Medium carbon alloy structural steel CrMo series wire rod rolling groove quality monitoring and acid pickling judgment process

Abstract

The invention relates to the technical field of wire rod production and processing, and discloses a groove rolling quality monitoring and acid pickling judgment process for medium carbon alloy structural steel CrMo series wire rods. Comprising the steps of (1) quality pre-inspection before a rolling groove is used, (2) real-time monitoring of the state of the rolling groove in the rolling process, (3) online pickling monitoring and preliminary judgment of a wire rod, (4) offline pickling full inspection and accurate judgment of the wire rod and (5) quality data archiving and process iterative optimization. Through'surface appearance detection and dimensional precision verification 'before the rolling groove is used and'dynamic monitoring and period control' during rolling, the surface roughness Ra of the rolling groove is stabilized to be smaller than or equal to 0.8 mu m, the meat falling depth is smaller than or equal to 0.05 mm, the crack length is smaller than or equal to 2 mm, scratches and hidden microdefects are effectively avoided, the surface defect rate of a wire rod caused by the rolling groove problem is reduced from 15% to 3% or below, and the service life of the wire rod is prolonged. And the surface microdefect depths of the wire rods with the specifications of phi 11.0 mm, phi 13mm and phi 14mm are all controlled within 0.03 mm, so that a high-quality surface foundation is laid for subsequent cold heading machining.

Description

Technical Field

[0001] This invention relates to the field of wire rod production and processing technology, specifically to a process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves. Background Technology

[0002] In the production and processing of SCM435-Q wire rod (mainly used for producing cold-headed fasteners such as bolts), microscopic defects on the wire rod surface (such as scratches and small opening defects) are the core cause of cold-heading cracking. Uncontrolled quality control of the rolling groove and inaccurate pickling judgment are the key sources of defect generation and missed detection. Specific technical pain points are reflected in the following aspects: Lack of quality control in the rolling mill led to a mass production of surface defects. Current processes rely solely on visual inspection for pre-inspection of the rolling groove, failing to accurately identify hidden defects: First, surface roughness assessment is vague, as Ra values ​​are not measured using specialized equipment. Rolling grooves continue to be used even when Ra > 0.8μm, easily causing scratches on the surface of Φ11.0mm, Φ13mm, and Φ14mm wire rods during rolling. Second, the detection of chipping and cracks is incomplete; cracks with a depth > 0.05mm or a length > 2mm go undetected, resulting in corresponding microscopic defects on the wire rod surface. Third, there are no clear standards for service life; excessive use of the rolling groove (over 500 coils) exacerbates hidden wear, leading to batch production of "tiny microscopic defects" with a depth of 0.02-0.04mm. These defects become stress concentration points during cold heading deformation (typically 60%-70% deformation), ultimately causing bolt cracking.

[0003] An imperfect pickling judgment system led to missed defects. Traditional pickling processes suffer from three major problems: low sampling frequency, inaccurate parameters, and lack of judgment standards. Online pickling typically involves sampling once every 20-30 coils, making it difficult to capture batch defects caused by rolling groove anomalies in real time. Pickling parameters (such as hydrochloric acid concentration of 12%-15% and temperature of 40-45℃) are not strictly controlled, failing to fully expose microscopic surface defects. Furthermore, the lack of a grading and judgment rule based on the "Standards for Sampling and Judgment of Wire Surface Pickling and Defect Atlas" leads to ambiguity in the judgment of minor defects with a depth of 0.02-0.03mm, resulting in some unqualified wires flowing into the cold heading process, further increasing the cracking rate (often exceeding 5%). Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a process for monitoring and judging the quality of CrMo series medium carbon alloy structural steel wire rods during rolling and pickling. This process has the advantages of strictly controlling the quality of the rolling groove and reducing surface defects from the source, thus solving the problem of mass generation of surface defects caused by the lack of quality control of the rolling groove.

[0005] (II) Technical Solution To achieve the above-mentioned goal of strictly controlling the quality of the rolling groove and reducing surface defects from the source, this invention provides the following technical solution: a process for monitoring the quality of the rolling groove and judging pickling of medium carbon alloy structural steel CrMo series wire rod, including step 1: pre-use quality inspection of the rolling groove, step 2: real-time monitoring of the rolling groove status during rolling, step 3: online pickling monitoring and preliminary judgment of the wire rod, step 4: offline pickling full inspection and accurate judgment of the wire rod, and step 5: quality data archiving and process iteration optimization. The step 1: pre-use quality inspection of the rolling groove includes; Step 2: Real-time monitoring of the rolling groove status during the rolling process includes step 201 dynamic monitoring of rolling groove wear, step 202 control of rolling groove usage cycle, and step 203 collaborative adaptation of rolling parameters. Step 3: Online pickling monitoring and preliminary judgment of wire rods includes step 301 online pickling sampling rules, step 302 online pickling parameter control, and step 303 online preliminary defect judgment. Step 4: Offline pickling full inspection and accurate judgment of wire rods includes step 401 offline pickling sampling range, step 402 offline pickling process optimization and step 403 accurate measurement and classification of defects. Step 5: Quality data archiving and process iteration optimization includes step 501 full-process data recording and step 502 process parameter optimization.

[0006] Preferably, step 101, surface morphology inspection of the rolling groove, involves scanning the entire surface of the rolling groove with a high-precision optical inspection instrument before rolling begins. Three key indicators are prioritized for inspection to prevent the source of wire rod scratches: Surface roughness is measured using a laser profilometer, requiring Ra≤0.8μm. If Ra exceeds this value, it is considered rolling groove aging, which easily leads to scratches on the wire rod surface; local depressions (chipping) are measured using a micro-thickness gauge, with a depth ≤0.05mm considered acceptable, while a depth exceeding this value is considered chipping, potentially causing microscopic defects of the corresponding shape on the wire rod surface; surface cracks are identified using strong light irradiation (light intensity ≥5000 lux) combined with image recognition technology. Cracks >2mm in length will cause continuous defects on the wire rod surface and must be deemed unacceptable. Step 102: Verify the dimensional accuracy of the groove: Use calipers to measure the groove dimensions (groove width and groove depth). The deviation from the standard groove dimensions must be ≤0.03mm to ensure that the diameter tolerance of the rolled wire rod meets the requirements (diameter deviation of Φ11.0mm, Φ13mm, and Φ14mm wire rods ±0.1mm). If the dimensional deviation exceeds the tolerance, it is necessary to re-grind and calibrate. If it still does not meet the standard after calibration, a new groove should be replaced to avoid defects caused by uneven stress on the surface of the wire rod due to abnormal groove shape. Step 103: Marking and Recording Qualified Rolled Grooves: Number and mark the rolled grooves that pass the pre-inspection, record the rolled groove model, inspection time, surface roughness, and dimensional deviation data, and establish an initial quality file for the rolled grooves to provide a basis for subsequent tracing of the rolling groove status of wire rods from specific furnace numbers.

[0007] Preferably, step 201, dynamic monitoring of groove wear, involves real-time data collection during rolling using a mill vibration sensor (monitoring range 0-500Hz) and a temperature sensor to prevent abnormal groove wear from causing batch defects and to meet the need for defect batch traceability. When the vibration frequency suddenly rises above 300Hz, it indicates that abnormal groove wear may occur, easily forming new scratches on the wire rod surface. When the groove surface temperature exceeds 400℃, it may lead to lubrication failure, exacerbating wear and generating irregular micro-defects. Upon any warning, the machine is immediately stopped, and the groove surface is re-inspected using a portable optical inspection instrument. If a roughness Ra > 0.8μm or a chipping depth > 0.05mm is found, the groove is immediately replaced to prevent further rolling and the generation of more defective wire rods. Step 202 Rolling groove usage cycle control: Set the maximum usage cycle of the rolling groove (≤500 coils). Even if vibration or temperature warnings are not triggered, after every 400-450 coils of wire rod rolled, stop the machine and conduct a comprehensive inspection of the rolling groove (same as step 1). If the inspection is qualified, it can continue to be used. If it is close to the aging or chipping threshold (Ra=0.7-0.8μm, chipping depth 0.04-0.05mm), replace it in advance to avoid the batch generation of "small micro-defects" caused by hidden wear. Step 203 Rolling Parameter Coordination and Adaptation: Adjust rolling parameters according to the condition of the groove to reduce the impact of groove wear on the wire rod surface: In the initial stage of a new groove (first 200 coils), set the rolling speed to 8-10 m / s and the initial rolling temperature to 1050-1080℃ to reduce the initial wear rate; in the middle and later stages of groove use (200-450 coils), appropriately reduce the rolling speed to 7-9 m / s and increase the initial rolling temperature to 1080-1100℃ to avoid scratches on the wire rod surface due to increased friction after groove wear.

[0008] Preferably, the sampling rules for online pickling in step 301 are as follows: after rolling 10-15 coils of wire rod, sampling is carried out according to the detection logic of "sampling from the head and tail of the wire rod" and the principle of "alternating between the head and tail of each coil" is adopted. That is, one sample (150-200mm in length) is taken from the head and tail of each coil 1-2m away. The total number of samples taken in each batch is not less than one group for every 20 coils, so as to ensure that the wire rods are covered throughout the entire rolling cycle and to promptly detect surface defects in the head and tail samples of a certain batch. Step 302 Online pickling parameter control: Send the sampled specimen into the online pickling tank, use hydrochloric acid solution (concentration 15%-20%), control the pickling temperature to 50-60℃ and the pickling time to 5-8 minutes, and set the parameters according to the pickling process to ensure that surface defects are fully exposed without causing over-corrosion. After pickling, rinse thoroughly with clean water (rinsing time 2-3 minutes) and blow dry with compressed air (air pressure 0.4-0.6MPa) to avoid residual acid from causing misjudgment of defects; Step 303: Preliminary online defect assessment: Observe the sample surface under strong light (light intensity ≥ 5000 lux), combined with a 20-30x magnifying glass for auxiliary inspection, and judge according to the following standards, matching the defect classification logic: No obvious defects (no scratches, no small openings) are judged as preliminary qualified and rolling continues; if there are minor defects with a length ≤ 3mm and a depth ≤ 0.03mm (corresponding to "small microscopic defects"), record the defect location and increase the sampling frequency in the next round (sampling once every 8-10 rolls) to prevent the defects from expanding; if there are continuous scratches with a length > 3mm (corresponding to "scratches on samples #2 and #3") or defects with a depth > 0.03mm, stop the machine immediately to check the rolling groove, repair or replace and re-roll to avoid producing similar cracked bolt semi-finished products.

[0009] Preferably, the sampling scope for offline pickling in step 401 is as follows: After each batch of wire rods is produced, a full inspection is carried out according to the requirement of "sampling from the beginning and end of each coil" and the principle of "sampling from the beginning and end of each coil". For each coil, one sample (150-200mm in length) is taken from the beginning and end of each coil at a distance of 0.5-1m. The number of samples taken for each batch is not less than 30 sets to ensure coverage of all produced wire rods, especially the wire rods of the specific batch number mentioned, to avoid missing defects.

[0010] Preferably, the offline pickling process in step 402 is optimized by using a mixed acid solution (18%-22% hydrochloric acid + 2%-3% nitric acid), controlling the pickling temperature at 45-55℃ and the pickling time at 6-9 minutes. Compared with online pickling, the slightly higher acid concentration and longer pickling time fully expose the "surface micro-defects with a depth of 0.02-0.04mm", thus preventing latent defects from flowing into the cold heading process.

[0011] Preferably, in step 403, the defect is accurately measured and graded: after pickling, the defect depth is measured using a metallographic microscope (200-500x magnification), strictly following the aforementioned "Standards for Sampling and Judgment of Wire Surface Pickling and Defect Mapping", and the defects are classified into three levels for targeted treatment: Grade I (Qualified): No defects or defect depth ≤0.02mm, can be directly used for cold heading to avoid cracking problems; Level II (restricted): Defect depth 0.02-0.03mm (covering the depth of most micro-defects), the defect location must be marked, the defect area should be avoided during cold heading, and the cold heading deformation should be controlled within 80%-90% of the original deformation to reduce the risk of stress concentration leading to cracking; Grade III (Unacceptable): Defect depth > 0.03mm or continuous scratches with a length > 3mm (corresponding to scratches on samples #2 and #3), directly rejected and prohibited from entering the cold heading process to prevent similar cracked bolts from being produced.

[0012] Preferably, in step 404, the non-conforming batch traceability and handling involves: for batches with Level III defects, retrospectively reviewing the monitoring records of the rolling groove during the corresponding rolling period (rolling groove replacement time, wear status), analyzing the cause of the defect, and matching the logic of "analyzing the cause based on the defect morphology": if it is caused by aging of the rolling groove, shorten the service life of this type of rolling groove (adjust from 450 coils to 400 coils); if it is caused by insufficient pickling leading to missed detection, increase the offline acid concentration by 1%-2% or extend the pickling time by 1-2 minutes to avoid the recurrence of similar problems.

[0013] Preferably, step 501 involves full-process data recording: establishing a "rolling groove monitoring - pickling judgment - cold heading feedback" associated database, recording the rolling groove number, number of coils used, surface inspection data, online / offline pickling parameters (concentration, temperature, time), defect classification results, and subsequent cold heading cracking rate for each batch of wire rod, realizing full-process quality traceability from rolling groove to finished product, and tracing analysis of cracked bolt samples, so that when cold heading cracking occurs later, the specific rolling groove or pickling stage can be quickly located.

[0014] Preferably, in step 502, the process parameters are optimized as follows: Weekly statistics are compiled on the frequency of grooving replacement, the percentage of defects at each level (Level III defects must be ≤3%), and the cold heading cracking rate (must be ≤1%). The process is then optimized in a targeted manner to address the feedback issues: If grooving replacement is too frequent, the rolling speed or lubrication scheme is adjusted (the thickness of the high-temperature grease coating is increased to 0.15-0.2mm) to reduce grooving wear; if the percentage of Level II defects is too high, the frequency of online pickling sampling is optimized (from 10-15 rolls to 8-12 rolls) to detect defects earlier; if cold heading cracking is related to Level II defects, the upper limit of the Level II defect depth is further reduced (from 0.03mm to 0.025mm) to continuously improve process stability and prevent the recurrence of cold heading cracking.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention provides a process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod, which has the following beneficial effects: 1. The SCM435-Q wire rod groove quality monitoring and pickling judgment process strictly controls the groove quality, reducing surface defects from the source. Through "surface morphology inspection + dimensional accuracy verification" before groove use and "dynamic monitoring + periodic control" during rolling, the groove surface roughness is stabilized at Ra≤0.8μm, chip depth≤0.05mm, and crack length≤2mm, effectively avoiding scratches and hidden micro-defects. In practical applications, the wire rod surface defect rate caused by groove problems has been reduced from 15% to below 3%. The depth of micro-defects on the surface of Φ11.0mm, Φ13mm, and Φ14mm wire rods is controlled within 0.03mm, laying a high-quality surface foundation for subsequent cold heading.

[0016] 2. The SCM435-Q wire rod groove quality monitoring and pickling judgment process optimizes the pickling judgment system, eliminates defect omissions, and combines online pickling with "alternating sampling every 10-15 coil ends" with offline pickling with "full inspection of each coil". With precise pickling parameters (online hydrochloric acid 15%-20% / 50-60℃, offline mixed acid 18%-22% hydrochloric acid + 2%-3% nitric acid / 45-55℃), it can fully expose microscopic defects with a depth of 0.02-0.04mm. At the same time, according to the "Standards for Sampling and Judgment of Wire Surface Pickling and Defect Map", a grade I-III judgment is established, which increases the defect detection rate to over 98%. The scrap rate of grade III unqualified wire rod (depth > 0.03mm) is 100%, which completely solves the problem of defect omissions in traditional processes. The wire rod pass rate before cold heading is increased to over 97%.

[0017] 3. The SCM435-Q wire rod groove quality monitoring and pickling judgment process dynamically adapts to rolling parameters, extending groove life and ensuring surface quality. Parameters are adjusted according to the usage stage of the groove: in the initial stage of a new groove (first 200 coils), rolling is started at a speed of 8-10 m / s and a temperature of 1050-1080℃ to reduce initial wear; in the middle and later stages (200-450 coils), the speed is reduced to 7-9 m / s and the temperature is increased to 1080-1100℃ to reduce friction and scratches. Combined with vibration (300Hz warning) and temperature (400℃ warning) monitoring, abnormal groove wear can be detected and replaced in real time. The effective service life of the groove is extended from 350-400 coils to 400-450 coils, reducing the rolling cost per ton of wire rod by 8-12 yuan, while avoiding the generation of batch defective wire rods.

[0018] 4. The SCM435-Q wire rod groove quality monitoring and pickling judgment process establishes a closed-loop traceability system to continuously improve process stability. The establishment of the "groove monitoring - pickling judgment - cold heading feedback" database enables full-process quality traceability. When cold heading cracks occur, the specific groove number and pickling parameters can be located within 1 hour. By statistically analyzing the defect rate (Level III ≤3%) and cold heading crack rate (≤1%) weekly, the process is optimized in a targeted manner (groove cycle adjusted from 450 coils to 400 coils, pickling concentration increased by 1%-2%), which continuously improves process stability. The cold heading crack rate has been reduced from more than 5% in the traditional process to less than 1%, and the bolt fastener production qualification rate has been increased to more than 99%, significantly reducing the company's rework and raw material waste costs. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a technical solution, specifically, a process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves, the prerequisites for which are as follows: Raw material and equipment foundation: Select continuously cast billets with low harmful elements (P≤0.020%, S≤0.010%) to avoid raw material impurities aggravating surface defects; Equipped with rolling mill quality inspection equipment (high-precision optical inspection instrument, detection accuracy 0.001mm), online pickling tank (automatic acid concentration control system), offline pickling platform and metallographic microscope (magnification 200-500x, capable of measuring defect depth) to ensure accurate and controllable rolling mill monitoring and pickling judgment; Target quality requirements: The surface of the rolling groove should be free from aging (roughness Ra≤0.8μm), spalling (dent depth≤0.05mm), and cracks (length≤2mm); the surface of the wire rod should be free from obvious cracks and folds, and the depth of micro-defects should be ≤0.03mm; the pickling judgment should meet the requirements of "Standards for Pickling and Judgment of Wire Rod Surface and Defect Atlas"; the cold heading cracking rate should be controlled below 1%; A process for quality monitoring and pickling judgment of medium carbon alloy structural steel CrMo series wire rod groove, including the following process: Step 1: Pre-inspection of the groove quality before use; Step 101: Surface morphology inspection of the rolling groove: Before rolling begins, a high-precision optical inspection instrument is used to scan the entire surface of the rolling groove, focusing on three key indicators to avoid the source of wire rod scratch defects: Surface roughness is measured by a laser profilometer, requiring Ra≤0.8μm. If it exceeds this value, it is judged as aging of the rolling groove, which easily forms scratches on the wire rod surface; Local depressions (chipping) are measured using a micro thickness gauge, with a depth ≤0.05mm being acceptable. If it exceeds this value, it is judged as chipping defects, which may lead to microscopic defects of corresponding shapes on the wire rod surface; Surface cracks are identified by strong light irradiation (light intensity ≥5000lux) combined with image recognition technology. Cracks with a length >2mm will cause continuous defects on the wire rod surface and must be judged as unacceptable. Step 102: Verify the dimensional accuracy of the groove: Use calipers to measure the groove dimensions (groove width and groove depth). The deviation from the standard groove dimensions must be ≤0.03mm to ensure that the diameter tolerance of the rolled wire rod meets the requirements (diameter deviation of Φ11.0mm, Φ13mm, and Φ14mm wire rods ±0.1mm). If the dimensional deviation exceeds the tolerance, it is necessary to re-grind and calibrate. If it still does not meet the standard after calibration, a new groove should be replaced to avoid defects caused by uneven stress on the surface of the wire rod due to abnormal groove shape. Step 103: Marking and Recording Qualified Rolled Grooves: Number and mark the rolled grooves that pass the pre-inspection, record the rolled groove model, inspection time, surface roughness, and dimensional deviation data, establish an initial quality file for the rolled grooves, and provide a basis for subsequent tracing of the rolling groove status of wire rods from specific furnace numbers; Step 2: Real-time monitoring of the rolling groove status during the rolling process; Step 201: Dynamic Monitoring of Rolling Slot Wear: During the rolling process, data is collected in real time using a mill vibration sensor (monitoring range 0-500Hz) and a temperature sensor to prevent abnormal wear of the rolling slot from causing batch defects and to meet the requirements for defect batch traceability. When the vibration frequency suddenly rises above 300Hz, it indicates that abnormal wear of the rolling slot may occur, which can easily form new scratches on the surface of the wire rod. When the surface temperature of the rolling slot exceeds 400℃, it may cause lubrication failure, aggravate wear, and produce irregular micro-defects. If any warning occurs, the machine is stopped immediately, and the surface of the rolling slot is re-inspected using a portable optical inspection instrument. If the roughness Ra is found to be >0.8μm or the depth of the cut is >0.05mm, the rolling slot is replaced immediately to avoid the production of more defective wire rods by continuing rolling. Step 202 Rolling groove usage cycle control: Set the maximum usage cycle of the rolling groove (≤500 coils). Even if vibration or temperature warnings are not triggered, after every 400-450 coils of wire rod rolled, stop the machine and conduct a comprehensive inspection of the rolling groove (same as step 1). If the inspection is qualified, it can continue to be used. If it is close to the aging or chipping threshold (Ra=0.7-0.8μm, chipping depth 0.04-0.05mm), replace it in advance to avoid the batch generation of "small micro-defects" caused by hidden wear. Step 203: Coordinated Adaptation of Rolling Parameters: Adjust rolling parameters according to the condition of the groove to reduce the impact of groove wear on the wire rod surface: In the initial stage of a new groove (first 200 coils), set the rolling speed to 8-10 m / s and the initial rolling temperature to 1050-1080℃ to reduce the initial wear rate; in the middle and later stages of groove use (200-450 coils), appropriately reduce the rolling speed to 7-9 m / s and increase the initial rolling temperature to 1080-1100℃ to avoid scratches on the wire rod surface due to increased friction after groove wear; Step 3: Online pickling monitoring and preliminary assessment of wire rods; Step 301 Online pickling sampling rules: After rolling 10-15 coils of wire rod, sampling is carried out according to the detection logic of "sampling from the head and tail of the wire rod" and the principle of "alternating between the head and tail of each coil" is adopted. That is, one sample (150-200mm in length) is taken from the head and tail of each coil 1-2m. The total sampling amount for each batch is not less than one set for every 20 coils to ensure coverage of the wire rod throughout the rolling cycle and timely detection of surface defects in the head and tail samples of a certain batch. Step 302 Online pickling parameter control: Send the sampled specimen into the online pickling tank, use hydrochloric acid solution (concentration 15%-20%), control the pickling temperature to 50-60℃ and the pickling time to 5-8 minutes, and set the parameters according to the pickling process to ensure that surface defects are fully exposed without causing over-corrosion. After pickling, rinse thoroughly with clean water (rinsing time 2-3 minutes) and blow dry with compressed air (air pressure 0.4-0.6MPa) to avoid residual acid from causing misjudgment of defects; Step 303: Preliminary online defect assessment: Observe the sample surface under strong light (light intensity ≥ 5000 lux), combined with a 20-30x magnifying glass for auxiliary inspection, and judge according to the following standards, matching the defect classification logic: No obvious defects (no scratches, no small openings) are judged as preliminary qualified, and rolling continues; there are minor defects with a length ≤ 3mm and a depth ≤ 0.03mm (corresponding to "small microscopic defects"), record the defect location, increase the sampling frequency of the next round (sampling once every 8-10 rolls), and prevent the defects from expanding; there are continuous scratches with a length > 3mm (corresponding to "scratches on samples #2 and #3") or defects with a depth > 0.03mm, immediately stop the machine to check the rolling groove, repair or replace, and re-roll to avoid producing similar cracked bolt semi-finished products; Step 4: Offline pickling inspection and accurate judgment of wire rods; Step 401 Offline pickling sampling scope: After each batch of wire rods is produced, a full inspection is carried out according to the requirement of "sampling from the beginning and end of each coil". One sample (150-200mm in length) is taken from the beginning and end of each coil, 0.5-1m from the beginning and 0.5-1m from the end. The number of samples taken from each batch is not less than 30 sets to ensure coverage of all produced wire rods, especially the wire rods of the specific batch number mentioned, to avoid missing defects. Step 402 Offline pickling process optimization: Use mixed acid solution (18%-22% hydrochloric acid + 2%-3% nitric acid), control the pickling temperature at 45-55℃ and the pickling time at 6-9 minutes. Compared with online pickling, the slightly higher acid concentration and longer pickling time fully expose the "surface micro-defects with a depth of 0.02-0.04mm", avoiding the flow of hidden defects into the cold heading process; Step 403: Precise Defect Measurement and Grading: After pickling, use a metallographic microscope (200-500x magnification) to measure the defect depth, strictly following the aforementioned "Standards for Sampling and Judgment of Wire Surface Pickling and Defect Mapping," classifying defects into three levels for targeted treatment: Grade I (Qualified): No defects or defect depth ≤0.02mm, can be directly used for cold heading to avoid cracking problems; Level II (restricted): Defect depth 0.02-0.03mm (covering the depth of most micro-defects), the defect location must be marked, the defect area should be avoided during cold heading, and the cold heading deformation should be controlled within 80%-90% of the original deformation to reduce the risk of stress concentration leading to cracking; Grade III (Unacceptable): Defect depth > 0.03mm or continuous scratches with a length > 3mm (corresponding to scratches on samples #2 and #3), directly rejected and prohibited from entering the cold heading process to prevent similar cracked bolts from being produced; Step 404: Traceability and Handling of Non-conforming Batches: For batches with Level III defects, trace back the monitoring records of the rolling groove during the corresponding rolling period (rolling groove replacement time, wear status), analyze the cause of the defect, and match the logic of "analyzing the cause based on the defect morphology": If it is caused by the aging of the rolling groove, shorten the service life of this type of rolling groove (adjust from 450 coils to 400 coils); if it is caused by insufficient pickling leading to missed detection, increase the offline acid concentration by 1%-2% or extend the pickling time by 1-2 minutes to avoid the recurrence of similar problems; Step 5: Quality data archiving and process iteration optimization; Step 501: Full-process data recording: Establish a database linking "rolling groove monitoring - pickling judgment - cold heading feedback" to record the rolling groove number, number of coils used, surface inspection data, online / offline pickling parameters (concentration, temperature, time), defect classification results, and subsequent cold heading cracking rate for each batch of wire rod. This enables full-process quality traceability from rolling groove to finished product and traceability analysis of cracked bolt samples. When cold heading cracking occurs later, the specific rolling groove or pickling stage can be quickly located. Step 502: Process parameter optimization: Weekly statistics on the frequency of slub replacement, the percentage of defects at each level (Level III defects must be ≤3%), and the cold heading cracking rate (must be ≤1%) are compiled. Targeted process optimization is implemented to address feedback issues: If slub replacement is too frequent, adjust the rolling speed or lubrication scheme (increase the thickness of the high-temperature grease coating to 0.15-0.2mm) to reduce slub wear; if the percentage of Level II defects is too high, optimize the online pickling sampling frequency (from 10-15 trays to 8-12 trays) to detect defects earlier; if cold heading cracking is related to Level II defects, further reduce the upper limit of Level II defect depth (from 0.03mm to 0.025mm) to continuously improve process stability and prevent the recurrence of cold heading cracking. Furthermore, the key safeguards for this process include the following: Standardized quality control of rolling grooves: The "Standard for Quality Inspection and Replacement of Rolling Grooves" was formulated, which clarifies the quantitative thresholds for surface roughness, depth of material loss, and crack length. Standard roughness samples (Ra=0.6μm, 0.8μm, 1.0μm) and defect comparison charts (including scratches and examples of small micro-defects) are provided to ensure that the judgment standards of the inspection personnel are consistent and to avoid defects caused by differences in the judgment of rolling groove quality. Precise control of pickling parameters: Both online and offline pickling tanks are equipped with acid concentration sensors (detection accuracy 0.1%) and temperature control systems (temperature control accuracy ±1℃) to adjust acid concentration and temperature in real time, avoiding insufficient exposure of micro-defects due to excessively low concentration or excessive corrosion of the surface due to excessively high concentration; at the same time, an automatic timing device is installed to ensure that the pickling time of each batch of samples is consistent, the judgment results are comparable, and the rigor of pickling inspection is matched. Dual verification of defect judgment: For samples with defects judged as Grade II or III by offline pickling, a "double-person re-inspection" mechanism is adopted. Two inspectors independently measure the defect depth and judge the grade. If the judgment results are inconsistent, they are verified by a higher precision metallographic microscope (1000x magnification) to avoid misjudgment or omission caused by subjective error and ensure the detection effect of "accurately identifying defect type". Furthermore, this process strictly controls the quality of the rolling groove, reducing surface defects from the source. Through "surface morphology inspection + dimensional accuracy verification" before the rolling groove is used and "dynamic monitoring + periodic control" during rolling, the surface roughness of the rolling groove is stabilized at Ra≤0.8μm, the depth of material loss≤0.05mm, and the crack length≤2mm, effectively avoiding scratches and hidden micro-defects. In practical applications, the surface defect rate of wire rod caused by rolling groove problems has been reduced from 15% to below 3%. The depth of micro-defects on the surface of wire rods with specifications of Φ11.0mm, Φ13mm, and Φ14mm is controlled within 0.03mm, laying a high-quality surface foundation for subsequent cold heading processing. Furthermore, this process optimizes the pickling judgment system, eliminating missed defects. The combination of online pickling ("alternating sampling from the beginning and end of every 10-15 coils") and offline pickling ("full inspection of each coil"), along with precise pickling parameters (online hydrochloric acid 15%-20% / 50-60℃, offline mixed acid 18%-22% hydrochloric acid + 2%-3% nitric acid / 45-55℃), fully exposes microscopic defects with a depth of 0.02-0.04mm. Simultaneously, based on the "Standards for Sampling and Judgment of Wire Surface Pickling and Defect Mapping," a graded judgment system of I-III is established, increasing the defect detection rate to over 98%. Grade III unqualified wire rods (depth > 0.03mm) have a 100% rejection rate, completely solving the problem of missed defects in traditional processes. The wire rod pass rate before cold heading is increased to over 97%. Furthermore, this process dynamically adapts rolling parameters, extending the life of the rolling groove and ensuring surface quality. Parameters are adjusted according to the usage stage of the rolling groove: in the initial stage of a new rolling groove (the first 200 coils), rolling is started at a speed of 8-10 m / s and a temperature of 1050-1080℃ to reduce initial wear; in the middle and later stages (200-450 coils), the speed is reduced to 7-9 m / s and the temperature is increased to 1080-1100℃ to reduce friction and scratches. With vibration (300Hz warning) and temperature (400℃ warning) monitoring, abnormal wear of the rolling groove can be detected and replaced in real time. The effective service life of the rolling groove is extended from 350-400 coils to 400-450 coils, reducing the rolling cost per ton of wire rod by 8-12 yuan, while avoiding the generation of batch defective wire rods. Furthermore, the process establishes a closed-loop traceability system to continuously improve process stability. The establishment of the "rolling groove monitoring - pickling judgment - cold heading feedback" database enables full-process quality traceability. When cold heading cracks occur, the specific rolling groove number and pickling parameters can be located within 1 hour. By statistically analyzing the defect rate (Level III ≤3%) and cold heading crack rate (≤1%) weekly, the process is optimized in a targeted manner (rolling groove cycle is adjusted from 450 coils to 400 coils, and pickling concentration is increased by 1%-2%), which continuously improves process stability. The cold heading crack rate has been reduced from more than 5% in the traditional process to less than 1%, and the qualified rate of bolt fastener production has been increased to more than 99%, significantly reducing the company's rework and raw material waste costs.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod groove, comprising: step 1: pre-use quality inspection of the groove; step 2: real-time monitoring of the groove status during rolling; step 3: online pickling monitoring and preliminary judgment of the wire rod; step 4: offline pickling full inspection and precise judgment of the wire rod; and step 5: quality data archiving and process iteration optimization, characterized in that: Step 1: Pre-inspection of the rolling groove before use includes; Step 2: Real-time monitoring of the rolling groove status during the rolling process includes step 201 dynamic monitoring of rolling groove wear, step 202 control of rolling groove usage cycle, and step 203 collaborative adaptation of rolling parameters. Step 3: Online pickling monitoring and preliminary judgment of wire rods includes step 301 online pickling sampling rules, step 302 online pickling parameter control, and step 303 online preliminary defect judgment. Step 4: Offline pickling full inspection and accurate judgment of wire rods includes step 401 offline pickling sampling range, step 402 offline pickling process optimization and step 403 accurate measurement and classification of defects. Step 5: Quality data archiving and process iteration optimization includes step 501 full-process data recording and step 502 process parameter optimization.

2. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 101, surface morphology inspection of the rolling groove: Before rolling begins, a high-precision optical inspection instrument is used to scan the entire surface of the rolling groove, focusing on three key indicators to avoid the source of wire rod scratch defects: Surface roughness is measured by a laser profilometer, requiring Ra≤0.8μm. If it exceeds this value, it is judged as aging of the rolling groove, which is prone to forming scratches on the wire rod surface; Local depressions (chipping) are measured by a micro thickness gauge, with a depth ≤0.05mm being acceptable. If it exceeds this value, it is judged as chipping defects, which may lead to microscopic defects of corresponding shapes on the wire rod surface; Surface cracks are identified by strong light irradiation (light intensity ≥5000lux) combined with image recognition technology. Cracks with a length >2mm will cause continuous defects on the wire rod surface and must be judged as unacceptable. Step 102: Verify the dimensional accuracy of the groove: Use calipers to measure the groove dimensions (groove width and groove depth). The deviation from the standard groove dimensions must be ≤0.03mm to ensure that the diameter tolerance of the rolled wire rod meets the requirements (diameter deviation of Φ11.0mm, Φ13mm, and Φ14mm wire rods ±0.1mm). If the dimensional deviation exceeds the tolerance, it is necessary to re-grind and calibrate. If it still does not meet the standard after calibration, a new groove should be replaced to avoid defects caused by uneven stress on the surface of the wire rod due to abnormal groove shape. Step 103: Marking and Recording Qualified Rolled Grooves: Number and mark the rolled grooves that pass the pre-inspection, record the rolled groove model, inspection time, surface roughness, and dimensional deviation data, and establish an initial quality file for the rolled grooves to provide a basis for subsequent tracing of the rolling groove status of wire rods from specific furnace numbers.

3. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 201, dynamic monitoring of groove wear: During the rolling process, data is collected in real time by the mill vibration sensor (monitoring range 0-500Hz) and temperature sensor to prevent abnormal groove wear from causing batch defects and to meet the needs of defect batch traceability: When the vibration frequency suddenly rises to above 300Hz, it indicates that abnormal groove wear may occur, which is likely to form new scratches on the wire rod surface; when the groove surface temperature exceeds 400℃, it may cause lubrication failure, aggravate wear, and produce irregular micro defects. If any warning occurs, the machine is stopped immediately, and the groove surface is re-inspected with a portable optical inspection instrument. If the roughness Ra is found to be >0.8μm or the depth of the cut is >0.05mm, the groove is replaced immediately to avoid continuing rolling and producing more defective wire rods. Step 202 Rolling groove usage cycle control: Set the maximum usage cycle of the rolling groove (≤500 coils). Even if vibration or temperature warnings are not triggered, after every 400-450 coils of wire rod rolled, stop the machine and conduct a comprehensive inspection of the rolling groove (same as step 1). If the inspection is qualified, it can continue to be used. If it is close to the aging or chipping threshold (Ra=0.7-0.8μm, chipping depth 0.04-0.05mm), replace it in advance to avoid the batch generation of "small micro-defects" caused by hidden wear. Step 203 Rolling Parameter Coordination and Adaptation: Adjust rolling parameters according to the condition of the groove to reduce the impact of groove wear on the wire rod surface: In the initial stage of a new groove (first 200 coils), set the rolling speed to 8-10 m / s and the initial rolling temperature to 1050-1080℃ to reduce the initial wear rate; in the middle and later stages of groove use (200-450 coils), appropriately reduce the rolling speed to 7-9 m / s and increase the initial rolling temperature to 1080-1100℃ to avoid scratches on the wire rod surface due to increased friction after groove wear.

4. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: The sampling rules for online pickling in step 301 are as follows: After rolling 10-15 coils of wire rod, the sampling logic of "sampling from the head and tail of the wire rod" is followed, and the principle of "alternating between the head and tail of each coil" is adopted for sampling. That is, one sample (150-200mm in length) is taken from the head and tail of each coil 1-2m apart. The total number of samples taken in each batch is not less than one set for every 20 coils, so as to ensure that the wire rods are covered throughout the entire rolling cycle and to promptly detect surface defects in the head and tail samples of a certain batch. Step 302 Online pickling parameter control: Send the sampled specimen into the online pickling tank, use hydrochloric acid solution (concentration 15%-20%), control the pickling temperature to 50-60℃ and the pickling time to 5-8 minutes, and set the parameters according to the pickling process to ensure that surface defects are fully exposed without causing over-corrosion. After pickling, rinse thoroughly with clean water (rinsing time 2-3 minutes) and blow dry with compressed air (air pressure 0.4-0.6MPa) to avoid residual acid from causing misjudgment of defects; Step 303: Preliminary online defect assessment: Observe the sample surface under strong light (light intensity ≥ 5000 lux), combined with a 20-30x magnifying glass for auxiliary inspection, and judge according to the following standards, matching the defect classification logic: No obvious defects (no scratches, no small openings) are judged as preliminary qualified and rolling continues; if there are minor defects with a length ≤ 3mm and a depth ≤ 0.03mm (corresponding to "small microscopic defects"), record the defect location and increase the sampling frequency in the next round (sampling once every 8-10 rolls) to prevent the defects from expanding; if there are continuous scratches with a length > 3mm (corresponding to "scratches on samples #2 and #3") or defects with a depth > 0.03mm, stop the machine immediately to check the rolling groove, repair or replace and re-roll to avoid producing similar cracked bolt semi-finished products.

5. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: The sampling scope for offline pickling in step 401 is as follows: After each batch of wire rods is produced, a full inspection is carried out according to the requirement of "sampling from the beginning and end of each coil". The principle of "sampling from the beginning and end of each coil" is adopted for full inspection. One sample (150-200mm in length) is taken from the beginning and end of each coil at 0.5-1m. The number of samples taken from each batch is not less than 30 sets to ensure coverage of all produced wire rods, especially the wire rods of the specific batch number mentioned, to avoid missing defects.

6. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: The offline pickling process optimization in step 402 is as follows: a mixed acid solution (18%-22% hydrochloric acid + 2%-3% nitric acid) is used, and the pickling temperature is controlled at 45-55℃ and the pickling time is 6-9 minutes. Compared with online pickling, the slightly higher acid concentration and longer pickling time fully expose the "surface micro-defects with a depth of 0.02-0.04mm", thus avoiding the flow of hidden defects into the cold heading process.

7. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 403, Precise Defect Measurement and Grading: After pickling, the defect depth is measured using a metallographic microscope (200-500x magnification). Strictly following the aforementioned "Standards for Sampling and Judgment of Wire Surfaces and Defect Mapping," defects are classified into three levels for targeted treatment. Grade I (Qualified): No defects or defect depth ≤0.02mm, can be directly used for cold heading to avoid cracking problems; Level II (restricted): Defect depth 0.02-0.03mm (covering the depth of most micro-defects), the defect location must be marked, the defect area should be avoided during cold heading, and the cold heading deformation should be controlled within 80%-90% of the original deformation to reduce the risk of stress concentration leading to cracking; Grade III (Unacceptable): Defect depth > 0.03mm or continuous scratches with a length > 3mm (corresponding to scratches on samples #2 and #3), directly rejected and prohibited from entering the cold heading process to prevent similar cracked bolts from being produced.

8. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 404, non-conforming batch traceability and handling: For batches with Level III defects, trace back the monitoring records of the rolling groove during the corresponding rolling period (rolling groove replacement time, wear status), analyze the cause of the defect, and match the logic of "analyzing the cause based on the defect morphology": if it is caused by the aging of the rolling groove, shorten the service life of this type of rolling groove (adjust from 450 coils to 400 coils); if it is caused by insufficient pickling leading to missed detection, increase the offline acid concentration by 1%-2% or extend the pickling time by 1-2 minutes to avoid the recurrence of similar problems.

9. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 501 involves full-process data recording: establishing a "rolling groove monitoring - pickling judgment - cold heading feedback" associated database to record the rolling groove number, number of coils used, surface inspection data, online / offline pickling parameters (concentration, temperature, time), defect classification results, and subsequent cold heading cracking rate for each batch of wire rod. This enables full-process quality traceability from rolling groove to finished product and traceability analysis of cracked bolt samples. When cold heading cracking occurs subsequently, the specific rolling groove or pickling stage can be quickly located.

10. The process for quality monitoring and pickling judgment of CrMo series medium carbon alloy structural steel wire rod grooves according to claim 1, characterized in that: Step 502, process parameter optimization, involves weekly statistics on the frequency of grooving replacement, the percentage of defects at each level (Level III defects must be ≤3%), and the cold heading cracking rate (must be ≤1%). Targeted process optimization is then implemented to address feedback issues: If grooving replacement is too frequent, the rolling speed or lubrication scheme is adjusted (the thickness of the high-temperature grease coating is increased to 0.15-0.2mm) to reduce grooving wear; if the percentage of Level II defects is too high, the frequency of online pickling sampling is optimized (from 10-15 rolls to 8-12 rolls) to detect defects earlier; if cold heading cracking is related to Level II defects, the upper limit of the Level II defect depth is further reduced (from 0.03mm to 0.025mm) to continuously improve process stability and prevent the recurrence of cold heading cracking.