Papers by Keyword: Intercritical Quenching

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Authors: Chun Ling Zhang, Da Yong Cai, Ke Qin Zhang, Bo Liao
Abstract: Dual-phase steels of 09CuPCrNi are prepared through intercritical quenching process. The influences of dual-phase treatment on the corrosion resistant property of the steels have been studied by electrochemical potentiodynamic tests and artificial salt spray tests. The results indicate that the corrosion behavior of DP780 and the as-received weathering steel in 5% sodium hydroxide, 3.5% sodium chloride, 5% sulphuric acid and various concentrations of hydrochloric acid solutions are identical, but dual-phase steels show least corrosion current as compared to the as-received steel. Rust layers of the as-received steel and DP780 are identical mainly consisting of three iron (hydr) oxides, goethite, akaganeite and lepidocrocite, and magnetite. Both the relative amount and morphology of phase constituents affect on the corrosion behavior of DP steels.
586
Authors: Min Huang, Yu Wang, Ya Ni Zhang, Yue Wei Xie, Shuo Feng Li
Abstract: In order to improve the toughness of oil casing steel N80 without the sacrifice of its original high strength, an intercritical quenching treatment was conducted under the temperature determined by a differential scanning calorimetry (DSC) analysis. Effects of intercritical quenching on the microstructure of oil casing steel N80 were characterized by means of optical microscope (OM) and scanning electron microscope (SEM). Tensile strength, reduction of cross-sectional area and microhardness were measured to evaluate the mechanical property of oil casing steel N80 after intercritical quenching treatment. The study results show that the tensile strength and microhardness of intercritical quenched oil casing steel N80 consisting of ferrite (F) and martensite (M) is slightly lower than that of tempered oil casing steel N80 composing of sorbite (S), yet which is still higher than that of full annealled oil casing steel N80 composing of pearlite (P) and a little amount of ferrite (F). In particular, the reduction of cross-sectional area of oil casing steel N80 intercritical quenched at 740°C is higher than those of tempered and full annealled. Additionally, both dimple and cleavage can be found on the impact fracture surface of N80 steel after intercritical quenching at 740°C. The toughness of oil casing steel N80 can be obviously improved by the intercritical quenching treatment at 740°C due to the formation of ferrite (F).
279
Authors: De Hui Zou, Zhi Fang Peng, Ping He Li, Ai Min Guo
Abstract: The Effect of intercritical quencing on microstructure and mechanical properties of ultra low carbon heavy steel plate were studied by utilizing SEM, TEM, tensile and impact tests. The specimens were firstly subjected to an annealing treatment at 930 oC followed by quenching to ambient temperature, then were repeatedly annealing at the temperatures being varied in the range of 600~870 oC, and then repeatedly quenched to ambient temperature in cold water. When the intercritical quenching was just slightly above Ac1, the strength and low temperature toughness were remarkably deteriorated attributing to the massive grain and some twins in the bainite islands. However, the more when the annealing temperature increased higher than Ac1 but still below Ac3, the more regions can be austenized, which cause the average of carbon content in the austenized regions to be relatively low. So it was difficult that these austenite regions changed into twin martensites after interctitical quenched. Then the comprehensive properties including low temperature toughness became good again.
1371
Authors: De Hui Zou, Zhi Fang Peng, Ping He Li, Ai Min Guo
Abstract: The microstructure and mechanical properties of the low carbon steel plates containing Niobium content of 0.038%, 0.063% and 0.082% with intercritical quenching were studied by SEM, TEM, tensile and impact tests. The results showed that the intercritical quenching steel with high Niobium content can gain the fine microstructure , but also easily obtain the martensite, which made the strength very high but low temperature toughness very low, however, the steel with low Niobium content can not reach enough austenitization level, which caused both low temperature and yield ratio high relatively. So in the given rolling and heat treatment process, there was suitable Niobium content can contribute to obtain the optimal austenization level resulting in the good combination of strength, yield ratio, elongation and low temperature toughness after intercritical quenching in the low carbon steel.
1382
Authors: De Hui Zou, Zhi Fang Peng, Ruo Min Wang, Shan Wang
Abstract: The Effect of tempering on microstructure and mechanical properties of ultra low carbon heavy steel plate with intercritical quenching were studied by utilizing SEM, TEM, tensile and impact tests. Mobile dislocations decreased, plenty of carbides and secondary phase particles precipitated dispersedly in the matrix, and then some dislocations were pinned by these precipitations, which made the YS increase when tempered from 180 to 450 oC. However, the bainite islands, formed after intercritically quenched, were still existed, the boundaries of which were clear but just laths broadening in the interior, so the UTS had a slight variation. With increasing tempering temperature from 450 to 630 oC, carbides became coarse, the bainite islands were gradually polygonized, even the boundary of which became fuzzy, dislocations transferred and formed the cellular sub-grain, which caused synthetically both YS and UTS decreasing evidently, the low temperature toughness gradually increasing, and the mixed fracture of impact specimens converting into ductile fracture.
1276
Authors: Xiao Lin Li, Qing Wu Cai, Wei Yu
Abstract: The effects of quenching at 820 °C 850 °C 940 °C and tempering at 600 °C on microstructure and properties of F550 ship plate steel were studied by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and other experimental methods. The results show that the highest value of the impact energy at-80 °C is 240 J when the steel is quenched at 850 °C and tempered at 600 °C. A full graumber of martensite-austenite (M-A) constituents which distribute in the shape of point-liner or gather among the grains, is larger compared with lamellarizing and tempering. Although the strength of the steel is higher, the value of the impact energy at-80 °C is lower and unstable. After intercritical quenching, the presence of minor ferrite and austenite grains refined could also be helpful to improve the low temperature toughness. Because polygonal ferrite (QF) is small and distributes uniformly between bainitic ferrite lathes acting as beneficial barriers to cleavage crack propagation.
391
Authors: Constantin Dulucheanu, Nicolai Bancescu, Traian Severin
Abstract: With this article, the authors present a number of technological characteristics determined for a dual-phase steel with 0.09% C and 1.90% Mn. This steel was obtained through intercritical quenching: heating at 740, 780 and 820 °C, maintaining for 30 minutes and then cooling in water, oil, oil in magnetic field of direct current (DC) and oil in ultrasonic field. It was determined the degree of cold upsetting, the ultimate tensile strength of the resistance butt welded joints and the cutting property based on the study of cutting forces and surface roughness; it was analyzed the influence of heat treatment parameters (heating temperature, quenching medium) and ferrite-martensite structure on these characteristics.
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Authors: Constantin Dulucheanu, Nicolai Bancescu, Traian Severin
Abstract: In this article, the authors have analysed the influence of quenching temperature (TQ) on the mechanical properties of a dual-phase steel with 0.094 % C and 0.53% Mn. In order to obtain a ferrite-martensite structure, specimens of this material have been the subjected to intercritical quenching that consisted of heating at 750, 770, 790, 810 and 830 °C, maintaining for 30 minutes and cooling in water. These specimens have then been subjected to metallographic analysis and tensile test in order to determine the volume fraction of martensite (VM) in the structure, ultimate tensile strength (Rm), the 0.2% offset yield strength (Rp0.2), the total elongation (A5) and the Rp0.2/Rm ratio.
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Authors: Constantin Dulucheanu, Nicolai Bancescu, Traian Severin
Abstract: In this article, the authors have analysed the influence of quenching temperature (TQ) on the microstructure of a dual-phase steel with a low carbon and manganese content (0,094 % C and 0,53 % Mn). The ferrite-martensite structures, typical of the dual-phase steels, has been obtained by intercritical quenching that consisted of heating at temperatures (TQ) ranging between 750 °C and 830 °C, maintaining for 30 minutes and cooling in water. After carrying out intercritical heat treatments, samples have been subjected to metallographic analysis through which the volume fraction of martensite (VM), the volume fraction of ferrite (VF), the carbon content of the martensite (CM), the morphology and distribution of these phases have been determined, and then, the influence of quenching temperature (TQ) has been established.
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