Welding process and method for evaluating the quality of the weld after welding
The four-step evaluation method combining acoustic and optical methods with supplementary mechanical tests solves the efficiency and accuracy problems in the quality evaluation of cold continuous rolling welds, achieving efficient and accurate weld quality evaluation and reducing strip breakage rate and production losses.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI TAIGANG STAINLESS STEEL CO LTD
- Filing Date
- 2026-03-18
- Publication Date
- 2026-06-12
AI Technical Summary
Existing weld quality assessment methods cannot balance accuracy and efficiency in high-efficiency cold rolling production, leading to frequent weld failures and fractures, which affects production efficiency.
An acoustic-optical combined evaluation method is adopted. By collecting the laser scattered light brightness and spatter size of the weld pool, the acoustic characteristics of the welding process, and the weld seam projected by a directional light source, forming defects is identified. Combined with supplementary cupping mechanical tests, a four-step collaborative evaluation system is formed.
It achieves efficient and accurate weld quality assessment under the fast production pace of cold continuous rolling, reduces the strip breakage rate to 0.02%, significantly reduces capacity and energy loss, and has significant economic benefits.
Smart Images
Figure CN122193222A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of welding quality assessment before cold rolling of stainless steel, and specifically relates to a method for assessing the quality of the welding process and the weld seam after welding. Background Technology
[0002] The core of cold continuous rolling production is to form a continuous material flow by welding the ends of the strip. The weld is a key link in the continuous rolling process, but it is also a risk point where the mechanical properties are weak. Taiyuan Iron & Steel's cold continuous rolling production line uses laser welding technology, and the production cycle of a single coil of strip is only 10-20 minutes, which is highly efficient. However, weld failure and fracture can cause the unit to stop production for 5-10 hours, which seriously affects production efficiency.
[0003] Current weld quality assessment mainly relies on three technical approaches: First, offline laboratory testing, such as tensile, cold bending, or metallographic testing, which has the disadvantages of being complex to operate, time-consuming, and unsuitable for the fast-paced production of cold continuous rolling; second, online single-factor monitoring, such as optical signal detection, acoustic signal detection, or visual inspection, but single-factor monitoring has the disadvantages of low accuracy and unsuitability for the complex working conditions of multiple steel grades and variable specifications in stainless steel cold continuous rolling; the third is multi-factor monitoring, but multi-factor monitoring systems are complex and costly, and cannot balance detection efficiency and accuracy.
[0004] Therefore, there is an urgent need for a rapid inspection method that requires no complex equipment, can be directly executed on the production site, and balances accuracy and efficiency, in order to solve the industry pain point of mismatch between weld quality and production rhythm. Summary of the Invention
[0005] In order to solve all or some of the above problems, the present invention aims to provide a method for evaluating the welding process and the quality of the weld after welding.
[0006] According to one aspect of the present invention, a method for evaluating the welding process and the quality of the weld after welding is provided, comprising: The laser-scattered light intensity information of the weld pool and the spatter size on both sides of the weld are collected, and based on the intensity information and the spatter size, a preliminary judgment is made as to whether the laser welding process is normal. Acquire the acoustic characteristics during the welding process, and then use the acquired acoustic characteristics to make a secondary judgment on whether the laser welding process is normal; A directional light source is used to project onto the weld seam, identify weld formation defects, and adjust the laser welding process based on the identification results.
[0007] Furthermore, the step of collecting the laser scattered light brightness information of the weld pool and the spatter size on both sides of the weld, and preliminarily judging whether the laser welding process is normal based on the brightness information and the spatter size, further includes: Using a distance of 2m-3m from the welding position as the acquisition location, the laser scattered light brightness information of the weld pool is acquired. If the acquired brightness information is less than 80cd / m², the laser welding process is determined to be abnormal; and if the acquired brightness information fluctuates by more than ±30% and the fluctuation time exceeds 0.5s, the laser welding process is determined to have an abnormal situation of weld pool instability. Additionally, the spatter size on the steel plate surface after welding is collected within 20mm on both sides of the weld. If the welded steel is nickel-based stainless steel and the spatter size is less than or equal to 0.5mm, the laser welding process is considered normal. If the welded steel is chromium-based stainless steel and the spatter size is less than or equal to 2.0mm, the laser welding process is considered normal.
[0008] Furthermore, the laser scattered light brightness information of the weld pool is collected at a distance of 2m-3m from the welding position. If the collected brightness information is less than 80cd / m², the laser welding process is determined to be abnormal. Specifically: Using a distance of 2m-3m from the welding position as the acquisition location, collect the brightness information of the laser scattered light in the weld pool. If the acquired brightness information is less than 80cd / m², check the actual power of the laser welding process, check whether the surfaces of the reflector and focusing lens are contaminated, and check whether there are faults in the electrical components.
[0009] Furthermore, the specific steps of acquiring sound characteristics during the welding process and using these characteristics to make a secondary judgment on whether the laser welding process is normal are as follows: Acquire the sound characteristics during the welding process, and determine whether there is a first frequency sound generated by the plasma gas laser through the keyhole effect and a second frequency sound of the side-blown protective gas flow based on the acquired sound characteristics. If it is determined that there is no first frequency sound or second frequency sound, it is determined that there is an abnormal protective gas flow rate problem in the laser welding process. The first frequency sound refers to the sound with a frequency of 2-3kHz, and the second frequency sound refers to the sound with a frequency of 500-800Hz. Furthermore, based on the acquired sound characteristics, it is determined whether the sound characteristics have a fluctuation amplitude exceeding ±15dB and a fluctuation time greater than or equal to 0.5s. If so, it is determined that the laser welding process has a shielding gas nozzle angle offset, welding wire X-axis position misalignment, or poor welding wire straightening.
[0010] Furthermore, the method of using a directional light source to project onto the weld, identifying weld formation defects, and adjusting the laser welding process based on the identification results further includes: The upper and lower surfaces of the weld are projected using a light source, and the angle between the light source and the weld is controlled to be 30°-60°. The light refraction of the light source is used to identify whether there is an undercut defect with a depth greater than 0.5mm or an incomplete penetration defect with a width greater than 0.2mm. If the undercut defect or incomplete penetration defect is identified, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the determination result. Observe whether there is any depression on the upper surface of the steel plate at the weld, and if the depression depth is greater than 0.5mm, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the judgment result.
[0011] Furthermore, after projecting the weld seam using a directional light source, identifying weld seam forming defects, and adjusting the laser welding process based on the identification results, the method further includes: Supplementary cupping mechanical tests are conducted to ultimately determine the weld quality.
[0012] Furthermore, the supplementary cupping mechanical test, used to ultimately determine the weld quality, specifically includes: Cut a 100mm×100mm standard weld sample and apply a pressure of 50-100MPa to the sample to obtain the cracking pattern of the weld area. If the obtained cracking pattern is a crack with a crack length greater than 3mm, it is determined that there is a quality problem with the weld and the laser welding process needs to be adjusted.
[0013] As can be seen from the above technical solution, the method for evaluating the welding process and post-weld quality provided by the present invention has the following beneficial effects: Improved assessment efficiency: No complex equipment is required; assessments can be completed on-site in real time, adapting to the rapid production pace of cold continuous rolling at 10-20 minutes per coil, thus solving the industry pain point of mismatch between weld quality and production pace during cold continuous rolling. Improved quality stability: After implementation, the weld breakage rate of the cold continuous rolling RAP line dropped to 0.02%, far below the equipment guarantee value of 0.3%; Significant economic benefits: Annual reduction of production capacity loss, non-conforming losses, and energy waste losses totaling 8.64 million yuan; Highly practical: The steps are clear and the judgment criteria are well-defined, making it easy for welders to quickly master and apply the techniques. Attached Figure Description
[0014] Figure 1 This is a flowchart illustrating a welding process and a method for evaluating the quality of the weld after welding, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the weld seam obtained by projecting a directional light source onto the weld seam. Figure 3These are five typical cracking patterns observed in pressure tests. Detailed Implementation
[0015] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.
[0016] When a range of values is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0017] Through long-term research on the laser welding process and weld characteristics, it has been found that there is a strong correlation between the acoustic and optical changes during the welding process and the surface formation state of the weld and the internal mechanical properties of the weld. Therefore, this invention embodiment forms a four-step collaborative evaluation system of "seeing, listening, illuminating, and top" by combining acoustic and optical changes, weld surface formation state, and mechanical verification under specific scenarios. Among them, "seeing" is the real-time core evaluation step, "listening" and "illuminating" are supplementary verification steps, and "top" is the final mechanical verification step under specific scenarios. Each step is progressive and mutually verifies. This invention embodiment is applicable to the rapid evaluation of weld quality in cold continuous rolling laser welding production lines with a single coil production cycle of 10-20 minutes and a strip thickness of 4-6mm.
[0018] Specifically, such as Figure 1 As shown, this invention illustrates a welding process and a method for evaluating the quality of the weld after welding, comprising the following steps: Step S001: Collect the laser scattered light brightness information of the weld pool and the spatter size on both sides of the weld, and make a preliminary judgment on whether the laser welding process is normal based on the brightness information and spatter size; Step S002: Acquire the sound characteristics during the welding process, and make a secondary judgment on whether the laser welding process is normal based on the acquired sound characteristics; Step S003: Project a directional light source onto the weld seam, identify weld seam forming defects, and adjust the laser welding process based on the identification results.
[0019] Specifically, step S001 is the aforementioned "observation" step, which is the core real-time optical evaluation step in this embodiment of the invention. Step S001 collects the laser scattered light brightness information of the weld pool and the spatter size on both sides of the weld, and based on the brightness information and spatter size, preliminarily determines whether the laser welding process is normal, further including: The laser scattered light brightness information of the weld pool is collected at a distance of 2m-3m from the welding position. If the collected brightness information is less than 80cd / m², the laser welding process is judged to be abnormal; and if the collected brightness information fluctuates by more than ±30% and the fluctuation time exceeds 0.5s, the laser welding process is judged to have an abnormal situation of weld pool instability. Additionally, the spatter size on the steel plate surface after welding is collected within 20mm on both sides of the weld. If the welded steel is nickel-based stainless steel and the spatter size is less than or equal to 0.5mm, the laser welding process is considered normal. If the welded steel is chromium-based stainless steel and the spatter size is less than or equal to 2.0mm, the laser welding process is considered normal.
[0020] In specific judgments, for example, a brightness of 75 cd / m², 70 cd / m², 65 cd / m², 60 cd / m², 55 cd / m², or 50 cd / m² can be considered as an abnormality in the laser welding process; while a brightness of 80 cd / m², 85 cd / m², 90 cd / m², 92 cd / m², 95 cd / m², or 100 cd / m² can be considered as a normal laser welding process. Here, cd / m² is the derived unit of brightness (luminance) in the International System of Units (SI), which is defined as the luminous flux emitted by a light source per unit area per unit solid angle in a given direction.
[0021] For this process, the laser scattered light intensity information of the weld pool is collected at a distance of 2m-3m from the welding position. If the collected intensity information is less than 80 cd / m², the laser welding process is considered abnormal. Specifically: Using a distance of 2m-3m from the welding position as the acquisition location, collect the brightness information of the laser scattered light in the weld pool. If the acquired brightness information is less than 80cd / m², check the actual power of the laser welding process, check whether the surfaces of the reflector and focusing lens are contaminated, and check whether there are any faults in the electrical components.
[0022] The spatter size on the steel plate surface refers to the size of metal particles that land on the steel plate being welded after splashing from the molten pool or the tip of the welding wire during the welding process. The surface spatter size can be measured using existing length measuring equipment in the workshop. If the steel being welded is nickel-based stainless steel and the spatter size is greater than 0.5 mm, or if the steel being welded is chromium-based stainless steel and the spatter size is greater than 2.0 mm, it indicates excessive spatter. Excessive spatter will reduce the amount of weld metal and decrease weld strength. If excessive spatter is found, it is determined that there is a problem with the wire feed speed, wire position, or the height of the wire from the steel plate, and adjustments should be made accordingly. In practice, if the steel being welded is nickel-based stainless steel and the spatter size is 0.4 mm, 0.3 mm, or 0.2 mm, it is considered normal spatter; if the steel being welded is chromium-based stainless steel and the spatter size is equal to 2.0 mm, 1.8 mm, 1.6 mm, or 1.4 mm, it is also considered normal spatter.
[0023] Step S002 involves acquiring the acoustic characteristics during the welding process and then using these characteristics to determine whether the laser welding process is normal. Acquire the sound characteristics during the welding process, and determine whether there is a first frequency sound generated by the plasma gas laser through the keyhole effect and a second frequency sound of the side-blown shielding gas flow based on the acquired sound characteristics. If it is determined that there is no first frequency sound or second frequency sound, it is determined that there is an abnormal shielding gas flow rate problem in the laser welding process. The first frequency sound refers to the sound with a frequency of 2-3kHz, and the second frequency sound refers to the sound with a frequency of 500-800Hz. Furthermore, based on the acquired sound characteristics, it is determined whether there are fluctuations in the sound characteristics exceeding ±15dB and with a fluctuation time greater than or equal to 0.5s. If such fluctuations exist, it is determined that the laser welding process has issues such as shielding gas nozzle angle deviation, welding wire X-axis position misalignment, or poor welding wire straightening.
[0024] Here, step S002 is the aforementioned "listening" step, which is a supplementary verification and evaluation step in this embodiment of the invention. This step is a real-time acoustic evaluation step of the welding process, that is, synchronously collecting the sound characteristics of the welding process, forming a complementary verification with the optical evaluation results of step S001, so as to determine for the second time whether the welding process is abnormal.
[0025] In the laser welding process, under normal conditions, there are two distinct and stable sound frequencies: a first frequency (high-frequency, sharp sound, 2-3 kHz) generated by the plasma gas laser passing through a keyhole effect, and a second frequency (a "whooshing" sound, 500-800 Hz) generated by the side-blown shielding gas flow. If either the first or second frequency sound is absent, it indicates an abnormal shielding gas flow rate. Adjusting the shielding gas flow rate to the standard value of 60 ± 5 L / min will resolve this. Furthermore, if the acquired sound characteristics show fluctuations exceeding ± 15 dB and a duration greater than or equal to 0.5 seconds, it indicates a shielding gas nozzle angle deviation > 5°, welding wire X-axis misalignment > 0.2 mm, or poor welding wire straightening. Immediate calibration of relevant equipment components is required. Specifically, the first frequency sound will fluctuate in pitch. Sounds with frequencies of 2kHz, 2.2kHz, 2.4kHz, 2.6kHz, and 2.8kHz belong to the first frequency range, while sounds with frequencies of 500Hz, 550Hz, 600Hz, 650Hz, 700Hz, 750Hz, or 800Hz belong to the second frequency range.
[0026] Step S003, which uses a directional light source to project onto the weld, identifies weld formation defects, and adjusts the laser welding process based on the identification results, further includes: The upper and lower surfaces of the weld are projected using a light source, and the angle between the light source and the weld is controlled to be 30°-60°. The light refraction of the light source is used to identify whether there is an undercut defect with a depth greater than 0.5mm or an incomplete penetration defect with a width greater than 0.2mm. If an undercut defect or an incomplete penetration defect is identified, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the determination result. Observe whether there is any depression on the upper surface of the steel plate at the weld, and if the depression depth is greater than 0.5mm, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the judgment result.
[0027] Here, step S003 is the aforementioned "illumination" step, which is a supplementary verification and evaluation step in the embodiment of the present invention. This step is a rapid detection step of the appearance of the weld after welding, that is, using a directional light source to project onto the weld to identify weld forming defects, so as to complete the closed-loop verification of process and result.
[0028] Step S003 includes using a light source to identify whether there is an undercut or incomplete penetration defect, and to identify whether there is a surface depression. When using a light source, the angle between the light source and the weld being welded is preferably 30°-60°. In specific implementations, angles of 35°, 40°, 45°, 50°, 55°, or 60° can be used, with 45° being the most preferred. For "undercut" defects, a depth greater than 0.5mm is considered an undercut defect. Specifically, depths of 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, or 1.8mm are all considered undercut defects. The corresponding measurements can be taken using a ruler. For "incomplete penetration" defects, a width greater than 0.2mm is considered an incomplete penetration defect. Specifically, widths of 0.2mm, 0.3mm, 0.4mm, 0.5mm, or 0.6mm are all considered incomplete penetration defects. The corresponding measurements can be taken using a ruler. (Reference) Figure 2 ,according to Figure 2 It can be determined that there are no "undercut" or "incomplete penetration" defects. Undercut or incomplete penetration defects are usually related to the laser power or wire feed speed in laser welding; adjusting these parameters accordingly will resolve the issue. Regarding the upper surface depression, a depression depth greater than 0.5mm is considered a depression defect. This defect is caused by excessive welding spatter or an excessively wide gap in the strip joint, such as a width > 0.4mm. Temporary adjustments to welding parameters are needed to control the defect's impact; the original parameters should be restored after equipment maintenance. For specific determinations of upper surface depression, depths of 0.5mm, 0.6mm, 0.7mm, 0.8mm, or 0.9mm are all considered depression defects. These can be determined by measuring the corresponding data using a ruler.
[0029] The method in this embodiment of the invention further includes: acquiring color information of the weld after welding annealing, and determining whether there is an abnormality in the welding based on the acquired color information. Specifically, if the color of the weld after welding annealing is a uniform light brown, the welding process is considered normal; if the color of the weld after welding annealing is too dark, such as dark brown or black, the annealing temperature is considered too high; if the color of the weld after welding annealing is too light, such as grayish-white, the welding process is considered insufficiently annealed, and the annealing parameters need to be adjusted accordingly.
[0030] Following step S003, the method of this embodiment further includes step S004: supplementing with a cupping mechanical test to finally determine the weld quality. This step is an abnormal scenario mechanical verification step; that is, when the previous three-step assessment identifies abnormal or high-risk conditions, a cupping mechanical test is performed to finally determine the weld quality.
[0031] Step S004, supplementing the cupping mechanical test to finally determine the weld quality, specifically involves cutting a 100mm×100mm standard weld sample, applying a pressure of 50-100MPa to the sample to obtain the cracking pattern of the weld area. If the obtained cracking pattern is a crack with a crack length greater than 3mm, it is determined that there is a quality problem with the weld, and the laser welding process needs to be adjusted.
[0032] This step, also known as the aforementioned "top" step, is used for cupping mechanical verification when abnormalities are detected in the "look, listen, and illuminate" steps but cannot be clearly determined. Regarding this step, since the probability of welding abnormalities is relatively high during the variable-specification production of ferritic stainless steel, the steps in this embodiment can be adapted to evaluate the welding process of variable-specification production of ferritic stainless steel.
[0033] The specific procedure for this step is as follows: Using a laser welding machine paired with a cupping machine, a 100mm × 100mm standard weld sample is cut. The sample is placed on the cupping machine, and the mechanical action of 50-100MPa pressure during continuous rolling is simulated to observe the cracking pattern in the weld area. Regarding the cracking pattern in the weld area, the following are some examples: Figure 3 The five typical cracking patterns shown are: cracking in the non-weld core area ( Figure 3 The first image on the left corresponds to a case of slight extended cracks with a length ≤3mm. Figure 3 (Based on the second image from the left) localized cracking at the edge ( Figure 3 (Based on the third image from the left) non-penetrating delamination cracking ( Figure 3 (The situation corresponding to the fourth image from the left) and direct fracture or brittle fracture occurring in the weld core area with a crack length > 3mm and penetrating the weld. Figure 3 (The situation corresponding to the first image on the right); For the above five cracking types, cracks with a length >3mm in the weld core area that penetrate the weld, or brittle fractures, are considered abnormal cracking. If the obtained cracking type is a crack with a length greater than 3mm, it is determined that the laser welding process needs adjustment. Welding operations should be immediately suspended, and the laser power (±1kW), welding wire position (X-axis offset ≤0.1mm), shielding gas parameters, etc., should be adjusted accordingly. After parameter optimization, the process must pass a final review before normal production can resume. That is, after parameter adjustment, a sample of the weld obtained after parameter adjustment needs to be cut and subjected to a pressure test again. Normal production can only resume if the cracking results obtained after the pressure test are cracks outside the weld core area, slight extended cracks with a length ≤3mm, localized edge cracks, or non-penetrating delamination cracks.
[0034] Regarding the method of this invention: The four-step evaluation method of this invention forms a progressive and complementary verification collaborative system, rather than a simple accumulation of conventional technologies. Specifically: The first step, "seeing": real-time initial screening, can quickly identify more than 80% of welding power abnormalities and molten pool instability problems, and simultaneously predict the weld filling amount by the spatter size of different steel grades; The second step, "listening": complementing optical signals, eliminating misjudgments caused by optical signal interference, and improving the real-time evaluation accuracy to over 95%; The third step, "illuminating": post-weld closed-loop verification, identifying forming defects such as undercut and incomplete penetration that cannot be detected in the first two steps, completing the full process-result verification; The fourth step, "top": bottom-line verification only for abnormal scenarios and high-risk working conditions, which does not affect the normal production rhythm and completely eliminates hidden defects, ultimately achieving an evaluation accuracy of 99.97%.
[0035] Compared with existing online single-factor monitoring technologies, the accuracy rate of using only optical signal monitoring is 82%, the accuracy rate of using only acoustic signal monitoring is 76%, and the accuracy rate of using only appearance inspection is 88%. However, the accuracy rate of the four-step collaborative evaluation method in this embodiment of the invention reaches 99.97%. The tape breakage rate after using the method of this embodiment of the invention is reduced to 0.02%. Therefore, the accuracy rate of the method of this embodiment of the invention is much higher than that of existing online single-factor monitoring technologies, and the tape breakage rate after using the method of this embodiment of the invention is much lower than the industry standard.
[0036] The method described in this invention has the following advantages: Improved evaluation efficiency: No complex equipment is required; evaluation can be completed on-site in real time, adapting to the rapid production rhythm of cold continuous rolling at 10-20 minutes / coil; Improved quality stability: After implementation, the weld breakage rate of the cold continuous rolling RAP line is reduced to 0.02%, far below the equipment guarantee value of 0.3%; Significant economic benefits: Annual reduction in capacity loss, non-coil loss, and energy waste loss totals 8.64 million yuan; Strong operability: The steps are clear and the judgment criteria are well-defined, making it easy for welders to quickly master and promote its application.
[0037] To facilitate understanding of the above-described embodiments of the present invention, the following specific examples are provided: Example 1: Evaluation of laser welds during the cold continuous rolling process of nickel-based stainless steel; Steel grade and specifications: Nickel-based stainless steel 321, thickness 5mm, single coil production cycle 15 minutes; Operating steps: If the laser scattered light brightness is 85 cd / m² and the brightness is consistent at different time points, and the spatter size is 0.4 mm, then it is determined that the laser power is sufficient and the molten pool is stable. Listen: If it is determined that the first frequency sound and the second frequency sound exist at the same time, and the sound volume is the same at different time points, then it is determined that the protective airflow rate meets the 60L / min standard. Illumination: When the flashlight is tilted at 45°, no defects such as "undercut" or "incomplete penetration" are found. The annealed area is observed to have uniform color and no defects such as sinking on the upper surface. Top: Because it is non-ferritic stainless steel, cupping inspection is not required; the weld is directly judged as qualified. Implementation results: The weld successfully passed the continuous rolling process with a deformation rate of over 70%, and there were no strip breakage accidents.
[0038] Example 2: Evaluation of laser welds in cold continuous rolling of chromium-based stainless steel; Steel grade and specifications: Chromium-based stainless steel 443, thickness 6mm, single coil production cycle 18 minutes; Operating steps: If the laser scattered light brightness is 88 cd / m² and the brightness is consistent at different time points, and the spatter size is 1.4 mm, then it is determined that the laser power is sufficient and the molten pool is stable. Listen: It was determined that the first frequency sound and the second frequency sound did not exist simultaneously, and the protective gas sound was muffled. The detection showed that the protective gas flow rate was 45L / min. After adjusting it to 60L / min, the sound returned to normal. Illumination: When the flashlight is tilted at 45°, no defects such as "undercut" or "incomplete penetration" are found. The annealed area is observed to have uniform color and no defects such as sinking on the upper surface. Top: Because it is non-ferritic stainless steel, cupping inspection is not required; the weld is directly judged as qualified. Results: The weld performance remained stable during continuous rolling, with no breakage observed.
[0039] Example 3: Evaluation of Laser Welds in the Production of Ferritic Stainless Steel with Variable Dimensions Steel grade and specifications: Ferritic stainless steel 430, thickness 4mm-5mm, variable specifications production, single coil production cycle 20 minutes; Operating steps: If the laser scattered light brightness is 90 cd / m² and the brightness is consistent at different time points, and the amount of sputtering meets the requirements, then it is determined that the laser power is sufficient and the molten pool is stable. Listen: If the first frequency sound and the second frequency sound are present at the same time, and the sound volume is the same at different time points, then it is judged that the protective airflow rate meets the 60L / min standard. Photo: When the flashlight is tilted at 45°, no visible defects are found, and the annealing color is uniform; Top: The cupping test showed minor cracking in the non-weld core area, and the result was deemed acceptable; Implementation results: The weld seam was rolled with a 75% deformation rate, resulting in continuous and stable production.
[0040] Regarding the method of this invention: the "look" step combines the brightness information of laser scattered light with the spatter size of different steel grades for judgment; the "listen" step includes the recognition threshold of protective gas and plasma gas sound and the abnormal handling plan; the "illuminate" step includes the operation method of flashlight tilt detection and defect recognition logic; and the "top" step explains the applicable scenarios, judgment criteria and parameter adjustment rules of cupping inspection.
[0041] The method described in this invention has been fully applied in the workshop for over 5 years, with a cumulative evaluation of over 300,000 welds, achieving excellent results and an accuracy rate exceeding 99.97% (with an overall breakage rate of approximately 0.02%). This method effectively solves the problem of mismatch between conventional testing methods and the high-efficiency production of cold continuous rolling. After implementation, the weld breakage rate has significantly decreased, generating annual economic benefits of 8.64 million yuan. It is highly practical, easy to promote, and provides strong technical support for ensuring the quality of welds in cold continuous rolling.
[0042] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A method for evaluating the quality of welding process and post-weld weld, characterized in that, include: The laser-scattered light brightness information of the weld pool and the spatter size on both sides of the weld are collected. Based on the brightness information and the spatter size, it is preliminarily determined whether the laser welding process is normal. Acquire the acoustic characteristics during the welding process, and then use the acquired acoustic characteristics to make a secondary judgment on whether the laser welding process is normal; A directional light source is used to project onto the weld seam, identify weld formation defects, and adjust the laser welding process based on the identification results.
2. The method according to claim 1, characterized in that, The process of acquiring the laser scattered light brightness information of the weld pool and the spatter size on both sides of the weld, and preliminarily determining whether the laser welding process is normal based on the brightness information and the spatter size, further includes: Using a distance of 2m-3m from the welding position as the acquisition location, the laser scattered light brightness information of the weld pool is acquired. If the acquired brightness information is less than 80cd / m², the laser welding process is determined to be abnormal; and if the acquired brightness information fluctuates by more than ±30% and the fluctuation time exceeds 0.5s, the laser welding process is determined to have an abnormal situation of weld pool instability. Additionally, the spatter size on the steel plate surface after welding is collected within 20mm on both sides of the weld. If the welded steel is nickel-based stainless steel and the spatter size is less than or equal to 0.5mm, the laser welding process is considered normal. If the welded steel is chromium-based stainless steel and the spatter size is less than or equal to 2.0mm, the laser welding process is considered normal.
3. The method according to claim 2, characterized in that, The laser-scattered light intensity information of the weld pool is collected at a distance of 2m-3m from the welding position. If the collected intensity information is less than 80 cd / m², the laser welding process is determined to be abnormal. Using a distance of 2m-3m from the welding position as the acquisition location, collect the brightness information of the laser scattered light in the weld pool. If the acquired brightness information is less than 80cd / m², check the actual power of the laser welding process, check whether the surfaces of the reflector and focusing lens are contaminated, and check whether there are faults in the electrical components.
4. The method according to claim 1, characterized in that, The specific steps of acquiring sound characteristics during the welding process and then using these characteristics to make a secondary judgment on whether the laser welding process is normal are as follows: Acquire the sound characteristics during the welding process, and determine whether there is a first frequency sound generated by the plasma gas laser through the keyhole effect and a second frequency sound of the side-blown protective gas flow based on the acquired sound characteristics. If it is determined that there is no first frequency sound or second frequency sound, it is determined that there is an abnormal protective gas flow rate problem in the laser welding process. The first frequency sound refers to the sound with a frequency of 2-3kHz, and the second frequency sound refers to the sound with a frequency of 500-800Hz. Furthermore, based on the acquired sound characteristics, it is determined whether the sound characteristics have a fluctuation amplitude exceeding ±15dB and a fluctuation time greater than or equal to 0.5s. If so, it is determined that the laser welding process has a shielding gas nozzle angle offset, welding wire X-axis position misalignment, or poor welding wire straightening.
5. The method according to claim 1, characterized in that, The method of projecting a directional light source onto the weld, identifying weld formation defects, and adjusting the laser welding process based on the identification results further includes: The upper and lower surfaces of the weld are projected using a light source, and the angle between the light source and the weld is controlled to be 30°-60°. The light refraction of the light source is used to identify whether there is an "undercut" defect with a depth greater than 0.5mm or an "incomplete penetration" defect with a width greater than 0.2mm. If the "undercut" defect or "incomplete penetration" defect is identified, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the determination result. Observe whether there is any depression on the upper surface of the steel plate at the weld, and if the depression depth is greater than 0.5mm, it is determined that the laser welding process needs to be adjusted, and the laser welding process is adjusted according to the judgment result.
6. The method according to claim 1, characterized in that, After projecting a directional light source onto the weld seam, identifying weld seam defects, and adjusting the laser welding process based on the identification results, the method further includes: Supplementary cupping mechanical tests are conducted to ultimately determine the weld quality.
7. The method according to claim 6, characterized in that, The supplementary cupping mechanical test, used to ultimately determine the weld quality, specifically includes: Cut a 100mm×100mm standard weld sample and apply a pressure of 50-100MPa to the sample to obtain the cracking pattern of the weld area. If the obtained cracking pattern is a crack with a crack length greater than 3mm, it is determined that there is a quality problem with the weld and the laser welding process needs to be adjusted.