CN114147382A - Electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device - Google Patents

Electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device Download PDF

Info

Publication number
CN114147382A
CN114147382A CN202111529323.6A CN202111529323A CN114147382A CN 114147382 A CN114147382 A CN 114147382A CN 202111529323 A CN202111529323 A CN 202111529323A CN 114147382 A CN114147382 A CN 114147382A
Authority
CN
China
Prior art keywords
welding
ultrasonic
spot welding
quality
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202111529323.6A
Other languages
Chinese (zh)
Other versions
CN114147382B (en
Inventor
徐国成
房湘荣
董娟
谷晓鹏
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jilin University
Original Assignee
Jilin University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jilin University filed Critical Jilin University
Priority to CN202111529323.6A priority Critical patent/CN114147382B/en
Publication of CN114147382A publication Critical patent/CN114147382A/en
Application granted granted Critical
Publication of CN114147382B publication Critical patent/CN114147382B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
    • B23K31/12—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to investigating the properties, e.g. the weldability, of materials
    • B23K31/125—Weld quality monitoring
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • B23K11/252—Monitoring devices using digital means
    • B23K11/257—Monitoring devices using digital means the measured parameter being an electrical current
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • B23K11/252—Monitoring devices using digital means
    • B23K11/258—Monitoring devices using digital means the measured parameter being a voltage
    • 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
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/36—Auxiliary equipment

Abstract

The invention relates to an electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device, belonging to the field of resistance spot welding quality nondestructive testing. The ultrasonic probe is fixed in the spot welding upper electrode and used for transmitting/receiving ultrasonic signals, the pressure sensor is arranged in the middle section of the lower electrode to monitor the pressure value between the upper electrode and the lower electrode in real time, and the current sensor and the voltage sensor monitor current and voltage signals at the output end of the spot welding machine. And establishing a workpiece contact state evaluation model and a nugget melting state analysis model by using the electric and ultrasonic signals. The monitoring method is characterized in that the quality of the spot welding joint in the pre-pressing stage and the quality of the workpiece in the electrifying stage are judged by analyzing the model, and automatic alarm can be realized for abnormal conditions. Has the advantages that: the on-line quality monitoring of all welding spots is realized, the quality of the spot welding head is judged from the angle of multiple parameters, the defects in the monitoring process of a single electric signal or a single ultrasonic signal are overcome, the condition of erroneous judgment is avoided as much as possible, and the monitoring result is more accurate and reliable.

Description

Electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device
Technical Field
The invention relates to the field of spot welding quality on-line monitoring, in particular to a resistance spot welding quality on-line monitoring method and device based on combination of electric and ultrasonic signals.
Background
The resistance spot welding has the advantages of low production cost, simple operation and easy realization of mechanization and automation, and is widely applied to the fields of urban rail trains, ships, aerospace and the like, so that the monitoring and the control of the resistance spot welding quality are very important. Resistance spot welding is a connecting method in which a workpiece to be welded is pressed between two electrodes, current is applied, and resistance heat generated by the current flowing through the contact surface and the adjacent area of the workpiece is heated to a molten state to form a nugget, so that the workpiece is combined with the metal. A large number of thin plate assembly parts exist in a welded workpiece, and poor assembly easily occurs due to tension of the welded workpiece when pressure is applied to the thin plate assembly parts; the formation process of the spot welding nugget is short in time and invisible in sealing, defects such as insufficient cold joint, insufficient nugget size, welding spatter and the like are easily generated, the strength of a spot welding joint cannot meet the quality requirement due to the defects, and therefore quality control and detection of the spot welding joint are particularly important.
Current testing modalities are typically destructive spot tests and non-destructive tests. Destructive detection needs steps of cutting, grinding and polishing, sample preparation, corrosion, metallographic observation and the like on a randomly extracted welding test piece, detection results are accurate and reliable, detection period is long, material waste is serious, sampling detection results are random, and quality detection cannot be performed on all spot-welded joints. The spot welding joint nondestructive detection method mainly comprises two major types, namely, the joint quality is evaluated according to an online monitoring signal in the welding process, and the spot welding joint quality is subjected to post-welding nondestructive detection. The on-line quality monitoring technology has high monitoring efficiency, can feed back the quality of the spot welding joint in real time, prevents the generation of defects of the spot welding joint to a certain extent, but cannot provide accurate quality assessment for the spot welding joint. The postweld nondestructive test is mostly ultrasonic detection, and ultrasonic detection has easy and simple to handle, and the security is good advantage, but ultrasonic detection easily receives external environment influence, and the detection precision remains to be improved.
Disclosure of Invention
The invention aims to provide an electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device, which solve the problems in the prior art. The invention introduces the electric signal to assist the ultrasonic signal, and the combination of the electric signal and the ultrasonic signal can realize the on-line quality monitoring of all welding spots in the spot welding process and can ensure the accuracy and the reliability of the monitoring result. The invention can realize the on-line monitoring of the process parameters including electrode pressure, welding current and welding voltage in the resistance spot welding process, and can also realize the judgment of the quality of the welding spot and the preliminary judgment of the defect type. The advantage of high efficiency and convenience of ultrasonic nondestructive testing is exerted, and meanwhile, the misjudgment rate of single ultrasonic signal for testing is reduced. The method has the advantages of strong practicability, high automation degree, no need of complex sensing technology and traceability of welding process parameters.
The above object of the present invention is achieved by the following technical solutions:
the electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method comprises the steps of placing an ultrasonic probe 2 in a spot welding upper electrode 1, and collecting ultrasonic signals; the pressure sensor 5 is arranged in the spot welding lower electrode 6, and a welding pressure signal is collected; collecting a welding current signal by using a current sensor 4; collecting a welding voltage signal by using a voltage sensor 7;
in the pre-pressing stage, the ultrasonic probe 2 transmits/receives ultrasonic signals, and the actual contact state of the welding workpiece is judged according to the echo characteristics; when the contact of the welding workpiece is good, the upper steel plate and the lower steel plate of the welding workpiece are tightly attached under the action of welding pressure, and part of ultrasonic beams penetrate through the interface of the upper steel plate and the lower steel plate and are incident into the lower steel plate; when the contact of the welding workpiece is poor, the ultrasonic beam is reflected from the bottom surface of the upper steel plate; meanwhile, the pressure sensor 5 collects a pressure signal, a welding workpiece prepressing effect evaluation model is established according to a welding pressure measured value and the contact state of the surface of the welding workpiece, and prepressing quality is judged;
in the electrifying stage, collecting a welding current signal and a welding voltage signal, and judging that the welding quality is unqualified when the current or voltage signal exceeds the limit; when the current signal and the voltage signal are not beyond the limit, calculating the heat input quantity Q of spot welding, simultaneously transmitting/receiving an ultrasonic signal by the ultrasonic probe 2, calculating the fusion depth D of the liquid nugget according to the echo characteristics, and establishing a nugget fusion state analysis model according to the heat input quantity Q and the fusion depth D so as to judge the welding quality.
The method for monitoring the quality of the resistance spot welding by compounding the electric signal and the ultrasonic signal comprises the following steps:
the method comprises the following steps of firstly, establishing a contact state evaluation model of a welding workpiece, and comprising the following substeps:
1.1) in the prepressing stage, analyzing the actual contact state of the welding workpiece through electrode pressure signals obtained by monitoring electrical parameters and echo signal characteristics of ultrasonic waves on the welding contact surface of the welding workpiece so as to evaluate whether the spot welding process conditions are normal or not; measured by welding pressure F1And the ultrasonic echo signal amplitude E at the contact surface of the welding workpiece1A prepressing effect evaluation analysis model I of the welding workpiece is established for variables, and the calculation method comprises the following steps:
P＝k1F1+k2E1 (1)
wherein P represents a welding work preload effect evaluation index, F1For the pre-pressing stage, the electrode pressure value measured by the pressure sensor, E1Echo signal amplitude of ultrasonic waves at the contact surface of a welding workpiece in a pre-pressing stage; k is a radical of1For the electrode pressure correction curve, k2Calibrating a curve for the ultrasonic echo signal; a plurality of groups of different prepresses are set to obtain a series of echo amplitudes at the contact surface of the welding workpiece under the corresponding prepresses, and k is obtained by performing curve fitting on the prepressing values and echo amplitude data1And k2Wherein k is1And k2Are determined by a welding system and an actual welding operation environment;
1.2) welding current stage, current I obtained by monitoring electrical parameters1And inter-electrode voltage signal U1Calculating heat input quantity Q in the spot welding process, calculating fusion depth D by analyzing ultrasonic echo characteristic signals in a fusion phase, analyzing a fusion state of the fusion, and evaluating the quality of a spot welding joint; by spot weldingProcess heat input Q and ultrasonic echo signal amplitude E at upper and lower surfaces of liquid nugget2、E3Establishing a nugget melting state analysis model II for the variables, wherein the calculation method comprises the following steps:
Q＝U1I1T0 (2)
D＝(v*△t)/2 (3)
W＝k3Q+k4D (4)
wherein Q is the heat input during spot welding, U1For measuring voltage values, I, for voltage sensors1For measuring the current value, T, for the current sensor0Is the energization time period; d is the fusion depth of the liquid nugget, v is the propagation speed of the ultrasonic signal in the liquid nugget, and Deltat is the echo signal E of the upper and lower surfaces of the received liquid nugget2、E3The time interval in between; w is the evaluation coefficient of spot welding quality, k3Correction of the curve for the heat input during spot welding, k4A fusion depth correction curve of the liquid nugget; wherein k is3And k4Are determined by a welding system and an actual welding operation environment;
and secondly, process analysis, which comprises the following substeps:
2.1) prepressing stage, after the monitoring system is started, monitoring the prepressing effect according to the model I, and when the electrode pressure F is actually measured1When the system parameter exceeds the threshold value, the audible and visual alarm automatically gives an alarm, namely the welding process is required to be stopped when the system parameter has errors, and the system parameter is immediately adjusted; when the electrode pressure F is actually measured1When the evaluation result is abnormal, the audible and visual alarm gives an alarm, and when the evaluation result is normal, the welding power-on stage is started;
Figure BDA0003411157690000041
2.2) electrifying stage, evaluating the quality of the spot-welded joint according to the model II, and performing actual measurement on the quality of the welded jointCurrent I1And welding voltage U1When the threshold value is exceeded, the audible and visual alarm gives an alarm; when welding current I1And spot welding voltage U1When the weld nugget is within the threshold range, calculating a quality evaluation coefficient W of the spot welding joint, and evaluating the nugget state;
Figure BDA0003411157690000042
the invention also aims to provide an electric and ultrasonic signal composite resistance spot welding quality on-line monitoring device, which comprises a spot welding machine, a spot welding upper electrode 1, a spot welding lower electrode 6, an ultrasonic probe 2, a high-temperature coupling agent 3, a full-function ultrasonic card 8, a pressure sensor 5, a current sensor 4, a voltage sensor 7, a data acquisition card 9, a computer 10 and an audible and visual alarm 11;
the ultrasonic probe 2 is a polycrystalline probe integrated with receiving and transmitting, can transmit ultrasonic signals, can receive the ultrasonic signals reflected by a welding workpiece, is fixed in the spot welding upper electrode 1, realizes direct coupling between the ultrasonic probe 2 and the bottom of the spot welding upper electrode 1 through the high-temperature coupling agent 3, is connected to the computer 10 through the full-function ultrasonic card 8, and the computer 10 controls the ultrasonic probe 2 to vertically transmit ultrasonic waves to the surface of the welding workpiece through the full-function ultrasonic card 8 and receives reflected echoes; the ultrasonic probe 2 is a polycrystalline probe integrated with receiving and transmitting, is fixed inside the spot welding upper electrode 1, and is directly coupled with the bottom of the spot welding upper electrode 1 through the high-temperature coupling agent 3 to vertically emit ultrasonic beams to the surface of a welding workpiece;
the pressure sensor 5 is located in the middle section of the spot welding lower electrode 6 and collects electrode pressure between the two electrodes in real time, the current sensor 4 and the voltage sensor 7 are both located at the output end of the spot welding machine and collect welding current and welding voltage in real time, electric signals are collected by the data collection card 9 and then transmitted to the computer 10 for automatic storage, and collection, monitoring and storage of electric signals in the spot welding process are achieved.
The invention has the beneficial effects that:
1. the ultrasonic probe is fixed at the center inside the spot welding upper electrode, the contact surface of the probe and the inside of the electrode is uniformly coated with the high-temperature couplant, and the electrode continuously applies proper pressure, so that the good coupling effect of ultrasonic monitoring is realized.
2. In the pre-pressing stage, the contact state of the surface of the workpiece to be welded is judged by combining the pressure signal and the ultrasonic signal, so that the follow-up welding electrifying process is continuously carried out under the condition of poor assembly at a high probability, and the defects of cold joint, small nugget diameter, local contact overheating and splashing can be reduced.
3. Ultrasonic testing in general is susceptible to interference from the external environment and the spot welding system itself, such as poor coupling, electrode wear, and the like. The detection result of the electric signal is stable and reliable, but the identification degree of the defect is limited, the defect of single signal detection can be overcome by combining the two signals, and the accuracy and the reliability of the detection are improved.
4. Above-mentioned ultrasonic monitoring device need not complicated sensing technology, convenient operation, and degree of automation is high, compares in traditional destructive testing mode, has practiced thrift material and artifical detection cost.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention.
FIG. 1 is a flow chart of the method for monitoring the quality of resistance spot welding by combining electric signals and ultrasonic signals on line;
FIG. 2 is a schematic structural diagram of an on-line monitoring device for the quality of resistance spot welding based on the combination of electric and ultrasonic signals according to the present invention;
FIG. 3 is a schematic diagram showing the condition of good ultrasonic echo of workpiece contact in the pre-pressing stage of the online monitoring method for the quality of resistance spot welding with electric and ultrasonic signal combination of the present invention;
FIG. 4 is a schematic diagram of ultrasonic echo condition of poor contact of a workpiece at the pre-pressing stage of the online monitoring method for the quality of resistance spot welding with electric and ultrasonic signal compounding of the invention;
FIG. 5 is a schematic diagram of the ultrasonic echo condition at the power-on stage of the method for online monitoring of the quality of resistance spot welding by combining electrical and ultrasonic signals.
In the figure: 1. spot welding an electrode; 6. spot welding the lower electrode; 2. an ultrasonic probe; 3. a high temperature coupling agent; 8. a full function ultrasound card; 5. a pressure sensor; 4. a current sensor; 7. a voltage sensor; 9. a data acquisition card; 10. a computer; 11. an audible and visual alarm.
Detailed Description
The details of the present invention and its embodiments are further described below with reference to the accompanying drawings.
Referring to fig. 1 to 5, the invention relates to an electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method and device, belonging to the field of resistance spot welding quality nondestructive testing. The ultrasonic probe is fixed in the spot welding upper electrode and used for transmitting/receiving ultrasonic signals, the pressure sensor is arranged in the middle section of the lower electrode to monitor the pressure value between the upper electrode and the lower electrode in real time, and the current sensor and the voltage sensor respectively monitor the current signal and the voltage signal in the welding power-on stage at the output end of the spot welding machine. And establishing a workpiece contact state evaluation model and a nugget melting state analysis model by using the electric and ultrasonic signals. The monitoring method is characterized in that the quality of the spot welding joint in the pre-pressing stage and the quality of the workpiece in the electrifying stage are judged by analyzing the model, and automatic alarm can be realized for abnormal conditions. The online quality detection of all welding spots is realized, the quality of the spot welding head is judged from the angle of multiple parameters, the defects in the detection process of a single electric signal or a single ultrasonic signal are overcome, the condition of erroneous judgment is avoided as much as possible, and the detection result is more accurate and reliable.
Referring to fig. 1 to 2, the method for monitoring the quality of resistance spot welding by combining electric and ultrasonic signals of the present invention effectively combines electrode pressure, welding current, welding voltage and ultrasonic signals by mainly establishing a workpiece contact state evaluation model and a nugget melting state analysis model. Arranging an ultrasonic probe 2 in the spot welding upper electrode 1, and collecting ultrasonic signals; the pressure sensor 5 is arranged in the spot welding lower electrode 6, and a welding pressure signal is collected; collecting a welding current signal by using a current sensor 4; collecting a welding voltage signal by using a voltage sensor 7;
in the pre-pressing stage, the ultrasonic probe 2 transmits/receives ultrasonic signals, and the actual contact state of the welding workpiece is judged according to the echo characteristics; referring to fig. 3, when the contact of the welding workpiece is good, the upper steel plate and the lower steel plate of the welding workpiece are tightly attached due to the action of welding pressure, and part of ultrasonic beams penetrate through the interface of the upper steel plate and the lower steel plate and are incident into the lower steel plate; referring to fig. 4, when the welded workpiece is in poor contact, the ultrasonic beam is reflected from the bottom surface of the upper steel plate; meanwhile, the pressure sensor 5 collects a pressure signal, a welding workpiece prepressing effect evaluation model is established according to a welding pressure measured value and the contact state of the surface of the welding workpiece, and prepressing quality is judged;
in the electrifying stage, collecting a welding current signal and a welding voltage signal, and judging that the welding quality is unqualified when the current or voltage signal exceeds the limit; referring to fig. 5, when the current and voltage signals are not in excess, the heat input Q of the spot welding is calculated, the ultrasonic probe 2 transmits/receives ultrasonic signals, the fusion depth D of the liquid nugget is calculated by echo characteristics, and a nugget fusion state analysis model is established according to the heat input Q and the fusion depth D to determine the welding quality.
The electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method is characterized in that: the method comprises the following steps:
the method comprises the following steps of firstly, establishing a contact state evaluation model of a welding workpiece, and comprising the following substeps:
1.1) in the prepressing stage, analyzing the actual contact state of the welding workpiece through electrode pressure signals obtained by monitoring electrical parameters and echo signal characteristics of ultrasonic waves on the welding contact surface of the welding workpiece so as to evaluate whether the spot welding process conditions are normal or not; measured by welding pressure F1And the ultrasonic echo signal amplitude E at the contact surface of the welding workpiece1A prepressing effect evaluation analysis model I of the welding workpiece is established for variables, and the calculation method comprises the following steps:
P＝k1F1+k2E1 (1)
wherein P represents a welding work preload effect evaluation index, F1For the pre-pressing stage, the electrode pressure value measured by the pressure sensor, E1Echo signal amplitude of ultrasonic waves at the contact surface of a welding workpiece in a pre-pressing stage; k is a radical of1For the electrode pressure correction curve, k2Calibrating a curve for the ultrasonic echo signal; a plurality of groups of different prepresses are set to obtain a series of echo amplitudes at the contact surface of the welding workpiece under the corresponding prepresses, and k is obtained by performing curve fitting on the prepressing values and echo amplitude data1And k2Wherein k is1And k2The welding method is determined by the specific conditions of a welding system, an actual welding operation environment and the like;
1.2) welding current stage, current I obtained by monitoring electrical parameters1And inter-electrode voltage signal U1Calculating heat input quantity Q in the spot welding process, calculating fusion depth D by analyzing ultrasonic echo characteristic signals in a fusion phase, analyzing a fusion state of the fusion, and evaluating the quality of a spot welding joint; using heat input quantity Q in spot welding process and ultrasonic echo signal amplitude E at upper surface and lower surface of liquid nugget2、E3Establishing a nugget melting state analysis model II for the variables, wherein the calculation method comprises the following steps:
Q＝U1I1T0 (2)
D＝(v*△t)/2 (3)
W＝k3Q+k4D (4)
wherein Q is the heat input during spot welding, U1For measuring voltage values, I, for voltage sensors1For measuring the current value, T, for the current sensor0Is the energization time period; d is the fusion depth of the liquid nugget, v is the propagation speed of the ultrasonic signal in the liquid nugget, and Deltat is the echo signal E of the upper and lower surfaces of the received liquid nugget2、E3The time interval in between; w is the evaluation coefficient of spot welding quality, k3Correction of the curve for the heat input during spot welding, k4A fusion depth correction curve of the liquid nugget; wherein k is3And k4The welding method is determined by the specific conditions of a welding system, an actual welding operation environment and the like;
and secondly, process analysis, which comprises the following substeps:
2.1) prepressing stage, after the monitoring system is started, monitoring the prepressing effect according to the model I, and when the electrode pressure F is actually measured1When the system parameter exceeds the threshold value, the audible and visual alarm automatically gives an alarm, namely the welding process is required to be stopped when the system parameter has errors, and the system parameter is immediately adjusted; when the electrode pressure F is actually measured1When the evaluation result is abnormal, the audible and visual alarm gives an alarm, and when the evaluation result is normal, the welding power-on stage is started;
Figure BDA0003411157690000081
2.2) electrifying, evaluating the quality of the spot-welded joint according to the model II when the actually measured welding current I1And welding voltage U1When the threshold value is exceeded, the audible and visual alarm gives an alarm; when welding current I1And spot welding voltage U1When the weld nugget is within the threshold range, calculating a quality evaluation coefficient W of the spot welding joint, and evaluating the nugget state;
Figure BDA0003411157690000082
referring to fig. 2, the device for monitoring the quality of resistance spot welding by combining electric signals and ultrasonic signals comprises a spot welding machine, a spot welding upper electrode 1, a spot welding lower electrode 6, an ultrasonic probe 2, a high-temperature coupling agent 3, a full-function ultrasonic card 8, a pressure sensor 5, a current sensor 4, a voltage sensor 7, a data acquisition card 9, a computer 10 and an audible and visual alarm 11;
the ultrasonic probe 2 is a polycrystalline probe integrated with receiving and transmitting, can transmit ultrasonic signals, can receive the ultrasonic signals reflected by a welding workpiece, is fixed in the spot welding upper electrode 1, realizes direct coupling between the ultrasonic probe 2 and the bottom of the spot welding upper electrode 1 through the high-temperature coupling agent 3, is connected to the computer 10 through the full-function ultrasonic card 8, and the computer 10 controls the ultrasonic probe 2 to vertically transmit ultrasonic waves to the surface of the welding workpiece through the full-function ultrasonic card 8 and receives reflected echoes; the ultrasonic probe 2 is a polycrystalline probe integrated with receiving and transmitting, is fixed inside the spot welding upper electrode 1, and is directly coupled with the bottom of the spot welding upper electrode 1 through the high-temperature coupling agent 3 to vertically emit ultrasonic beams to the surface of a welding workpiece;
the pressure sensor 5 is located in the middle section of the spot welding lower electrode 6 and collects electrode pressure between the two electrodes in real time, the current sensor 4 and the voltage sensor 7 are both located at the output end of the spot welding machine and collect welding current and welding voltage in real time, electric signals are collected by the data collection card 9 and then transmitted to the computer 10 for automatic storage, and collection, monitoring and storage of electric signals in the spot welding process are achieved.
Example (b):
an electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method comprises the following steps:
the method comprises the following steps of firstly, establishing a workpiece contact state evaluation model, and comprising the following substeps:
1.1, in the pre-pressing stage, the actual contact state of the welding workpiece is analyzed through electrode pressure signals obtained by monitoring electrical parameters and echo signal characteristics of ultrasonic waves on the welding contact surface of the welding workpiece, so as to evaluate whether the spot welding process conditions are normal or not. Establishing a welding workpiece contact state evaluation analysis model I by taking a welding pressure parameter value and an ultrasonic echo signal amplitude value as variables, wherein P is k1P1+k2E1In the formula P1For the pre-pressing stage, the electrode pressure value measured by the pressure sensor, E1And echo signal amplitude of ultrasonic waves at the contact surface of the welding workpiece in the pre-pressing stage. K1To correct the coefficient for electrode pressure, k2Correcting the coefficients for the ultrasonic echo signal, where k1And k2Are determined by the specific conditions of the welding system, the actual welding operation environment and the like.
1.2 welding current I obtained by monitoring electrical parameters1And inter-electrode voltage signal U1Calculating heat input Q in spot welding process, analyzing ultrasonic echo characteristic signal in melting phase of nugget, calculating melting depth, analyzing melting state of nugget, and evaluating spot-welded jointAnd (4) quality. Using heat input Q in spot welding process and ultrasonic echo liquid nugget state characteristic signal E2、E3Establishing a nugget melting state analysis model II for the variables, wherein W is k3Q+k4D, wherein Q is the heat input amount in the spot welding process, D is the melting depth of the liquid nugget, and k3Correction of coefficient of heat input for spot welding process, k4The fusion depth correction coefficient of the liquid nugget is obtained. Wherein k is3And k4Are determined by the specific conditions of the welding system, the actual welding operation environment and the like.
And secondly, process analysis, which comprises the following substeps:
2.1 prepressing stage, after the monitoring system is started, actually measuring the electrode pressure P by taking the model I as reference1When the threshold value is exceeded, the audible and visual alarm 11 automatically gives an alarm, namely, the welding process needs to be stopped when the system parameter has errors, and the adjustment is immediately carried out. If the electrode pressure P is actually measured1When the requirement of the threshold value is met, the ultrasonic probe continuously transmits/receives ultrasonic signals, and the contact surface of the welding workpiece has an obvious echo amplitude E1It is stated that there is a gap at the contact surface, tight fitting is not achieved, and there is a poor assembly condition, and the audible and visual alarm 11 automatically gives an alarm. If P is detectedIAnd E1All are normal, using model i, P ═ k1P1+k2E1And (5) performing operation, further evaluating the contact state of the welding workpiece in the pre-pressing stage, and entering a welding electrifying stage if the evaluation result meets the expectation.
2.2 the phase of energization, if the measured welding current I1Welding voltage U1And if the threshold value is exceeded, automatically alarming. If the measured welding current I1Welding voltage U1The requirement of a threshold value is met, and the heat input Q ═ U in the spot welding process is calculated1I1T0The computer 10 analyzes the ultrasonic echo signal and extracts the solid-liquid interface echo E on the upper layer of the nugget2And lower layer liquid-solid interface echo E3Calculating the depth of the nugget by using a formula D ═ (v × Δ t)/2, wherein v is the propagation speed of the ultrasonic signal in the liquid nugget, and Δ t is the echo E at the upper and lower interfaces of the nugget2、E3Time interval between, using model II to estimateThe nugget is in a molten state.
An on-line monitoring device for resistance spot welding quality of electric and ultrasonic signal composition comprises a spot welding machine, a spot welding upper electrode 1, a spot welding lower electrode 6, an ultrasonic probe 2, a high-temperature coupling agent 3, a full-function ultrasonic card 8, a pressure sensor 5, a current sensor 4, a voltage sensor 7, a data acquisition card 9, a computer 10 and an audible and visual alarm 11.
The ultrasonic probe 2 is a polycrystalline probe integrated with receiving and transmitting, can transmit ultrasonic signals, can receive the ultrasonic signals reflected by a welding workpiece, is fixed in the spot welding upper electrode 1, realizes direct coupling between the ultrasonic probe 2 and the bottom of the spot welding upper electrode 1 through the high-temperature coupling agent 3, is connected to the computer 10 through the full-function ultrasonic card 8, and the computer 10 controls the ultrasonic probe 2 to vertically transmit ultrasonic waves to the surface of the welding workpiece through the full-function ultrasonic card 8 and receives reflected echoes;
the pressure sensor 7 is located in the middle section of the spot welding lower electrode 6, electrode pressure between the two electrodes is collected in real time, the current sensor 4 and the voltage sensor 7 are both located at the output end of the spot welding machine, welding current and welding voltage are collected in real time, electric signals are collected by the data collection card 9 and then transmitted to the computer 10 for automatic storage, and collection, monitoring and storage of the electric signals in the spot welding process are achieved.
Referring to fig. 3 to 5, in the present embodiment, SUS301L stainless steel is used as an example of resistance spot welding of a spot welding sample, and the plate thickness combination is 2mm +2mm, the center frequency of an ultrasonic probe is 10MHz, the sampling frequency of a full-function ultrasonic card is 80MHz, the electrode pressure is 8KN, and the welding current is 11.5 KA. And comprehensively judging whether the quality of the welding spot is qualified or not by combining a workpiece contact state evaluation model in a prepressing stage and a nugget melting state analysis model in a power-on stage according to parameters such as electrode pressure, welding current, welding voltage and ultrasonic echo signal characteristics.
Referring to fig. 3 to 4, the ultrasonic propagation modes corresponding to different states in the spot welding process are also different. In the prepressing stage in the spot welding process, if the welding workpieces are not assembled well, the two welding workpieces are not deciphered and attached, and the ultrasonic wave is transmitted to the lower surface of the upper plate of the welding workpieceIs directly reflected back according to the original path and does not propagate downwards, and the ultrasonic echo signal amplitude E exists at the contact surface of the welding workpiece at the moment1(shown in FIG. 3); if the welding workpieces are well assembled, the surfaces of the two welding workpieces are tightly attached, the ultrasonic waves are straight to the lower surface of the lower plate of the welding workpiece and return along the original path, and at the moment, the amplitude E of the ultrasonic echo signal does not exist at the contact surface of the welding workpieces1(shown in FIG. 4);
referring to fig. 5, in the power-on stage of the spot welding process, a liquid nugget is formed, and at the time, a solid-liquid interface and a liquid-solid interface exist between the liquid nugget and the welding workpiece, and the ultrasonic wave generates a reflected echo signal E at the solid-liquid interface2Generating a reflected echo signal E at the liquid-solid interface3Upon reception of E by the ultrasonic probe2、E3The thickness of the nugget can be calculated according to the time interval Deltat.
The above description is only a preferred example of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like of the present invention shall be included in the protection scope of the present invention.

Claims (3)

1. An electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method is characterized in that: an ultrasonic probe (2) is arranged in the spot welding upper electrode (1) to collect ultrasonic signals; the pressure sensor (5) is arranged in the spot welding lower electrode (6) in an embedded mode, and welding pressure signals are collected; collecting a welding current signal by using a current sensor (4); collecting a welding voltage signal by using a voltage sensor (7);
in the pre-pressing stage, the ultrasonic probe (2) transmits/receives ultrasonic signals, and the actual contact state of the welding workpiece is judged according to the echo characteristics; when the contact of the welding workpiece is good, the upper steel plate and the lower steel plate of the welding workpiece are tightly attached under the action of welding pressure, and part of ultrasonic beams penetrate through the interface of the upper steel plate and the lower steel plate and are incident into the lower steel plate; when the contact of the welding workpiece is poor, the ultrasonic beam is reflected from the bottom surface of the upper steel plate; meanwhile, a pressure sensor (5) collects a pressure signal, a welding workpiece prepressing effect evaluation model is established according to a welding pressure measured value and the contact state of the surface of the welding workpiece, and prepressing quality is judged;
in the electrifying stage, collecting a welding current signal and a welding voltage signal, and judging that the welding quality is unqualified when the current or voltage signal exceeds the limit; when the current signal and the voltage signal are not beyond the limit, calculating the heat input quantity Q of spot welding, simultaneously transmitting/receiving an ultrasonic signal by the ultrasonic probe (2), calculating the melting depth D of the liquid nugget according to the echo characteristics, and establishing a nugget melting state analysis model according to the heat input quantity Q and the melting depth D so as to judge the welding quality.
2. The method for on-line monitoring the quality of electric and ultrasonic signal composite resistance spot welding according to claim 1, characterized in that: the method comprises the following steps:
the method comprises the following steps of firstly, establishing a contact state evaluation model of a welding workpiece, and comprising the following substeps:
1.1) in the prepressing stage, analyzing the actual contact state of the welding workpiece through electrode pressure signals obtained by monitoring electrical parameters and echo signal characteristics of ultrasonic waves on the welding contact surface of the welding workpiece so as to evaluate whether the spot welding process conditions are normal or not; measured by welding pressure F1And the ultrasonic echo signal amplitude E at the contact surface of the welding workpiece1A working and welding part preloading effect evaluation analysis model I is established for variables, and the calculation method comprises the following steps:
P＝k1F1+k2E1 (1)
wherein P represents a welding work preload effect evaluation index, F1For the pre-pressing stage, the electrode pressure value measured by the pressure sensor, E1Echo signal amplitude of ultrasonic waves at the contact surface of a welding workpiece in a pre-pressing stage; k is a radical of1For the electrode pressure correction curve, k2Calibrating a curve for the ultrasonic echo signal; a plurality of groups of different prepresses are set to obtain a series of echo amplitudes at the contact surface of the welding workpiece under the corresponding prepresses, and k is obtained by performing curve fitting on the prepressing values and echo amplitude data1And k2Wherein k is1And k2Are all formed by weldingDetermining a system and an actual welding operation environment;
1.2) welding current stage, current I obtained by monitoring electrical parameters1And inter-electrode voltage signal U1Calculating heat input quantity Q in the spot welding process, calculating fusion depth D by analyzing ultrasonic echo characteristic signals in a fusion phase, analyzing a fusion state of the fusion, and evaluating the quality of a spot welding joint; using heat input quantity Q in spot welding process and ultrasonic echo signal amplitude E at upper surface and lower surface of liquid nugget2、E3Establishing a nugget melting state analysis model II for the variables, wherein the calculation method comprises the following steps:
Q＝U1I1T0 (2)
D＝(v*△t)/2 (3)
W＝k3Q+k4D (4)
wherein Q is the heat input during spot welding, U1For measuring voltage values, I, for voltage sensors1For measuring the current value, T, for the current sensor0Is the energization time period; d is the fusion depth of the liquid nugget, v is the propagation speed of the ultrasonic signal in the liquid nugget, and Deltat is the echo signal E of the upper and lower surfaces of the received liquid nugget2、E3The time interval in between; w is the evaluation coefficient of spot welding quality, k3Correction of the curve for the heat input during spot welding, k4A fusion depth correction curve of the liquid nugget; wherein k is3And k4Are determined by a welding system and an actual welding operation environment;
and secondly, process analysis, which comprises the following substeps:
2.1) prepressing stage, after the monitoring system is started, monitoring the prepressing effect according to the model I, and when the electrode pressure F is actually measured1When the system parameter exceeds the threshold value, the audible and visual alarm automatically gives an alarm, namely the welding process is required to be stopped when the system parameter has errors, and the system parameter is immediately adjusted; when the electrode pressure F is actually measured1When the evaluation result is abnormal, the audible and visual alarm gives an alarm, and when the evaluation result is normal, the ultrasonic probe transmits/receives an ultrasonic signal and calculates the evaluation index of the prepressing effect according to the model IEntering a welding and electrifying stage;
Figure FDA0003411157680000021
2.2) electrifying, evaluating the quality of the spot-welded joint according to the model II when the actually measured welding current I1And welding voltage U1When the threshold value is exceeded, the audible and visual alarm gives an alarm; when welding current I1And spot welding voltage U1When the weld nugget is within the threshold range, calculating a quality evaluation coefficient W of the spot welding joint, and evaluating the nugget state;
Figure FDA0003411157680000031
3. a monitoring device suitable for the electric and ultrasonic signal composite resistance spot welding quality on-line monitoring method of claim 1, characterized in that: the spot welding device comprises a spot welding machine, a spot welding upper electrode (1), a spot welding lower electrode (6), an ultrasonic probe (2), a high-temperature couplant (3), a full-function ultrasonic card (8), a pressure sensor (5), a current sensor (4), a voltage sensor (7), a data acquisition card (9), a computer (10) and an audible and visual alarm (11);
the ultrasonic probe (2) is a polycrystalline probe integrated with a transceiver, can emit ultrasonic signals and receive the ultrasonic signals reflected by a welding workpiece, is fixed in the spot welding upper electrode (1), is directly coupled with the bottom of the spot welding upper electrode (1) through a high-temperature coupling agent (3), and is connected to a computer (10) through a full-function ultrasonic card (8), and the computer (10) controls the ultrasonic probe (2) to vertically emit ultrasonic waves to the surface of the welding workpiece and receive reflected echoes through the full-function ultrasonic card (8);
the pressure sensor (5) is located in the middle section of the spot welding lower electrode (6), electrode pressure between the two electrodes is collected in real time, the current sensor (4) and the voltage sensor (7) are both located at the output end of the spot welding machine, welding current and welding voltage are collected in real time, electric signals are collected by the data collection card (9) and then transmitted to the computer (10) for automatic storage, and collection, monitoring and storage of the electric signals in the spot welding process are achieved.
CN202111529323.6A 2021-12-14 2021-12-14 Method and device for on-line monitoring of electric and ultrasonic signal combined resistance spot welding quality Active CN114147382B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111529323.6A CN114147382B (en) 2021-12-14 2021-12-14 Method and device for on-line monitoring of electric and ultrasonic signal combined resistance spot welding quality

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111529323.6A CN114147382B (en) 2021-12-14 2021-12-14 Method and device for on-line monitoring of electric and ultrasonic signal combined resistance spot welding quality

Publications (2)

Publication Number Publication Date
CN114147382A true CN114147382A (en) 2022-03-08
CN114147382B CN114147382B (en) 2023-06-30

Family

ID=80451215

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111529323.6A Active CN114147382B (en) 2021-12-14 2021-12-14 Method and device for on-line monitoring of electric and ultrasonic signal combined resistance spot welding quality

Country Status (1)

Country Link
CN (1) CN114147382B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114700606A (en) * 2022-04-20 2022-07-05 无锡市力恩机械制造有限公司 System and method for monitoring weld quality
CN117436769A (en) * 2023-12-20 2024-01-23 山东方垠智能制造有限公司 Structural part welding quality monitoring method, system, storage medium and equipment

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1146907A (en) * 1965-06-08 1969-03-26 Deutsch Karl Method of and apparatus for the non-destructive testing of spot welds and other pressure welds
JPH04130266A (en) * 1990-09-20 1992-05-01 Hitachi Constr Mach Co Ltd Electromagnetic ultrasonic flaw detection method and apparatus
CN101523202A (en) * 2006-08-14 2009-09-02 Ge检查技术有限公司 Method for online ultrasound testing of a weld point produced using electrical resistance welding
CN105149762A (en) * 2014-12-27 2015-12-16 东北大学 Resistance spot welding quality evaluation device
CN106064282A (en) * 2016-07-13 2016-11-02 吉林大学 Joint for resistance spot welding quality ultrasound ripple online monitoring system and method
CN106124624A (en) * 2016-06-17 2016-11-16 武汉理工大学 A kind of thin plate point quality automatic detection device and method
CN106312312A (en) * 2016-10-12 2017-01-11 长春工程学院 Online monitoring device and method for lap joint laser welding penetration state
CN106735842A (en) * 2017-03-24 2017-05-31 上海骄成机电设备有限公司 A kind of supersonic welder of real-time detection welding quality
CN107931811A (en) * 2017-11-23 2018-04-20 西北工业大学 Nugget formation in resistance spot welding method for predicting diameter
CN109014544A (en) * 2018-08-17 2018-12-18 龙岩学院 Miniature resistance spot welding quality on-line monitoring method
CN109108445A (en) * 2018-11-05 2019-01-01 南京菲斯特焊接科技有限公司 A kind of suspension type electric resistance electric arc welder welding process parameter monitor and monitoring method
CN110726773A (en) * 2019-11-22 2020-01-24 吉林大学 Couplant-free in-situ pressure holding resistance spot welding ultrasonic detection device and method
CN112285211A (en) * 2020-11-03 2021-01-29 吉林大学 Resistance spot welding quality detection device and method

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1146907A (en) * 1965-06-08 1969-03-26 Deutsch Karl Method of and apparatus for the non-destructive testing of spot welds and other pressure welds
JPH04130266A (en) * 1990-09-20 1992-05-01 Hitachi Constr Mach Co Ltd Electromagnetic ultrasonic flaw detection method and apparatus
CN101523202A (en) * 2006-08-14 2009-09-02 Ge检查技术有限公司 Method for online ultrasound testing of a weld point produced using electrical resistance welding
CN105149762A (en) * 2014-12-27 2015-12-16 东北大学 Resistance spot welding quality evaluation device
CN106124624A (en) * 2016-06-17 2016-11-16 武汉理工大学 A kind of thin plate point quality automatic detection device and method
CN106064282A (en) * 2016-07-13 2016-11-02 吉林大学 Joint for resistance spot welding quality ultrasound ripple online monitoring system and method
CN106312312A (en) * 2016-10-12 2017-01-11 长春工程学院 Online monitoring device and method for lap joint laser welding penetration state
CN106735842A (en) * 2017-03-24 2017-05-31 上海骄成机电设备有限公司 A kind of supersonic welder of real-time detection welding quality
CN107931811A (en) * 2017-11-23 2018-04-20 西北工业大学 Nugget formation in resistance spot welding method for predicting diameter
CN109014544A (en) * 2018-08-17 2018-12-18 龙岩学院 Miniature resistance spot welding quality on-line monitoring method
CN109108445A (en) * 2018-11-05 2019-01-01 南京菲斯特焊接科技有限公司 A kind of suspension type electric resistance electric arc welder welding process parameter monitor and monitoring method
CN110726773A (en) * 2019-11-22 2020-01-24 吉林大学 Couplant-free in-situ pressure holding resistance spot welding ultrasonic detection device and method
CN112285211A (en) * 2020-11-03 2021-01-29 吉林大学 Resistance spot welding quality detection device and method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
王春生等: "不锈钢电阻点焊在线超声检查信号特征研究", 《电焊机》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114700606A (en) * 2022-04-20 2022-07-05 无锡市力恩机械制造有限公司 System and method for monitoring weld quality
CN117436769A (en) * 2023-12-20 2024-01-23 山东方垠智能制造有限公司 Structural part welding quality monitoring method, system, storage medium and equipment

Also Published As

Publication number Publication date
CN114147382B (en) 2023-06-30

Similar Documents

Publication Publication Date Title
CN114147382B (en) Method and device for on-line monitoring of electric and ultrasonic signal combined resistance spot welding quality
US9063059B2 (en) Three-dimensional matrix phased array spot weld inspection system
US11353430B2 (en) Phased array probe and method for testing a spot-weld
CN103808797B (en) A kind of method checking diffusion welding welding quality
CN105021142B (en) The measuring method and equipment therefor of a kind of laser lap weld width
CN106124624A (en) A kind of thin plate point quality automatic detection device and method
CN106064282A (en) Joint for resistance spot welding quality ultrasound ripple online monitoring system and method
CN101699279B (en) Ultrasonic defect detection method for T-shaped joint fillet weld of dual-phase steel and carbon steel
US10578586B2 (en) Weld analysis using Lamb waves and a neural network
CN110726773A (en) Couplant-free in-situ pressure holding resistance spot welding ultrasonic detection device and method
CN107478721A (en) A kind of point quality real-time ultrasound the cannot-harm-detection device and method
Yang et al. Measurement of weld penetration depths in thin structures using transmission coefficients of laser-generated Lamb waves and neural network
CN1332198C (en) Real time ultrasonic detection and monitoring method
Vasilev et al. Non-contact in-process ultrasonic screening of thin fusion welded joints
JPH06265529A (en) Method and apparatus for evaluating spot-welded part
CN112461920B (en) Method and device for judging high-temperature alloy spot welding defects based on ultrasonic measurement
Zhou et al. Research on evaluating laser welding quality based on two-dimensional array ultrasonic probe
CN201653957U (en) Resistance spot welding quality monitoring device
Karloff et al. REAL‐TIME ULTRASONIC EXPULSION DETECTION AND INDENTATION MEASUREMENT IN RESISTANCE SPOT WELDS
Stares et al. On-line weld pool monitoring and defect detection using ultrasonic
Acebes et al. Development of an automated ultrasonic inspection device for quality control of spot welds
CN201444148U (en) Inside burr automatic monitoring device in flaw detecting system
Liu et al. On-line measurement of nugget diameter in automatic resistance spot welding based on embedded ultrasound probe
Kustron et al. IN‐LINE ULTRASONIC INVESTIGATION OF SPOT WELD QUALITY USING MULTI‐TRANSDUCER SET‐UP
CN113740432B (en) Method for detecting connection quality in transient liquid phase connection

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant