ASTM A691 Grade 1 CR Alloy Steel Pipe

ASTM A691 is the standard specification for electric-fusion-welded (EFW) carbon and alloy steel pipe made from pressure-vessel-quality plate, intended for high-pressure service at high temperatures. Grade 1 CR designates pipe produced from ASTM A387 Grade 12 plate-nominal 1% chromium, 0.5% molybdenum ("chrome-moly") steel-with a tensile strength of 450–585 MPa and a minimum yield strength of 275 MPa. A691 1 CR is the welded counterpart to seamless ASTM A335 Grade P12; it is selected when large diameters are required that seamless A335 cannot economically supply. GNEE supplies A691 Grade 1 CR EFW pipe for refinery, petrochemical, and power-plant applications.

 

Available Sizes & Specifications

Item	Range
Outside Diameter (OD)	16 in. – 60 in. (406–1524 mm); larger on request
Wall Thickness	SCH 10 through SCH 160, XXS, or custom
Length	Single random, double random, or fixed lengths
Ends	Plain End (PE), Beveled End (BE), or welded flanges
Testing	Hydrostatic test; RT/UT of weld per class
Dimensions standard	ASME B36.10

 

Chemical Composition of A691 Grade 1 CR (A387 Grade 12 Plate)

Element	Composition, % (max unless shown as range)
Carbon (C)	0.05–0.17
Manganese (Mn)	0.40–0.65
Phosphorus (P)	0.035 max
Sulfur (S)	0.035 max
Silicon (Si)	0.50–0.80
Chromium (Cr)	0.80–1.15 (nominal 1%)
Molybdenum (Mo)	0.45–0.65 (nominal 0.5%)

 

Mechanical Properties of A691 Grade 1 CR Pipe

Property	Requirement
Tensile Strength	450–585 MPa (65–85 ksi)
Yield Strength (minimum)	275 MPa (40 ksi)
Elongation (200 mm gauge)	22% min
Hardness (Brinell, max)	201 HB

 

ASTM A691 Class Designations

The "Class" defines the post-weld heat treatment and the extent of radiographic and hydrostatic testing. Class 22 is the most common supply condition for high-temperature pressure service.

Class	Heat Treatment	Radiographic Exam	Hydrostatic Test
Class 12	None	Yes	Yes
Class 22	Stress relieved	Yes	Yes
Class 32	Normalized	Yes	Yes
Class 42	Normalized and tempered	Yes	Yes
Class 52	Quenched and tempered	Yes	Yes

For Grade 1 CR, post-weld stress-relief is typically 590–730°C (1100–1350°F); normalizing not to exceed 1010°C (1850°F); tempering minimum 620–745°C (1150–1375°F), per ASTM A387/A387M.

 

Manufacturing Process (EFW, Not ERW)

A691 Grade 1 CR pipe is produced by forming A387 Grade 12 plate into a cylindrical shape and joining the longitudinal seam by electric fusion welding (EFW), typically double-submerged-arc welding (DSAW) with filler metal added. This is fundamentally different from electric-resistance welding (ERW): ERW forms pipe from coiled strip using high-frequency current, whereas A691 EFW fuses plate with an arc, which is why A691 pipe is normally supplied in large diameters (16 in. / 406 mm and larger). After welding, the pipe receives the heat treatment defined by its class designation.

 

Applications of A691 Grade 1 CR Pipe

Refinery and petrochemical process piping at elevated temperatures

Power-plant boiler and main steam systems

Hydrogen and high-temperature, high-pressure transmission lines

Other services requiring creep resistance and strength above carbon-steel limits

A691 Grade 1 CR is not intended for low-temperature service or for highly corrosive environments that require stainless or higher-alloy grades. Select the grade and class to match the design temperature, pressure, and code of your system.

 

A691 Grade 1 CR Alloy Steel Pipe

 

About GNEE

GNEE supplies ASTM A691 Grade 1 CR EFW pipe with in-house heat treatment, non-destructive testing, cutting, beveling, and surface treatment, and provides mill test certificates per ASTM A387/A691. For quotations, technical data sheets, and inspection options, contact us at pipes@gneetube.com.

ASTM A691 Grade 1 CR EFW pipe factory

FAQ

What is ASTM A691 Grade 1 CR pipe?

ASTM A691 Grade 1 CR is an electric-fusion-welded (EFW) chromium-molybdenum alloy steel pipe. Grade 1 CR means the pipe is made from pressure-vessel-quality plate of nominal 1% chromium and 0.5% molybdenum composition, i.e. ASTM A387 Grade 12 plate. It is intended for high-pressure service at high temperatures, with tensile strength of 450–585 MPa and minimum yield strength of 275 MPa.

 

Is A691 Grade 1 CR the same as ASTM A335 P12?

They share the same nominal chemistry (1% Cr, 0.5% Mo), but not the same product form. A691 Grade 1 CR is an electric-fusion-welded (EFW) pipe made from plate, whereas ASTM A335 P12 is a seamless chrome-moly pipe. A691 is chosen when large diameters are needed that seamless A335 cannot economically supply.

 

What does the Class designation mean in ASTM A691?

In ASTM A691, the class defines the post-weld heat treatment and the extent of radiographic examination and hydrostatic testing. Common classes include Class 12 (no heat treatment, RT + hydrostatic), Class 22 (stress relieved, RT + hydrostatic), and Class 42/52 (normalized-and-tempered or quenched-and-tempered, RT + hydrostatic). Class 22 is the most widely supplied for high-temperature pressure service.

 

What are the chemical and mechanical properties of A691 1 CR?

Chemically (from A387 Grade 12 plate): Carbon 0.05–0.17%, Manganese 0.40–0.65%, Silicon 0.50–0.80%, Chromium 0.80–1.15% (nominal 1%), Molybdenum 0.45–0.65% (nominal 0.5%), Phosphorus and Sulfur each 0.035% max. Mechanically: Tensile Strength 450–585 MPa, Minimum Yield Strength 275 MPa, Elongation 22% min (200 mm gauge), Hardness 201 HB max.

 

What sizes are available for A691 Grade 1 CR pipe?

ASTM A691 covers pipe 16 in. (406 mm) in outside diameter and larger, produced from plate. A691 Grade 1 CR is typically supplied from 16 in. up to about 60 in. (1524 mm) OD, with wall thickness from SCH 10 through SCH 160, XXS, or custom, in single random, double random, or fixed lengths with plain, beveled, or flanged ends.

 

Where is ASTM A691 Grade 1 CR pipe used?

It is used in refinery and petrochemical process piping, power-plant boiler and steam systems, hydrogen and high-temperature high-pressure transmission lines, and other services where creep resistance and strength at elevated temperatures are required. It is not intended for low-temperature or highly corrosive (e.g. stainless-grade) environments.

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