CALCULATION OF TRANSFORMATION VOLUME FRACTION TO HQ590 HOT ROLLED STRIP STEEL DURING CONTINUOUS COOLING

On the basis of phase transformation kinetics, the transformation of γ→α,P,B have been investigated through considering the effect of deformation. The calculation methods of volume fraction have also been given. Comparing with common method, the simulated results are in more agreement with experiment results.     

CRYSTALLOGRAPHIC ANALYSIS OF THE LATH MARTENSITE TRANSFORMATION IN Fe-Ni-Mn ALLOY

1.IntroductionBased on the concept of an invariant plane strain (IPS), phenomenological theory of martensite transformation (PTMT) is established[1-3]. In this case, an invariant plane is obtained by self-accommoda-tion effect between different martensitic variants, and the formula which reveals this self-accommoda-tion effect can be written as …     

MODELING OF ISOTHERMAL PRECIPITATION KINETICS IN HSLA STEELS AND ITS APPLICATION

1.IntroductionMicroalloying elements, such as Nb, Ti and V in HSLA steels precipitate during hot-rolling pro-cesses, which plays an important role in determining mechanical properties of HSLA steels[1].In order to model the precipitation behavior, many quantitive models[2-8] have been proposed. These models, however, can only be applied to single microalloyed steels. As temperature decreases continu-ously during hot deformation processes, isothermal data can not be used directly to predic…     

THE PHYSICAL SIMULATION ON EXTRUSION PROCESS OF GLASS FIBER COMPOSITE WIRE COATED BY LEAD

The method of manufacturing the composite wire by extruding lead to coated glass fiber is described. The different composite wire that diameter is from 0.5 to 1.0mm has been produced by two kinds of different extruding technology (getting wire along horizontal direction and getting wire along perpendicular direction). The optimal extruding technological parameter has been given in different extruding technology by the physical simulation (H: 300℃, 550kN, 0.16mm. P: 300℃, 215kN, 0.16mm). The effect on the coating speed by other extruding technological parameters in the different extruding technology has been discussed. The extruding temperature and extruding force is higher, the coating speed is faster. It has been pointed, that the affection on the extruding technology by the extruding temperature has also behaved as the extruding temperature rising up spontaneously. The reason for exiting the minimum extruding force and maximum extruding force also has been discussion in this paper. It is also important to the extruding process and coating speed that is the coating clearance.     

Two- and three-dimensional equilibrium morphology of a misfitting particle and the Gibbs–Thomson effect

The equilibrium shapes of misfitting precipitates in elastically anisotropic systems are obtained in both two and three dimensions, and the corresponding Gibbs–Thomson equation is derived as a function of the characteristic ratio between elastic and interfacial energies, L′. The effect of elastic inhomogeneity is investigated systematically. For soft or moderately hard particles, the stable equilibrium shape bifurcates from a fourfold symmetric shape to a twofold symmetric one in 2D and from a cubic symmetric shape to a plate-like one in 3D. For a very hard particle, the shape bifurcation is not observed in 2D for the range of L′ investigated, but both plate-like and rod-like shapes are found in 3D. The computed Gibbs–Thomson equation is well approximated by a piecewise linear function of L′. Predictions are made for coarsening of many-particle systems based on an established mean-field theory. The results predict that the elastic stress has no effect on coarsening kinetics where most particles are highly symmetric (fourfold in 2D and cubic in 3D), and the exponent remains 1/3 but the rate constant increases if stress is sufficient to induce symmetry-breaking bifurcation on most particles.     

Electrochemical properties of Mg-based alloys containing carbon nanotubes

In this work, effects of partial substitution of Mg, Ni with AB₂ in Mg-based alloy and subsequent surface modification by further ball-milling with carbon nanotubes (CNTs) on electrochemical properties were investigated. Mg_1.9(AB₂)_0.1Ni_0.8 (AB₂=LaNi₂, LaNiCo and LaNiMn) alloys were prepared by solid-state diffusion method, the nanocrystalline Mg-based alloys were prepared by ball-milling the mixture of obtained Mg_1.9(AB₂)_0.1Ni_0.8 alloys and nickel powder. It was found that the electrochemical capacities of nanocrystalline Mg_1.9(AB₂)_0.1Ni_1.8 alloys were measured to be 460–490 mAh/g. The nanocrystalline Mg-based alloys containing carbon nanotubes (10 wt.%) obtained by ball-milling after 60 min were demonstrated to show improved electrochemical properties with respect to the original nanocrystalline Mg-based alloys. The electrochemical reaction activity was detected by electrochemical impedance spectra (EIS). Raman and X-ray photoelectron spectroscopy (XPS) proved the interaction between Mg_1.9(AB₂)_0.1Ni_1.8 alloys and carbon nanotubes after ball-milling, which resulted in an increase in the surface Ni/Mg ratio.     

A study on centrifugal casting of high speed steel roll

High speed steel (HSS) rolls can replace traditional rolls such as alloyed cast iron rolls and powder metallurgical (PM) hard alloy rolls. The main reasons for the replacement are that the wear resistance of low-cost alloyed cast iron rolls is poor and the cost of high-quality PM hard alloy rolls is very high. By means of centrifugal casting, HSS rolls having excellent wear resistance have been manufactured. The hardness of the HSS roll is 65～ 67 HRC, the range of variation is smaller than 2 HRC and its impact toughness is 15 J/cm2. The wear rate of HSS rolls used in the pre-finishing stands of high-speed hot wire-rod rolling mill reaches 2.5 × 10-4 mm per ton steel. Furthermore, the manufacturing cost of HSS rolls is significantly lower than that of PM hard alloy rolls; it is only 30 percent of that of PM hard alloy rolls.     

Resistance of Mo-bearing stainless steels and Mo-bearing stainless-steel coating to naphthenic acid corrosion and erosion-corrosion

Naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behavior of Mo-bearing (0-7.0 wt.%) stainless steels have been investigated in laboratory to evaluate the essential role of Mo on their NAC and NAEC resistance. The NAC and NAEC resistance of a high-velocity-oxygen-fuel (HVOF) thermal sprayed Mo-bearing stainless-steel coating was also investigated in both laboratory and an oil refinery. It was found that increasing the Mo content remarkably enhanced the NAC and NAEC resistance of stainless steels. The Mo-rich areas or phases in the steels played an importance role in resisting the NAEC. The HVOF coating showed excellent NAC and NAEC resistance in laboratory tests. The 700-day field test in an oil refinery revealed that the coating can effectively prevent the carbon-steel substrate from erosion-corrosion during long-term exposure in oil-refining environment. The corresponding NAC and NAEC mechanisms of the stainless steels and the beneficial role of Mo were discussed by taking account of inherent susceptibility of metal elements to corrosion, possible effects of Mo on surface films, and Mo-induced change in microstructure and microhardness.     

Effect of alloying elements on the electrochemical polarization behavior and passive film of Fe-Mn base alloys in various aqueous solutions

The corrosion properties of austenitic Fe-Mn, Fe-Mn-Al, Fe-Mn-Cr and Fe-Mn-Al-Cr alloys with compositions of 23-30 wt% Mn, 2.8-8.2 wt% Al and 4.9-6.9 wt% Cr in various aqueous solutions of pH −0.8 to 15.3 and the passivating mechanism induced by the presence of Al, Cr, or Al and Cr have been studied using electrochemical measurements and Auger electron spectroscopic/X-ray photoelectron spectroscopic analysis. Binary Fe-Mn alloys can be passivated only in 10-50% NaOH solutions, and alloying of binary Fe-Mn alloy with Al or Cr or combination of Al and Cr seems not so obviously beneficial to corrosion resistance in HNO₃ or Na₂SO₄ solutions. All of the experimental Fe-Mn based alloys and steels for comparison cannot passivate in either 10% HCl or 3.5% NaCl solution. The Fe-Mn based alloys containing Al or Cr or Al and Cr can passivate in 10-50% HNO₃ or 1 mol l⁻¹ Na₂SO₄ solutions and rainwater. In general, Fe-Mn based alloys can passivate in oxidizing acid, neutral and basic solution, but cannot passivate in reducing acid or solution containing active Cl⁻ ions. In the passive film formed on the surface of Fe-Mn base alloys in various aqueous solutions, bound water and hydroxides are present at the surface of the film, while mixed oxides of Al, Cr, Mn and Fe are located in the inner part. The resistance to corrosion is imparted by a barrier film of bound water, hydroxides and oxides of Al, Cr or Fe, while the Mn oxides in passive film reduce the corrosion resistance.     

Ce对共晶Al-Si合金微观组织的影响

研究了Ce的变质处理时间和加入量对共晶Al-Si合金微观组织的影响。结果表明,Ce对共晶Al-Si合金有明显的变质效果,经Ce变质处理后,共晶Si由长针状变为珊瑚状;Ce的变质处理时间和加入量也会影响变质效果,Ce在共晶Al-Si合金中的最佳加入量(质量分数,下同)为1%,最佳变质处理时间为60~90min。