Project Description
AISI 4320 Steel Round Bar – Nickel Chrome Molybdenum Alloy for Oil & Gas
Product Definition: AISI 4320 represents a premium nickel-chrome-molybdenum low alloy steel specifically engineered for critical oilfield applications requiring exceptional strength, toughness, and hardenability. This grade delivers superior mechanical properties in heavy sections through controlled Ni-Cr-Mo chemistry, making it the preferred choice for drill collars, tool joints, and heavy-duty downhole equipment.
Core Value Proposition: SHUNFU METAL supplies AISI 4320 in Q+T (Quenched & Tempered) condition with guaranteed full-section mechanical properties. Our manufacturing process ensures API Spec 7-1 compliance for drill collar applications and NACE MR0175 compatibility for sour service environments. Available in rolled, forged, and rough-turned conditions with comprehensive NDT certification.
Supply Formats: Round bars from 60mm to 1000mm diameter, forged blocks up to 3000mm length, rough-turned billets for CNC machining.
Critical Standards & International Equivalents
| Standard | Designation | Application Scope |
|---|---|---|
| ASTM A322 | 4320 | Alloy Steel Bars |
| AISI/SAE | 4320 | Standard Grade Designation |
| API Spec 7-1 | 4320 MOD | Drill Collar Steel (Modified Chemistry) |
| DIN/EN | 1.6582 (20NiCrMo7) | European Equivalent |
| JIS | SNCM220 | Japanese Equivalent |
| BS | 817M40 | British Standard |
The 4320 grade specifically targets applications where 4140 lacks sufficient hardenability in heavy sections. The nickel addition (1.65-2.00%) significantly improves core toughness and through-hardening capability, essential for large-diameter drill collars exceeding 200mm.
Chemical Composition & Metallurgical Control
| Element | ASTM A322 Range (%) | SHUNFU Control (%) | Metallurgical Function |
|---|---|---|---|
| Carbon (C) | 0.17-0.22 | 0.18-0.21 | Strength & Hardenability |
| Manganese (Mn) | 0.45-0.65 | 0.50-0.60 | Deoxidation & Hot Workability |
| Phosphorus (P) | ≤0.035 | ≤0.010 | Minimized for Toughness |
| Sulfur (S) | ≤0.040 | ≤0.010 | HIC Resistance (Oil & Gas) |
| Silicon (Si) | 0.15-0.35 | 0.20-0.30 | Deoxidation Agent |
| Nickel (Ni) | 1.65-2.00 | 1.70-1.90 | Core Toughness & Hardenability |
| Chromium (Cr) | 0.40-0.60 | 0.45-0.55 | Hardenability Enhancement |
| Molybdenum (Mo) | 0.20-0.30 | 0.22-0.28 | Temper Resistance & SSC Immunity |
SHUNFU Quality Edge: Our tight chemistry control, particularly S+P ≤ 0.015%, ensures superior transverse ductility and HIC resistance per NACE TM0284. The controlled Ni/Cr/Mo ratio optimizes hardenability while maintaining machinability for subsequent CNC operations.
Mechanical Properties – Quenched & Tempered Condition
Tensile Properties (Dia ≤ 100mm)
- Yield Strength: 758 MPa (110 ksi) minimum
- Tensile Strength: 930-1100 MPa (135-160 ksi)
- Elongation: ≥12% (50mm gauge)
- Reduction of Area: ≥40%
Hardness & Impact Properties
- Hardness: 28-35 HRC (NACE compliant ≤35 HRC)
- Charpy V-Notch: ≥20J at -40°C (Longitudinal)
- Charpy V-Notch: ≥15J at -40°C (Transverse)
- Grain Size: ASTM E112 Grade 6 or finer
Heavy Section Performance (Dia 200-500mm)
| Diameter (mm) | Yield (MPa) | Tensile (MPa) | Elongation (%) | Impact Energy (J) |
|---|---|---|---|---|
| 200-300 | 690 | 860-1030 | ≥10 | ≥15 (-40°C) |
| 300-400 | 655 | 825-995 | ≥10 | ≥12 (-40°C) |
| 400-500 | 620 | 790-960 | ≥8 | ≥10 (-40°C) |
This heavy-section capability differentiates 4320 from standard 4140, making it ideal for large-diameter drill collars where core properties are critical. Visit our hollow bar inventory for current stock availability.
Manufacturing Process & Quality Assurance
🔨 Forging & Heat Treatment
Minimum 4:1 forging ratio ensures complete breakdown of cast structure. Controlled cooling prevents segregation. Q+T cycle: Austenitize at 845°C, oil quench, temper 540-620°C for target hardness.
🔬 NDT Inspection Protocol
100% ultrasonic testing per ASTM A388 or SEP 1921 Class C/c. Magnetic particle inspection for surface integrity. Eddy current testing for near-surface defects in critical applications.
⚙️ Precision Machining
BTA deep hole boring capabilities up to 12m length with ±0.25mm straightness tolerance. CNC rough turning with Ra 6.3μm finish standard. Cut-to-length service with square-cut ends.
📋 Certification Package
Mill Test Certificate per EN 10204 Type 3.1. Chemical analysis by OES. Mechanical test results with Charpy impact data. Grain size verification. Third-party inspection available.
Value-Added Processing Services
As a manufacturer rather than trader, SHUNFU’s manufacturing capabilities include:
- BTA Deep Hole Drilling: ID from 20mm to 400mm, length up to 12 meters
- Rough Turning: Diameter tolerance ±2mm, surface finish Ra 6.3μm
- Heat Treatment: In-house Q+T facility with computerized process control
- Non-Destructive Testing: UT, MT, PT, ET capabilities with certified operators
- Straightening: Hydraulic press straightening to ±2mm/m tolerance
Applications in Oil & Gas Industry
Primary Applications
| Component | Size Range | Critical Requirements | Standards |
|---|---|---|---|
| Drill Collars | 120-500mm OD | Magnetic Properties, Fatigue Resistance | API Spec 7-1 |
| Tool Joints | 80-300mm | Thread Integrity, Impact Resistance | API Spec 7-2 |
| Stabilizer Blades | 100-250mm | Wear Resistance, Hardenability | API Spec 7K |
| X-mas Tree Components | 50-400mm | Pressure Rating, SSC Resistance | API Spec 6A |
| BOP Stack Parts | 200-800mm | Fracture Toughness, NACE Compliance | API Spec 16A |
Performance Advantages in Service
- Deep Well Capability: Maintains strength properties at temperatures up to 150°C
- Sour Service Compatibility: Mo content provides SSC resistance per NACE MR0175
- Fatigue Endurance: Clean steel practice extends rotating life in drill string applications
- Machinability Index: 65-70% relative to 1212 steel, enabling efficient CNC operations
Size Range & Delivery Specifications
| Product Form | Diameter Range | Length Range | Surface Condition | Tolerance |
|---|---|---|---|---|
| Hot Rolled Bars | 60-200mm | 3-12m | Black/Peeled | h11/h9 |
| Forged Bars | 150-1000mm | 1-6m | Rough Turned | ±3mm |
| Hollow Bars | 120-500mm OD | 3-12m | BTA Bored | ±0.5mm ID |
| Cut Pieces | As per drawing | Custom | Machined ends | ±1mm |
Standard Delivery Condition
- Heat Treatment: Quenched & Tempered (Q+T) to customer specification
- Hardness: 28-35 HRC unless otherwise specified
- Straightness: ≤2mm per meter length
- Surface Finish: Ra 6.3μm (rough turned), Ra 12.5μm (hot rolled)
- End Condition: Square cut, deburred edges
Technical FAQ & Procurement Guide
Common Procurement Questions
Q: What’s the minimum order quantity?
A: 5 metric tons for standard sizes. Custom specifications require 10MT minimum to justify setup costs.
Q: Can you provide NACE MR0175 certification?
A: Yes, our 4320 chemistry and hardness control meets NACE MR0175 requirements. SSC testing available per NACE TM0177 Method A.
Q: What’s the typical lead time?
A: Stock sizes: 2-3 weeks. Custom heat treatment/machining: 6-8 weeks from PO confirmation.
Q: Do you offer third-party inspection?
A: Yes, we accommodate SGS, Bureau Veritas, TUV, and other international inspection agencies.
Q: What’s the maximum diameter you can supply?
A: Forged: up to 1200mm diameter. We can coordinate with partner forges for larger sizes.
Quality Documentation Package
- Mill Test Certificate (EN 10204 Type 3.1)
- Chemical analysis report (Heat & Check analysis)
- Mechanical test results with stress-strain curves
- Charpy impact test data with temperature certification
- Ultrasonic test report with rejection criteria
- Hardness mapping for heavy sections
- Grain size verification per ASTM E112
- Dimensional inspection report
Ready to Specify AISI 4320 for Your Next Project?
Contact our technical sales team for detailed quotations, material certificates, and custom processing options. We guarantee API compliance and provide comprehensive quality documentation for your critical applications.
Phone: +86-731-89903933 | Email: [email protected]
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.
