S355J2H welded straight seam steel pipe and seamless steel pipe are two common steel pipe materials, they have different manufacturing processes and application fields.

1. S355J2H welded straight seam steel pipe: S355J2H refers to the grade of steel, indicating that the minimum yield strength of the steel is 355MPa, and the "H" of the steel pipe means "hollow". S355J2H Welded steel pipe is made by rolling hot or cold rolled steel plate into a tube shape and welding at high temperature. They can be welded by arc welding, high-frequency induction welding, laser welding and other methods.

S355J2H welded straight seam steel pipe has the following characteristics:

- Suitable for general structural purposes, such as buildings, Bridges, machinery and equipment.

- The manufacturing process is relatively simple and the production cost is low.

- High weld strength, suitable for applications under high pressure and load.

- Wide size range, can be customized according to different diameters and wall thickness of the pipe.

2. Seamless steel pipe: Seamless pipe is a pipe made by heating the whole steel to a high enough temperature and perforating it through the process of drawing and rolling. Seamless pipe does not need to go through the welding process, so it has the characteristics of no weld.

Seamless steel pipe has the following characteristics:

- No porosity and inclusions in the weld, with higher strength and corrosion resistance.

- Smooth inner surface, low fluid resistance, suitable for conveying high-precision fluids and gases.

Performs better in high-temperature and high-pressure environments, such as oil, gas, chemicals and nuclear power industries.

According to the specific application requirements and process requirements, it is very important to choose the right steel pipe material. Welded straight steel pipe and seamless steel pipe have their own application advantages and application scope in different fields and scenarios.

Chemical composition and mechanical properties of S355J2H steel pipe

The chemical composition and mechanical properties of S355J2H steel pipe are as follows:

Chemical composition:

Carbon (C) : not more than 0.22%

Silicon (Si) : not more than 0.55%

- Manganese (Mn) : 1.60% to 1.80%

- Phosphorus (P) : not more than 0.03%

- Sulfur (S) : not more than 0.025%

- Chromium (Cr) : not more than 0.30%

Nickel (Ni) : not more than 0.30%

Molybdenum (Mo) : not more than 0.08%

- Copper (Cu) : not more than 0.55%

- Vanadium (V) : not more than 0.20%

- Niobium (Nb) : not more than 0.07%

- Titanium (Ti) : not more than 0.03%

- Aluminum (Al) : not more than 0.02%

- Additional elements: the total amount of molybdenum (Mo), lead (Pb), tin (Sn), antimony (Sb), arsenic (As), etc., does not exceed 0.05%

Mechanical properties:

- Yield Strength: minimum 355 MPa

- Tensile Strength: 470 to 630 MPa

- Elongation: minimum 22%

- Impact Toughness: 20℃, minimum 27J

It should be noted that the above data is only a general guideline value, and the actual chemical composition and mechanical properties may vary according to different manufacturing standards and specifications.

Application of S355J2H steel pipe in sea condition

S355J2H steel pipe is widely used in sea conditions, especially in the field of offshore engineering and subsea oil and gas exploitation. The following are some main applications of S355J2H steel pipe under sea conditions:

1. Offshore platform structure: offshore platform structure includes drilling platforms, production platforms, gathering platforms, etc. These structures usually require the use of steel pipes with high strength and excellent corrosion resistance. S355J2H steel pipe has good mechanical properties and corrosion resistance, and can be used to manufacture pile legs, support structures, protective pipes and so on.

2. Subsea pipelines: Subsea oil and gas pipelines are key components that transport oil and gas from the seabed to land or other facilities. S355J2H steel pipe can be used in the manufacture of submarine pipeline conveyor sections, connectors and support structures. Due to the complex underwater environment, S355J2H steel pipe has high strength and corrosion resistance, and can withstand the requirements of seawater corrosion, high pressure and external load.

3. Marine structural engineering: Marine structural engineering includes ocean Bridges, offshore wind power facilities, docks and shipyards. In these projects, S355J2H steel pipes can be used to manufacture bridge support structures, wind turbine towers, dock facilities and dock structures. Due to the complexity of the Marine environment, S355J2H steel pipe needs to have high strength, corrosion resistance and fatigue resistance to ensure the safety and reliability of the structure.

In general, under sea conditions, the application range of S355J2H steel pipe involves the fields of offshore platforms, submarine pipelines and Marine structural engineering. Its high strength, good corrosion resistance and reliable mechanical properties make it an important material choice in Marine engineering. However, in specific applications, material selection and design need to be based on factors such as specific engineering requirements, environmental conditions and safety standards.