ASTM A691 GRADE 1 CR Alloy Steel Pipe

ASTM A691 Grade 1 CR is an electric-fusion-welded (EFW) alloy steel pipe made from ASTM A387 Grade 12 pressure-vessel plate. The base plate is a 1Cr-0.5Mo steel - roughly 1% chromium and 0.5% molybdenum - which gives the finished pipe good creep strength and oxidation resistance at elevated temperatures. Because it is welded from plate rather than drawn as a seamless tube, A691 can be supplied in heavy walls and large diameters that would be difficult or expensive to make any other way.

 

What "Grade 1 CR" Means

In ASTM A691, the grade name tells you which pressure-vessel plate the pipe is welded from. Grade 1 CR uses ASTM A387/A387M Grade 12 plate, a 1.25Cr-0.5Mo-Si steel. This is not a 9% chromium grade - that would be A691 Grade 9 CR, which uses A387 Grade 9 plate and belongs to a much higher alloy class.

A691 also assigns a class number that controls heat treatment and tensile testing:

Class 11 - A387 Gr 12 Class 1, as-rolled/annealed

Class 12 - A387 Gr 12 Class 1, normalized & tempered

Class 21 - A387 Gr 12 Class 2, normalized & tempered

Class 22 - A387 Gr 12 Class 2, quenched & tempered

If the purchase order only says "Grade 1 CR" without a class, ask the supplier for the class and matching mechanical properties. The design code usually decides this.

 

Specifications

Parameter	Typical Range
Standard	ASTM A691
Process	Electric fusion welded (EFW) from A387 Gr 12 plate
Grade	Grade 1 CR
Classes	11, 12, 21, 22
Outer diameter	1/2" – 48" (DN15–DN1200); larger on request
Wall thickness	SCH 10 to SCH 160 / XXS
Length	Single random, double random, fixed 5.8 m / 6 m / 12 m
Ends	Plain, bevelled, or threaded with couplings
Equivalent plate grades	ASTM A387 Gr 12, EN 10028-2 13CrMo4-5, DIN 17175 13CrMo44

 

A691 Grade 1Cr Chemical Analysis:

Designation	C	Mn	P	S	Si	Cr	Mo
ASTM A691 1Cr	0.05-0.17	0.40- 0.65	≤0.035	≤0.035	0.15–0.40	0.80–1.15	0.45-0.65

 

A691 Grade1Cr Physical Property:

Designation	Tensile strength ksi [MPa]	Yield strength, min ksi [MPa]	Elongation in 8 in. [200mm], min %
ASTM A691 Grade1 Cr	65 - 85ksi [450 - 585MPa]	40 ksi [275 MPa]	22

 

 

Why 1Cr-0.5Mo?

Chromium forms a stable oxide layer that slows scaling at temperatures where carbon steel would oxidize rapidly. Molybdenum adds strength at those temperatures and improves creep resistance, so the pipe keeps its shape under long-term load above the carbon-steel limit. Together they make Grade 1 CR a practical choice for pressure piping and boiler circuits operating above about 400°C, but below the range where you would step up to 2.25Cr-1Mo or 9Cr-1Mo.

 

Typical Applications

Power plant boiler and superheater piping

Refinery catalytic reformer and hydrotreater lines

Petrochemical heater tubes and transfer lines

Heat exchanger shells and channel covers

High-temperature process piping in chemical plants

Steam distribution headers

 

Testing and Inspection

ASTM A691 pipe is tested to match the service it will see. Standard tests include:

Chemical analysis of the base plate

Room-temperature tensile test

Transverse guided-bend test of the weld

Radiographic or ultrasonic examination of the weld (required for certain classes)

Hydrostatic test to prove leak tightness

Optional Charpy impact testing for low-temperature service

When the pipe is going into a pressure-vessel or power-plant code job, make sure the test certificates show the A691 class and that the weld examination matches the class requirement.

 

A691 Alloy Steel Pipe Factory

Contact now for A691 welded pipe

 

FAQ

Q: What does CR stand for in Grade 1 CR?

A: CR stands for Chromium. Grade 1 CR is the 1Cr-0.5Mo grade made from A387 Grade 12 plate.

 

Q: Is Grade 1 CR the same as Grade 9 CR?

A: No. Grade 1 CR has about 1% chromium; Grade 9 CR has about 9% chromium and uses A387 Grade 9 plate. They are different alloy classes and not interchangeable.

 

Q: Which A691 class should I order?

A: Class 11/12 correspond to A387 Grade 12 Class 1; Class 21/22 correspond to Class 2 and offer higher strength. Your pressure-vessel or piping code normally specifies the class.

 

Q: What temperature can Grade 1 CR handle?

A: It is commonly used up to about 540–565°C, depending on design stress and the applicable code. Above that range you generally move to a higher Cr-Mo grade.

 

Q: What is the typical delivery condition?

A: Normalized and tempered or annealed, depending on the A691 class ordered.

 

Q: What sizes do you stock?

A: Common stock covers NPS 1/2" to 48" (DN15–DN1200), schedules from SCH 10 to XXS. Larger diameters and heavier walls are made to order.

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