Papers by Keyword: Hot Forging

Abstract: In this study, the temperature increase of the Ti-17 alloy (Ti–5Al–2Sn–2Zr–4Cr–4Mo, wt.%) during isothermal forging in the (α + β) dual-phase region was investigated using large-size workpieces forged between hot dies in a 1500-ton forging press. The temperature increase was predicted using finite element analysis (FEA). The tip of a thermocouple was inserted into the center of the workpiece (diameter: 100 mm; height: 50 mm). The forging temperatures were 1023 K (750 °C) and 1073 K (800 °C) in the (α + β) dual-phase region. The strain rate was 0.05 s⁻¹ and 0.5 s⁻¹ at each temperature. Meanwhile, the compression percentage was 75%. The true stress–true strain curves were inversely obtained by fitting the load–stroke curves using the FEA. The predicted temperature was in a good agreement with that in the experimental results when the value of 1.0 was used as the conversion factor for plastic deformation energy to heat energy in the FEA under the current forging conditions. At the strain rate of 0.5 s⁻¹, the temperature instantly increased to a β-transus temperature in 3 s at 1073 K (800 °C). In contrast, the temperature logarithmically increased at both 1023 K (750 °C) and 1073 K (800 °C) at 0.05 s⁻¹ in 28 s (e.g., 42 K at 1023 K (750 °C)). The obtained true stress–true strain curves indicate that flow softening occurred during the forgings, which is attributed to dynamic recrystallization and/or dynamic recovery. The temperature increase in the Ti-17 alloy was smaller than that in the Ti–6Al–4V alloy under the same forging condition.

Abstract: The Cu/55vol.%diamond (Ti) composites were fabricated by hot forging of the cold-pressed powder preforms, consisted of elemental copper powders and Ti-coated diamond particles, at 800 °C (800C-Cu/55Dia composite) and 1050 °C (1050C-Cu55Dia composite), respectively. Well bonded interface was achieved between the diamond and the copper matrix for the 800C-Cu/55Dia composite, and the coverage of diamond by interface was about 96%, attributed to homogeneously distributed nanospherical TiC interface formed on the diamond surface. However, obvious coarse TiC particle size and spallation of the formed interface were observed in the 1050C-Cu55Dia composite, implying that the composite had a relatively low bonding strength. The formed chemical bonding, good wettability and strong mechanical interlocking between the diamond and the copper matrix enable the 800C-Cu/55Dia composite having a high tensile strength of 145 MPa and a strain at fracture of 0.35%, which are about 260% and 170% higher than those of the 1050C-Cu55Dia composite, suggesting that the 800C-Cu/55Dia composite has the potential to have a high thermal conductivity and use as high-performance heat sink materials.

Abstract: In this paper, twin roll casting of magnesium alloys with high aluminum content such as, Mg-11 mass%Al-0.2 mass%Mn, Mg-12 mass%Al-0.2 mass%Mn, Mg-13 mass%Al-0.2 mass% have been performed for the purpose of use as an original material for hot forging. Also the mechanical properties of the cast materials were examined. A 10 miri-meters thick strip was cast by the use of a horizontal twin roll caster. The microscopic observation was conducted to investigate into the precipitation of the metal compounds such as Mg₁₇Al₁₂, and the Vickers hardness of the cast strips test were performed. From the result of the roll casting experiments, a 10 mm thick strip was continuously cast at a roll speed of 3.1 m/min. The average grain size of the casting strips was about 46 micron meters. When the aluminum content was 13%, the hardness of the twin roll cast (TRC) strips became 1.7 times higher than that of extruded AZ 31. Also, a uniaxial compression test at elevated temperature was conducted to obtain a true strain-true stress curve for examining possibility of direct hot forging (DHF) of TRC magnesium alloys with high aluminum content.

Abstract: A method for determining the friction coefficient was developed and experimentally tested by comparing theoretical calculations of the relative volume of radial channels filling with various convergence angles of generating line for various friction coefficients and experimental data on the value of filling these channels. Relative volume of metal extruded into the channel was selected as criterion for simulation the channel filling conditions depending on the friction coefficient. Relative error of the experiment results doesn’t exceed 6% according to the linearized models of this criterion.

Abstract: The aim of present wor is, therfore, to investigated the effect of the damage value prediction equation on the formability of compression specimen and find the optimize forming condition.Although Inconel 625 alloys are excellent materials, Ni-base alloy cannot be formed at room temperature owing to limitation of formability. To improve the formability of Inconel 625, it is necessary to investigate the formability at a high temperature range.A high temperature compression test is performed with a Gleeble 3500 testing machine at various temperatures (approximately 900 1200°C) and strain rates (10/s and 30/s) to obtain high temperature deformation characteristics of Inconel 625. Furthermore, high temperature tensile tests results are used to measure elongations and reductions in the area of Inconel 625.A rigid-plastic finite element simulation is applied to the high temperature compression process to obtain the damage valueThe results of the hot deformation experiment and analysis are presented for various conditions of temperatures and strain rates, and it is expected that damage value will be used in hot forming processes such as hot extrusion and rolling process.

Abstract: This paper deals with characteristics of hot forging of twin roll cast magnesium alloyswhich have relatively high aluminum content. High tensile strength magnesium alloys containing 9 to12% aluminum, such as Mg-9%Al-1%Zn, Mg-10%Al-1%Zn, Mg-11%Al-1%Zn, andMg-12%Al-1%Zn have been made by twin roll casting. A new experiment was performed for hotforging of high strength magnesium alloys with high aluminum content was performed. From theresults, using magnesium alloys with high aluminum content yielded less compressive deformationresistance than AXM403. It was also demonstrated that hot forging of magnesium alloys with highaluminum content produces small magnesium crystals (about six micro meters) and crystallizedsubstances. The mean grain size of the microstructure of Mg-12%Al-1%Zn forged at 623K was lessten micrometers although that of the Mg-9%Al-1%Zn was about thirty micrometers. The small betaphase which precipitates in the twin roll cast Mg-12%Al-1%Zn was distributed uniformly comparingto Mg-9%Al-1%Zn. From the result of microscopic observation of the forged products, it has beenrecognised that the Hall-petch rule between mean grain size of forged materials and Vickers hardnesshas been proved. The effects of the dynamic recrystallization on the microstructures of the twin-rollcast products seem to be different in terms of aluminum content. Due to rapid cooling of twin-rollcasting process process, the fabricated magnesium material could be used for hot forging. By applyinga servo press machine, a hot-forging experiment was performed with development of high strengthmagnesium alloys. A novel material that show higher hardness have been fabricated by usingtwin-roll casting process. It has also been clarified that the aluminum content affect precipitation ofbeta phase as well as grain size.

Abstract: AISI H11 tool steel is a complex tool steel alloy used to manufacture hot forging dies. These dies however have a limited life, which depends upon the working conditions, the tool design, the heat treatment, and the quality of tool steels. In this paper, a novel wire-and powder-based laser metal deposition (WP-LMD) process was investigated to deposit H11 wire and niobium (Nb) powder simultaneously and develop a coating on existing forging dies for enhancing their life. The main aim was the development of a novel WP-LMD process, and consequently a new H11 tool steel with improved toughness and hardness. The developed WP-LMD process was later implemented to build a multilayer block made of the modified H11 tool steel. The overlap ratio was optimized in both, horizontal and vertical, directions, and were found to be 30% and 20% respectively in order to achieve a fully dense coating and avoid pores and unmelted Nb particles. The potential of the WP-LMD can be used to fabricate an outer layer of the modified H11 tool steel with improved toughness and hardness, which ultimately enhances the life of hot forging.

Abstract: The effect of pulsed (oscillating) ram motion control on lubrication was investigated in hot forging of stainless steel workpiece with oxide glass lubricant. During the retreat in the pulsed ram motion, the workpiece was re-lubricated by flow of lubricant through the gap between the workpiece and the die. A hot spike-type forging test on a servo press with pulsed ram motions was carried out to investigate the lubrication performance of the oxide glass. In the test, the workpiece with a temperature of 1223 K was extruded into the hollow part of the upper die together with oxide glass in a manner that combined pulsed and stepwise ram operations. The re-lubrication of the workpiece with oxide glass was confirmed by the test results showing 5–10% reduction in the forging load and 5% longer length of the backward extruded part of the workpiece under an appropriate pulsed ram motion.

Abstract: The significance matrix for the parameters of “material-billet-equipment-process-tool-personnel-environment” system was compiled using the systems approach to the assurance of forging dimensional accuracy, and the expert analysis revealed the most significant process parameters that affect the accuracy. The application of simulation modeling helped to establish the dependence of forging force on the dimensions of an incoming billet. The paper suggests a solution to increase the accuracy of the sized forgings.

Abstract: Multi-material solutions offer numerous benefits producing tailored-made hybrid components with enhanced application-optimized properties contrary to conventional monolithic parts. However, designing of corresponding manufacturing processes is often challenging due to various technical aspects. This paper represents a process route for the manufacturing of a hybrid bevel gear by means of tailored forming technology with a focus on die forging and describes the main challenges within the forming stage. Due to local material-specific properties, uncommon material flow and complex geometry of the final part, an individual forming tool system with a geared die was accurately designed. Besides the forming tool system, the FE-based design of the forging process as well as the necessary material characterisation will be presented. Finally, the initial results of the experimental forging investigations are shown.