FEM analysis of large thermo-deflection of strips being processed in a continuous annealing furnace

No matter what the flatness of a strip is, flat or defective, at an annealing furnace entrance, the strip can not keep its original shape and a remarkable change of its shape can be seen at the annealing furnace exit. By investigating this phenomenon at the 2030 mm continuous annealing line which belonged to Baosteel, a finite element model of thermo-mechanical buckling deformation of strips in a continuous annealing furnace were established, and the mechanism of flatness changing and the contributing factors were researched by the finite element software ANSYS.

Application of the waste heat recovery system and energy-saving in the strip continuous annealing furnace

The common problem of cold strip continuous annealing furnaces is high exhaust gas temperature and great energy consumption. Taking the cold-strip continuous annealing furnaces of Baosteel No. 4 cold mill plant as an example, several waste heat recovery systems in the annealing furnaces are compared and their advantages and disadvantages are analyzed through different energy-saving technologies.

Detection and analysis of gas tightness of continuous annealing furnaces

When a cold rolled strip is being treated in a continuous annealing furnace which is full of protective gas, the gas tightness of the furnace body, the connected facilities and the gas channels become an important indicator that directly affects the product＇s surface quality and shows the technical level of the design, the manufacture and the installation. By considering the problems of the gas tightness of a vertical annealing furnace in the installation and maintenance, this thesis evaluates the gas tightness indicator and gas tightness related level of the furnace body and the circulation duct, while studying and analyzing the technologies of negative-pressure leak detection and sealing.

Deviation Prevention Ability of Rollers in Continuous Annealing Furnace and Application

In order to reduce the strip deviation in the practical production procedure in the continuous annealing fur- nace, a dynamic simulation model was built through finite element method （FEM） to conduct the quantification cal- culation of the effect of regular roller contour types on strip deviation. The result reveals that comparing to the flat roller, forward roller contour can prevent the strip deviation to some degree. In terms of prevention ability, double- taper roller is the strongest, single-taper roller and crown roller are less stronger; and more roller contour values raise the prevention ability. Accordingly, optimization method was applied to continuous annealing furnace, and it largely reduced accidents such as strip break and limited speed that are caused by the deviation.

Modeling of Strip Heating Process in Vertical Continuous Annealing Furnace

The mechanism for heat transfer of radiation is usually adopted to heat strip in vertical continuous annealing furnace. The rate of heat transfer among strip and other objects can be hugely affected by the parameters of strip speed, geometry factors and radiating characteristic of surfaces of strip, radiating tubes and walls of furnace. A model including all parameters is proposed for calculating the heat transfer coefficient, predicting the strip tempera- ture and boundary temperature of strip through analyzing these parameters. The boundary temperature is a important datum and different from average arithmetic value of temperature of strip and temperature in furnace. Also, the model can be used to analyze the relation for temperature of strip and heat transfer coefficient, total heat transfer quantity and heating time. The model is built by using the radiating heat transfer rate, the Newtonrs law of cooling, and lumped system analysis. The results of calculation are compared to the data from production line. The comparisons indicate that the model can well predict the heating process. The model is already applied for process control in pro- duction line. Also, this research will provide a new method for analyzing the radiation heat transfer.

Enhancement of GMI Effect in Silicon Steels by Furnace Annealing

The ratio and sensitivity of giant magnetoimpedance （GMI） in grain oriented silicon steels （Fe-4.5%Si） are improved after furnace annealing in air for 20 min. By annealing at 800℃, the GMI sensitivity rises from 1.29%/Oe to 1.91%/Oe and the ratio increases from 237% to 294% with decreasing characteristic frequency. The results are attributable to an increase in the transverse magnetic permeability during the heat treatment. From simulation by finite element method, the GMI effect can be interpreted as the modification of the current distribution by the applied magnetic field via the transverse permeability. In the case of annealed samples,the larger transverse permeability allows a higher GMI ratio and sensitivity.

Comparison of Poly-Si Thin Films Prepared by Conventional Furnace Annealing and Pulsed Rapid Thermal Annealing

Amorphous silicon films prepared by PECVD on glass substrate were crystallized by conventional furnace annealing(FA) and rapid thermal annealing(RTA),respectively. From the Raman spectra and scanning electronic microscope(SEM),it found that the thin films made by RTA had smooth and perfect structure,while the thin films annealed by FA had a higher degree of structural disorder.

Application and practice of regenerative combustion technology on radiant-tube furnace

High Temperature Air Combustion(HTAC) based on regenerative theory has been used in developed countries in recent years,it has many advantages such as efficient recovery of waste heat,high temperature preheating air,low pollution discharge,and so on.This Technology can be used in various furnaces in mechanical,petroleum,chemical industry.To rebuild traditional radiant-tube combustion system with HTAC technology has become important.In the transformation process,The biggest difficulty encountered is that the stability of burner combustion and control system. Because the exhaust gas heat is absorbed by the regenerator,exhaust gas discharge can be controlled at a very low temperature to realize maximum waste heat recovery.At the same time,it improves the temperature uniformity and improve the heating intensity.Thermal efficiency of the device can reach more than 80%.And compared to the traditional air preheating,21.55%energy can be saved. Revamping on traditional radiant-tube combustion system is technically feasible,but a lot of problems will be involved since the rebuild work is on the old system,this article discusses on the main problem encountered in rebuild process in site. to optimize temperature control and obtain not so high exhaust gas temperature,digital combustion control system is necessary.This control loop consists of big loop and small loop,Big loop controls the load distribution of all burners in each heating zone.Small loop controls each heating zone burner's burning time. Compared performance of tradition radiant-tube heater with regenerative radiant-tube heater,result that regenerative radiant-tube heater have many advantage in consume fuel.Accordance with experience of replacing tradition radiant-tube heater with regenerative type,give a proposition in combustion control system, pilot burner,flame detection and prevent trouble to rebuild work of CAPL and CGL. It is recommended to use regenerative combustion technology in new annealing Line.Although the investment is 1/3 much more than the traditional combustion system,the energy saving effect is obvious and operating costs decreases.Revamping can be taken step by step according to different heating zones.Although taking a long time,it is safer and it influences the production less. Regenerative combustion burner revamping has become successful.However,the revamping work on different furnaces,particular on continuous annealing furnace with high request for temperature control,need further exploration and research.

The application of the regenerative combustion technology to a radiant-tube furnace and its practice

This study compares the regenerative radiant-tube heater with the traditional radiant-tube heater, showing the regenerative radiant-tube heaters have many advantages in fuel consumption. Based on the experience of changing a heating system with traditional radiant-tube burners to a heating system with regenerative combustion, propositions are given for the combustion control system, pilot burner, flame detection and for trouble prevention in rebuilding the continuous annealing production line（CAPL） and the continuous galvanizing line（CGL）.

Cause analysis of and solution to furnace roller pick-up in the high strength automotive steel sheet processing line

Cold-rolled high strength steel sheets for automobiles contain more Mn and Si based alloy elements, which, under the reducing atmosphere in the annealing furnace, will get enriched on the strip surface. Since the furnace rollers and the strips contact frequently, alloy elements on the roller surface will form hard protuberance. We call this protuberance ＂pick-up＂. In addition, with the increase of the amount of dust in the furnace atmosphere, the occurrence of furnace roller pick-up will also increase. Through chemical reaction and physical accumulation analysis combined with practical experience, the causes of pick-up in different furnace sections were analyzed. Methods of preventing furnace roller pick-up in the high strength steel sheet processing line were discussed and solutions to improving the strip surface quality in the continous annealing furnace were provided.

Solid-phase Crystallization of Hydrogenated Amorphous Silicon on Glass Substrates

Amorphous silicon films prepared by PECVD on glass substrate have been crystallized by conventional furnace annealing and rapid thermal annealing(RTA), respectively. From the Raman spectra, X-ray diffraction and scanning electron microscope, it is found that the grain size is crystallized at 850℃ in both techniques. The thin film made by RTA is smooth and of perfect structure, the thin film annealed by FA has a highly structural disorder. An average grain size of about 30nm is obtained by both techniques.