型材轧机轧辊用高铬铸铁

高铬铸铁是制造线材和型材轧机轧辊的很有发展前途的材料。过去开发的铬为14～16％的高铬铸铁,因铸态硬度太高难以机加工而阻碍了在轧机上的应用。为使高铬铸铁轧辊广泛用于精轧机轧辊,乌克兰冶金科研所全面研究了铸态和热处理状态高铬铸铁的组织和力学性能。 结果表明,含铬17～17.6％的轧辊组织由屈氏体基体和大量均匀分布的碳化物组成,铬>20％,主     

高铬铸钢轧辊的组织及其氧化行为

轧辊氧化膜形成及剥落显著影响轧辊的辊耗及钢板的表面质量。为控制轧辊的氧化行为,采用增重法研究离心铸造高铬铸钢轧辊在大气及水蒸气环境中的氧化行为,并采用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射(XRD)等方法研究了高铬铸钢组织及氧化膜的结构。结果表明,高铬铸钢组织为回火马氏体基体和共晶Cr7C3碳化物;氧化过程中基体优先被氧化,粗大碳化物表面几乎不被氧化;温度及环境对氧化膜生长及相结构都有一定的影响,高温及水蒸气环境加速氧化,并促进γ Fe2O3向γ Fe3O3转化。因此,控制轧辊的氧化,关键是控制轧辊的使用温度。     

凝固过程数值模拟技术在铸钢轧辊中的应用

本文介绍了铸造过程模拟优化CASTsoft系统,并对铸钢轧辊凝固过程中的温度场和应力场进行了模拟计算,对铸件整个凝固、冷却过程中的热裂、冷裂倾向性进行预测。温度场计算表明轧辊凝固过程中补缩通道发生变化。轧辊应力场模拟包括铸件凝固、冷却及落砂后冷却整个过程。以凝固过程中准固相区的等效应力与强度的比值分布规律为依据,对该铸件的缩孔、缩松区域进行了预测,给出了危险区的位置。通过对模拟结果与实际铸钢轧辊检测数据对比,进一步优化了铸造工艺,提升了收得率。     

铸钢轧辊生产中的温度控制

铸钢轧辊生产中,温度是影响轧辊质量的最重要工艺参数,对其优化和控制贯穿于轧辊生产全过程。铸钢轧辊生产由钢水熔炼、铸造成形、和热处理等工艺步骤完成。文章根据多年轧辊生产经验,提出了在钢水熔炼、铸造成形、热处理各个阶段的温度控制重点和控制要求。     

热处理对定向凝固CMSX-6合金组织及拉伸性能的影响

采用高速凝固法制备了CMSX-6镍基高温合金定向凝固试样。研究了热处理前后不同部位的显微组织和拉伸性能。结果表明,铸态试样先凝固部分比后凝固部分的枝晶组织更为细密,一次枝晶间距较小,共晶组织含量较少,而抗拉强度高,延伸率较小。热处理后初生相充分固溶形成了成分均一的组织,γ′相得到了明显的细化与均匀化,γ/γ′共晶也发生了溶解并存在固溶微孔。热处理略微提高合金的抗拉强度,但明显提高了合金的延伸率。试样断裂为脆性断裂,铸态为正断型断裂,热处理态为切断型断裂。     

高铬铸铁组织及元素分布的研究

研究了高铬铸铁的铸态和热处理后的组织，以及有关元素在铸铁组织中的分布。并利用X射线衍射研究了高铬铸铁中碳化物的结构。     

高碳铬钢凝固及热处理组织演变规律

摘要：系统研究了高碳铬钢复合轧辊工作层材质在凝固及热处理过程的组织演变规律。利用Thermo Calc软件进行平衡相图计算，阐明了平衡凝固过程及冷却过程中碳化物析出行为。通过热膨胀仪精确测定了奥氏体化温度对合金相变点的影响，获得了珠光体等温转变动力学曲线。结合扫描电镜、能谱分析和X射线衍射分析，确定了热处理工艺对最终显微组织的影响，明确了凝固过程中形成的一次碳化物M7C3和二次碳化物对热处理组织的影响规律，为高碳铬钢复合轧辊工作层材料的实际热处理工艺制定提供理论依据。     

高铌TiAl基合金热变形组织的均匀化

研究了热加工和热处理对大尺寸高铌TiAl基合金组织均匀化的影响.结果表明,两次包套锻造能够有效地破碎大尺寸高铌TiAl基合金铸态组织.锻造过程中,铸态组织发生较大程度的动态再结晶,合金锻后组织经过热处理未出现残留的粗大的片层组织.合金在凝固中由于偏析形成的高温β相通过热加工和随后的热处理得到了有效的消除,热处理后所获的双态组织均匀且细小.     

稀土对低合金耐磨铸钢组织和性能的影响

采用扫描电镜分析,硬度测试和摩擦性能测试等手段,研究了稀土对低合金耐磨铸钢组织和性能的影响。结果表明,在低合金耐磨铸钢中添加0.15%稀土,可细化合金铸态组织,增加铸态组织中的铁素体数量,减少珠光体数量,同时可细化热处理后合金的贝氏体组织,使铁素体形态和大小分布均匀,马氏体数量减少。添加稀土后可使铸态合金硬度提高9.4%,摩擦系数由0.136 9减小为0.081 9。     

钢管及冷弯型钢用高性能铸造轧辊的研制开发

以高碳、高铬、高镍、高钼为特征,采用多元合金变质强化,通过铸造、热处理和机加工,山东省四方技术开发有限公司开发出了高性能高铬辊。材料基体组织为奥氏体、贝氏体或马氏体,碳化物主要是M7C3,含量20%左右,显微硬度可达HM1800,并呈不连续的条块状、颗粒状和菊花状。抗拉强度540MPa,冲击韧性7.5J/cm2,距表面120mm处硬度达HRC59.3。用于矫直辊及焊管轧辊,材料利用率达77.5%以上。同时指出,轧辊制造的发展趋势是高性能、高合金化、以铸代锻及双金属结构等。     

侧封板传热对双辊板带铸轧凝固过程的影响

借助大型有限元分析软件ansys中的flotran CFD模块,对双辊板带铸轧的凝固过程进行了模拟分析,并对不同导热系数的侧封板对双辊板带铸轧凝固过程的影响进行了对比分析。此模拟结果可以为控制铸轧过程提供有效的参考。     

待定系数法确定双辊薄带铸轧中的边界热流

熔池与铸轧辊接触的边界热流是进行双辊薄带铸轧数值模拟研究的重点,通过铸轧过程中金属凝固机制和传热过程的研究,提出结晶辊和熔池接触的边界热流分布函数形式,利用凝固初始位置、薄带坯出坯厚度,再结合能量守恒原理进行求解,确定函数中的待定参数,避开传统方法需要求解坯壳和铸轧辊间气隙热阻的难题;通过施加所提出的边界热流函数对某试验铸轧辊温度场进行求解,结果与实测结果相吻合,这表明文中提出的边界热流分布函数形式与实际相符合。     

电加热冒口铸钢辊凝固过程数值模拟及优化

为提高某铸钢轧辊的工艺出品率,节约能源消耗,本研究针对该轧辊铸造过程进行数值模拟,依据无损探伤缺陷位置确定合理的换热边界换热条件,再现了缩孔缩松的位置,并评估了冒口降低的可行性。结果表明,在冒口上表面换热系数为2.4 W/(m2·K)、发热效率为25%时,该铸钢辊的缺陷模拟结果与实际探伤结果最为接近。基于此,当减小冒口高度低于100 mm时,铸件本体内凝固缺陷并未加重;而当冒口减少高度超过150 mm时,冒口内部凝固缺陷有进入铸件本体的风险。     

Microstructure of shot-blasting casting roll and effect on strip solidification during strip-casting process

In the strip-casting process,the surface topography of the casting roll has a significant influence on the solidification microstructure and surface quality of the as-cast strip. Shot-blasting treatment is an important way to achieve a suitable surface topography on the casting roll. In this study,a casting roll of beryllium copper alloy was shot blasted using steel pellets in the laboratory,resulting in a randomly distributed discontinuous peak and dent surface topography,in which cold deformation-slip bands and fine-deformation twins were formed. The thickness of the deformed copper alloy was about 100 μm during the shot-blasting process,and the copper hardness value increased significantly within 40 μm of the surface,with a maximum increase of more than 20% compared to the mean substrate hardness value. Within 60-100 μm of the surface,the hardness at the peak position was still higher than the copper substrate mean value,but the hardness at the dents was not,which was mainly due to the copper alloy slip and twinning deformation mechanisms. The surface hardness was similar to that of the substrate after the shot-blasted sample had been subjected to thermal shock. The molten steel first chilled and nucleated at the surface peaks of the casting roll;furthermore,fine dendrites grew and crossed over the middle of the dents. Therefore,the peak intervals of the shot-blasted surface are an important factor in solidification quality control.     

Modelling of Melt Flow and Solidification in the Twin‐Roll Strip Casting Process

A three‐dimensional mathematical model has been developed to simulate turbulent fluid flow, heat transfer and solidification in the pool of a twin‐roll strip caster. A Darcy‐porosity approach was used to study the fluid flow within the mushy solidification zone in the pool. The effect of the heat transfer coefficient and permeability constant on the flow and solidification was also predicted. It was shown that an even flow and temperature distribution of the pool can be obtained by using a suitable feeding system. The heat transfer between the rolls and the solidifying metal has a big influence on the location of the solidification end point. The permeability of the mushy zone is a key factor which affects the flow and solidification in the twin‐roll strip casting process.     

Solidification modelling of microstructure in twin-roller thin strip casting of stainless steels

The influence of process parameters on the dendritic microstructure of thin strips cast by the twin-roll method is analyzed in the framework of a one-dimensional solidification model and compared with experimental results. As a relevant characteristic the secondary dendrite arm spacing Λ₂ as a function of the distance x from the roll surface is investigated. The difference between the local dendrite arm spacing near the strip surface and the strip centre, respectively, increases with the strip thickness and only depends on the casting temperature to a small extent. An increase in the strip/roller heat transfer coefficient due to a rising casting velocity or possibly enhanced roll-separating forces leads to a decrease in the dendrite arm spacing. The effect of a sudden decrease in heat transfer during the solidification process, on the Λ₂(x) characteristics, e.g. by a local separation of the solidified shell from the roller surface, is discussed.     

双辊连铸不锈钢薄带凝固组织特点

 通过金相观察分析了同径双辊薄带连铸机上生产的奥氏体不锈钢薄带的凝固组织,结果表明：铸带凝固组织包括2个柱状晶区和1个等轴晶区,其等轴晶呈近球形或蔷薇形。与传统连铸板坯相比,其柱状晶区一次及二次枝晶的间距较小,等轴晶粒内部为非枝晶结构,其尺寸大约是连铸坯等轴晶的1/10,凝固组织更致密。     

双辊薄带钢铸轧过程的流场温度场耦合数值模拟

采用有限元法模拟了双辊铸轧不锈钢过程的流热耦合问题;分析了铸轧速度对熔池内流场,、温度场的影响以及流民温度场与温度场之间的相互影响,给出了凝固过程中熔池与铸轧辊之间的热流密度变化趋势及随铸连的变化规律,并把此模拟的结果与试验的结果相比较,吻合较好;通过熔池内温度场及温度梯度分析了熔池内凝固的发展及其对热流密度变化的影响。此     

The key technologies of controlling low carbon steel as-cast strip surface quality

This article is try to explain or analyze the key technologies of controlling the surface quality of low carbon steel as cast strip through investigation of interface heat transfer between solidified shell and liquid steel.The one of the key technologies of controlling surface quality of low carbon steel as cast strip is through the casting roll surface texture in order to achieve the homogeneous solidification on the casting roll.Another is through forming a thin film on the casting roll surface in order to achieve a balance between rapid solidification and homogeneous solidification.This film formed between the twin roll and the molten steel can be controlled by adjusting the chemical composition and inclusion in liquid steel through controlling the amount of all[O]and free[O].