The main differences between 2-series and 3-series stainless steel lie in their chemical composition, properties, and applications.

2-series stainless steels, such as 201 and 202, primarily contain high levels of manganese and nitrogen, with relatively low or no nickel.
3-series stainless steels, such as 304 and 316, primarily contain chromium and nickel as alloying elements, with a high nickel content. These two different chemical compositions lead to significant differences in their properties and applications.

3-series stainless steels contain higher proportions of chromium and nickel, making them significantly more corrosion-resistant than 2-series stainless steels. This is particularly true in corrosive environments, such as seawater and chemical plants, where 3-series stainless steels perform particularly well. 304 stainless steel is the most common grade, offering excellent corrosion resistance, heat resistance, low-temperature strength, and mechanical properties.

Because of its higher proportions of nickel and chromium, 3-series stainless steels generally offer better overall properties than 2-series stainless steels. While 2-series stainless steels may offer some corrosion resistance in certain situations, they are generally inferior to 3-series stainless steels.

Wire rod serves an extremely wide range of purposes in industry. 

First, in the construction sector, it is a vital element for building robust frameworks. It is used to reinforce concrete structures, enhancing the stability and seismic resistance of buildings.

In manufacturing, wire rods also plays a key role. For instance, in automotive production, wire can be processed into various components such as springs, screws, and rivets.

In the machining industry, wire rod is frequently used to manufacture transmission components like shafts and gears.

Wire also holds significant importance in the metal products sector. For instance, it is employed in the production of steel wire mesh, steel wire ropes, and similar products.

The "R" suffix of Q235R stands for the first letter of the Chinese pinyin for "container", which specifically identifies the special properties of pressure vessel steel.
Chemical composition: Q235R is designed with low low-carbon manganese silicon alloy system. Its typical composition is: carbon content 0.16%-0.20%, manganese content 0.40%-0.70%, silicon content not more than 0.35%, and contains trace amounts of alloying elements such as niobium and vanadium. This composition design ensures sufficient strength while taking into account good plasticity and toughness.
Mechanical properties: Q235R exhibits a balanced strength-toughness match. Its yield strength is not less than 235MPa, its tensile strength reaches 370-500MPa, and its elongation after break is not less than 26%. In the -20℃ low temperature impact test, Q235R can still maintain a high impact absorption energy. This good low temperature toughness makes it suitable for the manufacture of pressure vessels in cold areas.



Q345R steel plate is a low-alloy, high-strength steel plate specially designed for pressure vessels with a yield strength of 345 MPa. Chemical Composition of Q345R Steel Plate: Carbon (C): ≤0.20% (increased to 0.22% for thicknesses >60mm); Manganese (Mn): 1.20-1.70%; Silicon (Si): ≤0.55%; Sulfur (S): ≤0.010%; Phosphorus (P): ≤0.025%

Mechanical Properties of Q345R Steel Plate:
Yield Strength: ≥345 MPa for thickness ≤16mm, ≥265 MPa for thicknesses 150-200mm
Tensile Strength: 470-640 MPa
Elongation: ≥21%
Impact Toughness: V-type impact energy ≥34 J at 0°C, ≥27-34 J at -20°C or -30°C upon special request (e.g., Q345R (R-HIC))
High-Temperature Performance: Yield Strength ≥180 MPa at 500°C

Q245R and Q345R are two commonly used pressure vessel steel plate materials. The "R" in the designation stands for "vessel," and the number indicates the yield strength grade.

Yield Strength:
Q235R has a yield strength of approximately 235 MPa, while Q345R has a yield strength of up to 345 MPa. This means that under the same external force, Q345R is more resistant to deformation and offers greater structural safety.

Chemical Composition:
Q235R has a relatively high carbon content, while its manganese content is within a certain range. Q345R, on the other hand, has a lower carbon content and stricter control over impurities such as phosphorus and sulfur. This allows Q345R to maintain good strength while also exhibiting superior ductility, toughness, and weldability.

Q235R typically has a temperature limit of around 400°C, making it suitable for low- to medium-temperature and pressure environments. Q345R, on the other hand, boasts increased strength and thermal stability due to the addition of trace alloying elements, allowing for safe long-term use below 450°C. Both steels are widely used in petrochemical, boiler, and storage tank equipment, and the selection process should consider both operating temperature and pressure requirements.