CONFORM Continuous Extrusion Research Articles

Microstructural and mechanical properties of ZA10 alloy tubes and their weld seams prepared by Conform continuous extrusion

In the present work, Zn–10Al–2Cu–0.05Ti (ZA10) alloy tubes with a diameter of 12.5 mm and wall thickness of 1.2 mm were fabricated by one-pass and double-pass Conform continuous extrusion. A stabilizing heat treatment [350 °C, 30 min (furnace cooling) + 120 °C, 12 h (air cooling)] was also applied to some of the double-pass tubes to improve the quality of their weld seams. The yield strength, ultimate tensile strength, elongation and expansion ratio of the one-pass continuous extrusion tube were 268.4 MPa, 294.3 MPa, 13.8% and 5.5%, respectively. Double-pass continuous extrusion improved these values to 278.4 MPa, 317.2 MPa, 15.4% and 11.4%, respectively. Double-pass tubes also had fewer aggregations of Al-α precipitates along the welding seam, which improved seam quality and caused cracks to appear in the matrix, away from the weld-affected zone, during expansion testing. Heat-treated double-pass tubes exhibited superior yield strength (283.9 MPa) and ultimate tensile strength (328.5 MPa) but lower elongation (10.2%) and expansion ratios (10.3%). Additionally, the heat-treated tubes exhibited markedly lower elongation at room temperature due to the remarkable blockage of dislocation motions by fine-scale lamellar (α + η) eutectoid structures and a lower size effect when stretched.

EXTRUSION OF 01417 ALLOY INGOTS OBTAINED IN THE ELECTROMAGNETIC CRYSTALLIZER AT THE CONFORM UNIT

It is known that casting long ingots of small sections (∅8–12 mm) of 01417 alloy into an electromagnetic crystallizer makes it possible to obtain a dispersed structure with insignificant intradendritic segregation. Diffusion annealing of ingots (550 °C, 4–5 h holding time) eliminates intracrystalline segregation and reduces the level of internal stresses in metal thus providing the conditions for subsequent wire drawing. The paper demonstrates that high plastic deformation of ingots without diffusion annealing can be achieved by Conform continuous extrusion, which ensures high quality and geometrical accuracy of products. The analysis of various Conform units revealed an inherent weakness – the absence of connection between the system securing the fixed part of the detachable container (shoe) and the drive wheel shaft, which leads to an increased load in the operating mode. The purpose of the work was to upgrade the Conform unit by creating a connection between the shoe and the impeller shaft to obtain a high-quality billet for subsequent wire drawing of the ∅12 mm ingot cast into the electromagnetic crystallizer. An optimal temperature of ingot extrusion (300 °С) was found to eliminate the intense adhesion of wrought metal on the tool surface. The experimental ∅5 mm rod made of 01417 alloy obtained from the ∅12 mm ingot at the Conform unit features high processing ductility. This is indicated by an increase in its yield point and relative elongation. Metallographic studies demonstrated a fine-grained structure achieved in the extruded rod, which provides the conditions for subsequent wire drawing without annealing. The results of the study provide a basis for refining the process conditions of calibrated billet production on the Conform unit followed by wire drawing with required properties.

The microstructure and mechanical properties evaluation of UFG Titanium Grade 4 in relation to the technological aspects of the CONFORM SPD process

Abstract Processes based on severe plastic deformation (SPD) that are capable of producing microstructures with sizes on the order of nanometres are gaining importance these days. Their typical limitation is the small volume of the material processed. One of available ways to enhancing the productivity is to combine the CONFORM continuous extrusion process with the ECAP method. In the present study, commercially pure Grade 4 titanium was processed using the CONFORM SPD machine. The process was carried out at 220 °C. In total, three passes through the CONFORM SPD equipment were completed. The first pass through the CONFORM SPD machine led to a considerable reduction in grain size: from 12500 nm to 300–400 nm. Subsequent passes did not refine the grain any further. Instead, equiaxed grains were obtained. The mean grain size even increased after the third pass to values in the range of 400–450 nm. The first pass resulted in a marked increase in ultimate strength from 650 MPa to 750 MPa. Subsequent passes led to smaller increments that corresponded with the grain sizes attained. After the third pass, the ultimate strength reached 773 MPa. The present study highlights the potential of the continuous production of UFG materials by application of large deformation, and describes the dependence of materials characteristics on technological aspects of the process.

Investigation of Clad Wire Production by Conclad Extrusion with Twin Wheels

Abstract Conform continuous extrusion is a unique extrusion process in which the extrusion force originates in the frictional force between the feedstock and wheel. When this extrusion process is applied to conclad extrusions, however, the metal flow is highly complex and hitherto undetermined. In this study, a model experiment and numerical model were developed, to elucidate the material flow. Previous studies have shown that, in conform devices consisting of one wheel with twin grooves, dead metal in the chamber is incorporated into the product and the joining pressure is not strong. To address these problems, a novel experimental device, consisting of twin wheels, was designed, which succeeded in preventing the incorporation of dead metal into the product; however, numerous relevant characteristics and problems have not yet been elucidated. The present study investigated the effect of differing tool geometries in such a device. Based on experimental results using modeling material, it is clear that the feedstock diameter should be determined with consideration of the joining pressure and product yield ratio. Further, scrapers influence the metal flow in front of the abutment, and are clearly important for ensuring smooth metal flow along the path. Finally, based on the numerical simulation results, it is clear that the gap between the wheel groove and abutment is important for preventing the oxide surface of the feedstock from being incorporated into the product; however, as the gap increases, the joining pressure decreases.

Flow Analysis of Conclad Extrusion with Two Wheels

Conclad extrusion using one wheel with two grooves was developed from Conform continuous extrusion and is used to manufacture trolley wire for Japanese trains. On the other hand, we developed Conclad extrusion with two wheels and investigated metal flow in this process by model experiment. Conclad extrusion with two wheels had two clear advantages over the use of one wheel with two grooves, namely there was a decrease in the content of dead metal in the chamber and the flow conditions were more appropriate for bonding. It is clear that bonding condition is good in case that abutment angle is 60°.

Technological aspects of preparation of nanostructured titanium wire using a CONFORM machine

One of available ways to enhancing the efficiency of production of sections is combining the CONFORM continuous extrusion process and the ECAP method. This paper describes the initial experience with such a combined process deployed in the CONFORM 315i machine, which is equipped with a specially-designed die chamber. Process trials were performed to explore the effects of the set-up of the CONFORM equipment on the resulting microstructure of Ti wire. The feedstock was in the form of CP Ti grade 2 bars of 10 mm diameter. Crucial parameters of the process include the temperature of the die chamber, which was purposefully varied from the initial 500 °C to the final 200 °C, and the cooling stage, which was realized immediately upon the exit from the die chamber. The mean grain size, mechanical properties and thermal stability were measured and studied in the specimens upon forming. The smallest grain size was achieved by two passes at 200 °C.

Study of Thermal Stability of Ultra Fine-Grained Commercially Pure Titanium Wire Prepared in Conform Equipment

Titanium and its alloys are frequently used in many sectors, including the health care sector, where they outperform other materials. From the biocompatibility viewpoint, the preferred condition of these materials is ultrafine or nanostructured state. Processes based on severe plastic deformation (SPD) that are capable of producing microstructures with sizes of the order of nanometers are gaining importance these days. Their typical limitation is the small volume of material processed. One of available ways to enhancing the productivity is to combine the CONFORM continuous extrusion process with the ECAP method. This paper describes initial experience with this combined process in the CONFORM 315i machine, which is equipped with a specially-designed forming die chamber. Influence the number of passes through CONFORM machine on thermal stability was study by horizontal dilatometer and heat-flux calorimeter. The impact of deformation on the shift in recrystallization temperature of pure titanium was confirmed. The microstructure evolution and the grain growth behavior were investigated by electron back scattered diffraction (EBSD) technique. The deformed UFG titanium was annealed at a range of temperature (400-600 °C) for up to 6 h. The grain growth kinetics was characterized by calculating the grain growth activation energy Q and the time exponent n based on the experimental results for deformed material. Data for annealing temperatures of 550 and 600 °C allowed the values of the time exponent n = 0.19 and activation energy Q = 248 kJ/mol were calculated.

Investigation of Conclad Extrusion and Multi-Billet Extrusion

In Nihon University, Conform continuous extrusion and new extrusion processes which are called multi-billet extrusion have been investigated last ten years. Conclad extrusion which was developed from Conform continuous extrusion[1], is applied to manufacturing trolley wire for train in Japan. The trolley wire which is copper covered steel wire has shorter life cycle than expected one because of corrosion for acid rain. The quality of welding part of copper must be improved. In this paper, it is investigated how to decrease involving oxide films in welding part by experimental method. On the other hand, the multi-billet extrusion[2] is applied to manufacturing automotive frames, especially impact attenuators. The developed extrusion process has been done under experimental condition. However, it is capable to vary geometries of rib which is in the inside of closed profile extruded products by this process.

An analysis of the contact stress distribution at the surface of the tooling during the CONFORM process

The CONFORM continuous extrusion process provides outstanding features and the process has been widely used in non-ferrous metal production since it was invented. Although research and development has been quite extensive, theoretical analysis of the process has been based purely on the finite-element method, which is unable to give suitable analytical equations for calculating the stress distribution. Theoretical expressions for the contact stress distribution between the deforming material and the tools are derived in this article for the specific purpose of evaluating the load and power requirements of the machine. A simplified five sub-zone model is first established according to the different deformation characteristics in the different regions of the machine. Subsequently theoretical solutions are obtained based on simplified plasticity analysis and finally expressions are derived that can be used for calculating the load acting on the extrusion wheel and shoe. In addition, experimental verification of the theoretical results is reported.

Parametric investigation on the curling phenomenon in CONFORM process by three-dimensional finite element analysis

Owing to the circular material flow, a CONFORM continuous extrusion forming process exhibits more complicated process characteristics compared to conventional front- and side-extrusion processes. One remarkable thing is the curling phenomenon in the material flow after it passes through the die, and which is caused solely by the non-uniformity in material velocity profile at the die section. Since this process has been introduced, this phenomenon has not been intensively studied, and furthermore most of analytical and numerical studies for the process have been carried out with the simplified two-dimensional plane-state model. Through the three-dimensional finite element analysis of CONFORM process, we in this paper address the parametric investigation on the curling phenomenon together with the more realistic understanding of the flow characteristics in the die region. For the parametric experiments, we take the wheel velocity, the abutment height and the flash gap size as considering parameters.

CONFORM continuous extrusion process – its contribution to energy conservation

The introduction includes a brief résumé of the development of the CONFORM process, from its invention at the UKAEA Springfields Laboratories in 1971 to the present, at which time it has established itself as having many industrial applications in the extrusion of solid and hollow sections from many non-ferrous metals, in rod or particulate form, together with the potential for extruding direct from molten metal. Consideration is given to energy-saving aspects, especially when extruding from particulated metals, not only as an alternative to conventional press extrusion from billets, but also as an extension to powder metallurgical technology. Of particular relevance is the application of CONFORM to the reclamation both of prime metal waste from manufacturing operations and of used scrap. Irretrievable disposal and remelting to ingot and billet for subsequent fabrication are taken as the bases for assessing the energy savings attainable by integrating CONFORM with various pretreatments.