高纯Cr17钢板厚方向织构演变、成形性能及表面皱折

以高纯Cr17铁素体不锈钢为实验材料,对比研究了热轧不退火、退火两种工艺对其板厚方向织构演变、成形性及表面皱折的影响。采用金相显微镜、X射线衍射技术及背散射电子衍射技术观察两种工艺条件下的组织和织构演变。结果表明:成品板各层织构特征存在显著差异,这是由于低温轧制过程中沿板厚方向不同应变状态导致的热轧织构梯度遗传所致。与热轧不退火相比,热轧退火有利于成品板各层γ纤维再结晶织构增强,偏离{111}<112>组分的程度减弱,α纤维织构弱化;有利于弱化成品板的带状晶粒簇,促使晶粒簇分布均匀分散。     

超纯铁素体不锈钢织构演变与成形性能的研究

系统研究了超纯铁素体不锈钢(w(Cr)=17%)沿钢板厚度方向各层织构的演变规律和不同精轧温度对织构演变及成形性能的影响规律。采用X射线衍射仪分析了宏观织构演变。研究表明: 热轧及退火后, 钢板表层以剪切织构为主, 中心层由?和?纤维织构组成; 冷轧后, 各层均由较强的?纤维织构和较弱的?纤维织构组成; 冷轧退火后各层均形成?纤维再结晶织构。与高温精轧相比, 低温精轧有利于冷轧退火板?纤维再结晶织构的强化、偏离{111}<112>组分的程度降低, 从而显著改善冷轧退火板的成形性能。     

精轧温度对含铌、硼Cr17薄板成形性及表面皱折的影响

通过光学显微镜、X射线衍射及背散射电子衍射技术,研究了精轧温度,即高温精轧和低温精轧,对含Nb、B的超纯Cr17铁素体不锈钢薄板成形性及表面皱折的影响。结果表明：低温精轧有利于得到细小及均匀的冷轧退火组织。低温精轧有利于改善冷轧退火板织构的均匀性,促使冷轧退火板得到均匀、规则的γ纤维再结晶织构并形成更少的取向晶粒簇。因此,低温精轧是显著改善冷轧退火板成形性能及抗皱折性的有效工艺。     

Nb和Ti对超纯铁素体不锈钢凝固组织及表面起皱的影响

通过真空感应炉浇注实验和热力学软件分析研究了Nb、Ti稳定化元素和C、N间隙元素含量对超纯铁素体不锈钢凝固组织及晶粒簇的影响。结果表明,添加稳定化元素后实验钢的结晶区间变宽,通过控制稳定化元素和间隙原子含量使实验钢在凝固过程中析出较多TiN粒子,可以有效的提高凝固组织的等轴晶率。在充分退火条件下,与Ti单一稳定化实验钢相比,Nb、Ti复合稳定化实验钢中的晶粒簇较弱并具有较小的晶粒尺寸,有利于带钢的抗起皱性能。     

The sticking behavior of an ultra purified ferritic stainless steel during hot strip rolling

During hot rolling of ferritic stainless steels (FSSs), sticking can cause severe surface defects both on work rolls and strips especially for ultra purified FSSs with the total amount of carbon and nitrogen being less than 150 ppm. In the present paper, high temperature oxidization behavior of the ultra purified FSSs was characterized. A new experimental method was invented to simulate the sticking behavior of ultra purified 21%Cr FSS, by which specially designed specimens were hot compressed with different processing parameters to simulate hot strip rolling process. The specimens were surface conditioned prior to the simulation test, either by mechanically polishing or by pre-oxidization to form oxide scales with certain thickness. Observation on the cross-section of sticky regions indicated that cracks had been formed by cyclic heating and cooling during hot deformation had been acting as nucleation sites for sticking particles. The results indicated that oxide scale could avoid the direct contact between roll surfaces and rolled materials to help reducing the sticking occurrence. The temperature region for easy sticking occurrence in the ultra purified 21%Cr FSS has been measured to be from 900 to 1100 °C, which is enlarged as compared to other plain FSSs. The tendency for sticking occurrence decreased with increasing strain rate and decreasing the hammer or work roll surface roughness.     

终轧温度对443铁素体不锈钢组织、织构及成形性能的影响

通过光学显微镜、EBSD等分析技术,研究了终轧温度对443超纯铁素体不锈钢显微组织、织构、成形性能及抗表面起皱性能的影响规律。结果表明,降低终轧温度有利于促进443钢热轧退火态及冷轧退火态的再结晶,并使冷轧退火态组织更为细小均匀;降低终轧温度可有效强化冷轧退火态的γ纤维织构,是提高r值和杯突值、改善冷轧退火板成形性能、抗表面起皱性能的有效方式。     

热轧工艺对超纯Cr17铁素体不锈钢成形性能的影响

对一种铌、钛双稳定化的超纯Cr17铁素体不锈钢分别进行常规热轧和低温热轧,再依次进行相同的退火、冷轧及最终再结晶退火处理。对比研究两种热轧工艺对组织、织构演变及成形性能的影响规律。结果表明,与常规热轧相比,低温热轧能显著细化热轧组织、弱化α纤维织构并强化γ纤维织构,最终使冷轧退火板的γ纤维再结晶织构明显增强、偏离{111}<121>组分的程度显著降低,使珋r值增大、△r值减小。低温热轧是改善超纯Cr17铁素体不锈钢成形性能的有效途径。     

铁素体不锈钢表面皱折及其评价方法

皱折缺陷是中铬铁素体不锈钢发生较大塑性变形后容易出现的表面缺陷。这种缺陷往往破坏了不锈钢制品的外观,因此需要对制品进行研磨和抛光以消除皱折的影响。然而,额外的加工工序大幅增加了企业的生产成本,同时不可避免地造成了环境污染。那么,正确认识和评价铁素体不锈钢的表面皱折缺陷就显得非常重要。本文主要讨论界定铁素体不锈钢表面皱折缺陷,并简要介绍表面皱折缺陷的形成原因,进而厘清表面皱折缺陷的评价参数,最后针对已有测试方法存在的问题提出可供参考的解决办法。     

具有良好抗皱性能的SUS430型铁素体不锈钢冷板生产工艺技术的开发

着重于化学成分、连铸电磁搅拌、热轧、冷轧及退火工艺对SUS430型铁素体不锈钢抗皱性的影响规律进行了深入研究,在此基础上提出了获得良好抗皱性的工艺控制方法,使太钢大生产的SUS430型铁素体不锈钢冷板的抗皱性能达到B级以上,且γ值大于1.1。这些工艺控制方法以试验结果为依据,经生产实践证明是有效的。     

Characterisation of ferritic stainless steel by Barkhausen techniques

Magneto-acoustic emission (MAE) and magnetic Barkhausen noise (MBN) sensing techniques were developed and employed to characterise plastically deformed and heat-treated AISI 430 ferritic stainless steel samples. These results have been compared to the mechanical hardness, coercivity and residual stress of the samples. MAE and MBN were shown to decrease with increasing permanent material deformation. It was found that the inverse of MAE (absolute energy) and MBN (RMS) are linearly proportional to hardness. With increased deformation, the resultant change in dislocation density was found to effect material coercivity. It has been shown that the inverse of MAE absolute energy and MBN have an exponential relationship to the change in material coercivity. The results are explained in terms of the different mechanisms that effect dislocation-domain wall interactions. A new measurement parameter has been developed for microstructural characterisation called MAE absolute energy and has proved to be a useful quantitative method in MAE waveform measurement.     

Process technology for the continuous hot band annealing of 17%Cr ferritic stainless steel

As an alternative to time- and energy-consuming batch annealing, process technology for the continuous hot band annealing of 17%Cr ferritic stainless steel has been established. Process parameters (i.e., temperature and time) for the hot band annealing were optimized in the laboratory and, subsequently, plant trials were conducted. The impact toughness value of the annealed hot band was found to be the most crucial parameter to assess the cold rollability in the commercial run. When the hot bands were continuously annealed at 900 °C, the improved impact toughness values resulted in successful cold rolling to the desired thickness. The impact toughness value and subsequent cold rollability were found to be related to the formation of martensite volume%. Annealing the hot band in the lower temperature range of the two-phase (α+r) region (i.e., 900 °C) yielded the best result. Improvement in roping index has been reported as a result of the weakening of the texture of the continuous-annealed hot band.     

退火温度对21Cr-0.3Cu铁素体不锈钢组织性能的影响

通过光学显微镜、拉伸试验及背散射电子衍射,研究了退火温度对21Cr-0.3Cu超纯铁素体不锈钢显微组织、力学性能、成形性能和微观织构的影响。结果表明,试验钢经970 ℃退火时,晶粒细小且均匀,组织处于完全再结晶状态。退火温度低于970 ℃时,再结晶不完全;退火温度高于970 ℃时,再结晶晶粒异常长大,这两种情况均出现混晶组织。试验钢在970 ℃退火时,综合力学性能最佳,抗拉强度为473 MPa,屈服强度为315 MPa,伸长率35.7%。随退火温度的升高,试验钢的平均塑性应变比r_m值先增加后减少。当退火温度达到970 ℃时,r_m可以达到最大值1.82。γ纤维织构密度变化趋势与r_m值一致,退火温度为970 ℃时,γ纤维增强明显,此时其取向密度达到最大值f(g)=20.56,成形性能最佳。     

铁素体不锈钢板坯连铸机技术要点

结合铁素体不锈钢连铸过程高温凝固特性,拟新建的双流铁素体不锈钢板坯连铸机采用直弧型连续弯曲连续矫直的特殊技术,选用全程无氧化浇铸、大容量中间包、结晶器自动液面控制减少钢水中夹杂物;采用摩擦力监测、结晶器漏钢预报保证浇铸的连续性;合理设计动态一冷和二冷配水等提高铸坯表面质量,并设计采用电磁制动、低过热度浇铸、二冷电磁搅拌、二冷动态轻压下技术提高铸坯内部质量。     

B对Nb稳定化的超纯Cr17铁素体不锈钢性能的影响

以单独添加Nb及复合添加Nb和B的超纯Cr17铁素体不锈钢为试验材料,系统研究了微合金元素B对超纯Cr17铁素体不锈钢薄板的组织、织构和性能的影响。两种不同成分的坯料经相同热轧、冷轧及退火处理后,分别采用金相显微镜及X射线衍射技术观察两种成分下的组织和织构。研究结果表明,与单独添加Nb的相比,B的添加细化了再结晶组织,提高了再结晶温度;B的添加提高了成品板的强度,增加了成品板的Lüders应变;弱化了成品板的γ纤维再结晶织构,增加了强点偏离{111}〈112〉组分的程度,恶化了成品板的成形性能。     

退火温度对Cr17铁素体不锈钢成形性能的影响

对Cr17铁素体不锈钢冷轧钢板进行了不同温度的退火试验,利用显微组织观察、电子背散射衍射(EBSD)技术及力学性能试验探讨了退火温度对冷轧钢板的显微组织、微观织构与成形性能的关系。结果表明,随着退火温度的提高,α纤维织构变弱,取向密度逐渐降低,而γ纤维的织构强点为{111}<112>不变,取向密度逐渐增强,r值增加。当冷轧钢板在1040 ℃退火时,r值最大。     

加热温度对超纯铁素体含铜不锈钢热脆敏感性的影响

在Gleeble 3500热模拟机上对21Cr-1.4Cu超纯铁素体不锈钢铜进行高温拉伸试验,研究加热温度对试验钢铜脆敏感性的影响。采用扫描电子显微镜、激光共聚焦显微镜和能谱分析等方法对显微组织和化学成分进行了对比分析。结果表明：1300 ℃加热时,试验钢由于过烧产生了高温脆性。1150 ℃加热时,铜脆敏感性最高,产生铜裂。1200~1250 ℃加热时,铜脆敏感性较低,发生塑性变形。研究发现,加热温度为1150 ℃时,形成的氧化物开始呈液态,冷却后形成包裹状或共晶结构的硅酸盐细颗粒。这些脆性物质使晶界强度降低,结合松脆最后导致严重铜裂。     

Dissimilar spot welding of dual phase steel/ferritic stainless steel: phase transformations

Phase transformations in dissimilar resistance spot welds of dual phase steel and ferritic stainless steel are analysed. In contrast to a full martensitic microstructure predicted by the Schaeffler and Balmforth diagrams, a ferrite–martensite microstructure was observed in the fusion zone. The formation of ferrite phase in the fusion zone can be attributed to the rapid cooling rate of resistance spot welding, which suppresses the post-solidification ferrite–austenite transformation. The grain growth and martensite formation were main metallurgical features of the heat affected zone of ferritic stainless steel side. Microstructure gradient of heat affected zone in dual phase steel side was dictated by martensitic transformation. The effect of weld thermal cycle on the mechanical performance of the joint is discussed.     

纤维织构份额对430铁素体不锈钢表面起皱的影响

通过工艺控制得到含不同-纤维织构份额的430铁素体不锈钢样品,研究了-纤维织构份额对430不锈钢表面起皱程度的影响。结果表明：将冷轧430铁素体不锈钢在略低于再结晶温度下长时间保温,然后进行高温再结晶退火处理能够获得高份额的-纤维织构;随着显微组织中-纤维织构份额的提高,430铁素体不锈钢表面抗起皱性能增强。相比于{100}<011>和{112}<110>取向晶粒,-纤维取向晶粒平均塑性应变比高,并能在再结晶组织中较少形成取向相近的晶粒簇,减轻了铁素体不锈钢的表面起皱现象。     

罩式退火对430铁素体不锈钢成型性及抗起皱性的影响

研究了罩式退火(热轧卷板的退火)温度及保温时间对430铁素体不锈钢冷轧成品的织构、力学性能、成型性能及抗起皱性能的影响.结果表明,再结晶率随着罩式退火保温时间的延长而增加,但不能完全消除带状组织;罩退工艺对伸长率、成型性能及凸耳有明显的影响,较低的退火温度不利于改善伸长率及成型性能;合适的罩式退火工艺可产生更多理想的{ 111 ｝//ND-γ纤维织构,从而改善起皱现象.     

热处理对热轧不锈钢复合板组织性能的影响

对热轧奥氏体不锈钢复合板的热处理工艺进行了研究,利用金相显微镜对基层碳钢组织进行了观察,通过剪切、拉伸及冲击等试验对热处理前后的界面结合性能及力学性能进行了研究,并对复层不锈钢耐蚀性进行了测量.结果表明,热轧不锈钢复合板基层碳钢组织主要为铁素体和珠光体,强度较低,复层不锈钢的耐腐蚀性也较差;快冷处理后,复合板的强度增加,但由于快冷基层碳钢产生了大量的马氏体和贝氏体组织,塑性明显下降.回火后试样的塑性有明显改善,但仍不能满足使用要求.快冷+缓冷处理后,碳钢层组织为较细小铁素体、贝氏体和少量珠光体,不锈钢复合板力学性能符合标准要求.热处理后的不锈钢复合板抗剪切强度均＞ 380 MPa,界面结合性好;复层不锈钢的腐蚀速率从热轧后的36.2 g/(m2-h)降低到了2 g/(m2·h)左右.最佳热处理工艺为高温(1000℃)快冷+低温(500℃)缓冷.