ASTM A691 1Cr CL22 EFW Steel Pipe: The Entry-Level Chrome-Moly Grade for High-Temperature Service

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Womic Steel manufactures ASTM A691 1Cr CL22 electric-fusion-welded (EFW) steel pipe for high-pressure service at elevated temperatures. The 1Cr grade (approximately 1% chromium, 0.5% molybdenum) is derived from ASTM A387 Gr.12 pressure vessel plate and represents the lowest alloy content in the A691 chrome-moly family. It is specified where the operating temperature exceeds the practical limit of carbon steel but does not yet require the higher chromium content of 1.25Cr or 2.25Cr. Class 22 combines post-weld stress relieving, radiographic examination of the longitudinal seam, and hydrostatic testing. This page covers what the grade means, where it sits in the chrome-moly progression, real project applications, and what to specify when ordering.

Key search terms covered on this page: ASTM A691 1Cr CL22, A691 1Cr pipe, 1Cr EFW pipe, chrome moly EFW pipe, A387 Gr.12 welded pipe, high temperature EFW pipe, ASTM A691 Class 22, 1Cr vs 1.25Cr, A691 1CR CL22 power plant.

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What ASTM A691 1Cr CL22 Means

ASTM A691 covers carbon and alloy steel pipe, electric-fusion-welded with filler metal added, fabricated from pressure-vessel-quality plate, suitable for high-pressure service at high temperatures . The designation breaks into three parts.

Grade 1Cr identifies the base plate. This grade corresponds to ASTM A387 Gr.12, a chromium-molybdenum alloy steel plate with nominal chromium content of approximately 1% and molybdenum content of approximately 0.5% . The chromium provides modest oxidation resistance and elevated-temperature strength, while molybdenum contributes creep resistance. The pipe’s chemistry and mechanical properties follow the A387 Gr.12 plate specification.

Class 22 defines heat treatment and testing. Per the ASTM A691 class system, Class 22 requires the pipe to be stress relieved after welding, the longitudinal weld seam to be radiographically examined, and the finished pipe to undergo hydrostatic testing . This class provides PWHT and RT without the normalization required by Class 32 or the quenching-and-tempering of Class 42.

EFW indicates the manufacturing method: alloy steel plate is formed into cylindrical shape, and the longitudinal seam is welded using submerged arc welding with filler metal added.

What ASTM A691 1Cr CL22 Means

EFW indicates the manufacturing method: alloy steel plate is formed into cylindrical shape, and the longitudinal seam is welded using submerged arc welding with filler metal added.

Chemical and Mechanical Properties

Because 1Cr is tied to A387 Gr.12 plate, the finished pipe’s chemistry and strength follow that plate standard.

Property	Typical Value
Chromium	~1.00%
Molybdenum	~0.50%
Tensile Strength	Varies by plate heat, typically 415–585 MPa range
Yield Strength	Varies by plate heat
Max Operating Temperature	Up to 593°C (1100°F) per A691 scope

Actual test results on the mill certificate reflect the specific heat and plate used. Class 22 stress relieving does not alter the base chemistry.

Grade Comparison: 1Cr vs 1.25Cr vs 2.25Cr

The 1Cr grade sits at the bottom of the A691 chrome-moly progression. Understanding where it fits helps determine when it is the right choice versus when a higher grade is necessary.

Grade	Base Plate	Cr Content	Mo Content	Primary Driver for Selection
1Cr	A387 Gr.12	~1.00%	~0.50%	Moderate elevated temperature, lower alloy cost
1.25Cr	A387 Gr.11	1.00–1.50%	0.45–0.65%	General high-temp steam and process lines
2.25Cr	A387 Gr.22	2.00–2.50%	0.90–1.10%	Higher temperature, hydrogen service

1Cr is selected when the design temperature and pressure allow a lower alloy content than 1.25Cr, typically for moderate elevated-temperature service where the allowable stress of A387 Gr.12 is sufficient. It is more economical than 1.25Cr because the plate chemistry is less alloyed, but the difference in performance between the two grades is relatively small. In practice, many power plant specifications default to 1.25Cr for reheat and steam piping because the cost difference is minor and the higher chromium provides a margin of oxidation resistance.

Class 22 and the A691 Class System

Class 22 is one of several class designations in ASTM A691 that control heat treatment, radiography, and pressure testing.

Class	Heat Treatment	Radiography	Pressure Test	Typical Use
12	None	Full RT	Yes	As-welded, moderate service
22	Stress Relieved	Full RT	Yes	High-temp service with PWHT
32	Normalized	Full RT	Yes	Higher toughness demand
42	Normalized + Tempered	Full RT	Yes	Critical high-temp piping

For critical high-temperature piping in power plants, Class 42 is often the standard requirement in EPC specifications because it combines full RT with normalized-and-tempered heat treatment . Class 22 is appropriate where stress relieving alone is sufficient for the design code and the operating conditions do not demand normalized plate properties in the finished pipe.

Size Range and Manufacturing Options

Womic produces A691 1Cr CL22 pipe using LSAW with either single straight seam or double straight seam configuration. ASTM A691 nominally covers pipe 16 inches (400 mm) outside diameter and larger with wall thicknesses up to 3 inches (75 mm) .

Parameter	Range
Outside Diameter	16″ to 100″ (400 mm to 2,540 mm)
Wall Thickness	6 mm to 75 mm (heavier on request)
Length	6 m, 12 m standard; up to 18 m or 24 m on request
Manufacturing Method	EFW / LSAW with filler metal
Seam Type	Single straight seam or double straight seam

Single Straight Seam vs Double Straight Seam

Single straight seam is used when one plate can be rolled into a full cylinder. At Womic this covers OD up to about 1,422 mm with wall thickness up to 50.8 mm on the JCOE line. One longitudinal weld concentrates inspection and PWHT on a single seam.

Double straight seam is used when diameter or wall thickness exceeds what a single plate can form. Two plates are rolled into half-cylinders and each is welded longitudinally. This covers OD from about 1,200 mm to 2,540 mm with wall thickness up to 75 mm or more.

Applications for A691 1Cr CL22 Pipe

The 1Cr grade is used in moderate elevated-temperature service where carbon steel is inadequate but higher chrome-moly grades are not yet required.

Power plant reheat steam cold-end piping—A691 1CR CL22 has been used in Chinese power plant projects for reheat steam cold-end lines, in OD ranges of 610–1219 mm and wall thicknesses of 9.52–42 mm

Large-diameter alloy headers where seamless pipe above NPS 24 is impractical

High-temperature transfer lines in refineries and petrochemical plants operating in the moderate creep range

Boiler external piping where the design temperature falls within the allowable stress range of A387 Gr.12

Project Cases

Reheat Steam Cold-End Piping (China Power Plant, 2011)

A Chinese power plant project specified ASTM A691 1CR CL22 LSAW pipe for reheat steam cold-end piping. The pipe was produced in OD ranges of 610–1219 mm with wall thicknesses from 9.52 mm to 42 mm. This project was documented in a technical paper presented at the 14th China (Northern) Steel Pipe and Pipeline Technology Conference in 2011, confirming the grade’s acceptance in Chinese power plant applications where full RT and PWHT are required . The same production route used for this project applies to current 1Cr CL22 orders.

High-Pressure Bypass Piping (China Thermal Power, 2024)

A 2024 maintenance project at a 350 MW supercritical thermal power plant in China specified A691 Gr.2-1/4Cr CL22 pipe for high-pressure bypass downstream piping replacement. While this project used the 2.25Cr grade, it demonstrates the ongoing use of A691 CL22 EFW pipe in Chinese power plant maintenance and upgrade work. The scope included pipe installation with PWHT and NDT, confirming that A691 CL22 grades remain the standard choice for high-temperature power plant piping where seamless pipe is unavailable or uneconomical .

Refinery and Petrochemical High-Temperature Service

1Cr pipe is also specified for refinery transfer lines and petrochemical process piping where the operating temperature requires chrome-moly construction but the process stream does not contain the sulfur or hydrogen levels that would dictate 2.25Cr or 5Cr. The lower alloy content makes 1Cr more weldable and less costly than the higher chrome-moly grades, while still providing creep resistance superior to carbon steel.

Quality Documentation

Each shipment of A691 1Cr CL22 pipe from Womic Steel includes:

● EN 10204 3.1 mill test certificate with chemical composition and mechanical test results traceable to the plate heat number

● Radiographic examination report for the weld seam

● Hydrostatic test record

● Post-weld heat treatment chart with temperature and holding time

● Dimensional inspection report

● Third-party inspection available upon request (SGS, BV, TÜV)

Packaging and Shipping

Pipes are supplied with beveled ends protected by plastic caps, or plain ends as specified. The pipe surface receives a protective coating suitable for transport and storage. Small and medium diameters are bundled with steel straps; large diameters and heavy wall pipe are shipped individually with wooden dunnage. Third-party pre-shipment inspection can be arranged.

Frequently Asked Questions

Q: What is the difference between 1Cr and 1.25Cr in ASTM A691?

1Cr uses A387 Gr.12 plate with approximately 1% chromium, while 1.25Cr uses A387 Gr.11 plate with 1.00–1.50% chromium. The difference in alloy content is modest, and the two grades have similar elevated-temperature properties. 1Cr is often more economical, while 1.25Cr is more commonly specified in power plant piping because the slightly higher chromium provides additional oxidation resistance and the grade is more widely available from plate mills. Selection between them usually comes down to project specification preference and plate availability.

Q: What does Class 22 mean for A691 1Cr pipe?

Class 22 means the pipe is stress relieved after welding, the longitudinal weld seam receives full radiographic examination, and the finished pipe is hydrostatically tested . This class is common for high-temperature service where PWHT is required to stabilize the weld and heat-affected zone, and where full RT is specified for weld integrity verification.

Q: Can you supply A691 1Cr with impact testing?

Yes. Charpy V-notch impact testing is a supplementary requirement under ASTM A691. Specify the test temperature, specimen orientation, and acceptance criteria in the purchase order. Impact testing for chrome-moly pipe is less common than for low-temperature carbon steel, but can be arranged when the project specification requires it.

Q: What is the maximum temperature for A691 1Cr?

The A691 specification nominally covers service up to 593°C (1100°F) for the chrome-moly grades . Within that range, the allowable stress for A387 Gr.12 decreases as temperature rises. For service above approximately 540–565°C, higher chromium grades such as 1.25Cr or 2.25Cr are often preferred for additional creep and oxidation resistance.

Q: Is A691 1Cr the same as A387 Gr.12?

Not exactly. A387 Gr.12 is a steel plate specification. A691 1Cr is a pipe specification that uses A387 Gr.12 plate as starting material, forms and welds it into pipe, applies the heat treatment required by the class, and performs the specified testing. The finished pipe has chemistry and strength consistent with A387 Gr.12, but the product form and testing regime are governed by A691.

Q: Should I choose single straight seam or double straight seam?

The mill selects the seam configuration based on the ordered size. Single straight seam covers OD up to about 1,422 mm and wall thickness up to 50.8 mm at Womic. Double straight seam covers larger diameters and heavier walls. If your project specification restricts the seam type, state this in the purchase order.

Contact Womic Steel for ASTM A691 1Cr CL22 EFW pipe quotations. Provide the outside diameter, wall thickness, quantity, length, end finish, PWHT requirements, and any supplementary testing requirements. We will confirm availability and lead time within one business day.

Website: www.womicsteel.com
E-mail: sales@womicsteel.com

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