Effect of Water Vapor During Secondary Cooling on Hot Shortness in Fe-Cu-Ni-Sn-Si Alloys
- PDF / 5,301,390 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 48 Downloads / 154 Views
RODUCTION
STEELS produced via the recycling of scrap metal in the Electric Arc Furnace can undergo a cracking phenomenon known as surface hot shortness due to the formation of a Cu-rich liquid at the metal/oxide interface during high-temperature oxidation; the Curich liquid penetrates the metal grain boundaries leading to embrittling of the grain boundaries and cracking during the hot rolling process.[1] The formation of a separated Cu-rich liquid and the quantity of liquid at the interface is dependent on the balance between the alloy oxidation (corresponding to the Cu rejection at the interface) and the back diffusion of Cu into the bulk to reduce the concentration gradient at the interface. Both the oxidation rate and the Cu diffusivity in the bulk are dependent upon temperature; therefore these values will vary during a non-isothermal cycle and could alter the hot shortness behavior of the alloy as compared to isothermal oxidation experiments. Previous research ERICA SAMPSON, Post Doctoral Researcher, is with Carnegie Mellon University, Pittsburgh, PA. Contact e-mail: eesampson@ gmail.com SEETHARAMAN SRIDHAR, Professor, formerly with Carnegie Mellon University, Pittsburgh, PA, is now the TATA Steel/ Royal Academy of Engineering Joint Chair for Research into Low C Materials Technology, International Digital Laboratory, Warwick Manufacturing Group, The University of Warwick, Coventry, England. Manuscript submitted May 1, 2014. Article published online July 11, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
into the effect of Si on hot shortness under isothermal oxidation at 1423 K (1150 °C) in dry atmospheres determined that Si additions (between 0.1 and 0.2 wt pct Si) reduced hot shortness due to a combination of mechanisms: (1) the formation of fayalite (Fe2SiO4) in the scale near the metal/oxide interface reducing the oxidation of the alloy due to decreased Fe2+ diffusivity through the scale layer thereby reducing the formation of separated Cu-rich liquid and (2) increased occlusion of the Cu-rich liquid away from the interface and into the scale due to increased internal oxidation in the Sicontaining alloys.[2] Secondary cooling conditions deviate from the aforementioned ones in terms of non-isothermal temperatures and the presence of water vapor during a segment of the cooling. The addition of water vapor to an air atmosphere has generally been seen to have negative effects on hot shortness via an increase in oxidation by accelerating the oxidation rate and increased Cu-rich liquid penetration into the austenite grain boundaries; however, the mechanisms involved are not fully understood.[3–8] Water vapor can alter the properties of the oxides,[9] increase the porosity and oxygen transport through the scale,[8,10,11] increase the scale adherence via increased oxide plasticity from dissolved hydrogen in the scale,[7,8,11,12] decrease the effectiveness of protective scale layers by volatilization of oxides (such as FeO, Fe3O4, Fe2O3, SiO2, Cr2O3),[9] and increase the depth and width of hot shortness cracking and li
Data Loading...
