Germany’s Premium Refractory, Exclusively in India. Germany’s Premium Refractory, Exclusively in India. Founded in 1901, Dörentrup has been at the forefront of pioneering refractory products for Germany’s foundry industry. DFP was the first to introduce neutral lining and liquid sintering for induction furnaces. As a leader in refractory technology for both core and coreless induction furnaces, DFP’s innovative solutions have dramatically reduced plant losses. With over 100+