AISI 8740 Steel, oil quenched

AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper Product Information -:- For detailed product information, please contact sales. -: AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper Synonyms -:- For detailed product information, please contact sales. -:

AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper Product Information -:- For detailed product information, please contact sales. -: **Product Overview: AISI 8740 Steel (Normalized at 870°C / 1600°F)** This document provides a detailed technical introduction to **AISI 8740** alloy steel supplied in the **normalized** condition, processed at **870°C (1600°F)**. This specific heat treatment refines the microstructure to produce a balanced combination of strength, uniformity, and machinability, serving as the ideal starting material for components that will undergo final machining and heat treatment. --- ### **1. International Standard Designations** | System | Designation | Notes | |---------------|--------------------------------|-----------------------------------------------------------------------| | **AISI/SAE** | 8740 | Standard US designation for chromium-molybdenum-nickel alloy steel | | **UNS** | G87400 | Unified Numbering System | | **ASTM** | A29/A29M, A322 | Standard specifications for alloy steel bars, normalized condition | | **AMS** | AMS 6320, AMS-S-6049 | Aerospace Material Specifications (aircraft quality) | | **DIN** | 1.6546 (41CrMo4) | German standard - close equivalent | | **EN** | 1.7225 (42CrMo4) | European standard - widely recognized equivalent | | **JIS** | SCM440 | Japanese Industrial Standard | | **GB** | 42CrMo | Chinese National Standard | --- ### **2. Chemical Composition (Weight %)** AISI 8740 is characterized by a balanced alloy system that provides excellent hardenability, strength, and toughness. | Element | Content Range (%) | Primary Function | |---------------|-------------------|----------------------------------------------------------------------------------| | **Carbon (C)** | 0.38 - 0.43 | Provides base strength and hardenability potential | | **Manganese (Mn)** | 0.75 - 1.00 | Enhances hardenability and strength | | **Silicon (Si)** | 0.15 - 0.35 | Deoxidizer; increases strength and temper resistance | | **Chromium (Cr)** | 0.40 - 0.60 | Improves hardenability, wear resistance, and corrosion resistance | | **Nickel (Ni)** | 0.40 - 0.70 | **Key element:** Significantly enhances toughness and core hardenability | | **Molybdenum (Mo)** | 0.20 - 0.30 | Promotes deep hardening; improves strength and high-temperature properties | | **Phosphorus (P)** | ≤ 0.025 | Residual impurity - kept low for optimal toughness | | **Sulfur (S)** | ≤ 0.025 | Residual impurity - affects machinability | | **Iron (Fe)** | Balance | Base metal | **Note:** The nickel content distinguishes 8740 from similar grades like 4140, providing superior toughness. --- ### **3. Heat Treatment: Normalizing at 870°C (1600°F)** - **Process Parameters:** - **Austenitizing Temperature:** 870°C (1600°F) - **Soak Time:** 1 hour per 25 mm (1 inch) of thickness - **Cooling Method:** Still air cooling to room temperature - **Metallurgical Purpose:** - **Grain Refinement:** Eliminates coarse, non-uniform structures from prior hot working - **Stress Relief:** Reduces internal stresses from manufacturing processes - **Homogenization:** Creates uniform microstructure throughout the cross-section - **Improved Machinability:** Provides optimal hardness range for efficient machining - **Preparation for Hardening:** Ensures consistent response to subsequent heat treatment - **Resulting Microstructure:** Fine-grained mixture of **ferrite and pearlite** --- ### **4. Mechanical & Physical Properties (Normalized Condition)** #### **Typical Mechanical Properties:** | Property | Value Range | Comments | |----------------------------|-------------------------------|------------------------------------------------| | **Tensile Strength** | 655 - 795 MPa (95-115 ksi) | | | **Yield Strength (0.2%)** | 415 - 550 MPa (60-80 ksi) | | | **Elongation (in 50mm)** | ≥ 18% | | | **Reduction of Area** | ≥ 50% | | | **Hardness** | 200 - 250 HBW | Equivalent to ~93-103 HRB | | **Impact Toughness** | Good | Improved over as-rolled condition | #### **Physical Properties (at 20°C):** | Property | Value | |--------------------------------|----------------------------------| | **Density** | 7.85 g/cm³ (0.284 lb/in³) | | **Modulus of Elasticity** | 205 GPa (29,700 ksi) | | **Poisson's Ratio** | 0.29 | | **Thermal Conductivity** | 42.7 W/m·K | | **Specific Heat Capacity** | 460 J/kg·K | | **Coefficient of Thermal Expansion** | 12.3 × 10⁻⁶/K (20-100°C) | --- ### **5. Key Characteristics & Advantages** 1. **Superior Machinability:** The normalized structure offers an ideal balance of hardness and ductility for efficient machining operations. 2. **Excellent Hardenability:** The Ni-Cr-Mo alloy system provides deep hardening characteristics, suitable for large cross-sections. 3. **Enhanced Toughness:** Nickel content delivers superior impact resistance compared to nickel-free alloys. 4. **Uniform Microstructure:** Ensures consistent mechanical properties and predictable performance. 5. **Thermal Stability:** Molybdenum content provides good resistance to tempering and creep. 6. **Versatile Processing:** Can be further heat treated to achieve a wide range of mechanical properties. --- ### **6. Machining & Processing Guidelines** - **Machinability Rating:** 60-65% (relative to 1% carbon steel = 100%) - **Recommended Cutting Speeds:** 30-40 m/min for turning operations - **Tool Material:** Carbide or high-speed steel with positive rake angles - **Coolant:** Emulsified oils recommended for heavy cutting - **Post-Machining:** Stress-relief annealing may be required for complex, high-tolerance parts --- ### **7. Typical Applications** Normalized AISI 8740 serves as premium stock for high-performance components across multiple industries: #### **Aerospace & Defense:** - Landing gear components - Engine mounts and structural fittings - Helicopter rotor shafts - Missile and aircraft structural parts #### **Automotive & Transportation:** - Heavy-duty axle shafts - Transmission gears and shafts - Crankshafts and connecting rods - Steering components #### **Oil & Gas Industry:** - Drill collar components - Tool joints and subs - Valve bodies and stems - High-pressure fittings #### **Industrial & Heavy Machinery:** - Gear blanks for power transmission - Hydraulic cylinder rods - Machine tool components - Mining equipment parts #### **Other Applications:** - High-strength fasteners and bolts - Marine shafting - Agricultural equipment components - Die casting tooling bases --- ### **8. Available Forms & Specifications** | Form | Standard Sizes | Condition | |----------------------|-----------------------------------|------------------------------| | **Round Bars** | 10mm - 300mm diameter | Black, peeled, or turned | | **Flat Bars** | Thickness: 10-150mm; Width: 50-300mm | As-rolled or machined | | **Squares** | 10mm - 150mm | Black or machined | | **Billets & Blooms** | Custom dimensions | For forging operations | | **Forged Shapes** | Custom configurations | Rough or semi-finished | **Quality Certifications:** Available with Mill Test Certificates (MTC) per EN 10204 3.1 or 3.2, including chemical analysis and mechanical property verification. **Special Requirements:** Can be supplied with additional testing including: - Ultrasonic testing per ASTM A388 - Magnetic particle inspection per ASTM E709 - Hardenability testing per ASTM A255 --- ### **9. Subsequent Heat Treatment Options** Normalized AISI 8740 can be further processed to achieve various property profiles: | Final Treatment | Typical Tempering Temperature | Resulting Hardness | Key Applications | |-----------------------|-------------------------------|--------------------|--------------------------------| | **Quench & Temper** | 205-425°C (400-800°F) | 40-55 HRC | High-strength gears, shafts | | **Quench & Temper** | 425-650°C (800-1200°F) | 25-40 HRC | High-toughness components | | **Case Hardening** | N/A | Case: 58-62 HRC | Wear-resistant surfaces | | **Induction Hardening** | N/A | 50-58 HRC | Localized wear resistance | --- ### **10. Important Considerations** 1. **Section Size Sensitivity:** Final properties after subsequent hardening are dependent on cross-sectional dimensions. 2. **Decarburization:** Surface decarburization may occur during normalizing; machining allowance should be considered. 3. **Weldability:** Fair - requires pre-heating (150-260°C/300-500°F) and post-weld heat treatment. 4. **Corrosion Resistance:** Limited; appropriate coatings or plating are recommended for corrosive environments. 5. **Dimensional Stability:** Normalizing provides good stability for precision machining operations. --- ### **11. Ordering Information** When ordering AISI 8740 normalized material, specify: - Dimension and tolerances - Quantity and length - Certification requirements - Special testing requirements - Surface condition - Packaging and marking requirements --- **Disclaimer:** This technical data is for informational purposes only. The properties listed are typical values and may vary based on specific manufacturing processes, section size, and heat treatment parameters. For critical applications, consult with material engineers and perform appropriate testing. Always refer to the relevant material standards and specifications for design and manufacturing purposes. Final material selection should be based on comprehensive testing and validation for the specific application requirements. -:- For detailed product information, please contact sales. -: AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper Specification Dimensions Size： Diameter 20-1000 mm Length <6382 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 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°F) temper -:- For detailed product information, please contact sales. -:

Packing of AISI 8740 Steel, oil quenched 830°C (1525°F), 540°C (1000°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 2853 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