Type Analysis | Description | Corrosion Resistance | Physical Properties | Heat Treatment
Mechanical Properties | Workability

Type Analysis

Description

17-7 PH is a precipitation-hardening stainless steel that provides high strength and hardness, excellent fatigue properties, good corrosion resistance, good formability, and minimum distortion upon heat treatment.
The alloy provides valuable property combinations parcularly well suited for aerospace applications. This special alloy also provides benefits for other applications requiring high strength and good corrosion resistance, as well as excellent properties for flat springs at temperatures up to 600°F.

Corrosion Resistance

Corrosion resistance in Condition TH 1050 and RH 950 is generally superior to that of the standard hardenable chromium types of stainless steel such as Types 410, 420 and 431, but is not quite as good as chromium-nickel Type 304. Corrosion resistance in Condition CH 900 approaches that of Type 304 in most environments.

Physical Properties

Heat Treatment

This material requires three essential steps in heat treating:
1) Austenite conditioning.
2) Cooling to transform the austenite to martensite.
3) Precipitation hardening to Condition TH 1050 or RH 950.
To obtain the highest mechanical properties from the alloy, Condition A material is transformed to martensite the mill by cold reduction to Condition C. Hardening to Condition CH 900 is accomplished with a single, low-temperature heat treatment.

Mechanical Properties

Workability

Formability
In Condition A, the alloy can be formed comparably to Type 301. It work hardens rapidly and may require intermediate annealing in deep drawing or in forming intricate parts. Springback is similar to that of Type 301. This alloy is extremely hard and strong in Condition C. Therefore, fabrication techniques for such material must be used.

Weldability
The precipitation hardening class of stainless steel is generally considered to be weldable by the common fusion and resistance techniques. Special consideration is required to achieve optimum mechanical properties by considering the best heat-treated conditions in which to weld and which heat treatments should follow welding. This particular alloy is generally considered to have poorer weldability compared to the most common alloy of this stainless class, 17-4 PH Stainless Steel. A major difference is the high Al content of this alloy, which degrades penetration and enhances weld slag formation during arc welding. Also, the austenite conditioning and precipitation hardening heat treatments are both required after welding to achieve high strength levels. When a weld filler is needed, W 17-7 PH is most often specified.

17-7 PH - Current Inventory Stock