阅读说明：本技术 铝钢异种金属管件磁脉冲焊接界面与接头特性数值模拟方法 (Method for simulating magnetic pulse welding interface and joint characteristic numerical values of aluminum steel dissimilar metal pipe fitting ) 是由 苗莉莉 葛寒 白爱英 寇晓晨 于 2021-07-07 设计创作，主要内容包括：一种铝钢异种金属管件磁脉冲焊接界面与接头特性数值模拟方法,包括：进行磁脉冲焊接接头拉伸力学性能的影响规律分析；进行磁脉冲焊接接头的失效模式分析；建立基于焊接系数的可焊性窗口；进行磁脉冲焊接接头微观分析。通过数值模拟的方式对铝合金-高强钢焊接接头和界面进行工艺试验与性能评估,从而对铝钢磁脉冲焊接结构的应用提供了一定的参考,对铝钢焊接接头进行多参数的工艺试验,并对焊接接头进行准静态拉伸测试,随着焊接能量的提升,碰撞速度和碰撞角度的增加,实现母材断裂的焊接接头的几率大大提高。通过微观分析手段确定焊接失效与焊接碰撞速度和角度的关联性。(A method for simulating the characteristics of a magnetic pulse welding interface and a joint of an aluminum-steel dissimilar metal pipe fitting comprises the following steps: analyzing the influence rule of the tensile mechanical property of the magnetic pulse welding joint; analyzing the failure mode of the magnetic pulse welding joint; establishing a weldability window based on the welding coefficient; and (5) carrying out magnetic pulse welding joint microscopic analysis. The method is characterized in that a process test and performance evaluation are carried out on an aluminum alloy-high-strength steel welding joint and an interface in a numerical simulation mode, so that a certain reference is provided for application of an aluminum steel magnetic pulse welding structure, a multi-parameter process test is carried out on the aluminum steel welding joint, a quasi-static tensile test is carried out on the welding joint, and along with the improvement of welding energy, the increase of collision speed and collision angle, the probability of the welding joint with the breakage of a base metal is greatly improved. The correlation of weld failure to weld collision speed and angle was determined by microscopic analytical means.)

1. A method for simulating the magnetic pulse welding interface and joint characteristic numerical values of an aluminum steel dissimilar metal pipe fitting is characterized by comprising the following steps of:

step 1, analyzing the influence rule of the tensile mechanical property of the magnetic pulse welding joint;

step 2, analyzing the failure mode of the magnetic pulse welding joint;

step 3, establishing a weldability window based on welding coefficients;

and 4, carrying out magnetic pulse welding joint microscopic analysis.

2. The method for simulating the numerical values of the characteristics of the magnetic pulse welding interface and the joint of the aluminum-steel dissimilar metal pipe fitting according to claim 1, wherein the method comprises the following steps: the step 1 comprises the implementation of full-parameter welding tests of different welding intervals under the welding discharge energy of 26kJ, 28kJ, 30kJ, 32kJ and 34kJ, wherein the welding interval ranges from 1.0mm to 1.8mm, the incremental distance is 0.2mm, and workpieces after welding are not subjected to any secondary treatment.

3. The method for simulating the magnetic pulse welding interface and the joint characteristic of the aluminum-steel dissimilar metal pipe fitting according to claim 1, wherein the step 1 comprises the following steps:

step 11, analyzing the influence rule of different welding energy parameters on the welding joint: the effect of welding energy on a welded joint is not a positive correlation, but there is a critical optimum;

step 12, analyzing the influence rule of the welding distance on the strength of the welding joint under different welding energies: the influence of the welding distance on the welding quality is the comprehensive influence of the welding collision speed and the welding collision angle on the welding strength, and the change rule of the welding strength shows that the relation between the welding collision speed and the welding collision angle and the welding strength has the condition of critical optimization, the welding quality deviating from the optimal process parameter is difficult to form effective and firm welding quality under the condition of smaller collision speed and collision angle; excessive collision speed and collision angle can cause instability of a welding interface, generate a micro defect problem and cause strength reduction.

4. The method for simulating the magnetic pulse welding interface and the joint characteristic of the aluminum-steel dissimilar metal pipe fitting according to claim 1, wherein the step 2 comprises the following steps:

welding failure modes under different welding parameters comprise aluminum alloy base metal fracture failure and welding joint fracture failure; in a first failure mode, the final fracture form is ductile fracture, the aluminum-steel welding joint under the parameters obtains proper collision speed and collision angle, good metallurgical welding effect is obtained, a stable and firm welding joint is formed, the strength of the welding joint under the parameters is higher than that of an aluminum alloy base metal, and the aluminum alloy base metal is taken as a weaker area to be subjected to fracture failure under the action of external loading; for the second failure mode, namely the fracture failure of the welding joint, the final fracture form is brittle fracture, under the welding parameters, namely the collision speed and the collision angle are both large, the quality of the welding joint at the moment is general, the strength of the welding joint is lower than that of the aluminum alloy base metal, and the fracture occurs in the welding joint under the action of external load.

5. The method for simulating the magnetic pulse welding interface and the joint characteristic of the aluminum-steel dissimilar metal pipe fitting according to claim 1, wherein the step 3 comprises the following steps:

the full parameter test data is used as a basis, welding joint coefficients are introduced, welding energy and welding distance are used as process parameters, and a simplified process window of magnetic pulse welding is established, so that reference is provided for performance evaluation of the strength of the magnetic pulse welding joint.

6. The method as claimed in claim 5, wherein the welding coefficient is a ratio of strength of the welded joint to strength of the base metal, and is used to evaluate reliability of the weld quality. For effective evaluation of the welding quality, the welding coefficient is subjected to 5 levels of reliability division:

the welding strength is more than 90% of the base metal strength;

the welding strength is more reliable at grade-B, and reaches more than 80% of the base metal strength;

reliable-C grade, the welding strength reaches more than 70% of the base metal strength;

the reliability is poor to grade D, and the welding strength reaches more than 60 percent of the base metal strength;

unreliable-E grade, the welding strength reaches below 60% of the base metal strength;

the established welding window grades the welding coefficient by introducing the welding coefficient, and the welding energy and the welding distance are used as indexes, so that the strength grades of the welding joints under different parameters can be intuitively and quickly obtained.

7. The method for simulating the magnetic pulse welding interface and the joint characteristic of the aluminum-steel dissimilar metal pipe fitting according to claim 1, wherein the step 4 comprises the following steps:

step 41, performing interface microscopic analysis of different failure modes;

and step 42, performing welding fracture analysis.

8. The method of claim 7, wherein the step 41 comprises:

(1) metallographic analysis of a welding interface: determining the three-dimensional space morphology of an alloy structure by measuring and calculating the metallographic microstructure of a two-dimensional metallographic sample ground surface or a film, thereby establishing a quantitative relation among alloy components, structures and performances, and applying an image processing system to metallographic analysis, wherein equipment used for the metallographic analysis is an OLYMPUSCXBX 51 polarizing microscope;

(2) and (5) analyzing a welding interface by an electron microscope. The scanning electron microscope uses secondary electron signal imaging to observe the surface morphology of a sample, namely, the surface of the sample is scanned by an extremely narrow electron beam region, various effects are generated through the interaction between the electron beam and the surface of the sample, including secondary electron emission of the sample, secondary electrons can generate a feature image amplified on the surface of the sample, the feature image is established according to time sequence when the sample is scanned, namely, an amplified image is obtained by a point-by-point imaging method, the scanning electron microscope is provided with an X-ray energy spectrometer device, the observation of the microstructure morphology and the analysis of micro-region components are simultaneously carried out, and the tissue components of a welding interface are researched and analyzed through an environmental scanning electron microscope, wherein the model of the scanning electron microscope is FEI QUANTA 200.

9. The method of claim 7, wherein said step 42 of generating said fracture at the weakest point in the metal structure records information about the entire fracture process, said fracture having a morphology comprising a portion of pits and a portion of slip planes, and a fracture mode exhibiting a combination of ductile and brittle fracture modes. And respectively carrying out single-point EDS analysis on the fracture slip surface area and the fracture dimple to obtain the components and the proportion of the elements.

Technical Field

The invention belongs to the technical field of carrying equipment materials and dissimilar material processing, and particularly relates to a method for simulating a magnetic pulse welding interface and joint characteristic numerical values of an aluminum steel dissimilar metal pipe fitting.

Background

In the field of carrying equipment represented by automobiles, with the development of light weight technology, the adoption of material replacement and mixed use becomes a consensus of the automobile industry, and the realization and application of a mixed structure of dissimilar materials can effectively reduce the energy consumption of the equipment, so that the method is a research hotspot and a common topic of the current industry. However, due to the great difference of physical and chemical properties of heterogeneous materials, the traditional welding method is difficult to realize reliable connection, and intermetallic compounds are easily formed on a welding interface, so that the plasticity and toughness of a joint are reduced, and therefore, the connection technology is an important problem for limiting the development of the structure of the heterogeneous materials. In addition, aluminum steel and its mixed use are widely concerned, but aluminum steel has large characteristic difference, is difficult to be uniformly metallurgically smelted, is easy to form brittle substances, causes low joint plasticity and toughness, is easy to crack, and becomes an important difficult problem for the development of light weight.

At present, a great deal of research is carried out on the connection of dissimilar materials at home and abroad, and technologies such as bolt joint, riveting, friction stir welding, laser-assisted welding, gluing and the like are developed. For the aluminum steel connection problem, when self-piercing riveting and bolts are adopted, the connecting piece is high in cost and low in light weight effect; and friction stir welding is adopted, so that the cost is high, the efficiency is low, and the technical maturity is relatively low.

The magnetic pulse welding is a high-efficiency solid-phase welding technology, the welding principle of the magnetic pulse welding is similar to that of explosive welding, the magnetic pulse adopts electromagnetic force to replace detonation substances, and the magnetic pulse welding is environment-friendly, safe and easy to realize automation. In the magnetic pulse welding process, the metal does not have a melting process, and the generation of metal compounds is avoided or reduced. Compared with a heat input welding process, the magnetic pulse welding process does not generate any emission, and the whole process has no heating, no radiation, no smoke, no waste gas, no spark and no auxiliary material consumption, thereby being a low-carbon environment-friendly manufacturing technology. The magnetic pulse welding technology develops a bimetallic transmission shaft, a filter and the like abroad, forming equipment is mature, and a set of systematic construction method capable of guiding production is lacked.

In summary, with the development of the automobile industry, the dissimilar material connection technology has become a restrictive factor, and challenges such as cost, efficiency, reliability and the like are faced, and development and application of new technology are urgently needed. Therefore, a new aluminum-steel thin-walled tube magnetic pulse welding lightweight technology is researched for the important requirement of an aluminum-steel hybrid lightweight technology in the automobile industry, so that an exemplary sample is provided for automobile lightweight by applying the technology in the automobile industry, and the improvement of product quality and market competitiveness is driven to become a pending problem.

The development of the welding technology needs a large number of process tests as supports, so that better process parameters and analysis data of the characteristics of a processed product are obtained to serve as supports for process improvement, however, at present, the tests are lacked, even if the tests are carried out, a complex process test platform is usually required to be built, the influence of external noise disturbance is large, and the test data are inaccurate.

Disclosure of Invention

The invention provides a numerical simulation method for magnetic pulse welding interface and joint characteristics of an aluminum steel dissimilar metal pipe fitting, which is used for carrying out full parameter process tests under 5 kinds of discharge energy aiming at a movable part and a fixed part, obtaining process parameters from multiple angles to influence the mechanical property of the pulse welding joint, and carrying out performance analysis on the micro appearance and micro hardness of the aluminum steel electromagnetic pulse welding joint so as to obtain more optimal process parameters.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for simulating the characteristics of a magnetic pulse welding interface and a joint of an aluminum-steel dissimilar metal pipe fitting comprises the following steps:

step 1, analyzing the influence rule of the tensile mechanical property of the magnetic pulse welding joint;

step 2, analyzing the failure mode of the magnetic pulse welding joint;

step 3, establishing a weldability window based on welding coefficients;

and 4, carrying out magnetic pulse welding joint microscopic analysis.

Preferably, the step 1 comprises carrying out full parameter welding tests of different welding pitches under the welding discharge energy of 26kJ, 28kJ, 30kJ, 32kJ and 34kJ, wherein the welding pitch ranges from 1.0mm to 1.8mm, the increment distance is 0.2mm, and workpieces after welding are not subjected to any secondary treatment.

Preferably, the step 1 comprises:

step 11, analyzing the influence rule of different welding energy parameters on the welding joint: the effect of welding energy on a welded joint is not a positive correlation, but there is a critical optimum;

step 12, analyzing the influence rule of the welding distance on the strength of the welding joint under different welding energies: the influence of the welding distance on the welding quality is the comprehensive influence of the welding collision speed and the welding collision angle on the welding strength, and the change rule of the welding strength shows that the relation between the welding collision speed and the welding collision angle and the welding strength has the condition of critical optimization, the welding quality deviating from the optimal process parameter is difficult to form effective and firm welding quality under the condition of smaller collision speed and collision angle; excessive collision speed and collision angle can cause instability of a welding interface, generate a micro defect problem and cause strength reduction.

Preferably, the step 2 comprises:

welding failure modes under different welding parameters comprise aluminum alloy base metal fracture failure and welding joint fracture failure; in a first failure mode, the final fracture form is ductile fracture, the aluminum-steel welding joint under the parameters obtains proper collision speed and collision angle, good metallurgical welding effect is obtained, a stable and firm welding joint is formed, the strength of the welding joint under the parameters is higher than that of an aluminum alloy base metal, and the aluminum alloy base metal is taken as a weaker area to be subjected to fracture failure under the action of external loading; for the second failure mode, namely the fracture failure of the welding joint, the final fracture form is brittle fracture, under the welding parameters, namely the collision speed and the collision angle are both large, the quality of the welding joint at the moment is general, the strength of the welding joint is lower than that of the aluminum alloy base metal, and the fracture occurs in the welding joint under the action of external load.

Preferably, the step 3 comprises:

the full parameter test data is used as a basis, welding joint coefficients are introduced, welding energy and welding distance are used as process parameters, and a simplified process window of magnetic pulse welding is established, so that reference is provided for performance evaluation of the strength of the magnetic pulse welding joint.

Preferably, the welding coefficient is a ratio of the strength of the welded joint to the strength of the parent metal, and can be used for evaluating the reliability of the quality of the welding seam. For effective evaluation of the welding quality, the welding coefficient is subjected to 5 levels of reliability division:

very reliable-A grade (the welding strength reaches more than 90% of the base metal strength);

more reliable-class B (more than 80%);

reliable-class C (above 70%);

poor reliability-D level (above 60%);

unreliable-class E (60 or less);

the established welding window grades the welding coefficient by introducing the welding coefficient, and the welding energy and the welding distance are used as indexes, so that the strength grades of the welding joints under different parameters can be intuitively and quickly obtained.

Preferably, the step 4 comprises:

step 41, performing interface microscopic analysis of different failure modes;

and step 42, performing welding fracture analysis.

Preferably, the step 41 includes:

(1) metallographic analysis of a welding interface: determining the three-dimensional space morphology of an alloy structure by measuring and calculating the metallographic microstructure of a two-dimensional metallographic sample ground surface or a film, thereby establishing a quantitative relation among alloy components, structures and performances, and applying an image processing system to metallographic analysis, wherein equipment used for the metallographic analysis is an OLYMPUS BX51 polarizing microscope;

(2) and (5) analyzing a welding interface by an electron microscope. The scanning electron microscope uses secondary electron signal imaging to observe the surface morphology of a sample, namely, the surface of the sample is scanned by using an extremely narrow electron beam region, various effects are generated through the interaction between the electron beam and the surface of the sample, including secondary electron emission of the sample, secondary electrons can generate a feature image amplified on the surface of the sample, the feature image is established according to time sequence when the sample is scanned, namely, an amplified image is obtained by using a point-by-point imaging method, the scanning electron microscope is provided with an X-ray energy spectrometer device, the observation of the microstructure morphology and the analysis of micro-region components are simultaneously carried out, and the tissue components of a welding interface are researched and analyzed through an environmental scanning electron microscope, wherein the model of the scanning electron microscope is FEI QUANTA 200;

preferably, said fracture occurs at the weakest point in the metallic structure in said step 42, and information about the entire fracture process is recorded, said fracture morphology including part of the dimple and part of the slip plane, and its fracture mode exhibits a mixed mode of ductile and brittle fracture. And respectively carrying out single-point EDS analysis on the fracture slip surface area and the fracture dimple to obtain the components and the proportion of the elements.

Compared with the prior art, the invention has the following beneficial effects:

the method is characterized in that a process test and performance evaluation are carried out on an aluminum alloy-high-strength steel welding joint and an interface in a numerical simulation mode, so that a certain reference is provided for application of an aluminum steel magnetic pulse welding structure, a multi-parameter process test, particularly a full-parameter welding test under multiple energy and multiple intervals, is carried out on the aluminum steel welding joint, a quasi-static tensile test is carried out on the welding joint, and the probability of the welding joint with broken parent metal is greatly improved along with the improvement of welding energy, the increase of collision speed and collision angle is found. The relevance of welding failure and welding collision speed and angle is determined by a microscopic analysis means, good welding quality is difficult to form at a low speed and angle, and intermetallic compounds, microcracks and cavities are easy to form on a joint surface at a high speed and angle.

Drawings

Fig. 1 is a flow chart of a method according to a preferred embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, a method for simulating a magnetic pulse welding interface and a joint characteristic value of an aluminum-steel dissimilar metal pipe fitting includes:

s101, analyzing influence rules of the tensile mechanical property of the magnetic pulse welding joint;

s102, analyzing the failure mode of the magnetic pulse welding joint;

s103, establishing a weldability window based on a welding coefficient;

and S104, carrying out magnetic pulse welding joint microscopic analysis.

S101 comprises the step of carrying out full-parameter welding tests of different welding pitches under the welding discharge energy of 26kJ, 28kJ, 30kJ, 32kJ and 34kJ, wherein the welding pitch ranges from 1.0mm to 1.8mm, the incremental distance is 0.2mm, and workpieces after welding are not subjected to any secondary treatment. Wherein the step 1 comprises:

step 11, analyzing the influence rule of different welding energy parameters on the welding joint: the acting force of an aluminum alloy plate of the moving piece 5052 is increased along with the increase of welding energy, the impact acting force on a high-strength steel plate of a base plate HC420LA is also increased, in the change process that the welding energy is changed from small to large, the strength change trend of the welding pieces under different welding intervals is integrally kept consistent, a parabolic rule with a downward opening is presented, the impact speed of the moving piece under the small interval is insufficient, the impact speed forming a good welding effect cannot be achieved, the impact speed is gradually increased along with the increase of the welding intervals, the strength of a welding joint is gradually improved, when the welding intervals are increased to a certain value, such as under the interval of 1.4mm, the welding energy reaches 30kJ, the welding strength reaches a peak value, the welding effect is optimal at the moment, the technological parameters are the optimal parameters at the moment, then the impact speed is higher along with the increase of the welding intervals, the welding joint can generate micro-defect welding under the impact of an over-high speed, so that the welding section is stable, therefore, the strength of the welding joint begins to slide downwards, in the changing process, the welding distance is unchanged, the energy is continuously increased, and in essence, the welding collision speed is continuously increased, but the welding effect is from poor to excellent to poor, so that the influence of the welding energy on the welding joint is not in a positive correlation relationship, but a critical optimal condition exists.

Step 12, analyzing the influence rule of the welding distance on the strength of the welding joint under different welding energies: in the process that the welding distance is increased from small to large, the change rule of the strength of the welding joint under different welding energies also presents a lower parabolic rule, the change of the welding distance from small to large is essentially the comprehensive reflection of the change of the collision angle of the collision speed, because the magnetic pulse welding process is extremely short, the instantaneous collision angle is difficult to measure, so the change of the collision angle is qualitatively inspected by adopting the final deformation form, it can be found that the welding collision angle also increases continuously during the increase of the pitch, so that the effect of the welding pitch on the welding quality is essentially the combined effect of the welding collision speed and the welding collision angle on the welding strength, the change rule of the welding strength shows that the relation between the welding collision speed and the collision angle and the welding strength has the critical optimal condition, welding quality deviating from the optimal process parameter is difficult to form effective and firm welding quality under the condition of smaller collision speed and collision angle; excessive collision speed and collision angle can cause instability of a welding interface, generate a micro defect problem and cause strength reduction.

S102 includes:

and selecting welding pieces with welding intervals of 1.4mm and 1.6mm respectively by taking 30kJ discharge energy as a preferred embodiment, and inspecting welding failure modes under different welding parameters, wherein the fracture mode of the welding joint under the parameter of 30kJ-1.4mm is the fracture failure of the aluminum alloy base metal, and the fracture mode of the welding joint under the parameter of 30kJ-1.6mm is the fracture failure of the welding joint. For the first failure mode, the final fracture form is ductile fracture, and the aluminum-steel welding joint under the parameters obtains proper collision speed and collision angle, obtains good metallurgical welding effect and forms a stable and firm welding joint. The strength of the welding joint under the parameter is higher than that of the aluminum alloy base metal, so that the aluminum alloy base metal is used as a weaker area to be subjected to fracture failure under the action of external loading. For the second failure mode, namely the welded joint is broken and failed, the final fracture mode is brittle fracture, under the welding parameters, namely the collision speed and the collision angle are both large, the quality of the welded joint at the moment is general, the strength of the welded joint is lower than that of an aluminum alloy base metal, and therefore the welded joint is broken under the action of an external load.

S103 includes:

the influence of the process parameters (particularly the welding energy and the welding distance) on the magnetic pulse welding quality is very obvious and the regularity is obvious. In industrial applications, in order to perform scientific and intuitive performance evaluation on a welded joint to obtain an excellent welded joint, it is necessary to associate a process parameter with welding performance. In order to solve the problem in the explosive welding technology which is similar to the magnetic pulse welding mechanism, an explosive welding window concept is provided, the explosive welding window is divided into areas in a two-dimensional or three-dimensional coordinate graph through two or three welding parameter curves, the areas mark whether different metal combinations can be welded or not and whether the welding quality is good or bad, the quality of a welding joint is visually evaluated by establishing the explosive welding window and combining related detection equipment and ignoring the difference of welding materials. For magnetic pulse welding, the welding window has the same important significance. However, the traditional welding window is difficult to build, a large amount of test work needs to be carried out, and the welding window built on the basis of large sample data has high reliability. In order to save resources and simplify the program, the welding joint coefficient is introduced on the basis of full parameter test data, the welding energy and the welding distance are used as process parameters, and a simplified process window of the magnetic pulse welding of the aluminum alloy-HC 420LA steel is established, so that the reference is provided for the performance evaluation of the strength of the magnetic pulse welding joint. The welding coefficient is the ratio of the strength of a welding joint to the strength of a base metal, and can be used for evaluating the reliability of the quality of a welding seam. For effective evaluation of the welding quality, the welding coefficient is subjected to 5 levels of reliability division:

very reliable-A grade (the welding strength reaches more than 90% of the base metal strength);

more reliable-class B (more than 80%);

reliable-class C (above 70%);

poor reliability-D level (above 60%);

unreliable-class E (60 below).

The established welding window grades the welding coefficient by introducing the welding coefficient, and the welding energy and the welding distance are used as indexes, so that the strength grades of the welding joints under different parameters can be intuitively and quickly obtained.

S104 comprises the following steps:

step 41, performing interface microscopic analysis of different failure modes, including:

(1) metallographic analysis of a welding interface: the metallographic analysis is a means of experimental research of metal materials, and the three-dimensional spatial morphology of an alloy structure is determined by measuring and calculating a metallographic microstructure of a two-dimensional metallographic sample ground surface or a film by adopting a quantitative metallographic principle, so that the quantitative relation among the components, the structure and the performance of the alloy is established, an image processing system is applied to the metallographic analysis, and the metallographic analysis method has the advantages of high precision and high speed, and the working efficiency is greatly improved. To investigate the weld failure mode, a metallographic analysis was first performed using an OLYMPUS BX51 polarizing microscope. The effective weld lengths of the welded joints under different parameters are different. For example, the tensile load of a welding interface of 30kJ-1.4mm is 10219N, the fracture failure occurs in a base material, the tensile load of the welding interface of 30kJ-1.6mm is 7856N, the fracture failure occurs in a welding joint, and the welding conditions are good, which is consistent with that obvious waveform combination appears in the welding interface in a metallographic diagram. The difference in weld joint strength between the two parameters can be explained by the resultant wavelength, with a better weld quality joint interface, i.e., 30kJ-1.4mm, having a longer resultant wavelength of about 1000um, and a poorer weld quality joint interface, i.e., 30kJ-1.6mm, having a shorter resultant wavelength of about 500 um. For the wave-free parts on the two sides of the welding area, the wave-free part of the interface with better welding quality is still tightly attached, and the wave-free part of the interface with poorer welding quality is loose.

(2) And (5) analyzing a welding interface by an electron microscope. Scanning Electron Microscopy (SEM) uses secondary electron signal imaging to observe the surface morphology of a sample, i.e., scanning the surface of the sample with a very narrow electron beam field, producing various effects through the interaction of the electron beam with the sample surface, primarily the secondary electron emission of the sample. The secondary electrons can generate an amplified morphology image of the surface of the sample, the morphology image is established according to time sequence when the sample is scanned, namely, the amplified image is obtained by using a point-by-point imaging method, and a scanning electron microscope is provided with an X-ray energy spectrometer (EDS) device and can simultaneously observe the morphology of a microstructure and analyze the composition of a micro-area. And (3) analyzing the tissue components of the welding interface by an environmental scanning electron microscope, wherein the model is FEI QUANTA 200.

Firstly, the microscopic morphology of an aluminum-steel welding interface is observed, and a bonding area mainly comprises a waveform interface and a gray transition area. The appearance of the waveform interface is the result of the interaction between the shock stress wave and the material, reflects the process of forming welding by metal plastic deformation, and has the main explanation theory of a complex plate viscous flow complete mechanism, a flow unstable mechanism, a vortex shedding mechanism and a stress wave mechanism. The waveform interface shape is shear wave, that is, the aluminum base material and the steel base material are combined in a mutually embedded mode, and the deeper the embedding degree is, the better the connection effect is. As the welding pitch increases, the collision velocity increases, the collision angle increases, and the metal plastic deformation becomes more severe, so that the interface waveform size gradually changes from a relatively flat shear wave to a wave having large undulations.

Elemental analysis is carried out on the transition region of the aluminum-steel welding interface through EDS, and it is found that no electron distribution platform is found in the joint transition region with the distance of 1.4mm, which indicates that no second phase with fixed mass ratio of Al atoms to Fe atoms is present, and the transition region only has element diffusion, so that the performance is good. In the transition region of the joint with the distance of 1.6mm, the mass fractions of the two base material elements are approximately distributed in a platform shape in a certain range, which indicates that the elements in the region are diffused and form second phases, and the second phases which are hard and brittle have weakening effect on the welding quality.

For defects in a welding interface, obvious defects do not appear when the welding quality is good, and obvious holes and cracks appear when the welding quality is not good. Therefore, although the collision speed and the collision angle at the interval of 1.6mm are large, the plastic deformation of the metal is obvious, but the excessive collision speed and the excessive collision angle cause the violent deformation of the base metal, so that the welding removal of the microscopic defects occurs, and the reason of the performance difference of the welding joint under the two parameters is explained.

Step 42, performing welding fracture analysis;

the fracture always occurred at the weakest point in the metal structure and information was recorded about the entire fracture process. To further understand the failure mechanism of the welding parts, fracture analysis is carried out on the aluminum side fracture of the welding parts under the parameter of 30kJ-1.6mm, the fracture morphology comprises a part of tough pits and a part of slip planes, and the fracture form of the fracture presents a mode of mixing toughness and brittle fracture. Single-point EDS analysis was performed in the fracture glide region, which contains aluminum and iron in atomic ratios close to 4: 1, where intermetallic compounds of aluminum and iron or other second phase products may form, but since aluminum and iron do not have an atomic ratio of 4: 1, and thus the product is a solid solution of iron in aluminum. The second phase product has the characteristic of hard and brittle, so that failure occurs as a weak area, and the failure mode is represented as brittle fracture; the fracture dimple is subjected to single-point EDS analysis, the point is almost all aluminum element, the formed welding effect is good, the aluminum and the steel are combined tightly, the strength of the combination point is higher than that of the aluminum material, therefore, the combination point does not break under the load, and the fracture mode is the toughness fracture of the aluminum base material. The steel side fracture of the welded part under the parameter of 30kJ-1.6mm can determine that the fracture has a river-like pattern, which is characterized by brittle fracture. The fracture mainly comprises relatively flat depressions and spherical salient points, single-point EDS analysis is carried out on the flat depressions, and the analysis result shows that the main element in the fracture depressions is Fe element, and the weight percentage of the Fe element is 94.41%; the Al element and the Mg element are aluminum alloy elements, the mass percentages of which are only 4.27% and 1.31%, and there is no significant fracture feature, so that there is a high possibility that no welding effect is formed here, and it can be considered as a virtual weld point. Single-point EDS analysis at the salient point finds that the salient point is formed by mixing aluminum and iron elements according to a certain proportion, wherein the mass percent of the Fe element is 32.91%; the mass percent of Al element is 63.93%, Mg is taken as trace element, and the weight percent is 3.15%, which shows that the second phase of the generated aluminum-iron compound is generated, and fracture failure occurs due to the brittleness characteristic of the second phase. For an aluminum steel welding piece under the welding parameter of 30kJ-1.6mm, the collision speed and the collision angle of the aluminum alloy steel plate to the high-strength steel plate piece are overlarge in the welding process, so that the welding area is unstable and uneven. Although the local area forms a good welding effect, the generation of intermetallic compounds or other aluminum-iron second phases and the occurrence of cold joint caused by interface instability exist, and the local defects become weak areas of the welding part under the action of external loading, so that failure occurs.

The method is characterized in that a process test and performance evaluation are carried out on an aluminum alloy-high-strength steel welding joint and an interface in a numerical simulation mode, so that a certain reference is provided for application of an aluminum steel magnetic pulse welding structure, a multi-parameter process test, particularly a full-parameter welding test under multiple energy and multiple intervals, is carried out on the aluminum steel welding joint, a quasi-static tensile test is carried out on the welding joint, and the probability of the welding joint with broken parent metal is greatly improved along with the improvement of welding energy, the increase of collision speed and collision angle is found. The relevance of welding failure and welding collision speed and angle is determined by a microscopic analysis means, good welding quality is difficult to form at a low speed and angle, and intermetallic compounds, microcracks and cavities are easy to form on a joint surface at a high speed and angle.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.