Presented by David Wilson
Recarburiser Product Manager, The James Durrans Group
Assisted by Nathan Tucker also of James Durrans Group
David’s presentation began with a company profile. James Durrans Ltd was established in 1863 producing blackings for the UK foundry industry. The group now has four manufacturing units in the UK plus plants in Germany, South Africa, India and China. It also has a joint venture with Carbon International in France. The product range has grown significantly and includes refractory coatings, lubricants and machined graphite but the evenings presentation is the company’s range of recarburisers.
Recarburisers are used in both the steel and iron sectors and each has different demands in respect to the analysis of the recarburiser it purchases. The steel sector is primarily driven by cost and the consistency of the product is very much of secondary importance. The iron sector by comparison asks for close quality control and consistency. Recarburisers produced from coal require the coal to be dried and then calcined, the coal being typically anthracite. This is a reducing source of recarburiser and the majority is now produced from petroleum coke (petcoke) which itself is derived from oil distillation. After the light, medium and heavy oils have been extracted during distillation the remaining product is then calcined under pressure to produce petcoke or green coke.
Solubility, ash content, sulphur and nitrogen levels and grain size of product are key factors in the choice of recarburiser for a given customer. Grain size in the range 0.5 – 9mm is ideal. Smaller then this and the product is lost in the thermal currents above a melt, larger and the solubility is adversely affected. High ash contents give rise to slag and sulphur and nitrogen can be detrimental to the casting process. Grey iron producers want low nitrogen but can accept sulphur levels of up to 1.5%. SG producers are looking to keep sulphur below 0.2%.
Crushed graphite is a good recarburiser but is expensive and becoming harder to source. However the availability of petcoke for producing recarburiser is also under threat. The growth of the aluminium sector, particularly in China, with their demand for anode quality pet coke is depleting the market as is the growth in electric cars where the product is used in battery production. New sources of raw material are being developed from pitch resulting from the production of synthetic oil. Coke produced from pitch has a lower environmental impact compared with the distillation of coal. Typically 2.5 MW are needed to produce a low Sulphur Graphitised Pet Coke (GPC) whereas the 0.5 MW are needed to produce a similar pitch coke.
The reduced availability of suitable raw material has also led to other alternative being used. Bespoke blends of different recarburisers can result in variable solubility rates giving inconsistent carbon results from what was expected. Even organic material such as rice husks and ground coconut shells have been used but these tend to create a lot of slag which can find its way into finished product. Some product is still available produced from scrap tyres but the process is hazardous and the resulting product variable.
Durrans group aim to stay at the forefront of recarburiser technology and are working to ensure good quality product continues to be available despite the pressures that the growth of aluminium production and electric vehicles are putting on supply. David suggested that pitch cokes and coal based products are very likely the future for recarburiser production.
David Hall gave a vote of thanks for an excellent lecture full of good technical content after which the members and guests enjoyed a very good buffet sponsored by the Durrans Group.
