EFFECT OF OXYGEN CONTENT ON NITROGEN ABSORPTIVE MECHANISM IN WELD FOR FLUX-CORED WIRE

By measuring the content of oxygen and nitrogen in welds of six kinds of self-shielded flux-cored wires,the effect of oxygen on nitrogen content in weld is studied and the different absorptive mechanisms of nitrogen at a low oxygen level([O] lower than 0.02%) and a high oxygen level ([O] higher than 0.03%) have been discovered.The results indicate that the content of nitrogen in weld can be made lowest by modifying the composition of flux and controlling the content of oxygen to the range of 0.02%～0.03%.

CUTTING REGULARITY AND DISCHARGE CHARACTERISTICS BY USING COMPOSITE COOLING LIQUID IN WIRE CUT ELECTRICAL DISCHARGE MACHINE WITH HIGH WIRE TRAVELING SPEED

The analysis of cutting regularity is provided through using and comparing two typical cooling liquids. It is proved that cutting regularity is greatly affected by cooling liquid＇s washing ability. Discharge characteristics and theoretic analysis between two electrodes are also discussed based on discharge waveform. By using composite cooling liquid which has strong washing ability, the efficiency in the first stable cutting phase has reached more than 200 mm^2/min, and the roughness of the surface has reached Ra〈0.8 μm after the fourth cutting with more than 50 mm^2/min average cutting efficiency. It is pointed out that cutting situation of the wire cut electrical discharge machine with high wire traveling speed （HSWEDM） is better than the wire cut electrical discharge machine with low wire traveling speed （LSWEDM） in the condition of improving the cooling liquid washing ability. The machining indices of HSWEDM will be increased remarkably by using the composite cooling liquid.

Effects of process parameters on the depth-to-width ratio of flux-cored wire underwater wet welding

The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.

Microstructures and mechanical properties of a martensitic steel welded with flux-cored wires

This study was focused on wear-resistant material prepared by CO2 GMAW method to basically determine the alloys and hardfacing technology which could be employed into mining equipment. Three flux-cored wires with different chemical compositions, marked by DM-I, DM-II and DM-III were used in welding a martensitic steel for the comparison of the microstructures and mechanical properties of the welding metals and HAZ. The results show that DM-I weld metal contains martensite plus other reinforced phases, while both DM-II and DM-III alloys lead to mainly martensitic microstructures with little precipitates. Among all of the tested materials the DM-I alloy has the highest hardness and wear resistance but the lowest impact toughness among the experimental weld metals. Meanwhile, the hardness, impact toughness and wear resistance of the DM-II and DM-III alloys are close to those of the base metal but the DM-III is not as strong as DM-II. Dimples can be found on the impact fracture of the weld metals, but the steel fracture consists of both cleavage and dimples. Thus HAZ has less risk for cracking than the welds, and the DM-II wire which produces the weld having identical mechanical properties to the base metal is suitable for further application.

Force Modeling for Ultrasonic-assisted Wire Saw Cutting SiC Monocryatal Wafers

The advantages, such as a small cutting force, narrow kerf and little material waste make wire saw cut- ting suitable for machining precious materials like SiC, Si monocrystal and a variety of gem. As regards wire saw cutting fo wafer, however, in traditional wire saw cutting process, the cutting efficiency is low, the wear of wire saw is badly, the surface roughness of wafer is poor etc, which have a seriously impact on the cutting process stability and the use of wafers. Ultrasonic-assisted machining method is very suitable for processing a variety of non-conduc- tive hard and brittle materials, glass, ceramics, quartz, silicon, precious stones and diamonds, etc. In this paper, the force model of ultrusonic-assisted wire saw cutting of SiC monocrystal wafer, based on the kinematic and experi- mental analysis were established. The single factor and orthogonal experimental scheme for different processing pa- rameters such as wire saw speed, part rotation speed of and part feed rate, were carried out in traditional wire saw and ultrasonic-assisted wire saw cutting process. The multiple linear regression method is used to establish the static model among the cutting force, processing parameters and ultrasonic vibration parameters, and the model signifi- cance is verified. The results show, as regards ultrasonic-assisted wire saw cutting of SiC monicrystal wafer, both the tangential and normal cutting forces can reduce about 24. 5%-36% and 36. 6%-40%.

Research on the abrasive wear resistance of YDCrMoV coating produced by CO_2 shielded flux-cored wire surfacing

Caterpillar construction machines play an important part in many fields such as hydraulic and electric engineering, the construction of highway, for its particular of structure. The walking system of caterpillar construction machines is always under the condition of three-body abrasive wear. The abrasive wear of walking system is very severe, which always results in damages of components or structures of walking system of caterpillar construction machines. It is very important to repair the walking system by cladding technique. The abrasive wear properties of four kinds coatings produced by the shielded flux-cored wire surfacing for the repair of the damaged components of walking system of caterpillar construction machines have been studied experimentally on an MLS-23 type wet sand rubber wheel abrasive tester. The surfaces morphologies of the abrasively worn specimens and their microstructures are investigated by transmitting electron microscopy (TEM) after wear testing. Results show that the wear mechanism of cladding metals of the flux-cored wire No.1 and the No.2 is micro-cutting while that of the No.3 and the No.4 is micro-ploughing. The four kinds of flux-cored wire coatings present great potential applications for the repairing of caterpillar construction machines in the Three Gorges Engineering.

Cutting Characteristics of CFRP Boards Using Electroplated Diamond Wire Tools

CFRP （carbon fiber reinforced plastic）, which is composed of carbon fibers in a resin matrix, is an extremely strong and light composite material that has found use in the aerospace and automotive industries. CFRP boards are very difficult to machine using common machining processes. Various machining artifacts, such as burrs and delamination, occur frequently when machining CFRP. Adequate techniques for machining CFRP have not yet been established. Recently, electroplated diamond wire machining technology has found use in cutting hard, brittle materials such as silicon and sapphire. In this study, we used an electroplated diamond wire saw to cut a CFRP workpiece. We quantified the cutting forces imposed on the workpiece and observed the surface state of the workpiece after cutting. We demonstrated that an electroplated diamond wire tool is suitable for the high-quality machining of CFRP boards.

Challenges in Processing Diamond Wire Cut and Black Silicon Wafers in Large-Scale Manufacturing of High Efficiency Solar Cells

Texturing of diamond wire cut wafers using a standard wafer etch process chemistry has always been a challenge in solar cell manufacturing industry. This is due to the change in surface morphology of diamond wire cut wafers and the abundant presence of amorphous silicon content, which are introduced from wafer manufacturing industry during sawing of multi-crystalline wafers using ultra-thin diamond wires. The industry standard texturing process for multi-crystalline wafers cannot deliver a homogeneous etched silicon surface, thereby requiring an additive compound, which acts like a surfactant in the acidic etch bath to enhance the texturing quality on diamond wire cut wafers. Black silicon wafers on the other hand require completely a different process chemistry and are normally textured using a metal catalyst assisted etching technique or by plasma reactive ion etching technique. In this paper, various challenges associated with cell processing steps using diamond wire cut and black silicon wafers along with cell electrical results using each of these wafer types are discussed.

An Analysis of the Formation Mechanisms of Abrasive Particles and Their Effects on Cutting Efficiency

Magnetic induction-free abrasive wire sawing(MIFAWS)is a method that combines magnetic fields with traditional free abrasive wire sawing technologies.Magnetic abrasive particles(MAPs)are attracted on a magnetized wire,thus leading to an increase in their number into the cutting zone.The number of instantaneous-effective abrasive particles(IEAPs)adsorbed on the wire surface has a great influence on the cutting efficiency of the saw wire.In this study,a mathematic model of the movement of the MAP is presented,and the factors influencing the IEAPs number,including slurry-supply speed and slurry dynamic viscosity,are investigated both by means of simulation analysis and experiments.The results indicate that the number of IEAPs decreases with an increase in the slurry supply speed.The cutting efficiency increases gradually with the increase of slurry supply speed,but the growth rate of wire saw cutting efficiency slows down when the slurry supply speed exceeds a given threshold.The number of IEAPs adsorbed by saw wire increases with a decrease in the dynamic viscosity of the cutting fluid,while the cutting efficiency first increases and then decreases.The cutting efficiency attains its highest value when the dynamic viscosity of the cutting fluid is 0.0047 Pa⋅s.The experimental results agree with the simulation results,and provide some guidance for the practical application of the MIFAWS process.

DK7725E CNC Wire Cut EDM

The machine,a silver medal winnerfrom the state,is produced by theChangfeng Machinery General Factory.The products have been sold in the UK,Poland,Australia,Thailand,Singapore,

Surface Damage in Wire cut Silicon Wafers

The surface damage and the damage depth in wire-cut silicon wafers and inner-diameter (ID) cut silicon wafers were studied by means of thickness meter, scanning electron microscopy (SEM) and double crystal X-ray diffractometer. The results show that the surface of wire-cut silicon wafers is rougher than that of ID-cut silicon wafers and the surface damage in wire-cut silicon wafers is more serious than that in ID-cut silicon wafers, while the damage depth in wire-cut silicon wafers is smaller than that in ID-cut silicon wafers. The possible reasons for the generation of surface damage in wire-cut silicon wafers were also discussed.

Effect of Ti-Si-Mg-Al wire on microstructure and mechanical properties of plasma arc in-situ welded joint of SiC_p/Al composites

The influence of Ti-Si-Mg-AI wire on microstructure and mechanical properties of SiCp/A1 metal matrix composite joints produced by plasma arc in-situ weld-alloying was investigated. Argon-nitrogen mixture was used as plasma gas and Ti-Si-Mg-A1 flux-cored wires as filled composites. Weldments were submitted to tensile test. Meanwhile, the macro morphology and microstructure of the joints were examined. The result shows that the formation ofneedie-like harmful phase A14C3 is effectively inhibited and the wettability of molten pool is improved by adding Ti-Si-Mg-A1 flux-cored wires. With 15Ti-5Si-5Mg-A1 flux-cored wire as filled composite, the maximum tensile strength of the welded joint is 267 MPa, which is up to 83% that of the matrix composites under annealed condition.

Investigation of the impact toughness of self- shielded flux- cored wire girth welds for X80 pipelines

Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate, especially for remote construction sites in rugged terrain. From the perspective of pipeline safety, the impact toughness of the girth welds is an important factor in pipeline integrity ,which determines the crack arrest behavior in the girth welds. Therefore, improving the girth weld impact toughness is of primary importance in the field of pipeline girth welding. Three self-shielded flux-cored wires comprising different chemical composition systems have been applied to large diameter X80 UOE （U-ing-O- ing-Expanding） pipeline semi-automatic girth welding,and the impact toughness of the welds has been evaluated by girth weld chemical composition analysis and microstructural analysis using scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS） to investigate pipeline girth weld impact toughness and find ways to improve it. This helps in determining the main factors that influence girth weld impact toughness. Pipeline girth weld impact toughness is mainly determined by the final microstructure produced in the solid-state phase transition. In the as-weld state,acicular ferrite （AF） and fine bainite （FB） are a benefit to the impact toughness. For multilayer semiautomatic self-shielded flux-cored wire welding, the normalizing and tempering function of the latter beads to the initial beads plays an important role in the transition of girth weld microstructure, which affects the impact toughness. The original AF and FB and the corresponding heat treatment microstructure of the fine and uniform block ferrite and pearlite result in very good impact toughness. The following two mechanisms are found to promote the production of AF and FB in the girth weld. First, elements promoting the broadening of the austenitic region, such as Ni, C, Cu, and Mn, induce low temperature phase transitions and restrain the opposing function of Al, which is a benefit to the production of AF and FB. Second, dispersed high-melting-point inclusions, especially Al2O3 ,induce the nucleated production of AF. The advantageous function of inclusions is determined by their shape, distribution, and dimension. Dispersed spherical inclusions of small dimension are a benefit to the production of AF, and result in good impact toughness.

Over Voltage Fault due to Disconnection of Consumer’s Transformer Neutral Wire

Practically,the load currents in three phases are asymmetric in the power system.It means that the impedances are different in all three phases.If the consumer’s transformer neutral cut off and/or was disconnected from the neutral of power supply source,then there will be some trouble and failure occurred.The current in the neutral wire drops down to zero when the neutral wire is cut off and the phase currents of all three-phase equal to each other since there was no return wire.The currents are equal but the voltages at the phase consumers are different.Especially for residential single-phase consumers,the voltage at the consumers of the phase varies differently for three phase systems when the neutral wire was disconnected at consumer side and even the voltage at the consumers one or two of those three phases becomes over nominal voltage or reaches nearly line voltage.In this case,the electronic appliances in that phase will be fed by high voltage than the rated value and they can be broken down.In the power system of UB(Ulaanbaatar)city,there are some occasional such kind of failures every year.Obviously,many electronic appliances were broken down due to high voltage and the electricity utility companies respond for service charge of damaged parts.

RULED SURFACE MACHINING BY 4-AXES SIMULTANEOUS CONTROL WIRE-EDM

On the tasis of study in the mathematical model of 3-dimensional ruled surface (RS),this paper introduces a new concept of distance paramcter (DP) and also puts forward that themethod of modeling a RS depends on not only two boundary curves but also DP. According toabove theory, the formulas to calculate corresponding point coordinates to any kind of top and bot-tom profile of a workpiece and formulas to calcuate the maximum inclination angle of ruling linehave been obtained. Then a different top and bottom RS mathining method including profile withline-are combination as well as parametric curves has been achieved by 4-axes simultancous con-trol programming proposed.

T/CMTBA 1010—2021《数控往复走丝电火花线切割机床性能评价规范》团体标准解读

介绍了《数控往复走丝电火花线切割机床性能评价规范》团体标准的制定背景、目的和主要内容,并在检验项目、关键指标等方面与现行行业标准进行了比对,解读了该团体标准的先进性、科学性和实用性。

慢走丝线切割成本估算研究

慢走丝线切割中,零件表面质量要求越高,相应加工时间也就越长,加工时间的长短直接影响加工成本。通过引入粗糙度系数的概念,将加工总时间折算为与切割加工相关的时间,建立了慢走丝线切割成本估算模型,并采用切割实验验证了粗糙度对加工时间仅有较小的影响,合理降低了粗糙度系数取值。最后运用构建的成本模型计算某工件的加工成本,验证了该模型的合理性。

高速线切割机床上丝辅助装置设计

现有高速线切割机床的上丝装置在上丝过程中易发生断丝与张紧力不均衡现象,降低了机床切削稳定性和工件加工质量。通过分析现有装置的结构,提出增加推力球轴承,以防止锁紧螺母跟转而导致储丝盘卡顿引起断丝;根据丝线的拉力计算出弹簧压缩量及其他相关参数。经I-DEAS软件建模、装配、仿真表明,该装置可以满足生产要求。

基于响应面与狼群算法的电火花线切割加工性能与放电能耗建模及优化

结合电火花线切割加工绿色、精密、高效的发展趋势,提出面向加工性能与放电能耗的电火花线切割加工工艺建模与多目标优化方法。针对电火花线切割加工GH4169高温合金材料开展正交试验设计,以脉冲宽度、放电间隙、管数、加工限速为输入,以放电能耗EEV、表面粗糙度Ra和材料去除率MRR为输出,构建了电火花线切割加工性能与放电能耗多目标优化响应面模型,并采用改进的狼群算法对模型进行优化求解。优化结果与实验结果对比表明,Ra、EEV和MRR的平均误差均不高于10%,且随机优化实验结果优于75%以上的正交试验设计的实验结果,验证了优化模型及求解方法的有效性。

分层供液电火花线切割加工研究

分别采用常规供液和分层供液对缸筒类零件进行电火花线切割加工对比试验。结果表明,分层供液可在火花放电全过程实现电极丝顺向运丝加工,解决了常规供液方式下电极丝逆向运丝导致的缸筒类零件内部供液不足的问题;提高了极间工作液流速与流量,增强了排屑能力,扩大了放电间隙,改善了极间放电条件,从而提高了火花放电效率和稳定性,对工件切割速度的提高和表面加工质量的改善有重要意义。