Powder Compaction
Introduction
The main purpose of the compacting process is the forming of metal powders into compacts or desired shape with sufficient strength to withstand ejection from the tools and subsequent handling up to the completion of sintering, without breakage or damage it is the subsequent sintering operation which imparts the final strength.
Although there are various methods of powder compaction, only few of them are widely .employed commercially. It is convenient to group the various .,methods into the following classification :
(i) Pressure-less shaping , technique
(ii) Cold pressures shaping technique
(iii) Hot pressures shaping technique
Pressure less Shaping Technique
1) Loose sintering (loose shaping, gravity sintering, or pressure less Slater log).
In this process, metal powder is poured or vibrated mechanically into the mold which is a negative impression of the article and heated to the sintering temperature1. This is the simplest method involving low cost of equipment. It has been mainly employed to a large extension a commercial basis for producing product with porosities varying from 30% up to 90% by volume However this process is not used for the production of complex-shaped parts :
(a) the difficulty of part-removal from the mold after sintering
(b) flow characterieristics of the powder and
(c) considerable amount of shrinkage during sintering.
The die employed in this method must have adequate strength to contain the powder during sintering and usually carbide, graphite, stainless steel, or cast iron is used as the die material1.By selecting suitable powder, sintering temperature and time, it is possible to produce high density part of most metals and alloys, but in most of the cases, poor dimensional accuracy is obtained. This method may be employed to produce very large ingots ( up to 2 tons) from carbonyl iron and nickel powder which may be further treated by rolling or forging Highly porous filter materials such as bronze stainless steel, monel, tungsten, ets, are easily formed by this technique. Extremely porous nickel sheets used as electrodes and fuel cell and beryllium bars are another application of this process.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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