AISI 81B45 Steel Sheet,Plate

AISI 81B45 Steel Sheet/Plate Product Information -:- For detailed product information, please contact sales. -: AISI 81B45 Steel Sheet/Plate Synonyms -:- For detailed product information, please contact sales. -:

AISI 81B45 Steel Product Information -:- For detailed product information, please contact sales. -: ## **Product Specification: AISI 81B45 Boron-Treated Hardenability Steel** ### **Product Designation** * **Standard Name:** AISI 81B45 / SAE 81B45 * **UNS Number:** H50450 * **Type:** Medium-Carbon, Boron-Treated Alloy Steel * **Primary Processing:** Typically supplied hot-rolled or cold-drawn, annealed or normalized for machining. * **Key Feature:** **Boron addition** for enhanced hardenability at low alloy cost. ### **Overview** AISI 81B45 is a medium-carbon, **boron-treated alloy steel** belonging to the SAE "81Bxx" series. The defining characteristic of this grade is the intentional addition of a minute amount of **boron (typically 0.0005% - 0.003%)**, which drastically increases the hardenability of the steel with only a minimal increase in cost. This allows it to achieve through-hardening properties comparable to more highly alloyed steels, making it a **cost-effective alternative** for components requiring good strength and toughness in larger cross-sections. It is primarily used in the quenched and tempered condition. --- ### **1. Chemical Composition (Typical % by Weight, SAE/AISI Standard)** The composition is based on a standard medium-carbon manganese steel, with boron as the key performance enhancer. | Element | Content (%) | Role & Effect | | :--- | :--- | :--- | | **Carbon (C)** | 0.43 - 0.48 | Provides the fundamental capacity for strength and hardness through martensite formation upon quenching. | | **Manganese (Mn)** | 0.75 - 1.00 | Provides base hardenability and solid solution strengthening. The range is optimized to work synergistically with boron. | | **Phosphorus (P)** | ≤ 0.040 | Impurity; kept low. | | **Sulfur (S)** | ≤ 0.040 | Impurity; standard low level. | | **Silicon (Si)** | 0.15 - 0.35 | Deoxidizer and strengthens the ferrite matrix. | | **Boron (B)** | 0.0005 - 0.003 | **Core Element.** Segregates to austenite grain boundaries during quenching, dramatically increasing hardenability by delaying the transformation of austenite to softer phases (ferrite, pearlite). | | **Other Elements**| Trace amounts of Al, Ti, or Zr may be present to "protect" the boron by tying up nitrogen, ensuring its effectiveness. | | **Iron (Fe)** | Balance | | *Note: The "81" prefix historically indicated a specific Ni-Cr-Mo base, but in the boron "B" series, it primarily denotes a specific hardenability range. The chemistry is essentially that of a 15Bxx series steel with adjusted manganese.* --- ### **2. Physical & Mechanical Properties** **A. Physical Properties (Annealed/Normalized State)** * **Density:** 7.85 g/cm³ (0.284 lb/in³) * **Elastic Modulus (E):** ~205 GPa (29.7 x 10⁶ psi) * **Poisson's Ratio:** 0.29 * **Thermal Conductivity:** ~48 W/m·K * **Coefficient of Thermal Expansion:** 11.5 x 10⁻⁶ /K (20-100°C) **B. Mechanical Properties (As-Supplied, Annealed)** * **Hardness (Brinell):** 179 - 217 HB * **Tensile Strength:** 585 - 725 MPa (85 - 105 ksi) * **Yield Strength:** ~415 MPa (60 ksi) min. * **Elongation:** 20% min. * **Machinability:** Fair to good in the annealed condition. **C. Mechanical Properties (After Quenching & Tempering)** *Properties are highly dependent on section size and tempering temperature.* * **Typical Heat Treatment:** Austenitize at 830-850°C (1525-1560°F), **oil quench**, and temper. * **Surface Hardness (As-Quenched):** Up to 58-60 HRC. * **Tempered Hardness Range:** 25 - 50 HRC (Widely adjustable). * **Tensile Strength (e.g., at ~300-350 HB):** 1000 - 1200 MPa (145 - 174 ksi). * **Core Toughness:** Good at moderate hardness levels; impact strength decreases at very high hardness/strength levels typical of through-hardened steels. * **Key Advantage:** Achieves a deeper uniform hardness ("harder core") in larger sections than a standard 1045 or 1541 steel at similar cost. --- ### **3. Product Applications** AISI 81B45 is selected for medium-to-heavy section components where good through-hardening is needed economically. It often replaces more expensive Cr-Mo or Ni-Cr-Mo steels. * **Automotive Components:** * **Shafts:** Axle shafts, torsion bars, steering components, and less critical drive shafts. * **Fasteners:** High-strength bolts, pins, and studs. * **Gears & Forgings:** Medium-duty gears, differential cases, and other forged parts. * **Agricultural & Off-Highway Machinery:** * Implement parts, linkage components, and hydraulic cylinder rods. * **General Machinery:** * Spindles, pins, bushings, and lever arms requiring wear resistance and strength. * **Construction Equipment:** * Bucket teeth adapters, linkage pins, and other high-wear, high-strength parts. --- ### **4. International Standards & Designations** The boron steel concept is used globally, but the "81B45" designation is specific to the SAE system. Other standards have their own numbering for boron steels. | Standard System | Designation | Notes / Key Comparison | | :--- | :--- | :--- | | **SAE / AISI (USA)** | **SAE 81B45** | The standard designation. "B" denotes boron treatment. | | **UNS (USA)** | **H50450** | Unified Numbering System for boron steels. | | **ASTM (USA)** | **ASTM A304** (for H-band grades) or **ASTM A29** | Often supplied as a standard grade bar. | | **DIN / EN (Germany/EU)** | No direct equivalent. Conceptually similar to **~1.5530 (38MnB5)** or **1.5525 (34MnB5)**. | European boron steels are common (xxMnBx), but the exact manganese/carbon balance of 81B45 is not directly mirrored. | | **JIS (Japan)** | No direct equivalent. | Similar boron-treated steels exist (e.g., **S45C-B**), but are not standardized with an identical "81" prefix composition. | | **GB (China)** | **40MnB** or **45MnB** | These are the standard Chinese boron steels and are the **closest functional equivalents** to AISI 81B45. | --- ### **Key Considerations & Processing** 1. **Hardenability vs. Toughness:** Boron significantly increases hardenability but does not inherently improve toughness. The toughness of 81B45 is largely a function of its carbon and manganese content and the final tempered microstructure. 2. **Heat Treatment Sensitivity:** Boron's effectiveness is highly sensitive to austenitizing temperature and time. Overheating can reduce its hardenability-enhancing effect. 3. **Weldability:** Fair to poor. The carbon content and high hardenability make it prone to cracking in the heat-affected zone (HAZ). Pre-heat and post-heat treatments are usually necessary. 4. **Economic Advantage:** Its primary benefit is achieving the hardenability of a more expensive alloy steel (like a 41xx or 86xx series) at a cost closer to a plain carbon-manganese steel. ### **Summary** **AISI 81B45** is a **cost-optimized, high-hardenability steel** made possible by boron microalloying. It fills an important niche in engineering design, providing the ability to through-harden larger cross-sections for applications requiring good strength and wear resistance, where core toughness requirements are moderate and cost is a significant factor. While not as versatile or tough as higher-alloy grades like 4140 or 4340, it serves as a reliable and economical workhorse material for a wide range of automotive and general industrial components. Its closest global analogues are the **GB 40MnB/45MnB** grades. -:- For detailed product information, please contact sales. -: AISI 81B45 Steel Specification Dimensions Size： Diameter 20-1000 mm Length <4143 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 81B45 Steel Properties -:- For detailed product information, please contact sales. -:

Applications of AISI 81B45 Steel Sheet,Plate -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI 81B45 Steel Sheet,Plate -:- For detailed product information, please contact sales. -:

Packing of AISI 81B45 Steel Sheet/Plate -:- 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 Sheet/Plate 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 614 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