CN113009940B - Laser cladding molten pool temperature control system and method - Google Patents
Laser cladding molten pool temperature control system and method Download PDFInfo
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- CN113009940B CN113009940B CN202110204003.7A CN202110204003A CN113009940B CN 113009940 B CN113009940 B CN 113009940B CN 202110204003 A CN202110204003 A CN 202110204003A CN 113009940 B CN113009940 B CN 113009940B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/1927—Control of temperature characterised by the use of electric means using a plurality of sensors
- G05D23/193—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces
- G05D23/1931—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces to control the temperature of one space
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
Abstract
The invention relates to a laser cladding molten pool temperature control system and a method, and belongs to the field of online real-time temperature measurement and control in a laser cladding process. The system comprises a laser cladding molten pool temperature online real-time closed-loop control system; the system is based on a NET6043-S network data acquisition card digital sampling and RS-485 communication module so as to realize the online real-time detection and control of the temperature of the molten pool; selecting laser power as a control variable and applying a molten pool temperature PID controller developed by VC; a system for actually controlling the temperature of the thin-wall laser cladding molten pool; and a system for analyzing results of the thin-wall formed part. The invention can effectively eliminate the temperature accumulation phenomenon in the cladding process, obviously improve the dimensional precision of the formed part and provide a new way for controlling the shape and the controllability of laser cladding.
Description
Technical Field
The invention relates to a laser cladding molten pool temperature control system and a method, belonging to the field of online real-time temperature measurement and control in the laser cladding process.
Background
The laser cladding technology is to utilize high-energy and high-density laser beams to be injected into a metal matrix to form a molten pool, realize the combination between the metal matrix and cladding materials, form a cladding layer with the characteristics of wear resistance, corrosion resistance and the like, and be widely applied to the fields of metallurgy, medical treatment, aerospace and the like. In the laser cladding process, the shape and performance of a cladding layer are unstable due to the temperature change of a molten pool, and the key of the shape control and the performance control of the laser cladding is how to effectively control the temperature of the molten pool in the laser cladding process. Therefore, the research on the control system of the laser cladding molten pool temperature has important engineering significance for improving the appearance and performance stability of the laser cladding formed piece.
Disclosure of Invention
Aiming at the problems, the invention provides a laser cladding molten pool temperature control system and a method, develops an online real-time closed-loop control system for the laser cladding molten pool temperature, applies a two-color infrared thermometer to coaxially measure the temperature at fixed points and quickly, and builds a NET6043-S network data acquisition card based digital sampling and RS-485 communication module to realize real-time monitoring and feedback of the molten pool temperature. On the basis, the laser power is used as a control variable, VC (programming software) is applied to develop a molten pool temperature PID (proportion-integral-derivative controller) controller, the real-time molten pool temperature of each sampling point of a single layer of a cladding layer is used as a feedback value, the laser power is adjusted on line in real time, and the closed-loop control of the molten pool temperature is realized, so that the stability of the appearance and the performance of the cladding layer is improved.
The invention discloses a laser cladding molten pool temperature control system, which comprises a laser cladding molten pool temperature online real-time closed-loop control system; the system is based on a NET6043-S network data acquisition card digital sampling and RS-485 communication module so as to realize the online real-time detection and control of the temperature of the molten pool; selecting laser power as a control variable and applying a molten pool temperature PID controller developed by VC; a system for actually controlling the temperature of the thin-wall laser cladding molten pool; and a system for analyzing results of the thin-wall formed part. The hardware equipment of the laser cladding molten pool temperature online real-time closed-loop control system comprises a YLR-1000 fiber laser, an RC52 laser cladding head, an MCWL-50DTR water cooler, a VMC1100P vertical machining center, an RC-PGF-D-2 powder feeder, a PLC and laser operation integrated cabinet, RC-CAM rapid forming software, an industrial personal computer, a STRONG-GR-4020 type bicolor infrared thermometer, a NET6043-S network data acquisition card and an RS-485 communication adapter.
The invention relates to a laser cladding molten pool temperature control method, which comprises the following steps: s1, developing an online real-time closed-loop control system for the temperature of the laser cladding molten pool;
s2, building a NET6043-S network data acquisition card based digital sampling and RS-485 communication module to realize online real-time detection and control of the temperature of the molten pool;
s3, selecting laser power as a control variable, and applying VC to develop a PID controller of the temperature of the molten pool;
s4, actually controlling the temperature of the thin-wall laser cladding molten pool;
and S5, analyzing the result of the thin-wall formed piece.
Preferably, the hardware equipment of the laser cladding molten pool temperature online real-time closed-loop control system comprises a YLR-1000 fiber laser, an RC52 laser cladding head, an MCWL-50DTR water cooler, a VMC1100P vertical machining center, an RC-PGF-D-2 powder feeder, a PLC and laser operation integrated cabinet, RC-CAM rapid forming software, an industrial personal computer, a STRONG-GR-4020 type bicolor infrared thermometer, a NET6043-S network data acquisition card and an RS-485 communication adapter.
Preferably, the step S2 includes the following sub-steps:
specifically, in step S2: s21, measuring the temperature of the molten pool by using a STRONG-GR-4020 type two-color infrared thermometer;
specifically, in step S2: s22, building a NET6043-S network data acquisition card-based digital sampling and RS-485 communication module, and inputting an analog quantity voltage signal of which the temperature information of the molten pool measured by the bicolor infrared thermometer is 0-5V into the NET6043-S network data acquisition card;
specifically, in step S2: and S23, inputting the temperature value to the PID real-time controller through AD conversion by the data acquisition card. The voltage and temperature conversion formula is:
T1＝(V×T3)/5+T2
in the formula, T1For the current display of temperature, T2Outputting a starting value for the analog quantity corresponding to the temperature, T3Outputting the difference between the temperature corresponding to the end value and the temperature corresponding to the initial value for the analog quantity;
specifically, in step S2: and S24, outputting signals by a control algorithm in the controller, transmitting the signals to the data acquisition card again, outputting 0-10V voltage signals by DA conversion, transmitting the signals to the laser, monitoring the temperature of the molten pool in real time in an online manner by the whole system, and controlling the temperature of the molten pool by adjusting the laser power.
Preferably, the step S3 includes the following sub-steps:
specifically, in step S3: s31, designing an experiment of the influence of laser power on the temperature of a molten pool;
specifically, in step S3: s32, analyzing the experimental result, and selecting the laser power as a control variable;
specifically, in step S3: and S33, developing a PID controller of the molten pool temperature by applying VC.
Preferably, the step S5 includes the following sub-steps:
specifically, in step S5: s51, analyzing the temperature of the molten pool;
specifically, in step S5: s52, analyzing the forming size precision of the thin-wall;
specifically, in step S5: s53, microscopic structure analysis;
specifically, in step S5: and S54, hardness analysis.
Preferably, the step S33 includes the following sub-steps:
specifically, in step S33: s331, setting TmAnd T is the actual molten pool temperature in the cladding process measured in the current state. Let n be the current cladding sampling number in the laser cladding process, i.e. the actual temperature T and the ideal temperature T at the nth point of claddingmThe temperature difference e (n) therebetween is:
e(n)＝Tm-T(n)
specifically, in step S33: s332, in the whole process of cladding and stacking materials, outputting digital voltage through a correction data acquisition card at each sampling point, converting the digital voltage into analog voltage, and further correcting laser power, wherein the digital voltage variable delta u required by each sampling point can express a difference equation of a PID algorithm:
in the formula: kpTo proportional gain, KiTo integrate the gain, KdIs the differential gain;
specifically, in step S33: s333, the digital voltage variation between the two sampling points is the difference between the two powers:
Δu＝u(n+1)-u(n)
in the formula, n is the current sampling point, and n +1 is the next sampling point;
specifically, in step S33: s335, the PID control algorithm expression of the digital voltage can be obtained by the formula:
specifically, in step S33: s336, the DA output value in the data acquisition card is 0-4095, corresponding to 0-10V voltage and 0-1000W laser power, therefore, the output analog voltage can be expressed as:
specifically, in step S33: s337, deducing a PID control algorithm expression of the laser power as follows:
the invention has the beneficial effects that: the invention develops an online real-time closed-loop control system for the temperature of a laser cladding molten pool, which applies a two-color infrared thermometer to coaxially measure the temperature at fixed points and quickly, and builds a NET6043-S network data acquisition card-based digital sampling and RS-485 communication module to realize the real-time monitoring and feedback of the temperature of the molten pool. On the basis, the laser power is used as a control variable, a VC development molten pool temperature PID controller is applied, the real-time molten pool temperature of each sampling point of a single layer of the cladding layer is used as a feedback value, the laser power is adjusted on line in real time, the closed-loop control of the molten pool temperature is realized, and the stability of the morphology and the performance of the cladding layer is improved. The control system for researching the laser cladding molten pool temperature has important engineering significance for improving the appearance and performance stability of the laser cladding formed part.
Drawings
FIG. 1 is a diagram of a laser cladding bath temperature control system of the present invention;
FIG. 2 is a diagram of the bath temperature at different laser powers;
FIG. 3 is a flow chart of a closed loop control system for bath temperature according to the present invention;
FIG. 4 is a graph of open loop bath temperature data;
FIG. 5 is a graph of closed loop bath temperature data;
FIG. 6 is a view of an open loop thin wall;
FIG. 7 is a view of a closed loop thin wall;
FIG. 8 is a graph of open and closed loop thin wall height versus desired height;
FIGS. 9(a) and 9(b) are microstructure views of different regions of a closed-loop thin-wall, wherein FIG. 9(a) is the bottom and FIG. 9(b) is the top;
FIG. 10 is a graph of a statistical analysis of hardness.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, but it should be understood that the examples are illustrative of the present invention and are not intended to limit the present invention.
An online real-time closed-loop control system for the temperature of a laser cladding molten pool is developed, and fig. 1 is a diagram of the laser cladding molten pool temperature control system.
Furthermore, the hardware equipment of the laser cladding molten pool temperature online real-time closed-loop control system comprises a YLR-1000 fiber laser, an RC52 laser cladding head, an MCWL-50DTR water cooler, a VMC1100P vertical machining center, an RC-PGF-D-2 powder feeder, a PLC and laser operation integrated cabinet, RC-CAM rapid forming software, an industrial personal computer, a STRONG-GR-4020 type bicolor infrared thermometer, a NET6043-S network data acquisition card and an RS-485 communication adapter.
A NET6043-S network data acquisition card-based digital sampling and RS-485 communication module is built, and online real-time detection and control of the temperature of the molten pool are realized.
Furthermore, the temperature of the molten pool is measured by a STRONG-GR-4020 model two-color infrared thermometer.
Further, a NET6043-S network data acquisition card-based digital sampling and RS-485 communication module is set up, and analog quantity voltage signals with the temperature information of the molten pool measured by a bicolor infrared thermometer being 0-5V are set and input into the NET6043-S network data acquisition card;
further, the data acquisition card inputs the temperature value to the PID real-time controller through AD conversion. The voltage and temperature conversion formula is:
T1＝(V×T3)/5+T2
in the formula, T1For the current display of temperature, T2Outputting a starting value for the analog quantity corresponding to the temperature, T3The difference between the temperature corresponding to the end value and the temperature corresponding to the start value is output for the analog quantity.
Furthermore, signals output by a control algorithm in the controller are transmitted to the data acquisition card again, 0-10V voltage signals are output by DA conversion and transmitted to the laser, the whole system can monitor the temperature of the molten pool on line in real time, and the temperature of the molten pool is controlled by adjusting the laser power.
Selecting laser power as a control variable, and developing a molten pool temperature PID controller by applying VC.
Further, an experiment of influence of laser power on the temperature of the molten pool is designed.
Further, the experimental material for laser cladding formation was 304 iron-based self-fluxing alloy powder having a particle size of 200 mesh and the composition of which is shown in table 1. The substrate material is 45 steel plate substrate, and the size is 200mm multiplied by 10 mm.
TABLE 1304 iron-based self-fluxing alloy powder compositions (wt%)
Further, before the experiment, place powder drying-machine with metal powder and dry in, it is 3h to dry duration, and the temperature is 150 ℃, filters the powder with the sieve after the stoving, prevents that the powder is moist and thoughtlessly has large granule powder to lead to sending the powder pipe to block up.
Further, the experimental cladding length is designed to be 50mm, the laser spot diameter is 2mm (the defocusing amount is constant), the scanning speed is 480mm/min, the powder feeding speed is 13g/min, the temperature curve change is monitored and recorded in real time through industrial personal computer software, and the molten pool temperature change curve under different laser powers (550W, 750W and 950W) is obtained, as shown in fig. 2.
Further, analyzing the experimental result, and selecting the laser power as a control variable;
further, a VC is applied to develop a PID controller of the temperature of the molten pool.
Further, let TmAnd T is the actual molten pool temperature in the cladding process measured in the current state. Let n be the current cladding sampling number in the laser cladding process, i.e. the actual temperature T and the ideal temperature T at the nth point of claddingmThe temperature difference e (n) therebetween is:
e(n)＝Tm-T(n)
further, in the whole process of cladding and stacking materials, digital voltage output by a data acquisition card is corrected at each sampling point and is converted into analog voltage so as to correct laser power, and the digital voltage variable delta u required by each sampling point can express a difference equation of a PID algorithm:
in the formula: kpTo proportional gain, KiTo integrate the gain, KdIs the differential gain;
further, the variation of the digital voltage between the two sampling points is the difference between the two powers:
Δu＝u(n+1)-u(n)
in the formula, n is the current sampling point, and n +1 is the next sampling point;
further, the PID control algorithm expression of the digital voltage can be obtained from the above formula:
further, the output value of DA in the data acquisition card is 0-4095, which corresponds to 0-10V voltage and 0-1000W laser power, so the output analog voltage can be expressed as:
further, the expression of the PID control algorithm for deriving the laser power is as follows:
further, a laser cladding molten pool temperature PID control program is developed in the VC, as shown in fig. 3.
And actually controlling the temperature of the laser cladding molten pool of the thin-wall.
Further, a thin-wall cladding experiment is designed, the length of the thin-wall is 50mm, the number of layers is 30, the Z-axis lifting amount is 0.65mm, and the forming material is 304 iron-based self-fluxing alloy powder.
Furthermore, two groups of thin-wall cladding experiments are designed for verifying the effectiveness of the molten pool temperature control system.
Experiment 2 is a closed-loop thin-wall experiment with molten pool temperature control, except for laser power, other parameters are consistent with those of experiment 1, and ideal temperature 1450 ℃ is set.
The experimental process parameters are shown in table 2.
TABLE 2 thin-walled wall comparison experiment Process parameters
And (5) carrying out result analysis on the thin-wall formed piece.
Further, the open-loop and closed-loop thin-wall walls respectively obtain molten pool temperature data in the cladding process, as shown in fig. 4 and 5.
Furthermore, through comparison of experimental data, it can be found that in the thin-wall cladding experiment of fig. 7, the phenomenon that the temperature of the molten pool in the first three layers gradually rises along with the superposition of the layer number obviously disappears, and in the cladding process, the temperature of the molten pool is stable, except for the cladding inflection point, the temperature of the molten pool is kept to fluctuate up and down at 1450 +/-30 ℃, the temperature of the second half section of the cladding layer is close to that of the first half section, the temperature at the inflection point is also obviously reduced, and the temperature overshoot phenomenon is also effectively reduced.
Further, the dimensional accuracy was measured in fig. 6 and 7, and the data are shown in table 3.
TABLE 3 comparison of open-and closed-Loop thin-walled wall parameters
Furthermore, the height difference between the two ends of the thin-wall in the figure 6 and the middle height is 1.51mm and 1.55mm respectively, the length difference between the bottom end and the top end is 0.85mm, and the thin-wall is in a shape of a boss. The height difference between the two ends of the thin-wall in the figure 7 and the middle height is only 0.04mm and 0.01mm respectively, the length difference between the bottom end and the top end is 0.06mm, and the thin-wall is in a rectangular shape.
Further, the error between the forming height and the expected height of the thin-wall in fig. 6 is 9.69%, the difference between the forming height and the expected height of the thin-wall in fig. 7 is ± 0.03mm, and the error between the forming height and the expected height is only 1.02%. As shown in fig. 8.
Further, the microstructures of the two images of FIGS. 9(a) and 9(b) are similar, and the growth directions are consistent and perpendicular to the direction of the clad layer bonding region and away from the substrate.
Furthermore, the hardness value distribution of fig. 7 is more uniform relative to an open loop experiment, the hardness standard deviation of fig. 6 is 16.24, and the hardness value of fig. 7 is 6.37, and the hardness value is obviously improved, so that the mechanical property of a formed piece is effectively improved. As shown in fig. 10.
The above description is a preferred embodiment of the present invention, and is not intended to limit the present invention, and those skilled in the art may modify the above technical solutions or substitute some technical features of the above technical solutions. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. A laser cladding molten pool temperature control system is characterized by comprising:
a laser cladding molten pool temperature online real-time closed-loop control system applies a double-color infrared thermometer to carry out coaxial fixed-point rapid temperature measurement, wherein hardware equipment of the laser cladding molten pool temperature online real-time closed-loop control system is a YLR-1000 fiber laser, an RC52 laser cladding head, an MCWL-50DTR water cooler, a VMC1100P vertical machining center, an RC-PGF-D-2 powder feeder, a PLC and laser operation integrated cabinet, RC-CAM rapid forming software, an industrial personal computer, a STRONG-GR-4020 type double-color infrared thermometer, a NET6043-S network data acquisition card and an RS-485 communication adapter;
the system is used for realizing online real-time detection and control of the temperature of the molten pool based on a NET6043-S network data acquisition card digital sampling and RS-485 communication module, and in the system used for realizing online real-time detection and control of the temperature of the molten pool based on the NET6043-S network data acquisition card digital sampling and RS-485 communication module, the NET6043-S network data acquisition card digital sampling and RS-485 communication module is set, and an analog quantity voltage signal with the temperature information of the molten pool measured by a bicolor infrared thermometer being 0-5V is set to be input into the NET6043-S network data acquisition card;
the data acquisition card inputs the temperature value into the PID real-time controller through AD conversion, and the voltage and temperature conversion formula is as follows:
T1＝(V×T3)/5+T2
in the formula, T1For the current display of temperature, T2Outputting a starting value for the analog quantity corresponding to the temperature, T3Outputting the difference between the temperature corresponding to the end value and the temperature corresponding to the initial value for the analog quantity;
signals output by a control algorithm in the controller are transmitted to the data acquisition card again, and 0-10V voltage signals are output by DA conversion and transmitted to the laser, so that the whole system can monitor the temperature of the molten pool on line in real time, and the temperature of the molten pool is controlled by adjusting the laser power;
selecting laser power as control variable and applying VC to develop melting bath temperature PID controller, setting T in the melting bath temperature PID controller selecting laser power as control variable and applying VC to developmFor the ideal value of the molten pool temperature to be set, T is the actual molten pool temperature in the cladding process measured in the current state, and n is the current cladding sampling number in the laser cladding process, namely the actual temperature T and the ideal temperature T when the nth point is claddedmThe temperature difference e (n) therebetween is:
e(n)＝Tm-T(n)
in the whole process of cladding and stacking materials, digital voltage output by a data acquisition card is corrected at each sampling point and converted into analog voltage so as to correct laser power, and the digital voltage variable delta u required by each sampling point can express a differential equation of a PID algorithm:
in the formula: k ispTo proportional gain, KiTo integrate the gain, KdIs the differential gain;
the digital voltage variation between two sampling points is the difference between two powers:
Δu＝u(n+1)-u(n)
in the formula, n is the current sampling point, and n +1 is the next sampling point;
from the above formula, the PID control algorithm expression of the digital voltage:
the DA output value in the data acquisition card is 0-4095, corresponding to 0-10V voltage and 0-1000W laser power, so the output analog voltage can be expressed as:
the PID control algorithm expression for deducing the laser power is as follows:
a system for actually controlling the temperature of a thin-wall laser cladding molten pool is designed in the system for actually controlling the temperature of the thin-wall laser cladding molten pool, the length of a thin-wall is 50mm, the number of layers is 30, the lifting amount of a Z axis is 0.65mm, a forming material is 304 iron-based self-fluxing alloy powder, the granularity is 200 meshes, the components of the forming material are shown in Table 1, a 45 steel plate substrate is adopted as a substrate material, the size is 200mm multiplied by 10mm,
TABLE 1304 iron-based self-fluxing alloy powder compositions (wt%)
Before the experiment, place metal powder and dry in the powder drying-machine, it is 3h when drying, the temperature is 150 ℃, filter the powder with the sieve after drying, prevent that the powder is moist and thoughtlessly have large granule powder to lead to sending the powder pipe to block up, for verifying molten bath temperature control system validity, design two sets of thin wall cladding experiments, experiment 1 is the open-loop thin wall experiment that does not add molten bath temperature control, selects the technological parameter after orthogonal test optimizes: the laser power is 450W, the scanning speed is 480mm/min, the powder feeding speed is 13g/min as experimental process parameters, the experiment 2 is a closed-loop thin-wall experiment added with molten pool temperature control, the rest parameters are consistent with the parameters of the experiment 1 except the laser power, the ideal temperature is set to 1450 ℃, the experimental process parameters are shown in the table 2,
TABLE 2 thin-walled wall comparison experiment Process parameters
And
the system for analyzing the result of the thin-wall formed part performs molten pool temperature analysis, thin-wall formed size precision analysis, microscopic structure analysis and hardness analysis in the system for analyzing the result of the thin-wall formed part.
2. The laser cladding molten pool temperature control method is characterized by comprising the following steps of:
s1, developing a laser cladding molten pool temperature online real-time closed-loop control system, applying a double-color infrared thermometer for coaxial fixed-point rapid temperature measurement, wherein hardware equipment of the laser cladding molten pool temperature online real-time closed-loop control system is a YLR-1000 fiber laser, an RC52 laser cladding head, an MCWL-50DTR water cooler, a VMC1100P vertical machining center, an RC-PGF-D-2 powder feeder, a PLC and laser operation integrated cabinet, RC-CAM rapid molding software, an industrial personal computer, a STRONG-GR-4020 type double-color infrared thermometer, a NET6043-S network data acquisition card and an RS-communication adapter;
s2, building a NET6043-S network data acquisition card based digital sampling and RS-485 communication module to realize online real-time detection and control of the temperature of the molten pool, wherein the step S2 comprises the following substeps:
s21, measuring the temperature of the molten pool by using a STRONG-GR-4020 type two-color infrared thermometer;
s22, building a NET6043-S network data acquisition card-based digital sampling and RS-485 communication module, and inputting an analog quantity voltage signal of which the temperature information of the molten pool measured by the bicolor infrared thermometer is 0-5V into the NET6043-S network data acquisition card;
s23, the data acquisition card inputs the temperature value to the PID real-time controller through AD conversion, and the voltage and temperature conversion formula is as follows:
T1＝(V×T3)/5+T2
in the formula, T1Is at presentDisplay temperature, T2Outputting a starting value for the analog quantity corresponding to the temperature, T3Outputting the difference between the temperature corresponding to the end value and the temperature corresponding to the initial value for the analog quantity;
s24, outputting a signal by a control algorithm in the controller, transmitting the signal to the data acquisition card again, outputting a 0-10V voltage signal by DA conversion, transmitting the signal to the laser, monitoring the temperature of the molten pool in real time in an online manner by the whole system, and controlling the temperature of the molten pool by adjusting the laser power;
s3, selecting laser power as a control variable, and applying VC to develop a molten pool temperature PID controller, wherein the step S3 comprises the following substeps:
s31, designing an experiment of influence of laser power on the temperature of a molten pool;
s32, analyzing the experimental result, and selecting the laser power as a control variable;
s33, applying VC to develop a PID controller of the temperature of the molten pool, and the step S33 comprises the following sub-steps:
s331, setting TmFor the ideal value of the molten pool temperature to be set, T is the actual molten pool temperature in the cladding process measured in the current state, and n is the current cladding sampling number in the laser cladding process, namely the actual temperature T and the ideal temperature T when the nth point is claddedmThe temperature difference e (n) therebetween is:
e(n)＝Tm-T(n)
s332, in the whole process of cladding and stacking materials, outputting digital voltage through a correction data acquisition card at each sampling point, converting the digital voltage into analog voltage, and further correcting laser power, wherein the digital voltage variable delta u required by each sampling point can express a difference equation of a PID algorithm:
in the formula: kpTo proportional gain, KiTo integrate the gain, KdIs the differential gain;
s333, the digital voltage variation between the two sampling points is the difference between the two powers:
Δu＝u(n+1)-u(n)
in the formula, n is the current sampling point, and n +1 is the next sampling point;
s334, the PID control algorithm expression of the digital voltage is obtained by the formula:
s335, the DA output value in the data acquisition card is 0-4095, corresponding to 0-10V voltage and 0-1000W laser power, so the output analog voltage can be expressed as:
s336, the PID control algorithm expression for deducing the laser power is as follows:
s4, actually controlling the temperature of the thin-wall laser cladding molten pool, in the step S4, designing a thin-wall cladding experiment, wherein the length of the thin-wall is 50mm, the number of layers is 30, the Z-axis lifting amount is 0.65mm, the forming material is 304 iron-based self-fluxing alloy powder, the granularity is 200 meshes, the components of the forming material are shown in Table 1, the forming material adopts a 45 steel plate substrate, the size is 200mm multiplied by 10mm,
TABLE 1304 iron-based self-fluxing alloy powder compositions (wt%)
Before the experiment, place metal powder and dry in the powder drying-machine, it is 3h when drying, the temperature is 150 ℃, filter the powder with the sieve after drying, prevent that the powder is moist and thoughtlessly have large granule powder to lead to sending the powder pipe to block up, for verifying molten bath temperature control system validity, design two sets of thin wall cladding experiments, experiment 1 is the open-loop thin wall experiment that does not add molten bath temperature control, selects the technological parameter after orthogonal test optimizes: the laser power is 450W, the scanning speed is 480mm/min, the powder feeding speed is 13g/min as experimental process parameters, the experiment 2 is a closed-loop thin-wall experiment added with molten pool temperature control, the rest parameters are consistent with the parameters of the experiment 1 except the laser power, the ideal temperature is set to 1450 ℃, the experimental process parameters are shown in the table 2,
TABLE 2 thin-walled wall comparison experiment Process parameters
S5, analyzing the result of the thin-wall forming piece, wherein the step S5 comprises the following substeps:
s51, analyzing the temperature of the molten pool;
s52, analyzing the forming size precision of the thin-wall;
s53, microscopic structure analysis;
and S54, hardness analysis.
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