MnS inclusions in bearing steel have long been considered to significantly affect the fatigue life of bearing steel. In this paper, the sizes of inclusions in bearing steel with different sulfur contents were analyzed and the precipitation behavior of MnS was calculated using thermodynamics. Furthermore, the positive role of MnS in bearing steel was discussed. Results showed that when the size of inclusions in bearing steel was increased, the proportion of MnS components in composite inclusions gradually decreased. When the sulfur content was increased, the shape of inclusions changed from a particle shape to a strip shape. With increasing MnS content, the inclusion ratio of Al2O3 was significantly reduced in the Al2O3–CaO–MgO–MnS quaternary inclusion system, particularly for MnS proportions greater than 20%. The content of sulfur in bearing steel significantly affects the precipitation temperature of MnS. When sulfur content increases from 0.001% to 0.007%, the precipitation temperature of MnS increases from 1493 K to 1633 K as the precipitation of MnS moves from the austenite solid phase to the liquid and solid phases, and the precipitation size of MnS inclusions significantly increases. The size of oxide inclusions should be controlled to improve MnS wrap oxide inclusions in steel. Based on these results, a composition control with high sulfur levels and low oxygen levels should be adopted to improve the fatigue performance of steel.
Based on the understanding that the essence of secondary recrystallization of Goss texture is to restrain the abnormal growth of {110}, {210} and partial Goss texture {110}, it was concluded that making sharp Goss grow up becomes the only choice. It was proposed that the abnormal growth mechanism of Goss texture was the result of selective generation, directed inheritance, and selective growth. The mechanism explained that the Goss texture was the most easily formed shear texture. In directed inheritance, the Goss texture was required to be highly compatible with the near-constant of the second-phase particle inhibition force, providing an optimal environment for the abnormal growth of the Goss texture by controlling the inhibition force near-constant. The control of the near-constant inhibition force provides an optimal environment for the abnormal growth of the Goss texture. Based on that, the process technology for producing low-temperature nitrided-oriented silicon steels and steel products was successfully developed.
In this work, duplex stainless steel/low-alloy steel-clad rebars were fabricated using metal deposition and hot rolling. The interfacial characteristics of the rebar, such as element diffusion and phase composition, were investigated using an optical microscope and a scanning electron microscope with an energy-dispersive spectrometer. The mechanical properties of the rebar were evaluated by tensile and bending tests. The results show that the rebar interface is composed of a carburized layer on the duplex stainless steel side and a decarburized layer on the low-alloy steel side; they also show that the rebar exhibits good mechanical properties, with 435 MPa of yield strength, 630 MPa of tensile strength, and a 24.8% percentage elongation. The reduction in the cladding thickness at the rebar’s transverse rib root was studied using the ABAQUS software. The results show that the cladding thickness is reduced due to the effect of the groove shape during the rolling process. The rebar’s transverse rib root cracked after bending due to the thinning of the cladding and brittle fractures in the interfacial martensite layer.
1 October 2019 in IOP Conference Series: Materials Science and Engineering
In the present investigation, liquid-solid casting and hot rolling method was successfully used to manufacture stainless steel cladding (SSC) rebar. Stainless square tube that was surface treated by pellet blasting treatment was preheated to 1100 °C, and then liquid carbon steel which was heating up by induction furnace to 1620 °C was filled into the tube to cast the SSC billet. SSC billet was rolled in a wire and rod plant successfully due to metallurgical bond state between the tube and carbon steel. Soaking temperature and starting rolling temperature as well as finishing rolling temperature were exhibited 1180C, 1130C and 1000C. Uniaxial tensile testing of SSC rebar at room temperature exhibited an extremely yield strength of 433 MPa and a tensile strength of 599 MPa, while the elongation reached 24%. Positive and negative bending experiment showed no cracks during the deformation. Through metallographic analysis, it was found that the base structure of stainless steel was ferrite, and heterogeneous phases such as martensite and ferrite was discovered near the interface of carbon steel and stainless steel.