1.1 This specification covers iron-chromium-nickel, high-alloy tubes made by the centrifugal casting process intended for use under pressure at high temperatures.

1.2 The grades of high alloys detailed in Table 1 are intended for applications requiring strength and resistance to corrosion and scaling at high temperatures.

1.3 Optional Supplementary Requirements S1 to S11 are provided; these call for additional tests to be made if desired.

1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of each other. Combining values from the two systems may result in nonconformance with the specification.

TABLE 1 Chemical Requirements

Grade	Composition, %
Grade	Carbon	Manganese	Silicon	Chromium	Nickel	Phosphorus	Sulfur	Molybdenum
HC30	0.25-0.35	0.5-1.0	0.50-2.00	26-30	4.0 max	0.04 max	0.04 max	0.50 max
HD50	0.45-0.55	1.50 max	0.50-2.00	26-30	4-7	0.04 max	0.04 max	0.50 max
HE35	0.30-0.40	1.50 max	0.50-2.00	26-30	8-11	0.04 max	0.04 max	0.50 max
HF30	0.25-0.35	1.50 max	0.50-2.00	19-23	9-12	0.04 max	0.04 max	0.50 max
HH30	0.25-0.35	1.50 max	0.50-2.00	24-28	11-14	0.04 max	0.04 max	0.50 max
HH33^A	0.28-0.38	1.50 max	0.50-2.00	24-26	12-14	0.04 max	0.04 max	0.50 max
HI35	0.30-0.40	1.50 max	0.50-2.00	26-30	14-18	0.04 max	0.04 max	0.50 max
HK30	0.25-0.35	1.50 max	0.50-2.00	23-27	19-22	0.04 max	0.04 max	0.50 max
HK40	0.35-0.45	1.50 max	0.50-2.00	23-27	19-22	0.04 max	0.04 max	0.50 max
HL30	0.25-0.35	1.50 max	0.50-2.00	28-32	18-22	0.04 max	0.04 max	0.50 max
HL40	0.35-0.45	1.50 max	0.50-2.00	28-32	18-22	0.04 max	0.04 max	0.50 max
HN40	0.35-0.45	1.50 max	0.50-2.00	19-23	23-27	0.04 max	0.04 max	0.50 max
HT50	0.40-0.60	1.50 max	0.50-2.00	15-19	33-37	0.04 max	0.04 max	0.50 max
HU50	0.40-0.60	1.50 max	0.50-2.00	17-21	37-41	0.04 max	0.04 max	0.50 max
HW50	0.40-0.60	1.50 max	0.50-2.00	10-14	58-62	0.04 max	0.04 max	0.50 max
HX50	0.40-0.60	1.50 max	0.50-2.00	15-19	64-68	0.04 max	0.04 max	0.50 max