Extending the possibilities of cryogenic assisted grinding

在磨削操作中，金属加工液（MWF）用于最大限度地减少与热相关的问题，如表面裂纹，燃烧和拉伸残余应力。MWF的过滤、回收和处置是额外的成本因素。所有这些因素导致加强研究，以尽量减少或消除制造过程中的MWF。为了满足这些要求，开发了最小量润滑（MQL）和应用低温流体作为MWF的方法。在大多数情况下，与传统MWF类似，在整个过程中连续应用低温流体。低温气体的惰性和从工作环境中立即蒸发的特性有利于过滤、回收和处理成本。缺点是低温输送系统的额外成本和安全要求。在这个节骨眼上，我们的合作者（巴西研究小组）已经开发出一种预冷零件干磨的方法。在这种方法中，待加工的零件将在低温介质中冷却，然后在没有任何MWF供应的情况下进行磨削操作。然而，预冷零件在干磨中的性能取决于零件的形状、尺寸和大小。因此，在这个合作项目中，将进行调查，以确定预冷零件在干式磨削模式下的优点和缺点，这些优点和缺点具有广泛的变量（不同的磨削工艺，各种工件尺寸），这些变量到目前为止还没有得到关注。将考虑两种类型的研磨过程。德国研究小组将专注于平面磨削，而巴西研究小组将专注于圆柱切入磨削。为了研究冷却方法，选择标准和传热模拟将根据零件几何形状，车轮和工件的热性能一起进行，以分类合适的工件尺寸的预冷方法和原位部分预冷方法。在原位部分预冷方法中，仅预冷部分的一部分。根据模拟结果，将工件分为大型（不适合预冷方法）和小型（适合任何冷却方法），并相应地应用可能的冷却方法。在本项目中，与过程相关的响应（例如，力、温度、功率、车轮磨损、重力比）和地面（例如，显微结构变化、显微硬度、表面粗糙度）进行检查和讨论。通过比较每种冷却方法的优点和局限性，可以全面了解磨削中低温应用的能力。最终，研究成果的不受限制的交流将加强这一两国研究小组的关系。

In grinding operations, metal working fluids (MWF) are used to minimize the heat-associated problems such as surface cracks, burning, and tensile residual stresses. Filtration, recycling, and disposal of MWFs are additional cost factors. All these factors have led to intensify the research to minimize or eliminate the MWF from the manufacturing process. In response to these requirements, methods such as minimum quantity lubrication (MQL) and application of cryogenic fluids as MWF were developed. In the majority of the cases, cryogenic fluids are applied, similar as conventional MWF, continuously throughout the process. The inert nature and immediate evaporation of cryogenic from working environment makes benefit in terms of filtering, recycling and disposal costs. Drawbacks are the additional cost of the cryogenic delivery system and safety requirements. At this juncture, our collaborator (Brazilian research group) has developed a method of dry grinding with precooled parts. In this method, the parts to be finished will be cooled in a cryogenic medium, and then subjected to grinding operation without any MWF supply. However, the performance of the precooled parts in dry grinding depends on the shape, size, and dimensions of the part. Hence, in this collaborative project, investigations will be carried out to determine the advantages and disadvantages of the precooled parts in the dry grinding mode with a wide range of variables (different grinding processes, various workpiece dimensions), which were not given an attention so far. Two types of grinding process will be considered. The German research group will focus on surface grinding, whereas the Brazilian research group will focus on cylindrical plunge grinding. To investigate the cooling method, selection criteria and heat transfer simulations will be done together based on the part geometry, wheel and workpiece thermal properties to classify the suitable workpiece dimensions for a precooling method and in-situ partial precooling method. In the in-situ partial precooling method, only a portion of the part is precooled. Based on simulation results, workpieces will be classified as large (not suitable for precooling method) and short (suitable for any cooling method) type, and accordingly, possible cooling methods will be applied. During this project, responses related to process (e.g., forces, temperature, power, wheel wear, G-ratio) and ground surface (e.g., microstructural changes, micro hardness, surface roughness) will be examined and discussed. By comparing the benefits and limitations of each cooling method, a comprehensive knowledge on the capabilities of cryogenic application in grinding can be achieved. Ultimately, unrestricted exchange of the research results will lead to strengthen the relationship of this binational research group.