Continuous-casting protection slag for CAS treated ship plate structural steel

Abstract

The invention relates to continuous-casting protection slag for CAS treated ship plate structural steel. The protection slag is composed of, by weight, 30 percent to 39 percent of CaO, 24 percent to 33 percent of SiO2, six percent to 13 percent of Na2O, five percent to 9.5 percent of F, 0.9 percent to 1.9 percent of optimized elemental carbon, three percent to six percent of Al2O3, three percent to eight percent of MgO, 0.7 percent to 1.6 percent of Li2O, and 3.0 percent to 5.0 percent of Fe2O3. The viscosity of the slag is controlled between 0.07 Pa S and 0.08 Pa S. According to the physical properties of the continuous-casting protection slag, the melting point is 1020 DEG C to 1090 DEG C, the viscosity is 0.07 Pa S and 0.08 Pa S (1300 DEG C), CaO/SiO2 is 1.1 to 1.3, and H2O is smaller than or equal to 0.5 percent. According to the slag, the melting point of the slag can be reduced, the alkalinity can be improved, the unit consumption of the protection slag can be improved, the viscosity of the protection slag can be reduced, and therefore in the continuous casting process, the melting speed and the flowing-in speed are stably and dynamically balanced, and therefore lubrication of a primary blank shell of an inner plate blank of a crystallizer is ensured, and the aim of stable and smooth production of the CAS treated ship plate steel is achieved.

Description

technical field [0001] 本发明涉及一种用于炼钢连铸的冶金辅料,具体说有关一种用于炼钢连铸的连铸保护渣。 Background technique [0002] 连铸保护渣是钢水连续铸造过程中加入到结晶器内覆盖在钢水表面的一种人工合成的辅助材料。它是将含CaO、SiO 2 的原料、氟化物及含Na 2 O材料按合适的比例进行配制,在高温下熔化成预熔粉,然后配入一定的C质材料和各种添加剂,经混匀、干燥后制成。 [0003] 保护渣的主要作用是润滑、隔热保温、防止二次氧化、吸附钢水中的夹杂物等,其在结晶器内钢水液面上形成粉渣层、烧结层、富碳层、液渣层四层结构,总厚度一般为40-60mm。坯壳和结晶器之间的渣膜由固态渣膜和液态渣膜组成,固态渣膜又分为结晶体和玻璃体。结晶体对初生坯壳的传热影响较大,而玻璃体主要起润滑作用。随着结晶器的振动,保护渣熔融层流入坯壳和结晶器之间的缝隙,随着拉坯的不断进行,熔融层不断流入,同时新渣被不停地加入。 [0004] 密封吹氩合金成分调整(Composition Adjustment by Sealed Argon Bubbling,CAS)处理的中碳钢由于钢液内部气体以及夹杂物去除不充分,在连铸浇钢过程中,保护渣需要吸附钢液中的夹杂物,导致保护渣流动性变差,造成流入不充分,使结晶器内部润滑不足,从而发生漏钢等事故。这虽然可以通过真空循环脱气法进行处理,但是由于真空循环脱气法的生产成本高昂,不适合此工位处理。为了减少漏钢发生,一个主要方法,只能是从连铸保护渣入手解决。分析目前普遍使用的中碳钢保护渣,其粘度和熔点较高、碱度较低,并不适合CAS处理的钢种。例如发明专利申请公开第CN102218514A号所提供的一种中低碳钢的保护渣,其熔点在1060-1090℃,粘度在0.25-0.34Ps(1300℃),其熔点和粘度较高,而且由于其SiO 2 含量较高,容易发生纵裂等裂纹类缺陷。又如发明专利申请公开第CN101733377A号所提供的中高碳钢保护渣,其粘度为0.95Pa·S,同样过高,且CaO和SiO 2 的有效组分过低,不能实现吸附夹杂的作用,而且碱度过低,也解决不了CAS处理船板结构钢漏钢的问题。所以开发一种CAS处理的中碳船板结构钢用保护渣,显得尤为迫切。 Contents ...

AI Technical Summary

Problems solved by technology

For example, the mold powder for medium and low carbon steel provided by the invention patent application publication No. CN102218514A has a melting point of 1060-1090°C and a viscosity of 0.25-0.34Ps (1300°C). SiO 2 Higher content, prone to crack defects such as longitudinal cracks

Another example is the medium and high carbon steel mold powder