Fabrication of 310S 310H Stainless Steel

Alloys 309/309S and 310/310S stainless steel are widely used in the heat treatment/process industries due to high temperature properties and corrosion resistance. As such, they are commonly fabricated into complex structures. Mild carbon steel is generally treated as the standard for performance in most metal forming operations.

With respect to carbon steel, the austenitic stainless steel exhibit a significant difference – they are tougher and tend to work harden rapidly. While this does not alter the general methods used for cutting, machining, forming, etc., it does affect the specifics of those methods.

Cutting and machining the austenitic stainless steel is readily accomplished using standard techniques typically employed for common mild steel, with some modifications. Their cutting behavior can be quite different – they are tougher and tend to harden rapidly during working. The chips produced are stringy and tough and retain considerable ductility.

Tooling should be kept sharp and be rigidly held. Deeper cuts and slower speeds are generally used to cut below work hardened zones. Due to the low thermal conductivity and high coefficient of thermal expansion inherent to the austenitic stainless steel, heat removal and dimensional tolerances must be considered during cutting and machining operations.

The austenitic stainless steel are readily cold formable by standard methods such as bending, stretch forming, roll forming, hammer forming, flaring/flanging, spinning, drawing, and hydroforming. They work harden readily, which is manifested by steadily increasing amounts of force needed to continue deformation. This results in the need to use stronger forming machines and eventually limits the amount of deformation possible without cracking.

A relatively narrow range of temperature can be used for effective hot working of Alloys 309 and 310 due to numerous environmental and metallurgical factors. Forging should start in the temperature range 1800-2145°F (980-1120°C) and finish no cooler than 1800°F (980°C).

Working at higher temperature results in a fall-off of hot ductility due to environmental and metallurgical factors, particularly the formation of ferrite. Working at lower temperatures can cause the formation of brittle second phases, e.g., sigma and/or sensitization. Following forging, the workpiece should be cooled rapidly to a black heat.

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