Effect of ceramic work rolls on surface roughness of rolled SUS304 ultra-thin strips

Surface morphology and roughness are important parameters of surface quality of cold-rolled ultra-thin strip steel.In order to study the effect of Si_(3)N_(4) ceramic work rolls on the surface roughness of SUS304 ultra-thin strip,ABAQUS finite element model calculation,3D laser profilometry,and other methods were adopted based on the physical characteristics of Si_(3)N_(4) ceramic roll and 9Cr2MoV steel roll,like anti-flattening performance and oil wettability.The surface morphology and roughness of SUS304 ultra-thin strip rolled by different material work rolls under oil lubrication conditions were measured.The results showed that under the rolling force of 10 kN,the maximum flattening amount of Si_(3)N_(4) ceramic roll was reduced by 35.14%compared to that of 9Cr2MoV steel roll.The reduction rate of SUS304 ultra-thin strip rolled by ceramic roll was 34.19%,while that rolled by steel roll was only 22%;Si_(3)N_(4) ceramic roll can further increase the number of alternating convex peaks and concave valleys in the rolled thin strip,reduce the profile steepness,reduce surface roughness,and enhance the planarization effect of surface micro-convex bodies,with improving surface quality and surface glossiness.Finally,the mechanism of Si_(3)N_(4) ceramic roll significantly improving the surface roughness of rolled SUS304 ultra-thin strip was proposed.

脉冲电流辅助SUS304极薄带拉伸变形研究

为了研究脉冲电流对SUS304极薄带拉伸变形的影响,进行了室温拉伸、通电拉伸以及通电空冷拉伸试验,分析了热效应和非热效应对宏观力学性能与微观组织的影响。结果表明,脉冲电流辅助SUS304极薄带拉伸变形过程中热效应和非热效应同时存在,热效应导致材料流变应力减小,非热效应抑制TRIP效应,促进TWIP效应,改变了材料的塑性变形机制;没有高强度马氏体协调塑性变形,导致试样过早发生失稳断裂,其中试样的抗拉强度降低12.2%,断裂延伸率下降44.7%;同时,非热效应使试样在较低温度下发生了回复和再结晶现象;脉冲电流诱导了SUS304极薄带由韧性断裂向韧脆性断裂模式的转变,并且促进了变形织构生成。

超声能场对SUS 304精密极薄带轧制表面形貌的影响规律

为了解决不锈钢极薄带表面形貌在轧制后存在明显的轧制纹理以及较低的粗糙度等级等问题,将超声能场集成到精密极薄带轧制过程中,利用超声软化现象改善轧制过后极薄带的表面质量。在轧制实验研究基础上,利用形状测量激光显微系统表征了传统冷轧和超声辅助轧制后极薄带表面形貌,并且利用轧向线粗糙度Ra、幅度参数S_(q)和S_(a)和混合参数S_(dq)和S_(dr)技术指标评价了精密极薄带表面几何特性。在9.1%的压下率和21μm振幅下,超声辅助轧制后极薄带表面的轧向线粗糙度、幅度参数和混合参数均下降;相比于原始带材,超声辅助轧制后的极薄带表面形貌得到明显的改善。

Great reduction pratice of SUS304 in cold-rolling

SUS304 stainless steel is typical of austenitic stainless steel,which organization is metastable austenite,easily appears work hardening in cold rolling.According to the common process,the max reduction of cold rolling in one stage is below 80%,we try to rasie the max reduction to 90%in one stage (wecalled that "great reduction" ) from the view of cuting cost.Due to the work hardening,great reduction brings lots of problem(the difficulty of flatness control,strip break..etc)。This article analyzed the great reduction from properity of SUS304 steel,mill types,flatness control,rolling technics etc,supplied the corresponding solutions,and formed a sophisticated great reduction theory. This article focuses on the unusual thermal crown of raw materials(ie,abnormal distribution of horizontal thickness) and the rolling force fluctuations in "great reduction" rolling.First,the "distortion" phenomenon which caused by unusual thermal crown of raw materials is explained,wedge-shaped strip In coiling, because of a big difference in thickness on both sides,leads to different compressive stress on both sides of flatness roll,so that the flatness measurement is distorted;Second,the "strip shifting" phenomenon caused by wedge shape of strip is explained,we analysis the stress on both sides of the strip,concluded that the wedge-shaped strip on the coiler will shift to the thick side of the deviation,the amount of strip shifting is related to the wedge level;Because of the characteristics of SUS304,the strip is difficult to be rolled in the last few passes.so the strip breaking is easily occurred,we found the reasonable parameters(rolling speed, cooling oil,tension,etc) to solute that problem;The deviation of rolling force will cause the shape of the roll gap,thus affecting the shape control,especially in the head and tail part of the strip,It is important to minimize the deviation of rolling force;The "great reduction" process provide the favorable flatness(< 8I-unit) and thickness deviation which less than±3 um,with no significant difference between common process.In mechanical properties,the elongation of the great reduction strip is less than common products by 2%-3%,but that can be adjusted through the annealing process improvement.At present,we have been using this technology for mass production,achieving good economic benefits.

电脉冲辅助轧制SUS304极薄带的微观组织及力学性能

SUS304不锈钢极薄带是众多高精尖领域的重要原材料,但其变形抗力大导致极薄带的轧制生产工艺复杂。将脉冲电流加载至SUS304不锈钢极薄带的轧制变形中,研究脉冲电流辅助对极薄带轧制变形的影响。通过室温轧制和不同脉冲频率下的电脉冲辅助轧制试验,使用EBSD和XRD对轧后试样进行微观表征,研究了电脉冲辅助轧制对极薄带组织形貌、晶粒取向以及物相演变的影响。结合力学性能测试,分析了脉冲电流对轧制试样力学性能的影响。结果表明,电脉冲辅助轧制促使试样发生动态回复,增大电脉冲频率可加速其动态过程,600 Hz通电试样以亚结构晶粒为主(98.3%)。加载脉冲电流可改变极薄带的轧制变形机制,使其从相变马氏体转变为形变诱发孪晶。脉冲电流产生的热效应和非热效应皆可促进位错脱钉,使得相同变形量下电脉冲辅助轧制试样的位错密度明显低于室温轧制试样,加工硬化减弱、力学性能改善。同时,电脉冲辅助轧制有助于弱化轧制变形织构、增加织构类型,可改善变形试样的各向异性,有利于提高试样的塑性变形能力。对比室温轧制试样,600 Hz通电试样的显微硬度下降了33.4%,屈服强度降低了15.2%,断裂伸长率提高了249.6%,塑性变形能力恢复至原材料的30%。由此可见,电脉冲辅助SUS304不锈钢极薄带轧制变形,可减少加工硬化、降低变形抗力、提高塑性变形能力,有望突破最小可轧厚度,拓宽其应用领域。