using thermal insulation cotton to cover the sheet heater and the rope heater; The heat treatment parameters are set to perform heat treatment on the component.

[0007] Optionally, the thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, including: A temperature-controlling thermocouple of the rope-shaped heater is arranged at a groove position of the inclined weld surface relative to the first straight pipe section.

[0008] Optionally, the thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, including: A first temperature measuring thermocouple is arranged on the surface of the inclined weld with the temperature control thermocouple position of the rope heater as the other end of the diameter; A second temperature measuring thermocouple is arranged on the surface of the second straight pipe section at a position 5 mm to 10 mm away from the inclined weld.

[0009] Optionally, the thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, including: Two temperature-controlling thermocouples of sheet heaters are arranged circumferentially opposite to each other at a position of one time the pipe wall thickness and not less than 50 mm from the weld center on the surface of the first straight pipe section; two temperature-measuring thermocouples are arranged circumferentially opposite to each other at a position of two times the pipe wall thickness and not less than 100 mm from the weld center on the surface of the first straight pipe section; Three temperature-controlling thermocouples of sheet heaters are evenly arranged on the surface of the second straight pipe section at a position one times the pipe wall thickness and not less than 50 mm away from the center of the weld; three temperature-measuring thermocouples are evenly arranged on the surface of the second straight pipe section at a position twice the pipe wall thickness and not less than 100 mm away from the center of the weld.

[0010] Optionally, after thermocouples are respectively arranged at a plurality of predetermined positions on the surfaces of the first straight pipe section, the bevel weld, and the second straight pipe section, the method further comprises: The spot welding parts of each thermocouple are covered with heat-insulating cotton.

[0011] Optionally, the step of providing a rope heater on the surface of the bevel weld includes: A rope heater is evenly wound on the surface of the bevel weld from one side of the first straight pipe section to one side of the second straight pipe section.

[0012] Optionally, the sheet heater is circumferentially arranged on the surface of the first straight pipe section and the second straight pipe section, comprising: Two sheet heaters are arranged opposite to each other in the circumferential direction on the surface of the first straight pipe section; Three sheet heaters are evenly arranged on the circumference of the surface of the second straight pipe section.

[0013] Optionally, the axial length of the sheet heater relative to the reducer docking assembly is 450 mm.

[0014] Optionally, when the reducer docking assembly is placed horizontally, the thickness of the thermal insulation cotton coated on the top of the rope-shaped heater is smaller than the thickness of the thermal insulation cotton coated on the bottom of the rope-shaped heater.

[0015] Optionally, the heat treatment of the component includes: During the constant temperature stage, the temperature of each thermocouple is monitored and calibrated.

[0016] A heat treatment method for a reducer butt-joint assembly in an embodiment of the present disclosure adopts a combination of a sheet heater and a rope heater to achieve scientific configuration of heating power for pipes of different diameters and precise zone temperature control for heat treatment of welds of reducers. The rope heater is evenly wound to ensure density, the temperature control point and the temperature measurement point are scientifically selected, the thickness of the insulation cotton is optimized, and on-site temperature verification and other technical measures meet the technical requirements of the heating center being located at the center of the weld and reducing the circumferential and radial temperature gradients, thereby ensuring the effect and quality of post-weld heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a reducer docking assembly according to an embodiment of the present disclosure; Figure 2 The present invention is a schematic flow chart of a heat treatment method for a reducer butt joint assembly according to another embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0019] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0020] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0021] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present disclosure. As used in this disclosure, the term "and / or" includes any one of the associated listed items and all combinations of one or more.

[0022] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present disclosure, and therefore cannot be used to limit the protection scope of the present disclosure.

[0023] The embodiment of the present disclosure provides a heat treatment method for a reducer butt joint assembly. Figure 1 As shown, the reducer butt-jointing assembly includes a first straight pipe section (A), a bevel weld (B) and a second straight pipe section (C) connected in sequence, and the outer diameter of the first straight pipe section (A) is smaller than that of the second straight pipe section (B).

[0024] like Figure 2 As shown, the heat treatment method of the reducer butt assembly includes: Step S21, respectively setting thermocouples at a plurality of predetermined positions on the surface of the first straight pipe section, the bevel weld and the second straight pipe section.

[0025] Specifically, first determine the combination of rope heater and sheet heater and zoning control scheme according to the structural size of the reducer: confirm the material of the reducer, measure its specific specifications and dimensions (such as the diameter of the pipes at both ends, wall thickness, length of the bevel slope of the weld, etc.), determine the procedures and specifications for post-weld heat treatment according to the corresponding technical requirements, and determine the post-weld heat treatment temperature, single-sided heating width, number of circumferential zoning control zones of the straight pipe section and other information according to the procedures, and determine the specifications and dimensions (length * width) of the single-piece heating plate, power, length of the rope heater, etc. according to the regulations. Taking a D500*60mm / D600*60mm reducer with a slope length of 150mm and made of high alloy 10Cr9Mo1VNbN (P91) as an example, according to the DL\T819 specification, the straight pipe sections at both ends of the reducer adopt 2-zone and 3-zone circumferential temperature control arrangements, that is, the thermocouples of the first straight pipe section with a smaller outer diameter are installed at 12:00 and 6:00 respectively; the thermocouples of the second straight pipe section with a larger outer diameter are installed at 12:00, 4:00, and 8:00 respectively. The post-weld heat treatment temperature is 750℃~760℃, the constant temperature is 5 hours, the heating / cooling rate is 150℃\1h, the single-side heating width is 450mm, and the power is 10kw.

[0026] refer to Figure 1, arrangement of the thermocouples related to the rope heater: a temperature-controlling thermocouple (5) of the rope heater is arranged at a position of 12:00 on the surface of the inclined weld (B) relative to the groove center of the first straight pipe section (A); a first temperature-measuring thermocouple (6) is arranged at a position of 6:00 on the surface of the inclined weld (B) with the position of the temperature-controlling thermocouple (5) of the rope heater as the other end of the diameter, i.e., corresponding to the temperature-controlling thermocouple (5); and a second temperature-measuring thermocouple (2) is arranged at a position of 5 mm to 10 mm from the inclined weld (B) on the surface of the second straight pipe section (C). Arrangement of thermocouples related to the sheet heater: Referring to the scheme determined above, the thermocouples are installed circumferentially at the 12:00 and 6:00 positions of the first straight pipe section (A) and at the 12:00, 4:00 and 8:00 positions of the second straight pipe section (C), and a temperature-controlling thermocouple (7) is arranged axially at a distance of about δ (tube wall thickness) and ≥50mm from the center of the weld (specifically 60mm in this embodiment), and a temperature-measuring thermocouple (8) is arranged at a distance of twice δ (tube wall thickness) and ≥100mm from the center of the weld (specifically 120mm in this embodiment). That is to say, two temperature-controlling thermocouples of sheet-like heaters are circumferentially arranged opposite to each other on the surface of the first straight pipe section (A) at a distance of one time the pipe wall thickness and not less than 50 mm from the center of the weld; two temperature-measuring thermocouples are circumferentially arranged opposite to each other on the surface of the first straight pipe section (A) at a distance of two time the pipe wall thickness and not less than 100 mm from the center of the weld; three temperature-controlling thermocouples of sheet-like heaters are circumferentially evenly arranged on the surface of the second straight pipe section (B) at a distance of one time the pipe wall thickness and not less than 50 mm from the center of the weld; three temperature-measuring thermocouples are circumferentially evenly arranged on the surface of the second straight pipe section (B) at a distance of two time the pipe wall thickness and not less than 100 mm from the center of the weld.

[0027] The metal surface should be polished with a grinder at the thermocouple placement to expose the metallic luster, ensure that the thermocouple temperature measurement part is tightly fitted to the surface and spot welded firmly, and the thermocouple is fixed by energy storage spot welding to ensure the accuracy of the measured temperature. The thermocouple metal wires corresponding to the sheet heater are led out horizontally along the diameter pipe axis, and the thermocouple corresponding to the rope heater is led out along the gap between the rope heater and the sheet heater, and they are tied to the pipeline with iron wire for fixation. For example, the spot welding part of the thermocouple is covered with a small ball of thermal insulation cotton to avoid direct contact between the thermocouple and the heating plate, and reduce the influence of the heater on the measurement accuracy when measuring the pipeline wall temperature.

[0028] Step S22, a sheet heater is arranged circumferentially on the surface of the first straight pipe section and the second straight pipe section, and a rope heater is arranged on the surface of the inclined weld.

[0029] Specifically, refer to Figure 1On the surface of the bevel weld (B), from the side of the first straight pipe section (A) to the side of the second straight pipe section (C), the rope heater (3) is wound from the side with a smaller diameter to the side with a larger diameter, and the rope heater (3) is naturally wound and arranged on the surface of the bevel weld (B) in a dense and uniform manner by using the slope angle of the bevel. After the above winding is completed, 1 meter of excess wire is drawn out from both ends of the rope heater (3) to be processed into a power plug connector to facilitate the access of the heat treatment power supply, and the excess rope heater is cut off.

[0030] The sheet heaters (4) are arranged in different zones according to the different diameters D (unit: mm) of the straight pipe sections in accordance with the requirements specified above. Two sheet heaters are arranged opposite to each other in the circumferential direction of the surface of the first straight pipe section, and three sheet heaters are evenly arranged in the circumferential direction of the surface of the second straight pipe section. Figure 1 Specifically, as in the embodiment of this invention, two sheet heaters (4) are arranged in two zones in the first straight pipe section (A) and opposite to each other; the second straight pipe section (C) is divided into three zones, one on the top (10 o'clock to 2 o'clock direction) and two on the sides (2 o'clock to 6 o'clock direction; 6 o'clock to 10 o'clock direction). The heating width L1 of the single-side sheet heater (4), that is, the axial length L1 relative to the reducer butt joint assembly, is selected as the aforementioned intermediate value of 450mm. Tie each sheet heater (4) to the pipeline with iron wire for fixing. Be careful when arranging the sheet heaters, and be careful not to break the thermocouple spot welding position. The joint of the sheet heater is close to the outside and is led out horizontally along the pipeline axis, and the joint of the rope heater is led out from the middle.

[0031] Step S23: Use thermal insulation cotton to cover the sheet heater and the rope heater.

[0032] Specifically, the heat preservation measures are arranged in accordance with two layers of heat preservation cotton (9), and the thickness does not exceed 80 mm. Based on the horizontal placement of the reducer butt joint assembly of this embodiment, in order to reduce the temperature difference between the upper and lower parts of the pipeline, the thickness of the heat preservation cotton (9) coated above the heating area of ​​the rope-shaped heater (3) can be reduced to be smaller than the thickness of the heat preservation cotton (9) coated below the rope-shaped heater (3). The specific thinning degree can be determined by comparing the temperature of the temperature-controlling thermocouple (5) at 12 o'clock and the temperature of the corresponding temperature-measuring thermocouple (6) at 6 o'clock. When the temperature of the temperature-controlling thermocouple (5) is higher than that of the temperature-measuring thermocouple (6), the temperature difference between the upper and lower parts of the reducer can be reduced by gradually thinning the thickness of the heat preservation cotton (9) at the 12 o'clock position.

[0033] Step S24, setting heat treatment parameters and performing heat treatment on the component.

[0034] Specifically, the thermocouple temperature control temperature of the rope heater area is set according to the heat treatment temperature corresponding to the pipe material specified in the relevant regulations. In this embodiment, the post-weld heat treatment temperature is set to 760°C. The thermocouple temperature control temperature of the sheet heater area is set to 740°C, 20°C lower than the rope temperature control temperature. The temperature is kept constant for 5 hours, with a temperature rise / fall rate of 150°C\1h, and no temperature control below 350°C.

[0035] For example, to ensure the accuracy of constant temperature, several typical locations should be selected among the temperature-controlling thermocouples and the temperature-measuring thermocouples during the constant temperature stage, such as the preferred welding locations, for on-site temperature monitoring and calibration to ensure the temperature accuracy of the thermocouples and that the temperature of the measuring location is consistent with the actual disk temperature display.

[0036] A heat treatment method for a reducer butt-joint assembly in an embodiment of the present disclosure adopts a combination of a sheet heater and a rope heater to achieve scientific configuration of heating power for pipes of different diameters and precise zone temperature control for heat treatment of welds of reducers. The rope heater is evenly wound to ensure density, the temperature control point and the temperature measurement point are scientifically selected, the thickness of the insulation cotton is optimized, and on-site temperature verification and other technical measures meet the technical requirements of the heating center being located at the center of the weld and reducing the circumferential and radial temperature gradients, thereby ensuring the effect and quality of post-weld heat treatment.

[0037] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A heat treatment method for a reducer butt-jointed assembly, characterized in that: The reducer butt joint assembly comprises a first straight pipe section, a bevel weld and a second straight pipe section connected in sequence, wherein the outer diameter of the first straight pipe section is smaller than that of the second straight pipe section; the method comprises: Thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section; A sheet heater is arranged circumferentially on the surface of the first straight pipe section and the second straight pipe section, and a rope heater is arranged on the surface of the inclined weld; Using thermal insulation cotton to cover the sheet heater and the rope heater; The heat treatment parameters are set to perform heat treatment on the component.

2. The method according to claim 1, characterized in that The thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, comprising: A temperature-controlling thermocouple of the rope-shaped heater is arranged at a groove position of the inclined weld surface relative to the first straight pipe section.

3. The method according to claim 2, characterized in that The thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, comprising: A first temperature measuring thermocouple is arranged on the surface of the inclined weld with the temperature control thermocouple position of the rope heater as the other end of the diameter; A second temperature measuring thermocouple is arranged on the surface of the second straight pipe section at a position 5 mm to 10 mm away from the inclined weld.

4. The method according to claim 1, characterized in that The thermocouples are respectively arranged at a plurality of predetermined positions on the surface of the first straight pipe section, the inclined weld and the second straight pipe section, comprising: Two temperature-controlling thermocouples of sheet heaters are arranged circumferentially opposite to each other at a position of one time the pipe wall thickness and not less than 50 mm from the weld center on the surface of the first straight pipe section; two temperature-measuring thermocouples are arranged circumferentially opposite to each other at a position of two times the pipe wall thickness and not less than 100 mm from the weld center on the surface of the first straight pipe section; Three temperature-controlling thermocouples of sheet heaters are evenly arranged on the surface of the second straight pipe section at a position one times the pipe wall thickness and not less than 50 mm away from the center of the weld; three temperature-measuring thermocouples are evenly arranged on the surface of the second straight pipe section at a position twice the pipe wall thickness and not less than 100 mm away from the center of the weld.

5. The method according to claim 1, characterized in that: After thermocouples are respectively arranged at a plurality of predetermined positions on the surfaces of the first straight pipe section, the bevel weld, and the second straight pipe section, the method further comprises: The spot welding parts of each thermocouple are covered with heat-insulating cotton.

6. The method according to claim 1, characterized in that The step of arranging a rope heater on the surface of the bevel weld comprises: A rope heater is evenly wound on the surface of the bevel weld from one side of the first straight pipe section to one side of the second straight pipe section.

7. The method according to claim 1, characterized in that The sheet-shaped heater is arranged circumferentially on the surface of the first straight pipe section and the second straight pipe section, comprising: Two sheet heaters are arranged opposite to each other in the circumferential direction on the surface of the first straight pipe section; Three sheet heaters are evenly arranged on the circumference of the surface of the second straight pipe section.

8. The method according to claim 1, characterized in that: The axial length of the sheet heater relative to the reducer docking assembly is 450 mm.

9. The method according to claim 1, characterized in that: When the reducer butt-jointing assembly is placed horizontally, the thickness of the thermal insulation cotton coated on the upper side of the rope-shaped heater is smaller than the thermal insulation cotton coated on the lower side of the rope-shaped heater.

10. The method according to claim 1, characterized in that The heat treatment of the component comprises: During the constant temperature stage, the temperature of each thermocouple is monitored and calibrated.

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