GB/T 36915-2019Steel wire and wire products - General test methods (English PDF)

3.1 General requirements

The tensile test shall be carried out in accordance with GB/T 228.1. Determine

the mechanical properties such as tensile strength, yield strength, elongation,

percentage reduction of area, modulus of elasticity of the steel wire.

3.2 Preparation of specimens

The sample can be made according to GB/T 2975. Generally, the full section is

used, that is, the part where the steel wire is not machined. When the specimen

is straightened, damage should be avoided.

3.3 Cross-sectional area of specimen

In the calculation, the cross-sectional area uses the nominal size. When

specified in the relevant product standard, it shall be implemented in

accordance with the relevant standards.

For profiled steel wire, the cross-sectional area of the specimen may be

calculated with reference to formula (1):

Where:

A - Cross-sectional area of specimen, in square millimeters (mm2);

m - Mass of specimen, in grams(g);

rho - Density of specimen, in grams per cubic centimeter (g/cm3);

L - Length of specimen, in millimeters (mm).

3.4 Clamping method

In order to avoid the steel wire from breaking in the clamping zone, when the

diameter of the specimen is small (generally not more than 1 mm), it is

recommended to wrap the both ends of the steel wire around the round bar or

disc, then fix it.

3.5 Knotting tensile test

Make a single knot in the middle of the steel wire specimen. Perform a knotting

tensile test in accordance with GB/T 228.1.

3.6 Test of elastic modulus

When required by the product standard, it shall use the extensometer to

determine the elastic modulus (E) of the steel wire.

In the force-elongation curve, use the slope of the straight-line segment of 0.2

Fm ~ 0.7 Fm by the nominal cross-sectional area of the specimen to determine

elastic modulus (E). The slope may be obtained by linear regression of the

measured data or by the best-fit visual method. When determining the elastic

Table 1 -- Evaluation of fractures in torsion test

Type of fracture No. of type Appearance Descriptions of fracture characteristics

Fracture

plane

Normal torsional

fracture

1a

1b

Smooth fracture plane:

- Fracture plane is perpendicular (or slightly

inclined) to the axis of wire rod

- No crack on the fracture plane

Fragile fracture plane:

- Fracture plane is about 45° to the axis of

wire rod

- No crack on the fracture plane

Local crack fracture

or irregular fracture

(material has

defect)

2a

2b

Smooth fracture plane:

- Fracture plane is perpendicular to the axis

of wire rod and has local cracks

Stepped fracture plane:

- Local fracture plane is smooth and has local

crack

2c

Irregular fracture plane:

- No crack on the fracture plane

Spiral crack fracture

(spiral crack on the

full length or most of

the length of the

specimen)

It produces obvious

naked-eye-visible

cracks after less

torsions (3 times ~ 5

times)

3a

3b

3c

Smooth fracture plane: - Fracture plane is

perpendicular to the axis of wire rod. There is

local or whole-cross-section-penetrated crack

on the fracture plane

Stepped fracture plane: - Some fracture

planes are smooth. It has local or whole-

cross-section-penetrated cracks

Fragile fracture plane: - Fracture plane is

about 45° to the axis of the wire rod. It has

local or whole-cross-section-penetrated

cracks

OR

Irregular fracture plane: - It has local or whole-

cross-section-penetrated cracks on the

fracture plane

4.2 Two-way torsion test

The two-way torsion test shall be carried out in accordance with GB/T 239.2.

This test is used to test the surface defects of steel wire. It may also be used to

evaluate the ductility.

5.1 One-way bending test

or

or

or

Appendix B

(Informative)

Technical differences between this standard and ISO 22034-1:2007 and

their causes

Table B.1 gives the technical differences between this standard and ISO 22034-

1:2007 and their causes.

Table B.1 -- Technical differences between this standard and ISO 22034-

1:2007 and their causes

Clause number

of this standard Technical differences Causes

With regard to the normative references, it has made

technical adjustments in this part. The adjustments are

mainly reflected in clause 2 "Normative references". The

specific adjustments are as follows:

- Use GB/T 2975 to replace ISO 377;

- Use GB/T 2103 to replace ISO 404;

- Use GB/T 6394 to replace ISO 643;

- Use GB/T 224 to replace ISO 3887;

- Use GB/T 10561 to replace ISO 4967;

- Hardness test adopts GB/T 230.1, GB/T 231.1, GB/T

4340.1 instead of ISO 6508-1, ISO 6506-1, ISO 6507-1;

- Use GB/T 228.1 to replace ISO 6892;

- Use GB/T 239.1 to replace ISO 7800;

- Use GB/T 238 to replace ISO 7801;

- Use GB/T 2976 to replace ISO 7802;

- Use GB/T 239.2 to replace ISO 9649;

- The chemical composition is determined according to

relevant national standards or industry standards; it does

not use ISO/TR 9769;

- For segregation test, use YB/T 4413 to replace ISO

16120-1;

- Add GB/T 232, GB/T 1839, GB/T 2972, GB/T 4337,

GB/T 13298, GB/T 21839

3.1 In the tensile test, add the descriptions on the specific inspection items

Established according to the

actual inspection conditions

of domestic products

3.3

In the tensile test, modify the calculation method of cross-

sectional area, add the calculation method of cross-

sectional area of profiled steel wire

To facilitate the actual

inspection of products

......