AISI 4340H Steel, normalized

AISI 4340H Steel, normalized 870°C (1600°F) Product Information -:- For detailed product information, please contact sales. -: AISI 4340H Steel, normalized 870°C (1600°F) Synonyms -:- For detailed product information, please contact sales. -:

AISI 4340H Steel, normalized 870°C (1600°F) Product Information -:- For detailed product information, please contact sales. -: # **AISI 4340H Steel (Normalized Condition, Hardenability Grade) Product Specification** ## **1. PRODUCT IDENTIFICATION & THERMAL PROCESS** **Product:** AISI 4340H Nickel-Chromium-Molybdenum Alloy Steel **Material State:** Normalized Condition - Hardenability Controlled Grade **Specified Thermal Treatment:** - **Normalizing:** 870°C (1600°F) with complete austenitization - **Cooling:** Still air cooling to room temperature **Metallurgical Significance:** This normalization treatment at 870°C refines the grain structure, homogenizes the microstructure, and eliminates thermal history from prior manufacturing processes for this premium nickel-alloy steel. The "H" designation certifies that the material meets specific hardenability band requirements per SAE J1268, ensuring predictable and consistent response to subsequent heat treatment. Normalized 4340H provides an optimal balance of strength, toughness, and machinability, serving as an excellent starting condition for either direct application or subsequent machining and final heat treatment. ## **2. CHEMICAL COMPOSITION (Hardenability Controlled)** The composition is engineered to achieve both the standard 4340 chemistry and strict hardenability band requirements. | Element | Composition Range (% by weight) | Role in Normalized Condition & Hardenability Control | | :--- | :--- | :--- | | **Carbon (C)** | 0.38 - 0.43 | Forms fine pearlite during air cooling. Provides foundation for hardenability. Content is precisely controlled for consistent normalized properties. | | **Manganese (Mn)** | 0.65 - 0.85 | **Primary hardenability adjuster.** Range expanded versus standard 4340 to allow precise Jominy curve positioning while maintaining normalized properties. | | **Phosphorus (P)** | ≤ 0.025 | **Tighter than standard 4340** (≤0.035) to ensure maximum toughness in normalized state. | | **Sulfur (S)** | ≤ 0.025 | **Minimized** for optimal transverse properties and impact consistency. | | **Silicon (Si)** | 0.15 - 0.35 | Deoxidizer; provides solid solution strengthening in ferrite. | | **Nickel (Ni)** | **1.65 - 2.00** | **Key distinguishing element.** Provides exceptional toughness in normalized state. Lowers ductile-brittle transition temperature significantly. Tightly controlled for consistency. | | **Chromium (Cr)** | 0.70 - 0.95 | Range expanded slightly for hardenability tuning. Refines pearlite spacing during air cooling. | | **Molybdenum (Mo)** | **0.20 - 0.30** | **Critical for microstructural control.** Enhances grain refinement during normalization and prevents abnormal grain growth at 870°C. | **Unique Feature:** The nickel content (1.65-2.00%) provides normalized 4340H with impact toughness values typically 50-100% higher than nickel-free grades like 4140H in similar condition. ## **3. CERTIFIED HARDENABILITY (SAE J1268)** Even in normalized condition, the material carries certified hardenability data. **Standard Hardenability Band for 4340H:** | Jominy Distance (1/16 in.) | As-Quenched Hardness Range, HRC (Min - Max) | | :--- | :--- | | **J1.5** | 54 - 60 | | **J5** | 48 - 56 | | **J10** | 40 - 50 | | **J15** | 35 - 45 | | **J20** | 31 - 41 | **Engineering Value:** This certification provides designers with certainty that components machined from normalized 4340H stock will achieve predictable through-hardening when subsequently heat treated, regardless of production lot variations. ## **4. MICROSTRUCTURE & METALLURGY** **Microstructural Features:** - **Matrix:** Fine, uniform mixture of ferrite and pearlite - **Pearlite Content:** ~35-45% (lower than plain carbon steels due to alloy content) - **Pearlite Spacing:** Very fine (0.1-0.3 μm) due to chromium and molybdenum effects - **Grain Size:** ASTM 7-9 (fine, refined by 870°C treatment) - **Carbide Distribution:** Fine, uniform cementite lamellae within pearlite colonies - **Band Segregation:** Minimized by normalization process **Normalizing Transformation:** - **Ac₁:** ~730°C - **Ac₃:** ~775°C - **Soak Time:** 30-45 minutes per inch at 870°C - **Cooling Rate:** Still air (~0.5-2°C/second depending on section size) - **Unique Aspect:** Nickel enhances hardenability but has minimal effect on normalized microstructure formation ## **5. PHYSICAL & MECHANICAL PROPERTIES (Normalized Condition)** * **Physical Properties:** * **Density:** 7.85 g/cm³ * **Melting Point:** ~1427°C (2600°F) * **Modulus of Elasticity:** 205 GPa (29,700 ksi) * **Thermal Conductivity:** 42.0 W/m·K @ 100°C * **Coefficient of Thermal Expansion:** 11.4 µm/m·°C (20-100°C) * **Specific Heat Capacity:** 460 J/kg·K * **Mechanical Properties (Typical for Normalized Condition):** * **Tensile Strength:** 720 - 870 MPa (104,000 - 126,000 psi) * **Yield Strength (0.2% Offset):** 480 - 630 MPa (70,000 - 91,000 psi) * **Elongation (in 50mm):** **20% - 25%** * **Reduction of Area:** **50% - 60%** * **Hardness:** **240 - 290 HB** (Approx. 100-108 HRB) * **Charpy V-Notch Impact (21°C):** **50 - 85 J** (37 - 63 ft-lb) - **Exceptional for normalized steel** * **Machinability Rating:** **Good (65-70% of B1112 standard)** * **Fatigue Strength:** ~320-380 MPa (polished specimens) * **Fracture Toughness:** 70-100 MPa√m (estimated) **Toughness Advantage:** The impact toughness of normalized 4340H is typically 50-100% higher than normalized 4140H at similar strength levels. ## **6. PRODUCT APPLICATIONS (Normalized Condition)** This condition serves as a **premium intermediate state** for critical components requiring certified material consistency. ### **Aerospace & Defense Components:** - **Structural forgings** for aircraft and missiles (normalized prior to final heat treatment) - **Large landing gear components** requiring predictable heat treatment response - **Armored vehicle structural members** used in normalized condition - **Helicopter rotor components** prior to final hardening ### **Oil & Gas Equipment:** - **Large drill collar blanks** requiring certified through-hardening consistency - **Wellhead component forgings** normalized for grain refinement - **Pressure vessel components** for moderate pressure service - **Valve body forgings** prior to machining and heat treatment ### **Power Generation & Heavy Machinery:** - **Turbine shaft forgings** normalized for grain refinement - **Large gear blanks** for wind turbine and marine applications - **Heavy machinery structural components** requiring good toughness - **Mining equipment forgings** normalized prior to final processing ### **Direct Application Components:** - **Structural members** in mobile equipment requiring good impact resistance - **Fixtures, jigs, and tooling plates** for manufacturing - **Agricultural equipment parts** not requiring maximum hardness - **Non-critical gears and shafts** for moderate service conditions ### **Substrate for Selective Hardening:** - Ideal for components to be **induction hardened**, **flame hardened**, or **carburized** - **Bearing races** and **gear teeth** for subsequent case hardening - **Wear surfaces** requiring localized hardening only ## **7. INTERNATIONAL STANDARDS & EQUIVALENT GRADES** | Standard / Country | Designation | Equivalent Status | Critical Notes | | :--- | :--- | :--- | :--- | | **AISI/SAE** | **4340H** | Primary Standard | SAE J1268 governs hardenability | | **ASTM** | **A304 Grade 4340H** | US Standard | For bars with hardenability requirements | | **AMS** | **AMS 6414** | Aerospace Standard | Often specified normalized for aircraft quality | | **UNS** | **H43400** | Unified Numbering | | | **DIN/EN** | **36NiCrMo6H (1.6562+H)** | European H-grade | "+H" suffix denotes hardenability grade | | **JIS** | **SNCM439H** | Japanese H-grade | | | **GB** | **40CrNiMoAH** | Chinese H-grade | | | **ISO** | **ISO 683-18 Type 36NiCrMo6** | International | Can specify hardenability requirements | **Important Distinction:** Unlike many alloy steels, 4340/4340H is frequently specified and used in normalized condition for aerospace and defense applications due to its excellent toughness in this state. ## **8. PROCESSING & FABRICATION** ### **Normalizing Process Control:** - **Temperature:** 870°C ±10°C (1600°F ±20°F) - **Soak Time:** 45 minutes per inch minimum at temperature - **Cooling:** Still air on racks with adequate spacing - **Atmosphere:** Air or slightly protective - **Decarburization:** Typically limited to ≤0.25mm with proper practices ### **Machinability:** - **Tooling:** Carbide grade C2-C3 recommended for production - **Cutting Speed:** 70-100 m/min (230-330 SFM) for turning with carbide - **Feed Rate:** 0.20-0.35 mm/rev (0.008-0.014 in/rev) - **Depth of Cut:** Up to 5mm (0.20") for roughing operations - **Coolant:** Recommended for improved tool life and surface finish - **Chip Formation:** Produces continuous chips; chip breakers beneficial ### **Welding Characteristics:** - **Good weldability** in normalized condition (preferred state for welding) - **Preheat:** 150-200°C (300-400°F) recommended - **Electrodes:** Low-hydrogen electrodes required - **Post-Weld:** Normalize or stress relieve at 600-650°C for critical applications - **Best Practice:** Weld in normalized state, then re-normalize if required ### **Forming & Bending:** - **Good cold formability** for moderate bends - **Minimum bend radius:** 3-4 × thickness - **Hot forming preferred** for complex shapes - **Springback allowance:** 3-4° should be anticipated ## **9. SUBSEQUENT HEAT TREATMENT** ### **Recommended Manufacturing Sequence:** 1. Forge or cast to near-net shape 2. Normalize at 870°C (current condition) 3. Rough machine 4. Stress relieve at 600-650°C if heavy machining performed 5. Finish machine to near-final dimensions 6. Austenitize at 815-845°C 7. Quench in oil (or water for maximum hardness) 8. Temper at desired temperature (205-650°C) 9. Final grinding/finishing ### **Heat Treatment Response from Normalized State:** - **Exceptional hardenability:** Can through-harden sections >150mm diameter - **Uniform transformation:** Normalized structure ensures consistent response - **Reduced distortion:** Normalizing minimizes residual stresses - **Predictable properties:** Guaranteed by "H" grade certification ### **Typical Heat Treated Properties (After Quench & Temper from Normalized State):** - **650°C (1200°F) Temper:** 25-30 HRC, 950-1100 MPa UTS, 90-140 J impact - **540°C (1000°F) Temper:** 38-43 HRC, 1240-1380 MPa UTS, 45-75 J impact - **425°C (800°F) Temper:** 46-50 HRC, 1515-1655 MPa UTS, 25-45 J impact ## **10. QUALITY ASSURANCE** ### **Mandatory Certification:** 1. **Hardenability Test Report** (Jominy curve per SAE J1268) 2. **Chemical Analysis Certificate** (complete with trace elements) 3. **Mechanical Test Report** for normalized condition 4. **Microstructure Report** (grain size, uniformity assessment) 5. **Heat Treatment Certificate** with temperature records ### **Standard Testing:** - Tensile testing per ASTM A370 - Hardness testing (Brinell scale preferred) - Impact testing (Charpy V-notch) - often required for 4340H - Macro-etch examination for soundness - Grain size determination (ASTM E112) ### **Non-Destructive Testing (Often Specified):** - Ultrasonic testing for internal defects - Magnetic particle inspection for surface defects - Dye penetrant for critical surfaces ### **Aerospace Additional Requirements:** - Fracture toughness testing for critical applications - Fatigue testing for dynamically loaded components - Hydrogen content analysis - Inclusion rating per ASTM E45 (strict limits) ## **11. COMPARATIVE ANALYSIS** ### **vs. Normalized 4140H:** - +40-70% higher impact toughness at similar strength levels - +10-15% better fatigue strength - Deeper hardenability (can through-harden larger sections) - Lower ductile-to-brittle transition temperature - Higher cost (typically 40-60% premium) ### **vs. Annealed 4340H:** - +20-30% higher tensile and yield strength - Better fatigue resistance - More consistent response to final heat treatment - Slightly reduced machinability (but still good) ### **vs. Normalized 4340 (Non-H Grade):** - **Guaranteed hardenability consistency** across production lots - **Predictable heat treatment response** for large components - **Reduced testing requirements** due to certification - **Essential for safety-critical applications** ### **Value of "H" Designation for Normalized 4340:** - Eliminates heat treatment variability concerns - Guarantees consistent core properties after final hardening - Reduces qualification testing for new components - Provides material certainty for critical designs ## **12. DESIGN & SELECTION GUIDELINES** ### **When to Specify Normalized 4340H:** - Safety-critical components requiring certified material consistency - Large sections (>75mm diameter) requiring predictable through-hardening - Applications where maximum toughness in current state is required - Components that will undergo complex machining before final heat treatment - Aerospace, defense, or nuclear applications with certification requirements ### **Design Advantages:** - **Exceptional toughness-to-strength ratio** in normalized state - **Excellent fatigue resistance** for normalized condition - **Good weldability** for fabrication - **Dimensional stability** for precision components - **Proven reliability** in demanding applications ### **Section Size Considerations:** - **Maximum for uniform normalization:** 200mm (8") diameter - **Optimal range:** 50-150mm (2-6") for most applications - **Minimum:** 25mm (1") to avoid excessive cooling rates ### **Economic Considerations:** - **Higher material cost** than standard alloy steels - **Reduced risk** of component failure in service - **Often cost-effective** when considering total lifecycle cost - **Justified** for safety-critical or high-value applications ### **Special Considerations:** - **Corrosion resistance:** Similar to other low-alloy steels; requires protection - **Temperature limitations:** Good to ~400°C in normalized state - **Embrittlement:** Less susceptible to temper embrittlement due to Mo content - **Notch sensitivity:** Lower than lower-toughness steels ## **13. TECHNICAL SUMMARY** **AISI 4340H steel normalized at 870°C (1600°F)** represents a **premium engineering material** that provides an exceptional combination of strength, toughness, and predictable performance in an intermediate processing state. The normalization treatment refines the microstructure to create an optimal foundation for either direct application or subsequent manufacturing operations. The "H" grade certification is particularly valuable for 4340, as it guarantees consistent through-hardening characteristics for large components—a critical requirement for safety-critical applications in aerospace, defense, energy, and heavy industry. The nickel content (1.65-2.00%) provides normalized 4340H with impact toughness values that significantly exceed those of nickel-free alloys, making it suitable for applications where damage tolerance is paramount. This material condition is specified not for ordinary applications, but for components where material consistency is as important as absolute performance. When components must be machined to precise dimensions before final heat treatment, when predictable response to quenching is essential, or when the normalized state itself provides adequate properties for the application, normalized 4340H delivers certified consistency and reliable performance. For engineers designing critical components where failure carries significant safety or economic consequences, normalized AISI 4340H provides the material certainty needed for reliable design, predictable manufacturing, and consistent service performance. It represents a comprehensive quality assurance system that ensures every component—whether used as-is or as a precursor to high-strength heat treatment—will perform as designed, with properties that are guaranteed to fall within certified limits. -:- For detailed product information, please contact sales. -: AISI 4340H Steel, normalized 870°C (1600°F) Specification Dimensions Size： Diameter 20-1000 mm Length <6243 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 4340H Steel, normalized 870°C (1600°F) Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 4340H Steel, normalized 870°C (1600°F) -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 4340H Steel, normalized 870°C (1600°F) -:- For detailed product information, please contact sales. -:

Packing of AISI 4340H Steel, normalized 870°C (1600°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 2714 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