Effect of Lubrication during Hot Rolling on the Evolution of Through‐Thickness Textures in 18%Cr Ferritic Stainless Steel Sheet

Samples of a ferritic stainless steel sheet were hot‐rolled with and without application of lubrication. The effect of the different hot rolling processes on the evolution of texture and microstructure after hot rolling, cold rolling and subsequent recrystallization annealing was studied by means of macro and micro‐texture analysis and microstructure observations. After hot rolling, the sample rolled with lubrication displayed uniform rolling textures through the sheet thickness, while the sample rolled without lubrication showed shear textures in the outer layers of the sheet. The finite element method was employed to reveal the strain states during hot rolling with and without lubrication. The texture of the hot rolled sheet strongly influenced the formation of texture after cold rolling and final recrystallization and, therewith, planar anisotropy as well as the severity of ridging of the final gauge sheet. Hot rolling with lubrication was beneficial to the formation of strong recrystallization textures through the whole thickness layers leading to an enhanced planar anisotropy of the sheet. The recrystallized sheet hot‐rolled without lubrication displayed less severe ridging, however, which was attributed to a less frequent formation of orientation colonies in the outer thickness layers of the sheet.     

终轧温度对SUS444铁素体不锈钢抗起皱性能的影响

通过金相和EBSD等技术,研究了不同热轧终轧温度对SUS444铁素体不锈钢表面抗起皱性能的影响,讨论了热轧退火板表层所产生{110}001高斯织构的演变过程及其对抗起皱性能的影响。结果表明,860℃的终轧温度有利于SUS444铁素体不锈钢热轧及退火过程中由于受剪切应变而形成的{110}001高斯织构的形成,从而提高后续冷轧退火板表面的抗起皱性能。     

凝固组织对超低碳铁素体不锈钢皱褶和深冲性的影响

为了研究凝固组织对超低碳铁素体不锈钢成形性的影响,采用XRD和SEM等分析手段详细研究了材料的皱褶和深冲性能。研究发现:相对于等轴晶的试样,柱状晶试样展示了更高的皱褶高度,这主要同柱状晶试样中存在明显的晶粒簇有关;经最终的再结晶退火后,等轴晶试样也展示了更好的深冲性能,这同等轴晶试样形成了强烈的γ纤维织构紧密相关。     

Evolution of Through-Thickness Texture in Ultra Purified 17%Cr Ferritic Stainless Steels

 Texture inhomogeneity usually takes place in ferritic stainless steels due to the lack of phase transformation and recrystallization during hot strip rolling, which can deteriorate the formability of final sheets. In order to work out the way of weakening texture inhomogeneity, conventional hot rolling and warm rolling processes have been carried out with an ultra purified ferritic stainless steel. The results showed that the evolution of through-thickness texture is closely dependent on rolling process, especially for the texture in the center layer. For both conventional and warm rolling processes, shear texture components were formed in the surface layers after hot rolling and annealing; sharp α-fiber and weak γ-fiber with the major component at {111}<110> were developed in both cold rolled sheet surfaces, leading to the formation of inhomogeneous γ-fiber dominated by {111}<112> after recrystallization annealing. In the center layer of conventional rolled and annealed bands, strong α-fiber and weak γ-fiber textures were formed; the cold rolled textures were comprised of sharp α-fiber and weak γ-fiber with the major component at {111}<110>, and inhomogeneous γ-fiber dominated by {111}<112> was formed after recrystallization annealing. By contrast, in the centre layer of warm rolled bands, the texture was comprised of weak α-fiber and sharp γ-fiber, and γ-fiber became the only component after annealing. The cold rolled texture displayed a sharp γ-fiber with the major component at {111}<112> and the intensity of γ-fiber close to that of α-fiber, resulting in the formation of a nearly homogeneous γ-fiber recrystallization texture in the center layer of the final sheet.     

00Cr17Ti热带退火对冷轧薄板表面皱折的影响

 通过对00Cr17Ti经热带退火、不经热带退火两种工艺的冷轧板进行对比试验,在分析显微组织、织构的基础上,研究了热带退火对00Cr17Ti薄板表面皱折的影响。研究结果表明：与不经热带退火相比,经热带退火能使成品薄板的表面皱折大大减轻,最大粗糙度仅为12.06 μm,平均粗糙度仅为1.27 μm。两种工艺的成品板表面皱折程度的不同是由两者在显微组织、微织构上的差异造成的。与不经热带退火相比,经热带退火的成品薄板在板厚方向具有较均匀的组织,板宽方向的织构梯度较小,晶粒簇较间断、细窄、分散,所有这些使得成品薄板的表面皱折大大减轻。为了满足用户对薄板表面质量的严格要求,对热轧带进行退火是很有必要的。     

退火温度对Nb+Ti双稳铁素体不锈钢织构的影响

利用电子背散射衍射技术(EBSD)研究了不同退火温度对Nb+Ti双稳铁素体不锈钢织构的影响。结果表明,随着退火温度的升高,α织构逐渐减弱,γ织构逐渐增强,当退火温度为920℃时,α织构基本消失,材料以γ织构为主。对再结晶织构的形成机制的探讨认为,铁素体不锈钢具有较强的γ织构归因于定向形核和选择生长共同作用的结果。     

精轧温度对超纯21%Cr铁素体不锈钢织构演变和成形性能的影响

研究了超纯21%Cr铁素体不锈钢精轧温度对织构演变规律和成形性能的影响。将粗轧板坯切块并在900~750℃范围内进行精轧,随后经相同的热轧退火、酸洗、冷轧及退火处理,系统研究了试样的宏观织构、显微织构和成形性能的变化规律。结果表明:精轧温度对铁素体不锈钢的织构演变有重要影响,降低热轧精轧温度有利于增加热轧退火板中{111}再结晶织构组分;冷轧及冷轧退火板的织构分布具有明显的遗传性,热轧板中较高的{111}再结晶织构组分,促进了冷轧退火板中{111}再结晶织构的生成,从而提高了铁素体不锈钢的成形性能。     

Influence of the Cold Rolling and Annealing Sequence on the Ridging Behaviour of Ti‐Stabilized 18% Cr Ferritic Stainless Steel

The influence of the cold rolling and annealing sequence on the ridging resistance and the crystallographic texture distribution of AISI 439 type ferritic stainless steel was studied in order to determine optimal processing conditions for surface quality improvement. In the present study, the effect of two sequences of cold rolling and annealing were analysed: a single cold rolling and annealing, and an interrupted cold rolling with an intermediate and a final anneal. In the conventional single step cold rolling, the ridging resistance was found to deteriorate with increasing cold reduction ratio. For a fixed total cold reduction ratio in the two stage cold rolling, ridging was less pronounced when a higher reduction was applied in the second step. Band‐like clusters of grains with similar crystallographic orientations were observed in the mid‐thickness of sheets with severe ridging. The results show that severe ridging is related to the presence of band‐like clusters of 〈111〉//ND oriented grains. The two stage cold rolling was found to result in less band‐like clusters and an improved surface quality.     

初始凝固组织对Cr17铁素体不锈钢组织、织构及成形性的影响

 研究了初始凝固组织对Cr17铁素体不锈钢组织、织构、成形性的影响。分别对柱状晶、等轴晶铸坯进行热轧、退火、冷轧、退火实验。结果表明,等轴晶铸坯热轧试样在退火过程中的再结晶率高于柱状晶铸坯热轧试样。再经相同的冷轧退火工艺后,与柱状晶铸坯冷轧退火试样相比,等轴晶铸坯冷轧退火试样的{001}∥ND织构较弱,{111}∥ND γ织构较强,而且rm值较高。     

热轧温度对436不锈钢热轧织构的影响

利用EBSD技术研究了不同热轧温度下436不锈钢热轧织构的变化规律和显微组织特征.试验中选取不同的热轧初轧和终轧温度:分别在1 080和1 050℃开轧,850和800℃终轧.结果表明:较低温下开轧、终轧晶粒内部的缺陷较多,表现为较大的累积取向差,而较高温度下开轧、终轧其累积取向差明显低于低温热变形下的样品;在较高温条...     

异步轧制对SUS430铁素体不锈钢织构和深冲性能的影响

利用X射线衍射技术和金相显微镜观察等手段,研究异步轧制工艺对SUS430铁素体不锈钢组织织构与深冲性能的影响。结果表明:异步轧制技术可以适当细化再结晶晶粒,但是晶粒大小、分布不均匀。织构分析表明,采用异步一次冷轧工艺沿着板厚方向可获得均匀、完整的γ纤维织构,但强度相对较弱,而应用异步二次冷轧,经过两次退火工艺,再结晶织构弱化,获得接近随机的取向织构。综合分析表明,异步一次轧制有利于提高材料的深冲性能。     

终轧温度对超纯铁素体不锈钢组织、织构及成形性能的影响

研究了终轧温度对铌、钛双稳定化超纯Cr17铁素体不锈钢的组织演变、织构演变及成形性能的影响。研究结果表明,降低终轧温度能有效细化、均匀化热轧及退火组织。降低终轧温度能增强冷轧退火板的γ纤维再结晶织构、减轻偏离{111}121组分的程度。降低终轧温度是提高r值、降低Δr值、改善冷轧退火板成形性能的有效手段。     

精轧温度对含铌Cr17铁素体不锈钢组织、织构及成形性的影响

 以铌稳定化的Cr17铁素体不锈钢为试验材料,系统研究了精轧温度,即高温精轧和低温精轧,对组织、织构和成形性能的影响。2种不同工艺的热轧板经相同的热带退火、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2种工艺条件下的组织和织构演变。研究结果表明：与高温精轧相比,低温精轧有利于得到细小及均匀的冷轧退火组织;有利于冷轧退火板形成较强的γ纤维再结晶织构,并消除γ纤维再结晶织构的偏转。因此,低温精轧能够显著提高冷轧退火板的成形性能。     

热处理工艺对12%Cr铁素体不锈钢组织性能的影响

以12%Cr铁素体不锈钢为研究对象,研究了不同退火方式、退火工艺对12%Cr铁素体不锈钢热轧板和冷轧板组织、力学性能、耐腐蚀性能、成形性能的影响。结果显示,12%Cr铁素体不锈钢高温下存在铁素体—奥氏体相变过程,在双相区退火快冷后有马氏体组织生成。通过在热退过程中引入奥氏体相变和马氏体相变,可以显著细化最终产品晶粒,提高最终冷轧产品的强度、硬度,同时保持材料耐腐蚀性能不变。该工艺生产的产品可以适用于高强度的应用场合,打破了传统12%Cr铁素体不锈钢热轧后只能采用罩式炉退火的束缚,针对产品的最终用途可以采用不同的退火方式和退火工艺进行生产。     

铌与钛对铁素体不锈钢析出和成形性的影响

研究了铌、钛对铁素体不锈钢析出相、织构和成形性的影响。结果显示:添加铌、钛后的析出相主要是TiN和(Nb,Ti)C,其析出尺寸分别为4μm和200 nm;同时,铌、钛的添加抑制了冷轧薄板α纤维织构的生长,促进了γ纤维织构强度的增加。添加稳定化元素铌、钛后,冷轧薄板的平均r值由1.05增加到1.46,起皱高度也由29.1μm下降到18.9μm,薄板成形性能的改善同再结晶织构的变化密切相关。     

439铁素体不锈钢的研制

439是在430不锈钢基础上降低C＋N含量，添加Nb、Ti等稳定化元素发展起来的新型不锈钢材料，已逐步代替304不锈钢应用于电梯面板等行业。为开发满足用户使用要求的439不锈钢，试验室研究了成分、热处理制度对439不锈钢性能的影响，结果表明：Ti、Nb稳定化元素的添加对改善439不锈钢综合性能比较有利、热轧439退火再冷轧可明显改进深冲性能。生产试制结果表明，宝钢生产的439冷轧产品完全能满足用户对材料的性能要求。     

12%Cr铁素体不锈钢焊接接头组织及韧性研究

对四种不同成分的12%Cr铁素体不锈钢做了焊接性试验。分析焊接接头的组织,测量了焊接接头的低温冲击功。试验结果表明,随着碳含量的增加,焊接粗晶区组织由单相铁素体逐渐转变成以马氏体为主,粗晶区宽度变窄,晶粒尺寸变小。细晶区组织以马氏体为主,组织细小均匀。熔合线处和热影响区的低温冲击功相比母材均显著降低。断裂路径分析结果表明,窄的粗晶区宽度和小的晶粒尺寸使断裂路径经过更多的奥氏体焊缝区,提高了整体的冲击韧性。