Galling-Free Cold and Warm Forging of Titanium Wires to Flat Plates by SiC-Coated SiC dies

Pure titanium and titanium alloys were difficult to be forged and press-forged because of their easiness in galling to die and punch surfaces during metal forming. β-SiC coated SiC dies were developed to perform a galling free cold forging of pure titanium wire up to the higher reduction of thickness than 50%. Since the thickness of this SiC coating was 4 mm, various cavities and micro-punches were formed into coating by micro-machining. The pure titanium and β-phase titanium alloy wires were employed as a work for cold and warm forging to investigate the effect of flow stress on the forging behavior up to the reduction of thickness by 70% under the controlled holding temperature. The contact interface of β-SiC coating to the work was precisely analyzed to describe the in situ solid lubricating process on the interface. The free carbon agglomerates isolated at the center of contact interface from the carbon supersaturated β-SiC coating, and, worked as a solid lubricant to prevent the β-SiC coating punch and die from galling during forging under high reduction of thickness.

Die Design Architecture for Enhancing Tool Life Via Manipulation of the Elastic Strain Field of the Dies During Extrusion Processes

Forging and extrusion tools are often subjected to a combination of cyclic thermo-mechanical, chemical, and tribological loads. Strategies for minimizing these loads are critical for preventing premature tool failure and increasing productivity. A die design architecture for extrusion that minimizes the residual contact pressure at the die-workpiece interface during the ejection stroke is proposed. The underlying principle of this die design is that during the extrusion stroke, a tapered die can move in the direction of the extrusion load, thus inducing negative radial elastic strain on the die. When the extrusion load is removed, the elastic strain energy stored in the die is released, thus repositioning the die to its initial state. With this design architecture, the workpiece can be ejected at no load. The process was validated using finite element (FE) warm forging/extrusion simulations for a constant velocity (CV) joint and pinion gear shaft. These simulations showed that in addition to reducing residual contact pressure, which enhances tribological conditions, the new die design can easily lower die stresses, thus increasing die fatigue life. The FE simulations for CV joint and pinion gear shaft demonstrated residual pressure in certain locations of the die ranging from 30% to 100% of the pressure induced during the extrusion stroke. The case studies simulated showed that a total energy saving of up to 15% can be achieved with the proposed die setup.

Researching Conditions of Thermomechanical Process under Semihot Forging

Questions of thermomechanical parameters appointment under the semihot (warm) forging of metal preforms were considered. The international experience was analyzed as well. Economically effective thermomechanical conditions under semihot/warm forging, which is capable to provide a high complex of the mechanical properties of steel, are offered. The economical effect after the process integration to the industry was considered.

Simulation and Experiment of Manufacturing Process for Structural Aluminum Parts with Hard to Plastic Forming

A process comprising a hot extrusion process and a warm forging process was designed to form an umbrella-shaped aluminum structural component with a high degree of difficulty for the plastic forming method. A circular cylindrical part was extruded with a hot extrusion process, and then an embossing part was produced with a warm forging process. The formability and the maximum load required for forming were then determined using a forming analysis program. The hot extrusion process was executed at 450 °C under the extrusion speed at 6 mm/s, while the warm forging process was executed at 260 °C under the forging speed at 150 mm/s. The simulation results showed that the load required for hot extrusion was 1019 ton, while the load required for the warm forging was 534 ton. The umbrella-shaped part was manufactured by using a 1600 ton capacity press. The graphite lubricant was coated on the mold as well as the material. A forming experiment was performed under the same condition with the simulation condition. The portion where extrusion was done became elliptical with the α-Al phase elongated towards extrusion direction. Whereas, the α-Al phase became circular in the forged portion. The tensile strength value was found as 345 MPa, while elongation rate was 12%. Meanwhile, Vickers hardness value at the extruded portion was 105 HV, and it was 110 HV at the forged portion.