From Machinability of Powder Metallurgy Steels


With respect to an increased interest in chromium, chromium-molybdenum, and also manganese, chromium-manganese and chromium-manganese-molybdenum low-alloy steels for production of structural parts, the data about their machinability will gain importance [47]. These are the steels alloyed with the elements of high affinity for oxygen. Iron-silicon steels belong also to this group of materials. These steels form a new group of high strength steels with many possibilities to affect the final properties in order to meet special requirements for some parts, e.g. through heat treatment processes. Therefore, the machinability of these steels should be investigated in parallel to the processing parameters and mechanical properties. A short overview of tensile strength and hardness of some alloys based on chromium prealloyed powders and of some manganese steels is shown in the following figures for different carbon levels and manufacturing routes. Here it stands out clearly for Cr-steels that with increasing carbon content and increasing density of the materials, strength and hardness increase, Figs. 7.47 and 7.48; the sintering temperature is less relevant since higher sintering results in lower combined carbon content due to more effective deoxidation (see chapter 2.42; 5.13). The relationship between carbon content and mechanical properties is also evident with more complex alloy systems, as shown for Cr-Mo-X alloyed steels in Figs. 7.49 and 7.50.

Figure 7.47: Tensile strength of Cr-steels based on Astaloy CrM powder in dependence on manufacturing route (cold and warm compaction at 700 MPa, sintering temperature) and carbon...

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Topics of Interest

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