Thick Wall Steel Pipe

What is thick wall steel pipe?

Thick-walled steel pipe refers to a steel pipe with a large ratio of wall thickness to outer diameter, usually with a wall thickness of ≥10mm or an outer diameter/wall thickness ratio (D/t) ≤20. This type of steel pipe has the characteristics of high strength, high pressure resistance, and impact resistance, and is widely used in heavy industry, energy, military industry and other fields with strict requirements on material performance. It is mainly used as petroleum geological drilling pipes, cracking pipes for petrochemicals, boiler pipes, bearing pipes, and high-precision structural pipes for automobiles, tractors, and aviation.

The biggest difference between thick and thin-walled steel pipe is the wall thickness, in general, thin-walled steel pipes are drawing techniques, and general use of hot-rolled thick-walled steel pipe technology, if it is used to distinguish between units of measure, then, generally, the wall thickness / diameter equal to 0.02 is a watershed walled steel and thin-walled steel pipe, wall thickness / diameter thin-walled steel pipe is less than 0.02, greater than the thick-walled steel pipe, in use, the multi-walled steel pipe in the pipeline. The multi-walled steel pipe used in the hollow part of the blank. As well as the important use of pressure pipes. 

Classification of thick-walled steel pipes (manufacturing process):

a. Hot-rolled thick-walled pipes: high-temperature rolling, low cost
Suitable scenarios: building structures, ordinary pressure-bearing pipes

b. Cold-drawn thick-walled pipes: cold processing, high precision (±0.1mm)
Suitable scenarios: hydraulic cylinders, precision mechanical parts

c. Forged thick-walled pipes: high-pressure forging, high density
Suitable scenarios: nuclear power, key military components

5 Core features of thick-walled steel pipes:

1. Ultra-high pressure bearing capacity
The wall thickness is large, and the internal pressure resistance is high (up to 100MPa or more), suitable for high-pressure oil pipes and boiler pipes.

2. Strong deformation resistance
The radial and axial stiffness is high, and it is not easy to bend under external forces (such as mine support and bridge piers).

3. High temperature/low temperature resistance
Alloy steel thick-walled pipes can work stably in an environment of -50℃~600℃ (such as petrochemical reactors).

4. Difficult processing
Special equipment is required (such as large rolling mills, deep hole drilling), and welding requires preheating and slow cooling (anti-crack).

5. High cost
The material consumption is large, the process is complex, and the price is 30%~50% higher than that of ordinary steel pipes.

The key to thick-walled steel pipes - Uniform wall thickness

The quality of thick-walled seamless pipes depends on the uniformity of their wall thickness. If the wall thickness is not strictly controlled, it will directly affect the quality and use effect of the steel pipe. Thick-walled seamless steel pipes and large-diameter thick-walled steel pipes are often used in various mechanical processing and the manufacture of thick-walled parts.

The importance of wall thickness uniformity:
The wall thickness uniformity of thick-walled seamless pipes has a direct impact on the quality of subsequent processed parts. If the wall thickness cannot be controlled, the quality of the overall steel pipe will not be strictly guaranteed.

Storage environment requirements:
The place or warehouse for storing thick-walled seamless steel pipes should be clean and barrier-free, away from factories and mines that may produce harmful gases or dust. Weeds and debris should be removed on site to keep the steel pipes clean. Acids, alkalis, salts, cement and other materials that are corrosive to steel pipes shall not be stacked in the warehouse. Thick-walled seamless steel pipes of different varieties should be stacked separately to prevent confusion and contact corrosion.

Notes on open-air stacking:

Large-section steel, rails, steel plates, large-diameter thick-walled steel pipes, forgings, etc. can be stacked in the open air, but attention should be paid to moisture-proof and rust-proof measures.

By strictly controlling the uniformity of wall thickness and selecting a suitable storage environment, the quality and use effect of thick-walled seamless steel pipes can be ensured to meet the needs of various mechanical processing and thick-walled parts processing.

Precautions for welding thick-walled steel pipes:

When welding thick-walled pipes, you first need to clean the oil, paint, water, rust, etc. on the weld, and then make a groove according to the wall thickness. For steel pipes with thicker walls, the groove should be larger, otherwise it should be smaller. When welding, the gap of the weld is generally 1-1.5 times the diameter of the welding rod or wire. If the groove is too large, the gap can be appropriately reduced.

Spot welding should be at least three points, preferably four points, to ensure stability. During the welding process, a layered welding method should be adopted, especially when the wall thickness is large, the number of layers should be at least twice the width of the tube cavity, and the second layer can be welded only after the first layer is welded.

Application of thick-walled seamless pipes:

Thick-walled seamless pipes are mainly used in occasions with strict requirements such as high pressure, high temperature, and corrosion resistance, such as petrochemical, construction, fertilizer, metallurgy, electricity, shipbuilding, shipbuilding, air conditioning, boilers, etc. 

1. Petrochemical
The petrochemical industry is one of the main areas of use of thick-walled steel pipes. In the petrochemical production process, various pressure-resistant, corrosion-resistant, and high-temperature pipes are required. Thick-walled steel pipes are required to build high-temperature and high-pressure reactors, enhanced heat exchangers and other equipment. They are characterized by durability, corrosion resistance, high temperature and high pressure.

2. Construction industry
The construction industry is also an important application area of thick-walled steel pipes. Thick-walled steel pipes are mainly used as steel structures: bridge piling pipes; docks, roads, pipelines and other building structures.

3. Machinery manufacturing
The machinery manufacturing industry is also an important area of use for thick-walled steel pipes. In occasions such as transmission bearings and cold-bent profiles that need to withstand large impact loads, thick-walled steel pipes play an important role as the main mechanical components.

4. Boiler industry
The boiler industry is also one of the important uses of thick-walled steel pipes. With the advancement of the national energy policy, the construction and renovation of a new generation of supercritical boilers are constantly advancing, and higher requirements for pressure resistance, wear resistance, high temperature, corrosion resistance, and impact resistance are put forward for products. The pressure resistance and corrosion resistance of thick-walled steel pipes determine their irreplaceability in this field.

5. Aerospace
The aerospace field has very high requirements for the materials and technologies used in aircraft, requiring high material strength, light weight, strict compliance with various standards and specifications, and the need to withstand extreme environments of high temperature and high pressure. Therefore, in the aerospace industry, thick-walled steel pipes are indispensable materials.

6. Nuclear industry
Although the requirements for steel in nuclear power plants and nuclear power are not as high as those for other pressure vessels and equipment, the corrosion requirements for steel pipes are very strict. High corrosion-resistant steel must be used to seal and expand the use of welded steel pipes. Thick-walled steel, as an indispensable material in the nuclear industry, is widely used in various nuclear power plants, nuclear power equipment manufacturing and other industries.

7. Transportation
In order to ensure safety and strong bearing capacity, modern highway bridges use thick-walled steel pipes in design, which not only have a high bearing capacity, but also ensure structural solidification.

Conclusion: 
Thick-walled steel pipes have become the core material in the heavy industry due to their high strength, high pressure resistance, and extreme environment resistance. When selecting, you need to focus on the material, wall thickness calculation, process standards (ASME), combined with operating parameters (pressure, temperature, medium), and match the anti-corrosion solution (such as galvanizing, coating) according to the application scenario. For special needs (such as ultra-thick walls and special-shaped sections), it is recommended to cooperate with steel mills for customization.

Read more: Seamless Steel Pipe Sizes and Weights or Schedule 80 Carbon Steel Pipe