Patent ID: 7438771

Claim:
A high strength constant velocity joint intermediate shaft, comprising by wt %, C: 0.46 to 0.52%, Si: 0.6 to 0.8%, Mn: 0.7 to 0.9%, S: 0.01 to 0.05%, Mo: 0.3 to 0.5%, B: 0.0005 to 0.005%, Al: 0.002 to 0.05%, Ti: 0.02 to 0.09%, N: less than 0.007%, Cr: less than 0.15% (including 0%), P: less than 0.02% (including 0%), and the balance of iron and unavoidable impurities; and further comprising: a spline-vanishing part having a surface hardness of approximately 610 HV to 750 HV and an effective hardened layer depth of approximately 0.35 to 0.55 in terms of a ratio t/r, wherein t is the effective hardened layer and r is a radius, and a flat part having a surface hardness of approximately 630 HV to 770 HV and an effective hardened layer depth of approximately 0.55 to 1.0 in terms of the ratio t/r, and having a core hardness of approximately 250 HV to 340 HV.