黄培云双对数粉体压制方程的应用

本文以粉体等静压制实践为依据,着重介绍黄培云双对数粉体压制方程的推广应用。认为通过数学处理可将该式变化为非对数形式\[{{\rm{D}}_{\rm{c}}}{\rm{ = }}\frac{{{{\rm{D}}_{\rm{m}}}{{\rm{D}}_{\rm{o}}}{{\rm{e}}^{{{{\rm{(P/M)}}}^{{\rm{1/m}}}}}}}}{{{{\rm{D}}_{\rm{m}}}{\rm{ - }}{{\rm{D}}_{\rm{o}}}{\rm{ + }}{{\rm{D}}_{\rm{o}}}{{\rm{e}}^{{{{\rm{(P/M)}}}^{{\rm{1/m}}}}}}}}\]11种粉体等静压制实验数据验证表明,上式精度较高(D_c计/D_c实=1±0.01),具有实用价值。文中对该式进行了解析,指出上式即为粉体等静压制的压制压力——压坯密度曲线的数学表达式且其斜率为\[\frac{{{\rm{d}}{{\rm{D}}_{\rm{c}}}}}{{{\rm{dP}}}}{\rm{ = }}\frac{{{{\rm{D}}_{\rm{m}}}{{\rm{D}}_{\rm{o}}}{\rm{(}}{{\rm{D}}_{\rm{m}}}{\rm{ - }}{{\rm{D}}_{\rm{o}}}{\rm{)}}{{\rm{e}}^{{{{\rm{(P/M)}}}^{{\rm{1/m}}}}}}}}{{{\rm{M \cdot m[}}{{\rm{D}}_{\rm{m}}}{\rm{ - }}{{\rm{D}}_{\rm{o}}}{\rm{ + }}{{\rm{D}}_{\rm{o}}}{{\rm{e}}^{{{{\rm{(P/M)}}}^{{\rm{1/m}}}}}}{{\rm{]}}^{\rm{2}}}{{{\rm{(}}\frac{{\rm{P}}}{{\rm{M}}}{\rm{)}}}^{{\rm{1 - 1/m}}}}}}\]     

水雾化铁粉的粒径对工艺性能的影响

通过筛分分级得到0.147 mm(100目)以下的4种不同粒度的水雾纯铁粉粉末,研究了颗粒粒径对铁粉流动性、松装密度、压缩性和压坯孔隙结构的影响。结果表明,随着颗粒粒径的减小,铁粉的流动性降低、松装密度增大。应用方程F=(16πr2Pφm)/(Nmφ)对不同粒径的颗粒进行了受力分析,表明大颗粒压制时平均受到的压力比小颗粒的大。使用艾西压制方程对铁粉压制密度进行拟合分析,表明不同粒度的铁粉都能很好的符合艾西方程,其压缩系数β在0.002 178~0.002 323之间,颗粒粒径大的粉末其压缩系数大,压缩性好。在总孔隙度相当的情况下,粉末粒径小的压坯其孔隙尺寸较小、孔隙数量较多、孔隙的分布较均匀。     

初始凝固组织对Cr17铁素体不锈钢组织、织构及成形性的影响

 研究了初始凝固组织对Cr17铁素体不锈钢组织、织构、成形性的影响。分别对柱状晶、等轴晶铸坯进行热轧、退火、冷轧、退火实验。结果表明,等轴晶铸坯热轧试样在退火过程中的再结晶率高于柱状晶铸坯热轧试样。再经相同的冷轧退火工艺后,与柱状晶铸坯冷轧退火试样相比,等轴晶铸坯冷轧退火试样的{001}∥ND织构较弱,{111}∥ND γ织构较强,而且rm值较高。     

铁粉和石墨粒径对Fe-C系预混合粉性能的影响

以不同粒度分布的还原铁粉及石墨为原料,采用粘结剂处理工艺制备Fe-C系预混合粉。研究了铁粉粒度分布、石墨粒径对预混合粉石墨粘结效率、松装密度、流动性以及烧结件密度、抗弯强度、硬度等性能的影响。结果表明,粒度分布均匀的铁粉有利于提高预混合粉的松装密度、流动性和压坯性能,石墨粒度为-2 000目的预混合粉中,石墨分布更加均匀,石墨的粘结效率为98.3%,其工艺性能和烧结性能更好。     

国外粉末冶金用铁粉生产工艺的发展和质量的改进

氧化铁两步还原制取的海绵铁粉和水雾化铁粉在目前铁粉生产中居主导地位。粉末冶金用铁粉的质量提高表现在粉末压缩性、压坯强度和烧结件强度的逐渐改善,以及烧结件尺寸变化的日趋减小。而这主要归因于铁粉中氧、碳、氮含量的降低及粉末颗粒外形和结构的改善。本文从颗粒物理特征、化学成分、能量消耗与成本等方面,分析比较了海绵铁粉和水雾化铁粉之间的差异;指出这两种铁粉各有适合自己特点的不同应用和今后仍可能继续共存。     

热轧工艺对409L铁素体不锈钢深冲性的影响

对含有单一柱状晶的409L铁素体不锈钢连铸坯,采用不同终轧温度的热轧工艺,由常规热轧转变为温轧,再经过相同后续工艺;较低终轧温度的成品获得了较高rm值和较低△r值.终轧温度的降低使组织演变发生变化:热轧和冷轧组织中晶界和晶内剪切带增多,变形组织被细化、硬化,尤其是中心层附近的粗大带状晶粒;两者的增多又增加了退火过程中的再结晶形核点,使退火组织细化、均匀化.终轧温度的降低也使织构演变发生变化:热轧及其退火织构由{001～114}(110)向高ρ1和Φ值区域移动;冷轧织构峰值由{001}(110)转移至{335}(110);冷轧退火织构的γ组分增多,峰值由{334}(483)转移至{111}(112),而{001～114}(110)和(0°<Φ<35°,ρ1≈25°)组分减少.     

罩式退火温度对高强IF钢组织及性能的影响

为研究不同退火温度下高强IF钢的组织性能及织构的变化规律,采用温箱式电阻炉加热模拟罩式退火工艺,研究了不同退火温度下高强IF钢210P1冷轧板力学性能;对不同退火温度钢板的r90进行了统计并对其进行显微组织观察;采用X射线衍射仪及热场发射扫描电镜对不同退火温度的罩式退火成品板进行了织构分析。结果表明,在高强IF钢210P1冷轧板的罩式退火过程中,提高退火温度将使晶粒明显长大。随着退火温度的升高,屈服强度及抗拉强度下降,伸长率升高,n值略有上升,板材横向r值增加较明显,有利织构{111}取向密度增加,不利织构{100}取向密度降低。     

聚乙二醇基粘结剂铁基粉末温压行为的研究

以水雾化铁粉和合金钢粉为原料,聚乙二醇和少量添加剂为粘结剂进行了温压成形试验.对加入粘结剂的两种粉末的松装密度和流动性进行了测定,重点考察了粘结剂含量、温压温度和压力等对温压压坯密度的影响.实验结果表明,原料铁粉的性质、温压温度和粘结剂加入量等对温压压坯的密度都有影响,在温压温度和压力分别为75℃和600 MPa时,填加0.4%(质量分数)粘结剂的水雾水铁粉和合金钢粉压坯的生坯密度分别可达7.29 g/cm3和7.20 g/cm3;结合实验结果,对温压压坯密度和压制压力的关系进行了解析,以探讨温压成形的致密化规律.     

制备W-Mo复合靶时分层因素的探讨

讨论了粉末性能、压制压力、压坯形状对制备Ｗ－Ｍｏ复合靶分层的影响：实验表明引起Ｗ－Ｍｏ复合靶分层主要是Ｗ粉的粒度，Ｗ粉粒度越细越不好压制，压制后易产生分层和裂纹。粗Ｗ粉可以用较大的压力压制，而细粉很难成形，这是因为粉末越细，压缩性越差。与蝶形相比平板形压制后不易分层。一般而言，Ｗ粉粒度不宜太细，要根据不同的粉末粒度选用不同的压制压力，平板形压坯比蝶形压坯易成形，而且不易分层或出现裂纹。     

制备W—Mo复合靶时分层因素的探讨

讨论了粉末性能、压制压力、压坯形状对制备Ｗ－Ｍｏ复合靶分层的影响：实验表明引起Ｗ－Ｍｏ复合靶分层主要是Ｗ粉的粒度，Ｗ粉粒度越细越不好压制，压制后易产生分层和裂纹。粗Ｗ粉可以用较大的压力压制，而细粉很难成形，这是因为粉末越细，压缩性越差。与蝶形相比平板形压制后不易分层。一般而言，Ｗ粉粒度不宜太细，要根据不同的粉末粒度选用不同的压制压力，平板形压坯比蝶形压坯易成形，而且不易分层或出现裂纹。     

Pressing behavior of atomized iron powders

Conclusions The porous structure of the particles of an atomized iron powder depends on the chemical composition and sieve analysis of the starting powder and also, to a smaller extent, on its own sieve analysis, as determined by the conditions of milling of the sponge produced by annealing. In our study of various powder batches the best combination of degree of particle sponginess and agglomeration and hence pressing characteristics was found to be ensured by the use of a cast iron starting powder containing about 50% of a fine fraction, < 0.063 mm, with a comparatively low oxygen content (6.5%). With the atomized powders, the transition from the first stage of pressing to the second took place more gradually and at a higher pressing pressure (600 MPa) than with the reduced powder (450 MPa). It is shown that the compressibility of an iron powder is the better the greater the contribution from the first stage and hence the smaller the role of the volume plastic deformation of the particles in the attainment of a given density. The best compressibility with a low degree of contanimation with carbon and oxygen can be attained at minimum values of specific surface, degree of sponginess , and degree of agglomeration and also a maximum apparent density resulting from the use of powders of equiaxed particle shape close to spherical. The steady increase in compressibility with increasing apparent and tap densities that is characteristic of reduced iron powders is not always observed with powders pro-duced by atomization and annealing.Translated from Poroshkovaya Metallurgiya, No. 2(218), pp. 23–29, February, 1981.     

Pressing behavior of atomized iron powders

Conclusions The optimum zinc stearate content, ensuring the greatest compressibility of a powder at a given pressing pressure, is determined mainly by the volume of interparticle pores. The higher the density of a compact and the smaller the size of its pores, the smaller is the amount of zinc stearate it can hold. The weakening action of zinc stearate, which manifests itself in stress relief at interparticle contacts during pressing, substantially increases the density of compacts and at the same time decreases their strength. This phenomenon is particularly pronounced with compacts from powders of poor compactibility. After pressing at any given pressure, the strength of a compact with zinc stearate will be higher than that of a compact without a lubricant when the decrease of the contact surface brought about by the elastic aftereffect in the stearate is counterbalanced by the increase of this surface resulting from better compressibility of the powder. The addition of an optimum amount of zinc stearate to an iron powder is always more effective than lubrication of the die walls. A new mechanism of densification of iron powder with zinc stearate is proposed, in which the key factor is an intensification of stress relief at interparticle contacts by the solid lubricant.Translated from Poroshkovaya Metallurgiya, No. 5(221), pp. 16–22, May, 1981.     

基于离散元的不同粒径配比粉末压制相对密度与力链分析

利用PFC三维数值模拟软件,通过改变粉末颗粒粒径分布建立各组冷压模型,得到压制过程中相对密度变化规律与力链分布情况。在特定粉末粒径配比下,能够得到相对密度最高的压坯。结果表明:在大、中、小粒径颗粒质量比为60:15:25的粒径配比下,压坯相对密度最高,压坯相对密度并不会随着细粉比例不断增加而一直提高;在压制过程中,随着附加细粉占比上升,压制方向上能产生更大应变。侧压系数与泊松比受粉末粒径分布影响较小,且在压制后期,在压坯已获得较高相对密度的情况下,会因缺乏足够的驱动力与位移空间发生下降;混合粒径粉末试样的力链数量远大于单一粒径粉末试样,在强力链数目充足的前提下,结合大量的弱力链能获得更高的压坯相对密度。     

Sulfation Kinetics of Low-Grade Nickel–Copper Sulfide Ore in the Sulfuric Acid Roasting Process

The enormous demand for and consumption of nickel in industrial applications has induced the depletion of high-grade nickel sulfide ore, which has inevitably led to the utilization of the substantial deposits of depreciated low-grade nickel-copper sulfide ore. In this work, the mineral phase transformation and sulfation kinetics of nickel, copper, iron, and magnesium in the roasting process were studied. The kinetic parameters of the metals were calculated by using the sulfation rates under different roasting temperatures, ratios of acid to ore and particle size of ore. The results showed that the sulfation process of metals is fit well by the kinetic function $$1 - {{\text{2}} \mathord{\left/ {\vphantom {{\text{2}} 3}} \right. \kern-0em} 3}x - {{(1 - x)}^{{{{\text{2}} \mathord{\left/ {\vphantom {{\text{2}} 3}} \right. \kern-0em} 3}}}} = kt$$ (G–B equation) over 0–20 min and 30–150 min for nickel, copper, and iron, as well as over 5–30 min in the case of magnesium. Furthermore, internal diffusion (three-dimensional diffusion, D4) was the restricting factor in the sulfation processes of the metals, as suggested by experimental data regarding the ratio of acid to ore and the particle size of ore.     

Removal of Metallic Iron on Oxide Slags

It is possible, in some cases, for ground coal particles to react with gasifier gas during combustion, allowing the ash material in the coal to form phases besides the expected slag phase. One of these phases is metallic iron, because some gasifiers are designed to operate under a reducing atmosphere (p_O2{p_{\rm {O}_{2}}} of approximately 10⁻⁴ atm). Metallic iron can become entrained in the gas stream and deposit on, and foul, downstream equipment. To improve the understanding of the reaction between different metallic iron particles and gas, which eventually oxidizes them, and the slag that the resulting oxide dissolves in, the kinetics of iron reaction on slag were predicted using gas-phase mass-transfer limitations for the reaction and were compared with diffusion in the slag; the reaction itself was observed under confocal scanning laser microscopy. The expected rates for iron droplet removal are provided based on the size and effective partial pressure of oxygen, and it is found that decarburization occurs before iron reaction, leading to an extra 30- to 100-second delay for carbon-saturated particles vs pure iron particles. A pure metallic iron particle of 0.5 mg should be removed in about 220 seconds at 1400 °C and in 160 seconds at 1600 °C.     

Solvent debinding behavior of powder injection molded components prepared from powders with different particle sizes

It is generally accepted that the solvent debinding rate of powder injection molded (PIM) parts can be improved when coarse powder is used due to the larger pore size present in the compact. However, little hard experimental evidence on this has been reported. In this study, the as-received gas-atomized stainless steel powder was classified into four different particle sizes. Little difference in the debinding rate was found among these four groups. Similar results were also obtained using classified fine carbonyl iron powder and coarse water atomized iron powders. The diameter of the pore channel that was developed in the compact, while increasing as the particle size increased for both iron and stainless steel powders, did not affect the debinding rate. A comparison between the sizes of the pores and diffusing molecules suggests that the pores are significantly large for the small diffusing molecules. The calculation of the diffusion path or torturosity also indicates that the particle size does not affect the diffusion length and thus not the debinding rate.     

紧耦合气雾化技术制备选区激光熔化用18Ni300合金粉末的研究

基于紧耦合气雾化技术制备符合选区激光熔化用18Ni300合金粉末, 重点研究了雾化压力对粉末粒度(中值粒径, D₅₀)、粒度分布、球形度、氧含量、流动性和松装密度等特性的影响。结果表明: 雾化压力对上述粉末特性影响显著, 当雾化压力在3.5 MPa到4.5 MPa范围时, 随着压力的提高, 粉末粒度降低、表面形貌改善、流动性变好、松装密度增加。当雾化压力为4.5 MPa时, 所制备的粉末综合特性最优, 粉末粒度(D₅₀)为34 μm, 球形度为0.77, 氧含量为0.02%(质量分数), 流动性为17.4[s·(50g)-1], 松装密度为4.32g·cm-3, 15~53 μm粒径范围粉末收得率为38.1%, 满足选区激光熔化技术对金属粉末性能的要求。     

铁粉粒度对粉末冶金材料制动摩擦性能的影响

采用粉末冶金工艺制备含4种粒度(20μm、30μm、50μm、70μm)铁粉增强的铜基摩擦材料,研究铁粉粒度对材料力学性能和制动摩擦性能的影响。采用TM-1型惯性试验台测试材料的制动摩擦性能,试验初速度为50~380 km/h。结果表明:铁粉粒度从20μm增加到70μm时,材料硬度从55.67 HRB降低到31.83HRB,剪切强度从12.56 MPa下降到10.27 MPa。这种硬度和强度的下降使大粒度样品表现出反常的摩擦特性:随着制动速度的提高,铁粉粒度为70μm的F70样品的摩擦因数不降低反而升高,当制动速度从120 km/h上升到380 km/h时,摩擦因数从0.338持续升高到0.356,并且从350 km/h后摩擦因数稳定不变。这种高而稳定的摩擦因数是保证列车在高速下紧急制动、平稳停驶所必需的。     

Fe-0.5Mn-0.5C预混合钢粉性能及粘结剂作用机制

设计4种不同有机粘结剂,分别对合金元素Mn、石墨进行粘结处理,制备Fe-0.5Mn-0.5C预混合钢粉。研究4种粘结剂对预混合钢粉合金元素与石墨的粘结率、预混合钢粉的流动性、松装密度、压坯密度的影响。并通过对粉末表面基团的表征,研究高分子粘结剂与铁基体间的相互作用方式。结果表明:以丙烯酸类树脂制备的预混合钢粉工艺性能最好,其流动速率为24.3 s/50 g松装密度为24.3 s/50 g,在600 MPa压力下的压坯密度为3.03~3.23 g/cm3粘结剂中的极性基团与铁基粉末通过氢键作用相吸附。