Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Tomáš KVAČKAJ"

Measurement of roll temperature in stretch reducing mill DOI:10.15199/24.2017.8.24

  Introduction. During rolling of seamless steel tubes in a stretch reducing mill (SRW) the tubular feedstock passes several 3-roll stands with circular/oval rolling gap without any internal tool. The input feedstock of a mod erate length is usually stretched many-folds, depending on the final tube dimensions [1]. In this paper, we focused on the cooling effect of water sprayed onto the roll sur face during stretch reducing of various tube dimensions. In Železiarne Podbrezová tube rolling plant the thin- -walled tube dimensions appear to be critical for maintain ing sufficiently high rolling exit temperature (Tdov > Ar3). To solve this problem we must first measure the actual temperature of the rolls in order to decide whether there is a margin for further lowering of the water flow rate; too little cooling could be detrimental to the life span of the rolls. For this, two different approaches to temperature mea surement can be adopted. In 2016, roll temperature mea surements were carried out periodically using MICRO-EP SILON thermoME-TER LS portable laser pyrometer (Fig. 2) with spectral sensitivity (8 ÷ 14) μm and 200ms sensing period (time constant of the device is 150 ms). However, we were not measuring the working surface temperature direct ly; the measurements were carried out on the oxidized side surface of the rolls. In addition, test measurements of the glossy working surface of the rolls were performed, too, but the glossy nature of the surface with very small emisivity rendered these measurements unreliable. Next to the con tactless measurement method we also carried out contact measurem[...]

The comparison of cooling efficiency of twoo types of nozzles for roll cooling on selected stands in stretch reducing mill DOI:10.15199/24.2018.9.7

  Introduction. Stretch reducing mill (SRW) is a hot rolling mill for manufacturing of seamless tubes. Here, the final tube dimensions and final mechanical properties of hot rolled tubes are achieved after cooling [1-5]. During rolling of tubes in SRW the tubular feedstock (“the hollow") of a moderate length passes several stands with circular or oval rolling gap without using any internal tool. During stretch reducing the diameter and wall thickness of the hollow are changed, depending on the final dimensions. The stretch reducing mill can be used [1-9]: - To extend the production range of tubes of small dimensions, - To produce the tubes with small and medium diameter, - To reduce the production costs. Condition of the rolls in SRW stands are of vital importance for obtaining the final diameter and surface quality of the tube. Thus it is necessary to focus on the surface temperature of the hollow and optimal surface temperature of the rolls. Therefore, decision has been made to optimize the roll cooling process by means of a new set of nozzles with smaller nominal flow rate [1-10]. Methodology and instruments for temperature measurement. When choosing the appropriate methodology of temperature measurement, two basic methods were at our hand: contact and contactless. The contact method proved to be more suitable for measuring the surface temperature of the roll [9-14]. Contactless measurement would be very difficult to use for several reas[...]

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