Single-pass Reduction Research Articles

Reducing Mechanical Anisotropy in Dual-Phase Mg-9Li-1Zn Alloy by Control of Single-Pass Reduction during Asymmetric Rolling

Reducing Mechanical Anisotropy in Dual-Phase Mg-9Li-1Zn Alloy by Control of Single-Pass Reduction during Asymmetric Rolling

On-line heating rolling behavior of Mg9999 sheets under large single pass reduction

Pure magnesium foil has a great potential for rechargeable magnesium battery anode application, the formation of edge crack and break during Mg sheet rolling highly decreases the yield and thus increase the cost. In this paper, pure magnesium sheets of different thicknesses (0.3 mm, 0.4 mm, 0.5 mm and 0.6 mm) were prepared from 1 mm pure magnesium sheets by on-line heating rolling in a single pass. The edge cracking and breaking behavior of pure magnesium sheets were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscatter diffractometer (EBSD), energy dispersive spectroscopy (EDS) and laser scanning confocal fluorescence microscope (LSCM). The results show that the number of edge cracks of pure magnesium sheets increases with the increase of rolling reduction. As the rolling reduction increases to 70%, due to the severe edge crack of 0.3 mm thick sheet and the formation of grooves on the magnesium sheet surface, the breaking of pure magnesium sheets occurs. The mechanism of edge cracking and breaking of ultra-thin pure magnesium rolled sheet is discussed.

The twins of α2 phase in β-solidifying TiAl alloy during high strain rate rolling

High strain rate rolling (HSRR) was successfully used to produce TiAl alloy sheets at average strain rate of 7.23 s−1. In present study, β-solidifying Ti-42Al-9V alloys were rolled with a single pass reduction of 80 % within (α + γ) double phase region at 1250 °C. The microstructure of the Ti-42Al-9V alloy sheet was mainly composed of fine needle-like β/γ mixture structure and the block α2 phase which was divided into different contrast by mechanical twins. As investigated, {1 1 2¯ 2}〈1 1 2¯ 3¯〉 contraction twins are the main component. And few {1 0 1¯ 2}〈1 0 1¯ 1¯〉 extension twins are generated in {1 1 2¯ 2}〈1 1 2¯ 3¯〉 primary contraction twins, namely {1 1 2¯ 2}-{1 0 1¯ 2} secondary twinning. Besides, multiple parallel twins and intersectional twins were activated.

Comparison of edge crack behavior of Mg sheets prepared by online heating rolling

Low-alloying and low-cost magnesium alloy sheets have the potential for large-scale application. Therefore, the edge cracking developed during the rolling is of great importance. In this work, Mg-1.0Mn-0.5Al (MA10), Mg–2Zn-1.5Mn (ZM21), and Mg-3.0Al-1.0Zn (AZ31) alloy sheets were rolled at 150 °C in different single-pass reductions using online heating rolling. Their edge cracking behaviors at the edge of rolled sheets after large strain rolling were investigated and compared through the scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and digital image correlation (DIC) technique. The results show that compared with ZM21 and AZ31 rolled sheets, MA10 rolled sheets exhibit the most severe edge cracking behavior after large strain rolling. This is mainly attributed to the lower recrystallization degree and ultimate compressive strength, as well as higher strain localization during the plastic deformation. Meanwhile, both coarser second phase particles at the edge and larger grain size difference also promote the initiation and propagation of edge crack in MA10 alloy rolled sheets. In addition, the small crack is developed in front of the crack tip in all of Mg alloys rolled sheets after a single-pass reduction of 75% due to the stress concentration at triple junctions caused by large rolling reduction and maximum shear stress along the plane collinear with the major crack.

Reduction effect of final-pass heavy reduction rolling on the texture development, tensile property and stretch formability of ZWK100 alloy plates

• ZWK100 alloy sheets with initial casting structures was fabricated by final-pass heavy reduction rolling (FHRR) up to 70% single reduction after single-pass rough rolling, and subsequent annealing causes a symmetrical ‘oblique-line split’ texture instead of the traditional ‘TD split’ texture. • The high rollability for 70% reduction was ascribed to the significant activity of the prismatic 〈 a〉 slip facilitated by the off-basal textures formed after rough rolling • The ‘oblique-line split’ texture was correlated with the preferred growth of grains with [ 1 ¯ 2 1 ¯ 1 ] - [ 1 ¯ 2 1 ¯ 2 ] //RD during annealing. • The FHRR-annealed ZWK100 sheets reveal quasi-planar isotropy in mechanical properties ( Δr 2 ∼0.1), large uniform-elongation of ∼35% and excellent stretch formability of 8.1. Obviously planar anisotropy due to ‘TD split’ orthotropic texture (TD indicates Transverse direction) always exist in the Rare-earth (RE) or Ca containing Mg alloy sheets, which is likely caused by the low-reduction rolling (and annealing) as revealed in our previous research. In this work, the as-cast billets of a ZWK100 alloy were subjected to final-pass heavy reduction rolling (FHRR) at 500 °C with different reductions (30%-70%) after rough rolling, aiming to investigate the reduction effect on the microstructure and texture formation. The results show that FHRR with higher reductions above 50% is in favor of shear banding formation but has little effect on the as-deformed texture components, and the excellent formability with single-pass reduction up to 70% is mainly ascribed to the activation of prismatic 〈 a〉 slip. FHRR with reduction above 50% and annealing can generate uniform grain structures of ∼10 μm and symmetrical ‘oblique-line split’ texture in (0001) pole figures, with basal poles tilting by about 50° from ND (Normal direction) towards some oblique-line of TD and RD (Rolling direction) as well as uniform distribution of counter lines as an annular shape, resulting in excellent elongation to failure of ∼50% and ultra-low planar anisotropy Δ r 2 of ∼0.1 and high stretch formability (Erichsen value: 8.1). The formation ‘oblique-line split’ texture in (0001) pole figures is mainly correlated with the preferred growth tendency of grains with [ 21 1 ¯ 1 ] - [ 12 1 ¯ 2 ] //RD, which was suggested to relate to the high mobility of some special boundaries such as 40°-45° [ 10 1 ¯ 0 ] (∑14). The influences of starting textures on the mechanical properties, planar anisotropy and related deformation modes, as well as their correlations with the stretch formability were comparatively investigated with the ‘TD split’ orthotropic texture as a counterpoint.

A novel method for preparing Al/Mg/Al laminated composite material, processing maps and interface diffusion analysis

A novel method of “fully covered + friction stir welding + accumulative roll bonding” was developed to prepare an Al/Mg/Al laminated composite material (LCM). This work presents a rolling simulation of an Al/Mg/Al LCM using the DEFORM software and processing maps to show the hot rolling mechanism. The single pass reduction should be set at approximately 3–4 mm by finite element simulation. The edge damage value of the core Mg alloy plate in the Al/Mg/Al LCM decreased with the increasing hot rolling temperatures. The optimum process parameters were obtained by processing maps for deformation temperatures from 250 °C to 300 °C and 350–400 °C in the strain rate range of 0.01 s−1 to 0.1 s−1. The hot rolling temperature for the 11.5 mm-thick Al/Mg/Al LCM should be controlled at 400 °C, and the single pass processing rate should be selected in the range of 20–40%. With each increase in heat treatment temperature and time, the compound gradually increased, and the thickness of the transition layer gradually increased at the Mg/Al interface. The growth kinetic model formulas of the interface layer for the 1060/AZ31/1060 LCM under different rolling strain fields were obtained, which could have been predicted by the interface layer thickness at different rolling reduction rates and heat treatments.

Theoretical and experimental study on the producible rolling thickness in ultra-thin strip rolling

Abstract The cold rolling process of a thin strip is difficult to continue when the strip has been thinned to a certain thickness. A limit thickness, which is referred to as the limiting producible rolling thickness below which plastic deformation does not occur, exists even if the rolling force and the number of rolling passes are increased. The Stone formula is the most common approach for predicting this limit, but its results are inaccurate in experiments or in ultra-thin strip-rolling production. In this study, the variation laws of the contact profile and rolling pressure of ultra-thin strips with different thickness specifications at different reductions were obtained by finite element simulations, indicating that the Stone minimum thickness can be regarded as the critical thickness that exists when a neutral zone is present under a minimal reduction. A theoretical calculation model of producible rolling thickness for an ultra-thin strip based on Fleck theory was established and verified by experiments. When this model is used, the single-pass reduction can be obtained in accordance with the given unit width rolling force, the technical parameters of the rolling mill, the yield strength of the material, and the initial thickness of the strip. The formula for the conditional limiting producible thickness considering the restriction of rolling force was corrected. The relationship between single-pass reduction and the ratio of the initial thickness of the strip to the theoretical limiting producible thickness under the condition of the maximum allowable rolling force of the rolling mill was discussed. This study provides theoretical guidance for practical production by defining the product specification ranges and rolling regulations for existing rolling mills and determining the roller diameters and force and energy parameters for the design of rolling mills.

Microstructure and properties of Mg–Al–Mn magnesium alloy under shear deformation coupled tension rolling

Shear coupling tension rolling is based on equal diameter angle rolling, which meets the requirements of modern industrial development with high production efficiency and short process. It is of great significance to improve the defects of uneven texture distribution and insufficient grain refinement in continuous casting billet rolling process. In this study, the effects of different reduction rate, circular arc radius and tensile angle of shearing roll on the stress and strain of sheet metal were studied by means of high precision constitutive model and rigid plastic finite element analysis software. At the same time, the effects of different process parameters on the microstructure and mechanical properties of rolled magnesium plate were analyzed. The results show that the larger the single pass reduction rate is, the smaller the arc radius of the shear roll is and the smaller the tensile angle is, the greater the equivalent strain and equivalent stress at the corner are. The higher the reduction rate is, the greater the tensile strength and yield strength are and the smaller the extension is. The smaller the arc radius and tensile angle of the shear roll are, the greater the tensile strength and extension are, the smaller the yield strength is, and the easier it is to form dynamic recrystallization.

Effect of Reheating and Deformation Processes on DWTT Performance for Heavy Gauge Pipeline Steel

DWTT (Drop weigh tear test) is an effective way to evaluate the fracture propagation for pipeline steel. The effects of slab reheating temperature, soaking time, single pass reduction ratio during recrystallization zone rolling and transfer bar ratio during non-recrystallization zone rolling on DWTT performance were studied for heavy gauge pipeline steel. And the grain refinement and toughening mechanism were discussed. It was found that the grain in the core of the plate can be refined by reducing the reheating temperature, increasing the single pass reduction ratio during recrystallization zone rolling and setting suitable transfer bar ratio during non-recrystallization zone rolling, which promote the DWTT property improvement for heavy gauge pipeline steel. The 30.9mm heavy gauge pipeline steel plate was industrial produced and the X70 UOE welded pipe with dimension in Φ1219×30.9mm was manufactured. The DWTT 85%FATT (fracture appearance transition temperature) of pipe body is as low as -20°C.

Improving single pass reduction during cold rolling by controlling initial texture of AZ31 magnesium alloy sheet

Abstract The AZ31 magnesium alloy sheets obtained by multi-pass hot rolling were applied to cold rolling and the maximum single pass cold rolling reduction prior to failure of AZ31 magnesium alloy was enhanced to 41%. Larger single pass rolling reduction led to weaker texture during the multi-pass hot rolling procedure. The sheet obtained showed weak basal texture, while the value was only 1/3–1/2 that of general as-rolled AZ31 Mg alloy sheets. It was beneficial for the enhancement of further cold rolling formability despite of the coarser grain size. The deformation mechanism for the formation of texture in AZ31 magnesium alloy sheet was also analyzed in detail.

Cyclic-deformation system for the reduction of continuous-cast slabs

Introducing systems capable of profound reduction in a casting and rolling module improves the product quality, on account of the intense working of large continuous-cast slabs over the whole cross section and the production of uniform fine-grain structure of the metal, and also increases the cross section of continuous- cast billet. Analysis of the formation of nonmetallic inclusions and segregation in the axial zone of the thick rolled sheet is followed by analysis of the nonuniform deformation over the slag height in the reduction of large continuous-cast slabs at the 5000 mill at OAO Magnitogorskii Metallurgicheskii Kombinat. The structure of a cyclic-deformation system for preliminary deformation of large continuous-cast slabs is described, and its capabilities are explored. Hammers for preliminary deformation of large continuous-cast slabs are considered. Experimental data are presented for the deformation of continuous-cast steel 45 and 12Kh18N10T steel billet. The structure of the continuous-cast billet is assessed in the course of reduction on the cyclic-deformation system. The basic parameters of the system for preliminary deformation of large continuous- cast slabs are determined. The capabilities of the cyclic-deformation system are outlined in terms of increase in sheet quality. On that basis, the use of the cyclic-deformation system in the continuous-casting line for preliminary reduction of large continuous-cast slabs is recommended: it permits matching of the speed of continuous-casting and cyclic-deformation processes; and ensures 45–90% reduction in a single pass so as to obtain well-worked cast structure over the whole slab cross section. When using the cyclic-deformation system in the continuous-casting line, the continuous-cast slabs are reduced by means of the heat of the cast metal, thereby greatly reducing the energy consumption in billet production. The cyclic-deformation system may be used with thick-sheet and broad-strip mills for preliminary single-pass reduction of the hot slab, with improvement in sheet quality and reduction in the number of passes in the mills.

Supplemental treatment of air in airborne infection isolation rooms using high-throughput in-room air decontamination units

Evidence has recently emerged indicating that in addition to large airborne droplets, fine aerosol particles can be an important mode of influenza transmission that may have been hitherto underestimated. Furthermore, recent performance studies evaluating airborne infection isolation (AII) rooms designed to house infectious patients have revealed major discrepancies between what is prescribed and what is actually measured. We conducted an experimental study to investigate the use of high-throughput in-room air decontamination units for supplemental protection against airborne contamination in areas that host infectious patients. The study included both intrinsic performance tests of the air-decontamination unit against biological aerosols of particular epidemiologic interest and field tests in a hospital AII room under different ventilation scenarios. The unit tested efficiently eradicated airborne H5N2 influenza and Mycobacterium bovis (a 4- to 5-log single-pass reduction) and, when implemented with a room extractor, reduced the peak contamination levels by a factor of 5, with decontamination rates at least 33% faster than those achieved with the extractor alone. High-throughput in-room air treatment units can provide supplemental control of airborne pathogen levels in patient isolation rooms.

Effects of hot deformation and accelerated cooling on microstructural evolution of low carbon microalloyed steels

Using a Gleeble 1500 hot simulator, the effects of hot deformation parameters and accelerated cooling conditions on the microstructural characteristics of low carbon microalloyed steels were investigated by means of compression tests. It was found that the grain refinement effect of single pass reduction in the recrystallisation or unrecrystallisation temperature ranges is weaker than that of two pass reduction in the recrystallisation and unrecrystallisation temperature ranges. However, four pass deformation in the recrystallisation and unrecrystallisation temperature ranges could result in rather fine grained microstructures and, when coupled with moderately high cooling rate, partially acicular ferrite microstructure could be obtained. With the increase of cooling rate, the microstructure becomes finer and the content of acicular ferrite increases. Under similar deformation and cooling conditions, the specimens with relatively high carbon content have more refined microstructures.

A new method of urea removal using urease and expanded polytetrafluoroethylene membrane.

A new method for urea removal using a gas membrane is introduced along with some preliminary results. The membrane used was expanded polytetrafluoroethylene (E-PTFE) which is highly permeable to gaseous substances, while at the same time it is highly resistant to water permeation. In in vitro experiments using 10 mmol/L ammonia solution it was revealed that the single-pass reduction rate was approximately 95% at 30 degrees C at a flow rate of 200 ml/min. In animal experiments using four dogs, the extraction rate of urea was 40.4 +/- 4.4% after four hours of dialysis using 5 L dialysate. However, elevation of blood ammonia was observed in all dogs tested. Removal of ammonia by means of a gas membrane is considered to be feasible and has the possibility of being used for maintenance hemodialysis in combination with urease and charcoal.