铸态QT550-5球墨铸铁熔炼过程控制

从QT550-5球墨铸铁材质的要求出发,对铸态QT550-5球墨铸铁熔炼过程中化学成分的选择、铸造工艺、原材料选择、熔炼工艺、球化处理、孕育处理、质量检测等方面进行了分析说明。提出合理的成分配比、熔炼、球化、孕育处理工艺。经检测,所得材料的力学性能达到了QT550-5的要求,金相组织符合标准。     

QT500-14风电主轴的铸造工艺开发北大核心

高硅球墨铸铁QT500-14材料具有良好的力学性能，可应用于大功率风力发电机组的主轴，大幅度降低机组成本。通过严格控制材料QT500-14的化学成分、采用金属型铸造、通过MAGMA软件模拟主轴铸造工艺预测铸造缺陷，在主轴铸造过程中采取在预测缺陷位置处放置冷铁的控制措施，铸造出符合设计要求的风电主轴。     

退火对QT350-22球墨铸铁组织和性能影响

通过金相组织观察、硬度检测、冲击韧性测量和断口分析,综合分析退火处理前后QT350-22球墨铸铁的显微组织和性能。实验结果表明,由于QT350-22球墨铸铁的铸件基体组织存在一定数量的珠光体,因而其低温冲击韧性较低;退火处理可以减少基体中珠光体数量和细化铁素体晶粒,明显提高铸件的低温冲击韧性。优化QT350-22球墨铸铁的化学成分和严格控制铸造工艺参数,并配以适宜的退火工艺,可以改善QT350-22球墨铸铁的产品质量,满足低温抗冲击的性能需要。     

球墨铸铁QT450-10、QT500-7的退火工艺优化与组织分析

本文以球墨铸铁QT450-10、QT500-7为研究对象,根据铸件原热处理生产工艺中存在的组织形态粗大及分布不均匀等问题,提出了退火工艺的优化方案,研究了不同退火工艺条件下球墨铸铁的组织形态和铁素体、珠光体及石墨的含量,并对台车式退火炉的炉温不均匀问题提出了改进意见.实验结果表明,采用合理的退火工艺,并在生产条件下保证...     

QT 350-22与QT 600-10球墨铸铁的组织与性能分析

采用金相显微镜、扫描电镜、能谱仪、X射线衍射仪和硬度计对铁素体基球墨铸铁QT 350-22和QT 600-10进行了微观组织与断口形貌观察、相结构与成分检测和硬度测量。实验结果表明,由于两种球墨铸铁的Si含量明显不同,虽然其金相组织均为铁素体基体+颗粒状石墨+少量珠光体,但两者的力学性能和断口形貌差别很大。QT 350-22的拉伸强度较低,而冲击吸收功很高,其断口形貌呈典型的韧性断裂;QT 600-10的拉伸强度高,且延伸率较高,而冲击吸收功很低,其断口形貌呈典型的脆性断裂。随球墨铸铁中Si含量的提高,铁素体基体的Si固溶强化效果明显增加,这是由于Si原子溶入铁的晶体点阵而导致晶格畸变所致。本文的研究结果可以为优化铁素体基球墨铸铁的化学成分和铸造工艺提供重要的实验依据。     

QT400-18球墨铸铁焊补工艺研究

球墨铸铁铸造生产中难免产生铸造缺陷,根据铸件技术要求可以采用焊补修复。然而,球墨铸铁含碳量高,焊接性能差,焊补过程中易产生白口组织和裂纹。通过对QT400-18球墨铸铁焊补工艺进行研究,制定严格的焊补工艺,通过与母材对比结果表明,选用Z408焊补后的硬度稍高,不适合用于加工面的焊补处理,Z308焊条焊补后的硬度与母材接近,可以用于加工面的焊补处理,Z308焊条和Z408焊条焊补后的抗拉强度和屈服强度基本与母材一致,不影响铸件的使用性能。     

大批量稳定生产QT400-18铸态球铁工艺研究

介绍大批量生产大型拖车用球墨铸铁连接器的生产条件、铸造工艺、熔炼工艺。通过恰当选择化学成分、原材料，并采用适当的球化处理工艺，强化孕育，使铸件的铸态力学性能稳定达到QT400-18的要求。     

铸态QT850-5球铁曲轴的试验研究

介绍了铸态QT850-5牌号高强度、高伸长率球墨铸铁曲轴的试验研究和结果。在采用覆砂铁型铸造工艺条件下,研究了Cu、Sb、Sn等合金元素的不同组合以及开箱时间对曲轴本体力学性能的影响,最后确定,采用加Cu和加Sn复合强化工艺可以使曲轴铸态性能稳定达到QT850-5的要求。     

铍青铜的铸造技术

根据铍青铜铸造的理论依据,结合具体生产实践,对铍青铜的铸造工艺进行了实验研究和分析,并分别设计了相应的解决措施去消除缺陷,然后通过大批量生产和跟踪调查,对措施的有效性进行了改进、修正和评价,使铸造工艺更合理.综合多年的实践,介绍了铍青铜在生产工艺过程中的最优控制措施,通过严格控制化学成分及生产工艺过程,使除气效果较好,再合理热处理,达到了所需铍青铜的性能指标,获得了较好的技术经济效果.     

QT350-22L铸造风力机主机架应力有限元分析

以球墨铸铁QT350-22L风力机主机架铸造件为研究对象,分析了应力影响因素;采用六面体等参单元网格系统建立了风力机主机架应力分析模型,对主机架各个维度的应力场进行了计算。结果表明,应用有限元分析的方法可以较好地分析以球墨铸铁QT350-22L为原料铸造的风力机主机架的应力场,为产品设计优化和服役性能评估提供依据。     

Effects of Casting Size on Microstructure and Mechanical Properties of Spheroidal and Compacted Graphite Cast Irons: Experimental Results and Comparison with International Standards

The aim of this research was to investigate the effects of casting size (10-210 mm) on the microstructure and mechanical properties of spheroidal (SGI) and compacted (CGI) graphite cast irons. A comparison of the experimental mechanical data with those specified by ISO standards is presented and discussed. The study highlighted that the microstructure and mechanical properties of SGI (also known as ductile or nodular cast iron) are more sensitive to casting size than CGI (also known as vermicular graphite cast irons). In particular, in both types of cast iron, hardness, yield strength and ultimate tensile strength decreased, with increasing casting size, by 27% in SGI and 17% in CGI. Elongation to failure showed, instead, an opposite trend, decreasing from 5 to 3% in CGI, while increasing from 5 to 11% in SGI. These results were related to different microstructures, the ferritic fraction being more sensitive to the casting size in SGI than CGI. Degeneration of spheroidal graphite was observed at casting size above 120 mm. The microstructural similarities between degenerated SGI and CGI suggested the proposal of a unified empirical constitutional law relating the most important microstructural parameters to the ultimate tensile strength. An outstanding result was also the finding that standard specifications underestimated the mechanical properties of both cast irons (in particular SGI) and, moreover, did not take into account their variation with casting size, at thicknesses over 60 mm.     

应变速率对QT450-10球墨铸铁热塑性及石墨颗粒的影响

利用Gleeble-1500热模拟机研究了QT450-10球墨铸铁在不同压缩应变速率下的热塑性行为。结果表明:随着应变速率的增加,球墨铸铁在950℃下的极限压下量呈递减趋势。流变曲线随着真应变的增加,迅速达到一峰值后发生软化,即存在动态再结晶行为。利用光学显微镜观察了微观石墨球在明/暗场中的形貌,发现石墨颗粒在三向不等压应力作用下具有一定的塑性,但是应变速率对石墨颗粒的形貌及分布的直接影响并不明显。     

High Temperature Oxidation Behavior of Flake and Spheroidal Graphite Cast Irons

Flake and spheroidal graphite cast irons with similar composition were subjected to high temperature oxidation to investigate graphite morphology and distribution effects on the oxidation behavior. High temperature oxidation tests were conducted between 400 and 750 °C in air. For comparison low carbon steel was also tested.Graphite morphology obviously affected high-temperature oxidation resistance. The flake graphite cast iron exhibited the worst high-temperature oxidation resistance compared with spheroidal graphite cast iron. Since graphite flakes provide suitable sites for the iron oxide growth and are almost interconnected, the iron oxide grows faster and penetrates along the graphite flakes boundaries resulting in the subsurface oxidation. Due to the severe subsurface oxidation flake graphite cast iron parabolic rate constants are five times higher than that of the spheroidal graphite cast iron. However, spheroidal graphite cast iron parabolic rate constants and oxide layer thickness are similar to those of the low carbon steel. Therefore, graphite flakes have negative effect on the cast iron high temperature oxidation resistance.     

Cu、Mn元素对发动机球铁曲轴组织和性能的影响

研究了不同含量的Cu、Mn对球铁曲轴组织和性能的影响规律,同时对比分析了普通砂型和壳型填铁丸两种工艺条件下球铁曲轴的组织和性能。结果表明,当0．6wt％Cu与0．4wt％Mn配合时,可以获得抗拉强度较高的珠光体球铁,其强度与伸长率均满足QT600—3的要求。与普通砂型相比,壳型填铁丸工艺条件有利于球铁中总石墨球增多、圆整度提高及珠光体含量的提高,使性能得到改善。     

Effect of microstructure and mechanical properties on cutting force of different cast irons with similar tensile strength

Flake graphite iron,compacted graphite iron and spheroidal graphite iron with various tensile strengths were cast. They were selected and grouped according to roughly the same tensile strength,and then the main cutting force in each group was measured and compared. The microstructures of different cast irons were characterized. The relationship between the cutting force and microstructure was established. Results show that the graphite morphology in cast irons determines the strength. In order to obtain the same strength of the cast iron with sharply edged graphite,more or finer pearlite in the matrix is needed. Graphitic cast irons with high pearlite content and smaller pearlite interlamellar spacing have higher hardness. For the cast irons with different graphite morphologies,but almost the same tensile strength,the main cutting force is obviously different,along with the hardness. Harder cast irons have a greater cutting force,but the difference in cutting force is not proportional to hardness.     

用低碳当量球墨铸铁铸造黄麻织机伸缩杆

本文阐述了低碳当量球铁的特点及其生产工艺;论述了用低碳当量球铁铸造仲缩杆的可行性。     

Studying elastic deformation behaviour of cast irons by acoustic emission

Abstract

The deformation of metallic materials includes both an elastic and a plastic deformation. In the case of cast irons, the elastic region becomes less pronounced as the graphite changes from spheroidal to flake shaped, as observed in nodular and grey cast iron, respectively. The present study aims to correlate the shape of the graphite phase with the deformation behaviour, where the plastic deformation and other strain accommodating events are quantified by measurements of the acoustic emission events occurring in the interior of the material at loading. It also aims to explain how the appearance of cast iron stress–strain curves depends on the graphite morphology where, for instance, spheroidal graphite cast irons exhibit a seemingly linear elastic behaviour in contrast to flake graphite cast irons. The present study includes a series of pearlitic cast iron material grades with differences in nodularity and carbon equivalent, respectively. It is shown that as the roundness of the graphite phase increases, the ability to absorb energy increases. The measured acoustic emission indicates that plastic deformation occurs in the seemingly linear elastic region regardless of the cast iron grade, i.e. no cast iron grade exhibits perfect linear elasticity. The plastic deformation rate in the elastic region increases as the roundness of the graphite decreases and as the carbon equivalent increases. It is shown that the plastic deformation governs the resulting modulus of elasticity in all kind of cast irons, i.e. the modulus of elasticity decreases as the yielding of the material increases. The present study improves the understanding of the deformation behaviour in the elastic region of different cast irons. The survey shows that acoustic emission testing is a useful method when studying the deformation behaviour of cast irons.     

Effect of nodularity on mechanical properties and fracture of ferritic spheroidal graphite iron

Ferritic spheroidal graphite irons with nodularity from 72% to 96% were prepared. The relationship between the nodularity and the mechanical properties of the ferritic spheroidal graphite iron was investigated. The effect of nodularity on the mechanical properties and tensile fracture of the cast iron were studied. Results showed that the tensile strength Rm, yield strength R_(p0.2), elongation to failure A_5, and impact energy KV_2 of the cast iron had a good linear relationship with its nodularity. Nodularity and annealing treatment would obviously affect the fracture characteristics of ferritic spheroidal graphite iron. The annealed ferritic spheroidal graphite iron with 93% nodularity showed a completely ductile rupture. With the decrease of nodularity from 93% to 72%, the cleavage fracture area ratio increased gradually from 0% to 8.3%. Compared with as-cast ferritic spheroidal graphite iron, annealing treatment reduced the cleavage fracture area of the ferritic spheroidal graphite iron.     

生长条件对灰口铸铁共晶凝固过程石墨形态的作用

灰铸铁、蠕铁、球铁被统称为灰口铸铁,在现代工业中应用广泛.在主要成分相近情况下,由于微量元素等条件的不同引起石墨生长形态各异,从而同属灰口铸铁的三类铸铁性能迥异.懂得其基本规律及相关原理,有益于铸造工程技术人员在灰铁、蠕铁、球铁的生产实际中理性而有效地控制产品质量.本文基于灰口铸铁的奥氏体-石墨共晶凝固方式,从基本概念及原理、G形成过程、实际组织观察与分析的全新视角,主要针对灰铁和球铁概述了石墨形态的形成规律和机理.文中诸多图片等实例是以往国内教科书及专业书籍中未见的,文章内容也体现了对相关现象描述及观点上新的发展,有助于读者对该方面有关问题获得更为清晰的理解和认识.     

Modelling of compacted graphite cast iron solidification-Discussion of microstructure parameters

A melt maintained for hours in a press pour unit allowed the following changes over time from spheroidal graphite to compacted graphite iron by casting thermal cups at regular time intervals.This provided extensive experimental information for checking the possibility of simulating solidification of compacted graphite irons by means of a microstructure modelling approach.During solidification,compacted graphite develops very much as lamellar graphite but with much less branching.On this basis,a simulation of the thermal analysis records was developed which considers solidification proceeding in a pseudo binary Fe-C system.The simulated curves were compared with the experimental ones obtained from three representative alloys that cover the whole microstructure change during the holding of the melt.The most relevant result is that the parameter describing branching capability of graphite is the most important for reproducing the minimum eutectic temperature and the recalescence which are so characteristic of the solidification of compacted graphite cast irons.