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Hot rolling of steel with TWIP effect

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The TWIP effect (Twinning Induced Plasticity) is employed in steels with high manganese content to achieve elongation above 60 % and strength of more than 1,200 MPa. Chemical compositions of these steels are varied; with Mn content between 15 and 35 %, sometimes with 2 to 4 % Si or Al and the content of carbon of at least 0.5 to 1.0 wt %. The TWIP effect is based on inducing formation of mechan[...]

The Static Recrystallization Kinetics acquired from Stress Relaxation Method DOI:

  Recovery can be described using the Avrami equation, which yields the proportion of recrystallized structure as a function of various deformation- related variables. Modern technique uses the stress relaxation phenomenon. By analysing the stress vs. time plot, one can obtain information on the specimen's flow stress during the hold after deformation. A Gleeble simulator was used for an experiment with four temperatures (800 °C to 1 100 °C) and five strain rates (from 10-2 to 50 s-1) and the resulting strain magnitude of 0,2 or 0,4. Points denoting the start and end of recovery were identified on the curve. Constants of the Avrami equation were determined using these points. The advantages of stress relaxation tests include their simplicity, the opportunity to obtain a full-range curve for the volume fraction of recrystallized structure in a single test run and the effectiveness of mapping the softening phenomena. Zdrowienie może być opisane za pomocą równania Avramiego, co oddaje zależności stopnia zrekrystalizowania struktury w zależności od różnych zmiennych opisujących odkształcenie. Nowoczesna technika wykorzystuje zjawisko relaksacji naprężeń. Analizując zmiany naprężenia w funkcji czasu, można uzyskać informację na temat naprężenia płynięcia materiału próbki podczas wytrzymania po odkształceniu. Symulator Gleeble użyto do przeprowadzenia eksperymentu dla czterech wartości temperatury wybranych z zakresu od 800 °C do 1 100 °C, pięciu wartości prędkości odkształcenia od 10-2 do 50 s-1 oraz końcowego zakresu wartości odkształcenia 0,2 lub 0,4. Punkty oznaczające początek i koniec zdrowienia zostały zidentyfikowane na krzywej. Stałe równania Avramiego oznaczano za pomocą tych punktów. Zalety badania relaksacji naprężeń obejmują ich prostotę, możliwość uzyskania krzywej dla pełnego zakresu ułamka objętościowego frakcji zrekrystalizowanej w pojedynczej próbie oraz skuteczności odwzorowywania zjawisk podczas mięknięcia materiału. Key wo[...]

Slab FEM simulation of hot bar rolling

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It is proposed that three dimensional problem of shape rolling be simplified by solving in approximately by the finite element method. A computer software that has been developed on slab method basis to model the deformation of metal during shape rolling eliminates having to conduct multiply costly and time consuming commercial trials and allows innovations to be introduced more quickly. In the[...]

Computer and Practical Simulation of the Surface Crack reducing on the Billet during Bar and Wire rod rolling process

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The processors acting in the car industry make continuously a stress on producers of wires and rods to eliminate the occurrence of surface defects on the semi-finished products. A development of methods and working procedures aimed to avoid the occurrence of surface defects on wires and rods requires to know the origin of the defects and characteristics of their behaviour in the course of rolli[...]

Inverse analysis of a plane strain compression test results for the purpose of material mechanical and microstructural properties study

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Knowledge of mechanical and microstructural properties of a material is extremely important for performing the numerical analysis which is using for investigation of many metal-forming processes. The plain strain compression test (PSCT) is now generally accepted as one of the most reliable methods for the generation of flow stress data and microstructural investigation of flat rolling. However, the inhomogeneous character of deformation in local zones of a specimen makes it difficult to interpret the results of such tests. In this work, the inverse method has been applied for determination of flow-stress and microstructural data by analyzing of PCST results. A method for determination of static recrystallization kinetics parameters which makes it possible to take advantage of PSCT and[...]

Technological lubricants for cold-rolled sheet and theirs evaluation

  Method for the assessment of technological lubricants for cold rolled sheets with the criterion of efficiency is described. The evaluation of lubricants, currently used or tested once on the cold rolling mill 1700 in ArcelorMittal Temirtau JSC (“AMT" JSC), is described. It was reve- aled that there were no lubricants more efficient than the reference Quakerol 671 found. The less efficient lubricants are: Efirol-VP 5%, AKTO - 5%, Emulsol - 5%. The efficiency of various lubricants on technological parameters on the rolling mill 1700 of AMT JSC is considered. W pracy opisano metodę oceny smarów technologicznych w procesie walcowania blachy na zimno w oparciu o złożone kryterium efektywności. Ocenę przeprowadzono dla smarów stosowanych powszechnie lub wybranych do badań w warunkach walcowni na zimno 1700 w ArcelorMittal Temirtau SA ("AMT" SA). Wykazano, że nie ma bardziej skutecznego smaru niż wybrany Quakerol 671. Mniej wydajnymi smarami są: Efirol-VP 5%, Akto - 5%, Emulsol - 5%. Przeprowadzono rozważania nad wydajnością zastosowania różnych smarów i jej wpływem na parametry technologiczne w walcowni zimnej 1700 AMT SA. Key words: technological lubricants, quality, cold rolling, qualimetry, technological parameters Słowa kluczowe: smary technologiczne, jakość, walcowanie na zimno kwalimetria, parametry technologiczne.Introduction. Specificity of technological lubri- cants application at modern strip cold rolling mills is characterized by high speeds of rolling and productivi- ty, big consumption of lubrication and cooling liquids and capacities of systems for their supply. During cold rolling of sheets and strips most often applied lubricants are: Quakerol 671, mineral oil I-20, Emulsol T 5%, Mo- birolling . 5%, GreenEngineer . 5%, Efirol 7/15 . 5%, Efirol VP 5%, AKTO 5% [1]. Researchers and techno- logists as well as developers of rolling lubricant coolant for cold rolling of sheets are facing the problem of the complex comparative[...]

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