Discover the latest trends and innovations in the nickel alloy industry. We provide expert insights and in-depth analysis on the newest developments in nickel alloys.
In the Hastelloy corrosion-resistant alloy series, most alloys are easily shaped into various product forms through hot working. However, these alloys are more sensitive to strain and strain rate variations compared to stainless steel, and their hot working temperature ranges are relatively narrow.
To achieve optimal performance from these alloys, careful processing is essential. During hot working, certain characteristics of Hastelloy alloys must be taken into consideration, including their relatively low melting point, high high-temperature strength, sensitivity to strain rate, low thermal conductivity, and relatively high work hardening coefficient. Additionally, within the temperature range of hot working, the alloy's strength rapidly increases with decreasing temperature. Due to these characteristics, the ASTM Alloy recommends using relatively moderate levels of deformation and frequent reheating during each processing step. Furthermore, relatively slow hot deformation aids in obtaining higher-quality products by requiring lower forces and ensuring that heat accumulation during the process is kept within a reasonable range.
Below are the basic guidelines for forging Hastelloy corrosion-resistant alloys:
Maintain the entire forging at the forging temperature for 0.5 hours per inch (thickness).
Frequently rotate the billet to expose the cooler portions to the furnace air. Avoid direct contact of the alloy with open flames.
Begin forging immediately upon removal of the alloy from the furnace, as the temperature will decrease by 38°C-93°C after a short time. It is not advisable to raise the forging temperature to compensate for heat loss, as this may result in melting.
Higher reductions (25%-40%) can retain as much heat as possible, thereby minimizing grain size and reducing the number of heating cycles. Each pass should not exceed a reduction of 40%.
Avoid sudden changes in cross-sectional shape during the initial forming stages, such as transitioning directly from square to circular. It is preferable to transition from square to rounded square to polygonal before reaching circular shapes.
Remove all cracks or fissures generated during forging.
