Line Pipe Production Status in China

1. Production Process

Welded line pipe can be distinguished into three production process which are resistance welding, spiral submerged arc welding, longitudinal submerged arc welding. These three types of line pipe are applied in different fields according to the raw materials, molding, aperture size and quality varies. 

2. Straight seam electric resistance welded pipe (ERW Steel Pipe)

ERW steel pipe is a type of welded piep has widest range of applications, most production units (more than 2,000), highest production yield (about 80% of the total capacity of the steel pipe production quantity) and the earliest production line invested in China. In China, the production size of ERW steel pipe ranges from 20mm to 610mm which played a large role in the national economy construction. Since the 1980s, about 30 sets of the ERW steel pipe production units 219mm - 610mm units are imported from oversea advanced technology. After years of production pratice, the technology and equipment level have been achieve a great progress, and the product quality is improving. Because of the less improvement, quick wide range of applications and rapid development, in the future, the development of ERW steel pipe prodcution will  focus on producing low cost and reliable products. 

2. Spiral submerged arc welded pipes (SSAW steel pipe)

SSAW steel pipe requires less investment in equipment, low prices for raw materials to produce large diamter pipe, simple production process, low running costs. In China, the oil and gas transportation spiral welded pie has formed a steel plant-based oil system belongs basic format. Low residual stress and tube end forming machinery and expanding other advanced technology, strict quality control through the spiral welded pipe in the quality can be comparable with the Longitudinal. 

3. Longitudinal submerged arc welded pipe (LSAW steel pipe)

About the LSAW steel pipe production process, in the past we mainly use UOE technology. However, in the recent years progressive, JOCE technology is becoming the new mainstream technology for producing LSAW steel pipe. Compared with other welded pipe production process, the LSAW steel pipe production units require relatively large investment, higher cost of raw materials, more complex process, low productivity and high production cost. Because of the high pressure oil and gas pipeline requires large diameter 1 million tons every year. Regardless of the spiral welded pipe, LSAW steel pipe will complement the spiral welded pipe uncovered specifications. 

Line Pipe

In modern society, line pipe is belong to low or ultra low carbon steel pipe with micro-alloyed. Line pipe is a type of high tech and high value added products which is all applied in the areas of metallurgy technology nearly 20 years of new achievements. The development trend of pipeline project is applying large diameter, high pressure, high cold and corrosive, thick wall line pipe. Therefore, in modern society, line pipe should have a high strength, low bauschinger effect, high toughness and resistance, brittle fracture, low carbon volume and good weldability properties. Meanwhile, line pipe has high resistance to HIC and anti-H2S corrosion features is necessary. The optimized production strategies is to improve the steel cleanliness and organizations uniformity, C≤0.09%, S≤0.005%, P≤0.01%, O≤0.002%, and to take micro-alloying, vacuum degassing + CaSi, the continuous casting process under light pressure, multi-stage thermomechanical rolling and accelerated cooling versatile batch process. Domestic and international pipeline specification does pipelines toughness index of steel, pipe only to specific requirements:

(1) Minimum temperature (-5 ℃) DWTT≥85% SA;

(2) the lowest temperature (-5 ℃) Charpy impact energy ≥145J.

Pipeline Technical conditions commonly used by the American Petroleum Institute standards APISpec5L, but the domestic user's specific projects or specific orders and technical conditions are often much more stringent than the API standard.

Smelting technology with more stringent requirements, technical difficulties focused on:

1) content of impurity elements control;

2) inclusion control;

3) a narrow composition control.