Information on the most widely used ASTM standards within the materials testing industry
Steel Wire Testing
Steel wire testing is the core means to evaluate the mechanical properties, toughness and surface quality of steel wires, and the core items include repeated torsion, repeated bending, winding tests, etc., to verify the reliability of steel wires by simulating actual use conditions, following international/domestic unified standards, and widely used in the whole industry chain of metal products.
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Introduction about the Steel Wire Testing
As a key structural material, steel wire often endures complex stresses such as torsion, bending, and winding in use. The core purpose of this type of testing is to:
Check the plasticity, toughness and fatigue resistance of the steel wire to avoid failure due to deformation or fracture during use;
Evaluate the surface quality of the wire (e.g., cracks, decarburization layers) and internal uniformity (e.g., compositional segregation, inclusions);
Verify the stability of production processes (e.g., drawing, heat treatment) to ensure batch consistency.
The core test items are mainly destructive tests, and the results are intuitive and highly related to actual use performance, which is a mandatory test item for steel wire factory inspection and raw material factory verification.
The standard clarifies the test equipment, sample requirements, operating procedures, and result determination to ensure the accuracy and comparability of test data:
| Test items | ISO standards | ASTM standard | Chinese GB standard | Scope of application |
| Repeated torsion test | ISO 7800:2015 | ASTM A370-23 (General Principles) | GB/T 239.1-2012 | Metal wire rods (steel wire, copper wire, etc.) |
| Repeated bending tests | ISO 7801:2015 | ASTM E290-23 | GB/T 239.2-2012 | Metal wire and thin tape |
| Winding test | ISO 8491:2017 | ASTM A475-17 | GB/T 239.3-2012 | wire and wire rope |
| Comprehensive mechanics test | ISO 15630 (General Principles of Steel Wire) | ASTM A901-21 | GB/T 3083-2014 | All kinds of industrial steel wires |
Repeat torsion test
Definition: A test method that evaluates the resistance to torsional fatigue and plastic deformation of a steel wire by alternating forward and negative twists until it breaks or reaches a specified number of twists.
Test principle: Simulate the scenario where the steel wire is subjected to repeated torsional stress in practical applications (such as wire rope twisting, mechanical transmission wire), and the internal stress of the steel wire gradually accumulates during the torsion process until it breaks, and the performance is judged by the number of twists or the fracture form.
Key Test Steps::
Select steel wire samples without surface defects, and the length meets the standard requirements (usually 100-500mm, adjusted according to the diameter of the steel wire);
One end of the sample is fixed, and the other end is clamped on a rotatable fixture to ensure that the sample axis coincides with the torsional axis.
Set the torsion speed (generally 30-60 rpm) and the torsion direction (forward and negative alternate, each torsion angle can be fixed or continuous);
Start the test until the sample breaks, recording the total number of torsions at the time of fracture; If it is not broken, record the surface condition for the specified number of times.
Repeated bending test
Definition: The steel wire is repeatedly bent 180° alternately around the center of the specified diameter until it breaks, and its bending fatigue resistance is evaluated by the number of bends and the fracture morphology.
Test principle: Simulate the working conditions of repeated bending of steel wire in assembly and use (such as automobile brake lines, elevator wire ropes), when bending, the surface of the steel wire is tensile, internal pressure is affected, and fatigue cracks are easy to occur after repeated cycles, and finally break.
Key Test Steps::
1. Select a straight sample, and the length is adjusted according to the diameter of the bend center and the test equipment (usually 150-300mm);
2. Adjust the diameter of the bend center (generally 1-10 times the diameter of the wire, as specified by the standard or product requirements);
3. Fix the bend center, clamp one end of the sample so that the sample is close to the bend center, and bend it 180° alternately in clockwise and counterclockwise directions;
4. Each bend is recorded as a cycle until the sample breaks, and the total number of bends is recorded; If it is not broken, record the crack situation under the specified number of times.
Winding unwinding test
Definition: Tightly wrap the steel wire on a mandrel of the specified diameter, check whether there are cracks, peeling, fractures and other defects on the surface of the steel wire after winding, and evaluate its flexibility and surface quality.
Test principle: Simulate the winding conditions of steel wire when processing into coils, springs, wire ropes and other products, and test the surface integrity and internal toughness of steel wire in the process of plastic deformation.
Key Test Steps:
1. Samples without significant bending are selected and long enough to complete at least 2 loops (typically ≥ mandrel circumference ×3);
2. Choose a mandrel that meets the standard (mandrel diameter is 1-20 times the diameter of the wire, adjusted according to the hardness of the material);
3. Fix the mandrel, fix one end of the steel wire on the mandrel, and wrap it tightly at a uniform speed (no gaps);
4. After winding to the specified number of turns (generally 2-10 turns), use a magnifying glass to observe whether the surface has cracks, peeling off or other defects to determine whether it is qualified.
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