E. Dudrová, M. Kabátová, R. Bidulský - Microstructure, Mechanical Properties and Failure of Fe-3Mn-0.7C Sintered Steel

     Mechanical properties of Fe-3Mn-0.7C sintered steel were determined in tension and in bending following laboratory and industrial sintering at the temperatures of 1120, 1180 and 1200 °C in a H₂-rich atmospheres with the dew points of -33 °C and/or - 30 °C and -55 °C and/or - 60 °C. The microstructure of sintered specimens is complex and heterogeneous, formed by products of the diffusive and non-diffusive transformations. The highest strength properties of the tested alloy were recorded after sintering at 1200 °C in dry atmosphere: R_0.2 = 490 MPa, R_m = 642 MPa, bend strength of 1256 MPa, apparent hardness of 207 HV10, tensile and maximum bend strains were 1.02 and 3.6 %. The reproducibility of tensile and bend strengths data was high, characterised by Weibull module, m, of 12 - 38. The large pores or their agglomerates (50 - 70 µm in size) act as the failure originating sites in the tensile and bend specimens. pdf - 211 kB

V. V. Bukhanovsky, I. Mamuzić, V. A. Borisenko - The Effect of Thermal Treatment on the Mechanical Properties of Low-Alloyed Molybdenum Alloys over the Wide Range of Temperatures

     The article presents data on the short-time strength and ductility of thin rolled sheet made of low-alloy molybdenum TsM-10 of the system Mo-Al-B, TsM-6 of the system Mo-Zr-B, and TsM-12 of the system Mo-Zr-Hf-B in deformed, polygonized, and recrystalized states in the temperature range 290 - 2 270 K. It was established that heat treatment can increase the high-temperature strength of these alloys by a factor of 1.2 - 2.2 and 1.1 - 1.5, respectively. pdf - 327 kB

F. Kovac, M. Dzubinsky - Prediction of Deformation Resistance of Low Carbon Steels During Hot Rolling

     Deformation behaviour of low carbon steels under hot rolling service conditions is predicted utilising a combination of isothermic single step deformation test, anisothermic interrupted test and hot rolling simulation performed on torsion plastometer. The stress s_0.05 at strain level e = 0.05 and the restoring factor fr are proposed to be used for the description of the strengthening / restoring process during repeated deformation. pdf - 425 kB

J. Tušek - Bridging of Welding Gaps in Welding with a Multiple-Wire Electrode

     An investigation on bridging larger welding gaps between workpieces occurring in practice due to structural requirements or to defects in weld edge preparation is described. Some characteristic cases from practice where a larger root gap should be bridged or the space between two or three workpieces should be filled with a greater quantity of filler material are described. Submerged-arc welding with twin-wire and triple-wire electrodes was applied. pdf - 346 kB

A. Mockovčiaková, B. Pandula - Study of the Relation Between the Static and Dynamic Moduli of Rocks

     Non-destructive techniques based on the propagation of ultrasonic wave through the elastic medium were used for determination of dynamic modulus of selected samples of rocks in laboratory. The calculated values of dynamic modulus were compared with values of static modulus determined in laboratory on samples tested by applied loading. A method of estimation of the static modulus in situ conditions, where the measurements cannot be carried out, is discussed. pdf - 233 kB

R. Budzik - Titanium in the Process of Smelting Pig Iron with an Increased Silicon Content

     In connection with future utilization of magnetite - titanium ores deposited in Poland in the region of Suwałki - the test were performed to get information regarding the influence of titan and vanadium admixtures on the quality of pig iron and the run of blast furnace process. As a blast furnace charge, there were used magnetite - titanium concentrates similar to the ores deposited in the Suwałki region. The test consisted of iron ores sinter production and its usage in the process of preparation of foundry pig iron. The amount of TiO₂ charge into the blast furnace was equal to 10 kg/Mg of pig iron. It was ascertained that the quality of sinter remained the same, but the output of sinter was lower by proxy. 4 %, compared to the production without TiO₂ addition. These tests have proved the possibilities of utilization of titanium - bearing magnetite - concentrates in the portion up to 10 kg/Mg of pig iron, which gives possibilities to take advantages of entire deposit of titanium - bearing magnetite ores in Poland, using the blast furnace technology. pdf - 252 kB

N. Devčić, I. Mamuzić - 50 years of seamless tubes manufacturing in Croatia - Steel Works Sisak

    The paper resumes happenings starting with the planning of construction of seamless robe rolling mill (VBC) in Croatia, Sisak 1947, and continues until the state of today and presents some suggestions for improving the mentioned state. All activities referring to construction are presented in a sequence: getting down to work and improving of manufacture together with conditions having affected the success of business. pdf - 301 kB

R. Ulewicz - Quality Control System in Production of the Castings from Spheroid Cast Iron

     In work opinions of form incompatibility were executed during process of production of casting articles from spheroidal cast iron. Using the quality tools such as the Ishikawa diagram and the Pareto-Lorenz analyses one identified often-appeared defects and, were identified and qualified. Identification of critical points of productive system was executed and the range of correcting workings was qualified. On basis of data from analysis of causes of occurrence of incompatibilities and appointed critical points system of control of quality was worked out for serial and isolated production. Use of statistical method of casts in connection with active control of quality and selection of productive stages for serial production of casts from spheroid cast iron caused lower level of defects, and in economic aspect contributed to the reduction of costs of connected production with low level of quality. pdf - 204 kB

J. Selejdak - Influencing Factors onto Quality of Welded Pipes

     At days of market economies and large competitiveness in the world, the most important assignment for enterprises is maintenance of their customers. If an enterprise wants to execute this it has to take care about the very best quality of its articles and has to improve it constantly. It was decided to deal with quality problems in this paper which appear during compound technological production process of welded tubes. This process is a process of great frequency welding. The quality of welded tubes is largely influenced by batch material. Steel tapes should not contain unmetalic interpolations. Fragile unmetalic inclusions make difficult process of pipe welding as well as welds or area next to weld. These inclusions have unfavorably influence onto quality. In the paper different problems were described which appear during technological process of pipes welding such as bad cutting of the tape/batch, cold welds or else convexity of bands. It has also introduced proposal of prevention activities in future. pdf - 210 kB

M. Malina - Transition in Steel Works Sisak

    Transition coupled with agression towards Croatia, as well as the collapse of the former market have brought a series of dramatical and unplanned changes to Željezara Sisak. The much, needed business transformation is being achieved unsuccessfully by developing a series of Programs, hiring international management consultants as well as strategic business partners. However, due to the failure of previously set strategy the possible company recovery also fails, and Željezara Sisak ends up bancrupt. Because the first attempt at privatization was not successful, Željezara Sisak is now faced with a difficult decision regarding the choice of its new strategic partner/owner. pdf - 91 kB