Journal of Materials Processing Technology 179 (2006) 244–250 Repair welding of polymer injection molds manufactured in AISI P20 and VP50IM steels Wilson Tafur Preciado a,∗ , Carlos Enrique Ni ˜ no Bohorquez b a Mechanical Engineering Department, Federal University of Santa Catarina - UFSC, Campus Universit´ ario, Cx. Postal 476, CEP 88049-900, Florian´ opolis, SC, Brazil b Mechanical Engineering Department, Federal University of Santa Catarina - UFSC, Brazil Abstract The objective of this work was to determine the best practices to repair by welding AISI P20 and VP50IM steels during the manufacturing of polymer injection molds, in such a way to obtain similar characteristics in the weld and base metal, to uniformly respond to the processes of polishing and texturing. The welds by the wire feed TIG process were done using a similar filler metal for P20 steel, AWS A5.28-96 ER 80S-B2, and two filler metals for VP50IM steel, similar and dissimilar AWS A5.28-96 ER 80S-B6. The welds were deposited with different heat inputs (3.6–9.8 kJ/cm), using constant amplitude DC, and they were evaluated in relation to the quality obtained in the mirrored and textured surfaces. Those results were correlated with the chemical compositions, microstructures and hardness. © 2006 Elsevier B.V. All rights reserved. Keywords: Repair welding; Injection molds; TIG; Polishing; Texturing 1. Introduction Polymer injection molds frequently require some form of repair by welding: (a) during the manufacture, by errors in machining or by some change in the design of the part to be injected and (b) during the service, by the incidence of failures in the mold. For those repairs, TIG process is used frequently, because it allows the deposition of small amounts of material, without spatter, in such a way to obtain the complex geometries of the mold. Special processes and welding procedures are used due to the tight tolerances required and the high cost of the mold. The required quality of the weld is not only related to the suitable mechanical properties, but also to the weld and the heat affected zone (HAZ) behavior when finishing processes are applied to give a uniform and adequate texture to the mold cavity. Nowadays, the welding procedures applied for the repair of molds are elaborated having as a basis the recommenda- tions given by the manufacturers of steel, but it remains not clear what are the involved metalurgical phenomena, whose knowledge is necessary to define rational procedures, suitable ∗ Corresponding author. E-mail address: tafur@labsolda.ufsc.br (W.T. Preciado). for different materials, sizes and geometries of the molds to repair. The vast majority of the information available in the litera- ture about the repair of these steels focuses the aspects of weld techniques, without considering metallurgical aspects [1,2]. The efforts of mold steels manufacturing companies has led to the development of base materials and their filler metals as a way of increasing the weldability and dimensional stability of the mold after heat treatments. This is the case of VP50IM steel studied in this work. The P20 steel, also focused in this study, has a long successful history in the industry of polymer injection molds, although with severe problems when recovered by welding. 2. Objectives The primary objective of this work is to establish optimal conditions repair by welding P20 and VP50IM using the wire feed TIG process, in such a way to obtain that the weld metal (WM) and heat affected zone have behaviour similar to that of the base metal (BM) when the surface finishing processes are applied. 3. Theoretical revision After mechanizing the mold to obtain the geometry that makes it functional, its cavity is subjected to finishing processes 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.03.101