AA3003合金铸轧板预析出相对再结晶温度、组织的影响

通过光学显微镜、硬度测试仪、扫描电镜、双臂电桥等研究了AA3003铝合金铸轧板经不同均匀化处理后,预析出第二相颗粒对再结晶组织和再结晶温度的影响.试验表明,高温均匀化过程中析出的第二相对冷轧试样的再结晶具有显著的作用.经580℃均匀化处理的试样的再结晶温度降低了大约100℃,并且在520℃退火过程中得到了尺寸梯度很小的细小等轴晶组织.     

Investigation on Temperature Change of Cold Magnesium Alloy Strips Rolling Process with Heated Roll

Magnesium alloy strips are widely used in aerospace, automotive industry, etc., which are difficult to produce through cold forming process due to their poor deformation ability. In this article, we studied whether the rolling process with heated roll could be used to roll cold magnesium alloy strips. Thermal-mechanical finite element simulation of the rolling process, using heated roll and cold strips to produce the magnesium alloy strips, was carried out. Influences of roll temperature, rolling velocity, rolling reduction ratio, and initial strip thickness on the thermal field and the mean temperature of magnesium alloy strips were analyzed. Both the heated area in strips in rolling deformation zone and the mean temperature of strips at exit of rolling deformation zone increase with increasing the roll temperature and/or rolling reduction ratio, and/or with decreasing the rolling velocity and/or initial strip thickness. Finally, a formula was developed to predict the mean temperature of strips under different rolling conditions, which also could be used to calculate the critical value of parameters in rolling process.     

Response to annealing treatment of a twin-roll cast thin AlFeMnSi strip

Twin-roll cast AlFeMnSi thin strips show some marked differences with respect to conventional strips in their response to an annealing treatment. When annealed as-cast, the grain structure is rearranged by a growth process starting at 525 °C. The surface as well as the interior of the strip recrystallizes starting at 420 °C, when the thin strip is annealed after a cold rolling pass. Recrystallization of the surface relies entirely on the growth of the grains which have nucleated in the interior of the strip. The final strip structure in both cases is a coarse one with large grains across the section of the strip.     

Preparation of AZ31 magnesium alloy strips using vertical twin-roll caster

A newly developed technology for manufacturing magnesium alloy strip,vertical twin-roll strip casting,has been described.This manufacturing process is easy to be facilitated in an economical way to manufacture wrought magnesium alloy strips. As an example,AZ31 magnesium alloy was used to investigate the appropriate manufacturing conditions for vertical twin-roll strip casting by varying the temperatures of the molten materials and rolling speeds.The effects of manufacturing conditions on forming quality were clarified in terms of roll speeds and casting temperature.In addition,microscopic observation and X-ray diffraction of the as-cast strips were performed.It has been determined that AZ31 alloy strip of 1-3 mm in thickness can be produced at a speed of 30 m/min by a vertical twin-roll caster.The microstructure of as-cast strip only containsα-phase(Mg)and no other phase,and the twin-roll casting process can effectively refine the grain size.The fine equiaxed grain of as-cast strips is beneficial to the plastic deformation of the strips,and it is also suitable for direct cold-rolling with a maximum cold-rolling reduction of 40%.     

快速超薄铸轧机铸轧辊变形测量系统研究

针对铸轧工艺的特殊性,拟定了一套方便可行的铸轧辊变形测试方案.运用该方案对某铸轧机成功地进行了工业现场测试,掌握了铸轧辊在铸轧环境下变形的分布规律,测试实际铸轧过程中轧辊受力载荷与温度场作用下辊形变化规律、测试设备运行时的有关工艺参数与力能参数,以及设备参数,同时也为仿真模型提供边界条件及检证标准.     

铸轧辊温度场及热变形测定

针对铸轧工艺的特殊性，拟定了一套方便可行的铸轧辊温度场及热变形测试方案，运用该方案对某铸轧机成功地进行了工业现场测试，掌握了铸思辊在铸轧环境下温度场及热变形的分布规律，为铸轧板形控制及现场铸轧工艺优化提供了可靠依据。     

双辊薄带高速铸轧机新技术

本文介绍了近年来出现的MDTRC、METRC和HPTRC等新型双辊铸轧机,对设备和工艺特点以及所得铸带的组织性能等参数进行了对比分析,指出立式TRC、铜质铸辊、无润滑、低过热度和半固态铸轧是提高铸轧速度的有效方法.     

铸轧辊变形在线测量研究

针对铸轧工艺的特殊性，拟定了一套方便可行的铸轧辊变形测试方案。运用该方案对某铸轧机成功地进行了工业现场测试，掌握了铸轧辊在铸轧环境下变形的分布规律，测试实际铸轧过程中轧辊在力载荷与温度场作用下辊形变化规律、测试设备运行时的有关工艺参数与力能参数，以及设备参数，同时也为仿真模型提供边界条件及检证标准。     

双辊快速凝固AZ31镁合金薄带试验研究

在等径双辊连铸机上进行了AZ31镁合金薄带连铸的试验研究，掌握了诸如浇铸温度、铸辊转速、辊缝和侧封等合理的工艺参数，成功地铸出了AZ31镁合金薄带并对其显微组织进行了分析。     

Comparison of phosphor bronze metal sheet produced by twin roll casting and horizontal continuous casting

Much effort recently has been expended to study the strip casting process used to produce thin metal strip with a near final thickness. This process eliminates the need for hot rolling, consumes less energy, and offers a feasible method of producing various hard-to-shape alloys. The finer microstructure that results from the high cooling rate used during the casting process enhances mechanical properties. In this study, strips of phosphor bronzes (Cu-Sn-P) metal were produced using a twin roll strip casting process as well as a conventional horizontal continuous casting (HCC) process. The microstructures, macrosegregations, textures, and mechanical properties of the as-cast and as-rolled metal sheet produced by these two methods were examined carefully for comparative purposes. The results indicate that cast strip produced by a twin roll caster exhibit significantly less inverse segregation of tin compared to that produced by the HCC process. The mechanical properties including tensile strength, elongation, and microhardness of the products produced by the twin roll strip casting process are comparable to those of the HCC processed sheet. These properties meet specifications JIS H3110 and ASTM B 103M for commercial phosphor bronze sheet. The texture of the as-rolled sheet from these two processes, as measured from XRD pole figures, were found to be virtually the same, even though a significant difference exists between them in the as-cast condition.     

莱钢冷轧薄规格涂镀基板的开发

针对冷轧薄规格带钢生产中存在的因轧辊弹性压扁而造成负辊缝现象、板面热擦伤、轧制打滑、带钢表面残留乳化液斑等问题,山东钢铁集团莱芜钢铁有限公司板带厂通过优化道次绝对压下量以消除轧辊有害接触,优化乳化液温度、浓度、皂化值等指标以减少热擦伤,增设挡板、吹扫装置等以消除乳化液斑,优化压下规程、板形目标曲线、张力控制系统等以保证带钢尺寸和板形精度,成功地生产出了超设计极限的0.18mm薄规格冷轧涂镀基板。     

变形区形状参数对钽板组织均匀性的影响

通过控制每道次的轧制压下量,获得了两组轧制变形区形状参数,对高纯钽板进行周向轧制,得到了70%变形量的样品,并对样品进行了真空退火处理(1050℃/1 h)。应用X射线衍射(XRD)技术测量了轧制样品表面层与中间层的宏观织构,结合背散射电子衍射(EBSD)技术表征了轧制样品沿厚度方向上的变形组织与微织构,以及退火态样品的显微组织与织构。结果表明:大的变形区形状参数(2.01~3.29)在轧板表面引入了明显的剪切应变,沿钽板厚度方向易产生严重的织构梯度,钽板表面层形成{hkl}<110>织构以及{100}织构,中间层形成强烈的{111}织构。较小的变形区形状参数(1.67~2.28)有利于产生均匀变形,可以有效弱化中间层的{111}织构,增强{100}织构。轧制组织中增强的{100}织构可以抑制{111}取向再结晶晶粒的异常长大,对细化显微组织有利。     

立辊润滑工艺对铁素体区轧制Ti-IF钢组织性能及边部质量的影响

针对某热轧厂铁素体区轧制Ti-IF钢带钢边裂缺陷的问题,提出了采用立辊润滑的方法予以改善。分析认为,采用立辊润滑轧制工艺可减小立辊减宽过程中的摩擦力,减少低温下带钢边部表面的剪切力;同时,有利于立辊表面质量的改善,从而改善带钢边部质量。为此,研究了立辊润滑工艺对铁素体区轧制Ti-IF钢带钢微观组织、力学性能、析出物以及边部质量的影响。结果表明,采用立辊润滑轧制工艺,Ti-IF钢带钢的组织和析出物没有明显差异,但塑性显著提高;带钢边部表面的最大裂纹深度由361 μm减小到128 μm,边部缺陷数量明显减少;带钢截面形貌较为光滑,没有发现明显裂纹,边部质量得到明显改善。     

3A21铝合金板带材再结晶退火组织性能的研究

试验和讨论了3A21铝合金连续铸轧卷的成分,冷轧变形程度、退火温度与保温时间对该合金板带材再结晶退火后组织与性能的影响规律,提出了一些可获得良好晶粒度和机械性能的控制方法。     

Static Globularization of TC11 Alloy during Hot Working Process

研究TC11钛合金片层组织在两相区980～850℃,0.001,0.01和0.1s-1应变速率条件下的热变形组织以及在不同温度退火过程中静态组织的演变规律和机制。结果表明,温度较高、应变速率较慢的条件下,动态球化过程进行得较充分,退火组织的球化分数主要取决于变形过程中的动态球化过程;温度较低、应变速率较快的条件下,动态球化过程不能充分进行,则退火后的球化分数取决于变形状态和退火过程中的静态球化过程。α晶粒尺寸则主要取决于退火温度和时间。进一步对比分析动静态球化组织的EBSD测试结果,表明退火静态球化的机制是β相的静态再结晶和α相的静态回复,以及随后的球化和聚集粗化过程。     

Influence of Hot Deformation on Mechanical Properties and Microstructure of a Twin-Roll Cast Aluminium Alloy EN AW-6082

Thin strips of medium- and high-strength age-hardening aluminium alloys are widely used in the automotive industry. Reducing their production costs caused by high energy consumption is an actual challenge. The implementation of the twin-roll casting technology is promising. However, mechanical properties of directly cast high-alloyed thin aluminium strips are oftentimes inadequate to standard specifications. In this work, the influence of a hot deformation following a twin-roll cast strip process on the mechanical properties and microstructure is investigated. For this study strips of age-hardening aluminium alloy EN AW-6082—manufactured at a laboratory scaled twin-roll caster—were single-pass rolled at temperatures of 420 °C and true strains of up to 0.5. The mechanical properties of the as-cast and by different strains hot deformed material in the soft-annealed and age-hardened states were characterized by tensile tests. The results reveal that the twin-roll cast material features the necessary strength properties, though it does not meet the standard requirements for ductility. Furthermore, the required minimum strain during hot rolling that is necessary to ascertain the standard specifications has been determined. Based on micrographs, the uniformity of the mechanical properties and of the microstructure as a result of recrystallization due to hot metal forming and heat treatment were determined. A fine-grain microstructure and satisfactory material ductility after prior rolling with a true strain above 0.41 for the age-hardened state T6 and above 0.1 for the soft-annealed state O have been established.     

Coupled thermal-fluid-mechanics analysis of twin roll casting of A7075 aluminum alloy

Better understanding of temperature distribution and roll separation force during twin roll casting of aluminum alloys is critical to successfully fabricate good quality of aluminum strips. Therefore, the simulation techniques are widely applied to understand the twin roll casting process in a comprehensive way and to reduce the experimental time and cost of trial and error. However, most of the conventional approaches are considered thermally coupled flow, or thermally coupled mechanical behaviors. In this study, a fully coupled thermal-fluid-mechanical analysis of twin roll casting of A7075 aluminum strips was carried out using the finite element method. Temperature profile, liquid fraction and metal flow of aluminum strips with different thickness were predicted. Roll separation force and roll temperatures were experimentally obtained from a pilot-scale twin roll caster, and those results were compared with model predictions. Coupling the fluid of the liquid melt to the thermal and mechanical modeling reasonably predicted roll temperature distribution and roll separation force during twin roll casting.     

3D Numerical Simulation on Thermal Flow Coupling Field of Stainless Steel During Twin-Roll Casting

The surface crack and lateral crack of the AISI 304 stainless steel thin strip produced by twin-roll casting were observed. The temperature at the center of outlet during twin-roll-casting process was determined by infrared thermometer. In order to avoid the surface cracks of the casting strip, the thermal flow coupling field of AISI 304 stainless steel during twin-roll-casting process was simulated by a 3D fluid-structure coupling model. According to the simulation result, the effect of the casting speed on thermal flow field was analyzed and the process parameters were optimized. Moreover, by studying heat flux curves, the heat transfer mechanism between molten pool and roll was analyzed. The results show that, with the increase of the casting speed, the temperature of the molten pool increases and the solidification point moves toward the outlet. Meanwhile, the whirlpool above gets larger. Based on the solidification front position, the optimized process parameters are 1500 °C and 0.37 m/s. The heat transfer mechanism between molten pool and roll contains direct contacting heat transfer and air gap heat transfer.     

Effects of Al and Ca on microstructure and surface defect of magnesium alloy thin strip

Mg-Al-Zn alloy thin strips were prepared by vertical twin-roll casting.Effects of Al and Ca on the microstructure and the surface defects of the thin strips were investigated.The results show that with the increase of Al content,the quantity of surface cracks of the thin strips increases rapidly and their locations are moved to the center of the thin strips.The alloy melts with more than 0.10%Ca(mass fraction)stick on the roller and a poor surface quality of the thin strips appears.With the increase of Al content,the microstructure of the thin strips evolves from singleα-Mg phase,characterized by the uniform and equiaxed recrystallization grains, to the combination of dendriticα-Mg with Al supersaturatedα-Mg.The minor addition of Ca can obviously refine the grains of Mg-3Al-1Zn thin strip because the formation of Al2Ca and the finest grains are obtained by adding 0.08%Ca.     

Rolling of T-shaped profiled strip by the satellite mill

A new type of compact mill called a “satellite mill” is used for producing T-shaped profiled strip from flat strip. The mill comprises one large-diameter flat roll (central roll) and five smaller-diameter caliber rolls (satellite rolls) arranged along the periphery of the central roll. The flat strip is continuously passed through the five gaps between the central roll and the satellite rolls and formed into a T shape. All rolls are driven at an equal peripheral speed to restrain elongation of strip and to promote transversal metal flow. A guide shoe is provided between each two adjacent satellite rolls to prevent the strip from bulging out or buckling. Using aluminum as a model material, some rolling experiments were performed on the mill. T-shaped profiled strips with a thickness ratio (thickness of thick part per thickness of thin part) as high as three were rolled successfully. When deformation and force characteristics were investigated, it was found that, in comparison to a conventional multipass caliber rolling, the elongation of the strip is suppressed and the filling ability is much improved.