Q355B is a structural steel grade specified in China’s national standard GB/T 1591-2018. It is an upgraded version of Q345B steel with higher strength and corrosion resistance. The “Q” of Q355B represents structural steel, “355” represents the minimum yield strength of 355 MPa, and “B” represents the quality grade level, usually indicating cold-formed profiles or lightweight structural purposes.
Why would I introduce Q355B steel to you today? Because it is currently the most commonly used steel in building structures. It is also because Q345B has been changed to Q355B in the new national standard document. The meaning of this change will be explained below.
This change is in line with international standards, and from the brand point of view, it is obviously in line with European standards. Although it is based on ISO, in essence, in international trade, S355JR is the most used like my country’s Q345B.
1. Usage:
China and Europe have cooperated frequently in many fields in recent years. Many projects come to China to purchase steel, and different standards will cause a lot of trouble. For example, when purchasing S355JR steel, most of them require new orders from steel mills. After the implementation of the new national standard, S355JR will directly It can be replaced with Q355B, and it can be said that there is almost zero difference in docking, as long as the designer makes a slight change in the drawing markings.
2. Production:
Although the demand for European standard products has gradually increased in recent years, due to different standard systems, different component properties, and extremely inconvenient production organizations, production costs have increased. After this change, S355JR and Q355B can almost replace each other. Not only is B-level interoperability, but also several other levels are almost the same, such as S355J0, J2, etc.
3. Trade:
With the interoperability of steel standards, the import and export of steel structure buildings in China and Europe will become more convenient and cost-effective.
Q355B steel can not only replace European standard steel, but also standard steel in other regions. Follow me below to learn about the characteristics and advantages of Q355B steel.
Q355 is the structural steel grade specified in China’s national standard GB/T 1591-2018. According to this standard, the grade classification of Q355 steel is mainly based on its mechanical properties. Specifically, Q355 steel is graded according to its yield strength and tensile strength, including the following grades:
1. Q355B (symbol: Q): Indicates structural steel with the lowest yield strength of 355 MPa.
2. Q355C (symbol: Q): Indicates structural steel with a higher yield strength than Q355B, but the specific value is not generally published. The yield strength is usually greater than 355 MPa.
3. Q355D (symbol: Q): Indicates a structural steel with higher yield strength. The specific value may not be generally published, but the yield strength is higher than Q355C.
These grade classifications are mainly based on yield strength. The design use, strength requirements and specific engineering environment of the steel may require different grades of Q355 steel. In engineering applications, selecting the appropriate grade is determined by design requirements and performance requirements.
Q355B steel has the following main advantages:
1. High strength: Q355B steel has high yield strength and tensile strength, usually with a yield strength of 355 MPa, so it can provide good structural support and load-bearing capacity in many engineering applications.
2. Good plasticity and weldability: This steel has good plasticity and processability, is easy to bend, shape and weld, and can meet various engineering design requirements.
3. Excellent corrosion resistance: Q355B steel usually has good corrosion resistance, can resist corrosion and oxidation under some environmental conditions, and is suitable for a variety of engineering environments.
4. Lower cost: Relative to some higher strength steels, the cost of Q355B steel may be relatively low, making it economical and cost-effective in some projects.
5. Versatility: Q355B steel has a wide range of uses and is suitable for many fields such as building structures, bridges, machinery manufacturing, and shipbuilding.
These advantages make Q355B steel widely used in structural engineering and various construction fields, and can meet many engineering design and manufacturing requirements.
Q355B structural steel is widely used in various engineering fields and construction projects due to its excellent mechanical properties and corrosion resistance. Specific uses include but are not limited to:
1. Building structure: used for structural components such as beams, columns, trusses, stairs, etc. of buildings. Q355B’s high strength and good weldability make it a commonly used material in building structures.
2. Bridge engineering: Suitable for bridge support structures, beams, beams and other components. Its strength and corrosion resistance make it an ideal choice for bridge construction.
3. Ship manufacturing: In some light ships or marine engineering, Q355B can be used for hull structures, slipways and other components.
4. Machinery manufacturing: Suitable for construction machinery, equipment manufacturing and other fields, such as structural components of excavators, cranes, road rollers and other equipment.
5. Transmission and distribution towers: Structural support elements for transmission and distribution towers that can adapt to the requirements of different environments because of their strength and corrosion resistance.
6. Other applications: Including steel structural components, pipes, decorative materials and other fields. Its high strength and durability make it play an important role in engineering construction and manufacturing.
Overall, Q355B structural steel is widely used in various engineering and construction projects that require strength and durability due to its high strength, good workability and corrosion resistance.
The strength of steel can be divided and described by a variety of indicators. The following are some common steel strength indicators:
1. Yield Strength: Yield strength is the point at which a material begins to plastically deform, that is, the lowest stress at which the material begins to continue to deform. In tensile testing, the stress applied when a material begins to transition from a linear elastic phase to a plastic deformation phase is the yield strength.
2. Tensile Strength: Tensile strength is the maximum tensile stress of a material in a tensile test, indicating the maximum tensile force that the material can withstand. Tensile strength is usually the maximum stress a material can withstand before breaking in tension.
3. Compressive Strength: Compressive strength is the ability of a material to resist compression, that is, the maximum stress that a material can withstand when subjected to pressure.
4. Flexural Strength: Flexural strength is the bending resistance of a material under bending loading, that is, the maximum stress at which the material will not be damaged under bending loading.
5. Impact Toughness: Impact toughness describes the ability of a material to absorb energy without causing damage when subjected to impact load or sudden loading.
These strength indicators are commonly used parameters in materials engineering. Different projects and applications require steel to have different strength properties. Therefore, the selection of steel is often based on specific engineering requirements and use environment to determine the required strength index.
In general, steel materials are classified based on:
* Chemical composition: such as carbon steel, low alloy steel, stainless steel
* Smelting method: such as open hearth steel, converter steel, electric furnace steel
* Processing technology: such as hot-rolled steel and cold-rolled steel
* Product shape: such as thick plates, thin plates, strips, pipes and profiles, etc.
* Deoxidation methods: such as killed steel, semi-killed steel and boiled steel
* Microstructure: such as ferritic steel, pearlitic steel and martensitic steel, etc.
* Strength level: For example, the tensile strength of ASTM standard A420 Grade C is between 515Mpa and 655Mpa
* Heat treatment processes: such as annealing, quenching, tempering and thermomechanical processing
Steel is often divided into three broad categories based on carbon content:
* Mild Carbon Steels, such as: AISI 1005 to AISI 1026, IF, HSLA, TRIP, and TWIN steels
* Medium Carbon Steel, such as: AISI 1029 to AISI 1053
* High Carbon Steel such as: AISI 1055 to AISI 1095
In addition, according to European standard classification, steel can be divided into the following categories:
* Non-alloy steel, such as: EN DC01-DC06; S235; S275
* Alloy steel, such as: 2CrMo4 and 25CrMo4,
* Tool steels such as: EN 1.1545; AISI/SAE W110; EN 1.2436, AISI/SAE D6
* Electrical steel plates and strips, such as: EN 1.0890 and EN 1.0803.
Sometimes special grades may have different characteristics due to different standards. For example, 34CrMo4 is jointly defined by DIN and EN. There are six specifications (subgroups) in EN but a different specification in DIN. These steel specifications report changes in tensile properties due to various deformation heat treatments.
