What is ASTM A370?
ASTM A370 is the primary standard practice used to determine the mechanical properties of steel products, including carbon, alloy, and stainless steels. Unlike generic testing standards (like ASTM E8 for tension), A370 is specifically tailored to the unique geometries, heat treatments, and product forms of steel (bars, shapes, forgings, wire, tubing, and sheets). It serves as the mandatory reference for compliance with almost all other ASTM steel specifications (e.g., A106, A53, A193). The standard covers the definitions and methods for tension, bend, hardness, impact, and shear testing of steel products. It acts as the “umbrella” document referenced by specific product standards (e.g., “Tensile properties shall be determined in accordance with ASTM A370”).
What are the Key Test Types?
ASTM A370 integrates several fundamental mechanical tests into a unified framework for steel:
① Tension Test: Determines yield strength, tensile strength, and elongation. It specifies whether to use standard round specimens (for bars/thick plates) or rectangular strip specimens (for thin sheets/plates), and defines the gauge length based on specimen size.
② Bend Test: Assesses ductility and soundness by bending a specimen around a mandrel of a specified diameter. It is critical for verifying that steel can be formed without cracking.
③ Hardness Test: Measures resistance to indentation using Brinell, Rockwell, or Vickers scales. A370 provides conversion tables and specific procedures for testing curved surfaces or thin sections.
④ Impact Test (Charpy V-Notch): Evaluates toughness and susceptibility to brittle fracture at various temperatures. This is vital for structural steels used in cold environments or dynamic loading conditions.
⑤ Fatigue Test: Though less common for routine QA, it defines methods for determining endurance limits when required by product specifications.
Discovery and Evolution of Steel Testing Standards
As the steel industry expanded in the late 19th and early 20th centuries, inconsistencies in testing methods led to disputes over material quality and structural failures. The American Society for Testing and Materials (ASTM) developed A370 to consolidate disparate testing practices for different steel products (rails, beams, plates) into a single, coherent document. Over decades, A370 has evolved to address new manufacturing processes (like continuous casting), advanced high-strength steels (AHSS), and stricter safety requirements for pipelines and offshore structures. It acts as a “bridge” standard, referencing fundamental test methods (like ASTM E8, E10, E23) but tailoring their application specifically to the realities of steel production and product forms.
ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products
Product-Specific Geometry: Providing specific specimen dimensions for wires, rebars, tubes, and heavy forgings that general standards do not cover.
Yield Point Determination: Offering specific techniques for identifying the discontinuous yield point common in low-carbon structural steels.
Hardness-Tensile Correlation: Including official tables for converting steel hardness readings to estimated tensile strength, widely used in field inspections.
Retest Logic: Defining the exact statistical procedure for re-sampling and retesting when initial results do not meet specification limits.
The key contents covered by the standard include:
Definitions of mechanical terms specific to steel (e.g., yield point elongation, stretcher strains).
Tension testing: Specimen types (standard round, rectangular, tubular), grip requirements, and speed of testing.
Bend testing: Procedures for semi-guided and free bending to assess soundness and ductility.
Hardness testing: Brinell, Rockwell, Vickers, and portable hardness tester usage.
Impact testing: Charpy V-notch apparatus verification, specimen preparation, and temperature conditioning.
Shear testing: Methods for determining shear strength of bars and wires.
Reporting: Mandatory data points for certification.
Referenced Standards
ASTM E8/E8M: Tension Testing of Metallic Materials (General basis).
ASTM E10: Brinell Hardness of Metallic Materials.
ASTM E18: Rockwell Hardness of Metallic Materials.
ASTM E23: Notched Bar Impact Testing of Metallic Materials.
ASTM E140: Standard Hardness Conversion Tables for Metals.
ASTM A6/A6M: General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling.
ISO 6892-1: Metallic materials — Tensile testing (International counterpart).
ISO 148-1: Metallic materials — Charpy pendulum impact test.
ASME Boiler and Pressure Vessel Code, Section II, Part D: Uses A370 methods for material qualification.
API 5L: Specification for Line Pipe (heavily relies on A370 for tensile and impact).
AWS D1.1: Structural Welding Code (references A370 for weld metal testing).
Environment:
Temperature: Standard testing is at room temperature (65°F to 85°F / 18°C to 30°C). Impact testing requires precise cooling/heating to specific service temperatures (e.g., -40°F, -70°C).
Atmosphere: Ambient air, unless corrosion or hydrogen embrittlement is being studied (which requires special annexes or other standards).
Test Procedure:
- Specimen Selection: Identify the product form (plate, bar, pipe) and select the appropriate specimen type, location, and orientation as per the relevant Annex in A370.
- Preparation: Machine specimens to the specified dimensions. For impact tests, the V-notch must be machined with high precision using a broaching or milling tool to ensure the correct root radius and angle.
- Conditioning: For impact tests, immerse specimens in a cooling/heating medium for a specified time to reach the target temperature.
- Equipment Setup: Verify the testing machine (tension, impact, or hardness) according to referenced standards (E4, E23, etc.).
- Testing:
- Data Analysis: Calculate properties. For impact tests, plot energy vs. temperature if a transition curve is required.
- Reporting: Generate a report detailing the heat number, specimen orientation, location, test temperature, and all measured values.
Russian 
English 
Spanish