Environmental-friendly Ramming Materials for Mud Package and Taphole of Large-scaled Blast Furnaces

The compositions, structures and properties of envi- ronmental-friendly ramming materials for mud package and taphole of large-scaled blast furnaces were studied. The results show that the formation of silica fibers makes structure of ramming materials dense. During the process of extruding mud and ramming materials, SiC is partly oxidized ; CaO , F% 03 and carbon penetrate towards the outer wall. The improvement of ramming materials can inhibit the penetration of molten slag, iron and carbon. The bulk density of environmental-friendly ramming ma- terials dried at 200 ℃ is 2.90 g · cm-3, the cold com- pressive strength of this kind of ramming materials dried at 200 ℃ is about 17. 0 MPa and fired at I 450 ℃ is about 39. 2 MPa.

Carbon Ramming Materials for Blast Furnace Construction

1 Scope This standard specifies the definition, classifica- tion, technical requirements, test methods, quality ap- praisal procedure, packing, marking, transportation, stroage and quality certificate of carbon ramming mate- rials for blast furnace construction. This standard is applicable to carbon ramming materials for construction in leveling layer of blast furnace bottom, ramming layer upper or lower the cen- tral line of water cooling pipes, joints between carbon bricks, or joints between carbon bricks and cooling equipment.

Microwave Absorption Properties of the Carbonyl Iron/EPDM Radar Absorbing Materials

Employing carbonyl iron powder and Ethylene-Propylene-Diene Monomer （EPDM） as the absorbent and matrix, rubber radar absorbing materials （RAM） were prepared. Effects of the carbonyl iron volume fraction and the thickness of the RAM on the microwave absorption properties in the frequency range of 2.6-18GHz were studied, and a mathematical analysis was made using the electromagnetic theory. The experimental results indicate that the minimum reflectivity of the radar absorbing materials continuously decreases with the increase of the carbonyl iron volume fraction, and the absorption peak also moves towards the low frequency for the same thickness of the RAM. The minimum reflectivity of the 3.0 mm RAM is -21.7dB at 3.5 GHz when the volume fraction of carbonyl iron is 45%. The reflectivity of the RAM is not in direct proportional to the thickness of the RAM, when the RAM has the same volume fraction of the carbonyl iron. The reflectivity of the RAM presents a regular trend at a given carbonyl iron volume fraction in the frequency range of 2.6-18 GHz. With the increase of the thickness, the maximum absorption peak moves towards low frequency band, the minimum reflectivity firstly decreases and then increases, and the absorption bandwidth for reflectivity〈-10 dB firstly increases and then decreases. The microwave absorption properties of the RAM are determined by the thickness and the composition of the radar absorbing materials. Theoretical analysis indicates that the reflectivity of the RAM is determined by the matching degree of the air＇s characteristic impedance and the input impedance.

Interaction of Electromagnetic Waves with Two-Dimensional Metal Covered with Radar Absorbing Material and Plasma

A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material （RAM） and plasma when they cover the model together. Using the finite-difference time-domain （FDTD） method, the interaction of electromagnetic （EM） waves with the model can be studied. In this paper, three covering cases are considered： a. RAM or plasma covering the metal solely; b. RAM and plasma covering the metal, while plasma is placed outside; e. RAM and plasma covering the metal, while RAM is placed outside. The calculated results show that the covering order has a great influence on the absorption of EM waves. Compared to case a, case b has an advantage in the absorption of relatively high-frequency EM waves （HFWs）, whereas case c has an advantage in the absorption of relatively low-frequency EM waves （LFWs）. Through the optimization of the parameters of both plasma and RAM, it is hopeful to obtain a broad absorption band by RAM and plasma covering. Near-field attenuation rate and far-field radar cross section （RCS） are employed to compare the different cases.

Surface Reflection Coefficient of Impregnated RAM Honeycomb with Incident Normally Plan Wave to the Side Wall

The impregnated radar absorbing material(RAM) honeycomb is often used to fabricate parts of the war plane for reducing radar cross section. The incident wave vector may be divided into two components: one perpendicular to its hole and the other to its side wall. Until now, there has not been a program to calculate the input impedance or its equivalent electromagnetic parameters for the later case. In this paper, an approach for analyzing the reflection characteristics of the impregnated honeycomb when its side wall faces the incident plane wave is proposed. Experiments prove it an effective, accurate and fast solution to this subject.

Analysis of destructive effect of Zn on carbon brick and way of Zn into carbon brick

The service life of a blast furnace depends largely on the degree of damage to the carbon brick in the hearth.Carbon brick and ramming material in the hearth of a 1780 m3 blast furnace after shutdown were sampled and investigated.It was found that the substances in the cracks of the carbon brick near and above the taphole were ZnO and Zn_(2)SiO_(4),whereas the substances in the cracks of the carbon brick below the taphole were ZnS.The reaction of Zn with CO,SiO_(2),and Fes generates ZnO,Zn_(2)SiO_(4),and ZnS,resulting in volume expansion,which is an important reason for the cracking of carbon brick.Simultaneously,several obvious Zn vapor flow channels were found in the ramming material,through which Zn vapor could enter the carbon brick,causing damage to the carbon brick.Increasing the compactness of the ramming material is beneficial to preventing Zn vapor from entering the carbon brick through the voids in the ramming material,reducing the destructive effect of Zn on the carbon brick and further extending the service life of the blast furnace.

Fast coating analysis and modeling for RCS reduction of aircraft

In order to fast analyze the aircraft Radar Cross Section(RCS) and accurately reduce it with Radar Absorbing Materials(RAM), a comprehensive analysis method based on Higher-Order Method of Moments(HOMOM), termed Locally Coating Method(LCM), is proposed in this paper. There are two steps to fast analyze coatings for RCS reduction in this method: analyze the RCS of various parts before coating the aircraft;model a coating over the aircraft and analyze the wave absorbing effect of it. The aircraft RCS is calculated as a whole but analyzed in various parts by LCM, and thus the RCS contribution of different parts can be compared without disturbing the current continuity. A model expansion algorithm is also presented in LCM to model absorption coatings on specified aircraft parts for later stage RCS calculation of the coated aircraft.