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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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Journal ArticleDOI
TL;DR: In this article, a phenomenological constitutive model is developed to derive the flow stress at the onset of DRX and saturation stress of DRV as functions of the Zener-Hollomon parameter by the classical hyperbolic sine equation.
Abstract: The hot flow behavior of an Nb-Ti microalloyed steel is investigated through hot compression test at various strain rates and temperatures. By the combination of dynamic recovery (DRV) and dynamic recrystallization (DRX) models, a phenomenological constitutive model is developed to derive the flow stress. The predefined activation energy of Q = 270 kJ/mol and the exponent of n = 5 are successfully set to derive critical stress at the onset of DRX and saturation stress of DRV as functions of the Zener–Hollomon parameter by the classical hyperbolic sine equation. The remaining parameters of the constitutive model are determined by fitting them to the experiments. Through substitution of a normalized strain in the DRV model and considering the interconnections between dependent parameters, a new model is developed. It is shown that, despite its fewer parameters, this model is in good agreement with the experiments. Accurate analyses of flow data along with microstructural analyses indicate that the dissolution of NbC precipitates and its consequent solid solution strengthening and retardation of DRX are responsible for the distinguished behaviors in the two temperature ranges between T < 1100 °C and T ≥ 1100 °C. Nevertheless, it is shown that a single constitutive equation can still be employed for the present steel in the whole tested temperature ranges.

10 citations

Patent
25 Jul 2012
TL;DR: In this paper, a steel plate with ultra-high toughness and extreme thickness and a manufacturing method of the steel plate was presented, where a component system of low C-ultralow Si-medium Mn-(Ti+V+Nb+B) microalloyed steel is used as a basis, special rolling control and offline gradient tempering technology (QQQ+T) are optimized, so that microstructures of the produced steel plate are small tempered bainite+ tempered martensite, the average crystal colony size is less than 20 microns,
Abstract: The invention discloses a 80Kg grade steel plate with ultrahigh toughness and extreme thickness and a manufacturing method of the steel plate. The steel plate comprises the following components in percentage by weight: 0.08-0.13% of C, Si smaller than or equal to 0.10%, 0.80-1.20% of Mn, P smaller than or equal to 0.013%, S smaller than or equal to 0.0030%, 0.20-0.45% of Cu, 1.00-1.60% of Ni, 0.35-0.65% of Cr, 0.30-0.60% of Mo, 0.040-0.070% of Als, 0.010-0.030% of Nb, 0.030-0.060% of V, 0.004-0.010% of Ti, N smaller than or equal to 0.0050%, 0.001-0.004% of Ca, 0.0008-0.0016% of B, and balance of Fe. According to the manufacturing method, a component system of low C-ultralow Si-medium Mn-(Ti+V+Nb+B) microalloyed steel is used as a basis, special rolling control and offline gradient tempering technology (QQ+T) are optimized, so that microstructures of the produced steel plate are small tempered bainite+ tempered martensite, the average crystal colony size is less than 20 microns, excellent obdurability and plasticity match is obtained, and mechanical performance in the direction of the thickness of the steel plate is uniform.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the binding energy of Nb atom and vacancy was predicted to be 0.45 eV, indicating that Nb segregation by welding thermal cycle is probably a result of the nonequilibrium mechanism.
Abstract: Coarse-grained, welding heat-affected zone microstructure was simulated in a Nb-bearing microalloyed steel. The granular bainite with a great number of martensite-austenite (M-A) constituents was the predominant phase. Using atom probe tomography (APT), the distributions of niobium at prior austenite grain boundary (PAGB), ferrite/martensite-austenite (M-A) constituent interface (FMAI), and ferrite/ferrite interface (FFI) were investigated. The binding energy of Nb atom and vacancy was predicted to be 0.45 eV, indicating that Nb segregation by welding thermal cycle is probably a result of the nonequilibrium mechanism. The maximum enrichment of Nb was found at FMAI with enrichment factor of 3.50. Intermediate enrichment of Nb was at PAGB with enrichment factor of 3.12. The interfacial excess of Nb solute element ГNb at PAGB determined by APT was 0.27 × 1019 atoms/m2. The segregation energy was calculated to be 22.91 kJ/mol. The minimum enrichment of Nb was at FFI with an enrichment factor of 1.80.

9 citations

01 Jan 2007
TL;DR: In this article, the effects of tempering thermal treatment on microstructural and properties behavior of 0.22wt pct C microalloyed steel were investigated.
Abstract: In t his study, the effects of tempering thermal treatment on the microstructural and propert ies behaviour of 0.22wt pct C microalloyed steel were investigated. The m icroalloyed steel samples were austenitized and quenched to produce a l ath m artensite f ollowed by annealing i n i ntercritical region ( a+e) and subsequently quenched to produce a d ual phase of ferrite-martensite m icrostructure. The specimens were subsequently tempered at temperatures of 250, 350 and 450 C for 1 hour. The microstructures, tensile o and impact toughness properties of these s teels were a nalyzed and com pared wi th t he microalloyed s teel that were conventionally quenched and tempered. The result showed that tempered dual phase microalloyed steel sa mples sig nificantly exhibited superb mechanical p roperties inc luding higher te nsile strength, ductility and i mpact toughness as compared wi th t hat of conventionally quenched and tempered steel samples.

9 citations

Journal ArticleDOI
TL;DR: In this article, a stress-based forming limit diagram and fracture limit diagram was developed from the experimentally determined strain values for different stress or strain ratios for three HSLA steel sheets, namely, carbon-manganese steel sheet with 1.6mm thickness, microalloyed steel sheet of 1.2mm thickness and carbon manganese steels of 14mm thickness.
Abstract: This paper deals with the development of stress based forming limit diagram and fracture limit diagram from the experimentally determined strain values for different stress or strain ratios for three HSLA steel sheets, namely HSLA steel sheet with 1.6 mm thickness, microalloyed steel sheet of 1.2 mm thickness and carbon–manganese steel sheet of 1.4 mm thickness. Here, the forming and fracture behaviour of the above steels have been related with the mechanical properties and microstructure of steels. It is observed that carbon–manganese steel shows better formability in tension–tension and plane strain regions. The carbon–manganese steel, which exhibits high normal anisotropy and pancake type of microstructure, is highly found suitable for drawing operation. A good correlation between the void size and the strain ratios derived from Mohr's circle to the mean strain, namely (γ12/ɛm, γ23/ɛm and γ13/ɛm) have been found from the present investigation.

9 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202288
202164
202090
201986
201888