STRENGTHENING OF EXPANDERS FOR TUBE PROFILE PRESSES FOR THE PRODUCTION OF CORROSION-RESISTANT TUBES BY LIQUID CARBONITRIDING

In the creation of competitive products at the stage of technological development, one of the most important tasks of applied science is the development of new materials for advanced products and technologies for their strengthening. One of the types of hot metal deformation is hot pressing. It is widely used for the manufacture of products from many steels and alloys that are difficult to deform. With the development of production in various industries, a large number of varieties of the pressing process have emerged, and the number of alloys being pressed has sharply increased. Another most important advantage of pressed products is that they can be made in such a complex configuration that cannot be obtained by other methods of pressure processing or even cutting. The most widespread application of pressing is for the production of tubes from low-plasticity steels and alloys. The quality of tubes obtained by pressing is largely determined by the durability of the tool [1]. Blanks made of high-alloy steels are subjected to through drilling before pressing and, in some cases, expansion. The expansion process is used in the production of tubes from high-alloy steels because piercing them is difficult and leads to increased wall thickness variation. The expansion of the blank is carried out by an expander, with a piercing needle coaxially fixed at the front end of the expander, the length of which is 1.2–3.0 times the length of the drilled blank. Steels for hot pressing tools have prolonged contact with hot metal, and the working tool operates under conditions of high temperatures, intense sliding speeds, and significant specific pressure, which necessitates the use of high-alloy heat-resistant tool steels with increased toughness and strength as the material [2]. The article proposes and justifies the use of liquid carbonitriding after quenching and tempering of tool die steel 4X4VMFS for the manufacture of expanders for tube profile presses with the aim of increasing the strength, wear resistance, and operational durability of tube pressing tools for the production of tubes from corrosion-resistant high-alloy steels.