The 9% nickel alloy steel plates are generally manufactured in accordance with either ASTM A353 or ASTM A553 Type I. The following procedures for heat treatment are recommended in the standard mentioned above:

1. Double Normalize and Temper (NNT) – ASTM A353.

Heat the 9% nickel steel plates to a uniform temperature of 1650°F; hold at this temperature in the ratio of 1 hour per inch of thickness; but in no case less than 15 minutes; cool in air. Reheat until the plate attains a uniform temperature of 1450°F; hold at this temperature in the ratio of 1 hour per inch of thickness, but in no case less than 15 minutes; cool in air. Reheat to a uniform temperature within the range of 1050°F to 1125°F; hold at this temperature in the ratio of 1 hour per inch of thickness, but in no case less than 15 minutes per hour; cool in water or water quench, at a rate not less than 300°F per hour. If hot forming is performed within the range of 1650°F to 1750°F, the first normalize may be omitted.

2. Quench and Temper (QT) – ASTM A553

Heat 9% nickel steel plates to a uniform temperature of 1475°F; hold at this temperature in the ratio of 1 hour per inch thickness, but in no case less than 15 minutes; quench in water. Reheat until the plate attains a uniform temperature within the range of 1050°F to 1125°F; hold at this temperature in the ratio of 1 hour per inch thickness, but in no case less than 15 minutes; cool in air or water quench, at a rate not less than 300°F per hour.

3. Stress Relieve (SR) – ASTM A353 & A553

Stress relieving the 9% nickel alloy steel plate, when required, may be accomplished by heating at 1025~1085°F for a minimum of 2 hours for thicknesses up to 1 inch, plus an additional period in proportion to 1 hour for each additional inch of thickness, and cool at a minimum rate of 300°F per hour in air or water to a temperature not exceeding 600°F.