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1
Content available The Effects of Hot Deformation Parameters on the Size of Dynamically Recrystallized Austenite Grains of HSLA Steel
Gnapowski Sebastian, Opiela Marek, Kalinowska-Ozgowicz Elżbieta, Szulżyk-Cieplak Joanna
Advances in Science and Technology. Research Journal
|
2020
|
Vol. 14, no 2
76--84
EN
Materials scientists are seeking to produce metals with reduced weight and dimensions while maintaining the appropriate mechanical properties. There are several ways to improve the internal structure of metals, such as the ultrasound used to solidify liquid metal. The homogeneity of the grains and the uniformity of the metal structure affects its mechanical strength. This paper presents the results of investigations into the effects of hot deformation parameters in compression on the austenite grain size in the HSLA (High Strength Low Alloy) steel (0.16% C, 0.037% Nb, 0.004% Ti, 0.0098% N). The axisymmetric compression investigations were performed on cylindrical investigation specimens using a Gleeble 3800 thermomechanical simulator with the strain rate of 1÷15.9 s-1 and strain degree ε = 1.2. Before deformation, the research specimens were austenitized at TA = 1100÷1250 °C. The metallographic observations of the primary austenite grains were conducted with an optical microscope, while the structure of dynamically recrystallized austenite, inherited by martensite, was examined by using a scanning electron microscope.
2
Content available Effect of boron microaddition on hardenability of new-developed HSLA-type steels
Opiela M.
Archives of Materials Science and Engineering
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2019
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Vol. 99, nr 1/2
13--23
EN
Purpose: The paper presents the results of investigations on the effect of 0.003% boron microaddition on the hardenability of new-developed HSLA-type steels. In order to prevent the binding of the boron microaddition with nitrogen in BN nitrides, Ti microaddition at concentrations of 0.033% and 0.028% was also added into the tested steels. Design/methodology/approach: Evaluation of hardenability of the investigated steels was carried out on the basis of the Jominy test and the analytical method, according to the ASTM 255-89 standard, taking into account the effect of the boron microaddition. Additionally, developed of the CCT-diagram of investigated steel. A DIL 805A/D dilatometer with a LVDT-type measuring head was used to carry out the dilatometric test. Findings: Microaddition of boron, introduced into steel in a concentration of 0.003% along with Ti microaddition shielding (in concentration of 0.033% in steel A and 0.028% in steel B), advantageously improves hardenability. This is reflected in calculated ideal critical diameter DIB, which is equal 163 mm for steel A and 155 mm for steel B. The form of curves of phase transformations of supercooled austenite is typical for steels with microaddition of boron, with similar chemical composition. Research limitations/implications: Due to similar chemical composition of investigated steels, the kinetics of phase transformations of austenite, supercooled under continuous cooling, was determined for steel B containing 0.28% C, 1.4% Mn, 0.3% Si, 0.26% Cr, 0.22% Mo and Nb, Ti, V and B microadditions at 0.027%, 0.028%, 0.019% and 0.003% respectively. Practical implications: Tested steels have high hardenability and show the full usability for production of forged parts with the method of thermomechanical treatment, i.e., hotdeformed in the temperature range adjusted to the type of microadditions added to steel, with direct quenching of forgings from finishing forging temperature. The results of the tests may be useful for developing the parameters of heat treatment and thermomechanical treatment of investigated steels. Originality/value: The hardenability of new-developed HSLA-type steels was determined.
3
Content available remote Aging kinetics and mechanical properties of copper-bearing low-carbon HSLA-100 microalloyed steel
Sohrabi M. J., Mirzadeh H., Mehranpour M. S., Heydarinia A., Razi R.
Archives of Civil and Mechanical Engineering
|
2019
|
Vol. 19, no. 4
1409--1418
EN
The precipitation kinetics of HSLA-100 steel and the correlation between tensile and impact properties were studied. According to the modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis and based on the analysis of the time corresponding to the transformed fraction of 0.5 (t0.5), the activation energy for the precipitation of copper during aging of martensite was determined as ~111 and 105 kJ/mol, respectively. These values are much smaller than the activation energy for the diffusion of Cu in a-iron, which was related to the effect of high dislocation density of the quenched martensitic microstructure on the aging process. These results were verified based on the diffusional calculations. Based on the analysis of mechanical behavior, no reasonable correlation was found between strength of the material and the impact energy. However, the impact energy was found to be propor-tional to the UTS-YS, where the latter is an indicator of the work-hardening capability of the material. This revealed that the work-hardening capacity of the material is a much more important factor for determining the impact toughness compared to its strength.
4
Content available Influence of Molybdenum Addition on Mechanical Properties of Low Carbon HSLA-100 Steel
Bogucki R., Pytel S.M.
Archives of Metallurgy and Materials
|
2014
|
Vol. 59, iss. 3
859--864
EN
The results of mechanical properties and microstructure observation of low carbon copper bearing steel with high addition of molybdenum are presented in this paper. This steels were characterized by contents of molybdenum in the range from 1% to 3% wt. After the thermo -mechanical processing the steels were subsequently quenched and tempered at different temperatures (500-800°C) for 1h. The changes of mechanical properties as function of tempering temperature were typical for the steel with the copper addition. The sudden drop of impact resistance after tempering from 575°C to 600°C was caused probably by precipitates of Laves phase of type Fe2Mo.
PL
W pracy przedstawiono wyniki badań własności mechanicznych oraz obserwacji mikroskopowych nisko węglowych stali z dodatkiem Cu o podwyższonej koncentracji molibdenu w zakresie od 1 do 3% wg. Po obróbce cieplno-plastycznej stale były hartowane i odpuszczane w rożnych temperaturach (500-800°C) przez 1 godzinę. Przebieg zmian własności mechanicznych w funkcji temperatury odpuszczania był zbliżony do przebiegu stali z dodatkiem miedzi. Silny spadek udarności po odpuszczaniu od 575 do 600°C spowodowany był prawdopodobnie procesami wydzieleniowymi fazy Lavesa typu Fe2Mo.
5
Content available remote Application of vanadium precipitation for lower rolling force and enhanced strength of hot strip steel
Suwanpinij P., Dickert H.H.
Archives of Materials Science and Engineering
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2014
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Vol. 70, nr 1
39--44
EN
Purpose: In this paper the application of vanadium precipitation for lower rolling force and enhanced strength of hot strip steel was discussed. Design/methodology/approach: Fine precipitates of vanadium were firstly investigated by Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray Spectroscopy (EDX). Further quantitative characterisation for the precipitation and the addition of high amount of nitrogen will be discussed. Findings: The contribution for strength from different components, namely, grain refinement, second phase hard particles and precipitation strengthening was separately analysed. Research limitations/implications: Basic knowledge in thermodynamics of the precipitation of microalloying elements is applied for the process design of hot strip rolling for reduced rolling force and improved strengthening effect. Originality/value: A vanadium-added steel tends to need moderate rolling force through recrystallisation controlled rolling while the other with a small addition of 0.05% niobium requires significantly higher force.
6
Content available The nitrogen content effect on carbonitride coagulation in 40Cr8 steel with micro-additions V and V + Al
Głowacz E., Adrian H, Osuch W.
Archives of Metallurgy and Materials
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2013
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Vol. 58, iss. 2
607--611
EN
The work examines the effect of nitrogen and micro-additions V and V+Al on the austenite grain size and the coagulation of carbonitride precipitates in 40Cr8 steel. The analyzed materials underwent heat treatment consisting in holding the material at 1200ºC for 1h, which was next exposed to furnace cooling down to 820ºC and maintained at this temperature for 20hrs, and subsequently quenched in water. With the application of electron microscopy, the microstructure and the formed carbonitride precipitates were examined. The SigmaScanPro software was used to perform the quantitative metallographic analysis of the precipitates. The study demonstrated that increase in the content of nitrogen inhibits the coagulation rate of carbonitrides, whereas aluminium favours the tendency for coagulation and efficiently inhibits the austenite grain growth.
PL
W pracy badano wpływ azotu i mikrododatków V, V+Al na wielkość ziarna austenitu oraz koagulacje wydzieleń węglikoazotku w stali 40Cr8. Próbki z badanych wytopów poddano obróbce cieplnej polegającej na wygrzewaniu przy temperaturze 1200ºC przez czas 1h, następnym chłodzeniem z piecem do temperatury 820ºC i wytrzymaniu przy tej temperaturze przez czas 20h oraz chłodzeniu w wodzie. Przy wykorzystaniu mikroskopii elektronowej badano mikrostrukturę oraz powstałe wydzielenia węglikoazotku. Za pomocą programu SigmaScan Pro przeprowadzono ilościową analizę metalograficzną wydzieleń. Badania wykazały, że wzrost zawartości azotu hamuje szybkość koagulacji węglikoazotku, podczas gdy aluminium sprzyja skłonności do koagulacji i skutecznie hamuje rozrost ziarn austenitu.
7
Content available On the failure mode of resistance spot welded HSLA 420 steel
Pouranvari M.
Archives of Metallurgy and Materials
|
2013
|
Vol. 58, iss. 1
67-72
EN
Failure mode of resistance spot welds (interfacial vs. pullout) is a qualitative measure of resistance spot weld performance. Considering adverse effect of interfacial failure mode on the vehicle crashworthiness, process parameters should be adjusted so that the pullout failure mode is guaranteed ensuring reliability of spot welds during vehicle lifetime. In this paper, metallurgical and mechanical properties of HSLA 420 resistance spot welds are studied with particular attention to the failure mode. Results showed that the conventional weld size recommendation of 4t0:5 (t is sheet thickness) is not sufficient to guarantee pullout failure mode for HSLA steel spot welds during the tensile-shear test. Considering the failure mechanism of spot welds during the tensileshear test, minimum required fusion zone size to ensure the pullout failure mode was estimated using an analytical model. Fusion zone size proved to be the most important controlling factor for peak load and energy absorption of HSLA 420 resistance spot weld.
PL
Tryb uszkodzenia zgrzein (pękanie na granicy faz a wyrywanie) jest jakościowa miara zachowania zgrzein. Biorąc pod uwagę niekorzystny wpływ uszkodzenia na granicy faz na odporność pojazdu na uderzenia, parametry zgrzewania powinny być ustawione tak, ze trybem uszkodzenia jest wyrywanie co gwarantuje niezawodność zgrzein w czasie eksploatacji pojazdu. W pracy, badane sa metalurgiczne i mechaniczne właściwości zgrzein stali HSLA 420 ze szczególnym uwzględnieniem trybu uszkodzenia. Wyniki próby rozciągania i ścinania wykazały, ze konwencjonalne zalecenie rozmiaru spoiny 4t0:5 (t - grubość) nie jest wystarczające, aby zapewnić ze trybem uszkodzenia jest wyrywanie. Biorąc pod uwagę mechanizm uszkodzenia zgrzein w czasie próby rozciągania i ścinania, minimalna wielkość strefy stopionej wymagana do zapewnienia, ze trybem uszkodzenia jest najbardziej istotnym czynnikiem decydującym o maksymalnym obciążeniu i pochłanianiu energii przez zgrzewana stal HSLA 420.
8
Content available remote Ocena celowości zastosowania rur ze stali X70 oraz X80 na gazociągi strategiczne dużych średnic z uwzględnieniem ich spawalności
Klimpel A.
Biuletyn Instytutu Spawalnictwa w Gliwicach
|
2011
|
R. 55, nr 6
58-62
PL
Analiza stali stosowanych na rurociągi przesyłowe ropy i gazu oraz przykłady rurociągów zbudowanych ze stali X70 i X80. Opisano własności mechaniczne i spawalność stali X70 i X80 oraz zasady kontroli jakości złączy spawanych rurociągów przesyłowych w warunkach polowych. Na podstawie przeglądu piśmiennictwa oraz własnych doświadczeń autora przedstawiono ograniczenia, ale i zalety zastosowania nowoczesnych stali o wysokiej granicy plastyczności, jak np. stali X80 na wysokociśnieniowe rurociągi przesyłowe.
EN
Steels applied for construction of oil and gas pipelines have been analysed; examples of X70 and X80 steel pipelines have been given. It has been described mechanical properties and weldability of X70 and X80 steel as well as principles of quality inspection of pipelines performed at the building site. On the grounds of the literature survey and the author's own experience it has been presented both shortcomings and advantages of application of advanced high-yield- strength steels, for instance X80 steel, for construction of high-pressure pipelines.
9
Study of the hot forming conditions of HSLA steel on the tensile testing machine
Kozelsky P., Melecky J., Schindler I., Cagala M.
Hutnik, Wiadomości Hutnicze
|
2008
|
Vol. 75, nr 8
486-488
EN
The aim of the conducted experimental work was to study the deformation behaviour in the hot state and causes that lead to failure of compactness of a microalloyed steel determined for the tube production. The results of the formability testing are presented, performed by measurements of the strength and plastic properties by means of the tensile test performed at the forming temperatures and displacement speed of the cross beam in the range of 6 to 300 mm/min. It was shown that in the case of this material it is not essentially possible to avoid a defect formation after its cooling by a change of the forming speed.
PL
Celem przeprowadzonego eksperymentu było zbadanie technologicznej plastyczności stali HSLA w warunkach przeróbki plastycznej na gorąco, jak również przyczyn pękania stali mikroskopowych stosowanych do produkcji rur. Zaprezentowano zależność wytrzymałości i właściwości plastycznych badanej stali od warunków odkształcania. Próby rozciągania prowadzono dla temperatur z zakresu przeróbki plastycznej na gorąco tej stali z prędkością w zakresie od 6 do 300 mm/min. Wykazano, że w przypadku badanej stali zmiana prędkości kształtowania nie wpływa w istotny sposób na możliwość uniknięcia defektów po operacji chłodzenia.
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