目的 对合金化镀锌板表面白亮带缺陷进行微观表征和形成机理探讨。方法 利用聚焦离子束场发射扫描电镜（FIB）、能谱（EDS）、电子背散射衍射（EBSD）及透射电镜（TEM）等手段,对合金化镀锌板表面白亮带缺陷的微观形貌、物相组成及界面状态进行了系统研究。结果 白亮带缺陷区域因Fe原子扩散不充分,残留大量纯Zn相,镀层较薄且表面低洼光滑;正常区域则因合金化反应完全,完全转变为Fe-Zn合金相,镀层较厚且表面粗糙。在光整过程中,镀层较薄的缺陷区域因压入量不足,低洼光滑的纯Zn相表面产生镜面反射而呈白亮色,镀层较厚的正常区域则被充分压平形成漫反射的暗灰色表面。镀层与基板界面分析进一步揭示,缺陷区域界面附近存在连续且致密的硅锰氧化层;而正常区域界面附近的硅锰氧化层不连续且相对稀疏。结论 这种硅锰氧化层连续性和致密性的差异,使得Fe原子向镀层厚度方向的扩散速率受到影响,进而影响合金化反应的速率和镀层的厚度,通过系统化分析和图示化表征进一步探讨了界面附近硅锰氧化层的连续性和致密性差异可能是白亮带缺陷形成的根本原因。
Abstract
The work aims to reveal the formation mechanism of white band defects on the surface of galvannealed (GA) steel. Macroscopically, these defects manifest as discontinuous bright white band parallel to the rolling direction, which not only severely impairs the product's appearance but may also adversely affects its subsequent application performance. The experimental material is GA steel, with a base plate of bake-hardening steel, a thickness of 1 mm, and a chemical composition (wt.%) including: C 0.001 5-0.002 5, Si<0.12, Mn 0.5-0.7, Cr 0.02-0.04, and Ti 0.02-0.06. The steel was annealed at 800 ℃, galvanized in a zinc bath containing 0.1%-0.15% Al, and then alloyed at 490-550 ℃. Microstructural and compositional analyses were conducted via a focused ion beam field-emission scanning electron microscope combined with an energy- dispersive spectrometer, quantitative compositional analysis of the micro-regions was carried out by electron probe microanalysis, phase identification was performed through electron backscatter diffraction, and the coating cross-section was precisely sectioned via focused ion beam, followed by characterization of the nanoscale interfacial structure through transmission electron microscopy and energy-dispersive spectrometer mapping. The phase composition, elemental distribution, and interfacial oxide layer characteristics of the defect area and the normal area were compared and analyzed.
The experimental results showed that in the white band defect region, the average Fe content was only 7.20wt.%, significantly lower than the 11.32wt.% Fe content in the normal region. The Fe content decreased by approximately 36wt.%, directly indicating that the alloying degree in this region was markedly insufficient. Phase analysis revealed that the defect region retained pure η-Zn phase (Zn), as well as Γ phase (Fe3Zn10), δ1p phase (Fe13Zn126), and a small amount of ζ phase (FeZn13). In contrast, the normal region consisted of Γ phase, δ1p phase, and a very small amount of ζ phase, with no residual pure Zn phase. Further TEM analysis revealed that at the interface of the defect region, there existed an Fe2Al5 inhibition layer with a thickness of less than 20 nm, while at approximately 150 nm from the interface, a continuous and dense Si-Mn oxide layer composed of "rice- grain-shaped" oxide particles closely arranged in a point-chain pattern was found, with its main components being O, Si, and Mn. At the interface of the normal region, no Fe2Al5 inhibition layer was observed, and the Si-Mn oxide layer was sparse and discontinuous, with a small number of round Si-Mn oxide particles distributed. The significant differences in interfacial structure provided crucial evidence for understanding the formation of the defects.
During the annealing process, Si and Mn in the substrate underwent selective oxidation, forming a continuous and dense Si-Mn oxide layer and a thinner Fe2Al5 inhibition layer in the defect region. Subsequently, during the alloying process, this oxide layer acted as a physical barrier, hindering the diffusion of Fe atoms into the coating, while the Fe2Al5 inhibition layer failed to decompose in time. Consequently, the Fe-Zn alloying reaction was retarded, resulting in a large amount of residual pure Zn phase and a thinner coating. During skin passing, the defect region with a thinner coating, due to insufficient compression, exhibited a smooth and low-lying pure Zn surface that produced specular reflection, appearing bright white. In the normal region, because the Si-Mn oxide layer was discontinuous, the diffusion of Fe atoms into the coating was almost unaffected, and the Fe2Al5 inhibition layer decomposed rapidly, thus forming a fully alloyed, thicker coating with no residual pure Zn phase. Therefore, the regional difference in the continuity and compactness of the Si-Mn oxide layer on the substrate surface may be the fundamental cause of the bright white band defects.
关键词
合金化镀锌板 /
白亮带缺陷 /
EBSD /
FIB /
TEM
Key words
galvannealed steel sheet /
white band defects /
EBSD /
FIB /
TEM
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1] 徐秀清, 王顺兴. 连续热镀锌工艺进展与展望[J]. 表面技术, 2007, 36(1): 71-74.
XU X Q, WANG S X.Development and Prospect of Continuous Hot-Dip Galvanized Process[J]. Surface Technology, 2007, 36(1): 71-74.
[2] DIONNE S.The Characterization of Continuous Hot-Dip Galvanized and Galvannealed Steels[J]. JOM, 2006, 58(3): 32-40.
[3] 张启富, 刘邦津. IF钢合金化镀锌板镀层相结构对其性能影响研究的新进展[J]. 钢铁, 2002, 37(12): 65-68.
ZHANG Q F, LIU B J.Recent Development in Study of Effect of Coating Phase Structure of if Galvannealed Steel Sheet on Its Properties[J]. Iron and Steel, 2002, 37(12): 65-68.
[4] MARDER A R.The Metallurgy of Zinc-Coated Steel[J]. Progress in Materials Science, 2000, 45(3): 191-271.
[5] 姜贵松, 刘少先, 葛志勇, 等. 合金化热镀锌板表面条状缺陷原因分析[J]. 轧钢, 2022, 39(4): 126-131.
JIANG G S, LIU S X, GE Z Y, et al.Causes Analysis of Strip Defects on the Surface of Galvannealed Sheets[J]. Steel Rolling, 2022, 39(4): 126-131.
[6] CHAKRABORTY A, MONDAL A, AGNIHOTRI S, et al.Investigation of a Surface Defect and Its Elimination in Automotive Grade Galvannealed Steels[J]. Engineering Failure Analysis, 2016, 66: 455-467.
[7] JORDAN C E, GOGGINS K M, MARDER A R.Interfacial Layer Development in Hot-Dip Galvanneal Coatings on Interstitial Free (IF) Steel[J]. Metallurgical and Materials Transactions A, 1994, 25(10): 2101-2109.
[8] JIN X Y, BI W Z, WANG L, et al.Root Cause Analysis of Pinhole Defects on Painted Galvanized Steel Panel[J]. Engineering Failure Analysis, 2020, 115: 104598.
[9] JIN X Y, WANG L, LIU X.Investigation of Streaky Mark Defect on Hot Dip Galvannealed IF Steel[J]. Corrosion Science and Technology, 2010, 9(3): 112-119.
[10] HONG M H, PAIK D J.Investigation of Streaky Marks Formed on the Coating Surface of Hot-Dip Galvannealed Steel Sheets[J]. Practical Metallography, 2022, 43(5): 237-251.
[11] 李远鹏, 张启富, 江社明. 连续退火镀锌气氛中氢含量对Mn-Si双相钢表面选择性氧化的影响[J]. 金属热处理, 2012, 37(3): 89-93.
LI Y P, ZHANG Q F, JIANG S M.Effect of Hydrogen Content on Surface Selective Oxidation of the Mn-Si Dual Phase Steel during Continuous Annealing and Galvanizing Process[J]. Heat Treatment of Metals, 2012, 37(3): 89-93.
[12] MCDEVITT E, MORIMOTO Y, MESHII M.Characterization of the Fe-Al Interfacial Layer in a Commercial Hot-Dip Galvanized Coating[J]. ISIJ International, 1997, 37(8): 776-782.
[13] LIU H C, LI F, SHI W, et al.Influence of Dew Point on the Interfacial Structure of Hot-dip Galvanized Steel[J]. Surface and Coatings Technology, 2012, 206(15): 3428-3435.
[14] SUZUKI Y, YAMASHITA T, SUGIMOTO Y, et al.Thermodynamic Analysis of Selective Oxidation Behavior of Si and Mn-Added Steel during Recrystallization Annealing[J]. ISIJ International, 2009, 49(4): 564-573.
[15] CHO L, LEE S J, KIM M S, et al.Influence of Gas Atmosphere Dew Point on the Selective Oxidation and the Reactive Wetting during Hot Dip Galvanizing of CMnSi TRIP Steel[J]. Metallurgical and Materials Transactions A, 2013, 44(1): 362-371.
[16] 李坤, 贾涓, 谢欢, 等. 镀锌工艺对高强IF钢热镀锌层显微组织的影响[J]. 材料热处理学报, 2017, 38(6): 156-163.
LI K, JIA J, XIE H, et al.Effect of Galvanizing Process on Microstructure of Hot Dip Galvanizing Coating of High Strength IF Steel[J]. Transactions of Materials and Heat Treatment, 2017, 38(6): 156-163.
[17] 李守华, 卢淋, 江海涛, 等. 合金化时间对热镀锌IF钢板镀层相结构的影响[J]. 金属热处理, 2015, 40(11): 136-140.
LI S H, LU L, JIANG H T, et al.Effect of Galvanneal Time on Coating Phase Structure of IF Galvanized Sheet[J]. Heat Treatment of Metals, 2015, 40(11): 136-140.
[18] 张浩, 丁志敏, 苏苇, 等. 合金化时间对热镀锌镀层相结构与结合力的影响[J]. 材料科学与工艺, 2015, 23(2): 98-102.
ZHANG H, DING Z M, SU W, et al.Effect of Alloying Time on Microstructure and Adhesive Force of Galvanizing Coating Layer[J]. Materials Science and Technology, 2015, 23(2): 98-102.
[19] WANG K K, HSU C W, CHANG L W, et al.Role of Al in Zn Bath on the Formation of the Inhibition Layer during Hot-Dip Galvanizing for a 1.2Si-1.5Mn Transformation- Induced Plasticity Steel[J]. Applied Surface Science, 2013, 285: 458-468.
[20] 周建虎, 李岩, 定巍, 等. 0.2C-5.0Mn-0.5Si-1.0Al中锰钢选择性氧化的热力学及动力学分析[J]. 金属热处理, 2024, 49(11): 17-22.
ZHOU J H, LI Y, DING W, et al.Thermodynamic and Kinetic Analysis of Selective Oxidation of Manganese Steel in 0.2C-5.0Mn-0.5Si-1.0Al[J]. Heat Treatment of Metals, 2024, 49(11): 17-22.
[21] CHO L, KIM M S, KIM Y H, et al.Influence of Minor Alloying Elements on Selective Oxidation and Reactive Wetting of CMnSi TRIP Steel during Hot Dip Galvanizing[J]. Metallurgical and Materials Transactions A, 2014, 45(10): 4484-4498.
[22] NI L L, LU J, WANG S Z, et al.Effect of Dew Point on the Selective Oxidation and Reactive Wetting of DP980 Steel during Hot-Dip Galvanizing[J]. Steel Research International, 2024, 95(6): 2300678.
[23] 李沅沅, 梁健, 熊自柳, 等. 新型热镀锌双相钢的合金成分对界面层和镀层结构的影响[J]. 材料研究学报, 2024, 38(6): 446-452.
LI Y Y, LIANG J, XIONG Z L, et al.Influence of Alloying Elements on Interfacial Layer-and Galvanized Layer-Structure of New Hot-Dip Galvanized Dual-Phase Steel[J]. Chinese Journal of Materials Research, 2024, 38(6): 446-452.
[24] 蒋光锐, 刘李斌, 王海全, 等. 退火工艺对C-Mn-Si高强钢表面选择性氧化行为的影响[J]. 材料热处理学报, 2017, 38(12): 96-100.
JIANG G R, LIU L B, WANG H Q, et al.Effect of Annealing Process on Selective Oxidation Behavior of C-Mn-Si High Strength Steel Surface[J]. Transactions of Materials and Heat Treatment, 2017, 38(12): 96-100.
[25] 金鑫焱, 储双杰, 彭俊, 等. 露点对连续退火0.2%C- 1.5%Si-2.5%Mn高强钢选择性氧化及脱碳的影响[J]. 金属学报, 2023, 59(10): 1324-1334.
JIN X Y, CHU S J, PENG J, et al.Effect of Dew Point on Selective Oxidation and Decarburization of 0.2%C- 1.5%Si-2.5%Mn High Strength Steel Sheet during Continuous Annealing[J]. Acta Metallurgica Sinica, 2023, 59(10): 1324-1334.
PDF(13002 KB)
渝公网安备 50010702501715号 渝ICP备15012534号-3
