ISO 6934-3 Mechanical Test for Quenched and Tempered Steel Wire

Information on the most widely used ASTM standards within the materials testing industry

Descriptions of the most prominent lSO standards within the materials testing industry

Standards including EN, DIN, JlS, and more

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ISO 6934-3 — Steel for the Prestressing of Concrete — Part 3: Quenched and Tempered Wire

ISO 6934-3 specifically targets quenched and tempered high-tensile steel wires used in prestressed concrete structures, test include Tensile / Strength & Ductility, Reverse Bend, Bend, Relaxation, Fatigue. The wire covered is round, available in plain, ribbed, grooved or indented surfaces, and delivered in coils.

Series Standards (ISO 6934 Family)

ISO 6934-1:1991: General requirements (umbrella standard, defines universal definitions, manufacturing rules, basic acceptance criteria for all parts of the series; all test rules in Part 3 are based on this document).

ISO 6934-2: Cold-drawn prestressing wire.

ISO 6934-4: Prestressing steel strand.

ISO 6934-5: Hot-rolled prestressing steel bars

ISO 6934-3 Mechanical Test for Quenched and Tempered Steel Wire

Mechanical Tests Stipulated in ISO 6934-3 — The Complete List

Tensile / Strength & Ductility	tensile strength, 0.1% / 0.2% proof stress, total elongation	ISO 6892 (now ISO 6892-1) via ISO 6934-1
Reverse Bend	d ≤ 10 mm, Reverse bend test	ISO 7801:1984
Bend	d > 10 mm, simple bend test	ISO 10065:1990
Relaxation	1000-hour stress relaxation test (core long-term performance test)	Isothermal, 20°C, 1000 h— method ref. via ISO 6934-1
Fatigue	performed only when requested by purchasers	ISO 1099 framework (via ISO 6934-1 Annex A)

Test stipulated in the ISO 6934-3 details introduction:

1, Tension Test (Mechanical Strength)	Determines the basic Strength, Proof Stress, Elongation
Test Purpose	Measure nominal tensile strength, 0.1% proof stress (mandatory), 0.2% proof stress (for information), and total elongation at maximum force A_gt. These are the fundamental static mechanical indicators of the wire.
Test Sample Information	Wire diameter range: Nominal diameter from 6.0 mm to 16.0 mm (standard covered range). Specimen length: Sufficient length to meet the requirements of a universal tensile testing machine (gauge length follows general tensile test conventions for steel wire).
Test Equipment	Universal testing machine (UTM); Electronic Universal Testing Machine; Extensometer (Used to measure small strain for calculating 0.1% and 0.2% proof stress);
Key Test Stipulations	Stress calculation: Tensile strength and proof stress are calculated by dividing the measured force by the nominal cross-sectional area (actual area measurement is not required). Proof stress definition: The 0.1% proof stress is a mandatory acceptance index; the 0.2% proof stress is only for reference. Characteristic 0.1% proof stress is approximately 88% of nominal tensile strength, and 0.2% proof stress is approximately 90% of nominal tensile strength. Fracture requirement: All specimens must present a ductile fracture with visible necking to the naked eye; brittle fracture is unqualified.
2, Bend Test	Evaluate the bending resistance of large-diameter wires. (for wire nominal diameter ＞ 10 mm)
Test Sample	Straight wire segment cut from finished coil, original surface retained, no pre-damage.
Test Equipment	UnitedTest Universal testing machine (UTM) with bending fixtures. Or Bending testing machine with mandrel + supports; may use apparatus per ISO 10065.
Test Procedure	Place the wire on the specified mandrel. Apply force to bend the wire to 160°–180° at a uniform speed. Visually inspect the entire surface. Acceptance criterion: No visible cracks after bending.
Key Stipulations	Mandrel diameter = 10 times the nominal wire diameter (fixed requirement). Bending angle: Bend the wire to 160° ~ 180°. All wires must not crack after the corresponding bend test; cracking indicates unqualified ductility and potential construction fracture risks.
3, Reverse Bend Test	Evaluate the bending resistance of large-diameter wires. (for wire nominal diameter ≤ 10 mm)
Test Sample	Straight wire segment cut from finished coil, original surface retained, no pre-damage.
Test Equipment	Reverse bend testing machine (compliant with ISO 7801), UnitedTest standard bending mandrel.
Test Procedure	Mandrel and fixture dimensions follow ISO 7801. Repeatedly perform reverse bending on the specimen. Acceptance criterion: Withstand 4 reverse bends without visible cracks on the surface.
4, Tensile Stress Relaxation Test	1000-Hour Tensile Stress Relaxation Test (Core Mandatory Test); Measure the stress attenuation rate of the wire under constant tensile strain for 1000 hours, and classify the wire into different relaxation grades.
Test Sample	Straight wire specimen with complete original surface; no machining damage. Specimen length adapts to relaxation testing machine requirements (refer to ISO 3384 or EN 10319-1 for specimen size). Sampling: Randomly select samples from finished product coils.
Test Equipment	UnitedTest Tensile stress relaxation testing machine: Capable of maintaining constant strain for a long time (1000 h), with high-precision force and strain recording systems. Temperature control device: Keep test temperature stable (generally room temperature for conventional tests). Extensometer: Monitor and control constant total strain.
Test Procedure	Install the wire specimen on the relaxation machine and complete axial alignment. Apply tensile load to reach the specified initial stress (60% /70% /80% of nominal tensile strength). Switch to constant strain control mode to keep total strain unchanged. Continuously or periodically record residual stress and time for 1000 consecutive hours. Calculate the final stress relaxation rate. Classify the wire as Relax 1 or Relax 2 according to the test result.
Core Test Stipulations	Standard test condition: Test duration = 1000 hours; initial stress is set to 70% of the wire’s nominal tensile strength (basic test condition). Optional test conditions (on purchaser’s request): Additional tests at initial stress of 60% and 80% of nominal tensile strength are allowed.
5, Axial Force Fatigue Test	(On-Demand Test, Not Mandatory), evaluate the wire’s resistance to cyclic alternating stress in dynamic load environments (e.g., railway bridges, viaducts)ISO
Key Test Stipulations	Maximum cyclic stress: 70% of the wire’s nominal tensile strength. Stress range: Plain wire: 200 N/mm² Ribbed, grooved or indented wire: 180 N/mm² Fatigue life requirement: Withstand 2 × 10⁶ load cycles without fracture
Test Sample	Straight wire specimen with original surface; ribbed/grooved/indented wires are tested according to actual service conditions.
Test Equipment	UnitedTest High-frequency fatigue testing machine (tensile cyclic loading type), with accurate stress amplitude and cycle counting functions.
Test Procedure	Clamp the specimen on the fatigue testing machine. Set parameters: maximum stress, stress range and loading frequency. Start cyclic loading and automatically record the number of cycles. Stop the test after reaching 2×10⁶ cycles. Inspect the specimen: No fracture = pass; fracture = fail.

Additional Supplementary Inspection:

1, Coil Curvature Test

Requirement: When a 1 m-long wire is placed on a flat surface, the maximum bow height shall not exceed 30 mm. Excessive curvature affects clamping and alignment in mechanical tests.

2, Surface & Dimensional Inspection

Surface: Allowed to have a thin layer of scale; no severe scratches, cracks or corrosion.

Rib/groove/indent dimensions: Follow the dimensional tables in Annex A of ISO 6934-3 to ensure bonding performance with concrete.

Application Industry & Usage Scenarios

Core Industry

The primary application is civil engineering and prestressed concrete construction, which is the dominant field for this standard.

Typical Engineering & Products

Building Structures: High-rise buildings, large-span floor slabs, and framed structures using prestressed concrete.

Bridge Engineering: Highway bridges, railway bridges, viaducts (prestressed wires resist long-term structural tension and deflection).

Hydraulic Engineering: Dams, water tanks, and large concrete pipelines.

Special Civil Structures: Silos, stadium stands, and underground tunnel linings.

Function of the Wire

Quenched and tempered prestressing wires apply pre-compression to concrete to offset tensile stress generated by external loads. Ribbed, grooved or indented surface designs enhance bonding force between wire and concrete to prevent slippageISO. This standard ensures the wire maintains stable mechanical performance during decades of service.

Related Test Standard:

ASTM E328	Standard Test Methods for Stress Relaxation for Materials and Structures
EN 10319-1	Metallic materials. Tensile stress relaxation testing. Procedure for testing machines
ISO 6892-1	Tensile test method (Rm, proof stress, elongation)
ISO 7801	Metallic materials — Wire — Reverse bend test (for ductility evaluation of small-diameter wires).
ISO 10065	Steel bars for reinforcement of concrete — Bend and rebend tests (for bend tests of large-diameter wires).
ASTM A416	Standard Specification for Low-Relaxation, Seven-Wire Steel Strand for Prestressed Concrete
ASTM A1061	Standard Test Methods for Testing Multi-Wire Steel Prestressing Strand
EN 10138-3	Prestressing steels. - Part 3: Bars
XP A 35-045	PRESTRESSING STEELS - PART 1: GENERAL REQUIREMENTS
ISO 6934-4	Steel for the prestressing of concrete - Part 4: Strand
GBT 21839	Test methods of steel for prestressing concrete
GB/T 5224	Steel strand for prestressed concrete
JIS G 3536	Steel wires and strands for prestressed concrete
BS 5896	High tensile steel wire and strand for the prestressing of concrete. Specification
ISO 15630-3	Steel for the reinforcement and prestressing of concrete. Test methods - Part 3: Prestressing steel
AS/NZS 4672.2	Steel prestressing materials - Testing requirements
EN 10138-3	Prestressing steels - Part 3. Bars

Computer controlled steel strand tensile stress relaxation testing machine mainly used to check the prestressing steel material relaxation performance. This machine is use mechanical mode loading, computer control to complete the test. PC with control card to realize real time data collection.

High temperature furnace chamber for tensile testing machine, furnace have a columnar split structure, three stage control function. Mainly consists of furnace, temperature controller, high temperature pull rod, high temperature clamp, high temperature extensometer and supporting device.

Steel Strand Extensometer is a high-precision electronic instrument specifically designed for measuring the deformation (strain) of steel strands, prestressed tendons, and similar elongated specimens during tensile tests.

The Hydraulic universal testing machine can perform tension, compression, flexure/bending and shearing test for kinds of specimens. Suitable for metal and nonmetal material, such as iron, steel, steel bar, rebar, cement, concrete, rod and so on. Specially design for production, research, student training and industrial laboratory. Available in wide range of loadframe capacities (300kN to 2000kN)/(10Ton to 200Ton) and with combination of control panels (Digital, Computerized) makes United Test product range suitable for every customer requirement.

JWJ series metallic materials wire reverse bend testing machine manly used to measure metal wire material, like steel wire, steel bar, steel wire rope, steel strand, nude electrical wire, copper alloy wire etc., rotate the provision radius jaws ±90 degree repeat the reverse bending test; standard machine for 3-10mm (15mm) diameter wire samples, add suitable device, can do 0.3 to 3mm wire.

UnitedTest Fatigue Testing Machine mainly used at a variety of material and components, parts for both dynamic and static mechanical property testing, include tension, compression, low cycling test, match with high-low temperature chamber can execute the temperature test.

Metal Bending & Rebending Testing Machine is used for bending tests of metal materials such as rods, sheets and rebar for construction, and is loaded with two-way hydraulic cylinders, adjusting the roll spacing by hand wheels and being able to lock itself.

Metal bending test fixture used measure the ductility of metallic materials, bent the test specimen to a predetermined angle or until the specimen fractures. Conform with ASTM E290, ISO 7438, and JIS Z2248 standard.

Q1: What is ISO 6934-3, and what product does it regulate?

A: ISO 6934-3:1991 is an international standard under the ISO 6934 series for steels used in prestressed concrete. It specifically specifies technical requirements, manufacturing rules, delivery conditions and all test methods for quenched and tempered high-tensile steel wire. The wire is round, supplied in coils, and available with plain, ribbed, grooved or indented surfaces to improve bonding with concrete.

Q2: What is the position of ISO 6934-3 in the entire ISO 6934 series?

A: The ISO 6934 series has five parts for different prestressing steel products:

ISO 6934-1: General requirements (umbrella standard for all parts)

ISO 6934-2: Cold-drawn prestressing wire

ISO 6934-3: Quenched and tempered wire (this standard)

ISO 6934-4: Prestressing steel strand

ISO 6934-5: Hot-rolled prestressing steel bars

All test rules and property limits in ISO 6934-3 must comply with the general provisions of ISO 6934-1.

Q3: Which industries and engineering projects mainly use this wire and standard?

A: It is exclusively applied to prestressed concrete engineering, including high-rise buildings, highway/railway bridges, dams, water tanks, silos, stadiums and tunnel linings. The wire provides long-term pre-compression for concrete to resist tensile stress and structural deformation.

Q4: Why are ribbed, grooved or indented surfaces designed for the wire?

A: These special surface patterns greatly enhance the bond strength between steel wire and concrete, preventing relative slippage. Plain wire is only used for general structures, while patterned wire is preferred for critical projects with high anti-slip requirements.

Q5: Why is ISO 6934-3 essential for engineering and material quality control?

A:It ensures the long-term safety of prestressed concrete structures; unqualified wire will cause prestress loss, concrete cracking or structural collapse.

It unifies global test methods and performance indicators, supporting cross-border trade and consistent laboratory test results.

It classifies wires into different relaxation and ductility grades, enabling engineers to select suitable products for different service environments.

It acts as the mandatory acceptance basis for manufacturers, third-party inspectors and project supervisors during production and delivery.

Q6: What mechanical tests are stipulated in ISO 6934-3? Which are mandatory?

A: Four mechanical tests are defined:

Tensile property test (mandatory): Tensile strength, 0.1% proof stress, 0.2% proof stress and total elongation.

Bend/Reverse bend ductility test (mandatory): Evaluates anti-cracking performance under bending.

1000-hour stress relaxation test (mandatory): Assesses long-term stress loss.

Fatigue test (optional): Only conducted when requested by the purchaser for dynamic load scenarios.

Q7: What are the test conditions and classification rules for the 1000-hour stress relaxation test?

A: Standard test condition: Initial stress = 70% of nominal tensile strength, test duration = 1000 hours.

Optional conditions (purchaser’s request): Initial stress at 60% and 80% of nominal tensile strength.

Two relaxation classes based on maximum allowable relaxation rate:

Initial Stress	Relax 1 (Max Relaxation)	Relax 2 (Max Relaxation)
60%	2.0%	1.0%
70%	4.0%	2.0%
80%	9.0%	4.5%

Relax 2 is low-relaxation wire for key structures; Relax 1 is for general engineering.

Q8: What referenced standards must be followed during testing?

A:Mandatory normative references:

ISO 6934-1: General requirements for prestressing steel (basic rules)

ISO 7801: Wire reverse bend test method

ISO 10065: Steel bend and rebend test method

Commonly referenced test standards (for relaxation tests): ISO 3384, EN 10319-1, ASTM E328 (general stress relaxation test methods)

Q9: Can I use actual cross-sectional area to calculate tensile stress?

A: No. The standard clearly stipulates that tensile strength and proof stress shall be calculated using the nominal cross-sectional area, which is a unified rule for all inspection and acceptance work.

Q10: What will happen if the 1000-hour relaxation test result exceeds the limit?

A: Excessive stress relaxation means severe prestress loss. Such wire cannot be used for prestressed concrete structures, as it will lead to insufficient concrete pre-compression, cracking and even structural safety hazards.

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