- Excellent machinability
- Low cost
- Improved non-galling characteristics
- Poor weldability
- Poor formability
- Limited corrosion resistance
Grade 416 has poor weldability. If welding is necessary use Grade 410 low hydrogen electrodes. Pre-heat to 200-300°C. Follow immediately with annealing or re-hardening, or a stress relief at 650-675°C.
Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment.
Heat Treatment
Full Annealing - Heat to 815-900°C for ½ hour per 25mm of thickness. Cool at 30°C per hour maximum to 600°C and air cool.
Sub-Critical Annealing - Heat to 650-760°C and air cool.
Hardening - Hardened by heating to 925-1010°C, quenching in oil, and tempering to suit the mechanical requirements. See accompanying table.
Condition: Tensile Strength Range (N/mm² or MPa) QT 650: 650 - 850
QT 700: 700 - 850
QT 800: 800 - 950
QT 850: 850 - 1000
QT 900: 900 - 1050
Corrosion resistance is lower than the common austenitic grades.
Useful resistance to dry atmospheres, fresh water and mild alkalies and acids, but less resistant than the equivalent non-free-machining grades. Less corrosion resistant than the austenitic grades and also less than 17% chromium ferritic alloys such as Grade 430. High sulphur content free machining grades such as 416 are totally unsuitable for marine or other chloride exposure.
Maximum corrosion resistance is achieved in the hardened condition, with a smooth surface finish.
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