Resin-bonded, Al-containing magnesia refractories have been an alternative of rebonded fused-grains magchrome bricks to be used as inner lining in the snorkels and lower vessel of RH degassers, having the advantages o...Resin-bonded, Al-containing magnesia refractories have been an alternative of rebonded fused-grains magchrome bricks to be used as inner lining in the snorkels and lower vessel of RH degassers, having the advantages of being chrome-free and energy-saving(without burning), with a comparable performance. Microstructural investigations indicate that metal Al powder remains independent in the matrix after heating at 700 ℃ and 900 ℃, and Al_4C_3, Al_2OC and Al_4O_4C crystalline whiskers start forming from 1 100 ℃. The whiskers grow and connect into a network matrix with increasing temperatures,remaining up to 1 600 ℃. Comparison of used bricks from different snorkels indicates a strong whisker networks formation in the brick achieving long service life and superior performance, which is attributed to flexible network structure of stable and interwoven whiskers. On contrary, there is a strongly-oxidized layer on the hot face and almost no whisker found anywhere in the brick with the short service life. It is vital to form the bonding phase of whiskers at high temperatures,generating overall properties of high hot strength, high erosion resistance and thermal shock resistance, which are essential in the working conditions of RH snorkels.展开更多
In this paper both experimental and analytical approaches to provide the inputs for creep modeling of refractories including a newly developed high temperature compressive creep machine and an inverse estimation proce...In this paper both experimental and analytical approaches to provide the inputs for creep modeling of refractories including a newly developed high temperature compressive creep machine and an inverse estimation procedure of creep law parameters are briefly introduced.Besides,a modified shear test is applied to determine the cohesion and friction angle of refractories under shear state. A RH snorkel equipped with magnesia- chromite bricks is chosen for a case study of thermomechanical simulation applying the classical creep model and Drucker-Prager creep model available in the finite element code ABAQUS,respectively. Afterwards,thermal stresses and joint opening of magnesia- chromite bricks during a process cycle are compared to distinguish the impact of these two creep models.展开更多
Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternativ...Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternative of magchrome bricks with a comparable performance in the last decade.It is important to have found whisker formation in the matrix of Alcontaining magnesia bricks above 1100°C and in the correlation to their high performance of RH snorkels.In this paper,the bonding mechanisms of both refractories are investigated to differentiate from other refractories.In magchrome bricks,the bonding modes of fused magchrome grains are characterized by the reactions between magnesia and chrome ore at different burning temperatures.At 1500°C,liquid forms around chromite grains.It is sucked into surrounding magnesia and a gap forms around chromite grains at 1600°C.Plenty of Fe2O3,Cr2O3 and Al2O3 have diffused from chrome ore into magnesia at 1670°C.A complete dissolution of the chrome ore takes place at 1750°C,with chromite precipitating entirely.In unburnt,Al-containing magnesia bricks,a dense network of whiskers is formed during heating,which is a prevailing bonding feature,instead of traditional particle growing and merging.It is believed that the whiskers are formed by vapoursolid mechanism since there is no liquid droplet observed at the tip of whiskers.In most stringent working conditions of RH snorkels,the bonding mechanisms are emphasized for their application,instead of chromia component.展开更多
With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH s...With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH snorkel lining.High purity dead burned magnesia,fused magnesia and sintered spinel were used as raw materials and sulfite pulp waste as the binder,specimens of the refractories in the Mg0-Al_(2)O_(3) system were prepared for the purpose of investigating the influences in terms of the addition of three kinds of spinels,with Al_(2)O_(3) 50%,66% and 78%,by mass,respectively,and the size of MA50 spinel on properties of the specimens.Relatively superior comprehensive properties can be achieved when 16%of MA50 spinel with sizes under 1mm is adopted.展开更多
文摘Resin-bonded, Al-containing magnesia refractories have been an alternative of rebonded fused-grains magchrome bricks to be used as inner lining in the snorkels and lower vessel of RH degassers, having the advantages of being chrome-free and energy-saving(without burning), with a comparable performance. Microstructural investigations indicate that metal Al powder remains independent in the matrix after heating at 700 ℃ and 900 ℃, and Al_4C_3, Al_2OC and Al_4O_4C crystalline whiskers start forming from 1 100 ℃. The whiskers grow and connect into a network matrix with increasing temperatures,remaining up to 1 600 ℃. Comparison of used bricks from different snorkels indicates a strong whisker networks formation in the brick achieving long service life and superior performance, which is attributed to flexible network structure of stable and interwoven whiskers. On contrary, there is a strongly-oxidized layer on the hot face and almost no whisker found anywhere in the brick with the short service life. It is vital to form the bonding phase of whiskers at high temperatures,generating overall properties of high hot strength, high erosion resistance and thermal shock resistance, which are essential in the working conditions of RH snorkels.
基金supported by the Austrian competence centre programme COMET ( Competence Center for Excellent Technologies) with funds from the Federal Ministry for Transport,Innovation and Technology,the Federal Ministry of Economy,the provinces of Upper Austria and Styria,the Styrian Business Promotion Agency,and the Tyrolian Future Foundation
文摘In this paper both experimental and analytical approaches to provide the inputs for creep modeling of refractories including a newly developed high temperature compressive creep machine and an inverse estimation procedure of creep law parameters are briefly introduced.Besides,a modified shear test is applied to determine the cohesion and friction angle of refractories under shear state. A RH snorkel equipped with magnesia- chromite bricks is chosen for a case study of thermomechanical simulation applying the classical creep model and Drucker-Prager creep model available in the finite element code ABAQUS,respectively. Afterwards,thermal stresses and joint opening of magnesia- chromite bricks during a process cycle are compared to distinguish the impact of these two creep models.
文摘Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternative of magchrome bricks with a comparable performance in the last decade.It is important to have found whisker formation in the matrix of Alcontaining magnesia bricks above 1100°C and in the correlation to their high performance of RH snorkels.In this paper,the bonding mechanisms of both refractories are investigated to differentiate from other refractories.In magchrome bricks,the bonding modes of fused magchrome grains are characterized by the reactions between magnesia and chrome ore at different burning temperatures.At 1500°C,liquid forms around chromite grains.It is sucked into surrounding magnesia and a gap forms around chromite grains at 1600°C.Plenty of Fe2O3,Cr2O3 and Al2O3 have diffused from chrome ore into magnesia at 1670°C.A complete dissolution of the chrome ore takes place at 1750°C,with chromite precipitating entirely.In unburnt,Al-containing magnesia bricks,a dense network of whiskers is formed during heating,which is a prevailing bonding feature,instead of traditional particle growing and merging.It is believed that the whiskers are formed by vapoursolid mechanism since there is no liquid droplet observed at the tip of whiskers.In most stringent working conditions of RH snorkels,the bonding mechanisms are emphasized for their application,instead of chromia component.
文摘With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH snorkel lining.High purity dead burned magnesia,fused magnesia and sintered spinel were used as raw materials and sulfite pulp waste as the binder,specimens of the refractories in the Mg0-Al_(2)O_(3) system were prepared for the purpose of investigating the influences in terms of the addition of three kinds of spinels,with Al_(2)O_(3) 50%,66% and 78%,by mass,respectively,and the size of MA50 spinel on properties of the specimens.Relatively superior comprehensive properties can be achieved when 16%of MA50 spinel with sizes under 1mm is adopted.
