• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Variation of chemical composition of high strength low alloy steels with different groove sizes in multi-pass conventional and pulsed current gas metal arc weld depositions

    2015-11-01 07:13:56DEVAKUMARANANANTHAPADMANABANGHOSH
    Defence Technology 2015年2期
    關(guān)鍵詞:艾莉心理準(zhǔn)備秦川

    K.DEVAKUMARAN*,M.R.ANANTHAPADMANABAN,P.K.GHOSH

    aWelding Research Institute,Bharat Heavy Electrical Limited,Trichy 620014,Tamil Nadu,India

    bDepartment of Mechanical Engineering,M.A.M College of Engineering and Technology,Siruganur,Trichy 621 105,Tamil Nadu,India

    cDepartment of Metallurgical&Materials Engineering,Indian Institute of Technology Roorkee,Roorkee 247 667,India

    ?

    Variation of chemical composition of high strength low alloy steels with different groove sizes in multi-pass conventional and pulsed current gas metal arc weld depositions

    K.DEVAKUMARANa,*,M.R.ANANTHAPADMANABANb,1,P.K.GHOSHc,2

    aWelding Research Institute,Bharat Heavy Electrical Limited,Trichy 620014,Tamil Nadu,India

    bDepartment of Mechanical Engineering,M.A.M College of Engineering and Technology,Siruganur,Trichy 621 105,Tamil Nadu,India

    cDepartment of Metallurgical&Materials Engineering,Indian Institute of Technology Roorkee,Roorkee 247 667,India

    25 mm thick micro-alloyed HSLA steel plate is welded by multi-pass GMAW and P-GMAW processes using conventional V-groove and suitably designed narrow gap with 20 mm(NG-20)and 13 mm(NG-13)groove openings.The variation of weld metal chemistry in the multi pass GMA and P-GMA weld depositions are studied by spark emission spectroscopy.It is observed that the narrow groove GMA weld joint shows significant variation of weld metal chemistry compared to the conventional V-groove GMA weld joint since the dilution of base metal extends from the deposit adjacent to groove wall to weld center through dissolution by fusion and solid state diffusion.Further,it is noticed that a high rate of metal deposition along with high velocity of droplet transfer in P-GMAW process enhances the dilution of weld deposit and accordingly varies the chemical composition in multi-pass P-GMAweld deposit.Lower angle of attack to the groove wall surface along with low heat input in NG-13 weld groove minimizes the effect of dissolution by fusion and solid state diffusion from the deposit adjacent to groove wall to weld center.This results in more uniform properties of NG-13 P-GMA weld in comparison to those of NG-20 and CG welds.

    Pulsed current;Narrow gap;Weld metal chemistry

    1.Introduction

    The micro-alloyed high strength low alloy(HSLA)steels are widely used in engineering applications because of their relatively low cost,moderate strength and very good toughness and fatigue strength,together with their ability to be readily welded.Arc welding,including shielded metal arc welding(SMAW),gas metal arc welding(GMAW)andsubmerged arc welding(SAW),is widely used in fabrication of various components of the HSLA steel.Due to several merits of producing comparatively cleaner and continuous weld deposition with automation,the GMAW process is becoming widely popular,especially for welding of structural membersusedinpower,transportationanddefense industries.

    It is often found that the heterogeneity of weld metal chemical composition,especially for multi-pass welding of thick sections,gives the different weld joint properties primarily due to the repetitive influence of subsequent weld passes on thermal cycles and the dilution of base metal[1,2]. The most significant changes in the properties of weld joints are due to adverse development of residual stress,microstructure and corrosion resistance,etc[2].In case ofconventional GMAW process,it is not always possible to maintain the chemical composition of the weld deposit within a desired level with respect to its influence on thermal and mechanical effects primarily due to limited operating parameters such as welding current,arc voltage and welding speed,which is used to determine the heat input of the process[3]. The pulsed current gas metal arc welding(P-GMAW)process instead of the conventional GMAW process may be more useful due to its ability to precisely control the geometry of weld deposit dictated by appropriate selection of pulse parameters[4,5]and also operate at low heat input in producing a sound weld joint[6,7].However,the involvement of large number of pulse current parameters in P-GMAW,including peak current(Ip),base current(Ib),pulse on-time(Tp),pulse off-time(Tb)and pulse frequency(f),introduces a certain degree of complexity in controlling the process for desired welding.It is reported that the complexity of the process primarily arising due to the criticality in selection of pulse parameters can be solved by correlating the weld characteristics with a summarized influence of pulse parameters defined by a dimensionless factor?=(Ib/Ip)× fTb,where Tbis expressed as[(1/f)-Tp][8,9].Lots of research work has been done and reported in reference to the P-GMAW arc and metal transfer dictating thermal behavior and its influence on various characteristics of ferrous and non-ferrous materials weld joints[10-13],but the chemical heterogeneity of multi-pass weld deposit has been not reported.

    http://dx.doi.org/10.1016/j.dt.2014.11.001

    2214-9147/Copyright?2015,China Ordnance Society.Production and hosting by Elsevier B.V.All rights reserved.

    Thus,the present work has been carried out to investigate the effects of GMA and P-GMA welding parameters in the case of different groove sizes on the variation in the chemical composition of multi-pass weld deposit of 25 mm thick HSLA steel plate.The changing mechanism of its chemical composition during multi-pass weld deposition in the case of different groove design and welding parameters were discussed.A systematic understanding of these aspects may be beneficial in using GMAW process to produce desired weld quality.

    2.Experiment

    2.1.Welding

    The 25 mm thick plate of controlled rolled micro-alloyed high strength low alloy(HSLA)steel of SAILMA 410HI/ SA543 having chemical composition given in Table 1 were used in this work.250 mm×100 mm plates were butt welded by multi-pass and multi-seam deposition techniques using conventional V-groove(CG)as per AWS specification[15]and a suitably designed narrow groove with 20 and 13 mm groove openings,designated by(NG-20)and(NG-13),respectively,as shown in Fig.1.The plates were welded by autogenous gas tungsten arc welding(GTAW)root pass,followed by GTAW filling pass and subsequent filling pass,in the process of continuous current gas metal arc welding(GMAW)or pulsed current gas metal arc welding(P-GMAW).The GTAW was carried out using a water cooled torch with 7 mm diameter gas nozzle and 3.2 mm diameter with 2%thoriated tungsten electrode(AWS:5.12 EWTh-2)under the shielding of 99.95%pure commercial argon at a flow rate of 18 l/min. The GMAW and P-GMAW passes were carried out by using 1.2 mm diameter mild steel filler wire of specification AWS/ SFA 5.18 ER-70S-6.The shielding gas used for experimentation is argon(98.95%)at a flow rate of 17-18 l/min.Direct current electrode positive(DCEP)polarity is used with an electrode extension of 14-15 mm.The chemical composition of filler wires given by the supplier is also given in Table 1. The plates was weld using semi-automatic welding with mechanized torch travel.Prior to welding the plates were preheated at about 125-130°C for 60 s,and the inter-pass temperature during welding was maintained in the range from 150°C to 300°C.The welding was carried out by arranging the groove plates without root gap.The root was supported by a copper backing plate fitted in a thick mild supporting steel plate of a fixture,as shown in Fig.2.Prior to weld deposition,the base plates were thoroughly cleaned to remove the excess oxide layer and any dirt or grease adhering to the faying surface.The angles between the electrode/filler and the groove wall under different welding processes and groove size are given in Table 2.The P-GMA weld deposition under different weld groove sizes was carried out at two different levels of heat input(Ω)by varying φ within the range from 0.15 to 0.33.During welding all the conventional welding parameters were recorded with WMS 4000 software installed in a computer,and the pulse parameters were recorded with the help of a transient recorder appropriately connected to the electrical circuit of the welding power source. The welding parameters used in the preparation of GMA and P-GMA weld joints are shown in Table 3.A multi-pass and multi-layer welding procedure was adopted for preparation of weld joints.

    2.2.Chemical analysis

    The chemical analysis of the weld joints under different weldingprocesses,groovetypeandparameterswerecarriedoutby using spark emission optical spectroscopy with a spot of 3mmdiameteronsolidspecimens.Theanalysiswasperformed on weld metal at two different locations on the polished transversesection of theweld joint.The two locations on weld metal are defined along its central axis parallel to the edge of plate surface within 10 mm below from its top side(Location-T)and 6-15 mm above from its bottom side(Location-B)of the weld metal,as shown in Fig.3.In the case of conventional GMAW process,NG-13 with the smallest possible groove size is not analyzed because the weld joint does not meet the required quality in reference to the absence of defect in it.

    Table 1 Chemical compositions of base and filler materials.

    2.3.Microstructure

    Fig.1.Schematic diagram.(a)Conventional V-groove(CG),(b)20 mm width narrow groove(NG-20),(c)13 mm width narrow groove(NG-13).

    Fig.2.Schematic diagram of fixture.

    The microstructures of base metal and weld deposits of GMA and P-GMA weld joints having different groove sizes were studied under optical microscope.The sample was prepared as per metallographic procedure and etched with alcoholic solution of 2%HNO3.

    盡管做了最充分的心理準(zhǔn)備,可是當(dāng)秦川如期死去,艾莉還是感覺(jué)整個(gè)世界離她而去。她抱著秦川的頭,親吻著秦川布滿(mǎn)皺紋的嘴唇,她求秦川不要走不要走。她驚嘆自己竟然有著如此之多的眼淚。

    3.Result and discussions

    The variation behaviors of chemical composition in multipass GMA weld deposition under different groove designs were analyzed at a given heat input of 8.28±0.28 kJ/cm.In the case of multi pass P-GMA weld deposition under different groove designs,the variation behaviors of chemical composition were also analyzed by variation of factor φ and mean current(Im)under different heat inputs(Ω).The typical macrographs of conventional and pulsed current GMA weld joints are shown in Figs.4 and 5,respectively.

    3.1.Chemical composition of GMA weld under different weld groove sizes

    The chemical compositions at the different locations of weld deposit in the CG and NG-20 weld joints are shown in Fig.6.It is observed that the NG-20 weld joint has a higher carbon(C)content but lower silicon(Si),manganese(Mn)and copper(Cu)contents at the different locations of welds in comparison with CG weld joint.It may be because the effect of dilution in NG-20 narrow groove weld significantly extendsfrom the deposit adjacent to groove wall to the weld center through dissolution by fusion and solid state diffusion.However,the Fig.6 shows that the location-B of the weld has relatively higher C and Mn contents but lower Si and Cu contents than that the location-T has due to multi-pass weld deposition.

    Table 2 Angles of attack between electrode/filler and groove wall under different welding processes and groove sizes.

    Table 3 Welding parameters used in weld joint studies under different welding processes and groove type.

    3.2.Chemical composition of P-GMA weld under different weld groove sizes

    3.2.1.Conventional V-groove

    Fig.3.Schematic diagram and macrophotograph showing the measurement of chemical composition at two different locations on weld metal.

    The chemical compositions at different locations of PGMAweld deposit in the CG weld joint at a given arc voltage(V),mean current(Im),φ and heat input(Ω)are shown in Table 4.It has been observed that C content at any location of the weld deposit in CG P-GMAweld joint is about 30%higher than that of CG GMA weld joint and the changes in other elements are insignificant in it.In general,the axial spray metal transfer produces higher weld fumes than pulsed spray metal transfer[16].It indicates that the loss of elements(mainly C,Si and Mn)from the arc cavern is relatively higherin GMAW process than that in P-GMAW process.In addition to above high rate of metal deposition along with high velocity of droplet transfer in P-GMAW process the dilution of weld deposit is also enhanced[14],which may also play an important role in enhancing the C content in P-GMA weld. Table 4 further shows that C content is higher and Si content is lower at the location-B in comparison to those at the location-T,and other elements show insignificant variation in it.

    Fig.4.Typical macrographs of conventional GMA weld joints.(a)Conventional V-groove(CG),(b)Narrow groove with 20 mm groove width(NG-20),(c)Narrow groove with 13 mm groove width(NG-13).

    Fig.5.Typical macrographs of pulsed current GMA weld joints.(a)Conventional V-groove(CG),(b)Narrow groove with 20 mm groove width(NG-20),(c)Narrow groove with 13 mm groove width(NG-13).

    3.2.2.Narrow groove with 20 mm groove width(NG-20)

    Fig.6.The effect of weld groove size on chemical composition at different locations of GMAweld deposit for I=230±3A and Ω=8.28±0.28 kJ/cm.

    Fig.7 shows the effects of Imand φ on C contents at different locations of NG-20 P-GMA weld joints under two different heat inputs(Ω)of 7.61 and 5.28 kJ/cm at a given arc voltage(V)and φ=0.15 and 0.23.The Si,Mn and Cu contents are shown in Figs.8-10,respectively.It is also found that the C contents of NG-20 P-GMA weld joints at the locations B and Tof weld are about 20-25%higher than that of the CG P-GMA weld joint due to reduction in groove width,which is in agreement to those observed in NG-20 GMAweld joint(Fig.6).However,the Fig.7 shows that the C content at the location-B is higher than that at the location-T due to the effect of dilution in location-B in narrow groove weld in the case of different pulse parameters and Ω.It is also interestingly observed that,at a given Imof 230A,the C content at any locations of the weld increases with the increase in Ω and φ due to the increase in total heat transferred to the weld pool(QT)per unit length and projected arc diameter[11,12]respectively,which may give rise to more melting of base plate.On the other hand,it was reported that more fumes were generated when the angle of attack to groove wall surface and Ω were decreased by increasing the welding speed[16].In view of this,it is well understood that the final chemical composition of weld not only depends on the chemical compositions of electrode and base metal,but also depends on welding parameter and weld groove size.Fig.7 further depicts that,the decrease of Imfrom 230A to 160A decreases the C content significantly at both the locations of weld at 7.61 kJ/ cm due to the lower area of weld deposits and weld pool temperature(TWP),but C content shows an insignificant variation in it at 5.28 kJ/cm because of low TWP.

    As in case of carbon,the Si contents at different locations of weld are also correlated to the factorφ,Imand Ω,as shown in Fig.8.It has been observed that the Si contents at two different locations of the weld increase significantly with the increase of φ due to the increase of projected arc diameter[10,13]at any Ω of relatively low and high levels in the order of 5.28±0.41 and 7.61±0.38 kJ/cm and a given Im,resulting in large melting of base metal.However,F(xiàn)ig.8 also shows that,at a given φ at both the locations of weld,the Si contents are insignificantlyvaried with the increase of Ω from 5.5 to 7.61 kJ/cm,but they are appreciably enhanced with the decrease of Imfrom 230 to 200,and they decrease with the further decrease of Im.Such variations of Si contents as a function of Imand Ω are primarily attributed to the combined influence of heat transfer on the weld pool and fume formation rate from arc cavern.

    Table 4 Chemical compositions at different locations of CG P-GMA weld joint.

    Fig.7.Effects of Imand φ on Wt.%of C contents at two different locations of NG-20 P-GMA weld joints prepared at different Ω.(a)7.61±0.38 kJ/cm,(b)5.28±0.41 kJ/cm.

    Fig.8.Effects of Imand φ on Wt.%of Si contents at two different locations of NG-20 P-GMAweld joints prepared at different Ω.(a)7.61±0.38 kJ/cm,(b)5.28±0.41 kJ/cm.

    Fig.9.Effects of Imand φ on Wt.%of Mn contents at two different locations of NG-20 P-GMA weld joints prepared at different Ω.(a)7.61±0.38 kJ/cm,(b)5.28±0.41 kJ/cm.

    As in case of C and Si,the Mn and Cu contents at different locations of weld are also correlated to the factorφ,Imand Ω, as shown in Figs.9 and 10,respectively.It has been observed that the variations of Mn and Cu contents at both the locations of weld with the changes in φ,Imand Ω were not evident.

    Fig.10.Effects of Imand φ on Wt.%of Cu contents at two different locations of NG-20 P-GMA weld joints prepared at different Ω.(a)7.61±0.38 kJ/cm,(b)5.28±0.41 kJ/cm.

    3.2.3.Narrow groove with 13 mm groove width(NG-13)

    The effects of φ on C,Si,Mn and Cu contents at different locationsofNG-13P-GMA weldjointat230Aand 5.28±0.41 kJ/cm are shown in Fig.11.It has been observed Ccontent is lower but Si and Mn contents are insignificantly varied at any location of NG-13 P-GMA weld as compared to the NG-20 P-GMAweld.The lowering of C content in NG-13 P-GMA weld primarily happened due to lower angle of attack against the groove wall surface along with low Ω minimizes the effect of dissolution by fusion and solid state diffusion from the deposit adjacent to groove wall to weld center and also enhances the fume formation rate because of wider contact area of arc exposed to groove wall surface,resulting in a significant amount of element loss from arc cavern.In addition to above decrease of Ω with the increase of welding speed,the fume formation rate is also enhanced[16],which may also play an important role for decrease of C content in NG-13 PGMA weld.In this regard,for the given electrode chemical compositions,the change in weld groove size by varying groove angle provides a more efficient way to control the chemical composition of weld,and also play a favorable role in weld properties and microstructure.However,F(xiàn)ig.11 further shows the insignificant variation of the chemical compositions at both the locations of weld depicts,which indicates that the properties of the weld are more uniform in comparison to those of NG-20 and CG welds.Fig.11(d)shows that the Cu contents at different locations of NG-13 PGMAweld are comparatively lower than those of CG P-GMA and NG-20 P-GMA welds due to higher fume generation rate. However,the influence of φ on the chemical compositions at different locations of NG-13 weld shows an insignificant variation in it.In this regard,all the phenomena regarding the influence of pulse parameters and groove size on chemical compositions of P-GMA weld should be studied further in detail with the help of other experimental technique,like XRD,SEM-EDAX,etc.

    In the last few decades,the control of weld fumes in arc welding is a challenging task as the inhalable metal fumes pose a potential health hazard to the human body.In view of the above observations,the significant role of pulse parameters of P-GMAW process may give wider possibility to control the weld fumes.However,the study on fume generation rate under different pulse parameters and weld groove sizes of P-GMAW process is beyond the scope of the present work,but it should be studied further in detail.

    3.3.Microstructure

    The typical microstructure of 25 mm thick plate of microalloyed HSLA(SAILMA-350HI/SA533 grade)steel and its transverse direction are shown in Fig.12.The microstructure of base metal has been primarily found to consist of ferrite and pearlite along with the lamination of matrix typical of rolled structure.Due to the addition of micro alloying elements Ti,V,and Nb,the average grain size is around 18±3 μm and are comparatively finer than those observed in commonly used structural steel(24±3 μm)[17].

    Fig.11.Effect of φ on Wt.%of C,Si,Mn and Cu contents in NG-13 P-GMA weld joints at 5.28±0.41 kJ/cm(a)C,(b)Si,(c)Mn,(d)Cu.

    Fig.12.Typical microstructure of base metal.

    The significant change in the chemical composition of weld deposit with the change in welding processes and groove design should also influence its microstructure.Thus,it may be interesting to study the microstructure of weld deposits. The typical microstructures of CG and NG-20 GMA weld joints at two different locations of the weld deposit are shown in Fig.13.It is observed that,in comparison to the CG GMA weld,the NG-20 weld shows a larger amount of pearlites and a lower fraction of pro-eutectoid ferrite due to variation of chemical composition as explained earlier.The typical microstructures of CG,NG-20 and NG-13 P-GMAweld joints at two different locations of the weld deposit are in Fig.14.It is also observed that the microstructures of P-GMA weld deposits have the same features as those of the GMA weld deposits.However,relatively low thermal impact in P-GMAW weld shows a large proportion of ferrite in the matrix in comparison to the GMA welds.Further,it has been observed that the microstructure of NG-13 P-GMAweld deposits at two different locations show insignificant variation due to uniformly distributed chemistry in the weld deposits as explained earlier.

    4.Conclusions

    The present study provides a basic understanding of the effect of welding processes and groove size on variation of weld metal chemical composition in multi-pass weld deposition of HSLA steel.The observations on various critical aspects of GMA and P-GMAW processes may be primarily concluded as follows.

    1)Due to multi-pass GMA weld deposition,the chemical composition of weld metal is not uniform throughout the welding process,irrespective of change in groove size.

    2)The use of P-GMAW process enhances the dilution of weld deposit.Further,it is observed that,the NG-13 PGMA weld joint shows the uniform properties throughout the multi-pass weld deposition due to lower angle of attack against the groove wall surface along with low heat input.

    Fig.13.Typical microstructures of conventional GMA weld deposits.

    Fig.14.Typical microstructures of pulsed current GMA weld deposits.

    3)Finally,it is concluded that,for a given electrode chemical compositions,the change in weld groove size by varying groove angle provides a more efficient way to control the chemical composition of weld plays a favorable role in weld properties.Thus it may be considered further to characterize the microstructure of weld deposits.

    Acknowledgment

    The authors thankfully acknowledge the Indian Institute of Technology Roorkee(IITR),India for supporting to the research work.

    [1]Linnert G.Welding metallurgy.4th ed.,vol.1.Miami,F(xiàn)lorida:American Welding Society;1994.

    [2]Kou Sindo.Welding metallurgy.New York:John Wiley and Sons;1987.

    [3]Messler Jr Robert W.Principles of welding.New York:John Wiley and Sons;1999.

    [4]Ghosh PK,Gupta SR,Randhawa HS.Characteristics and criticality of bead on plate deposition in pulsed current vertical-up GMAWof steel.Int J Join Mater 1999;11(4):99-110.

    [5]Ghosh PK,Gupta SR,Randhawa HS.Characteristics of a pulsed-current,verticalupgasmetalarcweldinsteel.MetalTransA 2000;31A:2247-59.

    [6]Praveen P,Yarlagadda PKDV,Kang MJ.Advancements in pulse gas metal arc welding.J Mater Process Technol 2000;164-165:1113-9.

    [7]Rajasekaran S,Kulkarni SD,Mallya UD,Chaturvedi RC.Droplet detachment and plate fusion characteristics in pulsed current gas metal arc welding.Weld J 1998;6:254s-68s.

    [8]Ghosh PK.Decide pulse parameters for desired properties of pulsed current GMAW weld.In:International welding conference(IWC-99)on welding and allied technology”challenges in 21st century,”New Delhi;1999:Feb.15-17.p.18-28.

    [9]Ghosh PK,Dorn L,Goecke SF.Universality of co-relationships among pulse parameters for different MIG welding power sources.Int J Join Mater 2000;13(2):40-7.

    [10]Ghosh PK,Dorn L,Devakumaran K,Hofmann F.Pulsed current gas metal arc welding under different shielding and pulse parameters;part-1: arc characteristics.ISIJ Int 2009;49(2):251-60.

    [11]Ghosh PK,Goyal VK,Dhiman HK,Kumar M.Thermal and metal transfer behaviour in pulsed current GMA weld deposition of Al-Mg alloy.Sci Technol Weld Join 2006;11(2):232-42.

    [12]Ghosh PK,Dorn L,Hubner M,Goyal VK.Arc characteristics and behaviour of metal transfer in pulsed current GMAwelding of aluminium alloy.J Mater Process Technol 2007;194:163-75.

    [13]Ghosh PK,Dorn L,Kulkarni S,Hoffmann F.Arc characteristics and behaviour of metal transfer in pulsed current GMA welding of stainless steel.J Material Process Technol 2008;209:1262-74.

    [14]Kulkarni SG.Narrow gap pulse current gas metal arc welding of thick wall 304LN stainless steel pipe[Ph.D.Thesis].2008.IIT Roorkee,India.

    [15]Welding handbook,welding technology.8th Ed.vol.1.American Welding Society;1987.

    [16]Dennis John,H,Peter JH,Redding CAJ,Andrew DW.A model for prediction of fume formation rate in gas metal arc welding,globular and spray modes,DCelectrodepositive,vol.45(2).PergamonPress;2001.p.105-13.

    [17]Tamura I,Sekine Hiroshi,Tanaka Tomo,Ouchi Chiaki.Thermo-mechanical processing of high strength low alloy steels.Butterworth&Co. Metals Handbook;1988.

    11 September 2014;revised 13 November 2014;accepted 24 November 2014

    Available online 20 February 2015

    .Tel.:+91 9443689943.

    E-mail addresses:devakumaran@bheltry.co.in(K.DEVAKUMARAN),mrpadmanaban@yahoo.com(M.R.ANANTHAPADMANABAN),prakgfmt@ gmail.com,prakgfmt@iitr.ernet.in(P.K.GHOSH).

    Peer review under responsibility of China Ordnance Society.

    1Tel.:+91 9488090838.

    2Tel.:+91 1332 285699.

    Copyright?2015,China Ordnance Society.Production and hosting by Elsevier B.V.All rights reserved.

    猜你喜歡
    艾莉心理準(zhǔn)備秦川
    艾莉的煩惱
    傅雷的稱(chēng)贊
    做人與處世(2022年6期)2022-05-26 10:26:35
    換座
    做人與處世(2022年4期)2022-05-26 04:43:14
    在雨中“躲雨”的綿羊
    該得獎(jiǎng)的李老師
    丟失的皮鞋
    邁出第一步
    海濱城市尋找記
    神回復(fù)
    二寶媽坐月子 要有迎接挑戰(zhàn)的心理準(zhǔn)備
    媽媽寶寶(2017年3期)2017-02-21 01:22:10
    精品久久久久久久毛片微露脸| 欧美黑人精品巨大| 亚洲伊人色综图| 成人特级黄色片久久久久久久 | 动漫黄色视频在线观看| 肉色欧美久久久久久久蜜桃| 老司机靠b影院| 一本综合久久免费| 免费日韩欧美在线观看| 母亲3免费完整高清在线观看| 狠狠狠狠99中文字幕| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲国产欧美在线一区| 国产成人免费无遮挡视频| 王馨瑶露胸无遮挡在线观看| 国产日韩欧美视频二区| www.熟女人妻精品国产| 欧美+亚洲+日韩+国产| 最新美女视频免费是黄的| 中文字幕最新亚洲高清| 久久久久国产一级毛片高清牌| 国产成人免费观看mmmm| 成年人黄色毛片网站| 一夜夜www| 叶爱在线成人免费视频播放| 90打野战视频偷拍视频| 午夜福利在线免费观看网站| 十八禁网站网址无遮挡| 久久精品国产a三级三级三级| 国产亚洲av高清不卡| 在线十欧美十亚洲十日本专区| 一本大道久久a久久精品| 日日爽夜夜爽网站| 国产av国产精品国产| 制服人妻中文乱码| 欧美精品av麻豆av| 日本vs欧美在线观看视频| 欧美日韩视频精品一区| tocl精华| 老司机福利观看| 久久青草综合色| 淫妇啪啪啪对白视频| 精品少妇久久久久久888优播| 黑人操中国人逼视频| 色婷婷久久久亚洲欧美| 亚洲精品中文字幕在线视频| 国产又色又爽无遮挡免费看| 中国美女看黄片| 免费av中文字幕在线| 老熟妇乱子伦视频在线观看| 在线观看免费视频网站a站| 搡老乐熟女国产| 国产精品98久久久久久宅男小说| h视频一区二区三区| 男女下面插进去视频免费观看| 国产成人欧美在线观看 | 亚洲精品乱久久久久久| 亚洲av成人一区二区三| 搡老岳熟女国产| 久久人妻熟女aⅴ| 国产区一区二久久| 咕卡用的链子| 国产深夜福利视频在线观看| 少妇裸体淫交视频免费看高清 | 肉色欧美久久久久久久蜜桃| 久久久久视频综合| 亚洲专区国产一区二区| 日本精品一区二区三区蜜桃| 女警被强在线播放| 成人永久免费在线观看视频 | 中文字幕色久视频| 国产精品国产高清国产av | 国产日韩欧美亚洲二区| 99国产综合亚洲精品| 人人妻人人澡人人看| 中文字幕av电影在线播放| 精品国产超薄肉色丝袜足j| 少妇被粗大的猛进出69影院| 亚洲av国产av综合av卡| 天堂8中文在线网| 女同久久另类99精品国产91| 深夜精品福利| 青草久久国产| 黑人欧美特级aaaaaa片| 欧美 日韩 精品 国产| 国产精品二区激情视频| 在线观看免费午夜福利视频| 99九九在线精品视频| 亚洲全国av大片| 大香蕉久久网| 操出白浆在线播放| 欧美乱码精品一区二区三区| 日韩视频在线欧美| 这个男人来自地球电影免费观看| 欧美精品av麻豆av| 每晚都被弄得嗷嗷叫到高潮| 精品久久久久久久毛片微露脸| 国产精品秋霞免费鲁丝片| 91精品国产国语对白视频| 老熟妇仑乱视频hdxx| 黄色视频不卡| 国产极品粉嫩免费观看在线| 午夜福利影视在线免费观看| 久久精品熟女亚洲av麻豆精品| 大型av网站在线播放| 狂野欧美激情性xxxx| 国产精品久久久久成人av| 亚洲成人免费av在线播放| 亚洲九九香蕉| 国产成人欧美在线观看 | 国产淫语在线视频| 十八禁人妻一区二区| 丰满迷人的少妇在线观看| 亚洲欧美激情在线| 岛国毛片在线播放| 日韩中文字幕视频在线看片| 久久国产精品影院| 啦啦啦 在线观看视频| 操出白浆在线播放| 亚洲自偷自拍图片 自拍| 国产在线观看jvid| 汤姆久久久久久久影院中文字幕| 国产av国产精品国产| 亚洲 国产 在线| 亚洲人成77777在线视频| 桃花免费在线播放| 黄色成人免费大全| 黄色视频不卡| 亚洲国产av新网站| 欧美激情久久久久久爽电影 | 啦啦啦视频在线资源免费观看| 999久久久国产精品视频| 国产免费现黄频在线看| 首页视频小说图片口味搜索| 亚洲自偷自拍图片 自拍| 欧美日韩黄片免| 国产一区二区三区综合在线观看| 日本vs欧美在线观看视频| 又黄又粗又硬又大视频| 国产欧美日韩一区二区三| 国产精品偷伦视频观看了| 黄色怎么调成土黄色| 在线亚洲精品国产二区图片欧美| 91av网站免费观看| 制服人妻中文乱码| 国产在线一区二区三区精| 精品国产乱码久久久久久男人| 777米奇影视久久| www日本在线高清视频| 成年动漫av网址| 18在线观看网站| 看免费av毛片| 亚洲伊人色综图| 国产伦人伦偷精品视频| 国产精品一区二区在线不卡| 丝瓜视频免费看黄片| 俄罗斯特黄特色一大片| 成人18禁在线播放| 成人国产一区最新在线观看| 欧美精品一区二区大全| 免费在线观看日本一区| 日本欧美视频一区| 久久午夜亚洲精品久久| 国产成+人综合+亚洲专区| avwww免费| 黄片大片在线免费观看| 精品久久久精品久久久| 亚洲精品一二三| 国产欧美日韩一区二区精品| 不卡av一区二区三区| 久久精品aⅴ一区二区三区四区| 纵有疾风起免费观看全集完整版| 久久影院123| 少妇粗大呻吟视频| 男女免费视频国产| 免费在线观看日本一区| av在线播放免费不卡| 超色免费av| 国产1区2区3区精品| 精品亚洲成a人片在线观看| 纵有疾风起免费观看全集完整版| 黄色毛片三级朝国网站| 久久精品国产亚洲av香蕉五月 | 午夜免费鲁丝| 极品少妇高潮喷水抽搐| 久久性视频一级片| 在线十欧美十亚洲十日本专区| 蜜桃在线观看..| 中文字幕人妻熟女乱码| 老熟妇乱子伦视频在线观看| 久久精品人人爽人人爽视色| 久久久精品94久久精品| 97在线人人人人妻| 欧美成狂野欧美在线观看| 美女福利国产在线| 欧美变态另类bdsm刘玥| 精品一区二区三区四区五区乱码| 麻豆成人av在线观看| 国产在线免费精品| 久久久精品94久久精品| 国产男靠女视频免费网站| 电影成人av| 免费在线观看日本一区| 久热这里只有精品99| 美女主播在线视频| 老司机在亚洲福利影院| 国产成人精品在线电影| 欧美大码av| 日韩制服丝袜自拍偷拍| 久久精品成人免费网站| 丁香六月欧美| 国产又色又爽无遮挡免费看| 亚洲人成伊人成综合网2020| 中文亚洲av片在线观看爽 | 亚洲成a人片在线一区二区| 岛国在线观看网站| 久久精品人人爽人人爽视色| 欧美成人免费av一区二区三区 | 久热爱精品视频在线9| 欧美日韩中文字幕国产精品一区二区三区 | 国产区一区二久久| 女人被躁到高潮嗷嗷叫费观| 久久久久久久久久久久大奶| 9191精品国产免费久久| 亚洲成av片中文字幕在线观看| 一本色道久久久久久精品综合| 热re99久久精品国产66热6| 18禁国产床啪视频网站| 十八禁人妻一区二区| 中文字幕av电影在线播放| 久久精品国产a三级三级三级| 黑丝袜美女国产一区| 欧美精品人与动牲交sv欧美| 亚洲第一欧美日韩一区二区三区 | avwww免费| 日韩人妻精品一区2区三区| 国产片内射在线| 亚洲成人免费电影在线观看| 精品乱码久久久久久99久播| 制服诱惑二区| 一级毛片精品| 久久精品国产a三级三级三级| 香蕉丝袜av| 成人三级做爰电影| 欧美 亚洲 国产 日韩一| 国产在线观看jvid| 啪啪无遮挡十八禁网站| 成人18禁高潮啪啪吃奶动态图| 亚洲精品在线美女| 久久久国产精品麻豆| 无人区码免费观看不卡 | 叶爱在线成人免费视频播放| 黄色片一级片一级黄色片| 在线观看舔阴道视频| 少妇精品久久久久久久| 纵有疾风起免费观看全集完整版| 夫妻午夜视频| 亚洲欧美日韩另类电影网站| 免费在线观看完整版高清| 成年人黄色毛片网站| 日日爽夜夜爽网站| 免费看a级黄色片| 纵有疾风起免费观看全集完整版| 欧美大码av| 久久久久久人人人人人| 岛国毛片在线播放| 菩萨蛮人人尽说江南好唐韦庄| 中文字幕精品免费在线观看视频| 考比视频在线观看| 精品国产乱码久久久久久小说| 搡老熟女国产l中国老女人| 蜜桃在线观看..| 大码成人一级视频| 丁香六月天网| 国产国语露脸激情在线看| 日韩中文字幕欧美一区二区| 久久精品91无色码中文字幕| 美女国产高潮福利片在线看| 香蕉丝袜av| 国产1区2区3区精品| 国产伦理片在线播放av一区| 国产人伦9x9x在线观看| 国产av一区二区精品久久| 一本色道久久久久久精品综合| 三上悠亚av全集在线观看| 超色免费av| 老熟妇乱子伦视频在线观看| 叶爱在线成人免费视频播放| 午夜91福利影院| 久久久欧美国产精品| 国产精品美女特级片免费视频播放器 | 极品人妻少妇av视频| 老司机亚洲免费影院| 蜜桃在线观看..| 亚洲国产av新网站| 女同久久另类99精品国产91| 99精国产麻豆久久婷婷| 黄色丝袜av网址大全| 人人妻,人人澡人人爽秒播| 国产成人精品久久二区二区91| 黑人猛操日本美女一级片| 精品国产亚洲在线| 精品少妇黑人巨大在线播放| 大香蕉久久成人网| 伦理电影免费视频| 美女视频免费永久观看网站| 国产一区二区三区在线臀色熟女 | 亚洲精品粉嫩美女一区| 1024视频免费在线观看| 午夜免费鲁丝| 免费在线观看完整版高清| 别揉我奶头~嗯~啊~动态视频| 亚洲国产欧美网| 两个人免费观看高清视频| 一区在线观看完整版| 免费在线观看视频国产中文字幕亚洲| 1024香蕉在线观看| 女人精品久久久久毛片| 女同久久另类99精品国产91| 国产精品自产拍在线观看55亚洲 | 搡老乐熟女国产| 亚洲色图av天堂| 亚洲精品一二三| 一进一出抽搐动态| 色老头精品视频在线观看| 国产精品国产av在线观看| 这个男人来自地球电影免费观看| 少妇的丰满在线观看| 亚洲五月婷婷丁香| 亚洲国产欧美在线一区| 水蜜桃什么品种好| 久久精品熟女亚洲av麻豆精品| 一边摸一边抽搐一进一小说 | 人人妻人人澡人人看| 免费日韩欧美在线观看| 日本精品一区二区三区蜜桃| 精品一区二区三区四区五区乱码| 曰老女人黄片| 人人妻人人爽人人添夜夜欢视频| 国产成人av激情在线播放| 亚洲精品在线美女| 叶爱在线成人免费视频播放| 国产高清国产精品国产三级| 伊人久久大香线蕉亚洲五| 久久99一区二区三区| 久久影院123| 亚洲欧美色中文字幕在线| 亚洲成a人片在线一区二区| 黑人巨大精品欧美一区二区蜜桃| 国产精品美女特级片免费视频播放器 | 黄频高清免费视频| 国产成+人综合+亚洲专区| 俄罗斯特黄特色一大片| 超碰成人久久| 精品免费久久久久久久清纯 | 亚洲第一av免费看| 精品午夜福利视频在线观看一区 | 热99re8久久精品国产| 久久久久久人人人人人| 午夜老司机福利片| 男女午夜视频在线观看| 老司机午夜福利在线观看视频 | 最黄视频免费看| 国产成人欧美| 精品国产乱码久久久久久小说| 国产高清视频在线播放一区| 国产精品美女特级片免费视频播放器 | 国产精品 国内视频| 曰老女人黄片| 久久精品91无色码中文字幕| 丰满饥渴人妻一区二区三| 久久久久国内视频| 精品少妇一区二区三区视频日本电影| av超薄肉色丝袜交足视频| 777久久人妻少妇嫩草av网站| 久久亚洲真实| 欧美日韩精品网址| 亚洲av国产av综合av卡| 不卡一级毛片| 午夜精品久久久久久毛片777| 欧美日韩黄片免| 久久九九热精品免费| 国产一区二区三区视频了| 中文欧美无线码| 欧美亚洲日本最大视频资源| 欧美日韩一级在线毛片| 黑人巨大精品欧美一区二区蜜桃| 一本—道久久a久久精品蜜桃钙片| 狠狠精品人妻久久久久久综合| 亚洲天堂av无毛| 欧美日韩亚洲高清精品| 亚洲国产av新网站| 亚洲欧美色中文字幕在线| 自拍欧美九色日韩亚洲蝌蚪91| 国产又色又爽无遮挡免费看| 成人影院久久| 91精品三级在线观看| 日日夜夜操网爽| videosex国产| 搡老熟女国产l中国老女人| 肉色欧美久久久久久久蜜桃| 欧美日韩精品网址| 久久性视频一级片| 亚洲全国av大片| 国产麻豆69| 久久久国产欧美日韩av| 午夜激情久久久久久久| 国产91精品成人一区二区三区 | 成人亚洲精品一区在线观看| 高清欧美精品videossex| 久久99一区二区三区| av免费在线观看网站| 十八禁人妻一区二区| 国产一区二区三区视频了| 在线观看免费午夜福利视频| 在线观看人妻少妇| www.精华液| 国产主播在线观看一区二区| 少妇的丰满在线观看| 亚洲伊人色综图| 中文字幕人妻熟女乱码| 在线观看www视频免费| 日韩人妻精品一区2区三区| 在线观看舔阴道视频| 国产精品免费一区二区三区在线 | 99精品久久久久人妻精品| 亚洲精品成人av观看孕妇| 日本a在线网址| 美女福利国产在线| 人人妻人人爽人人添夜夜欢视频| 亚洲国产欧美在线一区| 亚洲少妇的诱惑av| 国产色视频综合| 9热在线视频观看99| 国内毛片毛片毛片毛片毛片| 国产精品电影一区二区三区 | 视频区欧美日本亚洲| 制服人妻中文乱码| 久久精品熟女亚洲av麻豆精品| 老司机午夜十八禁免费视频| 热re99久久精品国产66热6| 纵有疾风起免费观看全集完整版| 欧美久久黑人一区二区| 在线 av 中文字幕| 亚洲性夜色夜夜综合| 久久 成人 亚洲| 美女高潮喷水抽搐中文字幕| 亚洲欧美激情在线| 一夜夜www| 国产精品熟女久久久久浪| 黑丝袜美女国产一区| 黄色毛片三级朝国网站| 黄片小视频在线播放| 国产精品久久电影中文字幕 | 色视频在线一区二区三区| 热re99久久国产66热| 一区福利在线观看| 国产亚洲欧美精品永久| 久久精品国产a三级三级三级| 精品久久久久久电影网| 午夜精品国产一区二区电影| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲精品国产区一区二| 国产色视频综合| 动漫黄色视频在线观看| 桃红色精品国产亚洲av| 亚洲欧美日韩另类电影网站| 一级,二级,三级黄色视频| 黄色成人免费大全| a在线观看视频网站| 一级a爱视频在线免费观看| 女人久久www免费人成看片| 一级毛片女人18水好多| 亚洲,欧美精品.| 国产高清videossex| 蜜桃在线观看..| 婷婷丁香在线五月| 国产又色又爽无遮挡免费看| 欧美一级毛片孕妇| 亚洲欧美色中文字幕在线| 成年女人毛片免费观看观看9 | 丁香六月欧美| 亚洲,欧美精品.| www.熟女人妻精品国产| 精品一品国产午夜福利视频| 自拍欧美九色日韩亚洲蝌蚪91| 亚洲美女黄片视频| 极品人妻少妇av视频| 亚洲av成人不卡在线观看播放网| 久久精品亚洲av国产电影网| 亚洲欧美日韩另类电影网站| 交换朋友夫妻互换小说| 曰老女人黄片| 精品福利永久在线观看| 欧美精品啪啪一区二区三区| 性色av乱码一区二区三区2| 9191精品国产免费久久| 90打野战视频偷拍视频| 色播在线永久视频| 午夜福利免费观看在线| 丝袜美足系列| 露出奶头的视频| 黑人操中国人逼视频| 久久国产精品大桥未久av| 咕卡用的链子| 国内毛片毛片毛片毛片毛片| 一本久久精品| 狠狠婷婷综合久久久久久88av| 亚洲五月色婷婷综合| 亚洲人成电影免费在线| 久久精品熟女亚洲av麻豆精品| 亚洲欧美日韩高清在线视频 | 麻豆乱淫一区二区| 亚洲伊人久久精品综合| 国产欧美日韩一区二区三| 男男h啪啪无遮挡| 亚洲黑人精品在线| 欧美 日韩 精品 国产| 大码成人一级视频| 亚洲精品美女久久av网站| 不卡av一区二区三区| 欧美乱妇无乱码| 国产亚洲精品第一综合不卡| 久久国产精品人妻蜜桃| 国产伦理片在线播放av一区| 久久国产精品人妻蜜桃| 人妻一区二区av| 久久热在线av| 99re6热这里在线精品视频| 国产成人av激情在线播放| 十八禁网站网址无遮挡| xxxhd国产人妻xxx| 国产精品.久久久| 99久久99久久久精品蜜桃| 亚洲av电影在线进入| 亚洲成人手机| 俄罗斯特黄特色一大片| 高清欧美精品videossex| 狠狠狠狠99中文字幕| 色老头精品视频在线观看| 国产精品久久久久久人妻精品电影 | 91九色精品人成在线观看| 亚洲精华国产精华精| 好男人电影高清在线观看| 婷婷丁香在线五月| 19禁男女啪啪无遮挡网站| 激情在线观看视频在线高清 | 一区二区av电影网| 精品人妻在线不人妻| 国产av国产精品国产| 久久中文字幕一级| 中文字幕精品免费在线观看视频| 成年人免费黄色播放视频| av国产精品久久久久影院| 一二三四社区在线视频社区8| 窝窝影院91人妻| 俄罗斯特黄特色一大片| 高清欧美精品videossex| 亚洲av第一区精品v没综合| 一边摸一边抽搐一进一出视频| 亚洲av欧美aⅴ国产| 一级黄色大片毛片| 亚洲熟女精品中文字幕| 午夜精品国产一区二区电影| 精品一区二区三区四区五区乱码| 亚洲美女黄片视频| 大片电影免费在线观看免费| 日本精品一区二区三区蜜桃| 久久国产亚洲av麻豆专区| 国产一区二区激情短视频| 亚洲成人手机| 久久中文字幕人妻熟女| 免费在线观看视频国产中文字幕亚洲| 亚洲av欧美aⅴ国产| 少妇 在线观看| 日本av免费视频播放| 天天躁夜夜躁狠狠躁躁| 国产97色在线日韩免费| 日韩精品免费视频一区二区三区| 久久久精品94久久精品| 亚洲成av片中文字幕在线观看| 久久 成人 亚洲| 久久国产精品大桥未久av| 欧美人与性动交α欧美软件| 久久香蕉激情| 日韩欧美一区二区三区在线观看 | 精品福利观看| 操美女的视频在线观看| 男女床上黄色一级片免费看| 激情在线观看视频在线高清 | 咕卡用的链子| 制服诱惑二区| 午夜福利乱码中文字幕| 咕卡用的链子| 久久久国产成人免费| 久久久精品免费免费高清| 咕卡用的链子| 麻豆国产av国片精品| 国产av一区二区精品久久| 一本综合久久免费| 99精品久久久久人妻精品| 热99久久久久精品小说推荐| 夜夜骑夜夜射夜夜干| 亚洲av国产av综合av卡| 日韩免费av在线播放| 亚洲第一欧美日韩一区二区三区 | 人妻久久中文字幕网| a级片在线免费高清观看视频| 久久人人爽av亚洲精品天堂| 91成年电影在线观看| 亚洲自偷自拍图片 自拍| 男女之事视频高清在线观看| 成年版毛片免费区| 国产欧美日韩一区二区精品| 亚洲国产毛片av蜜桃av|