Table 4
API Releases Pipeline Steel Grade Note: 1972 API released U80 and U 100 standards, which were later changed to X80 and X 100.
Before 2000, X70 accounted for about 40% in the world, X65 and X60 both accounted for 30%, and X52 steel was used in a considerable number of small-diameter product oil pipelines, and most of them were resistance welded straight pipes (ERW steel pipes).
For more than ten years, China's metallurgical industry has vigorously developed pipeline steel. At present, we are working hard to tackle X70 wide plate. The chemical composition and mechanical properties of X70 and X80 of Shanghai Baoshan Iron and Steel Company and Wuhan Iron and Steel Company are listed in Table 5 ~ Table 9 respectively.
Table 5
Performance of WISCO X80 coil plate
Table 6
Mechanical Properties of X70 Grade Steel Pipe
Table 7
Test results of bending performance of X70 grade steel pipe
Table 8
Charpy impact toughness of X70 grade steel pipe
Table 9
Charpy Impact Toughness of High-strength Pipes Commonly used in China are spiral submerged arc welded pipe (SSAW), longitudinal submerged arc welded pipe (LSAW) and resistance welded pipe (ERW).
When the diameter is less than 152mm, the seamless steel pipe is selected.
From the end of 1960s to 1970s, the spiral welded pipe factory in China developed rapidly. Almost all crude oil pipelines are spiral welded steel pipes, and spiral welded steel pipes are also used in the first-class area of "West-East Gas Transmission".
The disadvantages of spiral welded steel pipe are large internal stress, poor dimensional accuracy and high defect probability.
According to the analysis, the principle of "walking on two legs" should be adopted. First, actively carry out technical transformation on the existing spiral welded pipe factory, which is promising; Second, vigorously develop China's longitudinal submerged arc welding pipe industry.
ERW steel pipe has the characteristics of smooth appearance, high dimensional accuracy and low price, and has been widely used at home and abroad.