High-strength steel is added with different amounts of alloying elements in steel. After heat treatment, the alloying elements strengthen the solid solution, and the metallographic structure is mostly martensite. It has large strength and high hardness, and its impact toughness is also higher than 45 steel. The cutting force during cutting will be 25%-80% higher than the cutting force of the cutting 45, the higher cutting temperature is, and harder chip breaking is. So, in actual production, how do high-strength steels cut?
1. The tool
For roughing and interrupted cutting, the tool is required to have thermal shock resistance. In addition to diamond tools, all kinds of tool materials can be cut. When selecting tool materials, they should be selected according to the cutting conditions.
A. High speed steel
The selection of high-performance high-speed steel for cutting high-strength and ultra-high-strength steel should be based on the properties, shape, processing method and rigidity of the process system, and comprehensively consider the heat resistance, wear resistance and toughness of the tool material. When the process system has high rigidity and the tool profile is simple, tungsten-molybdenum-based, high-carbon low-vanadium-containing aluminum high-speed steel or tungsten-molybdenum-based high-carbon low-vanadium high-cobalt high-speed steel can be used; under impact cutting conditions, tungsten-molybdenum can be used. High vanadium high speed steel.
B. Powder metallurgy high speed steel and Tin coated high speed steel
Powder metallurgy high-speed steel is a high-speed powder that is directly pressed at high temperature and high pressure, and then forged into the required tool shape. It is sharpened after processing and has high hardness and high wear resistance. It is suitable for high-strength steel and super. Cutting of high-strength steel.
C. Cemented carbide
Cemented carbide is the main tool material for cutting high-strength and ultra-high-strength steels. Generally, new high-performance hard alloys or coated hard alloys should be selected.
D. Ceramic knives
Its hardness and heat resistance are higher than that of hard alloys, allowing cutting speeds 1-2 times higher than cemented carbides. In the cutting of high-strength steel and ultra-high-strength steel, ceramic tools are mainly used in sheet metal working and precision machining.
2. Cutting amount
The cutting speed of turning high-strength steel should be 50%-70% lower than the cutting speed of general steel. The higher the strength and hardness of the workpiece material, the lower the cutting speed should be. Cutting speed of high-strength steel cutting high-strength steel is (3-10) m/min, carbide tool (10-60) m/min, ceramic tool is (20-80) m/min, CBN tool is (40 —220) m/min. The depth of cut and feed are the same as for general turning steel.
3. Chip breaking method
Due to the high tensile strength of high-strength steel, it is not easy to break the chip during turning, which brings great difficulty to the smooth running of the turning. It is necessary to pay more attention to this in the processing.