Skin-pass Rolling Research Articles

Research on the Flatness Control Performance and Parameter Influence Law of Four-High Skin Pass Rolling Mill

Research on the Flatness Control Performance and Parameter Influence Law of Four-High Skin Pass Rolling Mill

Abnormal Grain Refinement and Synergistic Enhancement of Strength and Plasticity of High-Purity Nickel via Cycle Skin-Pass Rolling Deformation

Abnormal Grain Refinement and Synergistic Enhancement of Strength and Plasticity of High-Purity Nickel via Cycle Skin-Pass Rolling Deformation

Experimental investigation of the effect of skin-pass rolling reduction ratio on corrosion behaviors of AISI 304 stainless steel sheet materials

This study was carried out in order to reveal the effect of reduction ratio, one of the parameters of the skin-pass rolling manufacturing process of sheet metal materials, on the corrosion behaviours. In this experimental study, AISI 304 stainless steel sheet material samples were subjected to skin-pass rolling process with different reduction ratios (0.5%, 2.0%, 4.2% and 7.2%). The corrosion behaviours of skin-pass rolled AISI 304 stainless steel sheet material samples in 3.5% chloride solution was determined by potentiodynamic polarization curves. The changes in the surfaces were evaluated together with the surface roughness measurements and microstructure images. It was concluded that the increase in skin-pass rolling reduction ratio increased the corrosion resistance. The arithmetic mean roughness (Ra) did not give sufficient results to prove the finding that corrosion resistance improves as the reduction increases. The change of valleys and peaks in the roughness profile of the skin-pass rolled samples before and after corrosion was found to be evidence that the increase in reduction ratio improves corrosion resistance. As the skin-pass rolling reduction ratio increased was determined in the microstructural images that the amount of oxide layer increased and this situation was clarified from x-ray spectroscopy (EDS) findings. Electrochemical measurements, surface roughness profiles, microstructure images, and EDS analyses were obtained with results that support each other.

Diffusion Behavior of Al in Zn Coating Layer of Zn-0.2mass%Al Hot-dip Galvanized Steel Sheets with and without Temper Rolling during Aging after Production

It is known that Al added to the Zn coating layer of hot-dip galvanized steel sheets (GI) diffuses to the surface at room temperature and forms Al-based oxides in air. In order to understand the diffusion behavior of Al in Zn coating layer, this study investigated the effect of the aging temperature on the segregation behavior of Al-based oxides in GI with and without temper rolling (skinpass rolling) using a material with a Zn coating weight of about 56 g/m2 with an Al content of approximately 0.20 mass%. The specimens were aged at -15, 5, 20, 38, 100 or 200 ºC in air after production, and the surface and cross sections were observed and analyzed by XRF, SEM-EDX, EBSD and TEM. As a result, up to the aging temperature of 38 ºC, the amount of Al-based oxides increased linearly to the square root of aging time, suggesting that the formation rate is determined by the diffusion of Al in Zn coating layer in this temperature range. However, this linear relationship did not hold at aging temperatures above 100 °C. In addition, in the temper-rolled GI, the formation rate of Al-based oxides is larger than that without temper rolling up to the aging temperature of 38 ºC, and then decreased drastically at aging temperatures above 100 °C. The segregation behavior of Al-based oxides is discussed in view of the diffusion behavior of Al and the changes in the macrostructure of the Zn coating layer during the aging after production.

Investigation of the Effect of Rolling Parameters in Roughness Transfer by Skin-Pass Rolling to AISI 304 Stainless Steel Sheet Materials

Sac malzemelerin yüzeyleri, boyanabilme ve şekillendirme açısından belli bir pürüzlülük profiline sahip olmalıdır. Yüzeyin pürüzlülüğünün az olması boya veya kaplamaların yapışmasını azaltabileceği gibi fazla olması boya veya kaplamanın yetersiz olması sonucunda paslanmaya neden olabilecek ayrıca boya veya kaplamanın fazla kullanılmasına sebep olarak maliyetlerin artmasına sebep olacaktır. Bu sebeplerden dolayı, sac malzeme yüzeyinin en uygun seviyede pürüzlülüğe sahip olması istenir. Sac malzemelerin yüzeylerine genellikle temper haddeleme olarak bilinen, özel pürüzlü merdanelerle pürüzlülük profili transfer edilir. Sac malzeme yüzeyine aktarılan pürüzlülük profili, haddeleme parametrelerinden etkilenir. Bu deneysel çalışmada otomotiv endüstrisinde yoğun bir şekilde kullanılan yüksek akma mukavemeti ve uzama kabiliyetine sahip olan AISI 304 paslanmaz çelik sac malzemelere temper haddeleme ile pürüzlülük transferine ezme miktarı, haddeleme hızı, merdane pürüzlülüğü, yağlama koşulları ve malzeme kalınlığının etkisi araştırılmış ve pürüzlülük dağılımı malzeme oranı eğrileri yardımıyla değerlendirilmiştir. Ezme miktarı arttıkça pürüzlülük transfer oranı arttı. Yağlayıcı kullanılan koşullar altında, merdane pürüzlülüğü, malzeme kalınlığı artışıyla birlikte pürüzlülük transfer oranı azaldı. Haddeleme hızının artışı pürüzlülük transfer oranına etkisi olmadığı sonucuna varıldı. Ayrıca düşük ezme miktarı, düşük haddeleme hızı, düşük pürüzlülüğe sahip merdane, kalın malzeme ve yağlı koşulların tercih edilmesi ile daha homojen bir pürüzlülük dağılımına ulaşılabileceği sonucuna varılmıştır.

Characterization and Modelling of Sheet Material with Graded Strength for more Accurate Finite Element Analysis

Many sheet materials do not exhibit constant properties over the sheet thickness. On the one hand, this can be caused by a rolling process with a pass reduction of 1-2%, the so-called skin pass rolling. This is mainly used for deep drawing steel grades to eliminate the pronounced yield strength of the base material. Another possibility is abrasive blasting or shot peening of sheet metal. This causes plastic deformation of the sheet surface and material strengthening. The grading can be used to locally strengthen components or locally adapt the roughness. Since many production processes today are designed numerically, the mapping of such a grading is necessary but currently not implemented in FE code. Aim of this research is, to correlate the material hardness to a plastic pre-strain with a newly developed characterization method. For this purpose, graded material properties are generated by means of abrasive blasting as an example process. The resulitng locally varying work hardening over the sheet thickness is further integrated in finite element analysis by the assignment of a starting condition of a 2d-shell element formulation. With this approach, it is possible to map the graded material properties easily in FE simulations with a very good accuracy.

Effects of granular bainite and polygonal ferrite on yield point phenomenon in API X65 line-pipe steels

Yield strength and yield-point (YP) phenomenon are regarded as crucial properties to be assured in practical applications such as line-pipe forming. In this work, the impacts of microstructural constituents on YP and yield ratio were explored in four API X65 line-pipe steel plates fabricated by altering the start or finish rolling temperature and plate thickness. The four steel plates were predominantly made up of granular bainite (GB) and polygonal ferrite (PF), along with the greater volume proportion of PF in the case of the lower start and finish rolling temperatures and the thicker plate thickness. According to the skin-pass rolling to reduce the YP elongation, the increased amount of mobile dislocations was greater in the PF than in the GB, indicating that the PF was more responsible for the YP alleviation than the GB because the more mobile dislocations were formed in the PF than in the GB. Thus, the decreasing rate of YP elongation was faster for the thicker plate and the low start or finish rolling temperature. On the other hand, the lower yield ratio was preferred for the thicker plates as they exhibited the shorter YP elongation and the higher strain-hardening rate, thereby leading to the rapid enhancement of yield strength in the YP range and consequently to the continuous increase in yield ratio. Thus, this work would be favorably utilized for designing optimal microstructural and TMCP parameters for securing the yield-strength guarantee in line-pipe steels.

Microstructural evolution in pure copper during accumulative skin pass rolling: experimental and crystal plasticity numerical investigations

Surface mechanical treatments are known to introduce deformation heterogeneity, thus entailing a combination of excellent strength and ductility in metallic metals. Accumulative skin pass rolling (ASPR) was employed to introduce heterogeneous structure in pure copper, which significantly improved yield strength and maintained high ductility. The experimental observations of the ASPR processed copper showed that surface grains possessed a much larger magnitude of misorientations and geometrically necessary dislocations (GNDs) than the centre grains. Crystal plasticity finite element modelling was utilised to provide an in-depth understanding of microstructure evolution during ASPR. It was found that the surface grains accommodated higher shear strain and had higher slip resistance than the centre grains. The multiple active slip systems in the surface grains induce the lattice rotations and then the formation of intragranular misorientations accompanied by a high density of GNDs, while the single active slip system in the centre grains can accommodate the applied material rotation without the lattice rotation.

Enhancing strength while preserving elongation: A study on copper after accumulative skin pass rolling

Current surface mechanical treatment techniques that produce gradient microstructures and return a combination of high strength and high uniform elongation are limited in terms of their industrial suitability. This study applies a modified surface rolling strategy, namely accumulative skin pass rolling (ASPR), to produce a gradient microstructure in copper and return an increase in yield strength while preserving high uniform elongation. Uniaxial tension combined with in-situ electron back-scattering diffraction compared the variations in mechanical properties and microstructure after annealing and ASPR. The increase in yield strength after ASPR is ascribed to the higher dislocation density at subgrain and grain boundaries, junctions and interiors whereas the preservation of uniform elongation is due to the gradient microstructure comprising a range of grain sizes across the sheet thickness. Finite element analysis of ASPR samples revealed strain heterogeneity along the gauge length and a transfer of load from softer grains in the sheet interior to harder grains closer to the sheet surface during tension. The results indicate that ASPR may be a promising new strategy for the continuous fabrication of sheets with gradient microstructures.

Mechanical properties and thermal stability of gradient structured Zr via cyclic skin-pass cryorolling

Gradient-structured Zr sheets were fabricated by cyclic skin-pass cryorolling and cyclic skin-pass rolling. The mechanical properties and microstructural evolution of the gradient-structured Zr after rolling and annealing were investigated. The results indicated that the cyclic skin-pass cryorolled samples exhibited higher tensile strengths (σb = 557 MPa) and slightly lower fracture elongations (εu = 17.1%) than the cyclic skin-pass rolled samples due to high dislocation storage. After annealing at 150 °C–450 °C for 1 h, high-resolution transmission electron microscopy results showed that the ultrafine-grained layer of the cyclic skin-pass cryorolled samples exhibited better thermal stability, which was attributed to the formation of nanoscale twins and incomplete recovery of dislocations.

Experimental Investigation of Roughness Transfer with Skin-Pass Rolling to High Strength Low Alloy (HSLA) Material

Experimental Investigation of Roughness Transfer with Skin-Pass Rolling to High Strength Low Alloy (HSLA) Material

How the skin-pass rolling reduction ratio affects the strain aging behaviour of low-carbon steel sheets

ABSTRACT When producing cold-rolled steel sheets, the penultimate annealing process is followed by a final skin-pass rolling (or temper rolling) whose purpose is to eliminate any discontinuous yielding which creates stretcher–strain markings when the steel sheets are formed. To find out the critical reduction ratio eliminating the discontinuous yield phenomenon, the samples were annealed at 820°C for 3 min and then subjected to the temper rolling at various thickness reductions at room temperature. Results showed that the discontinuous yield phenomenon could not be eliminated in the case of a thickness reduction less than 0.5%, that a certain reduction ratio should be exceeded to eliminate the discontinuous yielding, and that the aging time varied depending on the reduction ratio. In addition, while the low-carbon steels did not undergo strain aging in three months with a 1% thickness reduction, they underwent strain aging in at least four months with higher thickness reductions.

Effect of material thickness and reduction ratio on roughness transfer in skin-pass rolling to DC04 grade sheet materials

PurposeThe last stage of the cold rolling process is skin-pass rolling and one of its most significant goals is to obtain appropriate topography on the surface of the sheet steel used extensively such as in automotive industry. The purpose of this paper is to investigate the effect of thickness change and various reduction ratios on roughness transfer of DC04 grade sheet material.Design/methodology/approachDC04 grade sheet materials with different reduction ratios and several thicknesses were subjected to skin-pass rolling process in the rolling equipment with a two-high roll. Some roughness parameters were determined as a result of roughness measurements from the surfaces of roughened sheet materials.FindingsWhile the roughness transfer is higher in 1-mm thick material in reduction ratios up to 430 micrometers; in reduction ratios above 430 micrometers, it is higher for 1.5-mm thick materials. As the reduction ratio increases in DC04 grade sheet materials, the homogeneity of the roughness distribution in 1-mm thickness sheet material deteriorates, while the roughness distribution in 1.5-mm thickness sheet material is more homogeneous.Originality/valueThis paper demonstrates how material thickness and reduction ratio affect the roughness transfer in skin-pass rolling. The results obtained can be used by optimizing in manufacturing processes.

An Investigation into the Texture Transfer in the Process of Lubricated Skin Pass Rolling

Abstract This article investigates the surface texture transfer mechanisms in lubricated skin pass rolling of metal strips with three-dimensional rough surfaces of both regular patterns and random surface asperity distributions. Two important steps have been completed. The first is the successful establishment of an efficient numerical method for predicting the 3D texture transfer. It was identified that the new method can be used reliably with the key complex factors coupled in skin pass rolling, such as the effects of lubricant and surface roughness. The second is the exploration of the texture transfer mechanisms with the aid of this new method. In addition, the effects of hydrodynamic pressure on the texture transfer efficiency were comprehensively investigated by a dynamic explicit finite element analysis. It was found that lubrication plays a critical role in determining the surface texture transfer. The texture transfer ratio decreases with increasing the lubricant viscosity. A larger pressure coefficient brings about a lower texture transfer ratio, but a larger reduction ratio leads to a greater texture transfer.

Surface texture transfer in skin-pass rolling with the effect of roll surface wear

This paper presents a novel three-dimensional characterisation of the wear effects of a roll surface on the texture transfer in skin-pass rolling. The method integrates the interactions of the microscale elastic deformation of roll surface asperities with the microscale plastic deformation of strip surface asperities. An elasticity theory and a discrete fast Fourier transform were used to rationally predict the microscale elastic deformation of work roll in the rolling system. The microscale plastic deformation of the asperities on the soft strip surface was calculated by the material redistribution process. The Archard wear law was used to consider the wear effects with the random contact pressure, relative sliding and surface hardness. A multiscale analysis was carried out by the dynamic explicit finite element method (FEM), which fully coupled microscale surface contacts, macroscale elastic deformation of the work roll and the bulk plastic deformation of the metal strip. Due to the complexity associated with numerical simulation, a novel modularised approach was established to complete the calculation in a feasible and efficient manner. The study reveals that the roughness scale of a rolled metal strip decreases gradually due to the roll surface wear and that the rolling force, relative sliding and rolling speed at the roll-strip interface significantly affect the roll surface wear. It is expected that the method established can be used to control the surface texture transfer in skin-pass rolling under the continuous wear of roll surfaces.

Effect of the elastic deformation of rolls on the surface texture transfer in skin-pass rolling

This paper investigates the surface texture transfer with elastically deformed work rolls in skin-pass rolling. A numerical approach was developed to efficiently overcome the multiscale challenges associated with the numerical characterisations. To couple the microscale plastic deformation of strip surface asperities with the microscale elastic deformation of roll surface asperities, a specific method was first developed to generate the characteristics between normal contact pressure and interface separation. To deal with the three-dimensional deterministic rough surfaces, a material redistribution scheme was used to predict the plastic deformation of the strip surface asperities and a discrete fast Fourier transform algorithm was employed to efficiently calculate the elastic deflection of the roll surface asperities. These enabled the subsequent multiscale analysis in coupling the microscale interface contact with the macroscale deformation of the metal strip and work roll. As such, the stick/slip transition in the rolling bite due to the elastic deformation of the roll as well as the surface topography of the rolled strip have been quantified. The new method has successfully revealed the effects of elastic roll deformation, roll radius, and strip thickness/roughness on the resultant surface texture of strips in skin-pass rolling.

압하력, 장력에 따른 조질 압연에서의 소재 변형률 예측에 관한 연구

조질 압연은 소재의 잔류 응력 및 표면 평탄도 등의 제품 문제를 해결하기 위한 하나의 중요한 공정이다. 유한요소 해석을 기반으로 하는 기존의 연구들은 하나의 스탠드에서의 압연 상황만을 고려하였으며, 소재에 작용하는 장력에 의한 영향에 관하여 수행되지 않았다. 이에 본 연구에서는 2D 유한요소 모델을 통하여 압하력과 장력이 소재 압하에 어떠한 영향을 미치는지에 관한 분석을 수행하였으며, 임의의 해석 조건을 통하여 분석 결과를 검증하였다. 또한 3D 해석 모델을 통하여 소재 폭 방향에 대하여 압연 시 소재가 어떻게 변형하는지에 관한 분석을 수행하였다.

Influence of cathodic polarity during electrocleaning process on the brown stain defect formation after skin pass on cold‐rolled close annealed steel

AbstractSkin pass rolling is considered as the final forming stage in cold‐rolled close annealed steel. Surface properties and flatness are the key attributes for automotive customers. Efficient skin pass rolling overcomes surface defects that lead to material rejection. This study portrays a brown stain defect with higher defect severity. The brown stain defect is observed in a few coils that are processed through alkaline electrocleaning (ECL). Coils bypassing ECL do not show such defect. Defect characterization through scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy shows initiation of oxidation of steel substrate. The presence of skin pass fluid residues in the defected area is the root cause for the stain formation. Techniques such as glow discharge optical emission spectroscopy, Kelvin probe, Raman spectroscopy, and electrochemical tests emphasize the role of final electrode polarity in ECL with the nature of passive oxide film formed when skin pass fluid is applied on the steel surface. This study reveals that skin pass fluid applied on anodically cleaned coils provides a uniform passive surface that restricts the defect formation.

Study on effects of strong shear strain on recrystallized grain size of pure iron and microstructure control method

The effects of severe plastic deformation by orthogonal cutting on static recrystallization is discussed, and a simpler microstructure control method by using metal cutting and heat treatment is proposed. Pure iron was used as a test material. Large shear strain of 6.60 and 5.04 was induced by orthogonal cutting. Chips were straightened by skin-pass rolling to produce thin metal specimens. After rolling, the specimens were subjected to heat treatment under argon gas atmosphere at 500 °C and 600 °C for 1 min. Microstructure was analyzed by the SEM-EBSD method and mechanical properties were measured by a tensile test. Ultrafine grained sheets with average grain diameter of 0.2 µm were produced by cutting. It was observed that different recrystallized grain structure in different heat treatment temperature. The mechanical properties of the specimen could be controlled by heat treatment conditions. The proposed method is useful to produce an ultrafine grained sheet and to control mechanical properties.

Microstructure and mechanical properties of large-volume gradient-structure aluminium sheets fabricated by cyclic skin-pass rolling

ABSTRACTMaterials of a gradient structure have been shown to possess both high strength and high ductility. To date, materials of a gradient structure can only be produced in small quantities. In this paper, we report a novel ‘cyclic skin-pass rolling’ (CSPR) technique capable of producing sheets of gradient structure in large quantities. Both experimental and analytical/numerical investigations are reported. In the experiments on aluminium sheets, the outer layer was subjected to 40 passes of CSPR with a reduction ratio of 1% per pass. After CSPR, the sample surface shows an ultrafine-grained microstructure with a mean grain size of 206 nm, while the annealed microstructure is retained in the core of the sample. Compared with cold-rolled aluminium sheets fabricated with the same total reduction ratio, CSPR-processed aluminium sheets have the same yield stress but improved uniform elongation (2.4 times). The scanning electron microscopy was used to study the fracture surface, and The transmission electron microscopy to examine the microstructure near the fracture end, in order to analyse the improvement in ductility. In addition, the finite element method was used to simulate the roll-sample contact pressure and strain distribution as well as residual stress on the sheet surface during CSPR, and to better understand the mechanism leading to improvement of ductility of the sheets by the CSPR technique.