爆炸焊接真“疯狂”——钛钢复合板爆炸焊接后周边及端部撕裂的原因分析

边界效应是爆炸焊接过程中普遍存在的问题,特别是对厚覆层钛/钢复合板爆炸后存在起爆点对边被撕裂、掉角等问题,严重影响成品尺寸,降低产品成品率。文章通过对钛/钢复合板焊接后起爆点对边撕裂和掉角的原因分析,找出应力波是造成钛/钢复合板起爆点对边开裂、掉角的主要原因。可以通过精确计算炸药用量、不等厚度布药、选择小的间隙值控制爆轰载荷,减小应力波所造成的宏观开裂趋势。     

大面积、薄覆层钛/钢复合板爆炸-轧制工艺研究

探索了大面积、薄覆层钛／钢复合板生产工艺。分析了不同的轧制温度下爆炸一轧制钛／钢复合板的性能和组织。结果表明，配制低爆速混合炸药，在覆层与基层之间增加一层纯铁过渡层，采用合适的爆炸复合工艺制得轧板复合板坯，再在适当的热轧温度下轧制，可获面积超过35m^2、覆层厚度≤2．0mm的钛／钢双金属复合板且各项性能指标符合国家标准要求；此项研究填补了国内空白，满足了市场需求。     

采用自约束结构炸药的铜/钢爆炸焊接

为了提高爆炸能量的利用率,减少焊接药量,提出采用自约束结构炸药进行爆炸焊接。采用T2铜板和Q345钢板分别作为复板和基板,通过理论计算得到T2/Q345爆炸焊接窗口。采用双层蜂窝结构炸药作为自约束结构焊接炸药,对T2铜与Q345钢的爆炸焊接进行了试验研究。通过力学性能测试和显微组织观察,研究了T2/Q345复合板的结合性能。结果表明：与爆速为2505和3512 m·s^-1的单层炸药相比,T2/Q345复合板爆炸焊接采用的双层蜂窝结构炸药量分别减少了54.4%和31.4%;随着传播距离的增加,复合板的结合界面由直线结合向波状结合转变。复合板的抗拉剪切强度为237.0 MPa,满足T2/Q345复合板的结合强度要求。爆炸产生的硬化发生在结合界面附近,采用双层蜂窝结构炸药爆炸焊接得到的T2/Q345复合板具有良好的结合性能。     

钛箔/钢爆炸焊接的界面结合性能

为减小钛/钢爆炸焊接钛层的使用量,以低爆速乳化炸药作为焊接炸药,食盐作为传压层,成功实现厚度200 μm TA1钛箔与Q235钢的爆炸焊接.通过金相显微镜、扫描电镜和能谱仪对界面微观形貌进行分析,利用万能试验机对复合板试件进行拉伸、弯曲试验检测其结合性能. 结果表明,钛箔/钢界面呈规则的波形,主要以熔化层结合,具有良好的结合质量.靠近界面金属产生强烈的塑性变形,钢侧晶粒呈流线状.波后的旋涡内包含熔化块,未观测到孔洞、裂隙等缺陷.根据Ti和Fe元素原子比例,熔化块成分主要为FeTi,Fe₂Ti等金属间化合物.三点弯曲和拉伸试件的界面均未出现分离,复合板材界面具有良好的塑性变形能力和结合性能.拉伸试件断口两侧的钛层与钢层存在大小不一的韧窝,主要呈塑性断裂.     

大规格钛-钢复合板的制备及性能

采用爆炸焊接技术制备尺寸为4260 mm×4260 mm×(6.5+32) mm的钛-钢复合板。采用超声波无损检测、相控阵波形显微镜、金相显微镜和扫描电子显微镜对复合材料板材的力学性能和界面形态进行分析。结果表明，当爆速、密度、炸药高度和间隔距离分别为2200~2270 m/s、0.80~0.82 g/cm³、45.0~46.0 mm和8.0~11.0 mm时，制备出的板材各项力学性能满足技术指标ASTM B898-2020。界面的波形为典型波纹状结合，界面清晰均匀，波形在漩涡区存在少量熔化，波幅和波长的比值为0.15~0.25，且在比值为0.2左右时，产品的剪切强度最高。本研究为大规格钛-钢复合板的制备提供工艺方法，并发现大规格钛-钢复合板的界面特点，为后续优化复合板爆炸焊接工艺提供理论指导。     

炸药爆炸速度对铝/钛爆炸焊接复合管结合界面及性能的影响

通过在粉状乳化炸药中添加不同比例密度调节剂,配制了自然堆积状态下爆炸速度范围为1450~2550m/s的低爆炸速度炸药;采用该爆炸速度炸药进行了铝/钛复合管爆炸焊接试验,结合最小碰撞速度理论,对试验结果及其界面微观结构和结合强度测试进行了分析.结果表明,该复合管爆炸焊接的合适爆炸速度约为1950~2150m/s,其结合质量能够满足后续加工要求;爆炸速度对复合管的界面结合波形影响很大,且复合管前端波幅较小,沿着爆轰传播方向逐渐增大,至末端时又变小,波形且呈现不太规则的扁平波状结合现象,分析认为主要是因为在复合管的爆炸焊接环境和爆炸产物飞散条件与复合板不同所致.     

钛/铝复合板爆炸焊接技术研究进展

通过爆炸焊接技术制备的钛/铝复合板可兼具钛合金耐腐蚀性和铝合金低成本的优点。对钛/铝复合板爆炸焊接技术的研究进展进行介绍,论述了炸药种类、质量比R、基覆板间距及爆炸焊接窗口等主要工艺参数对钛/铝复合板组织和性能的影响;分析了影响钛/铝复合板结合界面的主要因素——金属间化合物种类、扩散层和界面波形;对钛/铝复合板硬度、抗剪切强度、抗拉强度及拉伸断口的研究进行了汇总分析。最后,指出了钛/铝复合板爆炸焊接工艺研究的重点发展方向。     

R60702/TAI/16MnⅢ复合板爆炸焊接数值模拟与试验

随着爆炸焊接技术的发展,锆-钢复合板作为一种特殊的耐蚀复合材料,结合了锆优良的耐蚀性能和钢的高强度的优点,在工业中的需求量也逐步增加.以爆炸焊接理论为基础,采用数值模拟和试验分析相结合的方法,在ANSYS/LS-DYNA软件中模拟R60702/TAI/16MnⅢ复合板不同间隙值组合下爆炸焊接的动态过程.分析间隙值对整个R60702/TAI/16MnⅢ复合板爆炸焊接成形的影响.结果表明,当锆-钛间距/钛-钢间距取值为12/6 mm时,可以实现良好焊接.对试验焊接后R60702/TAI/16MnⅢ复合板上不同位置处的试样进行扫描电镜分析,观察复合板界面的结合状况,为选择更合适的工艺条件提供数据支撑,有利于指导生产实践.     

R60702/TAI/16MnIII复合板爆炸焊接数值模拟与试验

随着爆炸焊接技术的发展,锆−钢复合板作为一种特殊的耐蚀复合材料,结合了锆优良的耐蚀性能和钢的高强度的优点,在工业中的需求量也逐步增加. 以爆炸焊接理论为基础,采用数值模拟和试验分析相结合的方法,在ANSYS/LS-DYNA软件中模拟R60702/TAI/16MnIII复合板不同间隙值组合下爆炸焊接的动态过程. 分析间隙值对整个R60702/TAI/16MnIII复合板爆炸焊接成形的影响. 结果表明,当锆−钛间距/钛−钢间距取值为12/6 mm时,可以实现良好焊接. 对试验焊接后R60702/TAI/16MnIII复合板上不同位置处的试样进行扫描电镜分析,观察复合板界面的结合状况,为选择更合适的工艺条件提供数据支撑,有利于指导生产实践.     

基于自约束结构炸药的T2/Q345爆炸焊接及数值模拟

为提高炸药能量利用效率、降低能量耗散,利用自约束结构炸药进行爆炸焊接研究.以T2铜和Q345钢分别作为复层与基层,自约束结构炸药作为焊接炸药,借助ANSYS/AUTODYN软件模拟爆炸焊接过程,并进行T2/Q345爆炸焊接试验,对复合板试件进行拉剪性能检测和微观形貌观察分析其焊接质量.结果表明,T2/Q345爆炸焊接的碰撞速度距起爆端100 mm后均大于临界碰撞速度345 m/s,距起爆端150 mm处碰撞速度达到最大值567 m/s.T2/Q345复合板起爆端呈直线结合,并随着传爆距离增加变为波形结合.T2/Q345复合板远离起爆端的平均剪切强度为237.0 MPa,断裂位置位于铜一侧.试件被拉剪破坏后的铜层出现加工硬化现象,远离结合界面的显微硬度和塑性变形程度呈增强趋势.自约束结构炸药可降低自身爆炸产物飞散,使炸药能量更多地转化为复层动能,提高能量利用率.     

Tube expansion by gas detonation

The expansion of tubes by direct application of gas detonation waves is an alternative forming method for hollow section workpieces. In particular the process can be used for typical hydroforming parts, for example car body or exhaust elements in automotive industry. The gas charge of oxygen and hydrogen is both pressure medium and energy source and has the potential to cause high forming velocities. The introduced process belongs to the category of high speed forming methods and provides typical advantages such as higher achievable strains compared to quasi-static methods using high water pressure. Another advantage of this process is the avoidance of high press forces by application of an “inertia-locked tool” system due to the extremely short process time. To develop a controllable process, good knowledge of the interdependencies in the system “medium, workpiece and tool” is essential. This can be achieved using simulations in combination with experimental investigations. The results are topic of this paper, also including special investigations on the material behavior at high strain rates and temperature gradients. This paper is based on investigations within the scope of a research project in the Priority Program SPP 1180, which is kindly supported by the German Research Foundation (DFG). The investigations were carried out by cooperation of: University of Dortmund, Institute of Forming Technology and Light-weight Construction; RWTH Aachen University, Shock Wave Laboratory; University of Hanover, Institute of Materials Science.     

Gas-particle interaction in detonation spraying systems

A model is developed to describe dynamic interaction of particles with the carrier gas during detonation spraying. Equations of mass, energy, and momentum conservation are integrated numerically for the two-phase particle-gas flow with the Hugoniot boundary conditions at the detonation wave front. Velocity and temperature of the sprayed powder and the gas parameters are calculated self-consistently, taking into account effects of friction and cooling of the gas in the vicinity of the gun barrel and effects of particle-gas interaction on the parameters of the gas phase. Calculations are performed for tungsten carbide particles of 30 μm diam and a 1.8 m long detonation gun using a stoichiometric mixture of oxygen and propane. Distributions of gas and particle parameters along the barrel are calculated for various moments of time. Tungsten carbide particles of 30 μm reach an exit velocity of 1278 m/s and a temperature of 1950 K. Exit particle velocity is a nonmonotonic function of the loading distance,L, with a distinct maximum atL = 75 cm. The proposed model can be applied to a broad range of problems related to detonation coating technology and allows evaluation of the effectiveness of various designs and optimization of operational parameters of detonation spraying systems.     

Dynamic hardness of detonation sprayed WC-Co coatings

The objective of the present work was to determine the dynamic hardness of WC-Co coatings from the dynamic hardness of the coating substrate system. It was also the purpose of this work to evaluate the influence of coating composition, coating thickness, and substrate materials on the dynamic hardness of the coating. To achieve the above-mentioned objectives, WC-12%Co and WC-17%Co coatings were deposited by detonation spraying on three different substrate materials: mild steel, commercially pure (CP) aluminum, and CP titanium. The dynamic hardness of the coating/substrate composite was evaluated by a drop weight system. The dynamic hardness of the coating independent of the substrate was determined from the dynamic hardness of the coating/substrate composite.     

Gas dynamical parameters of detonation powder spraying

An investigation is conducted of the gas dynamics of a gas detonation coating process and the mechanism of particle acceleration by the shock wave inside the coating apparatus. Velocities of gas detonation in different gas mixtures are analyzed by applying the conventional hydrodynamic theory of detonation, and the effect of addition gases on the velocity of detonation in oxygen/hydrogen and oxygen/acetylene mixtures is studied. The authors propose a model that allows calculation of particle acceleration and final velocity. This model utilizes the Chapman-Jouquet picture of detonation and assumptions about the linear distribution of the velocity of detonation products behind the front of the detonation wave. The kinetics of particle acceleration by a detonation wave exhibits several novel features and is distinctly different from particle acceleration in other methods of spraying, such as plasma and high-velocity oxyfuel. There is a nonmonotonic dependence of particle velocity upon its coordinate and change in the direction of particle acceleration. Loading distance and total barrel length are important parameters that affect final particle velocity. Results indicate that final particle velocity and, as a consequence, the quality of detonation coatings can be significantly affected by changing the gas mixture composition and the powder loading distance while keeping the remaining operational parameters constant.     

爆轰烧结氧化铝黏结型纳米聚晶金刚石微粉

爆轰烧结氧化铝黏结型纳米聚晶金刚石微粉,并用热重分析仪、扫描电子显微镜、透射电子显微镜、X射线衍射仪分析其热稳定性、形貌、晶体结构等。发现:聚晶粉体在空气中热稳定性良好,没有明显金刚石氧化现象;且粉体分散性较好,分散粒度在0.5～0.7 μm之间。聚晶金刚石粉体由粒径100～200 nm的大颗粒聚集而成,而大颗粒是由2～10 nm纳米金刚石颗粒经氧化铝紧密黏结而形成的聚集体。      

Gas detonation forming process and modeling for efficient spring-back prediction

Aluminum cylindrical cups are formed with gas detonation forming technology and finite element modeling of aluminum cylindrical cup production with the detonation forming technology is performed. The forming process simulation is carried out in two-step analysis. 2D and 3D computational models are constructed with both explicit and implicit dynamic analyses are performed. The effects of detonation pressure and die design parameters also are investigated. The thickness distribution and deformed geometry of the cups are compared with the experimentally determined values. The spring-back predictions based on the explicit and implicit methods are criticized in terms of deformed shape accuracy and elapsed time.     

Synthesis and properties of inorganic composite coatings containing detonation nanodiamonds

Electrodeposition from solutions based on Cr(III) compounds of composite chromium coatings with denotation nanodiamond (DND) particles and composite coatings (CCs) of silicon dioxide-DND obtained using the sol-gel method is studied. Physicomechanical properties and composition of these composite coatings (CCs) are investigated. It is found that the presence of DND particles produces a significant effect on chromium coatings and causes a 1.4-fold increase in their microhardness. Herewith, brittleness of coatings decreases. DND content in CCs reaches final values (12–14 vol % or 6.4–7.2 wt %) at an increase in the DND concentration in the solution to 30 g/L. The performed studies allow establishing the optimum DND concentration in chromium-plating solutions (17 g/L) and in CCs (10.5 vol % or 5.6 wt %) that provides the maximum microhardness and minimum brittleness of chromium-DND coatings. Application of thin films from SiO₂ sols modified by DND particles is studied. Dependences of microhardness and optical transmission of samples with coatings on the sol composition are established. The optical concentration of DND corresponding to the maximum coating microhardness is 0.5 wt %. An increase in DND content in the solution above 0.5 wt % causes a drastic decrease in the microhardness and optical transmission of samples with coatings and an increase in microbrittleness.     

爆炸喷涂Al-Cu-Cr准晶涂层的组织及硬度研究

为了研究热喷涂工艺对爆炸喷涂Al-Cu-Cr准晶涂层组织和硬度的影响规律，采用三种爆炸喷涂工艺参数在Q235A低碳钢基体上制备涂层，借助XRD、SEM和OM等技术手段对粉末和涂层的组织结构进行分析，并检测涂层横截面的孔隙率和显微硬度。结果表明，用于喷涂的A165Cu20Cr15准晶粉末中含有二十面体准晶相i-A165Cu24Cr11和极少量具有单斜结构的晶体相θ-Al13Cr2（即Al83Cu4Cr13）；而爆炸喷涂涂层中除i和θ两相外，生成了新相——体心立方结构的α-Al69Cu18Cr13（准晶i的晶体类似相）和Al2O3相。涂层呈典型层状结构，其它条件不变的情况下，涂层中各晶体相与准晶相i最强峰衍射强度的比值α／i、θ/i和Al2O3／i随爆炸喷涂工作气体流速的成比例提高而增加，同时涂层截面的孔隙率下降而显微硬度HV0.1升高。     

爆炸喷涂Al-Cu-Cr准晶涂层的组织及硬度研究

为了研究热喷涂工艺对爆炸喷涂Al-Cu-Cr准晶涂层组织和硬度的影响规律,采用三种爆炸喷涂工艺参数在Q235A低碳钢基体上制备涂层,借助XRD、SEM和OM等技术手段对粉末和涂层的组织结构进行分析,并检测涂层横截面的孔隙率和显微硬度.结果表明,用于喷涂的Al65Cu20Cr15准晶粉末中含有二十面体准晶相i-Al65Cu24Cr11和极少量具有单斜结构的晶体相θ-Al13Cr2(即Al83Cu4Cr13);而爆炸喷涂涂层中除i和θ两相外,生成了新相--体心立方结构的α-Al69Cu18Cr13(准晶i的晶体类似相)和Al203相.涂层呈典型层状结构,其它条件不变的情况下,涂层中各晶体相与准晶相i最强峰衍射强度的比值α/i、θ/i和Al2O3/i随爆炸喷涂工作气体流速的成比例提高而增加,同时涂层截面的孔隙率下降而显微硬度HV0.1升高.     

Physicochemical model of detonation synthesis of nanoparticles from metal carboxylates

We have shown previously that when metal carboxylates are subjected to a shock-wave action, diamond nanoparticles and nanoparticles of metals (Ag, Bi, Co, Fe, Pb) are formed and their characteristic size is about 30–200 Å. The metal nanoparticles formed are covered by an amorphous-carbon layer up to 20 Å thick. In this work we put forward a physicochemical model of the formation of diamond and metal nanoparticles from metal carboxylates upon shock-wave action. The energy released upon detonation inside the precursor is lower than in regions not occupied by the stearates. The characteristic time of temperature equalization has been estimated to be on the order of ～10^?3 s, which is greater by a factor of ～10³ than the characteristic reaction time. Due to the adiabatic nature of the processes occurring, the typical temperature of a “particle” will be lower than the temperature of the surrounding medium. In the framework of the model suggested, it has been assumed that the growth of metal clusters should occur by the diffusion mechanism; i.e., the “building material” is supplied through diffusion. The calculation using our previous experimental data on the reaction time and average size of metal particles has shown that the diffusion properties of the medium in which the metal nanoparticles are formed are close to those of the liquid state of the substance. The temperature and pressure under detonation conditions markedly exceed the analogous parameters characteristic of experiments on the thermodestruction of metal carboxylates. The small time of existence of the reaction mixture is compensated by the high mobility and concentration of reagents.