With preheating wire by resistance heat, laser hot wire welding improves process stability and wire deposition efficiency, which gives broad potential applications in sugracing and narrow gap welding. It is a critical...With preheating wire by resistance heat, laser hot wire welding improves process stability and wire deposition efficiency, which gives broad potential applications in sugracing and narrow gap welding. It is a critical issue to control the temperature of preheated wire in this process. The temperature which is so high that the wire fuses outside molten pool or so low that the wire cannot melt timely in the molten pool, results in poor wire transfer stability and bad weld formation. This paper is purposed to calculate the wire temperature for the prediction of wire transfer behavior under various welding parameters. A heat conduction model is set up. Heat sources of the wire include resistance heat and reflected laser, and the heat source of molten pool is laser. The calculated temperature of wire part outside the molten pool is verified by infrared ratio temperature measurement. The calculated temperature of wire part in the molten pool is verified by measurement of the molten pool size. Analyzing the wire temperature and welding process observed by the high speed video imaging, the temperature criteria of wire transfer behaviors are obtained. Thus, numerical simulation of the wire temperature can be used to predict wire transfer behaviors in laser hot wire welding.展开更多
TIG welding-brazing process with high frequency induction hot wire technology was presented to create joints between 5A06 aluminum alloy and SUS32! stainless steel using ER1100 filler wire with different temperature. ...TIG welding-brazing process with high frequency induction hot wire technology was presented to create joints between 5A06 aluminum alloy and SUS32! stainless steel using ER1100 filler wire with different temperature. The joints were evaluated by mechanical test and microstructural analyses. The welding procedure using hot fiUer wire （400 ℃ ） significantly increases strength stability by 71% and average value of tensile strength by 30. 8 % of the joints, compared with cold wire. The research of microstructures in interfaces and welded seams reveals that using 400 ℃ hot filler wire can decrease the thickness of intermetallic compounds （ IMCs ） from 6 to 3.5 txm approximately, which is the main reason of mechanical property improvement.展开更多
GeSi:H films are prepared by hot-wire chemical vapor deposition(CVD)with high hydrogen dilution,DH=98%.Effects of hot wire temperature(Tw)on deposition rate,structural properties and bandgap of GeSi:H films are studie...GeSi:H films are prepared by hot-wire chemical vapor deposition(CVD)with high hydrogen dilution,DH=98%.Effects of hot wire temperature(Tw)on deposition rate,structural properties and bandgap of GeSi:H films are studied with surface profilemeter,Raman spectroscopy,Fourier transformed infrared spectroscopy,and UV-VIS-NIR spectrophotometer.It is found that the deposition rate(Rd)goes up with increasing of Tw,but increasing rate of Rd declines when Tw≥1550℃.High Tw is beneficial to the formation of Ge-Si,but it has little effect on relative contents of the hydrogen bonds(Ge-H,Si-H,etc.)in the films.In the Tw range of 1400-1850℃,the maximum bandgap of the GeSi:H films is 1.39 eV at Tw=1450℃and the band gap decreases with Tw increasing when Tw≥1450℃.展开更多
Laser hot wire cladding,with the prominent features of low heat input,high energy efficiency,and high precision,is widely used for remanufacturing metal parts.The cladding process,however,needs to be improved by using...Laser hot wire cladding,with the prominent features of low heat input,high energy efficiency,and high precision,is widely used for remanufacturing metal parts.The cladding process,however,needs to be improved by using a quantitative method.In this work,volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers.Laser deposition experiments with FV520B,one of martensitic stainless steels,were designed by using the Taguchi method.Four process variables,namely,laser power(P),scanning speed(Vs),wire feed rate(Vf),and wire current(/),were optimized based on the analysis of signal-to-noise(S/N)ratio.Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method.A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks,which resulted in a good metallurgical bonding interface.展开更多
A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferr...A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferred in this Paper is described. By calculation and test, it is indicated that the error resulting from this method is about 0. 5% of the full scale and less than TSl's. By using this method we can set up the calibration curve according to the measurement range and the diameter of the hot wire at a certain accuracy.展开更多
Polycrystalline silicon （poly-Si） films were prepared by hot-wire chemical vapor deposition （HWCVD） at a low substrate temperature of 525 ℃. The influence of hydrogen on the epitaxial growth of ploy-Si films was ...Polycrystalline silicon （poly-Si） films were prepared by hot-wire chemical vapor deposition （HWCVD） at a low substrate temperature of 525 ℃. The influence of hydrogen on the epitaxial growth of ploy-Si films was investigated. Raman spectra show that the poly-Si films are fully crystallized at 525 ℃ with a different hydrogen dilution ratio （50%-91.7%）. X-ray diffraction, grazing incidence X-ray diffraction and SEM images show that the poly-Si thin films present （100） preferred orientation on （100） c-Si substrate in the high hydrogen dilution condition. The P-type poly-Si film prepared with a hydrogen dilution ratio of 91.7% shows a hall mobility of 8.78 cm2/（V-s） with a carrier concentration of 1.3 × 10^20 cm^-3, which indicates that the epitaxial poly-Si film prepared by HWCVD has the possibility to be used in photovoltaic and TFT devices.展开更多
The present work discusses the experimental study on wire-cut electric discharge machining of hot-pressed boron carbide.The effects of machining parameters,such as pulse on time(TON),peak current(IP),flushing pressure...The present work discusses the experimental study on wire-cut electric discharge machining of hot-pressed boron carbide.The effects of machining parameters,such as pulse on time(TON),peak current(IP),flushing pressure(FP) and spark voltage on material removal rate(MRR)and surface roughness(R_a) of the material,have been evaluated.These parameters are found to have an effect on the surface integrity of boron carbide machined samples.Wear rate of brass wire increases with rise in input energy in machining of hot-pressed boron carbide.The surfaces of machined samples were examined using scanning electron microscopy(SEM).The influence of machining parameters on mechanism of MRR and R_a was described.It was demonstrated that higher TON and peak current deteriorate the surface finish of boron carbide samples and result in the formation of large craters,debris and micro cracks.The generation of spherical particles was noticed and it was attributed to surface tension of molten material.Macro-ridges were also observed on the surface due to protrusion of molten material at higher discharge energy levels.展开更多
An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we...An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).展开更多
Microstructure of W-Cu alloy wire before and after hot-swaging was studied in this paper. Results show that a homogeneous microstructure of the W-Cu alloy wire was formed after hot-swaging treatment, and the tungsten ...Microstructure of W-Cu alloy wire before and after hot-swaging was studied in this paper. Results show that a homogeneous microstructure of the W-Cu alloy wire was formed after hot-swaging treatment, and the tungsten particles were embedded in copper phases to form a networking structure;the W-Cu alloy wire has a microstructure of body-centered-cubic tungsten particles and face-centered-cubic copper phase, and did not change after hot-swaging. The intermediate phases have not been found during the process, but the size of the tungsten particles in the copper matrix becomes smaller. After hot-swaging, the treated W-Cu alloy wire has a relative density of 105.1%, and a conductivity of 47.2% IACS, the tensile and bending strength can be as large as 644 and 1600 MPa, respectively.展开更多
基金This work was supported by the National Natural Science Foundation of China （Grant No. 51005125 ） and National Basic Research Program of China （Grant No. 2011CB013404）.
文摘With preheating wire by resistance heat, laser hot wire welding improves process stability and wire deposition efficiency, which gives broad potential applications in sugracing and narrow gap welding. It is a critical issue to control the temperature of preheated wire in this process. The temperature which is so high that the wire fuses outside molten pool or so low that the wire cannot melt timely in the molten pool, results in poor wire transfer stability and bad weld formation. This paper is purposed to calculate the wire temperature for the prediction of wire transfer behavior under various welding parameters. A heat conduction model is set up. Heat sources of the wire include resistance heat and reflected laser, and the heat source of molten pool is laser. The calculated temperature of wire part outside the molten pool is verified by infrared ratio temperature measurement. The calculated temperature of wire part in the molten pool is verified by measurement of the molten pool size. Analyzing the wire temperature and welding process observed by the high speed video imaging, the temperature criteria of wire transfer behaviors are obtained. Thus, numerical simulation of the wire temperature can be used to predict wire transfer behaviors in laser hot wire welding.
基金Acknowledgement The authors would like to appreciate the financial support from the National Natural Science Foundation of China （Grant No. 50874033 ）.
文摘TIG welding-brazing process with high frequency induction hot wire technology was presented to create joints between 5A06 aluminum alloy and SUS32! stainless steel using ER1100 filler wire with different temperature. The joints were evaluated by mechanical test and microstructural analyses. The welding procedure using hot fiUer wire （400 ℃ ） significantly increases strength stability by 71% and average value of tensile strength by 30. 8 % of the joints, compared with cold wire. The research of microstructures in interfaces and welded seams reveals that using 400 ℃ hot filler wire can decrease the thickness of intermetallic compounds （ IMCs ） from 6 to 3.5 txm approximately, which is the main reason of mechanical property improvement.
基金Supported by the National Key Research and Development Program of China(2018YFB1500400-2018YFB1500403)the National Natural Science Foundation of China(61741404,61464007)the Jiangxi Provincial Key Research and Development Foundation(2016BBH80043)
文摘GeSi:H films are prepared by hot-wire chemical vapor deposition(CVD)with high hydrogen dilution,DH=98%.Effects of hot wire temperature(Tw)on deposition rate,structural properties and bandgap of GeSi:H films are studied with surface profilemeter,Raman spectroscopy,Fourier transformed infrared spectroscopy,and UV-VIS-NIR spectrophotometer.It is found that the deposition rate(Rd)goes up with increasing of Tw,but increasing rate of Rd declines when Tw≥1550℃.High Tw is beneficial to the formation of Ge-Si,but it has little effect on relative contents of the hydrogen bonds(Ge-H,Si-H,etc.)in the films.In the Tw range of 1400-1850℃,the maximum bandgap of the GeSi:H films is 1.39 eV at Tw=1450℃and the band gap decreases with Tw increasing when Tw≥1450℃.
基金This work was financially supported by the National Basic Research Program of China(97 Program)(Grant No.2011CB013404).
文摘Laser hot wire cladding,with the prominent features of low heat input,high energy efficiency,and high precision,is widely used for remanufacturing metal parts.The cladding process,however,needs to be improved by using a quantitative method.In this work,volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers.Laser deposition experiments with FV520B,one of martensitic stainless steels,were designed by using the Taguchi method.Four process variables,namely,laser power(P),scanning speed(Vs),wire feed rate(Vf),and wire current(/),were optimized based on the analysis of signal-to-noise(S/N)ratio.Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method.A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks,which resulted in a good metallurgical bonding interface.
文摘A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferred in this Paper is described. By calculation and test, it is indicated that the error resulting from this method is about 0. 5% of the full scale and less than TSl's. By using this method we can set up the calibration curve according to the measurement range and the diameter of the hot wire at a certain accuracy.
基金Project supported by the Beijing City Science and Technology Project(No.D121100001812003)the National Basic Research Program of China(No.2011CBA00705)
文摘Polycrystalline silicon （poly-Si） films were prepared by hot-wire chemical vapor deposition （HWCVD） at a low substrate temperature of 525 ℃. The influence of hydrogen on the epitaxial growth of ploy-Si films was investigated. Raman spectra show that the poly-Si films are fully crystallized at 525 ℃ with a different hydrogen dilution ratio （50%-91.7%）. X-ray diffraction, grazing incidence X-ray diffraction and SEM images show that the poly-Si thin films present （100） preferred orientation on （100） c-Si substrate in the high hydrogen dilution condition. The P-type poly-Si film prepared with a hydrogen dilution ratio of 91.7% shows a hall mobility of 8.78 cm2/（V-s） with a carrier concentration of 1.3 × 10^20 cm^-3, which indicates that the epitaxial poly-Si film prepared by HWCVD has the possibility to be used in photovoltaic and TFT devices.
文摘The present work discusses the experimental study on wire-cut electric discharge machining of hot-pressed boron carbide.The effects of machining parameters,such as pulse on time(TON),peak current(IP),flushing pressure(FP) and spark voltage on material removal rate(MRR)and surface roughness(R_a) of the material,have been evaluated.These parameters are found to have an effect on the surface integrity of boron carbide machined samples.Wear rate of brass wire increases with rise in input energy in machining of hot-pressed boron carbide.The surfaces of machined samples were examined using scanning electron microscopy(SEM).The influence of machining parameters on mechanism of MRR and R_a was described.It was demonstrated that higher TON and peak current deteriorate the surface finish of boron carbide samples and result in the formation of large craters,debris and micro cracks.The generation of spherical particles was noticed and it was attributed to surface tension of molten material.Macro-ridges were also observed on the surface due to protrusion of molten material at higher discharge energy levels.
文摘An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).
文摘Microstructure of W-Cu alloy wire before and after hot-swaging was studied in this paper. Results show that a homogeneous microstructure of the W-Cu alloy wire was formed after hot-swaging treatment, and the tungsten particles were embedded in copper phases to form a networking structure;the W-Cu alloy wire has a microstructure of body-centered-cubic tungsten particles and face-centered-cubic copper phase, and did not change after hot-swaging. The intermediate phases have not been found during the process, but the size of the tungsten particles in the copper matrix becomes smaller. After hot-swaging, the treated W-Cu alloy wire has a relative density of 105.1%, and a conductivity of 47.2% IACS, the tensile and bending strength can be as large as 644 and 1600 MPa, respectively.
文摘双钨极热丝TIG堆焊技术热输入量可控、沉积效率高和稀释率低,在管道内壁堆焊时无刚性固定约束亦能有效保障管道直线度,是一种很有前途的堆焊技术.文中采用双钨极热丝TIG堆焊技术在输油管道高强钢内壁制备两层Inconel 625镍基合金堆焊层,用金相显微镜和扫描电镜对镍/钢堆焊复合板进行微观组织分析,对镍/钢复合板进行硬度测试,并分别在距离镍/钢界面0.5、1.0、1.5 mm处的镍基合金堆焊层取样,进行耐晶间腐蚀性能测试.结果表明:堆焊层的微观结构表现出细胞枝晶结构,沿沉积方向外延生长,枝晶间存在二次相(如Laves相和碳化物);镍/钢堆焊复合板焊态下镍合金堆焊层硬度大于高强钢基板大于钢侧热影响区;试验得出通过钨极热丝TIG堆焊技术得到的堆焊层晶间腐蚀敏感度(degree of sensitization,DOS)值小于1,具有优异的耐晶间腐蚀抗性;随着堆焊层的位置靠近钢侧距离的增加,堆焊层中Fe含量减少,镍基合金堆焊层耐腐蚀性能增加.
