“The Market Opportunities for Carbidic Austempered Ductile Iron (CADI)”

Wednesday, 7 February 2018

Dr Arron Rimmer
Technical and Sales Director
ADI Treatments Ltd.

Branch President Richard Heath, Prof MICME, welcomed members and guests to the February technical meeting and introduced Dr. Arron Rimmer and his paper The Market Opportunities for Carbidic Austempered Ductile Iron.

The presentation began with an introduction to ADI Treatments Ltd. which was formed in 1996 to provide ADI technology in Europe. Prior to then all the commercial development of the material had been done at Applied Process Inc in North America. The two companies still continue their association and work together on the development of austempering processes and systems. Since the forming of ADI Treatments Ltd. in 1996 it now employs 24 and in 2017 treated 6500 tonnes of Austempered irons and steels with Germany being the second largest of their markets after the UK. The facility consists of 2 furnaces with 49 tonne salt baths, 1 with a 100 tonne salt bath and a new much larger integrated furnace for the larger components. The two largest markets are large trucks, taking 40% of turnover, with agriculture second, taking 14%. An upcoming market is that of wind turbine manufacture.

The process of producing ADI begins with the austenisation cycle. The components are heated to 600°C and held for a while before raising them to around 900°C. Once fully austenised they are quenched in salt and held at a temperature between 230°C and 400°C. Finally there is a water wash to remove salt residues. Shape and section thickness of the component determines the process times.

A more recent development is Carbidic Austempered Ductile Irons (CADI). These have been developed for wear and durability thereby extending the market opportunities for producers. It is a ductile iron containing carbides that remain after austempering to produce an ausferrite matrix with carbides. An addition of molybdenum and chromium is the usual manufacturing route to creating stable carbides and this has the benefit of generating rounded carbides in the final structure. Development work is in hand to generate CADI without alloying as some foundries have concerns that there could be alloy contamination of other castings. In this case carbides may be created by chills or adding crushed carbides to the melt. As could be expected, as the amount of carbides increases so does wear resistance. This development has enabled CADI to replace Ni-Hard, high chrome white irons and manganese steels in some applications especially where toughness and wear resistance are beneficial.

The benefits of CADI are its inherent toughness and wear resistance but it has been also been found to have good corrosion resistance. It offers cost benefits over other traditional wear resistant metals in both its manufacture and some service situations. Whilst white irons may chip in operation CADI will wear significantly more evenly resulting in longer service life.

Arron concluded his presentation with details of markets and components where CADI is making an impact. These included the agriculture sector, mining, energy production, materials handling and many more. Anywhere that there is the crushing and transferring of materials, dredging, digging or cultivating soils, sands, minerals etc. is an opportunity to exploit the properties of carbidic austempered ductile iron. Examples of components include grinding balls, wear plates, pumps and impellors and conveyor parts. The markets are still to be fully explored and exploited.

During the Q&A session the following points were discussed:
1) 0.75% Mo and 1.5%Cr additions are typical though some CADI is produced with 3%Cr.
2) If fracking were to be developed in the UK then the drill bits could be CADI material.
3) China is the largest producer of CADI grinding balls but USA is the largest overall user and producer of ADI including CADI.
4) Machining of ADI is difficult but possible, machining of CADI is much more difficult but still possible.

A vote of thanks was given by Steve Smith, Prof MICME and then members and guests were able to enjoy the very good buffet sponsored by ADI Treatments Ltd.