Development and Strength Evaluation of Ring Projection Welding Process of the Microminiature Tube and Tubesheet

Yun, Young-hyun; Kim, Hyun-joon; Kim, Chang-soo; Cho, Sang-myung

JWJ > Volume 27(2); 2009 > Article

Journal of KWJS 2009 April;27(2) :63-68.
Published online May 18, 2009.

Development and Strength Evaluation of Ring Projection Welding Process of the Microminiature Tube and Tubesheet

Young-hyun Yun, Hyun-joon Kim, Chang-soo Kim, Sang-myung Cho

Correspondence: Published online May 18, 2009

ABSTRACT

Microminiature heat exchanger has been applied to the gas turbine in order to increase energy efficiency. During the production of microminiature heat exchanger, however, it is very difficult to weld tube to tubesheet. In this study, therefore, welding process of resistance ring projection was used, and weld tensile tests were performed. Sound weld joint was obtained as a result of applying resistance ring projection welding to microminiature heat exchanger to tubesheet. Cold weld occurred at under 1600A. Even though tensile strength was increased with increasing current, splash occurred and tensile strength decreased at 2000A due to the excessive current. Therefore it was determine that the optimal current is 1900A. As result of tensile tests based on ASME code for tube to tubesheet weldment, rupture position was weldment due to Fs (Fractured section) of nugget, which was smaller than tube thickness (t), and it was proven as a partial strength welding because of the average joint efficiency fr = 0.90.

Keywords: Microminiature heat exchanger;Ring projection welding;Tube;Tubesheet;Electrode tipangle;Tensile strength;Tube extension;Welding current