浸入式水口燃烧式烘烤预热温度场研究

浸入式水口在浇钢以前必须进行充分预热 ,利用燃烧的煤气烘烤水口是常用的预热烘烤方式。本工作运用有限元技术对浸入式水口燃烧式烘烤预热的瞬态传热过程进行了研究 ,得到了水口烘烤预热后的温度场分布和水口的升温曲线。研究结果表明 ,在燃烧式预热烘烤方式下 ,水口沿轴线方向的温度变化梯度较大 ,水口颈部预热后的温度较低 ,是导致水口颈部频繁断裂和较易出现竹节样裂纹的主要原因。欲提高水口颈部的预热温度 ,必须改进水口的预热烘烤方式     

Development of theoretical process maps to study the role of powder preheating in laser cladding

Cladding is the process of depositing a superior built-up layer by fusion on a substrate. In blown powder laser cladding process, the powder travels across the laser path, gets heated up by absorbing laser energy, and finally melts on the substrate under the intense laser beam; as the substrate moves away this melt pool solidifies to form a continuous built-up layer. The laser energy is partly absorbed by the solid powder during its flight path (termed preheating) and partly by the top surface of the melt pool. In the present study a two-dimensional conduction heat transfer equation has been solved using finite-volume method to model the cladding process. It is observed that preheating allows higher scanning speed resulting in thin clad layer with low dilution. Preheating also permits high powder feed rate resulting in thick cladding with low dilution.     

链篦机-回转窑铁矿氧化球团干燥预热工艺参数研究

利用程潮铁矿自产磁铁精矿,在膨润土添加量为1.0%~1.2%时,润磨后造球。通过模拟链篦机装置试验,研究了链篦机-回转窑氧化球团生产工艺中链篦机料层高度、鼓风干燥热风温度、抽风干燥热风温度、预热热风温度及风速(工况)等预热工艺参数。在此干燥预热工艺条件下,链篦机干球经回转窑焙烧固结后,球团矿抗压强度2828N/个,转鼓指数(+6.3mm)93%,耐磨指数(-0.5mm)3.53%,FeO<1%,成品球质量达到了优质球团质量的要求。     

Overlapping tracks processed by TIG melting TiC preplaced powder on low alloy steel surfaces

An overlapping composite track coating was produced on a steel surface by preplacing a 0·5 mm thick layer of TiC powder and then melting using a tungsten inert gas torch of constant energy input. The influence of the overlapping operation on preheating of the substrate, the dissolution of TiC particulates and the subsequent depth and hardness of the composite layer was analysed. The melt microstructure consisted of both undissolved and partially dissolved TiC particulates, together with a variety of morphologies and sizes of TiC particles precipitated during solidification. Preheating, resulting from the overlapping operation, occurred, producing additional melting of the TiC particulates and deeper melt depths but with a reduced volume fraction of TiC precipitates in the subsequent tracks. A maximum hardness of over 800 HV was developed in the composite layer. The high hardness was unevenly distributed in tracks melted at the initial and final stages, while it varied across the melt depths in other tracks.     

Effect of rapid curing process on the properties of carbon fiber/epoxy composite fabricated using vacuum assisted resin infusion molding

Long processing cycle makes vacuum assisted resin infusion molding (VARIM) only suitable for low and medium volumes of production, and shortening of curing time is critical to improving the processing efficiency of automotive composite parts. In this paper, unidirectional carbon fiber reinforced composite laminates were fabricated by VARIM. Three different processes (namely quick, quick-post and preheating) were employed, in which a kind of rapid curing epoxy resin is used. The preheating of mold and fiber was conducted to shorten the filling time compared with that of quick process. Quick-post process with a post cure stage was investigated to verify the composite properties fabricated by quick process. The cycle time was 16 min for preheating process, about 30% shorter than that of quick process, simultaneously, flexural strength and interlaminar shear strength (ILSS) were respectively improved by 29% and 7% compared with those of quick process. The non-uniformity of mechanical properties at different positions along resin flow direction under preheating process was found, but the processing quality of composite was good. The preheating process is confirmed to be suitable for the improvement of processing efficiency of VARIM with good mechanical properties. In addition, the composite fabricated by quick-post process has better mechanical properties, which is attributed to the alleviation of residual stress during post curing process.     

火烧油层点火方式研究

点火是决定火烧油层成败的关键因素,文章对目前火烧油层所采取的主要点火方式的适用条件进行研究分析,结合现阶段研究人员室内一系列先导试验及现场总结出的有价值的经验公式,研究分析各个相关因素(地层温度、电点火注气速率、孔隙度等因素)对点火的影响程度,总结出各因素的变化与点火时间的关系,对相关因素的影响进行进一步的整合、推导,考虑多因素前提下总结出一套可以服务于点火施工的设计方案。     

Pore formation mechanism and its mitigation in laser welding of AZ31B magnesium alloy in lap joint configuration

Magnesium is one of the lightest structural metals that has been used in different industries such as automobile, aerospace and electronics. However, in fusion joining of magnesium alloys, porosity is one of the main drawbacks to achieve a weld with desirable properties. The oxide layer existing on the surface of magnesium alloy is one of the causes of pore formation in the weld bead. In the current study, a fiber laser with a power of up to 4 kW is used to weld samples in a zero-gap lap joint configuration. Two groups of samples are studied: as-received (AR) surfaces (where an oxide layer remains on the surface) and treated surfaces. The surface treatment includes two techniques: mechanically removed (MR) and the use of a plasma arc (PA) as a preheating source. Also, a separate set of experiments are designed for preheating samples in a furnace for comparison with the PA-treated results. To reveal the chemical compositions of the welds and metal sheet surfaces, an energy dispersive spectroscopy (EDS) is performed. Surface chemical compositions are tested by X-ray photoelectron spectroscopy-reflected electron energy loss spectroscopy (XPS-REELS) to characterize the surface composition on AR and PA-treated samples. The dynamic behavior of the weld pool and laser-induced plasma plume is monitored in real-time using a high speed CCD camera to investigate the stability of the laser welding process. The presence of the oxide layer at the faying surface of two overlapped sheets results in an unstable process. The obtained results reveal that the preheating procedure can effectively mitigate pore formation at the interface of the two overlapped sheets.     

混合配置的PLC在邯钢7#高炉热风炉自动控制系统中的应用

本文简介了邯钢7#高炉热风炉的工艺状况，重点描述了基于Quantum PLC的热风炉本体仪控系统、基于西门子S7-400PLC（软件配置按PCS7系统模式）的热风炉热油预热控制系统和基于西门子S7与S5系列PLC混合配置的热风炉换炉电控系统的构成、软硬件配置、工作原理、主要控制功能和应用效果。     

竖炉式电弧炉的发展与现状

叙述世界炼钢工业中竖炉式电弧炉的发展概况及特点，对竖炉的形式、结构、工艺操作和节能优势等方面进行了分析和探讨，并对竖炉发展趋势提出了看法。     

埋地热油管道投产运行规律探讨与浅析

为了掌握原油管道投产运行规律,探讨了埋地热油管道投产过程中管内介质温度以及管外土壤温度场的变化规律,并分析土壤导热系数、输量对管内介质和管外土壤温度场的影响,并对不同预热方式进行浅析比选。结果表明：土壤导热系数和管道输量是埋地热油管道投产过程的主要影响因素;闷管预热的能量利用率最高,正向预热效果最好。