车轮钢大型夹杂形成机理研究

通过冷态试验，提出车轮钢中大型夹杂物的形成机理，一是浇注前期钢水从直孔型模底砖冲入模内后，会在中心液面上形成峰涌现象，将浮在液面上的大型夹杂物推向钢锭四周的凝固前沿，造成钢锭四周大型夹杂物富集带。另一是浇注后期，钢锭液面由于散热温度降低，钢水会信托浮在液面的大闪杂物进行非均质形核、凝固，当包裹着大型夹杂物的凝固层达到一定的体积后，其比重大于钢水的比重时，就会沉入锭底，形成沉积锥大型夹杂物分布带。本     

42CrMo钢中非金属夹杂物的研究

本文通过电炉冶炼的42CrMo钢冶炼过程的不同阶段钢样、渣样及耐火材料的系统分析,对该钢中夹杂物的性质和来源进行了研究。实验片果表明:42CrMo钢中夹杂物的生成与渣和耐火材料有密切的关系;出钢过程中钢渣混出能去除硫化物夹杂,但会使钢渣卷入钢液生成大尺寸夹杂物;浇注过程中使用的耐火材料会被钢水浸蚀进入钢液,它是42CrMo纲中外来夹杂物的一个重要来源。     

大型钢锭无铝脱氧工艺研究

研究了BOF+LF+VD-下注法生产大型钢锭流程采用无铝脱氧工艺、CaO-SiO2渣系的优点,以及在此工艺下如何实现钢锭的内在质量控制,满足钢锭在锻造、加工等后续工艺处理后的机械性能要求。试验结果表明,采用该工艺彻底解决了尖晶石夹杂物对钢的纯净度的影响,设计钢锭模钢水氢含量测定方法,实现了对浇注过程钢锭模内钢水气体含量的精确测定,确保大型钢锭内在质量较好满足后续产品需求。     

304不锈钢连铸坯中的非金属夹杂物数量分布

为研究304不锈钢连铸坯中夹杂物的数量分布,用金相检验法对铸坯中的夹杂物数量进行了统计分析.结果显示,铸坯中由外向内非金属夹杂物数量增加.304不锈钢铸坯表层中绝大多数5μm以上夹杂物为球状或近似球状的硅酸盐夹杂物.但随着凝固的进行,在铸坯内部会新生大量氧化铝、镁铝尖晶石、氮化物等点状夹杂物和不规则夹杂物.铸坯心部10μm以上的大颗粒夹杂物数量较多.     

重轨钢外来夹杂物特征的研究

人为地将保护渣、耐火材料、炉渣和钢锭模内残留物加入重轨钢中，采用金相显微镜及电镜能谱仪检测所形成夹杂物的特征。结果表明，不同的加入物所形成的夹杂物的能谱不同，从而可以根据夹杂物的特征确定夹杂物的来源。     

CSP中间包内腔优化的数值模拟

针对CSP中间包内冶金过程,建立中间包内钢水流场、温度场、夹杂物运动的数学模型,对不同挡墙和挡坝的5种组合方案的中间包钢水,从流动、传热和去夹杂能力等方面进行分析。结果表明:不同挡墙和挡坝的组合方案中,方案5效果最佳,其结构合理,钢液停留时间有效延长,利于夹杂物的上浮;没有明显的低温区域,中间包出口与入口的温差为5℃;对50μm的夹杂物能去除98.4%,对40μm的夹杂物去除率达到92.3%。     

中间罐中吹气搅拌对钢水流动的影响

连铸中间罐内钢水的流动对于成分和温度的均匀，非金属夹杂物的去除都有重要影响。本文在相似原理基础上，建立了中间罐水力学模型，通过刺激－响应试验，夹杂物模拟及高速摄影流场显示实验，研究吹气搅拌对钢液流动及夹杂物去除的影响。     

夹杂物对Cr13铸钢耐磨性的影响

本文研究了动载磨损条件下夹杂物的数量、形态与分布对铸钢耐磨性的影响及其作用机理．试验表明，夹杂物在动载磨粒磨损过程中的作用与磨损机理密要相关，夹杂物的存在，增加了裂纹形核的机率，导致磨损率增加．减少夹杂物的数量，改善夹杂物的形态与分布能提高铸钢的耐磨性     

冷轧带钢表面起皮缺陷分析

利用扫描电镜(SEM)、能谱仪(EDS)和金相显微镜观察冷轧带钢表面起皮缺陷处的微观组织,分析冷轧带钢表面起皮缺陷的形成机理,探究控制起皮缺陷的主要措施。结果表明:冷轧带钢表面起皮的主要原因为夹杂物、皮下气泡及擦伤;夹杂物主要为结晶器保护渣、耐火材料形成的夹渣及钢中氧化物与夹渣的反应产物,通过提高钢水纯净度、控制钢水成分可减少钢中夹杂物的产生;轧制时基体中的气泡受压力作用从表面逸出,产生针孔状或蜂窝状缺陷,通过缩短钢水在空气中的滞留时间、保证吹氩质量等可减少气泡缺陷;钢卷在开卷、卷取及吊运过程中,钢卷层与层间产生的相对滑动会引起擦伤类缺陷,通过采用合理的工作机组及工艺参数可避免此类缺陷。     

含硼氮中碳铝镇定钢中BN夹杂析出热力学分析

运用数值模拟方法对含硼氮中碳铝镇定钢中BN 析出的热力学条件进行分析,研究该钢种在冶炼浇注及加热奥氏体化过程中BN夹杂物的析出规律,并与试验情况进行了比较.结果表明,在钢液中初始ω（B）≤0.012%、初始w（N）≤0.03%的情况下,含硼氮中碳铝镇定钢浇注凝固过程中不能析出BN夹杂物,且钢液中B的富集程度远高于N,凝固末期残余液相中,B浓度是其初始浓度的20倍,N 浓度约为其初始浓度的2.1倍;钢中ω（B）为0.005%-0.01%、ω（N）为0.01%-0.03%时,在1470K奥氏体化温度以下,可以稳定析出BN夹杂物,B、N含量越高,BN夹杂开始析出的温度越高;在奥氏体化过程中,钢坯中酸溶铝含量越高,越容易析出BN夹杂物.     

Influence of flow control devices on metallurgical effects in a large—capacity tundish

The influence of flow control devices on metallurgical effects in large-capacity tundish has been studied carefully with elements tracing,sampling and theoretical prospecting,The results from the studies are(1) in the continuous casting of clean steel,bad control of tundish operation may deteriorate the cleanliness of steel;(2) the cleanliness of steel is deteriorated mainly at the unstady state;(3) large amount of macro inclusions come from the top slag and the refractory of tundish;(4) installing dam and weir can improve the cleanliness of steel and lighten the influence of steel fluctuation;and (5) the result of theoretical calculation suggests that the inclusions larger than the critical size of 92.6um can be floated out from the tundish bath completely.     

Numerical simulation of flow phenomena and optimum operation of tundish

1　INTRODUCTIONDuringthecourseofcontinuouscastingsteel,theflowofliquidsteelintundishwasafairlycomplexprocesscontainingmomentumtransfer,masstransfer,energytransferandphase changeofmultiphasecomponents .Ac cordingtoRefs.[1,2 ],someinfluencingfactorsincastingsteelwerefound ,includingthecompositionofliquidsteel,thetechnicalparametersoftundishandre oxidationofmoltenmetal.Theprocesswouldaffectdirectlysurfacedefectsandinternalstructureformationofthecastingsteelproductsaswellastherealizationofhig…     

BOF-LF-CSP与BOF-渣洗-CSP工艺生产Q235B钢中夹杂物对比分析

采用金相显微镜对BOF-LF-CSP与BOF-渣洗-CSP工艺所生产Q235B钢中非金属夹杂物数量和组成进行对比分析。结果表明,两工艺过程中各粒径颗粒夹杂物在总体上均减少,且粒径越小,其趋势越加明显;两工艺夹杂物总去除量分别为73.5%和72.3%,其中大部分夹杂物在转炉终点至LF前阶段被去除。BOF-渣洗-CSP工艺中夹杂物以Al2O3、FeS·MnS、CaO为主。两工艺过程中夹杂物演变规律相似,出钢渣洗效果明显,由此表明BOF-渣洗-CSP工艺生产可行。     

Effect of austenitizing temperature on microstructure in 16Mn steel treated by cerium

The change of inclusions and microstructure of 16Mn steel treated by Ce were observed,and the effect of austenitizing temperature on the microstructure was also examined.The results show that the inclusions are transformed from Si-Mn-Al composite oxide and MnS into AlCeO3,Ce2O2S,and MnS composite inclusions after being treated by Ce.Plenty of intragranular ferrites are formed in 16Mn steel conraining ～0.017wt％ Ce.A large amount of intragranular acicular ferrites are formed after being austenitized for 20 min at 1473 K.The prior austenite grain size fit for the formation of intragranular acicular ferrites is about 120 μm.     

OCr21Ni5Ti双相不锈钢超塑成形研究

在GLEEBLE1500热／力模拟实验机上首次对OCr21N6Ti双相不锈钢进行了超塑性能研究,并获得了良好的超塑性能,同时确定了其超塑性成形的最佳工艺参数将得出的最佳工艺参数应用于超塑性气压胀形工艺,在1000kN超塑性成形机上一次整体成形出了由OCr21N6Ti钢制造的一种带有侧凸的复杂零件     

Behavior of Non-metallic Inclusions in Centrifugal Induction Electroslag Castings

In order to know the behavior of non-metallic inclusions in centrifugal induction electroslag castings (CIESC), non-metallic inclusions in 5CrMnMo and 4Cr5MoSiV1 were qualitatively and quantitatively analyzed. The largest size of inclusions in the casting and the thermodynamic possibility of TiN precipitation in steel were also calculated. The results show that sulfide inclusions are evenly distributed and the content is low. The amount of oxide inclusions in CIESC 4Cr5MoSiV1 steel is close to the ESR steel and lower than that in the EAF steel, and there are some differences along radial direction. Nitride inclusions are fine and the diameter of the largest one is 3-4 μm. With the increase of the centrifugal machine's rotational speed, the ratio of round inclusions increases and the ratio of sharp inclusions decreases. According to the experiment and the calculation results, it is pointed out that the largest diameter of non-metallic inclusions in the CIESC 4Cr5MoSiV1 casting is only 6.6 μm, and [N%][Ti%] in 4Cr5MoSiV1 steel should be controlled less than 4.4× 10-5 in order to further reduce the amount and size of TiN inclusions.     

Susceptibility of two types of low-alloy hull steels to pit initiation

Four low-alloy hull steels with different alloy elements were selected. Their susceptibility to pitting corrosion was compared by means of electrochemical polarization test. The inclusions in the steels and their pitting corrosion characteristics were studied by an electron probe micro-analyzer (EPMA). The results indicate that some inclusions are the main sources of pitting corrosion. The susceptibility of nickel-chromium steel to pit initiation is less than that of manganese steel. Under the same conditions, nickelchromium steel is easier to passivate than manganese steel, and the passive films on nickel-chromium steel surface are more stable than that on manganese steel. In low-alloy steels, the higher the contents of nickel and chromium, the lower the critical passive pH value. In the same kind of steel, multi-phase inclusions containing sulfide are easier to initiate pitting corrosion than other inclusions.     

矩管混凝土柱-SRC梁型钢贯通节点抗震性能试验研究

提出一种适用于快速施工的新型矩管混凝土柱-SRC梁型钢贯通节点形式。参考实际两种建筑规格,设计4个节点试件,基于拟静力荷载试验,探讨节点试件抗震性能,分析各试件的破坏现象、滞回性能、刚度、延性及耗能能力等抗震性能。结果表明：节点的破坏形态为梁端混凝土压坏,型钢翼缘屈曲,形成塑性铰;试件的滞回曲线相对饱满,刚度退化明显,延性系数在2.33~3.8之间,等效黏滞阻尼系数在0.283~0.4之间。与已有节点对比,新型节点刚度大,同时避免了核心混凝土浇筑困难的问题。     

Stability of Ultra-fine Microstructures during Tempering

The stability of ultra-fine microstructure during tempering at 650℃ was investigated on a Nb-containing steel. The steel had undergone 5 passes controlled rolling, then was relaxed (air cooled) to 730 ℃ and cooled in water The evolution of microstructure was that, in early stage of tempering, no obvious change was detected by means of optical microscopy while dislocation cells were formed inside bainitic laths. With further tempering, bainitic laths started to coalesce in some regions. Finally, polygonal ferrite was formed while hardness decreased dramatically. Some samples taken from the same primary plate were reheated at 930 ℃for 0.5 h followed by quenching into water before tempering. Despite their lower original hardness, the reheated samples softened faster during tempering. Ferrite was quickly formed in the reheated samples. These results indicate that the evolution of microstructures towards equilibrium during tempering of the steel is mainly determined by whether dislocations are pinned rather than the dislocation density.     

易切不锈钢中非金属夹杂物在切削中的变形特性

采用金相显微镜、扫描电镜和能谱分析等手段,对OCr16Ni10CaS复合易切奥氏体不锈钢(牌号F176、F176B)的大量切屑根部磨片进行了观察与研究,在切削过程中,此钢中的非金属夹杂物流经不同变形区时,其变形特点是不同的;此钢中的氧化夹杂物主要是由MnS和FeS包裹着的多元氧化物CaO、MgO、Al_2O_3、SiO_2、MnO,在刀-屑接触区的高温高压作用下,可由刃口及滞流层的微裂纹中被挤出并涂抹到刀具表面上,为形成刀具表面覆盖膜创造了必要条件。