AISI 4320H Steel, annealed

AISI 4320H Steel, annealed at 850°C (1560°F) Product Information -:- For detailed product information, please contact sales. -: AISI 4320H Steel, annealed at 850°C (1560°F) Synonyms -:- For detailed product information, please contact sales. -:

AISI 4320H Steel, annealed at 850°C (1560°F) Product Information -:- For detailed product information, please contact sales. -: # Technical Specification: AISI 4320H Steel, Annealed at 850°C (1560°F) ## 1. PRODUCT OVERVIEW AISI 4320H steel processed through **full annealing at 850°C (1560°F)** represents a **hardenability-controlled** nickel-chromium-molybdenum alloy steel in its softest, most machinable condition. The "H" designation indicates controlled chemical composition ranges per SAE J1268 standards, ensuring predictable and consistent hardenability response. This annealing treatment involves heating above the upper critical temperature (Ac₃), followed by slow furnace cooling to produce a **coarse ferrite-pearlite microstructure** with optimal ductility, minimal residual stresses, and superior machinability. The 850°C annealing temperature ensures complete austenitization while preventing excessive grain growth, making this material particularly suitable for complex machining operations prior to final heat treatment in critical applications where consistency is paramount. ## 2. MATERIAL SPECIFICATIONS & STANDARDS | Parameter | Specification | Governing Standards | |-----------|---------------|---------------------| | Material Designation | AISI 4320H / SAE 4320H | SAE J1268 | | UNS Number | H43200 | ASTM A304 | | International Equivalents | — | ISO 683-11:2021 | | Heat Treatment Condition | Annealed | ASTM A29/A29M | | Annealing Temperature | 850°C ± 15°C (1560°F ± 25°F) | AMS 2759 | | Hardenability Band | Standard H-band per SAE J1268 | SAE J1268 | | Cooling Method | Furnace cooling (≤30°C/hour) | — | | Typical Hardness Range | 156-207 HB (83-95 HRB) | ASTM E10 | ## 3. CHEMICAL COMPOSITION (H-STEEL CONTROLLED RANGES) ### 3.1 SAE J1268 H-Steel Composition Limits | Element | Min (%) | Max (%) | Typical (%) | Metallurgical Function in H-Steel | |---------|---------|---------|-------------|----------------------------------| | Carbon (C) | 0.17 | 0.22 | 0.20 | Controlled for consistent case/core properties | | Manganese (Mn) | 0.45 | 0.65 | 0.55 | Precisely controlled for hardenability | | Phosphorus (P) | — | 0.035 | 0.015 | Residual element (tight control) | | Sulfur (S) | — | 0.040 | 0.025 | Optimized for machinability | | Silicon (Si) | 0.15 | 0.35 | 0.25 | Deoxidizer, solid solution strengthening | | Nickel (Ni) | 1.65 | 2.00 | 1.82 | Controlled for consistent toughness | | Chromium (Cr) | 0.40 | 0.60 | 0.50 | Precisely regulated for hardenability | | Molybdenum (Mo) | 0.20 | 0.30 | 0.25 | Controlled for grain refinement | | Copper (Cu) | — | 0.35 | 0.20 | Residual element (monitored) | | Iron (Fe) | Balance | Balance | Balance | Matrix element | ### 3.2 Hardenability Control Parameters - **Hardenability Band:** Certified to SAE J1268 H-band specifications - **Ideal Critical Diameter (D_I):** ~100 mm (4.0 in.) at 50% martensite - **Carbon Equivalent (CE):** 0.55-0.65 (tightly controlled) - **Jominy Curve Control:** Guaranteed within specified H-band limits - **Batch Consistency:** Reduced variation compared to non-H grades ## 4. ANNEALING PROCESS FOR H-STEEL ### 4.1 Thermal Cycle Parameters ``` Heating → Soaking at 850°C → Slow Furnace Cooling → Ambient Temperature ``` **Process Control Specifications for H-Steel:** - **Heating Rate:** 100-150°C/hour (180-270°F/hour) to 650°C, then 50-100°C/hour to 850°C - **Soaking Temperature:** 835-865°C (1535-1590°F) controlled range - **Soaking Time:** 90-120 minutes per inch of thickness (ensures complete homogenization) - **Atmosphere:** Protective (endothermic gas) to prevent decarburization - **Cooling Rate:** 15-30°C/hour (27-54°F/hour) through critical transformation range (750-550°C) - **Final Cooling:** To below 300°C in furnace, then air cooling - **H-Steel Specific Control:** Tighter temperature uniformity (±10°C) for consistent results - **Final Microstructure:** Coarse ferrite with pearlite islands, ASTM grain size 5-7 ### 4.2 Microstructural Characteristics | Microstructural Feature | Description | Importance for H-Steel Annealing | |------------------------|-------------|----------------------------------| | Matrix Structure | Coarse ferrite (70-80%) with pearlite islands (20-30%) | Optimizes machinability for complex parts | | Grain Size | ASTM 5-7 (coarse grain) | Provides stress-free condition for machining | | Pearlite Morphology | Lamellar colonies with controlled spacing | Consistent response to subsequent heat treatment | | Carbide Distribution | Lamellar in pearlite, minimal spheroidization | Maintains predictable hardenability | | Prior Austenite Grain Size | ASTM 4-6 | Larger than normalized but consistent | | Inclusion Content | Controlled (ASTM E45 ≤ 1.5 total) | Tighter control for critical applications | | Homogeneity | Excellent due to H-grade composition control | Reduced variability in final properties | ## 5. MECHANICAL PROPERTIES (ANNEALED CONDITION) ### 5.1 Standard Mechanical Properties | Property | Value Range | Test Standard | H-Steel Consistency | |----------|-------------|---------------|---------------------| | Hardness | 156-207 HB (83-95 HRB) | ASTM E10/E18 | Lower batch variation | | Ultimate Tensile Strength | 515-620 MPa (75-90 ksi) | ASTM E8/E8M | ±20 MPa typical variation | | Yield Strength (0.2% offset) | 275-415 MPa (40-60 ksi) | ASTM E8/E8M | More consistent values | | Elongation (in 50 mm) | 25-32% | ASTM E8/E8M | 2 inch gauge length | | Reduction of Area | 55-65% | ASTM E8/E8M | Longitudinal test | | Modulus of Elasticity | 200-205 GPa (29,000-29,700 ksi) | ASTM E111 | At room temperature | | Shear Modulus | 77-80 GPa (11,200-11,600 ksi) | ASTM E143 | — | ### 5.2 Hardenability Performance (Jominy End-Quench - As-Certified) | Distance from Quenched End | Hardness Range (HRC) | SAE J1268 H-Band Compliance | |----------------------------|----------------------|------------------------------| | 1.5 mm (J₁) | 36-45 | Within certified H-band | | 3.0 mm (J₂) | 35-44 | Within certified H-band | | 6.0 mm (J₄) | 33-42 | Within certified H-band | | 9.5 mm (J₆) | 31-40 | Within certified H-band | | 12.7 mm (J₈) | 29-38 | Within certified H-band | | 19.0 mm (J₁₂) | 26-35 | Within certified H-band | | 25.4 mm (J₁₆) | 24-33 | Within certified H-band | ### 5.3 Toughness Properties | Property | Test Temperature | Value Range | Test Standard | |----------|-----------------|-------------|---------------| | Charpy V-Notch Impact | 20°C (68°F) | 50-70 J (37-52 ft·lb) | ASTM E23 | | Charpy V-Notch Impact | 0°C (32°F) | 40-60 J (30-44 ft·lb) | ASTM E23 | | Charpy V-Notch Impact | -20°C (-4°F) | 30-50 J (22-37 ft·lb) | ASTM E23 | | Ductile-Brittle Transition | 50% FATT | -20°C to 0°C | Derived from CVN | ## 6. PHYSICAL PROPERTIES ### 6.1 As-Annealed Properties | Property | Value | Unit | Test Standard | |----------|-------|------|---------------| | Density | 7.85 | g/cm³ | ASTM B311 | | Thermal Conductivity (20°C) | 45.5 | W/m·K | ASTM E1225 | | Specific Heat Capacity (20°C) | 475 | J/kg·K | ASTM E1269 | | Mean CTE (20-100°C) | 12.3 × 10⁻⁶ | /K | ASTM E228 | | Mean CTE (20-200°C) | 12.8 × 10⁻⁶ | /K | ASTM E228 | | Mean CTE (20-400°C) | 14.0 × 10⁻⁶ | /K | ASTM E228 | | Electrical Resistivity (20°C) | 0.21 | μΩ·m | ASTM B193 | | Magnetic Properties | Ferromagnetic | — | ASTM A342 | ### 6.2 Transformation Temperatures (H-Steel Specific) | Transformation | Temperature Range | Notes for H-Steel Control | |---------------|------------------|----------------------------| | Ac₁ | 730-750°C (1345-1380°F) | Narrower range due to composition control | | Ac₃ | 800-820°C (1470-1510°F) | More predictable due to H-grade consistency | | Annealing Temperature | 850°C (1560°F) | 30-50°C above Ac₃ | ## 7. APPLICATIONS ### 7.1 Target Industries & Components | Industry | Typical Applications | H-Steel Advantages | |----------|---------------------|-------------------| | Aerospace | Critical gear blanks, complex structural parts | Certified consistency for safety-critical components | | Automotive | Transmission gears, differential components | Reduced variability in high-volume production | | Defense | Weapon system components, armored vehicle parts | Reliable performance in extreme conditions | | Heavy Machinery | Large gear blanks, mining equipment components | Consistent properties in large sections | | Power Generation | Turbine gears, generator components | Long-term reliability in demanding service | | Medical Equipment | Surgical instrument components | Precision and consistency for critical applications | ### 7.2 H-Steel Specific Benefits for Annealed Condition - **Predictable Machining:** Consistent chip formation and tool life across batches - **Reduced Setup Time:** Less process adjustment needed between material lots - **Improved Quality:** Lower rejection rates due to material consistency - **Better Dimensional Control:** More predictable material behavior during machining - **Optimized for CNC:** Consistent cutting forces enable optimized programming - **Certified Traceability:** Complete documentation chain for quality assurance ### 7.3 Recommended Subsequent Processing | Process | Purpose | H-Steel Performance Advantage | |---------|---------|------------------------------| | Carburizing | Case hardening for wear resistance | Consistent case depth and core properties | | Through-Hardening | High-strength components | Predictable hardenability pattern | | Precision Machining | Complex geometries | Stable dimensions, reduced tool wear | | Cold Forming | Shaping before final heat treatment | Consistent formability characteristics | ## 8. PROCESSING CHARACTERISTICS ### 8.1 Machinability (Annealed Condition - H-Steel Optimized) | Operation | Relative Rating | Optimum Parameters | Tool Recommendations | |-----------|----------------|-------------------|---------------------| | Turning | 75-80% (vs. 1212 steel) | Vc=150-180 m/min, f=0.30-0.45 mm/rev | Uncoated or TiN-coated carbide | | Milling | 70-75% | Vc=120-150 m/min, fz=0.20-0.30 mm/tooth | Carbide end mills with positive rake | | Drilling | 70% | Vc=30-40 m/min, f=0.20-0.30 mm/rev | HSS-Co or carbide drills | | Tapping | 75% | 70-80% of drilling speed | TiN-coated HSS taps | | Broaching | 65-70% | Appropriate for ferritic-pearlitic steels | HSS or carbide-tipped broaches | **H-Steel Machining Advantages:** - **Consistent Chip Formation:** Uniform microstructure produces predictable chips - **Reduced Tool Wear Variation:** Less variation in cutting forces extends tool life - **Stable Surface Finish:** More consistent Ra values across production runs - **Predictable Dimensional Changes:** Less springback and distortion variation ### 8.2 Formability & Cold Working | Forming Operation | Suitability | H-Steel Benefits | |-------------------|-------------|------------------| | Cold Bending | Excellent (R/t ≥ 1.5) | Consistent springback characteristics | | Cold Heading | Good | Predictable work hardening behavior | | Shearing | Excellent | Clean edges with minimal deformation | | Deep Drawing | Fair to Good | Consistent draw ratios achievable | | Roll Forming | Excellent | Stable forming characteristics | ### 8.3 Weldability Assessment for H-Steel | Parameter | Rating/Value | H-Steel Specific Recommendations | |-----------|--------------|----------------------------------| | Carbon Equivalent | 0.55-0.60 (controlled) | More predictable HAZ hardness | | Preheat Requirement | 100-150°C for >12mm thickness | Consistent requirements across batches | | Post-Weld Heat Treatment | Recommended, 590-650°C stress relief | Especially important for critical applications | | Filler Material | AWS ER80S-D2 or E8018-D2 | Matching or slightly undermatching | | Weldability Classification | Class II (Good) | More consistent due to composition control | ## 9. QUALITY ASSURANCE & TESTING ### 9.1 Mandatory H-Steel Testing Requirements | Test | Frequency | Standard | Acceptance Criteria | |------|-----------|----------|-------------------| | Chemical Analysis | Per heat | ASTM E415 | Within SAE J1268 H-limits | | Hardenability Test | Per heat | ASTM A255 | Within specified H-band | | Hardness Testing | Per batch | ASTM E10/E18 | 156-207 HB | | Microstructural Examination | Per heat treat lot | ASTM E3/E112 | Coarse ferrite-pearlite, ASTM 5-7 | | Inclusion Rating | Per heat | ASTM E45 | ≤ 1.5 total (tighter control) | | Decarburization Check | Per lot | Microscopic examination | ≤0.25mm total depth | ### 9.2 H-Steel Certification Documentation - **Hardenability Certificate:** Jominy curve data with heat number - **Chemical Analysis Report:** Showing compliance with H-steel limits - **Annealing Heat Treatment Records:** Complete temperature-time documentation - **Mill Certification:** Per ASTM A304 requirements - **Traceability Documentation:** Complete chain from melt to final product - **Statistical Process Control Data:** Demonstrating consistency ### 9.3 Additional Testing for Critical Applications - **Ultrasonic Testing:** ASTM A388 for internal quality assessment - **Magnetic Particle Inspection:** ASTM E1444 for surface defects - **Macroetch Testing:** ASTM E340 for segregation assessment - **Grain Flow Examination:** For forged products - **Dimensional Certification:** For precision-machined blanks ## 10. DESIGN & ENGINEERING GUIDELINES ### 10.1 Material Selection Considerations | Factor | H-Steel Advantage | Design Implication | |--------|-------------------|-------------------| | Consistency | Reduced property variation | Tighter design tolerances possible | | Predictability | Certified hardenability | More reliable performance predictions | | Traceability | Complete documentation | Essential for regulated industries | | Quality | Higher assurance level | Reduced safety factors possible | | Cost | Higher initial cost | Offset by reduced downstream variability | ### 10.2 Machining Allowance Guidelines for H-Steel | Operation | Minimum Allowance | Recommended Allowance | H-Steel Benefit | |-----------|------------------|----------------------|-----------------| | Rough Turning | 1.5 mm/side | 3.0 mm/side | More consistent stock removal | | Finish Turning | 0.25 mm/side | 0.5 mm/side | Predictable final dimensions | | Grinding | 0.10 mm/side | 0.25 mm/side | Consistent material removal | | Decarb Removal | 0.5 mm/side | 1.0 mm/side | If not protected atmosphere | ### 10.3 H-Steel Specific Design Recommendations - **Utilize Consistency:** Design for tighter tolerances where H-steel consistency allows - **Documentation Requirements:** Incorporate material certification into design files - **Batch Sizing:** Consider ordering complete heats for large production runs - **Supplier Collaboration:** Engage with H-steel specialists during design phase - **Prototype Validation:** Test with actual H-steel material when possible ## 11. COMPARATIVE ANALYSIS ### 11.1 AISI 4320H vs. Standard 4320 (Annealed Condition) | Aspect | 4320H Annealed | Standard 4320 Annealed | H-Steel Advantage | |--------|----------------|------------------------|------------------| | Composition Control | Tighter SAE J1268 ranges | Standard AISI ranges | More consistent properties | | Hardenability | Certified band | Typical values only | Predictable heat treatment | | Machining Consistency | Higher | Standard | Reduced setup changes | | Cost | 10-20% premium | Base cost | Justified for critical parts | | Documentation | Full certification | Standard mill cert | Complete traceability | | Quality Level | Premium | Commercial | Lower risk applications | ### 11.2 Annealed vs. Normalized for H-Steel Applications | Property | Annealed at 850°C | Normalized at 895°C | Application Guidance | |----------|-------------------|---------------------|---------------------| | Hardness | 156-207 HB | 187-229 HB | Annealed for heavy machining | | Machinability | Superior | Good | Annealed for complex parts | | Dimensional Stability | Excellent | Very Good | Both suitable, annealed better for precision | | Subsequent HT Response | Good | Excellent | Normalized slightly better | | Cost | Similar | Similar | Application dependent | | H-Steel Consistency | Both excellent | Both excellent | H-grade ensures consistency in both | ## 12. TECHNICAL ADVANTAGES OF H-STEEL ANNEALING ### 12.1 Key Benefits for Manufacturing 1. **Optimized Machinability:** Lowest hardness condition maximizes tool life and productivity 2. **Stress-Free Condition:** Eliminates residual stresses for dimensional stability 3. **Predictable Behavior:** H-grade consistency reduces process variability 4. **Certified Performance:** Documented hardenability ensures reliable final properties 5. **Quality Assurance:** Tighter controls throughout manufacturing chain 6. **Reduced Risk:** Lower probability of heat treatment-related failures ### 12.2 Economic Advantages - **Reduced Machining Costs:** Longer tool life, faster machining speeds - **Lower Rejection Rates:** Consistent material reduces quality issues - **Improved Productivity:** Less downtime for process adjustments - **Optimized Inventory:** Better predictability reduces safety stock requirements - **Warranty Reduction:** Fewer field failures due to material variability - **Lifecycle Cost:** Often lower despite higher initial material cost ## 13. LIMITATIONS & CONSIDERATIONS ### 13.1 Process Limitations | Limitation | Cause | Mitigation Strategy | |------------|-------|-------------------| | Higher Material Cost | Additional testing and control | Justify through total cost analysis | | Limited Suppliers | Fewer mills produce H-steel | Develop strategic supplier relationships | | Testing Lead Time | Jominy testing required | Include in project planning | | Minimum Order Quantities | Often larger for H-steel | Plan inventory accordingly | | Special Handling | Requires traceability maintenance | Implement robust material tracking | ### 13.2 Application-Specific Considerations - **Cost-Benefit Analysis:** H-steel premium must be justified by application needs - **Over-Specification Risk:** Standard grade may suffice for less critical parts - **Supply Chain Complexity:** Requires certified suppliers with proper documentation - **Design Integration:** Must incorporate H-steel characteristics into design - **Manufacturing Process Control:** Requires disciplined process management ## 14. STORAGE & HANDLING ### 14.1 Storage Requirements for H-Steel - **Environment:** Dry, controlled storage (<60% RH preferred) - **Identification:** Clear marking of heat number and H-steel designation - **Segregation:** Separate from non-H-grade materials - **Documentation:** Maintain all certificates with material - **Protection:** VCI or rust preventive for long-term storage - **Traceability:** Implement system to maintain material identity ### 14.2 Traceability Maintenance Best Practices 1. **Receiving Inspection:** Verify material against certificates 2. **Storage Labeling:** Clearly mark with heat number and status 3. **Issuance Control:** Track material from storage to production 4. **Remnant Identification:** Mark cut pieces with original heat number 5. **Final Component Marking:** Consider permanent marking for critical parts 6. **Documentation Archiving:** Maintain records for required period ## 15. INDUSTRY BEST PRACTICES ### 15.1 Procurement Strategy - **Supplier Qualification:** Audit H-steel production and testing capabilities - **Specification Clarity:** Clearly define all H-steel requirements - **Quality Agreements:** Establish expectations with suppliers - **Dual Sourcing:** Consider for critical applications (with proper qualification) - **Performance Monitoring:** Track supplier performance metrics ### 15.2 Manufacturing Implementation - **Personnel Training:** Educate on H-steel handling and importance - **Process Documentation:** Update to reference H-steel requirements - **Statistical Tracking:** Monitor material and process performance - **Feedback Loops:** Establish communication with material suppliers - **Continuous Improvement:** Use H-steel consistency to optimize processes ### 15.3 Quality System Integration - **Incoming Inspection:** Implement robust verification procedures - **Process Control:** Leverage H-steel consistency for tighter control - **Documentation Control:** Manage certificates and test reports - **Non-Conformance Handling:** Specific procedures for H-steel deviations - **Audit Preparedness:** Maintain complete traceability for regulatory audits --- **TECHNICAL NOTES:** 1. The "H" designation in AISI 4320H specifically refers to hardenability-controlled composition per SAE J1268 2. Annealing at 850°C provides the softest condition for maximum machinability while maintaining H-steel consistency 3. H-steel certification includes Jominy end-quench hardenability curve for each heat, providing predictability for subsequent heat treatment 4. This annealed condition is primarily intended as a superior starting material for critical components requiring complex machining before final heat treatment 5. The additional cost of H-steel is typically justified by reduced variability in manufacturing and improved component reliability in critical applications **CERTIFICATION & DOCUMENTATION:** - Hardenability certificate per SAE J1268 with Jominy curve data - Chemical analysis report showing compliance with H-steel limits - Annealing heat treatment records with temperature-time documentation - Mill certification per ASTM A304 requirements - Full traceability documentation from melt to final product - Compliance certificates as specified by customer requirements **REVISION:** 1.1 | **EFFECTIVE DATE:** October 2024 | **STATUS:** Production Specification --- *This specification details AISI 4320H steel in the annealed condition at 850°C, representing the premium machinable condition of this hardenability-controlled alloy. The H-steel designation ensures exceptional consistency and predictability, making this material particularly suitable for safety-critical components, high-volume production where consistency is paramount, and applications requiring complex machining before final heat treatment. While the annealed condition itself provides optimal machinability and minimal residual stresses, its primary value lies in establishing a consistent, predictable foundation for subsequent manufacturing operations and heat treatment processes.* -:- For detailed product information, please contact sales. -: AISI 4320H Steel, annealed at 850°C (1560°F) Specification Dimensions Size： Diameter 20-1000 mm Length <5629 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: AISI 4320H Steel, annealed at 850°C (1560°F) Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 4320H Steel, annealed at 850°C (1560°F) -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 4320H Steel, annealed at 850°C (1560°F) -:- For detailed product information, please contact sales. -:

Packing of AISI 4320H Steel, annealed at 850°C (1560°F) -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 2100 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition