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Ruukki, Finland

Valkonen I.,Rautaruukki Oyj
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013

In this paper, the failure criteria for high strength steel are defined using notched tension specimens of different thicknesses to reach various triaxial test levels in order to develop material parameters for FEM analyses. These results are used in component FEM analyses to verify the failure criteria and material models. Results from the experiments showed that the tests and calculations agree well. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).


Neimitz A.,Kielce University of Technology | Sorsa I.,Rautaruukki Oyj
International Journal of Fracture | Year: 2011

The European Standard EN 1993-1-10 contains design guidance to determine the maximum permitted thickness of the structural element made of steel. The element thickness should be smaller than the maximum value to avoid brittle fracture. The standard includes a table where the maximum thicknesses are listed for different steel grades, temperatures and loading. However, no theoretical justification for these recommendations is given. We derive a simple formula for the maximum permitted thickness that includes, in addition to the parameters in European Standard, the following parameters or quantities: the secondary stresses following from the welding process or temperature gradients, the shape and size of the structural element, the tensile properties of the material, the fracture toughness, the probability of fracture, and the in-plane constraint parameter, e.g. the Q-parameter. © 2010 Springer Science+Business Media B.V.


Eilola K.,Rautaruukki Oyj | Peramaki P.,University of Oulu
Analytical Letters | Year: 2011

The determination of ultra-trace levels of chromium and nickel in biological samples had previously been very difficult due to serious contamination problems in conventional laboratories. Contamination control in a conventional laboratory was studied and contamination due to various sources was minimized systematically. In addition to chromium and nickel, zinc was also determined as an indicator element prone to contamination. Measurements were carried out using electrothermal atomic absorption spectrometry (ETAAS). Contamination from the sample handling steps, digestion vessels, atmospheric fallout, and the effect of the liquid contact area were studied. In the sample handling steps, even simple procedures, such as transferring the sample solution from the volumetric flask by pouring, led to significant contamination due to the large area of liquid contact. This contamination source was eliminated by transferring the sample solution using an automatic pipette. The most suitable method for decontamination of the digestion vessels was steaming with boiling nitric acid as opposed to leaching with nitric acid at room temperature. Quartz was found to be a more suitable digestion vessel material than Teflon-PFA when Cr and Ni were determined. For Zn determination, Teflon-PFA was more suitable. Contamination from atmospheric fallout was highest in the fume hood and was reduced by simply closing the labware into Minigrip® bags before use. The surface area of the labware in contact with the handled liquid volume should be kept at a minimum because even a simple procedure, such as preparing standard solutions in volumetric flasks, can lead to significant contamination if the vessel surface area is too large. Finally, low enough contamination was achieved so that the total procedure blanks were below the instrumental detection limits for Cr and Ni. © Taylor & Francis Group, LLC.


Ye Z.,University of New South Wales | Gupta S.,University of New South Wales | Kerkkonen O.,Rautaruukki Oyj | Kanniala R.,Rautaruukki Oyj | Sahajwalla V.,University of New South Wales
ISIJ International | Year: 2013

Mineral matter of tuyere cokes from an operating blast furnace was characterized with emphasis on quantification of silicon bearing phases. Tuyere coke samples were obtained from a medium size blast furnace through core drilling. The core was divided into ten sections of 25 cm each from furnace wall and four regions, bosh region, raceway region, bird's nest region and dead man region. Core material was sieved into different size fractions. Feed coke was annealed in a horizontal alumina tube furnace at 1200, 1400 and 1600°C for 30 minutes under an argon atmosphere to calculate the stack height of carbon crystallite (Lc). Coke minerals were quantified using radiofrequency low-temperature oxygen plasma ashing to prepare a carbon-free mineral sample which was used for XRD measurements. SiC is mainly observed in the bosh and raceway cokes, and is generally accompanied by lower residual quartz amounts. The xifengite content was relatively higher in bosh and raceway region and was not seen beyond birdsnest.


Siltanen J.,Rautaruukki Oyj
29th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2010 - Congress Proceedings | Year: 2010

The use of ultra high strength steel (UHSS) is increasing in the engineering industry and many steel manufacturers are focusing more on its production. It is easy to predict that the trend is to have even higher strength steel available on the market. Further processing of UHSS needs special attention, as the bending and welding of it can be very challenging. Typical applications in heavy engineering where the use of UHSS brings clear benefits are in the structures of load handling and transportation vehicles and lifting equipment such as telescopic booms and cranes. The benefits that the use of UHSS brings are a higher payload, a longer structural lifetime and lower emissions with energy savings. This paper presents the main results of a project in which the processing of long and formed parts (up to 10 meters) made of steel Optim 960 QC was researched. This kind of structure is typical for a telescopic boom. Optim 960 QC is the trade mark for the steel with yield strength of 960 MPa made in Raahe by the Finnish steel mill Rautaruukki Oyj. Several targets were set for the research. These include determining the following: the quality level of bending and what kind of effect that will have on the laser gas-metal arc (GMA) hybrid welding, what kind of welding fixture is needed, and how to promote investment in the laser technology. The welded joint type was a butt joint with the dissimilar material thicknesses 4 and 5 mm. Laser-GMA hybrid welding tests were conducted using an IPG fibre laser with a maximum output of 10 kW laser power, an ESAB Aristo GMA power source and Precitec welding optics. A comparative welding test with gas-metal arc (GMA) welding was also performed. The power source used in the arc welding test was a new model with good arc pulsing properties that makes it possible to achieve a low value of heat input. The dimensions of the bent profiles were measured before and after welding. The mechanical properties of the welded joints were tested with both non-destructive and destructive methods in accordance with the standards EN-ISO 15614-1 and EN-ISO 15614-11. The results show that both the accuracy and the mechanical properties of laser-GMA hybrid welded products are mostly better than those of GMA welded joints. The achieved welding speed 2.3 m/min of the laser-GMA hybrid welding is clearly faster than the welding speed ∼1.0 m/min of GMA welding.

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