High strength steels refer to those steels that combine well in strength and toughness.
Low alloy steels have good mechanical properties after quenching and tempering.
When the tensile strength Rm is greater than 1200Mpa, it is called high-strength steel;
When its tensile strength Rm ＞ 1500MPa, it is called ultra-high strength steel.
Machining characteristics of high strength and ultra high strength steels
The common characteristics of high-strength steel and ultra-high strength steel are: high tensile strength, large plasticity, high toughness, especially large tendency of work hardening, low thermal conductivity, in addition, their linear expansion coefficient is also large.
Therefore, when cutting high-strength steel and ultra-high strength steel, the cutting force is large, the cutting temperature is high, the tool is very easy to collapse and wear, it is difficult to break chips, and the workpiece has large thermal deformation.
Specific measures for cutting high strength and ultra-high strength steels
The specific measures for cutting high strength steel and ultra-high strength steel are shown in table 7-6.
Table 7-6 specific measures for cutting high strength steel and ultra high strength steel
|Selection of tool materials||High speed steel tool materials should be high cobalt, high vanadium high speed steel, cobalt high speed steel, or powder metallurgy high speed steel and TN coated high speed steel.Cemented carbide is the first choice for cutting high-strength alloy steel and ultra-high strength steel. Generally, new high-performance, ultra-fine Grain Cemented Carbide and coated cemented carbide should be selected.Cubic boron chloride (CBN, PCBN) and ceramic tool materials are mainly used for semi finishing and finishing of turning and milling.|
|Selection of tool geometric parameters||Generally, the following parameters can be taken for carbide turning tools: γ0=- 3 ° ~5 °, α0=8 ° -12 °, λs=0 ° ~-10 °, γo1=-5 ° ~-15 °, br= (0.5-0.8) mm, rough machining: rξ=1-1.5mm, finish machining: rξ=0.4~0.8mm.|
|Selection of Cutting Parameter||1. High speed steel cutter: vc=3-10m/min; f=0.05-0.3nmmr,ap=0.5-1.5mm.|
2. Cemented carbide tools:
Rough turning vc=20~80m/min;
Finish turning yc=60~120/minm;
Rough turning f=0.3~1.2mm/r, ap=4-15mm;
Finish turning f=0.05-0.15mmr, ap=0.05~1mm.
3. cubic boron nitride cutter: vc=80~200m/mim; f=0.05~0.2mm/r,ap<0.8mm.