This paper describes the uphill quenching process which is applied in the heat treatment of aluminum alloys. This lesser known process was developed by Alcoa and first applied more than 50 years ago for aluminum alloys of several thicknesses. Uphill quenching has been reported to reduce residual stresses by > 80%. Typically, uphill quenching is applied after quenching and before aging of aluminum alloys. Uphill quenching consists of the immersion of the part in a cryogenic environment and after equilibration, the part is transferred immediately to a fixture in a superheated steam chamber to obtain a temperature gradient sufficient to maintain the improved mechanical properties gained with heat treatment that result in low residual stresses and superior dimensional stability. Assuming that most of the stresses that appear in aluminum alloys during heat treatment are due to the quenching process, then this intermediate treatment becomes a potentially effective tool for the heat treatment of aluminum alloys. The aim of this paper is to present an overview of recent work showing tensile test results obtained with uphill quenching relative to conventional quenching processes.

Though electron beam welding (EBW) causes minimum destruction to the base metal, significantly different microstructure exists at weld zone. Rapid heating and cooling during electron beam welding results in dendritic microstructure, which lowers mechanical properties. In order to recover the original mechanical properties, post weld heat treatments (PWHT) needs to be performed after EBW. This paper presents effect of PWHTs on mechanical and microstructural properties of electron beam welded SAE 5137 H steel. Welded steel plates were processed through different heat treatments like stress relieving, normalizing and hardening & tempering. Micro-structural and mechanical testing were performed to characterize these specimens. It was perceived that, different PWHT’s can be employed and selection depends on final mechanical property requirement from the weld joint.

The temperature profile in the Heat Affected Zone (HAZ) during induction welding is one of the most important factors determining the weld quality of High-Frequency Induction (HFI) welded steel tubes. In this work, numerical computation of the 3D temperature profile in the steel tube has been done by coupling the electromagnetic model with the thermal model. The high-frequency current and the magnetic fields in the tube, coil and impeder have been evaluated. The resulting power from the induced current is used to evaluate the temperature in the joining edges of the tube. The continuous tube movement has been implemented by considering an additional transport term in the heat equation. The simulations consider non-linear electromagnetic and thermal properties of the steel when it undergoes temperature rise to the welding temperature. The temperature profile from the resulting simulation gives information to control the subsequent process of joining the edges of the steel tube.

High frequency welding is a thermo-mechanical process that relies on precise heat input as well as mechanical control as strip edges are heated and forged together to result in a seam weld. Heat input can be defined as a way of characterizing the temperature distribution at the strip edges prior to forging them together. Heat input is affected by several process variables ranging from raw material properties to welder settings and weld area setup. These are summarized in this paper, with special attention on the effects of welder frequency, welder power, line speed, and steel alloy composition on heat input and the resulting weld quality. Frequencies in the range of 100 – 800 kHz are considered. Data from tube mills (including general data and controlled on-the-mill experiments) and laboratory evaluations are included in this paper.