热处理对4Cr5MoSiVl钢热疲劳裂纹扩展驱动力的影响

利用自制的高频感应加热、吹风冷却式试验机,对4Cr5MoSiVl钢缺口板状试样进行了Coffin型热疲劳试验。记录了热循环次数、热疲劳裂纹长度、试样中热应力变化之间的关系。分析了热循环过程中试样中应力的变化及热处理的影响。结果表明:热疲劳裂纹扩展驱动力为循环下限温度时的拉应力,驱动力的产生起源于循环上限温度时的压缩塑性应变,主要受钢的组织循环稳定性和钢的高温屈服强度所控制。4Cr5MoSiV1钢淬火后,经较高温度回火,使组织较为稳定时,可以得到较低的热疲劳裂纹扩展驱动力,从而具有较低的裂纹扩展速度。     

Non-metallic Inclusions in Continuously Cast Aluminum Killed Steels

In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Probe Microanalysis) and by analyzing the total oxygen. The results showed that in the slabs the total oxygen was quite low and the inclusions discovered were mainly small-sized angular alumina inclusions. This indicates that most inclusions have been removed by floating out during the continuous casting process. In addition, the countermeasures were discussed to decrease the alumina inclusions in the slabs further.     

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.     

30t转炉-小方坯连铸生产ML40Cr冷镦钢盘条的实践

阐述了ML40Cr冷镦钢生产情况,对采用氧气顶吹转炉→LF钢包精炼炉→小方坯连铸→高速线材轧制生产的冷镦钢盘条进行了综合检验分析.结果表明,生产的10 mm盘条金相组织为铁素体＋珠光体,晶粒度9～10级;钢中A、B、D类非金属夹杂物的级别分别为0.5级、1.0～1.5级和1.5～2.0级,单位面积内当量直径5μm的夹杂物个数为20～22个/mm2,夹杂物平均直径为3.656～3.891μm,夹杂物含量相对较少,夹杂物尺寸相对比较细小;轧材的综合力学性能良好,同时具有良好的塑性变形能力,可以满足标准件生产要求.     

激光熔凝对4Cr5MoSiV模具钢组织及性能的影响

采用激光熔凝对4Cr5MoSiV模具钢进行了表面改性处理,研究了激光熔凝处理对模具钢组织和力学性能的影响．结果表明,材料经熔凝处理后,由表及里依次为熔凝层、淬火层、热影响区和基体．熔凝层由典型的柱状晶组成,熔凝层和淬火层之间存在一层极薄的等轴晶区;淬火层的晶粒发生细化和超细化．强化层厚度达1．1mm,平均硬度比基体提高26％,热影响区的厚度为0．3mm左右,强化层的耐磨性和耐腐蚀性显著提高．     

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…     

MnS+TiN夹杂物对超高强度钢韧性的影响

超高强度钢中常见的两类夹杂物为MnS和TiN,它们共同对韧性的影响迄今尚未系统研究过。本文以D_6AC钢为基体,分别改变硫和氮的含量,使钢中含有8种不同含量的MnS+TiN夹杂物。通过板状试样拉伸实验,观察裂纹在夹杂物上形核和扩展的准动态过程,并测定了试样的常规机械性能和断型韧性。试验结果表明,夹杂物总体积分数fv和平均间距dT是影响K_1c和a_K值的两个重要参数。结果还表明,随着夹杂物尺寸的增加,裂纹临界形核应变降低。在相同尺寸情况下,裂纹在TiN上形核的临界应变比在MnS上形核小,因而MnS对韧性的影响低于TiN。     

多弧离子镀TiN涂层工艺及耐蚀性研究

为提高4Cr13马氏体不锈钢的耐蚀性,对其进行多弧离子镀处理,获得TiN涂层,并用X射线衍射仪、显微硬度计、扫描电子显微镜、电化学测量仪对涂层进行物相分析、表面形貌观察、硬度检测以及电化学腐蚀性能测试.结果表明:随着电流的增大,表面的液滴数目和尺寸增大,涂层厚度增加,薄膜硬度也增大;相结构主要为TiN,有明显的择优取向,且随着弧电流的增强,衍射峰强度略有增加.TiN试样在3.5％的NaCl溶液中耐蚀性与基体相当,在1 mol/L的H2SO4溶液中的耐蚀性比基体提高了800倍.     

20MnSi钢坯的断裂原因

本文根据生产工艺的跟踪调查和抽样检测，对造成20MnSi钢连铸坯断裂的主要工艺因素、非金属夹杂物的来源和危害、钢的化学成分、金相组织以及过热钢液浇铸的影响等进行了分析探讨．     

Study on Oxygen Content, Inclusions and Fatigue Properties of Bearing Steels Produced by Different Processes

The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continuous casting (CC) and electroslag remelting (ESR) have been investigated. The main results obtained are as follows: (1) Due to low oxygen content and dispersion inclusions in steel, the fatigue life of LF-VD-IC or CC is three times as high as that of EAF steel; (2) The oxygen content in steel produced by CC process is about 9.0× 10-6, the carbon segregation (C/C0) is from 0.92 to 1. 10 and the fatigue life of CC steel is equal to that of ladle refining ingot casting steel; (3) Although the amount of inclusion and oxygen in ESR steel is higher than that of LF-VD-IC or CC steel, the fatigue life of ESR steel is higher than that of the latter because of its fine and well dispersed inclusions.     

炉外喂钙丝与连铸水口堵塞的改善

针对连铸生产过程中水口堵塞现象，从炉外喂钙丝，改变非金属夹杂物形态，提高钢液洁净度，从而改善水口堵塞方面进行了分析研究，并论述了喂钙丝的主要控制参数及效果。     

奥氏体不锈钢离子渗氮-PECVD-TiN复合处理层组织与性能特性研究

对１Ｃｒ１８Ｎｉ９Ｔｉ 奥氏体不锈钢进行离子渗氮－ ＰＥＣＶＤ ＴｉＮ 复合处理, 研究了复合处理层的组织与性能。结果表明： 复合处理层具有优良的膜基结合强度; 较之不锈钢基体, 耐磨性显著提高; 在０－５ ｍｏｌ／Ｌ Ｈ２ＳＯ４ 溶液中, 复合处理层不仅比单一渗氮层的耐蚀性高, 在过钝化区还表现出比不锈钢基体更优越的耐蚀性。     

Microstructure analysis of AISI 304 stainless steel produced by twin-roll thin strip casting process

The microstructure of AISI 304 austenite stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vol% at the center and 6.77vol% at the surface of the casting thin strip, in vermicular and band shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of MnO·Al2O3, 2FeO·SiO2, and 2MnO·SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.     

Influence of calcium content on solid ratio of inclusions in Ca-treated liquid steel

1. IntroductionThe calcium treatment by wire feeding is applied asa routine process during steel making to eliminate noz-zle blocking [1-5]. Especially, it is an indispensabletechnology for producing pipeline steel [6-8].The calcium treatment can improve …     

Crl2系列冷作模具钢厚扁钢的生产试制

为满足市场对Cr12系列的厚扁钢的需求,填补Cr12系列厚扁钢生产的空白,对Cr12系列冷作模具钢中的典型进行试制,对轧制进行研究和分析,总结了Cr12系列冷作模具钢95～130 mm厚扁钢的轧制特点和轧制工艺,确定了Cr12系列厚扁钢的加热制度、坯料尺寸和压下规程。研究结果表明：所确定的工艺切实可行,试制钢的尺寸、外形和碳化物形态均满足了标准规定的要求,为厚扁钢生产摸索出一个具有指导意义的合理工艺     

Cr白口铸铁—钢复合铸造的组织与性能

采用铸造的方法，将不同直径的４５钢钢筋包覆在Ｃｒ白口铸铁芯部，试验研究了所得复合试样的组织与性能，结果表明，选用较大直径比并经适当热处理，可获得较理想的综合性能，外层Ｃｒ白口铸铁的硬度可达ＨＲＣ６１．５－６４．５，复合试样抗弯强度可达σｗ７００－１０００ＭＰａ，比单一Ｃｒ白口铸铁提高４０％左右。文章还对复合铸造的有关工艺参数进行了分析和讨论。     

钢中非金属夹杂物图像分形维数的研究

通过对304/304L不锈钢轧材中大型夹杂物和铸锭中显微夹杂物的图像进行处理,得到夹杂物边界的二值图像。采用计盒维数法对夹杂物轮廓的分形维数进行计算与分析,算法利用MATLAB编程实现。结果表明,夹杂物的分形维数与其组成和熔点密切相关,低熔点的Al2O3-SiO2-CaO系复合夹杂的形貌多为球形或类球形,其分形维数较小;高熔点的Al2O3夹杂物与SiO2夹杂物的形貌多为不规则形,其分形维数较大。     

Thermodynamic calculations and experiments on inclusions to be nucleation sites for intragranular ferrite in Si-Mn-Ti deoxidized steel

Microstructures and inclusions in the Si-Mn-Ti deoxidized steels after cooling in the furnace were investigated. The composition and morphology of the inclusions were analyzed using a field emission scanning electron microscope （FE-SEM） with energy dispersive X-ray spectrometry （EDS）. The kind and composition of the inclusions calculated from the thermodynamic database were in good agreement with the experimental results. There were two main kinds of inclusions formed in the Si-Mn-Ti deoxidized steels. One kind of inclusion was the manganese titanium oxide （Mn-Ti oxide）. Another kind of inclusion was the MnS inclusion with segregation points containing Ti and N. According to the thermodynamic calculation, those segregation points were TiN precipitates. The formation of intragranular ferrite （IGF） microstructures refined the grain size during the austenite-ferrite transformation. The mechanisms of IGF formation were discussed. Mn-Ti oxide inclusions with Mn-depleted zone （MDZ） were effective to be nucleation sites for IGF formation, because the MDZ increased the austenite-ferrite transformation temperature. TiN had the low misfit ratio with IGF, so the TiN precipitated on the MnS surface also promoted the formation of IGF because of decreasing interfacial energies.     

82A钢凝固过程中TiN夹杂析出热力学和动力学

用热力学和动力学方法研究82A钢液凝固过程元素偏析及其对TiN夹杂析出的影响。热力学分析表明,Ti的偏析比远高于N的偏析比;凝固冷却速度从6 K/min增至600 K/min过程中,凝固冷却速度对Ti、N凝固偏析比影响不大;钢液初始Ti含量降至0.000 2%、初始氮含量为0.002%~0.004%时,在凝固末期仍有TiN夹杂析出。动力学分析表明,随着钢液凝固冷却速度的加快,凝固析出的TiN颗粒尺寸明显变小。     

3-D Finite-Element Numerical Simulation of Centrifugal Induction Electrosalg Casting Solidification Process

A 3-D finite-element numerical simulation model of temperature field for CIESC casting solidification process was developed with the aid of ANSYS software and a series ofcorresponding experiments were made. The results showed that the good agreement was obtained between the numerical simulation and the experiments. Based on the numerical simulation results, the characteristics of tem- perature distribution in the castings during CIESC solidification process were analyzed and summarized. According to the G/R1/2 method and numerical simulation results, there is no any shrinkage defect in the CIESE casting and structure of casting is fine and compact.