SOME MECHANICAL PROPERTIES OF SAE 1045 STEEL JOINTS BONDED WITH SINTERED COMPACTS

Abstract

The physical and mechanical properties of plain steel (SAE 1045) butt joints, bonded with a sintered alloy as a filler material, are described. Sintered alloys were made from two types of iron powders–electrolytic and Swedish sponge– with various additions ranging from 7 to 20 wt.-% of an electrolytic copper powder, a prealloyed bronze powder (90% Cu+ 10% Sn), and a mechanically mixed elemental bronze powder.

The results showed that the tensile strength was not reduced as drastically as that of the copper-brazed joints, when the thickness of the bonding material (sintered alloy) was increased. The highest bond strength in tensile and fatigue testing was obtained with the sintered alloys comprising iron powder and 10 wt.-% pre alloyed bronze powder. The results indicate that there is a practical possibility of brazing steel using sintered compact as a filler material under a neutral or a reducing atmosphere.     

INFLUENCE OF THIN OXIDE FILMS ON THE MECHANICAL PROPERTIES OF SINTERED METAL-POWDER COMPACTS

Abstract

The influence of thin oxide films, in the range 200–1200Å thick, on the mechanical properties of sintered iron, copper, and nickel powder compacts has been investigated. As the thickness of the oxide film on the metal powders increased, the properties studied, namely, densification parameter, hardness, and tensile strength improved and attained a maximum at a critical oxide-film thickness, the value of which was ～ 625 Å for iron and nickel and ～ 500 Å for copper. Further increase in thickness to ～ 1200 Å led to a gradual decline in the properties. The improvement in the properties obtained with powders having the optimum oxide thickness was independent of the sintering atmosphere. A probable explanation in terms of activated sintering is given.     

THE PRODUCTION OF GRAIN-ORIENTED 50 : 50 NICKEL–IRON MAGNETIC STRIP BY COLD ROLLING FROM SINTERED COMPACTS

Abstract

50 : 50 nickel–iron strip was cold rolled from sintered compacts to thicknesses of 0·0015 and 0·004 in., with final reductions of 92–99%. After annealing at 1050°–1200° C., the cube texture developed, thus giving a material with a rectangular hysteresis loop when magnetized in either the rolling or the transverse direction.

The alloys with the best magnetic properties contained 48–50% nickel. In this range of composition the remanence ratio and coercivity varied from 0·91 to 0·94 and 0·11 to 0·19 respectively, depending upon the processing schedule used.

With the recommended processing schedule, values for the remanence ratio and coercivity of 0·92–0·94 and 0·11–0·13 respectively were obtained.

Unlike the texture of strip rolled from a conventionally cast ingot, the development of cube texture in strip rolled from a sintered compact is not critically dependent on the temperature of the final anneal.     

THE PRODUCTION OF SILICON-IRON MAGNETIC STRIP WITH THE (110) [001] TEXTURE,BY COLD ROLLING FROM SINTERED COMPACTS

Abstract

It is shown that secondary recrystallization and development of the (110) [001] texture in 3¼% silicon-iron strip can be obtained by control of the oxygen content of the hydrogen sintering atmosphere. The conditions required are described.

The sintered compact is then cold rolled according to a schedule used for rolling grain-oriented silicon-iron from a cast ingot.

It is found that the temperature of secondary recrystallization is higher than that for conventionally made strip.

It is suggested that a critical amount of silicon is oxidized to silica during sintering and that this silica acts as a dispersed phase in the inhibition-dependent mechanism known to be responsible for secondary recrystallization.

In an appendix, an account is given of a short X-ray method for checking the texture of the silicon-iron strip.     

THE NITRIDING OF SILICON POWDER COMPACTS

Abstract

The reaction-bonding process to prepare silicon nitride by nitriding silicon compacts was studied, and an examination made of the influence of raw material and process variables on the properties of the resulting silicon nitride. The silicon powder grain size and the impurities content were considered as powder variables, and the green density and thermal cycles as process parameters. The examination of green-density effects indicates that, under the experimental conditions, the gas permeation of nitrogen through the silicon compacts was the rate-determining step of the reaction-bonding process. Regarding the effect of nitriding temperature, the final conversion, Si to Si₃N₄, is an increasing function of the temperature in the range 1300–1400°C. As to the composition of silicon nitride obtained, α-phase formation is favoured when oxygen is present as an impurity in silicon powder. Finally, physical, chemical, and thermomechanical tests showed that reaction-bonded silicon nitride has good bending strength (21 kgf/mm²) and can be used in very severe conditions up to 1200°C.     

铁粉温压压坯的烧结行为

研究了铁粉温压压坯在真空和氢气中的烧结行为。压制铁粉时,粉末温度为110℃,模具温度为80～100℃。烧结时,压坯于室温装炉,升温速度为2.5℃／min。烧结温度分别为1100℃1150℃和1250℃。实验发现,不同温度下真空烧结1h和氢气中烧结1h,与压坯密度相比较烧结密度都降低,生坯密度越高,烧结密度下降越多。测量了真空或氢气中低温预烧结前后压坯重量和体积变化和不同预烧结制度对应的最终烧结密度,发现经真空预烧结后的压坯在1250℃真空烧结,可有效地提高温压压坯的烧结密度。实验表明,烧结铁的密度是温压及烧结两个过程综合作用的结果。在选择温压温度和方式时,有必要考虑温压压坯的烧结行为。     

SINTERED IRON-COBALT-MOLYBDENUM ALLOYS

Abstract

The magnetic properties and certain physical properties of sintered iron-cobalt-molybdenum alloys have been investigated, and a study made of the effect of processing variables, i.e. particle size, compacting pressure, sintering temperature and time. The compacting and sintering conditions which result in optimum properties have been determined. Consideration is also given to the influence on magnetic properties of variations in heat-treatment procedure, involving such factors as quenching temperature and media, ageing time and temperature, &c.

The substitution of ferro-molybdenum powder for elemental molybdenum powder reduces the cost of raw materials substantially without greatly diminishing the magnetic properties. Commercial powders with a normal particle-size distribution give good properties.

It was found that the alloys had somewhat better qualities than those made by casting.     

DEFORMATION DURING HOT ROLLING OF IRON POWDER COMPACTS

Abstract

Iron powder was compacted at three different pressures and heated to two temperatures, 900° and 1000°C, for 20 min before hot rolling. Metallographic examination indicated three stages in the deformation process of hot rolling. These were: restacking and rearrangement of particles during entry into the mill, followed by localized deformation and folding-over of the particles, and finally bulk deformation leading to elongation and recrystallization of the grain structure.     

SINTERING OF METAL POWDER COMPACTS CONTAINING CERAMIC OXIDES

Abstract

The dimensional change during sintering of cobalt and nickel powders containing an oxide dispersion has been studied. Generally, the presence of MgO or CaO in cobalt and nickel retards the densification of the metals, and this retarding influence has a maximum for a certain proportion of oxide in the metal. The wettability between the dispersed phase and the metal may explain differences in sintering behaviour.     

高强度烧结钢

为开拓粉末冶金材料新的应用领域，近年来对高强度烧结钢进行了大量的研究与开发。本文简要介绍Ｈｏｇａｎａｓ公司开发的一些高强粉末冶金材料及对一些高强度烧结材料尺寸变化的控制。     

STUDIES OF THE SINTERING AND HOMOGENIZATION OF NICKEL-COPPER COMPACTS

Abstract

Studies are described of the progress of sintering and alloying in compacts of similar compositions made from nickel-coated copper, copper-coated nickel, and mixed nickel and copper powders. Density losses observed in the early stages of sintering were lower in magnitude and were more quickly recovered in the case of the composite powder compacts. Alloying by diffusion at both 1900 and 2200°F (1040 and 1205°C) progressed most rapidly in compacts prepared from nickel-coated copper powders, and the probable reasons for this observation are discussed in detail. Electrical resistivity was used to follow homogenization of the compacts, and samples were rendered nearly 100% dense by cold working and annealing before making resistivity measurements. Resistivity / sintering-time curves for dense specimens showed no maxima of the type reported by earlier investigators for porous compacts, which were attributed to alloying effects.     

SINTERED STAINLESS STEEL: II—THE PROPERTIES OF STAINLESS STEEL POWDERS SINTERED IN DISSOCIATED AMMONIA

Abstract

Powders having compositions selected in accordance with the results of earlier work have been processed under conditions simulating industrial practice. The properties that can be obtained under such conditions are described.     

粉末冶金烧结铁基材料的耐磨性

用粉末冶金方法制备铁基材料，研究了铁基材料中加入不同合金元素进行烧结后，对耐磨性、密度和硬度的影响，得出了在铁基材料中加入RE、S、Mo、Cu、Sn、P、Mn等元素对耐磨性的提高均有利的结果，而综合分析Fe-C-RE和Fe-C-Cu—P-Mo粉末冶金材料具有较好的应用价值。     

CONTROLLING THE HARDENABILITY OF SINTERED STEELS

Abstract

The factors influencing the hardenability of sintered steels are discussed. Special problems are encountered in establishing hardenability tests suitable for porous materials. A dilatometric method is described by which the transformation characteristics of sintered steel may be determined. Such data can be used directly as a hardenability criterion. Data are given in the form of continuous cooling diagrams on some typical sintered steels.     

PRACTICAL WORKING CONDITIONS FOR SINTERED BEARINGS

Abstract

A disadvantage of porous bearings is that in operation some parts of the surface frequently become dry and air is admitted, causing the oil film to emulsify. This severely reduces the load capacity and PV factor. A new type of porous metal bearing is described in which this disadvantage is overcome by introducing an internal layer of very fine powder. The theory and practical implications are discussed.     

ASPECTS OF THE VOLUME PRODUCTION OF GREEN POROUS BEARING COMPACTS

Abstract

The history and method of manufacture of self-lubricating porous metal bearings are briefly outlined. The importance of achieving appropriate quality at each stage of manufacture, and particularly during compacting, is emphasized and the qualities desired in a green bearing compact are detailed. Various factors relating to the economic large-scale manufacture of green bearing compacts are then considered. The virtues of elemental powders and the influence of lubrication upon powder mix properties and pressing and ejection of compacts are discussed. The special powder flow problems associated with long, thin-walled bearings and the advantage, in this respect, of a moving core rod are described. The particular difficulties encountered in compacting such bearings are stated and special consideration is given to the ejection problems involved. It is concluded that limitations of bearing length and wall section must be accepted.     

INFLUENCE OF SINTERING ON FINE POWDER COMPACTS FOR CATALYST APPLICATION

Abstract

The sintering of porous bodies for catalytic purposes requires a compromise between strength and specific surface, since temperature and time have opposing effects on these properties. The present investigation on fine powder compacts of Cr₂O₃ and W was carried out to establish the conditions under which specific surface and strength could be optimized. Hence, sintering temperature and atmosphere were varied. Cylindrical specimens were used to measure specific surface (BET), permeability, and indirect tensile strength. Pore and surface structure were studied by electron-microscopic methods. It has been shown that sintering in nitrogen yields the best results as far as the combination of strength and accessible surface area is concerned. However, if high permeability and high strength are required, hydrogen is the best sintering atmosphere.     

THE EFFECT OF LUBRICATION ON THE PRESSING OF METAL POWDER COMPACTS

Abstract

Admixture of lubricant with metal powder can assist or retard densification according to the applied pressure and the lubricant content. Lubricant exuded on to the die wall under pressure seems to be the main lubricating factor. The change-over or transition pressure from lubrication to inhibition varies in a Gaussian manner with lubricant content. Molecular films of lubricant are sufficient, but for reduction in ejection pressure a minimum content of 0.2% lubricant is necessary. Die-wall lubrication is far more useful and effective than admixed lubricant. Simultaneous die lubrication and admixture is of no value.     

Fe-Cu-C烧结制品的工艺试验

本文介绍了含1%C,含1%-4%Cu的Fe-Cu-C材料的力学性能,对烧结和热处理性能进行了认证,为合理选择制品含铜量和热处理工艺制度提供了参考。     

INVESTIGATION OF THE DIMENSIONAL CHANGES IN SOFT METAL POWDER COMPACTS

Abstract

The variables affecting the radial/axial (R/A) shrinkage ratio in compacts made from spherical copper powder have been investigated, also the linear dependence of R/A on compacting pressure and sintering temperature. The values of R/A for spherical powder are higher than those for irregularly shaped powder. The effect of particle shape and height/dia. ratio of the compact on R/A have been studied. The differences in green-density distributions have been determined, together with the effect on these of pressure and height/dia. ratio of the compact. The observed variation of R/A is attributed to differences in density distribution in the green compacts, resulting in anisotropic stresses during sintering.