Details of the production process, standards, and applications of straight seam steel pipes

Straight seam welded steel pipes, also known as straight seam welded steel pipes, are steel pipes that are formed by curling steel plates or steel strips through high-frequency welding processes and then welding them along their longitudinal straight seams. As one of the basic materials widely used in modern industry, straight seam welded steel pipes have become an indispensable part of construction, machinery, petroleum, chemical industry, electricity, transportation, and other fields with their efficient production process, stable performance, and diverse specifications.

First, the technical origin and process innovation of straight seam welded steel pipes

The history of straight seam welded steel pipes can be traced back to the early 20th century. With the maturity of arc welding technology, the production monopoly of traditional seamless steel pipes was broken. In the 1950s, the breakthrough of high-frequency resistance welding (HFW) technology became a watershed in the industry-through the skin effect and proximity effect of high-frequency current, the edge of the steel plate is instantly heated to a molten state, and metallurgical bonding is achieved under the action of the extrusion roller. Compared with traditional processes such as submerged arc welding (SAW), high-frequency welding has the characteristics of faster speed (up to 20-30 meters/minute), narrower heat-affected zone, and lower energy consumption.

In terms of the production process, modern straight seam welded steel pipes need to go through five key stages:

1. Uncoiling and leveling: Unroll the steel coil and eliminate internal stress through a multi-roller leveling machine;

2. Forming welding: Use progressive bending technology to form the tube blank, and the high-frequency welder completes the weld at 1200-1500℃;

3. Online heat treatment: Eliminate welding residual stress through medium-frequency induction heating;

4. Sizing detection: Use a four-roller micro-tension sizing machine to control tolerances, and an eddy current flaw detector to detect weld defects;

5. Anti-corrosion treatment: Choose galvanizing, epoxy powder spraying, or 3PE anti-corrosion coating according to the application scenario.

Second, an in-depth analysis of the classification system and performance indicators

According to the forming method, straight seam welded steel pipes can be divided into two categories:

- Continuous roll-bending welded steel pipes: suitable for conventional pipes with a diameter of 20-610mm and a wall thickness of 1.2-12.7mm, such as galvanized water pipes under the GB/T3091-2015 standard;

- JCOE formed welded steel pipes: through multiple stamping and forming, large-diameter thick-walled pipes with a diameter of 406-1626mm and a wall thickness of 6-40mm can be produced, which are used for long-distance oil and gas pipelines, and their bursting pressure can reach more than 90% of seamless steel pipes.

Third, innovative expansion of application scenarios and industry challenges

In the field of traditional infrastructure, straight seam welded steel pipes support national projects such as the "West-East Gas Transmission" - data from China National Petroleum Corporation shows that the use of the third-generation pipeline steel X80 welded steel pipe has increased the pipeline operating pressure to 12MPa, and the annual gas transmission volume of a single pipe has increased by 36%.

However, the industry still faces technical bottlenecks:

1. Weld reliability: Statistics from the China Special Inspection Institute show that 72% of welded steel pipe failure cases are caused by weld inclusions or unfused defects;

2. Material upgrade: Deep-sea pipelines need to develop F-grade steel that can adapt to the low-temperature impact of -40℃;

3. Green production: The average power consumption per ton of welded steel pipe is about 180 degrees, and the pressure to reduce emissions has driven companies to introduce photovoltaic energy storage systems.

Fourth, international competition patterns and future trends

In the next five years, with the planning of high-end pipes in "Made in China 2025", straight seam welded steel pipes will present three major development directions:

1. Intelligent production: The visual inspection system based on the industrial Internet realizes real-time monitoring of weld quality;

2. Composite design: Functional composite pipes lined with plastic/ceramic will expand their application in the chemical industry;

3. Lightweight breakthrough: 980MPa-grade ultra-high-strength steel welded steel pipes are expected to reduce weight by more than 20%.