超高风温热风炉炉壳开裂原因分析及控制

CAUSE ANALYSIS AND CONTROL OF CRACKING OF SUPER HIGH TEMPERATURE HOT BLAST STOVE SHELL

热风炉炉壳安全是炼铁安全的基石,但随着热风炉风温的不断提高,超高温高压热风炉炉壳安全问题屡有发生。通过对热风炉炉壳开裂原因进行分析,认为由预燃室圆柱形几何体和燃烧室圆锥形几何体及燃烧室圆柱形几何体组合成的复杂炉壳结构,不仅容易在焊接过程形成应力集中,在使用过程中尺寸不连贯带也极易引起应力集中;常用炉壳材质Q345C中硫、磷、氢含量较高,易降低焊缝强度,促进晶粒粗化,引起焊缝开裂;焊缝夹渣清理不彻底,应力消除不彻底,焊接时坡口设置不合理等都会导致焊缝强度不达标;风温风压的提高使得炉壳所受应力增加,炉壳厚度由40 mm增加至48~56 mm,加工安装拘束应力加大,钢板的热脆、气孔、焊接瑕疵加剧,进一步增加了炉壳焊缝开裂的风险;超高温产生大量NO_(x)中的NO_(2)同低温炉壳与炉内高温温差形成的冷凝水珠反应生成更多的HNO_(3),腐蚀作用显著增强。通过选用豫兴悬链线拱顶结构、采用Q345R压力容器钢材、提升焊接施工工艺和采用低氮燃烧技术,可以较好地解决超高温高压热风炉炉壳开裂的问题。

The shell safety of hot-blast stove is the cornerstone of iron-making safety,but with the continuous increase in the temperature of hot-blast stove,ultra-high temperature and high pressure hot-blast stove shell safety problems often occur.Based on the analysis of the cracking reason of the shell of the hot blast stove,it is considered that the complex shell structure is composed of the cylindrical geometry of the precombustion chamber,the conical geometry of the combustion chamber and the cylindrical geometry of the combustion chamber,it is not only easy to form stress concentration in welding process,but also easy to cause stress concentration due to the discontinuous size band in using process,the commonly used furnace shell material is Q345C,which has high content of sulfur,phosphorus and hydrogen,and is easy to reduce the weld strength,the strength of weld is not up to the standard because of incomplete cleaning of slag,incomplete elimination of weld stress and unreasonable groove setting during welding With the increase of air temperature and pressure,the stress of furnace shell increases,the thickness of furnace shell increases from 40 mm to 48~56 mm,the stress of machining and installation increases,the hot brittleness,gas hole and welding defect of steel plate aggravates,furthermore,the cracking risk of the shell weld is increased,and the corrosion effect is significantly enhanced by the reaction of NO_(2)in the ultra-high temperature NO_(x)with the condensation water formed by the temperature difference between the low-temperature shell and the high-temperature inside the furnace.The cracking problem of the shell of super-high temperature and high pressure hot blast stove can be solved by choosing the structure of Yuxing catenary arch,adopting Q345R pressure vessel steel,lifting welding construction technology and adopting low nitrogen combustion technology.