AISI 4118H Steel, direct quench

AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth Product Information -:- For detailed product information, please contact sales. -: AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth Synonyms -:- For detailed product information, please contact sales. -:

AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth Product Information -:- For detailed product information, please contact sales. -: # **Product Technical Data Sheet: Direct Quenched Carburized AISI 4118H Steel** **Product Designation:** AISI 4118H / SAE 4118H Direct Quenched Carburized Steel **Heat Treatment:** Carburized, Direct Quenched, 150°C (300°F) Temper **Case Depth:** 1.6 mm (0.063 inch) Effective Case Depth (550 HV) **Condition:** Case-Hardened with optimized surface properties and hardened core **Hardenability Classification:** H-Grade (Guaranteed Hardenability Band) --- ## **1. Overview** AISI 4118H direct quenched carburized material represents an **advanced, efficient heat treatment process** for components requiring exceptional surface hardness and wear resistance. This process involves carburizing to achieve a specified **1.6 mm effective case depth**, followed by **direct quenching from the carburizing temperature** (eliminating intermediate cooling and reaustenitizing), and concluding with a **150°C (300°F) low-temperature temper**. As an "H"-grade material, it provides guaranteed hardenability within defined statistical limits, ensuring consistent case depth and hardness profile across production batches. This combination delivers superior **fatigue resistance, wear performance, and bending strength** for high-load applications where component reliability and durability are critical. ## **2. Chemical Composition (Weight %)** *Base material composition per SAE J404 4118H requirements with carbon enrichment in case.* | Element | Core Content (%) | Case Surface Content (%) | Function in Direct Quench Process | |---------|------------------|--------------------------|-----------------------------------| | **Carbon (C)** | 0.17 - 0.23 | **0.75 - 0.90** (at surface) | Core toughness; forms high-carbon martensite in case | | **Manganese (Mn)** | 0.60 - 0.95 | 0.60 - 0.95 | Enhances through-hardenability for consistent 1.6mm case | | **Silicon (Si)** | 0.15 - 0.35 | 0.15 - 0.35 | Deoxidizer, increases tempering resistance | | **Chromium (Cr)** | 0.35 - 0.65 | 0.35 - 0.65 | Enhances case hardenability, wear resistance, and tempering response | | **Molybdenum (Mo)** | 0.08 - 0.15 | 0.08 - 0.15 | Reduces grain growth during extended carburizing, enhances core toughness | | **Phosphorus (P)** | ≤ 0.035 | ≤ 0.035 | Strictly controlled residual | | **Sulfur (S)** | ≤ 0.040 | ≤ 0.040 | Machinability enhancement in pre-carburized state | | **Iron (Fe)** | Balance | Balance | Matrix element | **Direct Quench Chemistry Considerations:** - **Carbon Gradient:** Optimized for 1.6mm effective case depth with smooth transition - **Hardenability Elements (Cr, Mo):** Tightly controlled to ensure consistent case depth despite direct quenching variability - **Grain Growth Control:** Mo content critical for maintaining fine grain during extended high-temperature exposure ## **3. Physical Properties** | Property | Case Region | Core Region | Unit | Notes | |----------|-------------|-------------|------|-------| | **Density** | ~7.83 | ~7.85 | g/cm³ | Lower in case due to higher carbon | | **Modulus of Elasticity** | 190 - 200 | 200 - 205 | GPa | Case slightly reduced due to retained austenite | | **Thermal Conductivity** | 38 - 40 | 41 - 43 | W/m·K | Lower in high-carbon case | | **Coefficient of Thermal Expansion** | 12.0 × 10⁻⁶ | 11.7 × 10⁻⁶ | /°C | 20-100°C range | | **Electrical Resistivity** | 0.28 | 0.23 | μΩ·m | Higher in case due to carbon content | | **Magnetic Properties** | Ferromagnetic (reduced) | Ferromagnetic | - | Case has reduced permeability | ## **4. Mechanical & Metallurgical Properties** ### **Case Properties (0-1.6mm depth):** - **Surface Hardness:** **58 - 63 HRC** (typical 60-62 HRC) - **Effective Case Depth:** **1.6 mm** at 550 HV (0.063 inch) - **Total Case Depth:** ~2.0 - 2.4 mm (to core hardness) - **Case Microstructure:** Fine tempered martensite with **15-25% retained austenite** - **Surface Residual Stress:** High compressive stresses (600-900 MPa) ### **Core Properties (below case):** - **Core Hardness:** **35 - 45 HRC** - **Core Microstructure:** Tempered low-carbon martensite with good toughness - **Core Strength:** 1000 - 1300 MPa tensile strength ### **Hardness Profile (Typical):** | Depth from Surface | Hardness (HV) | Equivalent HRC | |-------------------|---------------|----------------| | **0 mm (Surface)** | 700 - 800 | 60 - 63 | | **0.4 mm** | 650 - 750 | 58 - 61 | | **0.8 mm** | 600 - 700 | 55 - 59 | | **1.2 mm** | 550 - 650 | 52 - 57 | | **1.6 mm (ECD)** | 550 | ~52 | | **2.0 mm** | 450 - 500 | 45 - 50 | | **Core** | 350 - 450 | 35 - 45 | ## **5. Direct Quench Process Details** ### **Process Sequence:** 1. **Carburizing:** 910-930°C for 8-12 hours (depending on component size) to achieve 1.6mm ECD 2. **Carbon Potential Control:** 0.80-0.90% at surface during boost, 0.70-0.75% during diffuse 3. **Direct Quenching:** Immediate oil quenching from carburizing temperature (~60°C oil, moderate agitation) 4. **Tempering:** 150°C (300°F) for 2-3 hours ### **Process Advantages:** - **Energy Efficiency:** Eliminates separate reaustenitizing cycle - **Reduced Distortion:** Single quench minimizes dimensional changes - **Fine Grain Structure:** Direct quenching can preserve finer austenite grain - **Process Consistency:** H-grade ensures predictable results ### **Quality Control Parameters:** - **Case Depth Uniformity:** ±0.15 mm across component - **Surface Carbon Control:** 0.75-0.90% at surface - **Retained Austenite:** Controlled through quench parameters - **Microstructure:** No excessive carbides or carbide networks ## **6. Material Characteristics & Performance Advantages** ### **Performance Benefits:** 1. **Superior Wear Resistance:** 58-63 HRC surface withstands abrasive and adhesive wear 2. **High Contact Fatigue Strength:** Optimized for gear tooth pitting resistance 3. **Excellent Bending Fatigue:** Compressive surface stresses resist crack initiation 4. **Good Core Toughness:** Withstands shock and impact loading 5. **Dimensional Stability:** Controlled distortion from direct quench process ### **Direct Quench-Specific Advantages:** - **Reduced Intergranular Oxidation:** Single high-temperature exposure minimizes surface oxidation - **Cost Effectiveness:** Lower energy consumption and shorter cycle time - **Consistent Case Properties:** H-grade hardenability ensures uniform case depth ## **7. Applications** ### **Primary Applications:** **Automotive & Transportation:** - Transmission gears and synchronizers - Differential gears and pinions - Heavy-duty truck transmission components - Axle shafts and drive components **Industrial Machinery:** - Gearbox components for heavy equipment - Power transmission gears - Bearing races and rolling elements - Hydraulic pump gears and components **Energy & Heavy Industry:** - Wind turbine gearbox components - Mining equipment gears and shafts - Construction machinery drive components - Oil field equipment gears ### **Component Examples:** - **Gears:** 50-150 mm pitch diameter, module 2-6 - **Shafts:** 20-80 mm diameter requiring wear-resistant surfaces - **Bearings:** 40-120 mm bore diameter - **Cams and Followers:** For high-wear applications ### **Why 1.6mm Case Depth?** - **Optimal for medium-heavy loading:** Balances surface durability with core support - **Common industrial standard:** Widely specified for automotive and industrial gears - **Technical balance:** Sufficient depth for contact stress distribution without excessive processing time ## **8. International Standards & Specifications** ### **Material & Process Standards:** | Standard System | Designation | Application/Requirement | |----------------|-------------|-------------------------| | **SAE/AISI** | 4118H | Base material specification (SAE J404, J1268) | | **ISO** | ISO 6336-5 | Calculation of load capacity of case-hardened gears | | **AGMA** | AGMA 2001-D04 | Gear material and heat treatment specifications | | **DIN** | DIN 3990 | Calculation of load capacity of cylindrical gears | | **JIS** | JIS G 4052 | Alloy steels for machine structural use | | **ASTM** | A304 | Alloy steel bars subject to end-quench requirements | ### **Case Depth & Quality Standards:** - **Effective Case Depth Definition:** Depth to 550 HV (ISO 2639) - **Microhardness Testing:** Per ASTM E384 - **Case Depth Measurement:** Per ISO 2639 or equivalent - **Retained Austenite Measurement:** XRD per ASTM E975 ## **9. Quality Assurance & Testing** ### **Mandatory Testing:** 1. **Case Depth Verification:** Microhardness profile minimum 3 locations 2. **Surface Hardness Testing:** Multiple point verification (HRC scale) 3. **Core Hardness Testing:** Below case-core transition 4. **Microstructural Examination:** Case and core at 400X and 1000X 5. **Retained Austenite Measurement:** Surface and subsurface ### **Acceptance Criteria for 1.6mm ECD:** | Parameter | Acceptance Criteria | Test Method | |-----------|-------------------|-------------| | **Effective Case Depth** | 1.6 ± 0.15 mm | Microhardness to 550 HV | | **Surface Hardness** | 58-63 HRC | Rockwell C scale | | **Core Hardness** | 35-45 HRC | Below case influence | | **Case Carbon** | 0.75-0.90% at surface | Spectroscopy or microanalysis | | **Retained Austenite** | 15-25% at surface | XRD or metallographic | | **Microstructure** | Fine martensite, no carbide networks | 1000X examination | ### **Non-Destructive Testing:** - **Magnetic Particle Inspection:** For surface defects - **Dimensional Verification:** Post-heat treatment measurements - **Gear Quality Testing:** AGMA or DIN quality grade verification ## **10. Design & Manufacturing Considerations** ### **Design Guidelines:** - **Optimal Section Size:** 20-80 mm diameter for uniform case development - **Case-Core Ratio:** Case depth typically 10-15% of radius for optimal performance - **Fillet Radii:** Minimum R = case depth to prevent case cracking - **Stress Concentrations:** Design to avoid sharp corners in case-hardened areas ### **Manufacturing Sequence:** 1. **Rough Machining:** 0.2-0.3 mm oversize on case-hardened surfaces 2. **Carburizing & Direct Quench:** With appropriate fixtures for distortion control 3. **Tempering:** 150°C for stress relief 4. **Finish Machining:** Hard turning or grinding of critical dimensions 5. **Final Inspection:** Case depth, hardness, and dimensional verification ### **Comparative Advantages over Conventional Quenching:** | Aspect | Direct Quench | Conventional Reheat Quench | |--------|--------------|---------------------------| | **Process Time** | Shorter (single cycle) | Longer (two cycles) | | **Energy Consumption** | Lower | Higher | | **Distortion Potential** | Generally lower | Potentially higher | | **Grain Size** | May be finer | May coarsen during reheat | | **Intergranular Oxidation** | Less | More potential | --- **Technical Significance:** The 1.6mm case depth represents an industry-preferred specification for many gear applications, providing optimal balance between surface durability and core support. Direct quenching offers manufacturing efficiency while maintaining high quality standards. The H-grade material ensures predictable hardenability for consistent case depth achievement. **Application Guidelines:** 1. **Component Design:** Consider distortion patterns when designing fixtures 2. **Material Selection:** Verify H-grade certification for critical applications 3. **Process Control:** Monitor carbon potential and quench parameters closely 4. **Quality Validation:** Implement statistical process control for case depth **Limitations and Considerations:** - **Section Size Limits:** Optimal for sections <100mm diameter - **Distortion Control:** Requires proper fixturing during quenching - **Quench Severity:** Must be optimized for specific component geometry - **Retained Austenite:** May require cryogenic treatment if <15% is specified **Industry Best Practices:** 1. Use direct quenching for high-volume production of similar components 2. Implement SPC for critical parameters (case depth, hardness) 3. Conduct regular process capability studies 4. Maintain correlation between Jominy data and actual case depth results **Disclaimer:** This technical specification applies to properly processed material with controlled direct quench parameters. Actual properties may vary based on specific component geometry, furnace characteristics, and quench conditions. Final validation through prototype testing is recommended for critical applications. -:- For detailed product information, please contact sales. -: AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth Specification Dimensions Size： Diameter 20-1000 mm Length <5580 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 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth -:- For detailed product information, please contact sales. -:

Packing of AISI 4118H Steel, direct quench, 150°C (300°F) temper, 1.6 mm case depth -:- 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 2051 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