Turning Work with Hardened Steel
1)The features of hardened steel
a)High hardness as HRC45~70.
b)Easily fragile
c)High strength:σb =2100～2600 MPa,it is 4 times than the 45# steel
d)Heavy turning force,unit turning force Kc is 4500MPa,which is 2.5 times than the 45# steel.
e)High turning temperature,its heat conductivity coefficient is 1/7 tims than the 45# steel.
2)Turning inserts and machining parameters.
a)Tunring inserts material:PCBN,ceramic,tungsten carbide etc.
b)The geometry parameters of the inserts:Usually γ0=0～-10°,α0=8～10°，κr=30～60°，λs=0～-3°
c)Machining condition:For tungsten carbide inserts the Vc=30～50m/min,ceramic ones is Vc=60～120m/min,PCBN ones is Vc=100～200 m/min,but if in intermittent machining style,the Vc is half of the mentioned parameters,and αp、f is 1/2 of the common steels.
Attention:as the hardened steel's heat-resistance is 200～400℃,and it is reduced with the increase of temperature,but the cutting inserts such as tungsten carbide,ceramic,and PCBN with good heat-resitance performance as 800～1000℃、1200℃、1400～1500℃ respectively,so taking advantage of this factor,in the constant machining condition,the Vc is unavailable to be too low,if in the drill work,have to choose the reasonable Vc and retract frequently.On the other hand,if in the intermittent machining environment,f has to be low,suitable Kr,but the γεhas to be enlarged and λs in negative value.
