ASTM A572 Grade 60 High-Strength Low-Alloy Steel Pipe

Position of ASTM A572 Grade 60 in the Series

ASTM A572/A572M defines a series of high-strength low-alloy structural steels, and Grade 60 is the highest strength grade normally produced in commercial quantity within that series. Its designation refers to a minimum yield strength of 60 ksi, approximately 415 MPa, which is more than 60 % above that of ordinary structural carbon steel. The strength is achieved by a combination of microalloying with niobium and vanadium and by controlled rolling practice, so the grade delivers high strength without the loss of weldability that a high carbon content would cause. Where the material is supplied in tubular form, the pipe is ordered against a pipe specification with the A572 Grade 60 chemistry and property requirements quoted, and the design engineer should treat the grade as a structural material rather than as a pressure pipe material.

Composition and Mechanical Requirements

Two points deserve attention when the certificate is reviewed. First, the elongation requirement of this grade is lower than that of the lower-strength grades in the series, which is a direct consequence of the higher strength level and must be considered whenever the design relies on plastic deformation. Second, impact toughness is not automatically part of the grade: where low-temperature or dynamic loading is expected, a Charpy V-notch requirement with a stated test temperature and minimum energy must be included in the order, because the property cannot be inferred from the tensile results. The specification also provides for ultrasonic examination of plate when the order calls for it, which is normally requested for heavily loaded welded connections.

Applications of Grade 60 Pipe and Tube

Long-span bridges, cable-supported structures and heavily loaded truss members.

Columns and transfer structures in tall buildings, where the strength-to-weight ratio reduces foundation loads.

Heavy machinery frames, press structures and mining equipment bodies.

High-voltage transmission towers and substation structures carrying heavy ice or wind loading.

Port and offshore handling equipment, large crane booms and heavy transport frames.

Welding, Forming and Fabrication Control

Welding Grade 60 requires a qualified procedure rather than shop habit. Use low-hydrogen consumables matched to the base metal strength, such as an E110 class electrode or an ER110S class wire where the joint is designed for matching strength, and store and handle them according to the manufacturer's instruction so that moisture does not introduce hydrogen into the weld. Preheat thick sections, typically to 150 to 200 °C when the wall or flange thickness reaches about 25 mm, and maintain interpass temperature within the qualified range. Control heat input carefully: the heat-affected zone of a microalloyed steel of this strength level loses toughness if it is overheated, and it can harden excessively if a very high strength consumable is used with minimum heat input on a thick, restrained joint.

Cold forming should be limited to generous bend radii, on the order of five times the pipe diameter or section depth, because the grade strain ages and a tight bend can develop embrittlement in service. Where the structure will be exposed to the weather, specify galvanizing or a coating system appropriate to the environment, and remember that tubular members must be sealed or vented to avoid internal corrosion. For critical welded connections, agree the inspection level in advance, covering ultrasonic or radiographic examination of the joints and the acceptance criteria to be applied.

Common Pitfalls in Selection and Procurement

The most frequent mistake is to treat the A572 grades as interchangeable. Grade 42, 50, 55 and 60 differ in yield strength, elongation and the welding procedure they demand, and a member designed in one grade will not be equivalent in another. A second risk is to assume that the higher grade automatically reduces cost: the price advantage depends on the wall thickness actually required, and on the welding and inspection cost that the higher strength brings. Finally, verify that the certificate reports the correct grade, the microalloying addition, and the tensile results with the elongation and test location, and that the physical marking of each piece matches the certificate before fabrication begins.

FAQ

Q: What is the minimum yield strength of ASTM A572 Grade 60?
415 MPa, equivalent to 60 ksi. The minimum tensile strength is 520 MPa, and the minimum elongation is 16 % on a 200 mm gauge length for the common structural thicknesses.

Q: How does Grade 60 differ from Grade 50?
Grade 60 has a minimum yield strength of 415 MPa against 345 MPa for Grade 50, with a correspondingly lower elongation requirement and a more demanding welding procedure. Substitution in either direction needs a design check.

Q: Is impact testing included in the grade?
No. Toughness testing must be specified as an additional requirement, with the test temperature and minimum energy appropriate to the service condition.

Q: Why is low-hydrogen welding consumable required?
Because hydrogen trapped in a thick, restrained, high-strength joint can cause delayed cracking. Low-hydrogen consumables, correct storage and preheat are the standard controls.

Q: Can Grade 60 tube be cold bent?
It can, with generous radii, generally on the order of five times the diameter. Tight radii should be qualified by test, and the part should be inspected afterwards for surface cracking.

Q: Which documents should be requested with the delivery?
A mill test certificate with heat number, chemistry including the microalloying addition, tensile and yield results, elongation and test location, plus any supplementary test report and the inspection certificate required by the order.