Advanced Materials Research Vols. 690-693

Abstract: By the equilibrium phases of the steels with temperature, the causation of being carbide network of CrWMn steel frequently in the manufacture was analyzed, and an alloy design for avoiding carbide network of CrWMn steel was researched. The analyse and research show that in austenite area the boundary precipitation of M₃C and M₆C carbides during cooling process after forging or hot rolling is preferential origin of carbide network, and in later ferrite area the precipitation and congregation of the carbides should lead on network aggravation. When CrWMn steel adding 0.3~0.4Mo as supplement, in austenite area M₃C carbide disappears and M₂₃C₆ carbide increases, and it is conceivable of lightenning congregation to austenite boundary as the transformation of M₂₃C₆ and M₆C reciprocally, and the distribution of diversified carbides should become fine too. The practice results show that the carbide network of CrWMnMo_0.35 steel is avoided under normal forging or hot rolling conditions, and the hardness after quenching at 850°C and tempering at 200°C is HRC62~63, which is agreement with alloy design forecast. The experiment and application show that the performance of CrWMnMo_0.35 steel is better than that of customary CrWMn steel for machinery knives.

Abstract: The atmospheric corrosion behavior of cast iron after six months immersion was studies by means of optical stereomicroscope and X-ray diffraction techniques. The results showed that active corrosion occurred on the rusted specimen covered with many thin spherical shells of solid material. The XRD analysis indicated the formation of β-FeOOH tends to increase with increasing exposure.

Abstract: The passive films formed on X80 and X70 pipeline steel in 0.5 mol·L^-1 NaHCO₃ solution are investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), and the corrosion resistance of both steel is compared. The results show that X80 steel has a much lower passive current density than X70 steel. EIS measurements indicate that the film formed on X80 steel is much more compact and uniform than that of X70 steel. Mott-Schottky analysis demonstrates that the passive film of X80 steel has a lower donor density and a thicker space charge layer than X70 steel. These factors lead to a better corrosion resistance for X80 steel than X70 steel.

Abstract: A new hot-rolled ship plate with high strength and high toughness is successfully developed through chemical composition design and TMCP process. Experimental methods, such as OM, TEM and X-EDS, were used to study the microstructure and precipitates of steel. The primary microstructural constituent is acicular ferrite, quasi-polygonal ferrite with second constituents along grain boundaries. Lath width of acicular ferrite is about 1μm. Cubic particles about several hundreds nanometers and nanometer particles exist in experimental steel. It can be concluded that acicular ferrite is the main reason for high strength and super toughness. precipitation hardening due to dispersed precipitations of carbonitrides can not be overlooked.

Abstract: The effect of rare earth element on structure and mechanical properties of the 430 ferrite stainless steel was studied by metallographic examination, scanning electron microscope (SEM), tensile test and impact test. The results show that the proper amount of RE can refine microstructure of 430 ferrite stainless steel. The fracture mode of 430 ferrite stainless steel is typical dimple fracture. 430 ferrite stainless steel containing 0.056% RE can improve its impact toughness and the high temperature strength, and the transverse impact toughness increases 37.2% at 253K respectively comparing with that of 430 ferrite stainless steel without RE. And at 1273K, the high temperature strength increases by 38.3% than that of 430 ferrite stainless steel without RE.

Abstract: In order to improve fatigue life of wheel steel, secondary-refining process is done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. By slag-steel-inclusion interaction, harmful inclusions could be controlled well to be eliminated by floation, lowering T[O] content to 0.0007% in round billets, enhancing fatigue life of wheel steel. It is found that (Al2O3) in slag is positive factor for decrease of T[O], while (CaO)/(Al2O3), (SiO2) in slag and [Al]s in molten steel is negative factor for it. As a result, by INSTRON fatigue testing machine, tested steel samples achieve ultra-high cycle of 108 above, realizing experimental purpose of improving fatigue life of wheel steel.

Abstract: Based on a system of macro & micro fracture appearance observation, energy spectrum analysis, metallurgical structure inspection and hardness test, the fracture mechanism and cause of specimen of 16Mn steel were obtained. The results showed that the large load was the main reason for the 16Mn steel specimen fracture, the fracture surfaces were different dimensional equiaxed dimples and some spherical particles which contain higher Mn, Si and O. The spherical particles may be an oxide which may be caused by the manufacturing process.

Abstract: According to the present situation of lack of systemic analysis for green manufacturing operation mode for iron & steel enterprise in domestic and overseas, and based on the theory and method of green manufacturing and the operation law of iron & steel enterprise, a kind of five layer structure of green manufacturing operation mode for iron & steel enterprise was put forward, a segmentation model for green iron & steel manufacturing system integrated operation based on the iron & steel product life cycle was established. The operation mode can provide guidance ideas for the iron & steel enterprises to implement green manufacturing.

Abstract: A method is proposed to improve both the gamma-ray radiation-and thermal stress-induced degradations of springback characteristics in Invar alloy. Invar foil was first subjected to a 30 kGy-irradiation followed by 60 cycles of hot-then-cold (radiation+hot-then-cold) treatments. It was found that both the radiation-and thermal stress-induced springback degradations in Invar foil tended to be stabilized after 5 cycles of radiation+hot-then-cold treatments. XRD analyses showed no difference between controls and experimental samples, thus excluding the possibility of structural or phase transformations. The weak bonds inside the foil possibly rearranged and recovered during the radiation+hot-then-cold processes, resulting in radiation-and thermal stress-hard springback behaviors.

Abstract: Intergranular corrosion behavior of 00Cr12 ferritic stainless steels with different amounts cerium was evaluated. For this evaluation, electrochemical measurements - polarization curves - were obtained for tested materials, and optical microscope was used to observe corrosive microstructure. Experimental results shows: cerium reduces grain sizes and improves intergranular corrosion resistance of test materials. Through mechanism analysis: cerium reduces grain sizes, increases grain boundary density, therefore might improve distribution aspects of carbides and nitrides, chromium depletion situation near grain boundary would be improved, this work worth further study.