Quality control method for high-frequency straight welded pipe
Technical Field
The invention belongs to the field of production of high-frequency welded pipes, and particularly relates to a quality control method for a high-frequency straight welded pipe.
Background
The high-frequency straight welded pipe is pressure welding without filling flux, and mainly utilizes the skin effect and proximity effect of high-frequency current to quickly raise the temperature of two sides of the welded seam to the welding temperature, and the two sides of the welded seam are melted into a whole by means of the pressure of a squeeze roll. Compared with a seamless steel pipe, the high-frequency straight welded pipe has the advantages of high production efficiency, good mechanical property, strong pressure resistance and the like, and is widely applied to the transportation of oil gas and the like at present. The proportion of welded pipes in oil well pipes used in developed countries such as the United states and Japan accounts for half, but China is only one tenth and is mostly used in the surface layer of oil wells. In recent years, welded pipes are gradually popularized in oil fields in China, the application range of the welded pipes on oil and gas pipelines is gradually expanded, and accidents such as water pressure leakage and bursting still occur occasionally. The direct cause of accidents is that the high-frequency straight welded pipe has quality problems of cold welding, pinholes, inclusions and the like at the welding seam. The main reasons of the problems are that the temperature distribution of the heat affected zone is not uniform, and the improvement of the temperature distribution of the heat affected zone can improve the quality of the welded pipe and the utilization ratio of the high-frequency straight welded pipe.
The high-frequency straight welded pipe mainly utilizes the skin effect of high-frequency current, so that the induced magnetic field at the welding seam has the highest magnetic induction intensity at the inner edge and the outer edge, the induced magnetic field generates induced current, the temperature of the inner edge and the outer edge of the side edge to be welded of the welding seam is overhigh due to the heat generation of the current, the temperature distribution temperature difference is larger, the welded pipe generates larger residual stress at the welding seam, and the quality of the welding seam is greatly reduced. In order to solve the problem, a high-frequency straight welded pipe quality control method is provided starting from the shape of the side edge to be welded so as to improve the welding environment and the welded pipe quality.
Disclosure of Invention
The invention overcomes the defects in the prior art, provides a quality control method for a high-frequency straight welded pipe, and is realized by the following technical scheme:
specifically, the quality control method for the high-frequency straight welded pipe comprises the following steps:
s1, acquiring technological parameters of actually producing the high-frequency welded pipe in a factory, and performing finite element temperature field simulation by adopting ANSYS according to the technological parameters to obtain temperature field distribution;
s2, setting each process parameter and determining corresponding numerical value, determining the lowest temperature point in the welding line direction according to the temperature distribution condition, temporarily setting the temperature point as the position of the point O, determining the numerical value of the distance k between the point O and the outer surface, setting the single-time increment delta of the outer corner alpha and the inner corner beta, taking the initial value of the simulation times i of the outer corner alpha as 0, taking the initial value of the simulation times j of the inner corner as 0, and taking alpha0=0,β0=0;
S3, determining the values of the outer corner alpha and the inner corner beta, and specifically comprising the following substeps:
s31, firstly, taking the outer corner alpha as 1 time increment delta, wherein i is 1, the inner corner beta is sequentially valued from small to large according to the multiple of delta increment until the inner corner beta is more than 15 degrees, carrying out temperature field simulation in times to obtain the temperature in the direction of welding seam COD, and recording the temperature difference delta T between the highest temperature and the lowest temperature in the direction of welding seam COD in the simulation result of each time of inner corner beta value simulation1j;
S32, taking the outer corner alpha as 2 multiplication quantity delta, wherein i is 2, the inner corner beta is sequentially valued from small to large according to the multiple of delta increment until the inner corner beta is more than 15 degrees, and carrying out temperature field simulation in different times to obtain the temperature in the direction of welding seam CODRecording the temperature difference delta T between the highest temperature and the lowest temperature in the COD direction of the welding seam in the simulation result of each internal corner beta value simulation2j;
S33, taking the external corner alpha as i-time increment delta, repeating the steps until the external corner alpha is more than 20 degrees, and then according to the recorded temperature difference delta TijDetermining the minimum temperature difference as TminAnd record the outer corner alpha at that timeiAnd inner edge angle betajI.e. the values of the outer and inner corners alpha, beta and the minimum temperature difference TminThe determination process is respectively shown as formula (1), formula (2) and formula (3);
Tmin=fmin{ΔT11,ΔT12,...ΔT1j,ΔT21,ΔT22,...,ΔT21,ΔT22,...ΔTij-1ΔTij} (3)
wherein i and j are both simulation times, alpha is an outer corner, beta is an inner corner, and TminTo a minimum temperature difference, Δ TijIs the temperature difference;
s4, adjusting and determining the optimal value of the O point position parameter k value, and using the outside corner alpha determined in the step S3iAnd inner edge angle betajChanging the k value in the step S2, setting the initial increment of the k value to be 0.05h, sequentially taking the k value from 0.05h to 1h in the simulation process, respectively carrying out temperature field numerical simulation on each parameter, recording the temperature difference delta T of each time, taking the k value when the temperature difference is minimum as the optimal value of the k value, wherein the specific calculation method is shown as a formula (4) and a formula (5);
Tmin=fmin{ΔT1,ΔT2,......ΔTr-1,ΔTr} (5)
wherein k is the distance from the point O to the outer surface, r is the k value adjustment times, and delta TrIs krTemperature difference under influence.
S5, according to the determined parameters, trimming the welding edge before welding, firstly determining the position of an O point on the side surface of the welding edge according to the determined optimal value of the k value, respectively adjusting the angle position of a cutter by taking the O point as the top point of the side surface according to the adjusted and determined outer corner alpha and inner corner beta, and then respectively finishing cutting the outer surface corner and the inner surface corner, and finishing the parameter regulation and control process.
Preferably, the outer corner α is an included angle between the side line OC after trimming and the original side line OA to be welded, and the inner corner β is an included angle between the side line OD after trimming and the original side line OB to be welded.
Preferably, the single increment Δ is set according to actual needs.
Preferably, the single increment Δ is set to 2 °, 3 °, or 5 °.
Preferably, the outside corner α is denoted by i times the increment Δ and the inside corner β is denoted by j times the increment Δ.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following beneficial effects:
1. according to the regulation and control method, the key parameters for controlling the shape of the welding edge and exploring the influence of each parameter on the temperature difference are defined, so that the outer corner alpha, the inner corner beta and the distance k from the point O to the outer surface of the three parameters are determined, the generation environment of induced current can be improved by regulating and controlling the three parameters, the temperature difference value of the highest temperature and the lowest temperature in the wall thickness direction of the welding line is reduced, more uniform temperature distribution is generated, and the welding quality of the welding line is improved.
2. Compared with the temperature distribution before adjustment, the adjustment result can ensure that the temperature of the inner surface and the temperature of the outer surface are not too high while ensuring that the temperature of the inner part of the welding seam reaches 1350 ℃, and can well avoid the defects of overheating and cold welding so as to ensure the welding quality.
3. The invention establishes the corresponding relation between the shape parameter and the quality of the welding edge through finite element software numerical simulation, provides a regulating and controlling method for changing the quality according to the shape of the welding edge, avoids the time and capital cost brought by a trial and error method in the actual production, improves the quality of the high-frequency straight welded pipe and greatly reduces the cost of the regulating process.
Drawings
FIG. 1 is a schematic diagram of a welding process of a high-frequency straight welded pipe quality control method of the invention;
FIG. 2 is a parameter position diagram of a high-frequency straight welded pipe quality control method according to the invention;
FIG. 3 is a schematic diagram of the method for controlling the quality of a high-frequency straight welded pipe according to the present invention;
FIG. 4 is a flow chart of a method for regulating and controlling the quality of a high-frequency straight welded pipe according to the invention;
FIG. 5 is a schematic diagram of the position of a first determined O point in the quality control method for high-frequency longitudinal welded pipes according to the present invention;
FIG. 6 is a graph showing the effect of the outer corner α on the weld temperature difference in the method for regulating the quality of a high-frequency straight welded pipe according to the present invention;
FIG. 7 is a graph showing the effect of the inner edge angle β on the weld temperature difference in the method for controlling the quality of a high-frequency straight welded pipe according to the present invention;
FIG. 8 is a graph showing the influence of the peak O point position parameter k value on the weld temperature difference in the high-frequency straight welded pipe quality control method of the present invention;
FIG. 9 is a comparison graph of temperature and magnetic induction intensity curves before and after the adjustment and control of the quality control method for the high-frequency straight welded pipe.
The reference numbers in the figures are as follows: 1-V-shaped angular peak, 2-extrusion roller, 3-tube blank, 4-electrode, 5-magnetic bar, 6-tube blank outer surface, 7-welding direction, 8-tube blank inner surface, 9-side edge to be welded and 10-extrusion direction.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In order to better understand the technical solution of the present invention, the following detailed description is made with reference to the accompanying drawings and examples. The feasibility of the method is verified by simulating the welding process of the ERW pipe, observing the trimming regulation process before welding of the pipe blank and observing the temperature distribution condition of the pipe blank. Selecting an ERW pipe made of X80 steel with the specification of phi 355.6 multiplied by 12.7, and carrying out numerical simulation.
Fig. 1 is a schematic diagram of the welding process of the present invention, wherein an electrode 4 is connected to an ac power source, and under the action of the electrode 4 and a magnetic rod 5, the temperature near the V-shaped vertex 1 starts to rise to the welding temperature due to the skin effect and other principles. The tube blank 3 moves along the welding direction 7 while being heated, and the squeeze roll 2 squeezes the circumference of the outer surface 6 of the tube blank at the welding point, so that the tube blank 3 is welded.
Figure 2 is a cross-sectional view of one side of the tube blank 1 according to the invention, the edge of the joint between the side 9 to be welded and the outer surface 6 and the inner surface 8 of the tube blank being cut off before welding, the position of the parameters being schematically shown in figure 2. The outer corner alpha is the angle between the edge OC and the original side edge OA, and the inner corner beta is the angle between the edge OD and the original side edge OB to be welded. Wherein h is the wall thickness of the tube blank 1.
Fig. 3 is a schematic diagram of the principle of the present invention, the left side diagram is a cross-sectional screenshot of a normal tube blank without trimming at the V-shaped angular vertex 1 of a welding point, under the action of the skin effect and the ring effect, the induced magnetic field is mainly concentrated in the regions i and ii, the induced magnetic field generates induced current, and finally the high temperature point is concentrated near the point A, B and gradually decreases towards the periphery. And the right graph is a schematic diagram after regulation and control of trimming, after trimming treatment, under the action of a skin effect and a circular ring effect, an induction magnetic field is mainly concentrated near a region III, a point C and a point D, but the highest magnetic field intensity is distributed in the region III, finally a high-temperature point is concentrated near three points O, C and D, the temperature of the point O is highest, and then the temperature is diffused from the three points to the inner direction of the tube blank 1. Compared with the two high-temperature points before regulation and control which are diffused to the periphery, the three high-temperature points after regulation and control are distributed, and when the lowest point reaches the welding temperature, a more uniform temperature field is easier to generate.
Fig. 4 is a block diagram of a calculation flow of the method for regulating and controlling the quality of the high-frequency straight welded pipe, which mainly includes the following steps:
step 1, acquiring technological parameters of ERW pipes produced in factories, wherein the parameters are shown in table 1. The ERW pipe welding process was numerically simulated using finite element software, wherein a schematic diagram of the process parameters is shown in FIG. 1, and a temperature field distribution is simulated as shown in FIG. 5.
TABLE 1 ERW pipe welding production Process parameters
And 2, setting each parameter and determining a corresponding numerical value. According to the temperature distribution, the lowest temperature point on the side 9 to be welded is determined, the point is tentatively set as the position of the point O, and the distance k from the point O to the outer surface is determined, as shown in fig. 5. Setting single increment delta of the outer corner alpha and the inner corner beta as the base number of the angle change of the regulation process, wherein the single increment delta can be respectively set to be 2 degrees, 3 degrees or 5 degrees, and the smaller the value of the single increment delta is, the more ideal the regulation effect is. The initial value of the simulation times i of the outer corner alpha is 0, the initial value of the simulation times j of the inner corner beta is 0, and alpha is0=0,β 00; for recording the number of angle changes.
And 3, determining the values of the outer corner alpha and the inner corner beta, firstly taking the outer corner alpha as 1-time increment delta, sequentially taking the inner corner beta from small to large according to the multiple of the increment until the value is more than 15 degrees, and carrying out temperature field simulation in times. Recording the temperature difference between the highest temperature and the lowest temperature in the COD direction of the welding seam as delta T in the simulation result of the beta value of the inner corner each timeijAnd finishing the outer corner alpha regulation and control process. Taking the outer corner alpha as 2 times increment, carrying out the same simulation process, and recording the corresponding temperature difference delta TijAnd regulating and controlling the outer corner alpha for the second time. The outer corner alpha is taken in turn according to the multiple of the increment until the angle is more than 20 degrees, and the recorded temperature difference delta T is usedijDetermining the minimum value and recording the outer corner alpha at the momentiAnd inner edge angle betaj。
Outer and inner corner alpha, beta and minimum temperature difference TminThe determination process is respectively shown as formula (1), formula (2) and formula (3);
Tmin=fmin{ΔT11,ΔT12,...ΔT1j,ΔT21,ΔT22,...,ΔT21,ΔT22,...ΔTij-1ΔTij} (3)
wherein i and j are both simulation times, alpha is an outer corner, beta is an inner corner, and TminTo a minimum temperature difference, Δ TijIs the temperature difference.
And 4, adjusting and determining the position parameter k value of the O point. Adopting the external corner alpha determined in the step 3iAnd inner edge angle betajChanging the k value in the step 2, setting the increment of the k value to be 0.05h, sequentially obtaining the k value from 0.05h to h according to integral multiple of the increment, respectively carrying out temperature field numerical simulation on each parameter, recording the temperature difference delta T of each time, and obtaining the k value when the temperature difference is minimum. The specific calculation method is shown as formula (4) and formula (5);
Tmin=fmin{ΔT1,ΔT2,......ΔTr-1,ΔTr} (5)
wherein k is the distance from the point O to the outer surface, r is the k value adjustment times, and delta TrIs krTemperature difference under influence.
The adjustment process in step 4 is to determine the optimal value of k, the k value determined in step 2 is only the value temporarily taken to determine the outer corner α and the inner corner β in step 3, and it is not determined whether the k value in step 2 is the optimal value, so that there is the step of determining the optimal value of k in step 4, and the specific adjustment process is shown in step 4.
The parameter degrees of freedom of the welding process have three parameters, namely k, alpha and beta, step 3 determines that only one degree of freedom k is left in the two subsequent degrees of freedom, and step 4 determines k. And (3) adopting the alpha and the beta determined in the step (3), taking the k value as increment of 0.05h, sequentially taking the k value till h, then taking each value as a tube blank process parameter to carry out temperature field numerical simulation, recording the temperature difference delta T of each simulation, and determining the optimal k value when the temperature difference delta T is minimum.
And 5, according to the determined parameters, performing trimming treatment on the welding edge before welding, firstly determining the position of an O point on the side surface of the welding edge according to the determined optimal value of the k value, respectively adjusting the angle position of a cutter by taking the O point as the top point of the side surface according to the adjusted and determined outer corner alpha and inner corner beta, and then respectively finishing cutting on the outer surface corner and the inner surface corner, and finishing the parameter regulation and control process.
The feasibility of the above-described judgment method is verified by analyzing the simulation results of fig. 6 to 9.
Fig. 6 is a graph of the result of adjusting the outer corner α alone, and it can be seen from the graph that the temperature difference of the weld seam shows a trend of decreasing and then increasing with the increase of the angle α, and the temperature difference is at least 105 ℃ when the outer corner α is 10 °, i.e. a minimum point appears, which indicates that the angle has a certain influence relationship on the welding quality. This result is caused because the change of the outer corner α directly changes C, O the induced magnetic field and current at two points, directly affecting the temperature at two points, such that the temperature at point C decreases and the temperature at point O increases, such that the lowest temperature point appears in the CO section or the OD section. Initially, the temperature of the lowest temperature point increases and the temperature difference decreases when the outer corner α changes, but a new low temperature point is generated when the outer corner α is large enough, which finally results in a higher temperature difference. And then the influence relationship between the outer corner alpha and the temperature difference of the welding seam can be generated.
Fig. 7 is a graph showing the result of adjusting the inner corner β alone, which is similar to the result of adjusting the outer corner α, in which the temperature difference of the weld is decreased and then increased as the inner corner β is increased, and in which the temperature difference is at least 115 ℃ when the inner corner β is 8 °. It is also stated that varying the parameters can independently affect the weld quality.
Fig. 8 is a graph showing the temperature difference change when the k value is adjusted using the optimum outer and inner corner α and β values of fig. 6 and 7, and it can be seen that when r is 8 and k is equal to 0.4h, the temperature difference is only 90 ℃. Compared with high-temperature differential distribution, the result greatly improves the welding quality.
FIG. 9 is a comparison graph of simulation result curves of temperature and magnetic induction intensity at 11 points uniformly in the thickness direction of the cross section at the vertex 1 of the V-shaped angle before and after adjustment. Wherein the shape I represents the shape of the side 9 to be welded before the regulation method is adopted, and the shape X represents the shape of the side 9 to be welded before the regulation method is adopted. It is obvious from the figure that the temperature distribution tendency and the magnetic induction intensity distribution tendency are consistent. Before the regulation and control are carried out, a high-temperature area is mainly concentrated on the outer surface 6 of the tube blank and the inner surface 8 of the tube blank, and the temperature difference is 210 ℃; after the regulation and control method is adopted, the high-temperature area is mainly concentrated on the outer surface 6 of the tube blank, the inner surface 8 of the tube blank and the inside of a welding seam, and the temperature difference is 90 ℃. By adopting the regulating method, the temperature distribution uniformity is obviously improved in the thickness direction of the cross section of the V-shaped vertex 1, the residual stress generated after welding is reduced along with the reduction of the temperature difference in the wall thickness direction of the welding line, and the welding quality is obviously improved. In addition, as can be seen from the figure, compared with the temperature distribution before adjustment, the adjustment result can ensure that the temperature inside the welding seam reaches 1350 ℃, meanwhile, the temperature of the inner surface and the outer surface is not too high, and the defects of overheating and cold welding can be well avoided, so that the welding quality is ensured.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.