AISI 8720 Steel Wire

AISI 8720 Steel Wire Product Information -:- For detailed product information, please contact sales. -: AISI 8720 Steel Wire Synonyms -:- For detailed product information, please contact sales. -:

AISI 8720 Steel Product Information -:- For detailed product information, please contact sales. -: ### **Product Introduction: AISI 8720 Steel** #### **1. Overview** AISI 8720 is a **boron-modified nickel-chromium-molybdenum (Ni-Cr-Mo-B) alloy steel** within the AISI 8700 series, specifically designed as a **high-performance case-hardening (carburizing) grade**. The intentional addition of **boron (B)**, typically in minute quantities (0.0005-0.003%), significantly enhances the hardenability of the steel without substantially increasing the alloying element content or cost. This results in a material that offers **excellent core hardenability and strength** at a favorable economic profile. Following carburizing heat treatment, AISI 8720 develops a deep, hard wear-resistant case over a tough, strong core, making it a **cost-effective alternative** to higher-alloy grades like AISI 8620/8622 for many medium-to-heavy duty applications. #### **2. International Standards & Designations** AISI 8720 is recognized under several international standards, with notable equivalents that account for its boron content. | Region/System | Standard Designation | Title / Purpose | | :--- | :--- | :--- | | **USA (AISI/SAE)** | **AISI 8720, SAE J404** | Standard Chemical Composition | | **USA (ASTM)** | **ASTM A322** | Standard Specification for Steel Bars, Alloy, Standard Grades | | **USA (ASTM)** | **ASTM A534** | Carburizing Steels for Anti-Friction Bearings | | **UNS Number** | **G87200** | Unified Numbering System | | **Europe (EN)** | **20NiCrMoS2-2 (with B)** | Equivalent Boron-Treated Grade (Note: Direct EN equivalent often references boron addition) | | **Germany (DIN/W-Nr.)** | **20NiCrMo2-2 +B** | Boron-Treated Equivalent Designation | | **Japan (JIS)** | **SNC815H / SNCM220H** | Similar Hardenability Grades | | **Boron Steel Ref.** | **ASTM A304 (Grade 86B20)** | Often cross-referenced for boron hardenability steels | #### **3. Chemical Composition** The key distinction of AISI 8720 lies in its boron content, which dramatically increases hardenability. Its base composition is similar to AISI 8620. | Element | Content (% by Weight) | Metallurgical Role | | :--- | :--- | :--- | | **Carbon (C)** | 0.18 - 0.23 | Provides base core strength; sufficient for effective case carburizing. | | **Manganese (Mn)** | 0.70 - 0.90 | Enhances hardenability and strength. | | **Phosphorus (P)** | ≤ 0.035 | Impurity control. | | **Sulfur (S)** | ≤ 0.040 | Impurity control; sometimes slightly increased for machinability. | | **Silicon (Si)** | 0.15 - 0.35 | Deoxidizer and strengthener. | | **Nickel (Ni)** | 0.40 - 0.70 | Enhances core toughness and hardenability. | | **Chromium (Cr)** | 0.40 - 0.60 | Increases hardenability and wear resistance of the case. | | **Molybdenum (Mo)** | 0.20 - 0.30 | Slightly higher range than 8620; increases hardenability and temper resistance. | | **Boron (B)** | **0.0005 - 0.003** | **Key Differentiator:** A potent hardenability intensifier. It segregates to austenite grain boundaries, delaying the transformation to softer phases (ferrite, pearlite) during quenching, thereby promoting deeper martensite formation. | | **Iron (Fe)** | Balance | Base metal. | #### **4. Mechanical & Physical Properties** *Properties are condition-dependent. The following represents typical ranges.* **As-Supplied (Annealed) Properties:** * **Hardness:** **149 - 197 HB** (Brinell) * **Tensile Strength:** **520 - 690 MPa** (75 - 100 ksi) * **Yield Strength:** **385 - 550 MPa** (56 - 80 ksi) * **Elongation:** **20% - 26%** * **Machinability:** **~60%** of B1112 steel. Good with proper tooling. **Properties After Case Hardening (Carburized & Hardened):** * **Surface Case Hardness:** **58 - 63 HRC** (Rockwell C) * **Effective Case Depth:** Can achieve greater depths for a given section size compared to non-boron grades like 8620, due to higher hardenability. * **Core Hardness:** **32 - 45 HRC** (Capable of higher values in larger sections than 8620). * **Core Tensile Strength:** **950 - 1300 MPa** (138 - 189 ksi) * **Core Yield Strength:** **750 - 1100 MPa** (109 - 160 ksi) * **Impact Toughness:** Good, maintained by nickel content. **Physical Properties (Core):** * **Density:** **7.85 g/cm³** * **Modulus of Elasticity:** **205 GPa** * **Poisson's Ratio:** **0.29** * **Thermal Conductivity:** **~45 W/m·K** at 100°C * **Coefficient of Thermal Expansion:** **12.5 × 10⁻⁶/°C** #### **5. Product Applications** AISI 8720 is widely used in applications requiring good hardenability and core strength at a competitive cost. It is often chosen as a substitute for more expensive alloy grades. * **Automotive Components:** Transmission gears, differential gears, pinions, shafts, and synchronizers in passenger cars and light trucks. * **General Industrial Gearing:** Gears and pinions for agricultural machinery, construction equipment, and material handling systems. * **Bearing Components:** Races and rollers for medium-duty bearings. * **Off-Highway Equipment:** Components for tractors, combines, and other mobile machinery. * **Fluid Power Components:** Gears and shafts in hydraulic pumps and motors. * **Fasteners & Pins:** High-strength bolts, studs, and dowel pins requiring case hardening. #### **6. Key Characteristics & Advantages** * **Cost-Effective Hardenability:** The primary advantage. Boron provides a significant boost in hardenability at a much lower cost than achieving similar depth of hardening through increased nickel, chromium, or molybdenum content. This makes 8720 a **high-value engineering material**. * **Good Core Strength in Larger Sections:** Capable of achieving satisfactory core properties in larger cross-sections than a non-boron grade like 8620, allowing for design flexibility. * **Deep Case Potential:** The enhanced hardenability supports the development of deeper effective case depths if required by the application. * **Good Toughness:** Maintains adequate impact resistance due to its nickel content. * **Good Machinability and Formability:** In the annealed condition, it can be readily machined and formed. * **Weldability:** Fair to good with proper precautions (preheat, low-hydrogen electrodes), though the boron content requires careful procedure to avoid cracking in the heat-affected zone. **Important Processing Notes:** * **Boron Effectiveness:** Boron's hardenability effect is most potent in leaner alloy steels and is maximized with sufficient titanium or aluminum to protect it by forming stable nitrides/oxides. * **Quenching:** Requires adequate quench severity to realize the boron hardenability benefit, typically oil quenching. * **Not for Nitriding:** Boron can adversely affect nitrided case properties; 8720 is not typically recommended for nitriding processes. **Conclusion:** **AISI 8720 is a strategically engineered, cost-optimized case-hardening steel that leverages the powerful hardenability effect of boron.** It delivers a performance profile often comparable to higher-alloy grades (like 8620/8622) at a more favorable material cost, making it a popular choice for **high-volume, cost-sensitive applications** across the automotive and general industrial sectors. Its success lies in providing an excellent balance of **performance, processability, and economics.** For designers and manufacturers seeking a reliable material for components that require a good combination of surface wear resistance and core strength without specifying premium alloy content, AISI 8720 presents a compelling and proven solution. -:- For detailed product information, please contact sales. -: AISI 8720 Steel Specification Dimensions Size： Diameter 20-1000 mm Length <5747 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 8720 Steel Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 8720 Steel Wire -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 8720 Steel Wire -:- For detailed product information, please contact sales. -:

Packing of AISI 8720 Steel Wire -:- 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 Wire 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 2218 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