Morphology and Tensile Properties as a Function of Welding Current in Thermoplastic Induction Welds

Compared to other conventional joining methods, induction welding offers the superiority of avoiding mechanical degradation and satisfying the need for weight reduction in the aircraft industry. In this paper, a metal mesh was adapted as an induction component in the induction welding of polyetheretherketone (PEEK) with various currents. The effect of welding current on the microstructure and mechanical properties of the induction welding joint was further investigated. The results indicate that induction welding joints with the narrow thickness of the fusion zone and high tensile strength can be attained in the welding current range of 7.05 A to 11.05 A. However, when the current exceeds 13.91 A, the excessive heat input leads to the unsteady flow of PEEK or even thermal oxidative degradation and thermal decomposition, which increases the thickness of the fusion zone and reduces the tensile strength of the joint. In addition, the principal fracture mode presents cohesive failure, thereby promoting the tensile strength of the joint.

Influence of flame straightening on the properties of welded joints made of X2CrNi22-2 duplex steel

The study investigates the optimal conditions associated with flame straightening of welded joints in duplex steel grade X2CrNi22-2. The research aimed to assess the influence of heat, applied during flame straightening of welded structures in X2CrNi22-2 grade steel, on the properties of the welded joints. Based on the macroscopic, microscopic, and strength tests conducted on welding joints in X2CrNiN22-2-grade duplex steel that have been subjected to flame straightening, it was ascertained that post-welding flame straightening of this grade of steel, at a treatment temperature of 730°C, should not take place for >1 min. The temperature of 730°C has been chosen as a reference because of the assumption that the welded joints are heated to the temperature of 700–730°C during straightening with an acetylene-oxygen flame. The paper scrutinizes the questions of (i) what changes occur in the welded joints as a result of flame straightening carried out in this temperature range and (ii) what impact those changes have on the joint strength. The results of our study indicate that the duration of post-welding flame straightening of X2CrNiN22-2-grade duplex steel, at a treatment temperature of 730°C, should not exceed 1 min.