CN115194368A - System and method for improving welding stability of medium-thickness plate aluminum alloy - Google Patents
System and method for improving welding stability of medium-thickness plate aluminum alloy Download PDFInfo
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- 238000003466 welding Methods 0.000 title claims abstract description 181
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- 238000009529 body temperature measurement Methods 0.000 claims abstract description 10
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- 230000000704 physical effect Effects 0.000 claims description 9
- 238000009434 installation Methods 0.000 claims description 7
- 238000003825 pressing Methods 0.000 claims description 7
- 238000010891 electric arc Methods 0.000 claims description 6
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K37/00—Auxiliary devices or processes, not specially adapted to a procedure covered by only one of the preceding main groups
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/08—Non-ferrous metals or alloys
- B23K2103/10—Aluminium or alloys thereof
Abstract
The invention provides a method and a system for improving the welding stability of a medium plate aluminum alloy, which comprises the following steps: step S1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot; step S2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method; and step S3: and the movement of a welding gun and the output current of a welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
Description
Technical Field
The invention relates to the technical field of welding, in particular to a system and a method for improving the welding stability of medium plate aluminum alloy.
Background
The aluminum alloy material is widely applied to the fields of aerospace, rail vehicles and the like by virtue of the advantages of high specific strength, good processing performance and the like, a large number of welding structural parts with high requirements on welding seam quality are designed in the fields, the argon tungsten-arc welding process with high welding quality is one of main welding methods of the aluminum alloy components, but the argon arc welding process has low energy density, large current is needed when 6-10mm of medium-thickness aluminum alloy material is welded, heat input is large, the aluminum alloy material generally has the characteristics of high heat conductivity, low liquid surface tension coefficient and the like, the temperature rises very fast in the heavy-current welding process, the volume of a molten pool is increased continuously, the phenomena of collapse, even burnthrough and the like of the back of the molten pool are easy to occur, and stable welding is difficult to realize.
Patent document WO2019000760A1 (application number: PCT/CN 2017/108918) discloses an online quantitative evaluation method for stability of a welding process, which comprises the following steps: monitoring and acquiring arc voltage U and welding current I in the welding process, and drawing a phase diagram of each U-I period; converting the phase diagram of each U-I period into a binary image K; solving the passing area J N of the dynamic working curve in the binary image K; solving a stability evaluation index P of the welding process according to a formula; and evaluating the stability of the welding process according to the obtained welding stability evaluation index P.
The invention provides a system and a method for improving the welding stability of a medium-thickness plate aluminum alloy, which are used for improving the stability of a welding process of the medium-thickness plate aluminum alloy material.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a system and a method for improving the welding stability of a medium plate aluminum alloy.
The method for improving the welding stability of the medium plate aluminum alloy provided by the invention comprises the following steps:
step S1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
step S2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
and step S3: and the movement of a welding gun and the output current of a welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
Preferably, the step S1 employs:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Indicating the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y-axis, when the welding gun moves along the X-axis, mu y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Of a correlation of 1 And σ 2 Are uncorrelated with each other, in which case ρ =0; order to
Preferably, the step S2 employs: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a non-linear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further deforming, the steps of:
writing equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the deduction, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial moment is T i And a data set D consisting of data collected by the n thermocouples at the time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out formula (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in formula (9);
combining the vertical type (4) to the formula (8) to obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A, sigma 1 、σ 2 The value of (2) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
Preferably, real-time temperature field data of the weld bead are obtained based on the plate heat distribution model, so that movement of the welding gun and output current of a welding power supply are regulated and controlled, and stability of the welding process is guaranteed.
Preferably, the workpiece to be welded is fixed by using a pressing block and a tooling tool, and the thermocouple is fixed to a position parallel to a welding bead of the workpiece to be welded by using a fixing device.
The system for improving the welding stability of the medium plate aluminum alloy provided by the invention comprises:
a module M1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
a module M2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
a module M3: and the movement of the welding gun and the output current of the welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
Preferably, the module M1 employs:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Indicating the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y-axis, when the welding gun moves along the X-axis, mu y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Of a correlation of 1 And σ 2 Are uncorrelated with each other, in which case ρ =0; order to
Preferably, the module M2 employs: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a nonlinear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further deforming, the steps of:
writing equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the deduction, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial instant is T i And a data set D consisting of data collected by the n thermocouples at the time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out formula (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in formula (9);
the joint type (4) to the formula (8) obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A and sigma are used 1 、σ 2 The value of (2) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
Preferably, real-time temperature field data of the weld bead are obtained based on the plate heat distribution model, so that movement of the welding gun and output current of a welding power supply are regulated and controlled, and stability of the welding process is guaranteed.
Preferably, the workpiece to be welded is fixed by using a pressing block and a tool, and the thermocouple is fixed to a position parallel to a weld bead of the workpiece to be welded by using a fixing device.
Compared with the prior art, the invention has the following beneficial effects: aiming at high-thermal-conductivity metals such as aluminum alloy and the like, welding parameters are corrected in real time by collecting information such as a temperature field and the like in real time, so that the interference influence of heat accumulation and preheating effects is avoided, and the welding quality is improved.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a flow chart of a method for improving the welding stability of a medium plate aluminum alloy.
FIG. 2 is a schematic view of thermocouple installation.
FIG. 3 is a schematic view of a measurement control device
FIG. 4 is a schematic view of a measurement control device
Fig. 5 is a schematic view of a welding process.
FIG. 6 is a schematic view of the temperature field of the sample.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
The invention is generally directed to high-thermal-conductivity materials such as aluminum alloy, and the like, and when the temperature of the materials is rapidly increased in the welding process, and parameters such as the same welding current and the like are always adopted, the rear part of a welding bead is easy to collapse due to the preheating effect, so that the welding parameters need to be adjusted in the welding process, for example, the welding current is always reduced along with the increase of the temperature of a sample.
Example 1
The invention provides a method for improving the welding stability of a medium plate aluminum alloy, which comprises the following steps:
step S1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
specifically, the step S1 employs:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Denotes the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y axis, mu when the welding gun moves along the X axis y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Is of a correlation of 1 And σ 2 Are not correlated with each other, when ρ =0; order to
Step S2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
specifically, the step S2 employs: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a nonlinear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further deforming, the steps of:
writing equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the derivation, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial moment is T i A data set D consisting of data collected by n thermocouples at time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out equation (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in equation (9);
the joint type (4) to the formula (8) obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A and sigma are used 1 、σ 2 The value of (3) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
And step S3: and the movement of the welding gun and the output current of the welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
The front welding bead can generate obvious preheating effect on the rear welding bead in the welding process of high-thermal-conductivity materials such as aluminum alloy and the like, and the defects of molten pool collapse and the like are prevented because the moving speed of a welding gun is properly increased or the current value is reduced according to temperature field data.
Specifically, real-time temperature field data of a weld bead are obtained based on a plate heat distribution model, so that movement of a welding gun and output current of a welding power supply are regulated and controlled, and stability of a welding process is guaranteed. For example: the current value can be adjusted according to the temperature increase, the welding gun speed or the welding current decrease, for example, the temperature increases by 10%, the current decreases by 10% or the welding gun speed increases by 10%.
Specifically, a pressing block and a tool are used for fixing a workpiece to be welded, and a fixing device is used for fixing a thermocouple to a position parallel to a welding bead of the workpiece to be welded.
The system for improving the welding stability of the medium plate aluminum alloy provided by the invention comprises:
a module M1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
specifically, the module M1 employs:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Indicating the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y axis, mu when the welding gun moves along the X axis y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Is of a correlation of 1 And σ 2 Are uncorrelated with each other, in which case ρ =0; order to
A module M2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
specifically, the module M2 employs: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a non-linear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further deforming, the steps of:
write equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the deduction, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial instant is T i A data set D consisting of data collected by n thermocouples at time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out equation (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in equation (9);
the joint type (4) to the formula (8) obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A and sigma are used 1 、σ 2 The value of (3) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
A module M3: and the movement of the welding gun and the output current of the welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
The front welding bead can generate obvious preheating effect on the rear welding bead in the welding process of high-thermal-conductivity materials such as aluminum alloy and the like, and the defects of molten pool collapse and the like are prevented by properly increasing the moving speed of a welding gun or reducing the current value according to temperature field data.
Specifically, real-time temperature field data of a weld bead are obtained based on a plate heat distribution model, so that movement of a welding gun and output current of a welding power supply are regulated and controlled, and stability of a welding process is guaranteed. For example: the current value can be adjusted according to the temperature increase, the welding gun speed or the welding current decrease, for example, the temperature increases by 10%, the current decreases by 10% or the welding gun speed increases by 10%.
Specifically, a pressing block and a tool are used for fixing a workpiece to be welded, and a fixing device is used for fixing a thermocouple to a position parallel to a welding bead of the workpiece to be welded.
Example 2
Example 2 is a preferred example of example 1
The invention provides a system for improving the welding stability of a medium plate aluminum alloy, which comprises the following components: control system, temperature measurement system, welding system, motion control system.
The control system comprises an upper computer, a plate heat distribution model is pre-established in the upper computer by using ANSYS software according to the thermal physical properties, the movement speed, the wire feeding speed and other parameters of the material to be welded and the heat source, the upper computer receives data from the thermocouple temperature measuring system in the welding process, the data are led into the plate heat distribution model to calculate the welding temperature field of the workpiece in real time, and the parameters of the movement and the output current of the welding gun are adjusted according to the calculation result of the temperature field.
The temperature measuring system mainly comprises a thermocouple, a temperature acquisition module and a thermocouple fixing device, wherein holes are formed in a substrate, a ceramic tube is placed in a position, outside the end part of a thermocouple wire, of the ceramic tube, the ceramic tube is in contact with the substrate, so that the measurement precision is affected, the thermocouple wire is inserted into the ceramic tube, the temperature of the substrate is measured by the end part and the substrate base, the other end of the thermocouple is connected with the acquisition module, and the acquisition module sends temperature data to an upper computer in real time to serve as a data basis for temperature field modeling and real-time adjustment of welding parameters. The thermocouple is adopted to measure and collect the temperature, so that the interference of welding arc light can be avoided, the thermocouple is in direct contact with a workpiece, the measuring accuracy is greatly improved, and the temperature collecting module can collect the temperature value at the highest frequency of 50Hz and send the temperature value to an upper computer through a 485 bus.
As shown in fig. 2. The thermocouple fixing device is provided with a row of through holes with the circle centers spaced by 1cm, and ceramic tubes with the same outer diameter as the inner diameter of the through holes are arranged in the air, so that the fixing device is prevented from interfering with the temperature measurement of the thermocouple.
The welding system comprises a wire feeder, a cooling water tank and a high-frequency pulse welding power supply, wherein the high-frequency pulse welding power supply is connected with an upper computer through a 485 bus, and can receive a control instruction of the upper computer and accurately control and adjust parameters such as the numerical value of output current, current polarity, duty ratio and current frequency in real time.
The motion control system comprises a robot body and a control system thereof, and can adjust the spatial position and the posture of the welding gun according to the instruction of the upper computer.
The invention also provides a method for improving the welding stability of the medium plate aluminum alloy, which comprises the following steps:
and determining welding parameters such as the numerical value, duty ratio and frequency of welding current, the wire feeding speed of a wire feeder, the movement speed of a robot and the like according to the type, actual thickness, groove form and the like of welding materials, and finishing initialization setting of various parameters in a control system and various devices.
And fixing the workpiece to be welded by using a pressing block, a tool and the like, and fixing the thermocouple to a position parallel to a welding bead of the workpiece to be welded by using a fixing device.
And moving the welding gun to an initial position, starting welding, continuously transmitting temperature data to an upper computer by the thermocouple temperature measurement module in the welding process, and updating a plate heat distribution model of a prefabricated member in ANSYS software by the upper computer by using the temperature data to obtain real-time temperature field data of a welding bead. And the upper computer regulates and controls the output current of the welding power supply according to the welding bead temperature field data updated in real time, so that the stability of the welding process is ensured.
The welding system provided by the patent is shown in figures 3-4:
the method for building the plate heat distribution model in the upper computer comprises the following steps:
solving the thermal field model in the upper computer according to the information such as the thermal physical property of the material to be welded, the physical property of the welding heat source, the moving speed and the like, wherein the solving mode is as follows:
as shown in fig. 4, a cartesian coordinate system is established on the sheet to be welded, and the thermal field formed by the arc on the sheet surface can be approximately regarded as a two-dimensional gaussian distribution without considering the residual temperature, i.e. the temperature at any point (x, y) in the coordinate system is:
in the formula, alpha T Is the maximum temperature of the temperature field; sigma 1 、σ 2 Rho is a model parameter, and specific values are determined according to different thermal fields, wherein when sigma is 1 ＝σ 2 When the temperature field contour is circular, ρ describes σ 1 And σ 2 The correlation of (c); mu.s x As coordinates of the welding gun on the X-axis, mu y As coordinates of the welding gun on the Y-axis, i.e. mu y ＝0；T p Is the pre-heating temperature of the sheet, is a constant known prior to calculation.
To further simplify the model, one can consider σ 1 And σ 2 Are uncorrelated with each other, in which case ρ =0. At the same time order
Equation 1 can now be written:
taking logarithm of two sides of formula 2 to obtain
Further deforming to obtain:
lnT＝ax 2 +by 2 +cx+dy+k (4)
the parameters in the formula are as follows:
the solution problem for the thermal field model becomes a binary quadratic polynomial fitting problem.
The mounting position of the ith thermocouple is set as (x) i ,y i ) The temperature of which measured at the initial instant is T i And a data set D consisting of data collected by the n thermocouples at the time t 0 Comprises the following steps:
and (4) carrying the data set into formula 4 and solving by using a least square method to obtain a plate heat distribution model at the time t.
The method for calculating the temperature field by utilizing the temperature information acquired by the thermocouple in real time comprises the following steps:
after the construction of the plate heat distribution model is completed, the temperature data collected by the thermocouple at any moment can be used for predicting the temperature field of the welding track in real time, and the prediction method comprises the following steps: when the time interval Δ t between the time t and the time t-1 is sufficiently small, the heat accumulation and consumption on the sheet material can be ignored, so that the temperature field is only different from the time t-1 in that the temperature field moves towards the positive x-axis direction along with the movement of the welding heat source, and the temperature field model at the time t predicted by the time t-1 is as follows:
after the temperature field information in front of the welding heat source is obtained, the amplitude of the welding current can be adjusted, so that the stability of the welding process is ensured.
As shown in FIG. 6, a plate temperature cloud chart is obtained through estimation and calculation according to a plate temperature field, and feasibility of the method is verified based on a sample temperature field schematic diagram.
Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A method for improving the welding stability of a medium plate aluminum alloy is characterized by comprising the following steps:
step S1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
step S2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
and step S3: and the movement of the welding gun and the output current of the welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
2. The method for improving the welding stability of the medium plate aluminum alloy according to claim 1, wherein the step S1 comprises the following steps:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Indicating the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y axis, mu when the welding gun moves along the X axis y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Of a correlation of 1 And σ 2 Are uncorrelated with each other, in which case ρ =0; order to
3. The method for improving the welding stability of the medium plate aluminum alloy according to claim 1, wherein the step S2 comprises the following steps: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a nonlinear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further modification, let:
write equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the derivation, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial instant is T i A data set D consisting of data collected by n thermocouples at time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out equation (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in equation (9);
the joint type (4) to the formula (8) obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A, sigma 1 、σ 2 The value of (2) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
4. The method for improving the welding stability of the aluminum alloy of the medium plate according to claim 1, wherein real-time temperature field data of a welding bead is obtained based on a plate heat distribution model, so that the movement of a welding gun and the output current of a welding power supply are regulated and controlled, and the stability of the welding process is ensured.
5. The method for improving the welding stability of the medium plate aluminum alloy according to claim 1, wherein the workpiece to be welded is fixed by a pressing block and a tooling tool, and the thermocouple is fixed to a position parallel to a weld bead of the workpiece to be welded by a fixing device.
6. The utility model provides a system for improve cut deal aluminum alloy welding stability which characterized in that includes:
a module M1: establishing a plate heat distribution model according to the materials to be welded, the thermophysical property of a heat source, the wire feeding speed of a wire feeder and the movement speed of a robot;
a module M2: in the welding process, temperature data are collected in real time through a thermocouple temperature measurement module, and real-time temperature field data of a welding bead are obtained by utilizing the collected real-time temperature data based on a plate temperature field estimation method;
a module M3: and the movement of the welding gun and the output current of the welding power supply are regulated and controlled according to the real-time temperature field data of the welding bead, so that the stability of the welding process is ensured.
7. The system for improving the welding stability of the medium plate aluminum alloy according to claim 6, wherein the module M1 adopts:
establishing a plate heat distribution model according to the information including the thermophysical properties of the materials to be welded, the physical properties of a welding heat source and the moving speed:
a Cartesian coordinate system is established on the upper surface of a plate to be welded, under the condition of not considering the residual temperature, the thermal field formed by the electric arc on the surface of the plate is approximately regarded as two-dimensional Gaussian distribution, and the temperature at any point (x, y) in the coordinate system is as follows:
in the formula, alpha T 、σ 1 、σ 2 ρ represents an unknown parameter; mu.s x Denotes the coordinates of the welding gun on the X-axis, mu y Indicating the coordinates of the welding gun on the Y-axis, when the welding gun is along the X-axisIn exercise, mu y ＝0；T p The preheating temperature of the plate;
ρ describes σ 1 And σ 2 Is of a correlation of 1 And σ 2 Are uncorrelated with each other, in which case ρ =0; order to
8. The system for improving the welding stability of the medium plate aluminum alloy according to claim 6, wherein the module M2 adopts: solving the unknown number in the plate heat distribution model by a plate temperature field estimation method;
the plate temperature field estimation method comprises two parts: the first part is mathematical transformation of a plate heat distribution model, and a nonlinear equation parameter solving problem which is difficult to solve is transformed into a polynomial fitting problem to be solved; and the second part is used for solving the plate heat distribution model, fitting the polynomial obtained by the first part based on the temperature data acquired by the thermocouple, and solving the unknown number in the plate heat distribution model to obtain the plate heat distribution model.
Wherein the first part is specifically:
taking logarithm of two sides of the formula (2) to obtain
Further modification, let:
writing equation (3) as:
lnT＝ax 2 +by 2 +cx+dy+k (9)
through the derivation, the plate heat distribution model described by the formula (2) is converted into a polynomial equation form shown by the formula (9), and the solving problem of the plate heat distribution model is changed into a binary quadratic polynomial fitting problem;
the second part is specifically as follows:
setting the installation position of the ith thermocouple at the current moment as (x) i ,y i ) The temperature of which measured at the initial instant is T i And a data set D consisting of data collected by the n thermocouples at the time t 0 Comprises the following steps:
wherein n is greater than or equal to 5;
data set D 0 Carrying out equation (9) and solving by using a least square method, namely obtaining values of five coefficients a, b, c, d and k in equation (9);
the joint type (4) to the formula (8) obtain the equation set shown in the formula (10):
the values of a, b, c, d and k are taken into formula (10), and alpha can be obtained by solving the equation system T 、σ 1 、σ 2 A value of (d); then the obtained A and sigma are used 1 、σ 2 The value of (2) is substituted into the formula (2), and the solution of the plate heat distribution model is completed.
9. The system for improving the welding stability of the aluminum alloy of the medium plate according to claim 6, wherein the real-time temperature field data of the weld bead is obtained based on the plate heat distribution model, so that the movement of the welding gun and the output current of the welding power supply are regulated and controlled, and the stability of the welding process is ensured.
10. The system for improving the welding stability of the medium plate aluminum alloy according to claim 6, wherein the workpiece to be welded is fixed by a pressing block and a tooling tool, and the thermocouple is fixed to a position parallel to a welding bead of the workpiece to be welded by a fixing device.
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