Wire rod, also known as wire rod, usually refers to small-diameter
round steel in coils.
The diameter of the wire rod is in the range of 5-19 mm (usually
6-9 mm), and the lower limit is the minimum size of the hot-rolled
steel section.
Chinese name wire rod
Foreign name steel wire rod
Alias wire
Diameter 5-19 mm
High-strength prestressed steel wire is an economical and efficient
steel material with high tensile strength and yield strength, good
plasticity, and low relaxation performance. It is widely used in
the construction of cement products, bridges, nuclear power plants,
high-rise long-span buildings, highways, etc. With the development
of my country's prestressed industry, the production and use of 82B
wire rods as raw materials for the production of high-strength
prestressed steel wires have attracted more and more people's
attention. Qinggang Iron and Steel Co., Ltd. has been producing 82B
wire rods since December 2003. In order to further improve the
quality of 82B wire rods, the central laboratory has specially set
up a technical innovation project group "82B wire rod quality
research" to comprehensively analyze the factors affecting 82B wire
rods. analysis and research.
Organizational requirements editor broadcast
82B wire rod is a hot-rolled wire rod for prestressed steel wire
and steel strand. Its domestic brand is 82MnA. Its chemical
composition is shown in Table 1.
The metallographic structure of the wire rod should mainly be
sorbite, and should not contain martensite, reticular cementite and
structures harmful to performance.
Shape editing broadcast
Wire rod is round steel with a relatively small diameter. The
product form is rolled into a coil and supplied. Common ones on
construction sites are 6, 8, 10, and 12 mm in diameter. They are
mostly made of low carbon steel and are generally not used for the
main bars of reinforced concrete structures. , mostly used to make
steel bar sleeves, and small-diameter ones are used for "brick
reinforcement" in brick-concrete structures.
Category editing broadcast
There are many varieties of wire rod. Among carbon steel wire rods,
low carbon steel wire rods are commonly known as soft wires, while
medium and high carbon steel wire rods are commonly known as hard
wires. Wire rod is mainly used as blank for drawing, and can also
be directly used as building materials and processed into
mechanical parts. Stainless steel wire rod is used to make
stainless steel wire, stainless steel spring steel wire, stainless
steel upset steel wire and stainless steel wire rope. With the
advancement of production technology, square,
Hexagonal, sector-shaped and other special-shaped wire rods; the
upper limit of diameter has been expanded to 38 mm; the plate
weight has increased from the original 40-60 kg to 3,000 kg. Due to
the development of a new post-rolling heat treatment process, the
iron oxide scale on the surface of the wire rod has been
significantly thinned, and the structural properties have also been
greatly improved.
Use Edit Broadcast
Wire rods need to be straightened and cut using a steel bar
straightening machine before use. At the same time, the oxidized
scale is removed in the machine, and the strength is improved to a
certain extent during repeated bending and stretching. For small
construction sites that do not have a straightening machine, it is
not advisable to use a winch to straighten the wire rod. Direct
pulling is not advisable as it may easily cause too much plastic
deformation. A pulley weight should be used at one end to control
the pulling force.
Factor Analysis Editor Broadcast
1. Influence of segregation of components in continuous casting
slabs
(1) Influence of central segregation
On the cross-section of the steel billet sample, use a Ø5.5mm drill
bit to take 4 samples from the edges and the middle, and 1 sample
from the center. Use an infrared carbon and sulfur meter to analyze
the carbon and sulfur content, and use chemical methods to analyze
Silicon, manganese and phosphorus content. The results show that
the maximum mass fraction of carbon in the center is 1. 06%, and
the segregation coefficient of each carbon in the center is 1. 33,
which far exceeds the standard requirements (the center carbon
segregation coefficient of billets for steel cords is ≤ 1. 05). The
degree of elemental segregation is small. The wire rod rolled from
this continuous casting billet is prone to brittle fracture when
the user draws it, and the fracture is cup-cone shaped. A
longitudinal section of the fracture sample revealed that there was
a "V" shaped crack in the center, and the metallographic structure
examination found that there was reticular or semi-reticular
cementite in the center.
Cementite itself is not easily deformed and is distributed in a
network or semi-network at the grain boundaries, which is very
harmful to the quality of the wire rod. The wire rod is prone to
cracks along the grain boundaries during drawing, and may break
brittlely during further drawing. The reason is that there is
central carbon segregation in the continuous casting billet itself.
Although the wire rod structure is in an austenitized state during
rolling and the rolling temperature is high, due to the limited
holding time, the central carbon segregation is difficult to
eliminate, thus destroying the wire rod. The uniform properties of
the matrix structure cause the wire to form a cup-cone-shaped
fracture during the drawing process and break. Central segregation
is a representative defect of continuous cast billets. The solution
is to use large-size rectangular billets for rolling. Because
large-size billets can increase the rolling ratio during rolling
and eliminate the above defects, so it is generally not suitable to
use smaller than rectangular billets. 120mm × 120mm continuous cast
billet, especially the rolled carbon mass fraction is greater than
0. 75% wire rod. In addition, the superheat of molten steel is
strictly controlled, electromagnetic stirring and light reduction
technology during continuous casting are adopted, and the cooling
intensity of the secondary cooling section of continuous casting is
strengthened to reduce central segregation.
(2) Effect of surface carburization
Part of the broken wire sample taken back from the user had a pen
tip-shaped fracture, and there was a series of fish scale cracks on
one side of the sample. According to past experience, it should be
caused by uneven local tissue on the surface. Metallographic
examination of the broken wire samples revealed that massive and
reticular cementite appeared in the structure near the fish scale
cracks.
This is due to improper operation during the continuous casting
process. The graphite carbon in the mold powder enters the mold
with the molten steel, causing local carbonization on the surface
of the continuous casting billet.
2. Influence of non-metallic inclusions
Through the inspection of non-metallic inclusions in 82B wire rod,
it was found that the non-metallic inclusions in 82B wire rod are
generally C and D type inclusions, and there are more type C
inclusions, up to C4.5e, and type D inclusions are generally 1 to 1
.Level 5. The maximum width of the observed inclusions is 30 μm,
which far exceeds the standard requirements (the standard requires
Class C ≤ 1, Class D ≤ 0. 5). Non-metallic inclusions exist in wire
rods, which mainly cause the following hazards to subsequent
processing of wire rods:
(1) When drawing and twisting deformation, the continuity of the
steel wire matrix is destroyed, causing stress concentration. Once
subjected to the action of tensile stress or shear stress, cracks
will occur along the direction of the inclusions, making the steel
wire easy to break during drawing and twisting. , and the fracture
is irregular;
(2) Non-metallic inclusions reduce the mechanical properties of the
steel wire, especially its transverse mechanical properties, which
reduces the plasticity of the steel wire, makes it easy to break
under high deformation, and reduces the bending and torsion values.
Non-metallic inclusions become the source of fatigue fracture of
the steel wire, causing The fatigue resistance limit of steel wire
is reduced;
(3) During the heat treatment of the steel wire, due to the
difference in the expansion coefficient of the non-metallic
inclusions and the steel wire matrix, the continuity of the steel
wire matrix is cut within the steel wire, acting as a local gap,
causing micro cracks to form during the heat treatment of the steel
wire. As the drawing continues, During twisting, microcracks expand
and cause the wire to break.
3. Effect of gas content
Through oxygen and nitrogen analysis of 82B wire rod, it was found
that the mass fraction of oxygen in the wire rod is (55 ~ 85)
×10-6, with an average of 68. 42 ×10-6, and the mass fraction of
nitrogen is (50 ~ 60) ×10- 6 , with an average of 54. 09 ×10- 6 ,
far higher than the standard requirements (wO ≤25 ×10- 6 , wN ≤30
×10-6 ). Excessive nitrogen content in steel will cause the
deterioration of the steel. Nitrogen can increase the effective
hardening of the steel, increase the strength and hardness of the
steel, and significantly reduce the plasticity, impact resistance
and toughness. Oxygen in steel can also have adverse effects on the
mechanical properties of steel. The degree of influence is related
to the concentration of oxygen and the type, distribution and
amount of oxygen-containing inclusions. Hydrogen in steel is
extremely harmful. As the hydrogen content in steel increases, the
plasticity and toughness decrease significantly. Especially for
high carbon steel such as 82B, this phenomenon is more serious
during the processing and cooling process.
4. Influence of rolling process
Since the rolling of high-wire wire rods is completed in a
prescribed pass system, the deformation conditions are basically
fixed, and the deformation parameters of each pass have been
determined. In actual production, it is mainly through the control
of the rolling temperature, that is, temperature-controlled
rolling. To achieve this. The main purpose of
temperature-controlled rolling is to refine grains: through
low-temperature opening rolling, the size of the original austenite
grains can be controlled; by lowering the final rolling
temperature, the formation of austenite grains can be prevented
from growing; by finishing rolling The rapid water cooling of the
wire after reaching the set spinning temperature not only quickly
transforms the deformed austenite into supercooled austenite, fully
preparing for the structural transformation, but also controls the
supercooled austenite grains. size. However, it should be noted
that due to the load limitation of the rolling mill equipment, the
rolling temperature cannot be too low, otherwise the equipment is
prone to accidents. In addition, if the opening rolling temperature
is controlled too low, it will easily lead to uneven heating of the
billet, uneven austenitization, insufficient dissolution of
carbides, and defects such as looseness in the billet that cannot
be completely eliminated, resulting in poor wire rod passing
performance and final structure. abnormal. Through the austenite
grain size inspection of 82B wire rod, it was found that the grain
size of 82B wire rod produced by Qinggang is grade 6 to 7. Compared
with those of Wuhan Iron and Steel, Baosteel, and Shagang (grade
8), the grain size is coarser. .
When the opening rolling temperature is controlled at 990 ~ 1 010
ºC, the austenite grain size is level 7; when the opening rolling
temperature is controlled at 1 000 ~ 1 050 ºC, the austenite grain
size is level 6. This shows that the opening rolling temperature
has a significant impact on the The austenite grain size has a
greater influence. Under the premise of normal production, the
opening rolling temperature should be controlled as low as
possible.
5. Influence of controlled cooling process after rolling
The main purpose of controlling cooling is to control the degree of
subcooling and cooling rate to obtain the sorbite structure
required for strengthening and toughening. According to the
principle of metal heat treatment, speeding up the cooling rate can
move the continuous cooling curve to the lower right, the faster
the cooling rate. For Stelmer's standard cooling mode - forced air
cooling, the cooling rate cannot reach the critical transformation
temperature for the formation of martensite. The faster the air
cooling speed, the easier it is for austenite to transform into
troostite. Therefore, a large air volume is used during actual
cooling to achieve rapid cooling. On the one hand, the amount of
ferrite precipitation can be controlled, and on the other hand,
undercooling can be increased. Spend. 82B wire rod has special
requirements for strength. Setting a higher spinning temperature
and increasing the cooling rate can achieve the effect of improving
strength.
As the spinning temperature increases, the tensile strength of the
wire rod increases significantly, which seems to contradict the
theory that the higher the spinning temperature, the coarser the
grains, and the lower the spinning temperature, the finer the
grains. In fact, this type of steel has been micro-alloyed, coupled
with temperature-controlled rolling during rolling. After recovery
and recrystallization, the deformed austenite grains are already
quite fine. Even if the spinning temperature is increased, the
coarseness of the grains will not be affected. The degree of
oxidation is relatively small, so the impact on strength is
negligible. It should be noted that the spinning temperature cannot
be too high, otherwise due to the limitations of the air cooling
equipment, the structural transformation of the high carbon steel
wire rod cannot be completely completed on the controlled cooling
line. Not only will the expected structure not be obtained, but
also thicker irregularities will easily form on the surface of the
wire rod. The iron oxide scale that is conducive to drawing reduces
the overall performance of the wire rod. It is necessary to
reasonably control the spinning temperature and the cooling rate
after rolling to obtain a fine sorbite structure so that the
finished product has high strength and good plasticity.
The structural inspection of 82B wire rod found that the structure
is S + P and there is no F structure, which meets the standard
requirements. However, the sorbitization rate is generally around
85%, which is still far behind the standard requirement of ≥95%.
Compared with Shagang and Baosteel, the local trostitization rate
is lower, only about 65% (Shagang 75%, Baosteel 85%). Its pearlite
groups are larger and the grains are coarser. Therefore, after
rolling, the 82B wire rod The controlled cooling process needs
further optimization.Zhengde Steel wire rod(s) is also called wire rod, which usually
refers to small-diameter round steel in a coil. The diameter of the
wire rod is in the range of 5-19mm (usually 6-9mm), and the lower
limit is the minimum size of the hot-rolled steel section. There
are many varieties of wire rods. Low carbon steel wire rods in
carbon steel wire rod(s) are commonly called soft wires, and medium
and high carbon steel wire rods are commonly called hard wires.
Wire rods are mainly used as blanks for wire drawing, and can also
be directly used as building materials and processed into
mechanical parts. Stainless steel wire rod(s) are used in the
manufacture of stainless steel wire, stainless steel spring steel
wire, stainless upset forging steel wire and steel wire for
stainless steel wire rope. With the advancement of production
technology, wire rods with square, hexagonal, fan-shaped and other
special-shaped sections have appeared; the upper limit of diameter
has been expanded to 38 mm; the weight of the coil has increased
from the original 40-60 kg to 3000 kg. Due to the development of a
new post-rolling heat treatment process, the iron oxide scale on
the surface of the wire rod has been significantly thinned, and the
structure and performance have also been greatly improved.
OD(mm) | Area(mm²) | Weight(kg/m) | L(m) | Weight(kg/s) |
Φ5.5 | 23.8 | 0.187 | 1000 | 187 |
Φ6 | 28.3 | 0.222 | 1000 | 222 |
Φ6.5 | 33.2 | 0.26 | 1000 | 260 |
Φ7 | 38.5 | 0.302 | 1000 | 302 |
Φ7.5 | 44.2 | 0.347 | 1000 | 347 |
Φ8 | 50.3 | 0.395 | 1000 | 395 |
Φ8.5 | 56.7 | 0.445 | 1000 | 445 |
Φ9 | 63.6 | 0.499 | 1000 | 499 |
Φ9.5 | 70.9 | 0.556 | 1000 | 556 |
Φ10 | 78.5 | 0.617 | 1000 | 617 |
Φ10.5 | 86.6 | 0.69 | 1000 | 690 |
Φ11 | 95 | 0.746 | 1000 | 746 |
Φ11.5 | 104 | 0.815 | 1000 | 815 |
Φ12 | 113 | 0.888 | 1000 | 888 |
Φ12.5 | 123 | 0.963 | 1000 | 963 |
Φ13 | 133 | 1.04 | 1000 | 1040 |
Φ13.5 | 143 | 1.12 | 1000 | 1120 |
Φ14 | 154 | 1.21 | 1000 | 1210 |
Φ14.5 | 165 | 1.3 | 1000 | 1300 |
Φ15 | 177 | 1.39 | 1000 | 1390 |
Φ15.5 | 189 | 1.48 | 1000 | 1480 |
Φ16 | 201 | 1.58 | 1000 | 1580 |
Φ17 | 227 | 1.78 | 1000 | 1780 |
Φ18 | 254 | 2 | 1000 | 2000 |
Φ19 | 284 | 2.23 | 1000 | 2230 |
Our Advantages
Quality first: production and inspection in strict accordance with
production standards;
Price advantage: discounts based on real market prices;
Transaction security: There will be no loss of customer funds;
After-sales guarantee: the customer's problem is our problem;
Long-term cooperation: quality assurance, price advantage, sincere
service can last for a long time.Detailed Photos
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Company Profile
Shandong Zhengde Metal Manufacturing Co., Ltd. is a production and sales company integrating hot-rolled steel
coils, cold-rolled steel coils, galvanized steel coils,
color-coated steel coils, section steel, steel pipes, steel wires,
metal mesh, stainless steel, aluminum, copper and other metal
products integrated large enterprises. Five production and sales
bases have been formed in Binzhou, Liaocheng, Wuxi, Tianjin, Jinan
and Tai'an, with more than 100 production lines, 4 nationally
recognized laboratories, 2 technical engineering centers, and 5
enterprise technology centers. Products are exported to more than
50 countries and regions such as North America, South America,
Europe, Middle East region, Russia, Africa, North America, and
other parts of the world.
Company Philosophy:
Quality first: production and inspection in strict accordance with
production standards;
Price advantage: discounts based on real market prices;
Transaction security: There will be no loss of customer funds;
After-sales guarantee: the customer's problem is our problem;
Long-term cooperation: quality assurance, price advantage, sincere
service can last for a long time.
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