热送热装工艺中板坯出连铸机温度的分析

用连铸坯凝固过程传热模型模拟了热送热装工艺中不同工况下铸坯凝固壳厚度和铸坏出连铸机的温度变化。模拟结果与实测值吻合很好。影响铸坯出连铸机温度的主要因素是铸坯尺寸、连铸机拉速和冷却制度。     

超宽板坯热装直送工艺实践研究

中厚板坯热装直送工艺可大幅度降低加热炉能耗，降低钢材生产成本。南钢超宽板坯因宽厚比大，极易产生纵向裂纹，南钢板材铸机表面纵向裂纹发生率高，且超宽板坯因铸坯平整度差去毛刺困难，且在热装直送过程中因两相区温度区间入炉，导致钢板表面产生了热装裂纹，因此宽板坯纵向裂纹、去毛刺和热装裂纹问题成为南钢板材铸机实现流程优化、铸坯热装直送和节能降耗的关键问题。详细描述了南钢超宽板坯铸机热装直送工艺实践过程，优化铸机去毛刺工艺，并对产生的板坯纵向裂纹和钢板表面热装裂纹产生原因进行分析，优化影响板坯表面纵向裂纹连铸生产工艺制度，同时根据钢种成分特点，调整优化不同钢种成分钢种坯料堆冷时间和控制入炉温度，避开热装裂纹敏感温度区，避免了热装裂纹，实现了超宽板坯热装直送工艺，降低了轧钢加热炉生产能耗。     

普通绞线钢的连铸二冷技术研究

通过热模拟试验研究了钢绞线用钢连铸坯的高温塑性曲线,结果表明为保证铸坯质量,须确定连铸拉矫温度在1 020℃,并建立了连铸二冷配水模型,通过PROCAST仿真模拟钢绞线用钢凝固过程的冷却曲线。射钉试验和生产实践证明采用该二冷配水技术可有效改善铸坯质量,降低铸坯低倍检验中的裂纹缺陷级别。     

攀钢板坯连铸二冷喷嘴性能的热态实验研究

基于钢坯的非稳态导热原理,采用金属试样单侧加热至二冷段金属表面温度再进行冷却的实验方法,模拟水/气-水喷嘴性能对钢坯冷却过程的影响.按攀钢板坯连铸的二冷段喷嘴布置方式和主要生产铸坯的品种规格,设计喷嘴特性与单、双喷嘴条件下铸坯强制冷却传热过程研究的实验方案.通过对喷嘴传热性能的测试,得到了水/气-水喷嘴在不同喷水压力下的传热系数;实验得到的双喷嘴平均传热系数与生产过程数据计算的传热系数的误差在5%～9%以内,研究结果表明喷嘴传热性能的热态实验可以为合理布置喷嘴、优化二冷制度提供依据.     

8流小方坯连铸机工艺设计特点

介绍了某钢铁生产基地2台8机8流方坯连铸机的设计特点,着重介绍设计采用的单中间罐浇注模式及有关对策;以及连铸机设计采用的适应不同热送和下线比例的双向高效出坯系统.生产实践表明,连铸机投产后设备运行良好,铸坯质量优良,达到了预期的设计效果.     

广西钢铁双流板坯提高铸坯热送率生产实践

<正>随着连铸、铸坯无缺陷技术的突破，以及热连轧工艺装备的发展，通过充分利用连铸坯白身温度，采用“热送热装”轧制技术，已成为钢铁生产节能降耗的发展方向。采用热送直轧工艺能简化生产工艺流程，缩短物流周期，提高加热炉和轧机的生产能力，减少烧损，大幅度节省能耗，提高成材率和生产效率，降低劳动强度。广西钢铁集团双流板坯连铸机于2020年投产，由于投产初期设备精度欠佳、工艺尚不成熟，加之生产组织及管理制度不完善等，导致铸坯热送率较低。集团通过不断提高设备精度、优化生产工艺，保证铸坯质量及优化生产组织，大幅提高了铸坯热送率、降低了加热炉煤气消耗，实现了节约能源低碳生产，取得了显著的经济效益。     

薄板坯连铸传热过程与应力状态仿真软件的开发

基于准稳态二冷凝固传热数学模型和高温弹塑性应力应变数学模型,开发了薄板坯连铸传热过程与应力状态仿真软件CISDI_HPSS FOR THIN SLAB R2009,其中详细考虑了二冷区存在的多种传热方式和铸坯宽度方向上喷淋冷却的非均匀性以及夹辊支承、钢水静压力、拉坯、矫直等因素对铸坯高温力学变形的影响,软件对凝固传热和应力应变的耦合计算功能强大,具有良好的通用性和适用性,其仿真结果可用于优化薄板坯连铸机的工艺和设备参数,为相关工艺技术的开发和铸机工程设计提供重要的理论支撑。     

热装,直接轧制技术的开发和应用

在概述了普钢热装，直接轧制技术的概况之后，着重论述了特殊钢热装和轧制技术的几亿问题。分析了无缺陷铸坯热装，直接轧制工艺的特点，介绍了铸坯的保温技术。     

特厚板坯连铸机基本半径确定方法的探讨

重点介绍了直弧形特厚板坯连铸机基本圆弧半径的选择思路,给出了直弧形特厚板坯连铸机基本圆弧半径确定的方法,即在经验公式的基础上,综合考虑在不同基本圆弧半径下的总变形率、浇铸区的鼓肚变形率、出坯辊面标高、是否凝固矫直等因素来确定。本方法应用于新余特厚板坯连铸机设计中,在生产实践中取得较好的效果,目前连铸机生产稳定,铸坯质量良好。     

高碳耐磨球钢大方坯连铸过程凝固性能的仿真分析

应用有限元分析软件建立290 mm×380 mm大方坯连铸过程凝固传热模型,模拟不同碳质量分数高碳耐磨球钢大方坯宽面和窄面凝固坯壳的生长规律。研究结果表明:该模型通过计算得到铸坯宽面的外壳温度还有铸坯宽面、窄面中心的凝固坯壳厚度进行对比分析,验证了该数学模型可以表达凝固坯壳厚度的分布情况,最终达到准确推测凝固终点位置的目的。在弯月面到二冷出口这一阶段,凝固时间和凝固坯壳厚度d显示出线性关系。在距弯月面10 m到凝固终点这一阶段,凝固时间t1/2和坯壳厚度d并不是线性关系,且铸坯中心等轴晶区域出现。     

某四缸发动机缸盖裂纹分析与解决

某发动机经过600 h交变负荷试验后,气缸盖鼻梁区出现裂纹。主要对缸盖的断口、材料、铸造工艺、冷却等4个方面进行分析。经分析发现缸盖产生裂纹的主要原因为铸造工艺问题导致的金相变质和硬度不达标,缸盖内部严重积瘤,从而导致火花塞周围冷却水通道截面减小,缸盖冷却不足,缸盖内部温度偏高,热负荷偏高。通过改进铸造工艺和缸盖水套圆角结构优化,提高了缸盖自身的机械性能和水套的冷却能力,进而使缸盖的抗热负荷能力提高;经过对优化后的缸盖进行试验验证,优化后的缸盖在600 h交变负荷后未出现裂纹,达到了试验需求。     

水管冷却技术在大型渡槽防裂中的应用研究

针对大型渡槽施工期间常见裂缝问题,采用三维有限元仿真分析软件,以南水北调某大型渡槽为例,对混凝土浇筑全过程进行了模拟,分析了一期水管冷却效果,并对水管冷却的通水温度进行敏感性分析.计算结果表明,水管冷却具有良好的导热降温作用,不同的通水温度对混凝土温度降幅基本一致,在确保降温效果的同时可适当提高通水温度以降低水管附近混凝土的拉应力,同样能有效防止施工早期和后期其他部位出现温度裂缝,可供类似工程在施工期的温控措施借鉴.     

Thermal performance analysis of a phase change thermal storage unit for space heating

This paper presents the results of a comprehensive numerical study on the thermal performance of an air based phase change thermal storage unit (TSU) for space heating. The unit is designed for integration into space heating and cooling systems. The unit consists of a number of one dimensional phase change material (PCM) slabs contained in a rectangular duct where air passes between the slabs. The numerical analysis was based on an experimentally validated model. A parametric study has been carried out including the study on the effects of charge and discharge temperature differences, air mass flow rate, slab thicknesses, air gaps and slab dimensions on the air outlet temperatures and heat transfer rates of the thermal storage unit. The paper introduces and discusses quantities called charge and discharge temperature differences which play an important role in the melting and freezing processes.     

新型活塞冷却油道的设计与成型技术

活塞作为内燃机中承受高温高压的部件,除了常规的冷却方式,不断地追求活塞结构上的改进,在不增加活塞质量和影响内燃机的功率的前提下,加强对活塞的冷却,将是活塞未来的发展方向,我们介绍了一种新型的冷却道活塞的设计技术,以及利用盐芯在铸造过程中形成冷却油道的生产技术。     

板坯连铸动态二冷配水技术的工业应用

基于耦合多元合金两相区凝固模型的板坯连铸凝固传热数学模型和恒间距切片单元跟踪方法,开发了板坯连铸动态二冷配水软件平台,其中内嵌二冷分区有效拉速和目标表面温度曲线两种控制模式,前者充分考虑了铸坯的冷却历史,后者则关注对铸坯表面温度沿铸流方向的合理控制,在实际生产中可以方便灵活地加以选择应用.该技术控制功能丰富、安全机制完...     

Influence of cooling medium characteristics on embedded tube fusion condition in the process of embedded tube sand mold casting

Embedded copper tube sand mold casting is the main manufacturing method of iron‐making blast furnace copper cooling stave, comparing embedded copper tube outer wall temperature with copper melting point is used to judge the fusion between liquid copper and embedded copper tube. On the basis that the computational model is reliable though experimental proof, the paper studies the influence of cooling medium characteristics on the embedded copper tube outer wall temperature. The calculated results show that the cooling medium thermal physical properties play a vital role on heat transfer between the liquid and embedded copper tube in the process of casting and determine the embedded copper tube outer wall temperature and the fusion. Through the numerical research, the cooling medium with suitable physical properties is found, adjusting the cooling media Reynolds number is an effective way to regulate the embedded tube outer wall temperature to the temperature required for fusion; in addition, modifying the cooling medium temperature entering the embedded tube is also a means adjusting the embedded tube outer wall temperature and improving the fusion between the embedded tube and liquid copper, but the method is not easy to operate in practice.     

Dynamic model for ladle preheater performance evaluation

Molten steel produced in an electric arc furnace is poured into a ladle and transported to a continuous casting machine. In order to minimize the heat losses during transportation, the inner surface of the ladle is lined with refractory material. Also, this inner surface needs to be preheated to prevent the cooling of the molten steel below the casting temperature. The paper describes a dynamic model for a ladle preheater with the objective of predicting the heat-up time. It has been validated by experiments performed on an existing ladle in an iron and steel mill. The results predicted by the model are sufficiently accurate for practical use. The model is further used to investigate several important operating parameters that are expected to shorten the heating time, conserve energy and increase the productivity.     

A multi-zonal integral method for problems involving unsteady one-dimensional heat conduction with change of phase

A method is presented for calculating the temperature in a solidifying slab of molten material with greatly differing cooling rates on the inner and outer surfaces. For the purposes of analysis the slab is divided into a number of zones having time-varying boundaries, e.g. solidification or conduction fronts. Appropriate approximations are made for the temperature profile and the heat-balance integral equation applied separately in each zone. This leads to systems of first-order ordinary differential equations which can be integrated numerically by using simple standard methods. Results are presented which correspond to the industrial casting of polypropylene film.     

日最大降温时堆石坝混凝土面板温度应力研究

以在建的公伯峡水电站混凝土面板堆石坝为例,针对面板施工期发生日最大降温 日温差 这一特殊气候条件,实时模拟面板的施工过程,对面板的温度场和温度应力进行了仿真分析,获得了在发生日最大降温情况下混凝土面板温度场和温度应力的变化及分布规律.     

Thermal analysis and management of proton exchange membrane fuel cell stacks for automotive vehicle

The thermal management of a proton exchange membrane fuel cell (PEMFC) is crucial for fuel cell vehicles. This paper presents a new simulation model for the water-cooled PEMFC stacks for automotive vehicles and cooling systems. The cooling system model considers both the cooling of the stack and cooling of the compressed air through the intercooler. Theoretical analysis was carried out to calculate the heat dissipation requirements for the cooling system. The case study results show that more than 99.0% of heat dissipation requirement is for thermal management of the PEMFC stack; more than 98.5% of cooling water will be distributed to the stack cooling loop. It is also demonstrated that controlling cooling water flow rate and stack inlet cooling water temperature could effectively satisfy thermal management constraints. These thermal management constraints are differences in stack inlet and outlet cooling water temperature, stack temperature, fan power consumption, and pump power consumption.