气孔对12％Cr铁素体不锈钢烧结体氮化行为的影响

气孔对１２％Ｃｒ铁素体不锈钢烧结体氮化行为的影响九州大学工学部将典型的。系不锈钢１２％Ｃｒ钢（ＳＵＳ４１０Ｉ－）用水雾化法制成粉末，再用涂布了硬脂酸锌的模具以５’８８ＭＰａ的压力将粉末压制成形，制成气孔率为（２０．０士０．５）％的粉末任坯。首先将粉末...     

二氧化锆与不锈钢混合粉末的挤压成形特性

研究了在二氧化锆与不锈钢的混合粉末中加入粘结剂时的挤压成形特性，并着重考察了混合粉的可挤上限条件，所用粘结剂为水溶性羟丙基在纤维素（ＨＰＭＣ）和水，结果表明，混合粉末的可挤压上限成分（质量分数）随不锈钢粉末含量的增加而上升，当不锈钢的粉末含量（体积分数）为７０－９０％时达到最大，粘结剂中ＨＰＭＣ的质量分类以１０％为宜。     

基于分形特性PIM成形坯导热率的计算

分析了粉末注射成形坯的分形特性,给出了其剖面颗粒面积分形维数的一般计算方法;利用剖面颗粒表面分形维数,计算了粉末注射成形坯剖面颗粒的各向异性局部面积占有率.进而基于多孔介质导热率的分形模型,推导出了粉未颗粒和粘结剂串并联及无量纲时的粉末注射成形坯各向异性有效导热率的计算公式,并以铁粉成形坯为例分析了有效导热率与剖面颗粒分形维数的关系.结果表明粉末注射成形坯的导热率随着分形维数的增加而增大.     

粉末注射成形喂料充模过程数值分析

在简化条件下，对粉末注射成形喂料熔体在圆柱状模腔内作一维非等温流动进行了分析，用有限差分法建立了控制方程对应的差分方程组，并给出了差分方程组的求解步骤     

由预合金和混合粉末制造的粉末冶金双相奥氏体－铁素体不锈钢

由预合金和混合粉末制造的粉末冶金双相奥氏体－铁素体不锈钢双相奥氏体－铁素体不锈钢由于其性能兼于纯铁索体钢和奥氏体钢之间所以用途越来越广泛。但是，从制造观点来看，双相钢的困难主要是由于要求精确控制化学成分以及在成形热处理时需要严格控制温度。这些困难的存...     

不锈钢球壳冲压成形CAM系统的弹塑性分析

运用弹塑性力学原理，提出了不锈钢球壳冲压成形过程的力学模型，给出了非线性有限元法的数值模拟计算方法。研究结果对不锈钢球壳冲压成形的全过程实现了数值模拟，对成形过程中的一些关键参数和过去只能用经验确定的参数做了定量计算，为不锈钢球壳的冲压模具设计和工艺参数确定提供了科学依据。为板料的成形过程的模拟提供了一种有效的手段。     

机械蓄能式粉末高速压制试验机的研制

在综合分析现有常见的高速压制设备的基础上,提出了一种机械蓄能式粉末高速压制成形方法.设计了机械蓄能式粉末高速压制成形试验机,介绍了其工作原理并推导了冲击锤速度和动能的数学模型.建立了试验机的虚拟样机模型,运用ADAMS软件的刚柔耦合仿真分析方法对试验机进行了动态仿真分析.最后成功制作了试验机,运用316 L不锈钢粉末高速压制试验测试了试验机的实际性能.实践表明,机械蓄能式高速压制成形方法能够实现粉末的高速压制,试验机具有较好的粉末成形加工能力.     

粉末特性与工艺参数对SLM成形的影响

通过试验研究了316L不锈钢粉末参数及工艺参数对选择性激光熔化（SLM）成形性能的影响规律．结果表明：单一粒径分布的粉末松装密度低于多种粒径混合后的松装密度;采用2种不同粒径粉末充分混合,最大松装密度达到59．83％;平均粒径小的粉末比平均粒径大的粉末成形性好,粒径分布范围宽的粉末成形时球化现象明显;利用平均粒径为26．36p．m的粉末和优化的工艺参数制造出测试件,最高致密度达99．75％,拉伸强度最高达1068MPa．     

选择性激光熔化316L不锈钢粉成形优化工艺

针对选择性激光熔化技术加工零件存在的致密度低、成形精度差和表面光洁度低的问题,利用正交实验的方法优化316L不锈钢粉末成形零件的工艺,研究激光功率、扫描速度、扫描间距对零件成形致密度的影响,分析了试样的表面形貌。实验结果表明:采用选择性激光熔化工艺的316L不锈钢粉末试样有较高致密度,其试样的致密度达80.1%。工艺优化后的参数为激光功率300 W、扫描速度800 mm/s、扫描间距0.08 mm,并在该组优化参数条件下成功制造零件。     

注射成形工艺参数优化

在CAE有限元分析技术的基础上,采用正交实验和对比实验,并在极差分析法的指导下,成功得出实验条件下,塑料注射成形和粉末注射成形各工艺参数对制品质量影响的先后次序和工艺参数的最优配置。     

振动力场对金属粉末注射熔体流变性能及相分离的影响研究

动态注射成型是一种将振动力场引入到注射成型工艺上的新技术,本文介绍了动态注射成型技术在金属粉末注射成型中的应用情况,应用蜡基粘结剂与平均粒径为10um的气雾化316L不锈钢粉末按各种装载量进行配比,探讨了振动频率、振幅对喂料熔体流变性能及相分离的影响。结果表明,振动力场的引入能改善金属喂料的流动性能,增加金属喂料在阿基米德螺旋模具中充模过程的流程长度;振幅、频率的改变能改善制品相分离的情况,在频率为10Hz、振幅为0.1mm时对相分离的改善作用最为明显。     

正压水煤气余热锅炉防磨瓦腐蚀失效分析

1Cr20Ni14Si2不锈钢防磨瓦在水煤气余热锅炉中运行被腐蚀甚至断裂,对正压水煤气立式余热锅炉过热器不锈钢防磨瓦断裂失效进行研究。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)设备对锅炉1Cr20Ni14Si2不锈钢失效防磨瓦的表面腐蚀褐色粉末、不锈钢表面和人为断面成分进行测试。XRD测试结果表明表面褐色粉末存在多种金属氧化物和硫化物;EDS实验检测结果表明：不锈钢表面含大量S和O。这说明1Cr20Ni14Si2不锈钢在焦化炉中易被S腐蚀而失去不锈钢特性。EDS结果分析发现不锈钢Ni含量明显低于国标要求含量,降低了不锈钢韧性并降低其防腐蚀性能。烟气中S、C和O经腐蚀孔隙进入材料内部加速不锈钢内部腐蚀。研究结果对水煤气余热锅炉防磨瓦材料选型和防磨结构优化具有指导意义。     

Fabrication and sintering behavior of high-nitrogen nickel-free stainless steels by metal injection molding

High-nitrogen nickel-free stainless steels were fabricated by the metal injection molding technique using high nitrogen alloying powders and a mixture of three polymers as binders. Mixtures of metal powders and binders with various proportions were also investigated, and an optimum powder loading capacity was determined as 64vol%. Intact injection molded compacts were successfully obtained by regulating the processing parameters. The debinding process for molded compacts was optimized with a combination of thermo-gravimetric analysis and differential scanning calorimetry analysis. An optimum relative density and nitrogen content of the specimens are obtained at 1360℃, which are 97.8% and 0.79wt%, respectively.     

M42高速钢粉末级配规律和注射成形工艺参数优化

研究了M42高速钢粉末的粒度级配对粉末振实密度的影响规律,并采用正交试验法研究了注射温度、注射压力、注射流量、保压压力及其交互作用对注射坯质量的影响．试验结果表明,粗细粉末进行级配能够有效提高粉体的堆积密度．与-400目粉末相比,＋140目与-400目的原料粉末通过级配,振实密度可提高44．3％～56．4％．注射工艺参数正交试验发现注射温度、保压压力及其交互作用对注射坯质量的影响最为显著．试验确定的标准长方体弯曲试样最佳注射工艺参数为：注射温度160℃、注射压力82MPa、注射流量42％及保压压力31MPa．     

Effect of weld line positions on the tensile deformation of two-component metal injection moulding

Knowledge of the mechanical properties of two-component parts is critical for engineering functionally graded components. In this study, mono-and two-component tensile test specimens were metal injection moulded. Three different weld line positions were generated in the two-component specimens. Linear shrinkage of the two-component specimens was greater than that of the mono-component specimens because the incompatibility of sintering shrinkage of both materials causes biaxial stresses and enhances sintering. The mechanical properties of 316L stainless steel were affected by the addition of a coloured pigment used to identify the weld line position after injection moulding. For the two-component specimens, the yield stress and ultimate tensile stress were similar to those of 316L stainless steel. Because 316L and 630 (also known as 17-4PH) stainless steels were well-sintered at the interface, the mechanical properties of the weaker material (316L stainless steel) were dominant. However, the elongations of the two-component specimens were lower than those of the mono-component specimens. An interfacial zone with a microstructure that differed from those of the mono-material specimens was observed; its different microstructure was attributed to the gradual diffusion of nickel and copper.     

Injection molding and debinding of micro gears fabricated by micro powder injection molding

Micro powder injection molding (μPIM) was investigated for possible mass production of micro-components at relatively low cost. However, scaling down to such a level produces challenges in injection molding and debinding. Micro gears were fabricated by μPIM from in-house feedstock. The effect of injection speed and injection pressure on the replication of the micro gear cavity was investigated. Solvent debinding and thermal debinding processes were discussed. The results show that micro gears can be successfully fabricated under the injection pressure of 70 MPa and the 60% injection speed. Either too low or too high injection speed can cause incomplete filling of micro gears. The same is the case with too low injection pressure. Too high injection pressure can bring cracks. Solvent debinding of micro gears was performed in a mixture of petroleum ether and ethanol. Subsequently, micro gears were successfully debound by a multistep heating schedule.     

Cavitation erosion behavior of WC coatings on CrNiMo stainless steel by laser alloying

The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction (XRD) analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy (SEM). The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.     

稀土在低硫16Mn钢中的作用

长条状的MnS夹杂对钢的横向韧塑性极为不利。喷吹Si—Ca或加入RE,通过脱硫和变质硫化物的作用,都可显著地消除其危害。喷吹Si—Ca变质硫化物的程度与钢中Ca/S有关。喷吹Si—Ca后加入少量RE,有利于控制MnS完全变质,此时钢中所需的RE/S可明显低于3。在大幅度脱硫的基础上加入少量RE,是使钢材韧塑性获得稳定大幅度提高的一条有效途径。