1.1 This specification covers heavy-wall carbon and alloy steel pipe (Note 1) made from turned and bored forgings and is intended for high-temperature service. Pipe ordered under this specification shall be suitable for bending and other forming operations and for fusion welding. Selection will depend on design, service conditions, mechanical properties and high-temperature characteristics.

Note 1 - The use of the word "pipe" throughout the several sections of this specification is used in the broad sense and intended to mean pipe headers, or leads.

Note 2 - The dimensionless designator NPS (nominal pipe size) has been substituted in this standard for such traditional terms as "nominal diameter," "size," and "nominal size."

1.2 Several grades of ferritic steels are covered. Their compositions are given in Table 1.

1.3 Supplementary requirements (S1 to S6) of an optional nature are provided. These supplementary requirements call for additional tests to be made, and when desired shall be so stated in the order, together with the number of such tests required.

1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.

TABLE 1 Chemical Requirements

Grade	Composition, %
Grade	FPA	FPB	FP1	FP2
Carbon	0.25 max	0.30 max	0.10-0.20	0.10-0.20
Manganese	0.27-0.93	0.29-1.06	0.30-0.80	0.30-0.61
Phosphorus, max	0.035	0.035	0.025	0.025
Sulfur, max	0.035	0.035	0.025	0.025
Silicon	0.10 min	0.10 min	0.10-0.50	0.10-0.30
Chromium	...	...	...	0.50-0.81
Molybdenum	...	...	0.44-0.65	0.44-0.65
Grade	FP5	FP9	FP11	FP12
Carbon	0.15 max	0.15 max	0.05-0.15	0.05-0.15
Manganese	0.30-0.60	0.30-0.60	0.30-0.60	0.30-0.61
Phosphorus, max	0.025	0.030	0.025	0.025
Sulfur, max	0.025	0.030	0.025	0.025
Silicon	0.50 max	0.50-1.00	0.50-1.00	0.50 max
Chromium	4.00-6.00	8.00-10.00	1.00-1.50	0.80-1.25
Molybdenum	0.45-0.65	0.90-1.10	0.44-0.65	0.44-0.65
Grade	FP21	FP22	FP91	FP92
Carbon	0.05-0.15	0.05-0.15	0.08-0.12	0.07-0.13
Manganese	0.30-0.60	0.30-0.60	0.30-0.60	0.30-0.60
Phosphorus, max	0.025	0.025	0.025	0.020
Sulfur, max	0.025	0.025	0.025	0.010
Silicon	0.50 max	0.50 max	0.20-0.50	0.50 max
Chromium	2.65-3.35	1.90-2.60	8.00-9.50	8.50-9.50
Molybdenum	0.80-1.06	0.87-1.13	0.85-1.05	0.30-0.60
			Others:	W 1.50-2.00
			Ni 0.40 max	V 0.15-0.25
			V 0.18-0.25	Cb 0.04-0.09
			Cb 0.06-0.10	N 0.030-0.070
			N 0.03-0.07	Ni 0.40 max
			Al 0.02 max	Al 0.02 max
			Ti 0.01 max	Ti 0.01 max
			Zr 0.01 max	Zr 0.01 max
				B 0.001-0.006