Cold-rolled Steel Sheets Research Articles

Компьютерный тренажер “Холодная прокатка листовой стали”: математическое моделирование процесса и 3D визуализация оборудования

In this paper contains a description of the simulator “cold-rolled steel sheet”. This simulator is designed for use in the educational process in the preparation of students for engineering and metallurgical enterprises. The simulator includes a theoretical module; module to study the sheet rolling mill design; module for modeling and studying the rolling conditions and their impact on energy-power characteristics of the process, as well as the control unit of knowledge. The simulator allows you to practice skills in the assembly/disassembly of the rolling mill stand and study design five-stand sheet mill. The article gives a detailed description of the mathematical model which is based on the theory of energy interaction between the rolls and the strip during rolling, the proposed Vydrin V. N. Software has been developed on the basis of a mathematical model. It allows the calculation of technological modes of rolling and conduct analytical studies. The article also contains examples of the use of the simulator in the training process.

異方硬化挙動を考慮した冷延鋼板の成形シミュレーション

異方硬化挙動を考慮した冷延鋼板の成形シミュレーション

Preventing surface defects in the uncoiling of thin steel sheet

The formation of surface defects when annealed thin cold-rolled steel sheet is uncoiled for temper rolling is analyzed. The appearance of such defects is mainly due to adhesion and welding of the contacting surfaces of the turns in the coil. The influence of the strip thickness, surface roughness, temperature, properties of the metal, and other factors on the stress–state of the coil and the likelihood of surface defects is analyzed. Preventive measures are recommended.

The change of work roll surface topography during skin pass rolling of steel sheets

Purpose – This paper aims to analyze changes in the surface topography of the work rolls during skin passing. Cold rolled steel sheets are additionally subject to skin pass rolling to form an appropriate surface topography. This operation should facilitate the process of further metal forming of steel sheets, such as deep drawing, painting, etc. The surface topography of steel sheets is determined by the surface topography of the work rolls as well as the skin pass rolling parameters (rolling speed, elongation, roll force, etc.). Suitable preparation and selection of roll surface topography influences the degree of rolls wear and the surface topography of steel sheets as well. Design/methodology/approach – Two-dimensional (2D) and three-dimensional (3D) roughness measurements of work roll surface before, during and after finishing of skin pass rolling of steel sheets are presented in the paper. The measurements were performed on four sets of work rolls with different surface topography. Findings – The appearance of the surface of rolls obtained from the analysis of 3D roughness, the values of selected parameters of the 3D roughness and relative changes of the roughness parameter Ra/Sa depending on the length of the skin passed steel sheets are presented. Practical implications – The wear of rolls is different depending on work surface topography. Originality/value – The aim of this paper is to analyze changes in the surface topography of the work rolls during skin passing. It was expected that the surface of work rolls with more summits at similar average roughness Ra will change much faster than the surface with fewer summits. For this purpose, preliminary tests were performed in an industrial environment on four pairs of work rolls, including two pairs of rolls that were hard chromium-plated.

Effect of texture and grain size on the magnetic flux density and core loss of cold-rolled high silicon steel sheets

The effects of texture and grain size on the magnetic flux density and core loss (50–20kHz) of 0.23mm-thick cold-rolled high silicon steel sheets are investigated by means of electron back-scattered diffraction (EBSD), loss separation, and anisotropy parameter (ε) calculation. A model of the hysteresis loss coefficient kh considering average grain size and ε is established. The magnetic flux density at 800A/m (B8) is closely related to the volume fraction of η-fiber-oriented grains, while the magnetic flux density at 5000A/m (B50) is closely related to the volume fractions of γ- and λ-fiber-oriented grains in high silicon steel. The hysteresis loss of high silicon steel can be greatly reduced by increasing the grain size and optimizing the texture of the sheets. Although increases in frequencies decrease the effect of texture on core loss, the effect cannot be ignored. As annealing temperature and time increase, the relative difference in core loss between the rolling direction (RD) and the transverse direction (TD) is maintained at higher frequencies because of increases in grain size, decreases in γ texture, and maintenance of a strong η texture. Texture and grain size jointly affect the high-frequency core loss of high silicon steel.

An experimental investigation on the influence of lubrication on roughness transfer in skin-pass rolling of steel strip

Skin-pass rolling (or temper rolling) is usually the final process in the production of cold-rolled steel sheets. In operation, skin-pass rolling is performed with roughened rolls, using a lubricant with a very low lubricating ability. However, relatively few studies in the literature have examined the effect of lubrication in skin-pass rolling. In this paper, the influence of lubrication on elongation and roughness transfer in skin-pass rolling is investigated by experimental rolling tests in which the relationship between lubrication behavior and the roll radius is clarified. As in a previous study of smooth rolls, the results with large, operational size rolls can be explained convincingly by height characterization parameters and are considered to be reasonable. It was also found that some characteristics of skin-pass rolling related to lubrication are not properly simulated using small radius, laboratory size rolls due to the insufficient contact length between the rolls and the workpiece.

Examination of Eddy Current between Steel Sheets without Insulation and a Criterion for Determining the Necessity of Insulation

SUMMARYIn the laminated core of transformers, motors, and so on, each electrical steel sheet is usually insulated in order to reduce the eddy current loss. It has been reported that insulation is not necessary in such a laminated core under some conditions. However, few studies have been performed in the form of a quantitative and systematic examination of the relationship between the insulation and eddy current. In this study, the eddy current losses of a core made of SPCC (cold rolled steel sheets) of different widths with and without insulation under various conditions are analyzed using the finite element method (FEM) and with the contact resistance taken into consideration. The equivalent circuit of a laminated core without insulation is presented, and can be used for determining the necessity of insulation. It is shown that the increase in the eddy current is affected by the ratio of the resistance of the steel to the contact resistance. An experimental investigation is also carried out.

Observation of co-segregation of titanium and boron at the interface between recrystallized and unrecrystallized grains in cold-rolled interstitial-free steel sheets

It has been reported that the addition of ppm levels of B strongly retarded the growth of recrystallized grain into unrecrystallized grains in the process of cold-rolling and annealing of Ti-added interstitial-free (IF) ferritic steels. This phenomenon was explained by solute drag effect based on the assumption that, during annealing, B atoms segregate at the interface between recrystallized and unrecrystallized grains where they interact with Ti atoms. To verify this, atom probe tomography analysis of the interface was performed in Ti-added IF steels with and without B addition. Needle tips containing the interface identified from electron backscattering diffraction analysis, were produced by focused ion beam milling with the lift-out method. To increase the experiment reliability, the misorientation angle of the aimed interface was compared with that estimated by field ion microscopy analysis. Considerable amount of Ti segregation was observed at the interface in the steel without B addition, which increased with increasing amount of B segregation in the steel with B addition. The results suggest that the retardation of the interface migration was caused by solute drag effect based on the simultaneous co-segregation of Ti and B due to their attractive interaction.

SPECIES FORMED ON IRON SURFACE DURING REMOVAL OF COPPER IONS FROM AQUEOUS SOLUTIONS

The subject of the research covered in this paper is the removal of copper (Cu 2+ ) cations from water at low pH (initial values of pH 3 and 6) by means of zero-valent iron. The chemical states and atomic concentrations of solids formed on the surface of zero-valent iron, and the type of deposited polycrystalline substances have been analyzed with the use of XPS and XRD. The type of process causing the copper removal from water at low pH, corresponding to the effect of acid mine drainage, has been identified by analyzing the changes of physicochemical parameters and specified chemicals content in water. Cu 2+ was removed from water for the initial pH of 6 was much more effective than at lower pH. The formation of CuxFe3-xO4 , where x≤1, and to a lesser degree Cu2O, Cu 0 and/or CuO and/or Cu2S, were the basic processes of the removal of copper at almost neutral pH of water (pH about 6), while the formation of copper in metallic form and Cu2O, as well as probably CuO, were the basic processes for lower pH (pH about 3). The adsorption of Cu 2+ on the surface of shell covering square-shaped cold-rolled steel sheet cell was an additional process causing the removal of copper from water at almost neutral pH.

Recrystallization of Boron Containing and Boron-Free Low Carbon Steels Investigated by Thermoelectric Power and Hardness Measurements

The measurement of thermoelectric power is a powerful method to investigate the metallurgical processes occurring in steels. In this study, four low carbon cold rolled steel sheets having different composition were investigated. The cold rolled sheets were heated up at heating rate 20 °C/hour up to different temperatures, whilst the change of thermoelectric power and hardness have been measured at room temperature after slow cooling. The thermoelectric power of steels increases with temperature until the recrystallization finishes. The raise of thermoelectric power during recrystallization is ranging between 50 and 160 nV/K, depends on the composition of the sheet. Specimens consist of boron exhibit lower thermoelectric power after recrystallization than the steel without any boron, probably due to metastable borocarbide dissolution. This fact could be a good starting point to investigate the effect of boron on thermoelectric power of steels.

Brittle intermetallic compound makes ultrastrong low-density steel with large ductility.

Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

Influence of Tensile Strain on Young’s Modulus in High-strength Cold-rolled Steel Sheets

The change of Young’s modulus accompanying tensile deformation was investigated for an anisotropic high-strength cold-rolled steel sheet with a high Young’s modulus value in the transverse direction and an isotropic steel sheet with no prominent development of texture. The characteristic phenomenon was the decrease in Young’s modulus in the transverse direction by tensile deformation in the transverse direction in the anisotropic steel sheet. The drop of Young’s modulus in the transverse direction was attributable to a decrease in the ODF intensity around {112}<110>. Young’s modulus in the diagonal direction also decreased somewhat as a result of tensile deformation in the rolling and diagonal directions in the anisotropic steel sheet. This change was caused mainly by an increase in ODF intensity around {001}<110>. Young’s modulus in the rolling direction displayed little change as a result of tensile deformation because the texture on the α-fiber and γ-fiber, which were mainly developed in cold-rolled steel sheets, showed an almost constant Young’s modulus in the rolling direction. In the isotropic steel sheet, Young’s modulus showed little change in any direction as a result of tensile deformation. Young’s modulus calculated by the Voigt model had relatively good correspondence with the measured results. Concerning simulation of crystal rotation, the Taylor model indicated that the crystals around the α-fiber from {112}<110> to {111}<110> rotated to the vicinity by tensile deformation in the transverse direction. The remarkable change of Young’s modulus was explained by the crystal rotation simulated by the Taylor model.

222 Fatigue Life Evaluation of Bending-Worked Cold Rolled Steel Sheet under Out-of-Plane Bending

222 Fatigue Life Evaluation of Bending-Worked Cold Rolled Steel Sheet under Out-of-Plane Bending

曲げ加工された冷間圧延鋼板の面外曲げ疲労強度

Fatigue tests were conducted on 90°V-shape bending-worked cold rolled steel sheet specimens under fully-reversed out-of-plane bending to investigate the fatigue strength of bending-worked plates. The tests were also performed on low-temperature annealed specimens with no work-hardened layer formed by the bending-work. For annealed specimens, the fatigue strength decreased with reduction in radius of curvature of bending. The fatigue life can be estimated with sufficient accuracy taking account of the influence of elastic-plastic stress concentration at critical location. For bending-worked specimens without annealing, the fatigue strength was relatively higher than those of annealed bent specimens in relation to the existence of work-hardened layer. The increase of fatigue strength due to work-hardening was estimated based on the difference in S-N diagrams of both specimens. Consequently, the fatigue life of bending-worked specimens without annealing can be evaluated taking the effects of stress concentration and work-hardening into consideration.

高強度冷延鋼板のリン酸塩処理性に及ぼす表面状態の影響

高強度冷延鋼板のリン酸塩処理性に及ぼす表面状態の影響

Исследование процесса старения холоднокатанного и горячеоцинкованного проката

In this paper, a study was conducted of the aging process of cold and hot dip galvanized sheet to obtain data on the timing guarantees the mechanical properties of rolled metal production of OJSC Magnitogorsk Iron and Steel Works (MMK) during storage and processing of consumers. Considered two basic types of aging, namely natural and artificial (deformation, thermal and thermodeformation). For the experiment was selected following assortment: hot dip galvanized sheet steel grades DX52D and 08ps; cold-rolled sheet steel production 08U of rolling mill № 5; cold-rolled sheet of steel grades 08U and 10ps production of rolling mill № 11 "Magnitogorsk Iron and Steel Works." The experimental part was carried out a tensile test to determine the change in mechanical properties as a result of the test assortment different types of aging. The experimental results were constructed depending that show changes in the mechanical properties and propensity to aging test sheet. It has been established that the supplier can store cold-rolled and hot dip galvanized sheet steel DX52D, 08U, 10ps in the warehouse for 3-6 months with guaranteed mechanical properties. Hot dip galvanized steel grade 08ps begins to age in 10 days. In turn, straightening, unwinding rolls, as well as other actions with a sheet accompanied by heating and plastic deformation leads to a change in the mechanical properties of steel. It is necessary to consider both suppliers and consumers of products.

New ultrahigh-strength Mn-alloyed TRIP steels with improved formability manufactured by intercritical annealing

We have developed novel ultrahigh-strength cold-rolled transformation-induced plasticity (TRIP) steel sheets manufactured by a simple intercritical annealing process, whose total and uniform elongation of are up to 24.8% and 9.3% respectively at the ultimate tensile strength of 1GPa; and 20.0% and 9.0% at 1.2GPa. They exhibit a better combination of the tensile properties than the present commercial cold-rolled steel sheets for automotive. Such an improvement is achieved by the new designs of chemistries and intercritical annealing (IA) process, i.e. alloying with the 5wt% Mn content and the IA of martensite rather than the conventional cold rolled microstructures. Both lead to ultrafine austenite grains with enhanced stability formed during IA and retained in the matrix of ferrite and martensite afterwards. Finally, the improvement of elongation is attributed to austenite-to-martensite TRIP effect during the tensile deformation.

초음파 진동 딥 드로잉 공정에서의 마찰감소효과 분석을 위한 유한요소해석 및 실험

The current study presents experimental and numerical results on the effect of ultrasonic vibrations on a cylindrical cup drawing of a cold rolled steel sheet(SPCC). An experimental apparatus, which can superimpose high frequency oscillations during deep drawing, was constructed by installing on the tooling ultrasonic vibration generators consisting of a piezoelectric transducer and a resonator. Conventional and vibration-assisted cylindrical deep drawing tests were conducted for various drawing ratios, and the limiting drawing ratios(LDR) for both methods were compared. To evaluate quantitatively the contribution from the ultrasonic vibrations to the reduction of friction between tools and material finite element analyses were conducted. Through a series of parametric analyses, the friction coefficients, which minimized the differences of punch load data between the experiments and simulations, were determined. The results show that the application of ultrasonic vibration effectively improves the LDR by reducing the friction between the tools and the material.

Influence of lubrication on roughness crushing in skin-pass rolling of steel strip

Skin-pass rolling (or temper rolling) is usually the final process in the production of cold-rolled steel sheets. In operation, skin-pass rolling is performed with a lubricant with very low lubricating ability. However, relatively few studies have been reported in the literature regarding the effect of lubrication in skin-pass rolling. In this paper, the influence of lubrication on roughness crushing in skin-pass rolling is investigated by experimental rolling tests as well as numerical analysis by elastic-plastic FEM, especially focusing on differences in lubrication behavior depending on roll radius. The results with a large, operational size roll are well explained by the height characterization parameters and are considered to be reasonable from the viewpoint of classical knowledge in deep drawing tests and plane strain upsetting. It was found that some characteristics of skin-pass rolling related to lubrication are not properly simulated using small radius, laboratory size rolls due to insufficient contact length.

Investigations on the Effect of Ultrasonic Vibration in Cylindrical Cup Drawing Processes

This paper presents experimental and numerical investigations on the effect of ultrasonic vibration on cylindrical cup drawing processes of a cold rolled steel sheet (SPCC). An experimental apparatus to superimpose high frequency oscillation on deep drawing processes was constructed by installing ultrasonic vibration generators consist of piezoelectric transducer and resonator to the die. Conventional and vibration-assisted cylindrical deep drawing tests were carried out for various drawing ratios, and the limiting drawing ratio (LDR) was compared. In order to evaluate the contribution of ultrasonic vibration to the reduction of friction between tools and a material quantitatively, finite element analyses were carried out. Through a series of parametric analyses, friction coefficients which minimize the differences of punch load histories between the experiment and simulation were determined. The results showed that the application of ultrasonic vibration make for improving LDR by reducing the friction between tools and the material, effectively.