MAIN TOPICS，ABSTRACTS & KEY WORDS

Researchstatusofrotaryfrictionweldingofaluminum/steeldissimilarmetals

Zhu Ruican1,4,5, Zhao Yanhua1, Wang Hao2, Qin Guoliang2,3, Liu Shungang3, Zhang Lingdong6

(1. Capital Aerospace Machinery Corporation, Beijing 100076, China; 2. Shandon University, Jinan 250061, China; 3. Power China Nuclear Power Engineering Company Limited, Jinan 250067, China; 4. Tsinghua University, Beijing 100072, China; 5. China Academy of Machinery Science and Technology, Beijing 100044, China; 6. The First Military Representative Office of the Pla Rocket Force in Beijing, Beijing 100076, China).p1-10

AbstractAccording to the characteristics of aluminum/steel dissimilar metal welding metallurgy and rotary friction welding process, it was considered that rotary friction welding was the most suitable welding process of aluminum/steel dissimilar metal axisymmetric parts. Effects of continuous drive friction welding and inertia friction welding on the microstructure and properties of aluminum/steel dissimilar metals joints were introduced respectively. The main scientific problems that urgently need to be solved in the development of metal friction welding technology were summarized as followed. In rotary friction welding of aluminum/steel, the influence law and mechanism of violent plastic flow on IMCs generation at the friction welded interface and its vicinity need further study. It was necessary to develop a corresponding process to promote the formation of Fe-Al IMCs as the symbol of metallurgical bonding on the interface of aluminum/steel joint and to homogenize the thickness of IMCs layer. In the end, the study revealed the metallurgical behavior of aluminum/steel friction welded interface IMCs such as formation mechanism, phase composition, morphology and distribution, which were of great significance to control microstructure and properties of aluminum/steel rotary friction welded joint, and which were also the theoretical basis to guarantee the performance of aluminum/steel dissimilar metals welding structure.

Keywords:aluminum/steeldissimilarmetals,rotaryfrictionwelding,weldingtechnology,mechanicalproperties,intermetalliccompounds

EffectofAgandZnonwettabilityofSn58Bisolderandmicrostructureofsolderedjoint

Ma Yiming1, Chu Jijun1, Lü Xiaochun1,2, Sun Fenglian2

(1. Harbin Welding Institute Limited Company, Harbin 150028, China; 2. Harbin University of Science and Technology, Harbin 150001, China).p11-15

AbstractThe solder was prepared by the induction melting method. The influence of Ag and Zn addition on the wettability of Sn58Bi solder and microstructure of soldered joint was studied. The composition and growth law of interface intermetallic compounds (IMCs) of the soldered joint after aging treatment were analyzed. The results showed that the added Ag or Zn could respectively produce Ag3Sn and Ag5Zn8with Sn, significantly reduce the content of dendrites in the solder and refine microstructure of solders, but not significantly promote the wettability of Sn58Bi solder. However, the added Ag together with Zn could not refine microstructure of solders or reduce the the wettability of solders. The added Ag together with Zn made a composite IMC layer formed by Cu8Zn5+Ag5Zn8at the interface of soldered joint. The composite IMC layer could significantly reduce the initial thickness of the IMC and reduce its growth rate.

Keywords:Sn58Bi,lead-freesolder,wettability,microstructure

MicrostructureandpropertiesofT2copper/304stainlesssteellaserbrazedjoint

Lu Guipeng, Yin Hongze, Liu Wei

(Changchun University of Technology, Changchun 130012, China).p16-19

AbstractLaser welder was used to weld T2 copper and 304 stainless steel with Cu-Mn-Ni brazing filler metal. Macroscopic morphology of brazed seam, mechanical properties of brazed joints and element diffusion of brazing filler metal were tested and analyzed by scanning electron microscope and tensile testing machine. The results showed that the influence of welding current on formation of brazed seam was the largest, the pulse frequency was second, and the pulse width was the least in laser brazing copper/stainless steel. The corresponding orthogonal test range were 17.35, 15.66 and 7.91, respectively. Good diffusion and solid solution were formed between the brazing filler metal and the base metal. Fe and Cr elements in the weld bead diffused obviously and there existed granular copper-based solid solutions. Under the optimal brazing parameters, shear strength of brazed joints reached 35.75 MPa.

Keywords:laserbrazing,formationofbrazedseam,microstructure,mechanicalproperties

EffectofheattreatmenttemperatureontheimpactpropertyofS460plate

Dang Hengyao1, Ye Hongde1, Guo Weihong1, Guo Haixia1, Zhang Xinyao1,2

(1. Luoyang Ship Material Research Institute, Luoyang 471023, Henan, China; 2. Henan Key Laboratory of Technology and Application of Structural Materials for Ships and Marine Equipment, Luoyang 471023, Henan, China).p20-26

Keywords:S460steel,heatinput,microstructure,lowtemperatureimpactabsorbingenergy

Effectofoxidefilmonstresscorrosioncracktipmechanicalfieldindifferentperiods

Yang Fan1, Sun Jianwei1, Zhang Wenjuan2

(1. Xi’an Aeronautical Polytechnic Institute, Xi’an 710089, China；2. Xi’an University of Science and Technology, Xi’an 710054, China).p27-29,34

AbstractThe tip mechanical state is one of the main factors affecting the rate of stress corrosion cracking (SCC) expansion of structural materials. According to the mechanical law of oxide stress on crack tip in different periods, the SCC life cycle finite element model was established and the oxide film was obtained with the change of the mechanical field of the crack tip in different crack propagation stages. The results showed that the crack was in the scratch stage, the oxidation film had the greatest influence on the failure stress and tensile stress, but appeared small influence range on the crack tip. With the increase of crack length, the influence of oxide on Misses stress, tensile stress and stress intensity factorKof crack tip was smaller.

Keywords:oxidestress,stresscorrosioncracking,cracktip,lifecycle

Effectofcarboncontentonmechanicalpropertiesof2.25Cr-1Mo-0.25VweldmetalbySAW

其次，兜底条款并非著作权法设权的基础性规则，而是法定类型的从属规则。只有在主要权利类型不能适用时，从属规则才有适用的空间。法院在适用法律时，既要保护权利人的合法权益，同时也要给予社会公众某种程度的关怀。因为利益平衡始终是著作权保护的重要支点。㊱ 孔祥俊著：《网络著作权保护法律理念与裁判方法》， 中国法制出版社2015年版，第3页。著作权法一方面要维护权利人的合法权益；另一方面也要促进知识的广泛传播，保障作品使用者的利益。易言之，对于被诉行为，法官首先应当寻找法律明确规定的条文进行适用，在法律条文未明确规定且通过法律解释仍不能适用的情形下，再适用兜底条款。

Fan Yangyang1,2, Miao Xingping1,2, Chu Chenggang1,2

(1.Sichuan Xiye New Material Co., Ltd., Chengdu 611730, China; 2. Sichuan Special Welding Materials Research and Development Engineering Laboratory, Chengdu 611730, China).p30-34

AbstractEffect of C on the conventional mechanical properties and high temperature rupture life of 2.25 CR-1MO-0.25 V weld metal by submerged arc welding (SAW) was systematically studied, and the key role of carbide on high temperature rupture life was revealed. The heat treatment decarburization process of wire rods could reduce the C content of the welding wire and deposited metal by about 20%, while other alloy elements remained unchanged. With the decrease of C content, 2.25 Cr-1Mo-0.25V weld metal by SAW showed characteristics of reduced strength, increased plastic toughness and reduced tendency of tempering embrittlement. Under the test temperature of 540 ℃ and the lasting stress of 210 MPa, the high temperature rupture time of low C weld metal was only 587 h, which was 30% shorter than 939 h of normal weld metal, which could not meet the technical requirements of ≥900 h. The precipitation density and size of carbide in low C welds were significantly lower than that of normal welds. The carbides played a key role of pinning effect to prevent migration of grain boundary sliding and dislocation, which could improve the high temperature rupture life of welds. During the design and product inspection of 2.25Cr-1Mo-0.25V SAW materials, it was necessary to monitor the carbon content of welding wire and weld metal to avoid low C content.

Keywords: 2.25Cr-1Mo-0.25Vsteel,SAW,decarburization,hightemperaturerupture,carbide

Designofautomaticargonarcweldingfixtureformixerlobecomponentsinaircraftengine

Zhao Bao1, Yang Yongbo1, Shan Yi2, Zhou Kun1, Zhao Yanjie2

(1. Harbin Welding Institute Limited Company, Harbin 150028, China; 2. Air China Development Shenyang Dawn Aero Engine Co., Ltd., Shenyang 110043, China; 3. Harbin Bo Shi Automation Co., Ltd., Harbin 150078, China).p35-39

AbstractThe finished product of mixer lobe components in aircraft engine was composed of several surface parts (sheet titanium alloy special stamping parts) by blank welding. Due to its complex and irregular curved shape, it was difficult to assemble, guarantee welding quality and control welding deformation. To solve the above problems and difficulties, The authors’ three companies in the paper developed a automatic argon arc welding fixture for mixer lobe components in aircraft engine, hand in hand together. The system composition, the structure and characteristics of the automatic argon arc welding fixture for mixer lobe components were introduced together with its working principle and operation process in the process of assembly welding. The results showed that the fixture could be used to assemble several single pieces continuously at one time. The fixture could effectively control the deformation of welding process. After welding, the size and surface quality of the finished product met the technical requirements, and could achieve mass production.

Keywords:mixerlobe,weldingdeformation,surfacewelding

Comparisonofassessmentmethodsandoptimizationproposalonrailwayvehiclematerialanditsjointstrength

Xu Baolei, Zhao Wenping,Du Fei, Li Ying, Du Jianqiang, Wang Shun

(CRRC Tangshan Co., Ltd., Tangshan 063035, Hebei, China).p40-47

AbstractStandards at home and abroad had different assessment methods for static and fatigue strength of base metal, HAZ and weld. The comparison among these standards were conducted in the article. The comparison result indicated that all standards had shortcomings illustrated as followed. There was no regulation on the fatigue strength of spot welded joint. No mention or correct regulation on strength of cold hardening stainless steel welding joint was given. Actual welded joint was hardly able to correlate to the welded joint listed in fatigue assessment standard. There existed no regulation on fatigue load in connection region between running gear and car shell, which resulted in several crack cases of car shell. The smaller allowable stress of dissimilar metals for groove welded joint was adopted. However, no consideration was given to the actual scenario that one sort of welding wire was generally used for all dissimilar metals. Strength ratio between all weld metal and base metal of each side was diversified. Incomplete penetration weld was often regarded as complete penetration weld to assess. For fillet, plug weld and slot weld, only the principal stress of corresponding node was checked whether it exceeded the allowable stress of weld/HAZ or not, but weld size, shear force and additional bending moment were left out. The optimization proposal was put forward pursuant to project experience.

Keywords:basemetal,HAZ,weld,staticstrength,fatigue

Repairweldingtechnologyoflargestarwheelgearplateinsinteringmachine

Lu Changchun, Zhang Xianhui

(MCC Baosteel Technology Services Co., Ltd., Shanghai 201999, China).p48-50,57

AbstractAccording to the structural characteristics, weldability and performance requirements of star wheel gear plate 50Mn2 of sintering machine, under conditions of the equipment without being disassembled, no preheating or postweld heat treatment, the on-line repair welding of star wheel gear plate was realized through process measures of welding electrode ENiCrMo-3, control of welding heat input (8 kJ/cm in root pass and 10 kJ/cm in the other pass) and peening weld. After repair welding, the surface hardness of star wheel gear plate could be stabilized at 40～43 HRC, which met the production requirements of sintering machine. The service life was equivalent to the new star wheel gear plate and the cost was only about 5% of the new plate.

Keywords：starwheelgearplate, 50Mn2,coldwelding,repairwelding

CausesofcracksinSA738Gr.Blapjointsofanuclearpowerplantsteelcontainment

Liu Lili1, Zhang Weidong1, Wang Dejun2, Dang Wenzhi1, Guo Yanhui3

(1. China Nuclear Industry 23 Construction Co., Ltd., Beijing 101300, China; 2. Ministry of Ecology and Environment, Beijing 100006, China; 3. Nuclear and Radiation Safety Center, Beijing 102401, China).p51-57

AbstractCauses of cracks in SA738 Gr.B lap joints by auto gas metal arc welding (auto-GMAW) and shield metal arc welding (SMAW) was studied in the construction test of steel containment in a nuclear power station. The microstructure and mechanical properties of the coarse grain heat-affected zone were emphatically discussed. The phase array ultrasonic test (PAUT) was firstly used to measure the cracks to confirm the cracks initiation position, and then the optical micrograph (OM) and electron back-scatter diffraction (EBSD) were used to analyzed the microstructure and grain boundary characterize around the cracks. Furthermore, microhardness, room temperature tensile and impact tests were carried out to get the mechanical properties around the cracks in lap joints. The experimental results showed that microstructure and mechanical properties of coarse grain zone in heat-affected zone of lap joints were different in different welding methods, and the mechanical properties mismatch under residual stress caused the cracks of lap joints.

Keywords:steelcontainment,overlapjointcrack,auto-GMAW,SMAW,mechanicalproperties