Effect of Selective Oxidation and Interfacial Reactions on the Reactive Wetting of Advanced Steels by the Continuous Galvanizing Bath

在汽车结构中使用先进的高强度钢是一项能够减少车辆重量和排放的技术，包括大规模的车辆电气化，同时保持乘客安全。对于先进的钢材，这种重量减轻是使用较薄的部件横截面实现的，这就需要保护它们免受腐蚀损害，以保持其性能并满足消费者的长寿需求。连续镀锌工艺，在钢材上涂上一层薄薄的牺牲锌层，是实现这一目标的最具成本效益的工艺。然而，用于生产高级钢的高强度和其他所需性能的合金元素(如锰、硅和铬)在连续镀锌过程中也会选择性地氧化，通过一种称为反应润湿的过程产生锌不能附着的表面。幸运的是，生产商和其他研究人员已经发现，适当操纵选定的镀锌工艺参数和合金化学可以产生促进反应润湿的表面，从而获得高质量的镀锌层。然而，目前还没有系统的研究将合金化学、连续镀锌工艺变量和工艺气氛组成等因素与反应润湿过程联系起来。这项建议将解决与在连续镀锌过程中发展这一理解相关的两个重要主题：(I)建立锰氧化物铝热还原的动力学模型；(Ii)建立合金硅/锰比、退火温度和时间、工艺气氛成分和反应润湿之间的定量关系。对这两个工艺的全面了解将使生产商能够以系统的方式操纵他们的工艺变量和合金设计，使先进钢的当前和未来成分能够成功镀锌，从而通过增加车辆轻量化促进未来车辆排放的减少。

The use of advanced high strength steels in automotive structures is an enabling technology for vehicle weight and emissions reductions, including large-scale vehicle electrification, while maintaining passenger safety. In the case of advanced steels, this weight reduction is achieved using thinner component cross sections, which necessitates that they be protected from corrosion damage in order to maintain their properties and satisfy consumer longevity demands. The continuous galvanizing process, in which steels are coated with a thin sacrificial Zn coating, is the most cost-effective process for achieving this aim. However, the alloying elements (e.g. manganese, silicon and chromium) used to produce the high strengths and other desirable properties of advanced steels also selectively oxidize in the continuous galvanizing process, creating surfaces to which the zinc cannot adhere via a process known as reactive wetting. Fortunately, it has been found by producers and other researchers that proper manipulation of selected galvanizing process variables and alloy chemistry can produce surfaces for which reactive wetting is promoted, resulting in high quality galvanized coatings. However, at this point in time no systematic study has been undertaken to link the factors of alloy chemistry, continuous galvanizing process variables and the process atmosphere composition to the reactive wetting process. This proposal will address two important topics linked to developing this understanding within the context of the continuous galvanizing process: (i) developing kinetic models for the aluminothermic reduction of manganese oxides and (ii) develop quantitative relationships between alloy Si/Mn ratio, annealing temperature and time, process atmosphere composition and reactive wetting. A complete understanding of these two processes will enable producers to manipulate their process variables and alloy designs in a systematic fashion to enable present and future compositions of advanced steels to be successfully galvanized, thereby promoting future reductions in vehicle emissions through increased vehicle light-weighting.