LU600007B1 - A process for high-frequency laser precision welding of high-carbon steel with controlled local heat treatment - Google Patents

Abstract

The invention relates to the field of welding technology and specifically relates to a method for high-frequency laser precision welding of high-carbon steel with controlled local heat treatment, comprising the following steps: S1: Selection of high-carbon steel and removal of surface contaminants by chemical cleaning and mechanical roughening; S2: Carrying out laser preheating before welding, with temperature and heating rate controlled to reduce thermal stresses and the risk of cracks during welding; S3: Adjusting the laser wavelength, focus position, scan speed and pulse mode; S4: Real-time monitoring of the welding process using infrared thermography and optical sensors, as well as dynamic adjustment of the parameters by a closed-loop control system to ensure the stability of the molten pool and the consistency of the weld seam; S5: Controlling the cooling rate and carrying out any necessary annealing treatments. By optimizing material selection, precise control of laser parameters, and real-time monitoring with feedback, the invention significantly improves the mechanical properties and stability of high-carbon steel welds.

Description

A process for high-frequency laser precision welding of high-carbon steel/600007 with controlled local heat treatment

Technical area

The invention relates to the field of welding technology and specifically relates to a

Process for high-frequency laser precision welding of high-carbon steel with controlled local heat treatment.

Technology in the background

High carbon steel is used in the

manufacturing industry, e.g., as tool steel and mold steel. Its high

However, the carbon content (0.6 - 0.9%) leads to the formation of hard and brittle carbides and hardened structures during the welding process, which in turn leads to cracks and other

This is caused by complex phase transformations that occur at high

heating and subsequent rapid cooling. Typically, the

Formation of martensite and welding cracks due to internal stresses. Traditional

Welding processes such as gas welding or arc welding encounter problems when used

High carbon steel faces significant challenges, mainly in the following

Points show: 1. High crack sensitivity: Cold cracks: High carbon steel contains a high proportion of carbon and other alloying elements (such as manganese and chromium), which during

welding process easily leads to the formation of hard and brittle martensite phase. This

Phase transformation creates significant internal stresses, which lead to the formation of cold cracks, especially during cooling after welding. These cracks seriously compromise the structural integrity and service life of the welded joint. Hot cracks: During the welding process of high-carbon steel, the stresses created by sudden temperature changes can also cause hot cracks. Hot cracks typically develop during welding due to uneven cooling and shrinkage caused by the

Fluidity of the liquid metal at high temperatures. 2. Problems in controlling the heat-affected zone (HAZ): Due to its small

Due to its toughness and high hardness, welding of high-carbon steel often results in a large and difficult to control heat-affected zone. The structure of the HAZ can be made of hardened

Martensite and brittle carbides, which increases the risk of brittle fractures.

Existing welding techniques (such as manual arc welding or gas shielded welding) cannot precisely control the heat input to minimize the size of the heat-affected zone and the formation of uneven structures. 3. Unfavorable microstructure: After welding, high-carbon steel tends to

Formation of coarse grains and uneven precipitation phases, which increases the mechanical

Properties of the welded joint are significantly reduced. Traditional

Post-heat treatments are often insufficient to refine the microstructure of the weld and adjacent areas, thus preventing the desired performance parameters (such as hardness and toughness) from being achieved.

Content of the invention

The purpose of the present invention is to provide a method for high-frequency

Laser precision welding of high-carbon steel with controlled local

heat treatment. By optimizing the material selection, the precise

By controlling the laser parameters and real-time monitoring with feedback, the mechanical properties and stability of the high-frequency laser welded joint dt/800007 of high-carbon steel are significantly improved.

In order to achieve the above-mentioned technical goal and to achieve the described effects, the invention is realized by the following technical solutions:

A process for high-frequency laser precision welding of high-carbon steel with controlled local heat treatment comprises the following steps:

S1: Material preparation and surface treatment: Selection of high-carbon steel that has undergone precise metallurgical processing. Surface contaminants are removed by chemical cleaning and mechanical roughening to ensure

To improve laser absorption and welding quality.

S2: Local heat treatment: Before welding, laser preheating is carried out, with temperature and heating rate controlled to reduce thermal stresses and the

To reduce the risk of cracks during welding.

S3: Optimization of laser welding parameters: By adjusting laser wavelength,

Focus position, scanning speed and pulse mode achieve efficient energy absorption and precise control so that the depth and width of the weld seam are suitable.

S4: Real-time monitoring and feedback control: Using infrared thermography and optical sensors, the welding process is monitored in real time.

The control system dynamically adjusts the parameters to ensure the stability of the melt pool and the consistency of the weld seam.

SS: Post-heat treatment: The cooling rate is controlled and necessary annealing treatments are carried out to remove the

To eliminate residual stresses and improve the microstructure of the weld.

S6: Quality control: The internal integrity and mechanical properties of the

Welds are comprehensively evaluated through non-destructive testing and mechanical testing to ensure that design standards are met.

The advantageous effects of the present invention:

By selecting high-carbon steel with excellent metallurgical

Properties and a low proportion of harmful impurities, the toughness and

The strength of the weld joint is significantly improved. During the material preparation process, the chemical composition of the steel is precisely tested using spectral analysis to ensure that the chemical components of the steel are within the ideal range. This is crucial to minimize the excessive formation of brittle phases during welding. The surface treatment improves the absorption of laser energy by the

Material. The removal of oxide layers and grease, as well as mechanical grinding, achieves the optimal surface roughness (Ra value between 1.6 - 3.2 µm). This effectively prevents the formation of pores and inclusions during the welding process and creates the basis for efficient energy coupling and transfer in the subsequent laser welding.

Welding phase.

The laser preheating carried out before welding not only reduces the

temperature gradients and thermal stresses during welding, but also optimizes the microstructure through precise temperature design (e.g., a heating rate of 15 °C/min and a preheating temperature of 780 °C). The formation and stabilization of the

Austenite range is crucial to avoid the hardening tendency of high-carbon steel.

The local heat treatment increases the degree of dissolution of the carbides and the

Uniformity of the austenite is controlled to ensure a correct phase transformation path after welding. This results in a fine, evenly distributed pearlite and

Ferrite structure, which increases the toughness and crack resistance of the weld. The entire

Heat treatment design is based on the combination of the thermophysical properties of the material and modern theoretical principles, which ensures optimal mechanical

Properties of the weld seam are guaranteed.

Through the precise control of laser power, welding speed, and focus position, an optimal adjustment of penetration depth and width is achieved during the welding process, which maximizes the strength and quality of the material connection. The optimization of the

Laser parameters take into account the thermal conductivity and melting point of high carbon

Steel to ensure adequate energy input and avoid overheating or insufficient heating. The use of a pulsed mode ensures that each laser action is more precise and the welding process is more stable. An appropriate

Shielding gas flow not only prevents oxidation but also controls the cooling rate to ensure an ideal microstructure in the weld zone.

Control of the energy input is carried out by precise calculations (e.g. Q = P / V), which

Welded joint achieves superior structure and performance.

By integrating real-time monitoring technologies such as infrared

Temperature measurement, laser power sensors and visual monitoring, a dynamic

Control of the entire welding process is achieved. Real-time data acquisition and intelligent feedback mechanisms ensure that temperature, power, and weld shape are always within the ideal range. If the parameters deviate from the target values, the

system quickly, e.g. by reducing the laser power to avoid overheating or by adjusting the welding speed to correct seam deviations.

Introduction of a convolutional neural network for weld seam image analysis and a fuzzy

Control system intelligent corrections and optimizations are carried out, which

The quality and consistency of the entire welding process can be significantly improved.

Application of the comprehensive feedback system enables the establishment of an efficient and reliable control for each welding process and ensures the output of

Welds with the highest quality standards.

Of course, a product implementing the present invention does not necessarily have to fulfill all of the above-mentioned advantages simultaneously.

Detailed description

In the following, the technical approach in the embodiments of the present invention is described clearly and completely. It is obvious that the described embodiments represent only a part of the invention and not all

Embodiments include. Based on the embodiments described in the invention, all other embodiments that can be achieved by those skilled in the art without creative effort fall within the scope of the present invention.

Example 1

The method for high-frequency

Laser precision welding of high-carbon steel with controlled local

Heat treatment includes the following steps:

Material preparation and surface treatment

High-carbon steel is prone to cracking during the welding process due to its high carbon content and possible alloying elements (such as manganese, chromium, etc.). These elements tend to form hard and brittle carbides at high temperatures.

Therefore, when selecting materials, attention should be paid to high-carbon steel that has undergone careful metallurgical processing to reduce the content of harmful

To reduce impurities. Surface cleaning by removing oxide layers and grease improves the reliability of the weld, as impurities can cause pores or inclusions in the weld. Pretreatments such as sandblasting or mechanical grinding increase the surface roughness, improve the absorption of

Laser energy and enable more even heating and better welding quality.

Local heat treatment

Laser preheating is performed prior to welding. This process effectively reduces the temperature gradient and thermal stresses during welding, thus reducing the risk of cracking. The design of the local heat treatment must consider the thermophysical properties and geometric shape of the material.

Achieving the desired microstructural change requires precise control of the temperature gradient and heating rate. An optimal preheat temperature is crucial to reduce the hardening tendency and effectively control post-weld hardness.

Optimization of laser welding parameters

Choosing the appropriate laser wavelength ensures that the energy is absorbed efficiently, taking into account the optical properties of the high-carbon steel. By adjusting the focus position, the laser energy input can be optimized so that it concentrates on the weld line, improving the weld depth-to-width ratio and welding efficiency. The scanning speed directly influences the

Heat input: A high scanning speed reduces the width of the heat-affected zone, but too high a speed can lead to a discontinuous weld.

Using the pulse mode improves the precision of welding. By controlling

Pulse frequency and energy allow the effect of each individual laser pulse to be precisely adjusted, making the welding process more controllable and stable.

Real-time monitoring and feedback control

By using advanced infrared thermography and optical sensors, real-time monitoring of the welding process enables the provision of dynamic

Temperature distribution data. These data form the basis for the adjustment of the

Laser power and scanning speed. The feedback control system analyzes the

Sensor data using algorithms and quickly adjusts the welding parameters to ensure stable weld quality. Such a closed-loop control system can actively correct negative trends during the welding process, thereby

Reliability and consistency of production is increased.

Post-heat treatment

Slow cooling reduces the internal stresses that develop during rapid cooling after welding. These stresses are one of the main causes of cracking in high-carbon steel. For certain high-carbon steels, post-annealing treatment is necessary. The annealing temperature and time must be determined according to the phase diagram of the specific material to eliminate the residual stresses created during welding and improve the microstructure of the weld and the adjacent areas.

In this embodiment, step S1 specifically includes:

S1.1: Material selection: The carbon content is between 0.6% and 0.9%, the manganese content between 0.3% and 0.6%, since the carbon content determines the hardness and brittleness of the

steel as well as the heat treatment effects during welding.

High-precision spectral analysis instruments (such as ICP-OES) are used to check the chemical

composition of the steel. This ensures that the fusion ratios are within an acceptable range to avoid the excessive formation of brittle phases such as FeS carbides (FeSCl) during welding.

S1.2: Surface cleaning: By combining chemical and mechanical

Methods are used to remove grease, oxide layers and other contaminants. The chemical

Cleaning is carried out with an industrial NaOH solution at a concentration of 7 = 9%, with the soaking time strictly limited to 15 minutes to ensure complete removal of

greases and oxides. The surface must then be cleaned several times with high-purity

Water to remove residues of the lye. The effectiveness of the

Surface cleaning is tested by contact angle measurement. A contact angle close to 0° is required, which indicates that the surface is fully wettable and the cleaning meets the requirements.

S1.3: Surface roughness treatment: With sandpaper of grain 120 - 240 the

The surface is evenly roughened to increase the surface roughness and thus improve the absorption of the laser energy. The surface roughness is checked with a roughness tester, whereby the Ra value must be in the range of 1.6 - 3.2 µm to ensure optimal

To ensure laser absorption. Roughness that is too high or too low would impair the interaction between the laser and the material, so strict control is required.

S1.4: Oxide layer treatment: The treatment is carried out by mechanical polishing or

Acid pickling with diluted hydrochloric acid at a concentration of 5%. The soaking time is limited to 5 minutes. This effectively removes surface oxides to prevent

The flowability and bonding properties of the weld pool during welding are not impaired. The thickness of the remaining oxide layer is analyzed by X-ray diffraction and must be less than 0.05 μm.

In this embodiment, step S2 specifically includes:

S2.1: Heating phase: The welding area of the high-carbon steel is heated to a certain

Temperature T to achieve austenitization. The selected temperature T is 780 °C, which is slightly above the critical point A1 (727 °C). This choice is based on the

Equilibrium phase diagram of the material and ensures that carbides in this

temperature is completely dissolved and a uniform austenite structure is formed.

To control the heating rate Rh, the formula Rn = (T - To) / tn is used, where To is the

Initial temperature (room temperature) and tn is the required heating time. Rn is set to 15 °

C/min to ensure a uniform temperature rise and the

To prevent the formation of thermal stresses and structural irregularities.

S2.2: Holding phase: After reaching the target temperature, a constant holding treatment is carried out. The holding time is set to 20 minutes. The calculation formula for the

Holding time is: LU600007 tw = C-d

Where C is a constant equal to 4 minutes per millimeter and d is the weld thickness.

For a welding area with a thickness of 5 millimeters, the holding time is 20 minutes.

The aim of this phase is to ensure a uniform austenite structure and the complete

dissolution of the carbides. Through this treatment, the material structure reaches a thermodynamically stable state, whereby stresses due to

Phase transformations are reduced during subsequent cooling.

S2.3: Slow cooling: After the holding phase, a slow cooling takes place in order to

To prevent martensite formation and the associated embrittlement of the material, the cooling rate Rc is controlled using the formula Re = (T - Tr) / tc, where Tr is the final temperature (usually room temperature) and tc is the cooling time. The cooling rate Rc must be strictly limited to 7 °C.

C/min. Controlling this slow cooling rate can promote the formation of a fine pearlite and ferrite microstructure in the weld area. These phases improve weld toughness and overall mechanical performance.

S2.4: Microstructure analysis and hardness testing: After heat treatment, the

Microstructure of the weld area can be analyzed using a microscope to determine

To confirm the ratio and distribution of pearlite, ferrite and the uniformity of carbides.

In addition, a hardness test is carried out, usually with a Brinell hardness tester.

The target hardness should be 220 HBW. This hardness ensures that the weld area has the necessary toughness and crack resistance under load conditions.

S2.5: Stress relief: A low-temperature stress relief treatment is performed. The welded assembly is heated to 200 °C and held for 1 hour. This helps to reduce internal stresses and promote the decomposition of incompletely transformed

To promote austenite. This treatment improves the stability of the weld area and prevents deformation and failure in later service.

In this embodiment, step S3 specifically includes:

S3.1: Laser power setting: The laser power is adjusted based on the physical

Properties of the material. For high-carbon steel, the thermal conductivity (50

W/mK). The required laser power is calculated using the formula P = kA (Tm-

T1), where A is the intended weld pool area, Tm is the melting point of the material (1535 °C), and T1 is the ambient temperature (25 °C). This setting ensures that the material is completely melted during welding without overheating.

S3.2: Determining the welding speed: The welding speed V is set depending on the material thickness and the required welding energy. The formula is: V=E/(P * t) where E is the required energy per unit length, P is the laser power, and t is the material thickness. The calculated speed is used to adjust the welding equipment to ensure a stable welding process and avoid welding defects.

S3.3: Adjusting the focus position: The focus position Zr of the laser influences the

;

LU600007

Melting depth and width. It is precisely determined by the formula Zr = f +Af, where f is the

Focal length of the laser system and Af is the experimentally determined focus correction. This ensures that the laser energy is concentrated on the weld surface or slightly below it to optimize material resolution and joint properties.

S3.4: Adjustment of the shielding gas flow: The shielding gas prevents the oxidation of the

Weld seam during welding and ensures a moderate cooling rate.

Shielding gas flow Fg is calculated using the formula Fg = Cg:S, where Cg is the gas flow coefficient (L/min) and S is the welding speed. The flow is optimized experimentally to

To avoid surface defects.

S3.5: Heat input control: The heat input Q is precisely controlled by the formula Q = P/ V, where P is the laser power and V is the welding speed. This

Control ensures uniform heat distribution during welding. Appropriate heat input ensures that the microstructure of the weld seam achieves the ideal

condition and has good mechanical properties.

In this embodiment, step S4 specifically includes:

S4.1: Data acquisition and sensor arrangement: Temperature sensors, camera monitoring devices and laser sensors are placed at the welding point and its surroundings to acquire temperature, image and power data during the welding process.

The data acquisition frequency is set to 1000 samples per second based on the welding speed and the dynamic changes of the weld pool to ensure high-precision real-time monitoring.

S4.2 Temperature monitoring and feedback control: With an infrared

The temperature measuring device monitors the temperature T in the welding area to ensure that the temperature remains within the specified range and overheating or insufficient heating is avoided. The temperature range is set from Tmin to

T max, where Tmin is 1530 ° C and T max is 1580 ° C.

If T > Trax, the laser power P is reduced, being adjusted by AP = k1-(T - Tmax), where kı is the control coefficient.

If T < Trin, the laser power P is increased, being adjusted by AP = ka (Tin -T), where ka is the control coefficient.

S4.3 Weld seam monitoring: A high-resolution camera captures real-time images of the

melt pool, which are then analyzed using a convolutional neural network (CNN). The CNN classifies and detects anomalies in the shape of the melt pool and the

Weld seam. By training with extensive annotated data, the CNN can precisely identify the different weld seam features and detect deviations such as

Detect seam misalignment or insufficient fusion depth. If visual monitoring detects a deviation in the weld shape, the system corrects it using b4/600007

Fuzzy logic algorithm (Fuzzy Logic Control) in real time. The fuzzy controller evaluates the

Deviations between the CNN output data and the ideal weld data and makes comprehensive adjustments to the laser focus position and welding speed. The fuzzy

The rule base is built based on different welding conditions and enables flexible adaptation to complex changes in the weld seam shape.

S4.4 Laser power monitoring and adjustment: A laser power sensor monitors

real-time laser power and ensures that fluctuations are within the specified narrow range. If the monitored deviation AP exceeds the fine-tuning range, the control system automatically adjusts the laser output using an adaptive

Control algorithm in real time so that the laser power is kept stable at the target value.

S4.5 Integrated feedback control: The distributed control system controls the

Welding parameters are analyzed and adjusted immediately. If the parameters are

quality standards, the priority of the corrections is determined using an algorithm, and laser power and welding speed are updated. The specific

The update formulas are: Pnew = Pola + AP and Snew = Sota TAS. The adjustment effects are automatically recorded, and the data is fed back to the control system to optimize subsequent welding processes. This precise, real-time monitoring and feedback system ensures high quality and consistency of the welding process.

In this embodiment, step SS comprises:

S5.1 Preheating treatment: Reduction of the temperature gradient during

Post-heat treatment to reduce the development of thermal stresses.

Preheating temperature Tpre is set to 600 °C and the time tpre to 30 minutes. In this

A temperature control device is used to ensure that the temperature of the entire workpiece is reached evenly. The temperature is monitored by a

Thermocouple type K. If the monitored temperature deviation AT > +5 °C, the heating power P of the device is adjusted. The adjustment is made according to the formula:

Puew = Poa + k'AT, where k is the control coefficient to quickly restore the target temperature.

S5.2 Main heat treatment: By using suitable temperature and time parameters, a

Precipitation hardening and recrystallization treatment of the weld seam.

Target temperature Tmain is set to 950 °C and the holding time tmain to 1 hour.

Temperature control is carried out using PID control algorithm to ensure constant

To maintain the treatment temperature, the PID control parameters are set as follows:

Proportional band Kp = 1.5, integration time Ti = 10 seconds and derivative time Ta = 1 second.

During the heating process, the temperature rise rate dT/dt must be controlled to below 10 °C/min to avoid thermal shocks.

S5.3 Slow cooling: Prevention of grain coarsening and re-

The cooling rate is set at 5 °C/min/600007 until the workpiece temperature reaches room temperature. During cooling, the

Flow of the cooling medium (including nitrogen or air) using a

The flow control valve is finely tuned. The cooling rate control formula is: Rnew = Rold +m AT, where m is the flow control coefficient and AT is the difference between the current temperature and the target temperature.

S5.4 Quality tests: Hardness tests, microstructure analyses and

Residual stress measurements. Hardness measurements are performed using a Vickers hardness tester, with the HV hardness values recorded and meeting the standard H Vmin <HV < HVmax. The microstructure is examined using a metallographic microscope to determine if there is insufficient grain bonding or uneven grain distribution.

Precipitation distribution occurs. The residual stress is measured using the X-ray diffraction method, with the results being within the preset limit of +50 MPa.

Example 2

The method for high-frequency

Laser precision welding of high-carbon steel with controlled local

Heat treatment also includes the following steps:

Quality tests

Non-destructive testing methods such as ultrasonic or X-ray testing enable the

Evaluation of the internal structure of the weld without damaging the workpiece. Possible defects such as pores, inclusions, and cracks can be detected. The analysis of the

Microstructure is an important part of materials science. By observing the

Microstructure in the weld area using a metallographic microscope allows the

Assess the influence of the welding process on the material's microstructure. Mechanical testing is a crucial step in ensuring welding quality and safety.

These tests check whether the strength, toughness and ductility of the weld meet the

meet design requirements.

Result feedback and process optimization

After completion of the entire welding process, all parameters and test results must be systematically recorded. This data not only serves to confirm the quality of the specific workpiece but also provides a basis for future

Process improvements. Through continuous data analysis and feedback, the

Welding process can be continuously optimized, especially with regard to the adaptation of

Laser parameters and local heat treatment. This ensures that the process meets the

meets the requirements of different production environments and materials.

In this example, the quality check specifically includes the following:

First, a hardness test is performed. A Vickers hardness tester is used to measure the hardness at several points on the weld and the heat-affected zone. The applied force is 9.8 Newtons, and at each measuring point, the length of the

Indentation diagonal d is recorded. The hardness is calculated using the formula HV = 1.854 x F/d, where F is the applied force of 9.8 Newtons and d is the length of the indentation diagonal. The hardness at the measuring points must be in the range of 290 HV to 320 HV.

Deviations from this range are the welding process parameters such as

Check welding speed or current and adjust if necessary, followed by another heat treatment.

Subsequently, a microstructure analysis is performed. After polishing and etching the sample, the microstructure of the weld is observed under a metallographic microscope at 1000x magnification. Uniform equiaxial grains and a reasonable amount of fine precipitates should be visible, evenly distributed, without abnormal grain boundary expansion. If coarse grains or an accumulation of

If excretions are observed, it must be checked whether the parameters of the

Post-heat treatment was correctly observed, such as the holding time of 1 hour at 950 °

C. If necessary, the post-heat treatment parameters are optimized to improve the microstructure.

This is followed by the measurement of the residual stress using the X-ray diffraction method.

The weld seam is irradiated with X-rays, and the displacement of the diffraction angle A20 is measured to determine the change in lattice spacing. The residual stress δ is calculated using the formula δ = E / (1 + v)-δ / d, where E is the elastic modulus of the material (MPa), V is the Poisson's ratio, δ is the change in lattice spacing, and d is the original

Lattice spacing. The measured residual stress must be in the range of -50 MPa to 50 MPa.

If the values are outside this range, the welding parameters must be adjusted or a

Stress relief annealing treatment must be carried out.

All the above measurement results are collected and evaluated to create a test report. Compliance with the specified standards for hardness, microstructure and

Residual stress is an indicator of quality conformity. In case of deviations, the causes of the deviation are analyzed in detail, such as insufficient

Treatment temperatures, insufficient holding times or errors in the process parameters.

Concrete measures such as a new heat treatment or the optimization of the

Process parameters are taken to ensure that the quality of the

Welded joints meet the design requirements. In this way, careful testing and adjustment steps ensure that the welded joints in the

In practice, they demonstrate reliable performance and a long service life.

Following the analysis, measures to adapt the process are taken immediately. If

Hardness deviations are detected, the heat input can be adjusted by adjusting the

welding voltage and welding current as well as by a moderate reduction of the

Welding speed must be controlled. If the microstructure does not meet the requirements, the heat treatment temperature and time are adjusted again to achieve a uniform grain size distribution. If the residual stresses are too high, a

The stress can be reduced by redefining the welding sequence or adding suitable stress relief annealing steps.

Process verification experiments are carried out after the adjustments. Based on the updated process parameters, a series of smaller verification experiments is carried out. This ensures that every measurement - from hardness to

From microstructure to residual stresses, the design standards are met. All experimental data are recorded, and the effectiveness of the adjustments is evaluated.

A detailed feedback report is prepared that fully documents the test results, the analysis process, the process adjustment measures, and the results of the verification experiments. It clearly demonstrates the extent to which the quality improvements have been achieved and their concrete impact on production. This report is made available to the relevant departments to ensure continuous process optimization and further improve welding quality.

The preferred embodiments of the present invention described above are merely illustrative of this invention. The preferred embodiments do not fully describe all details and do not limit the invention to the specific embodiments shown. It is obvious that based on the content of this

Many modifications and variations may be made without departing from the spirit and scope of this description. The selection and detailed description of these embodiments is merely intended to better explain the principles and practical applications of the invention so that persons skilled in the art can readily understand and apply the invention. The invention is limited exclusively to the

Claims and their entire scope and equivalents are limited.

Claims (7)

Claims LU600007 1. A high-frequency laser precision welding process for high-carbon steel with controlled local heat treatment, characterized in that it comprises the following steps: S1: Material preparation and surface treatment: Selection of high-carbon steel that has undergone precise metallurgical processing and removal of surface impurities by chemical cleaning and mechanical roughening to improve laser absorption and weld quality; S2: Local heat treatment: Performing laser preheating before welding, controlling the temperature and heating rate to reduce thermal stress and the risk of cracking during welding; S3: Optimization of laser welding parameters: By adjusting the laser wavelength, focus position, scanning speed, and pulse mode, efficient energy absorption and precise control are achieved to ensure the appropriate weld depth and width. S4: Real-time monitoring and feedback control: Using infrared thermography and optical sensors, the welding process is monitored in real time, while parameters are dynamically adjusted by a closed-loop control system to ensure the stability of the weld pool and the consistency of the weld; SS: Post-weld heat treatment: Control of the cooling rate and implementation of necessary annealing treatments to eliminate residual post-welding stresses and improve the microstructure of the weld. 2. The method according to claim 1, characterized in that it additionally comprises a quality inspection: through the use of non-destructive testing methods such as ultrasonic or X-ray testing, the internal structure of the weld is evaluated without damaging the workpiece in order to identify possible defects such as pores, inclusions and cracks; the microstructure in the weld area is examined using a metallographic microscope to evaluate the influence of the welding process on the microstructure of the material; mechanical tests ensure the quality and safety of the weld. 3. The method according to claim 2, characterized in that the quality inspection comprises the following: Hardness test: Using a Vickers hardness tester, the hardness is measured at several points on the weld and in the heat-affected zone; the applied force is 9.8 N, and the length of the indentation diagonal d is recorded at each measuring point. The hardness is calculated using the formula HV = 1.854 x F/d?*, where F is the applied force and d is the length of the indentation diagonal. The hardness values of the measuring points must be in the range of 290 HV to 320 HV. In case of deviations, the welding parameters must be checked and adjusted if necessary, followed by another heat treatment; Microstructure analysis: After polishing and etching the sample, the microstructure of the weld is observed under a metallographic microscope at 1000x magnification. Uniform equiaxial grains and a reasonable amount of fine precipitates should be visible, evenly distributed and without abnormal grain boundary expansion. If coarse grains or an accumulation of precipitates are found, it is necessary to check whether the heat treatment temperature and holding time were correctly maintained; if necessary, the post-heat treatment parameters are optimized to improve the microstructure. LU600007 Residual stress measurement: The weld is irradiated with X-rays, and the displacement of the diffraction angle A2 6 is measured to determine the change in lattice spacing. The residual stress © is calculated using the formula © = E/(1 + Vv) + Ad/d, where E is the elastic modulus of the material, v is the Poisson's ratio, A d is the change in lattice spacing, and d is the original lattice spacing. The measured stress must be in the range of -50 MPa to 50 MPa. If there are deviations, the welding parameters must be adjusted or a stress-relieving annealing treatment must be performed; All of the above measurement results are collected and evaluated, and a test report is prepared. Compliance with the standards for hardness, microstructure, and residual stress is an indicator of quality conformity. 4. A high-frequency laser precision welding process for high-carbon steel with controlled local heat treatment as described in claim 1, characterized in that step S2 comprises: S2.1: Heating phase: The welding area of the high-carbon steel is heated to a specific temperature T to achieve austenitization; the selected temperature T is 780 °C, slightly above the critical point Al of 727 °C. Based on the material's equilibrium phase diagram, this temperature ensures that the carbides are completely dissolved and a uniform austenite structure is formed. To control the heating rate Rn, the formula Rn = (T - To) / tn is used, where To is the initial temperature and tn is the required heating time. Rn is set to 15 °C/min to ensure a uniform temperature rise and prevent thermal stresses and structural irregularities. S2.2: Holding phase: After reaching the target temperature, a constant holding treatment is performed, the time being set to 20 minutes. The formula for calculating the holding time is: tw = C-d, where C is a constant of 4 minutes per millimeter and d represents the weld thickness. For a weld thickness of 5 millimeters, the holding time is 20 minutes. This ensures the uniformity of the austenite and the complete dissolution of the carbides. S2.3: Slow cooling: After the holding phase, slow cooling occurs to avoid martensite formation and the resulting embrittlement of the material. The cooling rate Rc is controlled using the formula Re = (T - Tr) / te, where Tr is the final temperature and tc is the cooling time. Re is strictly controlled at 7 °C/min. This slow cooling rate promotes the formation of fine pearlite and ferrite in the weld area. S2.4: Microstructure Analysis and Hardness Testing: After heat treatment, the microstructure of the weld area is analyzed using a microscope to confirm the ratio, distribution, and uniformity of pearlite, ferrite, and carbides. Hardness testing is performed using a Brinell hardness tester. S2.5: Stress relief: A low-temperature stress relief treatment is performed. The welded assembly is heated to 200 °C and held for 1 hour. LU600007 5.A high-frequency laser precision welding process for high-carbon steel with controlled local heat treatment as described in claim 1, characterized in that step S3 comprises: S3.1: Laser Power Adjustment: The laser power is determined based on the physical properties of the material. It is calculated based on the thermal conductivity. The required laser power is determined from the formula P = kA: (Tm-T1), where A is the intended melt pool area, Tm is the melting point of the material (1535 °C), and T1 is the ambient temperature (25 °C). S3.2: Determination of the welding speed: The welding speed V is calculated using the formula V = E / (P * t), where E is the required energy per unit length, P is the laser power and t is the material thickness. S3.3: Adjusting the focus position: The laser's focus position Zf influences the melting depth and width. It is precisely adjusted using the formula Zr = f +Af, where f is the focal length of the laser system and À f is the experimentally determined focus correction. S3.4: Shielding gas flow adjustment: The shielding gas flow prevents oxidation of the weld seam during welding and ensures a moderate cooling rate. The shielding gas flow rate Fe is calculated using the formula Fg = CoS, where Cg is the gas flow coefficient and S is the welding speed. S3.5: Heat input control: The heat input Q is precisely controlled by the formula Q = P/V, where P is the laser power and V is the welding speed. This ensures uniform heat distribution during the welding process. 6. A high-frequency laser precision welding process for high-carbon steel with controlled local heat treatment as described in claim 1, characterized in that step S4 comprises: S4.1: Data Acquisition and Sensor Layout: Temperature measurement sensors, camera monitoring devices, and laser power sensors are used to collect temperature, image, and power data from the weld site and its surroundings during the welding process. The data acquisition frequency is set to 1000 samples per second according to the welding speed and dynamic changes in the weld pool to ensure high-precision real-time monitoring. S4.2: Temperature monitoring and feedback control: The temperature T in the welding area is monitored using an infrared temperature measuring device U to ensure that it remains within the specified range and to avoid overheating or insufficient heating. The temperature range is set from Tmin to Tmax, where Tmin is 1530°C and Tmax is 1580°C. If T > Tmax, the laser power P is reduced, with the adjustment value calculated as AP = k1-(T - Tmax), where kı is the control coefficient. If T < Tmin, the laser power P is increased, with the adjustment value calculated as AP = k>-(Tmin - T), where k2 is the control coefficient. S4.3: Visual welding monitoring: A high-resolution camera captures real-time images of the weld pool. A convolutional neural network (CNN) then analyzes the weld shape. The CNN classifies and detects anomalies in the shape of the weld pool and the weld. After extensive training with annotated data, the CNN can accurately identify various weld features and detect shape anomalies such as weld misalignment or insufficient fusion depth. If visual deviations are detected, the system corrects them in real time using a fuzzy logic controller. The fuzzy controller evaluates the deviations between the CNN output data and the ideal weld data and makes comprehensive adjustments to the laser focus position and welding speed. The fuzzy rule base is created based on various welding conditions and enables flexible adaptation to complex changes in the weld shape. S4.4: Laser power monitoring and adjustment: A laser power sensor monitors the laser power in real time and ensures that fluctuations remain within a narrow, defined range. If the monitored power deviation AP exceeds the fine-tuning range, the control system automatically adjusts the laser power in real time using an adaptive control algorithm to keep the laser power stable at the target value. S4.5: Integrated feedback control: The welding parameters are analyzed and immediately adjusted by the distributed control system. If the parameters deviate from quality standards, the priority of the corrections is determined using an algorithm. Laser power and welding speed are updated according to the formulas Pnew = Pola +AP and Snew = Soild +AS. The adjustment effects are automatically recorded, and the data is fed back to the control system to optimize subsequent welding processes. 7. A high-frequency laser precision welding process for high-carbon steel with controlled local heat treatment as described in claim 1, characterized in that step S5 comprises: S5.1: Preheating treatment: Reducing the temperature gradient during post-heating treatment to reduce the generation of thermal stresses; the preheating temperature Tpre is set to 600°C and the time tpre to 30 minutes. A temperature control device is used to ensure that the temperature of the entire workpiece is heated evenly to the specified temperature. Temperature monitoring is performed using a K-type thermocouple. If the measured temperature deviation ΔT is > +5°C, the heater power P is adjusted according to the formula Pnew = Pola + k'ΔT, where k is the control coefficient, to ensure a rapid return to the target temperature. S5.2: Main heat treatment: Precipitation hardening and recrystallization treatment of the weld seam is carried out using suitable temperature and time parameters. The target temperature Tmain is set to 950 °C, and the holding time tmain is set to 1 hour. Temperature control is achieved using a PID control algorithm to maintain a constant treatment temperature. The PID control parameters are set as follows: proportional band Ky = 1.5, integration time Ti = 10 seconds, and derivative time Ta = 1 second. During the heating process, the temperature rise rate dT/dt must be controlled below 10 °C/min to avoid thermal shock. S5.3: Slow cooling: Prevents grain coarsening and the recurrence of undesirable internal stresses. The cooling rate is set at 5 °C/min until the workpiece temperature reaches room temperature. During cooling, the flow rate of the cooling medium is finely adjusted using a flow control valve. The cooling rate R is controlled according to the formula Rnew = Row + m : ΔT, where m is the flow control coefficient and ΔT is the difference between the current temperature and the target temperature. S5.4: Quality control: Hardness tests, microstructure analyses, and residual stress measurements are performed. Hardness measurements are performed using a Vickers hardness tester, with the HV values recorded and meeting the standards HVmin < HV < HVmax. The microstructure is examined using a metallographic microscope to determine whether there are defects at grain boundaries or an uneven distribution of precipitates. Residual stress measurements are performed using the X-ray diffraction method, with results that must be within the preset range of + MPa.