Influence of Phosphorus Content and Preheating Conditions on Grain Size of Cu-DHP Copper Tubes

“Cu-DHP” copper tubes are used in sanitary, plumbing and heat exchanger applications. For drawability and forming processes, grain size is an important factor. Grain size is affected by the process conditions and chemical content. The aim of this study is to examine the effect of phosphorus content on Cu-DHP copper tube products. For this examination, four copper billets with different phosphorus content were used to produce 9.52x0.30 mm copper tubes. The copper billets which are 305 mm in diameter and 580 mm in length were preheated in furnaces and the hot direct extrusion method was used for mother tube production. Shortened preheating time resulted in finer grain size in mother tubes. Mother tubes were cold drawn to the final dimension in subsequent steps and annealed at recrystallization temperature with the same parameters. Grain sizes of annealed 9.52x0.30 mm copper tubes are in the range of 17 to 20 µm. For the final tube dimensions, high amount of cold drawing ratio diminished the effect of the prior grain size of the mother tubes. According to the result of inspections, it is concluded that in cold-drawn and annealed products, phosphorus content has a grain coarsening effect on the final product.