Post‐crosslinking behavior of radiation crosslinked polyamide 66 during vibration welding

Vibration welding of radiation crosslinked polyamide 66 leads to a different relationship between process, structure, and properties. The radiation‐induced altered material properties result in an impeded squeeze flow and higher temperatures in the weld. It is possible to achieve weld strengths up the value of the base material. General theories cannot completely explain the adhesion for these crosslinked polymers. A possible explanation could be an additional temperature‐dependent adhesion mechanism. The high temperatures during vibration welding could affect the degree of crosslinking and lead to a post‐irradiation crosslinking of the polyamide. These additional links across the joining zone may be an additional adhesion mechanism and could explain the high weld strength of crosslinked polymers. The scope of this paper is to investigate the influence on the degree of crosslinking from material and welding parameters and to correlate these results with temperatures and weld strengths generated in a vibration welding process. POLYM. ENG. SCI., 56:735–742, 2016. © 2016 Society of Plastics Engineers     

Process data acquisition in vibration welding of thermoplastics

A measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process—such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane—and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.     

Ultrasonic and impulse welding of polylactic acid films

The weldability of polylactic acid (PLA) is examined in this article. Biaxially oriented PLA films of various thicknesses were joined with impulse and ultrasonic welding techniques. Relatively high weld strengths were achieved with impulse welding over a wide range of welding parameters. Ultrasonic welding produced high weld strengths with relatively short cycle times. In detail, ultrasonic welded samples had a weld factor (weld strength/base material strength) of 1 at cycle times of 0.25 sec. The weld factor was significantly lower at shorter weld times and weld times above 0.35 sec. In contrast, 100‐μm thick samples joined by impulse welding for 2–3 sec had a weld factor of 1 and a standard deviation of only ±5%. The peak temperature during the impulse welding was measured to determine the fusion temperatures of the films. Mechanical, thermal, and optical analysis was used to examine the properties of the PLA at various welding and annealing conditions. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Welding of thermoplastics reinforced with random glass mat

Thermoplastics reinforced with random glass mat have high strength and stiffness; the fibers dominate the mechanical behavior of these composites. The results of this investigation have shown that fibers are ineffective for reinforcing hot-tool and vibration welded butt welds. The maximum weld strengths attained with GMT are comparable to the strengths of good welds of the unfilled material. The optimum hot-tool welding parameters for the reinforced materials are different from those for the unfilled material. Unfilled polypropylene is easier to weld than unfilled polyamide. This characteristic is also true of the reinforced materials. In vibration welding, high welding pressures and high amplitudes result in lower mechanical properties. The optimum penetration depends on the fiber content of the bulk material. This penetration dependence is different from that for unfilled thermoplastic, for which the mechanical properties are independent of the penetration once a steady state has been attained.     

Influence of radiation cross‐linking of polyamide 66 on the characteristics of the vibration welding process

The conventional vibration welding process of polyamide 66 only has a continuous and steady melt flow during the quasi‐steady phase. The process and resulting welds have been thoroughly investigated. Radiation cross‐linking of polyamide 66 with electron beams alters the material's characteristics. Consequently, the resulting energy balance during vibration welding changes and the squeeze flow is impeded. Additionally, this causes the cross‐linking to attain a residual stiffness above the crystallite melting temperature, thereby influencing the characteristics of the vibration welding process. Further, higher weld temperatures and a change in meltdown behavior can be observed. This leads to a varied relationship amongst the process, structure, and properties for vibration welding cross‐linked polyamide. Hence, weld strengths up to the value of the base material strength are possible. The scope of this article is to investigate the influence of radiation cross‐linking on the material characteristics and, by extension, the resulting processing and welding characteristics. Calorimetric, chemical, rheological, mechanical, and optical investigations serve to highlight the influence of radiation cross‐linking on the vibration welding process of polyamide 66. POLYM. ENG. SCI., 55:2493–2499, 2015. © 2015 Society of Plastics Engineers     

Comparative study on the morphology and mechanical strength of induction welding joint of polyetheretherketone under different currents

There is an increasing need for joining technologies of polyetheretherketone (PEEK), in which induction welding technique is one of the most promising methods. The induction welding experiment of PEEK thin plates was conducted under different input currents in this research, while metal meshes were selected as induction components. The analysis of morphology, microstructure, and elemental composition of welding joints was performed by optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Moreover, the mechanical strength of the induction-welding joint was investigated by tensile test. The results indicate that the PEEK can be joined effectively when the metal mesh is selected as an induction component, and the welding joints with good appearance are formed under the appropriate process parameters. The more induced joule heat produced by the higher input current promotes the resin fusion at the interface, which is propitious to reduce the generation of defects. However, the excessive heat input results in the extreme melting and thermal decomposition of PEEK resin, which will deteriorate the morphology and property of the welding joints. When the input current is 5.2A, the induction-welding joint can reach a maximum mechanical strength of 125.63 MPa, which increases by almost 60.55% through the optimization of welding parameters.     

换热器管子和管板焊接接头浅见

通过对管板换热器设计参数、介质特性、使用环境以及承载情况的分析研究,比较不同焊缝接头形式以及焊接工艺过程的选择对最终焊接质量的影响,同时阐述了合理的焊缝检验工艺对于确保在焊接前、焊接过程中以及焊接完成之后保证焊接质量的重要意义,总结出管板换热器管子和管板焊接接头在制造过程中的关键控制点。     

Lap joint formed by friction stir spot welding between SiC and magnesium alloy containing aluminum

A lap joint between plates of SiC and AZX612-magnesium alloy containing aluminum was formed by friction stir spot welding using a drilling machine. The joint interface was analyzed by scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. Aluminum from the AZX612-magnesium alloy segregated along the joint interface suggesting that SiC and AZX612-magnesium alloy could be strongly joined by friction stir spot welding due to the formation of aluminum compounds. SiC and A1050-aluminum alloy plates were joined by friction stir spot welding and a tensile-shear test was performed. At 245 N, the lap joint fractured in the SiC matrix rather than the joint interface. These results confirmed that SiC and A1050-aluminum can be strongly joined due to the formation of aluminum compounds.     

深圳市天然气高压输配系统工程焊接工艺优化的研究

文章主要介绍了对焊接工艺技术优化的研究,根据环境气候、地理区域的不同,在高压输配系统工程中,适当调整管道焊接工艺参数,即提高焊道预热温度、提高焊道过程中的层间温度、改变焊道坡口尺寸,可以提高焊接质量和焊接效率。     

06Cr19Ni1O与Q235B的焊接工艺

承接了某公司PVC装置上的5台气体密封罐制造.其中罐顶材料为06Cr19Ni10,罐体加强箍为Q235B,两者相焊.第一台气体密封罐在焊接时出现了裂纹.后来调整了焊接工艺,顺利完成了其余4台设备的焊接,质量完全符合要求.     

奥氏体不锈钢的全自动气体保护焊焊接工艺试验

为了提高奥氏体不锈钢管焊接自动化程度,提高焊接效率,保证焊接质量,采用全自动气体保护焊接方法进行了焊接试验。通过试验分析、以及对焊缝的电镜检测,确立了一套适用的焊接工艺,实现奥氏体不锈钢管的全自动焊接。     

工业纯钛TA2焊接技术在刮板薄膜蒸发器上的应用

为了探索钛材TA2的焊接工艺技术,根据TA2材料的性能及焊接特点,从坡口的加工与处理、焊接操作方法和焊接保护工装等方面做了大量的试验。通过焊接工艺试验及分析,拟定了合理的焊接工艺参数和施焊过程中解决问题的措施。经过焊接工艺评定,最终确定了最佳的焊接工艺参数。试验和检测结果表明,采用该焊接工艺,焊缝的各项性能指标都符合设计要求,从而保证了产品的焊接质量。     

New results on the spin welding of plastics

Short welding times make spin welding particularly suitable for mass production. This paper presents an analysis of the friction phase, which makes it possible to estimate the influence of the welding parameters and the material being welded on the temperature in the welded zone, the melt rate, and the torque in the spin welding of semicrystalline thermoplastics. A comparison of experimental and calculated results shows an acceptable correlation. In addition, the influence of speed, axial pressure, and braking on the weld seam quality of different amorphous and semicrystalline thermoplastics is discussed.     

Characterization of fusion welded ceramics in the SiC-ZrB2-ZrC system

Various SiC-ZrB₂-ZrC ceramics were joined by fusion welding to determine the maximum silicon carbide content that could be joined. Commercial powders were hot pressed, machined, and preheated to 1450 °C before joining with a tungsten inert gas welding torch at 160–200 A. Resulting welds were cross-sectioned and analyzed to determine which compositions were weldable and to characterize microstructural evolution in welded samples. As compositions approached the ternary eutectic, the welds had smaller SiC grains and exhibited better weldability. Penetration depth of welds was controlled by a combination of current input and welding speed. The ternary eutectic in the system was found at 36.9 ± 1.3 vol% SiC, 42.7 ± 1.5 vol% ZrB₂, and 20.4 ± 1.9 vol% ZrC and its melting temperature was 2330 ± 23 °C. A ternary phase diagram for the SiC-ZrB₂-ZrC was constructed and proposed via microstructural analysis of arc melted pellets on binary joins between each binary eutectic and the ternary eutectic in the system.     

工艺参数对塑料板搅拌摩擦焊的影响

采用搅拌摩擦焊对聚丙烯塑料板材进行焊接试验。结果表明:搅拌头旋转速度、焊接速度及其对塑料板上表面的压力等因素都会影响焊接效果。但是,只要各参数选取恰当,焊接效果就会很好。     

SHS Joining of Aluminum Conductors in the Presence of Copper

Aluminum conductors joining is an important issue in electric transportation industry. In some conditions, electric arc welding or friction stir welding could not be used to join these conductors due to environmental conditions, lack of welding tools, etc. In these cases, SHS method can be used as an appropriate process. In this work, two aluminum conductors (with 9.3-mm diameter and 125-mm length) were joined by SHS method. The conductors were made of commercially pure aluminum (Al > 99%) and, to enhance the joint strength, different weight percentages of copper (0.73–2.4 wt %) were added to green blends. The joints were characterized by hardness testing, electrical resistance, and optical metallography. With increasing Cu percentage, the electrical conductivity of the joint was found to decrease while the strength and hardness, to increase. In the presence of copper, the grain size of the join material was found to decrease.     

Scale-up laws in heated tool butt welding of HDPE and PP

In order to achieve high fatigue strengths in heated-tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated-tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small-pipe to large-pipe welds are then based on the values of these nondimensional numbers.     

聚乙烯管材热熔对接接头抵抗慢速裂纹扩展性能评价

采用应变硬化试验(SH)对不同焊接工艺下的聚乙烯管材热熔对接接头抵抗慢速裂纹扩展（SCG）性能进行评价。通过建立焊接温度梯度（190~250 ℃）、焊接压力梯度（0.6~1.4 MPa）和吸热时间梯度（40~140 s）试验,分析在不同焊接工艺参数条件下,不同聚乙烯管材热熔对接接头耐SCG性能的变化规律,探索冷焊及过焊2种典型缺陷对管材接头耐SCG性能的影响。结果表明,焊接温度、焊接压力和吸热时间都是影响管材热熔对接接头耐SCG性能的重要工艺参数,试验测得PE100, d_n110, SDR11型管材的最佳焊接参数为焊接温度230 ℃,焊接压力1 MPa及吸热时间100 s,当焊接参数选取过高或过低时,会造成管材接头出现过焊或冷焊缺陷,降低管材接头的耐SCG性能。     

Structure and mechanical properties of optimized extrusion welds

A knowledge of how welding parameters affect the mechanical properties of welds is important. However, the mechanical properties of welds cannot be characterized by nondestructive testing methods. Because of its sensitivity to process conditions, extrusion welding of polypropylene-homopolymer (PP-H) was used to investigate the effects of welding parameters on the resulting mechanical properties of welds. Overall optimization of the welding process to obtain stable conditions during welding, which required a redesign of the welding shoe and the welding geometry, resulted in improved weld properties through better build-up of critical weld areas and suppression of void formation. Investigation of material heating characteristics led to a new air nozzle design. The effect of air temperature and welding velocity on the temperature and thickness of the molten layer was determined. The effects of individual process parameters on the structure and mechanical behavior of welds were established, thereby making it possible to specify narrow limits on the values of the weld parameters for producing high-quality welds. The quality of these joints cannot be determined by short-time tests because, even with severe testing conditions, cracks occur in the bulk material. Polarized optical microscopy was used to correlate crack behavior with the build-up of a specific multilayer structure in the weld area. Long-term tests demonstrated that, in both the time-to-crack and crack behavior, the joining area is not the weakest link in an extrusion weld when the welding parameters are chosen correctly.     

CO2气保焊的故障模式与影响分析

焊接是商用空调设备压力容器制造过程中的主要操作工序。CO2气体保护焊主要在蒸发器、冷凝器的装配过程中被使用。在实际生产过程中,焊接造成的故障泄漏严重影响产品质量,需要使用试验设计方法对焊接参数进行优化．但影响焊缝质量的因素众多,在进行参数设计之前,为使因素选择更准确、有效,使用FMEA（failure mode effects analysis）方法对气保焊故障模式进行分析,从中选择出关键因素。