ASTM A691 CM-75 Electric-Fusion-Welded Pipe

What does CM-75 mean in ASTM A691?

In ASTM A691 the grade letter group states the type of pressure-vessel plate the pipe is fabricated from. CM means carbon-molybdenum. Table 1 of A691/A691M maps CM-65, CM-70 and CM-75 to ASTM A204/A204M Grades A, B and C respectively. CM-75 is therefore pipe made from A204/A204M Grade C: 75–95 ksi (515–655 MPa) tensile, 43 ksi (295 MPa) minimum yield, 201 HB maximum.

Is A691 CM-75 a chrome moly pipe?

Not in the metallurgical sense. CM stands for carbon-molybdenum, and the matching plate A204/A204M Grade C carries 0.45–0.60% molybdenum with no deliberate chromium addition. The chromium-bearing A691 grades are the ones designated ½Cr, 1Cr, 1¼Cr, 2¼Cr, 3Cr, 5Cr, 9Cr and 91, all of which are made from A387/A387M plate. CM-75 is often listed as chrome moly in trade catalogues, which is a mislabel.

What is the difference between an A691 grade and an A691 class?

Grade names the plate: it fixes chemistry, strength level and the plate specification (for CM-75, A204/A204M Grade C). Class names what was done to the finished pipe: the heat treatment applied, whether the longitudinal weld was radiographically examined under Section 9, and whether the pipe was hydrostatically tested under 8.3. Classes run 10, 11, 12, 13, 20 … 53. Both must be stated on the purchase order.

What does Class 22 mean for A691 CM-75 pipe?

Class 22 combines three things: the pipe is stress relieved under A691 5.3.1, the weld is radiographically examined under Section 9, and the pipe is pressure tested under 8.3. It is the most common class specified for CM-75 in steam and process service. Class 12 is the same duty in the un-heat-treated condition, and Class 20 is stress relieved but not radiographed or pressure tested.

What size range does ASTM A691 CM-75 cover?

ASTM A691/A691M nominally covers pipe 16 in. (406.4 mm) in outside diameter and larger, with wall thickness up to 3 in. (75 mm) inclusive. Pipe of other dimensions may be furnished provided it meets all other requirements of the specification, so smaller diameters are possible by agreement but are outside the nominal scope. Lengths are commonly 5.8–12 m.

What are the mechanical properties of A691 CM-75?

The governing plate, A204/A204M Grade C, is specified at 75–95 ksi (515–655 MPa) tensile strength, 43 ksi (295 MPa) minimum yield strength, 20% minimum elongation in 2 in. (50 mm) and 16% in 8 in. (200 mm), with a maximum hardness of 201 HB under A691 Table 1. A691 Table 2 states the finished-pipe tensile requirements; both sets of values appear on the mill test report.

Does ASTM A691 require Charpy impact testing?

No. Impact testing is not a base requirement of A691. Charpy V-notch impact, hardness and metallographic examination sit in the supplementary requirements and only apply when they are written into the order. If you need CVN values, state the test temperature, the minimum absorbed energy and whether base metal, weld and heat-affected zone are all tested, otherwise the mill has no defined obligation.

Is electric fusion welding the same as electrofusion welding?

No, they are different processes on different materials. Electric fusion welding (EFW) is the arc welding of steel plate with filler metal added, and it is what ASTM A691 covers. Electrofusion welding is the socket-fusion joining of polyethylene pipe using an embedded heating coil, and it is covered by standards such as ISO 4427 and ASTM F1055. A691 CM-75 pipe is EFW pipe.

What size range and minimum order can you supply for A691 CM-75?

Our standard supply range for A691 CM-75 is outside diameter 406.4–1626 mm (NPS 16–64) with wall thickness 6–75 mm (0.236–3 in.), in classes 10 through 53, in lengths of 5.8–12 m standard and up to 18 m on request. The minimum order quantity is 30 tons per item, and mixed items on one order are quoted together. Dimensions outside this range are quoted case by case against plate availability.

What documents and third-party inspection come with the pipe?

Every order ships with an EN 10204 3.1 or 3.2 mill test report carrying the heat analysis and mechanical results, together with the plate mill certificate, radiographic examination reports, heat-treatment charts, hydrostatic test records, WPS/PQR and welder qualifications, and a packing list. SGS, BV, TUV, Intertek or a client-nominated agency can attend inspection before heat treatment, after heat treatment or before shipment, and the goods are not released until the release note is signed.