Selection of engineering materials for machining

Selection of engineering materials for machining

In the CNC processing plant, there is not much difference between steels; all steels are similar in terms of mechanical properties. They are selected on criteria such as brittleness, price, and availability. Not just because one steel contains 2% alloying elements and another steel contains 1%, the former has certain abilities that the latter does not, or a certain steel has a magical name. After heat treatment, any steel has a wide range of properties; this property also exists in alloy steels

Considerations about processing

The characteristics (hardness, strength, and machinability) of the final part of a cnc processing plant, rather than the forging characteristics, determine the choice of material. Forgeability has little to do with the final properties of the material; therefore, there is little value in improving the forgeability of the metal. High-carbon steel is difficult to forge. Large-sized grains are best if refined during subsequent heat treatment.

Low carbon at high temperatures, nickel-chromium alloy steels exhibit almost the same plasticity as ordinary steels with the same carbon content under impact of 520-ft · lb. Nickel reduces the malleability of medium carbon steels, but has little effect on low carbon steels. Chromium hardens the steel at forging temperatures, but vanadium has no significant effect; both processing methods have no effect on high carbon steels.

shape

The cold forming of steel is the result of a combination of its tensile strength and ductility. The tensile strength and yield point of a cnc processing plant cannot be too high, otherwise a lot of work needs to be done when bending occurs; similarly, steel should have high ductility, so that it can be formed without breaking. The magnitude of the working force depends on the yield point, because the steel only begins to deform above the yield point. At the same time, work hardening also occurs at the same time, and the metal becomes harder and harder to process, especially in mild steel

In this regard, it is quite interesting that you will find that sometimes large stretches can be done with one quick load, but two or three loads in a slow manner cannot be achieved. If the stretching stops halfway through, then annealing should be done before reworking, that is, whether the workpiece has time for work hardening. This is not a scientific way of saying it, but it does happen.