Keeping to form in the powder business

This work evaluated the influence of gas and water-atomised powders on form retention and mechanical properties of PIM 316L stainless steel components. Two different particle morphologies were used for powder mixtures varying the proportions of spherical and irregular powder -- gas and water atomised powders respectively — varying the content from zero through 25 per cent, 50 per cent, 75 per cent and 100 per cent by mass. The mixtures of gas and water-atomised powders with higher solids loading showed lack of homogeneity and inadequate moulding characteristics. The form retention of samples moulded with only water-atomised powder showed only small shrinkage anisotropy and distortion. The gas-atomised powder PIM samples also demonstrated minor anisotropy, but they showed more slump during chemical and thermal binder removal. Samples with the two powders presented a higher degree of geometric anisotropy. Best results for densification and mechanical properties were obtained by components using water-atomised powder showing 95 per cent of theoretical density and resistance up to 500 MPa.     

添加Cu粉对GCr15磨屑粉体性能的影响

分析了GCrl5轴承钢粉体的压制规律,探索了添加Cu对压坯密度、弹性后效、烧结密度和力学性能的影响及压制压力和烧结温度对材料密度、硬度的影响。结果表明:GCr15轴承钢粉体符合黄培云压制方程,在小于1 300MPa的压力下,压坯密度随压力的增大而增加;在低于1 300℃烧结温度下,烧结坯的密度随烧结温度的升高而增加;添加Cu可以提高压坯密度和烧结密度,但对弹性后效影响不大;压制压力为1 200MPa时,不含Cu的GCr15轴承钢磨屑粉压坯密度为6.60g/cm~3,弹性后效为1.73%,H_2气氛中1 150℃烧结2h后密度为6.91g/cm~3;添加5%Cu(质量分数)粉的压坯在H_2气氛中1 300℃烧结2 h后密度达7.23g/cm~3,硬度为36.3 HRC。     

Effect of particle size on the carbon and oxygen contents and particle structure of air-atomized cast-iron powder

Conclusions To obtain the best results at a minimum duration of treatment, in the hydrogen annealing of air-atomized cast-iron powder, use should be made of a fraction of particle size not more than 0.25 mm and not less than 0.063 mm.Translated from Poroshkovaya Metallurgiya, No. 2(170), pp. 1–5, February, 1977.     

Properties of bearing steel extruded from powder obtained by spraying of molten production chips

Conclusions Bearing steel bars may be produced by extrusion of powder produced by spraying of molten production chips with nitrogen. This makes it possible to introduce recycling of metal scrap in the production plant.Extruded powder metallurgy steel has the same density as cast steel and is at least as good in mechanical properties.The fracture toughness of the extruded steel in relation to austenitizing temperature is lower than for rolled steel. Heat treatment produces high strength properties. The extruded powder metallurgy steel has higher contact resistance than the cast. As the result of annealing of extruded powder metallurgy bearing steel a more uniform relationship of contact resistance to austenitizing temperature is obtained.It would be desirable to more thoroughly investigate the extrusion conditions, particularly the temperature and degree of reduction, and also the heat treatment conditions of extruded powder metallurgy steel in order to determine the possibilities of increasing its physicomechanical properties.Translated from Poroshkovaya Metallurgiya, No, 3(339), pp. 29–34, March, 1991.     

利用多晶硅切割废料制备SiC粉体

针对目前多晶硅切割废料大量堆积造成环境污染的问题,提出了以多晶硅切割废料为原料,经过盐酸浸出除Fe后,配加活性炭高温反应制备SiC的工艺。首先,对废料成分与碳的反应进行了热力学计算;然后,使用差热分析、X射线衍射和扫描电子显微镜等分析手段,研究了反应温度、反应时间以及废料中的Fe对产物物相组成和形貌的影响。结果表明,切割废料经过酸浸后的主要成分为SiC和Si。碳不能与Fe-Si系合金(FeSi、Fe_5Si_3等)中的Si反应生成SiC,所以为了制备纯度较高的SiC,多晶硅废料反应前必须预先除Fe。当反应温度高于1 400℃时,酸浸后的切割废料与活性炭的反应能够迅速地发生,且反应生成的SiC遗传碳颗粒的形貌。     

废弃玻璃粉对水泥砂浆力学性能的影响

废弃玻璃经球磨机研磨成粉可作为水泥砂浆的原料.本文通过正交试验研究了废弃玻璃粉掺量(0、10%、20%、30%)、水胶比(0.35、0.4、0.5、0.6)、胶凝总量(420、450、480、500 kg/m~3)和玻璃着色剂种类等因素对水泥砂浆的力学性能影响规律.结果表明,随着废弃玻璃粉掺量的增加,砂浆试块的抗压强度先增大后降低.最佳玻璃粉掺量为10%,水胶比为0.4,胶凝总量为450 kg/m~3;对废弃玻璃粉水泥砂浆强度影响最显著的因素为玻璃粉掺量,其次为水胶比,而胶凝材料总量和着色剂对强度的影响很小.废弃玻璃粉的火山灰活性效应不明显.利用废弃玻璃粉作为掺合料生产水泥砂浆是可行的.     

污泥铁粉改性生产微细铁粉的试验研究

用转炉炼钢炉尘经重选提取的金属铁粉即污泥铁粉,经过150μm(100目)筛分处理,筛下粉的全铁品位达80.00%(质量分数)以上,微观形貌为规则球状或类球状。采用3种不同方法将其微观形貌改为不规则形状,再将改性后的铁粉进行还原、破碎得到各项指标满足金刚石胎体要求的微细铁粉。几种改性方法的对比表明,物理改性工艺流程短、成本低、效果显著。     

废塑料与煤粉热解特性的研究

分别将4种废塑料和煤粉置于非氧化性气氛中研究其热解特性。研究结果表明,在氮气中废塑料的裂解过程主要分为三个阶段:缓慢裂解—急速裂解—缓慢裂解至结束,煤粉的裂解过程比较平缓;最大裂解速度对应的温度,废塑料平均超过400℃,煤粉为900℃;终了裂解量,不同品种废塑料为85%～100%,而煤粉仅22%,两者差异极大;废塑料的完全裂解表观活化能是煤粉的6～10倍。     

利用废弃银铜合金触点直接制备银铜双金属粉

研究了利用废弃银铜合金触点(Ag、Cu、Sn质量分数分别约为30%、60%和2%)直接制备银铜双金属粉的工艺。原料以硝酸溶解后,采用葡萄糖预还原和水合肼二次还原,在聚乙烯吡咯烷酮(PVP)的保护下制得了粒径在1μm左右类球形超细银铜双金属粉和超细铜粉。还原前加入尿素,控制反应温度在60℃温度下,加入抗氧化剂苯并三氮唑,均可防止铜粉的表面氧化,从而获得高质量的银铜双金属粉,银、铜的回收率达到99%以上。所得产品可再用于粉末冶金法制备银铜合金触点,或者直接用于制备电子浆料。该工艺可避免银、铜的分离过程,使废弃银、铜合金触点中银、铜的回收和深加工得到有效结合,从而实现节能减排的目标。     

复吹转炉底吹喷粉实验研究

在1:6物理模型上,通过水模实验对复吹转炉底吹喷粉时熔池搅拌情况进行了研究.结果表明:喷粉对熔池搅拌有明显的促进作用.喷粉条件下,均混时间随顶吹气体流量的增加存在最小值,最佳顶吹气体流量为117.0 m3/h,增加底吹气体流量对降低均混时间有利.在本实验范围内最佳顶吹流量为117.0 m3/h、最佳底吹流量为2.36 m3/h.