1. The Development of ASTM A335 P92

In order to improve the heat efficiency of reheating steam pipeline in power plant, the reheating-temperature can be designed as high as 621°C, which is known as the super-critical temperature. The Unite States firstly developed ASTM A335 P92 alloy steel in late 1980’s to meet the heat-resisting requirements of such a high-temperature power unit. The alloy steel P92 is an improved version of ASTM A335 P91 alloy which has deliberate addition of tungsten, vanadium, niobium, decreased amount of molybdenum to fine-tune to ferrite/austenite ratio, as well as carefully controlled amount of boron and nitrogen.

Designated as UNS K92460, ASTM A335 P92 is also known as 9Cr-2W alloy steel. Its equivalent includes ASTM A213 T92, ASME SA335 P92, ASME SA213 T92, as well as EN standard X10CrWMoVNb9-2. The Grade P92 are generally furnished as seamless pipes, tubes, or fittings.

2. Chemical Requirements of ASTM A335 P92

Element	Carbon	Manganese	Phosphorus	Sulfur	Silicon	Chromium	Molybdenum	Others
Content, %	0.07-0.13	0.30–0.60	≤0.020	≤0.010	≤0.50	8.50-9.50	0.30-0.60	*

*V: 0.15–0.25; N: 0.03–0.07; Ni: ≤0.40; Al: ≤0.040; Nb: 0.04-0.09; W: 1.50-2.00; B:0.001-0.006.

3. Mechanical Properties of ASTM A335 P92

Tensile Strength, min.		Yield Strength, min.		Elongation %, min.
ksi	MPa	ksi	MPa	Longitudinal	Transverse
90	620	64	440	-	20

*The tensile tests shall be conducted at room temperature.

4. Heat Treatment

The Grade P92 of ASTM A335 shall be normalized at 1900°F [1040°C] minimum and tempered at 1350°F [730°C] minimum as a final heat treatment. After heat treatment, the hardness shall not exceed 250 HB/ 265 HV [25 HRC].