Welded steel pipe, also known as welded pipe, is a steel pipe made of steel plate or strip after curling and forming.
Welded steel pipe has the advantages of simple production process, high production efficiency, more varieties and specifications, less equipment investment, but its general strength is lower than seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the progress of welding and inspection technology, the quality of weld seam has been continuously improved, the variety and specification of welded steel pipe has been increasing, and stainless steel seamless pipe has been replaced in more and more fields. Welded steel pipe is divided into straight welded pipe and spiral welded pipe according to the form of weld.
Longitudinal welded pipe has the advantages of simple production process, high production efficiency, low cost and rapid development. The strength of spiral welded pipe is generally higher than that of straight welded pipe. It can produce welded pipe with bigger diameter with narrower blank, and welded pipe with different diameter can also be produced with blank of the same width. However, compared with the straight seam pipe of the same length, the length of the weld increases by 30–100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes are welded by straight seam welding, while the larger diameter welded pipes are mostly welded by spiral welding.
Welded steel pipe for low-pressure fluid transportation (GB/T3091–2008) is also known as general welded pipe, commonly known as black pipe. It is a welded steel pipe used for conveying water, gas, air, oil, heating steam and other general low pressure fluids and other purposes. The wall thickness of steel pipe can be divided into ordinary steel pipe and thickened steel pipe, and the nozzle end can be divided into non-threaded steel pipe (smooth pipe) and threaded steel pipe. In addition to directly conveying fluids, welded steel pipes for low-pressure fluid conveying are also widely used as raw pipes for galvanized welded steel pipes for low-pressure fluid conveying.
1. Galvanized welded steel pipes for low pressure fluid transportation (GB/T3091–2008) are also called galvanized welded steel pipes, commonly known as white pipes. It is a hot dip galvanized welding (furnace welding or electric welding) steel pipe used for conveying water, gas, air oil, heating steam, warm water and other generally low pressure fluids or other purposes. The wall thickness of steel pipe can be divided into common carbon steel galvanized pipe and thick galvanized steel pipe, and the end of pipe can be divided into non-threaded galvanized steel pipe and threaded galvanized steel pipe. The specification of steel pipe is expressed by nominal diameter (mm), which is the approximate value of inner diameter. Commonly used inches, such as 1/2, 3/4, 1, 2, etc.
2. Common carbon steel wire sleeve (YB/T5305–2006) is a steel pipe used to protect wire in industrial and civil buildings, installation machinery and equipment and other electrical installation projects.
3. Longitudinal welded steel pipe (GB/T13793–2008) is a steel pipe with longitudinal parallel weld and steel pipe. Used in general structure, usually divided into metric welded steel pipe, welded thin-walled pipe and so on.
4. Spiral submerged arc welded pipe (SY/T5037–2000) for pressure fluid conveying is a spiral welded pipe with hot rolled steel strip coil as billet, which is spirally formed at normal temperature and welded by double-sided submerged arc welding for pressure fluid conveying. Steel pipe has strong pressure bearing capacity and good welding performance. It is safe and reliable to use after various strict scientific tests and tests. The steel pipe has large diameter, high conveying efficiency and saves investment in laying pipelines. It is mainly used for pipelines to transport oil and natural gas.
5. SY/T5038–2000 spiral seam high frequency welded steel pipe for pressure fluid transportation is a kind of spiral seam high frequency welded steel pipe for pressure fluid transportation, which is made of hot rolled steel strip coil and spirally formed at normal temperature and welded by high frequency lap welding method. The steel pipe has strong bearing capacity, good plasticity, and is easy to be welded and processed. Through various strict and scientific tests and tests, it is safe and reliable to use, large diameter of steel pipe, high transportation efficiency, and can save the investment of laying pipelines. It is mainly used for laying pipelines for oil and natural gas transportation.
6. Spiral seam high frequency welded steel pipes (SY/T5039–2000) for low-pressure fluid transportation are usually formed by hot-rolled steel strip coil at normal temperature. High frequency lap welding is used to weld high frequency spiral seam welded steel pipes for general low-pressure fluid transportation.
7. Spiral welded steel pipe for piles (SY/T5768–2000) is made of hot-rolled steel strip coil as billet, which is spirally formed at normal temperature and is welded by double-sided submerged arc welding or high frequency welding. It is used for steel pipe for foundation piles such as civil building structures, wharfs and bridges.
