AISI 4118H Steel, annealed

AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round Product Information -:- For detailed product information, please contact sales. -: AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round Synonyms -:- For detailed product information, please contact sales. -:

AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round Product Information -:- For detailed product information, please contact sales. -: # **Product Technical Data Sheet: AISI 4118H Annealed Steel Round Bar** **Product Designation:** AISI 4118H / SAE 4118H Annealed Steel **Condition:** Annealed at 870°C (1600°F), Furnace Cooled at 11°C/hour (20°F/hour) **Form & Size:** Round Bar, 25 mm (1 inch) diameter --- ## **1. Overview** AISI 4118H is a **hardenability-controlled** version of the standard AISI 4118 chromium-molybdenum low-alloy steel. The **controlled annealing process** at 870°C followed by an extremely slow furnace cooling rate of **11°C/hour (20°F/hour)** is designed to produce a fully softened, coarse pearlitic/ferritic microstructure with minimal residual stresses. This condition provides **optimal machinability, formability, and dimensional stability** for subsequent manufacturing operations. The 25mm round size is ideal for precision machining of small to medium-sized components that will later undergo carburizing or through-hardening heat treatments. The "H" suffix guarantees specific hardenability bands as defined by end-quench testing, ensuring consistent response to final heat treatment. ## **2. Chemical Composition (Weight %)** *Composition meets hardenability band requirements of AISI 4118H.* | Element | Content Range (%) | Hardenability Influence | | :--- | :--- | :--- | | **Carbon (C)** | 0.17 - 0.23 | Base hardenability control element | | **Manganese (Mn)** | 0.60 - 0.95 | Major contributor to hardenability band width | | **Silicon (Si)** | 0.15 - 0.35 | Deoxidizer, minor hardenability effect | | **Chromium (Cr)** | 0.35 - 0.65 | Increases hardenability depth, refines grain | | **Molybdenum (Mo)** | 0.08 - 0.15 | Strong hardenability enhancer, reduces band scatter | | **Phosphorus (P)** | ≤ 0.035 | Residual element (controlled) | | **Sulfur (S)** | 0.025 - 0.045 | **Intentionally elevated** for improved machinability | | **Iron (Fe)** | Balance | Matrix element | **Key Notes:** - Sulfur content is typically at the higher end of the range (0.030-0.040%) to form manganese sulfide inclusions that improve chip breaking during machining. - Composition is tightly controlled within the specified ranges to ensure the steel consistently meets the required hardenability band. ## **3. Typical Physical Properties (Annealed Condition)** | Property | Value | Unit | Notes | | :--- | :--- | :--- | :--- | | **Density** | 7.85 | g/cm³ | Typical for low-alloy steels | | **Melting Point** | ~1427 | °C | | | **Modulus of Elasticity** | 190 - 200 | GPa | Slightly reduced due to annealed microstructure | | **Thermal Conductivity** | 42.5 | W/m·K (at 100°C) | | | **Coefficient of Thermal Expansion** | 11.8 × 10⁻⁶ | /°C (20-100°C) | | | **Specific Heat Capacity** | 460 | J/kg·K | | | **Electrical Resistivity** | 0.22 | μΩ·m | | | **Microstructure** | Coarse pearlite + ferrite | | Result of slow furnace cooling | ## **4. Mechanical Properties (Annealed, 25mm Round)** | Property | Value | Unit | Test Standard | | :--- | :--- | :--- | :--- | | **Tensile Strength** | 480 - 550 | MPa (70 - 80 ksi) | ASTM E8 | | **Yield Strength (0.2% offset)** | 275 - 345 | MPa (40 - 50 ksi) | ASTM E8 | | **Elongation (in 50mm)** | 28 - 35 | % | ASTM E8 | | **Reduction of Area** | 60 - 70 | % | ASTM E8 | | **Hardness (Brinell)** | 140 - 170 | HBW | ASTM E10 | | **Hardness (Rockwell)** | 75 - 85 | HRB | ASTM E18 | | **Impact Energy (Charpy V-Notch)** | 90 - 120 | J (66 - 88 ft·lb) | ASTM E23 | ## **5. Hardenability (Jominy End-Quench Test)** *As required by the "H" designation per SAE J1268* | Distance from Quenched End (1/16 in.) | Typical Hardness (HRC) Range | | :--- | :--- | | **1.5** | 38 - 48 | | **4** | 35 - 45 | | **7** | 30 - 40 | | **10** | 25 - 35 | | **14** | 20 - 30 | | **20** | 18 - 28 | | **30** | 15 - 25 | *Note: The actual hardenability band (maximum and minimum HRC at each Jominy position) is defined in SAE J1268 for 4118H.* ## **6. Heat Treatment Process Details** ### **Full Annealing Cycle:** 1. **Heating:** Slowly heated to **870°C (1600°F)** to ensure complete austenitization. 2. **Soaking:** Held at temperature for 45-60 minutes to achieve complete phase transformation and temperature uniformity throughout the 25mm section. 3. **Controlled Cooling:** Furnace cooled at a precisely controlled rate of **11°C/hour (20°F/hour)** through the transformation range (approximately 750°C to 550°C). 4. **Final Cooling:** Air cooled from approximately 550°C to room temperature. ### **Resulting Microstructure:** - **Primary Structure:** Coarse lamellar pearlite in a ferrite matrix - **Grain Size:** ASTM 5-7 (relatively coarse due to slow cooling) - **Carbide Morphology:** Spheroidized carbides in some areas, improving machinability - **Internal Stresses:** Minimized due to slow cooling rate ## **7. Key Characteristics & Advantages** ### **Manufacturing Advantages:** - **Excellent Machinability:** Slow-cooled annealed structure combined with controlled sulfur content provides superior chip formation and extended tool life. - **Uniform Hardness:** Consistent hardness throughout cross-section (max 5 HBW variation). - **Minimal Distortion:** Low residual stresses minimize dimensional changes during machining. - **Good Formability:** Suitable for cold forming operations like bending or coining. ### **Heat Treatment Preparedness:** - **Predictable Response:** Hardenability band ensures consistent results in subsequent heat treatment. - **Uniform Austenitizing:** Homogeneous starting structure promotes even transformation during hardening. - **Minimal Decarburization:** Properly controlled annealing protects surface integrity. ## **8. Common Applications** ### **As-Annеaled Applications:** - **Precision Machined Components:** Where dimensional stability during machining is critical - **Cold Formed Parts:** Fasteners, brackets, and structural components - **Prototype Development:** Allows easy machining before final heat treatment validation ### **Applications for Subsequent Heat Treatment:** - **Carburized Components:** Gears, shafts, bearing races (after machining in annealed state) - **Through-Hardened Parts:** Hydraulic components, tooling elements - **Automotive & Machinery:** Critical components requiring predictable hardenability - **Aerospace:** Non-critical structural parts requiring consistent heat treatment response ## **9. International & Industry Standards** ### **Material Standards:** | Standard System | Designation | Specification Title / Notes | | :--- | :--- | :--- | | **SAE/AISI (USA)** | **4118H** | SAE J404, SAE J1268 (Hardenability Bands) | | **ASTM (USA)** | **A304** | Standard Specification for Carbon and Alloy Steel Bars Subject to End-Quench Hardenability Requirements | | **UNS (USA)** | **G41186** | Unified Numbering System (H-grade specific) | | **ISO** | **ISO 683-11** | Type 18CrMo4 (Hardenability variants specified separately) | | **DIN (Germany)** | **1.7139+H** | 16MnCr5+H (Similar hardenability-controlled grade) | | **JIS (Japan)** | **SCM418H** | Japanese equivalent with hardenability guarantee | | **AMS** | **AMS 2300** | Premium aircraft-quality steel (special cleanliness requirements) | ### **Hardenability Standards:** - **SAE J1268:** Hardenability Bands for Carbon and Alloy H-Steels - **ASTM A255:** Standard Test Method for End-Quench Test for Hardenability of Steel - **ISO 642:** Steel - Hardenability test by end quenching (Jominy test) ## **10. Quality Assurance & Testing** ### **Standard Testing (Per Heat Lot):** - **Chemical Analysis:** Complete spectrochemical analysis - **Jominy End-Quench Test:** Verification of hardenability band compliance - **Hardness Testing:** Brinell or Rockwell B scale, multiple locations - **Macroetch Test:** Assessment of internal soundness (ASTM E381) - **Decarburization Check:** Maximum allowed: 0.25mm (0.010") total depth ### **Optional Testing:** - **Microcleanliness:** Per ASTM E45 (inclusion rating) - **Grain Size:** ASTM E112 - **Mechanical Testing:** Tensile and impact testing of representative samples --- **Manufacturing Note:** This material in the specified annealed condition is supplied ready for machining operations. The combination of guaranteed hardenability and optimized annealed microstructure ensures both excellent manufacturing characteristics and predictable performance in final heat treatment. Components should be designed considering the eventual heat treatment process, with proper allowances for dimensional changes during quenching. **Disclaimer:** This datasheet provides typical information for reference purposes. Critical applications require confirmation of all specifications with the material supplier against current standards and specific application requirements. The slow furnace cooling rate specified is essential to achieve the desired microstructure and properties. -:- For detailed product information, please contact sales. -: AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round Specification Dimensions Size： Diameter 20-1000 mm Length <5574 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, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round -:- For detailed product information, please contact sales. -:

Packing of AISI 4118H Steel, annealed at 870°C (1600°F), furnace cooled at 11°C (20°F)/hour, 25 mm (1 in.) round -:- 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 2045 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