保护气体对含铌不锈钢药芯焊丝347L脱渣性的影响.

1、收稿日期:2005-11-17保护气体对含铌不锈钢药芯焊丝 347L脱渣性的影响赵雁潮，魏琪，栗卓新，任春岭（北京工业大学材料学院，北京100022摘 要:研究了不同保护气体C O 2,Ar和混合气体（C O 2+Ar对347L型含铌不 锈钢药芯焊丝脱渣性的影响，并在相同的条件下对自制的 G DQA347L （3号与TFW - 347L 和 AT-Y 347L型两种不锈钢药芯焊丝的脱渣性进行了对比，深入分析了熔渣的宏观形态和微观组织对脱渣性的影响。结果表明，研制的G DQA347L焊丝在Ar气保护下的脱渣性最好，混合气体保护下的脱渣性次之,C O 2保护气体的脱渣性最差，由于C2气体在高温下变

2、为活性气体的，具有很强的氧化性，容易造成脱渣困难；三种焊 丝在不同保护气体下熔渣的微观组织形态所表现的规律基本上一致，在熔渣微观组织中，当其条带状体的尺寸长、面积大时，对脱渣有利。关键词:347L型不锈钢药芯焊丝；脱渣性;保护气体中图分类号:TG 422文献标识码:A文章编号：0253-360X (200611-077- 04赵雁潮脱渣性是衡量不锈钢药芯焊丝工艺性能的重要指标。347L型不锈钢药芯焊丝由于加入铌后，铌优先和氧结合生成含铌氧化物, 产生严重的粘渣。在采用不同气体保护时，由于保护气成分的变化影响熔渣的微观 结构，从而造成保护气体对焊丝的脱渣性能影响很大。因此 ，研究保护气体对含铌不

3、 锈钢药芯焊丝脱渣性的影响规律对调配新配方焊丝具有一定的指导意义。1试验方法文中采用对比的方法，选择市售的两种焊丝为TFW -347L (1号和AT -Y 347L (2号型不锈钢药芯焊丝与处于研究试验阶段的自制的 G DQA347L (3号焊丝在同等试验条件下进行试验。焊后测定不同保护气氛下的脱渣率；收集熔渣，采用0 LY M 2PUS PMG 30金相显微镜观察熔渣的微观组织，观察熔渣形貌，并研究了保护气体对347L不锈钢药芯焊丝的脱渣性的影响。使用的试验设备及焊接材料有 TFW -347L焊丝,AT -Y 347L焊丝,及自制的GDQA347L焊丝,焊丝直径均为1.2mm。三种保护气体：

4、纯Ar气,C O 2及Ar气(80% 和C O 2(20%混合气体。将200mm x 100mm x 10mm的18-8型不锈钢钢板置于试 验台上，在选定的工艺参数(见表1下进行焊接，采用直流反接焊枪倾角80°焊丝的 脱渣率的测定采用45°/形坡口内堆焊的落锤法试验，钢球重3kg ,堆表1焊接工艺参数Table 1 Weldi ng p arameters保护气体类型焊接电流I nA电弧电压U nv焊接速度v w n (m? m in -1气流量Q n (L? m in -1焊炬高度h n mmAr415201520CO 216018028300.

5、5152010l5昆合气体16018028300.515201015焊后立即用钢球砸击焊道背面，砸击5次。然后取渣制样，采用光学显微镜观察、分析熔渣的微观组第27卷第11期2006年11月焊接学报TRANS ACTI ONS OF THE CHI NA WE LDI NG I NSTIT UTI ONV ol.27 N O.11N ovember 2006织。脱渣率按式（1计算D =L -(L 0+0.5L 1+0.2L 2LX100%,(1式中:D为脱渣率（%;L为焊道总长度（mm ;L 0为未脱渣长度（mm ;L 1为严重粘 渣长度（mm ;L 2为轻微粘渣长度（mm 。2试验结果211不

6、同保护气体下的脱渣率不同保护气体下脱渣性试验结果见表2。1号,2号丝在不同的保护气下，脱渣率都较好；而不同的保护气体对3号丝脱渣率的影响比较大。表2脱渣率（质量分数,%Table 2 Slag detachability rate焊丝型号CO 2气体保护混合气体保护Ar气体保护TFW -347L 98.598.8100AT -Y 347L 98.298.699.4G DQA347L80.192.497.6212熔渣的宏观形态及类型焊接熔渣呈褐色，其宏观形态大致有两种：一种为瓷状,结构密实，致密度高；另一 种为多孔状，结构疏松，质地较脆。试验焊丝的脱渣类型有以下几种：第一种焊后熔渣 自动翘起，或

7、伴有成段的横向开裂，熔渣全脱落或分段脱落，焊缝成形好；第二种焊后 渣中出现松脆现象，能自动开裂成多段，轻轻敲击后就能脱落；第三种焊后经落锤冲击 后,大部分已与焊缝脱开，但在焊道的边缘偶尔会出现细微的粘渣，不容易去除。3号焊丝在Ar气保护下焊接综合工艺性能好，电弧稳定,焊缝成形较好，焊后渣成形致密少孔，经落锤冲击后能整块脱落，几乎没有飞溅；在Ar +C O 2保护气体下焊接后，渣覆盖好，渣属于第二种，用铁锤轻轻敲击焊缝熔渣表面，熔渣基 本能够块状脱落，飞溅很小;而在C O 2保护气下体焊接后，熔渣属于第三种虽然也易脱落，掉落的熔渣 多为碎片，但焊缝边缘偶有细微粘渣存在，和前两种状态相比飞溅稍大，

8、部分焊道渣壳 翘起较早，焊道表面有轻微氧化现象。1号,2号丝在不同的保护气下焊接，对脱渣的影响不大，区别在于用混合气体保护时焊接工艺性能优于在C O 2保护气下焊接,Ar气保护时焊道成形不好。213熔渣微观结构图1,2,3为1号,2号,3号丝在Ar气体保护、Ar +C O 2混合气体保护和C O 2气体保护下，熔渣内表面的微观形貌。可以观察到，虽然不同的保护气体对1号,2号 丝的脱渣性影响不大，但在显微镜下观察渣的微观结构与 3号丝熔渣的微观组织的变化规律相同，即在不同的保护气氛下其微观形态都有明显的差异。Ar气保护下熔渣的微观形态多为条带状，并且条带状体的尺寸长而宽、i yr迂 f F -i

9、 1. i ；/ijw厂 J 1 一 ; >1L 111 - 11 t 1,1 f' 'dll'7 '1 n ''-"，心面积大，有一定的方向性;而在混合气体保护时，微观组织中条带状体尺寸变小， 方向性减弱；C O 2保护时，熔渣的微观组织中条带状体更少，几乎无方向性可言。3分析与讨论焊丝脱渣性取决于三个因素：一是渣壳与焊缝金属间是否生成了尖晶石形氧化 物;二是焊缝金属与熔渣间线膨胀系数之差的大小；三是熔渣松脆情况。脱渣性好的 条件是:焊缝金属与熔渣间没有生成尖晶石氧化物，两者间线膨胀系数差值较大，熔渣 松脆13图1 TFW -3

10、47L焊丝在不同保护气体下熔渣的微观组织Fig.1 M icro structure of slag of TFW 2347L at differe nt shield ing ga se s078焊接学报第27卷-1/ -I1 r -r.-i/ Apji图2 AT-347L焊丝在不同保护气体下熔渣的微观组织Fig.2 M icro structure of slag of AT 2347L at differe nt shieldi ng ga seFig.3311JUG DQA347L在不同保护气体下熔渣的微观组织M icro structure of slag of G DQA347L

11、at differe nt shieldi ng ga se s保护气氧化势对脱渣性的影响从以上的试验结果可以看出，由于3号焊丝还处于研制过程之中，不同的保护气氛对其脱渣有明显的影响。在Ar保护下的脱渣性最好，混合气次之,而在C O 2保护气下的脱渣性就有待提高。1977年国际焊接学会根据各国使用的保护气普查结果，提出按保护气的氧化势进行分类，规定氧化指标=0 2%+1C O 2%。C O 2气体在电弧高温下分解 C O和O 2,电弧气氛中同时有 C O 2,O 2和C O 存在4。因此保护气的氧化势增强，会使焊丝中的Cr ,Nb ,AI等元素的烧损量增大，过渡系数减小，容易生成 尖晶石氧化物

12、，就会对焊丝的脱渣造成影响。O 2高温下进一步分解为游离态的氧原子，当温度为3000K时,C O 2保护气氛中 将含有将近20%的氧，所以C O 2气体在高温时有很强的氧化性，这样在焊接的过程中，很容易使铁氧化(1与C O 2直接作用Fe +C O 2(g =FeO +C O (g。(2与高温分解出的原子氧作用O +Fe =FeO。由于这个变化，气相中的氧可透过熔渣层传递给金属熔池，氧化铁在熔渣和金属 之间发生着强烈的交换，上述反应的进行使得焊缝表面氧化，生成一层FeO氧化膜，它 的晶格结构是体心立方晶格，它搭建在焊缝金属aFe的体心立方晶格上，这层氧化膜牢固地粘在金属表面上。由于渣中存在着能

13、形成尖晶石形化合物的二价(NbO ,M nO 等和三价金属氧化物（Cr 20 3,Al 20 3等,它们便形成具有体心立方结构的尖晶石形 化合物（Me0 ? Me 20 3,它们的体心立方晶格又搭建在焊缝金属表面上的氧化铁的 晶格上，与氧化铁牢固地结合在一起。这样，氧化膜就像粘结剂一样，把熔渣和焊缝金 属牢固的粘在一起，使熔渣很难清除。Ar气是惰性气体，焊接时既不参与化学反应,也不溶解于液态金属中，在保护气体中,氩弧是最稳定的。Ar中含0,H量很低, 所以Ar气保护时,可以认为氩气泡对熔池中的氧气来说就像一个小的真空室一样这一小的真空室的氧的分压几乎等于零，根据西华特定律6，熔池中的氧不断的向

14、氩气泡中扩散，随着氩气的溢出而被去除，有利于焊缝中的脱氧，因此不会烧损焊丝的合金，不利于生成尖晶石形氧化物，焊接冶金反应变得简单和容易控制，对焊丝第11期赵雁潮，等:保护气体对含铌不锈钢药芯焊丝 347L脱渣性的影响79的脱渣无疑有很大的好处。所以 Ar保护气氛下的脱渣性最好。Ar+C 02混合气体保护时，和纯Ar相比,保护气中的氧化势有所增强，焊缝中的 含氧量增高，会加大焊丝中的Nb,Mn,Si等元素的烧损量,过渡系数减小，这样就会对 焊丝的脱渣造成影响；但和纯C0保护相比，由于C 02在混合气体中所占的比例比较小，混合气体的氧化势增强有限，所以只是影响 到熔渣的生成状态，并没有造成粘渣。3

15、12熔渣微观组织对脱渣性的影响347L不锈钢药芯焊丝的渣系为钛型渣系，焊丝熔渣中钛酸盐主要以FeT iO5和CrT iO2等形态存在。这些组织按含 T i量的多少，可分为带状、条状等，其 主要特点是组织方向性强，结构密实,而组织形态的不同对熔渣的脱渣性有很大的影 响。由试验结果可知在熔渣组织中，当其条带状体的尺寸长、面积大时，脱渣性要 高。从图1-图中可以观察到，Ar保护下的微观结构是方向性强的条带状，强化了固 态渣纵向的连接。这类组织的存在，不仅使渣的线膨胀系数与焊缝的差别增大，还使 得熔渣在凝固过程产生较大的纵向拘束力，致使渣壳自动剥离。这是因为冶金结晶 理论表明7,结晶凝固时，晶粒粗大或

16、组织不均匀材料中所引起的内应力比晶粒细小 材料中的大。物相的不等轴度越大，方向性越强，所产生的内应力就越大，脱渣就越容 易。Ar保护气体下的渣组织粗大，冷却时收缩量比较大，因此渣和焊缝金属之间的线 膨胀系数差值较大，脱渣容易。采用混合气体和 C O保护气体焊接时，随着保护气氧化势的增强，渣中T iO含量减少和含铌氧化物含量增加，渣中FeT iO25与针状CrSiO2交织在一起，方向性消失，此时脱渣性恶化，焊缝边缘出现细微粘渣物;而且细小的组织很有可能造成渣的结构疏松和多孔，这种渣内部结合力太小，在 冷却过程中不能使渣壳与金属在表面上分离，往往是渣壳内部先破裂，一层薄渣粘在 焊缝上，这是造成其粘

17、渣的另一个原因。(1在三种不同保护气体下的不锈钢药芯焊丝的脱渣性不尽相同，在Ar气保护下的脱渣性最好，混合气保护下的脱渣性次之,C O2保护气的脱渣性最差。(2C O2保护气高温下变为活性气体，具有很强的氧化性，是造成3号丝脱渣困难 的主要原因。(3熔渣的微观组织对不锈钢药芯的脱渣性有很大的影响 ，在熔渣组织中，当其条 带状体的尺寸长、面积大时，冷却时收缩量大，对脱渣有利。参考文献:1 Li Zhuox in ,Che n Ban ggu,Lei W angjun,et al.S tudy on the effectsof the flux2cored com p ositi on on th

18、e slag detachability of basic self2 shielded flux2cored wireJ.Chi nese Journal of M echa nical Engin eeri ng,2001,37(10:75-80.2 孙咸,赵兴国，陆路.熔渣的化学成分和组织特征对脱渣性的影响J.太原工业大学学报，1993,24(3:30-36.3 张智，张文钺,陈邦固，等.药芯成分对自保护药芯焊丝焊缝脱渣性的影响J.材料科学与工艺,1997,5(4:40-45.4 唐伯钢，尹士科,王玉荣.低碳钢与低合金高强度钢焊接材料M.北京:机械工业出版社，1987. 曲 英.炼钢学原

19、理M.北京:冶金工业出版社,1980.殷树言.气体保护焊技术问答M.北京:机械工业出版社,2004.7周振丰，张文钺.焊接冶金与金属焊接性M.北京:机械工业出版社,1988.作者简介:赵雁潮，男,1980年出生,硕士研究生。主要从事不锈钢药芯焊丝的研 制及开发，发表学术论文2篇，申请专利1项。Email:zyc2702780焊接学报第27卷welded joi nt of a liquefied p etroleum gas sp herical tank made of 16MnR steel.The hydroge n diffusi on without the effect of we

20、ld ing residual stress was als o take n into acco unt and com p ared.This method pro vides a refere nee for masteri ng the criteri on of hydroge n in duced crack ing of welded join t.The result shows that un der the weld ing residual stress field,the hydroge n diffuses and accumulates toward the hig

21、her stress zon e,atta ining stability through a p eriod of time.There is a low hydroge n concen tratio n value around the heat affected zon e,where the residual stress gradie nt and concen tratio n gradie nt are formed,which can cause the hydroge n Ion g2ra nge diffu2 sio n to the high stress zone.K

22、 ey w ords: hydroge n diffusi on; weld ing residual stress ;nu2 merical simulati onEva po rati on loss of Mg eleme nt in 5A06alumi nium alloy elec2 tron beam w eldi ngW ANG X in g2ju n,H UANG Wen2rong, WEI Qi2lo ng,SHE N X ian 2Fe ng(l nstitute ofMach inery Manu factur2 ing T ech no logy,Ch ina Acad

23、emy of Engin eeri ng P hysics,M ian ya ng 621900,S ichua n,Chi na. p61-64Abstract: Distributi on of Mg in melt pool and its effect on mecha ni cal prop erties of weld are inv estigated in 5A06alumi nium al2 loy electro n beam weldi ng,a nd the in flue nee of weld ing p arameters on eva po rati on lo

24、ss of Mg eleme nt is an alyzed1The follow ing results are obta in ed:with the fusi on pen etrati on in creas in g,the content of Mg grows,which means that eva po rati on loss of Mg reduces,a nd micro2hard ness in creases;with in creas ing of accelerati ng v oltage and beam curre nt,the fusi on pen e

25、trati on in creases,a nd the eva po rati on loss rate of Mg decreases;a nd with in creas ing of weldi ng sp eed,the eva po ratio n loss rate of Mg reduces while fusi on pen etratio n dimin2 ishesll n order to mini mize eva po rati on loss of Mg,the con siderable in creas ing of accelerat ing v oltag

26、e,beam curre nt and weld ing sp eed are p referredlK ey w ords: 5A06alu minium alloy;electr on beam weld ing; eva po rati on loss ofMgForm ati on of circle b and in terface of thermos onic flip chi p bonding W ANGFu2lia ng,H AN Lei,ZH ONG Jue(School of Mecha ni cal a nd E lectro nicalEngin eeri ng,C

27、e ntral S outh Uni versity, Cha ngsha410083,Ch in a. p65-68,72Abstract: The therm os onic fli p chip bonding has bee n real2 ized un der the p ressure con stra in p atter n of fli p chip.F ragme nt of p ad,circle band and ridge have bee n observed on the bonding in ter2 face.The ridge in dicates hig

28、h bonding stre ngth,a nd fragme nt of pad in dicates rem ove of in ter face sur face,a nd the circle band in dicates distributi on of bonding stre ngth.With the FE A tool,the value and distributi on of stress were calculated un der differe nt bonding p hases, and the formatio n theory of the circle

29、band in ter face has bee n re2 vealed on the term of stress.The edge of bonding in ter face has better stress con diti ons for sur face rem ove and atom diffusi on, which the p rimary factor for the formatio n of circle band in ter face.A nd the therm o2s onic vibrati on cha nged the distributi on o

30、f stress and stress field,which caused the edge of bonding inter face in better stress con diti on s,a nd prom oted the formatio n of circle band in ter face.K ey w ords: therm os on ic flip chi p bonding;p ressure con2 strain p atter n; circle band in ter face;fi nite eleme nt methodTw o2dime nsion

31、 sp ectrum entropy feature for metal m agn etic memory sig nalDI X in 2jie1,LI Wu2she n1,BAI Shi2wu1,2, LI U Fa ng2mi ng1,2,X UEZhen 2kui2(1.School of Materials Scie nee and Engin eeri ng,T ianjin Un iversity,T ianji n300072,Chi na;2. Research In stitute of Pip eli ne,Chi na P etroleum C orporatio n

32、,La ng2 fan g065000,Hebei,Ch in a. p69-72Abstract: Metal mag netic mem ory(M M Mis one of the m ost poten tial non 2destructive test ing methods which can diag nose weld ing crack in early stage.The distributio n regularities of metal magn etic mem ory tw o2dime nsion sp ectrum entropy were inv esti

33、gated in tension test con diti on with the X70pip eli ne steel.Us ing the fea2 ture of am p litude sp ectrum entropy and brayce ntre freque ncy,the support vector mach ine method can dist in guish the differe nt state of stress concen trati on. With the detecti on in sta nce,the diag no stic method

34、of stress concen trati on state in weld was gain ed.Research shows that the stress concen trati on state within the ferromag netic ma2 terial can be iden tified by the tw o2dime nsion sp ectrum entropy distri2 buti on of M M M sig nal.l t is a base for utilizi ng M M M to detect the micro2cracks.K e

35、w w ords: weld ing crack;metal magn etic mem ory;tw o2 dime nsion sp ectrum entropyI nv estigati on of w eldi ng seam ide ntify ing b ased on force sensing in remoteteach ingLI U Li2ju n1,2,G AO H on g2mi ng2,ZH ANG G uang2jun 2,W U Li n2(1.S tate K ey Laboratory of Adva need Weldi ng P roductio n T

36、 ech no logy,Harb in In stitute of T echno logy,Harbi n 150001,Chi na;2.School of Materials Scie nce&En gi neeri ng,Har2 binUn iversity of Scie nee and T ech nology,Harbi n150080,Chi na. p73-76Abstract: Because the ide ntify ing p recisi on of weld ing seam based on visi on sensing is too low to

37、 meet the requireme nts of rem ote weld ing teach in g,the weldi ngseam ide ntify in g(WSIsystem is de2 sig ned based on force sensin g,which mainly in eludes the collect ing system of WSI sig nal,s oftware system,the force m odel and WSI arithmetic.The teach ing point is accurately calculated out b

38、y the shar p cha nges of six2dime nsional force based on the WSI arithmetic. The exp erime ntal results show that the WSI sp eed is in creased,a nd the p recisi on and efficie ncy of the rem ote teach ing is im pro ved by WSI arithmetic.K ey w ords: rem ote weld in g;rem ote teach in g;weld ing seam

39、 ide ntifyi ngforce sensingE ffects of differe nt shieldi ng gases on slag detach ability of type 347L flux2coredwire for sta in less steels con tai ning NbZH AO Y an 2chao,WEI Qi,LI Zhuo2xi n,REN Chun 2li ng(The C ol2 lege of Material Scie nee and En gi neeri ng,Beiji ng Un iversity ofIV MAI N T OP

40、ICS,ABSTRACTS&KEY W ORDS2006,V ol.27,N o.112006 ,Vol . 27 ,No. 11 TRANSACTIONS OF THE CHINA WELDINGINSTITUTION V Tech no logy , Beiji ng 100022 , Chi na . p77 - 80 Abstract : The effects of differe nt shield ing gases CO2 , Ar and mixture gases ( CO2 + Ar on the slag detachability of type 347L f

41、lux2cored wire for sta in less steels containing Nb were in vestigated. the branch is large. slag detachability ; shield ing gas istry of Educati on ,Beiji ng 100084 , China . p81 - 85 el. source model ; nu merical simulati on versity of T echno logy , She nya ng 110023 , Chi na . p86 - 90 ties of s

42、urfaci ng metalCHENGJia ng2bo 3 1 1 ,2 2 microhard ness test ing and wet sand rubber wheel abrasi on'f(test ing. gen eously in the surface of surfaci ng layer with cha nging magn etic It the hard p hases are in creas ing and distributi ng homo2 s Key words : electromag netic stirri ng ; p lasma

43、arc surfaci ng ; Fracture tough ness tests of D406A steel welded joi ntsZOU 1 ,2 1 1 , J ING Hon g2ya ng , HUO Li2xi ng (1. School of Material parameters and the wear resista nee of surfac ing metal is in creas ing on the slag detachability of three type flux2cored wires were in vesti2 gated. The re

44、sults showed that the best slag detachabilityof the better slag detachability was un der the shield ing gas of mixture shieldi ng gas ofCO2 . Because the CO2 gas tran sfer into active gas at gas ( CO2 + Ar , and the worst slag detachability was un der the ing gases is similar. It is ben efit for the

45、 slag detachability whe n the ment difficult on the slag detachability , and it is pro ved that the reg2 n eeri ng ,Shan ghai Jiaot ong Un iversity , Shan ghai 200240 , Chi na ; 2. ular of microstructure of three flux2cored wires un der differe nt shield2 trunk of the stri p2sha ped slag microstruct

46、ure is long and the area of variati on and rep rese nt the p hysical n ature duri ngFSW p rocess. Key words : type 347L flux2cored wire for sta in less steels ; Key words : frictio n stir weldi ng ; temp erature field ; heat Ting ( Dep artme nt of Mecha nical' be fully characterized by the t hea

47、tEngin eeri ng , Tsin ghua Uni versity , Abstract :The heat gen erati on mecha nism and dependency ofmaterial prop erties on temp erature can source models used now. Accordi ng to frictio n mecha nics , a heat gen erati on model based on yield stre ngth was established. The dinal in termitte nt alte

48、r native magn etic field on low carb on steel with metal was an alyzed using op tical metallogra phy , X2ray diffract ion , model can make auto2ada ptati on to material prop erty and temp erature RM of the Academy of Armored Forces Engin eeri ng , Beiji ng 100072 , tio n stir weldi ngHon g2ke ,SHI Q

49、in g2yu ,ZHAO Hai2yan ,LI LI , XU Bin 2shi , LIU sults in dicates that the accuracy is quite good for this new heat mod2 structure and prop erties of surfaci ng metal duri ng the app lied Ion gitu2 high temp erature with stro ng oxidizability which will make detach2 G DQA347L flux2cored wire was un

50、der the shieldi ng gas of Ar , andAbstract : The effect of electromag netic stirri ng on the micro2 with that of TFW2347L flux2cored wire and AT Y347L flux2cored in 2 the same con diti on. The effects of slag microstructure and macrosc op p lasma arc surfaci ng are inv estigated and discussed. The s

51、urfaci ng Comp aris on betwee n exp erime nt of thermal field and simulatio n re2Zhen g2jun , WU Y2xi ong ( 1. School of Material Scie nee and En gi2 i Chi na ;3. School of Material Science and Engin eeri ng , Shenyang Uni2 Slag detachability of home2madeG DQA347L ( 3 # was comp ared Auto2ada pting

52、heat source model for nu merical an alysis of fric2 Key Laboratory for Adva need Materials Process ing Tech no logy , Min2Effect of electromag netic stirri ng on microstructure and proper2 Ji2qua n ters are 3 A ,10Hz. The exp erime ntal results in dicate that the op ti2 mal effect of grain refi ning

53、 can be gained with the proper magn etic p arameters and electromag netic stirri ng can con trol the morp hology of stri p and hexag on distributi on without magn etic field are shifted to hard p hase in surfac ing metal. The morp hology of hard p hases with only hexag on alig nment distributi on wi

54、th proper magn etic field , metal greatly. which it can improve the hard ness and wear resista nee of surfac ing Ion gitud inal magn etic field Scie nee & Engin eeri ng ,Tianjin Un iversity , Tianjin 300072 ,Chi na ; College , Tianjin 300402 ,Chi na . p91 - 94 2.School of Electromecha ni cal and Automati on , Tianjin Professi onal Abstract: In accorda nee with the fracture tough ness test cord ing to the sta ndard , the sp ecime n with p refabricated fatigue crack has a sta ndard 3 points bending sha pe that has a recta ngular secti on of B B 闭：sp ecime n t