Q345R Steel Plate / Alloy Plate 345R Thickness 6.0 - 250mm Custom
Cutting Any Size
What is Q345R Steel?
Q345R steel is a low alloy steel for pressure vessels with yield
strength of 345MPa grade, which has good comprehensive mechanical
properties and process performance. Phosphorus and sulfur content
is slightly lower than low alloy high strength steel plate Q345 (16Mn) steel, in addition to tensile strength, elongation
requirements than Q345 (16Mn) steel has increased, but also to
ensure impact toughness.
Q is the first letter of Chinese Pinyin, 345 represents yield strength, r is the first letter of Chinese Pinyin, and its brand naming
method is low alloy high-strength structural steel brand,
represented by the first letter of Chinese Pinyin for yield
strength value and pressure vessel capacity.
Chemical Composition of Q345R Steel
Q345R (16MnR) steel combines various elements, including carbon,
manganese, silicon, phosphorus, sulfur, and several other alloying
elements. The precise percentages of these elements determine the
steel’s unique characteristics, such as its strength, ductility,
and weldability.
| Grade | C % | Si % | Mn % | Cu % | Ni % | Cr% | Mo % | V % | Ti % | Alt % | P % | S % | Nb |
| Q345R | 0.2 | 0.55 | 1.2-1.7 | 0.3 | 0.3 | 0.3 | 0.08 | 0.05 | 0.03 | 0.02 | 0.025 | 0.01 | 0.05 |
Mechanical Properties of Q345R steel
Some of the key mechanical properties of Q345R steel include high
tensile strength, good elongation, and excellent impact resistance.
These properties make it suitable for applications that require a
material capable of withstanding extreme conditions, such as high
pressure and temperature.
| Thickness (mm) | > 3 ≤ 16 | > 16 ≤ 36 | > 36 ≤ 60 | >60 ≤ 100 | >100 ≤ 150 | >150 |
| Yield strength (≥Mpa) | 345 | 325 | 315 | 305 | 285 | 265 |
| Tensile strength (Mpa) | 510-640 | 500-630 | 490-620 | 480-610 | 470-600 |
Applications of Q345R Steel
Pressure Vessels
Q345R steel is widely used in manufacturing pressure vessels,
containers designed to hold gases or liquids at a pressure
significantly different from the ambient pressure. Its excellent
strength and durability make it an ideal choice for this
application.
Boilers
Boilers, used to generate steam or hot water for various industrial
processes, are another common application for Q345R steel. Its
ability to withstand high temperatures and pressures make it a
popular choice for boiler construction.
Heat Exchangers
Heat exchangers, which transfer heat between two or more fluids,
also rely on Q345R steel for construction. The steel’s excellent
thermal conductivity and corrosion resistance make it ideal for
this application.
Advantages of Q345R Steel
Strength and Durability
One of the primary benefits of Q345R steel is its high strength and
durability. Its excellent mechanical properties enable it to
withstand extreme conditions, making it an ideal choice for
applications that require a strong, reliable material.
Cost-Effectiveness
Q345R steel is also a cost-effective option compared to other
high-pressure steel grades. Its relatively low cost and wide
availability make it an attractive choice for many industries that
require pressure and temperature-resistant materials.
Weldability
Another advantage of Q345R steel is its excellent weldability. It
can be easily welded using various methods, making it convenient
for manufacturers to work with and assemble components. This
feature also contributes to its cost-effectiveness.
Comparison with Other Steel Grades
Q345R vs. Q245R
Q345R and Q245R are popular steel grades used for pressure vessels and boilers. However, Q345R offers
higher tensile strength and better impact resistance than Q245R,
making it more suitable for applications requiring higher pressure
and temperature resistance.
Q345R vs. Q370R
Q370R is another steel grade that shares similarities with Q345R.
Both are designed for pressure vessel applications, but Q370R
offers slightly higher strength and toughness. However, Q345R
remains popular due to its cost-effectiveness and widespread
availability.
Precautions for the use of Q345R
1. Must consider the operating conditions of the equipment (such as
design pressure, design temperature, characteristics of the
medium), welding properties of the material, hot and cold
processing properties, heat treatment and the structure of the
vessel.
2. Under the premise of meeting the first article, consider the
economic rationality of:
- ① When the required thickness of steel plate is less than 8mm,
between carbon steel and low-alloy high-strength steel, carbon steel plate should be
used as far as possible (except for multi-layer containers).
- ② In the stiffness or structural design-oriented occasions, should
try to use ordinary carbon steel. In the strength design-oriented
occasions, should be used according to the pressure, temperature,
medium and other restrictions, in order to choose Q235B, 20R (20g), Q345R (16MnR) and other steel plates.
- ③ Required stainless steel thickness greater than 12mm, should try
to use lining, composite, overlay welding and other structural
forms.
- ④ Stainless steel should be used as far as possible not as a design
temperature less than or equal to 500 degrees Celsius
heat-resistant steel.
- ⑤ Pearlite heat-resistant steel should be used as far as possible
not as the design temperature is less than or equal to 350 degrees
Celsius heat-resistant steel. In the must use pearl body
heat-resistant steel for heat-resistant steel or hydrogen-resistant
purposes, should try to reduce, merge the variety of steel,
specifications.
3. Thickness greater than 60mm Q345R steel plate, the upper limit
of carbon content can be increased to 0.22%.
4. Q345R steel plate can add niobium, vanadium, titanium elements,
the content should be filled in the quality certificate, the sum of
the above three elements content should not be greater than 0.050%,
0.10%, 0.12%.
What is Q345R steel plate?
- Q345R(R-HIC) steel plate is hydrogen resistant container plate,
with low P and S content in the steel plate and good welding
performance.
- Q345R(R-HIC) steel plate execution standard: Execution of
GB713-2014 standard.
Technical standards of Q345R(R-HIC) steel plate:
- The size, weight, shape and permissible deviation of Q345R(R-HIC)
shall conform to the provisions of GB/T709.
- The thickness deviation of Q345R(R-HIC) shall be executed according
to the deviation of class B in GB/T709.
- Delivery condition of Q345R(R-HIC) steel plate: Normalized, or the
delivery condition can be specified according to technical
requirements.
- Q345R(R-HIC) steel plate thickness direction performance
requirements: Z15, Z25, Z35.
- Q345R(R-HIC) steel plate flaw detection requirements: one probe,
two probe, three probe.
- Q345R(R-HIC) steel plate size: thickness 8mm-160mm, width
1600mm-2500mm, length 6000-12000mm.
- Q345R grade hydrogen resistant plates are Q345R(HIC) and
Q345R(R-HIC), other material hydrogen resistant plates:
Q245R(R-HIC)/SA516Gr70(HIC)/14Cr1MoR(H)/12Cr2Mo1R(H).
Q345R(R-HIC) steel plate production and cutting process
Smelted by electric furnace + extra-furnace refining, the smelting
process is Ca-treated, and because of the nature of fine-grain
steel, its actual grain size is grade 5 or above.
Production process:
Primary refining → LF refining → VD treatment → continuous casting
(die casting) → cleaning, heating → rolling → (stacking) → surface
inspection → batching → flaw detection → heat treatment → cutting and sampling → performance inspection
Cutting process: Q345R (R-HIC) steel plate factory inspection of the performance
indicators meet the requirements by the cutting and processing
process; you can cut processing and drawings under the material,
the general steel plate thickness is not greater than 20mm priority
to choose CNC plasma cutting or CNC laser cutting method, if the
thickness of the steel plate is greater than 30mm or more, usually
will choose CNC flame cutting, can control the cutting Accuracy and
time.
The Effect of Cold Deformation on the Recrystallization Temperature
of Hot Rolled Q345R Steel Plate
A hot-rolled Q345R steel plate may exhibit recrystallization
behavior in engineering applications, affecting product
performance. To study the effect of cold deformation on its
recrystallization temperature, a hot-rolled Q345R steel plate was
subjected to cold deformation with 0,5%, 10%, 15%, 31%, and 53%.
Afterward, samples were cut and kept at different temperatures of
450-700 ℃ for 1 hour, followed by hardness testing and
metallographic observation. The results show that when the
deformation is 15% or less, recrystallization will not occur at
450-700 ℃; When the deformation is 31% and 53%, the
recrystallization temperature range of the sample is 615-650 ℃ and
565-600 ℃, respectively.
At the end of steel plate production, recrystallization temperature
is important for the reasonable development of the steel plate
rolling process. For cold-rolled steel plates, the deformation
produced by cold rolling is large. It is necessary to eliminate the
internal stress and improve the microstructure through
recrystallization annealing to ensure the strength and toughness of
the steel plate. Therefore, the recrystallization temperature is
more studied. For hot-rolled steel plates, in the rolling process
through dynamic recovery, dynamic recrystallization, and grain
growth, accurate estimation of steel recrystallization temperature
is also critical.
At the application end of the steel plate, GB/T150.4-2011 “Pressure
Vessel Part 4: Manufacturing, Acceptance and Inspection” and
GB/T16507.5-2013 “Water Tube Boiler Part 5: Manufacturing” both use
“recrystallization temperature” as the cold (including warm
forming), hot forming temperature limit, but the standard does not
give the material recrystallization temperature but also does not
specify the recrystallization temperature acquisition method. When
a hot-rolled Q345R steel plate is used to manufacture head,
cylinder, and other pressure-bearing parts, especially under cold
and warm forming conditions, the deformation generated by forming
is superimposed on the deformation of the steel plate itself. The
austenite transformation organization and deformed ferrite
substructure organization may have an important impact on the
recrystallization behavior of the material and even trigger static
recrystallization and affect the product performance.
To study the recrystallization behavior of hot-rolled Q345R steel
plate in engineering applications, this paper refers to the forming
deformation rate of common steelhead and the forming heating
temperature or final stress relief heat treatment temperature of
the product and selects a steel mill hot-rolled Q345R steel plate
for cold deformation with less than 15% deformation and 31% and 53%
large deformation, and then conducts hardness test after heat
treatment at different temperatures to determine the
recrystallization temperature at different The recrystallization
temperature under the cold deformation is determined.
Test materials and methods
Test material
The test material is a steel mill hot-rolled Q345R steel plate; its
thickness is 16mm, the chemical composition is shown in Table 1,
its mechanical properties are shown in Table 2, and its
metallurgical organization is shown in Figure 1.
Table.1 Chemical composition of Q345R steel plate
| Project | C | Si | Mn | P | S | Al | V | Ti | Nb | Cr | Ni | Cu |
| Measured value | 0.18 | 0.29 | 1.36 | 0.015 | 0.003 | 0.041 | 0.003 | 0.003 | 0.0007 | 0.02 | 0.009 | 0.022 |
| GB/T 713 standard value | ≤0.20 | ≤0.55 | 1.20–1.60 | ≤0.025 | ≤0.015 | ≥0.020 | Sum ≤ 0.10 | ≤0.30 | ≤0.30 | ≤0.30 |
|
Table.2 Mechanical properties of Q345R steel plate
| Project | Yield strength/MPa | Tensile strength/MPa | Elongation after fracture (%) | Reduction of Area (%) | Impact absorption energy at 0℃/J | Brinell hardness (HBW2.5/187.5) |
| Measured value | 377 | 537 | 31 | 69 | 131 | 165,166,167 |
| GB/T 713 standard value | ≥345 | 510–640 | ≥21 | — | ≥34 | — |
Figure.1 Q345R steel plate microstructure
Specimen processing
Steel plate deformation
The deformation of the original steel plate is counted as 0; 5%,
10%, and 15% uniformly deformed steel plate is obtained by
stretching method; to obtain a larger deformation, the steel plate
is compressed by a press method at room temperature, and the
deformation is 31% and 53% respectively.
Specimen preparation
The specimens were processed into 15mm×10mm by wire-cutting method
and tested in a KSL-1100 chamber resistance furnace from 450-700℃
with an interval of 50℃ and holding time of 1h, and air-cooled; the
specimens after heat treatment at different temperatures were
inlaid, ground and polished, and after corrosion by 2% nitric acid
alcohol solution, their metallographic organization was observed,
followed by hardness testing.
Test Equipment and Methods
Metallographic testing
Use Nikon EPIPHOT 300 optical microscope (OM) to observe the
microstructure of the specimen section.
Hardness testing
The hardness of the ferrite region on the specimen cross-section
was measured using a 401MVD micro-Vickers hardness tester with 10
points per specimen uniformly tested at a test load of 4.903N
(500gf).
Test results and discussion
Vickers hardness
The relationship between the hardness of each deformation specimen
and the heat treatment temperature is shown in Figure 2.
Figure.2 Relationship curve between hardness and heat treatment
temperature of each deformation amount specimen
From Figure 2, it can be seen that the hardness of 0,5%,10%, and
15% deformation specimens in the range of 450-700℃, after heat
treatment at the same temperature, increases significantly with the
increase of deformation; 31%,53% deformation specimens below 550℃,
after heat treatment at the same temperature, the hardness
increases with the increase of deformation. It was also found that
the increase in hardness of the 31% and 53% deformation specimens
was smaller than that of the 15% or fewer deformation specimens.
Among them, the hardness of 0,5%,10%, and 15% deformation specimens
after heat treatment at 450-700℃, the trend of hardness change is
the same, i.e., it remains the same or slightly decreases; the
hardness of 31% of deformation specimens below 600℃ does not change
much, and the hardness of 600-650℃ decreases sharply, and the
hardness of unheated treated specimens (HV0.5) decreases from 258
to 153, a decrease of 41%. Similarly, the hardness of the deformed
53% specimens decreased significantly at 550-600°C.
With the increase in deformation, the hardness increases as a
result of deformation strengthening, the plastic deformation
increases, the dislocation density increases, and the dislocation
movement of mutual cross-cutting phenomenon intensifies, resulting
in fixed dislocation entanglement and other barriers, thus
increasing the resistance to dislocation movement to enhance the
deformation resistance of the material, the deformation continues
to increase will appear a large number of cross-slip shift, so that
the dislocation bypass the barrier forward, which is the
deformation of 31%, 53% specimens This is the intrinsic reason why
the strengthening effect is not as obvious as that of the specimens
below 15%. As the temperature rises, the deformed grains first
revert. When the energy is sufficient, the original elongated,
finely divided grains are equiaxed, defects such as dislocations
are greatly reduced, and the hardness changes significantly, called
recrystallization. After heat treatment of 0,5%,10%, and 15%
specimens, the hardness is basically unchanged or slightly
decreased, which should result from the reversion effect.
Deformation amount to 31% and 53% of specimens at 600-650 ℃ and
550-600 ℃, respectively, the hardness drops sharply; according to
the significant change in hardness, it can be determined that the
test material in this temperature range occurred recrystallization.
To accurately determine the recrystallization temperature range of
the material, the heat treatment was supplemented with 615,630°C
for the 31% deformation specimen and 565,580°C for the 53%
deformation specimen, and the holding time remained 1 h. Figure 3
shows the hardness versus heat treatment temperature curves for the
31% and 53% deformation specimens. It can be seen that the
recrystallization temperature range of the deformation is 31%, and
53% of specimens are 615-650℃ and 565-600℃ respectively; it can
also be seen that the larger the deformation, the lower the
insulation temperature of the hardness drop, the lower the
recrystallization temperature of the material, which is due to the
increase in deformation, the increase in deformation energy
storage, the greater the tendency to transform to a low energy
state, the lower the heating temperature required.
Figure.3 Supplementary test results of 31% and 53% deformation
specimens
Microstructure
The microstructure of a typical deformation specimen at partial
heat treatment temperature is shown in Figure 4. It can be seen
that: without heat treatment, compared with the deformation amount
of 15% specimen (a), the deformation amount of 31% specimen (d)
grain deformation is obvious, along the deformation direction grain
is flattened, while the deformation amount 53% specimen (g) grain
deformation degree is more serious, deformation grain is more
slender; deformation amount 15% specimen after heat treatment at
650 ℃ (b) and 700 ℃ (c), there is no obvious grain nucleation,
combined with After heat treatment at 615℃ (e), a small amount of
recrystallized grains appeared in the microstructure (arrowed in
the figure), and the original flattened grains tended to irregular
shape, which can be judged to have recrystallized; by 650℃ (f), the
deformed grains were close to equiaxed crystals, indicating that at
this temperature, the grains were heavily nucleated and grew, and
the recrystallization process was completed. The recrystallization
process is completed; similarly, the deformation of 53% specimen at
565 ℃ recrystallizations to 600 ℃ recrystallization is completed.
It can also be seen from the microstructure that the starting
temperature of pearlite aging of the microstructure of 15%, 31%,
and 53% deformation specimens decreases from 700, 650, and 565℃
respectively, which is caused by the energy storage of deformation
and further confirms the conclusion that the recrystallization
temperature decreases with the increase of deformation judged from
the hardness method.
Figure.4 Microstructure of deformation 15%, 31%, and 53% specimens
at partial heat treatment temperature
Recrystallization temperature
The recrystallization temperatures of different materials are
different. The recrystallization temperature of the same material
is not a definite value; it is not only related to the state of the
raw material but also to the cold deformation, deformation speed,
deformation temperature, grain size, solid solution strengthening
effect, the second phase, etc. In engineering, there are more
definitions of recrystallization temperature, such as the
temperature of 50% softening of material as recrystallization
temperature or the minimum temperature of recrystallization volume
fraction greater than 95% under large deformation, etc.
For this test of hot-rolled Q345R steel plate, 31% deformation
specimen at 615 ℃ that recrystallization, 53% deformation specimen
at 565 ℃ recrystallizations, the reason why the definition is
different from the previous because this test is to provide a basis
for the development of temperature forming process, in order not to
recrystallization, and therefore the recrystallization volume
fraction or hardness (strength) softening degree of the two is
different.
