冷轧及中间退火过程中GH4700镍基合金管组织演变规律研究

利用光学金相显微镜研究了GH4700合金在冷轧以及中间退火过程中的组织演变规律,建立了中间退火过程中再结晶晶粒长大方程。实验结果表明:随着冷轧变形量增大,晶粒的变形均匀性逐渐变好,GH4700合金的屈服强度和抗拉强度增大,延伸率降低;当退火温度为1130℃、保温时间为15min时,组织发生完全再结晶且分布均匀,是较合适的一次冷轧中间退火工艺;所建立的晶粒长大模型预测结果与试验值吻合较好。     

冷拉拔铜包铝细丝的退火工艺与组织性能研究

研究了冷拉拔铜包铝细丝合理的退火工艺及其对材料力学性能、铜包覆层组织及界面扩散层厚度的影响规律.结果表明:铜包铝细丝的最佳退火工艺为300℃×60min.低于200℃退火时,铜包铝细丝铜包覆层处于回复阶段,细丝强度从冷拉态的361MPa急剧下降到236MPa,延伸率略有降低;300℃退火后,铜包覆层的再结晶完成,细丝的抗拉强度下降至约152MPa,延伸率升到最高,达到16.3%;400℃退火后,铜包覆层晶粒显著长大,界面处生成脆性金属间化合物,延伸率急剧下降.界面扩散层的厚度随退火温度和保温时间的增加而增大,当退火温度低于300℃时,扩散层厚度随退火时间增加缓慢;当退火温度高于350℃后,扩散层厚度快速增大.延伸率随扩散层厚度的增加先升高后降低,当界面扩散层厚度为2μm时,铜包铝细丝的延伸率最高.     

高强汽车双相钢的连续退火与组织性能研究

目的 提升高强DP980双相钢的力学性能,优化连续退火工艺。方法 对高强汽车双相钢进行了连续退火处理,研究了连续退火均热温度、均热时间、过时效温度对冷轧双相钢显微组织、物相组织和力学性能的影响。结果 对于不同退火均热温度处理的双相钢,其组织均为铁素体(F)+马氏体(M),随着均热温度从715 ℃升高至865 ℃,残余奥氏体体积分数逐渐减小,抗拉强度、屈服强度先增后减,断后伸长率逐渐减小,在均热温度为815 ℃时,双相钢的抗拉强度和屈服强度达到最大值。随着均热时间从0.5 min延长至5 min,双相钢的晶粒尺寸逐渐增大,残余奥氏体体积分数先减后增,抗拉强度、屈服强度先增后减,断后伸长率先减后增,在均热时间为1.5 min时,抗拉强度和屈服强度达到最大值。随着过时效温度从245 ℃上升至395 ℃,双相钢中的马氏体体积分数逐渐减小,当过时效温度为395 ℃时,出现了贝氏体,奥氏体体积分数先增后减,抗拉强度、屈服强度逐渐减小,断后伸长率逐渐增大。结论 冷轧DP980双相钢适宜的连续退火工艺如下:均热温度为815 ℃、均热时间为3 min、过时效温度为295 ℃。此时双相钢具有较好的强塑性。     

连续退火和水淬+回火工艺对DP1000双相钢屈服特性的影响

分别采用连续退火和水淬+回火工艺模拟了1000MPa级冷轧双相钢的退火过程.连续退火工艺下双相钢的屈服强度较低,250℃过时效时屈服强度为472MPa;320℃过时效时屈服强度为454MPa.而水淬+回火工艺下双相钢的屈服强度较高,250℃回火时屈服强度为1083MPa;320℃回火时屈服强度为887MPa.金相分析显...     

加磷高强IF钢的最优冷轧压下率确定

为了确定加磷高强IF钢的最优冷轧压下率,以工业生产的加磷高强IF钢热轧钢板为试验材料,在实验室进行了冷轧试验和盐浴退火试验,研究了冷轧压下率对试验钢显微组织和力学性能的影响。结果表明:在试验条件下,试验钢冷轧压下率为50%～80%,退火温度为820～850℃时,再结晶完成;随着冷轧压下率的增加,晶粒变得细小均匀;冷轧压下率为50%～80%,退火温度为850℃时,屈服强度为160 MPa左右,抗拉强度为345 MPa左右,延伸率为35.0%左右,塑性应变比r值和应变硬化指数n值都较高,r值为1.5左右,n值为0.30左右。最终确定工业生产中最优冷轧压下率为60%～70%。     

退火温度对LH800空冷强化钢组织与力学性能的影响

为获得具备良好冷成形性能的空冷强化钢，以冷轧LH800为研究对象，采用SEM、EBSD、TEM等技术手段，研究了该钢种在罩式退火过程中的组织演变和力学性能变化。研究结果表明：在600～700℃退火得到了铁素体+碳化物组织，拉伸曲线出现明显的屈服平台，并且屈服平台长度随退火温度的升高而减小。随着退火温度升高，铁素体晶内纳米级碳化物数量逐渐减少，晶界粗大碳化物数量逐渐增多，小角度晶界体积分数逐渐减小，且局部取向差(KAM)值逐渐减小。当退火温度超过700℃时，显微组织为铁素体+马氏体+碳化物，拉伸曲线无屈服平台出现。随着退火温度的进一步升高，马氏体体积分数逐渐增加，KAM值也逐渐增大。力学性能结果显示：在700℃退火保温4 h,空冷强化钢的屈服强度和抗拉强度最低，延伸率最高，具备最佳的冷成形性能。本工作基于冷轧LH800退火过程的显微组织和纳米级碳化物的演变，揭示了LH800出现屈服平台现象的本质，并获得了该钢种具备最佳冷成形性能的关键工艺参数。     

深冲IF钢再结晶{111}纤维织构形成机制探讨

为了探讨深冲IF钢再结晶织构与退火温度之间的关系及{111}再结晶织构形成机制,采用X射线衍射三维取向(ODF)和背散射电子衍射(EBSD)分析技术并结合金相组织观察,利用Gibbs-Thom son方程对冷轧IF钢在不同退火温度下的再结晶织构演变规律及形成机制进行研究.实验结果表明:随着退火温度的增加,再结晶量逐渐增多,γ纤维织构强度亦相应增强,同时,α纤维织构强度则逐渐降低;冷轧IF钢再结晶初期的织构转变主要发生在γ纤维织构之间.研究表明,再结晶核心的形成主要以"显微择优形核"为主,晶核的长大则主要以择优生长为主,而Σ重位点阵晶界在再结晶γ纤维织构形成过程中起着重要作用.     

超低温轧制304奥氏体不锈钢马氏体逆相变及组织表征

目的 研究超低温轧制(Cryogenic Rolling,CR)亚稳态奥氏体不锈钢在不同退火温度下马氏体逆相变、组织演变及力学性能的变化规律。方法 首先,对实验原料304奥氏体不锈钢进行1 050 ℃保温30 min的固溶处理;其次,对实验钢进行总压下量为65%的超低温轧制,并在600~750 ℃下进行5 min退火处理;最后,对退火处理后的实验钢进行组织表征和力学性能测试,研究退火过程中组织演变及力学性能变化规律。结果 经总压下量65%超低温轧制后,实验钢组织中的奥氏体可全部转变为马氏体。随退火温度的升高,发生逆相变的奥氏体含量增加,组织由回复组织逐渐向再结晶组织演变。当退火温度为750 ℃时,晶粒尺寸约为420 nm。经退火处理后,实验钢硬度由超低温轧制态的566.2HV10降至750 ℃时的378.1HV10,屈服强度较固溶态的大幅度提高。经750 ℃退火处理5 min后,实验钢可获得抗拉强度896.5 MPa、延伸率52.7%、强塑积47.2 GPa.%的优异综合力学性能。结论 经超低温轧制及退火处理后,304奥氏体不锈钢可获得晶粒尺寸＜500 nm的亚微米/纳米组织,经700 ℃以上退火处理可获得优于固溶态的综合力学性能。     

退火温度对GH3600合金箔材组织与性能的影响

目的 探究退火温度对GH3600镍基高温合金箔材微观组织及力学性能的影响。为制备综合性能良好的GH3600箔材提供参考。方法 将厚度为2 mm的铸态板材反复轧制退火得到组织均匀的0.3 mm厚度带材,再利用四辊冷轧机将带材轧制成厚度为0.1 mm和0.05 mm的箔材,然后将2种厚度箔材在950、1 000、1 050 ℃下保温1 h后空冷。通过金相观察、电子探针、EBSD检测及XRD分析来研究箔材的微观组织演变。通过拉伸实验检测箔材的室温拉伸性能。结果 随着变形程度的增大,轧制态箔材晶粒沿轧制方向被拉长得更加明显。在相同热处理参数下,0.05 mm退火态箔材晶粒尺寸更小。退火后,箔材晶粒发生了回复再结晶并析出了细小的碳化物。随着退火温度的升高,晶内碳化物逐渐减少,孪晶界比例增大,再结晶程度及晶粒尺寸增大。0.05 mm箔材在1 050 ℃退火时,其晶粒迅速粗化,在厚度方向上出现单层晶,导致箔材的抗拉强度及延伸率出现异常降低的现象,即“越小越弱”的尺寸效应。结论 适宜的热处理工艺有助于改善箔材的微观组织,进而提高其力学性能。0.05 mm箔材在950 ℃下退火1 h时,其延伸率为19.1%,屈服强度以及抗拉强度分别达到293 MPa和560 MPa,综合力学性能良好。     

240 MPa级高强IF钢的冷轧压下率和退火温度

以工业生产的240MPa级高强IF钢为试验材料,进行了冷轧压下率和退火温度的实验室研究。结果表明:在试验条件下,不同退火温度下,冷轧压下率在75%~85%时,试验钢为完全再结晶组织,卷取温度较高在710℃的试验钢的屈服强度、抗拉强度、伸长率、屈服点伸长率、塑性应变比及应变硬化指数分别在260MPa,445MPa,37.5%,2.14%,0.25,2.0左右;卷取温度较低在670℃的试验钢的上述参数分别为235MPa,369MPa,38.8%,1.73%,0.26,2.1左右。最终提出了试验钢工业生产中退火温度为840℃左右,冷轧压下率为75%左右,为获得高强度和优良成型性能的最佳匹配。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。