镁钛复合处理对不锈钢凝固组织的影响及机制
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摘要
TiN是铁素体不锈钢有效的异质形核剂,但钢中大尺寸的TiN颗粒会对不锈钢板材表面质量带来不利影响。为此,提出依靠镁钛复合处理来细化TiN颗粒及控制宏观晶粒的方法。通过良好气氛保护的电阻炉试验,研究了添加Mg和Ti元素对于铁素体不锈钢宏观铸态组织和TiN颗粒细化效果的影响规律,并对其细化机理进行了详细分析。经研究得知,向铁素体不锈钢中添加了微量Mg和Ti元素后试样宏观等轴晶比例由37%提高至50%,TiN颗粒平均尺寸由处理前的5μm细化至2μm。镁钛复合处理后,钢液中形成的MgO和MgAl2O4与TiN之间的晶格错配度很低,分别为1.14和5.29,均属于有效形核范围,可以成为TiN异质形核核心,促进在晶内均匀析出更多的TiN。同时基于TiN与铁素体相之间的良好的晶格匹配关系,其进一步促进了δ-Fe形核,从而有效细化了铁素体宏观组织,这将有利于提高铁素体不锈钢力学性能和表面质量。
TiN is an effective heterogeneous nucleating agent for ferritic stainless steel.However,excessively grown TiN particles deteriorate the surface quality of the slab.Therefore,to refine TiN particles and control grain size by adding Mg and Ti elements is proposed.Through the experiment in resistance furnace with protective atmosphere,the refining effect of Mg-Ti addition on the microstructure of ferritic stainless steel and the refinement mechanism of TiN particles were theoretically analyzed.It was found that due to adding Mg and Ti elements,the equiaxed crystal ratio increased from 37%to 50%,and average size of TiN particles reduced from 5μm to 2μm.After Mg-Ti treatment,the lattice misfit of MgO and MgAl2 O4 with TiN was quite low,1.14 and 5.29,respectively,which were all in the effective nucleation range.It proved that MgO and MgAl2 O4 could become the heterogeneous nucleation core of TiN,which promoted the precipitation of TiN in the crystal.At the same time,based on the good lattice matching between TiN with ferrite phase,it further promoted nucleation of ferrite and effectively refined the macrostructure,which would be beneficial to improve mechanical properties and surface quality of ferritic stainless steel.
TiN is an effective heterogeneous nucleating agent for ferritic stainless steel.However,excessively grown TiN particles deteriorate the surface quality of the slab.Therefore,to refine TiN particles and control grain size by adding Mg and Ti elements is proposed.Through the experiment in resistance furnace with protective atmosphere,the refining effect of Mg-Ti addition on the microstructure of ferritic stainless steel and the refinement mechanism of TiN particles were theoretically analyzed.It was found that due to adding Mg and Ti elements,the equiaxed crystal ratio increased from 37%to 50%,and average size of TiN particles reduced from 5μm to 2μm.After Mg-Ti treatment,the lattice misfit of MgO and MgAl2 O4 with TiN was quite low,1.14 and 5.29,respectively,which were all in the effective nucleation range.It proved that MgO and MgAl2 O4 could become the heterogeneous nucleation core of TiN,which promoted the precipitation of TiN in the crystal.At the same time,based on the good lattice matching between TiN with ferrite phase,it further promoted nucleation of ferrite and effectively refined the macrostructure,which would be beneficial to improve mechanical properties and surface quality of ferritic stainless steel.
引文
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[14]梁高飞,宋长江,刘向阳,等.Au液异质形核价电子模型与基底触媒效用[J].稀有金属材料与工程,2005,34(10):1558.(Liang G F,Song C J,Liu X Y,et al.Valence electron model on heterogeneous nucleation of Au liquid and nuclei catalysis[J].Rare Metal Materials and Engineering,2005,34(10):1558.)
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[16]Bramfitt B L.The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron[J].Metallurgical and Materials Transactions,1970,1B(7):1987.
[17]Park J S,Lee C,Park J H.Effect of complex inclusion particles on the solidification structure of Fe-Ni-Mn-Mo alloy[J].Metallurgical and Materials Transactions,2012,43B(6):1550.
[18]潘宁,宋波,翟启杰,等.钢液非均质形核触媒效用的点阵错配度理论[J].北京科技大学学报,2010,32(2):179.(Pan N,Song B,Zhai Q J,et al.Effect of lattice disregistry on the heterogeneous nucleation catalysis of liquid steel[J].Journal of University of Science and Technology Beijing,2010,32(2):179.)
[19]潘宁,宋波,翟启杰,等.固态化合物对钢液非均质形核的触媒作用[J].金属学报,2009,45(12):1441.(Pan N,Song B,Zhai Q J,et al.Catalysis on heterogeneous nucleation of solid compounds in liquid steel[J].Acta Metallurgica Sinica,2009,45(12):1441.)
[20]李长荣,张凤珊,张迁,等.钢中第二相诱导铜元素析出的晶体学分析[J].钢铁研究学报,2016,28(3):63.(Li C R,Zhang F S,Zhang Q,et al.Crystallographic analysis on copper precipitating by second phases in steel[J].Journal of Iron and Steel Research,2016,28(3):63.)
[2]潘伟.氧化物冶金技术及应用研究[J].中国科技信息,2016(21):30.(Pan W.Oxide metallurgy technology and application research[J].China Science and Technology Information,2016(21):30.)
[3]Mizoguchi S,Takamura J.Control of oxides as lnoculants[C]//Proc Sixth Int Iron and Steel Congress.Tokyo,ISIJ,1990:598.
[4]尚德礼,吕春风.微合金钢中夹杂物诱导晶内铁素体析出行为[J].北京科技大学学报,2008,30(8):864.(Shang D L,LüC F.Precipitation behavior of inclusions-induced formation nucleation of intragranular ferrite in micro-alloyed steel[J].Journal of University of Science and Technology Beijing,2008,30(8):864.)
[5]Kato T,Ito Y,Kawamoto M,et al.Prevention of slab surface transverse cracking by microstructure control[J].ISIJ International,2003,43(11):1742.
[6]Kang Y,Mao W M,Chen Y J,et al.Influence of Nb content on grain size and mechanical properties of 18wt%Cr ferritic stainless steel[J].Materials Science and Engineering,2016,677A:453.
[7]Fu J,Nie Q,Qiu W,et al.Crystallography and growth mechanism of TiN in Fe-17Cr stainless steel during solidification[J].Journal of Materials Processing Technology,2018,253:43.
[8]田月美,陈兆平,徐迎铁,等.MgO-Al2O3-SiO2复合夹杂物对430不锈钢凝固组织的影响[J].钢铁研究学报,2014,26(6):61.(Tian Y M,Chen Z P,Xu Y T,et al.Effect of MgO-Al2O3-SiO2complex inclusion on the solidification structure of 430stainless steel[J].Journal of Iron and Steel Research,2014,26(6):61.)
[9]Kimura K,Fukumoto S,Shigesato G,et al.Effect of Mg addition on equiaxed grain formation in ferritic stainless steel[J].ISIJ International,2013,53(12):2167.
[10]Kang Y,Mao W M,Chen Y J,et al.Effect of Ti content on grain size and mechanical properties of UNS S44100ferritic stainless steel[J].Materials Science and Engineering,2016,677A:211.
[11]瞿勇,郑万,付学好,等.钙处理钛合金化钢中TiN析出行为[J].钢铁研究学报,2017,29(12):973.(Qu Y,Zheng W,Fu X H,et al.Precipitation behavior of TiNin Ti-alloyed steel with Ca treatment[J].Journal of Iron and Steel Research,2017,29(12):973.)
[12]Park J H.Effect of inclusions on the solidification structures of ferritic stainless steel:Computational and experimental study of inclusion evolution[J].Calphad-computer Coupling of Phase Diagrams and Thermochemistry,2011,35(4):455.
[13]Hultman L,Hesse D,Chiou W A.Mg-Ti-spinel formation at the TiN/MgO interface by solid state reaction:Confirmation by high-resolution electron microscopy[J].Journal of Materials Research,1991,6(8):1744.
[14]梁高飞,宋长江,刘向阳,等.Au液异质形核价电子模型与基底触媒效用[J].稀有金属材料与工程,2005,34(10):1558.(Liang G F,Song C J,Liu X Y,et al.Valence electron model on heterogeneous nucleation of Au liquid and nuclei catalysis[J].Rare Metal Materials and Engineering,2005,34(10):1558.)
[15]Koseki T,Inoue H,Fukuda Y,et al.Numerical simulation of equiaxed grain formation in weld solidification[J].Science and Technology of Advanced Materials,2003,4(2):183.
[16]Bramfitt B L.The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron[J].Metallurgical and Materials Transactions,1970,1B(7):1987.
[17]Park J S,Lee C,Park J H.Effect of complex inclusion particles on the solidification structure of Fe-Ni-Mn-Mo alloy[J].Metallurgical and Materials Transactions,2012,43B(6):1550.
[18]潘宁,宋波,翟启杰,等.钢液非均质形核触媒效用的点阵错配度理论[J].北京科技大学学报,2010,32(2):179.(Pan N,Song B,Zhai Q J,et al.Effect of lattice disregistry on the heterogeneous nucleation catalysis of liquid steel[J].Journal of University of Science and Technology Beijing,2010,32(2):179.)
[19]潘宁,宋波,翟启杰,等.固态化合物对钢液非均质形核的触媒作用[J].金属学报,2009,45(12):1441.(Pan N,Song B,Zhai Q J,et al.Catalysis on heterogeneous nucleation of solid compounds in liquid steel[J].Acta Metallurgica Sinica,2009,45(12):1441.)
[20]李长荣,张凤珊,张迁,等.钢中第二相诱导铜元素析出的晶体学分析[J].钢铁研究学报,2016,28(3):63.(Li C R,Zhang F S,Zhang Q,et al.Crystallographic analysis on copper precipitating by second phases in steel[J].Journal of Iron and Steel Research,2016,28(3):63.)