Types and processing characteristics of cast iron
Cast iron can be divided into gray cast iron, white cast iron, malleable cast iron, nodular cast iron, vermicular cast iron, alloy cast iron and so on according to its classification.
Among them, gray cast iron is widely used in the automobile industry, and the automobile industry has a large demand for CNC cutting tools, so processing plants often have processing requirements for gray cast iron.
What tools are used to process ordinary cast iron
The common cast irons referred to in this article are gray cast iron, nodular cast iron and austenitic cast iron, and the processing performance of gray cast iron is better. Excellent results are obtained when machining gray cast iron brake discs with PCBN tools.
The graphite content of ductile iron affects its processing performance. Generally, ceramic tools can be used for rough machining and semi-finishing. Finishing with CBN tools.
For processing ordinary cast iron, most of them can choose ceramic tools and CBN tools.
What tools are used for difficult-to-machine cast iron
Here we only take chilled cast iron as an example for the time being. Chilled cast iron is a kind of wear-resistant cast iron.
Usually, when casting cast iron, the surface layer of cast iron is cooled by accelerating the surface layer to obtain white cast iron structure, forming the characteristics of high hardness and high wear resistance.
Chilled cast iron can be divided into ordinary chilled cast iron, nickel-chromium chilled cast iron, high-chromium white iron and chrome-vanadium white iron.
▶Processing characteristics of chilled cast iron
Chilled cast iron has high hardness, high brittleness, and high unit cutting force, and its chips are in a broken shape.
Due to the short contact between the tool tip and the cutting edge, the cutting force and cutting heat are concentrated near the cutting edge, which is easy to cause wear and damage to the tool.
Most of the processed parts of chilled cast iron are blanks, and the machining allowance is large and uneven, which greatly increases the difficulty of cast iron processing.
▶Tool selection for machining chilled cast iron
When processing chilled cast iron, it is best to choose tool materials with high hardness, good wear resistance and certain strength. Alumina ceramic cutters and CBN cutters are generally used.
Experiments have proved that using CBN tools to process chilled cast iron can reduce the processing time by one-third compared to using cemented carbide tools.
▶Cutting parameters for machining chilled cast iron
CBN tools are suitable for fine turning high hardness chilled cast iron rolls, etc.
The cutting amount during turning is:
Vc=50～70m/min, αp=0.5～1mm, f=0.2～0.4mm/r.
The workpiece surface roughness Ra is 3.2-1.6 μm.
The processing efficiency is more than 10 times that of cemented carbide tools.
Ceramic cutting tools generally choose high-speed milling.
For rough machining and semi-finishing cast iron V=50~80m/min, for finishing machining V=80~120m/min.