Project Description
9CrMo1 UNS K90941 Steel Structure / Bar – SHUNFU METAL
Table of Contents
- 1. Introduction: The Sour Service Specialist
- 2. Critical Applications in Oil & Gas
- 3. Standards, Specifications & Equivalents
- 4. Chemical Composition Analysis
- 5. Sizes, Dimensions & Delivery Conditions
- 6. Heat Treatment & Metallurgy
- 7. Mechanical Properties & Performance
- 8. Machining & Processing Guide
1. Introduction: The Sour Service Specialist
In the aggressive environments of modern oil and gas extraction, material failure is not an option. 9CrMo1 UNS K90941 stands as a definitive solution for engineers and procurement managers dealing with “sour service” fields containing high levels of Hydrogen Sulfide (H₂S). SHUNFU METAL manufactures this premium martensitic stainless steel to bridge the gap between standard low-alloy steels and expensive duplex stainless variants.
This alloy is not merely about chromium content; it is about the precise balance of 8.0-10.0% Chromium and roughly 1% Molybdenum, engineered to resist Sulfide Stress Cracking (SSC). At SHUNFU METAL, we control the entire production lifecycle—from Electric Arc Furnace (EAF) melting to the final ultrasonic test. We deliver material that guarantees a minimum yield strength of 80ksi (552 MPa) while strictly capping hardness at 22 HRC, a non-negotiable requirement for NACE MR0175/ISO 15156 compliance.
Global buyers choose our steel pipe and bar solutions because we understand the stakes. Whether you are fabricating subsea manifolds or Christmas tree valves, the integrity of the raw material dictates the safety of the well. Our 9CrMo1 is refined via Vacuum Degassing to eliminate impurities, ensuring the internal cleanliness required for API 6A PSL 3 & 4 designations.
2. Critical Applications in Oil & Gas
The unique metallurgy of UNS K90941 makes it the material of choice where carbon steels fail due to corrosion and where standard 410 stainless lacks sufficient toughness. SHUNFU METAL supplies this grade primarily for pressure-containing parts in upstream oil and gas equipment.
Wellhead Equipment
Used extensively in API 6A Christmas trees, casing heads, and tubing hangers. The material withstands high pressure while resisting CO₂ and H₂S attack.
Valve Components
Ideal for valve bodies, bonnets, and stems in gate and ball valves. The hardness control prevents cracking under stress in sour environments.
Subsea & Downhole
Deployed in subsea manifolds, BOP (Blowout Preventer) rams, and downhole completion tools where maintenance is impossible and reliability is paramount.
3. Standards & Specifications
SHUNFU METAL ensures strict adherence to international standards. We do not just meet the minimums; we target the median-to-upper range of specifications to ensure processing reliability for our clients.
- UNS Designation: K90941
- NACE Compliance: MR0175 / ISO 15156 (Sour Service)
- Product Specification: API 6A (Wellhead & Christmas Tree Equipment)
- Testing Standards: ASTM A388 (Ultrasonic), ASTM A29 (Tolerances), API 6A PSL 3&4
4. Chemical Composition
The specific chemistry of UNS K90941 is tighter than generic 9Cr grades. The restriction on Sulfur (≤0.01%) is critical for impact toughness and inclusion control.
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| Carbon (C) | 0.09 | 0.15 |
| Chromium (Cr) | 8.0 | 10.0 |
| Molybdenum (Mo) | 0.90 | 1.10 |
| Manganese (Mn) | 0.30 | 0.60 |
| Silicon (Si) | – | 1.00 |
| Nickel (Ni) | – | 0.25 |
| Sulfur (S) | – | 0.01 |
| Phosphorus (P) | – | 0.03 |
| Aluminum (Al) | 0.015 | 0.050 |
5. Sizes, Dimensions & Delivery Conditions
SHUNFU METAL operates with flexibility. While standard stock focuses on the popular 3″ to 8″ range for valve manufacturing, our forging capabilities allow us to support massive wellhead block requirements. Visit www.gaslinepipe.com to view our current stock list.
Forged Bar / Block
- Diameter: 80mm – 1200mm
- Reduction Ratio: Minimum 4:1 (Crucial for center soundness)
- Surface: Rough Turned or Black
Hot Rolled Bar
- Diameter: 10mm – 300mm
- Standard Lengths: 3m – 6m (Cut-to-length available)
- Surface: Peeled, Polished, or Black
“For machining quality bar (ASTM A29), we recommend a minimum stock removal of 1% per side for peeled/turned bars and 1.6% per side for black bars to ensure the removal of any decarburization layer.”
6. Heat Treatment: The Core of Performance
The difference between a standard bar and a NACE-compliant bar lies in the heat treatment. SHUNFU METAL employs a rigorous cycle to ensure the microstructure is fully tempered martensite with controlled carbide distribution.
- Austenitizing: Performed in AMS 2750 calibrated furnaces to ensure temperature uniformity.
- Liquid Quenching: Rapid cooling is essential to achieve the martensitic transformation throughout the cross-section.
- Double Tempering: This is the SHUNFU standard. An initial temper followed by a second temper ensures the relaxation of internal stresses and stabilizes the austenite. This process is vital to hitting the narrow window of 18-22 HRC hardness required for sour service.
7. Mechanical Properties
Our 9CrMo1 UNS K90941 is supplied in the Quenched and Tempered condition. The data below represents the 80ksi Yield Strength variant (Variant 3), typical for 8″ mid-radius testing.
| Property | Minimum | Maximum |
|---|---|---|
| 0.2% Proof Stress (Yield) | 80 ksi (552 MPa) | 95 ksi (655 MPa) |
| Tensile Strength (UTS) | 100 ksi (690 MPa) | 120 ksi (827 MPa) |
| Elongation (%) | 20% | – |
| Reduction of Area (%) | 45% | – |
| Hardness (HRC) | 18 | 22 (Strict NACE Limit) |
| Impact Energy (CVN @ -10°C) | 45 J (Single) | 50 J (Average) |
8. Machining & Processing
Machining 9CrMo1 requires specific attention due to its toughness and tendency to work harden. While it machines similarly to other martensitic grades like 410, the molybdenum addition increases drag.
- Turning: Use carbide tools with chip breakers. Maintain a steady feed rate to prevent glazing the surface.
- Boring: Vibration can be an issue with deep bores. Ensure rigid setup and use dampened boring bars for internal geometries of valve bodies.
- Coolant: High-pressure coolant is recommended to clear chips and reduce heat buildup, which can affect the surface hardness.
Ready to secure your supply chain?
SHUNFU METAL provides full traceability with every shipment, including MTRs, Ultrasonic Test Reports (ASTM A388), and Heat Treatment charts. We are equipped to handle large-scale project orders with staggered deliveries to suit your production schedule.
Request a Quote for UNS K90941 Today
Contact our technical sales team for pricing and lead times.
We are committed to integrate steel resources in china and serve the global steel market. Our company has more than 15 years of experience in steel researching, production, managing and sales. And our team mostly are based on and worked in national famous steel enterprise before. In the aspect of resources and information, we have established cooperative relationship with nearly hundred enterprises, either state-owned or private owned in China.
What’s more, we have built long, deep and close business relationship with dozens of steel company, Sharing and holding equities with several steel enterprises. Because of the close cooperation with steel companies and our pioneering spirit, which can ensure us stay at the top competition, and ensure our customers get what they really want. We provide preffesional one-stop service to the Contractors of follows project:
- Oil and Gas Pipeline Construction
- Onshore and Offshore
- Boiler Manufacturers
- Oil Refining Equipment
- Petroleum and Chemical Plant Construction
- Fire Protection
- Heating & Air Conditioning
Our ability to purchase materials directly from leading mills at the best possible price will give you the competitive edge. This coupled with a skilled workforce dedicated to embracing the demands of the markets we serve. Just give us a call +86-731-89903933.
