seamless steel pipe VS welded steel pipe

The difference between seamless steel pipe and welded steel pipe
 
The seamless steel pipe is made of round billet by hot rolling, cold rolling or cold drawing, and the pipe body is seamless.
The welded steel pipe is made of flat steel plate and welded on the pipe body. Including ERW pipeline, LSAW pipeline, SSAW pipeline.

ABTERSTEEL tells you the differences in raw materials, manufacturing processes, performance, appearance, dimensions, applications, cost prices, etc. for seamless and welded tubes.

How to make seamless steel pipes.

API 5L and ASTM seamless steel tubes are passed through a porous tube using steel ingots or solid tubes as raw materials, which can then be hot rolled, cold rolled or cold drawn. Hot-rolled seamless steel tubes are made from steel billet forging, perforating, rolling, forming and other processes. For large diameter pipes and thick wall seamless pipes that are usually manufactured in this way. The cold drawn seamless pipe adopts cold drawing forming technology. The material is low in strength and has a smooth appearance and internal control surface. Small diameter and thin wall seamless tubes are typically manufactured in this manner. The seamless steel pipe is rolled from carbon structural steel, low alloy structural steel or alloy structural steel and stainless steel. Seamless steel pipes for different industries: pipeline piping, thermal services, machinery industry.

How is welded steel pipe manufactured?

API 5L or ASTM welded steel tubes include LSAW tubes, SSAW tubes and ERW tubes. These pipes are made of steel strip or steel. The manufacturing process first bends the steel sheet and then welds it into a circle, square and other shapes. Welded steel pipes have the characteristics of high production efficiency, low cost and material saving. It has been widely used in aviation, aerospace, energy, electronics, automotive, light industry and other industries. It has strong corrosion resistance in an acidic environment.

Why should you choose to buy seamless steel pipes?

The reason most people like to weld seamless steel tubes is that seamless tubes can withstand extremely high pressures without cracking. However, welds or welded pipes cannot do this because the welds are prone to cracking under high pressure. In addition, it is very easy to accurately calculate the pressure of the seamless pipe. Seamless tubes are thinner and lighter than welded tubes, and they are also uniform in shape due to the uniform extrusion of the alloy. 

Summary of differences in seamless butt welded steel pipes

There are some differences between API 5L / ASTM seamless steel tubes and ERW welded steel tubes as follows:

1. Appearance difference

Seamless steel tubes use steel billets as raw materials. The outer surface defects of the billet cannot be eliminated by the hot rolling process and are only polished after the product is completed. In the process of wall reduction, defects can only be partially eliminated.

The welded steel pipe with hot rolled coil as raw material has the surface quality of the coil as the surface quality of the pipe and is easy to control. The hot rolled coil has a high surface quality.

Therefore, the surface quality of welded steel pipes is much better than that of seamless steel pipes.

2. Molding process differences

A seamless steel pipe can be formed once during the rolling process.
Welded steel pipes are made of steel or steel, by bending and different welding processes.

3. Performance and use

Seamless steel tubes have better pressure bearing capacity and higher strength than ERW welded steel tubes. Therefore, it is widely used in high-voltage equipment, thermal engineering, boilers and other industries.
Generally, welds of welded steel pipes are disadvantages, and quality affects overall performance.

In general, the working pressure of welded steel pipes is 20% lower than that of seamless steel pipes. This reliability is a major factor in the choice of seamless steel tubes. In fact, all industrial pipes are made with seamless pipes, simply because the pipes are subjected to extreme thermal, chemical and mechanical workloads. Welded pipes are more popular in the relatively low-cost aerospace, automotive and electronics industries, as are the working pressures imposed on the pipeline.

4. Available size differences

For most seamless steel tube manufacturers in China, they produce original seamless steel tubes with a maximum outer diameter of 20 inches and 508 mm. Due to equipment limitations, it is typically less than 16 inches, or 406.4 mm. If the customer wants to purchase a seamless steel pipe of more than the above size, thermal expansion processing should be used. But usually the quality of this thermally expanded seamless steel tube is incomparable with the original seamless steel pipe.
In contrast, welded steel pipes do not have these limitations and can range in size from 1-1 / 2 inches 48.3 mm to 100 inches 2540 mm.

5. Cost and price

Due to raw materials, manufacturing equipment and processes, the cost of seamless steel pipes is generally higher than that of welded steel pipes. But sometimes due to market pressure, welded pipes are more expensive, so if you encounter this situation, don’t hesitate to buy seamless steel pipes of the same size.