ASTM A29/A29M is a technical specification for hot-worked carbon and alloy steel bars, applicable to round, square, and hexagonal bars, and is widely used in machining, forging, or further heat treatment. The standard is available in both imperial (A29) and metric (A29M) versions.

2. G51400 Material Basics

• UNS Number: G51400, corresponding to SAE/AISI 5140 steel, is a medium-carbon chromium-molybdenum alloy steel.

• Main Applications: G51400 is used in environments that require wear resistance and moderate toughness, such as gears, shafts, bolts, and high-strength structural components.

3. Chemical Composition (Typical Range)

• Carbon (C)：0.38–0.43%

• Manganese (Mn)：0.70–0.90%

• Chromium (Cr)：0.70–0.90%

• Molybdenum (Mo)：0.15–0.25%

• Silicon (Si)：0.15–0.35%

• Phosphorus (P)：≤0.035%

• Sulfur (S)：≤0.040%

4. Mechanical Properties (After Heat Treatment)

（1）Heat Treatment State: Typically quenched (oil-cooling) and tempered.

（2）Typical Properties:

• Tensile Strength: ≥850 MPa (123,000 psi)

• Yield Strength: ≥680 MPa (98,500 psi)

• Elongation (50mm gauge length): ≥12%

• Reduction of Area: ≥45%

• Hardness: Approximately 248–302 HB (depending on tempering temperature)

5. Heat Treatment Process

• Quenching: Heat to 830–860°C (oil-cooling).

• Tempering: Choose temperature based on requirements (e.g., 540–660°C) to adjust hardness and toughness balance.

• Annealing: Heat to 790°C and then cool slowly to improve machinability.

6. Processing and Inspection Requirements

• Surface Quality: No cracks, folds, or defects; light machining marks are acceptable.

• Dimensional Tolerances: Conforms to ASTM A29/A29M specifications for diameter/side length (e.g., hot-rolled bar tolerance ±0.8mm).

• Testing Methods:Tensile Testing (ASTM A370)、Hardness Testing (Brinell or Rockwell)、Chemical Composition Analysis (spectroscopy or wet method)

7. Corresponding Grades and International Standards

• SAE/AISI：5140

• DIN：41Cr4 / 1.7035

• JIS：SCr440(H)

• GB：40Cr (approx.)

8. Extended Knowledge

（1）Role of Alloying Elements:

• Chromium: Improves hardenability and wear resistance.

• Molybdenum: Enhances high-temperature strength and creep resistance.

（2）Alternative Materials:

• For higher strength, consider 4340 (G43400).

• For better corrosion resistance, choose stainless steel series.

9. Summary

In conclusion, G51400 offers a balanced combination of strength, toughness, and wear resistance, making it an ideal material for mechanical structures in diverse working conditions. With proper heat treatment and process control, its overall performance can be significantly enhanced, making it suitable for high-load applications across various industries.

10. About Suzhou Bolaisheng Metal

Suzhou Bolaisheng Metal Group Co., Ltd. specializes in providing high-quality alloy structural steels, copper alloys, and stainless steel material solutions. With advanced production equipment and a strict quality management system, Bolaisheng Metal offers reliable metal materials and customized services to global customers.

We have long been supplying various high-performance alloy steels, including G51400 (5140 steel), widely used in the automotive, mechanical engineering, and energy equipment industries. Whether standard products or special specifications customized to customer needs, we offer comprehensive heat treatment, precision machining, inspection services, and export packaging to meet various industrial requirements.

For more detailed information, professional material selection advice, technical support, and quotes for G51400 (5140 steel) and other materials, feel free to contact us.

Customer Service Hotline: +86 15370330359

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