Q:Q195 What is the corrosion resistance of the product?
A:Q195 steel itself has poor corrosion resistance and is prone to rust. After galvanizing, a zinc layer (Zn) is formed on the surface, which greatly extends the service life through electrochemical protection (zinc is more active than iron and corrodes first) and physical barrier effect (isolation of oxygen and water). ◦ The thickness of the hot-dip galvanized layer can reach 60-100μm, and the salt spray corrosion resistance can reach more than 500 hours (far exceeding bare steel), which is suitable for humid, acidic and alkaline environments (such as outdoor buildings and chemical equipment).
Q:What are the mechanical properties of Q195?
A:Base Q195 steel: yield strength 195MPa, elongation >=33%, excellent plasticity and toughness, easy to cold process (such as bending, stamping, welding), suitable for forming parts with complex shapes (such as bellows, brackets).
The galvanized layer does not affect the mechanical properties of the base: the galvanizing process (hot dip temperature of about 450℃) has no significant damage to the strength and plasticity of Q195 steel, and still maintains good processing performance.
Q:What are the cost-effectiveness advantages of Q195?
A:Compared with stainless steel or high alloy coated steel, Q195 galvanized steel costs more than 50% less and is suitable for large-scale industrial applications (such as construction, home appliances, packaging).
The galvanizing process is mature and the production efficiency is high (such as the continuous hot dip production line speed can reach tens of meters per minute), and standardized products (such as galvanized steel sheets, strip steel, steel pipes) can be supplied in batches.
Q:Q195 What are the disadvantages of galvanized steel?
A:1. Limited mechanical strength
Q195 steel is a low-carbon steel with low matrix strength (tensile strength of about 315-430MPa). It cannot be used in high-load scenarios (such as bridges and heavy machinery) after galvanizing.
2. Risk of coating defects
Hot-dip galvanizing: Surface defects such as "zinc nodules" and "leaking plating" may occur, affecting the appearance and anti-corrosion performance (need to be removed by quality inspection); uneven coating thickness (such as thick ends and thin middle of the pipe), and the edge is easy to fall off due to collision.
Electrogalvanizing: The coating is thin, and the corrosion resistance is only 1/3-1/2 of hot-dip galvanizing, and there is a risk of "hydrogen embrittlement" (hydrogen atoms penetrate into the matrix during the electroplating process, resulting in increased brittleness, and post-treatment is required to remove hydrogen).
3. Insufficient high-temperature performance
The melting point of zinc is 419.5℃. The hot-dip galvanized layer will oxidize and peel off when used for a long time at above 200℃, and lose its protective effect; the strength of Q195 steel itself decreases significantly at high temperatures (for example, the yield strength drops to 70% of that at room temperature at 300℃), and it is not suitable for heat-resistant scenes (such as boilers and exhaust pipes).
4. Limited environmental adaptability
Strong acid/alkaline environment: The zinc layer will react chemically with acids (such as hydrochloric acid) and alkalis (such as sodium hydroxide), resulting in rapid corrosion of the coating (such as chemical workshops and agricultural fertilizer storage areas need to use stainless steel or epoxy-coated steel instead).
High humidity + salt spray environment: Although the galvanized layer is resistant to salt spray, it will still gradually consume the coating if it is in coastal or industrial atmosphere for a long time (regular maintenance or the use of steel with higher coating weight is required).
5. Limitations of welding
During welding, high temperatures will burn the zinc layer, generating zinc vapor and welding slag, and the coating in the welding area needs to be polished in advance; "white rust" (zinc oxide corrosion product) is easily formed near the weld, and anti-rust paint needs to be applied.
Q:Q195 What are the scenarios where galvanized steel is not suitable?
A:Not recommended scenarios: high-load structures (such as bridges, cranes), high-temperature environments (＞200℃), and contact with highly corrosive media (such as chemical containers).