Advanced Materials Research Vols. 399-401

Abstract: Hot rolled 260MPa grade high strength Nb-IF steel sheet was used to study the effect of coiling temperature and cold reduction ratio on the microstructures and mechanical properties. The experimental results showed that the recrystallization has finished. Under 650°Ccoiling temperature and 75% cold reduction ratio, and under 600°C or 700°C coiling temperature and 65% cold reduction ratio, the plastic strain ratio r value and the strain hardening exponent n value were reached the maximum, and respectively, the r value was approximate 1.8, the n value was approximate 0.26. That obtains optimally match of high strength and punching property.

Abstract: The corrosion behavior of hot dipped Zn coating in freshwater with and without Zn(OH)₂ was investigated through weight loss test, polarization curve and impedance spectroscopy. The morphology of the corroded hot dipped Zn coating was analyzed by SEM, meanwhile, the effect of Cl^- on corrosion behavior of hot dipped Zn coating in saturated Zn(OH)₂ solution was examined using polarization curve. It was found that corrosion product Zn(OH)2 accelerate the corrosion of coating, Cl- promoted dissolution of anodic coating and incr_{Subscript text}eased the conductance of the solution, and the worst corrosion resistance of coating is Cl^-concentration of 1%.

Abstract: The relationship between texture and secondary work embrittlement of interstitial-free steels was studied by X-ray analysis technique and scanning electron microscopy analysis technique. The results indicated that the stronger the γ fiber texture was, the higher the plastic strain ratio (r-value) was, and Secondary work embrittlement temperature rose as r-value increased or γ fiber texture intensified. The mode of secondary work embrittlement fracture was a blend of cleavage fracture and intergranular fracture, and the fraction of cleavage fractures decreased gradually as secondary work embrittlement temperature rose.

Abstract: Microstructure evolution in low-carbon bainitic steel during tempering is investigated by hardness measurements and metallographical examinations. It is found that the microstructure evolution and the hardness variation can be divided into four stages when samples were tempered at 600°C and 700°C, and the evolution of bainte is similar to recovery and recrystallization of deformed metals. It is also found that the newly formed ferrite during recrystallization grows more rapidly along the long axis of bainite laths, and there is evidence of composition changing during recrystallization.

Abstract: The corrosion products formed on carbon steel exposed to seawater were studied. Morphology, composition, structure and porosity of the rust were analysed by different methods: OM, SEM, FTIR, XRD and BET. The results indicate that the inner and outer rust layers formed on carbon steel in seawater are different in morphology, composition and structure. With increasing of exposure periods, the rust layers become more and more compact, which exhibit a high resistance to corrosion.

Abstract: This study presents the effect of hardness and impact of 2.0% vanadium ductile iron after double quenching heat treatment method on different temperature. Addition of 2.0% Vanadium to ductile iron was produced through conventional CO2 sand casting method. The specimens were preheated to 500°C for 30 minutes, then oil quenched and austenitized at 900°C for 60 minutes before oil quenched again. After that, the specimens were tempered for 90 minutes at three different temperatures including (i) 500°C, (ii) 600°C, and (iii) 700°C respectively before cooled to room temperature by nature air. It is evident found that the addition of 2% Vanadium contributed to the slightly improved to the tensile strength properties but better hardness and impact compared to conventional ductile iron. The higher hardness and impact were found at 500°C and 600°C tempering temperature respectively.

Abstract: Stainless steel fiber is a new sort of soft industrial material developed in the past decades. The pure stainless fiber has a number of outstanding properties and is getting wider range of application in textiles which are used as industrial textiles. The tensile properties between stainless steel fiber and traditional textile fibers are quiet different. The property differences between stainless fiber and common textile fiber made the textile processing of stainless fiber difficult. Based on the testing of breaking force, breaking strength and breaking elongation rate, this paper analyzed the tensile characteristic of stainless fiber and discussed its effect on yarn quality.

Abstract: The Nb-contained austenitic heat-resistant steel 18Cr10NiNb(TP347H) has been widely used as super-heater and re-heater tube material for modern ultra-super-critical (USC) power plants in the world. High temperature structure stability is considered to be one of the most important factors for long-term service. Long-term aging at 650 °C for this steel was conducted till 10,000 hours. Effect of aging time on microstructure was studied by means of SEM and TEM. Tensile tests were carried out after aging at 650 °C for different times. Experimental results show that MX phase and M₂₃C₆ carbides are major strengthening precipitates in this steel. With increasing of aging time, fine nano-size MX particles precipitate in grains and its size keeps about 50 nm till 10,000 h at 650 °C. Carbide M₂₃C₆ mainly precipitates at grain boundaries but coarsens quickly. Investigation results show that MX phase plays the most important strengthening effect in grains. The amount of MX phase increases with increasing of Nb and C contents. The effects of Nb and C contents on mole fractions of MX phase in 18Cr10NiNb steel have been calculated by using Thermo-Calc software.

Abstract: The weight-loss method was used to study the effect of H₂S/CO₂ pressure on the corrosion behaviors of L360QCS in the environments with the existence of elemental sulfur and H₂S/CO₂. The morphologies, compositions and structure of corrosion products formed at different partial pressures were studied by the means of SEM, EDS and XRD techniques. The results show that the existing of H₂S/CO₂ increases the corrosion rate sharply and the corrosion rate increase dependence on H₂S/CO₂ pressure. At low gas pressure the production is mainly cubic FeS crystal while that is square FeS crystal at high pressure.

Abstract: The experiment has studied the effect of solidification process of Fe-C-S alloy treated RE on the distribution of elements and inclusions on the distribution of elements and inclusions after the electric pulse field is applied. The results show that Rare Earth in the molten steel has played a purification role and change the strip MnS inclusions into spherical sulfide inclusions. Meanwhile, the co-action of electric pulse field and Rare Earth can reduce and refine inclusions and improve the distribution of elements in solidification microstructure.