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Difference between seamless pipe and seam pipe

Date:2021-11-03View:2748Tags:seamless steel pipe, seam pipe, welded pipe

From the technological point of view, the seamless steel pipes is formed by rolling once, heated with round steel, pierced, hot rolled, sizing, and straightened.

Seam steel pipes are also called welded steel pipes. They are welded by bending deformation of steel plates or steel strips. There are straight seam welded pipes and spiral welded pipes (spiral welded pipes are generally of large diameter).

seam welded pipe

Seam steel pipes and seamless steel pipes are classified according to the method of steel pipe production.

1. According to production methods, seamless steel pipes can be divided into: hot-rolled seamless pipes, cold drawn pipes, precision steel pipes, hot expanded pipes, cold spinning pipes, and extruded pipes. Seamless steel pipes are made of high-quality carbon steel or alloy steel, and are divided into hot-rolled and cold-rolled (drawn).

2. Welded steel pipes (Seam steel pipe) are divided into furnace welded pipes, electric resistance welded (resistance welded) pipes and automatic arc welded pipes due to their different welding processes. Due to their different welding methods, they are divided into two types: straight seam welded pipes and spiral welded pipes. The end shape is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. Welded steel pipes are welded by butt seams or spiral seams of steel plates rolled into a tube shape. In terms of manufacturing methods, they are divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct coil welded steel pipes, and electric welded pipes. Seamless steel pipes can be used for liquid pressure pipes and gas pipes in various industries. Welded pipelines can be used for water pipelines, gas pipelines, heating pipelines, electrical pipelines, etc.

The difference between seamless steel pipe and seam steel pipe:

Different purposes: seamless steel pipe are mainly used as pipelines or structural parts for fluid transportation, mainly in the machinery industry, while seam steel pipes are mainly used in the construction industry, such as water, gas, compressed air and other low-pressure fluids. However, seamless steel pipes are used for all pressure pipelines. The price of seamless steel pipes is higher than that of seamed steel pipes.

Seamed pipes generally can withstand the maximum operating pressure of less than 20 kg, which is a safe range of use. It is generally used for low-pressure fluids such as water, gas, and compressed air.

Seamless steel pipe can withstand ultra-high pressure, of course, its wall thickness will increase accordingly, which needs to be designed according to pressure requirements. It is generally used for high-temperature and high-pressure equipment such as high-pressure oil pipes and boiler tubes. There are also seamless steel pipes for structural use, depending on the design requirements.

At present, there are also some seamless pipes with seam steel pipes, which are annealed to the weld seam, and the residual stress of the weld seam is made to make the weld seam equivalent to the base metal, and its pressure-bearing range is basically equivalent to that of seamless steel tube. Can also be considered for use.

Of course, there are also some seamless steel pipes on the market that use seamed steel pipes to be heated as a whole and then drawn or rolled with a core head. They are mainly small in size. This type of pipe is seamless steel pipe only in terms of appearance, and its quality is not very good. 

Advantages Of Seamed Steel Pipes Compared To Seamless Steel Pipes :

(1) The seamed steel pipe mainly refers to the welded steel pipe, and because of its low cost and high production efficiency, the seamless steel pipe is replaced in many fields. Although welded steel pipes replace seamless steel pipes, they still have essential differences. 

(2) The seamless steel pipe is formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn. The welded steel pipe is a steel pipe which is welded and formed by a steel strip or a steel plate to be deformed into a circular shape or a square shape, and has a joint on the surface. The blank used for welded steel pipes is steel plate or strip steel. From the above definition, the biggest difference between the seamless steel pipe and the welded steel pipe is that the welded steel pipe has seams.

(3) The production process of seamless steel tubes can be divided into cold drawing and hot rolling. The production process of cold rolled seamless steel tubes is generally more complicated than hot rolling. The tube blanks must first be rolled in three rolls, and the sizing should be carried out after extrusion. Test, if the surface does not respond to the crack, the tube is cut by a cutter and cut into a blank of about one meter in length. Then enter the annealing process, the acidification should be acid-washed with acid liquid. When pickling, pay attention to whether there is a large amount of foaming on the surface. If there is a large amount of foaming, the quality of the steel pipe will not reach the corresponding standard. 

(4) The appearance of cold-rolled seamless steel pipe is shorter than that of hot-rolled seamless steel pipe. The wall thickness of cold-rolled seamless steel pipe is generally smaller than that of hot-rolled seamless steel pipe, but the surface looks brighter than thick-walled seamless steel pipe, and the surface is not too More rough, not too many burrs in the caliber. 

The following are the advantages of welded tubes compared to seamless steel tubes or other seamed steel tubes:

(1) The electric welded steel pipe has a large size range, and can produce welded pipes with an outer diameter of 45 to 4000 mm and a wall thickness of 0.1 to 40 mm and a pipe length of up to several hundred meters. The wall thickness is smaller than that of the seamless steel pipe and smaller than the furnace pipe. The pipe diameter to the pipe wall thickness ratio can reach 100, and the seamless steel pipe also has a large-diameter seamless steel pipe and a small-diameter seamless steel pipe, and the furnace welded pipe is also small. The pipe diameter and wall thickness are 4~50 and 5~28 respectively. Therefore, the electric welded pipe can save metal. 

(2) It can produce steel pipes of various chemical compositions. 

(3) The emergence of new electric welding units, equipment and control systems continue to improve, so that the weld has a higher strength than the metal matrix. The use of heat treatment eliminates the welding stress of the weld and allows the welded pipe to obtain a uniform structure in cross section. Therefore, the quality of the welded pipe is not lower than that of the seamless steel pipe, and sometimes it can replace the seamless steel pipe. 

(4)Since the steel tube is formed in a cold state, the obtained steel pipe has high dimensional accuracy and surface roughness, and the general metal consumption is only 1.03% to 1.05%. 

(5)The electric welding steel pipe unit can stop the power supply and reduce the energy consumption. 

(6)The production process is easy to automate and continuous, with high productivity and good working conditions.

How To Choose Tubes & Pipes, Welded Or Seamless?

Despite many advantages with welded tubes, seamless tube is still treated better than welded type, especially used in rough environment, considered as higher strength, higher pressure, and better corrosion resistance.Depending on specific application and cost aspect, decide which type is better choice to use.Tubes and pipes can be produced in both seamless and welded types depending on application requirement.

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