Seamless steel pipe is manufactured by the round steel billet, through hot rolling, cold rolling or cold drawn processes, no seam on the pipe body.

Welded steel pipe is manufactured by flat steel plate, with welding seam on the pipe body. Including ERW pipe, LSAW pipe, SSAW pipe.

Here are the differences between seamless pipe and welded pipe on raw material, manufacturing processes, performances, appearances, sizes, applications, cost prices etc.

1. Appearance difference

Seamless steel pipe used steel billet as raw material. The outer surface defects of billet cannot be eliminated by hot rolling process, it is only polished after the product finished. In the process of wall reduction, the defect can only get partially eliminated.

Welded steel pipe made by hot rolled coil as raw material, the surface quality of coil is just the pipe’s surface quality, and easy to control.The surface of hot rolled coil have high quality.

So Welded steel pipe surface quality is much better than seamless steel pipe.

2. Molding process differences

Seamless steel pipe can be formed one time in the rolling process.

Welded steel pipe is manufacturing with steel strip or steel plate, through bending and different welding processes.

3. Performance and Usage

Seamless steel pipe has better pressure capacity, strength is higher than ERW welded steel pipe. So it is widely applied in high pressure equipment, and thermal, boiler industries.

Generally the welding seam of the welded steel pipe is the weak point, the quality affect overall performance.

In general, welded steel pipes can withhold 20% less working pressure than seamless ones. This reliability is the prime factor why people go for seamless steel pipe. As a matter of fact, all the industrial pipelines are done with seamless pipes only because the pipes undergo extreme thermal, chemical and mechanical workloads. Welded pipes are more preferred in aerospace, automobile and electronics industries where the budget is comparatively low, and so is the work pressure put on the pipes.

4. Available Sizes differences

For most of seamless steel pipe manufacturers in China, they produce original seamless pipe sizes maximum OD in 20 inch, 508 mm. Where usually is smaller than 16 inch, 406.4 mm, because of the equipment limits. And if client would like to purchase the seamless steel pipe more than above sizes, then hot expanding machining shall be used. But usually this kind hot expanded seamless steel pipe quality could not compare with the original seamless steel pipe.

On the contrary, welded steel pipe don’t have these limitations, sizes available from 1-1/2 inch 48.3mm to 100 inch 2540 mm.

5. Cost and prices

Usually the seamless steel pipe cost is higher than welded steel pipes, because the raw material, manufacturing equipment and processes. But sometimes by the market pressure, welded pipe is more expensive, so if you met this situation, don’t hesitate to purchase the seamless steel pipe for the same dimensions.