含碳滑板抗氧化涂料的研制与表征
摘要
滑板是钢包水口的关键构件,具有调节钢水流量的功能。随着钢包连铸工艺的发展,对钢包水口要求越来越高,含碳滑板因其良好的抗热震性被广泛应用与钢包滑动水口上,但含碳滑板由于碳的存在高温下极易被氧化,防止含碳滑板中碳的氧化成为研究的重点。
本实验采用球磨工艺制备了一种以鳞片石墨和六方氮化硼(hBN)为主要原料的铝碳质滑板抗氧化涂料。采用MICROTRAC-X100激光粒度分析仪测试涂料的粒度；以NDJ-8S数字式粘度计测试涂料的粘度；以NXS-11A型旋转粘度计测定涂料的流变特性；在箱式电阻炉中分别对试样进行高温抗氧化处理实验,测得其失重率；利用摩擦系数仪测定试样的摩擦系数；SEM技术观察含碳滑板高温氧化处理后的脱碳层深度及其氧化情况；利用XRD技术分析了涂料不同温度处理后的物相组成；DTA-TG技术分析涂料在不同温度的物理和化学行为；同时对涂料的高温抗氧化机理进行研究。
结果表明：本实验制得的涂料体系属于塑性流体,具有一定的触变性,在高的剪切速率下,涂料粘度低而易于流动,便于施工,静止后,涂料粘度增高,不至于产生沉淀或导致流挂。料球水比为1：3：2,球磨时间为25 h时,0～30μm粒度范围的体积含量占66%,涂料粘度为0.8～1.2 Pa·S,分层率<2%,此时涂料粒子间相互作用力大,涂料悬浮性较好,涂料存放稳定,且易于涂刷。高温氧化处理后,可以发现涂有本涂料的含碳滑板单位面积氧化失重率出现先降低后增高的趋势,900℃时单位面积氧化失重率为0.95%,1000℃时为0.5%,1200℃时为0.8%,均低于与涂有厂家提供涂料的含碳滑板。涂有涂料的含碳滑板氧化处理后,随着温度升高,其脱碳层深度、摩擦系数都出现先增加后降低的趋势,这与单位面积氧化失重率的变化趋势相一致。涂料DTA-TG结果显示,800℃以下,涂料中的鳞片石墨发生氧化,生成CO2、CO气体,生成的气体能够稀释氧化性气氛或者与之反应,一定程度上降低了氧化性气氛的浓度,保护滑板基体表面的碳不被氧化；800℃时,鳞片石墨氧化殆尽；900℃以上,hBN氧化生成B2O3等呈玻璃相的硼化物,阻隔了氧化性气氛与基体的接触,抑制了滑板表面的氧化；1000℃以上,B2O3由于蒸汽压较低而挥发。
Skate plate is the key composition of the ladle nozzle,it can regulate molten steel flow. With the development of continuous casting ladle, ladle nozzle must have more properties. Carbon skateboard is widely used in steel ladle slide gate because of its good thermal shock resistance,-but it is easily oxidized at high temperatures. It is important to prevent the oxidation of carbon in the carbon slide.
A high-temperature anti-oxidation coating was prepared by a milling process. The coating was mainly composed of flake graphite and hexagonal BN (hBN). The MICROTRAC-X100 laser particle size analyzer was used to test the size of the coating.The NDJ-8S digital viscometer was used to test the viscosity and the NXS-11A Rotary Viscometer was used to test the rheology. The oxidation resistance was test in the box-type resistance furnace.The weight-loss ratio per area was measured after teat treament.The coefficient of friction was tested by Friction and wear testing machine. The practical decarburized depth after oxidation treatment was observed using SEM. The phase composition of the coating after oxidation treatment was analyzed by XRD. The combined DTA-TG technique was used to detect the thermo-dynamic behavior of the coating. At the same time, the high temperature oxidation mechanism of the coating was studied.
The results showed that:In this study, the system what we obtained is a plastic fluid. Also, it has some thixotropy. At high shear rate, the coating was with low viscosity and was easily for flowing and construction. After Static storage, the viscosity increased, and would not precipitate or cause pasting. The ratio of material,ball and water was 1:3:2, when ball milling time was 25 h, the grain size in the range of 0～30μm held the volume content of 66%, the viscosity of coating was 0.8～1.2 Pa·S, the tiered rate was less than 2%.At this time,there was a large interaction force between particles of the coating, the suspension performance and the storage stability of the dope was good, and the coating was easily to brush. After high-temperature oxidation, it could be found that the oxidation weight loss rate increased,and decreased later while the temperature increasing.The oxidation weight loss rate was 0.95% at 900℃,0.5% at 1000℃,0.8% at 1200℃, and all these were lower than the sample painted with coating of manufacturers. Depth of decarburization and coefficient of friction were increased,and the decreased with the oxidation temperature increasing. DTA-TG showed that, flake graphites oxidized below 800℃, generating with gas of CO2 and CO, the generated gas could dilute oxidizing atmosphere or reacted with it. It reduced the concentration of oxidizing atmosphere at some extend,and protected the carbon in the surface of skateboard from oxidization. The flake graphite oxidized depleted at 800℃. Above 900℃,hBN oxidized and generated with boride in glass phase,such as B2O3 and so on. It prevented the contaction of oxidative atmosphere and substrate, inhibiting the oxidation of skateboard surface.Above 1000℃, B2O3 evaporates as low vapor pressure.
本实验采用球磨工艺制备了一种以鳞片石墨和六方氮化硼(hBN)为主要原料的铝碳质滑板抗氧化涂料。采用MICROTRAC-X100激光粒度分析仪测试涂料的粒度；以NDJ-8S数字式粘度计测试涂料的粘度；以NXS-11A型旋转粘度计测定涂料的流变特性；在箱式电阻炉中分别对试样进行高温抗氧化处理实验,测得其失重率；利用摩擦系数仪测定试样的摩擦系数；SEM技术观察含碳滑板高温氧化处理后的脱碳层深度及其氧化情况；利用XRD技术分析了涂料不同温度处理后的物相组成；DTA-TG技术分析涂料在不同温度的物理和化学行为；同时对涂料的高温抗氧化机理进行研究。
结果表明：本实验制得的涂料体系属于塑性流体,具有一定的触变性,在高的剪切速率下,涂料粘度低而易于流动,便于施工,静止后,涂料粘度增高,不至于产生沉淀或导致流挂。料球水比为1：3：2,球磨时间为25 h时,0～30μm粒度范围的体积含量占66%,涂料粘度为0.8～1.2 Pa·S,分层率<2%,此时涂料粒子间相互作用力大,涂料悬浮性较好,涂料存放稳定,且易于涂刷。高温氧化处理后,可以发现涂有本涂料的含碳滑板单位面积氧化失重率出现先降低后增高的趋势,900℃时单位面积氧化失重率为0.95%,1000℃时为0.5%,1200℃时为0.8%,均低于与涂有厂家提供涂料的含碳滑板。涂有涂料的含碳滑板氧化处理后,随着温度升高,其脱碳层深度、摩擦系数都出现先增加后降低的趋势,这与单位面积氧化失重率的变化趋势相一致。涂料DTA-TG结果显示,800℃以下,涂料中的鳞片石墨发生氧化,生成CO2、CO气体,生成的气体能够稀释氧化性气氛或者与之反应,一定程度上降低了氧化性气氛的浓度,保护滑板基体表面的碳不被氧化；800℃时,鳞片石墨氧化殆尽；900℃以上,hBN氧化生成B2O3等呈玻璃相的硼化物,阻隔了氧化性气氛与基体的接触,抑制了滑板表面的氧化；1000℃以上,B2O3由于蒸汽压较低而挥发。
Skate plate is the key composition of the ladle nozzle,it can regulate molten steel flow. With the development of continuous casting ladle, ladle nozzle must have more properties. Carbon skateboard is widely used in steel ladle slide gate because of its good thermal shock resistance,-but it is easily oxidized at high temperatures. It is important to prevent the oxidation of carbon in the carbon slide.
A high-temperature anti-oxidation coating was prepared by a milling process. The coating was mainly composed of flake graphite and hexagonal BN (hBN). The MICROTRAC-X100 laser particle size analyzer was used to test the size of the coating.The NDJ-8S digital viscometer was used to test the viscosity and the NXS-11A Rotary Viscometer was used to test the rheology. The oxidation resistance was test in the box-type resistance furnace.The weight-loss ratio per area was measured after teat treament.The coefficient of friction was tested by Friction and wear testing machine. The practical decarburized depth after oxidation treatment was observed using SEM. The phase composition of the coating after oxidation treatment was analyzed by XRD. The combined DTA-TG technique was used to detect the thermo-dynamic behavior of the coating. At the same time, the high temperature oxidation mechanism of the coating was studied.
The results showed that:In this study, the system what we obtained is a plastic fluid. Also, it has some thixotropy. At high shear rate, the coating was with low viscosity and was easily for flowing and construction. After Static storage, the viscosity increased, and would not precipitate or cause pasting. The ratio of material,ball and water was 1:3:2, when ball milling time was 25 h, the grain size in the range of 0～30μm held the volume content of 66%, the viscosity of coating was 0.8～1.2 Pa·S, the tiered rate was less than 2%.At this time,there was a large interaction force between particles of the coating, the suspension performance and the storage stability of the dope was good, and the coating was easily to brush. After high-temperature oxidation, it could be found that the oxidation weight loss rate increased,and decreased later while the temperature increasing.The oxidation weight loss rate was 0.95% at 900℃,0.5% at 1000℃,0.8% at 1200℃, and all these were lower than the sample painted with coating of manufacturers. Depth of decarburization and coefficient of friction were increased,and the decreased with the oxidation temperature increasing. DTA-TG showed that, flake graphites oxidized below 800℃, generating with gas of CO2 and CO, the generated gas could dilute oxidizing atmosphere or reacted with it. It reduced the concentration of oxidizing atmosphere at some extend,and protected the carbon in the surface of skateboard from oxidization. The flake graphite oxidized depleted at 800℃. Above 900℃,hBN oxidized and generated with boride in glass phase,such as B2O3 and so on. It prevented the contaction of oxidative atmosphere and substrate, inhibiting the oxidation of skateboard surface.Above 1000℃, B2O3 evaporates as low vapor pressure.
引文
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[4]S. T. Johansen. Multiphase modeling of metallurgical[J]. Experimental Thermal and Fluid Science,2002, (26):739-745
[5]李有奇,柯昌明,李楠.铝碳质滑板材料抗氧化研究进展[J].材料导报,2005,(10)：77～79,83
[6]吴武华,薛文东,高长贺,等.连铸中间包工作衬的历史及其最新研究进展[J].材料导报,2006,20,(7)：418～421
[7]许旭清,朱军.含碳质耐火材料中碳的测定[J],江苏陶瓷,2003,36(4)：23～25
[8]马北越,孙勇,于景坤,等.Al2O3-C耐火材料抗氧化性研究进展[J].腐蚀科学与防护技术,2009,(06)：560～562
[9]李连洲.MgO-C耐火材料在不同温度下于空气中的氧化机理[J].国外耐火材料,2001,(02)：48～53
[10]武七德,童元丰.碳化硅材料的氧化及抗氧化研究[J].陶瓷科学与艺术,2002,(01)：7～13
[11]今井久,王锦惠.碳的化学性质[J].新型碳材料,1986,(04)：60～71
[12]B. M. W. Andrew L. PurvisU. A study of the diffusional response of refractory and other elements in superalloy systems during diffusion coating[J]. Surface and Coatings Technology, 2000,133:23～27
[13]李红霞,刘国齐,程贺朋.钢液对连铸用含碳耐火材料的侵蚀作用研究[J].耐火材料,2007,41(03)：161～167
[14]朱小线,沈钟铭.宝钢连铸中间包涂层应用技术进展[J].冶金信息导刊,2008,(04)：41～46
[15]G. Aneziris, R. Barab. Microstructure evaluation of MgO-C refractories with TiO2～and Al-additions[J]. European Ceramic Society.2007,27:73～78
[16]郭圣涛,谢瑞宝.碳石墨材料高温氧化防护的研究[J].碳素,1991,5～10
[17]张文杰,李楠.碳复合耐火材料[M].科学出版社,1990
[18]叶方宝,陈方,钟香崇.加入Si, Si/AI对高碳Al2O3-C材料抗热震性的影响[J].硅酸盐通报,2009,28(3)：421～425
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