某带钢连续热浸镀机组卧式连续退火炉水冷炉辊的开裂原因

Cracking Cause of Water-Cooling Furnace Roller in Horizontal Continuous Annealing Furnace of a Strip Steel Hot Continuous Galvanizing Line

采用宏观和微观形貌观察、化学成分分析、显微组织观察、硬度测试等方法,对某带钢连续热浸镀机组卧式连续退火炉水冷炉辊的开裂原因进行了分析。结果表明:水冷炉辊辊套成分中不含铌元素,镍元素含量偏低,导致组织中形成网状富铬碳化物析出相;辊套内腔结垢、水冷不畅使水冷炉辊产生局部过热,导致工作侧辊套基体中粒状合金碳化物的析出和网状富铬碳化物的长大,使工作侧辊套的脆性增加;随着结垢的沉积,水冷炉辊出现轴承转动不畅,甚至堵转现象;在热应力、扭力作用下,裂纹在网状富铬碳化物析出相中形成并沿网状碳化物逐渐向基体内扩展,最终导致水冷炉辊的开裂。

The cracking cause of water-cooling furnace roller in horizontal continuous annealing furnace of a strip steel hot continuous galvanizing line was studied by macroscopic and microscopic morphology observation,chemical composition analysis,microstructure observation and hardness test.The results show that the composition of the water-cooling furnace roller sleeve contained no niobium element and a low content of nickel element,resulting in the formation of network rich chromiun carbide precipitates.The scaling of roller sleeve chamber and the poor water-cooling effect caused the local overheating of water-cooling furnace roller;then the granular alloy carbides precipitated,and network rich chromiun carbide of roller sleeve at working side coarsened resulting in the increase of brittleness of roller sleeve at working side.With the deposition of scale,the poor bearing rotation or even rotating-jam in water-cooling furnace happened.Under the thermal stress and torsion force,the crack originated from the network rich chromiun carbide,and gradually extended into the matrix along the network carbide,which finally caused the cracking of the water-cooling furnace roller.