Metallographic diagram of 08 steel (soft nitriding)

Q235B Steel Introduction and Applications

Q235B is a low-carbon structural steel under the standard GB/T700-2006. This type of steels are mainly used for making parts of buildings and bridges, and other structural and engineering purposes. Q235B steel has a certain elongation, strength, good toughness and casting, easy stamping and welding, widely used in the manufacture of general mechanical parts.

Q235B steel contains more alloying elements than general carbon steel, and has good plasticity, toughness and welding performance. It is suitable for welding, riveting and splicing. Q235B steel can also be used for welding and hardening for manufacturing mechanical components such as gear shafts and sleeves. The bending, torsion and compression properties of Q235B steel are good. It is a low-cost, easy-to-process material and is widely used in the manufacture of many metal products.

Q235B steels are produced by hot rolling or cold-forming methods, with slightly different chemical and mechanical properties. Its density is 7.85 g/cm³, tensile strength is about 370-500 MPa; yield strength is 225 MPa (data are for steel bar or steel plate diameter ≤ 16mm). The size of the tensile test is different and the value is significantly different. The yield point of the steel is not obvious. The elongation is generally 20-22%, the higher the yield point and the lower the elongation.

Microstructure and composition of Q235B steel

The microstructure of Q235B steel is usually ferrite and pearlite, and the chemical composition of Q235B steel is as follows (the percentage is the percentage by mass):

C: ≤ 0.22%

Si: 0.17-0.37%

Mn: 0.35-0.65%

S: ≤ 0.045%

P: ≤ 0.05%

Ti: ≤ 0.03%

Als: ≤ 0.05%

Cu: ≤ 0.3%

The trace element content of the composition largely affects the microstructure and properties of Q235B steel. The proportion of the alloying elements added to the steel is generally 5-10%.

CEV = Carbon Equivalent Value of Q235B steel

Carbon Equivalent Value (CEV) is a measure of the degree of pot weldability of steel. The greater the CEV value, the worse the weldability. The CEV value of Q235B steel is 0.24.

Standard specification of Q235B steel

GB/T700-2006 is the standard specification of Q235B steel in China. The standard of Q235B steel also covers Q235A, Q235C and Q235D. Mechanical properties of Q235 steel in GB/T700-2006:

Yield Strength (MPa): ≧ 225

Tensile Strength (MPa): 370-500

Elongation: 20-22%

Reduction Ratio: ≧50%

Applications of Q235B steel

Q235B steel is for making parts of buildings and bridges, and other construction and engineering purposes in a low-carbon and low-alloyed steel. Due to its low carbon and low alloy content, it has excellent welding performance and cold formability, and can be welded with common welding methods. The characteristics of Q235B steel make it suitable for many applications, including but not limited to:

• Construction of bridges and buildings

• Construction of ships, vehicles, engineering and other structures

• Automotive and aerospace applications

Q235B steel is an important material in many industries, like automotive and aerospace industry. It is also used in the manufacture of residential and commercial construction, office, and municipal facilities. Therefore, it is important that buyers of Q235B steel must be familiar with the specifications and composition of the material in order to ensure its suitability for the intended application.

JIS-SCM435 is a Japanese industrial standard steel grade. It is a low-alloy steel containing chrome, molybdenum, and rhenium, among others. The steel is heat-treated and hardened, and it has good strength, as well as moderate ductility and toughness. It is also highly corrosion-resistant and has good wear resistance.

Metallographic analysis of JIS-SCM435 is most often done with a light microscope. The sample is initially polished, then etched to reveal the microstructure. The microstructure for JIS-SCM435 can consist of a matrix of ferrite or pearlite, or both. The etching will reveal a fine lath-like structure with a fine grain interspersed with a pattern of secondary hardening.

In addition to the ferrite and pearlite, the microstructure can also consist of martensite. Martensite imparts toughness and wear resistance, while ferrite and pearlite provide strength. The martensite can have either a fine or coarse appearance, depending upon its precipitation.

The hardness of JIS-SCM435 is determined by quenching and tempering. Quenching and tempering are heat treating processes used to affect the strength and ductility of steel. Generally, JIS-SCM435 is quenched and tempered to a hardness greater than 30 HRC.

Finally, JIS-SCM435 is nitrided to achieve the highest level of wear resistance. Nitriding is a process that adds nitrogen to the steel surface. It adds several times the wear resistance of the base material, making it ideal for applications with high wear resistance requirements.

Overall, JIS-SCM435 is an excellent steel in both its strength and durability. Its heat treatment and nitriding also allow it to be used in applications where wear resistance is desired. The fine grain structure also makes it suitable for applications involving high ductility.