AISI 403CB (UNS S40300) — At a Glance
About AISI 403CB (UNS S40300) Stainless Steel
Figure 1: High-quality AISI 403CB forged steel round bars produced by Jiangsu Liangyi
AISI 403CB is a high-grade martensitic stainless steel modified with chromium and niobium, and it is used at tough high-temperature up to 600°C (1112°F).Compared with standard AISI 403, adding 0.15–0.45% niobium greatly improves creep resistance, toughness, and high-temperature strength, while keeping good corrosion resistance in mild environments. As a top Chinese manufacturer of AISI 403CB forgings based in Jiangyin, Jiangsu Province, we have refined our production processes to provide stable, high-quality UNS S40300 forged parts that meet strict international standards including ASTM, EN, DIN, and JIS.
Key Advantages of AISI 403CB Over Conventional Alloys
- Superior creep resistance at elevated temperatures up to 600°C
- Higher toughness and impact strength for critical applications
- Better weldability compared to similar martensitic stainless steels
- Excellent resistance to steam oxidation and corrosion
- Good machinability after proper heat treatment
- Cost-effective alternative to more expensive nickel-based alloys
- Proven performance in power generation and oil & gas industries
AISI 403CB vs Similar Stainless Steel Grades
Following is a detailed comparison between AISI 403CB, standard AISI 403, and AISI 410 stainless steel grades:
| Property | AISI 403CB | Standard AISI 403 | AISI 410 |
|---|---|---|---|
| Carbon Content (%) | 0.13-0.18 | 0.08-0.15 | 0.08-0.15 |
| Niobium Content (%) | 0.15-0.45 | None | None |
| Chromium Content (%) | 11.5-13.0 | 11.5-13.0 | 11.5-13.5 |
| Tensile Strength (MPa) | ≥ 828 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa) | ≥ 725 | ≥ 275 | ≥ 275 |
| Elongation (%) | ≥ 17.0 | ≥ 20.0 | ≥ 20.0 |
| Maximum Service Temperature (°C) | 600 | 450 | 450 |
| Primary Application | Steam turbine blades, high-temperature valves | General purpose stainless steel | Cutlery, general parts |
Comprehensive AISI 403CB Forged Product Range
As a professional AISI 403CB forging supplier from Jiangsu with over 25 years of experience, Jiangsu Liangyi manufactures a full range of forged steel products in different shapes and sizes, and all parts meet international standards and customer drawings. Our factory in Jiangyin is equipped with advanced forging equipment, including 6300T hydraulic presses and 5-meter ring rolling machines.
We invite you to explore our full product range and learn more about our advanced manufacturing equipment.
Forged Bars & Rods
- Round bars: up to 2000mm diameter
- Flat bars: up to 1500mm width
- Square bars: up to 800mm x 800mm
- Rectangular bars: custom dimensions
- Step shafts and turbine blade bars
Seamless Rolled Rings
- Diameter range: 500mm to 6000mm
- Height: up to 1000mm
- Weight: up to 30 tons
- Guide rings, seal rings, casing rings
- Labyrinth rings and packing seals
Hollow Parts
- Hubs, housings and shells
- Sleeves, bushes and bushings
- Hollow bars and heavy-wall cylinders
- Pipes, tubes and casings
- Outer diameter up to 3000mm
Custom Forged Parts
- Discs, disks and plates
- Turbine impellers and blisks
- Valve bodies, bonnets and stems
- Pump cases, impellers and shafts
- Fasteners, studs and bolts
Industrial Applications & Project Cases
Figure 2: AISI 403CB steam turbine blades - our flagship product for power plants worldwide
AISI 403CB forged parts from Jiangsu Liangyi have been successfully used in over 50 countries in many important industries. Our parts are accepted by top power generation companies, oil & gas operators and petrochemical plants around the world. Our strategic location in Jiangyin, Jiangsu Province allows us to efficiently serve both domestic and international markets.
Power Generation Industry (Primary Application)
AISI 403CB is the best choice material for steam turbine parts due to its exceptional high-temperature strength and creep resistance. Following are main area our products have been used in:
- Steam Turbine Blades: Supplied over 10,000 AISI 403CB forged flat bars for 50MW to 600MW steam turbines in thermal power plants across Asia, Europe and the Middle East
- Turbine Discs & Impellers: Manufactured turbine discs for combined-cycle power plants operating at temperatures up to 580°C
- Turbine Rotor Parts: Produced guide rings, seal rings and labyrinth seals for main turbine OEMs
- Gas Compressor Parts: Forged blades and discs for natural gas compressor stations
Oil & Gas and Petrochemical Industry
In the oil and gas sector, AISI 403CB is widely used for high-pressure, high-temperature (HPHT) applications:
- Valve Parts: Forged valve bodies, bonnets, stems, seat rings and discs for API 6A and API 6D valves
- Pump Parts: Pump cases, impellers, wear rings and shafts for crude oil and refined product pumps
- Pressure Vessel Parts: Flanges, nozzles and internal parts for refinery reactors and separators
- Pipeline Parts: Specialized fittings and connectors for high-temperature pipeline systems
General Industrial Applications
- Fasteners & Bolting: Double-headed studs, bolts, screws and pins for high-temperature equipment
- Heat Exchanger Parts: Tube sheets and baffles for high-temperature heat exchangers
- Marine Applications: Propulsion system parts and exhaust system parts
- Chemical Processing: Reactors, mixers and processing equipment parts
View our project references to learn more about our successful deliveries worldwide.
AISI 403CB Forging Manufacturing Process at Jiangsu Liangyi
Located in Jiangyin, Jiangsu Province, China’s top hub for advanced forging, Jiangsu Liangyi provides a full range of services from steel melting to final machining and inspection. Our modern equipment guarantees stable quality and accurate dimensional control for all UNS S40300 forged parts.
1. Steel Melting
We use a 30-ton electric arc furnace (EAF), along with ladle refining (LF) and vacuum degassing (VOD), to produce ultra-clean AISI 403CB steel with tightly controlled chemical composition.
2. Open Die Forging
Our hydraulic presses range from 2000T to 6300T and our electro-hydraulic hammers range from 1T to 9T. They all have enough forming pressure to make a best grain matrix and strong mechanical properties.
3. Heat Treatment
We strictly control the heat treatment including quenching and tempering in ten computerized heat treatment furnaces, to get the needed mechanical properties.
4. Machining & Finishing
Our CNC machining centers provide precise finishing operations to meet tight dimensional tolerances and surface finish requirements.
5. Quality Inspection
We provide full non-destructive testing (NDT), including ultrasonic testing (UT), magnetic particle inspection (MT) and dimension test, making sure all parts have high quality.
6. Certification & Delivery
Every shipment includes full EN 10204 3.1/3.2 Mill Test Certificates (MTC). We provide worldwide delivery to more than 50 countries.
Learn more about our manufacturing equipment and quality control processes.
Material Specifications & Properties
Chemical Composition (Weight %)
The precise chemical composition of AISI 403CB (UNS S40300) is carefully controlled to guarantee improved mechanical properties and corrosion resistance:
| Element | Minimum | Maximum |
|---|---|---|
| Carbon (C) | 0.13 | 0.18 |
| Silicon (Si) | - | 0.50 |
| Manganese (Mn) | 0.40 | 0.60 |
| Phosphorus (P) | - | 0.025 |
| Sulfur (S) | - | 0.010 |
| Chromium (Cr) | 11.5 | 13.0 |
| Nickel (Ni) | - | 0.60 |
| Niobium (Nb) | 0.15 | 0.45 |
Mechanical Properties (Room Temperature)
AISI 403CB has excellent mechanical properties after proper heat treatment.Following are the main mechanical properties:
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (σb) | ≥ 828 MPa | EN 10002-1 |
| Yield Strength (σ0.2) | ≥ 725 MPa | EN 10002-1 |
| Elongation (δ) | ≥ 17.0% | EN 10002-1 |
| Reduction of Area (ф) | ≥ 50.0% | EN 10002-1 |
| Hardness | 255 – 302 HB | ISO 6506-1 |
Standards Compliance
Our AISI 403CB forgings meet all main international standards including:
- ASTM A182 / ASME SA-182
- EN 10088-3
- DIN 1.4024 (equivalent)
- JIS G4303
- API 6A / API 6D (for oilfield applications)
- NACE MR0175 / ISO 15156 (sour service)
Explore our complete range of forging materials including stainless steel, alloy steel, nickel alloys and more.
Physical & Thermal Properties
Knowing well the physical and thermal properties of AISI 403CB is essential for part design, thermal stress analysis, and choosing machining parameters. Unless noted otherwise, the values below are for standard quenched and tempered material at room temperature (20°C).
| Property | Value | Unit |
|---|---|---|
| Density | 7.70 | g/cm³ |
| Elastic Modulus (Young's Modulus) | 215 | GPa |
| Poisson's Ratio | 0.28 | — |
| Thermal Conductivity (at 20°C) | 25.0 | W/(m·K) |
| Thermal Conductivity (at 500°C) | 27.5 | W/(m·K) |
| Mean Thermal Expansion (20–300°C) | 10.5 × 10⁻⁶ | K⁻¹ |
| Mean Thermal Expansion (20–600°C) | 11.5 × 10⁻⁶ | K⁻¹ |
| Specific Heat Capacity (at 20°C) | 460 | J/(kg·K) |
| Electrical Resistivity (at 20°C) | 0.60 | µΩ·m |
| Magnetic Permeability | Ferromagnetic | — |
| Melting Range | 1480 – 1530 | °C |
Note: Thermal expansion values increase gradually with temperature. Designers should use temperature-specific data for precision high-temperature component calculations.
International Equivalent Grades
When buying or specifying AISI 403CB forgings worldwide, buyers often find different national names for the same chromium‑niobium martensitic stainless steel.The table below lists the most common equivalent designations across major standard systems, for direct reference in purchasing, inspection, and engineering documents.
| Standard System | Grade / Designation | Remarks |
|---|---|---|
| USA — AISI / UNS | AISI 403CB / UNS S40300 | Reference grade — Nb-modified 403 |
| Europe — EN / DIN | X12CrNbS13 / 1.4024 (Nb-mod.) | EN 10088-3 nearest equivalent; Nb not always specified in base 1.4024 |
| Germany — DIN | X15CrNiSi20-12 (historical) | Older DIN turbine blade grade; composition varies |
| Japan — JIS | SUS403 (Nb-added variant) | JIS G4303; Nb addition confirmed by individual mill spec |
| China — GB / YB | 1Cr13Nb / 12Cr13 | GB/T 1220; Nb content must be confirmed in order specification |
| UK — BS | 403S17 (Nb-modified) | BS 970; limited direct equivalent — verify Nb via MTR |
| France — AFNOR | Z12C13 | NF A35-573 nearest equivalent; Nb content per order spec |
| Russia — GOST | 12X13 (Nb-variant) | GOST 5632; specify Nb requirement explicitly in purchase order |
| Sweden — SS | SS 2302 | Approximate equivalent for base composition only |
Important Note on Equivalent Grade Procurement
Different national standards do not specify niobium content in exactly the same way. When ordering equivalent grades of AISI 403CB from any supply chain, always clearly confirm the niobium content (0.15–0.45%) in your purchase order and verify it on the Mill Test Certificate (EN 10204 3.1 or 3.2).Jiangsu Liangyi produces all forgings to the AISI 403CB / UNS S40300 chemical composition as standard, and can provide dual certification to EN, JIS, GB or other standards upon request.
Heat Treatment of AISI 403CB Forgings
Proper heat treatment is the most important factor in making sure AISI 403CB forged parts meet their needed mechanical properties. As a martensitic stainless steel, AISI 403CB gets its high strength and hardness only from the hardening heat treatment process, not just from cold working or alloying.At Jiangsu Liangyi, every heat treatment run is done in fully computerized gas-fired furnaces with independent thermocouple checks and automatic time-temperature recording, to guarantee consistent results from batch to batch.
Standard Heat Treatment Cycle
| Process Stage | Temperature Range | Holding Time | Cooling Method | Purpose |
|---|---|---|---|---|
| Pre-heat (stress relief) | 600 – 650 °C | 1 h per 25 mm section | Slow furnace cool | Relieve residual forging stress; prevent cracking on heating |
| Austenitising (hardening) | 950 – 1020 °C | 1 – 2 h per 25 mm section | Oil or air quench (section-dependent) | Dissolve carbides; form austenite for full martensitic transformation |
| Tempering | 650 – 750 °C | 2 h per 25 mm section (min. 4 h) | Air cool to room temperature | Achieve target tensile / yield strength; restore toughness and ductility |
| Stress-relief anneal (optional) | 730 – 760 °C | 2 – 4 h | Slow furnace cool to below 300 °C | Post-weld stress relief or dimensional stabilisation for precision parts |
Tempering Temperature vs. Mechanical Properties
One of the most important process choices for AISI 403CB is choosing the tempering temperature. Higher tempering temperatures lower hardness and tensile strength but improve toughness and impact resistance — a balance that must be matched to your application’s service needs.The guide below shows typical material properties after austenitizing at 980°C and oil quenching:
| Tempering Temp. | Tensile Strength | Yield Strength | Hardness (approx.) | Typical Application |
|---|---|---|---|---|
| 650 °C | ~1000 MPa | ~860 MPa | 295 – 302 HB | High-strength fasteners, bolting |
| 690 °C | ~920 MPa | ~790 MPa | 270 – 285 HB | Turbine blade bars, valve stems |
| 720 °C | ~860 MPa | ~740 MPa | 255 – 270 HB | Turbine discs, guide rings, seal rings |
| 750 °C | ~830 MPa | ~725 MPa | 255 – 262 HB | Large-section pump casings, flanges |
All values shown are for reference only. Actual properties depend on section thickness, quenching intensity, and furnace load.Jiangsu Liangyi's metallurgy team chooses the exact tempering process for each order based on your required mechanical properties and the forging cross-section.
Critical Heat Treatment Cautions
Avoid the 425–600°C Temper Embrittlement Range
AISI 403CB must never be tempered or slowly cooled within the 425–600°C range. This temperature zone causes severe temper embrittlement, which sharply reduces room-temperature impact toughness, as phosphorus and sulfur segregate along the prior austenite grain boundaries. This damage cannot be reversed without a full re‑austenitizing cycle. All furnaces at Jiangsu Liangyi are programmed to pass quickly through this temperature range during both heating and cooling.
Welding & Post-Weld Heat Treatment
If AISI 403CB forged parts are welded during installation or manufacture, post-weld heat treatment (PWHT) at 730–760°C is mandatory to restore toughness in the heat-affected zone. It is also very important to preheat to 200–300°C before welding.Not doing PWHT could cause HAZ to crack and break easily when it is heated and cooled repeatedly. This is especially dangerous in steam turbine and pressure vessel applications.
Quality Assurance & Inspection
At Jiangsu Liangyi, quality is our top priority. We operate a strict quality management system certified to ISO 9001:2015 and provide complete inspection documentation for all AISI 403CB forged parts. Our factory in Jiangyin, Jiangsu is equipped with advanced testing and inspection equipment to make sure every product meets or exceeds customer requirements. We supply an EN 10204 3.1 inspection certificate and a detailed English-language Inspection and Test Plan (ITP) with every shipment. Following are our inspection documentation:
- Complete material identification and traceability
- Heat number and full chemical analysis including trace elements
- Ingot information and forging reduction ratio
- Detailed heat treatment records with temperature-time curves
- Full mechanical test results with specimen locations
- Non-destructive testing results (UT, MT, PT as required)
- Dimension test reports
- Magnetic properties testing (for turbine applications)
- Residual stress measurement results (if requested)
Third-party inspection services from SGS, BV, TÜV and other authorized agencies are available upon customer request.
Why Choose Jiangsu Liangyi as Your AISI 403CB Forging Partner?
Jiangsu Liangyi Competitive Advantages
- Industry Experience: Over 25 years of specialized forging manufacturing experience
- Strategic Location: Located in Jiangyin, Jiangsu Province, China's premier forging industry cluster with access to the best raw materials and skilled labor
- Advanced Equipment: 6300T hydraulic press, 5-meter ring rolling machine and complete in-house testing facilities
- Full Integration: From steel melting to final machining - all processes under one roof
- Quality Certifications: ISO 9001:2015 certified quality management system
- Global Reach: Exported to over 50 countries with reliable global shipping
- Custom Solutions: Ability to produce custom forgings according to customer drawings and specifications
- Competitive Pricing: Cost-effective solutions without compromising on quality
Frequently Asked Questions (FAQ)
A: AISI 403CB (UNS S40300) is a type of martensitic stainless steel that has been changed by adding chromium and niobium. It has 11.5–13.0% chromium and 0.15–0.45% niobium (columbium).Adding niobium makes the material much more resistant to creep at high temperatures, tougher, and stronger in tension (≥828 MPa) than standard AISI 403.In the oil and gas and power generation industries, it is mostly used for pump parts, valve parts, and steam turbine blades.Its highest working temperature is 600°C (1112°F), while the highest working temperature for regular AISI 403 is 450°C.
A: AISI 403CB contains 0.15–0.45% niobium (columbium), which significantly improves high‑temperature creep resistance, toughness and strength compared to standard AISI 403.So that it is the best choice material for steam turbine blades and other high‑temperature applications where standard 403 would fail prematurely.The niobium addition forms stable carbides that pin grain boundaries and resist creep deformation at elevated temperatures.Tensile strength of AISI 403CB is ≥828 MPa, compared with ≥485 MPa for standard 403, while its maximum service temperature reaches 600°C versus 450°C.
A: We can make AISI 403CB forgings that weigh up to 30 tons.The largest diameter for round bars is 2000 mm.The biggest diameter for seamless rolled rings is 6000 mm.The longest shafts can be is 15 meters.Please get in touch with us if you need parts that are shaped in a certain way. Send us your exact needs and drawings so we can give you a full quote.
A: As a standard, we give out EN 10204 3.1 mill test certificates. You can ask for EN 10204 3.2 certificates that have been checked by a third party. We can also give out certificates that meet the standards set by API, NACE, and other groups in the same field. All of the certificates are in English and show the full results of the chemical, mechanical, and dimensional tests.
A: The usual lead time for raw forgings is 4 to 6 weeks, and the usual lead time for machined parts is 6 to 8 weeks. We can also speed up production for orders that need to be done right away.Actual lead times depend on the current production schedule, the drawings, the dimensions, and the number of parts ordered. Please get in touch with us to find out the most up-to-date lead times for your needs.
A: Yes, we specialize in producing custom open‑die forgings.Please send us your detailed drawings, material specs and order quantity for a competitive quotation.Our engineering team will review your requirements and provide technical feedback if needed.We accept all common drawing formats including PDF, DWG and STEP files.
A: Yes. As a martensitic stainless steel, AISI 403CB (UNS S40300) is ferromagnetic in both annealed and hardened‑and‑tempered conditions.Its magnetic permeability is considerably higher than austenitic grades such as 304 or 316. This magnetic property is actually advantageous for steam turbine blade applications, where magnetic particle inspection (MT) is the main method to detect surface and near‑surface cracks during production and in‑service checks.Buyers needing non‑magnetic parts should consider austenitic or duplex stainless steels instead.
A: The closest European equivalent to AISI 403CB is DIN 1.4024 (X12Cr13 to EN 10088‑3) with a controlled niobium addition of 0.15–0.45%.Note that the standard 1.4024 grade does not specify niobium as a requirement — the Nb content must be clearly stated in the purchase order and verified on the Mill Test Certificate. Other equivalents include JIS SUS403 (with Nb addition), Chinese GB 1Cr13Nb, and BS 403S17.For a full cross‑reference table, please refer to the International Equivalent Grades section on this page.
A: The standard heat treatment for AISI 403CB forgings includes three stages:(1)Preheating at 600–650°C to relieve forging residual stresses;
(2)Austenitizing (hardening) at 950–1020°C, followed by oil or air quenching;(3)Tempering at 650–750°C to achieve the required mechanical properties (tensile strength ≥828 MPa, hardness 255–302 HB). The exact tempering temperature is determined according to the specified strength requirements and section thickness.Important warning: AISI 403CB must never be slowly cooled through or tempered within the 425–600°C range, as this will cause irreversible temper embrittlement. All heat treatment processes at Jiangsu Liangyi are computer-controlled, and complete time-temperature records are included in the inspection certificate.
Get Your Custom AISI 403CB Forging Quotation Today
Jiangsu Liangyi is your trusted Chinese manufacturer and supplier of AISI 403CB forgings .With our advanced production facilities in Jiangyin, Jiangsu Province, strict quality control systems and experienced engineering team, we can provide high-quality forgings in AISI 403CB, AISI 403 and UNS S40300 at competitive prices.
Whether you need turbine blades, valve parts, pump components or custom forgings, we have the professional expertise and production capacity to meet your demands.Contact us today to discuss your project!
We welcome you to send your custom drawings, material requirements and quantity details. Our technical team will respond within 24 hours with a detailed quotation. Visit our contact page for more information.