Deformation Behavior Of Oxide Scale Research Articles

Sensitivity Analysis of Oxide Scale Influence on General Carbon Steels during Hot Forging

Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of die and workpiece, and machine kinematics into account. In hot forging processes, the surface properties are strongly affected by the growth of oxide scale, which influences the material flow, friction, and product quality of the finished component. The influence of different carbon contents on material behaviour is investigated by considering three different steel grades (C15, C45, and C60). For a general description of the material behaviour, an empirical approach is used to implement mathematical functions for expressing the relationship between flow stress and dominant influence variables like alloying elements, initial microstructure, and reheating mode. The deformation behaviour of oxide scale is separately modelled for each component with parameterized flow curves. The main focus of this work lies in the consideration of different materials as well as the calculation and assignment of their material properties in dependence on current process parameters by application of subroutines. The validated model is used to carry out the influence of various oxide scale parameters, like the scale thickness and the composition, on the hot forging process. Therefore, selected parameters have been varied within a numerical sensitivity analysis. The results show a strong influence of oxide scale on the friction behaviour as well as on the material flow during hot forging.

Influence of uneven interface between steel and oxide scale on deformation behavior of oxide scale in hot ring compression

In order to control sliding between oxide scale and steel in hot forging of steel covered with oxide scale, the interface unevennesswas formed between the steel and the oxide scale by preparing grooves on the steel surface. The interface unevenness was aimed for improving the anti-peeling characteristic of the oxide scale from the steel during the hot forging. The plastic deformation of carbon steel workpiece covered with oxide scale was investigated in hot ring compression test. The oxide scale was confined between the die and the workpiece, and extended to be radial direction of the workpiece during ring compression test. The expanded ratio of the oxide scale formed on the concentric uneven interface was found to be approximately 1.1-1.3 times larger than that on the flat interface at a reduction in height of 50% in ring compression. As the result, the shear friction factor determined from the plastic deformation of the workpiece was reduced in the workpiece with concentric uneven interface by approximately 0.05-0.10, compared with that of the workpiece with flat interface.

Numerical Investigation of the Oxide Scale Deformation Behaviour with Consideration of Carbon Content during Hot Forging

Abstract Due to increasing product requirements the numerical simulation has become a powerful tool for the effective and efficient design of individual process steps as well as entire process chains. In order to model hot forging processes with finite element based numerical methods realistic models are required which consider the detailed mathematical description of the material behaviour during the forging process, the surface phenomena at die and workpiece as well as machine kinematics. Although this data exist for several steel grades, yet general mathematical models for steel groups based on alloying elements like carbon content are not available. In hot forging the surface properties are strongly affected by the growth of oxide scale, which influences material flow, friction as well as product quality of the finished components. The influence of different carbon contents on oxide scale growth and material behaviour is investigated by considering three different steel grades (C15, C45 and C60). For a general description of the material behaviour, an empirical approach is used to implement mathematical functions so as to express the relationship between flow stress and dominant influence variables like alloying elements, initial microstructure and reheating mode. The oxide scale consists of three different components namely wuestite, magnetite and haematite. In order to take the oxide scale into account, additional models are required to describe the growth kinematic and flow behaviour of the oxide scale components. The mathematical relationship between oxidation time, temperature, carbon content and oxide scale height is based on Arrhenius approach. The deformation behaviour of oxide scale is separately modelled for each component with parameterized flow curves. This paper gives first approaches on the numerical modelling of plastic deformation of oxide scale in a hot forging process. The main focus lies on the involvement of the different materials as well as the calculation and assignment of material properties in dependence of current process parameters by using subroutines. The numerical model and subroutines will be implemented in the FE-Software simufact.forming. A validation of the numerical model will be carried out by comparison of numerical results with experimental data.

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.

Evaluation of Deformation Behavior of Oxide Scale in Hot Rolling Process by Vacuum Hot Rolling Mill

A method for reproduce the oxide scale in hot rolling is proposed using the vacuum hot rolling mill. This method is possible to control of scale thickness and chemical composition in actual hot rolling process.From results, it is possible to clear the deformation behavior of state generated the oxide scale, oxide scale thickness is thick enough amount of Fe2O3 billets. The oxide scale thickness is proportional to the amount of Fe2O3. Some cracks appeared before the roll bite during rolling the oxide scale. Then, peeling or destruction occurred in roll bite for roll exit.

The effect of oxide scale of stainless steels on friction and surface roughness in hot rolling

Friction is one of the most significant physical phenomena influencing metal forming. The deformation or fracture of oxide scale significantly affects the roll–strip interface behaviour. Sticking occurs frequently during hot rolling of stainless steels especially ferritic stainless steels, which causes surface defects of both steel products and rolls. It is important to characterize the features of the oxide scale in hot rolling of stainless steel strips, but few studies have been carried out. This paper focuses on the deformation of oxide scale and roll–strip interface characteristics in hot rolling of austenitic stainless steel 304L and ferritic stainless steel 430. Oxidation tests in a short time in humid air with water vapour content of 7.0 vol.% were carried out using Gleeble 3500 thermo-mechanical simulator, and the oxidation characteristics of 304L and 430 steels were obtained. The deformation, surface morphology of oxide scale of the steels, and the friction in hot rolling were studied in hot rolling tests. Thick oxide scale of 304L steel shows high lubricative effect while the breaking of thin oxide scales of 430 steel may make the steel substrate to contact with the roll, which counteracts the lubricative effect of the oxide scale and results in friction coefficient increasing with an increase of reduction. A FEM simulation has been developed to analyse the deformation behaviour of oxide scale and surface roughness transfer during hot rolling of stainless steels and the model describing the rough surface profiles of the scales and steel has been integrated into the simulation.

Effect of Hot Rolling Conditions on Deformation Behavior of Oxide Scale at High Temperatures

Effect of Hot Rolling Conditions on Deformation Behavior of Oxide Scale at High Temperatures