Effect of Deoxidation Process on Inclusion and Fatigue Performance of Spring Steel for Automobile Suspension

摘要: 55SiCrA spring steel was smelted in a vacuum induction levitation furnace. The liquid treated by Si deoxidation, Al modification with Ca treatment and modification, the samples were obtained deformable Al2O3-SiO2-CaO-MgO inclusions closely contacted matrix, Al2O3-CaO-CaS-SiO2-MgO surrounded small voids or Al2O3(> 80 pct)-SiO2-CaO-MgO big voids, respectively. Effect of three types on fatigue cracks studied. perpendicular transverse around leading to fracture found vary behavior. Under applied stress amplitude 775 MPa, lives steels decreased from 4.0 × 107 3.8 × 107, 3.1 × 107 cycles. For 750 MPa, 5.2 × 107 4.1 × 107, 3.4 × 107 Based inclusions, equivalent size initial crack has been newly defined as $$ \sqrt {\frac{{{\text{area}}_{\text{inclusion}} }}{{(1 - {\text{CC}})}}} $$ , where contraction coefficient CC inclusion introduced. A reliable forecast model critical established incorporation actual width binclusion diameter dinclusion internal inclusion; prediction be agreement experimental results.