Steel products are widely used in construction for their high strength, durability, and versatility. To thoroughly ensure mechanical performance across many possible forms and intended applications, steel products must be tested by a few different test methods, all outlined in ASTM A370.
In this guide, we provide an overview of everything included in ASTM A370:
- Types of materials & forms covered by ASTM A370
- Test methods included in ASTM A370
- Tension testing: Recommended equipment, test procedure & variants
- Bend testing: Recommended equipment, test procedure & variants
- Hardness testing: Recommended equipment, test procedure & variants
- Impact testing: Recommended equipment & test procedure
Types of Materials & Forms Covered by ASTM A370
ASTM A370 defines and explains test methods for a variety of steels, stainless steels and related alloys. The standard also includes annexes that provide details specific to different products:
- Steel Bar Products
- Steel Tubular Products
- Steel Fasteners
- Round Wire Products
Test Methods Included in ASTM A370
ASTM A370 covers six different methods: tension, bend, impact, and three different types of hardness tests. It also references additional test variations and conditions, depending on the material type and intended application.
Tension Testing
To measure the tensile strength of steel products, the tension test applies force to the material gripped at one end while the other end is fixed. This effectively measures the material’s ability to resist forces that attempt to pull it apart, evaluating properties including:
- Yield Strength: The stress at which a material begins to deform plastically.
- Ultimate Tensile Strength: The maximum stress a material can withstand before breaking.
- Elongation: The percentage increase in length of a specimen before fracture, indicating ductility.
- Reduction of Area: The decrease in cross-sectional area after fracture, another measure of ductility.
Bend Testing
Bend testing evaluates the ductility of steel products by applying force to bend a specimen without fracturing. ASTM A370 cites E190 and E290 for the standard methods of performing a bend test.
Hardness Testing
Hardness testing determines a material’s resistance to penetration and can approximate tensile strength. ASTM A370 provides an overview of three different hardness scales:
- Brinell Hardness Test: Uses a ball indenter to evaluate a material’s resistance to indentation.
- Rockwell Hardness Test: Determines hardness based on the depth of penetration of an indenter under a specified load.
- Portable Impact Hardness Test: A field test method for assessing material hardness using portable equipment, if the fixed-location Brinell or Rockwell hardness test methods aren’t possible do perform due to part size, location, or other logistical reasons.
Impact Testing
A Charpy V-notch impact test evaluates a notched specimen’s toughness by striking and breaking it with a single blow. The test measures values including:
- Energy absorbed
- Percentage of shear fracture
- The lateral expansion opposite the notch
In the rest of this guide, we will review the recommended equipment and test procedure for each of the main types of tests covered in the comprehensive standard, including some of the variants.
ASTM A370: Tension Test
Recommended Equipment
A caliper to measure specimen dimensions: width and thickness for rectangular specimens, or diameter for round specimens. This is used to determine the cross-sectional area, which is essential for calculating stress.
A center punch, scribe marks, multiple device, or ink to gauge mark specimens, in order to determine the percent elongation. Or, an extensometer that can measure both strain and elongation.
A universal test machine that tests in tension by applying an axial force. Because of the variety of steel product forms included in ASTM A370, the test machine must be suitable for a range of load capacities. It should also include accessories for different test specimens, including grips for rebar/round tensile and flat tensile specimens, a bolt test set for threaded fasteners, and wire grips for strand cable/wire.
Forney’s Universal (tension) Testing Machine is specifically designed for testing a variety of materials in tension, compression and flexure – including cementitious and metallic materials like briquettes, cubes, cylinders, rebar, rebar with joints or T-Caps, and bolts, as well as other non-cementitious and non-metallic materials. Universal Testing Machines measure Force, Displacement, Velocity and Strain.
Tension Test Procedure
ASTM E8 gives the general test methods for tension testing, but ASTM A370 covers exceptions for steel testing. Here’s an overview of the process:
- Select test coupons in accordance with product specifications.
- Prepare and age specimens if applicable.
- Measure specimen dimensions and apply gauge marks.
- Secure the specimen in the grips of the testing machine, aligning it axially to minimize bending or twisting.
- Apply the load gradually, ensuring that the load is transmitted axially the entire time.
- Monitor strain and stress values as the test progresses.
- Determine key tensile properties:
- Yield Point: Measure when the material begins to deform permanently. This can be observed by a sudden pointer stop, a drop in the machine’s beam, or using a diagram to find the “knee” in the stress-strain curve.
- Yield Strength: Find where an offset line (e.g., 0.2%) meets the stress-strain curve or measure total strain at a set offset.
- Tensile Strength: Divide the highest load applied by the original cross-sectional area.
- Elongation: Measure the distance between gauge marks after the specimen fractures, and calculate the percentage increase in length.
Tension Test Variants by Product Forms
Steel Bars: Annex A1
- Usually tested lengthwise.
- Small carbon steel bars and most alloy steel bars aren’t typically tested as-rolled.
- Specimens are chosen based on whether bars are hot-rolled or cold-finished.
Steel Tubes: Annex A2
- Tested whole if possible, with metal plugs for gripping.
- If needed, strips can be cut lengthwise, avoiding welds.
- Transverse testing is rare and mostly for larger tubes.
- Special machines exist for testing tube rings.
Steel Fasteners: Annex A3
- Bolts are tested full-size when possible, ensuring they meet strength requirements.
- Tests include proof load (checking for permanent set), axial tension (failure should occur in the body, not the head), and wedge testing (head strength).
- Smaller bolts may need machined tests, and disputes can be settled with hardness testing.
Steel Wire: Annex A4
- Gripped with wedge/snubbing tools and tested at full cross-section.
- A 10-inch gauge length is standard.
- Permanent elongation is measured by fitting fractured ends together.
ASTM A370: Bend Test
Recommended Equipment
- A universal testing machine that performs the bend test with a support fixture that allows for different specimen sizes and types.
- A protractor or digital angle finder to verify the bend angle.
Bend Test Procedure
ASTM E190 and E290 give the standard test methods for bend testing, including guided bend tests, semi-guided bend tests, free bend tests, and bend-and-flatten tests. Here’s an overview of the most common test: the guided-bend test.
- Place the specimen symmetrically on the support fixture so it is supported at both ends.
- Apply force at the center until the specimen fails, a predefined bend angle is reached, or the maximum allowable angle for the fixture is achieved.
- Measure the bend angle by identifying the flat areas on either side of the bend, projecting lines along these flat areas, and determining the angle where those lines intersect.
- Inspect the specimen for cracks or surface irregulates and determine if the material has failed.
In the semi-guided bend test, the specimen is only supported at one end, meaning it is free to bend more. In a free bend test, the specimen is not supported at all—it’s simply held at two points (often at both ends) or suspended without any fixed support during the bending process. Finally, the bend-and-flatten test involves bending the specimen and then flattening it out again to check for any signs of failure or cracks that may have developed during bending.
Bend Test Variants by Product Forms
Steel Bars: Annex A1
- When bend tests are specified, follow Table A1.2 for selecting hot-rolled and cold-finished steel bars.
Steel Tubes: Annex A2
To prove ductility of tubular products, use these tests:
- Flattening Test: Rings from the tube are flattened between parallel plates to a prescribed degree, depending on tube dimensions. Specimens should be at least 2 1/2 inches long and flattened cold.
- Reverse Flattening Test: Used for electric-welded tubing to check for lack of weld penetration or overlaps. A tube section is split and flattened with the weld at the maximum bend point.
- Crush Test: A ring cut from the tube is crushed endwise to a distance specified by the material specifications.
- Flange Test: A ring cut from the tube has a flange turned over at a right angle to the tube’s body to determine the ductility of boiler tubes.
- Flaring Test: A tapered mandrel is driven into a tube section to expand the inside diameter to the extent required by specifications.
- Bend Test: For pipes 2 inches and under, a full-size pipe is bent cold through 90° around a mandrel with a diameter 12 times the pipe’s nominal diameter to determine its ductility and the soundness of weld.
- Transverse Guided Bend Test of Welds: Specimens are machined and bent with different surfaces against a plunger to assess the ductility of fusion welds. Failure depends on the appearance of cracks in the bend area.
Steel Wire: Annex A4
Conduct wrap and coiling tests:
- Wrap Test: Consists of coiling the wire in a closely spaced helix tightly against a mandrel of a specified diameter five times, unless otherwise specified). The wire tested is considered failed if the wire fractures or if any longitudinal or transverse cracks develop that can be seen by the unaided eye after the first complete turn.
- Coiling Test: Determines if imperfections are present to the extent that they may cause cracking or splitting during spring coiling and spring extension by closely winding the coil on an arbor. The closed coil is then stretched to a specified permanent increase in length and examined for uniformity of pitch with no splits or fractures.
ASTM A370: Hardness Test
Recommended Equipment
- Brinell Hardness Test Equipment: A Brinell hardness tester, steel or carbide ball, and measuring microscope to measure indention.
- Rockwell Hardness Test Equipment: A Rockwell hardness tester and diamond or steel ball.
- Portable Impact Hardness Test Equipment: A handheld or benchtop device with a built-in display and probe (striker).
Hardness Test Procedure
Brinell Hardness Test
- Place the specimen on the testing platform as per ASTM E10 requirements.
- Apply a steel or tungsten carbide ball (usually 10mm diameter) with a specified force for a set duration.
- Measure the indentation diameter using a microscope or automated system.
- Calculate the Brinell Hardness Number
Rockwell Hardness Test
- Position the specimen on the Rockwell hardness tester, as stated in ASTM E18.
- Apply a minor load (typically 10 kgf) to seat the indenter.
- Apply the major load (e.g., 60, 100, or 150 kgf) for a specified duration.
- Measure the indentation depth, which determines the Rockwell Hardness Number (HR)
Portable Impact Test
- Position a handheld impact tester on the material surface as per ASTM A956.
- Apply an impact force and measure the rebound velocity to impact velocity.
- Convert the reading to an equivalent hardness scale (Brinell, Rockwell, Vickers, etc.).
Hardness Test Variants by Product Forms
Steel Bars: Annex A1
- Remove a minimum of 0.015 inches to ensure accurate hardness penetration.
Steel Tubes: Annex A2
- Conduct on the outside surface, inside surface, or wall cross-section based on product specification limitations. Surface preparation may be needed for accurate readings.
- For thin-walled tubes, a 500-kgf load should be applied for Brinell tests, or inside stiffening should be used.
- Brinell testing isn’t applicable for tubes under 2 inches in outside diameter or 0.200 inches in wall thickness.
- Rockwell hardness tests are normally made on the inside surface, a flat on the outside surface, or on the wall cross-section depending upon the product limitation.
- Superficial Rockwell hardness tests are normally performed on the outside surface whenever possible and whenever excessive spring back is not encountered.
Steel Fasteners: Annex A3
- When specified, hardness test externally threaded fasteners.
- Tests are conducted on the wrench flats, top of head, unthreaded shank, or end of the bolt.
- For arbitration, hardness may be taken on two transverse sections through a sample fastener (see Fig. A3.6 in the standard).
Steel Wire: Annex A4
- On heat-treated wire of diameter 0.100 in. (2.54 mm) and larger, the specimen should be flattened on two parallel sides by grinding before testing.
- The hardness test is not recommended for any diameter of hard-drawn wire or heat-treated wire less than 0.100 in. (2.54 mm) in diameter.
- For round wire, the tensile strength test is greatly preferred over the hardness test
ASTM A370: Impact Test
Recommended Equipment
A pendulum-style tester with an interchangeable rounded, straight or instrumented striker designed to apply a controlled impact force to a specimen.
Impact Test Procedure
- Prepare notched specimens according to ASTM E23
- Condition the specimen at the required test temperature.
- Position the specimen in the impact testing machine, ensuring the notch faces the impact point.
- Release the pendulum (or drop-weight) to strike the specimen at a controlled energy level.
- Record absorbed energy and fracture behavior to assess toughness.
- Compare results with material standards for compliance.
Conclusion
These ASTM A370 testing methods ensure that steel products meet stringent mechanical property requirements – allowing products to deliver the high strength, durability, and versatility they’re valued for. While this simple guide outlines key test procedures and necessary equipment, please reference the latest ASTM standards for the most up-to-date requirements.
Forney has the machines, accessories, and software necessary for ASTM A370. Shop the Forney store today or find your machine.