How to identify inferior stainless steel welded pipes?

A stainless steel welded pipe, also known as welded pipe, is a type of steel pipe formed by welding common steel or steel strip after it is rolled and shaped using a unit and die. Its manufacturing process is relatively straightforward, resulting in high production efficiency and a wide range of specifications. The investment in equipment is lower compared to seamless steel pipes, but welded pipes generally have lower strength.

Thanks to its excellent corrosion resistance, high strength, and good sealing performance, stainless steel welded pipes are widely used across various industries such as oil and gas transportation, chemicals, pharmaceuticals, food, construction, machinery manufacturing, environmental protection, and water treatment. For example, in the oil and gas sector, these pipes can withstand extreme pressure and temperature, ensuring safe transportation. In construction, they are often used to create decorative components such as railings and handrails.

Dangers of Inferior Stainless Steel Welded Pipes

Using low-quality stainless steel welded pipes in construction can lead to significant safety risks over time. These pipes lack the necessary corrosion resistance and strength, which can result in structural failure. For instance, some small construction projects have used substandard welded pipes for stair handrails to reduce costs. After enduring multiple wind and rainstorms, these handrails became severely rusted and deformed, causing some to loosen and fall off, posing a major hazard to residents.

In the chemical industry, inferior stainless steel welded pipes used for transporting corrosive media can corrode and perforate quickly, leading to leakage. Such leaks not only pollute the environment but can also cause hazardous accidents, including fires and explosions, putting both personnel safety and corporate assets at risk.

How to Identify Inferior Stainless Steel Welded Pipes

- Folding in Stainless Steel Welded Pipes

Low-quality welded stainless steel pipes often show signs of folding. This occurs when excessive pressure is applied during manufacturing, resulting in fold lines running along the entire length of the pipe. These folds reduce the pipe's strength and cause it to crack when bent. Inferior pipes also tend to have a pockmarked surface due to severe wear on the rolling groove.

- Scarring on Stainless Steel Welded Pipes

The surface of inferior stainless steel welded pipes is prone to scarring, which typically occurs for two reasons: uneven material composition with impurities, and inadequate sanitation equipment in the manufacturing process. These impurities can get stuck on the rollers, leaving marks or scars on the pipe surface.

- Cracks in Stainless Steel Welded Pipes

Cracks often form on the surface of subpar welded pipes. The cause is usually the use of low-quality blank materials, which contain many pores. When the pipe undergoes cooling, thermal stress causes these pores to expand, resulting in cracks that appear after the pipe is rolled.

- Surface Quality of Stainless Steel Welded Pipes

Inferior stainless steel welded pipes often lack metallic luster and exhibit a dull reddish or pig iron-like color. This may occur because the raw material is of poor quality or the rolling temperature is not controlled properly. When the steel is not heated to the correct temperature, the resulting pipe fails to meet performance standards. Such pipes are also more likely to be scratched because the manufacturing equipment is poorly maintained, leading to burrs that can damage the pipe surface. Deep scratches further weaken the pipe's structural integrity.

- Specifications and Dimensions of Stainless Steel Welded Pipes

Poor-quality welded pipes often fail to meet dimensional specifications and tolerances. These pipes tend to contain excessive impurities, resulting in lower material density and poor size consistency. To check the quality, you can use a vernier caliper or, in the absence of one, weigh the pipe and compare it to the expected specifications.

Inferior stainless steel welded pipes are more likely to have thin and low transverse ribs, often failing to fill properly during the manufacturing process. This occurs when manufacturers increase pressure in the first few passes of the rolling process to achieve a larger negative tolerance, which distorts the pipe’s shape. As a result, the cross-section may appear oval instead of round.

In conclusion, identifying inferior stainless steel welded pipes is essential to prevent potential safety hazards and operational failures. Always ensure proper material selection, manufacturing quality, and regular inspection to guarantee the pipes' reliability and longevity in their intended applications.