For optimum corrosion resistance, surfaces must be free of scale and foreign particles. Finished parts should be passivated.

Do not forge below 1850 ^oF (1010 ^oC).

Finished forgings should be cooled in air to below 90 ^oF (32 ^oC) prior to further processing in order to obtain optimum grain size and mechanical properties.

Finally forgings will require to be solution annealed prior to age hardening as required.

Sections up to 75 mm -  Oil Quench To Below 90 ^oF (32 ^oC)

Sections over 75mm -  Air Cool To Below 90 ^oF (32 ^oC)

*Actual holding time should be long enough to ensure that the part is heated thoroughly through out its section

Therefore to ensure complete transformation to martensite, it is most important that parts are always cooled to below 90 ^oF (32 ^oC) within 24 hours following Solution Annealing and before Age Hardening Treatment which should also be followed by an air cool to below 90 ^oF (32 ^oC).

The age hardening tempers the martensite resulting in an improvement in toughness. The higher the ageing temperature the more refined the martensite leading to greater ductility but slightly lower strength.

N.B. Temperature control is critical during age hardening and any variations outside the given range could lead to less than satisfactory results.

In the solution annealed condition resistance to stress corrosion cracking is low - improving at age hardening temperatures from 1025 ^oF (550 ^oC) upwards to a maximum at 1150 ^oF (620 ^oC) double aged.

Condition A to condition H900 (H480) - contraction 0.0004/0.0006 M/M

Condition A to condition H1150 (H620) - contraction 0.0009/0.0012 M/M

Machinablity in the H900 (H480) condition is limited, improving as the age hardening temperature is increased to optimum machinability similar to 304 austenitic stainless steel grade in the H1150 (H620) condition.

Exposure to temperature range 600 - 900 ^oF (290 - 480 ^oC) long term may result in reduced toughness but this can sometimes be minimilized by using higher ageing temperatures. As a general guide for short term exposure at elevated temperatures the ageing temperature should be at least 50 ^oF (28 ^oC) above the working temperature.

Welding in the solution annealed condition may be carried out satisfactorily, however welding in the H1150 (H620) condition reduces the effects of high welding stresses.

Following welding in the solution annealed condition, parts can be directly age hardened as required, however those in the H1150 (H620) condition should be re-solution annealed and then age hardened as required.