We would like to have an electric car, solar cells on our roof or the latest model of cell phone, but do we really want to see the actual costs of production? The new wave of green economics highlights our ambition to create a more sustainable society. One step in this direction is a new national strategy, developed by the Swedish government, for a better circular economy and more sustainable production and product design.
Cast iron – an important part of the Swedish economy
Christina Windmark and Rebecka Lindvall, both researchers at SPI (the Sustainable Production Initiative) coordinated at the Faculty of Engineering (LTH) by Jan-Eric Ståhl, are trying to find out how grey cast iron can be managed more efficiently so that both its service life and value are maintained or even increased over time.
Grey cast iron is a material you have all around you in everyday life, in a frying pan you pick up, or in the decorative railings on your balcony, in a manhole cover in the street or in the flywheel of a truck. It is a material that originated in China but gained ground in Sweden with industrialisation in the 1800s and has been mass produced ever since. Grey cast iron consists of recycled cast iron, pig iron, recycled steel and alloying elements that make the material heavy, vibration-absorbing, heat-conducting and above all cheap to produce.
Cast iron is an important part of the Swedish economy and we produce 160 000 tonnes per year, mainly from recycled material. But the proportion of alloying elements continuously increases and contaminates, or pollutes, the cast iron. One consequence of this is that the material’s properties are affected, and tools used for cutting and lathing need to be replaced more often. This leads to longer production times and makes the process more expensive.
“We must get much better at recycling the material we have, or we must get better at having more secure, diversified ways of gathering the basic material”, says Christina Windmark. Her research colleague Rebecka Lindvall adds:
“Yes, we need to separate and recycle to a greater extent. This also concerns the critical materials, cobalt and tungsten, that are present in the cutting tools. My hope is to create new materials for tools, that are less dependent on these two elements and use smart materials solutions, thereby extending the service life of the tools. China possesses about 85 % of known reserves of tungsten, so what do we do if access to it is reduced? It would bring the manufacturing industry to a halt.”
Valuable materials disappear
Through their research, Christina Windmark and Rebecka Lindvall observe a clear problem in that the industry does not keep track of elements such as copper and chrome that are melted together, and how that affects the material properties of grey cast iron. The greatest risk is producing a blended material that will require a lot of resources to separate again.
“Currently, grey cast iron contains valuable elements as we mix materials in recycling that we ought to be using in a better way. As it is now, we deprive the valuable materials of their value while worsening the quality of the grey iron. There has to be a better way”, says Christina Windmark.
Positive attitude to circular economy
Consumers like to have craft products, preferably manufactured on a small scale. But if larger companies slim down their processes to become more energy-saving, it is a much more efficient use of resources. However, there is a long way to go.
“The attitude of industry towards working in more circular way is generally positive, but when producers realise how much is required, not many of them are prepared to go the whole way. It is not only about recycling materials, but also about changing company structures. How does the design department work, what interaction is there between different divisions and what expertise do purchasing officers need?” says Christina Windmark.
She also sees clearly how consumers need to accept that the industry must design for manufacture and recycling and not only for performance, and they must be willing to pay for it.
Allow cast iron to age
Rebecka Lindvall has closely studied how cast iron processing could be improved. Historically, the industry has known that cast iron is to be allowed to stand and age for a week to enable the material to be processed more easily when it comes to lathing and grinding.
“In lab tests, we observed an increased accumulation of trace elements, that should not be present in grey cast iron, which gives us an indication that the grey iron needs to be left to age for longer to be really good for processing. The material is more difficult to work with and tools wear out faster”, explains Rebecka Lindvall, continuing:
“In truck production, we have been able to show how best to lathe recycled material, which made the industry happy as it improved the economics of production. The results we arrive at are very positive if they can be implemented.”
As consumers, if we are going to buy a new car or a cast iron pan, how can we push for a sustainable circular economy?
“We can do that by demanding more information about the material we are buying. Where is it produced and what does it contain?” says Christina Windmark.
But she also thinks it should be easier for us to recycle correctly.
“When I go to my recycling centre, I find it strange that there is only one container for metal. There could be one for copper, one for aluminium and one for iron alloys. We need to keep track of what we are throwing out.”
The focus is now on more research into recycling grey cast iron and the obstacles in the way of the process.
“We want to work closely with the manufacturing industry and recycling companies to see how we are to address these issues over the long term and what we could solve more concretely. Materials are incredibly important in our society; how can we make the most of them, develop and extract them in the best possible way? We hope that companies will take more responsibility for the material and not only for their own processes”, says Rebecka Lindvall.
She also raises a warning:
“The supply of metals is finite, once we have mixed them up too much it is difficult to dilute them down to the right composition. Particularly if the element in question is in short supply.”