Alloy Steel Plates | ASTM A387 Cr-Mo Gr 11, 22, 91 Supplier

Chrome-Moly Alloy Steel Plates to ASTM A387 / ASME SA387

Dinesh Tube India supplies and exports alloy steel sheets and plates from Mumbai for boilers, pressure vessels, heat exchangers and refinery equipment that run at elevated temperature. "Alloy steel plate" in this service normally means chromium-molybdenum (chrome-moly, Cr-Mo) pressure-vessel plate to ASTM A387 / ASME SA387, in Grades 11, 12, 22, 5, 9 and 91, Class 1 or Class 2, with carbon-molybdenum plate to ASTM A204 for lower-alloy duty. Plates are supplied normalised and tempered, or quenched and tempered, with EN 10204 3.1 mill test certificates.

Chromium improves resistance to oxidation, sulphidation and hydrogen attack; molybdenum raises strength and creep resistance at high temperature. Higher grades (more Cr and Mo) are chosen as design temperature and hydrogen partial pressure rise.

Table of Contents

Which Standard and Grade?
How to Order Alloy Steel Plate
Specification & Sizes
Delivery Condition and Heat Treatment
Strength by Grade and Class
Chemical Composition by Grade
Cutting and Fabrication
Weight Table
Testing and Inspection
Applications
FAQs

Chrome-moly alloy steel plates to ASTM A387

Which Alloy Steel Plate Standard and Grade?

Standard / Grade	Nominal alloy	Typical use
ASTM A204 Gr A / B / C	C – ½Mo	Moderate-temperature boiler and vessel plate
A387 Grade 11	1¼Cr – ½Mo – Si	Boiler drums, vessels and heat exchangers to about 550–595 °C
A387 Grade 12	1Cr – ½Mo	Similar to Grade 11, lower silicon
A387 Grade 22	2¼Cr – 1Mo	Hydroprocessing reactors and high-temperature hydrogen service
A387 Grade 5	5Cr – ½Mo	Refinery heaters and sulphur-bearing hot service
A387 Grade 9	9Cr – 1Mo	Hot sulphur and oxidation-resistant refinery equipment
A387 Grade 91	9Cr – 1Mo – V – Nb	Power-plant headers and high-temperature, high-pressure parts

General requirements (tolerances, test methods, marking) for both A387 and A204 are given in ASTM A20 / ASME SA20.

How to Order Alloy Steel Plate

Standard, grade and class: for example "ASME SA387 Grade 22 Class 2".
Thickness, width and length: full plate size, or cut sizes, circles and rings to drawing.
Heat treatment: normalised and tempered, or quenched and tempered where required for heavy plate.
Supplementary requirements: for example simulated post-weld heat treatment of test coupons (A20 S3), ultrasonic testing (A435 / A578), Charpy impact tests (S5), and any step-cooling or hydrogen-service requirements.
Documents: EN 10204 3.1 or 3.2 certificate and any third-party inspection.

Delivery Condition and Heat Treatment

Normalised and tempered (N&T): the usual condition for A387 plate.
Quenched and tempered (Q&T): often needed in thick plate to reach Class 2 strength, and permitted by the specification when agreed.
Simulated PWHT: because vessels are stress relieved after welding, the purchaser can require test coupons to be given a simulated post-weld heat treatment, so the certified properties reflect the finished vessel.

Strength by Grade and Class (ASTM A387)

Grade	Class 1 Tensile (MPa)	Class 1 Yield min (MPa)	Class 2 Tensile (MPa)	Class 2 Yield min (MPa)
Grade 11	415–585	240	515–690	310
Grade 12	380–550	230	450–585	275
Grade 22	415–585	205	515–690	310
Grade 5	415–585	205	515–690	310
Grade 9	415–585	205	515–690	310
Grade 91	–		585–760	415

Thickness: A387 tensile and yield ranges do not change with plate thickness, but elongation requirements are adjusted for thickness under ASTM A20, and thick plates may need quenching and tempering to meet Class 2. Check the current ASTM A387 / A20 editions and the mill certificate for governing values.

Chemical Composition by Grade (ASTM A387, Heat Analysis, %)

Grade	C	Mn	Si	Cr	Mo	Other
11	0.05–0.17	0.40–0.65	0.50–0.80	1.00–1.50	0.45–0.65	–
12	0.05–0.17	0.40–0.65	0.15–0.40	0.80–1.15	0.45–0.60	–
22	0.05–0.15	0.30–0.60	0.50 max	2.00–2.50	0.90–1.10	–
5	0.15 max	0.30–0.60	0.50 max	4.00–6.00	0.45–0.65	–
9	0.15 max	0.30–0.60	1.00 max	8.00–10.00	0.90–1.10	–
91	0.08–0.12	0.30–0.60	0.20–0.50	8.00–9.50	0.85–1.05	V 0.18–0.25, Nb 0.06–0.10, N 0.030–0.070

Phosphorus and sulphur are limited to low maximums (typically 0.025% or lower) for all grades.

Cutting and Fabrication

Cut to size: flame, plasma or waterjet cutting to drawing, including circles, rings and nozzle blanks.
Preheat for cutting and welding: Cr-Mo steels harden in the heat-affected zone; preheat (typically 150–200 °C, higher for Grade 91) reduces the risk of cracking at cut edges and welds.
Post-weld heat treatment: required for most Cr-Mo vessel welds under the design code.
Filler metals: matching Cr-Mo consumables, such as ER80S-B2 for Grade 11, ER90S-B3 for Grade 22 and ER90S-B9 for Grade 91.

Alloy Steel Plate Weight Table

Thickness	kg per m²	2500 × 1250 mm (kg)	6000 × 2000 mm (kg)
5 mm	39.2	122.7	471
6 mm	47.1	147.2	565
8 mm	62.8	196.2	754
10 mm	78.5	245.3	942
12 mm	94.2	294.4	1130
16 mm	125.6	392.5	1507
20 mm	157.0	490.6	1884
25 mm	196.2	613.3	2355
32 mm	251.2	785.0	3014
40 mm	314.0	981.2	3768
50 mm	392.5	1226.6	4710
75 mm	588.8	1839.8	7065
100 mm	785.0	2453.1	9420

Weight (kg) = length (m) × width (m) × thickness (mm) × 7.85, using density 7.85 g/cm³.

Testing and Inspection

Per ASTM A387 / A20: heat and product chemical analysis, tension test, and dimensional and flatness checks.
Supplementary, on request: ultrasonic testing (A435 / A578), Charpy impact testing, simulated PWHT, hardness, PMI and third-party inspection.

Grade 11 Plates

1¼Cr-½Mo plate for boilers and vessels.

Grade 22 Plates

2¼Cr-1Mo plate for reactors and hydrogen service.

Grade 91 Plates

9Cr-1Mo-V plate for high-temperature power-plant parts.

Need alloy steel plates? Send the grade, class, thickness, sizes or cutting drawing, heat treatment and test requirements to kamlesh@dineshtube-india.com or call +91 83559 10913. You can also send an enquiry.

Alloy Steel Plate Applications

Boiler drums, headers and power-plant pressure parts
Hydroprocessing and hydrocracker reactors
Refinery and petrochemical pressure vessels
Heat-exchanger shells, channels and tubesheets
Furnace and heater components
High-temperature steam and process equipment

Boiler, refinery and pressure-vessel uses of chrome-moly alloy steel plates

Alloy Steel Sheets & Plates: FAQs

What is alloy steel plate?

In pressure-equipment service, alloy steel plate usually means chromium-molybdenum (chrome-moly) plate to ASTM A387 / ASME SA387, such as Grades 11, 22 and 91, or carbon-molybdenum plate to ASTM A204. These grades keep their strength and resist oxidation and hydrogen attack at elevated temperature.

Which standard covers chrome-moly plate?

ASTM A387 / ASME SA387 covers chromium-molybdenum alloy steel plate for boilers and pressure vessels, in Grades 2, 11, 12, 22, 5, 9 and 91. General requirements are in ASTM A20 / ASME SA20.

What is the difference between A387 Class 1 and Class 2?

Class 2 has higher tensile and yield strength than Class 1 for the same grade. For example, Grade 22 Class 1 requires 415–585 MPa tensile and 205 MPa minimum yield; Class 2 requires 515–690 MPa tensile and 310 MPa minimum yield.

Does alloy steel plate strength change with thickness?

The A387 tensile and yield ranges are the same for all thicknesses, but ASTM A20 adjusts the elongation requirement with thickness, and thick plates may need quenching and tempering instead of normalising to reach Class 2 strength.

Which A387 grade should I choose?

Grade 11 suits boilers and vessels at moderate high temperature; Grade 22 is common for hydroprocessing reactors and hydrogen service; Grades 5 and 9 for hot sulphur-bearing refinery service; Grade 91 for high-temperature power-plant parts. The design code and process conditions decide the final choice.

How do I calculate the weight of an alloy steel plate?

Weight in kg = length (m) × width (m) × thickness (mm) × 7.85. For example, a 6000 × 2000 × 20 mm plate weighs about 1884 kg.

What is the price of alloy steel plate?

The price depends on grade, class, thickness, size, heat treatment, testing and quantity. Send your requirement to kamlesh@dineshtube-india.com or call +91 83559 10913 for a current quote.

Export Destinations for Alloy Steel Plates

We supply chrome-moly alloy steel plates across India to boiler makers, refineries, fertiliser and power projects, and export to the Middle East (UAE, Saudi Arabia, Qatar, Oman, Kuwait, Bahrain), Asia (Singapore, Malaysia, Indonesia, Vietnam, Bangladesh), Africa (Egypt, Nigeria, South Africa) and Europe on request.

Alloy Steel (Chrome-Moly) Sheets & Plates