고온 비대칭압연이 알루미늄 합금의 미세조직과 성형성에 미치는 영향

정무섭,이종범,한준현,Jeong, Museob,Lee, Jongbeom,Han, Jun Hyun 한국재료학회 2019 한국재료학회지 Vol.29 No.10

In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, $200^{\circ}C$, $350^{\circ}C$, and $500^{\circ}C$, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (${\varepsilon}_{eq}$) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at $500^{\circ}C$. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (${\bar{r}}$) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (${\Delta}r$) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.

공형압연에서 롤의 비대칭 배치로 인한 소재단면형상의 변화

김성기,이동윤,이석의,정원태,남규한,나두현,이영석 대한기계학회 2024 大韓機械學會論文集A Vol.48 No.5

공형압연에서 롤을 지지하는 부품의 강성부족으로 발생한 롤의 비대칭 배치로 인해 압연된 소재의 FSP(free surface profile)가 대칭이 되지 않는다. 본 연구는 이런 점을 역이용하여 롤의 비대칭 배치가 압연된 소재단면의 FSP에 미치는 영향을 분석하였다. 롤의 비대칭 배치는 상/하부 롤이 수평방향으로 서로 어긋나 약간 평행 이동한 경우, 상/하부 롤의 좌/우측 롤 갭이 다른 경우 그리고 상/하부 롤이 압연방향으로 상반되게 약간 회전한 경우이다. 상기 세 가지 비대칭 압연조건에서 3종류의 티타늄 소재(Ti-Gr.4, Gr.19, Gr.23)를 압연하였다. 같은 압연조건에서 FE 해석을 수행하였고, 계산과 측정결과를 비교 분석하였다. 결과적으로 상기에서 언급된 3가지 비대칭 압연조건 중에서 상/하부 롤이 압연방향으로 상반되게 약간 회전한 경우가 FSP 변화에 가장 큰 영향을 주었다. In groove (or caliber) rolling, the free surface profile (FSP) of the rolled material is not symmetrical owing to the asymmetric arrangement of rolls caused by the insufficient stiffness of the components supporting the roll. This study utilizes this aspect to analyze the effect of the asymmetric arrangement of rolls on the FSP of materials departing from the rolls. The asymmetric arrangement of rolls is reflected in cases where the upper/lower rolls propagate parallel to the horizontal direction (x-direction), the left/right roll gaps of the upper/lower rolls are different, and the upper/lower rolls rotate in opposite directions along the rolling direction. Titanium of three grades (Ti-Gr.4, Gr.19, and Gr.23) are rolled under the abovementioned three asymmetric rolling conditions. We perform three-dimensional finite-element analysis under the asymmetric rolling conditions mentioned above and compare the predictions with the measurements. The results show that among the three asymmetric rolling conditions, the case where the upper/lower rolls rotate in opposite directions along the rolling direction exerts the most significant effect on variations in the FSP.

Effect of Asymmetric Hot Rolling on the Texture Evolution of Fe–3%Si Steel

Tae‑Wook Na,Hyung‑Ki Park,박창수,Hyung‑Don Joo,Jong‑Tae Park,Heung Nam Han,Nong‑Moon Hwang 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

In Fe–3%Si steel, the hot rolling process affects not only the hot rolling texture but also the primary recrystallization texture. Here, the effect of asymmetric hot rolling was studied by comparing the difference in the texture evolved between asymmetricand symmetric hot rolling. The effect of asymmetric hot rolling on the texture of primary recrystallized Fe–3%Si steel wasalso studied. The symmetric hot rolling of Fe–3%Si steel produces a rotated cube texture at the center but Goss and coppertextures near the surface. Asymmetric hot rolling tends to produce Goss and copper textures even at the center like thetexture near the surface. After primary recrystallization, the dominant texture at the center changes from {001} <210> to{111} <112> and the new texture has a higher fraction of the grains which make the low energy boundary with Goss grainsthan that of symmetric hot rolling.

Al-Mg-Si 합금의 초기 석출물이 비대칭 압연에 의한 전단변형에 미치는 영향 : 집합조직과 성형성

채원기,김봉규,이종범,한준현 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.10

Al-Mg-Si alloy was rolled asymmetrically at several temperatures to apply shear deformation, and the effects of the initial precipitate on shear deformation, texture evolution, formability, and plastic anisotropy were studied. Texture was analyzed using a EBSD, and the formability and plastic anisotropy of the specimen were evaluated using the value and value calculated from the plastic strain ratio (r-value) which was determined from the change in the length of the specimen during tensile deformation. Asymmetric rolling induces a larger equivalent strain than symmetric rolling, and the equivalent strain increases as the asymmetric rolling temperature increases. When a specimen with peak-aged initial precipitates was asymmetrically rolled, less shear deformation occurred at room temperature than in a solution-treated specimen without initial precipitates. In contrast, a larger shear deformation occurred at high temperatures (500°C). With asymmetric rolling at room temperature, the specimens without initial precipitates had higher formability and lower plasticity, while for asymmetric rolling at high temperature, the specimens with initial precipitates had higher formability and lower plastic anisotropy. This is due to the <111>//ND texture, such as {111}<110> and {111}<112> orientation that has similar and high r-values at 0°, 45°, and 90° to the rolling direction, developed by the shear deformation that occurred during asymmetric rolling.

Asymmetric and symmetric rolling of magnesium: Evolution of microstructure, texture and mechanical properties

Biswas, S.,Kim, D.I.,Suwas, S. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.550 No.-

In the present study, asymmetric rolling was carried out for incorporating a shear component during the rolling at different temperatures, and was compared with conventional (symmetric) rolling. The microstructures were investigated using electron back-scatter diffraction (EBSD). The strain incorporated was compared with the help of grain orientation spread (GOS). GOS was eventually used as a criterion to partition the microstructure for separating the deformed and the dynamically recrystallized (DRX) grains. The texture of the partitioned DRX grains was shifted by ~30<SUP>o</SUP> along the c-axis from the deformed grains. The mechanism of dynamic recrystallization (DRX) has been identified as continuous dynamic recovery and recrystallization (CDRR). The partitioned deformed grains for the higher temperature rolled specimens exhibited a texture similar to the room temperature rolled specimen. The asymmetric rolling introduces a shear component which shifts the texture fibre by ~5-10<SUP>o</SUP> from the conventional rolling texture. This led to an increase in ductility with little compromise on strength.

후판 압연공정에서 상 · 하 비대칭 변형거동의 수치적 · 실험적 예측 및 설정모델에 관한 연구

변상민(Sang-Min Byon),이영석(Young-Seog Lee),전언찬(Eon-Chan Jun) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.2

The thick plate produced by rolling process is used as the basic members of a ship structure. In this paper, we present a setup model to control the asymmetric factors causing plate bending in the upper or lower direction during rolling. A series of finite element analysis are conducted to predict the relationship between various asymmetric factors and plate bending. The setup model is developed by regressing the relationship to the linear equations with several non-dimensional parameters. The setup model is verified by a pilot rolling test and applied to actual rolling conditions. Results show that the model is substantial to predict the asymmetric deformation in the plate rolling process.

Effect of Asymmetric Rolling on the Microstructure, Mechanical Properties and Texture Evolution of Mg–8Li–3Al–1Y Alloy

Xiao Zhou,Ruirui Liu,Qiang Liu,Haitao Zhou 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5

Asymmetric rolling was applied to dual phase Mg–8Li–3Al–1Y alloy with different speed ratio and rolling reduction. Withincreasing reduction at the same speed ratio the population of β-Li grains decreased with a feature of fibered grains alongthe rolling direction. As for different speed ratio under the same reduction, β-Li grains kept equiaxed, but α-Mg phase wasfirst elongated and fibered and then transited to equiaxed small grains. The enhanced yield strength and tensile strengthwere achieved with the increase of rolling reduction and speed ratio. In particular, when speed ratio reached to 1:1.3 underthe same rolling reduction (30%), the optimal mechanical properties were obtained. As for texture evolution, we found thebasal texture was obviously weakened and some new weak texture was formed after asymmetric rolling. Interestingly, it wasnoted that the texture on the side of slow roll is distinct from that on the side of the fast roll due to the different rolling speed.

비대칭 압연과 시효 시퀀스가 Al-Zn-Mg-Cu합금의 미세조직과 기계적 특성에 미치는 영향

정민경,이종범,김수현,한준현 한국열처리공학회 2023 熱處理工學會誌 Vol.36 No.5

The effects of aging treatment sequence, specifically pre-aging and post-aging, on the microstructure and mechanical properties of Al-Zn-Mg-Cu aluminum alloys has been studied in comparison to symmetrically rolled specimens. In symmetrically rolled specimens, a straight-band precipitation distribution was observed, whereas asymmetrically rolled specimens exhibited a curved-band microstructure of fine precipitates. Notably, the asymmetrically rolled specimens displayed higher strengths. In the case of post-aging, the aging process occurred after rolling, and the dislocations generated during rolling acted as nucleation sites for precipitates during aging. This resulted in the formation of fine precipitates, contributing to improved mechanical properties compared to symmetric rolling. To enhance strength of the Al-Zn-Mg-Cu aluminum alloys, asymmetric rolling proves to be more effective than symmetric rolling, with post-aging showing greater efficacy than pre-aging.

Texture and microstructure evolution during the symmetric and asymmetric rolling of AZ31B magnesium alloys

Cho, J.-H.,Jeong, S.S.,Kim, H.-W.,Kang, S.-B. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.566 No.-

Differential speed warm-rolling (DSR) of AZ31B magnesium alloys was carried out, and the microstructure and tensile properties were systematically investigated at various working temperatures and reduction in area. Conventional rolling followed by DSR as a finishing pass revealed low basal intensity and effectively enhanced the mechanical properties. Asymmetric rolling resulted in lower basal intensity compared to symmetric rolling. The intensity of the basal texture decreased with an increase in the rolling temperature. During warm-rolling, fine and equiaxed grains created by dynamic recrystallization were observed. A shear band which formed during warm-rolling contained many twins and displayed an off-basal texture, with the overall grain size in this region smaller than that of other regions. The off-basal texturing and a fine grain size contributed to enhanced elongation. The double twinning strongly hindered the elongation of the AZ31B sheets.

A Simple Modeling of Asymmetric Rolling

A. Halloumi,Ch. Desrayaud,F. Montheillet 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Two complementary analytical approaches and the finite difference method are proposed for modeling asymmetric rolling (ASR) of metal sheet. The first analytical model is an upper bound method based on a uniform strain field depending on one single optimization parameter, viz. the entry velocity of the sheet. Its results can be straightforwardly used for practical applications. The second model uses a more refined analytical velocity field based on the classical parabolic estimation of the material flow lines in rolling. It involves an additional optimization parameter associated with the precise form of the velocity field. Local values of strain, strain rate and self-heating temperature are easily calculated, as well as the rolling force. Finally, the finite difference method is applied to compute heat transfers between the rolls and the sheet. In conclusion, the respective advantages of the three methods are discussed.