• 23MnB3 is a low-alloy, high-strength structural steel primarily alloyed with manganese (Mn) and boron (B), representing a typical material under the German DIN standard (material number 1.5507).

• Its designation follows a clear pattern:

“23” indicates a carbon content of approximately 0.23% (actual range 0.21–0.25%),

“Mn” represents manganese,

“B” denotes boron addition,

“3” reflects either manganese content.

2. Chemical Composition and Key Alloying Effects

（1）Main Elements (weight %):

• Carbon (C): 0.21–0.25% – provides basic strength and hardness.

• Manganese (Mn): 0.80–1.00% – improves hardenability and strength, while enhancing toughness.

• Boron (B): 0.001–0.005% – even trace amounts markedly increase hardenability, promoting uniform martensite formation and reducing distortion and cracking during quenching.

• Aluminum (Al): 0.02–0.08% – acts as a deoxidizer, preventing boron from forming harmful compounds with oxygen or nitrogen (e.g., BN or B₂O₃), ensuring effective boron solubility.

• Titanium (Ti): ≤0.06% – binds nitrogen in the steel, further stabilizing boron and improving hardenability.

• Silicon (Si): ≤0.15% – assists deoxidation and enhances strength.

• Phosphorus (P) & Sulfur (S): ≤0.015% – strictly controlled to ensure cleanliness and toughness.

（2）Element Interactions:
Precise control of aluminum and titanium is critical. Aluminum preferentially combines with oxygen to reduce dissolved oxygen, while titanium reacts with nitrogen to form TiN, minimizing boron loss. Excessive aluminum can form Al₂O₃ inclusions, potentially clogging continuous casting nozzles. Boron is highly reactive and must be added in low-oxygen, low-nitrogen environments to avoid non-metallic inclusions that weaken its strengthening effect.

3. Mechanical Properties and Heat Treatment

（1）Typical Properties (quenched & tempered):

Yield strength (Rp₀.₂): ≥668 MPa

Tensile strength (Rm): ≥673 MPa

Elongation (A): 24%

Impact energy (Akv, room temp): ≥42 J

Brinell hardness (HBW): 413

（2）Performance Highlights:

Balanced Strength & Toughness: Quenched and tempered 23MnB3 combines high tensile strength with excellent impact toughness, suitable for high-stress, impact-resistant applications.

Superior Hardenability: Boron addition allows uniform hardening in large cross-section components; parts up to 50 mm thick can achieve full hardening.

Wear Resistance: Surface carburizing or nitriding can reach HRC 50–60, making it ideal for heavily worn components.

（3）Heat Treatment Guidelines:

Quenching: 850–900°C, oil-cooled. Excessively high temperatures (e.g., 1100°C) can coarsen grains and reduce strength.

Tempering: 500–650°C depending on desired hardness. Low-temperature tempering (200–300°C) maintains high hardness but lower toughness, while high-temperature tempering (≥550°C) increases toughness with slight hardness reduction.

4. Production Process and Quality Control

（1）Melting & Refining:

Produced in basic oxygen or electric arc furnaces.

Calcium carbide added for pre-deoxidation; aluminum addition adjusted based on final carbon content (e.g., ≤0.10% final C requires 3.5–4.5 kg CaC₂ per ton of steel).

LF refining strictly controls slag FeO+MnO ≤2.0%, and aluminum, titanium, and boron are precisely added to ensure ≥90% boron recovery.

（2）Continuous Casting & Rolling:

Casting temperature: 1535±20°C with full protection (argon-sealed tundish, protective mold flux) to prevent secondary oxidation.

Air or slow cooling after rolling avoids Widmanstätten structure formation, maintaining toughness.

（3）Key Quality Factors:

Boron Recovery: Optimized deoxidation sequence (Al → Ti → B) and controlled acid-soluble Al (0.025–0.055%) maintain boron recovery at 85–95%.

Cleanliness: Vacuum degassing reduces hydrogen content (≤2 ppm) to prevent white spot defects.

5. Applications and Case Studies

（1）Core Applications:

Construction Machinery: Bulldozer and excavator track plates (e.g., heavy-duty 216 mm pitch), drive and support wheels, requiring high contact stress resistance.

Automotive Industry: Transmission gears, drive shafts, high-strength bolts, utilizing high hardenability and fatigue resistance.

Mining & Heavy Equipment: Crane booms, crusher hammers, scraper conveyor chains, demanding impact and wear resistance.

Other Fields: Railway turnouts, pressure vessel tie rods, agricultural plowshares, etc.

（2）Advantages:

Cost Efficiency: Boron micro-alloying achieves similar performance to chromium- or nickel-containing steels while reducing alloy cost by ~30%.

Lightweight Design: High strength allows smaller, lighter components—for example, using 23MnB3 in a gear reduced weight by 15% and increased lifespan by 20%.

6. Comparison with Other Materials

（1）Vs. 20MnB4: Slightly lower carbon (0.17–0.23%), higher manganese (1.0–1.4%), similar boron. 20MnB4 has slightly better hardenability (Rm up to 800 MPa) but lower toughness (A = 20%). Suitable for larger sections (>80 mm) but costlier; 23MnB3 is more cost-effective for medium and small parts.

（2）Vs. 20CrMnTi: Contains chromium (1.0–1.3%) and titanium (0.04–0.10%), no boron. Surface hardness after carburizing is higher (HRC 58–62), but core strength (Rm ≈1080 MPa) is lower than 23MnB3. 20CrMnTi is ideal for high-speed, high-load gears, whereas 23MnB3 balances core strength and surface wear resistance.

7. Recent Developments and Standards

（1）Standard Updates:

German DIN standard still follows the old version (DIN 17210), with no revision planned in 2025.

No direct Chinese equivalent exists, though some companies use similar compositions (e.g., 20MnB) as substitutes.

ISO is promoting boron steel standard integration, potentially unifying 23MnB3 requirements globally in the future.

（2）Technical Trends:

Green Production: Low-carbon steelmaking methods, such as direct hydrogen reduction, reduce CO₂ emissions. Some steel mills report 18% lower energy consumption in 23MnB3 production.

Smart Manufacturing: Big data optimization of Al and Ti additions reduced boron recovery fluctuations from ±15% to ±5%, significantly improving product consistency.

8. Procurement and Usage Recommendations

（1）Material Selection:

Identify load characteristics—choose higher Al/Ti ratio (Al ≥0.04%, Ti ≥0.05%) for impact-prone applications; increase carbon to 0.25% for wear resistance.

Request supplier-provided hardenability (Jominy) curves to ensure uniform hardness.

（2）Processing & Treatment:

Welding: Preheat 150–200°C; post-weld temper at 550–600°C to prevent cold cracking.

Surface Treatment: Carburizing at 880–920°C for 4–6 hours; optimal case depth 0.8–1.2 mm for balanced properties.

9. Conclusion

With its unique alloy design and precise production process, 23MnB3 has become a benchmark material for medium- to high-strength structural steel. Its key advantages are low-cost, high hardenability, and comprehensive mechanical performance, widely applied in construction machinery, automotive, and mining industries. With advances in green manufacturing and smart production, 23MnB3’s processing will continue to improve, extending applications to new energy equipment and high-end manufacturing sectors.

10. About Suzhou Bolaibao Metal

Suzhou Bolaibao Metal, with years of expertise in high-strength steel R&D and processing, provides one-stop solutions from metallurgical composition optimization and coating protection to precision hot forming, quenching, and laser cutting. Equipped with advanced BOF, EAF, continuous casting, and automated production lines, Bolaibao ensures each 23MnB3 steel plate meets strict international quality standards. Serving both domestic and global markets, the company delivers reliable, high-performance structural steel for automotive, heavy equipment, and industrial engineering applications.

Choose Bolaibao for enhanced reliability and superior performance.
Phone: +86 15366282159
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