No abstract

Drawing processes apply to obtain the bimetallic tubes from the different metals and alloys, combined in the solid state, which significantly affects the specificity of this process. The manufacturing of bimetallic tubes by drawing process depends on many factors which include: preparation of the surface of materials joined in the solid state, the geometric parameters of the working tool, technological parameters of the drawing process (drawing speed, type of lubricant, the use of back pull etc.). Generally, the cold drawing process of producing the bimetallic tubes refers to metals which have high ductility (copper, aluminum, etc.). The tube sinking (tube drawing without a mandrel) of bimetallic tubes together with joining them at the interface of the two metal in the solid-state is applied for tubes of the diameter range between 6 to 20 mm and based on of the reducing the diameter of the tube. However, a slight increase of wall thickness ca. 0.05 ÷ 0.10 mm can appear, which is not dangerous phenomenon in case of producing the bimetallic tubes by joining in the solid-state. The aim of the research was to investigate the technology of tubes drawing process from non-ferrous metal, drawing process of bimetallic tubes and the production of bimetallic tubes in layers composition: cooper Cu-ETP - brass CuZn37 and CuZn37 brass - copper Cu-ETP in the tube sinking process. The research program included: production of bimetallic tubes with a different composition (Cu- ETP-CuZn37 and CuZn37-Cu-ETP) and a different percentage of the cross-section components; analysis of changes of tube wall thickness and the layer composition of the bimetallic tube, based on measurements on the workshop microscope; analysis of the material flow in the process of the bimetallic tubes production based on the measurements results of a profilograph CP-200.

Processes for producing bimetallic tubes can be divided for: producing the bimetallic tubes in the cold process, with preheating or with the heat treatment after each pull. First method relates to the metal with high ductility (copper, copper alloys, aluminum, aluminum alloys, zinc, etc.), second to the metals or bi-metal components, in one of which has significantly different plastic properties from the second for example: low-carbon steel, high alloy steel, etc. One of the methods for the production of bimetallic tubes is hollow cold drawing process. In this process the wall thickness is changed, which means the wall becomes thicker, the wall becomes thinner or remains unchanged. The aim of the research was to determine the effect of the influence of the share of components of bimetallic cooper tube species M1E, and the copper tube - species M63 in the arrangement M1E - M63 and M63 - M1E in the tubes hollow drawing process for the distribution and size of deformation of the individual layers. The research program included:- production of the bimetallic tubes by hollow drawing with a different percentage of the cross-section components and with a variable arrangement of layers,- determination of the size and distribution of true strain of the individual layers on the cross-section of bimetallic tube,- determination of replacement/equivalent strain for the deformable wall of the bimetallic tube,- evaluation of the usability of the graph of changes in thickness of the tube wall in the hollow drawing process for the drawing process of the bimetallic tubes.

Limit stress diagram by Pelczyński was constructed in the coordinates σm - σH (σm - average stress for the process, σH - stress according to the Huber hypothesis) based on the hypothesis Huber - de Saint Venant and is consistent connection between the two hypotheses. This diagram allows for presentation the dangerous states of stresses for arbitrary stress state so plane and space (biaxial and triaxial). It also allows for the analysis of stress states occurring in various processes of plastic forming. To determine the state stresses occurring in the technological process starts from the components of the plastic deformation. In the case of a wire drawing process with a circular section in the inlet area of the die there is equality of deformation φ2 = φ3 and the equality of stress σ2 = σ3 (which is uniform biaxial compression), while in a outlet of the die there is a uniaxial tensile σ1, which cannot achieve a value equal to σp (yield strength), since in this case the wire could be deformed outside the die.The aim of this study was to construct the Pelczynski diagram in such a way to show on the example of brass wire M63, the course of the stresses in the drawing process.The research program included:- Realization of the drawing processes in order to obtain samples of varying degrees strengthening,- Determination on the basis of tensile strength the properties Rm, Rp0,2 and cohesive strength of R0 for varying degrees of strengthening,- Determine the influence of cold deformation for the course of curve of the yield strength,- Constructing a diagram of drawing process on a background of the diagram of yield strength in this process.

The article discusses the mathematical and practical methodology for evaluating the temperature on the surface of bimetallic wire after deformation in the drawing die. The components of bimetallic wire on the cross-section are the following materials: - a core, brass M63 (CuZn37) - shell M1E copper (Cu – ETP), - a core, aluminum Al (A199, 5) - shell M1E copper (Cu – ETP). An outer layer (shell) in such combinations is always a copper with two different thicknesses of 1.5 mm and 0.5 mm, which means that the proportion of copper on the cross section of the bimetal was respectively 64% and 32%. The bimetallic wires samples used for measurements were obtained by mechanical cladding. In the first step of the process, the cooper tubes M1E were put on the aluminium and brass wires M63, and then in a second step, each set combination was subjected to a simultaneous deformation with a total true strain φlc~ 1. Thus obtained the bimetal wires were the blank material for determining the surface temperature. In the drawing process there were used two different drawing speeds, and for each was applied the two individual size of deformation of 15% and 30%. The temperature on the surface of the layered wire depending on the single deformation and drawing speed was determined using a thermographic camera and it was also calculated according to mathematical formulas. The article discusses the preliminary results necessary to conduct further deliberations on the temperature decomposition on the longitudinal section of the bimetallic wire deformed in the drawing die.