AISI 4140 Steel, normalized

AISI 4140 Steel, normalized at 870°C (1600°F), air cooled Product Information -:- For detailed product information, please contact sales. -: AISI 4140 Steel, normalized at 870°C (1600°F), air cooled Synonyms -:- For detailed product information, please contact sales. -:

AISI 4140 Steel, normalized at 870°C (1600°F), air cooled Product Information -:- For detailed product information, please contact sales. -: # **AISI 4140 Steel (Normalized Condition) Product Overview** ## **1. Introduction & Material State Definition** **AISI 4140 Steel** is a versatile medium-carbon, chromium-molybdenum (Cr-Mo) alloy steel renowned for its excellent combination of strength, toughness, and hardenability. This document specifically describes the material in the **normalized condition**, achieved by heating to **870°C (1600°F)** followed by **air cooling**. Normalization refines the grain structure, improves microstructural uniformity, relieves internal stresses from prior manufacturing processes (e.g., casting, forging, hot rolling), and provides a consistent baseline for subsequent heat treatment operations. This condition offers improved machinability over the as-forged state and better mechanical properties than the annealed state. ## **2. Chemical Composition** The chemical composition of AISI 4140 is the foundation of its properties, providing a balance of strength and hardenability. | Element | Composition Range (% by weight) | Role in the Normalized Condition | | :--- | :--- | :--- | | **Carbon (C)** | 0.38 - 0.43 | Provides solid solution strengthening and forms fine pearlite during air cooling, contributing to increased strength. | | **Manganese (Mn)** | 0.75 - 1.00 | Enhances hardenability and solid solution strengthening. Helps refine the pearlite structure. | | **Phosphorus (P)** | ≤ 0.035 | Residual impurity, kept low to preserve ductility and toughness. | | **Sulfur (S)** | ≤ 0.040 | Residual impurity, kept low. | | **Silicon (Si)** | 0.15 - 0.35 | Acts as a deoxidizer during steelmaking and provides solid solution strengthening. | | **Chromium (Cr)** | 0.80 - 1.10 | Increases hardenability, refines grain size, and promotes the formation of fine carbides. | | **Molybdenum (Mo)** | 0.15 - 0.25 | Enhances hardenability, improves grain refinement, and increases resistance to temper embrittlement. | ## **3. Physical & Mechanical Properties (Normalized at 870°C / Air Cooled)** * **Physical Properties:** * **Density:** 7.85 g/cm³ (0.284 lb/in³) * **Melting Point:** ~1416°C (2580°F) * **Modulus of Elasticity:** 190-205 GPa (28,000-29,700 ksi) * **Poisson's Ratio:** 0.29 * **Thermal Conductivity:** ~42.6 W/m·K at 100°C * **Coefficient of Thermal Expansion:** 11.2 µm/m·°C (20-100°C) * **Microstructure:** Fine, uniform mixture of ferrite and pearlite. * **Mechanical Properties (Typical for Normalized Condition):** * **Tensile Strength:** 655 - 795 MPa (95,000 - 115,000 psi) * **Yield Strength (0.2% Offset):** 415 - 655 MPa (60,000 - 95,000 psi) * **Elongation (in 50mm):** 20% - 25% * **Reduction of Area:** 45% - 55% * **Hardness (Brinell):** 200 - 250 HB (Approx. 94-100 HRB) * **Charpy V-Notch Impact:** 30 - 60 J (22 - 44 ft-lb) at room temperature. * **Machinability:** Fair to Good (~65% of a 1% carbon steel standard). Better than as-forged, but slightly harder than annealed. ## **4. Product Applications (Normalized Condition)** Components are often used in the normalized state for applications requiring good strength and toughness without the full hardness of a quenched and tempered part, or as an intermediate step in manufacturing. * **Forging & Casting Conditioning:** Normalizing is a standard post-forging or post-casting process to refine the coarse grain structure and homogenize properties before final machining and heat treatment. * **Machining Pre-Treatment:** Serves as an excellent starting condition for parts that will undergo significant machining prior to final hardening and tempering, offering a good balance of machinability and strength. * **Non-Critical Structural Components:** Used for **gears, shafts, pins, and spindles** where high impact resistance and moderate strength are sufficient, and where the cost of quenching and tempering is not justified. * **Weldment Preparation & Post-Weld Treatment:** Normalizing is often applied to complex weldments to refine the grain structure in the heat-affected zone (HAZ) and relieve welding stresses, improving overall toughness and dimensional stability. * **Tooling & Die Pre-forms:** Blanks for dies, molds, and fixtures that may be used in the normalized state or later surface hardened. ## **5. International Standards & Equivalent Grades** | Standard / Country | Designation | Note / Status | | :--- | :--- | :--- | | **AISI / SAE (USA)** | **4140** | The primary reference standard. | | **ASTM (USA)** | A29 / A322 (Grade 4140) | Standard specification for alloy steel bars. Can be supplied normalized. | | **UNS** | G41400 | Unified Numbering System. | | **DIN (Germany)** | **42CrMo4** / **1.7225** | The most common direct equivalent in Europe. | | **EN (Europe)** | 1.7225 / 42CrMo4 | | | **JIS (Japan)** | **SCM440** | A very close equivalent. | | **GB (China)** | **42CrMo** | Widely used Chinese equivalent. | | **ISO** | **ISO 683-18: Type 42CrMo4** | International standard. | ## **6. Heat Treatment & Processing Notes** * **Normalization Process (As-Defined):** 1. Heat uniformly to **870°C (1600°F)**. 2. Soak for approximately 1 hour per inch of thickness (minimum 30 minutes). 3. Remove from furnace and cool in **still air** on a rack to ensure uniform cooling. * **Subsequent Processing:** * **Machining:** Good condition for machining. Stress relieving at 595-650°C (1100-1200°F) after heavy machining is recommended to prevent distortion during final hardening. * **Welding:** Good weldability in this condition. Standard practice: Preheat to 150-260°C (300-500°F) for thick sections; post-weld heat treatment (stress relief or re-normalization) is advised for critical applications. * **Final Hardening:** Normalized parts provide an ideal, uniform microstructure for subsequent austenitizing and quenching. They typically respond more consistently to hardening than as-forged parts. ## **7. Conclusion** **AISI 4140 steel normalized at 870°C (1600°F) and air-cooled** represents a critical and widely used intermediate or final state for this high-performance alloy. It provides a refined, homogeneous microstructure that ensures predictable behavior in subsequent manufacturing steps, such as machining and final heat treatment. Offering a favorable balance of strength, toughness, and machinability, it is an efficient and cost-effective choice for a vast array of structural and mechanical components across industries including automotive, aerospace, oil & gas, and heavy machinery. Whether serving as a final condition for non-critical parts or as a preparatory step for high-strength components, normalized 4140 is a cornerstone material in modern engineering. -:- For detailed product information, please contact sales. -: AISI 4140 Steel, normalized at 870°C (1600°F), air cooled Specification Dimensions Size： Diameter 20-1000 mm Length <6210 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 4140 Steel, normalized at 870°C (1600°F), air cooled Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 4140 Steel, normalized at 870°C (1600°F), air cooled -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 4140 Steel, normalized at 870°C (1600°F), air cooled -:- For detailed product information, please contact sales. -:

Packing of AISI 4140 Steel, normalized at 870°C (1600°F), air cooled -:- 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 2681 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