Papers by Keyword: Sticking

Abstract: Breakout is the most detrimental event associated with the continuous casting process, with the overview of the sticking breakout behavior, a lot of valuable things had been acquired. For the mechanism of the sticking breakout forming, the key for the breakout prevention is decreasing the probability of the hot spot; the content of the carbon or alloy element, the wear and tear of the mould corner, the mould flux, the fluctuation of the casting speed and the fluctuation of the meniscus are easy to cause the sticking; and with high casting speed and the funnel mould, the thin slab continuous casting is more easier to lead to sticking breakout than the normal strand.

Abstract: In hot rolling process of 2205 duplex stainless steel, it was found that bright line defects are mainly located at where is about distance of 200 mm from two sides of hot rolled plate. The forming reason of bright line defects is studied by means of metallographic microscope, scanning electron microscope (SEM) combined with energy dispersive spectrometer (EDS). It is concluded that the formation of bright line defects has associated with sticking and that the temperature reduction on the edge of hot rolling plate causes a high percentage of austenite phase which is network structure. In order to prevent or avoid the happening of the sticking phenomenon, it is necessary to uniformly distribute the oxide on the strip surface by controlled rolling process.

Abstract: Recent advances in continuous casting have facilitated remarkable improvement in the quality of cast steel. The focus of the present paper is directed towards understanding of the influence of chemistry and intrinsic solidification behaviour on the different quality issues of stainless steel. An attempt has been made, wherever possible in quantitative terms , to correlate the chemistry and the process parameters with the quality factors. The relevant theoretical background has been touched upon. Understanding has been developed on the role of the ratio of nickel equivalent and chromium equivalent. This factor can be used to represent the chemistry of any stainless steel grade. Under similar casting conditions, specific problem of mould sticking , strand bulging , or depression formation has been explained invoking this chemistry factor. Each quality issue owes its genesis to interaction between the high-temperature strength and ductility of the solidifying shell during casting. The important roles of micro-segregation , the effective shell thickness during the early stage of casting , and the temperature range of transformation for δ-ferrite to austenite have been highlighted. An approach of grade-specific casting practice has been suggested to formulate the specific casting parameters. The developed understanding has been utilised to address specific quality problems in continuously cast slabs and rolled products of different stainless steel grades. This integrated understanding can be useful for ensuring the quality of stainless steel of any chemistry.

Abstract: Influence of mixing MgO additive on fluidized bed reduction of iron ore fines using simulate COREX reducing gas was investigated. Experiments were conducted at 1073 K in a visualization fluidized bed. Mixing MgO additive was carried out using powder method and solution method. It was found that mixing MgO into ore fines using solution method could increase fluidization time from 12 to 80 minutes, and improve the metallization ratio from 22% to 81%. Reason was that coating MgO could effectively insulate the contact of metallic iron on particles, which provided the reaction time for carbon deposition and the production of Fe3C with low stickiness. Therefore, the decrease of metallic iron on particle surface led to the decrease of particle stickiness in fluidized bed reduction

Abstract: It is a good way that the fluidized bed is used as a substitute for reduction shaft in Corex process. Which can reduce energy consumption, environmental pollution and construction costs further, and also improve the competitiveness of Corex and blast furnace. At present, the sticking problem is present in iron ore reduction process and interrupts the reduction process, it has become a major obstacle on the development of fluidized bed. In this paper, a visualization hot model of fluidized bed is introduced. The influence factors on sticking behavior were analyzed from reduction temperature, gas velocity, atmosphere, degree of metallization or reduction and property of iron ore, the research provided a strong theoretical basis for controlling the sticking.

Abstract: Well KL11-2-1 is a wildcat well that located in KL11-2 structure, where sticking happened in position Ⅳ of Shahejie group, the accident happened again in the same position while drilling the sidetracked well KL11-2-1S on the base of Well KL11-2-1, Analysis reveals that the lithology in the place of the two sticking accidents is rufous mudstone. This kind of mudstone has the character of strong plasticity, swelling with water and very soft, the main reason of sticking is that the mud column pressure can not balance the soft mudstone creep pressure and the creep lead to borehole shrinkage. For solve the problem during drilling in this structure, this paper according to the characteristics of mudstone in this structure builted proper creep equation and creep mechanical computation module of soft mudstone, applied FLAC3D software to compute and analyze the creep characteristics, obtain borehole shrinkage rate plate with different depth and mud density, and the safe mud density that can inhibit the creep which lead to borehole shrinkage is given, the results show that for prevent the sticking accident occurred the safe mud density of the two sticking points of the well KL11-2-1/1S is 1.73 g/cm3 and 1.75 g/cm3.the results make significant sense in guiding the subsequent drill of the structure.

Abstract: A better understanding of friction modeling is really important for producing more realistic finite element models of machining processes. This paper presents a methodology to determine the friction at the tool-chip interface. By matching the measured values of the cutting forces with the predicted results from finite element simulations (FEM), a revised friction model on the tool-chip interface is developed. Reasonable distribution of the stress, strain and strain-rate, as well as the temperature fields at the tool-chip interface could be achieved by using this approach. An attempt is made by FEM to obtain a full understanding of relationships between the complex physical behavior and friction at the tool-chip interface. It is found that the sticking-sliding separated area is located at the points with the greatest temperature. And the corresponding relationship between cutting parameters and sticking-sliding friction separated area is found.

Abstract: Sticking phenomenon occurring during hot rolling of ferritic stainless steels, STS 430J1L and STS 436L, was investigated in this study. The simulation test results at 900 oC and 1000 oC revealed that STS 430J1L had a smaller number of sticking nucleation sites than the STS 436L. When the test temperature was 1070 oC, the sticking hardly occurred in both stainless steels as Fe- Cr oxide layers were formed on the surface of the rolled materials. These findings suggested that the improvement of high-temperature properties of stainless steels and the appropriate rolling conditions for readily forming oxide layers on the rolled material surface were required in order to prevent or minimize the sticking.

Abstract: During depositing a thin film as a structure layer, residual stress from thermal treatment of depositing process will cause deformation after release. Thus the yield ratio and deformation of the devices may be lowered. This work investigates the effect of sacrificial layer on deformation by residual stress causing when depositing a thin film as structure layer. A model is established by using theory of plates-and-shells to investigate the deformation caused by residual stress when the structure layers of the devices are center-anchored circular plate. Theoretically, it is found that the deformation would happen when depositing structure layer under higher temperature. And from the analysis, the thicker structure plate will cause less deformation. When the thickness of the structure layer is larger than 3μm , the maximum deformation will reduce to the order of μm. Furthermore, four cases of different sacrificial layer types and temperature distribution with effect on deformation are discussed. If the thickness of the structure layer is above 5μm, the deformation caused by residual stress is not so important. And it is found that if the thickness of structure layer is 10μm order or above, the residual stress effect on deformation can be neglected. It is found the sacrificial layer will affect the deformation. But it is found that with the same structure layer thickness, as the sacrificial layer thickness increasing, the four cases have different effect on deformation. The in-plane dimension effect is also considered. When the in-plane dimension of sacrificial layer is above 20 times of outer radius, the in-plane dimension effect is neglected and can considered as an infinite dimension.