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ASTM A370
Mechanical Test Methods for Steel

Standard Test Methods and Definitions for Mechanical Testing of Steel Products - PDF
 

ASTM A370 is the go-to standard for mechanical testing of steel, stainless steel, and related alloy products. It provides uniform test methods to determine the mechanical properties that dictate product performance, such as tensile strength, yield strength, elongation, hardness, and impact resistance.

Whether you're testing reinforcing bars, bolts, structural shapes, or sheet metal, ASTM A370 ensures consistent and reliable evaluation of mechanical properties across the steel industry.

This article explains the scope of ASTM A370, key mechanical tests it covers, common specimen types, and the equipment required to carry out compliant tests.

What Is ASTM A370?

ASTM A370, titled "Standard Test Methods and Definitions for Mechanical Testing of Steel Products," defines standardized procedures for measuring mechanical properties such as:

ASTM A370 does not specify acceptance criteria—it defines how to test, not what values must be achieved. Acceptance requirements are specified in product-specific standards like ASTM A36 (structural steel), ASTM A615 (rebar), or ASTM A307 (bolts).

Test Methods Covered Under ASTM A370

1. Tensile Testing

Performed on both round and flat specimens to determine:

  • Tensile Strength

  • Yield Strength or Yield Point

  • Elongation

  • Reduction of Area

Equation – Tensile Strength (psi):
Tensile Strength = Maximum Load (lbf) / Cross-sectional Area (in²)

Equation – Elongation (%):
Elongation (%) = [(Final Gauge Length - Original Gauge Length) / Original Gauge Length] × 100

Equation – Reduction of Area (%):
Reduction of Area (%) = [(Original Area - Fractured Area) / Original Area] × 100

2. Bend Testing

Bend tests are often required for welds or ductility evaluations. A flat or round specimen is bent over a mandrel to a specified angle or radius.

3. Hardness Testing

  • Rockwell, Brinell, and Vickers hardness scales are covered.

  • Required for many steel grades and often used for quality control.

4. Charpy V-Notch Impact Testing

Measures impact energy absorbed by a notched specimen at a specified temperature (often sub-zero), indicating toughness.

Equation – Impact Energy (ft-lbf or J):
Measured directly by the testing machine from the swing of the pendulum before and after fracture.

Common Specimen Types

ASTM A370 includes guidance for preparing standardized specimens. Selection depends on product shape and test type.

Product Type - Common Specimen - Dimensions

Plate or Sheet - Flat specimen - Width: 1.5" (typical), Gauge Length: 2"

Bar or Rod - Round specimen - Diameter: 0.505" (standard 0.2 in² area)

Welded Joints - Guided bend specimen - Width: 1.5", Radius per spec

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Note: ASTM A370 references the "standard 2-inch gauge length" for flat specimens and 4D (4×diameter) for round specimens.

Required Testing Equipment

To carry out ASTM A370-compliant tests, the following equipment is typically required:

1. Universal Testing Machine (UTM)

  • Performs tensile and bend tests

  • Must have an appropriate load range (typically 100 kN – 600 kN for steel)

  • Equipped with:

    • Grips or fixtures (wedge, hydraulic, or bolt-action)

    • Extensometer or strain measurement device for precise elongation/yield

2. Impact Tester (Charpy Pendulum Type)

  • Measures absorbed energy in ft-lbf or joules

  • Specimen support anvils must meet tight dimensional tolerances

  • Optional cooling chambers for sub-zero testing

3. Hardness Tester

  • Rockwell: For quick and easy hardness testing

  • Brinell: For large specimens or forgings

  • Vickers: For small or thin sections

4. Micrometers and Calipers

  • Precise dimensional measurements of gauge length and cross-sectional area

5. Bend Test Fixture

  • Guided mandrel and supports to test ductility and weld quality

Key Definitions in ASTM A370

  • Yield Point: The load at which a material exhibits a sudden elongation with no increase in load (common in low-carbon steels).

  • Yield Strength: The stress at which a material begins to deform plastically (0.2% offset method).

  • Ultimate Tensile Strength (UTS): The maximum stress the material can withstand.

  • Elongation: Total strain before fracture, indicating ductility.

  • Reduction of Area: Another ductility metric, sensitive to notch effects or internal flaws.

  • Fracture Location: Important when evaluating welds or heat-affected zones.

Applicable Materials

ASTM A370 is not limited to structural steel—it is used for:

  • Carbon steels

  • Alloy steels

  • Stainless steels

  • Rebar and wire

  • Pipe and tubing

  • Plates, bars, and forgings

  • Fasteners and weldments

Related Standards

ASTM A370 is often used in conjunction with:

Reporting Requirements

Test reports should include:

  • Specimen dimensions

  • Material grade and heat number

  • Yield strength and/or yield point

  • Ultimate tensile strength

  • Percent elongation

  • Reduction of area

  • Hardness or impact values, if applicable

  • Testing temperature and method used

Conclusion

ASTM A370 serves as the foundation for mechanical testing of steel products across numerous industries. By defining the procedures—not the performance criteria—it ensures that manufacturers and end users can rely on consistent, repeatable, and accurate test results.

With a properly calibrated universal testing machine, impact tester, hardness tester, and basic measurement tools, your lab can confidently perform ASTM A370 tests to support production quality, material certifications, and R&D investigations.

 

 

 

 

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