What are the cutting characteristics of cast iron?
Generally speaking, it is:
The higher the hardness and strength of cast iron, the lower the metal cutting performance and the lower the predictable life of the blade and tool. Cast iron used in metal cutting has good cutting performance for most types of metals. The machinability of metal is related to its structure, and the processing of harder pearlitic cast iron is more difficult. Flake graphite cast iron and malleable cast iron have excellent cutting properties, while nodular cast iron is quite poor.
The main wear types encountered in processing cast iron are abrasion, bonding and diffusion wear. Abrasion is mainly caused by carbides, sand particles, impurities and hard cast skin. Bond wear with chip tumors occurs at low cutting temperature and speed. The ferrite part of cast iron is most easily welded to the blade, but this can be overcome by increasing cutting speed and temperature.
On the other hand, diffusion wear is temperature dependent and occurs at high cutting speeds, especially when high strength cast iron grades are used. These brands are highly resistant to variants, leading to high temperatures. This kind of wear is related to the interaction between cast iron and tool, which makes some cast iron need to be machined with ceramic or cubic boron nitride (CBN) tool at high speed to obtain good tool life and surface quality.
Generally, the typical tool properties required for processing cast iron are: high thermal hardness and chemical stability, but also related to process, workpiece and cutting conditions; toughness, thermal fatigue wear resistance and cutting edge strength are required. Satisfaction in cutting cast iron depends on how the wear of cutting edge develops: rapid blunting means that hot cracks and notches occur, leading to premature fracture of cutting edge, workpiece damage, poor surface quality, excessive ripple, etc. Normal flank wear, balance and sharp cutting edges are what we usually need to strive to achieve.
(5) What are the main and common processing procedures in die manufacturing?
Cutting process should be divided into at least three types of processes:
Rough, semi-finish and finish machining, and sometimes even ultra-finish machining (mostly high-speed cutting applications). Residual milling is, of course, prepared for finishing after the semi-finishing process. It is very important to make every effort to leave a uniformly distributed margin for the next process. If the direction of the tool path and the workload rarely change rapidly, the tool life may be prolonged and more predictable. If possible, the finishing process should be carried out on special machine tools. This will improve the geometric accuracy and quality of the die in shorter debugging and assembly time.