Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Milan MOJŽIŠ"

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 [...]

Analysis of deformation in precision seamless tubes during cold drawing DOI:10.15199/24.2015.9.12


  This paper deals with the analysis of deformation in precision seamless tubes during cold drawing. The tubes were cold-drawn in five technological sequences, undergoing seven drawing passes in total. After each sequence the intermediate annealing took place. The main goal of the experiment was to evaluate the initial stage of the drawing process for E235 hot-rolled steel tube in Železiarne Podbrezová tube drawing plant, going from ∅ 31.8 × 2.6 mm to the final dimension of ∅ 6 × 1 mm while using specified reductions according to technological standards. The influence of selected reductions and the drawing technology on deformation of tubes was evaluated. The experiment described in this article is a part of the research project aimed at whether it is possible to determine the input technological parameters so that the resulting effect makes the tube production more effective. W artykule przedstawiono analizę odkształcenia precyzyjnych rur bez szwu podczas ciągnienia na zimno. W ramach pięciu ciągów zrealizowano łącznie 7 przejść. Po każdym ciągu następowało międzyoperacyjne wyżarzanie. Głównym celem eksperymentu była ocena wstępnego etapu procesu ciągnienia rur ze stali E235 w ciągarni rur 􀃤eleziarne Podbrezová. Walcowane na gorąco rury wsadowe w rozmiarze ∅ 31,8 × 2,6 mm ciągnięto do uzyskania końcowego rozmiaru ∅ 6 × 1 mm, stosując wielkości redukcji przekroju w kolejnych przepustach dobrane zgodnie z normami technologicznymi. Dokonano oceny wpływu wybranych wielkości redukcji przekroju i technologii ciągnienia na odkształcenie rur. Eksperyment przedstawiony w artykule jest częścią projektu badawczego, który ma wskazać, czy możliwe jest określenie wejściowych parametrów technologicznych umożliwiających bardziej efektywną produkcję rur. Key words: reduction, tube drawing, plastic deformation Słowa kluczowe: redukcja przekroju, ciągnienie rur, odkształcenie plastyczne.Introduction. Cold drawing technology used f[...]

The Change of Mechanical Properties of Material Using Various Reductions by Cold-Drawn Precision Seamless Tubes DOI:10.15199/24.2016.8.11


  Zmiana właściwości mechanicznych materiału dla różnych etapów redukcji przekroju poprzecznego w procesie ciągnienia na zimno precyzyjnych rur bez szwu The production of cold-drawn precision seamless tubes has an old tradition in Železiarne Podbrezová a.s. The production itself consists as a final operation of two previous operations, namely: steel plant - production of continued casting billet and hot-rolling plant - production of hot-rolled tubes. At steel plant, steel is produced in electric arc furnace with following continuous casting. The final product is biller with dimensions 200 × 200 × 400 mm. At hot-rolling plant, hot-rolled tubes serve as feed stock for cold-drawing. A hot-rolled tube can be adjusted to feed stock of cold-drawing plant from the material as well as from dimensional point of view. Based on these possibilities, technological process of production - number of passes, heat treatment and percentage of reduction can be altered by technologists. In this paper, we dealt with number of operations in technological processes of cold-drawing plant. As we have already mentioned, passes, reductions and heat treatment can influence the final tube in terms of mechanical properties (Rp0,2, Rm, A5, HV) and microstructural states. W hucie Žleziarne Podbrezová[...]

Numerical simulation of cold drawing of multi-rifled seamless steel tubes DOI:10.15199/24.2016.9.1


  Symulacja numeryczna ciągnienia na zimno rur stalowych bez szwu z wewnętrznym żebrowaniem Multi-rifled precision seamless steel tubes are produced by cold drawing technology, utilizing multiple drawing sequences with intermediate heat treatment. In this paper, numerical simulation of multi-rifled tube drawing is compared with the experiment regarding the dimensions of grooves on the inner surface of the tube. For numerical simulation, DEFORM-3D software was utilized. The numerical model considered drawing of a hollow feedstock with dimensions ∅ 36 mm × 8 mm into the multi-rifled tube with dimensions ∅ 28.6 mm × 6.3 mm. The analysed numerical results turned to be consistent with the dimensions of grooves obtained experimentally and measured by optical 3D scanning. Based on the validated model, further optimization of various technological parameters can be made, providing an effective method for enhancing product quality and lowering production costs. Precyzyjne rury bez szwu z wewnętrznym żebrowaniem są wytwarzane w procesie wielooperacyjnego ciągnienia na zimno z międzyoperacyjną obróbką cieplną. W artykule przedstawiono porównanie wymiarów rowków na wewnętrznej powierzchni rury uzyskanych eksperymentalnie z wynikami symulacji numerycznej przeprowadzonej w programie DEFORM 3D. Symulacja została przeprowadzona dla ostatniej operacji procesu ciągnienia rury żebrowanej o wymiarach ∅ 28,6 mm × 6,3 mm z rury o gładkich powierzchniach i wymiarach ∅ 36 mm × 8 mm. Analizowane wyniki symulacji numerycznych okazały się zgodne z wymiarami żeber uzyskanych eksperymentalnie, które zmierzono metodą przestrzennego skanowania optycznego. Zweryfikowany model może być wykorzystany do optymalizacji różnych parametrów technologicznych, stanowiąc efektywną metodę poprawy jakości wyrobów oraz zmniejszenia kosztów produkcji. Key words: seamless steel tube, FEM, numerical simulation, multi-rifled tube, cold drawing Słowa kluczowe: stalowa [...]

The technology of cold drawing of seamless steel tubes using numerical simulation DOI:10.15199/24.2017.8.17


  Introduction. At Zeleziarne Podbrezova a. s. (ZP), the drawing process of precision seamless steel tubes has a long tradition. Already in 1968, the construction of a new tube plant began. The tubes have been produced at ZP by draw􀀐 ing technology since 1971. After long time, this process has undergone great changes. Today, ZP is a major European producer of hot-rolled and cold-drawn seamless steel tubes. At present, it is possible to talk about high-tech technology. The drawing plant is equipped with 14 drawing benches with drawing force from 250 to 1000 kN. These devices enable to produce tubes with dimensions: outer diameter from Ø4 to Ø120 mm, with a wall thickness of 0,5 - 11mm and length from 2 - 16mm. The tubes are drawn to the final dimensions according to the customer´s requirements. For this particular technology, a hot rolled seamless steel tube serves as a feedstock for multiple cold drawing opera􀀐 tions with intermediate heat treatment. The reduction of the outer diameter and wall thickness must be set correctly for every pass. The aim is determine the lowest number passes because of low economy costs. In this technology, drawing with plug and hollow sinking are used. In the first passes, where the outer diameter and wall thickness is reduced, the drawing with the fixed plug is used. The fixed cylindrical or fixed conical plug is utilized depending on the wall thickness of input feedstock. The conical plug enables to use higher drawing velocity thanks to its geometry which provides better flow of material. Hollow sinking is a final process in which the wall thickness stays the same and the outer dimen􀀐 sion is reduced [1-3]. In general, the drawing process is determined by the mate􀀐 rial properties of the tube being drawn, the lubrication, and the tool ge[...]

The influence of reduction on the surface temperature in the process of drawing tubes DOI:10.15199/24.2019.8.12


  Introduction. Cold drawing technology used for manufacturing of precision seamless steel tubes in Železiarne Podbrezová depends on many factors, two of which are the initial and the final tube dimensions[1-4]. The proper selection of area reductions is therefore a crucial task as the improper reduction sequence may lead to excessive straining, possibly causing cracks or even material failure[1-3]. In plug drawing technology, the inner diameter of the tube takes the exact dimension while the wall thickness is being reduced. Cold drawing using a fixed plug is a versatile technology, sporting high productivity and relatively low demands on drawing tools. As the main tool, the reducing die is being used[1-3]. A cylindrical plug is inserted into the die orifice, being fixed on a mandrel. The proper alignment of the die and the plug is necessary for attaining correct dimensions of the tube after drawing and also for drawing in general, see Fig. 1 [1-3]. The drawing technology. The process of a tube cold drawing is schematically depicted in Fig. 2. The main production steps are as follows [2-4]: - feedstock pre-processing, - cold and hot pointing of tube ends, - chemical treatment of the tube (pickling, phosphating, lubrication), - cold drawing, [...]

Compare of the Dies and They Influence of Geometry Precision of the Cold Drawing Tubes with Small Dimensions DOI:10.15199/24.2017.8.22


  Introduction. The article deals with production of seam less precision cold drawing tubes drawing without plug and the influence of technological parameters with effect on the mechanical properties of the tubes. The aim of the ex􀀐 periment is to verify the possibility of drawing hot rolled tubes by one pass technology from dimension 18 × 0.9 m with tempering after drawing to dimension 6 × 1 mm by selected reductions which abide by the factory conditions of Železiarne Podbrezová a.s.. At the End of the article is comparison of both of these dies on geometry and mechani cal properties (Rp0.2, Rm, A5.65). Next is the same com parison in software DEFORM 3D. With consideration of specialization on production seamless precision tubes in Železia[...]

Theoretical analysis of tube drawing process DOI:10.15199/24.2019.8.2


  Introduction. The production of precise seamless tubes is a complex problem because it is a complex process involving a lot of factors influencing the production processes and subsequent properties of drawn tubes. There are factors related to preparation of an initial material by continuous casting, hot forming of a pre-tube, cold forming of a tube connected with deformation strengthening, as well as the intermediate and final heat treatment operations. Due to this complexity, the paper is focused only on some problems of cold tube drawing process. Tube drawing [1-7]. During tube drawing a hot-rolled pre-tube is drawn through a die and its outer diameter is reduced. During fixed plug drawing not only the outer diameter of a tube is reduced but also its wall thickness. A coefficient of tube elongation λ is the drawing process characteristic. The λ coefficient can be determined from the law of volume constancy: ( ) ( ) r r r o o o r o o r D s s D s s S S L L - - λ = = = ⋅ ( 1) where: Lo, So, Do, so - length, cross section area, diameter and wall thickness of a tube before drawing, respectively, while Lr, Sr, Dr, sr - length, cross section area, diameter and wall thickness of a tube after drawing, respectively. At drawing with more than one draw, the total coefficient of elongation is detemined as: c n λ =λ ⋅λ ⋅λ ⋅ ⋅λ 1 ..... 2 3 ( 2) where: λc - total coefficient of elongation, λ1, λ2, λ3, λn - coefficient of elongation after the first, second, third and n-th draw, respectively. The tube drawing is divided into: - tube sinking - free tube drawing, - fixed plug drawing - with cylindrical or shaped plug, - floating plug drawing. The paper is focused on fixed plug drawing. Stress-strain states at fixed plug drawing. A schematic representation of stress and strain states in the three subsequent areas of the deformation[...]

The influence of technological parameters for the manufacture of precision seamless tubes for automotive industry DOI:10.15199/24.2019.8.5


  Introduction. On the basis of the increasing demand of tubes for the automotive industry, which in recent years once with the requested commodities of each company is also Zeleziarne Podbrezová (ZP) market needs for this industry. Due to the very specific and complicated production with the need to observe high standards, whether it is a tolerance of geometric dimensions, or compliance with material properties, it is necessary to ensure, during the production itself, mapping of the entire technological flow. In this paper, we looked at two different technologies of pulling and comparing them in terms of geometric accuracy. The first method consisted of draws on mandrel and the second method being a hollow sinking. In these processes, due to the need to know the parameters affecting the drawing itself, we have measured the temperature of the tube surface just behind the tool working surface. The other parameters analysed were the properties of the material itself, which, both at the input and output, greatly affect the forming process itself. The technically cold drawing process of the tubes is shown in Fig. 1 and consists of several technological nodes. Due to the drawing process, it is necessary to properly set the parameters of these technological nodes, such as heat treatment, which must ensure good formability of the material. It is important to ensure the correct chemical treatment which reduces the coefficient of friction and thus also the actual drawing temperature. Other parameters th[...]

Microstructure aspects and comparison of mechanical properties of cold drawn precision seamless tubes DOI:10.15199/24.2019.8.8


  Introduction. In this paper, we focused on a detailed mapping of the selected cold drawing of tube production technology, which is commonly used in cold-drawn tube factory. Its essential foundation is to emphasize the input material with a view to microstructure and mechanical properties, emphasizing the possibilities of the following forming process. In previous experiments, a methodology for determining intense tensile strength by mechanical properties was proposed. Given the economic and technological savings, it is important to propose adjustments that modify the process while not compromising the microstructural properties of the material, necessary to apply additional limit deformations in the process itself. The whole technological process consists of individual technological nodes (Fig. 1), which must meet the necessary standards resulting from the set technological process. By modifying a specific technological node in this case of the drawing process, it allows for the omission of the entire process, which has an economic benefit and, last but not least, saving time and performance for individual employees. To meet these conditions, it is necessary to observe the conditions of the input material properties (Fig. 2) and this is in our case a rolled tube. This paper describes the first course of selected tube drawing technology in terms of microstructure and mechanical properties. In the first run, the starting material and two consecutive strokes are described without intermediate annealing and subsequent heat treatment [3]. Experimental material. The experimental material was selected on the basis of the ZP production portfolio. Considering the extensive experiments that were conducted to innovate [...]

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