摘要
在进行紫铜厚板的气体保护电弧焊时,热裂纹成为构件失效的主要原因。通常认为热裂纹的产生是由于在焊接过程中母材的氧化使晶界处偏聚Cu_2O与Cu的低熔共晶,在收缩应力下产生局部应力集中。本文首先从使用ERCu焊丝焊接紫铜厚板的研究出发分析氧元素在热裂纹中起的作用;降低氧含量对裂纹的影响以及氧对金属高温性能的影响。随后通过理论分析和试验研究指出ERCuNi焊丝可有效抑制热裂纹。
采用刚性拘束裂纹试验评定不预热GTAW焊接紫铜厚板的裂纹倾向。当ERCu焊丝为填充材料时,宏观裂纹几乎贯穿整条焊缝,在一次结晶的柱状晶晶间有微裂纹。研究表明,在柱状晶晶界处的Cu_2O与Cu的低熔共晶使晶界弱化,在应力的作用下开裂。由此可知ERCu焊丝中的脱氧元素Si、Mn、P的含量不足,无法去除焊缝中的氧。
为了考察降低焊缝含氧量对热裂纹的影响,自制了氩气仓,以实现良好的氩气保护,达到排除空气中氧的干扰的目的。并在这样的保护条件下用ERCu焊丝再次进行刚性拘束裂纹试验。焊缝表面无宏观裂纹产生。随后通过ERCu熔敷金属和ERCu焊丝高温性能的比较得出结论氧可以使脆性温度区间变宽。综上所述,对于紫铜厚板的GTAW,焊缝中的含氧量对热裂纹的产生与否起决定作用,因此可通过在焊丝中加足够多的脱氧元素来抑制热裂纹。
当用ERCuNi焊丝作为填充材料时,焊缝成形良好,表面裂纹率、断面裂纹率均为零。研究表明,Ni可与Cu_2O发生反应,生成Cu和NiO,在焊缝中起到脱氧的作用,进而抑制了Cu_2O与Cu的低熔共晶的产生,使热裂纹得到控制。同时由于ERCuNi焊丝的熔点高于母材熔点,使得焊缝凝固时最薄弱位置不在受热应力最大的焊缝中心,相当于减小了焊缝薄弱位置受到的应力,从而减小热裂纹倾向。
Hot cracking has became a main problem which plays a passive role in usage of copper, when we weld the copper plates with large demension. In general, the oxidation of base metal lead the low melting point of Cu_2O and Cu to get together in the boundary of crystals and stress concentration may occur in the effect of stress. In this paper, from the resarch on the rigid restraint cracking test using ERCu filler matal, we analyse the effect of oxygen on the hot cracking, the cracks in the condition of oxygen reducing greatly and the influence of oxygen on tensility in high temperature. In additon, ERCuNi is proved to suppress the hot cracking after the theoretical analysis and the experiments.
In the rigid restraint cracking test where ERCu is used as filler matal, the craking almost lies through all the joint. That’s because the deoxy element Si, Mn is insufficient, so in the boundary of the columnar crystals there is the low melting point of Cu_2O and Cu and the stress lead the boundary to crack.
A box for an anaerobic environment has been made and the rigid restraint cracking test in the box to make sure the effects of the tiny oxygen content on the cracking. The cracking has been suppressed well. Then from above all the results we can get conclusion that the oxygen content in the joint plays a crucial role in the existance of the hot cracking and we can use the filler metal which is added enough deoxy element to suppress the cracking for copper.
While ERCuNi is used in the rigid restraint cracking test, the joint is formed very well, and there is not a surface cracking and section cracking at all. Form thermodynamics anysis, we know Ni is more active than Cu, and it can deoxidize form the joint, then the low melting point of Cu_2O and Cu can be eliminated so that the cracking got be controlled. On the other hand, due to ERCuNi filler metal’s higher melting point, compared with Cu base metal, the weakest position doesn’t locate at the centre line of joint in the process of the solidification. So it can avoid the great tensile stress, and get little tendency of the hot cracking.
引文
[1] West E. G.铜和铜合金.陈兆盈[M].长沙:中南工业大学出版社,1987:2-14.
[2]百科robot.紫铜[DB/OL](2010.12.06). http://baike.baidu.com/view/ 511125.htm.
[3]季杰,马学智.铜及铜合金的焊接性[J].焊接技术,1999,(2):13-14.
[4]邹增大.焊接材料、工艺及设备手册[M].北京:化学工业出版社. 2001:604.
[5]闫久春,刘会杰.焊接冶金与焊接性[M].北京:机械工业出版社. 2007:232.
[6]李一楠.紫铜厚板GTAW热裂纹形成机理及抑制研究[D].哈尔滨工业大学,2010:2.
[7]杨志恒,李小兵.薄壁紫铜管的气焊.甘肃科技纵横[J],2004(05):67-76.
[8]魏福明.大厚度紫铜管的气焊[J].机械工人,1984(03):29-32.
[9] Salahaddin, D. Lutz. Metallophysical Processes in the Welding of Copper and Copper Alloys-welding Methods [J]. Welding and Cutting. 1988, (9):139-143.
[10] Spiller K R. Welding Copper by the Gas Shielded Arc Processes [J]. Metal Constr Brit Weld J. 1970, 2(2):45-53.
[11]闫久春.预热对紫铜厚板TIG焊接工艺性的影响[J].焊接,2005(09):25-38.
[12]张鹏.氩氮联合保护TIG焊在紫铜厚大件焊接上的应用[C]. 2001.中国陕西西安.
[13]郁雯霞,不预热紫铜TIG焊接的工艺研究[J].机械工程师,2008(11):128-130.
[14]李明利,刘占民.氩-氦和氩-氮TIG常温焊接厚板紫铜的试验分析[J].电焊机. 2006,(12):47-59.
[15] Kuwana T. Effects of Nitrogen and Titanium on Mmechanical Properties and Annealed Structure of The Copper Weld Metal By Ar-N2 Gas Metal Arc Welding[J]. Quarterly Journal of the Japan Welding Society, 1986,4(4):753-759.
[16] Kuwana T. Effects of Nitrogen and Titanium on Blow Hole Formation and Microstructure in Copper Weld Metal by Ar-N2 Gas Metal Arc Welding [J]. Quarterly Journal of the Japan Welding Society, 1984, 2(4):91-98.
[17] Littliton J, Lammas J, Jordan M. F. Nitrogen Porosity in Gas Shielded Arc Welding of Copper [J]. Welding Journal, 1974, 53(12):561-565.
[18] Kuwana T. Effects of Nitrogen and Titanium on Porosity and Micro -structure in Ar-N2 Gas Metal Arc Welded Copper [J]. Transactions of the Japan Welding Society. 1987, 18(2):69-76.
[19] Kobayashi T, Kuwana T, Ando M. Gas Metal-arc Welding of Copper [J]. Transactions of the Japan Welding Society. 1970, 1(1):61-71
[20]崔西会. Ni、Ti对紫铜氮氩气体保护GTAW焊接缺陷及微观组织影响[D].哈尔滨工业大学. 2005:14-50
[21] Yan Jiuchun, Li Yinan, Zhao Weiwei and Yang Shiqin. Heating Charac -teristics of Gas Tungsten Arc Welding of Copper Thick Plates with Shielding Gas of Argon, Helium or Nitrogen[J]. Key Engineering Materials. 2007, 353-358:2096-2099.
[22] Liu X S, Yan J C, Ma L, Li C F. Effect of Ti on Hot Cracking and Mechanical Performance of the Gas Tungsten Arc Welds of Copper Thick Plates[J]. Material and Design. 2010, 10:354-356
[23]马琳,Ti在紫铜厚板不预热GTAW中防裂机理研究[D]. 2009,哈尔滨工业大学.
[24]李一楠,刘雪松,闫久春.一种用于紫铜厚大构件熔化焊的铜合金焊丝及其制备方法[P].
[25]卓鸿逵.紫铜循环水管的钎焊[J].焊接,1958(09):30.
[26]郑文考.受压铜管钎焊对接[J].机械工人,1981(08):28.
[27]薛松柏,杜东. 600MW气轮发电机定子引线水管接头中频感应钎焊工艺研究[J].焊接. 1995, (4):17-19.
[28]钱红,李西恭,王增宏.高温钎焊紫铜管脆断原因分析[J].北京工业大学学报,1994(03):23-26.
[29]白津生,林嘉明.铜的GTAW钎焊工艺探讨[J].焊接技术. 1994(2):24-25.
[30]刘方军,王世卿,陈晓风等.大厚度紫铜电子束焊接的研究[J].中国机械工程,996(03):45-46.
[31] Durocher, Lipa M. TORE SUPRA Experience of Copper Chromium Zirconium Electron Beam Welding [J]. Journal of Nuclear Materials. 2002, 307-311(2):1554-1557.
[32] Durocher, Ayrault D. CuCrZr Alloy Hot Cracking during Electron Beam Welding [J]. Journal of Nuclear Materials. 2007, 367-370(2):1208-1212.
[33] Johnson L. D. Some Observations on the Electron Beam Welding of Copper [J]. Welding Journal. 1970, 49(2):55-60.
[34] Siewart T. A. Mechanical Properties of Electron Beam Welds in Thick Copper [J]. Advances in Cryogenic Engineering. 1990, 36(pt B) :1185-1192.
[35]邢丽.紫铜搅拌摩擦焊接工艺研究及接头组织分析[J].机械科学与技术,2003(06):986-988.
[36] Shen J. J, Liu H.J, Cui F. Effect of Welding Speed on Microstructure and Mechanical Properties of Friction Stir Welded Copper [J]. Materials and Design. 2010.
[37]《焊接裂纹金相分析图谱》.第一机械工业部哈尔滨焊接研究所[M].黑龙江.黑龙江科学技术出版社.1981:5.
[38] Cheng M, Chou C. P. Hot Cracking of Welds on Heat Treatable Aluminium Alloys. Science and Technology of Welding and Joining [J]. 2005, 10(3):345-347W.
[39] Pumthrey W. I, P. H. Jennings. A Consideration of the Nature of Brittleness at Temperatures above the Solidus in Casting and Welds in Aluminum Alloys [J]. Journal of Institute of Metals. 1948, 75:235-256.
[40] Borland J. C. Fundamentals of Solidification Cracking in Weld [J]. Welding and Metal Fabrication, 1979, 3: 99-107
[41] Rappaz M, Drezet J. M. A New Hot-Tearing Criterion [J]. Materials Science and Engineering A. 1999, 30(2): 449-455
[42] Niyama E, Some Considerations on Internal Cracks in Continuously Cast Steel [J]. Japan–US Joint Seminar on Solidification of Metals and Alloys, Japan Society for Promotion of Science, Tokyo. 1977:271-280
[43]方洪渊,董志波,许文立.随焊锤击防止薄板焊接热裂纹的工艺研究[J].焊接. 2002,(3):17-20.
[44]范成磊,方洪渊,陶军.随焊冲击碾压减小应力变形防止热裂纹应变场分析[J].焊接学报. 2004,25(6):47-50.
[45] Hernandez E, North D. H. The Influence of External Local Heating in Preventing Cracking during Welding of Aluminum Alloy Sheet [J]. Welding Journal. 1984, 3(6):84-90.
[46] Yang, P. Dong. A Hot-cracking Mitigation Technique for Welding High-strength Aluminum Alloy [J]. Welding Journal. 2000, 79(1): 9-17.
[47]王者昌.局部快冷在熔化焊中的应用[J].第九次全国焊接会议论文集.天津,1999: 66-69.
[48] Yang Y. P, Dong P. A Hot-cracking Mitigation Technique for Welding High-strength Aluminum Alloy [J]. Welding Journal. 2000, 79(1):9-17.
[49] Okamoto, Doi M, Hirano S. Fabrication of Backing Plate of Copper Alloy by Friction Stir Welding [C]. In 3rd International symposium on friction stir welding, Kobe, Japan, 2001, 9: 27-28.
[50] Zhang. Effect of Ti and Ta on Hot Cracking Susceptibility of Directionally Solidified Ni-based Superalloys IN792 [J]. Scripta Materialia. 2003, 48(6):677-681.
[51] Tang, S. Li S. Effect of Ca/Sr Composite Addition into AZ91D Alloy on Hot-crack Mechanism [J]. Scripta Materialia. 2005, 53(9):1077-1082.
[52] Ploshikhin W, Prikhodovsky A. Influence of the Weld Metal Chemical Composition on the Solidification Cracking Susceptibility of AA6056-T4 Alloys [J]. Welding Journal. 2006, 50(11-12):46-50.
[53] Ram J, Mitra T. K. Use of Inoculants to Refine Weld Solidification Structure and Improve Weldability in Type 2090 Al-Li Alloy [J]. Materials Science and Engineering A. 2000, 276(4):48-57.
[54] Mousavimg M. G., Cross C. E. Effect of Scandium and Titanium-boron on Grain Rrefinement and Hot cracking of Aluminum Alloy [J]. Sci Technol J 1999, 4(6):383-386.
[55] Li, Wang H. W, Wei Z.J, Zhu Z. J. The Effect of Y on the Hot-tearing Resistance of Al-5 wt% Cu Based Alloy [J]. Materials and Design. 2010, 31:2483-2487.
[56] Tang B, Li S. S. Effect of Ca/Sr Composite Addition into AZ91D Alloy on Hot-crack Mechanism [J]. Scripta Materialia. 2005, 53(9):1077-1082.
[57] Li M, Wang H. W, Wei Z.J, Zhu Z. J. The Effect of Y on the Hot-tearing Resistance of Al-5 wt% Cu Based Alloy [J]. Materials and Design. 2010, 31:2483-2487.
[58] Presedsky V. V, Vinogradov V. M. Fragmentation of Diffusion Zone in High-temperature Oxidation of Copper [J]. Journal of Solid State Chemistry. 2004, 177(2):4258-4268.