Topic
Microalloyed steel
About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.
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TL;DR: In this article, the nanometer-size carbides formed in ferrite matrix of Nb-Ti microalloyed steel at different finishing cooling temperatures and holding time have been investigated.
Abstract: The nanometer-size carbides formed in ferrite matrix of Nb-Ti microalloyed steel at different finishing cooling temperatures and holding time have been investigated. The characteristics of nanometer-size carbides in ferrite were observed by transmission electron microscopy, and mechanical properties of ferrite were detected by a nano-hardness tester. The results showed that interphase precipitation and diffusion precipitation were observed at different finishing cooling temperatures, and the interphase precipitation was planar and curved. Sheet spacing of interphase precipitation increased with the increase of finishing cooling temperature and changed a little when holding for 50 — 1000 s. Interphase precipitation shows higher nano-hardness at 640 °C compared with diffusion precipitation at 600 °C, and the contribution of interphase precipitation to the mechanical properties of ferrite was larger than that of diffusion precipitation.
10 citations
TL;DR: In this paper, the authors studied the intragranular nucleation of ferrite in a V microalloyed steel and applied the double deformation method known as back extrapolation to determine the recrystrallised fraction of austenite.
Abstract: The intragranular nucleation of ferrite has been studied in a V microalloyed steel (C� 0.103; Mn� 1.463; V� 0.139; N� 0.0100% mass). Using torsion tests and applying the double deformation method known as “back extrapolation”, the recrystrallised fraction of austenite has been determined for several deformation temperatures and two strain values (0.20 and 0.35) and has been plotted as a function of time. Recrystallisation-precipitation-time-temperature (RPTT) diagrams have then been drawn. The RPTT diagrams depict precipitation kinetics as a function of the temperature and time and this information has been used to study the intragranular nucleation of ferrite, cooling specimens from programmed temperatures and moments for which the precipitated volume and the average precipitate size (determined by TEM) are known. The results have allowed us to determine the contribution of intragranular nucleation to ferritic grain refinement, which was approximately 20%.
10 citations
TL;DR: In this article, a series of plain-carbon, vanadium- and niobium-microalloyed steels with or without titanium addition were used to evaluate the effect of a small amount of titanium addition on the properties of steels.
Abstract: A series of plain-carbon, vanadium- and niobium-microalloyed steels with or without titanium addition were used to evaluate the effect of a small amount of titanium addition on the properties of steels. Titanium inhibits austenite grain coarsening during reheating and grain refinement was observed when the reheating temperature was below the austenite grain coarsening temperature. The lower the reheating temperature, the less was the observed precipitation strengthening effect of V(C, N). The addition of titanium to microalloyed steels reduces the precipitation strengthening effect of V(C, N) but has no visible effect on that of Nb(C, N). The mechanism of reducing the strengthening effect of V(C, N) is possibly caused by the depletion of available nitrogen content for V(C, N) formation.
10 citations
TL;DR: In this article, a mathematical model is presented which enables three quantities to be calculated, the fraction of martensite, the carbon concentration of the martensites, and its ability to influence toughness.
Abstract: There is a confused and contradictory literature on the role of small concentrationsof niobium on the development of the so-called local brittle zones in steels. These zones consistof a mixture of martensite and austenite and hence, their formation should be predictable usingmodern microstructure calculation methods. Following an assessment of the most relevant literature,a mathematical model is presented which enables three quantities to be calculated, the fractionof martensite, the carbon concentration of the martensite, and its ability to influence toughness.Examples are presented for particular linepipe steels, and then the generic effect of alloying elementsother than niobium, on the development of local zones.
10 citations
TL;DR: In this article, the effect of cooling conditions experienced by steel in secondary cooling zone during continuous casting of C-Mn and C-mn-Nb steels has been simulated.
Abstract: Hot ductility studies have been performed on C-Mn and C-Mn-Nb steels with an approach to simulate the effect of cooling conditions experienced by steel in secondary cooling zone during continuous casting Thermal oscillations prior to tensile straining deteriorate hot ductility of steel by deepening and widening the hot ductility trough C-Mn steels are found to exhibit ductility troughs in three distinct zones whereas C-Mn-Nb steel shows drop in ductility only at low temperature in the vicinity of ferrite transformation temperatures Start of ferrite transformation in steels causes yield ratio to increase while work hardening rates and strength coefficient decrease with decrease in test temperature in presence of thermal oscillation prior to tensile testing Inhibition of recrystallization due to build-up of AlN particles along with the presence of MnS particles in structure and low work hardening rates causes embrittlement of steel in austenitic range Alloying elements enhancing work hardening rates in austenitic range can be promoted to improve hot ductility The presence of low melting phase saturated with impurities along the austenitic grain boundaries causes intergranular fracture at high temperature in C-Mn steels
10 citations