Effect of Deoxidation Process on Inclusion and Fatigue Performance of Spring Steel for Automobile Suspension
- PDF / 2,750,636 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 106 Downloads / 199 Views
used in the production of high-quality spring for automobile suspension. With the emphasis on lightweight development in modern automobile design, the spring component must have good fatigue-resistant properties, as well as long fatigue life.[1] There are multiple causes that could lead to the fatigue fracture in springs. Generally, when fatigue fractures occur in low-cycle fatigue life (< 105 cycles), the fatigue crack initiations are attributed to the
YANG HU is with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China and also with the Beijing Institute of Aeronautical Materials, Beijing 100095, China. Contact email: 13401162963@ 163.com WEIQING CHEN is with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing. CHANGJIE WAN, FANGJUN WANG, and HUAIBIN HAN are with the Henan Jiyuan Iron and Steel Group Co., Ltd, Jiyuan 459000, Henan, China. Manuscript submitted January 19, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
presence of defects such as decarburized layers and inclusions on the surface of spring steel. While, when the fatigue fractures occur in high-cycle fatigue life (< 107 cycles), or giga-cycle fatigue life (> 107 cycles), the fatigue crack initiations are attributed to the internal inclusions.[2,3] During the manufacturing process of suspension spring, voids often develop between the inclusions and the steel matrix, mainly due to incompatibility of the thermal expansion behavior, hardness, and formability between inclusions and steel matrix.[4,5] Under periodic loading conditions, stress concentration could develop in the proximity of inclusions, which could further lead to fatigue crack initiation, propagation, and finally, sudden failure.[6,7] At present, there are two processes to produce suspension spring steel. One process is characterized by an Al-killed practice to achieve ultra-low oxygen, where the total oxygen, T.[O], in steel can be controlled to less than 10 ppm. Al deoxidation products are normally the rigid and spherical Al2O3 inclusions. If the steel continues to be treated with Ca, the inclusions can be transformed to small spherical Al2O3-CaO-CaS inclusions, with good dispersion. Another process is characterized by a Si-killed practice. Though the T.[O] content of Si-killed steel is higher than that of Al-killed steel, the resulting Al2O3-CaO-SiO2 deoxidation
inclusions with low melting points and good formability can deform along the steel matrix.[8–10] However, so far, there are few evidences to determine which process is best for improving the fatigue performance of suspension spring. Moreover, in many previous studies, pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi the equivalent size of initial fatigue crack areacrack was assumed to be the equivalent size of inclusion leading to pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi fracture areainclusion in the reported forecast models for assessing fatigue strength and for determining the critical size of inclusion. No considerations were given to the effects of voids aroun
Data Loading...
