Elaboration of forging conditions on the basis of the precipitation analysis of MX-type phases in microalloyed steels

Opiela, M.; Grajcar, A.

doi:10.1016/j.acme.2012.06.013

Cited by 21 publications

(22 citation statements)

References 14 publications

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“…RESULTS AND DISCUSSION Figure 1 shows the relationship of average austenite grain size with reheating temperature in the range of 1173-1523 K. As can been seen, the mean austenite grain size increases gradually between 1173 and 1473 K and ranges from 6.5 mm at 1173 K to 43 mm at 1473 K. There is a parabolic relationship between austenite grain size and austenitizing temperature, which is typical for MA steels [14,19,20]. This fine-grained microstructure is most probably a result of the presence of significant fraction of N-rich V(C,N) particles, which could effectively inhibit the growth of austenite grains.…”

Section: Methodsmentioning

confidence: 85%

Enhancing the Mechanical Properties of Vanadium-Microalloyed Medium-Carbon Steel by Optimizing Post-Forging Cooling Conditions

Wang¹,

Zhang²,

Shao³

et al. 2015

Materials and Manufacturing Processes

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The effects of different cooling conditions after forging on the microstructural characteristics and mechanical properties of a kind of high-content V-microalloyed medium-carbon steel 37MnSiVS were investigated. The effects were studied by using optical microscopy, transmission electron microscopy and tensile tests. Increasing direct cooling rate after forging is found to increase strength while slightly decrease ductility. A significant increase of strength could be obtained after forced air cooling and then short time isothermal holding at 873 K, while strength decreases gradually with further increasing holding time. The variations of microstructural characteristics especially V(C,N) precipitation strengthening effects with cooling conditions are mainly responsible for these variations of tensile properties. For the investigated high V-containing MA steel, a direct cooling strategy after finish forging is proposed, which includes accelerated cooling with forced air in ferrite range, following by short time isothermal holding or very slow cooling at around 873 K and then air cooling.

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Section: Methodsmentioning

confidence: 85%

Enhancing the Mechanical Properties of Vanadium-Microalloyed Medium-Carbon Steel by Optimizing Post-Forging Cooling Conditions

Wang¹,

Zhang²,

Shao³

et al. 2015

Materials and Manufacturing Processes

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“…The TiC precipitation occurs in the temperature range from 1150°C to 1200°C. It was shown in 1,4,14,17,18 that the MX-type phases show mutual solubility. Hence, the austenite grain growth in steel A should be controlled with complex (Ti, V)(C, N) carbonitrides.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamic analysis of the precipitation of carbonitrides in microalloyed steels

Opiela¹

2015

Mater. Tehnol.

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The production of mass-products of microalloyed steels with a high strength requires a proper adjustment of the thermomechanical processing and the kinetics of the precipitation of the MX-type (M -microalloying element, X -metalloid) phases in austenite. The understanding of the effect of carbonitrides on the processes of hot-working and cooling from the finishing deformation temperature requires the knowledge of the mechanism of their formation and their stability in austenite. The research was carried out on newly manufactured Ti-V and Ti-Nb-V steels for forged machine parts with thermomechanical processing. The analysis of the precipitation of the carbonitrides with the stoichiometric compositions of TixV1-xCyN1-y and TixNbvV1-x-vCyN1-y was based on the Hillert-Staffanson model improved by Adrian. The effect of the austenitizing temperature in the range from 900°C to 1200°C on the grain size of the original austenite was investigated to verify the results of the calculation. The result provides the basis for a suitable design of the manufacturing process of the thermomechanical treatment to obtain high-strength forged elements of microalloyed steels. Keywords: microalloyed steels, MX-type phases, thermomechanical processing Proizvodnja masovnih izdelkov iz mikrolegiranih jekel z visoko trdnostjo zahteva pravilno prilagoditev termomehanske predelave in kinetike izlo~anja faze MX (M -mikrolegirni element, X -metaloid) v avstenitu. Razumevanje vpliva karbonitridov na procese vro~e predelave in ohlajanja iz temperature kon~ne deformacije zahteva poznanje mehanizma njihovega nastanka in stabilnosti v avstenitu. Raziskava je bila izvr{ena na novo izdelanih jeklih za odkovke Ti-V in Ti-Nb-V po postopku termomehanske obdelave. Analiza izlo~anja karbonitridov s stehiometri~no sestavo TixV1-xCyN1-y in TixNbvV1-x-vCyN1-y temelji na Hillertovem in Staffansonovem modelu, ki ga je izbolj{al Adrian. Preiskovan je bil vpliv temperature avstenitizacije v obmo~ju 900°C do 1200°C na prvotno velikost avstenitnih zrn, da bi preverili rezultate izra~unov. Rezultati omogo~ajo pridobitev osnove za pravilno na~rtovanje postopka izdelave s termomehansko obdelavo odkovkov z veliko trdnostjo iz mikrolegiranih jekel.

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“…For the energy savings reasons attempts are made to utilize heat attained in the metal after deformation, utilizing direct cooling from deformation-end temperature as a cost-effective alternative to traditional water or oil quenching and subsequent tempering, which sometimes can also be replaced. The required combination of static tensile strength and impact strength properties, superior to those typically provided for these steels after QT treatment, are to be obtained here with TMP employing controlled cooling directly after forging, taking advantage of synergic combination of several strengthening mechanisms, such as austenite grain refinement, austenite transformation and producing fine precipitates, mostly carbides and carbonitrides, on subsequent cooling to control its products fractions and morphology [5,6,7,8]. Assumed energy savings are associated with eradication reheating prior to normalization and quenching as well as the use of blast air instead of cooling media and facilities associated which call for costly installations [9].…”

Section: Introductionmentioning

confidence: 99%

Design of Controlled Processing Conditions for Drop Forgings Made of Microalloy Steel Grades for Mining Industry

Skubisz¹,

Żak²,

Burdek³

et al. 2015

Archives of Metallurgy and Materials

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Effect of plastic processing and controlled cooling on microstructure and mechanical properties of experimental steel grades with microalloyed with Ti, V and/or Nb, varying in the content of Mo is presented as an offer for mining industry for replacement traditionally heat-treatable hardenability grades. The goal of the work is producing microstructure condition, which after controlled hot forging and direct heat treatment, involving quenching and self-tempering, are meant to provide good combination of mechanical properties, such as TYS 800 MPa, UTS 1050 MPa, elongation to fracture at least A5 15% and/or impact strength at room temperature KCV 60 J/cm 2 . Hardenability assessment and dilatometric examination allowed formulation of direct heat treatment guidelines, taking into consideration fields of temperature and strain in a typical hot forging process, estimated numerically, with the use of plastometric tests results, as well as the use of unique cooling cycles after forging.On the basis of numerical analysis of thermomechanical parameters and temperature progression, hot forging and direct cooling conditions were selected to achieve assumed structural components, morphology and dispersion of both grain and precipitates. For established heat transfer model and experimentally plotted cooling curves numerical analysis of direct cooling, enabled by definition of characteristic points of austenite transformation and CCT diagrams was conducted. The modeling aided with dilatometric characterization enabled prediction of transformation products distribution. The formulated conclusions were verified in the experimental sampling of forging, evaluating the applicability of designed combinations of chemical composition and cooling cycle for selected forged part for mining industry.Keywords: microalloyed steel, thermomechanical processing, direct cooling, hammer forging, grain control Przedstawiono badania wpływu warunków odkształcania na gorąco i kontrolowanego chłodzenia na efektywność umocnienia eksperymentalnych stali z mikrododatkami Nb, Ti oraz V o zmiennej zawartości Mo. Pierwszym etapem pracy było zaprojektowanie składów chemicznych stali mikrostopowych, które po kontrolowanym kuciu na gorąco oraz obróbce cieplnej, polegającej na zahartowaniu i samoodpuszczeniu odkuwki bezpośrednio po kuciu, pozwolą na uzyskanie właściwości mechanicznych, tj.: granicy plastyczności 800 MPa, wytrzymałości na rozciąganie 1050 MPa, wydłużeniu A 5 15% i udarności w temperaturze otoczenia KCV 60 J/cm 2 . W oparciu o wyniki badań hartowności i analizę dylatometryczną opracowano wytyczne bezpośredniej obróbki cieplnej, uwzględniając obliczenia równowagi faz i wpływ temperatury na udział wydzieleń w wybranych wytopach oraz wyznaczone numerycznie pola temperatur dla typowego procesu kucia na gorąco, oparte o próby plastometryczne na symulatorze Gleeble 3800, oraz kontrolowane chłodzenie po kuciu.W oparciu numeryczną analizę parametrów termo-mechanicznych i zmian temperatury odkuwki modelowej dobrano warunki procesu kształtowania oraz sch...

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Elaboration of forging conditions on the basis of the precipitation analysis of MX-type phases in microalloyed steels

Cited by 21 publications

References 14 publications

Enhancing the Mechanical Properties of Vanadium-Microalloyed Medium-Carbon Steel by Optimizing Post-Forging Cooling Conditions

Enhancing the Mechanical Properties of Vanadium-Microalloyed Medium-Carbon Steel by Optimizing Post-Forging Cooling Conditions

Thermodynamic analysis of the precipitation of carbonitrides in microalloyed steels

Design of Controlled Processing Conditions for Drop Forgings Made of Microalloy Steel Grades for Mining Industry

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