Procedure to Make Tungsten Carbide Cutting Tools Ⅵ

In last part we know that grade powder is compacted by ways such as uniaxial pressting or isostatic pressing to form a blank shape of tungsten carbide cutting tool and then it goes for sintering. Here we go forward to the process of sintering.

Sintering

In order to increase the strength of the green compacts, they are subjected to heat treatment, which is called sintering. The main aim of sintering is densification in order to provide the metal with the necessary physical and mechanical properties and a density which is suitable for subsequent thermomechanical processing. Sintering of tungsten carbide is commonly carried out in a temperature range of 1500 up to 1500℃ under flowing hydrogen, either by direct sintering (self resistance sintering) or indirect sintering (resistance element heating systems). The density thereby obtained should be a minimum of 90% of the theoretical density, but is commonly in the range of 92% to 98%.

Let’s take tungsten carbide inserts for instance. After pressing, the form looks like oversized inserts and is fairly delicate. They are removed from the molds and placed on graphite or molybdenum trays, and go into a sintering furnace where they are heated in a low-pressure hydrogen atmosphere. The cobalt melts, and the insert consolidates into a solid, smaller size. After the inserts are removed from the furnace and cooled, they are dense and hard. After a quality control check, the inserts are ready for further machining.

 (To be continued-This article is divided into several parts and this is part 6, for part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80275-ti-10328; for part 7, please refer to http://news.chinatungsten.com/en/tungsten-information/80277-ti-10330)

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