Quench and tempering heat treating operations for tubular products are relying more on induction equipment. The reasons for this can be traced to the lower energy costs for operating induction equipment compared to gas furnaces and the greater flexibility that the induction lines offer compared to their furnace counterparts in regards to recipe control and product mix. However, there are limitations and special considerations for induction heat treating equipment and the induction coils used for these operations. This paper reports on the design and operation of a new induction heat treating line for API 5CT grade L80 and P110 casing and tubing with upset ends. Upset ends pose special technical challenges for induction heating; the generation of a uniform temperature distribution relies heavily on proper coil design as well as line layout and heating time. Simulations of induction heating have provided predictions of heating profiles, and on-the-line testing allowed recipe refinement and validation of simulation models. Results from this case study help to increase confidence in this heat treating process as well as create an improved induction heating line layout for future applications.

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.