CN112176175A - TP347 thick-wall pipeline stabilizing heat treatment method - Google Patents
TP347 thick-wall pipeline stabilizing heat treatment method Download PDFInfo
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- CN112176175A CN112176175A CN202011060936.5A CN202011060936A CN112176175A CN 112176175 A CN112176175 A CN 112176175A CN 202011060936 A CN202011060936 A CN 202011060936A CN 112176175 A CN112176175 A CN 112176175A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/40—Direct resistance heating
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/14—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes wear-resistant or pressure-resistant pipes
Abstract
A TP347 thick-walled pipeline stabilizing heat treatment method comprises the following steps: determining a heat treatment process; analyzing the reason for generating cracking in the stabilizing heat treatment according to the determined heat treatment process; and performing heat treatment construction, including treatment before heat treatment and treatment in the heat treatment implementation process. The stabilizing heat treatment method for the TP347 thick-wall pipeline disclosed by the invention has the advantages that the residual stress is reduced as much as possible on the basis of finishing the purpose of stabilizing heat treatment, and the stabilizing heat treatment method has important significance for industrial production. The invention can realize tp347 stabilization and heat treatment to ensure that the inner wall and the outer wall meet the temperature requirement. The invention can realize the effects of reducing the stress peak value and homogenizing the stress distribution while meeting the requirement of stabilizing the heat treatment temperature. The method is simple to operate and wide in applicability, and can realize the TP347 stabilization heat treatment process with different wall thicknesses.
Description
Technical Field
The invention relates to a heat treatment method for a pipeline. In particular to a stabilizing heat treatment method for a TP347 thick-wall pipeline.
Background
The TP347 material has good high-temperature oxidation resistance, wear resistance, corrosion resistance and thermal stability, so that the TP is widely applied to pipeline devices of high-pressure hydrogenation devices. Through statistical analysis of accidents of some hydrocracking devices, austenitic stainless steel welding seams and heat affected zones are the areas with the most serious corrosion damage, so that stabilizing heat treatment is necessary for welding seams processed on a construction site. In recent years, with the increase in the size of refining plants, the nominal diameter and the wall thickness of the TP347 stainless steel pipeline of a high-pressure hydrogenation plant are increasing, the probability of cracking of the butt-ring weld of the pipeline after on-site stabilization heat treatment is on the rise, and the problem of cracking is becoming more and more prominent. Whether the thick-wall stainless steel pipeline is subjected to postweld heat treatment at home and abroad is controversial.
In the traditional stabilizing heat treatment process, due to the reason that the pipe wall of a workpiece is too thick and the like, the temperature of a pipeline workpiece in the thickness direction is not uniform in the heat treatment process, and the problems of thermal stress, deformation, cracking, even scrapping and the like can be caused; in order to fully heat the inner wall and meet the requirements of a stabilizing heat treatment process, the temperature of the outer wall is often overhigh, so that the outer wall of the pipeline is overhigh to cause the problems of tissue damage and the like, thereby reducing the performance and the service life of the pipeline workpiece. And the thick-wall pipeline has large internal and external temperature difference and large thermal stress along the thickness direction and poor residual stress eliminating effect due to site construction conditions, so a new local heat treatment process is provided, the residual stress is reduced as much as possible on the basis of finishing the purpose of stabilizing heat treatment, and the method has important significance for industrial production.
Disclosure of Invention
The invention aims to solve the technical problem of providing a stabilizing heat treatment method for the TP347 thick-wall pipeline, which reduces the post-welding stabilizing heat treatment stress of the TP347 pipeline and avoids cracking after heat treatment.
The technical scheme adopted by the invention is as follows: a TP347 thick-wall pipeline stabilizing heat treatment method comprises the following steps:
1) determining a heat treatment process;
2) analyzing the reason for generating cracking in the stabilizing heat treatment according to the determined heat treatment process;
3) and performing heat treatment construction, including treatment before heat treatment and treatment in the heat treatment implementation process.
The heat treatment process determination in the step 1) is to determine the process parameters of heat treatment through finite element simulation analysis, and comprises the following steps:
(1.1) respectively calculating the heating rates of 60 ℃/h, 120 ℃/h, 180 ℃/h and 240 ℃/h, comparing the stress fields under the 4 heating rates, and obtaining the optimal heating rate by taking the stress field with the minimum stress peak value and uniform stress distribution as evaluation standards;
(1.2) respectively calculating the working conditions of 2h and 4h of heat preservation, comparing the stress distribution under different heat preservation time, and determining the optimal heat preservation time by taking the heat preservation time with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.3) calculating widths of heating belts of 300mm, 400mm and 500mm, comparing stress fields under different widths of the heating belts, and determining the optimal width of the heating belt by taking the width of the heating belt with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.4) calculating stress fields under two working conditions of air cooling and slow cooling, comparing the stress fields under the two working conditions, and determining an optimal cooling mode by taking a cooling mode with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.5) calculating two working conditions of smooth transition and non-smooth transition of the welding seam, comparing stress fields under the two working conditions, and determining the optimal welding seam form by taking the working condition of minimum stress peak value and uniform stress distribution as a judgment standard.
The reasons for the generation of cracks in the stabilizing heat treatment in the step 2) include:
(2.1) when the temperature difference between the inner wall and the outer wall is too large, large thermal stress is generated in the heat treatment process, so that large residual stress exists in the heat preservation process and after the heat preservation process and the heat treatment, and the risk of cracking of a welding seam is increased;
to the too big problem of inside and outside wall difference in temperature, through carrying out theoretical analysis to the radiating factor of influence pipeline inner wall, obtain to be certain-time at pipeline wall thickness, the inner wall temperature receives inner wall radiation and convective heat transfer's influence, and the inside and outside wall difference in temperature when the pipeline stabilization heat treatment promptly depends on how much of inner wall radiation and convection current, because can't carry out conventional heat preservation to the pipeline inner wall in the engineering reality consequently, take the inner wall to settle the heat preservation frock and carry out heat preservation to the inner wall and handle to through increasing heating tape width, the determination of heating tape width is: the wall thickness is more than or equal to 50mm, and the width of the heating belt is set to be 500-600 mm; the wall thickness is less than 50mm, and the width of the heating belt is set to be 400-500 mm, so that the radiation and convection heat exchange of the inner wall is reduced;
(2.2) the welding seam is not subjected to smooth transition, and local stress concentration is generated at the joint of the welding seam, so that the stress distribution at the welding seam is complex, and the cracking risk is increased;
for the form of the welding seam, in the engineering practice, the welding seam of the outer wall is polished into an arc with a radian of 8-10 degrees so as to reduce stress concentration in the heat treatment process;
(2.3) in the cooling process, rapidly cooling to ensure that the deformation of the welding joints with different thicknesses is inconsistent, and generating residual deformation to influence the product quality;
and for the selection of the cooling mode, after the heat treatment and heat preservation are finished, the power supply is switched off, the heat preservation cotton is not removed, and when the temperature is slowly reduced to 400 ℃, the heat preservation cotton is removed and naturally cooled in the air.
In step 3)
(3.1) the treatment before heat treatment, comprising:
(3.1.1) Heat treatment of documents, definition of tasks of heat treatment personnel and readiness of heat treatment equipment, in addition to ensuring good weather conditions for heat treatment and reliable guarantee of power supply, wherein,
the heat treatment file comprises a construction drawing, a technical file related to heat treatment, a construction scheme and a welding process rule;
clear heat treatment personnel task: the method comprises the steps of timely heat treatment operation, accurate and complete recording and various sudden accidents;
the heat treatment apparatus includes: preparing a tool, equipment and a tool, and ensuring that the heating wire, the temperature compensation wire, the thermocouple, the temperature control box and the paperless recorder with the sound-light alarm function are in good states;
(3.1.2) smooth transition of the surface of the welding seam and cleaning of the welding seam;
(3.1.3) spot welding of thermocouples and wiring thereof, wherein the thermocouples comprise two types of thermocouples: the temperature thermocouple at the welding seam and the temperature control thermocouple on the heating plate are electrically welded on the heat treatment pipeline, and the temperature control thermocouple on the heating plate is electrically welded in the highest temperature area of the heating plate; according to the arrangement diagram of the temperature thermocouple, scribing and spot welding are carried out at the spot welding position of a welding seam, and the connection between the temperature thermocouple and a paperless recorder is carried out; and for the temperature-controlled thermocouple on the heating plate, performing spot welding and connection of the temperature-controlled thermocouple corresponding to the heating plate, and checking to confirm good conduction.
(3.1.4) laying and fixing the heating sheet, firstly, not fixing the heating sheet after the heating sheet is in place, checking whether the wiring states of all temperature measuring and temperature controlling thermocouples are good or not, if no problem exists, fixing the heating sheet, setting the length of the heating sheet to be 500-600 mm, symmetrically distributing the heating sheet along two sides of a welding line, and using a steel wire fastening mode at the outer side of the heating sheet tool to ensure that the heating sheet is well attached to a steel plate; if the problem exists, the connection is reconnected;
(3.1.5) positioning, fixing and measuring point arrangement of the outer side heat insulation cotton, and positioning and fixing the heat insulation cotton tool after the heating sheet tool is fixed;
(3.1.6) installing and fixing an inner wall heat preservation tool, tightly winding heat preservation cotton on the heat preservation tool, and fastening the heat preservation cotton by using an iron wire, wherein the heat preservation cotton is ensured to have a set resilience space during fastening and can be tightly attached to the inner wall through free resilience, after the heat preservation cotton and the tool are assembled, the tool with the heat preservation cotton fastened is pushed to the position near the inner wall of a welding line by using a conveying device, the length of the heat preservation cotton on the inner wall is 700-800 mm corresponding to the length of the heat preservation cotton on the outer side, and the pushing device is taken out after the installation is finished, and conveying wires on the tool are retained outside the pipeline, so that the inner wall heat preservation tool is convenient;
(3.2) the heat treatment process of the present invention, which comprises:
(3.2.1) setting a heat treatment curve, setting the heat treatment curve of the temperature control box according to the determined heat treatment process, starting a power supply, ensuring free temperature rise below 300 ℃ in the heat treatment process, not limiting the temperature rise rate, reducing the temperature rise rate when the temperature rises to above 300 ℃, enabling the temperature rise rate to be 60 ℃/h, and slowly raising the temperature to the set temperature of 900 ℃;
(3.2.2) electrifying to heat up, setting the heating time, and after the heating process is finished, namely the temperature control thermocouple reaches the lower limit of the heat preservation range, preserving the heat for 4 hours to ensure that the temperature of each point tends to be stable;
(3.2.3) in the heat treatment heat preservation and heat preservation stage, observing the temperature of the temperature thermocouple, increasing the temperature control temperature of the corresponding heating sheet for the lower limit temperature measurement point close to the heat preservation range, and decreasing the temperature control temperature of the corresponding heating sheet for the upper limit temperature measurement point close to the heat preservation range, so that the temperature is maintained in the set heat preservation range, the heat preservation time of all welding seams of the cylinder in a single heat treatment cycle is ensured to reach the heat preservation time required by the standard, and meanwhile, the temperature reduction starting time is set;
(3.2.4) cooling, after heat preservation is finished, turning off a heat treatment power supply, not removing heat preservation cotton, slowly cooling a pipeline welding line to 400 ℃ under the heat preservation effect of the heat preservation cotton, then removing the heat preservation cotton and carrying out air cooling;
(3.2.5) exporting and storing the heat treatment data, recording the serial number of the paperless recorder when copying the data, and sorting and compiling the heat treatment record; and simultaneously, removing the heat treatment tool and the heating sheet, removing the thermocouple, and carrying out PT inspection on the point fixing area after the heat treatment tool and the heating sheet are removed.
The following treatment processes are adopted in the step (3.1.2):
(a) welding a transition area of the welding line and the base metal, and then performing a layer of cover surface welding to wrap the fusion line;
(b) performing repair welding on the place with the groove;
(c) polishing and grinding the welding line, wherein the grinding standard is that the welding line and the base metal realize smooth transition to form an 8-10-degree arc so as to ensure that no stress concentration exists;
(d) during heat treatment, the weld seam and the range of 500mm on both sides of the weld seam are free of grease, machining liquid, residues for detection and other pollutants harmful to the shell material after heating.
And (3.1.3) numbering the thermocouples one by one when the thermocouples are connected, wherein the numbers are simultaneously attached to two ends of a temperature compensation lead connected with the corresponding thermocouples and a display channel of a paperless recorder or a temperature control box so as to prevent misconnection and misconnection of the thermocouples and ensure the accuracy of temperature measurement and control.
In the step (3.1.4), when the heat-insulating cotton tool is laid, the fixed heating sheet and the fixed conducting wire are avoided from being touched, and the heat-insulating cotton tool is well attached to the cylinder; the laying length of the outside heat-preservation cotton is 700-800 mm, the outside heat-preservation cotton is symmetrically distributed along the two sides of the welding line and is fastened by iron wires, so that the heat-preservation cotton is tightly attached to the heating sheet, and the heat-preservation effect is ensured.
The stabilizing heat treatment method for the TP347 thick-wall pipeline disclosed by the invention has the advantages that the residual stress is reduced as much as possible on the basis of finishing the purpose of stabilizing heat treatment, and the stabilizing heat treatment method has important significance for industrial production.
1. The invention can realize tp347 stabilization and heat treatment to ensure that the inner wall and the outer wall meet the temperature requirement.
2. The invention can realize the effects of reducing the stress peak value and homogenizing the stress distribution while meeting the requirement of stabilizing the heat treatment temperature.
3. The method is simple to operate and wide in applicability, and can realize the TP347 stabilization heat treatment process with different wall thicknesses.
Drawings
FIG. 1 is a flow chart of a method for stabilizing heat treatment of a TP347 thick-walled pipe according to the present invention;
FIG. 2 is a graph showing the stress in the vicinity of a weld at the time of the most likely cracking in heat treatment according to example 2 of the present invention;
FIG. 3 is a graph showing the stress in the vicinity of a weld at the time of most likely cracking in heat treatment according to example 1 of the present invention;
FIG. 4 is a graph showing the stress in the vicinity of a weld at the time of the most likely cracking in the heat treatment according to example 1 of the present invention.
Detailed Description
The following describes a TP347 thick-walled pipe stabilizing heat treatment method in detail with reference to the following examples and accompanying drawings.
As shown in FIG. 1, the method for stabilizing and heat-treating the TP347 thick-wall pipeline comprises the following steps:
1) determining a heat treatment process, namely determining the process parameters of the heat treatment through finite element simulation analysis, wherein the process parameters comprise:
(1.1) respectively calculating the heating rates of 60 ℃/h, 120 ℃/h, 180 ℃/h and 240 ℃/h, comparing the stress fields under the 4 heating rates, and obtaining the optimal heating rate by taking the stress field with the minimum stress peak value and uniform stress distribution as evaluation standards;
(1.2) respectively calculating the working conditions of 2h and 4h of heat preservation, comparing the stress distribution under different heat preservation time, and determining the optimal heat preservation time by taking the heat preservation time with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.3) calculating widths of heating belts of 300mm, 400mm and 500mm, comparing stress fields under different widths of the heating belts, and determining the optimal width of the heating belt by taking the width of the heating belt with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.4) calculating stress fields under two working conditions of air cooling and slow cooling, comparing the stress fields under the two working conditions, and determining an optimal cooling mode by taking a cooling mode with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.5) calculating two working conditions of smooth transition and non-smooth transition of the welding seam, comparing stress fields under the two working conditions, and determining the optimal welding seam form by taking the working condition of minimum stress peak value and uniform stress distribution as a judgment standard.
2) Analyzing the reason for generating cracking in the stabilizing heat treatment according to the determined heat treatment process; the reasons for generating cracks in the stabilizing heat treatment comprise:
(2.1) when the temperature difference between the inner wall and the outer wall is too large, large thermal stress is generated in the heat treatment process, so that large residual stress exists in the heat preservation process and after the heat preservation process and the heat treatment, and the risk of cracking of a welding seam is increased;
to the too big problem of inside and outside wall difference in temperature, through carrying out theoretical analysis to the radiating factor of influence pipeline inner wall, obtain to be certain-time at pipeline wall thickness, the inner wall temperature receives inner wall radiation and convective heat transfer's influence, the inside and outside wall difference in temperature when pipeline stabilization heat treatment promptly depends on how much of inner wall radiation and convection current, because can't carry out conventional heat preservation (the cotton is difficult for laying and dismantling of heat preservation) consequently to the pipeline inner wall in the engineering reality, take the inner wall to settle the heat preservation frock and carry out heat preservation processing to the inner wall to through increasing heating tape width, the determination of heating tape width is: the wall thickness is more than or equal to 50mm, and the width of the heating belt is set to be 500-600 mm; the wall thickness is less than 50mm, and the width of the heating belt is set to be 400-500 mm, so that the radiation and convection heat exchange of the inner wall is reduced;
(2.2) the welding seam is not subjected to smooth transition, and local stress concentration is generated at the joint of the welding seam, so that the stress distribution at the welding seam is complex, and the cracking risk is increased;
for the form of the welding seam, in the engineering practice, the welding seam of the outer wall is polished into an arc with a radian of 8-10 degrees so as to reduce stress concentration in the heat treatment process;
(2.3) in the cooling process, rapidly cooling to ensure that the deformation of the welding joints with different thicknesses is inconsistent, and generating residual deformation to influence the product quality;
and for the selection of the cooling mode, after the heat treatment and heat preservation are finished, the power supply is switched off, the heat preservation cotton is not removed, and when the temperature is slowly reduced to 400 ℃, the heat preservation cotton is removed and naturally cooled in the air.
3) Performing heat treatment construction including treatment before heat treatment and treatment in the heat treatment implementation process, wherein,
(3.1) the treatment before heat treatment, comprising:
(3.1.1) Heat treatment of documents, definition of tasks of heat treatment personnel and readiness of heat treatment equipment, in addition to ensuring good weather conditions for heat treatment and reliable guarantee of power supply, wherein,
the heat treatment file comprises a construction drawing, a technical file related to heat treatment, a construction scheme and a welding process rule;
clear heat treatment personnel task: the method comprises the steps of timely heat treatment operation and accurate and complete recording, and various accidents such as large sound and abnormal falling of a thermocouple;
the heat treatment apparatus includes: preparing a tool, equipment and a tool, and ensuring that the heating wire, the temperature compensation wire, the thermocouple, the temperature control box and the paperless recorder with the sound-light alarm function are in good states;
(3.1.2) smooth transition of the surface of the welding seam and cleaning of the welding seam, and according to the step 1) and the step 3), the smoothness degree of the welding seam influences the integrity of the welding seam in the heat treatment process to a certain extent. The following processing procedures are adopted:
(a) welding a transition area of the welding line and the base metal, and then performing a layer of cover surface welding to wrap the fusion line;
(b) performing repair welding on the place with the groove;
(c) polishing and grinding the welding line, wherein the grinding standard is that the welding line and the base metal realize smooth transition to form an 8-10-degree arc so as to ensure that no stress concentration exists;
(d) during heat treatment, the weld seam and the range of 500mm on both sides of the weld seam are free of grease, machining liquid, residues for detection and other pollutants harmful to the shell material after heating.
(3.1.3) spot welding of thermocouples and wiring thereof, wherein the thermocouples comprise two types of thermocouples: the temperature thermocouple at the welding seam and the temperature control thermocouple on the heating plate are electrically welded on the heat treatment pipeline, and the temperature control thermocouple on the heating plate is electrically welded in the highest temperature area of the heating plate; according to the arrangement diagram of the temperature thermocouple, scribing and spot welding are carried out at the spot welding position of a welding seam, and the connection between the temperature thermocouple and a paperless recorder is carried out; and for the temperature-controlled thermocouple on the heating plate, performing spot welding and connection of the temperature-controlled thermocouple corresponding to the heating plate, and checking to confirm good conduction.
When the thermocouples are connected, the thermocouples are numbered one by one, and the numbers are simultaneously attached to two ends of a temperature compensation lead wire connected with the corresponding thermocouple and a display channel of a paperless recorder or a temperature control box, so that misconnection and misconnection of the thermocouples are prevented, and the accuracy of temperature measurement and control is ensured
(3.1.4) laying and fixing the heating sheet, firstly, not fixing the heating sheet after the heating sheet is in place, checking whether the wiring states of all temperature measuring and temperature controlling thermocouples are good or not, if no problem exists, fixing the heating sheet, setting the length of the heating sheet to be 500-600 mm, symmetrically distributing the heating sheet along two sides of a welding line, and using a steel wire fastening mode at the outer side of the heating sheet tool to ensure that the heating sheet is well attached to a steel plate; if the problem exists, the connection is reconnected;
when the heat-preservation cotton tool is laid, the fixed heating sheet and the fixed conducting wire are prevented from being touched, and the heat-preservation cotton tool is well attached to the cylinder; the laying length of the outside heat-preservation cotton is 700-800 mm, the outside heat-preservation cotton is symmetrically distributed along the two sides of the welding line and is fastened by iron wires, so that the heat-preservation cotton is tightly attached to the heating sheet, and the heat-preservation effect is ensured.
(3.1.5) positioning, fixing and measuring point arrangement of the outer side heat insulation cotton, and positioning and fixing the heat insulation cotton tool after the heating sheet tool is fixed;
(3.1.6) installation and fixed of inner wall heat preservation frock, closely twine the heat preservation cotton above the frock, and fasten with the iron wire, ensure during the fastening that the heat preservation cotton has the resilience space of settlement, can closely laminate through freely kick-backing and inner wall at the inner wall, after the assembly of heat preservation cotton and frock finishes, use conveyor with the fastening have near the frock propelling movement of heat preservation cotton to the welding seam inner wall, the cotton length of inner wall heat preservation is 700mm ~ 800mm with the outside correspondence is unanimous, take out pusher after the installation finishes, and stay the conveying silk hysteresis on the frock outside the pipeline, in order to make things convenient for the dismantlement of inner wall heat preservation frock.
(3.2) the heat treatment process of the present invention, which comprises:
(3.2.1) setting a heat treatment curve, setting the heat treatment curve of the temperature control box according to the determined heat treatment process, starting a power supply, ensuring free temperature rise below 300 ℃ in the heat treatment process, not limiting the temperature rise rate, reducing the temperature rise rate when the temperature rises to above 300 ℃, enabling the temperature rise rate to be 60 ℃/h, and slowly raising the temperature to the set temperature of 900 ℃;
(3.2.2) electrifying to heat up, setting the heating time, and after the heating process is finished, namely the temperature control thermocouple reaches the lower limit of the heat preservation range, preserving the heat for 4 hours to ensure that the temperature of each point tends to be stable;
(3.2.3) in the heat treatment heat preservation and heat preservation stage, observing the temperature of the temperature thermocouple, increasing the temperature control temperature of the corresponding heating sheet for the lower limit temperature measurement point close to the heat preservation range, and decreasing the temperature control temperature of the corresponding heating sheet for the upper limit temperature measurement point close to the heat preservation range, so that the temperature is maintained in the set heat preservation range, the heat preservation time of all welding seams of the cylinder in a single heat treatment cycle is ensured to reach the heat preservation time required by the standard, and meanwhile, the temperature reduction starting time is set;
(3.2.4) cooling, after heat preservation is finished, turning off a heat treatment power supply, not removing heat preservation cotton, slowly cooling a pipeline welding line to 400 ℃ under the heat preservation effect of the heat preservation cotton, then removing the heat preservation cotton and carrying out air cooling;
(3.2.5) exporting and storing the heat treatment data, recording the serial number of the paperless recorder when copying the data, and sorting and compiling the heat treatment record; and simultaneously, removing the heat treatment tool and the heating sheet, removing the thermocouple, and carrying out PT inspection on the point fixing area after the heat treatment tool and the heating sheet are removed.
Case one:
as shown in FIG. 2, an axisymmetric model is established with a thick-walled pipe having dimensions of
And (3) analyzing the pipeline welding and heat treatment processes by using a numerical simulation method, wherein the V-shaped groove comprises 30 total welding craters. The axial stress distribution at the warm-up time is shown in fig. 3 near the output duct weld along path P1. The ordinate in figure 3 represents the axial stress along the path of the pipe outer wall P1 and the abscissa represents 150mm from each side of the weld. As can be seen from FIG. 3, the heat treatment method for increasing the width of the heating band adopted by the invention can effectively reduce the axial stress value near the welding seam, change the stress distribution state, obviously reduce the stress at the moment of most easy cracking in the heat treatment, and effectively avoid the risk of pipeline cracking in the heat treatment process, the scheme has obvious influence on the final improvement effect, the heating band width is controlled to be 500mm, and the stress improvement effect is most obvious.
Case two:
as shown in FIG. 2, an axisymmetric model is established with a thick-walled pipe having dimensions of
And (3) analyzing the pipeline welding and heat treatment processes by using a numerical simulation method, wherein the V-shaped groove comprises 30 total welding craters. In the embodiment, the influence of the temperature difference between the inner wall and the outer wall on the stress in the heat treatment process is reduced by considering the internal heat-preservation tool. The axial distribution of the path P1 near the weld of the outer wall of the outlet duct is shown in fig. 4. In the figure 4, the ordinate represents the axial stress along the path of the pipeline outer wall P1, and the abscissa represents the distance of 150mm from each side of the welding line, so that the temperature difference between the inner wall and the outer wall in the heat treatment process can be reduced to 25 ℃ by the process of filling the heat-insulating cotton in the inner wall tool, and the requirement of stabilizing heat treatment can be met. By reducing the temperature difference between the inner wall and the outer wall, the stress value near the welding line can be obviously reduced, so that the stress peak value in the heat preservation process is reduced from 85MPa of the traditional stabilizing heat treatment process to 49MPaEffectively avoiding the risk of pipeline cracking caused by overlarge stress in the heat treatment process.
Claims (7)
1. A TP347 thick-wall pipeline stabilizing heat treatment method is characterized by comprising the following steps:
1) determining a heat treatment process;
2) analyzing the reason for generating cracking in the stabilizing heat treatment according to the determined heat treatment process;
3) and performing heat treatment construction, including treatment before heat treatment and treatment in the heat treatment implementation process.
2. The method as claimed in claim 1, wherein the determining the heat treatment process in step 1) is a process parameter determining the heat treatment by finite element simulation analysis, and comprises:
(1.1) respectively calculating the heating rates of 60 ℃/h, 120 ℃/h, 180 ℃/h and 240 ℃/h, comparing the stress fields under the 4 heating rates, and obtaining the optimal heating rate by taking the stress field with the minimum stress peak value and uniform stress distribution as evaluation standards;
(1.2) respectively calculating the working conditions of 2h and 4h of heat preservation, comparing the stress distribution under different heat preservation time, and determining the optimal heat preservation time by taking the heat preservation time with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.3) calculating widths of heating belts of 300mm, 400mm and 500mm, comparing stress fields under different widths of the heating belts, and determining the optimal width of the heating belt by taking the width of the heating belt with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.4) calculating stress fields under two working conditions of air cooling and slow cooling, comparing the stress fields under the two working conditions, and determining an optimal cooling mode by taking a cooling mode with the minimum stress peak value and uniform stress distribution as a judgment standard;
(1.5) calculating two working conditions of smooth transition and non-smooth transition of the welding seam, comparing stress fields under the two working conditions, and determining the optimal welding seam form by taking the working condition of minimum stress peak value and uniform stress distribution as a judgment standard.
3. The method of claim 1, wherein the stabilizing heat treatment of the TP347 thick-walled pipeline in the step 2) causes cracking, and comprises the following steps:
(2.1) when the temperature difference between the inner wall and the outer wall is too large, large thermal stress is generated in the heat treatment process, so that large residual stress exists in the heat preservation process and after the heat preservation process and the heat treatment, and the risk of cracking of a welding seam is increased;
to the too big problem of inside and outside wall difference in temperature, through carrying out theoretical analysis to the radiating factor of influence pipeline inner wall, obtain to be certain-time at pipeline wall thickness, the inner wall temperature receives inner wall radiation and convective heat transfer's influence, and the inside and outside wall difference in temperature when the pipeline stabilization heat treatment promptly depends on how much of inner wall radiation and convection current, because can't carry out conventional heat preservation to the pipeline inner wall in the engineering reality consequently, take the inner wall to settle the heat preservation frock and carry out heat preservation to the inner wall and handle to through increasing heating tape width, the determination of heating tape width is: the wall thickness is more than or equal to 50mm, and the width of the heating belt is set to be 500-600 mm; the wall thickness is less than 50mm, and the width of the heating belt is set to be 400-500 mm, so that the radiation and convection heat exchange of the inner wall is reduced;
(2.2) the welding seam is not subjected to smooth transition, and local stress concentration is generated at the joint of the welding seam, so that the stress distribution at the welding seam is complex, and the cracking risk is increased;
for the form of the welding seam, in the engineering practice, the welding seam of the outer wall is polished into an arc with a radian of 8-10 degrees so as to reduce stress concentration in the heat treatment process;
(2.3) in the cooling process, rapidly cooling to ensure that the deformation of the welding joints with different thicknesses is inconsistent, and generating residual deformation to influence the product quality;
and for the selection of the cooling mode, after the heat treatment and heat preservation are finished, the power supply is switched off, the heat preservation cotton is not removed, and when the temperature is slowly reduced to 400 ℃, the heat preservation cotton is removed and naturally cooled in the air.
4. The method for stabilizing and heat-treating the TP347 thick-walled pipeline according to claim 1, wherein in the step 3), the heat treatment is carried out
(3.1) the treatment before heat treatment, comprising:
(3.1.1) Heat treatment of documents, definition of tasks of heat treatment personnel and readiness of heat treatment equipment, in addition to ensuring good weather conditions for heat treatment and reliable guarantee of power supply, wherein,
the heat treatment file comprises a construction drawing, a technical file related to heat treatment, a construction scheme and a welding process rule;
clear heat treatment personnel task: the method comprises the steps of timely heat treatment operation, accurate and complete recording and various sudden accidents;
the heat treatment apparatus includes: preparing a tool, equipment and a tool, and ensuring that the heating wire, the temperature compensation wire, the thermocouple, the temperature control box and the paperless recorder with the sound-light alarm function are in good states;
(3.1.2) smooth transition of the surface of the welding seam and cleaning of the welding seam;
(3.1.3) spot welding of thermocouples and wiring thereof, wherein the thermocouples comprise two types of thermocouples: the temperature thermocouple at the welding seam and the temperature control thermocouple on the heating plate are electrically welded on the heat treatment pipeline, and the temperature control thermocouple on the heating plate is electrically welded in the highest temperature area of the heating plate; according to the arrangement diagram of the temperature thermocouple, scribing and spot welding are carried out at the spot welding position of a welding seam, and the connection between the temperature thermocouple and a paperless recorder is carried out; and for the temperature-controlled thermocouple on the heating plate, performing spot welding and connection of the temperature-controlled thermocouple corresponding to the heating plate, and checking to confirm good conduction.
(3.1.4) laying and fixing the heating sheet, firstly, not fixing the heating sheet after the heating sheet is in place, checking whether the wiring states of all temperature measuring and temperature controlling thermocouples are good or not, if no problem exists, fixing the heating sheet, setting the length of the heating sheet to be 500-600 mm, symmetrically distributing the heating sheet along two sides of a welding line, and using a steel wire fastening mode at the outer side of the heating sheet tool to ensure that the heating sheet is well attached to a steel plate; if the problem exists, the connection is reconnected;
(3.1.5) positioning, fixing and measuring point arrangement of the outer side heat insulation cotton, and positioning and fixing the heat insulation cotton tool after the heating sheet tool is fixed;
(3.1.6) installing and fixing an inner wall heat preservation tool, tightly winding heat preservation cotton on the heat preservation tool, and fastening the heat preservation cotton by using an iron wire, wherein the heat preservation cotton is ensured to have a set resilience space during fastening and can be tightly attached to the inner wall through free resilience, after the heat preservation cotton and the tool are assembled, the tool with the heat preservation cotton fastened is pushed to the position near the inner wall of a welding line by using a conveying device, the length of the heat preservation cotton on the inner wall is 700-800 mm corresponding to the length of the heat preservation cotton on the outer side, and the pushing device is taken out after the installation is finished, and conveying wires on the tool are retained outside the pipeline, so that the inner wall heat preservation tool is convenient;
(3.2) the heat treatment process of the present invention, which comprises:
(3.2.1) setting a heat treatment curve, setting the heat treatment curve of the temperature control box according to the determined heat treatment process, starting a power supply, ensuring free temperature rise below 300 ℃ in the heat treatment process, not limiting the temperature rise rate, reducing the temperature rise rate when the temperature rises to above 300 ℃, enabling the temperature rise rate to be 60 ℃/h, and slowly raising the temperature to the set temperature of 900 ℃;
(3.2.2) electrifying to heat up, setting the heating time, and after the heating process is finished, namely the temperature control thermocouple reaches the lower limit of the heat preservation range, preserving the heat for 4 hours to ensure that the temperature of each point tends to be stable;
(3.2.3) in the heat treatment heat preservation and heat preservation stage, observing the temperature of the temperature thermocouple, increasing the temperature control temperature of the corresponding heating sheet for the lower limit temperature measurement point close to the heat preservation range, and decreasing the temperature control temperature of the corresponding heating sheet for the upper limit temperature measurement point close to the heat preservation range, so that the temperature is maintained in the set heat preservation range, the heat preservation time of all welding seams of the cylinder in a single heat treatment cycle is ensured to reach the heat preservation time required by the standard, and meanwhile, the temperature reduction starting time is set;
(3.2.4) cooling, after heat preservation is finished, turning off a heat treatment power supply, not removing heat preservation cotton, slowly cooling a pipeline welding line to 400 ℃ under the heat preservation effect of the heat preservation cotton, then removing the heat preservation cotton and carrying out air cooling;
(3.2.5) exporting and storing the heat treatment data, recording the serial number of the paperless recorder when copying the data, and sorting and compiling the heat treatment record; and simultaneously, removing the heat treatment tool and the heating sheet, removing the thermocouple, and carrying out PT inspection on the point fixing area after the heat treatment tool and the heating sheet are removed.
5. A method for stabilizing heat treatment of TP347 thick-walled pipeline according to claim 4, characterized in that the step (3.1.2) adopts the following treatment processes:
(a) welding a transition area of the welding line and the base metal, and then performing a layer of cover surface welding to wrap the fusion line;
(b) performing repair welding on the place with the groove;
(c) polishing and grinding the welding line, wherein the grinding standard is that the welding line and the base metal realize smooth transition to form an 8-10-degree arc so as to ensure that no stress concentration exists;
(d) during heat treatment, the weld seam and the range of 500mm on both sides of the weld seam are free of grease, machining liquid, residues for detection and other pollutants harmful to the shell material after heating.
6. The method for stabilizing and heat-treating the TP347 thick-walled pipeline according to claim 4, wherein in the step (3.1.3), the thermocouples are numbered one by one during the connection of the thermocouples, and the numbers are simultaneously attached to two ends of a temperature compensation lead wire connected with the corresponding thermocouple and a display channel of a paperless recorder or a temperature control box, so that the misconnection and the misconnection of the thermocouples are prevented, and the accuracy of temperature measurement and temperature control is ensured.
7. The method for stabilizing and heat-treating the TP347 thick-wall pipeline according to claim 4, wherein in the step (3.1.4), the insulation cotton tool is laid without touching the fixed heating plate and the fixed conducting wire, so that the insulation cotton tool is well attached to the cylinder; the laying length of the outside heat-preservation cotton is 700-800 mm, the outside heat-preservation cotton is symmetrically distributed along the two sides of the welding line and is fastened by iron wires, so that the heat-preservation cotton is tightly attached to the heating sheet, and the heat-preservation effect is ensured.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113361157A (en) * | 2021-05-27 | 2021-09-07 | 燕山大学 | Motion simulation method for electromagnetic heat treatment of offshore oil steel pipe |
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| CN106319191A (en) * | 2016-10-21 | 2017-01-11 | 中国化学工程第六建设有限公司 | Postweld stabilizing thermal treatment method for pipeline made of TP347 material |
| CN110396590A (en) * | 2019-08-29 | 2019-11-01 | 中国石油大学(华东) | Large pressurized vessel case heat treating method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106319191A (en) * | 2016-10-21 | 2017-01-11 | 中国化学工程第六建设有限公司 | Postweld stabilizing thermal treatment method for pipeline made of TP347 material |
| CN110396590A (en) * | 2019-08-29 | 2019-11-01 | 中国石油大学(华东) | Large pressurized vessel case heat treating method |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113361157A (en) * | 2021-05-27 | 2021-09-07 | 燕山大学 | Motion simulation method for electromagnetic heat treatment of offshore oil steel pipe |
| CN113361157B (en) * | 2021-05-27 | 2022-06-24 | 燕山大学 | Motion simulation method for electromagnetic heat treatment of offshore oil steel pipe |
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