槽形表面镀铬层的等离子弧强化

采用等离子弧工艺,对槽形表面结构进行强化处理,研究工艺参数对镀层结构和性能的影响,并分析了其界面强化机理.结果表明,等离子弧强化热输入量对镀层质量有明显的影响,热输入量过小难以实现镀层与基体的冶金结合,过大则引起"过加热",使镀层附近晶粒长大严重,降低镀层附近硬度及强化质量.采用合理的阴线、阳线、倒转侧面制定合理的强化工艺规范,可取得最佳强化效果.等离子束处理镀层界面成分变化分析结果表明,镀层中的Cr与基体Fe发生相互扩散,界面基体组织发生马氏体相变,使镀层与基体之间形成相变硬化层,达到冶金结合,改善了基体微观组织结构.     

等离子弧表面硬化

经试验研究,通常只用于金属材料切割和焊接的等离子弧已能用作表面硬化处理,试验表明,以氮气作为保护气体的等离子弧表面硬化,在淬火的同时还有渗氮作用,从而使材料表面的硬度和耐磨性大为改善。     

镀铬层等离子束流界面强化工艺

针对高温化学气流冲刷烧蚀的使用状态，提出了等离子束流界面强化解决镀Cr层与基体结合强度不足的技术问题，用非转移等离子束流对镀铬钢件表面进行快速加热进行界面强化处理的工艺方法，介绍了等离子束流界面强化原理，进行了等离子束流强化工艺试验，并对试验结果进行了检测和分析研究，结果表明，镀Cr层与基体产生了冶金结合，较为显著地提高了镀层与基体的结合强度。     

铝合金纳米镀层等离子弧扫描强化研究

利用高速电喷镀技术与等离子弧扫描强化工艺相结合制备出了等离子弧强化纳米复合TiN镀层。研究表明,等离子弧扫描强化后镀层与基体的结合强度提高,镀层的硬度增加,抗腐蚀性能有所改善。     

金属及表面强化层氩弧重熔工艺研究进展

作为一种应用十分广泛的金属材料表面后处理工艺,氩弧重熔技术具有均匀金属材料的表层组织、减缓焊接接头的残余应力、改善金属基体与强化层之间的界面结合状态等优点,在一定程度上可以提高金属及表面强化层的性能.综述了氩弧重熔工艺的原理、特点及工艺参数(重熔电流、移动速度、氩气流量和电弧长度)对重熔效果的影响,着重介绍了氩弧重熔技术在金属表面(铸铁、钢和合金)及其表面强化层(涂层、热浸镀层、渗层和堆焊层)后处理过程中的应用进展.最后探讨了金属及表面强化层氩弧重熔工艺的发展方向:1)强化内在机理研究及界面反应状态研究;2)完善快速凝固理论和界面结构研究;3)提升强化层的结构设计与氩弧重熔工艺条件的契合度;4)加强相关的数值模拟研究.     

谈谈等离子弧电极

等离子弧发生器是等离子弧焊接和切割的主要部件。其中关键的零件是喷嘴和电极,它直接关系到等离子弧的产生、稳定、压缩、刚度、电流密度等工艺性能。可以说,喷嘴和电极是电能转换为热能的“关口”。本文着重谈谈“电极”的材料、性能和发展状况。等离子弧发生器的电极担负着热电子的发射任务,要求电极材料熔点高,电子     

数控等离子弧切割工艺

数控等离子弧切割是一种先进的热切割技术，结合所研制成功的数控火焰／等离子弧切割机分析了等离子弧切割工艺、切割工艺方法、工艺参数的选择及调整、切割后工件质量和常见的切割问题及产生原因。     

铸铁表面等离子弧快速熔凝处理

采用等离子弧对球铁表面进行快速熔凝处理,测定了电流、电极移动速度与熔深和硬度间的关系。     

Al－Si合金氩弧表面强化工艺的研究

研究了Al-Si合金氩弧表面合金化和氩弧堆焊工艺。氩弧表面合金化包括合金焊丝直接熔入法、预涂合金粉末直接熔入法以及合金元素间接熔入法。研究表明：Al-Si合金氩弧表面强化工艺具有表面质量好、合金元素过渡系数高、强化效果明显、强化层深度可在较大范围内控制调节,对设备要求不高等优点。     

Determination of arc pressure and current density on the molten pool surface in plasma arc welding

A unified numerical model is developed to couple the plasma arc, weld pool and keyhole in a self consistent way. The plasma arc/anode interface and the melt/solid interface are treated specially, the VOF method is used to trace the moving keyhole wall, and the fluid flow and heat transfer in both the plasma arc and weld pool are numerically simulated. The distributions of current density and arc pressure on the weld pool surface during the keyhole formation process are analyzed using the coupled model. The predicted arc pressure and current density are compared with the experimentally measured results, and both are in good agreement.     

Pulsed plasma arc cladding

A prototype of Pulsed Plasma Arc Cladding system was developed, in which single power source supplies both transferred plasma arc (TPA) and non-transferred plasma arc (N-TPA). Both plasmas work in turn in a high frequency controlled by an IGBT connecting nozzle and workpiece. The working frequency of lGBT ranges from 50～7000 Hz, in which the plasmas can work in turn smoothly. Higher than 500 Hz of working frequency is suggested for promotion of cladding quality and protection of IGBT. Drag phenomenon of TPA intensifies as the frequency goes up, which tends to increase the current proportion of TPA and suppress N-TPA. The occupation ratio of IGBT can be regulated from 5%～95%, which balances the power supplies of both plasmas. An occupation ratio higher than 50% gives adequate proportion of arc current for N-TPA to preheat powder.     

Experimental study of magnetic arc blow for plasma arc cutting

Oxygen plasma arc cutting (PAC) is widely used in various industrial fields. In the case of cutting magnetized plates, the magnetic field is concentrated around the cutting front according to the progress of the cutting, and the electromagnetic force induced by leakage magnetic field deflects the plasma jet. The deflected plasma jet causes poor cutting quality and sometimes causes fatal damage on the electrode and the nozzle by a double arc as abnormal discharge. This phenomenon is called magnetic arc blow, and it is a critical issue of applying plasma cutting on magnetized plates. The purpose of this study is to investigate the arc blow behaviour and to devise a method to prevent it. We examined the relationship between operating conditions and double arc with external magnetic fields on the plasma jet. We found criteria of operation conditions that induce the arc blow. In addition, we have succeeded in suppressing the double arc generation attributed to the external magnetic field with a mild steel shield cap attachment around the nozzle tip.     

不锈钢活性剂等离子弧焊焊接电弧

针对活性剂等离子弧焊焊接过程,对焊接电弧外形的变化,焊接电弧电压与活性剂之间的关系进行了研究,采用红外热像伪着色法测定了活性剂等离子弧焊焊接电弧温度场,并建立了活性剂等离子弧焊焊接电弧热流密度径向分布模型.研究结果表明,活性剂等离子弧焊焊接电弧收缩,弧尾翼消失,尾焰加大,电弧穿透力增强,电弧电压升高;活性剂等离子弧焊焊接电弧的温度分布比较紧凑,温度场外形窄,温度分布范围较集中,电弧径向温度梯度较大;电弧径向温度分布呈现正态Gauss分布模式;使用活性剂后的焊接接头性能与未使用活性剂焊接接头相当.     

变极性等离子电弧形态对电弧力的影响

研究了变极性等离子弧焊接工艺中,电弧形态及力学行为随焊接过程变化的现象,提出了变极性等离子电弧力学行为随电弧形态的改变而变化的规律。通过高速摄像以及对电弧力和电流的同步检测,证实了联合型等离子弧在反极性时间内易形成双弧的事实。     

Simulation analysis of double arc in plasma arc welding

Aimed at plasma arc welding, a mathematic model was established according to the theory of magnetic fluid dynamics. The model was numerically analyzed by ANSYS software. The temperature, current density and plasma velocity distributions of normal arc had been simulated and compared with those of double arc. The results show that the appearance of double arc has made the temperature of the nozzle rise up to 5 000 K. The appearance of side arc could make the current density of the main arc decrease, and also make the maximal temperature of the arc reduce.     

等离子弧焊中电弧反翘现象的数值模拟

根据流体的质量、动量、能量守恒方程,建立了穿孔等离子弧焊接过程中的等离子电弧三维数学模型,用磁矢量法求解磁场问题.模型包括了一部分喷嘴和钨阴极,小孔也被包含进模型中.利用ANSYS有限元分析软件求解模型,得到等离子电弧的温度分布,以研究等离子弧焊中电弧反翘现象.结果表明,等离子电弧反翘随小孔尺寸的增大而减弱,电弧尾焰随小孔尺寸的增大而增强;而适当的增加焊接速度以使小孔轴线与电弧轴线之间形成一定的偏差是形成等离子电弧反翘现象的必要条件;焊接电流主要是通过改变小孔尺寸而对电弧反翘产生影响.