Surface condition Effects on Advanced High Strength Steels Processing for the automotive industry

热镀锌是一种典型的用于生产不同工业产品(如汽车工业)耐大气腐蚀的镀锌板产品的技术。这一过程可以从轧制到最终的涂层产品连续运行，从而获得高生产率，这是满足生产需求所必需的。连续镀锌过程中遇到的一个困难与温度控制有关。在可控气氛炉中高速移动的钢板使热电偶的使用变得困难。温度在相当程度上是由发射率读数间接控制的，使用高温计可以提供更大的灵活性。然而，它们对材料的发射率很敏感，而发射率在很大程度上受表面性质的影响。由于送入镀锌生产线的带材在粗糙度和厚度分布上可能会有变化，因此发射率变化是不可避免的。研究表明，厚度变化2-3%可导致16-22°C的温度变化。这一偏差在先进高强度钢的亚温退火过程中具有重要意义。拟议项目的目标是了解和验证各种表面特征对镀锌产品质量的影响。该项目将首先量化表面特性对温度读数的影响，从而对过程控制产生影响。其次，将利用先进的表征技术研究温度变化对先进高强度钢的机械性能和锌粘着的影响。这项工作的结果将为加拿大钢铁公司提供必要的信息，这些公司需要决定是否值得投资于昂贵的温度监测技术，如多波长高温计。它还将有助于通过更好地了解工艺参数和质量之间的关系来提高产品质量。此外，这个合作项目将创造一个完美的环境，在三年内培养三名研究生。项目目标将结合两所加拿大大学的知识和国际锌协会(IZA)的专门知识来实现。

Hot dip galvanization is a technology typically used to produce Zinc-coated sheet products for atmospheric corrosion protection of different industrial products (e.g. automotive industry). This process can be run continuously from Rolling to the final coated product leading to high production rate, which is necessary to meet production demand. One difficulty encountered during continuous galvanization is related to temperature control. Steel sheets moving at high speed in a controlled atmosphere furnace make the use of thermocouples difficult. Temperature is rather controlled indirectly by emittance readings using pyrometers that give more flexibility. However, they are sensitive to the material emissivity which is largely influenced by surface properties. Since strip delivered to the galvanizing line can have variations in roughness and thickness profiles, emissivity variation is inevitable. It has been shown that 2-3% variation in thickness can results in a 16-22°C temperature variation. This deviation is of significant consequence during intercritical annealing of advanced high strength steels. The objective of the proposed project is to understand and validate the effects of various surface characteristics on the quality of galvanized products. The project will first quantify the influence of surface characteristics on temperature readings and consequently on the process control. Second, the effect of temperature variation on mechanical properties of Advanced high-strength steels and zinc adherence will be studied using advanced characterization techniques. The results of this work will provide the necessary information to Canadian steel companies that need to decide if it is worth investing in costly temperature monitoring technologies such as multiple wave length pyrometers. It will also contribute to improve product quality through a better understanding of the relationships between process parameters and quality. Moreover, this collaborative project will create the perfect environment to train three graduate students over three years. The project objective will be achieved putting together the knowledge of two Canadian universities and the know-how of the International Zinc Association (IZA).