A method for heat treating a reducer butt joint assembly

Abstract

Embodiments of the present disclosure provide a method for heat treatment of a reducer butt joint assembly. The reducer butt joint assembly comprises a first straight pipe section, a bevel weld and a second straight pipe section connected in sequence, and the outer diameter of the first straight pipe section is smaller than that of the second straight pipe section. The method comprises: arranging thermocouples at a plurality of predetermined positions on the surfaces of the first straight pipe section, the bevel weld and the second straight pipe section, respectively; arranging a sheet-shaped heater circumferentially on the surfaces of the first straight pipe section and the second straight pipe section, and arranging a rope-shaped heater on the surface of the bevel weld; wrapping the sheet-shaped heater and the rope-shaped heater with heat insulation cotton; and setting heat treatment parameters to perform heat treatment on the assembly. Embodiments of the present disclosure adopt a combination of sheet-shaped heaters and rope-shaped heaters, achieve scientific configuration of heating power of pipes with different diameters, accurate partition and temperature control of the weld of the reducer, meet technical requirements, and ensure the effect and quality of post-weld heat treatment.

Description

TECHNICAL FIELD

[0001] The embodiment of the present disclosure belongs to the technical field of hot processing of reducer butt joint assemblies, and particularly relates to a hot processing method of reducer butt joint assemblies. BACKGROUND

[0002] The reducer assemblies are used in engineering practice in large quantities, which are formed by welding butt joint of one side of straight pipe pipeline assemblies and the other side of valves, tees, elbows and other two-end structures with inconsistent sizes, especially inconsistent sizes of inner and outer walls and significant thickness differences. For such assemblies, the national standards and industry standards have certain provisions for how to transition, but limited by manufacturing and processing capacity or production practice, there are a large number of reducer assemblies with abrupt shapes and wall thicknesses in engineering practice. This part of the welded joints needs to be subjected to on-site post-weld heat treatment after on-site construction or welding repair, so as to improve the welding process performance, metallographic structure, mechanical properties and stress state of the workpiece.

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

[0004] The relevant welding heat treatment procedures, such as DL / T819-2019 “Welding Heat Treatment Technical Procedures for Thermal Power Plants”, have requirements for the heat treatment process, including that the heating center of the pipe weld should be located at the center of the weld, and measures should be taken to reduce the circumferential and radial temperature difference; the heating width should be selected according to the heating method and the ratio of the outer diameter (D) to the wall thickness (δ), and when induction heating is used, the single-sided heating width is 5-6 times the wall thickness, and when flexible ceramic resistance heating and far-infrared radiation heating are used, the single-sided heating width is 6-9 times the wall thickness. How to combine the above principle with the actual pipe assemblies to achieve the expected effect and realize the technical requirements of the heating width, the heating center located at the center of the weld and the reduction of the circumferential and radial temperature difference in the procedure to ensure the welding heat treatment effect and quality is a technical problem at present. SUMMARY

[0005] The embodiment of the present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a hot processing method of reducer butt joint assemblies.

[0006] The reducer butt joint assembly comprises a first straight pipe section, a bevel weld and a second straight pipe section connected in sequence, and the outer diameter of the first straight pipe section is smaller than that of the second straight pipe section; and the method comprises:

[0007] A thermocouple is arranged at each of a plurality of predetermined positions on the surface of the first straight pipe section, the bevel weld and the second straight pipe section.

[0008] A sheet heater is provided circumferentially on the surface of the first straight pipe section and the second straight pipe section, and a rope heater is provided on the surface of the inclined weld.

[0009] The sheet heater and the rope heater are wrapped with insulating cotton.

[0010] Set the heat treatment parameters and perform heat treatment on the component.

[0011] Optionally, the step of setting thermocouples at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section includes:

[0012] A temperature-controlling thermocouple for the rope heater is installed on the surface of the inclined weld relative to the bevel position of the first straight pipe section.

[0013] Optionally, the step of setting thermocouples at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section includes:

[0014] A first temperature measuring thermocouple is installed on the surface of the inclined weld, at the other end of the diameter corresponding to the position of the temperature control thermocouple of the rope heater;

[0015] A second temperature measuring thermocouple is installed on the surface of the second straight pipe section at a position 5mm to 10mm away from the inclined weld.

[0016] Optionally, the step of setting thermocouples at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section includes:

[0017] Two temperature-controlling thermocouples for plate heaters are arranged circumferentially opposite each other on the surface of the first straight pipe section at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; two temperature-measuring thermocouples are arranged circumferentially opposite each other on the surface of the first straight pipe section at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld.

[0018] Three temperature-controlling thermocouples for plate heaters are evenly arranged circumferentially on the surface of the second straight pipe section at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; three temperature-measuring thermocouples are evenly arranged circumferentially on the surface of the second straight pipe section at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld.

[0019] Optionally, after thermocouples are respectively installed at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section, the method further includes:

[0020] Use insulating cotton to cover the spot welded areas of each of the thermocouples.

[0021] Optionally, the provision of a rope heater on the surface of the beveled weld includes:

[0022] A rope heater is uniformly wound around the surface of the inclined weld from one side of the first straight pipe section to one side of the second straight pipe section.

[0023] Optionally, the step of circumferentially arranging plate heaters on the surfaces of the first straight pipe section and the second straight pipe section includes:

[0024] Two plate heaters are arranged circumferentially opposite each other on the surface of the first straight pipe section;

[0025] Three plate heaters are evenly arranged circumferentially on the surface of the second straight pipe section.

[0026] Optionally, the axial length of the plate heater relative to the reducing pipe docking assembly is 450 mm.

[0027] Optionally, when the reducing pipe assembly is placed horizontally, the thickness of the insulation cotton covering the top of the rope heater is less than the thickness of the insulation cotton covering the bottom of the rope heater.

[0028] Optionally, the heat treatment of the component includes:

[0029] During the constant temperature stage, the temperature of each thermocouple is monitored and verified.

[0030] This disclosure discloses a heat treatment method for a reducing pipe assembly, employing a combination of sheet heaters and rope heaters to achieve scientific configuration of heating power for pipes of different diameters and precise zoned temperature control for the weld heat treatment of the reducing pipes. Technical measures such as uniform winding of the rope heaters to ensure density, scientific selection of temperature control and measurement points, optimized insulation thickness, and on-site temperature verification meet the technical requirements of locating the heating center at the weld center and reducing circumferential and radial temperature gradients, thus ensuring the effectiveness and quality of post-weld heat treatment. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a reducing pipe docking assembly according to an embodiment of the present disclosure;

[0032] Figure 2 This is a schematic flowchart of a heat treatment method for a reducing pipe assembly according to another embodiment of this disclosure. Detailed Implementation

[0033] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0034] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0035] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0036] 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. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any and more of the associated listed items.

[0037] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0038] Embodiments of this disclosure provide a heat treatment method for a reducing pipe mating assembly. For example... Figure 1 As shown, the reducing pipe assembly includes a first straight pipe section A, a beveled weld seam B, and a second straight pipe section C connected in sequence, wherein the outer diameter of the first straight pipe section A is smaller than that of the second straight pipe section C.

[0039] like Figure 2 As shown, the heat treatment method for the reducing pipe assembly includes:

[0040] Step S21: Thermocouples are respectively installed at multiple predetermined positions on the surfaces of the first straight pipe section, the inclined weld, and the second straight pipe section.

[0041] Specifically, based on the structural dimensions of the reducer, the combination of rope heaters and plate heaters and the zonal control scheme are determined: confirm the material of the reducer, measure its specific specifications (such as the diameter of the pipes at both ends, wall thickness, length of the weld bevel, etc.), determine the procedures and specifications for post-weld heat treatment according to the relevant technical requirements, and determine the post-weld heat treatment temperature, single-sided heating width, number of circumferential zonal control zones for straight pipe sections, etc., according to the procedures and specifications. Calculate and determine the specifications (length * width), power, and length of the rope heater for each heating plate according to the procedures. Taking a D500*60mm / D600*60mm reducer with a 150mm bevel length and made of high-alloy 10Cr9Mo1VNbN (P91) as an example, according to the DL / T819 standard, the straight pipe sections at both ends of the reducer are arranged with 2-zone and 3-zone circumferential temperature control, respectively. 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℃, constant temperature for 5 hours, heating / cooling rate is 150℃ / 1h, single-sided heating width is 450mm, and power is 10kw.

[0042] refer to Figure 1The arrangement of thermocouples related to the rope heater: A temperature control thermocouple 5 for the rope heater is set at the 12:00 position on the surface of the inclined weld seam B relative to the bevel center of the first straight pipe section A. A first temperature measuring thermocouple 6 is set at the other end of the diameter of the temperature control thermocouple 5 on the surface of the inclined weld seam B, that is, at the 6:00 position corresponding to the temperature control thermocouple 5. A second temperature measuring thermocouple 2 is set at a position 5mm~10mm away from the inclined weld seam B on the surface of the second straight pipe section C. Thermocouple arrangement for the plate heater: Referring to the scheme determined above, circumferential thermocouples are installed at the 12:00 and 6:00 positions of the first straight pipe section A and the 12:00, 4:00 and 8:00 positions of the second straight pipe section C. A temperature control thermocouple 7 is installed at a distance of approximately δ (pipe wall thickness) and ≥50mm (60mm in this embodiment) from the center of the weld seam, and a temperature measuring thermocouple 8 is installed at a distance of twice δ (pipe wall thickness) and ≥100mm (120mm in this embodiment) from the center of the weld seam. In other words, two temperature-controlling thermocouples for plate heaters are circumferentially arranged opposite each other on the surface of the first straight pipe section A at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; two temperature-measuring thermocouples are circumferentially arranged opposite each other on the surface of the first straight pipe section A at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld; three temperature-controlling thermocouples for plate heaters are circumferentially arranged evenly on the surface of the second straight pipe section C at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; and three temperature-measuring thermocouples are circumferentially arranged evenly on the surface of the second straight pipe section C at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld.

[0043] The metal surface at the thermocouple location should be ground with a grinder to expose its metallic luster, ensuring a tight and secure spot weld between the thermocouple measuring part and the surface. The thermocouple should be fixed using an energy storage spot weld method to guarantee the accuracy of the measured temperature. The thermocouple wires corresponding to the plate heater should be led out horizontally along the diameter of the pipe, and the thermocouples corresponding to the rope heater should be led out along the gap between the rope heater and the plate heater. Both should be secured to the pipe with wire. For example, the spot welded area of ​​the thermocouple can be covered with small wads of insulation cotton to prevent direct contact between the thermocouple and the heating element, reducing the impact of the heater on the measurement accuracy when measuring pipe wall temperature.

[0044] Step S22: A plate heater is circumferentially arranged 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.

[0045] Specifically, refer to Figure 1On the surface of the inclined weld B, from one side of the first straight pipe section A to the other side of the second straight pipe section C, the rope heater 3 is wound gradually from the side with the smaller pipe diameter towards the side with the larger pipe diameter, naturally and evenly wound on the surface of the inclined weld B using the slope angle. After completing the above winding, 1 meter of excess wire is led out from both ends of the rope heater 3 to be processed into power plug connectors for easy access to the heat treatment power supply. The excess rope heater is then cut off.

[0046] The plate heaters 4 are arranged in zones according to the different pipe diameters D (unit: mm) of the straight pipe sections, as specified above. Two plate heaters are arranged circumferentially opposite each other on the surface of the first straight pipe section, and three plate heaters are evenly arranged circumferentially on the surface of the second straight pipe section. (Reference) Figure 1 Specifically, as described in this embodiment, in the first straight pipe section A, two plate heaters 4 are arranged in two sections, one above the other, facing each other. In the second straight pipe section C, one plate heater 4 is arranged in three sections, one on 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 each plate heater 4, i.e., the axial length L1 relative to the reducing pipe connection assembly, is selected as the aforementioned intermediate value of 450mm. Each plate heater 4 is fixed to the pipe with wire. Care must be taken during the arrangement of the plate heaters to avoid breaking the thermocouple spot welds. The joints of the plate heaters are located on the outer side and extend horizontally along the pipe axis, while the joints of the rope heaters extend from the middle.

[0047] Step S23: Wrap the sheet heater and the rope heater with insulating cotton.

[0048] Specifically, the insulation measures are arranged with two layers of insulation cotton 9, with a thickness not exceeding 80mm. Based on the horizontal placement of the reducer assembly in this embodiment, in order to reduce the temperature difference between the upper and lower parts of the pipe, the thickness of the insulation cotton 9 covering the heating area above the rope heater 3 can be reduced to be less than the thickness of the insulation cotton 9 covering the lower part of the rope heater 3. The specific degree of thinning can be achieved 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 thickness of the insulation cotton 9 at the 12 o'clock position can be gradually reduced to reduce the temperature difference between the upper and lower parts of the reducer.

[0049] Step S24: Set the heat treatment parameters and perform heat treatment on the component.

[0050] Specifically, the thermocouple temperature control temperature in the rope heater area is set according to the heat treatment temperature corresponding to the pipe material specified in relevant regulations. In this embodiment, the post-weld heat treatment temperature is set to 760℃. The thermocouple temperature control temperature in the plate heater area is set to 740℃, which is 20℃ lower than the rope temperature control temperature. The temperature is maintained for 5 hours, with a heating / cooling rate of 150℃ / 1 hour. Temperature control is not applied below 350℃.

[0051] For example, to ensure the accuracy of the constant temperature, during the constant temperature stage, several typical locations should be selected from each temperature-controlling thermocouple and temperature-measuring thermocouple, such as the weld seam, for on-site temperature monitoring and verification to ensure the accuracy of the thermocouple temperature and that the temperature at the measured location is consistent with the actual plate temperature display.

[0052] This disclosure discloses a heat treatment method for a reducing pipe assembly, employing a combination of sheet heaters and rope heaters to achieve scientific configuration of heating power for pipes of different diameters and precise zoned temperature control for the weld heat treatment of the reducing pipes. Technical measures such as uniform winding of the rope heaters to ensure density, scientific selection of temperature control and measurement points, optimized insulation thickness, and on-site temperature verification meet the technical requirements of locating the heating center at the weld center and reducing circumferential and radial temperature gradients, thus ensuring the effectiveness and quality of post-weld heat treatment.

[0053] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A heat treatment method for a reducing pipe assembly, characterized in that, The reducing pipe assembly includes a first straight pipe section, a beveled weld seam, 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 includes: Thermocouples are respectively installed at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section; wherein, A temperature-controlling thermocouple for a rope heater is installed on the surface of the inclined weld relative to the bevel position of the first straight pipe section; and, A first temperature-measuring thermocouple is installed on the surface of the inclined weld, at the other end of the diameter corresponding to the position of the temperature-controlling thermocouple of the rope heater; and, A second temperature-measuring thermocouple is installed on the surface of the second straight pipe section at a position 5mm to 10mm away from the inclined weld; and... Two temperature-controlling thermocouples for plate heaters are circumferentially arranged opposite each other on the surface of the first straight pipe section at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; two temperature-measuring thermocouples are circumferentially arranged opposite each other on the surface of the first straight pipe section at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld; and, Three temperature-controlling thermocouples for plate heaters are evenly arranged circumferentially on the surface of the second straight pipe section at a distance of one pipe wall thickness and not less than 50 mm from the center of the weld; three temperature-measuring thermocouples are evenly arranged circumferentially on the surface of the second straight pipe section at a distance of two pipe wall thickness and not less than 100 mm from the center of the weld. A sheet heater is provided circumferentially on the surface of the first straight pipe section and the second straight pipe section, and a rope heater is provided on the surface of the inclined weld. The sheet heater and the rope heater are wrapped with insulating cotton. Set the heat treatment parameters and perform heat treatment on the component.

2. The method according to claim 1, characterized in that, After placing thermocouples at multiple predetermined positions on the surfaces of the first straight pipe section, the beveled weld, and the second straight pipe section, the method further includes: Use insulating cotton to cover the spot welded areas of each of the thermocouples.

3. The method according to claim 1, characterized in that, The provision of a rope heater on the surface of the inclined weld includes: A rope heater is uniformly wound around the surface of the inclined weld from one side of the first straight pipe section to one side of the second straight pipe section.

4. The method according to claim 1, characterized in that, The step of circumferentially arranging plate heaters on the surfaces of the first straight pipe section and the second straight pipe section includes: Two plate heaters are arranged circumferentially opposite each other on the surface of the first straight pipe section; Three plate heaters are evenly arranged circumferentially on the surface of the second straight pipe section.

5. The method according to claim 1, characterized in that, The axial length of the plate heater relative to the reducing pipe docking assembly is 450 mm.

6. The method according to claim 1, characterized in that, When the reducing pipe assembly is placed horizontally, the insulation cotton covering the top of the rope heater is less thick than the insulation cotton covering the bottom of the rope heater.

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

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