CN109570808B

CN109570808B - Method and device for improving weld joint quality of narrow lap welder

Info

Publication number: CN109570808B
Application number: CN201710909237.5A
Authority: CN
Inventors: 龚辉; 李宏; 李辉; 唐智雁
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2021-08-13
Anticipated expiration: 2037-09-29
Also published as: CN109570808A

Abstract

A method and a device for improving the weld quality of a narrow lap welder comprise the following steps: 1) controlling automatic tracking of the welding seam by the temperature probe, 2) keeping the temperature detected by the temperature probe constant, and 3) carrying out online detection and evaluation on the welding seam quality. Firstly, determining the optimal temperature to be detected by a temperature measuring probe during welding; performing a welding experiment on the substrate plate, determining an optimal quality information curve and a maximum defect allowable quality curve, and establishing a quality curve database; the quality information curve is matched with the weld quality information curve detected in real time, the similarity between the quality information curve (optimal curve similarity) in the database and the weld quality information curve detected in real time is more than 80%, the display module displays 'qualified', the similarity between the quality information curve (optimal curve similarity) in the database and the weld quality information curve detected in real time is less than 80%, the display module displays 'unqualified', and the alarm device gives an alarm.

Description

Method and device for improving weld joint quality of narrow lap welder

The technical field is as follows:

the invention relates to the technical field of metallurgical welding, in particular to a method and a device for improving the weld quality of a narrow lap welder in the welding technology of a sheet strip steel coil joint.

Background

In order to ensure the continuity of the production of the tin plate, the forward strip steel and the subsequent strip steel need to be connected by a welding method before the substrate enters the pickling process section.

In the whole electroplating process, the substrate is bent under the condition of repeatedly bearing large tension through the tension roller, and the strip breakage often occurs at the welding seam connection part. And the broken belt can cause the damage of the working roller, even can cause the shutdown of the whole unit, reduce the production efficiency, cause the very big loss to the production of the tinned plate.

The average thickness of the thin specification of the tin plate is usually only about 0.15mm, the strip steel is usually connected by adopting a narrow lap welding machine for welding, the welding principle of the welding machine is that when an upper welding wheel and a lower welding wheel roll on the joint of the head and the tail of two steel coils, the welding wheels pass current, the heat generated by the contact resistance between the head and the tail of the strip steel and between the strip steel and the welding wheels by using the resistance of the strip steel per se is utilized to increase the temperature of the strip steel, the head and the tail of the two molten steel coils are finally welded by the pressure of a pneumatic cylinder of the welding wheels, and the welding line is flattened by a rolling wheel to form a rolled welding line, so that the flatness of the welding line is improved.

However, the field investigation shows that the narrow-gap resistance welding seam has defects of unfused, burn-through and the like, and the seam defect is a main cause of belt breakage accidents and seriously influences the continuity of the production of the tin plate.

The quality of the welding seam of the strip steel on the current production line is mainly observed by the visual experience of workers, the judgment method has large human factors, can not completely analyze the defects of the welding seam, and has great limitation. The method for detecting the quality of the welding seam at home and abroad mainly comprises the following steps: temperature field detection, coaxial real-time detection and video sensing system. The mode of temperature field and coaxial real-time detection is to indirectly monitor the welding process, while the video sensing system can only detect the defects on the upper surface of the welding seam, and the three methods can not timely, accurately and reliably reflect the quality of the welding seam.

By searching for 'weld defects' and 'eddy current testing', relevant patents are not found; 5 invention patents and 9 utility model patents are found in total by searching for 'narrow lap welding machine'. According to the similarity, the following representative patents are subjected to technical comparison, and similar technologies and methods are not found.

Patent No. CN201110040990.8 "a method for adding an online annealing function to a full-automatic narrow lap welder" and patent No. CN201110040881.6 "a method for annealing a 45 steel weld on a narrow lap welder", are characterized in that after welding is completed, current is again applied to the weld to heat the weld to an annealing temperature to achieve annealing. And three parameters of loading current, pressure and running speed are set on a human-computer interface, so that the heating temperature of the welding seam meets the requirement of an annealing process. The technology is applied to cold-rolled strips, and although the internal stress of the welding seam can be effectively changed to improve the quality of the welding seam, the technology does not relate to the welding seam quality detection technology, and the defects caused during welding cannot be prevented.

The patent No. CN201510235330.3 'narrow lap welding process of cold-rolled dual-phase steel strip' and the patent No. CN201610162706.7 'welding method of 980MPa grade cold-rolled dual-phase steel' mainly relate to welding methods of cold-rolled dual-phase steel, and the welding methods adopt a narrow lap welding machine to weld, the tail of a front-winding steel strip and the head of a rear-winding steel strip are cut, then the front-winding steel strip and the rear-winding steel strip are lapped with each other to be welded, parameters such as welding current, welding speed, welding wheel pressure, welding lap amount, welding compensation amount and the like are determined, the narrow lap welding operation of the cold-rolled dual-phase steel strip is realized, and conditions are provided for the continuous production of the cold-rolled dual-phase steel strip. The patent relates to continuous production of tin plates, and provides a dynamic method for detecting welding seams and improving the quality of the welding seams, and the two methods are not necessarily connected.

Patent No. CN201610997659.8 "narrow overlap joint welding machine of roll extrusion and welding process and activity welt" mainly aims at solving because there is the unreasonable problem of structure in the current activity welt of the narrow overlap joint welding machine of roll extrusion, it is often damaged by shear band head, tape trailer short slab in production operation, cause the welding machine to hinder and can not accomplish welding process smoothly because of removing the card, and then lead to the problem such as aluminium zinc plating unit deceleration shut down even, its patent point is mainly on the setting of activity welt, irrelevant with this patent technology.

In addition, patent number CN201621137054.3 "rolling wheel of belted steel narrow lap welder"'s utility model, through structural improvement, make rolling wheel change into rolling friction by original sliding friction, solved rolling wheel body motion unsmooth, the problem of crushing the welding seam easily, do not have the technical relevance with this patent.

The utility model provides a when the adhesion takes place for the tape head of two-layer belted steel after the shearing, carry out magnetism respectively to belted steel through magnetism suction part to the utility model of patent No. CN201020524439.1 "three formula clamping device of narrow lap welder" solves and to separate the tape head of two-layer belted steel by force, avoids taking place rosin joint or unable welded problem because of the tape head adhesion, does not have technical relevance with this patent.

Patent No. CN201120196230.1 "a narrow lap welder current control device" utility model, it comprises signal amplifier, change over switch, filter circuit, current control circuit, timing circuit and can eliminates the welding error signal, solves the too big problem of welding start in-process electric current fluctuation, makes the wheel that welds not add the electric current when just contacting belted steel to avoid welding the damage of wheel, do not have technical relevance with this patent.

Through technical comparison and field investigation, the quality of the welding seam is related to factors such as welding current and welding pressure in the process of forming the welding seam of the strip steel, and the factors are concentrated on the temperature of the welding seam, so that the temperature plays a key role in the quality of the welding seam in the process of forming the welding seam. At present, the quality of a welding seam is generally monitored by a method of monitoring the temperature of the welding seam, and the detection precision can be ensured only when a temperature measuring point is relatively fixed. As a main factor influencing the continuous production of the tin plate, the broken strip of the welding seam has close relation with the defect of the welding seam. Therefore, the key point for reducing the strip breakage rate of the thin-specification tin plate is to control, improve the welding quality and accurately evaluate the welding seam quality.

Disclosure of Invention

Aiming at the conditions that only welding state variables (welding current and welding pressure) are monitored and estimated in the welding process of a narrow lap welder, the welding seam quality cannot be directly detected and evaluated, and the welding seam defect cannot be rapidly detected on line, a set of system and a device capable of directly and accurately adjusting and evaluating the welding seam quality according to the actual conditions on site are designed.

The flow chart of the welding machine system of the invention is shown in figure 1, and the welding machine system is mainly controlled automatically through the temperature measuring point of the temperature measuring probe; parameters of the welding machine are automatically adjusted through feedback of temperature information; the welding machine can accurately adjust and evaluate the quality of the welding seam through real-time conditions by analyzing and judging the quality of the welding seam through pulse eddy current detection and the like.

The technical scheme of the invention is as follows:

a method for improving the weld quality of a narrow lap welder is characterized by comprising the following steps:

1) control of automatic tracking of welding seam by temperature probe

The temperature measurement driving module 7 is arranged at the front end of the lower welding wheel 8 and is close to the welding position, the temperature measurement driving module 7 comprises a stepping motor, a displacement sensor, a temperature measurement probe 15 and a probe bracket 13, the displacement sensor detects the temperature of welding points of the temperature measurement probe in the vertical direction (namely the gravity direction of the Y axis) and the Z direction vertical to the X axis and the Y axis,

when the welding seam fluctuates in the vertical direction, information is collected through the Y-direction displacement sensor 16, the information is transmitted to software embedded in a computer after A/D conversion, the software analyzes data of the sensor, determines whether the Y direction needs to be adjusted and the amount of adjustment, then sends an instruction to the ARM7 module, and the ARM7 controls the Y-direction stepping motor 12 to enable the temperature measuring probe 15 to act to ensure that the Y-direction position of the temperature measuring point is relatively fixed;

similarly, the displacement difference between the lower welding wheel 8 and the upper welding wheel in the Z direction is detected by the Z-direction displacement sensor, and the movement of the Z-direction stepping motor 11 is finally controlled by the analysis of the AD module and the computer, so that the relative position of the temperature measuring probes 15 in the Y direction and the Z direction is ensured simultaneously, the control of automatic tracking of the welding seam is realized,

2) the temperature detected by the temperature probe is kept constant,

the temperature measuring probe 15 transmits the detected temperature information to the temperature data processor, the temperature data processor performs primary processing on the information, the processed data is transmitted to the temperature data acquisition module, the temperature data acquisition module further processes the information, the processed information is transmitted to embedded software of a computer, and the software compares the information further processed by the temperature data acquisition module with an optimal temperature value and sends an adjusting instruction to automatically adjust the real-time welding current of the welding machine so as to ensure that the temperature detected by the temperature measuring probe is kept constant;

3) the welding seam quality is detected and evaluated on line,

firstly, determining the influence degree of welding parameters on the welding quality of a welding seam through an orthogonal experiment, and determining the optimal temperature to be detected by a temperature measuring probe during welding;

b, performing a welding experiment on the substrate plate, determining an optimal quality information curve and a maximum defect allowable quality curve through experience and 25-35 cup bulge experiments, and establishing a quality curve database;

c, detecting the quality information of the welded welding seam in real time, transmitting the detected quality original data of the welded welding seam to a quality data processor, preliminarily processing the original data by the quality data processor, and transmitting the processed data to a quality data acquisition module;

d, the quality data acquisition module further processes the data, transmits the processed data to computer embedded software, matches the quality information curve in the database with the weld quality information curve detected in real time by calling the quality information curve,

e, if the similarity between the quality information curve (the optimal curve similarity) in the database and the weld quality information curve detected in real time is more than 80%, the display module displays 'qualified' and the alarm device is silent;

if the similarity between the quality information curve (the optimal curve similarity) in the database and the weld quality information curve detected in real time is below 80%, the display module displays 'unqualified', and the alarm device gives an alarm.

According to the invention, the method for improving the weld quality of the narrow lap welder is characterized in that,

and e) displaying the adjustment condition of welding parameters of the welding machine, the information of the welded steel coil, a real-time information curve of the welded welding seam quality, a final analysis and judgment result and the like in real time by the display module.

in the step 3), when the welding experiment is carried out on the substrate plate in the step a), the thickness of the steel coil in the front row is 0.14-0.19mm, the thickness of the steel coil in the rear row is 0.14-0.19mm, and the welding and cup-convex experiments are carried out for 25-35 times to determine the optimal temperature to be detected by the temperature measuring probe during welding.

in the step 3), when a welding experiment is carried out on a common substrate plate, a quality information curve is fitted by a least square method, and an optimal quality information curve and a maximum defect allowable quality curve are determined by human experience and 25-35 cup bulge experiments to establish a quality curve database.

in step 1), a temperature measurement driving module 7 is arranged at the front end of a lower welding wheel 8 close to a welding position, and the temperature of a welding spot during welding is detected.

and in step 3), installing a temperature measurement driving module 7 behind the upper rolling wheel 3, and detecting the quality information of the welded welding seam in real time.

and b) determining an optimal weld quality information curve y (x), a maximum defect allowable quality curve a (x) for generating burn-through defects when the welding current is too large and a maximum defect allowable quality curve b (x) for generating unfused defects when the welding current is too small through experimental data such as eddy current detection, tensile test, metallographic test and the like, field working conditions and human experience.

at step 3) e:

(1) if the similarity between the welding seam quality curve y (x) and the optimal quality information curve y x (x) is less than 80%, judging that the welding seam quality is unqualified, and re-welding the welding seam; otherwise, judging the product is qualified and allowing the product to pass;

(2) if the similarity between y (x) and the maximum defect allowable quality curve a x (x) is more than 95%, judging that the welding seam is unqualified and the welding seam needs to be re-welded; otherwise, judging the product is qualified and allowing the product to pass;

(3) if the similarity between y (x) and the maximum defect allowable quality curve b x (x) is more than 95%, judging that the welding seam is unqualified and the welding seam needs to be re-welded; otherwise, the product is judged to be qualified, and the product is allowed to pass.

(4) A/D conversion is carried out on the data through a data acquisition card, and the analog quantity data is converted into a digital quantity voltage value Volt (i); if the data Volt (i) is larger than the allowed maximum defect peak value, namely the defect threshold MAX1 corresponding to the unfused defect value, calculating the number N1, if the ratio N1/N is larger than 60%, judging that the quality of the welding seam is unqualified, and welding the welding seam again;

otherwise, judging the product is qualified and allowing the product to pass;

n is the total number of the detected data, and N is the total number of the numbers which are greater than the defect threshold MAX1 in all the data Volt (i);

(5) if the data Volt (i) is less than the defect threshold MAX2, calculating the number N2, and if the ratio N2/N is more than 30%, judging that the quality of the welding seam is unqualified and the welding seam needs to be welded again;

otherwise, judging the product is qualified and allowing the product to pass;

(6) if the data Volt (i) is larger than the average value AVG of all the data, calculating the number N3 of the data, if the ratio N3/N is larger than 50%, judging that the quality of the welding seam is unqualified and the welding seam needs to be welded again;

otherwise, judging the product is qualified and allowing the product to pass;

the data average value AVG is the sum of all data volt (i) divided by the total number of data detection data.

(defect threshold MAX1 corresponding to the value of unfused defect: when the weld current is small, there is unfused defect, the larger the eddy current signal shows the amplitude, the more serious the separation of the upper and lower weld plates of the corresponding weld, and conversely, the smaller the eddy current signal shows the amplitude, the smaller the separation of the upper and lower weld plates of the corresponding weld.)

At (6), the standard mainly judges whether the fluctuation of the eddy current signal is smooth, and if the ratio is more than 50%, the peak value and the valley value of the eddy current signal are large, and the welding defect exists. The higher the fluctuation frequency of the eddy current signal is, the lower the tensile strength of the welding seam is; the eddy current signal suddenly changes, and the tensile strength of the welding seam is smaller.

at step 3) e:

(7) if the numerical values of Volt (i) and Volt (i +1) are greatly different, judging that the local part of the welding seam has a burn-through condition, prompting an operator to check the surface condition of the welding seam in time, adjusting parameters of the welding machine and the like.

(8) If the Volt (i) continuously exceeds the defect threshold value and the fluctuation is very small, the situation that the burn-through or the non-fusion is large in the length direction of the welding seam exists in the range is shown, the welding seam is judged to be qualified or not according to the length of the axial crack, and the situation that the welding seam is judged to be unqualified when 20% of the length is adopted and needs to be welded again.

the establishment of the database is judged,

experiments are carried out on the substrate plates welded by narrow-gap resistance welding, different welding modes, different welding parameters and the like, and a set of complete database is established.

For example: the width and the thickness of the forward strip steel are 838mm and 0.15mm, and the forward strip steel is low-carbon steel; the width of the subsequent strip steel specification is 838mm, the thickness is 0.17mm, and the subsequent strip steel specification is also low-carbon steel. According to the situation, 100 welding seams are welded, different welding currents are controlled to weld, the obtained welding seams are firstly subjected to eddy current detection, the detected data are subjected to fitting of a welding seam quality curve through the principle of least square, then different parts of the welding seams are subjected to tensile tests, the tensile strength of the welding seams is determined, and the optimal welding seam quality information curve y (x), the maximum defect allowable quality curve a (x) for burning-through defects caused by overlarge welding current and the maximum defect allowable quality curve b (x) for non-fusion defects caused by overlong welding current are determined according to the situation of work of a welding seam site.

According to the research of the relationship between the eddy current signal and the quality of the welding seam, the quantitative relationship between the eddy current signal and the tensile strength of the welding seam is determined, and the one-to-one correspondence relationship between the tensile strength of the welding seam and the magnitude of the eddy current signal is established, namely the larger the magnitude of the eddy current signal is, the lower the tensile strength of the welding seam is; the higher the fluctuation frequency of the eddy current signal is, the lower the tensile strength of the welding seam is; the eddy current signal suddenly changes, the tensile strength of the welding seam is smaller, and the like. The selection of the defect threshold value is an accurate and reliable numerical value obtained by statistically analyzing the recording result of the ACCESS database and the actual on-site strip breakage condition after on-site operation.

Recording an optimal welding seam quality information curve y (x), a maximum defect allowable quality curve a (x) for generating burn-through defects when the welding current is too large and a maximum defect allowable quality curve b (x) for generating unfused defects when the welding current is too small, simultaneously recording a defect threshold MAX1, a defect threshold MAX2 and an average value AVG, programming through VB6.0, writing into detection and evaluation software, and establishing a quality curve and defect threshold database. The establishment of the database can realize automation of the evaluation of the detection and evaluation system, so that the evaluation result is more accurate and reliable, and the quality operation of the detection and evaluation system is ensured.

The method for improving the weld quality of the narrow lap welder is characterized by comprising the following steps of,

the differential probe sensor is adopted to scan and detect the sample, and when the differential probe sensor is installed, the constant distance between the probe and the surface of the welding seam needs to be kept at 1-2 mm.

A differential probe is one type of eddy current probe. The differential probe consists of two or more identical balancing coils that interact with the test piece. The device is designed to selectively respond to the sharp change of a test piece, such as cracks, air holes and the like, is not sensitive to the slow change of materials or geometric shapes and long continuous defects, but is convenient for extracting and processing response signals generated by different influencing factors. Since the defects mainly existing in the weld are weld-through, non-fusion, and the like, and belong to the mutant defects, the differential probe sensor is used for scanning the sample.

when the differential probe sensor is used for scanning and detecting a sample, the differential probe sensor moves along a gap between two clamping tables, the gap between the two clamping tables is 8-10mm, and the diameter of the differential probe is 6-10 mm.

Preferably, the differential probe diameter D is 8 mm.

The diameter of the differential probe is too small, which affects the winding of the probe and the signal acquisition, and the diameter D of the probe is 8mm after the balance is achieved.

the maximum temperature of the metal core temperature profile in the differential probe is less than 200 ℃.

The device for improving the weld quality of the narrow lap welder is characterized in that,

the temperature measurement driving module 7 is arranged at the front end of the lower welding wheel 8 and is close to the welding position to detect the welding spot temperature during welding, the temperature measurement driving module 7 comprises a stepping motor, a displacement sensor, a temperature measurement probe 15 and a probe bracket 13, the displacement sensor detects the welding spot temperature of the temperature measurement probe in the vertical direction (namely the gravity direction of the Y axis) and the Z direction vertical to the X axis and the Y axis,

if the welding seam fluctuates in the vertical direction, information is collected through the Y-direction displacement sensor 16, the information is transmitted to software embedded in a computer after A/D conversion, the software determines whether the Y direction needs to be adjusted and the amount of adjustment after analyzing the data of the sensor, then an instruction is sent to an ARM7 module, and the ARM7 controls the Y-direction stepping motor 12 to enable the temperature measuring probe 15 to act to ensure that the Y-direction position of the temperature measuring point is relatively fixed;

similarly, the displacement difference between the upper welding wheel 8 and the lower welding wheel 8 in the Z direction is detected through a Z-direction displacement sensor, and the motion of the Z-direction stepping motor 11 is finally controlled through the analysis of an AD module and a computer, so that the relative positions of the temperature measuring probes 15 in the Y direction and the Z direction are ensured simultaneously, and the control of automatic tracking of the welding seam is realized.

when the temperature measuring probe is installed, the constant distance between the temperature measuring probe and the surface of the welding seam is kept to be 1-2 mm.

the differential probe sensor is adopted to scan the sample, and during detection, the differential probe sensor moves along a gap between the two clamping platforms, the gap between the two clamping platforms is 8-10mm, and the diameter of the differential probe is 6-10 mm.

the maximum temperature of the temperature profile of the metal core in the probe is below 200 ℃.

The method and the device for improving the weld quality of the narrow lap welder are characterized in that the establishment of a database is judged

For example: the width and the thickness of the forward strip steel are 838mm and 0.15mm, and the forward strip steel is low-carbon steel; the width of the subsequent strip steel specification is 838mm, the thickness is 0.17mm, and the subsequent strip steel specification is also low-carbon steel. According to the situation, 100 welding seams are welded, different welding currents are controlled to weld, the obtained welding seams are firstly subjected to eddy current detection, the detected data are subjected to fitting of a welding seam quality curve through the principle of least square, then different parts of the welding seams are subjected to tensile tests, the tensile strength of the welding seams all day long is determined, and the optimal welding seam quality information curve y (x), the maximum defect allowable quality curve a (x) for burning-through defects caused by overlarge welding current and the maximum defect allowable quality curve b (x) for unfused defects caused by undersize welding current are determined according to the situation of work of a welding seam site.

According to the invention, it comprises: a first part:

displacement control of the temperature probe, temperature control of the welding seam and judgment of the quality of the welding seam.

As shown in FIG. 2, the temperature measurement driving module 7 is installed at the front end of the lower welding wheel 8, close to the welding position, and detects the temperature of the welding spot during welding.

As shown in fig. 3, the temperature measurement driving module 7 mainly includes a stepping motor, a displacement sensor, a temperature measurement probe 15, a probe holder 13, and the like. The movement in the X-axis direction (horizontal direction) is synchronous with the lower welding wheel 8, so that the position in the X-axis direction is ensured not to be changed.

In order to ensure that the position of the temperature measuring point of the temperature measuring probe is relatively fixed, the change of two axial positions of the temperature measuring probe is detected by a displacement sensor. Respectively as follows: the vertical direction (gravity direction) is defined as the Y-axis direction and is controlled by a Y-direction stepping motor 12. The direction perpendicular to the X and Y axes is called the Z direction (the direction from inside to outside and from outside to inside), and is controlled by a Z-direction stepping motor 11.

The two stepping motors are vertically fixed together, wherein a Y-direction stepping motor 12 is fixed on a screw rod of a Z-direction stepping motor 11, a probe bracket 13 is arranged on the Y-direction stepping motor, and a temperature measuring probe 15 and a displacement sensor are arranged on the probe bracket 13. Therefore, when the Z-direction stepping motor 11 moves in the Z-axis direction, the motor in the Y-direction is driven to displace in the Z-axis direction, and the temperature measuring probe also displaces in the Z-axis direction.

If the welding seam fluctuates in the vertical direction, the Y-direction displacement sensor 16 collects information, the information is transmitted to software embedded in a computer after A/D conversion, the software analyzes the data of the sensor, determines whether the Y direction needs to be adjusted and the amount of adjustment, then sends an instruction to an ARM7 module, and the ARM7 controls the Y-direction stepping motor 12 to enable the temperature measuring probe 15 to act to ensure that the Y-direction position of the temperature measuring point is relatively fixed.

Similarly, in the Z axis, the displacement difference between the lower welding wheel 8 and the Z direction can be detected by the Z displacement sensor, and the movement of the Z stepping motor 11 is finally controlled through the analysis of the AD module and the computer. Therefore, the relative position of the temperature measuring probe 15 in the Y direction and the Z direction is ensured simultaneously, and the control of automatic tracking of the welding seam is realized.

Temperature control of weld

As shown in figure 1, in actual production, temperature probe 15 transmits the detected temperature information to a temperature data processor, the temperature data processor performs primary processing on the information, the processed data are transmitted to a temperature data acquisition module, the temperature data acquisition module further processes the information, the processed information is transmitted to embedded software of a computer, the computer is connected with a welding machine through a serial port, the software automatically adjusts the real-time welding current of the welding machine by comparing with the optimal temperature value, so as to ensure that the temperature detected by the temperature probe is kept constant, and the welding quality is ensured.

Determination of weld quality

Firstly, the patent determines the influence degree of welding parameters on the welding quality of a welding seam through an orthogonal experiment, and determines that welding current is the primary influence factor. The welding test was conducted on a conventional substrate plate material, for example, a forward coil thickness of 0.14mm and a backward coil thickness of 0.14 mm. And performing 30 times of welding and cup-convex experiments on the condition to determine the optimal temperature to be detected by the temperature measuring probe during welding.

Then, a welding test is performed on a conventional substrate plate material, for example, the thickness of the preceding coil is 0.14 to 0.19mm, and the thickness of the following coil is 0.14 to 0.19 mm. And (3) performing 30 times of welding on the condition, fitting a quality information curve by a least square method, and determining the optimal quality information curve and the maximum defect allowable quality curve through human experience and 30 cup convex experiments to establish a quality curve database.

Install the vortex probe in last rolling wheel 3's rear, real-time detection welding seam quality information after the welding, the raw data transmission who detects gives the quality data processor, the quality data processor does primary processing to raw data, give the quality data acquisition module with the data transmission who handles, the quality data acquisition module is to further processing of data, give the embedded software of computer with the data transmission who handles, match through the quality information curve of calling in the database and the welding seam quality information curve of real-time detection. The similarity with the optimal curve is more than 80%, or the similarity with the maximum defect allowable quality curve is 100%, the computer sends the quality, the display module displays 'qualified' and the alarm device is silent; on the contrary, the display module displays 'unqualified' and the alarm device gives an alarm prompt.

The display module displays the adjustment condition of welding parameters of the welding machine, the information of the welded steel coil, the real-time information curve of the welded welding seam quality, the final analysis and judgment results and the like in real time.

The alarm device gives an alarm prompt when the display module displays 'unqualified'; the opposite alarm device remains silent.

According to the invention, it also comprises: a second part: and establishing a judgment criterion and a database in a judgment system and designing the eddy current detection probe.

1. And establishing judgment criteria.

Through experimental data such as eddy current testing, tensile testing, metallographic testing and the like, field working conditions and human experience, an optimal weld quality information curve y (x), a maximum defect allowable quality curve a (x) for generating burn-through defects due to overlarge welding current and a maximum defect allowable quality curve b (x) for generating unfused defects due to overlarge welding current are determined. The criteria are as follows:

(1) the similarity between the welding seam quality curve y (x) and the optimal quality information curve y x (x) is less than 80 percent, the welding seam quality is judged to be unqualified, and the welding seam needs to be welded again; otherwise, the product is judged to be qualified, and the product is allowed to pass.

(2) The similarity between y (x) and the maximum defect allowable quality curve a x (x) is more than 95%, the welding seam is judged to be unqualified, and the welding seam needs to be welded again; otherwise, the product is judged to be qualified, and the product is allowed to pass.

(3) The similarity between y (x) and the maximum defect allowable quality curve b x (x) is more than 95%, the welding seam is judged to be unqualified, and the welding seam needs to be welded again; otherwise, the product is judged to be qualified, and the product is allowed to pass.

(4) Calculating the number N of the data Volt (i) which is larger than the defect threshold MAX1, wherein the ratio N/N is larger than 60%, judging that the quality of the welding seam is unqualified, and welding the welding seam again; otherwise, the product is judged to be qualified, and the product is allowed to pass. (n is the total number of detected data)

(5) Calculating the number N of the data Volt (i) which is larger than the defect threshold MAX2, wherein the ratio N/N is larger than 30%, judging that the quality of the welding seam is unqualified, and welding the welding seam again; otherwise, the product is judged to be qualified, and the product is allowed to pass. (n is the total number of detected data)

(6) The data Volt (i) is larger than all the data average value AVG, the number N is calculated, the ratio N/N is larger than 50%, the quality of the welding seam is judged to be unqualified, and the welding seam needs to be welded again; otherwise, the product is qualified and allowed to pass. (n is the total number of detected data)

2. And (4) establishing a database in the system.

And establishing a database in the detection evaluation system according to the summarized evaluation criteria. Experiments are carried out on the substrate plates welded by narrow-gap resistance welding, different welding modes, different welding parameters and the like, and a set of complete database is established.

3. Design of eddy current testing probe

Design of eddy current probe bearing device

The differential probe is an eddy current probe, the eddy current probe is in a high-temperature state during detection, and if a common probe is adopted for detection, the detection performance of the probe is greatly influenced, so that a high-temperature resistant eddy current probe must be developed. When the eddy current probe is installed, the constant distance between the eddy current probe and the surface of the welding seam is required to be kept between 1 mm and 2 mm.

According to the requirements of field working conditions and the characteristics of eddy current detection, the mounting bracket is designed as shown. The design of the waist holes ensures the adjustability of the bracket in the left and right directions and ensures that the phenomenon of welding machine interference can not occur when the probe is installed; the platform is designed for the installation and matching of the eddy current probe, the eddy current probe is arranged on the bracket and can be adjusted up and down, and the requirement on the distance between the eddy current probe and the surface of a welding seam is ensured.

The material selected for the eddy current probe bearing device is high-strength plastic, so that the electromagnetic field of the eddy current probe is not influenced, and the excellent detection effect is ensured. The plastic has the advantages of high temperature resistance, flame retardance, outstanding mechanical property, good rigidity and toughness, stable material, no toxicity and no smell. The eddy current probe is relatively fixed in position due to good mechanical performance, and the high temperature resistance can meet the requirement of high temperature under the field working condition.

According to the invention, it also comprises: and a third part: and (5) detecting and evaluating the system.

3.1 a complete working flow is formed from the beginning of welding to the end of welding, the eddy current sensor detects the defects of the welding seam, the detection and evaluation software displays and evaluates the defects in real time, the working flow is repeatedly executed, and each welding seam is detected, analyzed and evaluated, so that the online real-time detection and evaluation of the quality of the welding seam of the narrow-gap resistance welding are realized.

3.2 Transmission of data

The transmission process of the data signal is as shown in fig. 3-2, the original data of the weld quality detected by the eddy current sensor is transmitted to the eddy current flaw detector, the eddy current flaw detector preprocesses the data, the processed data is transmitted to the data acquisition card, and the data is transmitted to the computer through A/D conversion. The sampling frequency of the eddy current detection equipment is 100Hz, namely 100 defect signal data can be acquired every second, in order to prevent the interference of the surrounding environment to data transmission, a special anti-interference signal wire is adopted to connect the eddy current sensor and the eddy current flaw detector, and connect the eddy current flaw detector and the data acquisition card, the data acquisition card is selected from a USB5936 model, and the data acquisition card is connected with a computer through a USB interface.

3.3 processing of data

The data processing process is divided into three stages, namely a first stage, wherein the eddy current signals of the defects in the welding seams are output to corresponding analog quantities; the second stage, the collection of analog quantity, the conversion process of digital quantity of analog quantity; and in the third stage, data analysis, processing and image display of digital quantity are carried out according to the quality of the welding seam. In the first stage, i.e. the detection of weld defects, the identification of the defect signals is particularly critical, since the detection of the defect signals is essential for the quality of the eddy current test, and the first stage of data processing is shown in detail in fig. 3-3.

The signal generating circuit generates alternating current which is supplied to a detection coil in the electric eddy current sensor, the coil generates an alternating magnetic field around the coil, the alternating magnetic field generates eddy current in a detected welding seam, the eddy current is acted on the coil in a reverse mode when being affected by defects in the welding seam and on the surface of the welding seam, so that the impedance of the coil is changed, the eddy current cannot be changed under the condition that the welding seam has no defects, a change signal generated by the detection coil is very small, and firstly, the amplifying circuit amplifies a weak detection signal; during detection, the relative position between the detection coil and the welding seam is changed due to mechanical vibration and the like to generate noise, the amplitude of the noise signal is generally larger than the signal amplitude caused by tiny defects, and the characteristics of different phases of the defect signal and the relative position noise signal are utilized to realize the analysis of the phase and the inhibition of interference through a phase-sensitive detector, so that the purpose of inhibiting the interference and detecting the defects is achieved; after the phase-sensitive detection processing, the output signals may also include information such as the shape, size, electromagnetic characteristics and the like of a welding seam besides defect signals, and the signals need to be further processed to suppress invalid information and obtain useful defect information; after the above processing, there may be some remaining small residual noise that is not suppressed, such as interference noise in the surrounding environment, and the detection and filtering cannot completely suppress it, an amplitude discrimination circuit is used to set an effective reference level, and when the input voltage is lower than the reference level, the circuit does not output, and when the input voltage exceeds the preset value, the signal is output, as shown in fig. 3-4.

The second stage is to perform analog-to-digital conversion on the data output in the first stage, convert the output analog quantity data into digital quantity data, and then perform the data processing operation in the next stage. Since the signal outputted in the first stage is a continuous voltage signal corresponding to the defect, which cannot be identified, received and processed by the computer, it needs to be converted into a discontinuous digital voltage signal corresponding to the defect, and a/D conversion is performed by the data acquisition card to make it into data which can be read and written and operated by the computer. The data acquisition card is selected to perform A/D conversion on data, and is suitable for batch reading of a large amount of data and high-speed continuous acquisition of a large amount of data, and the equipment is stable and reliable to use and simple to operate. The money data acquisition card well meets the characteristics of rapidity, instantaneity, large quantity and the like of data detection of the welding seam quality detection system. For the welding seam quality information, the more the detected data is, the more truly and accurately the good and bad welding seam quality can be reflected.

The data format is used as the key of A/D conversion, and for the system, the value range of AD original data after being converted into the voltage value Volt is the same, and the voltage value Volt is stored in a TXT file.

And in the third stage, analyzing and processing digital quantity data, displaying images, prompting results and the like according to the quality of the welding seam. The data is processed through the processes of reading, storing, curve fitting, matching evaluation, emergent display, result prompting and the like through the processes shown in the figures 3-5. The A/D acquisition module is in an open state, and when a welding start signal is received, a scribing subprogram is called to perform fitting display on the data acquired in real time; meanwhile, reading and storing data, when a welding end trigger signal is received, finishing data access, closing an A/D acquisition module, and storing original data in a TXT file; next, matching a curve fitted by the original data with a quality curve in a database, automatically evaluating the result as a qualified welding line through evaluation of an evaluation criterion, prompting in a display module, and storing the result in an ACCESS database for future statistics and investigation; on the contrary, the welding seam with unqualified automatic evaluation result is also displayed in the display module, the unqualified result information is also stored in the ACCESS database, and meanwhile, the alarm device can automatically give a warning to prompt an operator to check the unqualified detection result and perform the next operation, such as the adjustment of parameters of the narrow-gap resistance welding machine, the re-welding of the welding seam and the like.

The ACCESS has the capability of data processing and statistical analysis, and meanwhile, the inquiry function of the ACCESS can be utilized to carry out statistics such as various summarizations, averages and the like. The statistical analysis of the production condition in the later period and the analysis of the service condition of the welding seam detection system are met, and a large amount of data information is provided for continuously improving and optimizing the welding seam detection system.

As described above, the eddy current sensor is in the shape of a pen having a diameter of 8mm, and detects weld quality information. The sensor detects that the original data needs to be preprocessed, the preprocessed data are processed through an amplifier, a wave detector, a phase shifter, a filter and the like, finally, the processed data are transmitted to a data acquisition card through a signal wire for preventing external interference, and analog quantity data are converted into digital quantity through A/D conversion.

The voltage data of the digital quantity is curve-fitted by the least square method. The least square method is selected to fit the curve, because the actual requirement is well met in the process of processing the welding seam quality information curve, the actual state is approached, and the method is simple and effective in data processing.

According to the invention, the problem that the temperature measuring point of the temperature measuring probe is relatively fixed is solved, and the information is fed back to the welding machine according to the temperature measuring point, so that the parameters of the welding machine are automatically adjusted, and the welding quality is ensured; the quality of the welding seam is analyzed and judged through pulse eddy current detection, misjudgment caused by manual visual detection is effectively avoided, and the equipment failure rate is reduced.

The online adjusting and detecting device for the quality of the welding seam is successfully applied to a No. 2 tinning unit of a Bao steel strand tinning plate factory. After the device is adopted, the strip breakage rate of the welding seam is as follows: less than or equal to 1 thousandth, thereby ensuring the continuous production of the tin plate, effectively reducing the occurrence of strip breakage accidents, greatly improving the quality control level of welding seams and ensuring the high-level production efficiency. In the production process of the continuous tin plate, the broken strip is the main reason for influencing the continuous production and reducing the efficiency. Because China has a plurality of tinned plate production lines, all the production lines are provided with welding seam quality on-line detection devices, and therefore, the application prospect is wide.

Description of the drawings:

FIG. 1 is a flow chart of a welder system of the present invention.

FIG. 2 is a schematic view of the welder apparatus of the present invention.

Fig. 2-1 is a schematic view of a mounting bracket.

Fig. 2-2 is a schematic view of a (differential) eddy current probe.

Fig. 2-3 are schematic diagrams of the temperature field distribution inside the (differential) eddy current probe during welding.

FIG. 3 is a schematic diagram of a temperature measurement driving module according to the present invention.

FIG. 3-1 is a flowchart of a scheme of a weld quality detection and evaluation system.

Fig. 3-2 is a flow chart of data signal transmission.

Fig. 3-3 are schematic diagrams of data signal processing flow.

Fig. 3-4 are schematic diagrams of amplitude analysis.

Fig. 3-5 are block diagrams of data processing flows.

In the figure, 1- (differential type) eddy current probe, 2-welder bracket, 3-upper rolling wheel, 4-lower rolling wheel, 5-upper welding wheel, 6-welding seam, 7-temperature measurement driving module, 8-lower welding wheel, 11-Z direction stepping motor, 12-Y direction stepping motor, 13-probe bracket, 14-Z direction displacement sensor, 15-temperature measurement probe and 16-Y direction displacement sensor.

In the case of the figures 2-3,

A-B represents a temperature field of +6.200e + 02- +5.700e + 02- +5.200e +02,

C-D represents a temperature field of +5.200e + 02- +4.700e + 02- +4.200e +02,

E-H represents a temperature field of +4.200E + 02- +3.700E + 02-3.200E + 02- +2.700E + 02-2.200E +02,

I-J represents a temperature field of +2.200e + 02- +1.700e + 02- +1.200e +02,

K-L represents a temperature field of +1.200e +01 to +7.000e +02 to +2.000e + 01.

Detailed Description

Example (b):

system parameter

The welding condition of narrow lap resistance welding and the thickness of the substrate plate is 0.14-0.19 mm.

The temperature measuring probe 15 is selected to be anti-electromagnetic interference and dust-proof, when the temperature measuring probe is installed, the vertical distance between a temperature measuring point and the welding line 6 is 3mm, the linear distance between the temperature measuring point and the center of the lower welding wheel 8 is 105mm, and the center of the temperature measuring point is ensured to be aligned with the center of the welding wheel and synchronously move with the welding machine.

The detection of the welded seam quality adopts a (differential type) eddy current probe, is arranged behind a rolling wheel 3 on a narrow lap resistance welding machine, is more than 51m away from an upper welding wheel, moves synchronously with the welding machine, and ensures the real-time detection. The advantages of selecting the pulse eddy current detection are that the detection sensitivity is higher, the noise is easily inhibited during the detection signal processing, and the penetration depth is larger during the detection.

The

displacement sensors

14 and 16 respectively detect the position changes of the Y axis and the Z axis of the temperature measuring probe 15, the change information is transmitted to software embedded in a computer after A/D conversion, the software sends an instruction to an ARM7 module, the ARM7 sends a pulse signal to control the actions of the Z-direction stepping motor 11 and the Y-direction stepping motor 12, a lead screw is driven to move, the position of the temperature measuring probe 15 is finely adjusted, the temperature measuring point is guaranteed to be relatively fixed, and accurate temperature measurement is guaranteed.

The temperature probe 15 transmits the detected temperature information of the welding seam 6 to the temperature data processing device, the temperature data processing device conducts primary processing on the information, the processed data are transmitted to the temperature data acquisition module, the temperature data acquisition module conducts further processing on the information, the processed information is transmitted to embedded software of a computer, the computer is connected with a welding machine through a serial port, the software sends an instruction to automatically adjust the real-time welding current of the welding machine by comparing the optimal temperature value, and the temperature detected by the temperature probe is guaranteed to be constant.

The (differential type) eddy current probe detects the quality information of the welded welding seam 6 in real time, the detected original data are transmitted to the quality data processing device, the quality data processing device conducts preliminary processing on the original data, the processed data are transmitted to the quality data acquisition module, the quality data acquisition module conducts further processing on the data, the processed data are transmitted to computer embedded software, and the quality information curve in a database is matched with the welding seam quality information curve detected in real time through calling. When the similarity with the optimal curve is less than 80 percent or the similarity with the maximum defect allowable quality curve is less than 100 percent, the computer sends an instruction, the display module displays that the judgment result is unqualified, and the alarm device gives an alarm.

The display module displays the position condition of a temperature measuring point, the adjustment condition of welding parameters of the welding machine, the information of the front and rear welded steel coils, the real-time information curve of the welded welding seam quality, the final analysis and judgment results and the like in real time.

The alarm device gives an alarm prompt when the display module displays 'unqualified'; when the display module displays 'qualified', the alarm device keeps silent.

Effects of use

Before and after the welding seam quality evaluation system is installed and used, the broken strip number of the 1220 tin plating unit is obviously reduced.

Number of broken bands of each month before and after using surface weld quality evaluation system

Before the system is installed and used, the average number of broken belts from January to May is 6, after the system is used, from June to August, the average number of broken belts per month is 2, and the broken belt increase in 8 months is caused by the general reduction of the quality of welding seams due to the failure of welding machine equipment. The use of the welding seam quality evaluation device obviously reduces the number of broken welding seams, and the system can be seen to play an effective role in improving the welding seam quality of the tinning unit and preventing the broken welding seams.

The factors influencing the strip breakage of the welding seam are more, such as different specifications produced in each month, different forward strip steel and backward strip steel and accidental faults of a welding machine are potential factors causing the strip breakage, so that the strip breakage condition in each month has quite large fluctuation, but the direct reason causing the strip breakage of the welding seam is the inaccuracy of an operator in judging the quality of the welding seam, and the defective welding seam enters a rolling mill to cause the strip breakage. After the system is installed and used, the phenomenon of welding line breakage is greatly reduced, because the quality of the welding line is improved, the accuracy in the aspect of judgment is also greatly improved, and the problem that the welding line enters the subsequent process is reduced.

Design of eddy current probe bearing device

The eddy current probe is in a high-temperature state during detection, and if a common probe is adopted for detection, the detection performance of the probe is greatly influenced, so that a high-temperature-resistant eddy current probe must be developed. When the eddy current probe is installed, the constant distance between the eddy current probe and the surface of the welding seam is required to be kept between 1 mm and 2 mm.

Design of eddy current probe

Since the defects mainly existing in the weld are weld-through, non-fusion, and the like, and belong to the mutant defects, the differential probe sensor is used for scanning the sample. When the probe is detected, the probe moves along the gap between the two clamping tables, the gap between the two clamping tables is 10mm, the diameter of all the probes is smaller than 10mm, but the diameter of the probe is too small, the winding of the probe and the acquisition of signals can be influenced, and the diameter D of the probe is weighed to be 8 mm.

According to the welding temperature calculation result, the probe structure is optimally designed with the aim that the temperature of the metal core in the eddy current is not higher than 200 ℃, and finally the eddy current probe with the size as shown in figure 2-2 is obtained.

The eddy current probe is 1000mm away from the welding gun, the temperature at the bottom of the probe is about 320 ℃ during welding, and the temperature distribution inside the probe is shown in figures 2-3 during welding.

The temperature distribution of the metal core in the probe is shown in figures 2-3, the maximum temperature is lower than 200 ℃, and the requirement of the maximum working temperature is met. Through on-site actual measurement, the probe can completely bear the thermal shock in the whole welding process, has good and stable performance, and can effectively detect the defects in the welding seam. When the probe is used for on-site detection, the received signal noise is low, the state is stable, and the on-site detection requirements are completely met. In addition, the coil is not easy to have poor disconnection, low in cost, good in coil discreteness distribution, good in performance and capable of having long service life. The probe is not easy to have poor wire breakage, low in cost, good in coil discreteness distribution, good in performance and capable of having long service life.

Claims

1. A method for improving the weld quality of a narrow lap welder is characterized by comprising the following steps:

1) control of automatic tracking of welding seam by temperature probe

The temperature measurement driving module (7) is arranged at the front end of the lower welding wheel (8) and is close to the welding position, the temperature measurement driving module (7) comprises a stepping motor, a displacement sensor, a temperature measurement probe (15) and a probe bracket (13), the displacement sensor detects the position change of the temperature measurement probe in the vertical direction, namely the gravity direction of the Y axis, and the position change of the temperature measurement probe in the vertical direction, namely the horizontal direction and the Z direction of the Y axis,

when the welding seam fluctuates in the vertical direction, information is collected through a Y-direction displacement sensor (16), the information is transmitted to software embedded in a computer after A/D conversion, the software analyzes the data of the sensor and determines whether the Y direction needs to be adjusted and the amount of adjustment, then an instruction is sent to an ARM7 module, and an ARM7 controls a Y-direction stepping motor (12) to enable a temperature measuring probe (15) to act to ensure that the Y-direction position of a temperature measuring point is relatively fixed;

similarly, the Z-direction displacement sensor (14) is used for detecting the displacement difference between the temperature probe and the lower welding wheel (8) in the Z direction, and the motion of the Z-direction stepping motor (11) is finally controlled through the analysis of the AD module and the computer, so that the relative positions of the temperature probe (15) in the Y direction and the Z direction are ensured simultaneously, the control of automatic tracking of the welding seam is realized,

2) the temperature detected by the temperature probe is kept constant,

the temperature measurement probe (15) transmits detected temperature information to the temperature data processor, the temperature data processor performs primary processing on the information, processed data are transmitted to the temperature data acquisition module, the temperature data acquisition module further processes the information, the processed information is transmitted to embedded software of a computer, and the software compares the information further processed by the temperature data acquisition module with an optimal temperature value and sends an adjusting instruction to automatically adjust real-time welding current of the welding machine so as to ensure that the temperature detected by the temperature measurement probe is kept constant;

3) the welding seam quality is detected and evaluated on line,

firstly, determining the influence degree of welding parameters on the welding quality of a welding seam through an orthogonal experiment, and determining the optimal temperature to be detected by a temperature measuring probe during welding; when a welding experiment is carried out on a substrate plate, the thickness of a steel coil in the front row is 0.14-0.19mm, the thickness of a steel coil in the rear row is 0.14-0.19mm, and 25-35 times of welding and cup-convex experiments are carried out to determine the optimal temperature to be detected by a temperature measuring probe during welding;

d, further processing the data by the quality data acquisition module, transmitting the processed data to computer embedded software, and matching the quality information curve in the database with the weld quality information curve detected in real time;

e, if the similarity of the quality information curve in the database, namely the optimal curve and the weld quality information curve detected in real time is more than 80%, the display module displays 'qualified', and the alarm device is silent;

if the similarity between the quality information curve in the database, namely the optimal curve and the weld quality information curve detected in real time is below 80%, the display module displays 'unqualified', and the alarm device gives an alarm prompt;

the display module displays the adjustment condition of welding parameters of the welding machine, the information of the welded steel coil, a real-time information curve of the welded welding seam quality and a final analysis and judgment result in real time;

the differential probe sensor is adopted to scan and detect the sample, and when the differential probe sensor is installed, the constant distance between the differential probe sensor and the surface of the welding seam is required to be kept to be 1-2 mm.

2. The method for improving the weld quality of a narrow lap welder according to claim 1,

and in step 3) b, determining an optimal weld quality information curve y (x), a maximum defect allowable quality curve a (x) for generating burn-through defects when the welding current is too large and a maximum defect allowable quality curve b (x) for generating unfused defects when the welding current is too small through eddy current detection, tensile test, metallographic test experimental data and field working conditions and human experience.

3. The method for improving the weld quality of a narrow lap welder according to claim 1,

the maximum temperature of the metal core temperature distribution within the differential probe sensor is less than 200 ℃.

4. A device for improving the weld quality of a narrow lap welder is characterized in that,

similarly, the displacement difference between the Z direction and the lower welding wheel (8) is detected through a Z-direction displacement sensor (14), and the motion of a Z-direction stepping motor (11) is finally controlled through the analysis of an AD module and a computer, so that the relative positions of the temperature probes (15) in the Y direction and the Z direction are ensured simultaneously, and the control of automatic tracking of the welding seam is realized.