FORMING
Mild steel and heat resisting alloys handle forming and cutting differently, thus it is best to know what product you are working with to yield the best results.
Spinning and Deep Drawing
Spinning and deep drawing can be accomplished by taking into consideration the physical properties, work hardening, and annealing.
Spinning and Deep Drawing
RA330 spins rather well, roughly comparable to 304 stainless. None of the heat resistant alloys will deep draw as well as 304 stainless.
Dies for drawing the heat resistant alloys ought not be proofed with 304, as results will be different.
Shearing
Best for alloys with higher tensile strength and stronger heat resisting in the annealed condition than mild steel
Shearing
On our shear rated 3/8” (9.5 mm) mild steel, we regularly shear 1/4” (6.35 mm) heat resisting alloy. The hydraulic shear, rated 3/4” (19 mm) mild steel, will handle 1/2” (12.7 mm) alloy plate. Good shearing practice cuts about 20% of the metal and fractures the remaining 80%. Heavier thickness plate is best cut by abrasive wheels, which produce a smooth, close tolerance surface.
Forging
Hot forging should be used only if cold pressing cannot do the job. Working ranges are narrow, and close control of temperature, time, heating atmosphere and reduction are all important when it comes to forging
Forging
Heat resistant alloys must be heated throughout the section thickness. Typically, forging should begin when the metal is around 2100-2200F (1150-1200C), and finish before the metal cools below 1700F (930C); however, the exact temperature ranges from alloy to alloy. Forging either too hot or, more likely, too cold may cause cracking.
Never, attempt to bend or form any austenitic alloy in the 1100-1600F (590-870C) temperature range. Whether 304 stainless or nickel alloy 600, all will tear when formed at these temperatures. Unlike carbon steel, heating locally with a torch to make bending easier just doesn’t work. It is too difficult to heat nickel alloys uniformly hot enough throughout the section.
Bending and Forming
Austenic heat resisting alloys should never be bent cold; however, RA446 does not form well at room temperature.
Bending and Forming
Every lot of RA material is checked for hardness, elongation, reduction of aea, and the mill certifications of the material delivered to you are kept on file for ten years at Rolled Alloys. Records on your order are kept by Rolled Alloys for six years.
After work hardening, but before rupturing, the material can be restored to its original mechanical properties by annealing. The process varies per alloy, the mass, and the hardness.
These solid solution strengthened materials, therefore, can be hardened only by cold working, and softened by annealing. Occasionally tooling for aerospace requires to be stress relieved after rough machining, which in the case of RA330, may be accomplished by heating for one hour per inch (25 mm) of thickness to 1800°F (982°C), and furnace cooling until black, then air cooling.
The first sign of over stretching is an orange peel appearance. This in itself is seldom detrimental, but the fracture soon to follow with further forming is incurable except by welding. It is far better to avoid a design that makes use of minimum radii. A generous radius is better for keeping the metal solid in service as well as during forming, because it gives the structure freedom to expand and contract, minimizing the thermal stresses created by heating and cooling.
RA 602 CA, RA333, and RA 253 MA are the strongest metals of the group in most temperature ranges; so they are slightly tougher to work. RA309 and RA310 are a little weaker. RA600 is somewhat softer and weaker for Its' high nickel makes it “gummier” than alloys with more iron, while the ferritic RA446 is less ductile and requires preheating before bending.
