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The application of PVD coating for tools used at tube straightening

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Straightening is a technology that is used to remove undesirable distortions. Curvature of the product axis arises as a result of the production technology [1]. Straightening leads to the elimination or reduction of curvature in the metal products using external forces. In practice, the tube runs between the straightening rolls that are rotated to the direction of straightening at an angle (Fig. 1). The roll’s profile is not the tube’s radius. The profile is hyperbolic; the contact roll touches the tube at just three points (Fig. 2). The tube rotates as it passes through the straightening machine. While passing through the machine, the tube is subjected to two specific straightening forces: 1. Pressure straightening. Each pair of rolls can be adjusted so that the gap between them is slightly smaller than the outside diameter of the tube. As the tube passes through this restricted gap, it is subjected to pressure which, if sufficient, will cause the tube walls to be strained past their elastic limit, thereby causing some straightening of the tube. If this ability to squeeze the tube is used correctly, the tube will be "rounded up," removing some or all of its ovality (Fig. 3) [2]; 2. Bend, or offset, straightening. One or more pairs of rolls can be adjusted to cause the tube to follow a curved path through the machine (F[...]

Optimalization of tempering parameters for 15313 steel grade DOI:10.15199/24.2015.9.7

  Tube production range in Železiarne Podbrezová involves a wide range of heat resistant steels for high-temperature applications up to 650°C. The tubes produced are being delivered to the customers as rolled and heat treated. Upon the costumer request they could be further processed as precision cold drawn tubes. The aim of our experiment is to provide more precise chemical composition, technological parameters of tube production and optimization of heat treatment. In this paper, results obtained for 15 313 steel grade are presented. This steel grade belongs to the class of heat resistant hot-rolled steels with guaranteed creep resistance up to 560 °C. To meet the required values of strength, plastic- ity, and creep resistance the ferritic-bainitic microstructure is required. In this paper, the influence of heat treatment on the microstructure and mechanical properties is investigated. The result of this analysis is the optimization of microstructure, expressed as a volume fraction of bainite and also a ferritic grain size. This can be linked to optimal conditions for normalizing using rapid quenching and subsequent temper- ing. The presented results allow us to optimize the chemical composition of 15 313 steel grade and the heat treatment parameters so to obtain the optimal ferritic-bainitic microstructure for safe, long-term and trouble-free applications in power industry. Zakres produkcji rur w przedsiębiorstwie 􀃤eleziarne Podbrezová obejmuje szeroki wybór stali żaroodpornych do użytku w wysokich tempe- temperaturach, aż do 650°C. Rury produkowane tutaj są dostarczane do klientów po walcowaniu i obróbce cieplnej. Na życzenie klienta mogą one być poddane dalszej obróbce, takiej jak precyzyjne ciągnienie rur na zimno. Celem naszego eksperymentu jest ustalenie bardziej precyzyjnego składu chemicznego, technologicznych parametrów produkcji rur oraz optymalizacja obróbki cieplnej. Niniejsza praca prezentuje otrzymane rezultaty dla typu [...]

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