CHINA WELDING Vo1.11,No.2,November,2002

Contents

1. The integrated intelligent system for welding seam error and penetration depth identification
Zhang Hua , Hu Jing , Peng Shao-bin and Zou Chun-hua 
Abstract: A integrated intelligent system for seam tracking and penetration control is given. The system received information of welding seam error and penetration depth from only one sensor, then, it realized seam tracking and penetration control simultaneously. This paper introduces constitution of the system, methods of information recognition, design of the neural-fuzzy controller and results practically.
Key Words: seam tracking, penetration depth identification, neural network, fuzzy control.

2. Mathematical model and magnetic-control
mechanism of the stability of rotating spray transfer* Yin shuyan ，Chen shujun , Wang jun，and Xu luning
Abstract: To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding-gas and extending the welding current range of traditional MAG welding process. In this paper, the magnetic-control mechanism 
of the rotating spray transfer is stated and mathematical model is given. Theoretic basis is established, 
which implements high deposition rate MAG welding process with magnetic-control instead of helium in 
shielding-gas.
Key Words: magnetic-control, rotating spray transfer, high deposition rates MAG welding process, 
mathematical model

3. Developing of robot flexible processing system for shipbuilding profile steel 
Yao Shun Qiu Tao Lou Songnian Wang Hongjie
Abstract:A robot flexible processing system of shipbuilding profile steel was developed. The system consists of computer integrated control and robot. An off-line programming robot was used for marking and 
cutting of shipbuilding profile steel. In the system the deformation and position error of profile steel can be detected by precise sensors, and figure position coordinate error resulted from profile steel deformation can be compensated by modifying traveling track of robotic arm online. The practical operation results show that the system performance can meet the needs of profile steel processing.
Key word:robot, off-line programming control, profile steel processing, error compensating

4. Novel approach of LY12 alloy brazing
Xue Song bai , Qian Yiyu , Dong Jian and Lv Xiaochun
Abstract: The LY12 Al alloy was brazed with the adoption of the improved KF-CsF-AlF3 flux matching 
Ag-Al-Cu-Zn filler metal. The shear strength of brazed joint could reach 80% of that of the substrate and 
the tensile strength of butt brazed joint will be 70% of that of the substrate. This was the great progress against the traditional claim that Al alloy reinforced by heat treatment could not be brazed. The 
experimental results and theoretical analysis had proved that it was the key issue to remove the MgO oxide film below 503oC. The addition of rare earth La was the effective way to obtain better mechanical 
properties of the filler metal as well as brazed joints. 
Key words: LY12 Al alloy, brazing, Novel approach 

5. Moiré method analysis for tensile strain field of 2024 aluminum alloy welded joint
Xu Wenli1，Li Shiping2，Liu Xuesong1，Fang Hongyuan1，Zhao Min1, Tian Xitang1
Abstract: Using experimental mechanics method of moiré analysis, strain field distributions of 2024 
aluminum alloy welded joints under different conditions were investigated. The results show that moiré 
stripes of welded joint without trailing peening just before fracture are not only few and scattered but also uneven, and the stress mainly concentrates on the poor position-welded toes during the tensioning process with the relatively poor mechanical properties of welded joints; When the method of welding with trailing peening is adopted, moiré stripes of welded joint just before fracture are relatively thick and even due to the strengthening welded toes during the welding process, and fracture position transfers from the welded toes to weld, at the same time the mechanical properties of welded joints are improved greatly than conventional welding which can show that the technology of trailing peening is effective to strengthen welded joints of aluminum alloy with high strength.
Key words: tensile stress；welding with trailing peening；moiré analysis；joint strengthening

6. A welding document management software package based on a Client/Server structure
Wei Yanhong, Yang Chunli and Wang Min
Abstract: According to specifications for Welding Procedure Qualification of ASME IX Section and 
Chinese code, JB 4708-2000, a software package for managing welding documents has been rebuilt. 
Consequently, the new software package can be used in a Limited Area Network (LAN) with 4 different 
levels of authorities for different users. Therefore, the welding documents, DWPS (Design for Welding 
Procedure Specifications), PQRs (Procedure Qualification Records) and WPS (Welding Procedure 
Specifications) can be shared within a company. At the same time, the system provides users various 
functions such as browsing, copying, editing, searching and printing records, and helps users to make 
decision of whether a new PQR test is necessary or not according to the above codes as well. Furthermore, 
super users can also browse the history of record modification and retrieve the records when needed.
Key words:C/S structure, welding procedure qualification, database, LAN

7. Comparisons of particles thermal behavior between Fe-base alloy and boron carbide during plasma 
transferred-arc powder surfacing 
Wang Xibao
Abstract: Comparisons of particle’s thermal behavior between Fe-base alloy and boron carbide in plasma 
transferred-arc (PTA) space was made based on theoretical evaluation results in this article. It was found that most of the Fe base particles would be fully melted while they transporting through the central plasma field with 200A surfacing currents. And the particles with a diameter less than 0.5×10-4m might be fully evaporated. However, for the boron carbide (B4C) particles, only the one with a diameter less than 0.5×10-4m could be melted in the same PTA space. Most of B4C particles are only preheated at its solid state when they were fed through the central field of PTA plasma when the surfacing current is equal to or less than 200A. When the arc current was smaller than100A, only the particles smaller than 0.5×10-4m could be melted in the PTA space for the Fe-base alloy. Almost none of the discussed B4C particles could be melted in the 100A PTA space.
Key words: comparison, particle, Fe-base alloy, B4C, plasma transferred-arc

8. Improving the fatigue performance of longitudinal welded joints by low transformation temperature 
electrodes*
Wang Wenxian, Huo Lixing, Wang Dongpo, Zhang Yufeng, Jing Hongyang and Yang Xinqi **
Abstract: For a longitudinal welded joint, the tensile residual stresses are as high as the yield stress of the metal, so that the weld toes are sensitive to fatigue load. In this case a low transformation temperature electrode (LTTE) is one of the most useful methods used to improve the fatigue strength of the longitudinal welded joint, because the tensile residual stress is reduced or changed into compressive stress. Three kinds of longitudinal welded joints were selected to conduct fatigue tests. The tests results show that the fatigue strengths at 2×106 cycles of the joints welded with LTTE were improved by 41%, 47% and 59% respectively compared with those of the joints welded with E5015, and the fatigue lives at 162MPa were improved by 9.9 times, 9.6 times and 46.8 times respectively. Furthermore, the LTTE method is not necessary to add process after welding and so that it can be valuable method to improve the fatigue performance of longitudinal welded joints.
Key words :fatigue performance, longitudinal welded joints, compressive residual stress, low transformation temperature electrodes (LTTE)


9. Test and analysis of mechanism and influential elements of axial drifting of weldment on turning rolls
Wang Zheng, Qiao Jisen ,Xu Wentao1,Shen Fenggang2
Abstract: The mechanism of axial drifting of weldment on welding turning rolls was investigated. The 
simulation test for influential element has been carried out as well. The results show that axial drifting is caused by unparallel between the axis of roller and weldment resulting in axial force. When the helical 
angle λ between rolls and weldment is form 1°to 6°, the tanλ is linearly related to axial drifting speed 
V. Increase of number of deflected rollers causes non-linear increase of V. the angle of λ makes more 
effect on speed V than what the angle of deflection does. The turning speed of weldment is proportion to 
axial drifting speed V. the dead weight of weldment has little effect on speed V.
Key Word: welding turning rolls, axial drifting, axial force

10. Realizing precision pulse TIG welding with arc length control and visual image sensing based weld 
detection*
Sun Zhenguo, Chen Nian and Chen Qiang
Abstract: Methods of arc length control and visual image based weld detection for precision pulse TIG 
welding were investigated. With a particular all-hardware circuit, arc voltage during peak current stage is sampled and integrated to indicate arc length, deviation of arc length and adjusting parameters are 
calculated and output to drive a step motor directly. According to the features of welding image grabbed 
with CCD camera, a special algorithm was developed to detect the central line of weld fast and accurately. 
Then an application system were established, whose static arc length error is ±0.1mm with 20A average 
current and 1mm given arc length, static detection precision of weld is 0.01mm, processing time of each 
image is less than 120 ms. Precision pulse TIG welding of some given thin stainless steel components with 
complicated curved surface was successfully realized.
Key words: pulse TIG welding, visual image sensing, arc length control, weld detection

11. Single-peak distribution model of particulate size for welding aerosols
Shi Yuxiang, Li Ainong
Abstract: A large number of particulate size distributions of welding aerosols are measured by means of 
DMPS method, several distribution types are presented. Among them the single-peak distribution is the 
basic composing unit of particulate size. The research on the mathematic models and distributions 
functions shows that the single-peak distribution features the log-normal distribution. The 
diagram-estimating method (DEM) is a concise approach to dealing with distribution types, obtaining 
distribution functions for the particulate sizes of welding aerosols. It proves that the distribution function of particulate size possesses the extending property, being from quantity distribution to volume, as well as high-order moment distributions, with K-S method verifying the application of single-peak distribution and of DEM.
Key words: welding aerosols, distribution function, log-normal distribution, diagram-estimating method 
(DEM), welding fume

12. Microstructure and strength of brazed joints of TiB2 cermet to TiAl-based alloys*
Li Zhuoran, Feng Jicai and Cao Jian
Abstract: In this study, TiB2 cermet and TiAl-based alloy are vacuum brazed successfully by using 
Ag-Cu-Ti filler metal. The microstructural analyses indicate that two reaction products, Ti(Cu, Al)2 and Ag based solid solution (Ag(s.s)), are present in the brazing seam, and the interface structure of the brazed joint is TiB2/TiB2+ Ag(s.s) /Ag(s.s)+Ti(Cu, Al)2/Ti(Cu, Al)2/TiAl. The experimental results show that the shear strength of the brazed TiB2/TiAl joints decreases as the brazing time increases at a definite brazing temperature. When the joint is brazed at 1223K for 5 min, a joint strength up to 173MPa is achieved.
Key words: TiB2 cermet, TiAl, vacuum brazing, interface structure, strength0 IntroductionTiAl-based alloys have a great potential to become important candidates for replacing heavier nickel-based superalloys and titanium alloys in future jet-engines owing to their promising properties such as low density, high elevated-temperature strength, and excellent oxidation resistance. However, in order to produce larger or more complex structural parts, it is necessary to bond TiAl-based alloys to themselves or to other materials. In recent years, the bonding technologies of TiAl-based alloys to themselves or to other materials have progressed[1-3]. This paper aims to study the vacuum brazing technology of a TiB2 cermet to TiAl-based alloy, and the focus is placed on the interface structure and bonding strength of the joints brazed with Ag-Cu-Ti filler metal.

13. The study on interfacial bonding strength of Ag-Ni, Ag-Cu in cold pressure welding
Li YunTao, Du ZeYu, andChen Liping
Abstract:The area of combination actually is a kind of interfacial phenomena that exist on the surface or thin film. The properties of interface have important effect on the whole welding joint, even decide directly the interfacial bonding strength.The bonding strength of metals in cold pressure welding such as Ag-Ni (they are hardly mutual soluble) and Ag-Cu(they are limited soluble) are discussed in this paper. The results of the tensile test suggest that two kinds of welding joints have enough strength to satisfy with the demand for being used. Moreover, thermodynamics, crystal logy, physics and metal electronic microscopic analysis etc are adopted to further calculate the bonding strength. The results of test and theoretical analyses prove that Ag-Ni, Ag-Cu, especially, for Ag-Ni(they hardly have solubility) can form strong welding joint which is higher than that of the relative soft base metals in cold pressure welding. 
Key words: cold pressure welding, interface, bonding strength

14. A method of initial welding position guiding for arc welding robot based on visual servo control*
Guo Zhenmin, Chen Shanben, Qiu Tao and Wu Lin
Abstract:In order to solve the visual guiding task of initial welding position for arc welding robot, this paper presents a practice-prone image-based visual servo control strategy without calibration, and we 
perform validating experiments on a nine-DOF arc welding robot system. Experimental results illustrate 
presented method has the function to fulfill the task of welding robot initial positioning with certain 
anti-jamming ability. This method provides a basis for guiding welding gun to initial welding pose with real typical seam's image properties to replace flag block properties, and is a significant exploit to realize visual guiding of initial welding position and seam tracing in robot welding system.
Key words: visual servo, initial welding position, without calibration, image Jacobian

15. Temperature field simulation of laser-TIG hybrid welding
Chen Yanbin Li Liqun Fang Junfei Feng Xiaosong Wu Lin
Abstract: The three-dimensional transient temperature distribution of laser-TIG hybrid welding was 
analyzed and simulated numerically. Calculations were based on a finite element model, in which the 
physical process of hybrid welding was studied and the coupling effect of the laser and arc in the hybrid 
process was fully considered. The temperature fields and weld cross-sections of the typical welding 
parameters are obtained using present model. The calculation results show that the model can indicate the 
relationship of energy match between laser and arc to joints cross-sections objectively, and the
simulation results are well agreed with the experimental results.
Key word: laser-TIG hybrid, temperature field, numerical simulation