A new surface tension modeling method suitable for laser active welding

Abstract

The application belongs to the technical field of laser active welding simulation, and discloses a novel surface tension modeling method suitable for laser active welding, which adopts a segmented modeling mode for the surface tension model, comprehensively considers the deposition of the oxide film and the active effect of oxygen elements, and can simultaneously explain the two experimental phenomena of the enhanced laser penetration ability and the inhibited collapse defects. The surface tension model of the application adopts a three-section modeling method, and divides the temperature interval in the surface tension model into three sections, namely, a low-temperature interval close to the melting point, a transition interval, and a high-temperature interval close to the boiling point. In the low-temperature interval close to the melting point, due to the existence of the secondary elements (other elements except the main metal elements) in the metal material, the deposition of the high-melting-point oxide film will occur in the welding process. Therefore, in the low-temperature interval, the surface tension model of the application adopts a linear fitting model obtained through experimental measurement, namely, sigma 1 (T).

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of laser active welding simulation technology, and particularly relates to a novel surface tension modeling method suitable for laser active welding. Background Technology

[0002] Laser active welding is a welding method that utilizes activators such as oxides to regulate the behavior of the molten pool, building upon laser welding. It has demonstrated its application value in high-efficiency welding of thick plates and ultra-high-power laser welding. Compared to conventional laser welding, this method can improve laser penetration and suppress the collapse defect of fully penetrated welds. In the numerical simulation of this type of welding process, the surface tension of the molten pool directly affects the direction of the driving force on the surface of the molten pool, the internal flow pattern of the molten pool, the heat transfer path, and the final weld formation. Therefore, the setting of the surface tension model is crucial to whether the simulation results can reflect the actual welding phenomena.

[0003] In existing laser active welding simulations, the surface tension modeling methods that are relatively close mainly fall into two categories. The first category simplifies the surface tension relationship to a two-phase relationship involving the interaction of the main metal element and the active element. This method can reflect the influence of oxygen on the surface tension temperature coefficient of the molten pool and the flow direction of the molten pool, and has some applicability in explaining the enhancement of laser penetration capability. However, this method mainly focuses on establishing the relationship based on the effect of the active element and does not include the influence of the oxide film precipitated during the welding process on the surface tension of the molten pool in a unified temperature range. In penetration welding simulations, this can easily lead to an increase in weld collapse depth, which is inconsistent with the experimental phenomenon that collapse defects are suppressed in laser active welding.

[0004] The second method uses experimentally measured surface tension followed by linear fitting to establish the model. This method can reflect the surface tension changes of the base material in the molten state after the oxide surfactant is applied, and it has some applicability in explaining the suppression of weld collapse defects. However, this method mainly describes the change of surface tension with temperature based on experimental fitting relationships, and does not express the effect of active elements on the flow of the high-temperature molten pool based on the actual increase in oxygen content in the weld. In the simulation of the penetration process, it is easy to find that the penetration time is longer than that of conventional laser welding, which is inconsistent with the phenomenon of enhanced penetration ability in laser active welding.

[0005] Therefore, in laser active welding simulation scenarios, neither using the two-phase relationship of active elements alone nor the experimental linear fitting relationship alone can simultaneously address the two actual phenomena of enhanced penetration and suppression of slump defects. Especially in ultra-high power laser welding of thick plates, penetration time and slump depth are synchronously sensitive to the surface tension model of the molten pool. Existing models lack a unified modeling mechanism based on the composition of the base material, the oxygen content of the weld, the composition of the oxide film, and the temperature range, making it difficult for simulation models to accurately account for both penetration behavior and weld formation behavior. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a novel surface tension modeling method suitable for laser active welding.

[0007] This invention is implemented as follows: a surface tension modeling method suitable for laser active welding, comprising:

[0008] Measure the content of each element in the metal base material;

[0009] Laser active welding experiments were conducted, and the coating density of the oxide activator was recorded by the quality difference method before welding, denoted as ρ1;

[0010] After the welding experiment was completed, metallographic samples of the base material cross section and the weld cross section were prepared in the same manner.

[0011] The oxygen content a1 on the center line of the base material cross section and the oxygen content a2 on the center line of the weld cross section were obtained by using the same measurement method. The difference in oxygen content a of the weld was obtained by subtracting a1 from a2.

[0012] Based on the difference in oxygen content 'a' in the weld and the content of each element in the base metal, the composition of the oxide film precipitated during the welding process is determined, and the transition temperature range T1 to T2 is determined based on the minimum T1 and maximum T2 of the melting point of the oxide film composition.

[0013] The surface tension of the base material sample after the oxide surfactant was coated was measured by the seat drop method. Before the measurement, the oxide surfactant coating density ρ2 was controlled to be close to ρ1. Based on the measurement results, a surface tension model σ1(T) for the low temperature range was established. Its applicable temperature range is from the melting point T0 of the base material to T1.

[0014] The surface tension of the base material sample without oxide activator was measured by the seat drop method during melting. Combined with the difference in oxygen content a in the weld, a surface tension model σ3(T) in the high temperature range was established. The applicable temperature range is from T2 to the boiling point T3 of the base material.

[0015] A surface tension model σ2(T) for the transition range is established. σ2(T) is the weighted average of the surface tension model σ1(T) for the low temperature range and the surface tension model σ3(T) for the high temperature range with respect to temperature. Its applicable temperature range is from T1 to T2.

[0016] By combining σ1(T), σ2(T), and σ3(T), a three-segment numerical model of surface tension is obtained, which is continuous from the melting point T0 of the base material to the boiling point T3 of the base material.

[0017] Furthermore, the surface tension model σ1(T) in the low-temperature range is obtained by linear fitting, where σ1(T) is equal to A1 minus B1 multiplied by T, and A1 and B1 are fitting coefficients, and T is the temperature;

[0018] The establishment of the surface tension model σ3(T) in the high-temperature range includes: first, linearly fitting the surface tension measurement results of the base material without surfactant to obtain A2 minus B2 multiplied by T; then, adding a correction term based on the difference in oxygen content a in the weld to obtain σ3(T) equal to A2 minus B2 multiplied by T minus R multiplied by T multiplied by Γ multiplied by the natural logarithm, where the argument of the natural logarithm is 1 plus k multiplied by a multiplied by e, negative ΔH divided by RT raised to the power of RT, where R, Γ, k, and ΔH are constants.

[0019] Furthermore, the weighted average calculation formula for the surface tension model σ2(T) in the transition interval is: σ2(T) equals the difference between T2 and T divided by the difference between T2 and T1 multiplied by σ1(T), plus the difference between T and T1 divided by the difference between T2 and T1 multiplied by σ3(T).

[0020] The three-segment surface tension numerical model σ(T) is as follows: when the temperature T is greater than or equal to T0 and less than T1, σ(T) takes the value of σ1(T); when the temperature T is greater than or equal to T1 and less than or equal to T2, σ(T) takes the value of σ2(T); when the temperature T is greater than T2 and less than or equal to T3, σ(T) takes the value of σ3(T).

[0021] This invention also provides a novel surface tension modeling method suitable for laser active welding, comprising:

[0022] Step 1: Measure the content of each element in the metal base material;

[0023] Step 2: Conduct welding experiments; conduct laser activated welding experiments, and record the coating density of the oxide activator using the quality difference method before welding, denoted as ρ1.

[0024] Step 3: Prepare metallographic samples of the base material and weld cross-section; After the laser active welding experiment is completed, prepare metallographic samples of the base material and weld cross-section in the same manner.

[0025] Step 4: Measure the oxygen content in the weld.

[0026] Step 5: Confirm the upper and lower temperature limits of the transition zone;

[0027] Step 6: Establish a surface tension model for the low-temperature range;

[0028] Step 7: Establish a surface tension model for the high-temperature range;

[0029] Step 8: Establish the surface tension model for the transition zone.

[0030] Further, the measuring the oxygen element content in the weld seam: the same measurement method is used to measure the oxygen element content on the base metal and the center line of the weld cross-section on the metallographic sample respectively, the measurement results are recorded as a1 and a2 respectively, then the oxygen element content a in the weld seam is a=a2-a1.

[0031] Further, the determining the upper and lower temperature limits of the transition interval: based on the oxygen element content in the weld seam and the content of each element in the base metal, the composition of the oxide film precipitated during the welding process is confirmed, and the temperature range of the transition interval is determined according to the minimum value T1 and the maximum value T2 of the melting points of the oxide film composition, which is recorded as [T1, T2].

[0032] Further, the establishing the surface tension model for the low-temperature interval: the sessile drop method is used to measure the surface tension of the base metal sample after melting with the oxide activator coated on the surface, before the measurement, it is necessary to ensure that the coating density ρ2 of the oxide activator is close to ρ1 in step 2, that is, ρ2≈ρ1; after the measurement, a linear model is used to fit the measurement results, and the fitting result is recorded as σ=A1-B1T; the surface tension model for the low-temperature interval is: σ(T)=σ1(T)=A1-B1T, T0≤T<T1; where T0 and T1 are the melting point of the metal base metal and the lower temperature limit of the transition interval confirmed in step 2, respectively.

[0033] Further, the establishing the surface tension model for the high-temperature interval: the surface tension of the base metal sample after melting without coating the oxide activator is measured in the same manner as in step 6, and a linear model is used to fit the measurement results after the measurement, and the fitting result is recorded as σ=A2-B2T; the surface tension model for the high-temperature interval is: σ(T)=σ3(T)=A2-B2T-RTΓln(1+kae -ΔH / RT ), T2<T≤T3; where R, Γ, k and ΔH are all universal constants, a is the oxygen element content obtained in step 4, and T2 and T3 are the upper temperature limit of the transition interval confirmed in step 2 and the boiling point of the metal base metal, respectively.

[0034] Further, the establishing the surface tension model for the transition interval: the surface tension model for the transition interval is a weighted average of the surface tension models of the low-temperature interval and the high-temperature interval with respect to temperature, and the calculation formula is: σ(T)=σ2(T)=(T2-T) / (T2-T1)*σ1(T)+(T-T1) / (T2-T1)*σ3(T), T1≤T≤T2. By combining σ1(T), σ2(T), and σ3(T) obtained in steps 6 to 8, a complete and continuous three-segment surface tension numerical model can be obtained, that is, σ(T)=σ1(T), T0≤T<T1; σ2(T), T1≤T≤T2; σ3(T), T2<T≤T3.

[0035] Another object of the present invention is to provide a novel surface tension modeling system suitable for laser active welding, comprising:

[0036] The element content measurement module is used to measure the content of each element in the metal base material;

[0037] The welding module is used to conduct welding experiments; it conducts laser active welding experiments and records the coating density of the oxide activator by the quality difference method before welding, denoted as ρ1.

[0038] The preparation module is used to prepare metallographic samples of the base material and weld cross-section; after the laser active welding experiment is completed, metallographic samples of the base material and weld cross-section are prepared in the same way.

[0039] Oxygen content measurement module, used to measure the oxygen content in the weld;

[0040] The confirmation module is used to confirm the upper and lower temperature limits of the transition range.

[0041] The model building module is used to build surface tension models for the low-temperature range, the high-temperature range, and the transition range.

[0042] Another object of the present invention is to provide a computer device including a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the steps of the novel surface tension modeling method applicable to laser active welding.

[0043] Another object of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the novel surface tension modeling method applicable to laser active welding.

[0044] Another objective of this invention is to provide an information data processing terminal for implementing the novel surface tension modeling system suitable for laser active welding.

[0045] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0046] The advantage of this invention is that it adopts a segmented modeling approach for the surface tension model, which comprehensively considers the precipitation of oxide film and the active effect of oxygen elements, and can simultaneously explain the two experimental phenomena of enhanced laser penetration and suppression of collapse defects.

[0047] The surface tension model of this invention adopts a three-segment modeling method, which divides the temperature range in the surface tension model into three segments: a low-temperature range near the melting point, a middle transition range, and a high-temperature range near the boiling point.

[0048] In the low-temperature range close to the melting point, due to the presence of secondary elements (elements other than the main metallic element) in the metallic material, a high-melting-point oxide film will precipitate during the welding process. Therefore, in the low-temperature range, the surface tension model of this invention adopts a linear fitting model obtained through experimental measurement, namely σ1(T).

[0049] In the high-temperature range near the boiling point, the conditions for oxide film precipitation are not met due to the high temperature, and the active effect of oxygen is dominant. Therefore, in the high-temperature range, the surface tension model of this invention adopts a two-phase model of "main metal element - active element", namely σ3(T). At the same time, considering the influence of secondary elements, the coefficients in σ2(T) were also corrected based on experimental measurement results.

[0050] In the transition region, considering the gradual process of oxide film precipitation and to prevent abrupt changes in surface tension in the model, the surface tension model of this invention adopts a weighted average of σ1(T) and σ3(T).

[0051] Because of its three-segment structure, the surface tension model of this invention comprehensively considers the precipitation of oxide film and the active effect of oxygen, and can simultaneously explain the two phenomena of enhanced laser penetration and suppression of collapse defects, thus solving the problem that the two phenomena cannot be taken into account in the simulation model.

[0052] The expected benefits and commercial value of the technical solution of this invention after transformation are as follows: The surface tension modeling method provided by this invention can significantly improve the accuracy of the simulation model, realize accurate prediction of weld formation, thereby greatly shorten the welding process development cycle and effectively save the cost of welding experimental materials required in the process exploration.

[0053] The technical solution of this invention solves a technical problem that people have long desired to solve but have never been able to achieve: the surface tension modeling method provided by this invention effectively solves the technical problem that in the simulation of single-pass double-sided forming of traditional laser active welding, the model is difficult to accurately predict both laser penetration behavior and weld formation behavior at the same time. Attached Figure Description

[0054] Figure 1 This is a flowchart of a novel surface tension modeling method for laser active welding provided in an embodiment of the present invention.

[0055] Figure 2 This is a structural block diagram of a novel surface tension modeling system for laser active welding provided in an embodiment of the present invention.

[0056] Figure 3 This is a comparison chart of the melting time provided in the embodiments of the present invention.

[0057] Figure 4 This is a comparison result diagram of the collapse depth provided in the embodiment of the present invention.

[0058] Figure 5 A comparison of the laser active welding simulation results and experimental results obtained based on the surface tension model provided by this invention.

[0059] Figure 6 A key dimensional comparison between the simulation results and experimental results of laser active welding based on the surface tension model provided by this invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0061] like Figure 1 As shown, the novel surface tension modeling method for laser active welding provided in this embodiment of the invention includes the following steps:

[0062] S101, measuring the content of each element in the metal base material;

[0063] S102, Conduct welding experiments; conduct laser activated welding experiments, and record the coating density of the oxide activator using the quality difference method before welding, denoted as ρ1.

[0064] S103, prepare metallographic samples of the base material and weld cross-section; after the laser active welding experiment is completed, prepare metallographic samples of the base material and weld cross-section in the same way;

[0065] S104, measures the oxygen content in the weld;

[0066] S105, confirm the upper and lower limits of the temperature in the transition zone;

[0067] S106, Establish a surface tension model in the low-temperature range;

[0068] S107, Establish a surface tension model for the high-temperature range;

[0069] S108, Establish the surface tension model for the transition zone.

[0070] The present invention provides a method for measuring the oxygen content in a weld: the same measurement method is used to measure the oxygen content on the center line of the cross-section of the base material and the weld on the metallographic sample, and the measurement results are recorded as a1 and a2, respectively. Then the oxygen content in the weld is a = a2 - a1.

[0071] The upper and lower temperature limits of the transition interval provided by the embodiments of the present invention: the composition of the oxide film precipitated during the welding process is determined based on the oxygen element content in the weld and the content of each element in the base material, and the temperature range of the transition interval is determined according to the minimum value T1 and the maximum value T2 of the melting points of the oxide film composition, which is denoted as [T1, T2].

[0072] Establishing the surface tension model for the low-temperature interval provided by the embodiments of the present invention: the sessile drop method is used to measure the surface tension of the molten base material sample after the surface is coated with an oxide activating agent. Before the measurement, it is necessary to ensure that the coating density ρ2 of the oxide activating agent is close to ρ1 in step 2, that is, ρ2≈ρ1; after the measurement is completed, a linear model is used to fit the measurement results, and the fitting result is denoted as σ=A1-B1T; the surface tension model for the low-temperature interval is: σ(T)=σ1(T)=A1-B1T, T0≤T<T1; where T0 and T1 are respectively the melting point of the metal base material and the lower temperature limit of the transition interval determined in step 2.

[0073] Establishing the surface tension model for the high-temperature interval provided by the embodiments of the present invention: the surface tension of the molten base material sample without coating the oxide activating agent is measured in the same manner as in step 6, and a linear model is used to fit the measurement results after the measurement is completed, and the fitting result is denoted as σ=A2-B2T; the surface tension model for the high-temperature interval is: σ(T)=σ3(T)=A2-B2T-RTΓln(1+kae -ΔH / RT ), T2<T≤T3; where R, Γ, k and ΔH are all universal constants, a is the oxygen element content obtained in step 4, and T2 and T3 are respectively the upper temperature limit of the transition interval determined in step 2 and the boiling point of the metal base material.

[0074] Establishing the surface tension model for the transition interval provided by the embodiments of the present invention: the surface tension model for the transition interval is the weighted average of the surface tension models of the low-temperature interval and the high-temperature interval with respect to temperature, and the calculation formula is: σ(T)=σ2(T)=(T2-T) / (T2-T1)*σ1(T)+(T-T1) / (T2-T1)*σ3(T), T1≤T≤T2. By combining σ1(T), σ2(T) and σ3(T) obtained in steps 6 to 8, a complete and continuous three-segment surface tension numerical model can be obtained, that is, σ(T)=σ1(T), T0≤T<T1; σ2(T), T1≤T≤T2; σ3(T), T2<T≤T3.

[0075] The novel surface tension modeling method provided in this invention is mainly used for the numerical description of the surface tension of the molten metal pool as a function of temperature during laser active welding. Its working principle is as follows: First, the content of each element in the base metal is measured to provide basic data for determining the composition of the oxide film that may form during welding. Then, a laser active welding experiment is conducted, and the coating density of the oxide activator is recorded using the quality difference method before welding, ensuring that the subsequent surface tension measurement conditions correspond to the actual welding conditions. After welding, metallographic samples of the base metal and weld cross-sections are prepared in the same manner, and the oxygen content on the centerline of the base metal cross-section and the centerline of the weld cross-section are measured respectively. The actual increase in oxygen content in the weld is obtained by subtracting the oxygen content on the centerline of the base metal cross-section from the oxygen content on the centerline of the weld cross-section. This oxygen content reflects the oxygen level entering the weld region after the activator participates in welding.

[0076] After obtaining the oxygen content of the weld and the elemental content of the base metal, the composition of the oxide film precipitated during welding was confirmed based on these data. The transition temperature range was then determined according to the minimum and maximum melting points of the oxide film components. This range describes the transition process of the oxide film's influence on surface tension as it changes from a low-temperature to a high-temperature state. For the low-temperature range, the surface tension of the base metal sample after melting was measured using the droplet method. Before measurement, the oxide activator coating density during the droplet method was ensured to be close to that in the laser activated welding experiment. The measurement results were fitted using a linear model, and the fitted low-temperature linear surface tension relationship was used as the low-temperature surface tension model within the range from the melting point of the metal base metal to the lower limit of the transition temperature range.

[0077] For the high-temperature range, the surface tension of the base material sample after melting without oxide surfactant was measured in the same manner, and linear fitting was performed. Based on this, a correction term determined by the oxygen content of the weld was introduced to establish a high-temperature surface tension model ranging from the upper temperature limit of the transition range to the boiling point of the base metal. The relevant parameters in the high-temperature range surface tension model are universal constants, and the boiling point of the base metal is used as the upper temperature limit of the high-temperature range. For the transition range, the surface tension models of the low-temperature range and the high-temperature range are weighted by temperature to obtain the transition range surface tension model. Finally, the surface tension models of the low-temperature range, the transition range, and the high-temperature range are combined to form a complete and continuous three-segment surface tension numerical model from the melting point to the boiling point of the base material.

[0078] like Figure 2 As shown, an embodiment of the present invention provides a novel surface tension modeling system suitable for laser active welding, comprising:

[0079] The element content measurement module is used to measure the content of each element in the metal base material;

[0080] The welding module is used to conduct welding experiments; it conducts laser active welding experiments and records the coating density of the oxide activator by the quality difference method before welding, denoted as ρ1.

[0081] The preparation module is used to prepare metallographic samples of the base material and weld cross-section; after the laser active welding experiment is completed, metallographic samples of the base material and weld cross-section are prepared in the same way.

[0082] Oxygen content measurement module, used to measure the oxygen content in the weld;

[0083] The confirmation module is used to confirm the upper and lower temperature limits of the transition range.

[0084] The model building module is used to build surface tension models for the low-temperature range, the high-temperature range, and the transition range.

[0085] Another object of the present invention is to provide a computer device including a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the steps of the novel surface tension modeling method applicable to laser active welding.

[0086] Another object of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the novel surface tension modeling method applicable to laser active welding.

[0087] Another objective of this invention is to provide an information data processing terminal for implementing the novel surface tension modeling system suitable for laser active welding.

[0088] The following section uses laser active welding of 20mm thick EH36 steel as an example to introduce the implementation steps and effects of the present invention.

[0089] Implementation steps

[0090] 1) Measure the content of each element in the base metal. Before the welding experiment, the content of each element in the EH36 steel base metal was measured using ICP technology. In the measurement results, the oxygen-loving elements and their contents are as follows: Al 0.0355%, Si 0.0707%, Mn 1.2774%. The oxygen affinity is ranked as follows: Al>Si>Mn.

[0091] 2) Welding Experiment. A laser active welding experiment was conducted on 20mm thick EH36 steel. The welding parameters were: laser power 24kW, welding speed 20mm / s, defocusing amount 0, laser tilt angle 5°, shielding gas Ar, and shielding gas flow rate 30L / min. The welded joint was a butt joint, and Fe2O3 was uniformly coated on the butt joint surface before welding. By measuring the change in workpiece mass before and after coating, the Fe2O3 coating density ρ1 was calculated to be 3.7833 ± 0.1376 mg / cm³. 2 .

[0092] 3) Preparation of metallographic samples of the base material and weld cross-section. After the welding experiment is completed, samples with a size of 10*5*20mm are cut from the base material and weld area respectively by wire cutting. Then, the samples are prepared by three processes: mounting, grinding and polishing.

[0093] 4) Measure the oxygen content in the weld. The oxygen content on the center line of the base metal and the weld cross-section was measured using EPMA line scanning technology. The measurement results were 0.9110% and 0.9701% respectively. Therefore, the oxygen content in the weld is a = 0.9701% - 0.9110% = 0.0591%.

[0094] 5) Confirm the upper and lower temperature limits of the transition zone. Based on the measurement results of steps 1 and 2, calculations show that the oxygen content in the weld is only sufficient to support the precipitation of Al2O3 and SiO2. That is, the main components of the oxide film precipitated during welding are Al2O3 and SiO2. Therefore, the upper and lower temperature limits of the transition zone are set to the melting points of Al2O3 and SiO2, so the temperature range of the transition zone is [1986K, 2327K].

[0095] 6) Establish a surface tension model for the low-temperature range. The surface tension of EH36 steel samples coated with Fe2O3 after melting was measured using the seated drop method. The Fe2O3 coating density ρ2 was 3.754 mg / cm². 2 The result is close to ρ1 in step 2, i.e., ρ2≈ρ1. After the measurement, a linear model was used to fit the measurement results, and the fitting result was σ = 3926.44-0.82T. The surface tension model in the low-temperature range is: σ(T) = σ1(T) = 3926.44-0.82T, 1768K≤T<1986K. Wherein, 1768K and 1986K are the melting point of EH36 steel and the lower limit of the transition range temperature confirmed in step 2, respectively.

[0096] 7) Establish a surface tension model for the high temperature range. Measure the surface tension of the molten EH36 steel sample without Fe2O3 coating in the same manner as in step 6, and fit the measurement results using a linear model after the measurement is completed. The fitting result is σ = 3521.40-0.91T. The surface tension model for the high temperature range is: σ(T) = σ3(T) = 3521.40-0.91T-RTΓln(1+kae -ΔH / RT ), 2327K<T≤3134K. Where R, Γ, k and ΔH are all universal constants, a is the oxygen element content obtained in step 4, and 2327K and 3134K are respectively the upper limit of the transition range temperature confirmed in step 2 and the boiling point of EH36 steel.

[0097] 8) Establish a surface tension model for the transition range. The surface tension model for the transition range is a weighted average of the surface tension models of the low temperature range and the high temperature range with respect to temperature, and the calculation formula is: σ(T) = σ2(T) = (2327-T) / 341*σ1(T) +(T-1986) / 341*σ3(T), 1986K≤T≤2327K.

[0098] 9) By combining σ1(T), σ2(T) and σ3(T) obtained in steps 6 to 8, a complete and continuous three-segment surface tension numerical model for EH36 steel laser active welding can be obtained, that is, σ(T)=σ1(T), 1768K≤T<1986K; σ2(T), 1986K≤T≤2327K; σ3(T), 2327K <T≤3134K.

[0099] Implementation Effects

[0100] Import the surface tension numerical model obtained in the above step 9 into the CFD simulation example of laser active welding, and the welding parameters in the example are shown in Table 1. Then run the simulation program, and after obtaining the results, compare them with the simulation results of laser welding under the same parameters. The comparison results are shown in Figure 3 and Figure 4 . Figure 3 and Figure 4 , the control group is the laser welding simulation result, and the experimental group is the laser active welding simulation result based on the surface tension model established by the present invention. Figure 3 shows the comparison results of penetration time. It can be found that the penetration time of the experimental group is shorter than that of the control group, which indicates that the laser penetration capability of laser active welding is enhanced compared with that of laser welding; Figure 4The results show a comparison of the collapse depth. It can be observed that the collapse depth in the experimental group is smaller than that in the control group, indicating that the laser active welding process can suppress collapse defects. In summary, based on the surface tension numerical model established in this invention, the simulation examples can simultaneously explain both the enhanced laser penetration capability and the suppression of collapse defects, thus solving the problem that simulation models cannot simultaneously account for both phenomena.

[0101] Table 1 Welding parameters in CFD simulation examples

[0102]

[0103] Figure 3 and Figure 4 The results show that, based on the surface tension numerical model established in this invention, the simulation examples can simultaneously explain the two experimental phenomena of enhanced laser penetration and suppressed collapse defects, thus solving the problem that the two phenomena cannot be taken into account in the simulation model.

[0104] Figure 5 and Figure 6 The comparison between the simulation results and experimental results of laser active welding in the embodiments is shown, wherein... Figure 5 The comparison shows the cross-sections of the welds. Figure 6 The display focuses on the comparison of important dimensions. It can be observed that... Figure 5 and Figure 6 The simulation results and experimental results are in good agreement, which shows that the simulation examples can accurately predict the experimental results based on the surface tension numerical model established in this invention.

[0105] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A surface tension modeling method suitable for laser active welding, characterized in that, include: Measure the content of each element in the metal base material; Laser active welding experiments were conducted, and the coating density of the oxide activator was recorded by the quality difference method before welding, denoted as ρ1; After the welding experiment was completed, metallographic samples of the base material cross section and the weld cross section were prepared in the same manner. The oxygen content a1 on the center line of the base material cross section and the oxygen content a2 on the center line of the weld cross section were obtained by using the same measurement method. The difference in oxygen content a of the weld was obtained by subtracting a1 from a2. Based on the difference in oxygen content 'a' in the weld and the content of each element in the base metal, the composition of the oxide film precipitated during the welding process is determined, and the transition temperature range T1 to T2 is determined based on the minimum T1 and maximum T2 of the melting point of the oxide film composition. The surface tension of the base material sample after the oxide surfactant was coated was measured by the seat drop method. Before the measurement, the oxide surfactant coating density ρ2 was controlled to be close to ρ1. Based on the measurement results, a surface tension model σ1(T) for the low temperature range was established. Its applicable temperature range is from the melting point T0 of the base material to T1. The surface tension of the base material sample without oxide activator was measured by the seat drop method during melting. Combined with the difference in oxygen content a in the weld, a surface tension model σ3(T) in the high temperature range was established. The applicable temperature range is from T2 to the boiling point T3 of the base material. A surface tension model σ2(T) for the transition range is established. σ2(T) is the weighted average of the surface tension model σ1(T) for the low temperature range and the surface tension model σ3(T) for the high temperature range with respect to temperature. Its applicable temperature range is from T1 to T2. By combining σ1(T), σ2(T), and σ3(T), a three-segment numerical model of surface tension is obtained, which is continuous from the melting point T0 of the base material to the boiling point T3 of the base material.

2. The method according to claim 1, characterized in that, The surface tension model σ1(T) in the low-temperature range is obtained by linear fitting. σ1(T) is equal to A1 minus B1 multiplied by T, where A1 and B1 are fitting coefficients and T is the temperature. The establishment of the surface tension model σ3(T) in the high-temperature range includes: first, linearly fitting the surface tension measurement results of the base material without surfactant to obtain A2 minus B2 multiplied by T; then, adding a correction term based on the difference in oxygen content a in the weld to obtain σ3(T) equal to A2 minus B2 multiplied by T minus R multiplied by T multiplied by Γ multiplied by the natural logarithm, where the argument of the natural logarithm is 1 plus k multiplied by a multiplied by e, negative ΔH divided by RT raised to the power of RT, where R, Γ, k, and ΔH are constants.

3. The method according to claim 2, characterized in that, The weighted average calculation formula for the surface tension model σ2(T) in the transition interval is: σ2(T) equals the difference between T2 and T divided by the difference between T2 and T1 multiplied by σ1(T), plus the difference between T and T1 divided by the difference between T2 and T1 multiplied by σ3(T). The three-segment surface tension numerical model σ(T) is as follows: when the temperature T is greater than or equal to T0 and less than T1, σ(T) takes the value of σ1(T); when the temperature T is greater than or equal to T1 and less than or equal to T2, σ(T) takes the value of σ2(T); when the temperature T is greater than T2 and less than or equal to T3, σ(T) takes the value of σ3(T).

4. The novel surface tension modeling method for laser active welding as described in claim 1, characterized in that, The measurement of the oxygen element content in the weld seam: the same measurement method is adopted to measure the oxygen element content on the base metal and the center line of the weld cross-section on the metallographic specimen respectively, the measurement results are recorded as a1 and a2 respectively, then the oxygen element content a in the weld seam is a=a2-a1.

5. The novel surface tension modeling method for laser active welding as described in claim 1, characterized in that, The confirming of the upper and lower temperature limits of the transition interval: the composition of the oxide film precipitated during the welding process is confirmed according to the oxygen element content in the weld seam and the content of each element in the base metal, and the temperature range of the transition interval is determined according to the minimum value T1 and the maximum value T2 of the melting points of the oxide film composition, which is recorded as [T1,T2].

6. The novel surface tension modeling method for laser active welding as described in claim 1, characterized in that, The establishing of the surface tension model for the low temperature interval: the sessile drop method is used to measure the surface tension of the base metal sample after melting with the oxide active agent coated on the surface. Before the measurement, it is necessary to ensure that the coating density ρ2 of the oxide active agent is close to ρ1 in step 2, that is, ρ2≈ρ1; after the measurement, a linear model is used to fit the measurement results, and the fitting result is recorded as σ=A1-B1T; the surface tension model of the low temperature interval is: σ(T)=σ1(T)=A1-B1T, T0≤T<T1; wherein, T0 and T1 are the melting point of the metal base metal and the lower temperature limit of the transition interval confirmed in step 2, respectively.

7. The novel surface tension modeling method for laser active welding as described in claim 1, characterized in that, The establishing of the surface tension model for the high-temperature interval: measure the surface tension of the molten base material sample without the oxide active agent coated thereon in the same manner as in Step 6, and fit the measurement results using a linear model after the measurement is completed, the fitting result is denoted as σ=A2-B2T; the surface tension model for the high-temperature interval is: σ(T)=σ3(T)=A2-B2T-RTΓln(1+kae -ΔH / RT ), T2<T≤T3; wherein R, Γ, k and ΔH are all universal constants, a is the oxygen element content obtained in Step 4, and T2 and T3 are respectively the upper limit of the transition interval temperature confirmed in Step 2 and the boiling point of the metal base material.

8. The novel surface tension modeling method for laser active welding as described in claim 1, characterized in that, The establishing of the surface tension model for the transition interval: the surface tension model of the transition interval is the weighted average of the surface tension models of the low temperature interval and the high temperature interval with respect to temperature, and the calculation formula is: σ(T)=σ2(T)=(T2-T) / (T2-T1)*σ1(T)+(T-T1) / (T2-T1)*σ3(T), T1≤T≤T2. By combining σ1(T), σ2(T) and σ3(T) obtained in steps 6 to 8, a complete and continuous three-segment surface tension numerical model can be obtained, that is, σ(T)=σ1(T), T0≤T<T1; σ2(T), T1≤T≤T2; σ3(T), T2<T≤T3.

9. A novel surface tension modeling system for laser active welding, implementing the applicable method as described in any one of claims 1-8, characterized in that, The novel surface tension modeling system suitable for laser active welding includes: An element content measurement module, configured to measure the content of each element in the metal base metal; A welding module, configured to perform welding experiments; perform laser active welding experiments, and record the coating density of the oxide active agent by the mass difference method before welding, which is recorded as ρ1; A preparation module, configured to prepare metallographic specimens of the cross-sections of the base metal and the weld seam; after the laser active welding experiment is completed, prepare the metallographic specimens of the cross-sections of the base metal and the weld seam respectively in the same manner; An oxygen element content measurement module, configured to measure the oxygen element content in the weld seam; A confirmation module, configured to confirm the upper and lower temperature limits of the transition interval; A model establishment module, configured to establish a surface tension model for the low temperature interval; establish a surface tension model for the high temperature interval; establish a surface tension model for the transition interval.

10. An information data processing terminal, characterized in that, The information data processing terminal is configured to implement the novel surface tension modeling system suitable for laser active welding as described in claim 9.

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