Chapter 7: Technology of molding materials

Franz Hofmann: Technologie der Giessereiformstoffe. (Schaffhausen : Georg Fischer AG, 2. Auflage, 1966).

published February 2016

The favorite book of Linda Streckfuss

Linda Streckfuss spent a week in 2015 as Scholar in Residence at the Iron Library, where she researched for her bachelor's thesis in industrial engineering. Her thesis deals with the implementation of machine learning methods in the iron foundry of GF Automotive in Singen. What fascinates Linda about her favorite book is the complexity of manufacturing good greensand suitable for casting.

The reader

Linda Streckfuss

... trained as an industrial manager and then studied industrial engineering, after completing commercial vocational school. She has worked for Georg Fischer Ltd in Singen since October 2014, first as a student intern and from June to September 2015 she wrote her bachelor's thesis – both times in Materials Engineering. The thesis was also the reason why she was a scholar-in-residence at the Iron Library, where she was able to conduct in-depth literature searches. She was taken on as a permanent employee at the Georg Fischer plant in Singen in October 2015. She first worked in a project team for Quality Management & Logistics and in December 2015 moved back to Materials Engineering as an assistant.

I would love to play a role in this book:
Peter Ustinov: Der alte Mann und Mr. Smith

This book needs a sequel:
Bernard Cornwell: Der Heidenfürst (2014)

The book on my nightstand:
Bernard Cornwell: Das Zeichen des Sieges (2009)

The book

Franz Hofmann: Technologie der Giessereiformstoffe. (Schaffhausen : Georg Fischer AG, 2. Auflage, 1966).

I'm fascinated by the complexity of producing good green sand suitable for casting. For one thing, I'm interested in the properties of the raw materials and how they are changed during preparation and manufacturing; for another I'm intrigued by the impact on the quality of the castings, i.e. the likelihood of defects.

The "Technology of Molding Materials" gives the reader a solid overview of the complex world of green sands. Even though this material consists in the main of only four components – quartz or silica sand, bentonite, the coal dust and water – it's no simple matter to get the green sand just right. A number of factors are crucial in the process of preparation and manufacturing.

Sand circulation system in a foundry

The material changes in the course of mulling, molding, casting, cooling, shaking out and recycling. As a result of the entire process cycle and the thermal, mechanical and chemical stresses to which the green sand is subjected, the four basic components give rise to additional elements such as the coating of sintered bentonite on the individual quartz sand grains as well as the formation of clay and inert materials.

The properties of the sand components also impact on the behavior of the green sand. Take, for instance, quartz sand, which expands considerably at temperatures of between 300 and 575°C, thereby changing its density. This effect has to be compensated for by the other components and should be taken into account when producing the green sand.

Expansion behaviour of sands of different mineralogical composition, bound with 5% bentonite.

This little book deals in detail with the individual components of green sands and with the molding material as a whole as well as the changes it undergoes in the entire process. The book closes with a chapter on how sand expansion defects arise and how to deal with them.

I am especially fascinated by the mechanisms and modes of action of the green sand components and their interdependencies. The system's complexity is a challenge to conduct further investigations in order to constantly improve monitoring of the process and perfect our knowledge of how to control green sand production.