Wet tensile strength testing in neutron radiography - cause-property relation studies in bentonite bonded molding sands

中子射线照相湿拉伸强度测试 - 膨润土粘结型砂的因果关系研究

• 批准号: 268662032
• 负责人: Professor Dr. Guntram Jordan
• 金额: --
• 依托单位: Arbeitsgebiet für anorganische und biogene Geomaterialien
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/268662032?language=en
• 关键词: Wet; tensile; strength; testing; neutron

Bentonite bonded molding sand is among the most common mold materials used in founding. One reason for the common acceptance is its reusability. However, the binding quality of used molding sand is reduced to some degree. Therefore, 5% of new mold material is added after each cast. The quality loss of the re-used molding sand is caused by alterations of the clay minerals in the mold material and results in a reduced wet tensile strength among other effects. One consequence of the quality loss is the increased susceptibility to water-related casting flaws such as scabbing. These casting flaws are caused by ruptures which originate from the interaction of increased compressive stress in the hot area facing towards the melt on the one hand and reduced wet tensile strength in the neighboring cooler area on the other hand (the so called condensation zone, in which the moisture from the hot area re-condenses).In spite of the high significance of the condensation zone on the physical properties of the mold material it is still unknown what exactly takes place in the condensation zone while moving through the mold. For instance in the context of rupture, momentary temperatures and water concentrations at the weakest position in the mold material are insufficiently known. Also the dependence of the position and moment of rupture on precedent temperature and water gradients is unknown. A primary aim of the research project, therefore, is to investigate these relations quantitatively. For this purpose, wet tensile strength testing will be conducted in-situ in a neutron radiograph. By these experiments, water concentrations and temperature at the position and moment of rupture as well as the according tensile strengths and the precedent temperature and water gradients can be measured quantitatively. Moreover, the dependence of all these factors on the most important technical mold material parameters such as compactibility and permeability can be investigated.On the basis of the new quantitative data it is possible to analyze which properties in re-used mold material are caused by which mechanisms and processes. Such a scientific quantitative understanding of the cause-property relations by far exceeds the mostly empirical knowledge existing so far. The insights, therefore, can essentially contribute to a development of strategies for an effective improvement of the re-usability of bentonite bonded molding sands.

膨润土粘结型砂是铸造中最常用的模具材料之一。被普遍接受的一个原因是它的可重用性。然而，旧型砂的粘结质量有一定程度的下降。因此，每次浇注后都要添加5%的新模具材料。再利用型砂的质量损失是由于型砂材料中粘土矿物的变化造成的，并导致湿拉伸强度降低等影响。质量损失的一个后果是增加了对与水有关的铸造缺陷的敏感性，如结痂。这些铸造缺陷是由破裂引起的，一方面是面对熔体的热区增加的压应力，另一方面是邻近的冷却器区(所谓的冷凝区，来自热区的水分在其中重新凝结)中湿拉伸强度的降低。尽管冷凝区对模具材料的物理性能具有很高的重要性，但当冷凝区通过模具时，冷凝区到底发生了什么仍然是未知的。例如，在破裂的情况下，模具材料中最薄弱位置的瞬时温度和水浓度是不充分的。此外，破裂的位置和时刻与先前的温度和水梯度的关系也是未知的。因此，该研究项目的一个主要目的是定量地研究这些关系。为此，将在中子照相机中现场进行湿抗拉强度测试。通过这些实验，可以定量地测量断裂位置和断裂时刻的水分浓度和温度，以及相应的抗拉强度和先前的温度和水梯度。此外，还可以研究这些因素与最重要的模具材料参数(如紧实度和透气性)的相关性。在新的定量数据的基础上，可以分析重复使用的模具材料的哪些性能是由哪些机制和工艺造成的。到目前为止，这种对因果关系的科学定量理解远远超过了迄今存在的主要经验知识。因此，这些见解基本上有助于制定战略，有效提高膨润土粘结造型砂的可重复使用性。

项目成果

Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

热驱动水传输对膨润土结型砂抗拉强度影响的中子射线研究

• DOI: 10.1007/s11242-017-0968-z
• 发表时间: 2018
• 期刊: Transport in Porous Media
• 影响因子: 2.7
• 作者: Schiebel K;Jordan G;Kaestner A;Schillinger B;Boehnke S;Schmahl W.W.
• 通讯作者: Schmahl W.W.

Effects of heat and cyclic reuse on the properties of bentonite-bonded sand

热和循环再利用对膨润土砂性能的影响

• DOI: 10.1127/ejm/2018/0030-2784
• 发表时间: 2018
• 期刊: European Journal of Mineralogy
• 影响因子: 2.1
• 作者: Schiebel K;Jordan G;Kaestner A;Schillinger B;Georgii R;Hess K.-U;Böhnke S;Schmahl W.W.
• 通讯作者: Schmahl W.W.