Searching for an effective method of producing bimetallic blanks (which are most commonly obtained by joining two alloys with different properties), skew rolling experiments were conducted in which workpieces were passed between three rollers in a CNC (Computerized Numerical Control) rolling mill. This limits the applicability of bimetallic materials to the production of small parts. An additional drawback is the relatively small size of the bimetallic blanks obtained using these technologies. It should be noted, however, that in many cases, the process of joining two different materials is relatively expensive and complicated, and does not guarantee the formation of a permanent joint. Studies have also been carried out on plastic forming of two materials during which they are welded to yield a monolithic part characterized by unique physico-chemical properties. One example are axle shafts, in which the hub is fastened to the axle shaft in the process of frictional butt-welding. The automotive industry also uses bimetallic materials for the production of drive system components. Another area of application of bimetallic materials is the manufacture of various types of cutting tools in which the working part is made of tool materials characterized by very high strength properties, and the gripping part is made of much cheaper general-use construction materials. As a result, a low weight part with increased corrosion resistance is produced. Because magnesium alloys have very low corrosion resistance, the surface layer of such parts is mechanically covered with a layer of aluminum alloys, which are much more resistant to corrosion. Bimetallic aircraft parts are made of very light magnesium alloys clad with a layer of aluminum alloys. One example of the application of such materials is the production of parts used in aviation. Joining technologies can be used to produce a permanent joint between two metals or alloys (usually of a similar grade) which is characterized by high strength parameters. Bimetallic materials for the production of machine parts that carry larger loads are typically welded or fusion-welded. Depending on the intended use and required mechanical properties, bimetallic materials can be joined by bonding, adhesive bonding, press-fitting, or shrink-fitting. However, for bimetallic parts to operate properly, they have to be made of high quality materials that can be permanently joined over the entire contact surface. This is because components made of such materials have unique physical and chemical properties. Recently, bimetallic materials, i.e., materials produced by permanently fastening two or more metals or metal alloys, have been increasingly used in machine construction. The results reported in this paper are preliminary and constitute a prelude to a more detailed analysis of bimetallic rod rolling. In addition, the distribution of stress in the tool–workpiece contact zone may make welding of the materials difficult. The results of numerical modeling indicate that the material near the surface tends to flow, which may have a negative impact on the welding process. When the rods are heated without protective atmospheres, the surface layer of the core gets decarburized and the surfaces of the materials being joined together are oxidized, which hinders the welding process and adversely affects the physical and chemical properties of such products. However, proper fastening of the two materials depends on the geometrical parameters of the billets, and the quality of bimetallic rods depends on the heating method used. The results demonstrate that the proposed method can be successfully used in the production of bimetallic rods. During the tests, bimetallic rods were rolled from billets whose cores and outer sleeves (bushings) were made of different types of steel. The experiments were conducted using a numerically controlled three-roller skew rolling mill. The present article reports selected results of a preliminary study of the process of skew rolling of bimetallic rods.
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