双相区热处理对430铁素体不锈钢热轧板组织和性能的影响

研究了α+γ双相区热处理对430铁素体不锈钢热轧板显微组织和力学性能的影响,并与工业罩式炉退火后的热轧板显微组织和力学性能进行了对比分析。结果表明:在双相温度区间对430不锈钢热轧板进行热处理,分割了热轧板轧向的条带状组织,抑制了聚集组织的形成。与常规罩式炉退火工艺相比,双相区热处理显著提高了430不锈钢热轧板的伸长率,降低了屈服强度和硬度,有利于改善最终冷轧产品的冲压性能和抗起皱性。     

稀土元素对430铁素体不锈钢组织和性能的影响

对常规430铁素体不锈钢进行了稀土微合金化改进,最终开发出高品质430RE铁素体不锈钢冷轧退火带钢,并研究了稀土微合金化对430不锈钢的力学性能、深冲性能、抗皱性能、显微组织和织构的影响。通过稀土微合金化,430不锈钢中尺寸较粗大的CaO·SiO₂和Al₂O₃·CaO夹杂物,大多转变为430RE不锈钢中尺寸较细小、分布密度较高的富含稀土元素的夹杂物。与采用基本相同热轧、冷轧和退火工艺的430不锈钢相比,430RE热轧板和冷轧退火板的强度水平均有所降低、塑性水平均明显升高;430RE生产过程中的宏观织构演变表现出更强的高塑性应变比(r值)γ-织构组分形成趋势,这使得430RE冷轧退火板的深冲性更优;430RE冷轧退火组织中沿轧向偏聚、低r值取向晶粒簇减少,这使得430RE冷轧退火板的抗皱性更优。     

轧制方式对SUS430铁素体不锈钢组织和性能的影响

 采用X射线衍射技术和光学显微分析等方法,研究了同步和异步冷轧方式对SUS430铁素体不锈钢微观组织、织构演变以及力学和成形性能的影响。结果表明,与同步冷轧相比,由于异步轧制剪切变形的引入,可使异步冷轧板材的平均晶粒尺寸减小。在同步冷轧过程中,其二次冷轧再结晶织构为完整的γ纤维织构,导致铁素体不锈钢的最终性能优于同步一次冷轧;而在异步冷轧过程中,异步一次冷轧再结晶织构为强点{111}<[1][1]2>的γ纤维织构,异步二次冷轧再结晶织构属于随机取向织构,其结果是异步一次冷轧板材的性能优于异步二次冷轧。综合分析表明,与异步二次冷轧方式相比,同步二次冷轧方式有利于铁素体不锈钢性能的提高。     

再结晶晶粒取向分布对铁索体不锈钢起皱的影响

针对铁素体不锈钢拉伸后的表面起皱现象,研究了再结晶晶粒取向分布对起皱程度的影响.将厚度3mm的430铁素体不锈钢热轧退火板,经2种工艺(一次冷轧、多次冷轧)轧制和再结晶退火后得到最终厚度均为0.1mm的冷轧板,分析了再结晶晶粒取向、轴向拉伸后表面起皱程度以及二者的相关性.结果表明,{211)〈011〉和{100}〈011〉取向晶粒的存在是引起表面起皱的内因;铁素体不锈钢中各个晶粒取向均匀分布,削弱了塑性各向异性,从而抑制起皱的产生.铁素体不锈钢在拉伸变形后,相近取向的相邻晶粒表面呈现单滑移痕迹,这是形成起皱的主要原因.多次冷轧-中间退火为减轻铁素体不锈钢表面起皱提供了一种新途径.     

Effect of hot rolling on the dendritic texture of directionally solidified steel ingots

Directionally solidified ingots of three commercial steels—AISI 1010, Fe-3.4 pct Si, and Type 430 stainless steel—were hot-rolled at 1850°F in order to study the effect of hot deformation on the as-cast dendritic texture. The strong dendritic (100) orientation of both the Fe?Si and Type 430 alloys was completely destroyed by the heavy reductions typical of the commercial hot rolling of ingots. The primary effect of hot rolling is to eliminate the texture present in the ingot, and to create certain new textures. These new textures are in every case weak. For example, the AISI 1010 steel, which had very little of the dendritic <100> orientation in the ingot stage, has a combination of two weak textures after hot rolling: (100) [011] and (110) [110]. Likewise, with the other two materials, which had a strong dendritic <100> orientation in the ingot stage, hot rolling resulted in weak textures: (110) [001] with a rotation of this orientation of ±45 deg about the [001] rolling direction, followed by (110) [001] rotated ±35 deg about the [110] in the transverse direction.     

退火温度对430不锈钢冷轧板组织和力学性能的影响

针对现场生产的430不锈钢冷轧板,通过高温连续退火实验研究了退火温度对材料显微组织、强度、塑性以及各向异性性能的影响.通过实验得到了合理的两段式加热连续退火工艺:选取中间温度为600℃,加热II段的加热速率为2.3℃·s-1,最高加热温度为840℃.随着退火温度的升高,薄板的屈服强度和硬度呈明显的两阶段降低趋势,延伸率呈"S"型趋势增加,平均塑性应变比基本保持不变（1.25左右）,而轧制平面各向异性指数有一定的降低.针对430不锈钢冷轧板分别建立了屈服强度与退火软化率和延伸率之间的定量关系.      

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。     

SUS430热轧带钢工艺研究及质量控制

SUS430是铁素体不锈钢钢种之一.由于该钢种所固有的特性,在热轧生产中易产生加工缺陷.为了避免缺陷产生,研究了该钢种的加工特点,针对容易产生的问题,制订出相应的轧制工艺和有效的预防措施,以生产出高质量的SUS430热轧带钢.     

不锈钢/碳钢复合板平整轧制过程板形翘曲行为

 针对不锈钢/碳钢复合板在平整轧制过程中极易出现不均匀延伸并导致板形翘曲的行为,建立了不锈钢/碳钢复合板平整轧制过程的有限元数值模拟模型,对已实现工业化批量生产的不锈钢/碳钢复合板平整轧制过程的不均匀变形行为及其可能导致的板形翘曲缺陷进行数值模拟研究。在此基础上,对比分析了均质板、非对称不锈钢/碳钢复合板以及对称不锈钢/碳钢/不锈钢复合板平整轧制过程板形的遗传与演变规律,发现仅非对称不锈钢/碳钢复合板在平整轧制过程中极易产生板形翘曲缺陷,同时对比分析了平整和常规轧制对非对称不锈钢/碳钢复合板轧后翘曲缺陷的影响。揭示了不锈钢/碳钢复合板厚向分层特征以及复合板尺寸参数、平整工艺和平整机设备参数等对其板形翘曲缺陷的影响规律,研究表明,对复合板尺寸参数而言,平整过后翘曲高度与厚度比呈正比。对于平整工艺而言,当等张力平整轧制时,平整过后翘曲高度与张力呈正比;当不等张力平整轧制时,前张力的变化对平整过后翘曲缺陷的影响较大;同时平整过后翘曲高度与轧辊和碳钢层表面摩擦因数呈反比。对平整设备参数而言,平整过后翘曲高度与碳钢层表面接触的轧辊辊径、入口侧防皱辊抬起高度以及不锈钢层表面接触轧辊偏向入口侧的距离均呈正比关系。最后,采用轧制试验对数值模拟结果进行了验证,证明了复合板平整轧制模型的准确性。基于上述研究结果,提出了相应的工艺对策,为金属复合板平整轧制过程的板形翘曲控制提供了理论依据。     

Microstructure of the spray formed Vanadis4 cold work die steel and its evolution during hot rolling and heat treatment

A high alloyed Vanadis4(V4) steel was produced by spray forming process in Baosteel,and the microstructure of the as-sprayed steel and its evolution during hot rolling and annealing processes were characterized.It was found that the as-sprayed V4 steel has a homogeneous and fine scale microstructure with uniform dispersion of carbides.The hot rolling temperature is the key factor in controlling the evolution of type,morphology and distribution of carbides,as well as the matrix microstructure of the as-rolled steels.The optimized processing parameters for the as-sprayed V4 steel are rolling at 1 050℃ and then annealing at 900℃.The microstructural evolution mechanisms during hot rolling and annealing are determined according to the microstructural analyasis of the material at different stages.     

SAF 2205双相不锈钢织构与冲压特性

研究SAF 2205双相不锈钢冷轧退火板的冲压特性以及冷轧和退火织构对其冲压性能的影响.实验钢冷轧退火板表现出较差的深冲性能和明显的45°制耳,其r平均值和Δr值分别为0.7和-0.27,这主要与其在冷轧及退火后形成的织构有关.ODF图显示,退火后SAF 2205双相不锈钢中铁素体相未形成γ纤维再结晶织构,仍然为分散的α纤维织构.实验钢中铁素体相的织构强度明显高于奥氏体相,其对钢板成形性的影响更显著,即其各种〈110〉退火织构组分均不利于实验钢r平均值的提高,并且使得Δr<0.此外,奥氏体相的{110}〈001〉织构也对钢板成形性能产生一定程度的影响.      

罩式炉退火对430系不锈钢表面质量的影响

 研究了罩式炉退火对430系不锈钢表面氧化铁皮结构变化的影响,并对这种变化在后续冷轧工序中造成的质量问题进行了分析。首次对长期存在的“退火印”缺陷做出了完整的理论解释,并根据现场工艺试验结果,提出了解决方案。     

变薄拉深对430不锈钢表面起皱的影响

 为了研究变薄拉深对430不锈钢表面起皱的影响，采用DEFORM-2D分析0.56、0.79和1.00 mm 430不锈钢冷轧退火板的拉深-变薄过程，最大变薄率分别为32.14%、26.58%和26.00%，并对0.79 mm厚的板材进行试验验证，测得最大变薄率约为30.38%，与模拟结果接近；通过表面粗糙度数据，可知变薄率越大，改善起皱效果越明显，最优变薄率约为20%，但变薄率太大时，拉深件表面出现明显摩擦划痕；通过EBSD测量，变薄拉深并未改变与起皱相关的{111}〈112〉与{111}〈110〉织构的晶粒体积分数，初步判定通过物理挤压作用可以改善起皱。     

不锈钢典型夹杂物在轧制过程的衍变分析

不锈钢对冷板表面质量要求高,轧制过程中夹杂物是产生表面缺陷的主要原因之一。为了明确夹杂物对轧制过程表面缺陷的影响规律,通过中试模拟试验研究了热轧、退火和冷轧过程硬质镁铝尖晶石和低熔点硅酸盐2种典型夹杂物的变形特点,并采用数值模拟对冷轧过程夹杂物的变形机理进行了分析。结果表明,热轧过程高熔点的镁铝尖晶石不变形,低熔点的硅酸盐夹杂物在1 200～1 250℃热轧温度下为半熔融状态,具有良好的变形能力。硅酸盐夹杂物长宽比高、抗拉强度低,冷轧过程更容易断裂延伸,随着轧制的进行,断裂后夹杂物之间的距离逐渐增加,尺寸减小。相反,镁铝尖晶石不容易断裂、延伸,而且存在断裂延伸的临界尺寸,该临界尺寸随冷轧变形量的增加而减小。由于镁铝尖晶石容易造成不锈钢轧制缺陷,因此生产过程中应尽量避免其生成或控制其粒径。     

Static Recrystallization Kinetics and Crystallographic Texture of Nb-Stabilized Ferritic Stainless Steel Based on Orientation Imaging Microscopy

In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol⁻¹, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554}〈225〉 orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554}〈225〉 component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.

     

The effects of cold working on sensitization and intergranular corrosion behavior of AISI 304 stainless steel

The effects of prior cold rolling of up to an 80 pct reduction in thickness on the sensitization-desensitization behavior of Type AISI 304 stainless steel and its susceptibility to intergranular corrosion have been studied by electrochemical potentiokinetic reactivation (EPR) and Strauss-test methods. The results indicate that the prior deformation accelerated the sensitization as compared to the undeformed stainless steel. The deformed Type 304 stainless steel experienced desensitization at higher temperatures and times, and it was found to be enhanced by increased cold deformation. This could be attributed to the increased long-range chromium diffusion, possibly brought on by increasing pipe diffusion and vacancies. The role of the deformation-induced martensite (DIM) and texture, introduced by uniaxial cold rolling, on the sensitization-desensitization kinetics has also been discussed. This study could not reveal any systematic relationship between texture and the degree of sensitization (DOS) obtained. The effect of DIM on DOS seems to be pronounced at 500 °C when the steel retained significant amounts of DIM; however, the retained DIM is insignificant at higher sensitization times and temperatures.     

酒钢不锈钢冷轧连续退火炉技术

从不锈钢冷轧退火工艺开始,介绍了酒钢不锈钢冷轧连续退火炉设备特点和生产工艺。     

提高430铁素体不锈钢成型性能工艺研究

研究了430铁索体不锈钢成型性能的主要机理,并以此为基础对影响其成型性的关键工艺参数进行了分析;通过调整化学成分,优化连铸、热轧、冷轧等主要工艺,并经过实际生产试制验证,提高了430不锈钢的成型性,满足了深冲制品行业用户的特殊需求。     

M23C6析出相对节镍型奥氏体不锈钢冷轧表面裂纹的影响

为找出生产的节镍型奥氏体不锈钢冷卷表面裂纹形成原因,通过光学显微镜、扫描电镜对表面裂纹进行检测分析并结合热处理试验及热力学软件JMatPro进行分析计算研究。检测分析发现裂纹处晶界存在大量的析出相,据此推测析出相是导致钢材冷轧形成表面裂纹的主要原因。模拟连续退火工艺开展热处理试验,结果表明正常退火工艺无法完全消除热轧工序钢卷晶界处聚集的大量析出相。计算研究该成分体系下奥氏体不锈钢的平衡相图,结合能谱及透射电镜衍射斑点分析,结果表明M₂₃C₆碳化物的沉淀温度范围为500～925 ℃,钢卷从高温缓慢冷却下来会析出M₂₃C₆碳化物,析出鼻温区为850～900 ℃。以此结合实际工艺流程对减少钢卷中M₂₃C₆碳化物析出提出了可能的措施。     

2205不锈钢-碳钢复合带肋钢筋的热轧

 为了研究覆层为2205不锈钢的复合钢筋的热加工范围,利用Gleeble-3800进行热模拟试验,得出2205不锈钢的高温流变曲线及热加工图,并最终确立复合钢筋的开轧温度不低于1 150 ℃。利用有限元软件对复合钢筋的粗轧和精轧道次进行数值模拟,结果表明,粗轧变形时,应变集中在轧件表层和1/4位置,随着变形不断向芯部渗透,塑性应变较大的位置不锈钢覆层较薄;在精轧k1道次变形时,发现在横肋根部的不锈钢覆层厚度最薄,在横肋顶部的覆层厚度最大。对复合钢筋的界面进行研究后发现,Cr、Ni、Mo的扩散距离为18~20 μm,从碳钢侧到不锈钢侧的微观组织依次为铁素体和珠光体、脱碳组织、复合界面、奥氏体不锈钢组织、铁素体和奥氏体不锈钢双相组织。