Cold Upsetting Research Articles

Workability Studies in Forming of Sintered Fe-0. 35C Powder Metallurgy Preform During Cold Upsetting

An experimental investigation on the workability behaviour of sintered Fe-0. 35C steel preforms under cold upsetting, have been studied in order to understand the influence of aspect ratio and lubrication condition on the workability process. The above mentioned powder metallurgy sintered preform with constant initial theoretical density of 84% of different aspect ratios, namely, 0.4 and 0.6 respectively were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 °C. Each sintered preform was cold upset under nil/no and graphite frictional constraint, respectively. Under the condition of triaxial stress densification state, axial stress, hoop stress, hydrostatic stress, effective stress and formability stress index against axial strain relationship was established and presented in this work. Further more, attained density was considered to establish formability stress index and various stress ratio parameters behaviour.

Carbide morphology in steel subjected to cold deformation

Spheroidizing annealing is an important step in the manufacture of metal products by cold upsetting. Deformational and thermal treatment ensures high levels of cementite spheroidization with highly uniform product structure and properties.

Deformation Behavior of Sintered Fe-C-Mn Composite During Cold Upset Forming

Experimental investigations were undertaken in order to understand the mechanism of deformation and densification behavior during cold upset forming operation on sintered Fe-C-Mn composite preforms of two initial aspect ratios 0.45 and 0.60. The preforms were prepared out of mixed elemental powders of Fe, C (0.05, 0.10, 0.15, and 0.20 %), and Mn (0.20 %) and compacted by 1 MN Universal Testing Machine with pressure of 1.1 GPa and then sintered in electrical muffle furnace for an hour and followed by cooling to room temperature in the furnace itself. The material properties of sintered Fe-C-Mn composite preforms were ascertained from the uniaxial compression test. Deformation experiments were carried out in several steps. Analysis of the experimental data showed an increasing trend in the attained density ratio with respect to the strain factor. Preforms having lower aspect ratio had enhanced densification qualities, compared to preforms possessing higher aspect ratio for any given initial preform density. The instantaneous Poisson's ratio with respect to the density ratio attained three distinct stages and approaches to the value of 0.50 of Poisson's ratio. Also an attempt has been made to find the relation between axial stress and axial strain with different aspect ratios and different percentage of carbon content.

Optimization of Molding Process Parameters for Steel Ball Billet

Such evaluation standards as plumpness, roundness, force of cold upsetting, and the volume are made through the research on cold upsetting steel ball. Through a designed orthogonal test and the DEFORM simulation analysis, the process of ball billet is explained reasonably after primary selection and screening. Thus through comparison, it is seen that the original process is improved to a large degree.

Influence of carbon content on densification behaviour in forming of sintered plain carbon steel preforms

Complete experimental investigation on the deformation and densification behaviour of sintered plain carbon steel cylindrical preforms with carbon contents of 0, 0.35, 0.75 and 1.1 per cent, under cold upsetting, have been studied in order to understand the influence of various forming parameters such as true axial strain, flow stress, Poisson's ratio, forming limits and formability stress index on the densification process. The above-mentioned powder metallurgy sintered preforms with constant initial theoretical density of 84 per cent and aspect ratio of 0.4 were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 °C. Each sintered preform was cold upset under two different frictional constraints, namely, nil/no and graphite lubricant conditions. Densification–true strain and fracture strain–carbon content relationship was established and presented in this work. Further, attained density is considered to establish flow stress and formability stress index behaviour. The present work provides a guideline for producing P/M components free from open surface pore.

Microstructure, cold workability and strain hardening behavior of trimodaled AA 6061–TiO2 nanocomposite prepared by mechanical alloying

In the present work, the improvement of compressive ductility while maintaining high strength and toughness for nanocrystalline materials by cold upsetting (incremental loads) of bulk trimodaled composite was studied. Mechanically alloyed nanocrystalline (NC) AA 6061 alloy powders reinforced with nano TiO2 were blended with 0, 5, 10, 15, 20, 25, and 30 wt.% coarse grain (CG) elemental powders related to AA 6061 alloy composition to produce trimodal microstructure. The synthesized composite preforms were characterized by optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffraction. The room temperature compressive deformation behavior was evaluated under triaxial stress state condition. With increasing percentage of CG phase in the nanocomposite, the gradual improvement in compressive ductility was observed at the cost of a small amount of strength but it favored the ease of deformation. The 15% CG trimodal composite exhibited an extremely high compressive strength of 935 MPa due to non-coalescence of individual CG particles and effective load transfer occurred in multi scale microstructures. But the 30% CG trimodal composite showed an incremental compressive ductility of around 16% while sacrificing a small amount of strength (845 MPa) and this composite displayed improved toughness (area under true effective stress and true effective strain curve) of over 600% than nanocomposite (0% CG). Also, the percentage cold workability of 30% CG composite was six times higher than that of 0% CG composite. Hence, the 30% CG trimodal composite was observed to be the good one as it exhibited a better strain hardening behavior while maintaining considerable strength and toughness.

Effect of glass in aluminum matrix on workability and strain hardening behavior of powder metallurgy composite

A complete experimental investigation on workability behavior of the Al–Glass has been carried out during cold upsetting. The present study has been performed to evaluate the effect of different percentage of Glass addition in Powder metallurgy (P/M) preforms of Al–Glass composite on workability behavior. The material studied in this paper is aluminum with glass as reinforcement. Glass content has been varied from 0% to 8% with particle size of 60μm. The experimental results were analyzed for workability under triaxial stress state condition as a function of the relative density. The formability stress index (β), stress ratio parameters (σθ/σeff) were obtained for each percentage addition of Glass. It is found that as percent content of Glass increases, the workability parameter also increases. The addition of glass in Aluminum matrix affects the strain hardening index (n) of the composite.

Workability studies on cold upsetting of sintered copper alloy preforms

The major concern of the design for manufacturability is to accomplish the require deformation without failure of work material. The degree of deformation that can be achieved in a particular metal forming process without creating condition is termed as workability. The present investigation pertains to study the cold workability behaviour of Cu-7%Al-1.8%Si sintered preforms. Cold upsetting of these preforms with various aspect ratios were carried out and the working behaviour of the preforms at various stress state conditions was computed. The analysis measured for different components such as stress formability index and obtained density during secondary deformation as a function of induced strain. Similarly various computed stress ratio parameters with induced strain.

Ductility improvement methods for commercial AZ31B magnesium alloy in cold forging

In order to realize cold forging of magnesium alloys in practical application, some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy (Mg-3%Al-1%Zn, mass fraction) at room temperature were suggested. The effects of heat treatment before forging and hydrostatic pressure during forging on the ductility were investigated in cold upsetting and cup forging. High-temperature annealing was effective to reduce the degree of the texture anisotropy of the specimen, and it was found that the forging limit of the annealed specimen was improved in cold forging. On the other hand, cold cup forging of the annealed specimen was carried out with applying counter pressure. By applying counter pressures of 100-200 MPa during forging, the critical punch stroke for forging limit of the specimen without crack was improved by 25% in punch stroke.

Analysis of workability behavior of Al–SiC P/M composites using backpropagation neural network model and statistical technique

Abstract This paper presents an artificial neural network (ANN) model for predicting and analyzing the workability behavior during cold upsetting of sintered Al–SiC powder metallurgy (P/M) metal matrix composites (MMCs) under triaxial stress state condition which is the multifaceted technological concept, depending upon the ductility of the material and the process parameters. The input parameters of the ANN model are the preform density, the particle size, the percentage of reinforcement and the applied load. The output parameters of the model are the axial stress, the hoop stress, the axial strain, the hoop strain, the instantaneous strain hardening index, and the instantaneous strength coefficient. This model is a feed forward backpropagation neural network and is trained and tested with pairs of input/output data. A very good performance of the neural network, in terms of good agreement with the experimental data has been achieved. As a secondary objective, quantitative and statistical analyses were performed in order to evaluate the effect of the process parameters on the workability and the plastic deformation behavior of the composites.

A study on an effect of geometric singularities on ductile fracture

This paper describes the appearance of fractures in the vicinity of geometric singularities in cold upsetting of three series of slightly different samples between flat and spherical dies. The main goal of the research is to understand an effect of geometric singularities on ductile fracture. To this end, the series of tests are designed such that the site of fracture initiation moves to the geometric singularity, as compared to conventional tests, independently of its effect on the ductile fracture process. The paper concerns with a qualitative effect of geometric singularities on ductile fracture initiation rather than with quantitative values of parameters controlling the ductile fracture process.

NUMERICAL SIMULATION OF BULK METAL FORMING BY MESHLESS METHOD

Conventional finite element (FE) analysis of bulk metal forming processes often breaks down due to severe mesh distortion. In recent years, meshless methods have been considerably developed for structural applications. The main feature of these methods is that the problem domain is represented by a set of nodes, and a finite element mesh is unnecessary. This new generation of computational methods can avoid time-consuming meshing and remeshing. A meshless method based on reproducing kernel particle method (RKPM) is applied to bulk metal forming analysis. The displacement shape functions are developed from a reproducing kernel (RK) approximation that satisfies consistency conditions. The shape function is modified to impose essential boundary conditions accurately and expediently. A material kernel function that deforms with the material is introduced to assure the stability of the RKPM shape function during large deformations. A program based on RKPM is developed to simulate two examples of bulk metal forming process such as ring compression and cold upsetting, and numerical results demonstrate the performance of the meshless method in bulk metal forming analysis.

Material formability at cold upsetting of cylinder by different plates as a base for metal forming technology design

Upsetting of cylinder by flat dies is one of the elementary bulk metal forming operation. But, upsetting of cylinder can also be performed by the dies different than flat, which influences the stress-strain state and material formability. This paper describes the formability analysis at cold upsetting of cylinder and hollow cylinder by different plates (flat plates, hollow plates and hollow plates whit concentric channels). The aim of this investigation is determination of influences of die and workpiece geometry on stress-strain state and material formability. The obtained results are integrated in formability limit diagram, which represents relationship between limit strain (ϕe1) and stress indicator (ß). Experimental investigations have been performed on steel specimens C4146 (EN: 100Cr6). The determined diagram is a base for metal forming technology design, as it enables to predict damages of material structure during plastic deformation.

Effect of particle size of SiC in aluminium matrix on workability and strain hardening behaviour of P/M composite

A complete experimental investigation on workability behaviour of the Al–SiC has been carried out during cold upsetting. The present study has been performed to evaluate the effect of particle size of silicon carbide addition in P/M preforms of Al–SiC composite on workability studies. The material studied in this paper is aluminium with SiC reinforcement. SiC content has been varied from 0% to 20% with different particle sizes namely 50, 65 and 120 μm. The experimental results were analyzed for workability under triaxial stress state condition as a function of the relative density. The formability stress index ( β), stress ratio parameters namely σ θ/ σ eff and σ z/ σ m, strain hardening index ( n) value and strength coefficient ( K) value were obtained for each percentage addition of SiC and its particle sizes. It is found that these parameters have shown tremendous variations in their values for different particle sizes and percentage content of SiC.

Some aspects on plastic deformation of copper and copper–titanium carbide powder metallurgy composite preforms during cold upsetting

The densification, workability and strain hardening behaviour of sintered copper and Cu–7.5%TiC powder metallurgy (P/M) composite preforms during cold upsetting were investigated by the constitutive model using the experimental data. Cold upsetting of copper and Cu–7.5% TiC composite preforms having different aspect ratios were carried out and the formability behaviour of the preforms under triaxial stress state was determined. The mechanisms most likely involved in the constitutive model, namely, densification and strain hardening were studied. The effects of aspect ratio and addition of titanium carbide to copper on the formability behaviour and various constants involved in the constitutive model, namely, instantaneous density coefficient, instantaneous strain hardening index, instantaneous strain rate sensitivity and instantaneous strength coefficient were discussed in detail.

Cold and hot deformation and densification studies on sintered Fe-C-Cr-Ni low alloy P/M steels

The present research work pertains to the study of the densification behaviour of sintered low alloy P/M steels with Ni and Cr during cold and hot deformation processing. Elemental powders of atomized iron, graphite, chromium and nickel were mixed in suitable proportions using a ball mill, compacted and sintered in order to yield the following alloy compositions: Fe-0.2% C, Fe-0.2% C-1% Cr, Fe-0.2% C-2% Cr and Fe-0.2% C-1% Cr-2% Ni. The compaction was performed in a 1000 kN hydraulic press using suitable cylindrical die-punch combination. Sintering of the ceramic-coated cylindrical preforms was carried out at 1000 ± 10°C in a muffle furnace for a period of 180 minutes. Cold and hot upsetting studies on the sintered preforms were undertaken in order to study the densification and plastic deformation behaviour of the low alloy P/M preforms under various applied loads. Further, microstructural analysis was done on the cold and hot worked alloy preforms in order to correlate the deformation behaviour with the metallurgical structure of the alloys. Among the various alloys under consideration, the plain carbon steel preforms exhibit better densification and deformation behaviour under hot upsetting. The addition of Ni and Cr as alloying elements to the plain carbon steel preforms promotes better densification characteristics during cold upsetting. However, the deformation of the alloy preforms with Ni and Cr is found to be sluggish compared to that of the plain carbon steel preforms. So, it is contended that the presence of carbide phase in the case of alloy steel preforms containing Ni and Cr additions strongly influences the deformation behaviour of alloy preforms.

Effect of carbon content on instantaneous strain-hardening behaviour of powder metallurgy steels

Complete experimental investigation on the instantaneous strain-hardening behaviour of powder metallurgy preforms of pure iron and steels containing 0.4% and 0.8% carbon were carried out. The above-mentioned powder metallurgy sintered preforms with two different aspect ratios namely 0.39 and 0.59 were cold upset with graphite as lubricant and their strain-hardening behaviour under triaxial stress state condition was evaluated. For all the above-said preforms the stress–strain relationship was established, instantaneous strain hardening index was determined and its variation with respect to the axial strain and the relative density were plotted, studied and discussed relative to their as-sintered microstructures. Also the characteristics of the instantaneous strength coefficient with respect to the relative density was analyzed and presented.

Experimental study of the plastic deformation and densification behaviour of some sintered low alloy P/M steels

Abstract Elemental powders of atomized iron, graphite, molybdenum, copper and titanium were mixed in suitable proportions using a ball mill, then compacted and sintered in order to yield the alloy compositions such as Fe–0.5% C, Fe–0.5% C–2% Mo, Fe–0.5% C–2% Cu, Fe–0.5% C–2% Mo–2% Cu–2% Ti, Fe–0.5% C–2% Mo–2% Cu–4% Ti. The compacts were prepared in a 1000 kN hydraulic press using suitable cylindrical die-punch combination. Indigenously developed ceramic coated cylindrical preforms were sintered at 1000 ± 10 °C in a muffle furnace for a period of 120 min. In order to study the plastic deformation and densification characteristics of the low alloy powder metallurgy (P/M) preforms under various axial loads, the sintered cylindrical preforms were subjected to cold upsetting, hot upsetting and cold repressing. Further, microstructural analysis was carried out on the cold forged, hot forged and cold repressed alloy samples in order to correlate the plastic deformation and densification characteristics with the metallurgical structure of the sintered and forged alloys. Plain carbon steel preforms were observed to attain the highest levels of densification and axial deformation. Addition of Ti and Mo resulted in reduced levels of deformation as well as densification, irrespective of the mode of forming. The behaviour of the preforms containing Cu and Mo was intermediate between the plain carbon steel and the Ti-based steel. Microstructures of the Mo-containing alloy reveal the presence of fine particulates of Mo, TiC and pearlites, which account for the reduction in densification and deformation levels.

Economical preparation of 40X steel for cold upsetting of bolts

If hot-rolled 40X steel bar is prepared for cold upsetting by the energy-saving technology here proposed, the production costs of the resulting bolts will be reduced.

Deformation behavior of Al–4Cu–2Mg alloy during cold upset forging

Upsetting of cylinders is a standard test which determines the ability of material to be forged either in cold or warm worked condition without cracking. In the present work, cylindrical specimens of aluminum–4% copper–2% magnesium alloy are upset between flat platens to study the metal flow at room temperature. Lubrication at the interface of the die/work piece and the specimen aspect ratio ( H 0/ D 0) are studied as process parameters. Lubrication minimized the barreling of lateral free surface. Microstructural studies reveal the non-uniform deformation within the specimen. This effect is pronounced with high friction and low aspect ratio. Machine Vision system using PC-based video recording with CCD camera is used to study the pre-drawn square grid deformation at the equatorial plane of the specimen. The system is used to measure the axial and circumferential strain components during deformation. Finite element analysis of cold upsetting process is carried out in both dry and lubricated conditions with aspect ratios of 1.0 and 1.5. Rigid-flexible contact analysis is performed for the forming process. When the stress values obtained from finite element analysis are compared to the measurement of grids using the Machine Vision system it is found that they are in close proximity.