高速钢粉末低压热压的研究

INVESTIGATION ON HOT PRESSING OF PM HIGH SPEED STEELS AT LOW PRESSURE

采用电脑测控法研究了高速钢粉末低压热压过程中的致密化现象,随热压温度由1215℃升高至1238℃时,有效屈服应力由3～4MPa降至2～3MPa以下。在1220～1230℃和4 5MPa压力下制备了Mo系高速钢剃齿刀,相对密度达到99 85%,碳化物的粒度为3～7μm。与普通高速钢刀具相比,低压热压法制备的M4粉末高速钢剃齿刀寿命明显提高,减少残余孔隙度对改善刀具的疲劳寿命是很重要的。充用利用材料在高温下,特别是在接近固相线温度时的屈服现象,可以实现在低压下的粉末材料致密化,其压力比热等静压低一个数量级,这可能是一条较为经济的技术途径。

The Densification phenomenon of high speed steels (HSS) powder during hot pressing at low pressure was investigated using a computer measuring system. When the hot pressing temperature elevated from 1215℃ to 1238℃, the effective yielding stress decreased from 3-4 MPa to less than 2～3 MPa. A type of slotter tools of Molybdenum Based HSS Alloys was prepared at the temperature of 1 220～1 320 ℃ and the pressure of 4.5 MPa. Its relative density reached 99.85% and the particle size of carbide was nearly 3～7 μm.The cutting experiment shown that its working life could be obviously improved comparing with conventional high speed steels. The experiment results also indicated that the decreasing of residual porosity of tools has an impotent role on improving its fatigue properties. Densification of powder during hot pressing at low pressure could be realized because of the yielding phenomenon at more high temperature reaching the solidus of the materials. The pressure can be decreased more than an orders of magnitude comparing with hot isostatic pressing. This technology may be a more economic method.