Investigation On Performance Of Resin Bonded Al-Al₂O₃-MgO-ZrO₂ Composites At High Temperatures In Nitrogen

Al4O4C,(Al2OC)1-x(AlN)x,Zr2Al3C4 and MgAlON have excellent physical and chemical properties,which makes the non-oxides and oxides refractory as a mainstream direction applied in ultra-low carbon steel or clean steel.Based on the design concept of Al@AlN+C core-shell structure and uniformly distributed and amorphous carbon generated by phenolic resin at high temperatures,Al4O4C,(Al2OC)1-x(AlN)x,Zr2Al3C4 or MgAlON bonded Al2O3 refractories were successfully prepared.Effect of temperature and MgO content on phase composition,organization structure and performance of phenolic resin bonded Al-Al2O3-ZrO2 system refractories was investigated.The results are shown as follow:To realize preparation of novel ultra-low carbon refractories,effect of putting in coke,industrial nitrogen and high purified nitrogen on relationship among AlxOy partial pressure,temperatures and oxygen partial pressure was discussed and analyzed.Its resuts show that partial pressure of both A12O(g)and Al(g)is higher than that of AlO(g),Al2O2(g)and AlO2(g),in which partial pressure of Al(g)is higher than that of Al2O(g)under high purified nitrogen.Phenolic resin with high carbon content was chosen to replace graphite and carbon black as carbon raw materials of novel ultra-low carbon refractories.Al@AlN and Al@AlN+C core-shell structure were designed to enhance reaction temperature among Al,C and N2.Novel ultra-low carbon Al4O4C-(Al2OC)1-x(AlN)x-Al2O3 refractories were successfully prepared based on Al@AlN+C core-shell structure at high temperatures in nitrogen.The prepared novel ultra-low carbon refractory has good properties that cold crushing strength is above 230 MPa,hydration resistance time is more than 180 d and molten iron cannot penetrate into and corrode with the refractory.The formation mechanism of(Al2OC)1-x(AlN)x can be described as below:under nitrogen at high temperatures,Al(l/g)overflows and escapes from the broken Al@AlN+C core-shell structure and reacts with C and N2 to form Al4C3 and AIN;then,Al4C3 reacts with Al2O3 to form Al4O4C;further,Al4O4C reacts with Al4C3 to form Al2OC;finally,(Al2OC)1-x(AlN)x forms through solid solution reaction of AIN into A12OC.Novel ultra-low carbon Al4O4C-(Al2OC)1-x(AlN)-Zr2Al3C4-Al2O3 refractories were successfully prepared based on Al@AlN+C core-shell structure at temperatures in nitrogen,and formation mechanism of Zr2Al3C4 was investigated.The prepared novel ultra-low carbon refractory has good properties that cold crushing strength is above 170 MPa,hydration resistance time is more than 210 d and molten iron cannot penetrate into and corrode with the refractory.The formation mechanism of Zr2Al3C4 can be described as below:under nitrogen at high temperatures,Al(l/g)overflows and escapes from the broken Al@AlN+C core-shell structure and reacts with C and ZrO2 to form A14C3 and ZrA13;and then Al4C3 reacts with ZrAl3 to form ZrZAl3C4.Phase composition,organization structure of magnesium aluminum sol bonded Al-Al2O3-MgO refractory was investigated at high tempretures in nitrogen,and formation mechanism of MgAlON spinel was explored.MgAlON spinel with two morphologies forms due to gas phase mass transfer and liquid phase mass transfer of aluminium.AIN and AIN polytype adheres to flake MgAlON spinel.Formation mechanism of MgAlON spinel can be described as below:Al(l/g)is nitride as AlN:Al2O3 reacts with MgO to form Al2O3-rich spinel;and then AIN reacts with Al2O3-rich spinel to form MgAlON spinel through solid solution reaction.Novel ultra-low carbon MgAlON-Zr2Al3C4-(Al2OC)1-x(AlN)x-Al2O3 refractories were successfully prepared based on Al@AlN+C core-shell structure at high temperatures in nitrogen.The prepared novel ultra-low carbon refractory has good physical properties and good steel ladle slag resistance.Reaction slag layer composed of spinel,zirconium oxide solid solution and calcium scapolite forms on the surface of the novel refractory after steel ladle slag experiment and spinel solid solution layer forms between the novel refractory and steel ladle slag.The effect of MgO addition content on phase composition,organization structure and physical properties of phenolic resin bonded Al-Al2O3-ZrO2 refractory was investigated at high temperatures in nitrogen by building Al@AlN+C core-shell structure.MgO addition has changed phase composition,organization structure and physical properties of phenolic resin bonded Al-Al2O3-ZrO2 refractories.Cold crushing strength decreases to 184 MPa,apparent porosity increases to 11.38%and hydration resistance time is greatly more than that of traditional carbon refractories.Without MgO,combination phase is Al4O4C and(Al2OC)1-x(AlN)x,with gas-gas reaction production being(Al2OC)1-x(AlN)x.With addition of MgO,combination phase is Al4O4C,(Al2OC)1-x(AlN)x or MgAlON spinel and gas-gas reaction production is Mg-(Al2OC)1-x(AlN)x or MgAlON spinel;in addition,Al4O4C disappears and flake MgAlON appears when MgO addition content reaches to 9wt%or above.