Showing papers on "Forging published in 2013"

Softening of Al during multi-axial forging in a channel die

Abstract: Multi-axial forging of Al was carried out at room temperature in a confined channel die as a means of achieving severe plastic deformation (SPD). The microstructures of the 3, 6 and 9 pass samples were quantified using electron back scattered diffraction to obtain the distribution of boundary spacing and fraction of high angle boundaries. Subsequent compression tests at room temperature were carried out to determine their strength and strain rate sensitivity. Softening was observed beyond 6 passes both in terms of the pressing stress as well as the subsequent compression tests. Beyond 6 passes the fraction of high angle boundaries increased and the geometrically necessary dislocations (GND) density decreased. It was estimated that during SPD, Al had a higher hardening contribution due to GND and subgrain walls than that due to Hall–Petch type grain boundary strengthening. It was shown that as the fraction of high angle boundaries increased with increasing deformation, the dislocation strengthening term decreased and the Hall–Petch term increased, resulting in a net softening effect.

Decision Making With the Analytical Hierarchy Process (AHP) for Material Selection in Screw Manufacturing for Minimizing Environmental Impacts

Abstract: This study is an approach to investigate the environmental impact of screw manufacturing and to choose suitable material for selected screw-making processes for the best performance with minimum environmental impact. The parameters involved were types of material and screw-making process using the environmental data available in Asia region. The two different manufacturing approaches being evaluated were machining and forging. The types of material considered were low carbon steel, stainless steel, titanium alloy and aluminium alloy. As for machining process, the materials being considered in screw manufacturing were low carbon steel, stainless steel, titanium alloy, aluminium alloy, magnesium alloy and cast iron. The information of environmental impact are generated by SolidWorks. Sustainability tool was used in the formation of pair-wise comparison matrices for Analytic Hierarchy Process (AHP). Then, the ranking of global priorities had enabled the determination of appropriate material to be used for those selected screw manufacturing process. As a result, aluminium alloy was found to give minimum environmental impact for forging process whereas cast iron was found to excel in machining process. At the same time, titanium alloy was not suggested to be used in either process.

Strain-induced grain evolution in an austenitic stainless steel under warm multiple forging

Abstract: The dynamic processes of ultrafine grain evolution in an S304H austenitic stainless were studied in multiple forging tests at temperatures ranging from 500 °C to 700 °C. The multiple forging was accompanied by the development of dynamic recrystallisation (DRX), which resulted in the formation of ultrafine grained structures. The size of the DRX grains decreases from 0.3 μm to 0.1 μm with a decrease in the temperature from 700 °C to 500 °C. The continuous DRX makes the main contributions to the overall recrystallisation process, although the discontinuous DRX plays an important role in the new grain development at moderate to large strains at 700 °C. The variation in the DRX mechanisms results in a change in the DRX kinetics. The fraction of high-angle boundaries can be expressed as FHAB∼0.2 e in the range of 0

Method for manufacturing forged steel roll

Abstract: A method for manufacturing a forged steel roll comprises: casting, by the ESR method, a steel ingot which contains, by mass %, C: 0.3% or more, Si: 0.2% or more, Cr: 2.0-13.0% and Mo: 0.2% or more, and further contains Bi at 10-100 ppm by mass; and forging the steel ingot to manufacture the roll. According to this method, since freckle defects can be sealed near the center of the steel ingot, the roll can be stably used over a long period of time.

Processing and characterization of Al–Cu–Li alloy AA2195 undergoing scale up production through the vacuum induction melting technique

Abstract: The inherent properties of lithium, such as high reactivity and toxicity, relatively low density, low melting point, along with its high cost requires a special technological approach to cast Al–Cu–Li alloy AA2195 as compared to the conventional Direct Chill (DC) casting of aluminum alloys. This paper describes the processing requirements for melting and casting of 200 kg of Al–Cu–Li alloy in a Vacuum Induction Melting (VIM) furnace under dynamic inert atmosphere. The as-cast billets have been homogenized to remove microsegregation as well as to avoid incipient melting, and subsequently subjected for secondary metal processing operations viz., forging and rolling. The product in the form of 4 mm thick sheets was subjected to various heat treatments in T8 (Solution Treatment+WQ+CW+Aging) condition. Mechanical properties were evaluated at room temperature and were correlated with microstructures of the sheets processed under different conditions using transmission electron microscopy (TEM).

Plastic Flow and Microstructure Evolution during Thermomechanical Processing of a PM Nickel-Base Superalloy

Abstract: Plastic flow and microstructure evolution during sub- and supersolvus forging and subsequent supersolvus heat treatment of the powder-metallurgy superalloy LSHR (low-solvus, high-refractory) were investigated to develop an understanding of methods that can be used to obtain a moderately coarse gamma grain size under well-controlled conditions. To this end, isothermal, hot compression tests were conducted over broad ranges of temperature [(1144 K to 1450 K) 871 °C to 1177 °C] and constant true strain rate (0.0005 to 10 s−1). At low temperatures, deformation was generally characterized by flow softening and dynamic recrystallization that led to a decrease in grain size. At high subsolvus temperatures and low strain rates, steady-state flow or flow hardening was observed. These latter behaviors were ascribed to superplastic deformation and microstructure evolution characterized by a constant grain size or concomitant dynamic grain growth, respectively. During supersolvus heat treatment following subsolvus deformation, increases in grain size whose magnitude was a function of the prior deformation conditions were noted. A transition in flow behavior from superplastic to nonsuperplastic and the development during forging at a high subsolvus temperature of a wide (possibly bi- or multimodal) gamma-grain-size distribution having some large grains led to a substantially coarser grain size during supersolvus annealing in comparison to that produced under all other forging conditions.

Thermomechanical warm forging of Ti–V, Ti–Nb, and Ti–B microalloyed medium carbon steels

Abstract: Conventional quenched and tempered steels have long been used to fabricate mechanical components, such as plates, shafts, and axles. All of these components are mainly fabricated employing medium carbon hot forged steels in the quenched and tempered condition. In the last decade, thermomechanical forging at intermediate (warm) temperatures of microalloyed medium carbon steels is increasingly adopted to reduce or eliminate quenching and tempering heat treatments in hot forged components. However, the use of these steels is still limited, being difficult to achieve a toughness comparable to that of fully heat treated ones. In an effort to improve toughness, an experimental campaign was performed to assess strength and toughness properties of three selected microalloyed medium carbon steels after thermomechanical forging simulations at warm temperatures, performed on a thermal and mechanical Gleeble 3800 ® apparatus. Microstructures and mechanical properties of these steels are shown to be highly dependent upon steel composition and thermomechanical schedule. The experimental results suggest that thermomechanical schedules can be designed to produce microalloyed medium carbon steels with refined microstructures, and therefore to realize improved strength and machinability; yet, toughness is still the most critical property as compared to that of quenched and tempered steels.

Characterization for Dynamic Recrystallization Kinetics Based on Stress-Strain Curves

Abstract: Most metals and alloys have become increasingly important in a variety of applications. The most important of these properties are ease of high strength, relatively good ductility, and good corrosion resistance. One of the ways of acquiring the best combination of these prop‐ erties is to select the microstructure, which in turn depends on thermo-mechanical history as well as on chemical composition [1]. An optimization of the thermo-mechanical process can be achieved through an understanding of the entire forming process and the metallurgical variables affecting the micro-structural features occurring during deformation operations carried out during deformation operations carried out at high temperatures. Most applications of these alloys are in the chemical process equipment, petrochemical, aerospace industry, and medical tools. The understanding of metals and alloys behavior at hot deformation condition has a great importance for designers of hot metal forming processes (hot rolling, forging and extrusion) because of its effective role on metal flow pattern, and the constitutive relationships are often used to describe the plastic flow properties of metals and alloys in a form that can be used in computer code to model the forging response of mechanical part members under the prevailing loading conditions [2].

Basic study on the process combination of deposition welding and subsequent hot bulk forming

Abstract: Today most technical parts and components are made of monolithic materials. Nevertheless, the previously used monolithic materials reach their technological and constructive limits, so that an improvement of the component properties can be realized by hybrid parts. Forging of previously joined semi-finished products to net shape hybrid components is a promising method to produce functional adapted parts in a few process steps. This new process chain offers a number of advantages compared to other manufacturing technologies. Examples are the production of specific load-adapted forging parts with a high level of material utilization, an improvement of the joining zone caused by the followed forming process and an easy to implement joining process because of the simple geometries of the semi-finished products. This paper describes the production process of hybrid steel parts, which are produced by a combination of a deposition welding process with a subsequent hot forging (upsetting) or cross-wedge-rolling. It could be shown that the innovative process chain enables the production of hybrid parts whereby the forging processes lead to an improvement of the mechanical properties of the laser deposited material.

Indigenous development and airworthiness certification of 15–5 PH precipitation hardenable stainless steel for aircraft applications

Abstract: In this paper, we discuss the optimization of chemical composition, processing (forging and rolling) and heat treatment parameters to obtain the best combination of mechanical properties in case of a Fe–15Cr–5Ni–4Cu precipitation hardenable stainless steel. The e-copper precipitates that form during aging are spherical in shape and coherent with the matrix and principally provide strengthening in this alloy. The orientation relationship is found to be Kurdjumov–Sachs (K–S), which is common in fcc–bcc systems. Results obtained from metallurgical evaluation (mechanical property and metallography) on 15–5 PH alloy during type certification on 3 different melts were used for the optimization, attempted in this study. The mechanical properties following strain deformation has been carried out using optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). In the aged conditions, the 15–5 PH alloy exhibited brittle failure with extensive cleavage and/or quasicleavage fracture. This paper reports all results and also factually shows that indigenously developed and produced 15–5 PH stainless steel matches in its properties with the equivalent aeronautical grade precipitation hardening stainless steels globally produced by internationally renowned manufactures.

Effect of Operating Temperature on Direct Recycling Aluminium Chips (AA6061) in Hot Press Forging Process

Abstract: A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430°C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520°C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process.