AISI 8640H Steel, quenched

AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper Product Information -:- For detailed product information, please contact sales. -: AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper Synonyms -:- For detailed product information, please contact sales. -:

AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper Product Information -:- For detailed product information, please contact sales. -: # **Technical Datasheet: AISI 8640H Alloy Steel** ## **H-Grade Steel, Oil Quenched & Low-Temperature Tempered Condition** --- ### **1. Material Identification** **Product Designation:** AISI 8640H / UNS H86400 **Heat Treatment:** Oil Quenched from 845°C (1550°F) + Tempered at 425°C (800°F) **Condition:** High-Strength Tempered Martensite **Material Classification:** Nickel-Chromium-Molybdenum (Ni-Cr-Mo) Medium-Carbon Alloy Steel (H-Grade) **Characteristic Profile:** The "H" designation indicates controlled hardenability within specified Jominy band limits. This low-temperature tempering treatment produces very high tensile and yield strength with moderate toughness, creating an optimal balance for applications requiring maximum strength-to-weight ratio and wear resistance where extreme toughness is not the primary concern. --- ### **2. Standard Compliance & Specifications** **International Standard References:** - **UNS:** H86400 - **ASTM Standards:** - A304: Standard Specification for Steel Bars, Alloy, Subject to End-Quench Hardenability Requirements - A914/A914M: Steel Bars Subject to Restricted Hardenability Requirements - **SAE/AISI:** SAE J1268 (Hardenability Bands), SAE J1868 (H-Steel Specification) - **ISO Equivalent:** 683-11 with hardenability requirements - **European Norm (EN):** No direct equivalent; similar to 1.6546 with controlled hardenability **Hardenability Specification:** Complies with SAE J1268 Hardenability Band limits for 8640H --- ### **3. Chemical Composition** **Base Chemistry (Weight Percent) - H-Grade Ranges:** | Element | Standard Range | H-Grade Control Purpose | |---------|----------------|--------------------------| | **Carbon (C)** | 0.37 - 0.44% | Controlled for consistent hardenability response | | **Manganese (Mn)** | 0.70 - 1.05% | Primary hardenability control element | | **Silicon (Si)** | 0.15 - 0.35% | Secondary hardenability influence | | **Nickel (Ni)** | 0.35 - 0.75% | Controlled within tighter bands for predictable response | | **Chromium (Cr)** | 0.35 - 0.65% | Critical for hardenability consistency | | **Molybdenum (Mo)** | 0.15 - 0.25% | Refines hardenability control | | **Phosphorus (P)** | ≤ 0.035% | Minimized for consistency | | **Sulfur (S)** | ≤ 0.040% | Typically lower for H-grades | | **Iron (Fe)** | Balance | Matrix element | **H-Grade Distinction:** Chemical composition ranges are specifically controlled to ensure consistent hardenability within defined Jominy end-quench curve limits, providing predictable heat treatment response regardless of production heat variations. --- ### **4. Hardenability & Heat Treatment Specifications** **Jominy Hardenability Band (SAE J1268):** - **Distance from Quenched End:** Corresponding Rockwell C Hardness Range - **1.5 mm (1/16")**: 45-57 HRC - **3.0 mm (1/8")**: 44-55 HRC - **5.0 mm (3/16")**: 41-52 HRC - **7.0 mm (1/4")**: 38-49 HRC - **10.0 mm (3/8")**: 33-44 HRC - **15.0 mm (5/8")**: 28-39 HRC **Standard Processing Sequence:** 1. **Austenitizing:** 845°C ± 10°C (1550°F ± 20°F) - Strict temperature control 2. **Quenching:** Rapid oil quench (Fast quenching oil, controlled temperature) 3. **Tempering:** 425°C ± 10°C (800°F ± 20°F) - Hold time: 1-2 hours per inch 4. **Cooling:** Air cool (avoid water quenching after tempering) **Critical Heat Treatment Parameters:** - **Hardenability Assurance:** Guaranteed within SAE J1268 band limits - **Section Size Capability:** Predictable hardening to approximately 50 mm (2") diameter - **Quenching Medium:** Oil mandatory for controlled cooling rate - **Temper Embrittlement Risk:** Higher due to low tempering temperature - rapid cooling recommended --- ### **5. Mechanical Properties** **Typical Properties for 25 mm (1 inch) Round Section:** | Property | Typical Value | Test Standard | H-Grade Advantage | |----------|---------------|---------------|-------------------| | **Tensile Strength** | 1240 - 1380 MPa | ASTM A370 | 180 - 200 ksi | | **Yield Strength (0.2% offset)** | 1100 - 1240 MPa | ASTM A370 | 160 - 180 ksi | | **Elongation (in 50 mm / 2")** | 10 - 14% | ASTM A370 | Consistent lot-to-lot | | **Reduction in Area** | 35 - 45% | ASTM A370 | Predictable behavior | | **Hardness** | 40 - 46 HRC | ASTM E18 | 375 - 430 HB | | **Charpy V-Notch Impact (Room Temp)** | 20 - 35 J | ASTM E23 | 15 - 26 ft-lb | | **Charpy V-Notch Impact (-18°C / 0°F)** | 12 - 25 J | ASTM E23 | 9 - 18 ft-lb | | **Fatigue Strength (Rotating Beam)** | 550 - 650 MPa | ASTM E466 | 80 - 94 ksi | | **Endurance Limit / Tensile Strength** | 0.44 - 0.47 | - | Slightly reduced ratio | | **Modulus of Elasticity** | 205 GPa | ASTM E111 | 29.7 × 10⁶ psi | | **Shear Strength** | 830 - 930 MPa | - | 120 - 135 ksi | **Section Size Consistency (H-Grade Benefit):** - **25 mm (1") diameter:** Properties as listed with minimal variation - **38 mm (1.5") diameter:** Strength variation < 5% from 25 mm values - **50 mm (2") diameter:** Predictable properties within 8% of listed values - **Beyond 50 mm:** Gradual property decrease but predictable curve --- ### **6. Physical Properties** | Property | Value | Units | Notes | |----------|-------|-------|-------| | Density | 7.85 | g/cm³ | 0.284 lb/in³ | | Melting Point | 1420 - 1470 | °C | 2590 - 2680°F | | Thermal Conductivity (at 100°C) | 41.8 | W/m·K | Slightly reduced from annealed | | Coefficient of Thermal Expansion | 11.3 × 10⁻⁶ | /°C | 6.3 × 10⁻⁶ /°F | | Specific Heat Capacity | 460 | J/kg·K | Similar to standard 8640 | | Electrical Resistivity | 0.23 | μΩ·m | Slightly increased | --- ### **7. Material Characteristics & Advantages** **H-Grade Specific Advantages:** 1. **Predictable Hardenability:** Guaranteed within SAE J1268 band limits 2. **Consistent Properties:** Reduced lot-to-lot variation in heat treated properties 3. **Reliable Heat Treatment Response:** Predictable transformation behavior 4. **Design Confidence:** Engineers can design closer to material limits 5. **Reduced Testing:** Less extensive mechanical testing required **Performance Attributes:** 1. **Maximum Strength:** Achieves near-maximum tensile strength for 8640 composition 2. **Excellent Wear Resistance:** High hardness provides good abrasion resistance 3. **Good Fatigue Strength:** Suitable for high-cycle fatigue applications 4. **Dimensional Stability:** Minimal dimensional change during heat treatment 5. **Consistent Machinability:** Predictable tool life and cutting parameters **Limitations & Considerations:** - **Reduced Toughness:** Lower impact resistance compared to higher tempers - **Temper Embrittlement Susceptibility:** Must be rapidly cooled through 375-575°C range - **Notch Sensitivity:** More sensitive to stress concentrations - **Limited Service Temperature:** Maximum 300°C (570°F) for sustained loading --- ### **8. Applications** **Primary Industrial Sectors Utilizing H-Grade Consistency:** **Automotive Transmission Systems:** - High-stress transmission gears - Synchronizer hubs and sleeves - Clutch components - Constant velocity joint components **Aerospace Components:** - High-strength fasteners and fittings - Actuator components - Control system parts - Secondary structural elements **Industrial Machinery:** - High-wear gears and pinions - Heavy-duty shafts - Press tooling components - Injection molding machine screws **Oil & Gas Equipment:** - Downhole tool components - Valve trim parts - Pump shafts in controlled environments - Specialty fasteners **Defense Applications:** - Firearm components (receivers, bolts) - Armor system attachments - Vehicle transmission parts - Weapon system mechanisms **Precision Manufacturing:** - Tool holders and adapters - Spindle components - Linear motion components - High-strength couplings --- ### **9. Manufacturing & Processing Guidelines** **Machinability Considerations:** - **Preferred Condition:** Machine in annealed condition (BHN 187 max) - **Hard Machining:** Possible but requires specialized tooling - **Machinability Rating:** 55% (H-grade consistency improves predictability) - **Cutting Tools:** Carbide or ceramic recommended for hardened state - **Coolant Requirement:** Essential for heat management **Welding Procedures (Restricted):** - **Weldability Rating:** Poor (not generally recommended) - **If Required:** Full annealing before welding - **Preheat Temperature:** 300-400°C (570-750°F) - **Post-Weld Treatment:** Re-austenitize and temper - **Filler Metals:** AWS A5.28 ER110S-G or similar high-nickel electrode **Heat Treatment Quality Control:** - **Process Control:** Statistical process control (SPC) recommended - **Temperature Uniformity:** ±5°C tolerance for critical applications - **Quench Agitation:** Controlled for consistency - **Tempering Time:** Extended times (2+ hours per inch) for stress relief --- ### **10. Quality Assurance & Testing** **H-Grade Specific Requirements:** 1. **Hardenability Test:** Jominy end-quench test on each heat 2. **Chemical Analysis:** More frequent checks for composition control 3. **Microcleanliness:** Inclusion rating per ASTM E45 4. **Grain Size:** ASTM E112, typically 7-8 **Standard Testing Protocol:** - Jominy hardenability test (mandatory for H-grade) - Full chemical analysis per heat - Mechanical testing from representative locations - Hardness traverse on critical sections - Non-destructive testing as specified **Certification Requirements:** - Hardenability test report with Jominy curve - EN 10204 3.2 certificate - Heat treatment records - Traceability to original heat number --- ### **11. Comparative Analysis** **Vs. Standard 8640 (Same Heat Treatment):** - More consistent properties heat-to-heat - Predictable hardenability depth - Reduced property scatter in production - Higher confidence in heat treatment results **Vs. 8640H at Higher Temper Temperatures:** - 25-30% higher tensile strength - 40-50% lower impact toughness - Better wear resistance - Higher risk of brittle fracture **Alternative H-Grade Materials:** - **For Higher Hardenability:** 4340H - **For Lower Cost:** 4140H - **For Better Toughness:** 4340H with higher temper --- ### **12. Technical Notes & Recommendations** **Design Considerations:** 1. **Stress Concentrations:** Avoid sharp corners and notches 2. **Loading Conditions:** Best for compressive and shear loading 3. **Temperature Limits:** Avoid sustained temperatures above 300°C 4. **Corrosion Protection:** Essential in all environments **Procurement Specification Example:** ``` Material: AISI 8640H Alloy Steel Bar Specification: ASTM A304, SAE J1268 Hardenability Band Heat Treatment: Oil Quench 845°C, Temper 425°C Hardness: 40-46 HRC (as heat treated) Certification: EN 10204 3.2 with Jominy Test Report Testing: Full mechanical properties from mid-radius ``` **Safety Considerations:** - **Grinding Burns:** Avoid excessive grinding that could cause re-tempering - **Hydrogen Embrittlement:** Risk with certain plating processes - **Stress Corrosion:** Susceptible in aggressive environments --- ### **13. Storage & Handling** - **Storage:** Dry, controlled environment - **Protection:** Rust preventive coating recommended - **Identification:** Clear heat number marking essential - **Handling:** Avoid impact damage to finished surfaces --- ### **Disclaimer** This technical datasheet provides characteristic values for AISI 8640H steel in the specified condition. H-grade materials provide greater consistency but actual properties in specific applications must be verified through appropriate testing. The information presented is for technical reference only and does not constitute a material specification or warranty. --- **Revision:** 1.1 **Issue Date:** March 2024 **Document Control:** QMS-8640H-04 **Approval Authority:** Materials Engineering Director -:- For detailed product information, please contact sales. -: AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper Specification Dimensions Size： Diameter 20-1000 mm Length <6349 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 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper -:- For detailed product information, please contact sales. -:

Packing of AISI 8640H Steel, quenched 845°C (1550°F), 425°C (800°F) temper -:- 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 2820 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