Laurent Langlois

Some Approaches on Industrial Installation of Steel Thixoforged Processes

Based on several years of research, this paper presents some approaches on industrial installation on thixoforging steel with an important potential of an innovative technology. The possibility of Thixoforging industrialization makes it possible to consider new steel components production. From billet to final part with complex shape obtained in one step, several “keys” are developed as heating system, transfer system, part and die design.

Experimental & Numerical Study of the Hot Upsetting of Weld Cladded Billets

The presented work is dedicated to studying the forgeability of bimaterial cladded workpiece. Hot upsetting tests of cylindrical low carbon steel (C15) billets weld cladded (MIG) by stainless steel (SS316L) are experimentally and numerically studied. Upsetting tests with different upsetting ratios are performed in different tribology conditions at 1050°C which is within the better forgeability temperature range of both substrate and cladding materials[ ]. Slab model and finite-element simulation are conducted to parametrically study the potential forgeability of the bimaterial cladded workpiece. The viscoplastic law is adopted to model the friction at the die/billet interface. The friction condition at the die/billet interface has a great impact on the final material distribution, forging effort and cracking occurrence. With Latham and Cockcroft Criterion, the possibility and potential position of cracks could be predicted.

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.

In Situ Microstructure Observation Of Steel Grades In The Semi-Solid State For Thixoforging Process By Using Confoncal Laser Scanning Microscopy

It is necessary to well understand the microstructure evolution during high speed heating and forming for steel thixoforging, since it determines the thixotropic flow behavior of materials in the semi-solid state. A new in situ technique - high temperature Confocal Laser Scanning Microscopy (CLSM) - was developed and used for studying the microstructure evolution directly at high temperature where the microstructure in the semi-solid state could not be preserved by quenching experiments for conventional 2D characterization. Several steel grades (C38LTT, 100Cr6 and M2) were investigated during heating from the as-received state to the semi-solid state and finally cooled to the solid state).It has been found that there is a significant difference in diffusion rate of alloying elements between these grades during heating and cooling. In M2, thanks to the high content of alloying elements and their low diffusion rate, the semi-solid temperature range is greater and its microstructure in the semi-solid state could be preserved by quenching or even at a low cooling rate, which means the microstructure of M2 in the semi-solid state can be characterized in room temperature on quenched M2 samples. On the contrary, the microstructure of other steel grades 100Cr6 and C38LTT in semi-solid state can only be revealed by CLSM at high temperature because of the lower volume fraction of alloying elements and their high diffusion rate. It is very interesting to use high temperature CLSM to in situ investigate the microstructure evolution in the semi-solid state, especially at low liquid fraction.

Identification of Drilling Parameters during the Flow Drill Screw Driving Process

The automobile manufacturing industry, until recent years, has been using steel for car body components and the main method for joining these components has always been Resistance Spot Welding. However, since the global trends toward CO2 reduction and resource efficiency have significantly increased, the importance and usage of lightweight materials has enhanced as well. New lightweight materials such as aluminum and magnesium alloys, carbon-fiber-reinforced plastics, etc., have become a reality, thanks to the new fastening technologies. Flow drill screw driving (FDS) is a one–sided thermomechanical assembly process based on heat generation by frictional force and plastic deformation. A special screw, known as hole forming and self-tapping screw, is used in this process as both fastener and tool. Moreover, rotational and translation movements are applied to the screw to create special friction conditions with the workpiece. Furthermore, unlike traditional drilling and thread milling processes, there is no chip or waste of material in FDS and the machining operations are realized through plastic deformation. This paper explores flow drilling steps and the parameters which influence heating and local softening of the aluminum sheet 5182-0. An experimental study has been carried out by varying process parameters (rotational speed, drilling force), coating and geometry of the screw. As a result, an increase of rotational speed and drilling force allows significant reduction in drilling time and introduce an important variation of the torque installation. In addition, a strong dependence is observed between drilling time and torque on the one hand, and related to the screw parameters geometry and coating on the other hand. Finally, an evaluation of the heating effect on the thread forming operation is also undertaken.

Impact of tool wear on cross wedge rolling process stability and on product quality

Cross wedge rolling (CWR) is a metal forming process used in the automotive industry. One of its applications is in the manufacturing process of connecting rods. CWR transforms a cylindrical billet into a complex axisymmetrical shape with an accurate distribution of material. This preform is forged into shape in a forging die. In order to improve CWR tool lifecycle and product quality it is essential to understand tool wear evolution and the physical phenomena that change on the CWR process due to the resulting geometry of the tool when undergoing tool wear. In order to understand CWR tool wear behavior, numerical simulations are necessary. Nevertheless, if the simulations are performed with the CAD geometry of the tool, results are limited. To solve this difficulty, two numerical simulations with FORGE® were performed using the real geometry of the tools (both up and lower roll) at two different states: (1) before starting lifecycle and (2) end of lifecycle. The tools were 3D measured with ATOS triple sc...

A Contribution on Manufacturing Process Development for Composite Material Forming

The author presents an approach to study an innovative manufacturing process developed to produce composite parts with new geometrical possibilities. The aim of this first study is to understand the motions of fibers during the forming of this kind of composite parts and to explore the feasibility of this forming process by an experimental analysis and FEM simulations with Forge3©. The reliability of the simulation tool and its potential, never exploited in this area, will be evaluated.

FSW Process Tolerance According to the Position and Orientation of the Tool: Requirement for the Means of Production Design

Friction Stir Welding (FSW) is an innovative welding process increasingly used by industry for the welding of aluminum alloys. In order to reduce the high investment costs of a dedicated FSW’s machine and in order to offer more flexibility to weld complex geometry, high payload robots may be used. A serial kinematics robot meets these specifications but under the stresses generated during welding, its structure readily deforms. The consequences are deviations of the tool nominal position with respect to the seam. The work presented here proposes to study the process tolerances with tool positioning defect. An experimental study enables to evaluate the influence of the tool position disorientation on weld quality, the travel force and torque generated. The objective is to estimate the impact of the disorientation on the tool mechanical interactions when welding using a serial kinematics robot.

Development of a tool design method in cross wedge rolling: description and applications

Till now, the definition of cross wedge rolling dies requires know-how and important expertise from the designers. A decision-making methodology is being developed to provide sequential and logical steps to draw easier and faster the tool geometry. This methodology is based on designing rules found in literature that link the geometrical parameters of the desired rolled part and the geometrical parameters of the tool. Nevertheless, in the literature, the rules are not always consistent because the admissible domain for a parameter can differ from one author to another. In order to take into account this variability, a stability index is associated to each rule and to the designed tool. The methodology allows updating of the existing rules and the implementation of new rules. The set of parameters defining the geometry of the tool can be exported in the CAD/CAM software and FEM software. A case-study is presented to illustrate and validate the methodology.

Application of X-ray Microtomography to Quantify the Liquid Fraction of M2 Steel for Semi-solid Forming process

Thixoforging, one variant of semi-solid metal processing in which the metallic alloys are processed at low liquid fraction (0.1< Fl < 0.3), is used to produce complex parts with high mechanical properties. Steel thixoforging faces more challenges as compared to that of low melting point materials due to high processing temperature and lack of understanding of the thermomechanical behavior of materials in the given conditions. It is crucial to study the microstructure at the semi-solid state to improve the understanding of the thixoforging process since the material behavior strongly depends on main parameters: the liquid fraction, its distribution as well as the coherence of the solid skeleton. The microstructure has a great influence on the viscosity of the material, on the flows and finally on the final shape and mechanical properties of the thixoforged parts. Here, the characterization of the volume percentage and distribution of liquid fraction at the semi-solid state with high energy 3D X-ray microtomography was investigated on M2 steel grade as a ‘model’ alloy. The obtained results have been compared to 2D observations using EDS technique in SEM on heated and quenched specimens. They showed a good correlation making both approaches very efficient for the study of the liquid zones at the semi-solid state.