ASTM A193 B7 Screw

QS Fastener: ASTM A193 B7 Screw

Name: ASTM A193 B7 Screw
Standard: ASTM
Material: A193 B7
Size: 1/2 to 4 inch
Thread: 4-1/2 UNC
Length: 30 to 1000 mm
Grade: A
Application: Oil Pipeline, Machinery, Chemical Industry, Building

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The ASTM A193 B7 Screw is a high-performance fastener that complies with ASTM standards. Made from chromium-molybdenum alloy steel, it offers high strength and corrosion resistance, making it suitable for high-temperature and high-pressure environments. It is available in sizes ranging from 1/2 to 4 inches, with lengths of 30 to 1000 mm, and features 4-1/2 UNC threads. The Grade A classification ensures exceptional quality. The ASTM A193 B7 Screw is widely used in oil pipelines, mechanical equipment, the chemical industry, and construction projects, serving as a reliable choice for demanding working conditions.

In the production process of the ASTM A193 B7 Screw, material inspection is a critical step to ensure product quality. To guarantee that the raw materials fully meet ASTM standards, the following professional inspection methods are employed:

1. Chemical Composition Analysis
Spectrometers (such as OES or ICP) are used to analyze the chemical composition of raw materials, ensuring compliance with ASTM A193 standards for chromium-molybdenum alloy steel.

Key element content ranges:
Chromium (Cr): 0.80%-1.10%
Molybdenum (Mo): 0.15%-0.25%
Carbon (C): 0.37%-0.49%
Manganese (Mn): 0.65%-1.10%
Silicon (Si): 0.15%-0.35%
Testing standard: Compliant with ASTM A751 chemical composition testing methods.

2. Mechanical Properties Testing
Tensile and impact tests are conducted to evaluate the mechanical properties of the material, ensuring they meet the strength requirements of the ASTM A193 B7 Screw.

Tensile test:
Tensile strength: ≥ 125 ksi (862 MPa)
Yield strength: ≥ 105 ksi (724 MPa)
Elongation: ≥ 16%

Impact test:
Charpy V-notch impact value: ≥ 20 J (tested at -18°C).
Testing standards: Compliant with ASTM E8 (tensile test) and ASTM E23 (impact test).

3. Metallographic Analysis
Metallographic microscopes and scanning electron microscopes (SEM) are used to observe the material’s microstructure, ensuring uniformity and the absence of defects such as inclusions or voids.

Microstructure requirements: Tempered martensite or bainite, with grain size controlled to levels 5-8 (ASTM E112 standard).

4. Hardness Testing
Rockwell or Brinell hardness testers are used to measure material hardness, ensuring it meets standard requirements.
Hardness range: HRC 26-32 or HB 269-341.

Testing standards: Compliant with ASTM E18 (Rockwell hardness) or ASTM E10 (Brinell hardness).

5. Non-Destructive Testing
Ultrasonic testing (UT) and magnetic particle testing (MT) are used to detect internal and surface defects, ensuring the absence of cracks, inclusions, or other flaws.

Testing standards: Compliant with ASTM E2375 (ultrasonic testing) and ASTM E1444 (magnetic particle testing).

6. Heat Treatment Verification
Heat treatment process monitoring and hardness distribution testing are conducted to ensure the material undergoes proper quenching and tempering, achieving the required mechanical properties and microstructure.

Heat treatment process: Quenching temperature 850°C-900°C, tempering temperature 550°C-650°C.

Through the above inspections, the raw materials for the ASTM A193 B7 Screw are ensured to fully comply with standard requirements, providing a solid foundation for the product’s high performance and reliability.

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