Investigation of the in-situ gas cooling of carbon steel during wire and arc additive manufacturing

Abstract

Wire and arc additive manufacturing (WAAM) is a promising technology for fabricating large-sized metal parts. However, to use this method efficiently, it is necessary to overcome the problem of severe heat accumulation that reduces manufacturing efficiency and deteriorates material properties. This paper proposes a new method using the in-situ gas cooling (ISGC) for reducing heat accumulation. Three parts were manufactured via the proposed method utilising CO 2 , N 2 , and air as cooling gases, respectively. A fourth part was fabricated with natural cooling (NC), without cooling gas. The temperature data measured by thermocouples and infrared pyrometers indicated that compared with NC, ISGC considerably reduced the temperature of the whole part and CO 2 had the best cooling effect. ISGC efficiently mitigated heat accumulation, due to the large heat transfer coefficient and the great temperature difference between the high-temperature region behind the torch and the cooling gas. Numerical simulations verified by the experimental data further denoted that in ISGC, high-temperature areas near the molten pool shrank sharply and heat dissipation conditions in the molten pool were improved markedly. ISGC not only improved the surface quality of the parts, but also strengthened the mechanical properties of the parts by obtained fine grains. The maximum ultimate tensile strength (UTS) and yield strength (YS) increased to 483 MPa and 358 MPa, respectively, which represented an increase of 4.1 % and 4.7 % respectively. The average hardness was enhanced to 161.3 HV, representing an improvement of 3.7 %.