Analysis of the technology of rolling 5,5 mm-diameter wire rod of cold upsetting steel in the morgan block mill

The commercial technology of rolling 5,5 mm-diameter wire rod in Poland’s most modern rolling line has been examined within the study. The material used for the investigation was the 20MnB4 steel intended for subsequent cold working. From the performed analysis of the investigation results it has been found that the technology of rolling wire rod of cold upsetting steel, which is used currently in the Rolling Mill under examination, allows the production of finished products that can be deformed with a relative reduction of about 33 %. At larger plastic deformations,cracks occur in the material, which disqualifies it from further cold working

Determination of characteristics of plasticity of selected medium and high carbon steel grades in hot torsion test

This study presents results of the examinations aimed at determination of rheological properties of selected grades of medium and high-carbon steel grades ( C45 and C72D). The examinations were carried out for the hot torsion test using STD 812 torsion plastometer. The results of experimental studies were approximated with the function used for determination of yield stress depending on strain, strain rate and temperature. The study allowed for development of mathematical models of rheological properties of steel grades studied in the analysed scope of parameters of strain and temperature

Analysis of the microstructure evolution during thermo-mechanical treatment of the steel plates in grade X80-X100

In the work the results of the physical modeling of plate rolling process of HSLA steel were presented. The simulations were carried out using the Gleeble 3800 device and the anvils set for plane strain compression study. The aim of the simulation were a determination of a influence of changes in chemical composition of steel on obtained final structure and tensile strength of specimens after controlled deformation and accelerated cooling to room temperature. During investigation three grades of steels with a little different chemical composition were examined

Theoretical and experimental analysis of the backward extrusion process with a rotational die of AZ31 alloy

In this work theoretical and experimental analysis of the backward extrusion with a rotary die of the AZ31 alloy has been performed. The modification of the classical extrusion was based on the use of a rotary die. The results of theoretical research have confirmed that the use of the modified backward extrusion causes the appearance of shear stress in deformed material, which could affects the activation of additional mechanisms of deformation. The numerical modelling of the rotating extrusion of AZ31 alloy has been conducted by using the computer program Forge®. The experimental tests were carried out in the conditions of the STD 810 torsion plastometer using newly designed tools

High-temperature characteristics of 20MnB4 and 30MnB4 micro-addition cold upsetting steels and C45 and C70 high-carbon-steels

The paper analyzes the high-temperature plasticity characteristics of 20MnB4 and 30MnB4 with micro-additives, intended for cold upsetting and high-carbon steels C45 and C70 in the “solid phase-liquid” during heating and cooling. The investigation was conducted to determine the plastic formability of the examined alloy under hot plastic working conditions. Experiments were carried out on the simulator Gleeble 3800 with the aim of determining the susceptibility of 20MnB4, 30MnB4, C45 and C70 steels to cracking at high temperature. The nil strength (NST), nil ductility (NDT) and ductility recovery temperatures (DRT), and the fracture toughness factor and the BRT (brittleness temperature range) have been determined

Analitičko i numeričko utvrđivanje prostiranja temperature na traci hlađenoj zrakom

The paper analyzes the distribution of temperature of 60S2A steel strip cooled in air. Both analytical and numerical methods were applied in investigation. From among the known analytical methods of temperature distribution determination, Tselikov’s [1], and the Fourier’s [2] methods were used. The numerical examination of temperature distribution presented in the paper involved carrying out a computer simulation of strip air cooling. For this purpose, the Forge 2D software [3] was employed, which relies on the finite-element method in performing computations. Comparison of results obtained by analytical methods with numerical computation results and for the real technological process has also been made within the study.U radu se analizira prostiranje temperature u čeličnoj traci 60S2A hlađenoj zrakom. Tijekom istraživanja primjenjivala se i jedna i druga metoda. Između poznatih analitičkih metoda utvrđivanja prostiranja temperature koristile su se Tselikova [1] i Fourierova [2] metoda. Numeričko ispitivanje temperature koje je prikazano u radu uključuje i provođenje kompjuterske simulacije hlađenja trake zrakom. U tu je svrhu primijenjen Forgeov software 2D [3] koji se u računanju oslanja na metodu konačnih elemenata. Unutar studije je također provedena i usporedba rezultata dobivenih analitičkim metodama s numeričkim izračunima

11 beta-hydroxysteroid dehydrogenase type 1 regulates glucocorticoid-induced insulin resistance in skeletal muscle

OBJECTIVE: Glucocorticoid excess is characterized by increased adiposity, skeletal myopathy, and insulin resistance, but the precise molecular mechanisms are unknown. Within skeletal muscle, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts cortisone (11-dehydrocorticosterone in rodents) to active cortisol (corticosterone in rodents). We aimed to determine the mechanisms underpinning glucocorticoid-induced insulin resistance in skeletal muscle and indentify how 11beta-HSD1 inhibitors improve insulin sensitivity. \ud RESEARCH DESIGN AND METHODS: Rodent and human cell cultures, whole-tissue explants, and animal models were used to determine the impact of glucocorticoids and selective 11beta-HSD1 inhibition upon insulin signaling and action. \ud RESULTS: Dexamethasone decreased insulin-stimulated glucose uptake, decreased IRS1 mRNA and protein expression, and increased inactivating pSer$^{307}$ insulin receptor substrate (IRS)-1. 11beta-HSD1 activity and expression were observed in human and rodent myotubes and muscle explants. Activity was predominantly oxo-reductase, generating active glucocorticoid. A1 (selective 11beta-HSD1 inhibitor) abolished enzyme activity and blocked the increase in pSer$^{307}$ IRS1 and reduction in total IRS1 protein after treatment with 11DHC but not corticosterone. In C57Bl6/J mice, the selective 11beta-HSD1 inhibitor, A2, decreased fasting blood glucose levels and improved insulin sensitivity. In KK mice treated with A2, skeletal muscle pSer$^{307}$ IRS1 decreased and pThr$^{308}$ Akt/PKB increased. In addition, A2 decreased both lipogenic and lipolytic gene expression.\ud CONCLUSIONS: Prereceptor facilitation of glucocorticoid action via 11beta-HSD1 increases pSer$^{307}$ IRS1 and may be crucial in mediating insulin resistance in skeletal muscle. Selective 11beta-HSD1 inhibition decreases pSer$^{307}$ IRS1, increases pThr$^{308}$ Akt/PKB, and decreases lipogenic and lipolytic gene expression that may represent an important mechanism underpinning their insulin-sensitizing action

Analysis of the temperature change over the continuous ingot length on the parameters of round bar rolling process

The paper presents results of theoretical and experimental studies on the effect of feedstock end overcooling before the first rolling stand on the plastic flow of metal and on the energy and force parameters during bar rolling process. From the obtained investigation results it has been found that the uniform heating of the feedstock in the stepped furnace does not insure the uniform plastic flow of metal over the rolled band length. Therefore, it is necessary to modify the method of feedstock heating in the stepper furnace in order to obtain a uniform temperature over the length of the feedstock before the first rolling stand