technique. New perspectives for steel by low-pressure pouring By Markus HAGEDORN - Dortmund Gravity pouring is still the dominant process for the production of cast steel materials. The principle is simple and has remained basically unchanged for several centuries. However:To comply with filigree and complex component geometries as well as increasing quality demands, the process- relatedlimitations lead to significant challenges for foundry staff and foundry engineers. Consequently, achieving the target geometry is only possible by using large quantities of liquid material with, in some cases, simul- taneously high rejection rates. Consequent alternative is low-pressure pouring, which requires much smaller sprue cups and feeder system than gravity pouring. Low-pressure pouring of aluminum com- OCN-25 furnace system from ABP Induction. ponents is state-of-the-art, with a recycling material content of less than 20 per cent advantage: It is easy to handle in common Low-pressure pouring opens up the possibility of the weight of the component, compared and globally available final assembly of pouring thin-walled parts. «In automotive processes and suitable for fast repairs. It is engineering, this means that structural with 100 per cent for gravity pouring [1]. therefore worthwhile to take a look at steel components as well as nodal elements in The capacities saved in the area of melting processing in low-pressure pouring processes. the chassis area and also axle components result in valuable savings and additional sales are becoming the direct focus of attention,» potential for the foundries. >>> GOOD REASONS FOR explains Dipl.-Ing. F.-J. Wöstmann [4], Head LOW-PRESSURE POURING of the Foundry Technology and Lightweight >>> CAST STEEL AS A MATERIAL Construction Department at the Fraunhofer IN LIGHTWEIGHT MOLD One major advantage of low-pressure pouring, Institute for Manufacturing Technology and as already mentioned in the introduction, is Applied Materials Research (IFAM). In his CONSTRUCTION the smaller sprue / feeder system (Fig. 1 a/b) opinion, steel demonstrates its unique com- and thus the smaller amount of circulation bination of high strength, ductility and rigidity Given the intensified focus on lightweight material. However, less circulation material in thin-walled production. construction in the automotive sector, it is not only means that less feedstock is also interesting to look at thin-walled cast required, and production costs are reduced, steelas a material: Although composite but also that the costs of the downstream He believes this applies not only to the materials such as CFRP and lightweight process steps (separating, fettling, deburring, passenger car sector but to the commercial materials such as aluminum or magnesium ...) are significantly reduced [3] (Table 1). Duevehicle sector as well. The additional advan- have outstanding lightweight construction to the poe tage here is that the more rigid structures potential, both materials also have numerous the share of low-pressure pouring in aluminum allow higher payloads and are therefore more drawbacks in comparison with steel. For one processing is rising steadily. Gravity pouring efficient and resource-saving in operation.. thing, the primary material is significantly in the aluminum sector is used today for well more expensive and the joining technology below 50 percent of components. to adjacent components is more complex. In the case of construction material mixes, this requires additional costs for corrosion protection and makes repair concepts more expensive [2]. Materials such as aluminum are also not suitable for all cast parts (e.g. tur- bocharger housings). By low pressure pour- ing, steel components can be cast a way that is load-bearing and has thinner walls. Thus, the material can bring about a significant Figure 1a/b .Stylized illustration of the savings of recycling material for thin-walled components N°19 • SEPTEMBRE 2020 • 19