ASTM A370 — Mechanical testing of steel products

Active designation: ASTM A370-24a (approved October 2024).

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Legal notice

The information on this page is a summary prepared by Vector Scientific Testing Devices based on a review of the applicable standard; it does not replace the official standard. For the authoritative, complete text, obtain ASTM A370 from ASTM International or your national standards body through official channels. Vector accepts no liability for direct or indirect loss arising from reliance on this summary.

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1. Purpose and principle

ASTM A370 is the umbrella standard for mechanical verification of steels, stainless steels, and related alloys in North American and global procurement chains. Product specifications cite A370 to require tension, bend, hardness, and impact properties; the standard defines which test applies, how specimens are taken, and how results are reported — while delegating detailed methodology to referenced ASTM E-standards.

Purpose: Confirm that manufactured steel products meet specified limits for yield strength, tensile strength, ductility, hardness, and impact toughness required for structural safety and regulatory compliance.

Primary mechanical properties:

Property	Symbol (common)	Test family
Yield / proof strength	R_eH, R_p0.2	Tension (ASTM E8/E8M)
Tensile strength	R_m	Tension
Elongation	A	Tension
Reduction of area	Z	Tension (round specimens)
Impact energy	KV, KU	Charpy (ASTM E23)
Hardness	HB, HRC, HRB	Brinell / Rockwell / portable (ASTM E18, ISO 6506-1, ISO 6508-1)

When a product specification conflicts with these general procedures, the product specification controls (Section 1.1).

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2. Laboratory climate and test conditions

• Ambient tension and hardness: Tests are normally performed between 10 °C and 35 °C (50 °F to 95 °F) unless the product specification states otherwise.
• Tension speed control: Crosshead separation rate or strain-rate control must stay within limits defined in A370 and ASTM E8/E8M so yield values are not artificially raised by strain-rate hardening.
• Impact thermal conditioning: For sub-zero Charpy programmes, specimen temperature in the bath must be held within ±1 °C for at least 5 minutes (liquid media) or 30 minutes (gas media) before transfer to the machine.
• Transfer time: Move conditioned Charpy specimens from the bath to the anvils within 5 seconds (ASTM E23).

Machine force verification follows ASTM E4; extensometer classification follows ASTM E83 (referenced by A370 for yield tracking).

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3. Apparatus — the A370 laboratory set

A370 describes a suite of verification equipment rather than a single instrument:

Role	Requirement summary	Vector equipment
Tension & bend	Servo-hydraulic or electromechanical frame; controlled load or strain rate; meets E4 accuracy	Hydraulic universal testing machine, 100–300 kN UTM
Grips & fixtures	Wedge, hydraulic, or V-jaw systems for round bar, sheet, tube, and rebar without slip	Hydraulic grips, V-jaws, bending fixtures
Strain measurement	Class B1 or B2 extensometer for offset yield; gauge lengths 2 in, 8 in, 50 mm, 200 mm as specified	UTM accessory channels (extensometer-ready frames)
Charpy impact	Pendulum machine with rigid anvils; verified energy scale; optional sub-zero bath	Robo Charpy system, pendulum impact tester
Hardness	Brinell (E10), Rockwell (E18), or approved portable methods	See ASTM E18, ISO 6506-1, ISO 6508-1 summaries

3.1 Universal testing machine

• Force indication shall meet ASTM E4 within ±1 % over the verified range used for acceptance.
• For rebar and heavy structural products, high-capacity wedge or hydraulic grips are required to prevent jaw slip above 200 kN class loads.
• Bend and guided-bend programmes use compression platens or dedicated bending fixtures on the same frame.

3.2 Extensometers

• 0.2 % offset yield and 0.5 % extension-under-load methods require a verified extensometer on the gauge length.
• Ribbed reinforcing bar surfaces demand rugged clip-on or side-mount extensometers that maintain contact through yield and early necking.

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4. Tension test procedure

Detailed execution is in ASTM E8/E8M; A370 adds product-form sampling and reporting rules.

1. Preparation: Measure initial cross-section A_0 and mark gauge length L_0 (punch or scribe per product annex).
2. Mounting: Align the specimen axially; eliminate bending moments; attach extensometer when offset yield is required.
3. Loading: Apply tensile load at a controlled rate — during yield determination, do not exceed 0.05 in/min per in of gauge length (customary) or the SI equivalent stated in the product specification.
4. Fracture: Record maximum force; fit broken ends together and measure final gauge length L_u and minimum neck area where reduction of area is required.

Annexes cover tubular products, wire, multi-wire strand, and reinforcing bars (sampling location, full-section vs machined specimens).

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5. Bend and ductility tests

Section 15 and product annexes reference bend and guided-bend programmes (ASTM E290 and E190 are normative references in A370-24a). Specimens are bent around a mandrel of specified diameter until a defined angle or until fracture, per the governing product specification.

For reinforcement steel, re-bend tests after initial bending may be required — fixture capacity and grip opening must accommodate the bent geometry.

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6. Hardness testing

A370 Sections 16–19 organize Brinell (ASTM E10), Rockwell (ASTM E18), and portable hardness methods for mill verification and dispute resolution. Indentation location (surface, mid-thickness, weld HAZ) is defined in the product specification and annex.

International laboratories often run parallel programmes to ISO 6506-1 (Brinell) and ISO 6508-1 (Rockwell) while reporting to ASTM-oriented customers.

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7. Charpy V-notch impact testing

Charpy procedures follow ASTM E23 (ISO counterpart: ISO 148-1).

• Full-size specimen: 10 × 10 × 55 mm with 45° V-notch, 2 mm deep, 0.25 mm root radius (tolerances per E23).
• Sub-size: Widths 7.5 mm, 5 mm, 2.5 mm when product thickness limits full-size bars.
• Reporting: Absorbed energy (J or ft·lbf), percent shear fracture appearance, and lateral expansion where specified.

A370 Annex on significance of notched-bar impact testing explains how energy and appearance criteria relate to product acceptance.

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8. Calculations and test validity

Tensile strength:

R_m = P_max / A_0

0.2 % offset yield:

R_p0.2 = P_0.2% / A_0

Draw a line parallel to the linear-elastic portion of the stress–strain curve, offset by 0.002 strain (0.2 %). The intersection defines P_0.2%.

Use the tensile stress–strain calculator for training checks only; binding acceptance remains A370, E8, and your accredited quality system.

Invalid tests: Discard results if fracture occurs outside gauge marks, obvious casting or lamination defects dominate, or grip slip occurs during the recording interval.

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9. Relation to ISO standards and procurement

Topic	ASTM A370 context	International overlap
Metal tension	Sections 7–14 + E8	ISO 6892-1
Charpy impact	Sections 20–30 + E23	ISO 148-1
Machine accuracy	E4 reference	ISO 7500-1
Rebar programmes	Annex — reinforcing bars	ASTM A615/A615M, ISO 15630-1 (when specified internationally)
Structural bar specs	Often paired with A370 tension	ASTM A615 (product specification)

When a tender lists both ASTM A370 and ISO 6892-1, the same calibrated UTM and grip set can often satisfy both after method-template and reporting-format adjustments.

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10. Practical laboratory notes

1. Rebar grips: Flat serrated jaws slip on ribbed reinforcing bar — use V-notched or hydraulic wedge systems designed for round bar (hydraulic grips, V-jaws).
2. Notch quality: Charpy energy is sensitive to notch root radius (0.25 ± 0.025 mm). Verify broach or machining profile periodically.
3. Alignment: Small crosshead misalignment introduces bending stress and can lower apparent yield and distort elongation — check grip symmetry and load-string alignment per E8.
4. Annex selection: Tubular, wire, strand, and rebar annexes change specimen location and geometry — confirm the correct annex before cutting material.

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This document is a comprehensive summary of ASTM A370-24a. For official use, obtain the current standard from ASTM International.