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合金钢轧辊激光快速熔凝组织及性能研究
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摘要
轧辊是轧机的主要部件,也是生产中的主要消耗部件之一,尺寸大,价格比较昂贵,降低辊耗是生产中面临的一个很重要的问题。而采用激光加热的方法对金属材料进行快速凝固加工可制备出具有优异物理化学性能的微晶、非晶、准晶等非平衡亚稳组织,从而获得成分、组织及性能完全不同于零件基材、具有细小均匀快速凝固非平衡组织特征,可显著提高材料的性能。因此,进行“轧辊激光表面快速熔凝组织与性能的研究”具有很重要的实际意义和理论价值。
     本文通过采用5KW横流CO_2激光器对轧辊钢进行了激光熔凝试验,对熔凝过程对材料的组织、硬度、裂纹敏感性等进行了探讨;并采用大型有限元软件SYSWELD对激光熔凝过程进行了数值模拟,分析了温度场、应力场、硬度场变化规律。
     激光熔凝后,改性层显微组织可分为三个区:熔凝区、热影响区和基体。熔凝区主要由胞状晶+树枝晶组成,显微组织为马氏体、残余奥氏体和弥散分布的碳化物,热影响区主要由马氏体、残余奥氏体和碳化物组成。轧辊激光快速熔凝处理,沿层深方向硬度呈现梯度分布,熔凝层硬度稍有降低,热影响区出现硬度最大值,且当功率和光斑直径一定时,熔凝层深与扫描速度成反比。激光快速熔凝处理的宏观质量受扫描速度的影响很大,随着扫描速度的增大,表面裂纹敏感性增加,熔池的深度逐渐减小,而熔池宽度逐渐减小,得到的△H/W之比逐渐增大。激光快速熔凝单道扫描在熔凝区两侧均出现裂纹,进行搭接处理,当搭接量较小时在搭接区都出现了裂纹,搭接量达到光斑直径的一半时,搭接区域组织较为均匀且无裂纹出现,搭接区存在回火软化现象,硬度值下降。
     建立了激光宽带三维体热源模型,利用此热源模型能够模拟出符合深/宽尺寸情况的激光熔凝熔池形状,计算得到的激光熔凝区宽度和深度与实测值符合得较好,验证了模型的适用性。该模型对激光宽带加工温度场的模拟结果更符合实际。
     根据数值模拟的结果,激光熔凝过程是一个快速加热、快速冷却的过程,其温度变化率可达10~4℃/s数量级;经过激光熔凝后的材料硬度得到了显著的提升,中心部位的硬度小于熔凝区其它区域的硬度;熔凝区的残余应力为压应力,而热影响区则存在着较大的拉应力,成为形成裂纹的危险区域;碳含量的不均匀变化导致熔凝区的压应力分布不均。
     激光熔凝加工后得到不同工艺参数下熔凝区的不同残余应力分布。熔凝层表面和层深方向的Mises应力和平均应力分布规律相似,扫描速率过大或者过小,应力幅值均有所降低。当激光束扫描速率V=600~1000mm/min时,熔凝区得到了残余压应力分布,有利于提高工件的使用性能。激光熔凝区残余应力的产生与熔凝区材料发生组织转变,得到了硬脆的马氏体相有关。
Roller is the most important part of the rolling mill, and also is one of the main consuming parts during production, which has a large size and is very expensive, so reducing the consuming of the roller is an important problem in the production. Fast solidification process on the metal material by Laser heating technology can produce the non-equilibrium and metastable microstructures such as minicrystal, amorphous, quasi-crystal and so on, which is fine, uniform and metastable, and different from the matrix in elements, microstructures and properties, and then improves the properties of the materials. Therefore, studying on "Research on the microstructures and properties of roller by laser surface melting" is provided with a large practical significance and theoretical value.
     In this paper laser surface melting (LSM) is performed on the roller steel with a 5kW continuous wave CO_2 laser, and the microstructures, hardness and cracking are studied; also numerical simulation was carried out about the process of laser surface melting with the software SYSWELD, what's more, the varying regularities of temperature field, stress field and hardness field has been achieved.
     After laser surface melting, the sectional region on roller steel is divided into three distinctive zones, namely, laser melted zone, heat-affected zone (HAZ) and the substrate, which can not be delimited strictly. Laser melted zone is composed of cellular structure and dendritic crystals, and the microstructures are martensite, residual austenite and disperse carbide, also HAZ is mainly composed of martensite, residual austenite and carbide. Hardness of the roller after laser surface melting has a gradient distribution along the depth of melted zone, which in melted zone is lower after laser surface melting, however, the maximum value appears at HAZ. And while the laser power and the diameter are given, the depth of the melted zone has an inversely-proportional relationship with the velocity. The macroscopic quantity is influenced by scanning velocity significantly. With the increase of the scanning velocity, the cracking susceptibility increases, and the depth of melted zone decreases gradually as well as the width, so the ratio ofΔH and W increases gradually. Cracks were found on both sides of molten pool under the experimental conditions. While overlapping and with a small overlapping fraction, cracks appear in the overlapping, but when the overlapping fraction reaches half of the diameter of the spot, and also the microstructures in the overlapping are uniform and free of cracks, but the softening occurs with the hardness decreasing.
     There-dimension model of the laser source was established, and the shape of the laser surface melting according with the depth and width can be simulated, which is concordant with the calculated values, so the model is applicable. The temperature field can be simulated with the model concordant with practice
     According to the results of simulation, laser surface melting is a process of quick heating and cooling, in which the temperature can reach 10~4℃/s; the hardness of the material after laser surface melting increases, and in the center of the melted zone is larger than that of the other zones; and the residual stress is compressive in the melted zone, but which is tensile at HAZ, being the dangerous zone of cracking; the non-uniform variation of the carbon content results in the non-uniform distribution of compression stress in the melted zone.
     Different distributions of residual stress appear under different progress parameters by laser surface melting. The distributions of the Mises stress and average stress in the surface of melted zone are similar to that along the depth of the melted zone, that is to say, the value of stress will decrease when the scanning velocity is too larger or too small. While the scanning velocity varies from 600mm/min to 1000mm/min, compression stress can be obtained which is in favor of improving the property of the workpiece. The generation of the compression stress in the melted zone is related to the hard brittle martensite created during the microstructural transformation
引文
1 任喜来.冷轧辊的失效分析及其修复.轧钢,2002,19(13):45-47
    2 姚玉玺,文成秀.1150初轧机轧辊脆性断裂研究.机械科学与技术,1998,17(5):801-803
    3 张建宇,杨久霞,张进锋,冯伟.轧辊表面激光强化的应用分析与展望.冶金设备,2002.6:29-30
    4 Li ZHOU,Da-le SUN,Chang-sheng LIU and Qiong WU.Fatigue Behavior of High Speed Steel Roll Materials for Hot Rolling by Laser Impacting.Journal of Iron and Steel Research,International,Volume 13,Issue 6,November 2006:49-52
    5 Hongshuang Di,Xiaoming Zhang,Guodong Wang and Xianghua Liu.Spheroidizing kinetics of eutectic carbide in the twin roll-casting of M2 high-speed steel.Journal of Materials Processing Technology,Volume 166,Issue 3,20 August 2005:359-363
    6 Yichuan Pan,Hua Yang,Xiangfa Liu and Xiufang Bian.Effect of K/Na on microstructure of high-speed steel used for rolls.Materials Letters,Volume 58,Issues 12-13,May 2004:1912-1916
    7 魏金山,李超.GCr15钢激光淬火层的奥氏体晶粒尺寸.金属热处理,1995,3:11-13
    8 梁工英,李成劳,周家瑾.激光表面熔凝处~$ZMSil2合金的亚结构特征.金属学报,1994,30(10):B472-B475
    9 王贵,王建国,周新初,麻永林.轧辊钢激光熔凝处理组织及性能研究.金属热处理,2001,26(3):35-37
    10 王贵,周新初,顾永强,等.搭接参数对激光熔凝处理层显微组织和性能的影响.金属热处理,2001,26(6):16-18
    11 王长贵,李志远,黄安国.75CrMnMo铸钢轧辊激光熔凝强化的组织及性能分析.钢铁,2004,39(9):61-63,68
    12 许巧玉,于青,李铸刚,等.70Mn2Mo铸钢热轧辊的激光表面强化.金属热处理,2002,27(8):32-34
    13 杨森,黄卫东,刘文今,等.激光表面快速熔凝过程中熔区组织重构.应用激光,2001,21(4):225-228,224
    14 姚建华,陈智君,熊缨,等.40Cr钢大面积激光相变硬化中的硬度分布特征.浙江工业大学学报,2002,30(4):3 19-322
    15 姜幼卿,黄安国,周龙早,等.冶金用铸钢轧辊激光熔凝强化的研究和应用.中国机 械工程,2006,17(16):1756-1759
    16 蔺荣岩,汪家道,孔宪梅,等.激光合金化冷轧辊的技术研究.新技术新工艺,2002,(1):30-31
    17 K.A.Gschneidner,K.Nancy.Thermo-chemistry of the Rare Earths.Report Is-RIC-6,1973
    18 余宗森.稀土在钢铁中的应用.冶金工业出版社.1987:251-262
    19 钟华仁.钢的稀土化学热处理.国防工业出版社.1998:33-35
    20 高瑞珍,王明华.稀土元素对45钢组织和性能的影响.中国稀土学会第一届稀土在钢中应用学术会议论文集,1982:84-88
    21 沈以赴,陈继志,冯钟潮,等.稀土在激光熔覆涂层中的分布和行为.中国稀土学报,1997,15f4):344-349
    22 刘桂芝,刘庄,吴肇基,等.大型冷轧辊模拟件残余应力的研究.东北电力学院学报,1994,14(1):25-31
    23 刘宗昌.我国机械类热处理现状及发展.包头钢铁学院学报,1998,17(3):20-23.
    24 李会山,杨洗陈.激光再制造过程熔池温度场的数值模拟.天津工业大学学报,2003,22(5):9-12
    25 H.E.Cline,T.R.Anthony.Heat treating and melting material with a scanning laser or electronbeam.J.Appl.Phys.,1977,48(9):3895
    26 T.Chande,J.Mazumder.Two-dimensionnal,transient model for mass transport in laser surfacealloying.J.Appl.Phys.1985,57(6):2226
    27R.L.AppsandD.R.Milner.WeldingJ.,1971,(50):163-173
    28 M.Von allmen.Laser drilling velocity in metals.J.App.phy.,1976,47(12):5460
    29 C.Chan,J.Mazumder,M.M.Chen.A two-dimensional transient model for convection in laser melted pool.Metall.Trans.A,1984,15A:2175
    30 Picasso M,Hoadley AF A.Int J Meth Heat Fluid Flow,1994,4:6
    31 M.K.Chun,K.Rose.Interaction of High-intensity laser beams with metals.J.Appl.Phys.,1992,71(6):2560
    32 Biswajit Basu.Numerical study of steady state and transient laser melting problems-Ⅰ.Characteristics of flow field and heat transfer,int,J.Heat Mass Transfer,1990,33(6):1149
    33 A.Kar,T.Rockstroh,J.Mazumder.Two-dimensional model for laser-induced materials damage.Effects of assist gas and multiple reflections inside the cavity,J.Appl.Phys.,1992,71(6):2560
    34 T.R.Anthony,H.E.Cline.Surface rippling induced by surface-tension gradients during laser surface melting and alloying.J.Appl.Phys.,1977,48(9):3888
    35 M.K.Chun,K.Rose.Interaction of High-intensity laser beams with metals.J.Appl.Phy.,1970,41(2):614
    36 H.E.Cline,T.R.Anthony.Heat treating and melting material with a scanning laser or electronbeam.J.Appl.Phys.,1977,48(9):3895
    37 K.Lu,Y.Li.Homogeneours nucleation catastrophe as a kinetic stability limit for superheated crystal.Physical Review Letters.1998,8(20):4474
    38 刘晓魁.激光相变硬化的数值模拟:[硕士学位论文].西北工业大学,陕西:2003
    39 管一弘.激光淬火温度场及材料性能的数值模拟.中国激光,1999,Vol.26(3):45-47
    40 M.Davis.Heat Hardening of Metal Surface with A Scaning Laser Beam.GRA,1984,84:19
    41 李俊昌.激光热处理优化控制研究.北京:冶金工业出版社,1995
    42 W.Cerri,L.G.P.Mored.D.Schuocker,et al.The important role of modeling in laser hardening process design in High power lasers.Belingham,WA,Society of Photo-optical instrumentation engingeers,1987
    43 邓忠民,赵亦兵,洪友士.激光熔凝覆盖率对材料表面力学性能影响的模拟.固体力学学报,2002,23(2):212-216
    44 姚国凤,陈光南.激光熔凝加工中瞬时温度场及残余应力数值模拟.应用激光,2002,22(2):241-244
    45 Janez Grum,Roman Sturm.Influence of laser surface melt-hardening conditions on residual stresses in thin plates.Surface and Coatings Technology 100-101(1998):455-458
    46 张建宇,高立新,杨久霞.辊面激光强化过程的瞬态应力分析.激光技术,2004,28(5):472-475
    47 Hernandez J,Vannes A.Laser surface cladding and residual stress.Proc.3rd Inter.Conf.On Laser in Manufacturing 3-5 June 1986 Paris France:181
    48 Pilloz M,Pelletier J M,Vannes A B.Residual stresses induced by laser coatings:phenomenological analysis and predictions.Mater.Sci,1992,27:1240-1244
    49 朱允明,张人诘.激光熔凝镍基热喷涂层残余应力的x射线衍射分析.中国激光,1993,A20(7):530-535
    50 U.K.Ma,R.Dekumbis.Controlling residual stress in laser cladding layer.LIM6,Birmingham,1989
    51 邹昌谷,王慧萍.新型激光吸收涂料产品研制与开发.热处理,2002,17(4):21-23
    52 刘其斌,李海,李珊,等.激光热处理用新型吸光涂料与碳墨汁的比较研究.现代机械,2003,(5):89-91
    53 国玉军,刘常升.激光表面硬化预涂层用89—1涂料的研究.激光技术,2002,26(4):252-254
    54 R.Komanduri,Z.B.Hou.Thermal analysis of laser surface transformation hardening —optimization of process parameters.International Journal of Machine Tools &Manufacture,2004,44:991-1008
    55 董秀花,郭俊良.激光强化处理参数对轧辊表面性能的影响.包头钢铁学院学报,2003,22(3):242-246
    56 张光钧,曹沛军.激光硬化对金属表面耐磨性影响的工艺研究.第六届全国激光热处理学术年会论文集:41-43
    57 J.C.Ion.Laser transformation hardening.Surface Engineering,2002,18(1)654
    58 骆有东.35CrMo旋转接头激光表面硬化技术的试验研究.农机化研究,2006,3(3):141-142
    59 Juan de Damborenea.Surface modification of metals by high power lasers.Surface &Coating Technology,1998,100-101(1-3):377-382
    60 张三川,晁明举,姚建铨.白口铸铁磨辊表面的激光淬火强化工艺.电加工与模具,2001,(2):42-44
    61 徐庆鸿,郭伟,田锡唐.激光扫描速度对激光熔覆宏观质量的影响规律.航天工艺,1997,(4):1-4
    62 Janez Grum,Roman Sturm.Microstructure analysis of nodular iron 400-12 after laser surface melt hardening[J].Materials characterization,1996,37:81-88.
    63 李炳均,吴化,李军,等.模具钢H13复合热处理的表面组织分析.金属热处理学报,1999,20(4):54-57
    64 姚辉,叶拥拥,陆传荣,等.缸体材料激光处理后的残余应力测试及分析.传动技术,2003,(3):39-41
    65 周继烈,程耀东.Ni基WC金属陶瓷激光熔覆开裂敏感性的试验研究.电加工与模具,2003,(4):32-34
    66 J.Grum,J.M.Slabe.Effect of laser-remelting of surface cracks on microstructure and residual stresses in 12Ni maraging steel.Applied Surface Science,2006,252(14):4486-4492
    67 赵玉珍,史耀武.Cr12激光表面熔凝处理的组织和性能研究.应用激光,2002,22(6):525-527
    68 B.C.柯瓦林科,等著.零件的激光强化[M].北京:国防工业出版社,1989:11-14.
    69 高传玉,周明.激光快速熔疑40Cr钢表面硬度与残余应力研究.应用激光,2002,22(1):19-22
    70 许越,纪红,陈湘.一种激光—稀土复合处理金属表面改性的新方法.高技术通讯,2000,(12):71-73
    71 Help of SYSWELD2004.ESI Ltd.
    72 蔡志鹏,赵海燕,鹿安理,等.串热源模型及其在焊接数值模拟中的应用.机械工程学报,2001,37(4):25-28,43
    73 王煜,赵海燕,吴甦,等.高能束焊接双椭球热源模型参数的确定.焊接学报,2003,24(2):67-70
    74 Goldak John,Chakravarti Aditya,Bibby Malcolm.New finite element model for welding heat source.Metallurgical transactions B(Process metallurgy),1984,15B(2):299-305
    75 莫春立,钱百年,国旭明,等.焊接热源计算模式的研究进展.焊接学报,2001,22(3):93-96
    76 张文钺.焊接传热学.北京,机械工业出版社,1989
    77 Tailor G A,Hughes M,Pericleous K.The application of three dimension finite volume method to the modeling of welding phenomena.Modeling of casting,welding and advanced colidification process Ⅸ,San Diego.2000:852-859
    78 SYSWELD培训教程.ESI公司提供
    79 葛继平,陈美龄,刘书华.Fe-2.88C白口铸铁激光熔凝处理的研究.表面工程,1996,2:25-28
    80 崔中圻.金属学与热处理,机械工业出版社,1999:264
    81 Bekir Sami Yilbas.Theoretical and Experimental Investigation Melting of Steel Samples into Lase.Optics and Lasers in Engineering 21(1997) 297-307
    82 L.X.Yang,X.F.Peng,B.X.Wang.Numerical modeling and experimental investigation on the characteristics of molten pool during laser processing[J].International Journal of Heat and Mass Transfer 44(2001)4465-4473
    83 姚国凤,陈光南.激光熔凝加工中瞬时温度场及残余应力数值模拟.应用激光,2003,22(2):241-244
    84 X.F.Wang,X.D.Lu,G.N.Chen,etc.Research on the temperature field in laser hardening.Optics & Laser Technology,2006,38:8-13
    85 Ahmet N.Eraslan.Von mises yield criterion and nonlinearly hardening variable thickness rotating annular disks with rigid inclusion.Mechanics Research Communications 29(2002) 339-350
    86 T.Mann.The influence of mean stress on fatigue crack propagation in aluminium alloys.International Journal of Fatigue 29(2007) 1393-1401.
    87 耿立艳,杨新岐,许海生,等.铝合金焊接接头疲劳评定的应力平均法.机械强度,2006,28(2):266-270
    88 J.Grum,J.M.Slabe.Effect of laser-remelting of surface cracks on microstructure and residual stresses in 12Ni maraging steel.Applied Surface Science 252(2006)4486-4492.
    89 张罡,武颖娜,梁勇,等.激光重熔工艺参数对热障涂层热震性能的影响.激光技术,2002,26(5):334-337
    90 蔡伟平.马氏体不锈钢激光表面熔化处理后的表层残余应力.中国激光,1994,21(3):228-229

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