Drawing Pass Research Articles

Improved uniform ductility in a high-carbon pearlitic steel via microstructural homogeneity architecture

In this work, the nucleation and growth kinetics of pearlitic transformation are quantitatively investigated to unveil the distinctive microstructural evolution behavior under a high undercooling degree. Both intra-granular and inter-granular nucleation increasingly occur with 1-2 orders of magnitude increase in nucleation rate N˙. However, a moderate increase in the growth rate GV, namely a larger N˙/GV ratio, leads to a 30%–40% size reduction in pearlitic colonies. The avalanche-type increase in nucleation events induces a more random distribution of ferrite orientation among colonies that possess a slight increase in relative misorientation but a pronounced increase in accumulative misorientation, and an arbitrary alignment of Fe3C lamellas in colony interior. Such improved microstructural homogeneity ensures more uniform and localized deformability, which allows compatible deformation between colonies or within colonies and prevents the expansion of newly-formed cracks. These results provide guidance for industrial manufacture of high-carbon pearlitic products with high safety and reliability, resulting from the improvement in localized deformability, and for low-cost wires via reducing the drawing passes, stemming from the significant increase in uniform deformability.

High strength and ductility in a new Mg–Zn–Ga biocompatible alloy by drawing and rotary forging

A comparative study of the effect of drawing and rotary forging on the structure, mechanical and corrosion properties of a new biodegradable magnesium alloy Mg–2Zn–2Ga was carried out. The original 6 mm diameter bars obtained by hot extrusion were reduced to the diameters in the range 5.5–3.3 mm by drawing or rotary forging. Optical microscopy, scanning electron microscopy and EBSD grain orientation mapping were used to characterize the material microstructure. Tensile testing was performed to determine the mechanical properties. The optimum temperature for rotary forging and annealing after each drawing pass for defect-free bar production was found to be 300 °C. The combination of the highest strength and ductility was achieved in the 4.2 mm diameter drawn bar and is explained by the formation of numerous twin boundaries in the alloy structure. The 3.3 mm diameter bar obtained by drawing as well as the 5.5 mm diameter bar obtained by rotary forging showed a balance between high strength (260–310 MPa) and large elongation (9–12 %). The analysis of the stress-strain curves using Hollomon's equation was conducted. The hydrogen evolution test in Hanks' solution revealed that the drawn bars of diameters 4.2 and 5.2 mm, as well as the rotary forged bar of 5.5 mm possessed 3 times lower corrosion resistance reduced in comparison with the original 6 mm extruded bar. The 3.3 mm diameter drawn bar exhibited the lowest nominal corrosion rate of 0.11 mm/year that offers excellent opportunities for use in medical implants.

Shortening the manufacturing process of degradable magnesium alloy minitube for vascular stents by introducing cyclic extrusion compression

Due to its excellent biocompatibility and biodegradability, Mg and its alloys are considered to be promising materials for manufacturing of vascular sent. However, the manufacture of high-precision and high-performance Mg alloys minitubes is still a worldwide problem with a long manufacturing processing caused by the poor workability of Mg alloys. To solve this problem, the cyclic extrusion compression (CEC) was used to pretreat the billet by improving the workability of Mg alloys, finally shortening the manufacturing process. After CEC treatment, the size of grains and second phase particles of Mg alloys were dramatically refined to 3.2 µm and 0.3 µm, respectively. Only after three passes of cold drawing, the wall thickness of minitube was reduced from 0.200 mm to 0.135 mm and a length was more than 1000 mm. The error of wall thickness was measured to be less than 0.01 mm, implying a high dimensional accuracy. The yield strength (YS), ultimate tensile strength (UTS) and elongation of finished minitube were 220±10 MPa, 290±10 MPa and 22.0 ± 0.5%, respectively. In addition, annealing can improve mechanical property and corrosion resistance of minitubes by improving the homogeneity of the microstructure and enhancing the density of basal texture.

Analysis of the properties and microstructure of ultra-thin tube

In order to satisfy the requirement of the engine heat exchangers, ultra-thin tubes with higher dimensional accuracy and better performance are required. Inconel 718, as the basic material of ultra-thin tube, is one of the materials that can meet the requirements of the engine heat exchanger. In this study, ultra-thin tubes with diameters and thicknesses of 1.50mm and 0.050mm were prepared by floating plug drawing process. The results showed that the yield strength increased and the corresponding elongation decreased with the increase of drawing passes. The wall thickness of the ultra-thin tube can be controlled by floating plug drawing. And the inner surface quality was greatly improved compared with the initial tube. The inner surface roughness can be controlled below 1.7μm. The average grain size after drawing can be reduced from 4.9μm to 2.1μm.

Property profile development during wire extrusion and wire drawing of magnesium alloys AZ31 and ZX10

This paper deals with the impact of the wire manufacturing process on the mechanical property development of two magnesium alloys, AZ31 and ZX10. For this study, wires were produced with different diameters of up to 0.2 mm via direct one-step extrusion as a hot forming route and were directly compared to conventional cold drawing manufacturing routes with diameters up to 0.3 mm and associated heat-treatment. The alloy dependent microstructure development is resolved with respect to the underlying recrystallization mechanisms, which determines the texture development and concurrently the strength and ductility properties of the wires. The experimental results clearly show that the manufacturing process, the degree of deformation (wire diameter) as well as the alloy itself have a major impact on the texture development and mechanical properties of the wires. While AZ31, does not enable a strong impact on the microstructure development, ductility in ZX10 is enhanced with a concurrent weak texture development due to adjusted dynamic recrystallization during hot forming. In contrast, such microstructures cannot be adjusted in the cold forming routes due to static recrystallization. However, it is possible to improve of the properties significantly by drawing, which is limited by the first two drawing passes.

Multi-pass cold rolling and wire drawing process of gadolinium and its magnetocaloric effect

Owing to low ductility of magnetocaloric material (MCM)s, the plastic deformation process is quite challenging, and information available on the deformation process of MCMs is limited. In this study, the cold rolling and wire drawing processes of Gd wire including heat treatment were conducted. Uniaxial compression test of as-cast and heat treated Gd rod was conducted to evaluate the material property. The magnetocaloric effect (MCE) of drawn Gd wire was indirectly measured using a vibrating sample magnetometer (VSM). Pass schedule of cold rolling and wire drawing process for the Gd wire of Ø1.0 was designed. Finite element (FE) simulation of drawing process was conducted to investigate the drawing force for each drawing pass and strain distribution. Friction coefficient between the drawing die and Gd wire was evaluated via FE simulation and drawing experiments using a lubricant. Magnetic properties of the deformed and annealed Gd wire were evaluated and compared. The evaluated magnetic properties have shown that the presented process schedule is reasonable for manufacturing magnetocaloric wire without diminishing the magnetocaloric effect.

Process Stability and Reproducibility of the Dieless Drawing Process for AZ31 Magnesium Wires

Magnesium (Mg)-based wires are in the focus of interest for numerous applications like micro-forming technologies or medical engineering. Manufacturing thin Mg-based wires is widely realized by applying a conventional multiple pass cold wire drawing process. This requires a complex manufacturing schedule of multiple passes with intermediate heat treatments to overcome work hardening, because of the cold forming process. Especially Mg and its alloys are known for their rather low formability at room temperature associated with the hexagonal close-packed lattice structure. The dieless drawing process uses local heating to initialize a localized plastic zone under an external tensile load to achieve higher reductions in diameter in a single wire drawing pass. It can therefore present a solution for a more efficient warm manufacturing process of Mg-based wires. In this study, the stability of the steady state material flow during a dieless wire drawing process and its reproducibility was investigated. For this purpose, a variation of process parameters was selected and wire manufacturing was carried out using magnesium alloy AZ31. A single and double dieless drawing process was applied. Additionally, a conventional cold wire drawing process including a die with the same forming schedule was executed as a benchmark experiment. The results of this study show, that the dieless drawing process is not only a stable process after reaching the steady state, but it is also a reproducible and accurately adjustable process. Moreover, the dieless drawing process maintains the property profile of the starting material to a large extend.

Experiments and numerical analyses on splitting fracture of wire under multi-pass drawing

The splitting phenomenon during drawing will cause the quality decline of wire. A clear understanding of formation mechanism of splitting can help to promote the development of engineering drawing. Therefore, the splitting fracture and microstructure are analyzed by SEM. The experimental results indicate that the main crack run through the core and surface of both sides of wire. Furthermore, multi-pass drawing of different material properties and die angles is simulated by using FEM with the developed damage modeling. The results show that after each drawing pass, the damage and section stress are formed near the center and surface of wire, respectively. Meanwhile, the damage will be enhanced with the increase of die angle, drawing strain and material properties. Among these influencing factors, the die angle has little effect on the section stress, but the increase of the other two factors will lead to the gradual increase of section stress. Moreover, wire core becomes the source of crack due to its larger damage, and then crack propagates to the surface of wire under the action of stress, thus forming splitting fracture.

Tube Drawing with Tilted Die: Texture, Dislocation Density and Mechanical Properties

Anisotropic behavior is a key characteristic for understanding eccentricity in tubes. In this paper, the effect of using a tilted die during tube drawing on eccentricity, texture, dislocation density, and mechanical properties is shown. Copper tubes were drawn with a ±5° tilted die for two passes. The increase or decrease in eccentricity can be controlled by controlling the angle of the tilted die. Two types of textures have been developed during tube drawing, namely plane strain and uniaxial types. Plain strain type texture is mainly characterized by the β fiber with a dominant copper component {112}<111>. The uniaxial deformation type is dominated by the <111> fiber, as commonly found by wire drawing. Texture sharpness increases with increasing drawing strain, and the texture varies significantly between the maximum and minimum wall thickness. This texture variation between maximum and minimum wall thickness has no significant influence on mechanical properties, which are more or less similar, but the increase in strength after each drawing pass is apparent. The dislocation density is low for the as-received tubes due to recovery and recrystallization. This is consistent with the as-received texture dominated by the cube component {001}<100>. During tube drawing, dislocation density increases as a function of the deformation strain. The variation of dislocation density between the maximum and minimum wall thickness in the tube deformed with −5° tilted die is higher than the variation in the tube deformed with +5° tilted die.

Texture Evolution during Cold Drawing of Steel Tube with Respect to the Stress - Strain State

Cold tube drawing is a metal forming process that enable to manufacturers to produce high precision tubes. The dimensions of the tube are reduced by drawing it through a conical converging die with or without inner tool. There are four types of tube cold drawing process. Their difference relies on the technique used for inner diameter calibration. Therefore, the main objective was determining the difference in development of crystallographic texture and stress-strain state between drawing with the fixed plug and hollow sinking process. The input feedstock (with E235 steel grade) after the recrystallizing anneal was cold drawn (drawing with the fixed plug, hollow sinking) by one drawing passes. Electron BackScatter Diffraction (EBSD) analysis was used to evaluate the changes of grain structure and texture connected with tubes manufacturing. The stress-strain state in the tube material during drawing was calculated using DEFORM-3D software and the crystallographic orientation with respect to the cylindrical reference frame (Z-direction = drawing direction). A significant difference in stress-strain state between drawing with the fixed plug and hollow sinking process was recorded in radial direction.

Effect of Drawing Pass on Softening or Plasticizing of Q235 Steel Bar during Electrochemical Cold Drawing

In this work, the effect of drawing pass on the surface layer softening or plasticizing of Q235 steel bar during electrochemical cold drawing (ECD) was studied, as well as cold drawing in air (DIA) for comparison. The results indicate that the softening or plasticizing degree gradually decreases with increasing drawing pass. The reason for this should be that dislocations generated in surface layer are only partially overflowed from the surface in the form of additional dislocation flux. The general dislocation density thereby gradually increases with the increase in drawing pass, resulting in the increase in the work hardening degree of the surface layer, and thus, the drawing stress. In this case, the texture orientation of the bar surface layer is gradually enhanced. In contrast, the dislocation density, and thus the work hardening degree of DIA bar, are higher than those of the ECD partner, resulting in larger drawing stress. ECD can obtain a product with excellent comprehensive mechanical properties compared with DIA, and there are no cracks on the fracture surface of ECD bar drawn for at least seven passes.

Achieving homogeneous distribution of high-content graphene in aluminum alloys via high-temperature cumulative shear deformation

Homogeneous dispersion of high-content graphene nano-platelet (GNP) in metals is challenging due to the serious aggregation tendency of graphene. Traditional secondary processing such as extrusion usually has too limited shear strains to reach a desirable GNP dispersion state. Our previous work demonstrated that 1.0 vol% GNP/Al composite was successfully produced via multiple wire-drawing at ambient temperature. However, the fabrication of 5.0 vol% GNP/Al composite was not successful because of the limited cumulative shear strains. Here we described fully dispersed state of 5.0 vol% GNP in Al by hot-drawing at an elevated temperature 400 °C. The evolution of the microstructures and mechanical properties were investigated in relation to the number of drawing passes. The ultra-fine grains with size 372 nm were obtained via dynamic recrystallization after drawing for six passes (cumulative strain 94%). In particular, stripping of the GNP into thin layers and their preferential alignment in the wire axis occurred during the shear deformation. As a result, 5.0 vol% GNP/Al composite produced by six-pass drawing possessed improved yield strength (σs, 449 MPa) and ultimate tensile strength (UTS, 461 MPa). The results demonstrated the feasibility of dispersing high-content GNP in aluminum alloys by extrusion followed by multi-pass hot drawing techniques.

Simulation of two hollow sinking passes in one tool

The paper deals with optimization of hollow sinking process of seamless steel tube E235. Specifically, the last two sequences are merged into one drawing pass by one tool. Saving one hollow sinking operation will save rebuilding on the drawing bench, tube handling and increase drawing capacity in short time. The input feedstock with outer diameter Ø18 mm and wall thickness 0.9 and 1.0 mm was drawn into tube with final dimension Ø10 × 1.0 mm by single-die and double-die. The aim of the numerical simulations was to compare the flow of material by means of monitored values (stress, deformation) in different technologies. The final drawn tubes differed in wall thickness. This is due to the stress-strain state in the deformation zone. Both simulation and experiment of cold drawing of Ø18 × 0.9 (1.0) mm hollow into Ø10 × 1.0 mm tube confirmed that the double-die configuration is inferior to the single-die one when it comes to the optimum material flow.

Microstructural evolution of equal channel angular drawn purity titanium at room temperature

Thin commercial-purity titanium (CP–Ti) wire was successfully acquired by equal channel angular drawing (ECAD) at room temperature with route Bc using a 90° die at a relatively high drawing speed of 10 mm s−1. The as-drawn CP–Ti wires were of good quality free of cracks and segmentation on their surface. The grain size of CP–Ti was reduced from ∼32 μm for the as-annealed wire to ∼700 nm for 12-passes equal channel angular drawn wire. The grain experienced transition from microband to thin lath and to equiaxed subgrains with the increment in drawing passes. Face-centered cubic (FCC) phase was triggered obviously to accommodate the large shear strain induced by ECAD at the drawing rate of 20 mms−1. The thickness of the FCC phase increased with an increase in drawing passes, and no equiaxed subgrains were formed in CP–Ti. Accordingly, the drawing speed significantly affects the deformation mode and microstructural evolution of CP–Ti during ECAD. A lower drawing speed provides a longer time for the structure recovery, thus resulting in the occurrence of dynamic recovery when ECAD was performed at room temperature. Additionally, {101¯2} tension twinning and {112¯2} compression twinning occurred simultaneously to accommodate ECAD shear deformation. The success in processing CP–Ti rods at room temperature through multiple passes of ECAD provides a new perspective to efficiently fabricate ultrafine grained small-sized materials continuously.

Evolution of deformation texture in cold drawing of steel tubes using EBSD analysis and FEM simulation

Cold drawing of steel tubes is the manufacturing process characterized by anisotropic material flow during drawing. In this paper, the micro structural of the E235 steel tube after recrystallization annealing and cold drawing were characterized by optical microscopy and EBSD (Electron BackScatter Diffraction) analysis performed on a scanning electron microscope. The input feedstock after recrystallization annealing with dimensions of ø 25.0 mm × 1.5 mm (O.D × W.T.) was cold drawn in two drawing passes with fixed plug to the final dimensions of ø 18.0 mm × 0.9 mm (O.D × W.T.). The development of crystallographic texture (both qualitative and quantitative) was analysed on a longitudinal section of the tube. The stress-strain state in the tube material during drawing was calculated by FEM (Final Element Method) software and the development of the texture depending on the stress-strain state in three different directions using cylindrical coordinates with respect to the drawing direction was evaluated. We have investigated the ratio of individual crystallographic planes depending on stress state during drawn tube. The main objective was to define the development of crystallographic grain orientation from stress-strain state during cold drawn tube.

Experimental Research on Influencing Factors of Basic Mechanical Properties of Stainless Steel Wire

The effects of drawing process, heat treatment temperature and drawing rate on the basic mechanical properties of stainless steel wire were studied by room temperature tensile test. Results indicated that with the increase of drawing passes, the tensile strength and the yield strength of stainless steel wire increased gradually and the elongation after fracture decreased gradually. With the increase of heat treatment temperature, the tensile strength decreased and the elongation after fracture increased gradually. Under the same heat treatment temperature, the tensile strength of the specimens treated by the two-drawing process was greater than that of those treated by the one-drawing process, while the elongation after fracture was less than that of those treated by the one-drawing process. The increase in drawing rate would increase the strength and modulus of elasticity of the stainless steel wire.

Effect of Cold Drawing Pass Schedule on Mechanical Properties and Microstructure of ST 52 during Cold Drawing of Seamless Tubes and its Influence on Springback

Effect of Cold Drawing Pass Schedule on Mechanical Properties and Microstructure of ST 52 during Cold Drawing of Seamless Tubes and its Influence on Springback

Possibilities of Stereological Analysis of Grain Boundary Orientation in Longitudinal Sections of Precision Cold Drawn Seamless Steel Tubes

Cold drawing of steel tubes refers to a forming operation where a precision steel tube is being formed in a die while reducing tube cross-section, altering the wall thickness and making the final tube much longer than the original hollow. The forming itself takes several drawing passes (a.k.a. draws) depending on the final tube dimension requested. The selection of relative reduction for a particular tube diameter plays an important role because an excessive reduction during drawing causes stresses that induce substantial plastic deformation, eventually leading to cracking. In this paper we evaluate the effect of selected reductions on the longitudinal grain boundary orientation in cold drawn tubes, taking tube sample measurements and making necessary calculations of grain boundary orientation in selected planes.

On numerical modelling of multi-rifled tube drawing

Abstract Production of precision seamless steel tubes in Zeleziarne Podbrezova is divided into several technological steps, with final cold drawing determining final tube dimensions. The drawing itself usually takes several drawing passes with intermediate heat treatment. For multi-rifled tubes, the last drawing pass utilizes a special, free-to-rotate plug with multiple helical grooving so to produce a helical rifling pattern on the inner surface of the tube. A crucial factor to meet stringent dimensional tolerances on rifling geometry is to determine proper input dimensions of the tube just before the final rifling pass. Also, drawing velocity is another key factor that not only determines the overall productivity but the quality of the rifling as well. Due to the high costs of plant trials in early stage of technology development, computer simulation approach can easily serve the purpose very well, thus saving us from laborious and costly pilot experiments. Numerical modelling software DEFORM-3D has been utilized in Zeleziarne Podbrezova for drawing technology development and optimization for T12 steel tubes with 28.6 × 6.3 mm (O.D. × W.T.) In particular, both input dimensions and drawing velocity were optimized while meeting rather strict dimensional requirements on tube rifling. Resulting tube & rifling dimensions were in good accordance with dimensions from experimental proofing trials, where the actual dimensions were obtained via 3D optical scanning of multi-rifled tubular samples.

Deformation prediction and Finite Element Analyses of precision seamless tubes during cold drawing

This paper deals with the deformation of precision seamless tubes during the cold drawing process, using Finite Element Methods. The value of strain obtain by stereology measurement of degree grain boundaries deformation are compared with simulation result for each drawing pass. The material chosen was the E235 and E355 steel grade, which is drawn from the initial dimension of Φ 70 × 6.3 mm to the final dimension of Φ 50 × 3.75 mm by two passes. FEM Software DEFORM 2D with the Lagrangian method is used to numerical analyses of the cold drawing process.