Rolled Material Research Articles

Research on Roll Variable Speed Grinding Based on Adaptive Fuzzy Control

The traditional method of improving the machining precision is mainly on account of changes in the workpiece and the grinding wheel in grinding process, including, considered the weakest of the workpiece from the axial stiffness, using center frame to increase the stiffness of the workpiece, take error compensation, and analyze the mechanism of gear grinding and the suppression measures of variable speed grinding and grinding chatter. Based on the analysis of the relationship among gear grinding mechanism, variable speed grinding and grinding chatter suppression and grinding precision, the variable speed micro-feed grinding process strategy based on adaptive fuzzy control is put up, that is according to the roller material and structure to reasonably determine the characteristics of grinding wheel and the parameters of grinding process. And with full consideration of roll grinders, changes of roller system along the axial stiffness and the deformation control in the roll grinding process, a new strategy of variable speed grinding micro-feed adaptive control optimization based on adaptive fuzzy control is proposed, which for improving the accuracy of the grinding roll presents a new and effective solution.

Effect of Extreme Pressure Additives on the Deformation Behavior of Oxide Scale during the Hot Rolling of Ferritic Stainless Steel Strips

High-speed steel (HSS) materials are universally used as work rolls for the hot rolling of stainless steels. Their use has increased the output of the rolling mill and decreased roll material consumption and grinding. Sticking defects often occur, however, during the hot rolling process. In this article, extreme pressure (EP) additives were dropped on the HSS samples at high temperature. Zinc dialkyl dithiophosphate (ZDDP) was chosen as the most effective EP additive by scratch tests on the HSS samples. In order to determine the optimum proportion of ZDDP in the lubricant, two reduction rates were tested on a Hille 100 experimental rolling mill by hot rolling ferritic stainless steel 445J1M at five different concentrations of ZDDP. The mechanism of EP additive action during the hot rolling process was also investigated. By analyzing the deformation behavior of the oxide scale of samples after hot rolling using different proportions of ZDDP, it was found that 20% ZDDP in the lubricant is the preferred concentration for industrial application.

Application of neural networks to minimize front end bending of material in plate rolling process

This study proposes an approach that combines a trained neural network with a bisection algorithm to minimize the front end bending of material that occurs during plate rolling. With finite element analysis of plate rolling, front end bending data set was generated under conditions where the three rolling parameters (percentage reduction, entry material thicknesses, and percentage difference in peripheral speed between the top and bottom work rolls) varied at regular intervals. The finite element model was validated by comparing the computed roll forces, with the ones measured from a pilot plate rolling test. The pilot hot plate rolling test, wherein the rotational speeds/rates of two work rolls were independently controlled, was also performed, to validate the proposed approach. The proposed approach predicted the percentage difference in peripheral speed that minimized front end bending of the rolled material within 1 s. When the percentage difference in peripheral speed determined for the selected reduction and entry material thicknesses were input, the measured front end bending was only up to about 5 mm, which is negligible value because the ratio of the front end bending to roll diameter in the pilot plate rolling mill is only 0.0071 (5/700 mm), which is much lower than the ratio (0.02) in an actual plate rolling mill.

Modelization of the Rolling Mill with a FE Code

To reduce production costs and to improve performances of hot rolled products, it is necessary to optimize the production line. The rolling mill is one of the major factors which affect the internal quality. In fact the process tends to reduce the size of defects during the strain. The production line consisting of 24 stands has been modeled with a commercial FE-code FORGE®. First, a model has been developed and adjusted according to industrial data. Then a parametric study was carried out in order to estimate the influence of the process parameters on the internal quality of the rolled material.

Finite-element modeling of thermal aspects in high speed cold strip rolling

An integrated model based on finite-element method has been proposed to examine the mechanical and thermal responses of strips and work-rolls in tandem and reverse cold rolling operations. The model has been developed such that the influence of various process parameters, such as lubrication, rolling speed, frictional state and back-up rolls, can be examined. Thermal behaviors of the rolled material and the work-rolls have been analyzed using stream-line upwind Petrov–Galerkin approach, in order to make the model applicable to high-speed rolling processes, as well. The results have been compared to the actual on-line measurements and shown to be of acceptable accuracy. Such modeling approach can be considered as a useful means, providing a detailed insight on the thermo-mechanical response of strips, as well as work-rolls, during high-speed cold rolling of steel strips. Additionally, special attention has been drawn towards the prediction of the occurrence of the metallurgical phenomenon dynamic strain aging based on the results obtained from the numerical modeling in this work.

Influence of Particle Size of Wheat Powder on Roller Wear Properties

Wheat milling process involves multiple grinding procedures, the wheat powder particles size in different grinding procedure are difference. In order to study the influence of particle size of wheat powder on roller wear performance in different grinding procedure, abrasion experiments were carried out by MLS-225 three-body abrasive wear tester, while different sizes were chosen as abrasive, alloy white iron which frequently used as roller metal materials was chosen as wear sample, wear weight loss and surface microstructure were chosen as the main evaluation indicators. The results showed that the weight loss of samples were showed a linear relationship with wheat the size of wheat powder. The main wear behavior was mainly mechanical polishing while particle sizes was smaller one. For the larger size, wear was made by multiple plastic deformation and low cycle fatigue wear mechanism.

Spectral database solutions to elasto-viscoplasticity within finite elements: Application to a cobalt-based FCC superalloy

We present a computationally efficient, multi-scale model based on crystal plasticity theory for simulations of heterogeneous plastic deformation of metallic components in commercial finite element (FE) codes. Although the model can handle a single crystal, the primary purpose with the present model is to embed a meso-scale polycrystal homogenization at a FE integration point, with the meso-scale homogenization being a Taylor-type model. The responses of single crystals are obtained using a recently developed non-iterative solver, which is based on databases of discrete Fourier transforms allowing for fast retrieval of pre-computed crystal plasticity solutions. We have shown that, when this non-iterative solver is used in place of the Newton–Raphson iterative solver, substantial wall-clock speedups can be achieved. Additionally, the implementation presented here takes the advantage of calculations of the elastic properties based on the spectral representation. To calibrate and validate the new FE elasto-viscoplastic model, we use stress-strain curves and texture data of the cobalt-based face-centered cubic superalloy Haynes 25. For this purpose, the material was deformed monotonically in compression over a wider range of strain rates and temperatures. The model is subsequently applied to simulate the macro-scale mechanical response of the material in compression and rolling. We show that the predictions of the model compare favorably with experimental measurements in terms of the mechanical response and texture evolution. Finally, the evolution of the underlying crystallographic texture in rolling predicted by the new model is compared against the corresponding predictions from the finite element visco-plastic self-consistent (FE-VPSC) model. It is observed that both implementations produce similar predictions, but the model presented here is substantially faster.

High Temperature Oxidation Investigation of Hot Roll Material with High-Speed Steel

High-speed steels are successfully manufactured to make work rolls in hot rolling steel mills. An understanding of their oxidation behaviour is crucial to the degradation of work rolls and the surface quality of rolled strip. In this paper, the high temperature oxidation behaviour of a work roll with high-speed steel material was investigated under isothermal conditions from 550 to 750 °C for 30 min in 20% humid air. The results indicate that molybdenum-rich carbides M2C are oxidised and protrude out of the surface, vanadium-rich carbides MC and iron and chromium-rich carbides are easily identified and less influenced, but the oxides grown on the matrix are relatively even at 550 and 600 °C. However, at higher temperature, MC carbides are severely oxidised and extend to their nearby areas, whereas M7C3 zones can still be recognised but with more small particles grown on them.

Magnet properties of Mn70Ga30 prepared by cold rolling and magnetic field annealing

The remanence and coercivity of arc melted Mn70Ga30 can be substantially improved by cold rolling. For best performance the rolled material should be annealed at T=730K in the presence of a magnetic field of 1T. The so-obtained magnet has a remanence of 0.239T and a coercivity of 1.24T at room temperature. The underlying reason for the high coercivity and remanence is the increase of the content of a metastable ferrimagnetic D022 phase at the expense of the normally stable anti-ferromagnetic D019. Magnetic field significantly increases the nucleation rate of the ferromagnetic D022 phase that leads to grain size refinement and as a consequence of improving remanence and coercive field.

Comparison of thermomechanical stresses produced in work rolls during hot and cold rolling of Cartridge Brass 1101

Thermomechanical stresses play an important role in defining the life of the work roll used in hot rolling process. In this research temperature dependent mechanical properties of cartridge brass are determined experimentally using high temperature compression tests at different temperatures and strain rates. Real life measurements are made from a brass rolling mill as input data for the simulation boundary conditions. Hot rolls are made of AISI H11 hot work tool steel. Temperature dependent mechanical properties of AISI H11 steel are used. Thermal and mechanical stresses produced in the work rolls during hot rolling process are predicted using a thermoplastic finite element approach in the ABAQUS Standard software. Hot rolling is compared with cold rolling to determine the effects produced on the work rolls. A criterion is introduced to compare the severity of stresses produced on the rolling surfaces in case of hot rolling and cold rolling based on the yield stress of the roller material for different temperatures. A method for separating thermal and mechanical stresses in the simulation is also described.

Biocorrosion and biodegradation behavior of ultralight Mg–4Li–1Ca (LC41) alloy in simulated body fluid for degradable implant applications

Biocorrosion and biodegradation behavior of Mg–4Li–1Ca alloy were investigated for industrially important end product conditions, namely the homogenized, rolled, and rolled + annealed ones. Among the three, homogenized material showed the highest corrosion rate (27.2 mm/year) in a simulated body fluid (SBF) owing to its coarse grain structure containing long dumbbell-shaped eutectic phase. Rolled + annealed material exhibited the lowest corrosion rate (0.94 mm/year) corresponding to the highest corrosion resistance (1.854 kΩ cm2) in SBF. This higher corrosion resistance is associated with a uniform distribution of corrosion sites and a lower occurrence of twins in the microstructure. However, the rolled material showed a greater corrosion rate due to an appreciable volume fraction of {10\( \bar{1} \)1} compression twins, {10\( \bar{1} \)2} tension twins, and {10\( \bar{1} \)1}–{10\( \bar{1} \)2} double twins, which form galvanic couples with the adjacent grains that enhances localized corrosion. A mechanism of biodegradation at the alloy/SBF interface is proposed. It involves the formation of bone-like hydroxyapatite and metastable octa calcium phosphate, along with other degradation products, such as magnesium hydroxide and lithium hydroxide.

Failure analysis of work rolls of a thin hot strip mill

In hot rolling mills, premature failure of rolls is a major concern as it adversely affects the mill operation as well as production. Analysis of failed roll materials and actual rolling conditions in service are therefore necessary to understand the roll failure mechanism and thereby improve the wear resistance and extend the service life of rolls.The hot strip mill referred here consists of six stands wherein high chromium (Hi-Cr) iron rolls and Indefinite Chilled Double Poured (ICDP) cast iron rolls are being used for finishing rolling of the strips in the last two stands. The thin strip mill produces strips in the thickness range of 1.0–12.7mm. This work describes two different types of roll failure cases and their analysis which was carried out using destructive as well as non-destructive testing techniques (NDT). The cases are as follows:(a)Case I: enhanced ICDP bottom roll of fifth stand (F#5) which failed from the neck portion.(b)Case II: analysis of sub-surface defect of ICDP rolls of the last stand (F#6).Destructive testing (including metallography and chemical analysis) was carried out on the failed roll samples in the first case and gross abnormality in microstructure was observed. Some foreign particle/entrapment was observed after dressing of the working surface of roll at 566mm diameter (initial diameter of roll was 620mm and scrap diameter was projected to be 540mm). The chemical composition of the particle was analyzed by a portable X-Ray Fluorescence (XRF) alloy analyzer and it was confirmed that the particle is basically a ferroalloy which was entrapped in the shell of the roll, probably during casting/manufacturing of roll.

Tribological Aspects of Advanced Roll Material in Cold Rolling of Stainless Steel

Tribological Aspects of Advanced Roll Material in Cold Rolling of Stainless Steel

Characteristics of Wear and Rolling on Fiber Reinforced Metal at High Temperature

Possibility of applying new roll materials (FRM (Fiber Reinforced Metal) roll materials), which are consisted of high speed tool steel reinforced with alumina fiber, to work rolls for hot rolling process is investigated by several laboratory tests. The FRM roll material expected to have superior tribological and mechanical properties, have been manufactured using sintering method (Hot Isostatic Pressing process) with which ceramic content can be increased. Wear resistance and mechanical properties and hot rolling characteristics of the FRM roll materials were investigated. As the results, it was clarified that the FRM roll material had three times or more wear resistance, a little lower rolling force and friction coefficient, and good thermal crack resistance and higher tensile strength in comparison with conventional casting roll materials such as a high speed steel roll material. Therefore, FRM roll materials can expectantly be used for hot rolling mill as high performance roll materials instead of high speed steel roll material.

Dry sliding wear behaviour of cast roller materials

In this study, wear behaviour of roller materials produced by different casting techniques was investigated. Static and centrifugal casting techniques were used to produce roller materials having pearlitic and martensitic matrices due to the processing method and alloy composition. The roller materials were examined using light and scanning electron microscopes to determine the matrix phase. The samples were tested using 'ball–on–disc' type tribometer to study the wear characteristics of cast morphologies. DIN 100Cr6 steel ball with a 5 mm diameter was used as counterface, load force was selected as 50 N and total sliding distance was 500 m. After wear tests, the surfaces of cast parts were examined by light and scanning electron microscopes to evaluate the wear mechanisms under dry sliding condition. The friction coefficient, weight loss and type of wear mechanisms were determined. It was concluded that the material having finer martensitic matrix produced by centrifugal casting had a higher wear resistance than the one produced by static casting.

Cr-Cu圧延材とCr-Cu/Cuクラッド圧延材の熱特性

Thermal properties of Cr-Cu for heat-sink application are required to be close to those of Mo-Cu and W-Cu. The rolled and Cu-clad and rolled Cr-Cu infiltrated compacts are investigated to improve the thermal properties. In the rolled Cr-Cu material, Cr phases are significantly elongated and flattened, resembling a fibrous structure. Such a fibrous structure of Cr phases makes the thermal expansion coefficient much lower than that predicted from the rule of mixture. While the flattened Cr structure promotes thermal flow in the in-plane direction, it deteriorates that in the thickness direction. To improve thermal conductivity in thickness direction, the Cr-Cu compact was bonded with a Cu plate and rolled. The clad and rolled structure enables the improvement of thermal conductivity in the thickness direction without degrading the thermal expansion coefficient in the rolling direction.

Technological Aspects of High Speed Direct Laser Deposition Based on Heterophase Powder Metallurgy

The article deals with physical peculiarities and technology of high speed processes of direct laser deposition. On the base of theoretic research and computer modeling the powder transfer has been optimized, increasing process stability and productivity. Principles of nozzles design also have been developed in accordance with technological needs. An influence of process mode on product properties and material structure was defined for heat resisted Ni-based superalloys. Developed technology provided the mechanic properties of products on the level of rolled material and allows avoid heat treatment and HIP in production process. Possible ways for increasing process performance and economic efficiency also have been discussed.

Development of micro rotary swaging tools of graded tool steel via co-spray forming

In order to meet the requirements of micro rotary swaging, the local properties of the tools should be adjusted properly with respect to abrasive and adhesive wear, compressive strength, and toughness. These properties can be optimally combined by using different materials in specific regions of the tools, with a gradual transition in between to reduce critical stresses at the interface during heat treatment and in the rotary swaging process. In this study, a newly developed co-spray forming process was used to produce graded tool materials in the form of a flat product. The graded deposits were subsequently hot rolled and heat treated to achieve an optimal microstructure and advanced properties. Micro plunge rotary swaging tools with fine geometrical structures were machined from the hot rolled materials. The new forming tools were successfully applied in the micro plunge rotary swaging of wires of stainless steel.

Influence of hot-working conditions on a structure of X11MnSiAl17-1-3 steel for automotive industry

The investigations are focused on high-manganese austenitic steel used for reinforcing elements of a car body. The main purpose of this paper is to determine the effect of various conditions of thermomechanical treatment carried out on Gleeble 3800 simulator being on equipping Scientific and Didactic Laboratory of Nanotechnology and Materials Technologies, Institute of Engineering Materials and Biomaterials, Silesian University of Technology in Gliwice Poland, and LPS module for semi-industrial hot-rolling on the structure and phase transformations occurring during cold plastic deformations. Thermomechanical treatment consists of a four passovers with a planned true strain equal 4 × 0.23. There were three variants of cooling after thermomechanical treatment: cooling in water, natural air-cooling and cooling in water after isothermal holding for 30 s at the temperature of last deformation 850°C. After thermomechanical treatment of high-manganese austenitic steel performed in the laboratory Gleeble 3800 simulator and industrial conditions of LPS module can be concluded that simulation in laboratory conditions allows to obtain fine-grained austenitic structure. Rolling performed in the semi-industrial conditions in the LPS rolling mill did not allow to achieve the assumed parameters of thermomechanical treatment, such as temperature and planned strain during successive deformations. These factors have led to the lack of a uniform structure fragmentation of the rolled material, and also have an influence on mechanical properties obtained during cold plastic deformation.

Development of micro rotary swaging tools of graded tool steel via co-spray forming

In order to meet the requirements of micro rotary swaging, the local properties of the tools should be adjusted properly with respect to abrasive and adhesive wear, compressive strength, and toughness. These properties can be optimally combined by using different materials in specific regions of the tools, with a gradual transition in between to reduce critical stresses at the interface during heat treatment and in the rotary swaging process. In this study, a newly developed co-spray forming process was used to produce graded tool material in the form of a flat product. The graded deposit was subsequently hot rolled and heat treated to achieve an optimal microstructure and advanced properties. Micro plunge rotary swaging tools with fine geometrical structures were machined from the hot rolled material. The new forming tools were successfully applied in the micro plunge rotary swaging of wires of stainless steel.