Shipbuilding
Advantages of galvanized seamless tube:
1. High pressure resistance: hot-dip galvanized seamless tube can withstand higher pressure.
2. Long average service life: paints with an average adhesion of 500g/m2 can be kept for more than 50 years without maintenance in dry and suburban environments.
3. No maintenance required during use: Hot-dip galvanized seamless tubes have excellent weather resistance and long service life, and require no maintenance costs. Compared to painting, it requires regular maintenance, which saves a lot of money and social costs.
4. Good sturdiness, can withstand mechanical damage from handling and lifting: The galvanized layer is an alloy structure with very good hardness and mechanical properties.
5. Local damage or minor defects are still protective: Since zinc is more chemically active than iron, even minor defects can protect exposed steel, which is the protective property of sacrificial anodes.
6. Comprehensive protection, no dead angle: the working characteristics of hot-dip galvanized seamless tube must fully immerse the workpiece in liquid zinc, so that every corner of the workpiece can be in contact with each other, especially the sharp angle and concave surface can thicken the coating, which It is also a place that cannot be reached by spraying.
7. Does not affect the mechanical properties of the original design: hot-dip galvanizing has no effect on the mechanical properties of the seamless tube (SMLS).
Processing technology of galvanized seamless steel tube:
1. Since the shortening of fine casting of seamless tubes is much greater than that of cast iron, in order to avoid the defects of shrinkage holes and shrinkage of seamless tubes in castings, methods such as risers, cold iron and subsidies are mostly used in the casting process to achieve sequential condensation.
In order to avoid the defects of shrinkage, shrinkage, pores and cracks in the seamless tube casting, the seamless tube should have a uniform wall thickness, avoid sharp and right-angle structures, add sawdust in the molding sand for casting, and add coke in the core. , and the use of hollow cores and oil sand cores to improve the concession and air permeability of sand or cores.
2. Due to the poor fluidity of molten steel, in order to avoid cold insulation and lack of pouring of seamless steel castings, the wall thickness of steel castings should not be less than 8mm; dry casting or hot casting should be used; the pouring temperature should be properly increased, generally as from 1520°C to 1600°C, due to the high pouring temperature, the superheat of molten steel is large, and the liquid state lasts for a long time, and the fluidity can be improved. However, if the pouring temperature is too high, the seamless tube will cause defects such as coarse grains, thermal cracking, pores and sticky sand. Therefore, generally small, thin-walled and complex-shaped fine castings have a pouring temperature of about 150 °C, the melting point of steel.
